triacylogliceroli

Triacilgliceroli, also known as triacylglicerols (TAGs), are a class of neutral lipids formed by the esterification of glycerol with three fatty acids. The glycerol backbone provides three ester linkages to fatty acyl chains, which vary in length and saturation. TAGs are nonpolar and hydrophobic, making them insoluble in water; they accumulate as lipid droplets in adipocytes and serve as the body’s primary energy reserve. They are the main constituents of animal fats and most vegetable oils and contribute significantly to dietary energy intake.

In digestion, TAGs are hydrolyzed by pancreatic lipase, primarily at positions sn-1 and sn-3, yielding free fatty acids and 2-monoacylglycerol. These products are absorbed by enterocytes and re-esterified to form TAGs again, which are packaged into chylomicrons for transport through the lymphatic system and bloodstream. In tissues, TAGs can be broken down by lipases (lipolysis) to release fatty acids for beta-oxidation, while glycerol is released to the liver and can be used in gluconeogenesis or glycolysis-derived pathways.

Biosynthesis of TAGs occurs mainly via the glycerol-3-phosphate pathway. Glycerol-3-phosphate is acylated by acyl-CoA derivatives in a series of steps catalyzed by GPAT, AGPAT (LPAAT), and DGAT enzymes to yield triacylglycerol. Regulation involves hormonal signals (e.g., insulin promotes storage) and the energy status of the cell. TAGs are thus central to energy storage, metabolism, and dietary fat transport.