GPD2 and diabetes mellitus: OXPHOS was further impaired in ICM-DM by the impairment of FADH2 oxidation in three pathways: (1) Oxidation via CII and the citrate cycle; (2) FAO FADH2 synthesis by the downregulation of acyl-CoA dehydrogenases; and (3) Oxidation by GPD2 via glycerol metabolism (Alcazar-Fabra et al, 2016; Mracek et al, 2013).