Skeletal Muscle Composition and the Effects of Exercise and/or Prebiotic Fiber in Preventing Diet Related Morbidities

Background: We established a model of diet-induced obesity in Sprague-Dawley rats that produces, in addition to obesity, metabolic syndrome and musculoskeletal degeneration. Prebiotic fiber and aerobic exercise interventions have been shown to rescue bones and joints from degeneration, but it has yet to be shown if muscle degeneration can also be stopped with these interventions. Objectives: This study was aimed at determining if prebiotic fiber supplementation and/or aerobic exercise can prevent muscular alterations in our rat model of obesity. Methods: Using a high-fat/high-sucrose (HFS) diet-induced rat model of obesity, 12-week-old male Sprague-Dawley rats were randomly divided into sedentary (HFS, n = 12), exercise (HFS + E, n = 12), prebiotic fiber supplementation (HFS + F, n = 12), or combined intervention (HFS + F + E, n = 12) groups for 12 weeks, with eight chow-fed animals as controls. Muscle triglyceride levels were measured using colorimetric assays, collagen content was assessed histologically, and CD68 immunohistochemistry was performed on the vastus lateralis (VL) and soleus muscles. Group comparisons were conducted using the Kruskal-Wallis test and chi-squared effect statistics (χ2). Results: VL triglyceride (χ2 = 10.481, p = 0.033) and collagen content in both VL and soleus (χ2 = 23.148, p < 0.001 and χ2 = 34.166, p < 0.001 respectively) were higher in all HFS-diet intervention groups compared to the chow-fed Control group. Lean body mass did not differ among groups (χ2 = 3.9192, p = 0.417). The HFS group exhibited increased total cholesterol and triglyceride levels (χ2 = 11.693, p = 0.019; and χ2 = 21.663, p < 0.001 respectively) and starkly reduced whole-body insulin sensitivity (χ2 = 18.046, p = 0.001) compared to the Control or to the exercise and fiber supplementation groups. Conclusions: Despite the effectiveness of aerobic exercise and prebiotic fiber supplementation in preventing the systemic metabolic disturbances induced by the HFS diet, muscular alterations persisted. Prebiotic fiber supplementation led to the highest muscle collagen content, suggesting potential adaptative muscular response to the systemic insult caused by the HFS diet.