Lipid Metabolism  (脂代谢)

Lipids are essential components of cellular membranes and the nervous system and also act as a second messenger that carries signals within the cell. Lipids are stored as triglycerides for use as energy, which are formed by glycerol and fatty acids through esterification reaction.

Free fatty acids and glycerol are released by lipase hydrolysis. Glycerol is catalyzed by glycerol kinase and glycerol phosphate dehydrogenase to form dihydroxyacetone phosphate, which then enters the glucose metabolism. The fatty acids are transported to the mitochondrial matrix for β-oxidation to produce acetyl-CoA, NADH and FADH2.

Lipids are mainly synthesized in the liver through the following pathways: 1. triglyceride is produced by dihydroxyacetone phosphate or free glycerin from glucose metabolism via the glycerin α-phosphate pathway. 2. Acetyl-CoA hydroxylase catalyzes the allosteric formation of acetyl-CoA into malonyl-CoA, which is converted into fatty acids through repeated addition reactions.

Disorders of lipid metabolism most commonly lead to dyslipidemia. Dyslipidemia can increase the risk of atherosclerotic disease, including coronary heart diseases and cerebrovascular diseases, which in severe cases may cause stroke, myocardial infarction, cerebral infarction, pancreatitis, etc.