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Relationship between Serum Leptin Concentration and Low-Density Muscle in Postmenopausal Women

University of Alabama at Birmingham (UAB), Department of Nutrition Sciences, Division of Physiology and Metabolism, and UAB Clinical Nutrition Research Center, Birmingham, Alabama 35294-3360

Address all correspondence and requests for reprints to: Barbara A. Gower, University of Alabama at Birmingham, Department of Nutrition Sciences, 427 Webb Building, 1675 University Boulevard, Birmingham, Alabama 35294-3360. E-mail: bgower{at}uab.edu.

The accretion of fat within skeletal muscle has been associated with metabolic abnormalities. Leptin increases muscle fatty acid oxidation and triglyceride hydrolysis. Therefore, leptin concentrations may affect muscle fat content. The objective of this study was to determine if serum leptin concentrations were associated with im lipid content, as reflected in the mid-thigh low-density skeletal muscle area (LDMA). In addition, we evaluated whether hormone replacement therapy (HRT) or ethnicity affected this relationship. Our study population consisted of 80 postmenopausal women aged 45–55 yr, (72 Caucasian and 8 African-American). Both HRT users (n = 50) and nonusers (n = 30) were recruited. Total fat mass was estimated using total body dual-energy x-ray absorptiometry. Fat and muscle areas at the mid-thigh were measured using computed tomography scanning. Results showed that, after adjusting for total fat mass, higher-density muscle area, and ethnicity, higher serum leptin concentration was associated with lower LDMA (P < 0.05). African-American women had greater LDMA than Caucasian women, after controlling for leptin concentration (P < 0.05). Use of HRT did not significantly influence LDMA. These results support the hypothesis that leptin decreases skeletal muscle lipid content, promoting lipid oxidation.

This work is supported by Grant K01-AG-00740 from National Institute on Aging, GCRC Grant M01-RR-00032, and Clinical Nutrition Research Unit Grant P30-DK-56336.

Abbreviations: AMPK, AMP-activated protein kinase; CT, computed tomography; HRT, hormone replacement therapy; IML, intramyocellular lipid; LDMA, low-density skeletal muscle area; TG, triglyceride.