Growing evidences indicate that a small birthweight, resulting from maternal malnutrition or others prenatal alterations, is associated with an increased neonatal morbidity and mortality and may lead to higher propensity to develop a metabolic syndrome (including type 2 diabetes, obesity, hypertension and dyslipidemia) in adulthood. However, the physiopathological mechanisms acting in utero on the programming of the offspring's metabolic profile remain confused and may implicate numerous molecules and physiological systems. Several data suggest that the placental alterations may have long-lasting consequences and could thus contribute to the programming of adult metabolic diseases. The placenta is the primary means of communication and nutrient delivery to the fetus and is also involved in fetal homeostasis. Thus, the placenta may constitute an appropriate organ for investigating how differences in maternal food consumption are sensed by the fetus along the pregnancy. Because of the increasing proportion of women eating inadequately during pregnancy and because such nutritional disturbances may have huge repercussions on adult health of the offspring, we urgently have to better understand how the placenta elaborates adaptive responses to maternal food intake modulations. My PhD aimed at identifying new placental pathways implicated in fetal growth restriction in rat, and investigated in human placental samples, the expression of these factors in pregnancies with fetal growth disturbances.As maternal malnutrition constitutes an important part in the etiology of intrauterine growth restriction (IUGR), we used an experimental model performed in rats which consists of a reduction (from 50% to 70%) of the daily maternal food intake during the gestation. These regimens lead to profound growth disturbances of the feto-placental unit revealed by drastic reductions of both placental and birth weights at term. To identify new placental pathways implicated in IUGR, we have used two different strategies: a proteomic approach and the evaluation of two proteins recently characterized in the placenta.First, we investigated the placental proteome in IUGR rats from undernourished mothers using 2D-PAGE electrophoresis and mass spectrometry identification. This strategy allowed the discovery of new pathways modulated by IUGR. Surprisingly, major modulations were observed for several proteins localized in mitochondria, suggesting specific effects of maternal undernutrition on these organelles. Thereafter, using multiple molecular, proteomic and functional analyses, we have shown that these organelles develop adaptive responses to maternal nutrient restriction that may have functional consequences on the regulation of the fetal growth. Secondly, we studied two others atypical proteins: the brain-derived neurotrophic factor and the hormone apelin. Our findings suggest that both of these factors may be implicated in the control of fetal growth at the placental level in rat and putatively in human. As actual clinical methods do not permit to diagnose precisely fetal growth disturbances, our results may permit to better understand the placental physiological pathways implicated during these pathologies and could lead to the development of markers and/or treatments in order to improve both placental functions and fetal growth.
Intrauterine growth restriction and vulnerability to the metabolic syndrome : research of placental markers by proteomic analysis in rats and experimental and clinical evaluation