Brown rice‐specific γ‐oryzanol as a promising prophylactic avenue to protect against diabetes mellitus and obesity in humans

Abstract

Chronic overconsumption of animal fats causes a variety of health problems, including diabetes mellitus and obesity. Underlying molecular mechanisms encompass leptin resistance, a decrease in rewarding effects of physical activities, xanthine oxidase-induced oxidative stress in vasculature and peripheral tissue, impaired activation of incretin signaling, deviation in food preference, and dysbiosis of gut microbiota. Based on our clinical observation that daily intake of brown rice effectively ameliorates bodyweight gain, impaired glucose tolerance/insulin resistance and dependence on fatty foods in obese, prediabetes men, a line of research on brown rice (rice bran)-derived γ-oryzanol in mice experiments, cultured cells and human clinical trials is underway in our laboratory. Our works in mice showed that γ-oryzanol, an ester mixture of ferulic acid and several kinds of phytosterols, acts as a molecular chaperone, thereby attenuating the strong preference for animal fats through suppression of endoplasmic reticulum stress in the hypothalamus. In pancreatic islets from both high-fat diet-induced and streptozotocin-induced diabetic mice, γ-oryzanol ameliorates endoplasmic reticulum stress and protects β-cells against apoptosis. Noticeably, γ-oryzanol also acts as a potent inhibitor against deoxyribonucleic acid methyltransferases in the brain reward system (striatum) in mice, thereby attenuating, at least partly, the preference for a high-fat diet through the epigenetic modulation of striatal dopamine D2 receptor. Because dopamine D2 receptor signaling in the brain reward system is considerably attenuated in obese humans and rodents, γ-oryzanol might represent a unique property to ameliorate both hedonic and metabolic dysregulation of feeding behavior, highlighting a promising prophylactic avenue to protect against metabolic derangement.

Brown Rice Versus White Rice: Nutritional Quality, Potential Health Benefits, Development of Food Products, and Preservation Technologies

“…Mice and cellular experiments have revealed that BR specific γ‐oryzanol acts as a molecular chaperone, ameliorates reticulum stress in hypothalamus, protects β‐cells against apoptosis, and inhibits DNA methyltransferases in brain reward system. Therefore, partly attenuating the high‐fat‐diet preference via the epigenetic modulation of striatal dopamine D2 receptor, improves fuel dyshomeostasis, and improves insulin resistance (Kozuka et al., , ; Masuzaki et al., ). The germination was also found to enhance antidiabetic potential of BR.…”

“…The concentration of these nutrients and bioactive compounds may vary depending on influences such as rice variety, production environment or geographical origin, and postharvest treatments or processing conditions. The whole BR grain, germinated BR grain (GBR), or their derived extracts and fractions have shown several potential health benefits such as antioxidant, antidiabetic, anticancer, neuroprotective, and cholesterol lowering effects (Chompoopong et al., ; Chung, Rico, Lee, & Kang, ; Li, Chou, & Shih, ; Lim, Yong, Mohtarrudin, & Loh, ; Masuzaki et al., ; Pang et al., ). Therefore, the objective of this work is to review the last updates in research performed for purposes of evaluating of nutritional quality and potential health benefits of the whole BR to provide recent information to interested researchers and consumers, which may help in promotion of the whole BR consumption as a promising functional food and for its potential contribution to human well‐being.…”

Factors Related to Change Staple Foods in “GENKI Study 2” Population

“…diabetes [3], and obesity [4][5][6][7], and some interventional studies for Type 2 diabetes [9][10][11]. It has been reported that brown ricederived γ-oryzanol can act on the brain reward system [18]. The system is related to satisfaction of the meals, and it is attenuated in obese humans.…”

A rice mutant with a giant embryo has increased levels of lipophilic antioxidants, E vitamers, and γ‐oryzanol fraction

“…This fraction in rice bran oil and extracts is associated with cholesterol lowering properties (Cicero & Gaddi, 2001). Furthermore, in animal models, γ-oryzanol was shown to reduce preference in obese mice for choosing high animal fat food, thus having the potential to decrease the risk of obesity (Masuzaki et al, 2019). It was also shown to protect β-cells of the pancreatic islets against apoptosis, therefore having protection against developing diabetes mellitus (Masuzaki et al, 2019).…”