Microbiome Imbalance and Pediatric Type 1 Diabetes Mellitus: An Updated Systematic Review of Gut Dysbiosis Evidence

Emerging evidence suggests that alterations in the gut microbiota may play a significant role in the development of type 1 diabetes mellitus (T1DM), particularly during childhood, when the immune and metabolic systems are still maturing. This systematic review aims to synthesize recent findings on the composition, diversity, and functional characteristics of gut microbiota in children with T1DM. A comprehensive literature search was conducted on PubMed, Cochrane Library, and Google Scholar for studies published between January 2019 and July 2025. Eligible studies included observational studies examining the gut microbiota in children with T1DM using validated sequencing methods. Six studies met the inclusion criteria and were analyzed for microbial composition, diversity, and associated immune and metabolic alterations. Most studies reported reduced microbial diversity and depletion of short-chain fatty acid (SCFA)-producing bacteria, such as Faecalibacterium and Roseburia, in T1DM children. An increased abundance of pro-inflammatory genera, including Bacteroides, Blautia, and Dorea, was frequently observed. Several studies have also identified elevated levels of gut permeability markers, such as zonulin and lipopolysaccharide (LPS), suggesting compromised intestinal barrier function. Notably, while some studies reported decreased abundance of Parasutterella in T1DM, one study observed its increased abundance, indicating regional or methodological variability. Gut dysbiosis, characterized by reduced diversity, loss of beneficial microbes, and increased intestinal permeability, is consistently associated with pediatric T1DM. However, the heterogeneity of specific taxa highlights the need for standardized longitudinal research. Understanding gut microbial alterations may provide novel opportunities for early intervention and disease modulation in at-risk children.