Interestingly, a reduction in the mitochondrial proteins mitofusin (MNF)1, MNF2, optic atrophy 1 (OPA1) and the dynamin-related protein 1 (DRP1) has been associated with an impairment of OXPHOS capacity, as well as defects in energy production in several metabolic diseases, including type 2 diabetes and obesity [11,12,13]. This evidence concerns the gene OPA1 and obesity due to melanocortin 4 receptor deficiency.