HDL: High density lipoprotein

HDL: High density lipoprotein.

Origin: Liver and partly by intestinal cells.

Chemical Nature: Cholesterol and phospholipid rich.

Half life: 4 – 6 days.

Clearance of mature HDL:

1.      HDL goes to liver and binds with hepatocytes where HDL offloads cholesterol.

2.      From hepatocytes offloaded cholesterol is disposed subsequently by three mechanism:

a.      Excretion with bile as free cholesterol.

b.      Conversion to bile acid and then excretion with bile.

c.       Repackaged into VLDL and then secretion into blood.

Functions of HDL:

1.      Supports reverse cholesterol transport to keep serum cholesterol normal.

2.      Carries cholesterol from peripheral tissues back to liver for biliary excretion.

3.      Acts as reservoir of appoproteins and helps in chylomicron and VLDL metabolism by providing apo-C and apo-E.

4.      Supports steroid genesis by providing cholesterol to relevant organs.

5.      Shows active antioxidant activity.