Metformin and rosiglitazone affect motility, lipid peroxidation and mitochondrial activity of thawed equine spermatozoa

Maintaining sperm energy homeostasis in vitro is very important to improve the efficacy of stallion sperm preservation. Equine spermatozoa preferentially utilize oxidative phosphorylation over glycolysis to generate ATP. Metformin and rosiglitazone are antidiabetic compounds that enhances metabolic flexibility and glucose utilization. The aim of this study was to evaluate metformin and rosiglitazone supplementation of the freezing medium on quality and oxidative status of thawed stallion semen. A total of 15 ejaculates from five horses were collected and supplemented before freezing with metformin at 20 (M20), 50 (M50) and 100 mM (M100) and with rosiglitazone at 10 (R10), 50 (R50) and 100 µM (R100). A control group without supplementation was added. Semen cryopreservation was performed using a programable freezing protocol. Post-thaw, motility and kinetics, vitality (SV), morphology, plasma membrane integrity (PMI), mitochondria membrane potential (ΔΨM), reactive oxygen species (ROS) and lipid peroxidation (LP) of sperm were evaluated. Mixed models were adjusted and means were compared using Tukey tests. Total motility of post-thawed semen increased with M20; M100 reduced motility and most of the sperm kinetic parameters, as well as SV and PMI (p < 0.05). A reduction in LP was observed with M20 and R100; also, M100 produced a higher population of spermatozoa with low and high ΔΨM (p < 0.05). No treatment, except R50, generated an overproduction of ROS. In conclusion, a dose of 20 mM metformin in the freezing extender for stallion semen could improve total motility and reduce lipid peroxidation of thawed spermatozoa.