PPARGC1A and type 2 diabetes mellitus: PGC-1α is involved in regulating glucose homeostasis by co-activating FOXO1 (Puigserver et al., 2003), and polymorphisms in PPARGC1A are associated with increased risk for T2D (Pihlajamäki et al., 2005; Yang et al., 2011), which may play a similar functional role in modifying PGC-1α activity as promoter DNA methylation.