Hyperadiponectinemia in newborns: relationship with leptin levels and birth weight.

OBJECTIVE: Adiponectin is the only adipose-specific hormone that, despite its exclusive production by adipose tissue, is reduced in obesity and is inversely correlated with leptin levels in adults. The aim of this study was to evaluate the adiponectin concentration in umbilical cord blood at different gestational ages and to investigate its possible associations with leptin levels and birth weight. RESEARCH METHODS AND PROCEDURES: Umbilical cord blood was obtained from 132 newborns (male = 65, female = 67, gestational age: 35 to 42 weeks). The anthropometric variables of the newborns studied were birth weight, birth length, body weight/body length, and ponderal index. Adiponectin, insulin, and leptin levels were measured by radioimmunoassay methods. RESULTS: Adiponectin levels in males were not different from those in females (24.10 +/- 0.81 vs. 25.62 +/- 0.84 micro g/mL, p = 0.280). Adiponectin concentrations were positively correlated with birth weight (p < 0.05), birth length (p < 0.05), body weight/body length (p < 0.05), gestational age (p < 0.01), and leptin levels (p < 0.01). DISCUSSION: These findings indicate that adiponectin is present in umbilical cord blood after 35 to 42 weeks of gestation, with higher levels than those usually found in adults, no gender differences, and a positive correlation with birth weight and leptin. These results suggest that not only could neonatal hyperadiponectinemia be associated with the increase of adiponectin production by fetal adipose tissue but also with a possible reduction in an unknown mechanism related to the suppression of adiponectin observed in adults.

Leptina como marcadora do dimorfismo sexual em recém-nascidos / Leptin as a marker of sexual dimorphism in newborn infants

OBJETIVO: Avaliar os níveis de leptina do cordão umbilical em recém-nascidos adequados para a idade gestacional conforme sexo, peso, comprimento e índice ponderal de nascimento. MÉTODO: Estudo tipo transversal, envolvendo 132 recém-nascidos adequados para idade gestacional (68 do sexo feminino, 64 do sexo masculino), com idade gestacional de 35-42 semanas. Os dados foram obtidos mediante entrevista com as mães na maternidade, pelo estudo antropométrico dos recém-nascidos e pela dosagem de leptina, estradiol e testosterona no cordão umbilical por meio da coleta imediata após o parto. RESULTADOS: Os recém-nascidos do sexo feminino apresentaram níveis de leptina significativamente maiores que os do sexo masculino (8,34±0,65 ng/ml versus 6,06±0,71 ng/ml; p = 0,000). Os níveis de estradiol e testosterona não variaram conforme o sexo. A leptina se correlacionou positivamente com idade gestacional (r = 0,394, p < 0,01), peso (r = 0,466, p < 0,01), comprimento (r = 0,335, p < 0,01) e índice ponderal (r = 0,326, p < 0,01) dos recém-nascidos. CONCLUSÕES: A leptina do cordão umbilical se correlaciona positivamente com idade gestacional, peso, comprimento e índice ponderal do recém-nascido, sugerindo sua participação no processo de crescimento neonatal. Além disso, os recém-nascidos do sexo feminino têm níveis séricos de leptina maiores que os do sexo masculino, sugerindo que o dimorfismo sexual relacionado à composição corporal já possa existir em recém-nascidos.