Natural food science based novel approach toward prevention and treatment of obesity and type 2 diabetes: Recent studies on brown rice and γ-oryzanol

SummaryThe prevalences of obesity and type 2 diabetes mellitus are dramatically increasing, and there is a strong need for more effective and safer therapies. However, some of drugs show limited efficacy and considerable adverse effects. Furthermore, artificial energy-dense foods and non-caloric foods may promote overeating and weight gain. In this context, a natural food-based approach may represent a valuable means of tackling the obesity–diabetes syndrome. Although recent studies have shown that brown rice improves glucose intolerance and prevents obesity and type 2 diabetes in humans, the underlying molecular mechanisms remain unclear. We found that one of the major components of brown rice, γ-oryzanol (Orz), plays an important role in the metabolically beneficial effects of brown rice. Orz acts as a chemical chaperone and decreases high fat diet (HFD)-induced endoplasmic reticulum (ER) stress in the hypothalamus, thereby leading to a significant shift in preference from fatty to healthy foods. Orz also decreases HFD-induced ER stress in pancreatic β-cells and improves β-cell function. Notably, Orz directly acts on pancreatic islets and enhances glucose-stimulated insulin secretion (GSIS). This evidence highlights food preference as a promising therapeutic target in obesity–diabetes syndrome and suggests that brown rice and Orz may have potential for the treatment of obesity and type 2 diabetes in humans.