Glucose as a fetal nutrient: dynamic regulation of several glucose transporter genes by DNA methylation in the human placenta across gestation☆ , ☆☆ Boris Novakovic a,b , Lavinia Gordon c , Wendy P. Robinson d , Gernot Desoye e , Richard Saffery a,b, ⁎ a Cancer and Disease Epigenetics, Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Victoria 3052, Australia b Department of Paediatrics, University of Melbourne, Parkville, Victoria 3052, Australia c Bioinformatics, Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Victoria 3052, Australia d Department of Medical Genetics, University of British Columbia, Child and Family Research Institute, Vancouver, BC, Canada e Department of Obstetrics and Gynaecology, Medical University of Graz, Auenbruggerplatz 14, A-8036 Graz, Austria Received 9 January 2012; received in revised form 10 May 2012; accepted 8 June 2012 Abstract The human placenta ensures proper fetal development through the regulation of nutrient and gas transfer from the mother to the fetus and the removal of waste products from the fetal circulation. Glucose is one of the major nutrients for the growing fetus. Its transport across the placenta to the fetus is mediated by a family of facilitative transporter proteins, known as the glucose transporters (GLUTs), encoded by the SLC2A family of genes. There are 14 members of this gene family, and the expression of several of these has been shown in human placenta; however, aside from GLUT1 and GLUT3, little is known about the role of these proteins in placental function, fetal development and disease. In this study, we analysed previously generated genome-scale DNA methylation and gene expression data to examine the role of methylation in GLUT expression throughout gestation. We found evidence that DNA methylation regulates expression of GLUT3 and GLUT10, while the constitutively expressed GLUT1 showed no promoter methylation. We further analysed the level of DNA methylation across the promoter region of GLUT3, previously shown to be involved in glucose back-flux from the fetal circulation into the placenta. Using the Sequenom EpiTYPER platform, we found increasing DNA methylation of this gene in association with decreasing expression as gestation progresses, thereby highlighting the role of epigenetic modifications in regulating the GLUT family of genes in the placenta during pregnancy. These findings warrant a reexamination of the role of additional GLUT family members in the placenta in pregnancy and disease. Crown Copyright © 2013 Published by Elsevier Inc. All rights reserved. Keywords: Human placenta; Glucose transport; DNA methylation; Epigenetics; GLUT3 1. Introduction The placenta is a tissue of limited lifespan that performs a diverse range of functions including the transport of maternal nutrients to the fetal circulation to ensure adequate fetal growth. Not surprisingly, therefore, the placenta has been implicated in pathologies associated with aberrant fetal growth, including gestational diabetes mellitus (GDM) and fetal growth restriction (FGR) [1–3]. The fetus has a very low capacity for glucose production, so fetal glucose levels are primarily controlled through placental transport from the maternal circulation [4,5]. This is largely a result of facilitated diffusion mediated by a family of transporter proteins, the glucose transporters (GLUTs), encoded by 14 different genes of the SLC2A family. To date, several GLUTs have been described in the placenta [6,7]. The ubiquitous GLUT1 is found in all cells at all gestational ages [8]. GLUT3, which is the high-affinity glucose transporter, is expressed in a cell-specific manner depending on developmental stage. Both GLUT1 and GLUT3 not only accept glucose as sole substrate but are also involved in the uptake and presumably transfer of dehydroas- corbic acid (vitamin C) [9]. In the first trimester, GLUT3 expression can be detected in villous and extravillous cytotrophoblasts, but not the syncytiotrophoblast layer, suggesting that its expression is localised to rapidly proliferating and poorly differentiated cells [10], whereas in the third trimester, placenta GLUT3 is primarily localised to endothelial cells of the fetoplacental vessels and in stromal cells [10]. GLUT3 protein expression decreases over pregnancy, suggesting a greater role for this protein in glucose transport and fetal growth early in pregnancy [11]. GLUT4 is an insulin-dependent transporter localised to villous stromal cells [12] and the syncytiotrophoblast Available online at www.sciencedirect.com Journal of Nutritional Biochemistry 24 (2013) 282 – 288 ☆ Authors' contribution: B.N. designed the study, performed methylation experiments and analysis, and wrote the draft manuscript. L.G. performed methylation and expression array analysis. G.D. and W. R. participated in critical discussions and edited the manuscript. R.S. designed the study and wrote the manuscript. All authors approved the final version of the manuscript. ☆☆ Funding sources: National Health and Medical Research Council (Australia). B.N. is supported by a National Health and Medical Research Council (Australia) Dora Lush Biomedical Postgraduate Scholarship. The Murdoch Childrens Research Institute is supported by the Victorian Government's Operational Infrastructure Support Program. ⁎ Corresponding author. Murdoch Childrens Research Institute, Parkville, Victoria 3052, Australia. Tel.: + 61 3 83416341. 0955-2863/$ - see front matter. Crown Copyright © 2013 Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jnutbio.2012.06.006