Background: A moderately high fructose diet fed to rat dams shifts the secondary sex ratio in the litters towards males. These dams, as well as diabetic pregnant mice, have elevated plasma glucose. Hence, high uterine fluid glucose or a hormone that may mark high glucose, may result in preferential selection of Y-bearing sperm at the point of fertilisation through effects of glucose on sperm motility. In this study, we assessed sperm motility after incubation in media with/without physiologically high glucose.
Methods: X and Y bearing spermatozoa were separated using flow cytometry. Motility was measured using computer-assisted sperm analysis (CASA; Hobson sperm tracker 7). Straws were de-thawed and semen was added to fertilisation media with/without 5 mM glucose. Sperm motility parameters were measured hourly from 06 h, in 10 µl samples added to a slide on a heated stage (37 °c). Approximately 100 spermatozoa were tracked in quadruplicate at each time point. Parameters of interest included motion linearity and velocity and the percentage motile, active and/or hyperactive.
Results: Sex sorted spermatozoa (n=3 replicates) had significantly reduced baseline motility compared to unsorted spermatozoa (n=6). Furthermore, motile sexed spermatozoa predominantly moved in circles (as oppose to straight line) and the majority became immotile after only 3 hours (compared to 6 h for unsorted semen). Incubation in 5 mM glucose appeared to decrease sperm linear velocity and the percentage motile (P<0.05) but this did not appear to be influenced by spermatozoa sex.
Conclusions: In this pilot study, sex-sorted spermatozoa have very different motility characteristics to unsorted spermatozoa and preliminary evidence suggests that Y-bearing spermatozoa may respond more favourably to a high glucose environment, although this hypothesis has to be confirmed with further replicates.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.