What is the exogenous pathway of lipoprotein metabolism?
The exogenous lipoprotein pathway starts in the intestine. Dietary triglycerides (approximately 100 grams per day) are hydrolyzed to free fatty acids and monoacylglycerol by intestinal lipases and emulsified with bile acids, cholesterol, plant sterols, and fat-soluble vitamins to form micelles.
What are the cholesterol metabolism pathways?
Cholesterol is synthesized via a cascade of enzymatic reactions known as the mevalonate pathway. This series of reactions is primarily regulated by a rate-limiting step involving the conversion of hydroxyl-methyl glutaryl-coenzyme A (HMG-CoA) into mevalonate.
What is exogenous cholesterol?
Exogenous cholesterol is derived from bile and from dietary sources, which predominantly comprise animal and dairy food products.
What is endogenous cholesterol?
We define endogenous cholesterol as body cholesterol derived principally from biosynthesis and, to a lesser extent, from absorbed dietary cholesterol.
What is exogenous pathway?
The exogenous pathway is utilized by specialized antigen-presenting cells to present peptides derived from proteins that the cell has endocytosed. The peptides are presented on MHC class II molecules. Proteins are endocytosed and degraded by acid-dependent proteases in endosomes; this process takes about an hour.
What is cholesterol catabolism?
The pathway of cholesterol catabolism is comprised of many steps to degrade the side chain and cyclic framework to simple metabolites acetyl-CoA, propionyl-CoA, succinyl-CoA, and pyruvate and to generate NADH [10].
What are exogenous triglycerides?
The exogenous pathway starts with the intestinal absorption of triglycerides and cholesterol from dietary sources. Its end result is the transfer of triglycerides to adipose and muscle tissue and of cholesterol to the liver. After removal of the triglyceride core, remnant chylomicron particles are formed.
What lipoprotein transports exogenous cholesterol?
Major lipoproteins include: Chylomicrons – large particles that carry dietary lipid. Very low density lipoprotein – carry endogenous triglyceride and some cholesterol. Intermediate density lipoprotein – carry cholesterol esters and triglycerides.
What carries exogenous cholesterol?
What is exogenous lipid?
Lipids are body fats that are either synthesized within cells (endogenous lipids) or derived from dietary fat (exogenous lipids). These TAG-rich lipoproteins are remodelled under the action of lipoprotein lipase and lipid transfer proteins into smaller chylomicron remnants and low-density lipoproteins (LDLs).
What is endogenous pathway?
(a) Endogenous pathway shows viral antigens that enter the host cells by the intracellular route. Once internalized, the viral antigens are degraded into peptides by proteasomes. In the endosomal-lysosomal compartments, the antigens are degraded into peptides followed by packaging of the peptides onto MHC-II complexes.
What is an exogenous antigen?
Exogenous antigens are antigens that enter from outside the body, such as bacteria, fungi, protozoa, and free viruses. These exogenous antigens enter macrophages, dendritic cells, and B-lymphocytes through phagocytosis or pinocytosis.
What is the exogenous pathway for lipid metabolism?
Exogenous pathway for lipid metabolism: Dietary cholesterol and fatty acids are absorbed. Triglycerides are formed in the intestinal cell from free fatty acids and glycerol and cholesterol is esterified.
What is the pathophysiology of cholesterol synthesis?
In the endogenous pathway, cholesterol is synthesized by the liver and extrahepatic tissues, and enters the circulation as a component of lipoproteins, or is secreted into bile. In the exogenous pathway, cholesterol from dietary and biliary sources is absorbed in the intestine and ultimately enters the circulation as a component of chylomicrons.
Is dietary cholesterol endogenous or exogenous?
Dietary cholesterol or “exogenous” cholesterol accounts for approximately one-third of the pooled body cholesterol, and the remaining 70% is synthesized in the body (endogenous cholesterol). Increased dietary cholesterol intake may result in increased …
What is the cholesterol absorption pathway?
In the exogenous pathway, cholesterol from dietary and biliary sources is absorbed in the intestine and ultimately enters the circulation as a component of chylomicrons. A new class of drugs, the selective cholesterol absorption inhibitors, offers a different approach to current strategies available for the management of hypercholesterolaemia.