Gestational protein restriction induces alterations in placental morphology and mitochondrial function in rats during late pregnancy

The placenta acts a regulator of nutrient composition and supply from mother to fetus and is the source of hormonal signals that affect maternal and fetal metabolism. Thus, appropriate development of the placenta is crucial for normal fetal development. We investigated the effect of gestational protein restriction (GPR) on placental morphology and mitochondrial function on day 19 of gestation. Pregnant dams were divided into two groups: normal (NP 17 % casein) or low-protein diet (LP 6 % casein). The placentas were processed for biochemical, histomorphometric and ultrastructural analysis. The integrity of rat placental mitochondria (RPM) isolated by conventional differential centrifugation was measured by oxygen uptake (Clark-type electrode). LP animals presented an increase in adipose tissue and triacylglycerol and a decrease in serum insulin levels. No alterations were observed in body, liver, fetus, or placenta weight. There was also no change in serum glucose, total protein, or lipid content. Gestational protein restriction had tissue-specific respiratory effects, with the observation of a small change in liver respiration (13 %) and considerable respiratory inhibition in placenta samples (37 %). The higher oxygen uptake by RPM in the LP groups suggests uncoupling between respiration and oxidative phosphorylation. In addition, ultrastructural analysis of junctional zone giant cells from LP placenta showed a disorganized cytoplasm, with loss of integrity of most organelles and intense vacuolization. The present results led us to hypothesize that GPR alters placental structure and morphology, induces sensitivity to insulin, mitochondrial abnormalities and suggests premature aging of the placenta. Further studies are needed to test this hypothesis.