Central resetting of body weight control and decrease of body fat induced by exercise in rats.

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Dynamic exercise modifies energy metabolism and autonomic functions. It is well established decrease in body weight due to the exercise is due to not only the increase in energy expenditure but also the changes central regulation of energy metabolism. However, mechanisms underling the modification of control of energy metabolism is not known. The purpose of the present experiments is to study the mechanisms of central resetting of the set point of energy balance induced by exercise. Following three series of experiments were performed to achieve this aim.Oxygen consumption, respiratory quotient and renal sympathetic nerve activity were measured before, during and after 30min treadmill exercise in rats. Respiratory quotient and renal sympathetic nerve activity decrease in sustained fashion over 2hrs after cessation of the exercise. This data indicate that the sympathetic nervous system involves in regulation of ratio of nutrient utilization for energy production.The glucoprivation incluced by 2-deoxy-D-glucose (2-DG) results in an increase in relative utilization of lipid for energy production. The sympathetic nerve activity measured by renal nerve suppressed in a sustained manner due to the 2-DG administration. These data suggest that the autonomic nervous system may involve in regulating the relative utilization of lipid and carbohydrate for energy production during glucoprivation in conscious rats.Beta-endorphin (0.5 and 1.0nmol) in saline solution was injected into the lateral cerbroventricular space in conscious rats. The injection of beta-endorphin increased renal sympathetic nerve activity by 75% at 70min in 1 nmol group and 70% in 0.5nmol group. Renal sympathetic nerve activity and systemic arterial pressure increases in similar manner of the increase in oxygen consumption. These results suggest that central activation of sympathetic nervous system may involve in regulating energy metabolism in rats.