Maternal nutrition alters the expression of insulin-like growth factors in fetal sheep liver and skeletal muscle

We investigated the influence of maternal dietary restriction between days 28 and 80 of gestation followed by re-feeding to the intake of well-fed ewes up to 140 days of gestation (term is 147 days) in sheep, on expression of mRNA for insulin-like growth factor (IGF)-I, IGF-II and growth hormone receptor (GHR) in fetal liver and skeletal muscle. Singleton bearing ewes either consumed 3·2-3·8 MJ/day of metabolisable energy (ME) (i.e. nutrient restricted - approximately 60% of ME requirements, taking into account requirements for both ewe maintenance and growth of the conceptus) or 8·7-9·9 MJ/day (i.e. well fed - approximately 150% of ME requirements) between days 28 and 80 of gestation. All ewes were then well fed (150% of ME requirements) up to day 140 of gestation and consumed 8-10≥9 MJ/day. At days 80 and 140 of gestation, five ewes were sampled from each group and fetal tissues taken. There was no difference in fetal body weight or liver weights between groups at either sampling date, or skeletal muscle (quadriceps) weight at 140 days. IGF-I mRNA abundance was lower in livers of nutrient-restricted fetuses at day 80 of gestation (nutrient restricted 2·35; well fed 3·70 arbitrary units), but was higher than well-fed fetuses at day 140 of gestation, after 60 days of re-feeding (restricted/re-fed 4·27; well fed 2·83; S.E.D. 0·98 arbitrary units, P=0·061 for diet x age inter-action). IGF-II mRNA abundance was consistently higher in livers of nutrient-restricted fetuses (80 days: Nutrient restricted 7·78; well fed 5·91; 140 days: Restricted/re-fed 7·23; well fed 6·01; S.E.D. 1·09 arbitrary units, P=0·061 for diet). Nutrient restriction had no effect on hepatic GHR mRNA abundance, but re-feeding of previously nutrient-restricted fetuses increased GHR mRNA compared with continuously well-fed fetuses (80 days: Nutrient restricted 70·6; well fed 75·1; 140 days: Restricted/re-fed 115·7; well fed 89·4; S.E.D. 10·13 arbitrary units, P=0·047 for diet x age interaction). In fetal skeletal muscle, IGF-I mRNA abundance was not influenced by maternal nutrition and decreased with gestation age (