"Descrizione" by Kevin-Wooderly (155 pt) | 2021-Mar-30 19:41 |
Evaluation | N. Experts | Evaluation | N. Experts |
---|---|---|---|
1 | 6 | ||
2 | 7 | ||
3 | 8 | ||
4 | 9 | ||
5 | 10 |
Lipoprotein lipase is an enzyme that is secreted after being synthesized by parenchymal cells. It is localized in the capillaries, in the small vessels of tissues that use lipids the most, therefore especially in muscle cells and adipocytes that produce it and excrete it by exocytosis. Once excreted, it is bound to endothelial cells.
In the presence of apo C-2, lipoprotein lipase functions and thanks to apo C-2, LPL can bind to the chylomicron and digest the first triglycerides it comes in contact with. The lipase can hydrolyze the triglyceride in multiple places causing the release of free fatty acids and glycerol.
Fatty acids can move immediately from the endothelial cell to the underlying tissue, where they will have different fates depending on whether it is adipose or muscle tissue.
Chylomicrons repeatedly attach and detach to different lipoprotein lipases gradually reducing in size.
On hepatocytes, there are two types of receptors that bind remnant chylomicrons and IDLs. The LDL receptor, LDL receptor, is the LDL-related receptor, LRP or more commonly called the apo-E receptor.
The difference is that LDR-E binds both B100 and apo-E so it is also called apo BE receptor.
LDL receptor binds LDL, remnant chylomicrons and VLDL.
LRP binds only apo-E, so it binds only remnant chylomicrons and IDLs.
The endothelial cells of the hepatic sinusoids have spaces that allow the passage of remnant chylomicrons, and as they pass into the endothelium they are in the subendothelial space called Disse's space.
On the other side of Disse's space are the hepatocytes that have membrane eversions, villi, that optimize absorption.
On the surface of the hepatocytes is hepatic lipase. Hepatic lipase further demolishes triglycerides but also demolishes phosphoglycerides by further demolishing chylomicron remnant.
After this further reducing action there is binding between apo E and its receptor causing the chylomicron to be absorbed by endocytosis. The endosome becomes a lysosome within which acid lipases in addition to acid proteases are also found, because these enzymes work optimally at acidic pH, which demolish the chylomicron.
The half-life of a chylomicron is relatively short, about ten minutes.
In conclusion, dietary cholesterol intake, called the exogenous pathway, is carried by chylomicrons, transported to the liver via remnant presenting apo E as a ligand of the apo E receptor present in the liver itself.
Evaluate |