Maternal nutritional manipulation of placental growth and glucose transporter 1 (GLUT-1) abundance in sheep

Glucose transporter 1 (GLUT-1) is the predominant glucose transporter in th e placenta but the extent to which its abundance is nutritionally regulated is unknown. This study investigated the effects of restricted maternal nut rition between day 28 and day 80 of gestation followed by re-feeding to eit her meet or to exceed the total energy requirements on placental size and G LUT-1 abundance at mid-gestation (that is, day 80) and near to term (that i s, days 140-145 of gestation; term = 147 days). Singleton bearing ewes eith er consumed 8.7-9.9 MJ day(-1) of metabolizable energy (that is, well fed) or 3.2-3.8 MJ day(-1) of metabolizable energy (that is, nutrient restricted ) from day 28 to day 80 of gestation, after which stage they consumed eithe r 6.5-7.5 MJ day(-1) (that is, adequately fed) or 8.0-10.9 MJ day(-1) (that is, well fed) of metabolizable energy until near to term. In all ewes, at both sampling dates, the abundance of GLUT-1 was higher in the maternal com ponent than in the fetal component of the placenta. Immunohistochemistry co nfirmed that GLUT-1 was located in the maternal uterine syncytium. At day 8 0 of gestation, placental mass was lower (P < 0.05) in the nutrient restric ted group, but there was no difference in the abundance of GLUT-1 between t he nutrient restricted group and the well fed group. At near term, placenta l mass was greater (P < 0.05) in ewes that were nutrient restricted during early to mid-gestation and then adequately fed up to term compared with ewe s that were well fed during early to mid-gestation. This increase was assoc iated with a higher (P < 0.05) abundance of total placental GLUT-1 and a la rger fetus. There was no effect of previous nutrient restriction on placent al mass, fetal weight or GLUT-1 abundance at term, when ewes were well fed in the second half of gestation. In conclusion, maternal nutrient restricti on between early to mid-gestation alters placental growth but has no effect on placental GLUT-1 abundance. Increasing maternal feed intake to meet cal culated energy requirements in previously nutrient restricted ewes during t he second half of gestation, increases placental mass and fetal weight, and the abundance of GLUT-1, an adaptation not observed if maternal food intak e is increased above requirements.