Heat-treated brown rice starch structure and effect on short-chain fatty acids and mouse intestinal microbiota

Rice with high resistant starch (RS) exhibits the potential to improve glucose metabolism, insulin sensitivity. In this study, using two rice varieties-Samgwang, a medium-amylose rice, and Dodamssal, a high-amylose rice containing RS-we analyzed the composition and molecular structural characteristics of brown rice and its starch and the effects on fasting blood glucose levels, fecal short-chain fatty acid (SCFA), and gut microbiota after 8 weeks of consumption in mice. The amylose content of heat-treated Samgwang (HS) and -Dodamssal (HD) was 21.0 ± 0.2 and 47.5 ± 0.3 %, respectively, while RS contents were 0.8 ± 0.0 and 14.7 ± 1.0 %. HD exhibited a C-type starch crystallinity with a lower proportion of short chains and a higher proportion of long chains compared to HS. HD-fed mice exhibited lower fasting blood glucose levels and the highest SCFA levels in their feces. They also had the highest abundance of Ruminococcus bromii, an RS-degrading bacterium, the highest positive correlation with Faecalicatena fissicatena (r = 0.9), and the highest negative correlation with Lachnoclostridium scindens and Lawsonibacter asaccharolyticus (r = -0.8). Overall, HD consumption can improve glucose metabolism by increasing intestinal SCFA production and can serve as a prebiotic dietary ingredient to improve obesity and diabetes.