Probiotics and Their Metabolites Alleviate Type 2 Diabetes Mellitus by Regulating Glucagon-Like Peptide-1: A Review of Recent Research

Type 2 diabetes mellitus (T2DM), a chronic metabolic disease caused by an imbalance between carbohydrate intake and metabolism, is one of the most difficult metabolic diseases to treat worldwide. The main symptoms of T2DM include hyperglycemia, insufficient insulin secretion, insulin resistance, polydipsia and polyuria. T2DM is often accompanied by many complications such as atherosclerosis, renal function injury and non-alcoholic fatty liver disease. Glucagon-like peptide-1 (GLP-1) is a polypeptide composed of 31 amino acids, which is mainly used to maintain glucose homeostasis in vivo and relieve T2DM. However, its half-life is short and it is easily degraded in vivo. This article introduces probiotics and their metabolites that regulate GLP-1 in the host, and also discusses the alleviative effect of GLP-1 on T2DM, including the association between GLP-1 and T2DM, the clinical application of metformin and GLP-1 agonists, the insufficiency of GLP-1 in alleviating T2DM and the regulation of the GLP-1 content by related prebiotics. Finally, the regulatory mechanisms of probiotics and their metabolites on GLP-1, including short-chain fatty acids, bile acids (BAs), tryptophan and its derivatives and extracellular polysaccharides, are summarized in order to provide some references for studies on the regulatory effects of probiotics and their metabolites on GLP-1 production and release in the host as well as their alleviative effects on T2DM.