This study aims to investigate how Bifidobacterium breve BBr60 improves obesity-related metabolic disorders by modulating the gut microbiota-SCFAs axis, thereby affecting inflammatory factors and metabolic hormones. A randomized, double-blind, placebo-controlled trial was conducted. A total of 75 individuals with obesity subjects (BMI ≥ 28) were enrolled and randomly assigned to either the BBr60 intervention group (10 billion CFU daily) and the placebo group. After the 12-week intervention, 65 participants (BBr60: n = 33; placebo: n = 32) completed the study and were included in the primary analysis. All participants received standardized nutritional counseling aimed at a moderate energy intake (~ 1800 kcal/day, including a daily intake of 25 g of dietary fiber.). Every week, we call participants at a fixed time to inquire about their weekly diet and weight changes, and provide dietary suggestions for the following week based on the inquiry results. Participants were instructed to maintain their usual physical activity levels throughout the study. The composition of the gut microbiota was analyzed by 16 S sequencing, fecal SCFAs were detected by GC-MS, and serum levels of IL-27, IL-1β, and metabolic hormones were measured using ELISA technology. Metabolic indicators such as body weight, body fat percentage, and HOMA-IR were also assessed. The BBr60 intervention significantly increased fecal butyrate levels (p < 0.001), accompanied by a decrease in IL-1β levels (p < 0.05) and an upregulation of IL-27 (p < 0.01). In terms of metabolic hormones, leptin (LEP), adiponectin (ADPN), connecting peptide (C-P), pancreatic polypeptide (PP), peptide YY (PYY), Glucose-dependent insulinotropic polypeptide (GIP), and Glucagon-Like Peptide-1 (GLP-1) were all significantly elevated (p < 0.05), while Homeostasis Model Assessment for Insulin Resistance(HOMA-IR) was significantly reduced in the BBr60 group (p < 0.05). In the control group, C-P, PP, and GIP were significantly increased (p < 0.05), whereas LEP, ADPN, PYY, GLP-1, and HOMA-IR showed no difference before and after the 12-week period. Correlation analysis indicated that butyrate levels were significantly positively correlated with GLP-1 and IL-27, and negatively correlated with IL-1β. Bifidobacterium breve BBr60, by remodeling the gut microbiota-SCFAs axis, inhibits the pro-inflammatory factor IL-1β, activates the anti-inflammatory signal IL-27, and synergistically regulates the metabolic hormone network (such as GLP-1, ADPN), significantly improving obesity-related metabolic disorders. This study provides a theoretical basis and intervention targets for the clinical application of probiotics targeting the "microbiota-SCFAs-inflammation/hormone axis," and future research can explore precise probiotic treatment regimens based on individual microbiota characteristics.
