Effect of the Substitution of High-Fat Diet by Instant Rice with Added Coarse Grain on Glucose and Lipid Metabolism in Mice with Type 2 Diabetes Mellitus

Instant rice with added coarse grain (IR/CG) is a new type of coarse grain product which is self-heating and convenient to eat and has the nutritional value of coarse grains. However, its health effects are not clear yet. Therefore, in this study, the effect of IR/CG on glucose and lipid metabolism was explored in mice with type 2 diabetes mellitus (T2DM) induced by high fat diet (HFD) combined with intraperitoneal injection of streptozotocin. The mice were fed on HFD alone (model), its mixture with IR/CG in different ratios: 25% (low-dose IR/CG, IR/CG-L), 50% (medium-dose IR/CG, IR/CG-M), and 75% (high-dose IR/CG, IR/CG-H), IR/CG alone, or a basal diet (control). During the dietary intervention, the body mass, fasting blood glucose, food intake and glucose tolerance of the mice were measured. After the IR/CG intervention for four weeks, the organ coefficients were calculated, and the pathological changes in liver and pancreas tissues were examined by hematoxylin and eosin (HE) staining. Fasting insulin levels, blood glucose and lipid levels, and proinflammatory cytokines levels were determined. The experimental results showed that dietary supplementation of IR/CG improved blood glucose and lipid levels in T2DM mice to different extents, and this effect was more prominent in the IR/CG-H and IR/CG groups. In addition, IR/CG-H and IR/CG significantly mitigated insulin resistance, decreased insulin secretion, glucagon and HbA1c levels, and reduced oxidative stress injury and inflammatory cytokine levels in T2DM mice. By analyzing the organ index and pathological sections of liver and pancreas tissues, it was found that IR/CG intervention could effectively alleviate liver steatosis and partially restore the structure of the pancreatic islets in mice. Therefore, the substitution of high-fat diet by IR/CG has a significant effect on regulating blood glucose and lipids in T2DM mice, which can provide a theoretical basis for the development of self-heating rice products and functional foods with coarse-grain.