Intestinal-related substances in obesity regulation: A comprehensive review

Figure 1 Bidirectional mechanisms of gut microbiota in obesity regulation. The immune pathway involves B cells, T cells, dendritic cells, neutrophils, and macrophages. The neuroactive substance pathway includes metabolites such as gamma-aminobutyric acid, short-chain fatty acids, and tryptophan. The microbial pathway encompasses microbiota-derived signals. The endocrine pathway features gut peptides such as peptide YY and glucagon-like peptide-1 secreted by enteroendocrine cells. The neural pathway is mediated by the vagus nerve. The hypothalamic-pituitary-adrenal axis involves corticotropin-releasing factor, adrenocorticotropic hormone, and cortisol, which interact with gut hormones to regulate physiological processes.