Preventive effect of fermented brown rice and rice bran on spontaneous type 1 diabetes in NOD female mice

[Display omitted] •Brown rice and rice bran fermented with A. oryzae (FBRA) is a processed food.•Dietary administration of 0.5% FBRA delayed the spontaneous onset of type 1 diabetes.•FBRA significantly reduced the insulitis score with 0.5% addition being the optimal.•The number and ratio of intact islets were maintained in 0.5% FBRA-treated NOD mice. Consumption of brown rice and rice bran fermented with Aspergillus oryzae (FBRA) suppresses spontaneously occurring diabetes in female NOD mouse. While control diet-fed mice showed glucosuria and hyperglycemia at around 20 week of age and the ratio reached to 57% at 30 weeks of age, the ratio did not increase in the 0.5% FBRA-containing diet-fed group. The FBRA-fed group at 30 weeks of age kept higher ratio of intact islets and showed significantly lower insulitis score compared to the control diet group, with dose-dependency from 0.25% to 0.5% dietary concentration of FBRA. The percentage of diabetic mice was significantly lower at 24 weeks of age as compared to the control group (p = 0.01, log rank test). These results indicate that the suppressive effects of dietary administration of 0.5% FBRA in delaying the spontaneous onset of diabetes in NOD mice is probably achieved by maintaining the number of intact islets.