INS and obesity due to melanocortin 4 receptor deficiency: A colonization experiment demonstrated the positive role of Lachnospiraceae (a family of Clostridia) in the development of obesity and diabetes in germ-free ob/ob mice, including increased liver and adipose tissue weights and fasting blood glucose levels and decreased plasma insulin levels and homeostasis model assessment of β-cell function (HOMA-β) values30.