Microbial–enzymatic co-fermentation enhanced the beneficial effects of highland barley bran on preventing metabolic disorders and gut microbiota dysbiosis induced by a high-fat diet in obese mice

Abstract

Highland barley bran (HBB) is rich in phenolic compounds, but they predominantly exist in bound forms, which severely affects their bioavailability and efficacy. This study aimed to investigate the effect of microbial–enzymatic co-fermentation on the release of phenolic compounds from HBB and the consequent anti-obesity effects. The results showed that the free phenolic acid contents of HBB were significantly increased by microbial–enzymatic co-fermentation. Moreover, compared with unfermented HBB, fermented highland barley bran (FB) could more effectively alleviate the high-fat diet-induced obese phenotype, dyslipidemia, glucose intolerance, and hepatic steatosis in mice. The mechanisms involved the downregulation of hepatic genes for cholesterol and lipid synthesis (SREBP-2, HMGCR, and FAS) and the upregulation of genes for fatty acid oxidation (CPT-1 and PPAR-α). Moreover, FB intervention reshaped the gut microbiota composition by increasing the relative abundances of beneficial bacteria (Dubosiella, norank_f_Muribaculaceae, Turicibacter, and Bifidobacterium) and reducing the relative abundances of harmful bacteria (norank_f_Lachnospiraceae and Colidextribacter). This study confirmed microbial–enzymatic co-fermentation to be an effective strategy to enhance the lipid-lowering activity of HBB, enabling a more potent health effect from reduced usage.