Metabolism of Chylomicron

Apo B-48

After ingestion of a meal, dietary fat (triglyceride) and cholesterol are absorbed into the cells of the small intestine and are incorporated into the core of nascent chylomicrons.

The triacylglycerol, cholesterol ester and phospholipid molecules along with apoproteins B48, and apo-A are incorporated into chylomicrons.
 

Four major groups of lipoproteins:

• Chylomicrons, derived from intestinal absorption of triacylglycerol and other lipids.
• Very low density lipoproteins (VLDL, or pre–lipoproteins), derived from the liver for the export of triacylglycerol.
• Low-density lipoproteins (LDL, or -lipoproteins), representing a final stage in the catabolism of VLDL.
• High-density lipoproteins (HDL, or -lipoproteins), involved in cholesterol transport and also in VLDL and chylomicron metabolism.

Triacylglycerol is the predominant lipid in chylomicrons and VLDL, whereas cholesterol and phospholipid are the predominant lipids in LDL and HDL, respectively.

Ref: Botham K.M., Mayes P.A. (2011). Chapter 25. Lipid Transport & Storage. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper’s Illustrated Biochemistry, 29e.

Chylomicrons are produced by enterocytes (intestinal epithelial cells), using gut luminal triglycerides for the source of the lipid. The chylomicrons are secreted into the gut lymphatic system, and from there drain eventually into the systemic venous system from the thoracic duct, and hence into the serum portion of the blood. They are initially large and have a very high triglyceride content. With time, lipoprotein lipase releases triglycerides from the chylomicron core by hydrolyzing them to more easily absorbed fatty acids. The enzyme is located on the external surface of the vascular endothelium of tissues with triglyceride needs such as skeletal muscle, cardiac muscle tissue, and lactating breast. The result of lipoprotein lipase activity is that the chylomicrons shrink in size.

A i.e. Apoprotein B

Ans. is ‘c’ i.e., B-48