INS and obesity due to melanocortin 4 receptor deficiency: This was shown in mice where heterozygous ATX (gene name Enpp2) knockout protected from diet-induced obesity and insulin-resistance and restored mitochondrial function in skeletal muscle [47], or in adipocyte-specific Enpp2-/-mice that, on a high-fat diet, showed smaller body weight gain and less insulin resistance than control mice [48].