Origin of chylomicrons in lipoprotein metabolism Chylomicrons, the lipoproteins that transport dietary triacylglycerols, are synthesized in which tissue?

Introduction / Context:
Chylomicrons ferry dietary lipids from the intestine through lymph into the bloodstream. Correctly assigning their site of assembly is fundamental for understanding postprandial lipid metabolism and disorders such as abetalipoproteinemia and familial chylomicronemia syndrome.

Given Data / Assumptions:

• Dietary fats are digested to fatty acids and monoacylglycerols.
• Enterocytes re esterify these into triacylglycerols.
• Lipoprotein assembly requires apolipoprotein B48 and microsomal triglyceride transfer protein (MTP).

Concept / Approach:

Within enterocytes, TAGs, cholesterol esters, and phospholipids are packaged with ApoB48 to form nascent chylomicrons. These particles enter lacteals, travel via lymph to the thoracic duct, and then enter the bloodstream. In capillaries, lipoprotein lipase hydrolyzes TAGs, delivering fatty acids to tissues; remnants are cleared by the liver.

Step-by-Step Solution:

Verification / Alternative check:

Genetic absence of ApoB48 or MTP blocks chylomicron formation, causing fat malabsorption and low postprandial triglycerides, confirming intestinal origin.

Why Other Options Are Wrong:

Liver synthesizes VLDL, not chylomicrons. Plasma is a transport medium, not a synthetic site. Pancreas produces lipases, not lipoproteins; adipocytes store fat but do not assemble chylomicrons.

Common Pitfalls:

Confusing chylomicrons (dietary origin) with VLDL (endogenous TAGs) or assuming all lipoproteins come from the liver.

Final Answer:

Intestinal enterocytes (small intestine)