PPARGC1A and type 2 diabetes mellitus: Muscle-biopsy studies performed in T2DM patients revealed mitochondrial dysfunction and a reduced expression of peroxisome proliferator-activated receptor gamma coactivator 1 (PGC1α), which is an essential regulator of mitochondrial biogenesis and function since it interacts with co-activating transcription factors (namely, nuclear respiratory factors, peroxisome proliferator-activated receptors (PPARs), thyroid hormone and also glucocorticoid and estrogen-related α- and γ-receptors).