Theme 2: Lipids

Question 1

which lipoproteins are triglyceride rich?

Answer 1

chylomicrons and very low density lipoproteins

Question 2

which lipoprotein is the main cholesterol carrier?

Answer 2

low density lipoproteins

Question 3

what are the functions of apolipoproteins?

Answer 3

structural 
ligand binding 
receptor recognition 
activation/inhibition of lipolysis 
cholesterol efflux

Question 4

what is the enzyme which removes free fatty acids from lipoproteins in circulation?

Answer 4

lipoprotein lipase

Question 5

which lipoprotein delivers cholesterol to tissues?

Answer 5

LDL

Question 6

which enzyme is involved in the conversion of IDL into LDL?

Answer 6

hepatic triglyceride lipase (HTGL)

Question 7

which enzyme is the rate limiting enzyme in cholesterol synthesis?

Answer 7

HMG CoA reductase

Question 8

what is the function of ABCA1 in reverse cholesterol transport?

Answer 8

transfers excess cholesterol from peripheral tissues to nascent HDL

Question 9

which lipoprotein is involved in reverse cholesterol transport?

Answer 9

HDL

Question 10

which lipoprotein is involved in the formation of atherosclerotic plaques?

Answer 10

LDL

Question 11

what causes familial hypercholesterolaemia and what will be the results on a lipid profile?

Answer 11

reduction in receptor mediated clearance of LDL

lipid profile- elevated LDL, high total cholesterol normal fasting triglycerides

Question 12

what causes familial combined hyperlipidaemia and what will be the results on a lipid profile?

Answer 12

overproduction of VLDL and apoB

lipid profile- elevated LDL, triglyceride and total cholesterol, may have low HDL

Question 13

what causes remnant (type III) hyperlipidaemia and what will be the results on a lipid profile?

Answer 13

reduction in receptor mediated remnant clearance

lipid profile- elevated total cholesterol and triglycerides, cholesterol rich remnants present

Question 14

what causes familial hypertriglyceridaemia and what will be the results on a lipid profile?

Answer 14

deficiency in lipoprotein lipase of apoCII

lipid profile- elevated triglyceride, may have low HDL

Question 15

what is the mechanism of action of statins?

Answer 15

inhibits HMG-CoA reductase in cholesterol synthesis
up regulates LDL receptor expression which increases LDL clearance
net effect- —LDL,-TG,+HDL

Question 16

what is the mechanism of action of fibrates?

Answer 16

agonists at PPAR-alpha receptor which regulates lipid metabolism. results in:
1. reduces TG and VLDL by increasing synthesis of lipoprotein lipase and stimulating fatty acid oxidation in liver
2. increases expression of apoA-I and apoA-II which increases HDL
3. increases hepatic LDL uptake
net effect- –VLDL, –TG, -LDL,+HDL

Question 17

what is the mechanism of action of ezetimibe?

Answer 17

inhibits intestinal absorption of cholesterol by interfering with the NPC1L1 transport protein
net effect- reduces LDL and VLDL

Question 18

what is the mechanism of action of cholestipol and cholestyramine?

Answer 18

they are bile acid binding resins which bind to bile acids in the gut preventing reabsorption and diverting hepatic cholesterol to bile acid synthesis. also causes increase in LDL receptors so LDL clearance increases

Question 19

what is the mechanism of action of nicotinic acid?

Answer 19

1. reduces VLDL synthesis
2. reduces catabolic rate of HDL- increasing HDL
3. activates lipoprotein lipase
   net effect- -LDL,-VLDL, -TG, +HDL