Leptin serum levels in normal weight and obese children and adolescents: relationship with age, sex, pubertal development, body mass index and insulin

Abstract

OBJECTIVE: Leptin, the product of the ob gene, is present in higher concentrations in blood of obese subjects than of lean subjects. There is scarce information on the role of leptin in the pathogenesis of human obesity and little is known about leptin serum levels in obese children. DESIGN, SUBJECTS AND MEASUREMENTS: To evaluate the in¯uences of age, sex, pubertal development and weight excess on serum leptin levels, we have studied 390 obese subjects (OS) and 320 normal weight subjects (NWS) aged 5±16 y. Fasting insulin concentrations were assayed in NWS, and an oral glucose tolerance test was carried out in OS and total insulin area under the curve (TIA) was calculated. RESULTS: Log-transformed values of leptin serum concentrations appeared to be distributed according to an acceptable Gaussian pattern. As observed in adults, serum leptin concentrations in children and adolescents were also increased (4±5 times) in OS as compared to NWS. In both males and females, subdivided according to pubertal stages, serum leptin varied signi®cantly in stage IV±V as compared to the lower stages, with a reduction in males and an increase in females. On comparing the two sexes, greater serum leptin concentrations were observed in females of both NWS and OS. A signi®cant linear correlation was found in both groups, subdivided according to sex and pubertal stage, between log values of serum leptin and standard deviation scores (SDS) of body mass index (BMI), and logtransformed relative body weight (RBW). Using partial correlation analysis in subjects subdivided according to sex and pubertal stages, log values of serum leptin and fasting insulin values, adjusted by age and SDS of BMI, correlated signi®cantly with a weaker correlation in males than in females. In OS, the leptin concentrations correlated better with TIA than with fasting insulin. A weight reduction program (WRP) was carried out in 141 OS and signi®cant reductions of serum leptin and fasting insulin were observed, showing a reduction of RBW. There was a correlation between the reduction of RBW and of serum leptin, but not of fasting insulin. No variation was found in non-responsive OS. RBW reduction correlated with leptin, but not with insulin (fasting and TIA), evaluated before the therapeutic program started. CONCLUSION: As observed in adults, obese children and adolescents have higher serum leptin concentrations. However, several conditions should be taken into account when evaluating leptin concentrations in children. There are differences, independent of BMI, relative to pubertal stage and sex, females having greater leptin concentrations than males. There is evidence of a possible role for leptin in the effectiveness of a weight reduction program in OS.

Leptin Levels in Children and Adults with Classic Galactosaemia

“…These differences and age-dependence of leptin concentrations become especially evident after appropriate logarithmic transformation (Blum et al 1997). Essentially, there is a significant correlation of leptin, or log-transformed values of leptin, and BMI in healthy males and females of a wide age range (5-77 years) (Isidori et al 2000;Gómez et al 2003;Falorni et al 1997). Contrary to what is expected, there was a lack of a correlation between log-leptin and BMI in adult males with Gal and in our entire adult Gal cohort.…”

Plasma leptin is associated with insulin resistance independent of age, body mass index, fat mass, lipids, and pubertal development in nondiabetic adolescents

“…These were consistent with previous reports in adults, as well as in children. 31,32,35,36 Studies have demonstrated that leptin may exert part of its function directly on the peripheral lipid metabolism. 20,37 Plasma leptin levels were found to be correlated to plasma lipids, traditionally related to adverse CVD risk, in our present study.…”

Plasma leptin concentrations and obesity in relation to insulin resistance syndrome components among school children in Taiwan—The Taipei Children Heart Study

“…43 Leptin concentration is signi®cantly higher in obese children than non-obese, which suggests that resistance to the effects of leptin may start in early childhood. 43,47 The relationship between plasma leptin and insulin levels is complicated and may be bi-directional. Although plasma leptin concentrations are highly correlated with BMI, insulin levels and insulin sensitivity in humans, 14,15,22 ± 28,38,48,49 it is not yet known whether leptin has a direct effect on insulin sensitivity or if it is only a marker of obesity and related disorders.…”