Metformin blocks mitochondrial membrane potential and inhibits sperm motility in fresh and refrigerated boar spermatozoa

Contents Metformin is clinically used to treat diabetes. Given its role-impacting metabolism, metformin has been also added to semen cryopreservation media showing specie-dependent effects. We aimed to investigate metformin effects in both fresh (38.5 degrees C for 2, 24hr) and refrigerated (17 degrees C for 10days) boar spermatozoa. Metformin (2hr) does not affect fresh sperm viability, membrane lipid organization nor acrosome integrity. However, metformin (24hr) blocks sperm m and significantly reduces % motile spermatozoa (65%), % progressive spermatozoa (50%), % rapid (100%), velocities VCL (69%), VSL (86%), VAP (78%) and motility coefficients. Metformin-including extender does not modify sperm viability, membrane lipid organization or acrosome integrity. Furthermore, it significantly reduces high -population spermatozoa at refrigeration day 4. Metformin also significantly reduces sperm motility during refrigeration. Summarizing, metformin inhibits both boar sperm and motility in any sperm condition studied: fresh and refrigerated. These findings dissuade metformin as an additive to improve boar sperm quality.