GCG and obesity due to melanocortin 4 receptor deficiency: Among these gut-derived factors related to obesity, we will summarize existing knowledge on the potential of gut microbiota and its metabolites (including LPS, SCFAs, and butyrate), and gut hormones (GLP-1, Ghrelin) directly or indirectly modulate the activation of ATMs and mediate the pathogenesis of obesity-related inflammation.