lipogenezis

Lipogenesis is the metabolic process by which fatty acids and glycerol are synthesized from non-carbohydrate sources, such as glucose and amino acids. This process is primarily carried out in the cytoplasm of cells, particularly in the liver, adipose tissue, and mammary glands. Lipogenesis is essential for storing energy in the form of triglycerides, which can be mobilized when the body's energy demands increase.

The pathway begins with the conversion of glucose to acetyl-CoA, a two-carbon molecule that serves as the primary building block for fatty acids. Acetyl-CoA is then carboxylated to malonyl-CoA, a crucial regulatory step in lipogenesis. This reaction is catalyzed by acetyl-CoA carboxylase (ACC), an enzyme that is itself subject to allosteric regulation and hormonal control. Once malonyl-CoA is formed, it is condensed with acetyl-CoA by fatty acid synthase (FAS), a multi-enzyme complex. FAS then catalyzes a series of reduction and condensation reactions, adding two-carbon units from malonyl-CoA to a growing fatty acid chain, ultimately producing palmitate, a 16-carbon saturated fatty acid.

Further elongation and desaturation of fatty acids can occur in the endoplasmic reticulum. Glycerol is typically supplied from the breakdown of glucose via glycolysis, where it is phosphorylated to glycerol-3-phosphate. Triglycerides are then formed by the esterification of three fatty acids to a glycerol backbone. Hormones like insulin promote lipogenesis, while hormones like glucagon and epinephrine inhibit it. This intricate regulation ensures that energy storage and release are coordinated with the body's metabolic needs.