Pyruvate dehydrogenase kinase 4 (PDK4) is a mitochondrial protein that regulates the TCA cycle.PDK4, a vital mitochondrial protein, controls the switch between glycolysis and oxidative phosphorylation based upon nutrient availability.Pyruvate dehydrogenase kinase 4 (PDK4) mRNA has been reported as an up-regulated gene in the heart and skeletal muscle of carnitine-deficient juvenile visceral steatosis (JVS) mice under fed conditions. PDK4 plays an important role in the inhibition of glucose oxidation via the phosphorylation of pyruvate dehydrogenase complex (PDC).PDK4 gene expression is stimulated by thyroid hormone (T(3)), glucocorticoids, and long chain fatty acids.