Comparison of the anti-diabetic effects of various grain and legume extracts in high-fat diet and streptozotocin-nicotinamide-induced diabetic rats

The anti-diabetic properties of whole groats and dietary fibers from various grains and legumes are well known. Nevertheless, studies on the anti-diabetic effects of their extracts are limited, and it is difficult to compare their efficacy. This study investigated the anti-diabetic potential of ethanol extracts from oats (OE), sorghum (SE), foxtail millet (FE), proso millet (PE), adzuki bean (AE), and black soybean (BE) in a high-fat diet and streptozotocin-nicotinamide-induced diabetic rat models. The extracts, obtained using 99.9 % ethanol, were orally administered to diabetic rats for four weeks. Various parameters were evaluated, including fasting blood glucose levels, glucose tolerance, insulin sensitivity, serum insulin levels, and pancreas histological analysis. OE and SE effectively reduced fasting blood glucose levels and the area under the curve (AUC) in the oral glucose tolerance test. Only OE significantly decreased the AUC in the insulin tolerance test and increased insulin concentration and homeostatic model assessment of the beta-cell function index, indicating improved insulin sensitivity and beta-cell function. Histological and immunohistochemical analysis of the pancreas supported these findings, demonstrating that OE protected against pancreatic cell damage. In contrast, FE, PE, AE, and BE did not have a significant effect on diabetes-related parameters. These findings identify OE as the most promising natural intervention for diabetes management.