Endocrinology and metabolomics of uterine fluid after breeding in the mare

• Published in: Journal of equine veterinary science 2023-06, Vol.125, p.104721, Article 104721
• Main Authors: Kalpokas, Irene, Radcenco, Andres López, Pardié, Mateo, Gómez-Cuetara, Concepción, Villar, Lucia, Rotella, Franco, Moyna, Guillermo, Meikle, Ana
• Format: Article
• Language: English
• ISSN: 0737-0806; 1542-7412
• DOI: 10.1016/j.jevs.2023.104721

Understanding the endocrinology and metabolome variations in the uterine milieu is essential for pregnancy success (Assman and Finlay; Journal of Clinical Investigation. 2016; 126(6):2031-2039). The aim of the study was to determine adipokines and metabolites in uterine fluid after breeding. Healthy oestrous mares (n=6; age 5 to 12 years), monitored by ultrasound for follicle development and screened for uterine inflammation were inseminated with fresh semen. Eight hours after insemination, a low volume uterine flush (50 ml of PBS) was performed and the supernatant was obtained for analysis. Adiponectin and leptin were assessed by radioimmunoassays, while metabolites were determined by spectrophotometry and 1H nuclear magnetic resonance (NMR) spectroscopy. The concentration of adiponectin ranged from 5.6 to 17.6 ng/mL and leptin from 0.11 to 16.1 ng/mL. Albumin concentration ranged from 0.4 to 0.9 g/L, glucose 40 to 70 umol/L, globulins 0.8 to 1.5 g/L, and urea 0.4 to 1.8 mmol/L. Triglycerides and cholesterol were not detected in some samples or maximum concentrations were up to 12.4 mg/dL and 0.08 mmol/L respectively. NMR spectroscopy detected amino acids such as creatine, valine, isoleucine and taurine in the uterine fluid. High concentrations of lactate were observed, while lower contents of pyruvate, citrate, beta-hydroxybutirate and acetate were found (Figure 1). While albumin and globulins are present in equine uterine fluid (Tunón. et.al. Theriogenology.1998; 50(6): 821-831), this is the first report on adipokines and metabolites in uterine fluidafter breeding. Many of the metabolites are considered biomarkers of cell signaling regulation (Tríbulo.et.al. Molecular Reproduction and Development. 2019; 86(1):75-87) and metabolic stress in cattle (López Radcenco.et.al. Dairy 2021; 2:356-366) and may affect sperm transport and bacterial removal from the uterus. Adipokines and metabolome variations in uterine fluid as diagnostic markers may allow to investigate therapeutic strategies and thus improve reproductive performance in the mare.