Since administration of either the cell-free supernatantlive or live A. muciniphila, but not bacterial pellet, increased systemic GLP-1 secretion, Yoon et al. identified an 84 kDa protein in the culture supernatant, named P9, which accounts for the induction of GLP-1 secretion in HFD-fed mice and L cells.36 Administration of P9 to HFD-fed mice prevented obesity and improved glucose tolerance by regulating GLP-1 secretion and inducing brown adipose tissue thermogenesis. Here, GCG is linked to obesity due to melanocortin 4 receptor deficiency.