Investigation of equine testis contribution to vitamin D bioactivation

Marion Rouge (1) , Razan Elkhatib (1) , Christelle Delalande (1) , Juliette Cognié (2) , Fabrice Reigner (3) , Philippe Barriere (3) , Stefan Deleuze (4) , Matthieu Cousty (5) , Florence Legendre (6) , Philippe Galéra (6) , Vincent Hanoux (1) , Hélène Bouraima-Lelong (1)

1 OeReCa - Œstrogènes, reproduction, cancer
2 PRC - Physiologie de la reproduction et des comportements [Nouzilly]
3 UE PAO - Unité Expérimentale de Physiologie Animale de l‘Orfrasiére
4 Université de Liège
5 Centre Hospitalier Vétérinaire Equin du Livet
6 BIOTARGEN - Biologie, génétique et thérapies ostéoarticulaires et respiratoires

Although vitamin D acts in various biological processes, it plays a critical role in the maintenance of bone health, and regulates calcium homeostasis. In humans and rodents, the main tissues involved in vitamin D metabolism are the liver and the kidneys, however it has been shown that the testis has strongly participated in its bioactivation. Indeed, in these different species, enzymes metabolizing vitamin D (CYP27A1, CYP27B1 and CYP2R1) have been demonstrated in this tissue. Moreover, men with hypogonadism have shown a decrease in circulating levels of vitamin D. In equine species, the castration of males is a regular practice to reduce the behavior of stallions deemed too aggressive. Castration is carried out at various ages: in foals during their growth or in adulthood once they have reached their optimum size. Although horses exhibit atypical vitamin D metabolism with low circulating levels of vitamin D, it was suggested that testis may contribute to its activation as has been described in rodents and humans; castration could therefore be likely to affect its metabolism. In this study, blood levels of bioactive form of vitamin D (1 α,25[OH] 2 vitamin D 3 ) were measured before and after castration at different ages: 1 wk, after puberty (2 yr) and at adulthood (6 yr). The gene expression of enzymes involved in vitamin D metabolism has been sought in the testis of different experimental groups. No change in bioactive vitamin D3 levels was observed after castration regardless of the age at the time of surgery. The exceptional status of equine species is confirmed with a low or a lack of testis contribution to vitamin D metabolism, regardless of testicular development. This is demonstrated by a low or a lack of signal from enzymes involved in vitamin D bioactivation. Therefore, horses constitute a unique model in comparative endocrinology.

Mots clés: Equine specie; Testis; Vitamin D bioactivation

Domaines: Sciences du Vivant [q-bio]

Marion Rouge, Razan Elkhatib, Christelle Delalande, Juliette Cognié, Fabrice Reigner, et al.. Investigation of equine testis contribution to vitamin D bioactivation. Domestic Animal Endocrinology, 2022, 79, pp.1-9. ⟨10.1016/j.domaniend.2021.106691⟩. ⟨hal-03478703⟩