AB0045 EFFECTS OF AEROBIC EXERCISE AND PREBIOTIC FIBRE SUPPLEMENTATION ON THE VASTUS LATERALIS AND SOLEUS MUSCLES IN A RAT MODEL OF DIET-INDUCED OBESITY

Abstract

BackgroundA high-fat/high-sucrose (HFS) diet leads to osteoarthritis-like damage in the knee and shoulder (Collins et al., 2018), and to a low-level systemic inflammation that is accompanied by a decrease in insulin sensitivity. Recently, we demonstrated in a rat model, that when prebiotic fibre supplementation, aerobic exercise, or their combination is started at the onset of the HFS diet exposure, the development of the osteoarthritis-like lesions in the knee joints and the metabolic dysfunction is prevented (Rios et al., 2019).A central role in the altered metabolic state of rats fed a HFS diet is thought to be played by skeletal muscle (Collins et al., 2018). Besides the detrimental effect on metabolic and inflammatory regulation, muscular dysfunction might be a contributor to the decline in running endurance and coordination observed with prolonged exposure to a low quality diet (Clayton et al., 2022).ObjectivesTo evaluate the changes in insulin sensitivity and vastus lateralis and soleus muscle composition in a HFS diet rat model and determine whether the expected muscle alterations can be prevented with a prebiotic fibre supplementation, aerobic exercise, or their combination.MethodsTwelve-week-old male Sprague Dawley rats fed a high-fat/high-sucrose diet (HFS, Diet #102412, Dyets) were randomized into a sedentary (HFS, n=12), moderate aerobic exercise (HFS+E, n=12), prebiotic fibre supplementation (HFS+F, n=12), or moderate aerobic exercise combined with prebiotic fibre supplementation (HFS+F+E, n=12) group for 12 weeks. Eight chow-fed (Diet #5001) age- and sex-matched animals were used as controls.Whole body insulin sensitivity (composite insulin sensitivity index – CISI) was determined at the end of the intervention period and, after sacrifice, the VL and soleus muscle composition was evaluated through a triglyceride colorimetric assay and histological analysis of collagen with picrosirius red staining. Non-parametric Kruskal-Wallis testing with pairwise comparisons was used to compare groups.ResultsHFS group rats had less than half (40%, p = 0.001) of the whole-body insulin sensitivity of control rats while rats in the HFS+E, HFS+F and HFS+F+E groups were similar to control.Rats that were fed the HFS diet showed increased VL (p = 0.033) but not soleus (p = 0.644) triglycerides content compared to control (Figure 1 A). Both VL and soleus showed increased collagen content in the groups fed the HFS diet compared to the control group (p<0.001 for VL and soleus) (Figure 1 B). Moderate aerobic exercise, prebiotic fibre supplementation, or their combination did not prevent the observed alterations in muscle composition in the groups fed the HFS diet.ConclusionWhile a positive effect of prebiotic fibre and exercise in managing metabolic disturbance was present with a clear recovery of insulin sensitivity to control levels in the groups that were fed the HFS diet, the protective effect of exercise and prebiotic fibre that has been previously described for knee joints in this model was not observed for the VL and soleus muscles. The HFS diet led to alterations in muscle composition that seem to be muscle-specific and cannot be prevented by combining prebiotic fibre or exercise with the HFS diet.