INS and obesity due to melanocortin 4 receptor deficiency: HFD-fed wild-type C3H/HeN mice colonized with B29 showed markedly degenerated hepatocytes, a significant increase in NAFLD activity score, obesity, and an insulin-resistant phenotype, unlike the corresponding HFD-fed GF control mice, after 15 weeks of HFD treatment (Fig. S5 and S6).