Maternal high-fat (HF) diet negatively affects maternal metabolism and placental function. This study aimed to determine whether gestational exercise prevents the effect of HF diet on placental amino acid transporter expression and nutrient-sensing signaling and the fetal response. Pregnant Sprague-Dawley rats were either fed with a CHOW (13.5% fat) or HF (60% fat) diet during gestation and further divided into two subgroups: voluntary exercised and sedentary. Placentae were collected on gestational day (GD) 14 and GD20, and male placentae were used in this study. We found that gestational exercise ameliorated the detrimental effects of HF diet on dams' adiposity, plasma leptin, and insulin concentrations. Maternal exercise did not influence fetoplacental growth but affected male fetal hypothalamic Leprb, Stat3, Insr, Agrp, and Pomc expressions on GD20. Maternal HF diet decreased placental labyrinth thickness and increased system A amino acid transporter SNAT2 expression, while these changes were normalized by exercise. The activation of placental mechanistic target of rapamycin complex 1/4E-BP1 and LepRb/STAT3 signaling might contribute to the increased placental SNAT2 expression in HF-fed dams, which were reversed by exercise on GD20. These data highlight that gestational exercise reverses HF-diet-induced placental alterations during late gestation without influencing fetal growth. However, maternal exercise altered fetal hypothalamic gene expression, which may affect long-term offspring health.

Summary sentence

Gestational exercise reverses high-fat diet induced placental alterations during late gestation without influencing fetal growth, but altered male fetal hypothalamic gene expression.