Effects of highland barley β-glucan on blood glucose and gut microbiota in streptozotocin-induced, diabetic, C57BL/6 mice on a high-fat diet

•Highland barley β-glucan attenuated a high-fat diet and streptozotocin-induced obesity and lipid metabolism disorders in type-2 diabetic mice•Highland barley β-glucan improved hyperglycemia and insulin resistance in type-2 diabetic mice•Highland barley β-glucan changed the structure of gut microbiota•Gut microbiota was correlated with type-2 diabetic-related biochemical indicators This study aimed to investigate the hypoglycemic effect of highland barley β-glucan (HBG) on mice with type 2 diabetes (T2D), and determine whether the hypoglycemic effects are related to modulations of the gut microbiota. T2D was induced with a high-fat diet and streptozotocin in the mice. HBG was orally administered to mice with T2D for 4 wk, and biochemical indices were analyzed in the serum and liver. Fecal samples were collected and analyzed with high-throughput 16S ribosomal RNA sequencing. Intake of HBG for 4 wk suppressed the body weight, as well as liver and heart indices, and regulated the levels of fasting blood glucose, serum insulin, blood lipid, oxidative damage, and inflammatory reaction in mice with T2D. Furthermore, HBG reversed the gut microbiota dysbiosis in mice with T2D by increasing the abundance of Lachnospiraceae_UCG-006, Streptococcaceae, and Eggerthellaceae, and by decreasing the abundance of Parasutterella. Our findings indicate that the antidiabetic abilities of HBG might be related to the improvement of gut microbiota imbalance.