ESPE Abstracts

Background: Fetal growth is the fastest of all periods of growth in human life, mainly due to cellular hypertrophy and proliferation. It was recently discovered that the metabolic and mitogenic effects of Insulin are mediated by two Insulin Receptors (IR) isoforms, IR-A and IR-B. High expression of IR-A indicates proliferation and differentiation whereas IR-B indicates metabolic dominance.

Objective and hypotheses: The aim of the study was to examin the expression of IR isoforms and IGF-1R in placentas according to the size of the newborn.

Method: The study population included healthy women aged 21–41 years. The embryos were divided into four weight groups: appropriate (AGA), small (SGA), large (LGA) for gestational age and intrauterine growth restriction (IUGR). Immediately after birth, biopsies were taken from the following areas in the placenta: central, peripheral, maternal and fetal.

Results: IGF-1R was significantly different between the four groups, P<0.0072. The main difference in IGF1-R expression was between the center and the peripheral fetal placenta. IGF1-R expression in the peripheral SGA placentas was 48% lower than in the AGA placentas, 14% than in the IUGRs and 32% of the LGA placentas. In the central SGA placenta IGF-1R expression was 57% lower than in the AGA placentas. IR-A expression in the central placentas of the IUGR group was 50% lower than in the peripheral placentas in both the maternal and fetal tissues.

Conclusions: These findings support the claim that quantitative expression of IGF-1R is important for the development of both the placenta and the fetus. Expression of IRs in the IUGRs placenta is unique and unlike that of the other embryonic weight groups. The absence of differences in IR-B expression may indicate that IR-A is the dominant isoform in fetal tissues, while IR-B appears primarily in insulin target tissues during postnatal life and has mainly a metabolic function.