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Metabolic perspectives and nutrition > week 9 > Flashcards

week 9 Flashcards

(48 cards)

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1
Q

What is the overall aim of endurance exercise

A

To disturb homeostasis to induce beneficial adaptations to improve maximal oxygen uptake

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2
Q

Predictors of endurance exercise

A
  • Maximal oxygen consumption
  • Aerobic enzymes
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3
Q

What is the primary predictor of mortality

A

Blair et al 1989
- Greater aerobic capacity reduces risk of mortality
- Independent of co-morbidity including hypertension, high cholesterol, smoking and glucose levels

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4
Q

What can cause aerobic capacity to decline

A

Tanaka and Seales 2003
- Age

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5
Q

What causes the decline with age?

A

Barazzoni et al 2000
- Reduced mitochondrial content, assessed by mtDNA

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6
Q

What is another way to measure

A

Mitochondrial enzymes involved in the ETC, TCA and beta-oxidation
- CS
- COX enzymes

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7
Q

4 ways to mt biogenesis measured

A
  1. altered gene expression
  2. altered protein expression
  3. altered enzyme activity
  4. altered synthetic rates
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8
Q

Outline initial work investigating endurance training on mitochondrial increase

A

Holloszy 1967
- Trained rats 5x/w with progressive overload
- Increase maximal oxygen uptake
- Increase mt protein
- Increase cytochrome oxidase and succinate oxidase

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9
Q

Provide further evidence by Holloszy on endurance training

A

Holloszy 1970
- Identified CS as a marker of mt biogenesis

Overall this the original research underpinning MB

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10
Q

How are enzyme activities calculated

A
  • Enzyme extracted from muscle
  • Amount of pre-reaction is calculated by identifying amount of by-product
  • Change in light absorbance via colormetric directly corresponds to amount of by-product
  • This determines enzyme activity
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11
Q

Why is there limited understanding on the biochemical and molecular regulation of skeletal muscle?

A

Most studies are conducted in animals, specifically rodents, in which research is not translatable

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12
Q

What happens to enzymes with ET in humans?

A

Spina et al 1970
- initial work in humans
- 7-10 days ET in small sample
- Rapid increase in enzymes
- Findings correlate to those in animals
- Therefore enzyme response may be an early response to exercise, not necessarily mtDNA

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13
Q

What are the effects of detraining in sub-max?

A

Coyle et al 1985
- Rapid reduction in mt enzyme activity

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14
Q

Does mt content differ between fibre types?

A

Egan and Zierath 2013
- Greater content in type 1
- Genetic component to proportion of fibres in individuals, therefore will be variability

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15
Q

How is mt content regulated in skeletal muscle?

A

Seo et al 2010
- fission and fusiom
- fusion of mt to expand in size
- once reached upper limit go through fission to increase number
- the process does not go on forever as mt degrade via mitography

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16
Q

What are the regulating enzymes in fusion and fission?

A

Fusion - Mfn1 and Mfn2
Fission - DRP and Fis1

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17
Q

What effect does ageing have on the regulation of mt in terms of fission and fusion?

A

Greater fission = fragmented mt
Greater fusion = enlarged mt
- Both consequences lead to decreased ETC activity, respiration, aerobic capacity and cell death

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18
Q

What mediators are involved in regulating MB?

A

Transcriptional co-activators

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19
Q

Why is transcriptional control important in response to exercise training?

A

This can increase or decrease the amount of RNA produced by specific gene, which will alter the function of the skeletal muscle

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20
Q

How can transcriptional control be altered?

Study These Flashcards
A
  1. Increase/decrease promoter - signals how much RNA is made
  2. Transcription factors - directly change the rate of transcription
  3. Co-activators - indirectly change rate of transcription
21
Q

What happens to transcription post-exercise

Study These Flashcards
A

Egan and Zierath 2013
- Rapid increase in transcription due to increase mRNA
- Therefore one of the first changes in ET

22
Q

What technique is used to mRNA and provide the steps

Study These Flashcards
A

Real-time PCR
1. Isolate RNA
2. Reverse transcription produces complementary DNA template
3. Identify desired gene and add primers
4. polymerase chain reaction amplifies section of gene
5. fluorescent dye added to measure desired RNA

23
Q

Name an unbiased hypothesis approach to measuring mRNA

Study These Flashcards
A

Transcriptomics

24
Q

How is transcription increased - 5 methods

Study These Flashcards
A
  1. Make more transcription activator
  2. Make more co-activator
  3. Increase activity of transcription activator
  4. Relocate co-activator or repressor
  5. Change activity of co-activator or repressor
25
What in ET leads to an increase in MB?
PGC1a
26
Which trco-activator and transcription factor play a role in the browning of adipose?
PGC1a and PPARy
27
What is transgenesis?
Chenouard et al 2021 - Research method that allows us to KO/overexpress desired genes - Therefore allowing ability to research MB - CRISPR is a genetic scissor by Charpeniter and Doudna 2020 allows for gene editing
28
What are the 2 types of respiration?
Coupled - Generation of ATP via ATP synthase driven by movement of protons across membrane Uncoupled - Movement of proteins through UCP1. Does not generate ATP
29
How is transcription altered with transgenesis
- Scissor enters nucleus via inert virus - virus fuse with cells and implant proteins that edit genes - fluorescent tags added to track activity of the gene - completed in cell culture or single cell embryo
30
Measuring what is happening in a cell via respiration
Wu et al 1999 - Oligomycin shuts down ATP synthase to measure amount of UCP - FCCP allows protons to flood matrix to measure total respiratory capacity of a cell
31
What mechanisms control MB and respiration
Wu et al 1999 - PGC1a overexpressed in rodent ] - This lead to the increase of mtDNA - Also increased basal, FCCP and oligomycin Therefore PGC1 has role in MB, and subsequently respiration
32
What happens if PGC1a is KO?
Lin et al 2002 - No increase in MB - Overexpression of PGC1a leads to increased activity of Cox enzymes
33
How does PGC1a increase MB?
Calvo 2008 - PGC1a overexpression mice run faster for longer at lower RER - Due to increased number of genes in FA transport, OX phosphorylation, CHO met and TCA cycle - Increase gene expression = increased MB
34
Name the 3 processes in which PGC1a is activated in skeletal muscle.
1. Increase PGC1a transcription 2. Increase PGC1a nuclear abundance 3. Increase PTM of PGC1a
35
How does the Akimoto et al 2004 link with PGC1a transcription
- Mice leg electrically stimulated - Electroporation used to identify activation of PGC1a via fluorescence - Greater PGC1a transcribed with electrical stimulation - MEF2 and CRE/AFT2 upstream of PGC1a - KO ablates PGC1a activity
36
What links PGC1a and improved performance?
Wright et al 2007 - Transcription co-factor in the nucleus - The increase in PGC1a in the muscle after rodent swims corresponds to the increase in PGC1a in the nucleus - Therefore PG1a translocation to nucleus is pivotal step in initiating MB
37
Provide of PGC1a transcription in the nucleus of humans
Little et al 2011 - Acute bout of HIIT - Resulted in increase in PGC1a mRNA and CS mRNA 3 hours post-exercise - due to increase in PGC1a in the nucleus - NO total protein content of PGC1a increase, only in nucleus - only in nucleus there is a sig increase
38
How is AMPK phosphorylated
AMP by product of ATP breakdown and phosphorylates AMPK Greater breakdown in ET It has been proposed as an energy 'sensing' mechanism in skeletal muscle
39
ET on the signalling of AMPK
Chen et al 2003 - Greater intensity = AMPK - AMPK phosphorylates ACC - Increased ACC phosphorylation with exercise intensity Is there a role of AMPK in ET
40
Does muscle use AMPK to mediate adaptations?
Egan et al 2010 - long exercise bout - AMPK activity associated with increased PGC1a Therefore AMPK and PGC1a may interact to promote endurance adaptations
41
What does overexpressing AMPK in mice do?
Garcia-Roves et al 2008 - Increases transcriptions factors, mt markers mRNA, mtDNA, PGC1a, respiration - therefore MB
42
What happens if you KO b1 and b2 complex of AMPK?
O-Neill 2011 - Reduced speed and distance ran - due to lower CS, cytochrome c oxidase activity and lower protein expression in the ETC and lower mtDNA - due to reduced MB
43
Does AMPK phosphorylate PGC1a?
Jager et al 2007 - in human - uses AICAR to mimic AMP - Overexpressed PGC1a response to removed complex (T177A s538A) ablated Therefore AMPK and PGC1a linked
44
Summarise the acute response Moore et al 2018 - the effect of exercise on DRP1
Gene level - PGC1a and DRPincreased with acute bout of exercise, but not change in mtDNA Protein level - No change in DRP1 content as consequent of exercise, but increase phosphorylation, therefore promoting fission
45
Chronic training in mice
- Measured bodyweight to ensure they are exercising - Reduced fat mass including white adipose - expansion of the heart gene level - PGC1a stimulated - reduction in fission genes - may be due to timing of measurement for this decrease protein level - no increase in DRP1 - increase of inhibition of DRP1, indicating fusion - increase in genes in OX phos
46
What about training + acute bout?
gene level - stimulation of PG1a, DRP1 and mtDNA protein level - DRP1 activated (fission) - No change in fusion signalling
47
What about in dysglycaemic men?
- DRP1 gene expression is reduced in men - DRP1 expression can increase with 12 week ET
48
What happens if DRP is KO?
- Reduced running time and latency to fall

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