Elsevier

Placenta

Volume 64, April 2018, Pages 44-52
Placenta

Placental function and structure at term is altered in broodmares fed with cereals from mid-gestation

https://doi.org/10.1016/j.placenta.2018.02.003Get rights and content

Highlights

  • Feeding cereals to broodmares in late gestation alters the vasculature development of placentas.

  • Feeding cereals to broodmares in late gestation alters the placental transcriptome.

  • Insulin resistance in late gestation in the horse alters the placental structure and function as observed in obese women.

Abstract

Introduction

Feeding pregnant broodmares with cereal concentrates has been shown to increase maternal insulin resistance and affect foal metabolism in the short and long-term. These effects are likely to be mediated by the placenta. Here, we investigated feto-placental biometry and placental structure and function at term in mares fed with or without cereals concentrates.

Material and methods

From 7 months of gestation, 22 multiparous mares were fed forage only (group F (n = 12)) or received forage and cracked barley (group B (n = 10)) until foaling. Foals and placentas were weighed and placental samples were collected above the umbilical cord insertion at birth. Placental histological structure was studied by stereology. A RNAseq analysis was performed on 9 placentas of each group. Enrichment of gene sets was analysed using the Gene Set Enrichment Analysis (GSEA) software using the KEGG and GO databases.

Results

No difference in feto-placental biometry was observed between groups. The volume of microcotyledonary vessels was decreased in B placentas and the vascular wall of allantoic arterioles was thickened. Gene sets involved in neutral amino acids, folate and anions transport and fatty acids, cholesterol and folate degradation were down-regulated while gene sets involved in RNA expression, inflammation and vascularisation were up-regulated in B placentas.

Conclusion

Feeding pregnant mares with concentrates from mid-gestation alters the placental function and structure as observed in other species in cases of maternal insulin resistance.

Introduction

Since the early nineties, epidemiological studies in the Human species and experimental studies in model animals demonstrated that alterations of the maternal environment from periconception affects offspring development and health at adulthood [1]. This concept, called Developmental Origins of Health and Diseases (DOHaD), has also been demonstrated in the equine species [2].

In the horse, placentation is diffuse and epitheliochorial. The haemotrophic exchanges between maternal and fetal blood occur through the placental microcotyledons, that are intensely branched vascular structures covered with a haemotrophic trophoblast. The microcotyledons form interdigitations with the maternal endometrium to maximize nutrient exchanges. Additionally, histotrophic exchanges are mediated by pseudo-stratified trophoblastic cells specialized in the transfer of nutrients secreted by the uterine glands and take place across areolae located in-between the microcotyledons [[3], [4], [5]].

In the equine industry, breeders often feed broodmares with cereals in late pregnancy. In two previous studies, we demonstrated that feeding broodmares with cereals from mid-gestation increases maternal insulin resistance and the development of osteochondrosis in the foals, with potential detrimental effects on the horse industry economy [6,7]. Nevertheless, no studies have yet been conducted to understand the effect on the structure and function of the placenta. The present study follows up these previous works and investigates the effects of feeding broodmares with a moderate amount of cereals from mid-gestation on the structure and function of the placenta at term. Placentas were measured at delivery and their structure was analysed using the stereology method and the ImageJ software. Placental function was assessed through the analysis of gene expression after RNA sequencing.

Section snippets

Animals

The animal studies received ethical approval from the local ethics committee (« Comité Régional d’Ethique pour l’Expérimentation Animale du Limousin ») under protocol number 5-2013-5.

Twenty-two multiparous Saddlebred mares (median age 9y; range 6-19y) were fed cracked barley and forage (B, n = 10) or forage only (F, n = 12) from the 7th month of gestation until foaling. Management of mares from insemination to parturition has been previously described by Peugnet et al. [6]. In the present work,

Feto-placental biometry

Feto-placental biometry results are shown in Table 1.

At parturition, no difference was observed between groups for birthweight nor for placental weight, surface, volume and efficiency. Females tended to be heavier than males (+14.3%, p = 0.05) and had a heavier placenta (+5.5%, p = 0.049).

Placental morphometry

Stereological results are shown in Table 1.

  • -

    Microcotyledonary region: No difference in volume and surface was observed between both groups for haemotrophic trophoblast and connective tissue. The volume of

Effect of cereal ingestion on placental structure and function

In the present study, feeding pregnant mares with cereals from mid-gestation affected the structure and function of the placenta at term.

We observed previously that broodmares fed with cereals were more insulin resistant in late gestation and maintained an hyperglycaemic state throughout the day compared to mares fed with forages only [6]. In fact, In their paper on the same group of mares, Peugnet et al. concluded from the IVGTT data that F mares must have been insulin resistant [21]. Careful

Conclusion

In conclusion, feeding the pregnant mares with cereals from mid gestation alters the feto-maternal exchanges in the placenta by affecting the placental structure and function of the vessels and increasing the placental inflammation. Modifications of placental structure and function observed in placentas of insulin resistant dams are similar to those observed in diabetic and/or obese women and laminitic broodmares.

Conflicts of interest

There are no conflicts of interest for all authors.

Acknowledgments

This work was funded by grants from the "Institut Français du Cheval et de l’Equitation" and by the "Fonds Eperon" (FOETALIM project). The funders had no role in study design, data collection and analysis, decision to publish, nor preparation of the manuscript. The authors are grateful to the staff of the Institut Français du Cheval et de l’Equitation (IFCE) experimental farm (Domaine de la Valade, Chamberet, France) for care and management of animals.

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