Exercise intensity–dependent metabolic adaptations in streptozotocin-induced diabetic rats: modulatory effects of apple cider vinegar on inflammatory and endocrine biomarkers

Background Diabetes mellitus is characterized by metabolic dysregulation and chronic inflammation, leading to impaired hormonal and biochemical homeostasis. Both exercise and nutritional interventions, such as apple cider vinegar (ACV), have been suggested as potential strategies to improve metabolic and inflammatory responses in diabetic conditions. However, the combined effects of ACV and different exercise intensities remain unclear. Objective The present study aimed to evaluate the effects of apple cider vinegar supplementation, alone and in combination with different exercise intensities, on metabolic and inflammatory biomarkers, as well as adiponectin, betatrophin, and irisin levels in streptozotocin-induced diabetic rats. Methods A total of 80 rats were randomly assigned into 10 groups (n = 8 per group), including control, sham, diabetes, diabetes+supplementation, diabetes+low-, moderate-, and high-intensity treadmill exercise, and diabetes+supplementation combined with low-, moderate-, and high-intensity exercise. Diabetes was induced using streptozotocin, and ACV was administered via oral gavage. Following a one-week adaptation period, exercise groups performed treadmill training at different intensities for 4 weeks. Following euthanasia by decapitation, blood samples were collected from the jugular vein and analyzed using ELISA. Statistical analyses were conducted using paired samples t-tests for within-group comparisons and one-way ANOVA with Tukey’s post hoc test for between-group comparisons. Results Diabetic rats showed significant impairments in adiponectin, betatrophin, irisin, IL-1β, IL-6, TNF-α, AST, ALT, and insulin levels compared to controls. ACV supplementation alone significantly improved several biomarkers, including betatrophin, IL-6, TNF-α, AST, ALT, and insulin. Exercise interventions also led to significant improvements, with low- and moderate-intensity exercise demonstrating greater benefits than high-intensity exercise. Moreover, the combination of ACV and low-intensity exercise was associated with the most favorable biomarker profile across multiple metabolic and inflammatory markers. Conclusion In this STZ-induced rat model, ACV supplementation and low-to-moderate intensity exercise modulate metabolic and inflammatory biomarkers more effectively than higher-intensity protocols. Whether these findings translate to clinical settings requires confirmation in human studies; no synergistic effects or therapeutic recommendations can be concluded without formal interaction testing and clinical validation.