Leptin interacts with heart rate but not sympathetic nerve traffic in healthy male subjects

Objective Administration of leptin to animals increases sympathetic nerve a ctivity and heart rate. We therefore tested the hypothesis that plasma lept in is linked independently to muscle sympathetic nerve activity (MSNA) and heart rate in healthy humans. Methods We measured plasma leptin, plasma insulin, body mass index (BMI), p ercent body fat, waist:hip ratio, MSNA, heart rate and blood pressure in 88 healthy individuals (50 men and 38 women). Results In men, plasma leptin concentration correlated significantly with B MI (r= 0.75, P < 0.001), percent body fat (r= 0.70, P< 0.001), waist:hip ra tio (r= 0.69, P< 0.001), insulin (r= 0.37, P= 0.009), and age (r= 0.38, P= 0.006). Only BMI and waist:hip ratio were linked independently to plasma le ptin concentration (r= 0.78, P< 0.001), Plasma leptin concentrations also c orrelated with heart rate (r= 0.39, P= 0.006) and mean arterial pressure (M AP; r= 0.38, P= 0.007), but not with MSNA (r= 0.17, P= 0.24), After adjustm ent for BMI and waist:hip ratio, plasma leptin concentration correlated sig nificantly only with heart rate (r= 0.29, P= 0.04), and not with MAP (r= 0, 21, P= 0.14). Individuals were divided into high-leptin and low-leptin subg roups on the basis of plasma leptin concentrations adjusted for BMI and wai st:hip ratio. Those with high leptin concentrations had significantly faste r heart rates than those with low leptin, MAP and MSNA were similar in both subgroups. No relationship between leptin and either heart rate or MSNA wa s evident in women. Conclusions In normal men, heart rate, but not MSNA, is linked to plasma le ptin concentration. This sex-specific relationship between heart rate and p lasma leptin is independent of plasma insulin, BMI, waist:hip ratio and per centage body fat.