Role of placental growth factor in glucose metabolism

Pre-eclampsia: connecting angiogenic and metabolic pathways

Pre-eclampsia is a hypertensive disease of pregnancy with a worldwide incidence of 5-8%. This review focuses on recent developments in pre-eclampsia research related to angiogenesis and metabolism. We first address the 'angiogenic imbalance' theory, which hypothesizes that pre-eclampsia results from an imbalance of factors that promote or antagonize angiogenesis, such as soluble fms-like tyrosine kinase (sFlt1), 2-methoxyestradiol (2-ME) and catechol-O-methyltransferase (COMT). Next, we analyze the association between pre-eclampsia and dysfunctional metabolism of both homocysteine and placental glycogen. We hope that illuminating some of the various connections existing between angiogenesis and metabolism in pre-eclampsia will facilitate the update or reconsideration of old models of pathogenesis.

Adverse adipose phenotype and hyperinsulinemia in gravid mice deficient in placental growth factor

Pregnancy-induced metabolic changes are regulated by signals from an expanded adipose organ. Placental growth factor (PlGF), acting through vascular endothelial growth factor receptor-1, may be among those signals. There is a steep rise in circulating PlGF during normal pregnancy, which is repressed in gravidas who develop preeclampsia. PlGF-deficiency in mice impairs adipose vascularization and development. Here we studied young-adult PlGF-deficient (PlGF(-/-)) and wild-type mice on a high-fat diet in the nongravid state and at embryonic day (E) 13.5 or E18.5 of gestation. Litter size and weight were normal, but E18.5 placentas were smaller in PlGF(-/-) pregnancies. PlGF(-/-) mice showed altered intraadipose dynamics, with the following: 1) less blood vessels and fewer brown, uncoupling protein (UCP)-1-positive, adipocytes in white sc and perigonadal fat compartments and 2) white adipocyte hypertrophy. The mRNA expression of beta(3)-adrenergic receptors, peroxisome proliferator-activated receptor-gamma coactivator-1alpha, and UCP-1 was decreased accordingly. Moreover, PlGF(-/-) mice showed hyperinsulinemia. Pregnancy-associated changes were largely comparable in PlGF(-/-) and wild-type dams. They included expanded sc fat compartments and adipocyte hypertrophy, whereas adipose expression of key angiogenesis/adipogenesis (vascular endothelial growth factor receptor-1, peroxisome proliferator-activated receptor-gamma(2)) and thermogenesis (beta(3)-adrenergic receptors, peroxisome proliferator-activated receptor-gamma coactivator-1alpha, and UCP-1) genes was down-regulated; circulating insulin levels gradually increased during pregnancy. In conclusion, reduced adipose vascularization in PlGF(-/-) mice impairs adaptive thermogenesis in favor of energy storage, thereby promoting insulin resistance and hyperinsulinemia. Pregnancy adds to these changes by PlGF-independent mechanisms. Disturbed intraadipose dynamics is a novel mechanism to explain metabolic changes in late pregnancy in general and preeclamptic pregnancy in particular.