Short-Chain Inulin and Inulin Neoseries Oligosaccharides from Red Onions Enrich Beneficial Gut Taxa and Attenuate Obesity-Related Outcomes in a Rat Model

Prebiotic-mediated gut microbiota modulation is a promising approach for obesity management. Red onions have been identified as a potential source of inulin and inulin neoseries oligosaccharides. This study evaluated the in vivo effects of short-chain inulin and inulin neoseries oligosaccharides (SCIINOs) on the fecal microbiota of obese rats and assessed their potential role in obesity attenuation. Male Wistar rats were fed a high-fat diet (HFD) for 16 weeks to induce obesity, while control rats received a normal diet (ND). From weeks 16 to 24, HFD-fed obese rats were randomly assigned to four groups: SCIINOs at 0.5 g/day, SCIINOs at 1 g/day, atorvastatin (10 mg/kg/day), or no intervention. Obesity status was confirmed by increased body weight, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and higher food and energy intakes. SCIINOs were enzymatically hydrolyzed and purified by yeast treatment and chromatographic methods. After 8 weeks of SCIINO administration (1 g/day), the fecal microbiota was markedly enriched in Bifidobacterium and Allobaculum, whereas Blautia abundance significantly decreased. SCIINOs also increased taxa negatively associated with obesity-related parameters, including Dubosiella, Rothia, Parabacteroides, Eubacterium, and Coriobacteriaceae UCG-002, which correlated with reductions in body weight, triglycerides, TC, LDL-C, and fasting blood glucose, along with increased high-density lipoprotein cholesterol (HDL-C). In parallel, SCIINOs increased fecal acetate and butyrate levels, which was consistent with the enrichment of Bifidobacterium and butyrate-producing bacteria. Overall, SCIINOs derived from red onions show promise as a prebiotic candidate for obesity attenuation through selective microbiota modulation and enhanced short-chain fatty acid production.