Reference values for leptin/adiponectin ratio in healthy children and adolescents.

BACKGROUND: Leptin and adiponectin are two key adipocyte secreted hormones and both are involved in several essential physiological mechanisms. Due to their central role in energy homeostasis their ratio, the leptin/adiponectin ratio, is believed to be a marker of metabolic derangement. Pediatric reference values are needed for the risk stratification of individual-measured ratios. METHODS: Blood samples were drawn from healthy, Danish schoolchildren following an overnight fast. A ratio was calculated from serum leptin and adiponectin quantifications done using commercially available ELISA Kits. RESULTS: Nine hundred eighty-three participants (583 girls) aged 6-18 years were included. Smoothed percentile curves and age-group specific percentiles were calculated. A correlation with age was demonstrated, with a gradual increase with age in girls and a negative parabolic relation, with a peak in age group 10-14, in boys. The leptin/adiponectin ratio was positively correlated to the body mass index standard deviation score for both girls and boys (p < .001). CONCLUSION: The leptin/adiponectin ratio is correlated to age and differs between the sexes in healthy children and adolescents.

Standardization of amniotic fluid leptin levels and utility in maternal overweight and fetal undergrowth.

OBJECTIVE: Leptin is an adipokine that regulates energy homeostasis. The objective of this study was to establish a gestational age-specific standard for amniotic fluid leptin (AFL) levels and examine the relationship between AFL, maternal overweight and fetal growth restriction. STUDY DESIGN: Amniotic fluid was obtained at mid-gestation from singleton gravidas, and leptin was quantified using enzyme-linked immunosorbent assay. Amniotic fluid samples from 321 term pregnancies were analyzed. Clinical data, including fetal ultrasound measurements and maternal and infant characteristics, were available for a subset of patients (n=45). RESULTS: The median interquartile range AFL level was significantly higher at 14 weeks' gestation (2133 pg ml(-1) (1703 to 4347)) than after 33 weeks' gestation (519 pg ml(-1) (380 to 761), P trend<0.0001), an average difference of 102 pg ml(-1) per week. AFL levels were positively correlated with maternal pre-pregnancy body mass index (BMI) (r=0.36, P=0.03) adjusting for gestational age at measurement, but were not associated with fetal growth. CONCLUSIONS: AFL levels are higher at mid-gestation than at late gestation, and are associated with maternal pre-pregnancy BMI.

The first international standard for human leptin and the first international standard for mouse leptin: comparison of candidate preparations by in vitro bioassays and immunoassays.

In an international collaborative study, two preparations of human sequence recombinant leptin and two preparations of mouse sequence recombinant leptin were evaluated, using in vitro bioassays and immunoassays, by eight laboratories, in three countries, for their suitability to serve as the international standard (IS) for human and mouse leptin respectively. The bioassays detected the human and mouse leptin with similar potency, while the immunoassays showed a greater response to the leptin of the species against which the antibody preparation had been raised. Comparison of the candidate standards with the various preparations of leptin of the same species currently assayed in the participating laboratories showed that immunoassay measurements cannot be used to predict the biological potency. On the basis of the results reported here, in October 1999 the Expert Committee on Biological Standardization of the World Health Organization established the preparation coded 97/594 as the first IS for human leptin, with an assigned unitage of 4000 IU/ampoule, and the preparation coded 97/626 as the first IS for mouse leptin, with an assigned unitage of 4000 IU/ampoule. The ISs for leptin are distributed by the National Institute for Biological Standards and Control, UK, http://www.nibsc.ac.uk.