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29 May 2013 Insulin Enhances Leptin Expression in Human Trophoblastic Cells
Antonio Pérez-Pérez, Julieta Maymó, Yesica Gambino, Pilar Guadix, José L. Dueñas, Cecilia Varone, Víctor Sánchez-Margalet
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Leptin, one of the adipokines that controls energy metabolism via the central nervous system, also has pleiotropic peripheral effects, acting as a proinflammatory cytokine. Leptin is also produced by trophoblastic cells in the placenta, where leptin seems to function as a trophic autocrine hormone. Leptin expression is regulated by various tissue-specific factors, such as insulin, in the adipocyte. However, the complete regulation of leptin production in the placenta is still poorly understood. That is why we investigated the regulation of leptin expression by insulin in JEG-3 trophoblastic cells and human placental explants from normal pregnancies. Western blot analysis and quantitative real time RT-PCR was performed to determine the leptin expression level after treatment of cells or trophoblast explants with different concentrations of insulin (0.1–100 nM). Leptin promoter activity was evaluated by transient transfection with a plasmid construct containing different promoter regions and the reporter luciferase gene. We found a stimulatory, dose-dependent effect of insulin on endogenous leptin expression in human placental explants. Maximal effect was achieved at 10 nM insulin, and this effect can be totally prevented both by blocking phosphatidylinositol 3 kinase (PI3K) pathways and mitogen-activated protein kinase (MAPK). Moreover, insulin treatment significantly enhanced leptin promoter activity up to 40% in JEG-3 trophoblastic cells. Deletion analysis demonstrated that a minimal promoter region between −1951 and −1546 bp is necessary to achieve insulin effects. In conclusion, we provide evidence suggesting that insulin induces leptin expression in trophoblastic cells, enhancing the activity of leptin promoter region between −1951 and −1546 bp, via both PI3K- and MAPK-signaling pathways.

Antonio Pérez-Pérez, Julieta Maymó, Yesica Gambino, Pilar Guadix, José L. Dueñas, Cecilia Varone, and Víctor Sánchez-Margalet "Insulin Enhances Leptin Expression in Human Trophoblastic Cells," Biology of Reproduction 89(1), (29 May 2013).
Received: 15 March 2013; Accepted: 1 May 2013; Published: 29 May 2013
hormone action
leptin/leptin receptor
signal transduction
Trophoblast cells
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