High serum leptin levels in children with type 1 diabetes mellitus: contribution of age, BMI, pubertal development and metabolic status

OBJECTIVE Children with diabetes mellitus are prone to develop obesity and to experience a delay in onset of the pubertal process. In order to underst and the role of leptin in these abnormalities, serum leptin levels were ana lysed in children with type 1 diabetes mellitus. SUBJECTS Twenty diabetic girls, 23 diabetic boys and 66 healthy children (s elected from a reference population of 706 normal children), age-, sex- and BMI-matched with diabetic patients, were studied. MEASURMENTS Standing height, weight and BMI were determined in each child. Serum testosterone, oestradiol and leptin were measured by specific radioim munoassays, and HBA1c by high performance liquid chromatography. RESULTS Both diabetic girls and boys showed higher leptin levels than the n ormative healthy population and a group of age-, sex- and BMI-matched norma l children. In an age-related analysis, leptin levels in diabetic girls ros e from 7 .4 +/- 2 and 8.1 +/- 2.1 mu g/l for the 5-7.99 and 8-10.99 year gr oups, to 12.6 +/- 2.4 mu g/l for the 11-13.99 year group, and to 12.6 +/- 4 .0 mu g/l in the 14-15.99 year group in parallel with body weight. Leptin c oncentrations were parallel but higher (P<0.05) than those of healthy girls . Diabetic boys had lower leptin levels than girls and, in contrast with no rmal boys, did not show a drop after the 10-year period. Leptin levels were 4.9+/-2.2, 3.9 +/- 0.2, 5.5 +/- 0.6 and 5.1 +/- 0.9 mu g/l for the 5-7.99, 8-10.99, 11-13.99 and 14-15.99 year groups, respectively. When divided by pubertal stage, leptin levels in the prepuberty stage of diabetic girls (8. 6 +/- 1.0 mu g/l) were higher (P < 0.05) than those in the controls (4.1 +/ - 0.4 mu g/l). In overt puberty girls, leptin was higher (P < 0.05) for dia betic (15.9 +/- 2.9 mu g/l) than for healthy girls (9.2 +/- 1.1 mu g/l). In prepubertal boys, differences were observed in leptin levels (4.9 +/- 0.5 mu g/l for diabetic boys and 3.4 +/- 0.6 mu g/l for healthy boys). in the o vert puberty stage, diabetic boys showed higher (P < 0.05) levels of leptin (5.2 +/- 0.7 mu g/l) than the healthy matched controls (2.1 +/- 0.2 mu g/l ). A multiple step regression analysis in the diabetic children revealed no associations between leptin and other relevant variables such as glycosyla ted haemoglobin, daily insulin dose, or years of suffering from the disease . CONCLUSION Serum leptin levels were higher in diabetic than in healthy chil dren. These differences were not attributable to age, adiposity or stage of pubertal development, and were probably conditioned by the metabolic pertu rbation intrinsic to the diabetic state, or the chronic hyperinsulinemia.