MUC5AC and obesity due to melanocortin 4 receptor deficiency: Based on these results, we speculate that the mucus layer of mice, which is thinned by obesity or diabetes (Everard et al., 2013; Shin et al., 2014), induces the expression of proteins capable of inducing a probiotic effect in A. muciniphila, resulting in the upregulation of the Muc3 gene and the regeneration of mucin, so that A. muciniphila is able to restore and colonize the mucus layer.