Date of Award

12-17-2023

Document Type

Dissertation

Abstract

Environmental factors and physical activity have the potential to modulate skeletal muscle physiology in beneficial ways. Cold exposure and endurance exercise, specifically, may improve aerobic capacity and atrophy resistance. I utilized three models to examine the effect of cold exposure and activity level on skeletal muscle physiology: quantitation of body composition and energy expenditure estimates in humans participating in a transmountain race, comparative proteomic analysis of skeletal muscle in hibernating and summer active American black bears (Ursus americanus), and an experimental study of the combined effects of cold exposure and endurance training on white adipose tissue, and gastrocnemius and soleus muscles in Sprague-Dawley rats. Body composition analysis of participants of the transmountain race revealed significant fat but not lean body mass loss despite significant caloric deficit. Proteomic analysis of American black bear skeletal muscle revealed an upregulation of glycolytic, inflammatory, immune response, and lipid transport proteins, and a decrease of lipid, and amino acid catabolism proteins during hibernation. Modulation of metabolism and the immune system during hibernation appears to mitigate skeletal muscle atrophy, despite prolonged inactivity and fasting. In Sprague-Dawley rats, cold or exercise alone have similar effects on body composition but exert unique effects on oxidative and glycolytic skeletal muscles that overall supports enhanced aerobic capacity. When combined, cold and exercise appear to improve oxygen diffusion via reduced cross-sectional area of some fiber types in oxidative skeletal muscle but have opposing effects in glycolytic muscles. In summary, skeletal muscle is highly plastic and perturbations such as cold, fasting, and endurance training result in cellular remodeling and changes in protein expression that improves aerobic capacity and conserves skeletal muscle mass across species.

Handle

http://hdl.handle.net/11122/14959

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