Metformin Improves Quality of Post-Thaw Canine Semen

Sperm cryopreservation is an assisted reproductive technique routinely used in canine species for genetic conservation. However, during cryopreservation, the DNA damages are still elevated, limiting the fertilization rate. The present study was conducted to evaluate whether supplementation of canine semen extender with a molecule limiting the metabolic activities can improve the quality of frozen-thawed canine spermatozoa. We used metformin, known to limit the mitochondrial respiratory and limit the oxidative stress. Before and during the freezing procedure, metformin (50µM and 500µM) has been added to the extender. After thawing, sperm exposed to metformin conserved the same viability without alteration in the membrane integrity or acrosome reaction. Interestingly, 50µM metformin improved the sperm motility in comparison to the control, subsequently increasing mitochondrial activity and NAD⁺ content. In addition, the oxidative stress level was reduced in sperm treated with metformin improving the sperm quality as measured by a different molecular marker. In conclusion, we have shown that metformin is able to improve the quality of frozen-thawed dog semen when it is used during the cryopreservative procedure.