The Comparison of the Gut Microbiome Composition, Serum Inflammatory Markers and Faecal Short-Chain Fatty Acids Among Individuals With Type 1 and 2 Diabetes Mellitus With Healthy Controls: A Case–Control Study

Background: This study aimed to compare the gut microbiome (GM) composition, serum inflammatory markers and faecal short-chain fatty acids among individuals with type 1 and type 2 diabetes mellitus (DM) and healthy controls. Methods: This case–control study examined 49 subjects with type 2 DM, 21 with type 1 DM and 40 healthy controls. Blood and faecal samples were collected. Serum inflammatory markers, including CRP, IL-1β, IL-6, TNF-α and IFN-γ, were measured using enzyme-linked immunosorbent assays (ELISA). Bacterial populations were quantified using RT-qPCR and NGS. Faecal metabolites were analysed using gas chromatography. Results: Simpson's alpha diversity was higher among types 1 and 2 DM than in the control. The frequency of the bacterial genera Gemmiger, Dorea, Collinsella, Escherichia/Shigella, Dialister, Coprococcus, Achromobacter, Intestinimonas and Allisonella in type 2 DM was higher than in the control, and the frequency of the genera Romboutsia and Clostridium was decreased in type 2 DM. The frequency of the Prevotella, Bacteroides and Faecalibacterium genera in type 1 DM was lower than in the other groups. Acetate, propionate and butyrate levels were significantly higher in type 2 DM patients compared to the other groups. Participants with diabetes had significantly higher hs-CRP, IL1-β, TNF, IL-6 and IFG levels compared to the controls. Compared to healthy controls, both T1DM and T2DM patients showed a significant increase in the abundance of the Lactobacillus genus (p = 0.01) and a decrease in Faecalibacterium (p = 0.02). Additionally, serum levels of IL-6 and TNF-α were significantly elevated in T2DM patients (p = 0.003 and p = 0.005, respectively). Faecal levels of butyrate were significantly reduced in both diabetic groups compared to the controls (p = 0.004). Conclusion: By determining the GM alterations in patients with diabetes, interventional strategies could be designed to modulate the GM composition as an adjunctive therapy in diabetes.