Abstract: BACKGROUND: Recent studies have shown that exercise modulates gut microbiota and glucose metabolism; however, the mechanism linking exercise to gut microbiota and short-chain fatty acid production in type 2 diabetes remains unclear.
OBJECTIVE: To investigate the mechanism by which exercise modulates gut microbiota composition and short-chain fatty acid metabolism to treat type 2 diabetes.
METHODS: Twenty male Sprague-Dawley rats were randomly divided into a control group (n=6) and a model group (n=14). The rats in the model group were fed a high-sugar, high-fat diet for 8 weeks to induce insulin resistance. Following 12 hours of fasting (water allowed), rats received a tail vein injection of 1% streptozotocin solution (35 mg/kg) to damage pancreatic β-cells and elevate blood glucose, establishing type 2 diabetes models. Following successful modeling, feeding protocols remained unchanged. Twelve type 2 diabetes rats were divided into a model group (n=6) and an exercise group (n=6), and the exercise group were subjected to 12 weeks of aerobic exercise. Following the final aerobic exercise, blood samples were collected for glycemic parameter analysis, and fresh fecal samples were obtained for short-chain fatty acid determination using gas chromatography-mass spectrometry. Total microbial DNA was extracted from fresh feces for PCR amplification and purification, followed by high-throughput sequencing using the NovaSeq platform to obtain raw sequence data. Species annotation was performed using the SILVA database. Differential microbiota were screened based on effect sizes from linear discriminant analysis. MetaCyc functional pathways were used to explore associations between exercise intervention and pathways related to glucose and lipid metabolism. Correlations between key microbiota and biochemical indicators were analyzed using heatmaps and visual network diagrams.
RESULTS AND CONCLUSION: (1) After 12 weeks of aerobic exercise, glucose and lipid metabolism disorders were significantly improved, inflammatory response was significantly reduced, insulin sensitivity was significantly reduced, and fasting blood glucose significantly decreased rats in the exercise group (P < 0.01). (2) α-Diversity analysis showed that gut microbiota richness (Chao index), coverage (Coverage index), diversity (Shannon index), and evenness (Simpson index) were significantly enhanced in the exercise group compared with the model group (P < 0.05). (3) Abundance charts, correlation heatmaps, and network visualization analyses showed that the abundance of short-chain fatty acids produced in the Firmicutes was significantly increased in the exercise group, such as Colidextribacter and Intestinimonas, which showed strong positive correlations with the levels of short-chain fatty acids, such as hexanoic acid and valeric acid, while simultaneously suppressing the production of pathogenic bacteria within the phylum Proteobacteria, such as Klebsiella and Turicibacter, which showed negative correlations with short-chain fatty acid levels. Lactobacillus promotes short-chain fatty acid production (e.g., butyric acid) and negatively correlates with glycolipid metabolism, inflammatory markers, fasting blood glucose, and interleukin-6 (P < 0.05). (4) Metabolic function predictions based on KEGG and MetaCyc reveal that aerobic exercise reshapes energy homeostasis by bidirectionally regulating microbial metabolic pathways. Exercise significantly downregulates pathways associated with excessive glycogenolysis and lipolysis as well as pro-inflammatory metabolism, while simultaneously upregulating key short-chain fatty acid synthesis pathways and glycolytic homeostasis pathways. This functional remodeling highly correlates with the restoration of short-chain fatty acid-producing Firmicutes abundance and the suppression of pathogenic Proteobacteria (P < 0.05). (5) These findings suggest a closed-loop regulation where the dynamic balance of gut microbial metabolic pathways interacts with improved host glucose and lipid metabolism and reduced inflammatory markers, indicating that gut microbiota, short-chain fatty acid synthesis, and metabolic function remodeling constitute the core mechanisms by which exercise ameliorates the pathological progression of diabetes.

Key words: PICRUSt2, 16S rDNA sequencing, gut microbiota, short-chain fatty acids, aerobic exercise, type 2 diabetes, glycolipid metabolism, inflammation