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AA Fisher, SL Goh, W Srikusalankul, EN Southcott and MW Davis
The American Heart Hospital Journal Volume 7 No.1

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To evaluate whether there is a relationship between admission serum leptin concentrations and peri-operative myocardial injury, 238 consecutive older patients (mean age 81.9-7.9 years; 172 women) with low-trauma hip fracture were assessed. Myocardial injury as defined by elevated serum cardiac troponin I was associated with lower leptin levels analyzed as continuous or categorical variables. Patients with serum leptin concentrations < 12ng/ml (medium value) had a two-fold greater increased risk for such complications compared with those with higher leptin levels (odd ratio 2.13, 95% confidence interval 1.06-4.28; p=0.033).This association remained significant after adjustments for age, gender, clinical (history of coronary artery disease [CAD], stroke, hypertension, diabetes, dementia), hematological (red, white, and lymphocyte count, hemoglobin, hematocrit), metabolic (parathyroid hormone [PTH], albumin), renal (creatinine, urea, glomerular filtration rate [GFR]), and inflammatory (C-reactive protein [CRP], ferritin) factors.The predictive value of lower leptin levels increased significantly when used in combination with traditional risk factors for myocardial injury.

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Leptin, the product encoded by the obese (ob) gene, is a 16kDa non-glycosylated polypeptide synthesized mainly by white adipocyte but also by other cells.^1-4 It plays a fundamental role in regulation of bodyweight and energy balance. Leptin receptors are expressed in almost all cell types, and leptin, like other members of the long-chain helical cytokine family, has a wide spectrum of central and peripheral effects and participates in a variety of cardiovascular, endocrine, and immunological actions. It plays an important role in regulation of cardiomyocyte function and structure, angiogenesis, inflammation, insulin resistance, coagulation, platelet aggregation, fibinolysis, and bone remodeling.^2,3,5

Elevated circulating leptin levels have been found in a number of cardiovascular disorders, including obesityrelated metabolic syndrome,^6-8 as well as in coronary artery disease,^9-12 hypertension,^13,14 left ventricular hypertrophy,¹⁵ and heart failure,^16,17 independent of the presence of obesity. Hyperleptinemia has been associated with acute myocardial infarction and stroke independently of traditional cardiovascular risk factors and obesity status.^9,10,18,19,

Despite extensive studies, the cardiac effects of leptin are still not completely understood and contradictory findings have been reported. Data on the role of leptin in human cardiovascular morbidity and mortality are not consistent.^20-22 Some studies reported no association between elevated leptin levels and cardiovascular events,^22-24 or even a protective effect.^25-27 Cardiovascular complications are recognized as the main cause of morbidity and mortality in older patients undergoing hip fracture (HF) surgery.^28,29 We have shown that in this population peri-operative myocardial injury, defined as an elevated level of cardiac troponin I (cTnI), is common and associated with prolonged length of hospital stay, need to be discharged to a long-term (permanent) residential care facility, and mortality.³⁰ Given the global HF epidemic and its enormous medical and communal burden, understanding the predisposing and precipitating causes of this association is imperative.

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