Unveiling the presence of epigenetic mark by Lactobacillus supplementation in high-fat diet-induced metabolic disorder in Sprague-Dawley rats.

Gut dysbiosis, particularly bacteria from Firmicutes and Bacteroidetes phyla, plays a fundamental role in the progression of metabolic disorders. Probiotics have shown to restore the gut microbiota composition in metabolic disorders with subsequent beneficial effects. Recent studies have reported that several species of Lactobacillus as probiotic supplementation improve insulin sensitivity and glucose metabolism. Nonetheless, whether Lactobacillus could influence the epigenetic modifications that underlie insulin-resistant conditions is still unexplored. Therefore, the current study examined the therapeutic effects and underlying epigenetic mechanisms of three different species of Lactobacillus in the high-fat diet (HFD)-induced insulin-resistant rats. Three different species of Lactobacillus; Lactobacillus casei, Lactobacillus gasseri, and Lactobacillus rhamnosus were individually supplemented orally (10 CFU/mL) to insulin-resistant SD rats for 12 weeks. Lactobacillus supplementation led to a significant reduction in the hyperglycemia, hyperinsulinemia, and hyperlipidemia associated with HFD-induced insulin resistance. Histopathological examination also indicated the protective effects of Lactobacillus supplementation against the hepatic and intestinal damage caused by the high-fat diet. Lactobacillus supplementation also down-regulated the expression of FOXO1, a major transcription factor of insulin signaling. In addition, at the epigenetic level, Lactobacillus supplementation predominantly prevented methylation and demethylation of H3K79me2 and H3K27me3, respectively. Chromatin Immunoprecipitation (ChIP) coupled with quantitative PCR (ChIP-qPCR) assay revealed the presence of cross-talk between these two histone modifications at the promoter region of FOXO1. Taken together, this is the first report to observe that the effects of Lactobacillus supplementation involve alteration in FOXO1 expression via cross-talking between H3K79me2 and H3K27me3 histone modifications.