Changes in gene expression associated with vitamin A metabolism in the corpora lutea and endometria during d 15 of the estrous cycle and throughout gestation in gilts

Abstract

Abstract Retinoids (i.e. vitamin A and metabolites) have biological importance for functions involved in growth and development, immunity, and reproduction. Previous studies involving retinoids have demonstrated positive associations with increased luteal progesterone (P4) concentrations, and similarly, progesterone has been implicated in the regulation of uterine secretion of retinol-binding protein (RBP), warranting further investigation. Therefore, the aim of this study was to identify the expression of various enzymes and binding proteins involved in vitamin A metabolism in corpora lutea (CL) and endometria during d 15 of the estrous cycle and throughout various points of gestation in gilts. Sexually mature, crossbred gilts were ovariohysterectomized on d 11, 15, 60, or 90 of pregnancy, or d 15 of the estrous cycle (cyclic d 15). Plasma was collected for P4 and vitamin A analysis. Corpora luteal and endometrial tissues were analyzed for mRNAs associated with vitamin A metabolism. There were no differences in CL count, P4 concentrations, or vitamin A concentrations by cyclic or gestational day (P > 0.05). Corpora lutea expression of aldehyde dehydrogenase 1 family member A1 (ALDH1A1) and RBP4 mRNAs were greater on d 15 of pregnancy compared cyclic d 15 gilts (P < 0.05). Moreover, corpora lutea mRNA expression of ALDH1A1 (P = 0.0003), RBP2 (P = 0.02), and alcohol dehydrogenase 1C (ADH1C, P = 0.07) were greater on d 11 of pregnancy. Corpora lutea expression of lecithin retinol acyltransferase (LRAT) mRNA were not different (P > 0.05). Endometrial mRNA expression of ALDH1A1 was greater on cyclic d 15 compared to d 15 of pregnancy (P = 0.002). Endometrial mRNA expression of ALDH1A1 and LRAT were greater on d 60 and 90 of pregnancy compared to d 11 and 15 of pregnancy (P ≤ 0.0001). Endometrial expression of RBP4 mRNA was greater on d 11 and 60 compared to d 90, and greater on d 60 compared to d 15 (P = 0.01). Endometrial expression of ADH1C and RBP2 mRNAs were not different (P > 0.05). These results suggest that genes encoding enzymes involved in vitamin A metabolism (ALDH1A1, ADH1C, RBP2, and RBP4) are elevated in the CL during the period of early gestation when the anti-luteolytic mechanism of maternal recognition of pregnancy is occurring. Additionally, certain genes encoding enzymes involved in vitamin A metabolism (ALDH1A1 and LRAT) are elevated mid- to late-gestation in the endometrium of pregnant pigs.