Relation of Plasma leptin to lipoproteins in overweight children undergoing weight reduction

BACKGROUND: In obese children, plasma leptin is elevated and correlates wit h the body mass index (BMI), In obese adults, plasma leptin decreases durin g weight reduction. Since the leptin system changes dynamically in puberty, we asked whether weight reduction in obese adolescents has similar consequ ences for plasma leptin as in overweight adults. In plasma, a portion of le ptin is bound to several as yet uncharacterised proteins. We therefore stud ied the possible association of leptin with plasma lipoproteins. SUBJECTS AND METHODS: We measured plasma leptin, lipoprotein cholesterol an d apolipoproteins (apo) A-I and B in 34 obese children (age 12.5 +/- 1,9 y, relative BMI 165.0 +/- 28.1%) before and after three weeks of weight reduc tion in a dietary camp. Lipoprotein binding of endogenous and exogenously r adiolabelled leptin was studied by preparative ultracentrifugation. RESULTS: Plasma leptin was higher in obese children than in normal weight c ontrols and fell from 16.5 +/- 9.8 ng/ml to 10.0 +/- 8.6 ng/ml after weight reduction (P < 0.001). In multivariate regression, relative BMI and apoA-I were significant predictors of baseline leptin and accounted for 38% (P = 0.003) and 15% (P = 0.006) of the variance of baseline leptin concentration s in obese children. Only the difference in plasma high-density lipoprotein (HDL)-cholesterol independently predicted the change of plasma leptin that was associated with weight reduction, explaining 29% of the variance of le ptin changes (P= 0.0032). A substantial portion of both endogenous and exog enously labelled leptin was recovered with HDL isolated by ultracentrifugat ion. CONCLUSIONS: We conclude that plasma leptin decreases in overweight childre n undergoing short term weight reduction. In obese children, plasma apoA-I and HDL-cholesterol are independent predictors of leptin concentrations dur ing weight loss, respectively. In addition, HDLs transport a variable porti on of leptin in the circulation.