Regulation of fatty acid metabolism

Fatty acid metabolism requires a balance between degradation and synthesis according to the energy need of cells and an organism as a whole. It is obviously dependent on the metabolism of carbohydrates and proteins. In humans the liver plays a role in lipid blood homeostasis analogous to its role as glucostat organ. For the control of beta oxidation the major regulatory mechanism is the availability of substrate. In liver, fatty acids come from three major sources: (i) as fatty acids released by extra cellular lipase from triglycerides coming from fat absorption in the form of chylomicrons, (ii) as unesterified (free) fatty acids in blood plasma (complexed with albumin) originating from adipose tissue (adipocyte lipase), and (iii) from intracellular triglycerides where a liver specific lipase deesterifies triglycerides releasing free fatty acids. The cellular lipases of adipocytes and hepatocytes are under hormonal control, with glucagon activating the lipase and insulin inhibiting it. Other hormones that activate lipase are epinephrine and nor-epinephrine, and ACTH (C02017; adrenocorticotropic hormone). These positive stimulators all work through cAMP mediated kinase phosphorylation.