Aim: To investigate the in vitro effects of insulin and leptin on human sperm motility, viability, acrosome reaction and nitric oxide (NO) production.

Methods: Washed human spermatozoa from normozoospermic donors were treated with insulin (10 μIU) and leptin (10 nmol). Insulin and leptin effects were blocked by inhibition of their intracellular effector, phosphotidylinositol 3-kinase (PI3K), by wortmannin (10 μmol) 30 min prior to insulin and leptin being given. Computer-assisted semen analysis was used to assess motility after 1, 2 and 3 h of incubation. Viability was assessed by fluorescence-activated cell sorting using propidium iodide as a fluorescent probe. Acrosome-reacted cells were observed under a fluorescent microscope using fluorescein-isothiocyanate–Pisum sativum agglutinin as a probe. NO was measured after treating the sperm with 4,5-diaminofluorescein-2/diacetate (DAF-2/DA) and analyzed by fluorescence-activated cell sorting.

Results: Insulin and leptin significantly increased total motility, progressive motility and acrosome reaction, as well as NO production.

Conclusion: This study showed the in vitro beneficial effects of insulin and leptin on human sperm function. These hormones could play a role in enhancing the fertilization capacity of human spermatozoa.

Keywords: insulin, leptin, spermatozoa, nitric oxide, motility, acrosome reaction

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