Postnatal Changes of Leptin Levels in Full-Term and Preterm Neonates: Their Relation to Intrauterine Growth, Gender and Testosterone

Abstract

The present study was carried out to investigate leptin levels in arterial and venous cord serum and in amniotic fluid in full-term infants at birth and on the 5th postnatal day to define the relationship of leptin to intrauterine growth rate, gender and early postnatal life. The relation of weight gain to serum leptin levels in male preterm infants was determined measuring leptin concentration weekly in the first 5 postnatal weeks. Testosterone levels were determined simultaneously to explore a possible relationship between leptin and testosterone concentrations.Fifty-three term newborn infants with mean birth weight and gestational age of 3,419 g (range 2,150–4,480) and 38.9 weeks (range 36–41) and 19 preterm male infants (mean birth weight and gestational age were 1,416 g (770–1,800) and 30.2 weeks (26–35) were enrolled into the study. Leptin and testosterone levels were determined by radioimmunoassay. It was demonstrated that serum leptin levels were markedly elevated in the cord blood without discernible arteriovenous differences. Cord blood leptin was found to correlate with birth weight (r = 0.40, p < 0.002), weight to length ratio (r = 0.40, p < 0.002) and body mass index (r = 0.35, p < 0.005). It was significantly lower in boys as opposed to girls (p < 0.01) and there was an apparent fall by the 5th postnatal day (p < 0.001). Amniotic fluid contained leptin in much less concentration than cord blood and it proved to be independent of intrauterine growth or gender. Serum leptin concentration in preterm infants at 1 week of age was significantly lower compared with term infants (p < 0.002) and it increased progressively with age (p < 0.01). An inverse relationship was found between leptin and testosterone level (r = –0.358, p < 0.01) and a positive correlation between leptin level and weight/height ratio (r = 0.674, p < 0.01).It is concluded that leptin derived either from placenta or fetal adipose tissue may be involved in regulating fetal growth and development and it may be related to energy intake, storage and expenditure. In preterm male infants serum leptin concentration increases with postnatal weight and testosterone may suppress leptin synthesis.

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

“…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).…”

“…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). Not consistent with these observations, Matsuda et al (12) reported that serum concentrations of estradiol and testosterone did not differ between male and female neonates and did not correlate with leptin concentration suggesting that the existence of this gender difference in the fetus might also depend on genetic factors.…”

“…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).…”

Markers of bone metabolism, serum leptin levels and bone mineral density in preterm babies

“…Higher leptin levels can be found in babies with diabetic mothers. There is increased accumulation of adipose tissue, which is characteristic for such infants (12,13). The serum leptin level reveals that the level of nutrition is equal to the level of hormones.…”

Hypoxia-induced leptin production in human trophoblasts does not protect from apoptosis

“…It is well known that leptin contributes to a physiological pregnancy by regulation of implantation, energy balance of placenta and conceptus, as well as an angiogenic factor (14 -16). During pregnancy, leptin expression undergoes dramatic changes in maternal plasma in parallel with the rising of cytokine levels during the first trimester (17) returning to normal levels after delivery (18). The production of placental leptin is reported to be increased by interleukin-1a, 17b-estradiol and hypoxia (19 -21).…”