Path Flashcards
Where is cholesterol in the intetstine from?
- diet
- bile duct
How is cholesterol in the intestine solubilised?
in mixed micelles
Where are bile acids reabsorbed?
terminal ileum
What effect does cholesterol have on HMG-CoA-reductase?
it inhibits the enzyme
fates of cholesterol in the liver
- hydrolysed via 7-alpha-hydroxylase into Bile Acids, released via bile ducts (major determinants of cholesterol absorbtion)
- esterified via ACAT to cholesterol ester; incorporated with triglyceride and apoB into VLDLs with transfer protein MTP
How are triglycerides moved from small intestine to plasma?
via chylomicrons
How is LDL taken up by cells?
- binds to LDL R
- coated pits
- invagination
processed by lysosomes
How common is homozygous and heterozygous familial hypercholesterolaemia?
homozygous: 1 in 10^6
heterozygous: 1 in 500
What is PCSK9? What happens in gain and loss of function mutations?
a chaperone protein
its role is to bind to the LDL receptor and promote its degradation
gain of function mutations -> high LDL (because more LDL R is degraded and LDL not taken up by liver)
loss of function mutations -> low LDL
What medications are used to lower cholesterol? What effects do they have on HDL, LDL and TG?
statins - good reduction in LDL, slight reduction of TG, slight elevation of HDL
fibrates - very good at lowering TG, slight reduction/increase in LDL/HDL
resins - bind bile acids
Pharmacological approaches to obesity
orlistat - inhibits pancreatic lipase -> not hydrolysed, not absorbed, excreted via stool
surgical approaches to obesity (and indication)
bariatric surgery
if BMI >40
Different types of bariatric surgery
- gastric binding
- roux-en-Y bypass
- biliopancreatic diversion
Why can people with sarcioud have high Ca?
1-a-hydroxylase can be expressed lungs; uncontrolled; activation of vitamin D -> high CA
25-hydroxylase is found where?
Liver
Where is 1-alpha-hydroxylase found?
KIDNEYS
can be ectopiicallly expressed in sarcoid
When do you prescribe cholecalciferol and calcitriol?
calcitriol is dangerous because it is active Vit D3; only prescribed in renal failure; easy to overdose;
cholecalciferol - OTC, has to be activated;
Compare osteoporosis vs osteomalacia
Osteoporosis: reduced bone density with normal biochemistry
Osteomalacia: bone demineralisation; Blood: low Ca, low phos, high ALP/PTH?
How do you calculate corrected calcium?
CC = measured calcium + 0.02x(40-albumin)
T-score vs Z-score
T-score SD of 20yo
Z-score is SD from age-matched
Causes of osteoporosis
- childhood illness
- menopause
- corticosteroid therapy
- lifestyle: sedentary, EtOH, smoking, low BMI/nutritional
- endocrine: hyperprolactinaemia, thyrotoxicosis, Cushingโs
- other e.g. genetic, prolonged intercurrent illness
Mx of osteoporisis
lifestyle: weight bearing exercise, stop smoking, reduce etoh
Drugs
- vit D / Ca
- bisphosphonates (e.g. alendronate) -> decreased bone resorption -> very strong bone, not biodegradable; unnatural phosphate; osteoblasts Can use it, casts struggle with breakdown. do not have it with calcium, taken 1x/w on empty sttomach with water and nothing else. gut irritant.
alternative is 1/year IV zonlendronate
- teriparatide (PTH) derivative - anabolc;
- Strontium: anabolic + anti-respoptive
- oestrogens/HRT
- SERMs e.g, raloxifene (
Tamoxifen actions
Tamoxifen agonist in bone, antagonist in breast
raloxifene similar; good for bone and prevent Br ca but worsen Sx of menopause.
Which antibiotic groups belong to beta lactams?
Penicllins
Cephalosporins
Carbopenems
Monobactams