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Chylomicrons

Underrated, rather large for a lipoprotein, but absolutely crucial - especially for those that relish late night deep dish pizza and bacon eggs benedict (with extra hollandaise) for brunch. Without it dietary lipids are meticulously hydrolyzed, only to go nowhere. Like hors d'oeuvres with no caterers, they result in a party of famished extra-hepatic tissue. With triglycerides (TAG) and cholesterol esters (CE) at the core as well as phospholipids, free cholesterol (FE) and apolipoproteins at the surface, the chylomicron transports lipids to tissues, especially adipose and muscle, that need it the most.

However, as esteemed as they are, chylomicrons require sidekicks even before they go…

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Articles of Interest

Chylomicrons - Biomedics Online

These lipoproteins are named as chylomicrons since they are drained into chyles in the lymphatic system and their size is about one micron in diameter. They are synthesized in the epithelial cells (enterocytes) of small intestines. The lipid components are synthesized from the absorbed dietary fatty acids and glycerol. The apolipoproteins (apoB48 and apoA) are synthesized in the rough endoplasmic reticulum by the ribosomes. The lipids are assembled with apolipoproteins in the glogi apparatus and then packed into the secretory vesicles and they are secreted by exocytosis into the intercellular space. The chylomicrons in these forms are known as nascent chylomicrons.

Chylomicron metabolism

Chylomicrons are assembled in intestinal mucosal cells and carry dietary (exogenous) TAG, cholesterol, fat-soluble vitamins, and cholesteryl esters to the peripheral tissues. [Note: TAG account for close to 90% of the lipids in a chylomicron.]

Chylomicrons - LM World

Chylomicrons are the largest of the lipoproteins. Their primary function is to transport the dietary or exogenous triglycerides and cholesterol from the intestinal lumen to sites of metabolism or storage. In the lumen of the GI tract, dietary fat is degraded into free fatty acids and monoglycerides. These substances enter the intestinal villi, where they are reconstructed into a triglyceride particle.

Chylothorax

Chylothorax occurs when chyle from the thoracic duct empties into the pleural space. Chyle is a milky white fluid with a high concentration of triglycerides, chylomicrons, and white blood cells

Difference Between Chylomicrons and VLDL

Chylomicrons are synthesized in the small intestine, and transport exogenous dietary products while VLDL synthesizes in the liver and transport endogenous dietary products. This is the key difference between chylomicrons and VLDL.

The Biogenesis of Chylomicrons

The absorption of dietary fat is of increasing concern given the rise of obesity not only in the United States but throughout the developed world. This review explores what happens to dietary fat within the enterocyte.

The Chylomicron: Relationship to Atherosclerosis

In conclusion there is clear evidence that chylomicron metabolism is abnormal in diabetes, a condition which is associated with a heavy burden of atherosclerosis. There is good evidence to implicate the chylomicron directly in the atherosclerotic pathological process, and there is good evidence that abnormal chylomicron metabolism is associated with an atherogenic LDL profile.

The Formation and Intracellular Transport of Chylomicrons

Dietary fat requires hydrolysis within the intestinal lumen prior to absorption. Once absorbed, the fatty acids (FA) and sn-2-monoacylglycerol (MAG) must be rapidly disposed of or the enterocytes risk membrane disruption. This is accomplished by their incorporation into the physico-chemically inert triacylglycerol (TAG). The TAG crosses the ER membrane and is incorporated into the developing chylomicron in a two-step process.

What Are Chylomicrons?

Once food is digested, particles of cholesterol and triglycerides need to be absorbed into the blood stream. These particles generally can’t pass into the blood stream on their own, and do not dissolve by themselves. Cells in the intestines called enterocytes typically absorb proteins and fatty acids, and form chylomicrons, which are particles with lipoprotein coatings that can pass fat-based substances into the blood circulation. Cholesterol and vitamins that are fat soluble are typically contained inside the particle.

What is the Difference Between Chylomicrons and VLDL

Chylomicrons are the largest form of lipoproteins responsible for the transportation of lipids throughout the body. Generally, lipoproteins are carrier molecules, which transport hydrophobic molecules inside their core, especially lipids such as triglycerides and cholesterol esters. Moreover, chylomicrons are the form of lipoproteins that contain the highest amount of triglycerides. The source of their triglycerides is dietary triglycerides and cholesterol. Usually, chylomicrons are responsible for the transport of these triglycerides into the peripheral tissues and liver for storage.

Cholesterol: The good, the bad and the ugly

After a meal, the cholesterol from digested food enters the small intestine and gets absorbed along with other fats, most notably, triglycerides. The fats are packed into transport molecules called chylomicrons (kye-lo-MY-cronz) Chylomicrons are like microscopic shuttles traveling through the blood, dropping off the bits of fats to cells that need it for energy. As many of us know all too well, some of those fats can be dropped off at fat cells for unlimited storage! The final destination of the chylomicron shuttles is the liver, which picks up the leftover shuttle remnants.

Discovery May Break Down Cholesterol Mystery

Researchers have known about chylomicrons for decades, but it took Proctor's initial research with his colleagues in Australia to discover how they are broken down after a meal. Using unique and specially designed imaging tools, Proctor and his colleagues tracked the formation and delivery pathways of chylomicrons in rabbits. Their research showed that chylomicron remnants form smaller lipoproteins, which can build up more quickly in arteries than any other type of cholesterol-carriers, including LDL.

Lipoprotein Function

Chylomicrons are produced for the purpose of transporting dietary triglycerides and cholesterol absorbed by intestinal epithelia. Chylomicron assembly originates in the intestinal mucosa. Excretion into the plasma is facilitated through the lymphatic system. In the plasma, chylomicrons acquire apo-CII and apo-E from HDL.

Lipoprotein-based drug delivery

Chylomicrons have the lowest density of all LPs (below 0.950 g/cm3) and a broad size range (80–1000 nm), which is dependent on the amount of ingested dietary lipids. Chylomicrons are synthesized in the digestive tract by enterocytes, which are cells specialized in biomolecular absorption of numerous small molecules (e.g., ions, water, sugars, peptides, amino acids, lipids, and vitamins).

The Blood Sample Looks Like Milk!

Another component of blood that creates a milky appearance is chylomicrons - a combination of fat globules and protein. This combination occurs in the small intestine, and moves through the intestinal walls into the lymph vessels. These vessels ascend to the upper thorax, merge into the thoracic duct which joins the left subclavian vein.

Resources

BusyAt.com

Chylomicrons are lipoprotein particles that consist of triglycerides (85–92%), phospholipids (6–12%), cholesterol (1–3%), and proteins (1–2%). They transport dietary lipids from the intestines to other locations in the body.

Labpedia.net

This is the primary lipoprotein that is responsible for the transportation of fat from the diet, which is the exogenous source. Chylomicron is the class of lipoproteins; this is responsible for transporting exogenous cholesterol and triglyceride from the small intestine to the tissues after the meal.

StatPearls

Chylomicrons are large triglyceride-rich lipoproteins produced in enterocytes from dietary lipids—namely, fatty acids, and cholesterol. Chylomicrons are composed of a main central lipid core that consists primarily of triglycerides, however like other lipoproteins, they carry esterified cholesterol and phospholipids.