Biology Of Ageing

Question 1

Define ageing

Answer 1

Process of change in properties of material occurring over a period of time - oxford dictionary
Collection of changes that render human beings progressively more likely to die
Decline of biological functions and of organisms ability to adapt to metabolic stress

Many age related changes appear in the fourth decade but some can be as early as age 10 eg hearing loss

Question 2

Medical classification of age

Answer 2

Prenatal life - fertilisation to 40 weeks
Birth
Neonate - newborn to week 2
Infancy - week 3 to 1 year
Childhood - 2-9 in females and 2-12 males 
Prepubertal - 10+ females 13+ males
Adolescence - 6 years following puberty
Adulthood - 20-65
Senescence - 65+

Question 3

WHO age classification

Answer 3

Young old - 60-74
Old old - 75-84
Oldest old - 85+
Centenarians - 100+

Question 4

Functional reserve capacity purpose

Answer 4

Most systems have spare capacity to prevent system failure - reserved to have more than the level required to maintain homeostasis

Question 5

Theories of ageing

Answer 5

Deterministic - programmed ageing where genes continue to turn on ageing similar to development. Evidence - species specific lifespans, twin studies, limited cell division, fast ageing syndromes like progeria. Gerontogenes. Gershon&Gershon observed built in programme in genome activated at certain stage in organisms life cycle leading to death via self destruct and autoregulatory mechanisms.
Non-deterministic - random damage accumulation from wear and tear. Protein damage and autophagy. Energy metabolism and ageing. Free radical theory. DNA damage theory.
Evolutionary theories - force of natural selection declines with age. Antagonistic pleiotrophy. Disposable soma.

Question 6

Species specific lifespan evidence for deterministic ageing

Answer 6

Evidence supporting the deterministic ageing theory.
Species specific max lifespan correlates with How long it takes to reach sexual maturity - maturity is genetically programmed so may also be ageing is too.

Question 7

Twin studies evidence for deterministic ageing

Answer 7

Danish cohort study 1870-1910
24% variation in twins lifespan accounted for by genetics - McGue et al 1993.
Genetic influences more obvious in later life
After age 70 up to 50% of variation in twins lifespan was accounted for by genetics suggesting genetics do not determine ageing ! It’s the interaction with the environment that determines this

Question 8

Limited cell division evidence for deterministic ageing

Answer 8

Hayflick limit
Cells in culture can divide only a set number of times suggesting genetic influences mean they must age
Senescent cells are in cell cycle arrest, but remain metabolically active and display gene expression patterns typically express p16INK4a
can be subject to morphological changes, reduced strength, secrete pro-oncotic factors increasing cancer risk, secrete MMPs degrading tissues and lack of cell division reduced tissue wound repair.
How long it takes to reach the hayflick limit correlates with max lifespan - Rickleffs&Finch 1996.
Against this theory - End regions of chromosomes - telomeres are also lost with cell divisions gradually making them less stable as the telomeres get shorter suggesting genetics determine ageing. Telomeres are lost because during cell division DNA polymerase can’t make new DNA to the ends of the chromosomes resulting in some telomere region being lost. ageing of senescence cells can’t be programmed by this as there’s no gene for telomerase, is only due to imperfect copying of DNA.
Unlikely to function in post mitotic organisms like c elegans or drosophila

Question 9

Fast ageing syndrome - Werner’s syndrome

Answer 9

Is a premature ageing disease
Symptoms - premature white hair, reduced skin suppleness, cataracts, diabetes, osteoporosis, vascular disease, cancer.
In vitro fibroblasts typically show abbreviated cellular lifespan in culture and in vivo affected tissues contain division contentment cells
WRN gene mutation on chromosome 8(recessive) in gene for recQ ATP dependent Helicase which unwinds DNA in replication, protein synthesis and DNA repair. Enhances telomere loss and causes ageing of tissues
Mutation causes dysfunctional Helicase stopping DNA synthesis meaning cells reach senescence early.
However this isn’t a model of programmed ageing as it’s still due to poor DNA copying, repair and new protein production.

Question 10

Gerontogenes

Answer 10

Genes which effect lifespan when mutated or expression is altered eg C elegans age-1 gene increases duration of expression causes max lifespan from 31 to 58 days.
Other genes - daf genes in worm also increase lifespan. Does this by mutation stopping normal effects of insulin and worms think they’re starving.
In drosophila fly additional genes increase antioxidants and lifespan by 30%. Extra antioxidants reduce free radical damage.
Johnson 2005 and cutler 2005
All gerontogenes increase resistance to physical stressors like free radicals, UV light etc. Suggest these environmental factors can drive ageing.

Question 11

Programmed ageing evidence summary

Answer 11

No good evidence as of yet
Genes are important in build up of damage counteracted by genetically regulated mechanisms
Genes involved are all those involved in cell maintenance (70% all genome) - hayflick limit prevented by re expression of telomerase gene, progeria - Re express Helicase gene, gerontogenes - additional genes and protective agents against stress damage

Question 12

Evolutionary ageing theories

Answer 12

Natural selection - only beneficial traits are selected for survival but senescence isn’t beneficial so why does it occur
Adaptive theory - programmed ageing. Age for a reason and are designed to age. Similar to genetics controlling development. Prevents overcrowding, increases generation turnover, aiding evolutionary change, but there aren’t enough old to contribute to overcrowding, and turnover of generations depends on rate of reproduction not death.
Non- adaptive theory- non programmed suggest ageing is passive result of inability to better itself and withstand deteriorative processes. Has no purpose or benefit. Defect of organism design. Late acting gene theory and antagonistic pleiotropy say ageing is adverse side effect of function ie reproduction. Disposable soma theory is organisms can’t withstand deteriorative process and soma (body cells) are sacrificed to maintain germ cells

Question 13

Late acting gene theory - Peter Medawar 1952

Answer 13

Ageing as by product of natural selection- force of selection declines with age
Probability of reproduction changes with age - increases from birth to adulthood and decreases due to probability of death from external causes.
Therefore the greatest contribution to create new generation comes from young organisms so deleterious mutations expressed during reproductive phase are severely selected against. While mutations in later life are neutral to selection as genes are already transmitted to next generation and so these aren’t removed. Concept of selection shadow where older ages may permit accumulation of late acting mutations as hazardous genes persist and build up. Eg Huntington disease or apolipoprotein E4 for Alzheimer’s and CV disease

Question 14

George Williams 1957 antagonistic pleiotropy hypothesis

Answer 14

Pleiotropy - one gene influences two or more unrelated traits
Builds on late acting gene theory some genes may benefit in younger life but be detrimental in later life. These are favoured in selection when reproductive but may have bad effects later on. Small benefits to reproduction such as the gene for colourful long feathers in peacock males may be favoured over large deleterious effects such as escaping prey or poor camouflage. Oestrogen in early life is necessary for reproduction but in later life in linked to cancer. Sickle trait protects from malaria early on but late can cause haemorrhage and organ failure, Huntingtin gene increases fertility in early life but causes cognitive and movement disorders later.

Question 15

Disposable soma hypothesis

Answer 15

Maintenance of germline at expense of soma cells is observed in humans and all species. Germline is kept separate from soma.
August Weismann 1891
Soma cells may be sacrificed to maintain germ cells - Tom kirkwood 1979
By this theory species in hazardous environments should have poor somatic cell maintenance - and when lifespan increases a decrease in fertility would be seen. Supporting this - cell maintenance correlates with max lifespan per species and long lived species are less fertile - could be confounding factors involved.

Question 16

Examples of ROS/RNS

Answer 16

Radicals

Non - radicals - hydrogen peroxide, nitric oxide etc

Question 17

OIL RIG

Answer 17

Oxidation is loss

Reduction is gain of electrons

Question 18

Sources of ROS/RNS - superoxide

Answer 18

Variety of cell sources including mitochondria, NADPH, oxidases (NOXs), coupled/uncoupled nitric oxide synthase NOS etc
Main source of superoxide from mitochondria during oxidative phosphorylation - many free electrons, H ions and oxygen molecules for H2O2 formation. This is influenced by PO2. Forms 0.1-0.2% all superoxide. Major site of ROS generation is complex III in basal mitochondria. ROS are removed by cytosolic and mitochondrial ROS scavenging systems. In pathological conditions backflow of electrons in complex I also increases ROS generation.

Question 19

NOS reactions

Answer 19

Coupled NOS forms NO important for vasodilation, uncoupled NOS forms O2- which decreases NO bioavailability by reacting and forming ONOO-.
BH4 is essential for NOS activity
Reduced BH4 or L arginine uncouples NO synthesis from NADPH consumption to generate superoxide
Vit C stabilises BH4 and increases levels in endothelial cells promoting eNOS coupling.

Question 20

constitutive Antioxidant systems

Answer 20

Cells contain constitutive antioxidant systems to detoxify ROS eg superoxide dismutase to detoxify superoxide.
SOD catalyses reaction converting SO to hydrogen peroxide and oxygen. SOD1 Found In cytosol and outer mitochondrial memb. SOD2 In mitochondrial matrix and SOD3 In cytosol. Catalase CAT removes hydrogen peroxide to water and oxygen.
Cellular glutathione GSH synthesis within cells is abundant and is responsible for reducing oxidised proteins and can detoxify ROS through selenium containing enzyme glutathione peroxidase GPx
Peroxiredoxin and thioredoxin systems can reverse protein oxidation.

Question 21

Inducible antioxidant systems

Answer 21

Nrf2 nuclear factor E2 related factor 2 defence pathway - regulates transcription of hundreds of cytoprotective genes.
Target genes - GSH related genes like cystine transporter xCT, GCLM, heme oxygenase 1 (HO-1), NADPH quinone oxidoreductase (NQO1).

Question 22

Mitochondrial function in health and age

Answer 22

Healthy - more ATP and less ROS produced

Unhealthy/aged cells - less ATP and more ROS generation

Question 23

Why are mitochondria susceptible to oxidative damage

Answer 23

Mitochondrial organelles make the majority of ATP and free radicals in mammalian cells.
MtDNA susceptible to mutation - encodes 37 genes, 2rRNA, 22 tRNA, 13 ETC proteins (complex I, III, IV and V)
Highly mutable - lacks histone proteins, few repair enzymes, circular DNA with few introns.
also damaged mitochondria aren’t degraded so continue to produce more ROS and damage healthy proteins.
The more mitochondrial dysfunction, the more ROS generation and spread of mutation there is and mutation also increases with age

Question 24

ROS underlying ageing controversies

Answer 24

ROS production increased in mice and DNA mutations also increased
Mice without ROS antioxidant pathways had much shorter lifespan however still showed the same amount of DNA damage suggesting ROS not responsible for the damage shown
Causes of mitochondrial swelling may be from
Oxidative damage or could be independent of ROS formation as same morphology seen in ROS normal and excessive cells

Question 25

Consequences of mitochondrial dysfunction

Answer 25

Decline in function increases ROS production in lipid membranes and transmits to neighbouring cells Necrosis occurs from lack of respiration and insufficient ATP production - inflammation and enzyme release including degrading enzymes which cause more damage to neighbouring cells lifespan is shortened There is a gender difference in DNA damage seen in monkeys - more prevalent in males, females are better at protecting from damage? No direct evidence so far so may be result of other processes rather than causal.

Question 26

MnSOD2 knockout mice

Answer 26

Lack mitochondrial SOD but have cytoplasmic SOD | Show reduced life span and reduced activity in complex I and III

Question 27

Polg exonuclease mutant mice

Answer 27

Hereto and homozygous mice More mutant errors seen Limited evidence suggesting accumulation of mitochondrial mutations reduced lifespan - no effect seen in heterozygous and young mouse survival rate not much different despite mutation rate. Likely multiple contributors to ageing, just mitochondrial insufficiency alone isn’t enough to drive ageing

Question 28

Dietary coenzyme q 10 and vit E And p66shc mice for mitochondrial function

Answer 28

Coenzyme Q10 transfers electrons from complex I And II to iii lowering oxidative stress and reducing superoxide generation. Increases lifespan in c elegans mustangs for MeV-1. P66shc mutant mice reduce H2O2 production and increases lifespan

Question 29

Beneficial mitochondrial DNA mutations in humans

Answer 29

More likely that centenarians like gene for. Complex V, increasing lifespan and resistance to disease and more efficient production of ATP Gene for complex I - mt5178 Increases longevity, more antioxidant Gene for complex iii seems to do the same

Question 30

Role of ROS in insulin receptor kinase activation

Answer 30

Ligand interaction leads to production of superoxide and hydrogen peroxide involved in autophosphorylation and activation of receptor kinase

Question 31

ROS excess consequences

Answer 31

Protein modification, lipid perocidation, DNA damage Lipid peroxidation - hydroxyl radicals attack lipid membranes particularly PUFAS resulting in lipid peroxyl radicals and further lipid damage. Termination occurs when radical species react together or terminated by vitamin E and C. DNA damage - hydroxyl radicals or aldehydes can induce DNA damage particularly mitochondrial DNA. Protein modification - can occur during ROS mediated cell signalling or result in abnormal function

Question 32

Oxidative damage theory of ageing

Answer 32

In health there is equilibrium between ROS generation and removal by endogenous defences - redox homeostasis, But with age this shifts favouring higher ROS production and decreases antioxidant defences leading to DNA damage and cellular dysfunction Metabolic rate is thought to be inversely proportional to lifespan - higher metabolic mammals like mice have much shorter lifespan than lower metabolic animals like elephants Markers of oxidative damage also correlate with lifespan and antioxidant capacity - higher capacity increasing lifespan With age these decline. However this isn’t necessarily the whole story and many other factors may also be involved Not all free radical evidence is supporting - glutathione levels of the naked mole rat are roughly similar to mice however mice live 2-3 years while NMR live 25-30 years. Some antioxidant markers thought to be more important than others and it may not be the actual molecule, but the ability to diffuse to and from cells and interact and bind (it’s coproteins) that are of importance!

Question 33

Ageing population

Answer 33

Ageing population are those in which proportion of elderly people is increasing Difference between growth of older population and population ageing Less developed countries are ‘younger’ and more developed countries are ‘older’ Caused by: Declining fertility: started in Europe/north America and spreading to rest of world Increased life expectancy: Not many young people because of fertility decline, but there was big birth cohorts that occurred before the fertility decline and those cohorts are ageing Migration?

Question 34

Implications of ageing populations

Answer 34

Slower economic growth (demographic divided) Health and healthcare (mortality, morbidity/disability) Intergenerational social and family support Labour force participation and retirement Pension and old-age security Nations growing old before growing rich: dependent on economic systems and institutions, policies that channel intergenerational flows

Question 35

Why are we living longer

Answer 35

``` Gains in life expectancy reflect achievements at older ages Medical and technological advancements Rapid mortality declines at oldest ages Causes of death contributing to decline Mostly CV disease Cancer Respiratory diseases and infections ```

Question 36

Population health is measured by

Answer 36

Life expectancy: average number of years remaining to be lived Healthy life expectancy: Average number of years to be lived without disease Active (disability-free) life expectancy: Average number of years to be lived without disability

Question 37

How long will we live in future?

Answer 37

Depends on how you measure it: as an average maximum life span or by individual life span Mortality has been improved the longer humans have been around But we will spend a good portion of our lives disabled when bodily function starts to decline (compression of morbidity theory) Morbidity is where disability starts With life extension lifespan increases, but disability starts at the same time (spend more time disabled) With a shift to the right you live longer and get sick later Compression of morbidity (most ideal scenario) you are disabled for a shorter amount of time. No compression of morbidity means growing numbers of chronically ill and disabled elderly, creating increased burden on health systems

Question 38

Proteostasis

Answer 38

The maintenance of proteome homeostasis Proteome homeostasis is the sum total of: Protein synthesis (translation) Post-translational processing and transport Folding Assembly and disassembly into macromolecular complexes Stability and clearance Achieved by an integrated network of several hundred proteins: Molecular chaperones: Heat shock proteins (HSPs) that prevent protein misfolding and aggregation The ubiquitin-proteasome system (UPS) and autophagy: major pathways of protein degradation function in the cell

Question 39

Proteotoxicity

Answer 39

The adverse effects of damaged or misfolded proteins on the cell Most cells have a sophisticated proteolytic apparatus which ensures rapid elimination of altered proteins (implies altered proteins are deleterious (toxic) to cell survival) The causes behind the formation of these altered proteins are: Mutation and biosynthetic errors (can happen at any point in life) Post-synthetic damage by ROS/RNS, reactive aldehydes and glycating agents Protein misfolding Incomplete proteolysis

Question 40

Protein modification by deleterious agents

Answer 40

Protein carbonylation This is the irreversible, non-enzymatic modification of proteins Reactive carbonyl compounds are molecules with highly reactive carbonyl (C=O) groups Introduced into proteins by a variety of oxidative pathways: Direct oxidation of proteins by ROS yields highly reactive carbonyl derivatives resulting either from Oxidation of side chains of Lys, Arg, Pro or Thr residues (metals are catalysts) Cleavage of peptide bonds by the alpha-amidation pathway or by oxidation of glutamyl residues Indirect oxidation through conjugation by reactive species: Lipid peroxidation Glycation

Question 41

Lipid peroxidation

Answer 41

formation of ALEs (advanced lipid peroxidation end products) ALEs are a class of covalent adducts which are generated by the non-enzymatic reaction of reactive carbonyl compounds (RCCs), produced by lipid peroxidation and lipid metabolism with the free amino groups of cellular and tissue proteins. Oxidative stress involved in mechanism of formation. Lipid peroxidation is the oxidative deterioration of polyunsaturated lipids Polyunsaturated fatty acids (PUFAs) are the building blocks of biological lipids, and comprise the membranes that surround cells and organelles The lipid hydroperoxide formed by lipid peroxidation is important because this product can fragment to yield reactive intermediates: toxic reactive aldehydes (RCCs) Note 1: Proteasomes are abundant in young people, and destroy misfolded proteins Note 2: Aggregates are not good as they inhibit proteasome

Question 42

Protein glycation

Answer 42

Formation of AGEs (Advanced glycosylation end products) AGEs are a class of covalently modified proteins (adducts) generated through a nonenzymatic reaction between reducting sugars and free amino groups of cellular and tissue proteins. Oxidative stress involved in mechanism of formation. Non-enzymatic glycosylation: the Maillard Reaction Spontaneous chemical reaction between sugars and protein, increased by ROS Maillard reaction is one of the most important chemical reactions taking place during thermal processing of food by frying, roasting or baking Any reactive aldehyde or ketone can react non-enzymatically with amino groups present on proteins, nucleic acids and aminolipids, forming cross-links

Question 43

Malliard reaction

Answer 43

Non-oxidative pathway Takes weeks/months of rearrangement to form AGE Forms glucosepane Glucosepane: major collagen crosslink between collagen fibres, causes changes in structural protein and disorders in extracellular matrix Oxidative pathway I: fast Schiff base/Amadori product oxidised by ROS -> fragmentation -> RCCs RCCs + protein (free amino group) -> (fast formation of) protein-RCC adduct (AGE) Glucose auto-oxidation Autooxidation by ROS Forms RCCs which react with NH2 to form AGE (CML, carboxymethyl lysine)

Question 44

Methylglyoxal

Answer 44

Methylglyoxal is a RCC that leads to the formation of AGEs Excessive glycolysis might promote protein glycation via increased MG Formed from glyceraldehyde-3-phosphate (G3P) and dihidroxyactone phosphate (DHAP) which are two normal glycolytic intermediates Routes of formation are from glucose and fructose, MG is a major cause of secondary complication of diabetes

Question 45

Glyoxalase

Answer 45

``` MG is detoxified by the glyoxalase system into D-lactate Increased levels of MG and MG-derived AGE and dysfunction of glyoxalase system linked to several age-related health problems i.e.: Diabetes CVD Cancer Disorders of the central NS Overexpression of glyoxalase in C. elegans Decreased MG-mediated protein expression Decreased mitochondrial dysfunction Decreased ROS production Increased lifespan Glyoxalase activity decreases with age ```

Question 46

Origin of AGEs

Answer 46

Sugar consumption Glucose is the least reactive of common biological sugars Only 0.25% of glucose exists in reactive chain form (aldehyde group available for reaction, In cyclic structure group unavailable) But because glucose is typically consumed in high quantities, it poses a threat Galactose Fructose (fruit sugar) Ribose (in RNA) Exogenous (dietary AGEs) Present in food and drink

Question 47

Role of AGEs/AGLs in ageing

Answer 47

Lower plasma AGEs predicted increased survival in human data 2 consequences of AGE accumulation Protein aggregates Leads to proteins becoming dysfunctional, damaging cells and overwhelm/inhibit proteolytic apparatus They interact with normal proteins particularly via cross-links Random protein aggregation, protein is dysfunctional Cannot be broken down; accumulate and damage cells Proteolytic apparatus (proteasomes and lysosomes) having a difficulty coping with cross-linked structures Cross-linked structures can inhibit proteasome activity, leading to accumulation of more cross-linked proteins Cellular signalling pathways AGEs may activate intracellular signals through several receptor/non-receptor mediated mechanisms Leads to increased ROS and increased inflammatory cytokines

Question 48

Receptors of AGEs

Answer 48

MSR (macrophage scavenger receptor) and AGER (age-specific receptor) Responsible for maintaining AGE homeostasis through regulation of their degradation and removal Overexpression of AGER enhances AGE binding and degradation and suppresses RAGE-mediated ROS generation and inflammatory response in mouse mesangial cells RAGE (receptor for AGE) Distinct from scavenger receptors Promotes oxidant-stress-dependent NF-kB activation and inflammatory gene expression “Inflammageing”: many age-related pathologies involve an inflammatory condition which includes ROS generation Autophagy decreases with age, cellular ability to degrade protein-AGEs via AGE-R1 becomes compromised Some AGEs and ALEs have the same structure, since they arise from common precursors e.g. carboxymethyl lysine (CML) which is generated by glyoxal, which in turn is formed by both lipid and sugar oxidative degradation pathways.

Question 49

Proteotoxicity and ageing

Answer 49

``` AGEs contribute to: AD Atherosclerosis Arteriosclerosis Bone fragility Skin wrinkling Renal failure AGEs increase with age Diabetic complications resemble premature ageing (but earlier in diabetes) Cataract Vascular disease Retinopathy Neuropathy Skin changes Kidney failure ```

Question 50

Accumulation of altered proteins in ageing

Answer 50

Breakdown of proteostasis contributes to ageing and age-related pathologies: Proteasome and autophagic system can be damaged by ROS and glycation agents Damage can also affect the chaperone proteins which normally assist in correct protein folding Manifests as: Lipofuscin (skin pigment): age spots on skin and organs Yellow-brown granular material that accumulates progressively over time in the lysosomes of postmitotic cells Produced mainly by peroxidation of unsaturated FA in complex with cross-linked proteins Metals (mercury, Al, Fe, Cu and/or Zn) present in lipofuscins Ageing: proteostasis dysfunction = poor removal of oxidised proteins, which accumulate causing tissue damage and deposition of lipofuscin alpha-crystallin: cataracts (crystalline aggregates in eye lens) Cartilage protein, collaged: hip joint surface, arteries (atheromas) Normal cartilage/collagen proteins: The shape of these proteins are important for function In AGE accumulation the protein strands randomly cross-link and become stiff and irregular Bad in hip joints Bad in arteries - makes them stiff and contributes to formation of atheromas

Question 51

Protein aggregates in age-related neuropathies:

Answer 51

alpha synuclein: Lewy bodies in Parkinson’s disease amyloid plaques and tau tangles in Alzheimer’s disease Prions in Creutzfeldt-Jacob disease

Question 52

Modulation of AGEs

Answer 52

Calorie restriction Deoxyglucose (non-metabolisable) (decrease glucose levels) Carnosine (Beta-alanyl-L-histidine) (readily glycated by RCCs) mTOR (mammalian target of rapamycin) inhibition (decreases glycolysis, stimulates mito function) AGE cross-link breaker improved heart function in aged dogs (increased stroke volume and end-diastolic (ventricular) volume after 4 week treatment

Question 53

What is calorie restriction

Answer 53

Dietary restriction of energy intake by 30-40% normal calories but with adequate nutrition: normal levels of vitamins, minerals, essential amino acids and fats must be maintained.

Question 54

Only intervention consistently increases life expectancy

Answer 54

Calorie restriction Episodes from human past - Denmark 1917 WW1: adequate intake of whole grain cereals, veg and milk reduced mortality by 34% Norway WW2: whole grain cereals, veg, potatoes and fish reduced mortality by 30% Animal models had 30-50% fewer calories, normal vitamins, minerals and essential aas and fats showed 30% increase in maximum lifespan even from Middle Ages models. Postpones hypertension, cancers, immune system dysfunction, kidney pathology, brain ageing, cataract formation, diabetes. Rhesus monkeys had 30% CR and showed increase in 20+ years of lifespan

Question 55

Human calorie restriction trial

Answer 55

Redman et al 2011 Comprehensive assessment of long term effect of reducing intake of energy 25% restriction in non obese humans 6 month results show reduced body weight and fat mass and body temp, insulin and CV risk by 28%

Question 56

Disadvantages of calorie restriction

Answer 56

Lower growth rate and smaller maximum body size achieved Delayed puberty Lower fertility Compromised thermogenesis

Question 57

Calorie restriction mechanisms for lifespan

Answer 57

Advanced glycation end products and oxidative stress and the mitochondrion Glycation end products - advanced glycation end products AGE is reduced by calorie restriction Lower human plasma AGE predicts increased survival. Oxidative stress also increases with age but CR Changes ROS activity, free radical generation, antioxidant defences, mitochondria production etc. CR means there is little NADPH and all is used to drive ETC making ATP and inner membrane becomes more permeable to H ions and membrane potential is reduced (polarised) therefore less ROS and heat is produced. Increases cellular lifespan. Also generate less free radicals per Oxygen atom used in the ETC.

Question 58

Molecular mechanisms involved in effect of Calorie restriction on longevity

Answer 58

Decrease in calorie in diet activates systems involved in: More efficient metabolism Higher protection against cellular damage Activation of remodelling mechanisms Less efficient metabolism and synthetic pathways are blocked Mitochondrial gene expression changes in CR. Increasing SIRT1 expression due to high NAD:NADH ratio. SIRT1 is silent info regulator decreases apoptosis enhances glucose production, lipid metabolism and fat mobilisation, angiogenesis and decreases tumour formation. Increasing sir2(animal SIRT1 equivalent) increases lifespan. CR mice with SIRT1 knockout DO NOT live longer. Activation of this gene therefore important for longer survival. SIRT1 can be activated by drugs and resveratrol - natural polyphenol. PGC-1alpha increases due to high AMP:ATP ratio due to little excess of ATP. AMP activates AMP kinase and inhibits TOR as part of signalling pathway increasing gene expression and mitochondrial biogenesis. More mitochondria mean less electron leak forming ROS. Metabolic rate doesn’t alter in CR. SIRT1 and PGC1 are linked and activate together.

Question 59

Nutrient sensing pathways and calorie restriction

Answer 59

Nutrients activate systems to increase cell growth and storage of nutrients - IGF1 increases cell division and size and insulin increases uptake and storage of glucose by cells. Calorie restriction reduces these molecules and so reduces these effects. This has unexpected benefits. IGF1 knockout in animal models increases lifespan show 23% average increase Low IGF1 induced expression of mitochondrial antioxidant. Low signalling promotes translocation of FOXO3a to nucleus (normally inhibited by IGF1) where it induces MnSOD and GPx glutathione peroxidases which promotes removal of hydrogen peroxide. Enhances MnSOD lowers superoxide levels and peroxynitrite formation. also associated with reduced apoptosis.

Question 60

Define intrinsic and stressed ageing

Answer 60

Intrinsic (deterministic) - time dependent functional decline despite optimal conditions often observable in laboratory animals and on a cellular levels Stressed (non deterministic) - physiological or functional decline in wild organisms reflecting exposure to stress or inactivity etc. Potentially - Animals die because of intrinsic ageing repair mechanisms being unable to keep up with molecular damage.

Question 61

Evidence for genetic involvement in ageing

Answer 61

Heritability Family studies Progeria syndromes Animal studies of age

Question 62

Progeria

Answer 62

Extremely rare genetic condition causing advanced ageing at early ages Symptoms closely relate to ageing including wrinkles, hair loss, delayed growth. Have normal development up to 18 months and suddenly stop gaining weight and display stunted height. Progeria becomes more severe as they age - average life expectancy is 12 years old Affects the nuclear membrane disrupting normal nuclear architecture leading to DNA damage and impaired replication Is a defective splicing of pro-lamin A meaning a sticky membrane is produced instead of smooth. Humans show effects on CV ageing and function but mice do not - exploring these differences may give insight into ageing and the disease.

Question 63

Define fragility

Answer 63

Poor resilience to external stressors Results from ageing related declines across physiological systems Vulnerability to adverse outcomes

Question 64

C. Elegans and DAF2/16

Answer 64

C. Elegans can arrest their development in adverse conditions halting ageing to survive. DAF2 is a gene similar to the insulin gene. A mutation in this gene prolongs their lifespan, DAF16 is also important in lifespan - DAF2 is dependent on DAF16. If DAF16 isn’t present lifespan decreases as it’s a transcriptional regulator for multiple DNA sites involved in antioxidant pathways, antimicrobial pathways and protective pathways DAF2 switches this pathway off so when mutated does not block DAF16 and therefore extends the animals lifespan.

Question 65

Sirtuins and DAF16 pathways

Answer 65

Over expression of sir2 extends lifespan in yeast, worm, flies. SIRT1 is the mammalian homologue but effect is controversial in mammals Common pathway - sir2, HSP And JNK all act through the same DAF16 Pathway DAF16 mammalian analogue is the FOXO regulatory element. Regulates multiple downstream genes which effect longevity These pathways are conserved across many species of worm, flies and rodents.

Question 66

Rapamycin and insulin pathway interference

Answer 66

Inhibits mTOR which interacts with the insulin pathway - conserved across many species : yeast, nematodes, flies, mice, human progeria syndromes. Interference with the insulin pathway can extend the lifespan of those affected Changes seen in liver, heart when administered Restricting diet increases lifespan this is thought to have a similar effect.

Question 67

Growth hormone and lifespan

Answer 67

Mammalian target as GH links diet growth pathways In Ames and snell Dwarf mice loss of function mutations in prop1 and pit1 genes reducing trophic hormones like GH, prolactin, IGF1 etc. Loss of the GH means no calorie restriction response occurred suggesting GH mediates link between two pathways

Question 68

Pathways related to ageing

Answer 68

Decreasing insulin IGF1 signalling increases stress resistance and lifespan TOR decreased signalling causes increased lifespan increasing autophagy, and decreased protein translation. Mitochondrial function severe dysfunction causes decreased lifespan but modestly decreased function has been shown to increase lifespan Sirtuins can increase or decrease lifespan in different contexts Calorie restriction causes increased lifespan when optimally done.

Question 69

Defective Mitochondrial polymerase gamma

Answer 69

In mouse causes weight loss, alopecia, osteoporosis, cardiomyopathy, hypogonadism but mice don’t show neurological disease degeneration which is why they cannot apply them to human studies whereas rats have a more similar pathways to humans.

Question 70

Drosophila ageing defects

Answer 70

Mitochondrial dysfunction POLG gene causes premature ageing | Mito

Question 71

Longevity and fragility inheritability

Answer 71

25% heritable

Question 72

How do cells count division

Answer 72

Two categories | Telomere erosion and telomere independent mechanisms

Question 73

Telomeres and telomerase

Answer 73

Structures present at the natural end of linear chromosomes enabling it to behave differently from double stranded DNA break in the genome Functions: Stop natural ends fusing with other chromosomes Stop ends activating genome damage checkpoints Prevent loss of sequence by exonuclease attack Deal with end replication problem With each cell division telomeres erode meaning every replication is progressively shorter. Telomeres prevents the actual DNA being shortened, telomerase is a reverse transcriptase that adds TTAGGG onto chromosome ends to maintain the telomeres. hTR is the RNA template from TTAGGG synthesis. hTERT is the catalytic protein subunit. Shelterins are protein complexes that protect telomeres in eukaryotes as well as regulating telomerase activity. GWAS also regulates telomere elongation Telomere length is shorter when there is: cell division, nuclease action, chemical damage, DNA replication And is longer when there is: telomerase expression, recombination between telomeres repeats, shelterins. Telomerase expression is highest in germ line cells, haemopoietic and intestinal villus stem cells and in 85-90% malignancies. Low in mortal primary cells and many differentiated human cells and fibroblasts.

Question 74

Telomere erosion and senescence

Answer 74

In fibroblasts telomerase is not present and they show telomerase erosion when cultured However if treated with hTERT mRNA by viral transfection cells become telomerase positive and no longer show senescence - cellular immortality There’s also indirect evidence in vivo recording proliferative cell history Telomere length declines with age in several human tissues and length may be associated with age related disease but this is difficult to test Twin studies show strong associations with leukocyte telomere length and increased fragility independent of age. However mixed results with all fragility, longevity, immune functions studied in humans. Many short lived animals age and die with long telomeres such as mice, c elegans, zebra fish and drosophila don’t even have telomeres contradicting this evidence. Experimental deletion of telomere repair mechanisms in these models does cause premature ageing phenotypes to emerge however!

Question 75

Inherited telomere syndromes

Answer 75

Mostly Alzheimer’s disorders 11 human genes to date code for telomerase components - TERC, TERT, DKC1 etc. And telomerase bonding proteins like TINF2, POT1 Disorders are varied - include pulmonary fibrosis, myelodysplastic syndrome, dyskeratosis congenita

Question 76

Telomeres and ageing

Answer 76

Still unknown if telomeres are a cause or byproduct of ageing - shortening can directly contribute to aspects of ageing, be a consequence of disease and progression and set up a cycle interacting with other disease processes

Question 77

Telomeres, senescence and DDR

Answer 77

Telomere erosion leads to dysfunction - uncapped telomeres Leads to chronic DNA damage response DDR at telomeres Can visualise with telomere stains and markers like 53BP1 TIF assay for senescent cells allows detection of cells in vivo. Thought to be Dependent on p53 Activation, p21 accumulation and p16 activation

Question 78

Characteristics of senescent cells

Answer 78

``` Prevents replication of damaged DNA Profound chromatin changes Increased expression of cell cycle inhibitor p16INK4a Replication arrest Other secretome changes Resistance to apoptosis ```

Question 79

How to senescent cells cause age related pathologies

Answer 79

Can impact organ function by non dividing - many tissues require division as part of function such as immune system Adult stem cell renewal declines with age affecting tissue function and regenerative ability Senescent cells also influence local tissue microenvironment via altered gene expression - MGP up regulation in VMSC promotes vascular calcification and elevated CVD risk Show elevated range of proteins - senescence associated secretory phenotype SASP. Proteins include cytokines, ECM metabolising professes SASP is caused by prolonged DDR and needs key mutations to occur like mutant RAS. Doesn’t occur in cells made senescent by forced overexpression of p16INK4a

Question 80

Senolytics

Answer 80

Screening for agents which start apoptosis in senescent cells like dasatinib and quercetin or flavonoid fisetin. These agents can go everywhere including crossing blood brain barrier Human trials in senolytics need to assess long term outcomes Targets senescent cells Rescues age related osteoporosis in mice

Question 81

Why did telomere driven senescence evolve

Answer 81

Antagonistic pleiotropy - systems have alternative benefits that outweigh these downfalls Adaptive theory - Accumulation of senescent cells and contribution to age related pathologies are non-selected late life deleterious effects. Evolved as tumour suppressor mechanism to allow large long loved species to live long enough to reproduce ?

Question 82

Cancer and cell proliferation

Answer 82

Cancer is disease of uncontrolled unlimited cell division Somatic genetic disease driven by accumulation of genetic changes Main hallmarks - cell division, angiogenesis, invasion etc. Cell division necessary to create the diseases

Question 83

Early hallmark of CV disease

Answer 83

Hypertension caused by increased endothelial cell dysfunction no longer generating NO in response to ACh and so acetylcholine stimulates smooth muscle cells directly and contracts the muscle creating faster blood flow

Question 84

Atherosclerotic plaque types

Answer 84

Vulnerable - thin vessel wall and small lumen increases blood pressure until vessel wall thickens becoming stabilised or ruptures and thrombosis forms. Stabilised - lumen size reduced but thick vessel wall means is unlikely to rupture. If the thrombus doesn’t clear or occluded entire vessel then blood flow is prevented leading to MI etc.

Question 85

Evolution of fatty streak

Answer 85

Hypercholesterolemia Adherence of monocytes to arterial endothelium Penetration of monocytes into artery Oxidation, aggregation our immune complexing occurs and smooth muscle vascular tone alters Phenotypic modulation, expression of scavenger receptors, inhibition of modified LDL fatty streak made up mainly of cholesterol rich foam cells.

Question 86

LDL in atherogenesis

Answer 86

Oxidant stress if presumed mediator of endothelial dysfunction in atherogenesis LDLs can be oxidised worsening plaque build up - foods with constant boiling or reheated oils like BBQs and fish and chips are very oxidised and so increase atherogenesis Apo-B100 regulates uptake in liver is receptor on LDL - is also oxidised meaning isn’t recognised by liver and so remains in the blood increasing risk of CV disease The body does have protective pathways against this oxidation - such as Vitamin E limits LDL oxidation or antioxidant pathways Involving ROS formation - increases in ROS production increases atherogenesis. Some diets increase antioxidant pathways and so decrease atherogenesis Studies of 6 years of taking vitamins E and C have shown to slow progression of carotid atherosclerosis.

Question 87

CV risk factors

Answer 87

``` Age Gender Foetal nutrition Hypercholesterolemia - LDL Hypertension Metabolic syndrome, diabetes, obesity Smoking, dietary fat, antioxidant status Coagulation factors and platelet reactivity ```

Question 88

Foetal nutrition and CV disease

Answer 88

Too small or large at birth predisposes babies to CV disease or non insulin dependent diabetes as adults More of a trend in men as women have oestrogen protective effect and therefore less incidences before menopause Mothers age at birth also affects CV disease prevalence.

Question 89

Interheart study 2004

Answer 89

Major modifiable risk factors account for 90% of MI, regardless of population

Question 90

PKSC9 and LDL

Answer 90

Regulates uptake of LDL mainly in the liver Changes in expression alter levels of LDL and therefore risk of CV disease Increasing expression decreases LDL and risk of disease Mutations or knockouts increases LDL and risk of disease

Question 91

Molecular mechanisms of atherogenesis

Answer 91

Lipid accumulation and lipid oxidation Endothelial cell dysfunction or injury Monocytes emigration and macrophage accumulation Smooth muscle cell migration and proliferation Cell death in neo-intima Platelet activation and thrombosis

Question 92

Superoxide production in normal and atherosclerotic arteries

Answer 92

Kojda et al 1999 Fed rabbits high fat cholesterol diet and measured superoxide production Production much higher in high fat diet group Removing endothelial cells returns superoxide concentration to normal levels again suggesting its endothelial dysfunction that causes this excess generation

Question 93

Smooth muscle cells in atherogenesis

Answer 93

Changes in contraction, proliferation, ECM, inflammation and apoptosis in response to altered mediators in the blood or from endothelial cells increases risk of atherogenesis Vascular calcification - can lead to heart failure and ischaemia in the intima and media layers caused by changes in SMC. Ageing is also risk factor for calcification

Question 94

Ageing and peripheral arterial disease

Answer 94

Is a risk factor for atherosclerosis and medial arterial calcification MAC. Mineral dysregulation and proinflammatory metabolic state of diabetes mellitus feed into increased oxidative stress burden leading to cellular damage and nuclear lamina defects which accelerate vascular smooth muscle cell senescence Senescence associated secretory phenotype SASP of VSMC undergoing oestrogenic differentiation signals may act as inflammatory cues that promote atherosclerotic Plaque progression and rupture which could lead to occlusion of peripheral arteries In addition peripheral neuropathy also increases risk of MAC and PAD.

Question 95

Prelamin A and ageing

Answer 95

In response to oxidative stress or DNA damage VSMC downregulate FACE1 expression and accumulate prelamin A which interferes with DNA repair causing persistent irreparable damage leading to cell death or senescence - therefore promotes vascular ageing and dysfunction Senescent VSMCs are proinflammatory and May promote systemic inflammation leading to elevated BMP2, IL6 and OPG. Blocking ATM pathway with prelamin A accumulation and DNA damage can improve oestrogenic differentiation.

Question 96

Ageing affects in the endocrine system

Answer 96

Can affect : | Hormone synthesis, release, receptor binding, receptor expression, signal transduction, response, clearance.

Question 97

Growth hormone and IGF-1 axis normal physiology

Answer 97

GH secreted by somatotrophs Stimulates growth and IGF-1 production in childhood Hepatic IGF-1 production Bone and muscle growth and maintenance Decreases fat mass and increases energy use Hypoglycaemia and stress stimulates GH Somatostatin inhibits GH secretion Glucose and fatty acids inhibit GH action

Question 98

GH and IGF-1 with age

Answer 98

GH and IGF-1 levels decline with age GH pulse in young healthy adults has nocturnal peak - this does not occur in ageing people. Peaks at ages 16-25. GH secretion decreases from age 25 onwards Progressive decline in GH secretion called SOMATOPAUSE. The number of somatotrophs might not decrease however Exogenous GHRH increases GH Exogenous GH stimulates IGF-1 Therefore the hypothalamic GHRH decline causes age related decline in GH and IGF-1

Question 99

GH treatment for ageing

Answer 99

GH replacement in people over age 60: increased lean body mass, decreased fat mass(10% change), effects only seen short term (as long as GH acts in the body), no change in muscle strength suggesting GH not necessarily associated with functional ability so may slow down loss of muscle and bone strength but is not a treatment for anti ageing ``` Adverse side effects: Acromegaly Diabetes mellitus CV disease Arthralgia Carpal tunnel syndrome Hypertension ```

Question 100

HPA axis normal physiology

Answer 100

POMC cleaved to ACTH released by corticotrophs Cortisol main human glucocorticoid Immune functions and anti inflammatory properties Glycogenolysis in liver and muscle Inhibits protein synthesis and storage freeing up amino acids Homeostasis and stress response Involved

Question 101

HPA axis and ageing

Answer 101

Basal ACTH and cortisol levels don’t decline with age One study states circadian rhythms and concentrations are maintained in elderly compared to young - WALTMAN et al 1991. Cortisol levels may show more variation and appear less well controlled in older subjects Ability to return glucocorticoid levels to normal in response to stress declines with age - higher cortisol levels persist for longer, exogenous CRH given to both young and old subjects demonstrated similar responses in ACTH and cortisol release BUT elderly subjects showed slower cortisol decline EVAL- reason evidence may be so conflicting is with age you lose the ability to trigger the negative feedback system likely from accumulation of stress exposure over your lifetime. Perception of stress also varied hugely between individuals. Age related changes in HPA axis may be gender specific - enhanced response to external stress is more pronounced in older women than older men but elevated cortisol response persists more in elderly men than women. Glucocorticoid receptor expression and or activation in liver, muscle and brain changes - just because little changes in circulating levels of glucocorticoids doesn’t mean that response is triggered the same in elderly.

Question 102

Effects of HPA axis dysregulation

Answer 102

Chronic elevation and repeated exposure to higher glucocorticoid levels may be induced by stress or ageing Toxic to hippocampal neurones in rats, which have high receptor expression Can cause Hippocampal atrophy, memory and learning deficits Sleep disturbance in elderly due to changes in amplitude and timings of circadian cortisol control - no morning peaks present Bone mineral density reduced, increased adiposity, and CV disease

Question 103

HPT axis normal physiology

Answer 103

TSH secreted by thyrotrophs T4 thyroxine main hormone secreted Deiodination in liver produces T3 (active compound) Calorigenesis, O2 consumption, and Na, K ATPase activity increased Lower circulating cholesterol Increase CO and decrease peripheral resistance Increase body temp Involved in Maintenance of nervous system and mental health

Question 104

HPT axis and ageing

Answer 104

T4 secretion reduces with age as is clearance TSH reduces with age Free T3 declines because less peripheral conversion from T4 - difference in bioavailability of T3 May be greater between youth and elderly than free circulating hormone suggests Reduced T4 should actually increase TSH but this isn’t the case in elderly, thought to be because of changes in set points in the HPT axis feedback system. Changes in T3 might affect receptor expression in compensatory manner - in healthy people receptor expression is INVERSELY related to hormone concentration. This may be the case in elderly people still but it’s possible that decreased TSH and T3 May be buffered by up-regulating receptor expression. Serum anti thyroglobulin and anti thyroperoxidase autoantibodies increase with age - bind to hormone and make them inactive Thyroid antibodies - rare in healthy centenarians but frequently found in hospitalised elderly - may be relegated to ageing problems Decline in hormone secretion is mild and yet physical symptoms of of dysfunctional HPT axis is experienced by old people, suggesting its effects of ageing and changes occur primarily at the target tissue level. Graves and Hasimotos disease incidence increases with age Changes in cellular and nuclear receptor function also with age Affects of decline - morphological changes, lumps, nodules, fibrosis Thyroid cancer - 3x more prevalent in women than men Decreases basal metabolic rate and cellular o2 consumption Increases susceptibility to hypothermia and heat stroke and increases serum cholesterol.

Question 105

Fertility and age in women

Answer 105

Decline in oocyte pool - oocyte number peaks during foetal life and declines thereafter Born with finite oocyte number Follicles recruited to grow throughout life and majority become atretic (cell death) <0.1% follicles ovulate Loss of fertility begins years before menopause

Question 106

Pregnancy and ageing

Answer 106

Higher risk of implantation failure or difficulty, of embryo abnormality and aneuploidy, pre-eclampsia, gestational diabetes, labour complications, postpartum haemorrhage C-section and assisted delivery, premature births, perinatal mortality, impaired myometrial contractile function in labour

Question 107

Menopause transition and hormones

Answer 107

Early transition phase - 39-40 transition begins, elevated FSH in follicular phase. No change in LH, E2, P4 May fluctuate more. Regular cycles, ovarian inhibin B secretion declines due to depleting follicular pool. Late transition phase - irregular anovulatory cycles. 3-5 years to final menstrual period. Decreasing P4 and increasing LH and FSH. E2 levels don’t decline until 1-2 years before FMP then they decrease Menopause - 12 months without a menstrual period. Median age is 51.4.

Question 108

Menopause effects and symptoms

Answer 108

Psychological mood swings, cognitive and sleep issues, memory problems. CV disease, increase LDLs and decrease HDL, coronary heart disease and stroke increase risk Urinary frequency increases, dysuria or incontinence. Rapid loss of bone mass Increased fat mass Hot flashes after LH surge with no E2

Question 109

HRT

Answer 109

Postmenopausal period is up to 40% life and is getting longer Increased risks of Alzheimer’s, CVD and osteoporosis E2 therapy might prevent these risks However long term use is not recommended so other treatments specific to conditions acquired is recommended and lifestyle changes.

Question 110

Male reproductive axis

Answer 110

LH and FSH secreted by gonadorophs Leydig and Sertoli cells produce testosterone E2 and inhibin GnRH LH and T are all secreted in pulses LH and T peak in mornings before 9:30 T-E2 conversion by aromatase is important for feedback regulation Formation and maturation of spermatogenic cells is constant

Question 111

Fertility decline in men

Answer 111

Testicular volume decreases with age Sertoli/leydig/germ cells number decreases Less vascularisation and more fibrosis and apoptosis Testicular atrophy Sperm production and count and percentage normal morphology decreases and viability Conception difficulties lower pregnancy rates and live birth rate Change in sexual activity, alcohol and smoking may affect fertility

Question 112

Paternal ageing

Answer 112

Male germ cells - continuous cell division throughout reproductive years Increase in DNA replication errors and mutations in spermatozoa Schizophrenia, autism and bipolar disorder in children if the fathers are >55 years old Paternal age effect disorders - apert, crouzon, pfeiffer, muenke syndrome etc Skeletal deformities, growth retardation, heart defects, skin hyperpigmentation, cancer. Changes in male steroidogenesis

Question 113

Changes in male steroidogenesis

Answer 113

Bioavailability T levels decline progressively No specific age point of start Diurnal rhythm of T production is lost LH and FSH level rises but not in proportion to T decline: impaired HPG axis feedback Adiposity, chronic illness and medication affect T levels

Question 114

Ageing male effects and symptoms

Answer 114

Decline in verbal and visual memory, spatial ability and depression Loss of body hair Reduced testicular volume, poor libido, erectile dysfunction Decreased muscle mass, strength and power Insulin resistance and diabetes

Question 115

Testosterone replacement therapy

Answer 115

T supplementation May decrease fat and increase lean mass Improves physical function Sexual activity and function increase Lack of large scale, placebo controlled, randomised, long term trials Effects on bone density, psychological and neurocognitive function, prostate cancer risk and CVD risk.

Question 116

Kidney functions

Answer 116

``` Remove waste products Regulate body salts and water Maintain homeostasis Activate vitamins D Secrete erythropoietin in response to anaemia ```

Question 117

Acute kidney injury

Answer 117

Affects 13-18% patients in UK Sudden onset present for less than three months often reversible if managed correctly Pre renal causes - conditions causing CV shock and reducing blood flow to kidneys Intrinsic causes - conditions directly damaging kidney tissue Post renal causes - conditions blocking flow of urine from kidneys

Question 118

Chronic kidney disease

Answer 118

Gradual onset, present for longer than three months Not reversible but may be stabilises if managed properly Stages - 1- GFR greater than 90ml/min/1.73m2 with some signs of kidney damage on tests like proteinurea but if all other tests are normal is not CKD. 2- GFR 60-90 some kidney damage but if all but one tests normal is no CKD 3- GFR 30-59 moderate kidney dysfunction 4- GFR 15-29 severe reduction kidney function 5- GFR less than 15 established kidney failure when dialysis or kidney transplant is needed

Question 119

Chronic kidney disease and ageing

Answer 119

About half adults over 70 now have GFR less than 60ml/min/1.73m2 threshold often used to diagnose CKD. Ageing changes - decreased kidney mass, calcification, renal masses or cysts. Decreased glomeruli numbers, glomerular hypertrophy Decreased tubular length, tubular atrophy, interstitial fibrosis and increased diverticula. Atherosclerosis Decreased plasma RA and aldosterone, increased EPO in healthy adults but decreased EPO response to anaemia and decreased vitamins D activation. Nephrosclerosis represents nephron loss and is found in 2.7% kidney donors <30 years old, 58% aged 60-69 and 73% donors ages >70 Also found in patients with hypertension but doesn’t correlate with age related decline in GFR or indicate presence or other risk factors for developing chronic kidney disease.

Question 120

Functional glomerular changes and age

Answer 120

Glomerulosclerosis leads to reduced total surface area Compensatory changes occur to maintain GFR: Afferent arteriole resistance decreases and efferent arteriole resistance increases in remaining intact glomeruli Glomerular pressure increases and single nephron GFR rises Subsequent damage to glomerular BM leads to proteinurea Prolonged glomerular hypertension and proteinurea leads to more nephron loss and overall GFR drop. Brenners theory of hyper filtration.

Question 121

Functional tubular and vascular changes in kidney in ageing

Answer 121

Tubular - progressive tubular atrophy and intestinal fibrosis are associated with: Decreased Na reabsoption, K excretion and urinary concentrating capacity. Vascular - increased renal sympathetic tone leads to increased vasoconstriction, renal vasodilators such as atrial natriuretic peptide, NO and amino acids becomes less effective Decreased NO production with increasing age

Question 122

KLOTHO

Answer 122

Gene encoding novel protein regulating multiple functions Mutation in mouse klotho gene leads to syndrome resembling ageing Exists in membrane bound and soluble form Is key for maintaining healthy Ca and phosphate metabolism Reduction in expression associated with renal ageing and CV disease Effects on kidney - knockout in mice have normal renal function and mild fibrosis but are very fragile and die after 8-10 weeks Heterozygous live to 16 weeks and gradually develop CKD phenotype with mild renal impairment, vascular changes and fibrosis. Also more susceptible to renal disease. Supplementation in normal mouse models of unilateral ureteric obstruction, adriamycin nephropathy And ischaemia reperfusion injury, markedly attenuated renal fibrosis. Modulated Wnt signalling promoting pro fibrotic pathways in response to injury. As levels fall in ageing Wnt signalling increases promoting fibrosis and vascular calcification. Peroxisome proliferator activated receptor PPAR is a nuclear receptor with activity that decreases with age. PPARgamma agonsists like pioglitazone increases klotho expression. PPARgamma pathway protects against oxidative stress and improves vascular function in klotho dependent manner KLOTHO inhibits oxidative stress by inhibiting IGF1 which also impacts renal fibrosis development

Question 123

Kidneys and ageing

Answer 123

Aldosterone II increases in ageing rats, increasing vascular tone, hypoperfusion, atherosclerosis and vascular events. Prolitazone reduces renal fibrosis and cell senescence in ageing kidneys

Question 124

Cell senescence and renal ageing

Answer 124

Cellular senescence that is transient (acute) are beneficial whereas prolonged signalling and aberrant accumulation of senescent cells (chronic) impairs renal function and promotes kidney disease Chronic cells accumulate in the kidney during natural ageing and have been casually linked to age related decline in renal function Senescent cell accumulation also occurs in association with several renal diseases and therapeutic damage, and correlates with disease progression or deterioration in several instances Therapeutic interventions that target these cells (senotherapies) have potential to attenuate age related renal dysfunction and improve disease outcome and ensure success of kidney transplantation. Development of effective and safe senotherapitics should benefit from future research aimed at understanding the location origin and properties of senescent cells in more detail.

Question 125

Insulin receptor actions

Answer 125

Acts via receptors with intrinsic tyrosine kinase activity Main target tissues for metabolic effects are liver, skeletal muscle, adipose tissue. Causes increased expression and translocation of GLUT4 to fat and muscle cell membranes. Reduces plasma glucose levels by increasing uptake from blood

Question 126

Causes of Insulin resistance

Answer 126

Increased visceral adiposity increases with age due to: Imbalance of diet and exercise Reduced oestrogen and testosterone levels occurring with increased age Expanded adipocytes secrete adipokines such as TNFalpha - obese And elderly people have chronically elevated TNFalpha Mice without TNFalpha have lower fasting plasma insulin, improved glucose tolerance and better insulin sensitivity so is important. Increased free fatty acid levels in diet also cause insulin resistance from diet of saturated fats: FFAs activate inflammatory signalling, decrease mitochondrial function and stimulate DAG accumulation and ROS generation. DAG activates PKC And ROS activate JKN and IKKb which are kinases that increase serine phosphorylation of insulin resistance proteins IRS1/2. Therefore promote resistance by inhibiting insulin/receptor interaction. Decreased skeletal muscle - mitochondria in aged skeletal muscle produce less ATP and more ROS promoting oxidative stress and insulin resistance reducing rate of calorie intake and exacerbated problems caused by increased adiposity.

Question 127

Free fatty acid promotion of insulin resistance

Answer 127

Increased DAG activates PKC isoforms by de novo synthesis or mitochondrial dysfunction FFA stimulate toll like receptor 4 activating JNK and IKKbeta which are also activated by increased ROS PKC, JNK and IKKbeta phosphorylate IRS1/2 on serine residues to inhibit insulin receptor interaction. Decreased IRS1/2 tyrosine phosphorylation results in reduced insulin signalling

Question 128

Causes of insufficient insulin secretion

Answer 128

Impaired beta cell stimulus secretion due to: Increased ROS and decreased ATP and Ca. ageing islet mitochondria malfunction, reducing Ca entry and mobilisation from SER stores impairing Ca oscillations in response to glucose. Associated with impaired glucose induced insulin release in vitro. Islet amyloid deposition and increased beta cell apoptosis - commonly seen in type 2 diabetes. Amyloid deposition triggers protein complex called inflammasome leading to production of pro inflammatory agent IL-1beta which can induce beta cell apoptosis. Protein misfolding and ER stress - accumulation of midfielder insulin and amyloid triggers ATF6, IRE1 and PERK sensor kinase pathways in response to ER stress triggering inflammatory signals through NF-KB and JNK dependent pathways. With ROS this promotes beta cell apoptosis. Reduced beta cell proliferation - islets B cells in young respond to insulin resistance increasing proliferation to counteract. With ageing B cells the higher level of p16INK4a a cell cycle inhibitor. Prevents interaction with cyclin D. Results in reduced phosphorylation of RB leading to E2F remaining bound to RB so cell cycle arrest and senescence occurs.

Question 129

Hyperglycaemia and cell damaged

Answer 129

Causes ROS generation Free radical generation and apoptosis of cells - superoxide generates in mitochondria concerted to hydrogen peroxide by superoxide dismutases This can generate hydroxyl radicals or be converted to water by catalase Formation of mitochondrial transition pore by OH- radicals results in leakage of cytochrome C from mitochondria and induction of apoptosis Glycation of proteins - non enzymatic attachment of sugars to amino groups on proteins. Early glycation products combine forming complex cross linked structures AGES. Breakdown of these is usually cleared from plasma but impaired renal function in diabetes leads to accumulation. This decreases survival of cells. AGE activation of RAGE leads to retinal cell death. Increased ROS and NF-KB and cytokines production promoting inflammation and cell apoptosis. Activation of PKC - increases glycolysis and DAG activating PKC. This promotes cell dysfunction via growth factors and signals. Activation of polyol pathway - Glucose reduced to sorbitol by Aldose reductase. Doesn’t cross cell membranes so accumulates intracellularly. Can damage cells via osmotic effects. Breaks down slowly and high conc causes swelling of lens and retinal pericyte damage. Sorbitol dehydrogenase oxidises sorbitol to fructose which promotes glycation of intracellular proteins.

Question 130

Benefits of low calorie diet and role of SIRT genes

Answer 130

Calorie restriction up regulated SIR2 in yeast. Slows metabolism so more NAD is available to SIR2 Removes acetyl groups from histones leading to gene silencing This deacetylase activity of SIR2 associated with increased lifespan Longevity pathway is conserved in mammals also Activation of insulin receptors and IGF-1 receptors phosphorylates IRS proteins on tyrosine residues which stimulates PI3 kinase activity resulting in PKB/AKT phosphorylation and activation. AKT phosphorylates And inactivates FOXO1 Inactivation of insulin/IGF-1 receptor receptor pathway promotes longevity in mammals through increased activity of FOXO1. SIRT1 activation induced lifespan extension through deacetylation and activating FOXO1

Question 131

Summary of SIRT1 benefits

Answer 131

Positively regulated by calorie restriction and SIRT activating compounds like resveratrol and negatively by SIRT inhibitors Activation induces survival of cardiomyocytes, protects neurones from cell death and mitochondrial loss, increases insulin secretion by repressing mitochondrial uncoupling protein 2 UCP2 in beta cells SIRT1 decreases white adipose formation though repression of PPARgammas and promotes gluconeogenesis in response to fasting through PGC-1apha Also stimulates mitochondrial biogenesis in brown adipose and muscle through PGC-1alpha activation

Question 132

SIRT3 actions

Answer 132

Protects against ROS damage ROS generated primarily by complex I and III Oxygen radicals detoxified by SOD into hydrogen peroxide which is converted into water by glutathione peroxidase GPX GPX needs reduced glutathione GSH for enzymatic activity Oxidised glutathione GSSH is reduced by glutathione reductase GSR which needs NADPH generated from NADP by isocitrate dehydrogenase 2 IDH2 By activating SOD2 and IDH2 and inhibiting ROS generation, SIRT3 can decrease oxidative damage in cells

Question 133

SIRT6 function

Answer 133

Protects against diet induced obesity Fat specific SIRT6 mice have increased inflammation in adipose and they are more susceptible to high fat diet induced insulin resistance SIRT6 could be target for treating obesity in type 2 diabetes

Question 134

Bone tissue

Answer 134

Continuously turns over Purpose to support, enable movement, haematopoesis, resevoir for calcium, phosphate etc. And helps homeostasis Cells involved - osteoblasts, osteocytes, lining cells, osteoprogenitor cells and chondrocytes Osteoblasts promote bone formation and osteoclasts promote reabsorption. Regulated by osteoblasts RANKL bonding to osteoclasts RANK receptors which promotes bone formation. Osteoclasts secrete osteoprotegrin which acts to competitively inhibit this binding and therefore promotes absorption. Chondrocytes form hyaline cartilage. Osteoblasts and chondrocytes are derived from skeletal stem cells. Osteoclasts are derived from haematopoetic stem cells.

Question 135

What is ossification

Answer 135

Bone formation Intramembranous ossification - bone formed directly from precursors eg flat bones of skull, clavaria or clavicle. Formed in membrane or condensation, direct formation of osteoblasts precursors, formation of periosteum, differentiation to osteoblasts, matrix deposition, mineralisation, vascularisation, blood vessels, continued growth and remodelling. Endochondral ossification - bone formed via cartilage intermediate eg long bones or vertebrae. Formation of cartilage model, perichondrium. Cartilage mineralisation. Formation of bony collar, periosteum. Capillary invasion, osteoclasts migration and invasion. Primary ossification centre. Secondary ossification centre, epiphyses.

Question 136

Define nociception

Answer 136

The response of nervous system to perceived or actual tissue damage ie physiological events associated with delivery of tissue damaging noxious stimulus A noxious stimulus is a stimulus potential damaging or damaging

Question 137

Classical pain descriptions

Answer 137

Transduction - conversion of energy of noxious thermal, mechanical or chemical stimulus into electrical energy by sensory neurones called nociceptors Transmission - neural signals from site of transduction in periphery to spinal cord and brain Perception - appreciation of signals arriving in higher structures as pain Modulation - descending inhibitory and facilitatory inputs from Brain modulating nociceptive transmission at level of spinal cord

Question 138

Descending pathways brain to spinal cord

Answer 138

Rely information from higher centres back to spinal cord where they modulate processing of sensory information Descending pathways controlled by interactions with higher brain centres Excitatory synaptic connections from brain centres mainly via PAG activating cells in the RVM activating descending inhibition of spinal cord processing.

Question 139

Pain transmission summary

Answer 139

Operates in healthy individuals to allow differentiation between damaging and non damaging stimuli Conveys information regarding high intensity stimuli and results in transient localised perception of pain Type of pain perceived related to type of stimulus due to: specialisation of primary afferent fibre type, activation thresholds and conduction properties. Topographical organisation of input to spinal cord - enables retention of primary afferent encoding of stimulus modality, intensity, location and duration.

Question 140

Modulation of pain: endogenous inhibition

Answer 140

Nervous system has various modulators mechanisms to regulate the perception of pain Modulation involves local spinal networks and descending networks from supraspinal sites Involves inhibitory neurotransmitters and receptor systems: GABA and receptors GABA A And B Opioids Serotonin Cannabinoids CB1/2 Resulting in decreased firing and hyperpolarisation of cell

Question 141

Spinal transmission mechanisms

Answer 141

Transmission between nociceptive afferents and dorsal horn neurones is mediated by: Glutamate activates AMPA receptors evoking fast excitatory post synaptic potentials (NMDA receptor is blocked) Neuropeptides mainly substance P which acts via NK1 receptor to elicit slow excitatory post synaptic action potentials at many synapses regulating dorsal horn response to input Input from multiple synapses is required for AP generation retaining predictable stimulus - response function

Question 142

Primary sensation- peripheral sensitisation

Answer 142

Peripheral sensitisation due to injury leads to localised area of: primary hyperalgesia (sensation of noxious stimuli) Involves C fibres and produces sensitivity to heat, pressure and impact stimuli Involves activation and sensation of peripheral nociceptors by locally produced inflammatory mediators decreasing threshold for activation by further stimuli: axon reflex/neurogenic inflammation.

Question 143

Central sensitisation: physiological plasticity

Answer 143

Increase excitability of CNS neurones triggered by peripheral injury or increased nociceptive input Manifests in 3 ways: decreased threshold for activation, increase receptive field size and recruitment of novel input, increased spontaneous background activity of neurones Input from low threshold non nociceptive fibres can activate nociceptive specific dorsal horn neurones and therefore activate nociceptive pathway. Fundamental to clinical pain generation is characterised by allodynia, hyperalgesia and spontaneous pain

Question 144

State dependent pain transmission

Answer 144

Mechanism of pain depend on its state: normal state the pain is perceived is transient and reflects the location, duration and intensity of noxious stimulus Sensitised state pain is perceived longer than the stimulus lasts. Response characteristics of neurones change lowering threshold for activation. Leads to heightened sensation of pain (hyperalgesia) and perception of innocuous stimuli as painful (allodynia) involves peripheral and central changes - sensitisation and plasticity.

Question 145

Microglia

Answer 145

Specific population in CNS paranchyma ehich below to yolk sac lineage different from bone marrow lineage of monocytes and macrophages 10% total cells in adult CNS In healthy CNS microglia perform immune surveillance and exhibit ramified processes which are highly motile under normal conditions express low levels of cell surface immune molecules During lost natal period microglia play critical roles in CNS development, refinement and sculpting CNS ACTIVATED - respond rapidly to direct insults to CNS but also react acutely to PNS insults Show amoeboid morphology, increased phagocytic activity, enhanced migratory capacity within the brain and increased expression of cell surface glycoproteins including CD45 and MHC-II.

Question 146

Effect of age on pain sensitivity

Answer 146

Sensitivity is the somatosensory systems decreases with advancing age due in part to diminished numbers of specialised peripheral receptors combined with deterioration of supporting tissue Peripheral nerves show reduction in unmyelinated and myelinated fibres The number and size of sensory neurones in dorsal root ganglia DRG increases throughout early adulthood peaks at mid life 13-18 months then decreases after In addition altered expression of neurotransmitters and receptors is observed in the spinal cord of old animals and human post mortem material. Eg decrease labelling of substance P in dorsal horn, loss of serotoninergic and noradrenergic terminals= reduced descending modulatory pathways

Question 147

Effect if age on microglia

Answer 147

Microglia undergo cellular senescence Dystrophic microglia: abnormal morphology, cytoplasmic aberrations, twisted processes, de-ramified processes Fragmented processes and cytoplasmic fragmentation are typical of neurodegenerative diseases. No nuclear changes which are features of apoptosis causing accidental death Cytorrecthic microglia can be found sporadically in brain of elderly healthy humans.

Question 148

Pain in Alzheimer’s disease

Answer 148

Pain impacts substantially on mood, behaviour and quality of life Perception of pain involves a number of areas affected by AD pathology but it’s unclear if patients pain results from altered pain tolerance or impaired ability to communicate sensations. In AD patients the experience and processing of pain can be altered and non discriminative components of pain experience can be greatly affected. Bali one really establishes normal sensitivity in six month olds mice, potential treatment for AD pain.

Question 149

Why remodel bone

Answer 149

Vital for blood calcium regulation and homeostasis regulated via endocrine system and negative feedback Maintain skeletal homeostasis and bone mass Adaptation to mechanical forces and stresses which may damage older tissue so need replacement

Question 150

How does bone remodelling occur

Answer 150

Activation-reabsorption-formation system ARF Quiescence - balance formation and removal Resorption - osteoclasts remove bone tissue Reversal - osteoblasts enter and recruit proliferation line cells only where osteoclasts have removed tissue Formation - matrix synthesis Finally mineralisation leading back to quiescence. Whole process takes roughly 6 months Occurs at rate of 10% skeletal mass replaced per year. Rather high turnover rate Osteoblasts mediate differentiation of osteoclasts via balance between RANKL and OPG controlling osteoclastogenesis.

Question 151

Factors regulating bone remodelling

Answer 151

Systemic hormones - parathyroid, vitamin D3, glucocorticoids, estrogens And androgens, calcitonin Growth factors - TGF beta, BMPs, IGFs, FGFs, Wnts, macrophage colony stimulating factor, receptor activator of NF-kB ligand (RANKL) and osteoprotegrin Local factors - prostaglandins Transcription factors - Runx2, osterix, Fos, NF-KB, etc.

Question 152

Harold frost 1960s bone turnover theory

Answer 152

Theory states that bone stays in steady state but is affected by activity such as weight lifting etc. This increases bone mass proliferation inducing overall gain while remaining more sedentary or ageing can lead to bone tissue loss overall

Question 153

Sclerosteosis and van Buchem disease

Answer 153

Mutation in sclerostin gene inducing high bone mass Sclerostin expressed in osteocytes specifically and relates to mechanical loading Secretion decreases with mechanical loading leading to bone formation via increased Wnt signalling Potential therapeutic for this is anti-sclerostin antibody.

Question 154

Osteoporosis and ageing

Answer 154

After menopause the prevalence of osteoporosis increases markedly with age from 2% at age 50 to more than 25% at 80 years

Question 155

Regulation of peak bone mass controlled by:

Answer 155

Genetics Nutrition Gonadal status Physical activity

Question 156

Calcium homeostasis during ageing

Answer 156

``` Calcium and vitamin D3 alter throughout ageing decreasing intestinal Ca absorption, vitamin D resistance, synthesis of 1,25(OH)2D3 by kidney Increased 24(OH)ase expression increasing catabolism of 1,25(OH)2D3 increasing age related bone loss ```

Question 157

Bone cells during ageing

Answer 157

Osteoclasts: lack of oestrogen eg menopause enhances reabsorption Uncoupling of reabsorption and formation Osteoblasts: mesenchymal stem cells reduce in number and proliferation capacity and differential potential Differentiation altered in linage distribution - osteoblasts vs adipocytes, reduction in osteogenic, increase in adipogenic potential Also impacts fracture healing Increases senescence

Question 158

Current treatments in osteoporosis

Answer 158

Anti resorptive - oestrogen and SERMs, bisphosphonates, calcitonin, calcium and vitamin D, calcitriol, denosumab Anabolic - stimulators of bone formation - parathyroid hormone, anti-sclerostin Senolytics?

Question 159

Osteoblasts and haematopoiesis

Answer 159

Osteoblasts form part of HSC niche Increasing osteoblasts increases number of HSC Paradoxically HSC numbers may increase with ageing in independent mice strains but with skewed differentiation and disease susceptibility with long term repopulating activity decreased

Question 160

Air pollution and lung function

Answer 160

Air pollution during pregnancy affects lung function in newborns - pregnancy cohort study Latzin et al 2009. Reduced growth of lung during childhood - Southern California children’s health study Gaudermann et al 2007 Accelerated loss of lung function in adults - Downs et al 2007

Question 161

Sendentary ageing muscle changes

Answer 161

Sarcopenia - loss of muscle mass, loss of type II fibres size, decrease motor unit number and increase in motor unit size from partial reinnervation of abandoned or dying motor units Associated with fast fibre atrophy Selective atrophy of fast fibres in a whole mixed muscle would increase overall proportion of fast myosin, often confused with a switch in fibre type Decreased type II fibre area with less MHC II expression Increased hybrid fibres co-expressing MHC forms Fibre type grouping shows evidence of collateral sprouting Fat and connective tissue infiltration from altered metabolic regulation In addition there is less cross bridge formation, less capillary density and O2 delivery and utilisation by mitochondria Specific muscle can experience greater loss than others for example decline is isometric knee extensor force is greater than decline in quads. Elderly show less release of Ca, less CaATPase and Ca repuptake Might just be related to lack of exercise and activity not necessarily ageing as many studies show elite athletes like cyclists maintain muscle quality and mass.

Question 162

Why might muscle of ageing people be more fatiguable

Answer 162

Sedentary ageing reduces mitochondrial number and volume Increased deletions and mutations of mtDNA which impair respiratory function Difficult to understand effects ageing and sedentary activity has in mitochondria but decreased O2 delivery and uptake basically In whole body mass exercise they show decreased athletic performance, VO2 max (10% decline per decade), increased %VO2 max needed for given work load Isolated muscle groups - decreased ability to repetitively lift absolute load and increase maximum strength needed to lift given load Extent of aerobic power is dependent on how data is expressed - flaw of research Some show similar or lower blood lactate at same VOmax, fatigue tests of single muscle groups show similar evoked isometric fatigue Mitochondria show similar enzyme activity levels and capillary density in young and old muscle when controlled for levels of physical activity - coggan et al 1990 Mice fibres show identical fatigue rates in young and old profiles however this is incredibly controlled and so variables in real life mean this isn’t applicable

Question 163

Factors associated with sarcopenia

Answer 163

Changes in circulating anabolic hormones eg decreased GH/IGF-1, testosterone etc. Metabolic dysregulation - increased reactive O2 species Inflammation increasing degradation Anabolic resistance to feeding and exercise decreasing protein synthesis - basal rate of protein synthesis unchanged in healthy elderly muscle in study Rennie et al 2010. Reduced synthetic response of aged muscle to amino acids feeding (anabolic resistance) Cuthbertson et al 2005 Also show lower rates of proteins synthesis in older muscle subject to same relative resistance training exercise Kumar et al 2009 Thought that anabolic signalling deficits may underlie amino acid resistance of ageing muscle Decreased regeneration from exercise induced damage from compromised satellite cell behaviour - rodent models have demonstrated age related impairment in recovery from damage in eccentric exercise

Question 164

Satellite cells and ageing

Answer 164

Delayed increase in satellite cells in older men following single bout of high resistance exercise - Snijdjers et al 2014 However have shown functioning satellite cells in 96 year old 17 days after death!! 2012 Differentiation ability in young and old is similar Problems seem to occur from age of host not the muscle itself The local environment regulating satellite cells includes blood, ECM, IF, adjacent myofibres and ageing of these cells altered satellite behaviour.

Question 165

Age related alterations in Notch, TGF beta signalling

Answer 165

Notch stimulates proliferation, TGF beta inhibits it, Wnt directs cell fate dysregulation of these alters differentiation In young people there is a balance of these signals and satellite cells are available for regeneration In older patients decreased Notch and increased TGF beta imbalance causes satellite cell increased proliferation impairments Attenuation of TGF beta in old injured muscle restores regeneration to satellite cells Carlson et al 2008 TGF beta1 at senescent concentrations inhibits differentiation in both young and old human cells - but effects are reversible

Question 166

Cell DNA in young and old

Answer 166

No difference in DNA damage in young and old cells but DNA damage is much more precedent in senescent cells

Question 167

amyloid beta generation and clearance

Answer 167

Precursor is amyloid precursor protein - transmembrane protein, c terminus faces cytoplasm, n terminis out of cell. Cleaves by beta secretase using the BACE1 enzyme first, producing an APP C terminal fragment. Then by gamma secretase within the transmembrane domain resulting in release of amyloid beta proteins with differing C terminal variants predominantly ABeta40 and 42. Is produced in early endosomes which act as stations for the peptide production and is where the BACE1 enzyme cleaves the precursor protein etc. APP is internalised by endocytosis, is then cleaved in early endosome vesicles, before release by exocytosis. Clearance - hypothesised to be outside of neurones unlike generation using LDL receptor related proteins

Question 168

Amyloid cascade hypothesis

Answer 168

Amyloidogenic processing of APP missense mutations in APP, presenilins aggregation/oligomerization of amyloid beta diffuse plaques Hyperphosphorylated tau-tangles microglia activation/neuroinflammation mitochondrial dysfunction/oxidative injury Early onset of Alzheimer’s is much more relative to amyloid beta but later onset is more related to microglia and immune dysfunction. Synaptic dysfunction neurodegeneration dementia

Question 169

Can we target BACE1 for Alzheimer’s therapy

Answer 169

Very difficult to get compounds past blood brain barrier and into endosomal compartment etc Cannot block enzyme unless drug acts within early endosomal compartment as this is where the enzyme is active and no where else so would only have an inhibitory effect here Developed a membrane anchoring and endosomal targeting of beta secretase inhibitor This was successful in being endocytosed and inhibiting beta secretase in vitro but in a cellular complex didn’t work at all because couldn’t be endocytosed correctly in vivo. Sterol linked inhibitor is effective in vivo in mice models!

Question 170

Risk genes for Alzheimer’s and amyloid beta production

Answer 170

Risk genes involved in late onset AD don’t seem to be involved with amyloid beta production - Bali et al 2012

Question 171

Role of insulin/nutrient sensing on microglia mediated amyloid clearance and synaptic pruining

Answer 171

Selective depletion of TDP-43 from microglia promotors amyloid clearance from neurones and also removes synapses Increased CD68+ phagocytic structures in microglia lacking TDP-43

Question 172

Biphasic metabolic model integrating amyloid formation and synapse loss in dementia

Answer 172

Amyloid phase: aB generated by metabolic activity forms toxic oligomers Synaptic phase: switch of metabolism to catabolic dominant state leading to synaptic loss

Question 173

COPD

Answer 173

lung diseases limiting air flow and not fully reversible Symptomatic treatments available just disease management and palliative care only no cures Two main pathologies: Chronic bronchitis- chronic inflammation and excess mucus production and presence of chronic productive cough. Large airways of trachea and bronchi but small bronchioles, mucus hypersecretion, inflammation, chronic bronchitis, peribronchiolar fibrosis, airway obstruction. Emphysema - damage to alveolar units of lung and chronic cough. Acinus (respiratory bronchiole, alveolar duct and alveoli) have loss of elastic recoil and emphysema Smoking is a primary risk factors responsible for 80-90% Prolonged exposure to harmful particles and gases from second hand smoke, industrial smoke, chemicals and gases etc. Oxidative stress worsens COPD And amplified lung inflammation

Question 174

Chronic bronchitis

Answer 174

Chronic irritation, defensive increase in mucus production with increase numbers of epithelial cells especially goblet cells Poor relation to functional obstruction Rise in sputum production and increased infection risk Non reversible obstruction May have reversible asthmatic component in some cases Basement membrane thickens, basal cell metaplasia occurs

Question 175

Emphysema

Answer 175

Increase beyond normal size of air spaces distal to terminal bronchiole due to tissue destruction Holes in alveoli High rate of emphysema in rare genetic condition of alpha 1 antitrypsin deficiency - likely involved Inflammatory cells increase, macrophages, CD8+ lymphocytes etc Unpairs respiratory function by diminished alveolar surface area for gaseous exchange Loss of elastic recoil and support for small airways leads to tendency for collapse with obstruction

Question 176

Telomere length in COPD

Answer 176

COPD Patients compared to healthy subjects show excess telomere shortening supporting the theory of accelerated ageing in COPD decreased telomere length marks cellular turnover, exposure to oxidative and inflammatory damage and biological age so has clinical significance in COPD as increases all of these factors leading to decreased telomere length

Question 177

Structure of skin

Answer 177

Two main layers: Outer epidermis - keratinocytes high turnover, melanocytes (antigen presenting cells), no direct vascularisation Inner dermis - low turnover largely acellular but with fibroblasts, mostly ECM proteins such as collagen and elastin, blood vessels and nerve cells present. Subcutaneous tissue under dermis

Question 178

Collagen fibril

Answer 178

Triple helix with 3 alpha chains | Each with triple amino acids repeats Gly-X-Y- etc.

Question 179

Functions of skin

Answer 179

Barrier to external agents: physical, UV, chemical, biological virus, bacteria etc. Water retention Thermoregulation Immunological organ - inmate and acquired Sensory organ - pain etc Photosynthesis of vitamin D

Question 180

DNA damage in skin

Answer 180

Skins DNA very susceptible to environmental damage Solar UVB and UVA can cause different types of DNA damage Solar UVR induces DNA damage even at low doses without causing sunburn This damage can accumulate with daily solar exposure because natural DNA repair of some types of damage is slow Failure to repair DNA damage may result in mutations leading to skin cancer

Question 181

Photoageing - clinical

Answer 181

``` Age or liver spots (lentigines) Mottled pigmentation Loss of elasticity Sagging Dryness Fine and deep wrinkles Dilated blood vessels ```

Question 182

Difference between chronological and photoageing skin

Answer 182

Chronological - epidermis: flattened dermo-epidermal junction, variable epidermal thickness, variable keratinocytes size, loss of melanocytes Dermis: atrophy, decreased collagen, elastin, proteoglycans and vascularity Photoageing - epidermis: flattened dermo-epidermal junction, early epidermal thickening but later on epidermal atrophy, variable keratinocytes size, increased melanocytes, melanin content and atypia. Dermis: collagen degradation, increased elastin with elastic fibre degradation and proteoglycans. Thickening of blood vessel walls and low grade perivascular inflammation

Question 183

Matrix metalloproteinases MMP

Answer 183

Enzymes that degrade ECM collagens and elastin Normally very low activity in skin Kept in check by tissue inhibitors of MMPs called TIMP UVR induces expression of MMP mRNA and protein activity UVR has little effect of TIMP meaning more MMPs with no regulation Changes

Question 184

Photocarcinogenesis

Answer 184

DNA damage especially CPD that’s results in characteristic mutations CPD implicated in immunosuppressive been shown to have role in SCC in mice and suspected of similar role in humans Action spectrum based on SCC in mice is similar to that for human erythema

Question 185

Prevention of photoageing and skin cancers

Answer 185

Sun avoidance especially in fair skinned Avoid peak sun two hours either side of solar noon - but this is also best time to get vitamin D only low doses necessary Shade seeking Clothing with UV protection factor Sunscreens with High sun protection factor

Question 186

Developmental programming

Answer 186

Process which a stimulus or insult establishes a permanent response Exposure during critical periods in development may influence later metabolic or physiological functions in adult life

Question 187

Studies of developmental programming

Answer 187

Hertfordshire Cohort Meticulously midwifery records from 1920s enabled cohort to follow up Found low birthweight associated with abdominal obesity Law et al 1992 Association of birthweight with raised blood pressure in Hertfordshire Population - low birth weight shows increase blood pressure later in life Fall et al 1995 low birthweight also associated with adulthood hypertension, coronary heart disease, insulin resistance, adult obesity, dyslipidaemia

Question 188

Barker hypothesis

Answer 188

Adverse in utero environment Impaired foetal growth in critical periods Structural changes within organs leading to poor childhood growth and catch up growth, metabolic and endocrine dysfunction all causing disease in later life

Question 189

Dutch famine 1944-45 cohort study developmental programming

Answer 189

Daily rations cut to 400-800kcal from Dec to April: exposure to famine in mid or late gestation caused impaired glucose tolerance in offspring Exposure in early gestation caused atherogenesis lipid profile, obesity, increased risk of CHD all independent of birth weight

Question 190

Thrifty phenotype hypothesis

Answer 190

Suggests growth restriction or malnutrition in utero leads to foetal adaptations which favour post Natal survival in a similarly deprived environment and that disease ensues when the diet is richer than anticipated Hales and Barker 1992

Question 191

Rapid infant growth - catch up growths

Answer 191

Small GA babies showing catch up growth 6-12 months have increase risk of obesity - BMI or skin fold thickness (Parsons 2001) Meta analysis by Ong and Loos 2006, showed 2-3 fold increase in overweight and obesity in individuals who crossed at least one weight centipede in first two years irrespective of birth weight Other studies in term infants have identified catch up growth in first 8 days of life as critical to later risk of obesity Stettler et al 2005 - implication of feeding practices too No ability to standardise feeding practices !

Question 192

Breast feeding and risk of obesity

Answer 192

Systemic review estimates beneficial effect on childhood obesity varying from 22-7% vs formula fed More recently WHO estimated 22% reduction in overweight or obesity studies are observational subject to residual confounding Beneficial effect of breastfeeding may be due to: reduced intake compared to Bottle fed babies, slower weight gain in breast fed babies, milk borne hormones may be protective (leptin/insulin), composition of formula (high protein) affects growth. Formulations with lower protein content are now more common and may reduce estimated benefit of breast milk

Question 193

Accelerated post natal weight gain

Answer 193

High intake of growth enhancing nutrients eg protein Eg High plasma and tissue levels of insulinogenic amino acids Enhanced secretion of insulin or IGF-1 Weight gain up to 2 years and adipogenic activity Long term risk of obesity and associated disorders

Question 194

Inheritance and susceptibility to childhood obesity

Answer 194

Estimates of heritability from twin studies upward of 50% Souran et al 2008 Common obesity is a polygenic disorder with no observable simple Mendelian genetics Common variants of the fat mass obesity FTO gene and genetic variants in LEPR, MC4R and MC3R involved in satiety Currently known common genetic variants fail to predict childhood obesity in birth cohorts Mirandi et al 2012 Childhood obesity - an interaction between several genetic and or environmental mechanisms eg nutrition Tounian et al 2011

Question 195

Trans generational cycle and obesity amplification

Answer 195

Maternal obesity Glucose, insulin, leptin, lipids, inflammatory response Placenta modifies materno placental nutrient supply Foetal developmental plasticity Post natal weight trajectory Obesity, CH and diabetes risk

Question 196

Risks associated with maternal obesity

Answer 196

``` Hypertensive disorders Gestational diabetes mellitus Thromboembolic events Caesarean section Evidence for persistent metabolic and CV effects on offspring ```

Question 197

Maternal pre pregnancy BMI and gestational weight gain and risk of offspring obesity: Hochner 2012 Jerusalem study

Answer 197

Greater maternal pre pregnancy BMI is associated with higher offspring BMI, waist circumference at 32 years of age The observed associations were independent of characteristics reflecting pre or Peri and post natal environment including current measures of SES and lifestyle Children born to mothers before and after surgical weight loss - children born after surgical weight loss showed greater insulin sensitivity, improved lipid profile, lower C reactive protein, increased ghrelin.

Question 198

Undernutrition in rat pregnancy models

Answer 198

Induces increased fat mass and reduces offspring locomotor activity

Question 199

Set point theory of ageing physiological function

Answer 199

The set point/amount of physical activity to avoid muscle loss of function comorbidities Controlled and integrated age related decline of physiological function - curve displaying decrease in physiological function Most fall below this set point while athletes tend to be above this Below this set point leads to insufficient physical activity, which interacts negatively with ageing and leads to uncertain health trajectory and non optimal ageing with extended morbidity. Vice versus for athletes above set point physical activity Those following set point shoe sufficient activity to counteract inactivity, optimal ageing and compressed morbidity

Question 200

Measuring ideal and sedentary activity level functional decline and ageing

Answer 200

Pollock et al 2015 Took participants ages 35-75 of sufficient physical activity levels - road cyclists who had to complete set tests Measured VO2 max all had same training Showed age decline in VO2 max - suggesting age does cause decline despite fit physical age Sedentary participants - some 45 YO would have same VO2 max as 80 YO due to lack of physical activity!! However the reliance on cross sectional data means that a range of people ages 55-75 could have the same VO2 max and this isn’t relevant as isn’t longitudinal evidence - need longitudinal studies to compare ageing effects really. Also classifications of data is problematic - eg FEV1/FVC <70 is considered clinical COPD but many athletic cyclists had his value so important to distinguish activity levels too due to the type of exercise they undertake doesn’t work the lungs Cyclists may also have bone problems like osteoporosis due to being wrong mechanism to activate bone only activated muscle

Question 201

Age function relationships

Answer 201

Corrections between age and function tend to be driven by extremes in data Large assumptions need to be made about linearity across lifecourse Inflammageing shown in cyclists No age related decrease in type II fibre size seen in cyclists No age related decrease in capillaries in cyclists No reduction in OPA1 which is reduced in sedentary individuals. Therefore these factors aren’t age related they’re sedentary related.

Question 202

Is exercise protective of motor unit loss in ageing?

Answer 202

Power et al 2010 Looked at old, young and master runner participants Showed age effects prevented or removed by exercise However data by piasecki et al 2016 carried out the same study but demonstrated that the master runners were no better off than either group suggesting that this was an inherent ageing effect not protected by exercise Conflicting and inconclusive research atm

Question 203

Weightlifting and muscle ageing

Answer 203

Best way to protect muscles from ageing | Weightlifters shown to have fictional advantage of around 25 years younger than actual age!!

Question 204

Countermeasures for gravity induced de-conditioning in space and in ageing

Answer 204

Have to carry out two hours of exercise per day to compensate for lack of gravity Resistance training, running etc all combined to maintain mass and muscle In ageing best approach is resistance training to preserve muscle and function in elderly people

Question 205

Why is exercise so difficult to study

Answer 205

Naturally activates multiple systems and so has multiple effects systemic and local hard to isolate and study them all Can’t study sedentary individuals as there’s too many confounding factors at play such as diet etc skewing evidence

Question 206

Does exercise prevent ageing effects

Answer 206

No but prolonged threshold set point at which muscle mass declines causing morbidities so allows longer functional physical activity

Question 207

Drugs vs exercise for protecting muscle mass against ageing

Answer 207

Testosterone - evidence of efficacy (not all studies) but potential side effects Growth hormone - no evidence of efficacy with adverse side effects Myostatin inhibitors - effects unknown, some evidence for increased muscle mass but reduction in force per unit area Exercise - proven effect at all ages with benefits to other tissues. Muscle as endocrine organ etc. Psychological and social benefits all round better Should always try and treat with exercise as this is the most efficient and beneficial treatment

Question 208

Leptin in development

Answer 208

Postnatal leptin surge in rodents is key developmental signal for hypothalamus - Ahima 1998 Leptin in early life modulates formation of neural circuits in hypothalamus - Bouret eg al 2004 Maternal undernutrition can influence timing and amplitude of leptin surge Attig et al 2008 In genetic models of obesity leptin deficiency results in suboptimal neurodevelopment of hypothalamus Exogenous leptin rescues arcuate nucleus development in neonatal but not adult leptin resistant mice - Bouret et al 2004

Question 209

Development of selective leptin resistance

Answer 209

Selective leptin resistance - CV action of leptin is preserved with intact renal SNA response causing obesity induced hypertension Rats offspring show elevated systolic blood pressure, increased renal sympathetic outflow indirect by renal NA content, increased reactivity to stress, sympathetic component of HRV and pressor response to leptin Renal sympathetic hypertension is primary programmed event in offspring obesity rats Excessive weight gain in pregnancy programmes selective resistance in offspring. Show loss of metabolic action of leptin promoting obesity but preservation of sympathetic nerve activation causing greater sympathetic tone, leading to hypertension.

Question 210

Low protein maternal diet in rats and ageing associations

Answer 210

Associated with reduce lifespan Shorter telomeres in kidney than age matched controls Renal failure Folate supplementation in rats shows increased DNA methylation status altering expression maybe targeting these effects and acting to reverse

Question 211

Epigenetics

Answer 211

Phenotype of individual as result of complex interactions between genotype and current, past and ancestral environments leading to lifelong remodelling of epigenomes Changes in gene expression by mechanisms other than changes in underlying DNA sequence Fundamental cellular differentiation during normal development - genes activated and silenced in epigenetically inheritable pattern usually leading to terminal differentiation in sex specific manner Adverse influence - many teratogens affect epigenetic processes, cancers cause epigenetic dysregulation, environmental influences in earliest stages of life may predispose to disease in adulthood Carried out by methylation, deacetylation etc. Of DNA residues causing switching on or off of genes therefore altering expression of the genes. Both reversible and heritable across somatic and germline cells

Question 212

Paternal nutritional status and epigenetics of offspring

Answer 212

Beta cell dysfunction High fat diet leading to adiposity, glucose intolerance, insulin resistance in father rats cause female offspring (sex specific?) impaired glucose intolerance, insulin secretion to glucose challenges at 6 and 12 weeks Differential expressed islets genes and altered DNA methylation status thought to be cause Paternal high fat diet alters epigenome of offspring in sex specific manner

Question 213

Ageing and diabetes

Answer 213

Elderly have increased visceral adiposity - consequence of imbalance between diet and activity, reduced oestrogen and testosterone, expanded adipocytes secreting adipokines like TNFalpha (elderly have chronic raised TNFalpha levels) and increased FFA from diet. Impaired beta cell stimulus-secretion coupling in older people - increase in ROS and decreased ATP with age. Normally ATP synth driven by NADH/FADH and ROS inactivated by SOD and catalase. However in ageing increased glycolysis under hyperglycaemia overloads mitochondria driving ROS production. Beta cells have low SOD and catalase levels so are susceptible to damage with increased ROS. Impaired beta cell mitochondrial function decreases ATP and therefore ability to exocytosis and secrete insulin. With age inflammatory response is higher - possibly due to accumulation of misfolded insulin and amyloid Less capacity to cope with insulin resistance in elderly - islet cells in young have high proliferation, can re enter cell cycle while elderly islet cells have higher expression of cell cycle inhibitor p16Ink4a prompting cell senescence and arresting division.

Question 214

Bone disease and ageing

Answer 214

Osteoporosis is a skeletal disorder characterised by compromised bone strength predisposing individuals to fracture and poor healing Common sites affected: spine, neck of femur and wrists Peak bone mass declines with age, men have a higher peak bone mass than women especially after menopause due to the oestrogen decline. Regulators of peak bone mass: genetics, nutrition, physical activity, gonadal status. Calcium homeostasis also declines with age: decreased interstitial Ca from reduced Ca channels causes vitamin D resistance, decreased vitamin D synthesis in kidneys and increased expression of 24(OH)ase and increase of vitamin D catabolism leading to bone loss. Osteoclasts reabsorption increases and uncouples from formation and lack of oestrogen exacerbates this Bone marrow becomes replaced with adipocytes with age: osteoblasts and adipocytes both derived from MSCs and bone proliferation decreases with age while adipocytes formation increases leading to reduction in osteogenesis and increase in adipogenic potential. This impacts fracture and healing as less new bone is formed. Increased cell senescence means senolytics like dasatinib, quercetin, apoptosis inhibitor can rescue age related osteoporosis (only in mice so far) by decreasing bone reabsorption. Current osteoporosis treatments: Anti reabsorption - estrogens and SERMs (raloxifene), bisphosphonates, calcitonin, calcium and vitamin D, calcitrol, denosumab Anabolic stimulators of bone formation - parathyroid hormone (teriparatide) and anti sclerostin (romosozumab) Potentially senolytics