Effects of GLP-1 agonists on the gut microbiota in type 2 diabetes mellitus: a systematic review.

Diabetes mellitus (DM) is a metabolic disease characterised by chronic hyperglycemia. The Glucagon-Like Peptide-1 Receptor Agonists (GLP-1 RAs) used in type 2 diabetes mellitus (T2DM) have been highlighted for their potential benefits to the gut microbiota in the context of this pathology. Therefore, it is important to investigate the relationship between microbiota and GLP-1 RAs used in T2DM. This review aimed at evaluating the effects of GLP-1 agonists on gut microbiota in T2DM individuals. The protocol was previously registered in PROSPERO, and the search was conducted in PubMed, Scopus, Web of Science, and Embase databases in March 2025. Two reviewers have read the titles and abstracts and selected the included articles based on established criteria. The initial search identified 5532 publications, of which 17 studies were included: 12 preclinical and 5 clinical. Most were conducted in China between 2016 and 2025. GLP-1 agonists have been shown to modulate the gut microbiota, characterised by an increase in Bacteroidetes, Akkermansia muciniphila, and Lactobacillus. These changes are accompanied by an improvement of intestinal villi, increase in occludin expression, as well as an improvement in colonic inflammation. We identified a higher abundance of bacterial species associated with intestinal balance (eubiosis), accompanied by reduced inflammation and insulin resistance. Conversely, there was a lower abundance of bacteria related to dysbiosis, such as Firmicutes and Proteobacteria, which can be unfavourable when in excess. GLP-1 agonists influence the intestinal microbiota, improving metabolic parameters and anti-inflammatory effects. However, further clinical studies are needed to corroborate the findings of this review.