Peroxisome Proliferator-Activated Receptor-γ and Retinoid X Receptor Signaling Regulate Fatty Acid Uptake by Primary Human Placental Trophoblasts

Abstract

Transplacental transfer of fatty acids from the maternal to the fetal circulation is essential for fetal development. The nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARgamma) regulates fatty acid transport and storage in adipocytes and other cell types. This study tested the hypothesis that PPARgamma and its heterodimeric nuclear receptor partner, retinoid X receptor (RXR), regulate fatty acid uptake by human trophoblasts. Prospective basic laboratory in vitro research was conducted using primary term human trophoblasts. The study was performed in the perinatal biology laboratory of an academic medical center. Study materials were obtained from healthy pregnant women at a gestational age of 37-41 wk. There were no interventions. Fat uptake and accumulation in human placental trophoblasts were measured. We initially demonstrated that activation of PPARgamma and/or RXR with selective agonists increased the accumulation of neutral lipids in trophoblasts as well as uptake of free fatty acids. Furthermore, activation of PPARgamma and RXR enhanced the expression of the fat droplet-associated protein adipophilin along with fatty acid transport protein (FATP)4, whereas expression of FATP2 was decreased by activation of RXR. Finally, we found that inhibition of p38 MAPK, which diminishes the activity of PPARgamma in trophoblasts, inhibited fatty acid uptake and blocked the PPARgamma- and RXR-dependent increases in adipophilin and FATP4 expression, yet stimulated the expression of FATP1, FATP2, and FATP3. These data support a role for PPARgamma and RXR in regulation of fatty acid transport and storage in human placental trophoblasts.