Leptin concentrations in maternal serum and amniotic fluid during the second trimenon: differential relation to fetal gender and maternal morphometry

Leptin, a hormone produced by adipocytes, provides information on the avail ability of fat stores to the hypothalamus and acts as an afferent satiety s ignal regulating appetite and energy expenditure in both rodents and humans [Zhang Y, Proenca R, Maffei M, Barone M, Leopold L, Friedman JM. Positiona l cloning of the mouse obese gene and its human homologue. Nature 1994;372: 425-432; Sinha MK. Human leptin: the hormone of adipose tissue. fur J Endoc rinol 1997;136:461-4; Campfield LA, Smith FJ, Guisez Y, Devos R, Burn P. Re combinant mouse ob protein: evidence for a peripheral signal linking adipos ity and central neural networks. Science 1995;269:546-9; Halaas JL, Gajiwal a KS, Maffei M, Cohen SL, Chait BT, Rabinowitz D, Lallone RL, Burley SK, Fr iedman JM. Weight-reducing effects of the plasma protein encoded by the obe se gene. Science 1995;269:543-6; Saladin R, De Vos P, Guerre-Millo M, Letur que A, Girard J. Staels B, Auwern J. Transient increase in obese gene expre ssion after food intake or insulin administration. Nature 1995;377:527-9; C ampfield LA, Smith FJ, Burn P The OB protein (leptin) pathway - a link betw een adipose tissue mass and central neural networks. Horm Metab Res 1996;28 :619-632; Blum WF, Kiess W, Rascher W, editors. Leptin - the voice of the a dipose tissue. J&J Edition, JA Earth Verlag, Heidelberg, 1997]. In addition , leptin is thought to play an important role for reproduction and during g estation [Kiess W, Blum WF, Aubert ML. Leptin, puberty and reproductive fun ction: lessons from animal studies and observations in humans. fur J Endocr inol 1997;138:1-4; Barash IA, Cheung CC, Wigle DS, Ren H, Kabitting EB, Kui jer JL, Clifton DK, Steiner RA. Leptin is a metabolic signal to the reprodu ctive system. Endocrinology 1996;133:3144-47; Chehab F, Lim M, Lu R. Correc tion of the sterility defect in homocygous obese female mice by treatment w ith the human recombinant leptin. Nature Genetics 1996;12:318-20; Kiess W, Schubring C, Prohaska F, Englaro P, Rascher W, Attanasio A, Blum WF. Leptin in amniotic fluid at term and at midgestation. In: Blum WF, Kiess W, Rasch er W, editors. Leptin - the voice of the adipose tissue. J&J Edition, JA Ea rth Verlag, Heidelberg, 1997]. The purpose of this study was to gain more i nsight into a putative role of leptin during midgestation. Therefore we hav e measured leptin concentrations in maternal serum and amniotic fluid using a specific radioimmunoassay (RLA) employing human recombinant leptin for t racer and standard preparation [Blum WF, Kiess W, Rascher W editors, Leptin - The voice of the adipose tissue. J&J Edition, JA Earth Verlag, Heidelber g, 1997; Blum WF, Englaro P, Heiman M, Attanasio Am, Kiess W, Rascher W. Cl inical studies of serum leptin. In: Blum WF, Kiess W, Rascher W. Leptin - T he voice of the adipose tissue. J&J Edition, JA Earth Verlag, Heidelberg, 1 997; Blum WF, Englaro P, Heiman M, Attanasio AM, Kiess W, Rascher W. Plasma leptin levels in healthy children and adolescents: dependence on body mass index, body fat mass, gender, pubertal stage and testosterone. J Clin Endo crinol Metab 1997;82:2904-2910]. In addition, estriol, hCG and alphafetopro tein were measured in maternal serum. We have asked whether or not leptin c oncentrations in maternal serum and amniotic fluid were related to maternal BMI and skinfold thickness. Sixty-three healthy pregnant women who were la ter found to deliver healthy, term children and as a control group 39 healt hy non-pregnant women were included in the study. Maternal age was 35 years (median, range 23-46) and gestational age at amniocentesis 14-17 weeks (ra nge). Leptin concentrations in maternal serum at amniocentesis were 3.2-51. 9 ng/ml (range) and in amniotic fluid 2.3-30.2 ng/ml (range). Serum leptin levels from non-pregnant women were 2.7-55.4 ng/ml (range). Ma ternal leptin serum concentrations at the time of amniocentesis correlated significantly with BMI (r=0.54, P<0.001), and with maternal skinfold measur ements (iliac r=0.53, P<0.001, subscapular r=0.44, P<0.001; triceps r=0.39, P<0.002 and biceps r=0.41, P<0.001). Similar relations of leptin serum lev els and BMI (r=0.53, P=0.001) and skinfold thickness (iliac r=0.65, P<0.001 , subscapular r=0.55, P<0.001, triceps r=0.34, P<0.036 and biceps r=0.38, P <0.016) were found in the non-pregnant control group. In contrast, leptin l evels in amniotic fluid did not correlate with maternal BMI, skinfold thick ness and leptin levels in maternal serum at midgestation. interestingly, th e amniotic fluid leptin levels of girls were significantly higher than thos e of boys (2.6-30.2 ng/ml (range) versus 2.3-15.6 ng/ml (range)). In conclu sion high leptin concentrations are found in maternal serum and amniotic fl uid at midgestation. Maternal leptin levels and leptin levels in amniotic f luid seem to be derived from different sources. We hypothesize that leptin plays gestation-specific differential roles for the mother and the fetus. ( C) 1999 Elsevier Science Ireland Ltd. All rights reserved.