Lipids are hydrophobic but otherwise chemically diverse molecules that play a wide variety of roles in human biology. They include ketone bodies, fatty acids, triacylglycerols, phospholipids and sphingolipids, eicosanoids, cholesterol, bile salts, steroid hormones, and fat-soluble vitamins, and function as a major source of energy (fatty acids, triacylglycerols, and ketone bodies), are major constituents of cell membranes (cholesterol and phospholipids), play a major role in their own digestion and uptake (bile salts), and participate in numerous signaling and regulatory processes (steroid hormones, eicosanoids, and sphingolipids). Because of their poor solubility in water, most lipids in extracellular spaces in the human body are found as complexes with specific carrier proteins. Regulation of the formation and movement of these lipoprotein complexes is a critical aspect of human lipid metabolism, and lipoprotein abnormalities are associated with major human disease processes including atherosclerosis and diabetes.
Aspects of lipid metabolism currently annotated in Reactome include lipid digestion, trafficking of dietary sterols, triacylglycerol synthesis (fatty acid synthesis and triacylglycerol assembly), hormone-sensitive lipase-mediated triacylglycerol breakdown, and beta-oxidation of fatty acids, ketone body metabolism (synthesis and utilization), the synthesis of cholesterol, bile salts, and steroid hormones, and sphingolipid metabolism. Three aspects of lipoprotein function are currently annotated: chylomicron-mediated lipid transport, HDL (high density lipoprotein)-mediated lipid transport, and LDL (low density lipoprotein) endocytosis and degradation.
Reactionmap