Inappropriately low plasma leptin concentration in the cachexia associated with chronic heart failure

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Abstract
BACKGROUND Cardiac cachexia is a syndrome of generalised wasting which caries a poor prognosis and is associated with raised plasma concentrations of tumour necrosis factor α (TNFα). TNFα increases secretion of leptin, a hormone which decreases food intake and increases energy expenditure. OBJECTIVE To determine whether an inappropriate increase in plasma leptin concentration contributes to the cachexia of chronic heart failure. DESIGN Retrospective case–control study. SETTING Tertiary referral cardiology unit. PATIENTS 110 human subjects comprising 29 cachectic chronic heart failure patients, 22 non-cachectic chronic heart failure patients, 33 patients with ischaemic heart disease but normal ventricular function, and 26 healthy controls. INTERVENTIONS Measurement of: body fat content by skinfold thickness (cachectic males < 27%, females < 29%); plasma leptin, TNFα, and noradrenaline (norepinephrine); central haemodynamics in chronic heart failure patients at right heart catheterisation. MAIN OUTCOME MEASURES Plasma leptin concentration corrected for body fat content, plasma TNFα and noradrenaline concentration, and central haemodynamics. RESULTS Mean (SEM) plasma leptin concentrations were: 6.2 (0.6) ng/ml (cachectic heart failure), 16.9 (3.6) ng/ml (non-cachectic heart failure), 16.8 (3.0) ng/ml (ischaemic heart disease), and 18.3 (3.5) ng/ml (control) (p < 0.001 for cachectic heart failure vall other groups). Plasma leptin concentration remained significantly lower in the cachectic heart failure group even after correcting for body fat content and in spite of significantly increased TNFα concentrations. Thus plasma leptin was inappropriately low in cachectic chronic heart failure in the face of a recognised stimulus to its secretion. There was no significant correlation between plasma leptin, New York Heart Association class, ejection fraction, or any haemodynamic indices. CONCLUSIONS Leptin does not contribute to the cachexia of chronic heart failure. One or more leptin suppressing mechanisms may operate in this syndrome—for example, the sympathetic nervous system.