Serum Leptin Levels in Children with Obesity

ABSTRACT

PURPOSE: The identification of the ob gene and its adipocyte-specific protein leptin has provided the first physiologic links to the regulatory system controlling body weight. In adults, elevations of serum leptin concentrations correlated closely with the percentage of body fat. This study investigated whether leptin concentrations were elevated in obese children, and the relationship between leptin concentrations and gender and pubertal stage. METHODS: The obese group was composed of 84 children (56 boys and 28 girls) with mean age 9.9 +/- 1.7 years. All obese children had an obesity index greater than 20. Twenty-five normal children (19 boys and 6 girls) with mean age 9.5 +/- 3.1 years constituted the control group. All in children of the control group had an obesity index less than 20. We measured height, weight, blood pressure, midarm circumference, triceps skinfold thickness, waist and hip circumference in all subjects. Body mass index (BMI) was calculated by weight in kilograms divided by the square of height in meters. Arm fat was calculated from the measured midarm circumference and triceps skinfold thickness according to the formulas provided by Must et al. We measured serum AST/ ALT, total cholesterol, HDL-cholesterol, LDL-cholesterol and triglyceride concentrations in all subjects. Radioimmunoassay for serum leptin was performed on a blood sample collected from each child after an overnight fast. RESULTS: The mean serum concentration of leptin in the obese group (14.5 +/- 7.0ng/ml) was significantly higher than that in the control group (4.7 +/- 3.1ng/ml)(P<0.05). Serum leptin concentrations significantly correlated with obesity index (r=0.54), BMI (r=0.50), and arm fat (r=0.46)(P<0.05). Girls had significantly higher leptin level than boys (P<0.05). Tanner stage had no effect on leptin concentration. CONCLUSION: As in adults, obese children have high concentrations of serum leptin, which highly correlates with obesity index, arm fat and BMI. Increased adipose tissue in children is associated directly with serum leptin concentration. Compared to boys, girls had higher leptin concentrations.