High glucose in the extender impacts the metabolic phosphoproteome and modifies the phosphorylation of AKAP4 in stallion spermatozoa

Commercial extenders for equine semen typically contain high glucose concentrations; however, recent research indicates that these supraphysiological concentrations of glucose may be detrimental. Spermatozoa lack translational activity and depend on post-translational protein modifications for their regulation. Supraphysiological glucose concentrations are known to modify cell regulation, and we hypothesize that post-translational modification deregulation associated with supraphysiological glucose concentrations occurs in spermatozoa extended in high glucose media; and increasing the concentration of pyruvate in the media, may prevent this deregulation. Stallion ejaculates were split into different media containing 67 mM glucose and 1 mM pyruvate or 67 mM glucose and 10 mM pyruvate. After three hours of incubation at 38ºC, aliquots were taken for proteomic and kinematic analysis. Spermatozoa incubated in the high glucose (67 mM), low pyruvate (1 mM) media showed an alteration of the phosphorylation of the AKAP4 (P < 0.01), and modifications in gene ontology terms linked to sperm functionality. The incorporation of 10 mM pyruvate prevented all these changes, also kinematic efficiency was improved in the 67 mM glucose 10 mM pyruvate media. It is concluded that supraphysiological glucose concentrations alter the post-translational modifications of proteins essential for sperm function, and that this effect can be reduced in the presence of 10 mM pyruvate.