AHR and obesity due to melanocortin 4 receptor deficiency: Actually, supplementation with microbial tryptophan metabolites such as indoles, IAA, and IPA and Lactobacillus reuteri strain has been shown to ameliorate the features of some metabolic diseases such as inflammatory bowel diseases (IBDs) and diet-induced obesity by rescuing the impaired AhR activity and regulating gut barrier function (33, 34).