Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) is a protein that in humans is encoded by the PPARGC1A gene. PPARGC1A is also known as human accelerated region 20 (HAR20). It may, therefore, have played a key role in differentiating humans from apes. PGC-1α is the master regulator of mitochondrial biogenesis. PGC-1α is also the primary regulator of liver gluconeogenesis, inducing increased gene expression for gluconeogeneis. PGC-1α is a transcriptional coactivator that regulates the genes involved in energy metabolism. Peroxisome proliferator-activated receptor gamma coactivator 1-beta is a protein that in humans is encoded by the PPARGC1B gene. The protein encoded by this gene stimulates the activity of several transcription factors and nuclear receptors, including estrogen receptor alpha, nuclear respiratory factor 1, and glucocorticoid receptor. The encoded protein may be involved in fat oxidation, non-oxidative glucose metabolism, and the regulation of energy expenditure. This protein is downregulated in prediabetic and type 2 diabetes mellitus patients. Certain allelic variations in this gene increase the risk of the development of obesity.