Plasma leptin concentrations and energy expenditure in heart failure patients.

Leptin, the protein encoded by the obese gene, is a newly described hormone implicated in the regulation of energy balance. To examine the possible role of leptin in the energy dysregulation that frequently accompanies chronic heart failure, we examined plasma leptin concentrations and energy expenditure in 18 heart failure patients (aged 71 +/- 6 years) and 46 healthy elderly controls (66 +/- 6 years). Plasma leptin concentrations were measured by radioimmunoassay, daily energy expenditure by doubly labeled water, and body composition by dual-energy x-ray absorptiometry. Fat mass was lower (P < .01) in heart failure patients compared with healthy controls, whereas fat-free mass did not differ between groups. Plasma leptin concentrations were not different between heart failure patients and healthy controls (5.1 +/- 4.2 v 6.8 +/- 4.4 pg/mL) and remained similar after statistical control for fat mass (6.0 +/- 3.1 v 7.1 +/- 3.2 pg/mL). Plasma leptin was related to fat mass in heart failure patients (r = .92, P < .01) and healthy controls (r = .69, P < .01). Free-living daily and physical-activity energy expenditures were lower (P < .01) in heart failure patients compared with healthy controls. Plasma leptin concentrations were related to both daily (r = .67, P < .01) and resting (r = .67, P < .01) energy expenditure in heart failure patients, but not in healthy controls (r = .09 and r = .33, respectively). In conclusion, we found an association between plasma leptin concentrations and energy expenditure in heart failure patients, but not in healthy controls. Thus, leptin may participate in the regulation of energy expenditure and body energy stores in heart failure patients.