Autonomic nervous system-leptin interactions: Impact on metabolic rate and body weight regulation

Leptin is the peptide hormone product of the obese (ob) gene expressed predominantly in adipose tissue. Leptin has profound effects on the control of body weight, appetite, and energy balance. In studies of both obese and nonobese subjects, it has been shown that autonomic nervous system activity is also related to body weight regulation. The sympathetic nervous system is crucial in the regulation of lipolysis: sympathetic denervation leads to an increase in adipose tissue weight, while nerve stimulation results in fatty acid release and sympathetic blockade inhibits the mobilization of lipid. Recently, leptin has been shown to increase sympathetic nervous system activity. In fact, adipose tissues are innervated mostly by sympathetic fibers. Leptin gene expression and circulating leptin levels are affected by factors that either mimic or involve the sympathetic nervous system, such as catecholamines, fasting, cold, and exercise. Pulsatility and circadian variation in leptin could also be determined by changes in sympathetic nervous system activity. In the central nervous system, leptin seems to inhibit the pathways that stimulate food intake and promote weight gain, whereas it stimulates the pathways that promote anorexia and weight loss.