Dietary Intervention with Resistant Starch-Rich Unripe Plantain Flour Restores Gut Microbiome–Metabolome Axis and Ameliorates Type 2 Diabetes in Rats

Plantain (<i>Musa</i> spp., AAB group) possesses a complex triploid genetics originating from interspecific hybridization, which underlies its agronomic traits and nutritional composition, making it a vital global staple food crop. Unripe plantain flour (UPF), a rich source of resistant starch (RS), has demonstrated anti-diabetic properties in diabetic rats, yet its mechanisms of action remain unclear. This study investigated whether unripe plantain flour attenuates type 2 diabetic traits in rats made diabetic with a high-fat diet plus streptozotocin through regulation of the gut microbiome-metabolome axis, including short-chain fatty acids and bile acids. We found that UPF intervention significantly ameliorated gut microbiota dysbiosis. It enriched beneficial bacteria, particularly SCFA producers (<i>Lachnoclostridium</i>, <i>Blautia</i>, <i>Butyricicoccus</i>) and others (<i>Bifidobacterium</i>, <i>Akkermansia</i>), while inhibiting harmful genera (<i>Romboutsia</i>, <i>Allobaculum</i>). Consequently, UPF altered bile-acid composition by lowering hydrophobic species (e.g., cholic acid and deoxycholic acid) while elevating hydrophilic species (e.g., ursodeoxycholic acid and tauroursodeoxycholic acid). It also enhanced the excretion of secondary bile acids (lithocholic acid). These coordinated changes in the gut ecosystem are conducive to improved glycolipid metabolism. Spearman correlation analysis further reinforced the close relationships between the altered microbiota and metabolites. Our results elucidate that UPF exerts its anti-diabetic effects by remodeling the gut microbiota and modulating its associated metabolites, highlighting a novel dietary intervention strategy for diabetes management.