GLP1R and obesity due to melanocortin 4 receptor deficiency: In this section, we will describe the role that the gut microbes, particularly Akkermansia muciniphila, play in protecting the host from diabetes and obesity, via the release of a protein that induces the secretion of glucagon-like peptide 1 (GLP-1) from intestinal L-cells (Rodrigues et al., 2022).