Effect of blended grains with different processing treatments on the anti-diabetic activity in type 2 diabetic rats

Abstract

Several studies confirmed that grain intake is associated with preventing type 2 diabetes mellitus (T2DM). However, the studies that examined the diabetes amelioration effect of whole grains with different processing treatments are limited. Here, we investigated the anti-diabetic effects of non-processed (raw), roasted, and extruded-puffed blended grains (BG) supplementation on 45 kcal% high-fat diet (HFD) to streptozotocin-nicotinamide (STZ-NA) induced diabetic rats for six weeks. BG was a blend of oat, sorghum, adzuki bean, finger millet, and proso millet in a ratio selected through preliminary research. A group of normal rats fed a standard diet (NC) and diabetic rats were assigned to four dietary groups: HFD (MC), HFD with 40% non-processed BG (NBG), roasted BG (RBG), and extruded-puffed BG (EPBG). As a result, no significant differences were exhibited after NBG, RBG, and EPBG administration in body weight, while the fasting blood glucose levels (FBG) were remarkably decreased in EPBG (p < 0.05). Moreover, we demonstrated EPBG remarkably improved glucose tolerance measured by oral glucose tolerance test (OGTT) and insulin resistance assessed with insulin tolerance test (ITT) compared with MC (p < 0.05). Glycosylated hemoglobin (HbA1c) levels were lower in NBG, RBG, and EPBG than in MC, and in particular, EPBG significantly decreased HbA1c levels compared to NBG and RBG (p < 0.05). NBG, RBG, and EPBG showed no significant differences in serum total cholesterol (TC), triglycerides (TG), high-density lipoprotein (HDL), and low-density lipoprotein (LDL) compared to MC. EPBG improved degenerative pathological changes in the liver and pancreas and increased insulin immunoreactivities in pancreatic β-cells. In addition, EPBG dramatically down-regulated hepatic mRNA expressions of phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) related to gluconeogenesis (p < 0.05). Taken together, EPBG mostly attenuates hyperglycemia, suggesting the potential of extruded-puffed BG as a new functional food rather than raw or roasted BG for T2DM management.