Cholesterol metabolism

Question 1

6 key fns of CE

Answer 1

membranes/myelin, signal transduction, precursor to bile acids, steroid hormones, and vitamin D, and embryo formation

Question 2

rate limiting step for CE synthesis, product of this step

Answer 2

HMG CoA reductase makes mevalonate, precursor to CE

Question 3

insulin role in CE synthesis

Answer 3

insulin stimulates HMG CoA reductase (and lipoprotein lipase to release TGs from lipoproteins to tissues)

cholesterol and fat are synthesized during the fed state in response to high insulin, incorporated into lipoproteins

Question 4

free cholesterol impact on CE synthesis

Answer 4

lowers HMG CoA reductase expression and fn, reduces LDL receptors too via oxysterols

Question 5

2 ways to increase intracellular CE

Answer 5

biosynth w/ HMG CoA and uptake via LDL receptors

Question 6

2 ways to decrease intracellular CE

Answer 6

catabolism and excretion as bile acids via 7alpha hydroxylase

or storage from ACAT enzyme

Question 7

saturated fat effect on intracellular CE

Answer 7

inhibits PUFAs in ACAT rxn to esterify and store cholesterol

Question 8

fiber role in CE homeostasis

Answer 8

fiber binds bile acids in intestine which lowers the amount in circulation= lower bile acids drives rxn of intracellular CE towards bile acids

Question 9

main enzyme for bile salt formation

Answer 9

7 alpha hydroxylation

Question 10

fns of bile acids

Answer 10

emulsify dietary fats prior to digestion, absorption of fat soluble vitamins, eliminate cholesterol from body (only way),

Question 11

impact of western diet on cholesterol regulation

Answer 11

high extracellular cholesterol=lower LDL receptor, saturated fat blocks CE storage, low fiber leads to higher bile acids and less CE catabolism