Lipoproteins

Question 1

what are the 3 pathways involved in lipoprotein metabolism

Answer 1

1. exogenous pathway
2. endogenous pathway
3. reverse cholesterol pathway

Question 2

name the pathway: which pathway is described by the following:
Chylomicrons formed in the intestine, with dietary lipids (TAGs, cholesterol and cholesterol esters) deliver TAGs to adipose (and other peripheral organs) and are converted to remnants, which are taken up by the liver, with their dietary cholesterol still resident in the particle.

Answer 2

the exogenous pathway

Question 3

name the pathway:
VLDL particles formed in the liver, with “endogenous” lipids (TAGs, cholesterol and cholesterol esters) deliver TAGs to adipose (and other peripheral organs) and are
converted to IDLs and then to LDLs (alternatively, VLDL remnants). Cholesterol is, along the way, delivered to peripheral organs or returned to the liver.

Answer 3

The endogenous pathway

Question 4

name the pathway:
HDL particles, derived from a few sources, acquire cholesterol from other lipoproteins and from peripheral organs and deliver it to the liver.

Answer 4

The reverse cholesterol pathway

Question 5

Statins

Answer 5

a large class of drugs which act as competitive
inhibitors of the regulatory enzyme of cholesterol
synthesis
-competitively inhibit HMG‐CoA reductase

Question 6

Statins, are competitive inhibitors of HMG CoA reductase, the enzyme involved in the committed step for cholesterol synthesis. What affects do statins have on the Km and the Vmax of HMG CoA reductase??

Answer 6

Km: is increased

Vmax is not changed

Question 7

Ezetimibe

Answer 7

An inhibitor of dietary cholesterol

absorption. Acts on the cholesterol transporter

Question 8

Cholesterylamines

Answer 8

Cholesterol binding resins, that
chelate cholesterol and bile acids/salts in the intestine
and are passed in the feces. This forces the recruitment
of cholesterol from liver reserves to replenish bile
acid/salt stores for future use in digestion/absorption.

Question 9

The statin \_\_1\_\_\_\_\_ HMC‐CoA reductase.
The chain of events:
•Liver cholesterol reserves \_\_2\_\_\_ as input
from de novo synthesis \_\_\_3\_\_\_\_.
•LDL receptor expression levels
\_\_\_\_4\_\_\_\_, in response.
•HMG‐CoA reductase levels \_\_\_\_5\_\_, in
response.
•Statin levels are maintained.
•Circulating LDL concentrations
\_\_\_\_\_.

Answer 9

1. inhibits
2. drop
3. declines
4. increase
5. increase
6. decrease

Question 10

Peroxosome proliferator activated receptor

Answer 10

-a family of nuclear receptors
-when bound to ligand it binds to transcriptional
regulatory sequences on DNA and influences mRNA synthesis rates at specific loci

Question 11

name some of the functions promoted by PPARalpha

Answer 11

Increased β‐oxidation in the liver
Decreased hepatic triglyceride secretion
Increased lipoprotein lipase activity, and thus increased
VLDL clearance
Increased HDL
Increased clearance of remnant particles
Increased antiinflammatory and antiproliferative effects

Question 12

The fibrates are agonists of the _____

receptor.

Answer 12

PPARα