LEP and gestational diabetes: For example, a wide range of hormones and cytokines such as insulin, leptin, insulin-like growth factors (IGFs), and molecular signaling pathways, including the mammalian target of rapamycin (mTOR), phosphatidylinositol 3-kinase (PI3K), and mitogen-activated protein kinases (MAPK), have been reported to be activated in the maternal-facing microvillous (MVM) of human placentas affected by GDM (6, 9, 10).