PSI-19 Poor maternal nutrition during gestation alters placental IGF-I, IGF-II, and IGFBP-3 mRNA expression in sheep

Abstract

Abstract Insulin-like growth factors (IGF) modulate placental and fetal growth and development through nutrient sensing and endocrine signaling. We hypothesized that poor maternal nutrition during gestation would alter IGF-I, IGF binding protein (IGFBP)-2, and IGFBP-3 mRNA expression in the ovine placenta, but would not affect IGF-II mRNA expression. Pregnant ewes (n = 57) were individually fed: 60% (RES), 100% (CON), or 140% (OVER) of National Research Council requirements for TDN starting at day 30±0.2 of gestation. Ewes were euthanized and cotyledon and caruncle samples were collected at days 45, 90, and 135 of gestation. Relative mRNA expression of IGF-I, IGF-II, IGFBP-2, and IGFBP-3 was quantified using real-time PCR. Data were analyzed using the MIXED procedure in SAS. Relative IGF-I mRNA expression increased during gestation in the caruncle (d45: 0.96±0.06; d90: 1.28±0.06; d135: 1.38±0.05; P < 0.001). In the caruncle, IGFBP-2 expression was greater at d90 and d135 than d45 (d45: 0.67±0.20; d90: 1.90±0.20; d135: 1.65±0.18; P < 0.001). There was no observed effect of diet or day of gestation on IGF-II or IGFBP-3 expression in the caruncle. In the cotyledon, IGF-I expression tended to be greater in RES than OVER, which was similar to CON (CON: 0.96±0.07; RES: 1.10±0.06; OVER: 0.89±0.07; P = 0.08). Relative IGF-II mRNA expression was greater in RES cotyledons than OVER (CON: 1.30±0.35; RES: 1.96±0.31; OVER: 0.54±0.32; P = 0.01). During gestation, IGFBP-2 expression decreased in the cotyledon (d45: 1.26±0.12; d90: 0.93±0.12; d135: 0.59±0.11; P < 0.001). Relative IGFBP-3 mRNA expression was less in RES cotyledons than in OVER or CON (CON: 1.84±0.64; RES: 0.03±0.57; OVER: 3.62±0.66;P < 0.001). The changes in IGF expression in the cotyledon to a greater extent than in the caruncle in response to poor maternal diet suggest a potential mechanism by which maternal-fetal exchange may be modified to restrict placental and fetal growth.