Leptin as a marker of sexual dimorphism in newborn infants

Abstract

Fonte financiadora: Fundação de Amparo à Pesquisa do Estado de São Paulo -FAPESP.Artigo submetido em 17.12.03, aceito em 26.04.04. AbstractObjective: To determine cord blood leptin levels in newborns appropriate for gestational age, according to gender, birth weight, birth height and ponderal index.Methods: A cross-sectional study was carried out with 132 term newborns appropriate for gestational age (68 females, 64 males), gestational age between 35-42 weeks. Data were collected through interviews with the mothers at the maternity, anthropometrycal study of the newborns, and cord blood estradiol, testosterone and leptin assays obtained immediately after birth.Results: The levels of leptin were significantly higher in females than in males (8.34±0.65 ng/ml versus 6.06±0.71 ng/ml; p = 0.000). The concentrations of estradiol and testosterone did not differ between males and females. Leptin levels were positively correlated with gestational age (r = 0.394, p < 0.01), birth weight (r = 0.466, p < 0.01), birth length (r = 0.335, p < 0.01) and ponderal index (r = 0.326, p < 0.01).Conclusions: Leptin concentration in the umbilical cord is positively correlated with gestational age, birth weight, birth height, and ponderal index, suggesting its participation in the neonatal growth process. In addition, a gender difference with higher levels of leptin in females neonates was observed, suggesting that the sexual dimorphism in relation to body composition already exists in newborns. ResumoObjetivo: 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. ARTIGO ORIGINAL IntroduçãoA leptina (palavra grega leptos, que significa magro ) é uma p...

Leptin levels at birth and in early postnatal life in small- and appropriate-for-gestational-age infants

“…These observations are compatible with findings that infants with congenital leptin deficiency or leptin receptor gene mutation have normal birth weights (15,16). On the contrary, cord leptin concentration explained up to 15% of the variance in infants' skinfold AGA -appropriate for gestational age; SGA -small for gestational age.…”

“…In this study, cord leptin levels were markedly higher in female than in male infants, and this difference was independent of birth weight and gestational age. Although the sexual dimorphism in leptin levels becomes most apparent at the onset of puberty, a significant gender difference in leptin levels at birth has previously been reported by some (9,(15)(16)(17)(18), but not all studies (12,20). It is discussed that these gender differences might reflect the transient perinatal elevation in sex steroids, as estrogens are associated with higher leptin concentrations, while androgens are inversely related to leptin levels (18).…”

“…Accordingly, small-for-gestational-age (SGA) newborns have significantly reduced serum leptin concentration (9,(11)(12)(13)(14). A gender dimorphism, with higher leptin concentrations in female newborns, was observed in some (9,(15)(16)(17)(18), but not all studies (12,20).…”

Meta-analysis of sex difference in testosterone levels in umbilical cord blood

“…To date, studies have produced mixed evidence regarding a sex diff erence in umbilical vein T. Some studies have found that compared with female newborns, male newborns have more umbilical vein T (Herruzo et al 1993), less (Pardo et al 2004), or virtually identical levels (van de Beek et al 2004). Establishing a norm for umbilical cord T is diffi cult because the commonly used ' direct ' assay methods (described below) lack the sensitivity to accurately detect T at levels below 10 nmol/l (Rosner et al 2007).…”

Sobrecarga e restrição de cloreto de sódio durante a gestação: repercussão sobre a estrutura cardíaca e renal no neonato

“…Muito possivelmente, o mecanismo responsável por este dimorfismo não é um mecanismo que envolve hormônios sexuais (Pardo et al, 2004). As consequências fisiológicas e os mecanismos envolvidos na ontogenia sexoespecíficos das variáveis estudadas que apresentaram diferenças no presente estudo merecem mais observações.…”