Blueberry Supplementation Influences the Gut Microbiota, Inflammation, and Insulin Resistance in High-Fat-Diet-Fed Rats

Background: Gut microbiota dysbiosis has been linked to obesity-associated chronic inflammation. Microbiota manipulation may therefore affect obesity-related comorbidities. Blueberries are rich in anthocyanins, which have anti-inflammatory properties and may alter the gut microbiota. Objective: We hypothesized that blueberry supplementation would alter the gut microbiota, reduce systemic inflammation, and improve insulin resistance in high-fat (HF)-diet-fed rats. Methods: Twenty-four male Wistar rats (260-270 g; n = 8/group) were fed low-fat (LF; 10% fat), HF (45% fat), or HF with 10% by weight blueberry powder (HF_BB) diets for 8 wk. LF rats were fed ad libitum, whereas HF and HF_BB rats were pair-fed with diets matched for fiber and sugar contents. Glucose tolerance, microbiota composition (16S ribosomal RNA sequencing), intestinal integrity [villus height, gene expression of mucin 2 (Muc2) and beta-defensin 2 (Defb2)], and inflammation (gene expression of proinflammatory cytokines) were assessed. Results: Blueberry altered microbiota composition with an increase in Gammaproteobacteria abundance (P < 0.001) compared with LF and HF rats. HF feeding led to an similar to 15% decrease in ileal villus height compared with LF rats (P < 0.05), which was restored by blueberry supplementation. Ileal gene expression of Muc2 was similar to 150% higher in HF_BB rats compared with HF rats (P < 0.05), with expression in the LF group not being different from that in either the HF or HF_BB groups. Tumor necrosis factor alpha (Tnfa) and interleukin 1 beta (Il1b) gene expression in visceral fat was increased by HF feeding when compared with the LF group (by 300% and 500%, respectively; P < 0.05) and normalized by blueberry supplementation. Finally, blueberry improved markers of insulin sensitivity. Hepatic insulin receptor substrate 1 (IRS1) phosphorylation at serine 307: IRS1 ratio was similar to 35% higher in HF rats compared with LF rats (P < 0.05) and HF_BB rats. Conclusion: In HF-diet-fed male rats, blueberry supplementation led to compositional changes in the gut microbiota associated with improvements in systemic inflammation and insulin signaling.