Carnitine and β-Oxidation

Fatty acids represent the major fuel for energy production. The substrate fatty acids either are mobilized from triglycerides stored in a adipose tissue and transported via the bloodstream to tissues or are derived from plasma lipoproteins by the lipoprotein lipase. Following uptake into tissues by specific transport proteins, fatty acids are either stored as triglycerides or used for energy production. This latter process, called β -oxidation, is localized within the mitochondria and involves activation of fatty acids in the cytosol, the carnitine-dependent uptake of activated fatty acids into mitochondria, and their sequential oxidative chain shortening yielding acetyl-CoA and reducing equivalents (flavin adenine dinucleotide, nicotinamide adenine dinucleotide). Complete oxidation of fatty acid-derived acetyl-CoA in the citric acid cycle produces additional reducing equivalents. The energy in the form of ATP is formed during the reoxidation of reducing equivalents in the electron transport chain coupled with ATP synthesis.