COMPONENTS OF ENERGY EXPENDITURE IN THE MDX MOUSE MODEL OF DUCHENNE MUSCULAR DYSTROPHY

Previous observations showing that basal heat production rates and glucose metabolism were reduced inmdx mouse skeletal muscles incubated in vitro led us to study the components of total energy expenditure by open-circuit indirect calorimetry in the intact, free-movingmdx mouse. Our purpose was to verify if themdx mouse exhibited whole-body alterations in energy metabolism. The results revealed that total and basal energy expenditure, as well as spontaneous activity, energetic cost of activity, and, therefore, energy expended in relation to activity were not significantly different in C57B1 / 10 (control) and in dystrophic (mdx) mice. In contrast, the thermic effect of food was 32% larger inmdx than in control mice and was accompanied by significant differences in postprandial glucose and lipid oxidation. The present in vivo study could not show a direct demonstration that impaired glucose metabolism by skeletal muscles participated in this phenomenon. However, since postprandial glucose metabolism by skeletal muscles contributes a significant part of the thermic effect of food, the present data are in line with previous studies in vitro that show thatmdx mouse skeletal muscles probably suffer an impaired control of their energy metabolism.