Exercise initiated during pregnancy in rats born growth restricted alters placental mTOR and nutrient transporter expression

Key points

Fetal growth is dependent on effective placental nutrient transportation, which is regulated by mTORC1 modulation of nutrient transporter expression. These transporters are dysregulated in pregnancies affected by uteroplacental insufficiency and maternal obesity. Nutrient transporters and mTOR were altered in placentae of mothers born growth restricted compared to normal birth weight dams, with maternal diet‐ and fetal sex‐specific responses. Exercise initiated during pregnancy (PregEx) downregulated MTOR protein expression, despite an increase in mTOR activation in male associated placentae, and reduced nutrient transporter gene abundance, which was also dependent on maternal diet and fetal sex. Limited changes were characterised with exercise initiated before and continued throughout pregnancy (Exercise) in nutrient transporter and mTOR expression. Maternal exercise during pregnancy (PregEx) differentially regulated mTOR and nutrient transporters in a diet‐ and sex‐specific manner, which likely aims to improve late gestational placental growth and neonatal survival.

Abstract

Adequate transplacental nutrient delivery is essential for fetoplacental development. Intrauterine growth restriction and maternal obesity independently alter placental nutrient transporter expression. Although exercise is beneficial for maternal health, limited studies have characterized how the timing of exercise initiation influences placental nutrient transport. Therefore, this study investigated the impact of maternal exercise on placental mTOR and nutrient transporter expression in growth restricted mothers and if these outcomes were dependent on maternal diet or fetal sex. Uteroplacental insufficiency (Restricted) or sham (Control) surgery was induced on embryonic day (E) 18 in Wistar‐Kyoto rats. F1 offspring were fed a Chow or High‐fat diet from weaning and at 16 weeks were randomly allocated an exercise protocol; Sedentary, Exercised prior to and during pregnancy (Exercise), or Exercised during pregnancy only (PregEx). Females were mated with normal males (20 weeks) and F2 placentae collected at E20. PregEx reduced mTOR protein expression in all groups and increased mTOR activation in male associated placentae. PregEx decreased the expression of amino acid transporters in a diet and sex‐specific manner. Maternal growth restriction altered mTOR and system A amino acid transporter expression in a sex and diet specific manner. These data highlight that maternal exercise initiated during pregnancy alters placental mTOR expression, which may directly regulate amino acid transporter expression, to a greater extent than exercise initiated prior to and continued during pregnancy, in a diet and fetal sex dependent manner. These findings highlight that the timing of exercise initiation is important for optimal placental function.

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