Date of Completion

Spring 4-27-2020

Thesis Advisor(s)

Sarah Reed

Honors Major

Animal Science

Disciplines

Animal Sciences | Sheep and Goat Science

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% (restricted fed; RES), 100% (control fed; CON), or 140% (over fed; 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 was less at day 45 than at days 90 and 135 in the caruncle (P < 0.001; d45: 0.96 ± 0.06, d90: 1.28 ± 0.06, d135: 1.38 ± 0.05). In the caruncle, IGFBP-2 expression was less at day 45 than at days 90 and 135 (P < 0.001; d45: 0.67 ± 0.20, d90: 1.90 ± 0.20, d135: 1.65 ± 0.18). There was no detectable impact of diet or time on IGF-II or IGFBP-3 expression in the caruncle (P > 0.12). In the cotyledon, IGF-I expression tended to be greater in RES than OVER, which was similar to CON (P = 0.08; RES: 1.10 ± 0.06, OVER: 0.89 ± 0.07, CON: 0.96 ± 0.07). Relative IGF-II mRNA expression was greater in RES than OVER cotyledons (P = 0.01; RES: 1.96 ± 0.31, OVER: 0.54 ± 0.32, CON: 1.30 ± 0.35). Relative IGFBP-2 mRNA expression decreased over time in the cotyledon (P < 0.001; d45: 1.26 ± 0.12, d90: 0.93 ± 0.12, d135: 0.59 ± 0.11). Relative IGFBP-3 mRNA expression was less in RES than in OVER or CON cotyledons (P = 0.009; RES: 0.03 ± 0.57, OVER: 3.62 ± 0.66, CON: 1.84 ± 0.64). In response to poor maternal diet, changes in IGF expression in the cotyledon were greater than in the caruncle, suggesting a potential mechanism by which maternal-fetal exchange may be modified to restrict placental and fetal growth.

Download

Share

COinS