Isolation and comparison of expression of novel glucose transporters, GLUT3 and GLUT14, in bovine utero-placental tissues from days 16 to 50 of gestation

Abstract Text: Glucose transporters, GLUT3 and GLUT14, have not previously been isolated in ruminant utero-placenta. The glucose transporter GLUT14 is a duplicon of GLUT3 with 95% shared homology. We hypothesized that maternal nutrition and day of gestation would impact mRNA expression of GLUT3 and GLUT14 in heifers, and that there would be a difference in mRNA expression between the two transporters. Crossbred Angus heifers (n = 49) were synchronized, bred via AI, assigned to nutritional treatment (CON = 100% of requirements to gain 0.45 kg/d; RES = 60% of CON) and ovariohysterectomized on d 16, 34, or 50 of gestation (n = 6 to 9/d); non-pregnant (NP) controls were not bred and ovariohysterectomized on d 16 of the synchronized estrous cycle (n = 6). The resulting treatment arrangement was a 2 × 3 factorial + 1. Utero-placental tissues (caruncle, CAR; intercaruncular endometrium, ICAR; fetal membrane [chorioallantois], FM; cotyledon, COT; intercotyledonary placenta ICOT; and amnion, AMN) were obtained from the pregnant uterine horn immediately after ovariohysterectomy. For NP controls, only CAR and ICAR were obtained. Comparison of expression across tissues was achieved by utilizing NP CAR and ICAR tissues as the baseline. For FM, COT, ICOT and AMN, NP endometrium served as the baseline. Expression of GLUT3 was greater (P < 0.05) on d 50 in CAR compared with d 16 CAR. In FM, GLUT3 was greater (P < 0.05) on d 16 compared with to d 50 FM. There also was a significant day × tissue interaction for GLUT3, which was greater (P < 0.01) in d 50 CAR compared with all other tissues and days. Expression of GLUT14 in CAR was greater (P < 0.05) on d 50 compared to d 16 and 34. Direct comparison of the two genes showed that GLUT14 expression was five-fold greater (P < 0.01) than GLUT3 expression across all days, tissues, and treatments. There was a significant gene × tissue interaction (P < 0.01), such that GLUT14 was greater in ICAR and intermediate in CAR compared with FM and compared with GLUT3 in all tissues. These data demonstrate that glucose transporters GLUT3 and GLUT14 are expressed in ruminant utero-placenta, and also supports our hypothesis that the magnitude of mRNA expression of GLUT3 differs from that of GLUT14. There were no effects, however, of nutritional treatment or day of gestation within gene.

Keywords: early gestation, facilitated transporters, glucose