The aim of this study was to examine the relationships between gestational nutrition, fetal ovarian development and offspring fertility in female sheep and to highlight the potential mechanisms underlying these relationships. Adult sheep (n = 79) were fed either a maintenance or 0.6 of maintenance plane of nutrition for the first 55 days of gestation and thereafter fed ad libitum. Fetuses were collected for analysis at days 55 and 75 of gestation. Female offspring were monitored from birth until 19 months of age. Effects of restricted nutrition were observed on maternal plasma concentrations of progesterone, creatinine, albumin and Ca2+ at day 55 and creatinine at day 75. Concentrations of metabolic factors and steroid hormones in day 75 fetal plasma were not affected by the restricted maternal plane of nutrition. At day 55 of gestation, fetal ovarian germ cell development was not affected by maternal plane of nutrition. At day 75 of gestation ovaries from fetuses whose dams were exposed to restricted nutrition contained more germ cells but had lower germ cell proliferation rates than controls. For female offspring at 8 months of age, the dams gestational plane of nutrition did not affect the onset of puberty, ovulation rate (OR) and antral follicle counts (AFC). At 19 months of age, ewes from dams exposed to the restricted plane of gestational nutrition had higher OR, AFC and progesterone concentrations while concentrations of FSH were lower. In conclusion, while effects on fertility per se are yet to be determined, a reduced maternal plane of gestational nutrition can improve indicators of fertility in female offspring.
Peter Smith, Jo-Ann L Stanton, Laurel Quirke and Jennifer L Juengel
Peter Smith, Jennifer Juengel, Paul Maclean, Christy Rand and Jo-Ann L Stanton
A number of studies have demonstrated effects of gestational undernutrition on fetal ovarian development and postnatal female fertility. However, the mechanism underlying these effects remains elusive. Using a cohort of animals in which altered gestational nutrition affected indicators of postnatal fertility, this study applies RNAseq to fetal ovaries to identify affected genes and pathways that may underlie the relationship between gestational plane of nutrition and postnatal fertility. Pregnant ewes were exposed to either a maintenance diet or 0.6 of maintenance for the first 55 days of gestation followed by an ad libitum diet. Complementary DNA libraries were constructed from 5 to 6 fetal ovaries from each nutritional group at both days 55 and 75 of gestation and sequenced using Ion Proton. Of approximately 16,000 transcripts, 69 genes were differentially expressed at day 55 and 145 genes differentially expressed at day 75. At both gestational ages, genes expressed preferentially in germ cells were common among the differentially expressed genes. Enriched gene ontology terms included ion transport, nucleic acid binding, protease inhibitor activity and carrier proteins of the albumin family. Affected pathways identified by IPA analysis included LXR/RXR activation, FXR/RXR activation, pathways associated with nitric oxide production and citrullination (by NOS1), vitamin C transport and metabolism and REDOX reactions. The data offer some insights into potential mechanisms underlying the relationship between gestational plane of nutrition and postnatal fertility observed in these animals. In particular, the roles of nitric oxide and protease inhibitors in germ cell development are highlighted and warrant further study.