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Paul R Shorten, Erin L Legacki, Pascale Chavatte-Palmer, and Alan J Conley

Hormone secretion by the maternal ovaries, trophoblast/placenta and fetus occurs sequentially, creating distinct steroid metabolomic ‘signatures’ in systemic blood of pregnant mares that vary with gestational stage. Algorithms were developed to predict the gestational day (GD) from the maternal steroid metabolome (nine steroids; pregnenolone (P5), progesterone (P4), 5α-dihydroprogesterone (DHP), 17α-hydroxyprogesterone, allopregnanolone, 20α-hydroxy-DHP, 3β,20α-dihydroxy-DHP, DHEA and androstenedione) determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) of eight thoroughbred mares sampled longitudinally throughout pregnancy. A physiologically based model was developed to infer rates of steroid secretion during chorionic gonadotropin secretion, the luteo-placental shift and by the equine feto-placenta unit, demonstrating more variability in P5 and DHP than P4. The average of four empirical models, using nine steroids to predict GD, was calibrated (five mares, R2 = 0.94, RMSE = 20 days) and validated (three mares, R2 = 0.84, RMSE = 32 days). Validation performance was improved using paired samples taken 14 or 30 days apart (RMSE = 29 and 19 days, respectively). A second validation used an independent dataset (single serum samples from 56 mixed breed mares, RMSE = 79 days) and an additional longitudinal subset from the same population sampled monthly throughout gestation (seven mares, RMSE = 42 days). Again, using paired samples improved model performance (RMSE = 32.5 days). Despite less predictive performance of the mixed breed than the thoroughbred datasets, these models demonstrate the feasibility and potential for using maternal steroid metabolomic algorithms to estimate the stage of gestation in pregnant mares and perhaps monitor fetal development.

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Alison Mostyn, Linda Attig, Thibaut Larcher, Samir Dou, Pascale Chavatte-Palmer, Monia Boukthir, Arieh Gertler, Jean Djiane, Michael E Symonds, and Latifa Abdennebi-Najar

Intrauterine growth restriction (IUGR) may be accompanied by inadequate thermoregulation, especially in piglets that are not considered to possess any brown adipose tissue (BAT) and are thus entirely dependent on shivering thermogenesis in order to maintain body temperature after birth. Leptin can stimulate heat production by promoting non-shivering thermogenesis in BAT, but whether this response occurs in piglets is unknown. Newborn female piglets that were characterised as showing IUGR (mean birth weight of approximately 0.98 kg) were therefore administered injections of either saline or leptin once a day for the first 5 days of neonatal life. The dose of leptin was 0.5 mg/kg, which is sufficient to increase plasma leptin by approximately tenfold and on the day of birth induced a rapid increase in body temperature to values similar to those of normal-sized ‘control’ piglets (mean birth weight of ∼1.47 kg). Perirenal adipose tissue was then sampled from all offspring at 21 days of age and the presence of the BAT-specific uncoupling protein 1 (UCP1) was determined by immunohistochemistry and immunoblotting. UCP1 was clearly detectable in all samples analysed and its abundance was significantly reduced in the IUGR piglets that had received saline compared with controls, but was raised to the same amount as in controls in those IUGR females given leptin. There were no differences in gene expression between primary markers of brown and white adipose tissues between groups. In conclusion, piglets possess BAT that when stimulated exogenously by leptin can promote increased body temperature.