Plasma Leptin in Children: Relationship to Puberty, Gender, Body Composition, Fat Oxidation, and Insulin Sensitivity † 368

Leptin has been demonstrated to reflect body fat mass (FM) in humans, but the regulation of leptin levels during childhood growth and development is poorly understood. We therefore studied the relation between plasma leptin, fasting insulin, insulin sensitivity and substrate oxidation in twenty-two prepubertal (Tanner I) (age: 10.5±0.2 yrs) and 27 pubertal (Tanner II-IV) (age: 13.5±0.2yrs) healthy subjects. Body composition was assessed by H₂¹⁸O dilution principle, insulin sensitivity by a hyperinsulinemic (40 mu/m²/min)-euglycemic clamp, substrate oxidation by indirect calorimetry, and leptin by RIA. Table Plasma leptin correlated with FM (r=0.77, p<0.001) and% body fat (r=0.66, p<0.001). There were no gender differences in leptin after controlling for FM differences. In prepubertal and pubertal subjects plasma Leptin correlated with fasting insulin independently of FM (r=0.60, p=0.001), but did not correlate with insulin sensitivity independently of body fat content. In a multiple regression analysis plasma leptin was the major determinant of postabsorptive fat oxidation (r=-0.55, p=0.017). We therefore conclude that in normal children 1) plasma leptin reflects body fat content, 2) leptin concentrations do not vary with puberty independent of adiposity, 3) there are no gender differences in leptin independent of adiposity, 4) leptin correlates with fasting insulin but not insulin sensitivity, 5) leptin may play a role in preserving fat stores through a peripheral mechanism of decreasing fat oxidation during childhood growth and development.

Table 1