Effects of Maternal Nutrition on Fructose Concentrations and Expression of GLUT5 in Bovine Utero-Placental Fluids and Tissues from Days 16 to 50 of Gestation

Fructose is the main hexose sugar found in fetal fluids of ungulates. Therefore, we tested the hypotheses that the concentration of fructose in maternal and fetal fluids and mRNA expression of fructose transporter GLUT5 in utero-placental tissues would be influenced by day of gestation and maternal nutrition. Angus-cross heifers (n = 49) were estrus synchronized, bred via AI, assigned to nutritional treatment (CON = 100% of requirements for 0.45 kg/d gain and RES = 60% of CON), and ovariohysterectomized on d 16, 34, or 50 of gestation (n = 6 to 9/d). Some heifers (n = 6) were not bred to serve as non-bred non-pregnant (NB-NP) controls and were ovariohysterectomized on d 16 of the synchronized estrous cycle. Tissues collected include: caruncules from the pregnant uterine horn (P-CAR), and non-pregnant uterine horn (NP-CAR); inter-caruncular tissue from pregnant uterine horn (P-ICAR) and non-pregnant uterine horn (NP-ICAR); and chorioallantois (fetal membranes; FM). Fluids collected include: maternal serum, histotroph from the pregnant uterine horn (P-histotroph) and non-pregnant uterine horn (NP-histotroph), allantoic, and amniotic fluid. The resulting arrangement was a 2 × 3 + 1 factorial analyzing day, tissue, and day × tissue, or day, fluid, and day × fluid. Fetal tissues and fluids were not collected in NB-NP heifers due to lack of FM, allantoic and amniotic fluids. Expression of GLUT5 in P-CAR was greater (P = 0.02) on d 34 compared with d 16 and 50. In NP-CAR, expression was greater (P < 0.01) on d 34 and 50 compared with d 16. In FM, GLUT5 expression was greater (P = 0.04) on d 16, compared with d 34 and 50. Serum fructose concentrations were greater (P < 0.01) in NB-NP heifers compared with pregnant heifers. Concentrations of fructose in P-histotroph and NP-histotroph were greater (P < 0.01) on d 50, compared with d 16 and 34. Fructose in amniotic fluid was influenced by a day × treatment interaction (P = 0.04), with d 34 RES being greater (P ≤ 0.05) than d 50 CON, which was greater (P ≤ 0.05) than d 50 RES. We interpret these data to imply that the expression of GLUT5 and concentrations of fructose are more greatly influenced by day of gestation than maternal nutrition; however, potential partitioning of fructose between treatments in amniotic fluids on d 50 of gestation warrants further investigation.