LEP and obesity due to melanocortin 4 receptor deficiency: To evaluate possible effects on the hypothalamic–pituitary–adrenal axis38, we evaluated circulating leptin and corticosterone levels, and found genotype-dependent changes in mice fed with CD, but not with HFD (Fig. 3d)—like the neurotransmitter studies, these findings did not implicate a CNS-based effect of AIF1 deficiency in the observed resistance to HFD-induced obesity.