Rice-Flour-Based Diet Is Associated with Reduced Obesity-Related and Glucose-Related Outcomes and Increased Ucp3 Expression in KK-Ay Mice

This study investigates whether, in a mouse model under ad libitum feeding conditions, substituting a wheat-flour-based diet with a rice-flour-based diet influences body-weight- and glucose-related outcomes. Using female KK-Ay mice, we compared diets containing wheat or rice flour. After seven weeks, the rice-flour-based diet was associated with significantly lower body weight (8.5% lower) and improved glucose tolerance compared with the wheat-flour-based diet; however, no significant improvement in insulin sensitivity was observed. Gene expression analysis revealed that Ucp3 mRNA expression in skeletal muscle was significantly higher in the rice-flour-based diet group than in the wheat-flour-based diet group, whereas no significant differences were observed in the expression of genes encoding enzymes involved in pyruvate oxidation and the TCA cycle. These results suggest that the lower body weight and improved glucose tolerance observed in the rice-flour-based diet group may be associated with increased skeletal muscle Ucp3 mRNA expression; however, whether this increase reflects altered UCP3 protein activity or energy expenditure remains unclear and requires further functional validation. Overall, substituting the wheat-flour-based diet with the rice-flour-based diet was associated with lower body weight and improved glucose tolerance in this model.