Metformin Targets Intestinal Immune System Signaling Pathways in High-Fat Diet-Induced Type 2 Diabetes Mouse Model

Research findings of the past decade have highlighted the gut as the main site of action of the oral antihyperglycemic agent metformin despite its pharmacological role in the liver. Extensive evidence supports metformin’s modulatory effect on the composition and function of gut microbiota, nevertheless, the underlying mechanisms of the host responses remain elusive. Our study aimed to evaluate metformin-induced alterations in the intestinal transcriptome profiles at different metabolic states. The high-fat diet-induced type 2 diabetes mouse model of both sexes was developed in a randomized block experiment and bulk RNA-Seq of the ileum tissue was the method of choice for comparative transcriptional profiling after metformin intervention for ten weeks. We found a prominent transcriptional effect of the diet itself with comparatively fewer genes responding to metformin intervention. The overrepresentation of immune-related genes was observed, including pronounced metformin-induced upregulation of immunoglobulin heavy-chain variable regioncoding Ighv1-7 gene in both high-fat diet and control diet-fed animals, supporting the contribution of intestinal immunoglobulin responses. Finally, we provide evidence of the downregulation NF-kappa B signaling pathway in the small intestine of both hyperglycemic and normoglycemic animals after metformin treatment. Moreover, our data pinpoint the gut microbiota as a crucial component in the metformin-mediated downregulation of NF-kappaB signaling evidenced by a positive correlation between the Rel and Rela gene expression levels and abundances of Parabacteroides distasonis, Bacteroides spp., and Lactobacillus spp. in the gut microbiota of the same animals. We provide bulk RNA-Seq data of the distal part of the small intestine of high-fat diet-fed and metformin-treated C57BL/6N mice of both sexes with appropriate control arms. Experimental units/cages were organized in three blocks (one unit per each block), and animals were randomly divided into eight groups according to three different factors (sex, diet, and therapeutic intervention): (1) high-fat diet-fed (HFD-fed) male mice receiving metformin; (2) HFD-fed male mice with no metformin intervention; (3) HFD-fed female mice receiving metformin; (4) HFD-fed female mice with no metformin intervention; (5) control diet-fed (CD-fed) male mice receiving metformin; (6) CD-fed male mice with no metformin intervention; (7) CD-fed female mice receiving metformin; (8) CD-fed female mice with no metformin intervention. a type 2 diabetes mellitus (T2DM)-like phenotype was induced by HFD for 20 weeks. After week 20 metformin therapy was provided for randomly selected animals (half of both HFD-fed and CD-fed mice) with drinking water for 10 weeks in a concentration of 50 mg/kg body mass/day.