Lipids 5

Question 1

What two enzymes affect activity of hormone sensitive lipase (HSL)?

Answer 1

cortisol–induces HSL so increases the release of FA’s from adipose tissue
insulin–inhibits HSL–prevents release of free FA’s in well fed state
Glucagon–HSL response to glucagon is mediated by cAMP and PKA–stimulates HSL

Question 2

Apoprotein A, B, C and E

Answer 2

ApoA: activates LCAT -> extracts lipids from cell membranes and transfers them to the core of lipoprotein particles
ApoB: structural protein that gives lipoprotein its shape; also interacts with lipoprotein receptors and mediates uptake of the particle
ApoC: modulates function of lipoprotein lipase -> liberates free fatty acids and glycerol from lipoprotein
ApoE: important for the removal of lipid-depleted lipoproteins (remnant particles) from circulation

Question 3

Chylomicrons Function

Answer 3

distribution of dietary lipids throughout the body–chylomicrons are packed by enterocytes

Question 4

VLDLs

Answer 4

VLDL synthesized by liver to distribute synthesized lipids to peripheral tissues; made up of TAG’s, cholesteryl esters, phospholipids/cholesterol on surface, ApoB100 for structural component, ApoC/E for interacting w/ lipases and receptors; gradually lose TAG’s by action of lipases and over time accumulate cholesteryl esters and ApoE proteins; after losing certain amount of lipid they can be taken up by liver; HOWEVER, not all VLDLs are cleared from blood, some lose more TAG’s and acuire more cholesteryl esters and become –> IDLs then LDLS

Question 5

What if VLDL remnants are not cleared from blood?

Answer 5

They will continue to lose TAG’s and gain cholesteryl esters going from VLDL’s–>IDL’s–>LDL’s; cells that have demand for LDL’s will take them up; DON’T want macrophages taking them up but they will if they are in large excess–cannot break them down and lead to CVD

Question 6

HDL’s

Answer 6

reverse cholesterol transport; synthesis begins in liver and small intestine w/ synthesis of nascent HDL; empty HDL’s will circulate picking up ApoE and phospholipids and also cholesterol from other tissues (most important!); USE ABCA-1 to actively transport cholesterol out of cell membranes; chole. is transferred to HDL’s and esterfied by LCAT