Plays a role of stimulator of transcription factors and nuclear receptors activities. Activates transcriptional activity of estrogen receptor alpha, nuclear respiratory factor 1 (NRF1) and glucocorticoid receptor in the presence of glucocorticoids. May play a role in constitutive non-adrenergic-mediated mitochondrial biogenesis as suggested by increased basal oxygen consumption and mitochondrial number when overexpressed. May be involved in fat oxidation and non-oxidative glucose metabolism and in the regulation of energy expenditure. Induces the expression of PERM1 in the skeletal muscle in an ESRRA-dependent manner. Interacts with hepatocyte nuclear factor 4-alpha/HNF4A, Sterol regulatory binding transcription factor 1/SREBF1, PPAR-alpha/PPARA, thyroid hormone receptor beta/THRB and host cell factor/HCFC1. Interacts with estrogen-related receptor gamma/ESRRG and alpha/ESRRA. Interacts with PRDM16 (By similarity). Interacts with estrogen receptor alpha/ESR1. Ubiquitous with higher expression in heart, brain and skeletal muscle. Repressed by saturated fatty acids such as palmitate and stearate in skeletal muscle cells. Induced by insulin and reduced by aging in skeletal muscle biopsies. Down-regulated in type 2 diabetes mellitus subjects as well as in pre-diabetics. Contains 2 Leu-Xaa-Xaa-Leu-Leu (LXXLL) motif, which are usually required for the association with nuclear receptors. Variation of PPARGC1B may contribute to the pathogenesis of obesity, with a widespread Ala-203 allele being a risk factor for the development of this common disorders. Lacks LXXLL motif 1 and has a reduced ability to enhance the hormone-dependent activity of estrogen receptor alpha.