COPPER DEFICIENCY SHIFTS ENERGY SUBSTRATE UTILIZATION FROM CARBOHYDRATE TO FAT AND REDUCES FAT MASS IN RATS

The influence of copper deficiency on energy metabolism and body compo sition was examined in rats. Weanling male Sprague-Dawley rats were as signed to two dietary treatments: copper-adequate (102.2 mu mol/kg) an d copper deficient (9.0 mu mol/kg). After 4 wk of treatment, rats were individually housed in metabolic cages within indirect calorimetry un its for measurements of respiratory quotient to determine sub strate u tilization. Body composition was measured by total body electrical con ductivity. Net energetic efficiency and fasting heat production were d etermined from regression analysis of metabolizable energy intake and energy retention (metabolizable energy intake-heat production). Rats w ere given free access to their respective diets for almost tile entire study but were restricted to 70% of normal energy intake for 2 d to p rovide a range of energy intake required for the regression analysis. Energetic evaluations were determined for 12 d at normal intake and 2 d at a modest restriction (30%). Copper deficiency reduced the respira tory quotient values (0.85 to 0.80), carbohydrate utilization (7.9 to 5.2 g/d), energy retention [8.4 to -66.9 kJ/kg(0.75).d)] energy effici ency (97.8 to 87.7%). However, daily metabolizable energy intake and a bsolute fasting heat production were not altered. Reductions in final body weights (289 to 263 g), absolute fat mass (65.7 to 51.5 g) and pr oportion of body fat (22.7 to 19.6 g/100 g) were observed in copper-de ficient rats compared with controls when all indirect calorimetry meas urements were completed after 7 wk of treatment. Thus, copper deficien cy increased utilization of fat as Substrate for energy and reduced bo dy fat mass in rats.