Proceedings of The Physiological Society
University of Cambridge (2008) Proc Physiol Soc 11, PC36
Effect of weight and adiposity at conception and gestational dietary intake on pregnancy outcome in young adolescent sheep
R. P. Aitken1, J. S. Milne1, J. M. Wallace1
1. Rowett Research Institute, Aberdeen, United Kingdom.
Adverse pregnancy outcome is common in young adolescent girls. To date studies using adolescent sheep have focussed on the role of maternal diet after conception. However girls become pregnant from diverse nutritional backgrounds which may interact with subsequent gestational intake to influence pregnancy outcome. This aspect has been examined here. Singleton pregnancies to a single sire were established by embryo transfer in two groups of adolescents of identical age but different initial weight and adiposity score (mean ± sem; 47±0.3kg and 2.6±0.02 units vs. 37±0.3kg and 2.1±0.01 units), and classified as good (G) vs. poor (P) body mass index (BMI), respectively. Thereafter, ewes were either offered a moderate intake to maintain maternal adiposity throughout pregnancy (optimally nourished control [C]), undernourished to maintain weight at conception but deplete maternal body reserves (UN, 0.75 x C), or overnourished to promote rapid maternal growth and adiposity (ON, 2.25 x C), resulting in a 2 x 3 factorial, n=15 /group). Blood samples were collected at 28- day intervals to assess metabolic status in relation to pregnancy outcome. Maternal glucose handling and sensitivity to insulin were additionally assessed at the end of the second third of gestation following either i.v. glucose or insulin. Conception rate was 82 % and was independent of initial BMI and gestational intake. For the G-C, P-C, G-UN, P-UN, G-ON and P-ON dams, respectively the average gestational change in external adiposity score was 0, +0.1, -0.8, -0.5, +0.6 and +0.9 units. Length of gestation and colostrum yield at term were independent of initial BMI but influenced by gestational intake (145.1, 146.2, 143.3 days and 362, 309,152 g in C, UN and ON groups respectively, P<0.001, ANOVA). Lamb birth weight was influenced by initial BMI (P<0.03) and gestational intake (P<0.001) and was 5631, 5218, 4942, 4592, 4504 and 3950g for the G-C, P-C, G-UN, P-UN, G-ON and P-ON groups, respectively. Placental and total fetal cotyledon weights were similarly influenced by both initial BMI and gestational intake (P<0.002). At Day 0, maternal insulin, glucose, non-esterified fatty acid (NEFA) and urea concentrations were similar between groups and leptin was higher in G versus P (P<0.05). By Day 28 of gestation, insulin, glucose, NEFA and urea concentrations began to diverge and thereafter directly reflected current gestational intake (ON>C>UN for insulin, glucose, urea; UN>C>ON for NEFA). Initial BMI did not influence glucose or insulin sensitivity but ON dams had higher insulin secretion after glucose administration (P<0.008) and higher glucose concentrations after insulin (P<0.001) compared with the C and UN groups, which were equivalent. Thus, the dominant negative effect on pregnancy outcome was gestational intake with ON>UN compared with C.
Where applicable, experiments conform with Society ethical requirements