This study was aimed at testing if rats with a high inherent aerobic capacity are protected from musculoskeletal degeneration in the presence of an obesogenic diet.
Thirty-five, 25-week old, N:NIH rats selectively bred for either high running capacity (HCR) or low running capacity (LCR) were used in this study. Animals were fed an HFS diet or a standard chow diet (CD) for 12 weeks, resulting in four experimental groups (HCR-CD; HCR-HFS; LCR-CD; LCR-HFS). Following 12 weeks on their respective diets, animals were sacrificed, and the Biceps Brachii (BB), Pectoralis Major (PM), Vastus lateralis (VL), and Soleus (Sol) muscles were harvested. Muscles were prepared for histological analysis, and 10 µm mid-belly muscle sections were used to determine the amount of fibrosis using Picro Sirius Red staining and the amount of fat infiltration using Oil Red-O staining. All tissue sections were imaged using an optical microscope and quantified using ImageJ software.
Exposure to the HFS diet resulted in a significant increase in muscle fibrosis in both the HCR and LCR group rats in the BB, with significantly lower fibrosis in the HCR than in the LCR group. The HFS diet resulted in an increase in fibrosis in VL of the LCR group rats. There was a significant increase in fat infiltration in VL and PM for the HCR and LCR group rats exposed to the HFS diet. There were no detectable differences in Sol fibrosis or fat infiltration between groups and diets.
Our study is the first to provide evidence that a high inherent running capacity is protective against fibrosis in a muscle-specific manner suggesting a somewhat systemic protective role of aerobic capacity against the development of musculoskeletal dysfunction in the presence of an obesogenic diet.
Our findings may have important and unexplored implications for the development of novel early prevention and rehabilitation strategies for people at risk of suffering from obesity and associated musculoskeletal degeneration. Physiotherapy education programs should emphasize the importance of increasing aerobic capacity from an early age to mitigate the impacts of obesity, should it potentially occur.
Aerobic capacity
Muscle health
