Gut Microbiome Dysbiosis and Its Association with Type 2 Diabetes Mellitus in Adults in Ibadan, South West Nigeria: A Metagenomic Study

Accumulating evidence implicates alterations in gut microbial composition in the pathogenesis of type 2 diabetes mellitus through mechanisms involving short-chain fatty acid production, intestinal permeability, and systemic inflammation. This study investigated the association between gut microbiome dysbiosis and type 2 diabetes mellitus in adults attending the diabetic clinic of University College Hospital Ibadan, Oyo State, South West Nigeria. A case-control study was conducted among 80 type 2 diabetic adults and 80 age, sex, and BMI-matched non-diabetic controls. Fresh stool samples were collected and DNA extracted using standardised protocols. 16S rRNA gene sequencing targeting the V3-V4 hypervariable region was performed on the Illumina MiSeq platform. Bioinformatic analysis employed QIIME2 and R packages for alpha and beta diversity, taxonomic profiling, and differential abundance testing. Diabetic subjects showed significantly reduced microbial alpha diversity. Firmicutes-to-Bacteroidetes ratio was elevated in diabetic participants. Genera including Bifidobacterium and Faecalibacterium prausnitzii were significantly depleted in diabetics, while Desulfovibrio and Escherichia were enriched. Glycaemic control correlated with specific microbial abundance patterns. Short-chain fatty acid-producing taxa were significantly less abundant in poorly controlled diabetics. The study provides the first Nigerian metagenomic characterisation of the gut microbiome in type 2 diabetes and recommends follow-up interventional studies exploring dietary modulation and probiotic supplementation as adjunctive diabetes management strategies. Keywords: gut microbiome, type 2 diabetes, 16S rRNA sequencing, dysbiosis, Ibadan