Cholesterol Biosynthesis, Transport and Genetics Part 2

Question 1

how does the body get most of its cholesterol

Answer 1

de novo synthesis

Question 2

what are the ideal levels of total cholesterol, LDL, HDL and triglycerides for children

Answer 2

total: less than 170
LDL: less than 110
HDL: less than 45
triglycerides: less than 150

Question 3

what are considered high levels of total cholesterol, LDL, HDL and triglycerides for children

Answer 3

total: over 200
LDL: over 130
HDL: over 45
triglycerides: 200+

Question 4

what do chylomicrons carry

Answer 4

large particles that carry dietary lipids

Question 5

what does VLDL carry

Answer 5

endogenous triglyceride and some cholesterol

Question 6

what does IDL carry

Answer 6

cholesterol esters and triglycerides

Question 7

what does LDL carry

Answer 7

cholesterol esters

Question 8

what does HDL carry

Answer 8

cholesterol esters

Question 9

what are the 3 major normal lipoprotein metabolic pathways

Answer 9

1. exogenous
2. endogenous
3. reverse cholesterol transport

Question 10

what happens in the exogenous pathway

Answer 10

1. dietary cholesterol and fatty acids are absorbed
2. triglycerides are formed in the intestinal cell from free fatty acids and glycerol and cholesterol is esterified
3. triglycerides and cholesterol combine to form chylomicrons
4. chylomicrons enter the circulation and travel to peripheral sites
5. in peripheral tissues, free fatty acids are released from the chylomicrons to be used as energy, converted to triglyceride or stored in adipose
6. remnants are used in the formation of HDL

Question 11

what happens in the endogenous pathway

Answer 11

1. VLDL is formed in the liver from triglycerides and cholesterol esters
2. these can be hydrolyzed by lipoprotein lipase to form IDL or VLDL remnants
3. VLDL remnants are cleared from the circulation or incorporated into LDL
4. LDL particles contain a core of cholesterol esters and a smaller amount of triglyceride
5. LDL is internalized by hepatic and nonhepatic tissues
6. in the liver, LDL is converted into bile acids and secreted into the intestines
7. in non hepatic tissues, LDL is used in hormone production, cell membrane synthesis or stored
8. LDL is taken up by macrophages and other cells which can lead to excess accumulation and the formation of foam cells which are important in plaque formation

Question 12

what happens in the reverse cholesterol transport pathway

Answer 12

1. pre beta HDL particles initiated the efflux of cholesterol and phospholipids from cell membranes via interaction with the ATP transporter A1
2. subsequent action of the LCAT esterifies cholesterol in pre beta HDL particles and converts them to mature alpha HDL particles
3. mature HDL can deliver cholesterol to the liver by one of the two pathways: directly via the SR-B1 or indirectly exchange of cholesterol esters to chylomicrons, VLDL, or LDL
4. the uptake of apoB rich particles occurs via hepatic LDL receptors
5. the lypolysis of TG in TG rich HDL by hepatic lipase and endothelial lipase leads to a smaller HDL which re enters the RCT cycle

Question 13

what are the contributing factors to familial hypercholesterolemia

Answer 13

family history of early cardiac events and high LDL cholesterol

Question 14

what is the biggest lipoprotein to the smallest

Answer 14

chylomicrons, VLDL, IDL, LDL, HDL

Question 15

what are the sequential steps in the LDL receptor pathway

Answer 15

1. decrease in HMG CoA reductase
2. increase in ACAT
3. decrease in LDL receptors

Question 16

what are some drugs used to manage cholesterol levels

Answer 16

-statins
- bile acid resins
- soluble fiber
-niacin
- ezetimibe

Question 17

what are apolipoproteins

Answer 17

proteins that bind lipids to form lipoproteins