Chylomicrons: Definition and Overview

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What Are Chylomicrons & Where Are They Made

What are chylomicrons?

Chylomicrons are one of the five types of lipoproteins, or combinations of proteins, triglycerides (the body’s main storage form of fat), and cholesterol that circulate throughout the bloodstream. Lipoproteins are classified according to their density and their ratio of cholesterol and triglycerides to protein. The five main classifications of lipoproteins are chylomicrons, very-low-density lipoproteins (VLDL), low-density lipoproteins (LDL), intermediate-density lipoproteins (IDL), and high-density lipoproteins (HDL).

Chylomicrons are one of the largest, most buoyant lipoproteins, with relatively more triglycerides within their core and less cholesterol than LDL and HDL particles. The fact that they are comprised of about 90% triglycerides, which are less dense than cholesterol, gives them their buoyancy.

Where are chylomicrons made?

Chylomicrons are made in the intestines following the absorption of digested fat. From there, they are transported in the bloodstream to such tissues as skeletal muscle, body fat, and the liver. In these tissues, an enzyme called lipoprotein lipase breaks down the triglycerides within the chylomicrons into free fatty acids. These free fatty acids are then either used by muscle cells to create energy, stored in muscle or fat tissue, or broken down and transformed into other substances by the liver.

People with Type 2 diabetes, who have a twofold to fourfold increased risk for coronary heart disease, tend to have elevated triglyceride levels and decreased levels of HDL cholesterol, the so-called “good” cholesterol. Their high triglyceride levels may be due at least in part to the reduced action of insulin on lipoprotein lipase, which results in reduced breakdown and clearance of the triglyceride-rich lipoproteins, VLDL, and chylomicrons. Because of their high risk of dyslipidemia (blood lipid abnormalities) and cardiovascular disease, people with Type 2 diabetes should have their blood lipid levels monitored regularly (at least once a year in most cases) and treated if they are abnormal.

Originally Published November 19, 2009

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