Melatonin intake since weaning ameliorates steroidogenic function and sperm motility of streptozotocin-induced diabetic rats

Melatonin may be used as an antioxidant in therapy against systemic sequelae caused by oxidative stress in diabetes. However, as melatonin has a major role in regulating reproductive activity, its consequence on reproductive parameters under diabetes needs to be better clarified. We have studied whether prior and concomitant treatment of juvenile Wistar rats with low doses of melatonin interferes in reproductive damage induced by experimental diabetes after 1 and 8weeks. The consequences of melatonin administration since weaning on reproductive parameters of healthy rats at adulthood were also evaluated. Melatonin was provided in drinking water (10g/kg b.w./day) after weaning (5-week-old). Diabetes was induced by streptozotocin injection (4.5mg/100g b.w.) at 13-week-old rats, and rats were euthanized 1 and 8weeks after disease onset. Diabetes decreased circulating testosterone levels (similar to 35% to 1week; similar to 62% to 2months; p<0.01) but did not affect testes sperm counts. Twomonths of diabetes reduced the sperm reserve and led to atrophy of epididymal cauda. Both 1-week and 2-month diabetes impaired sperm motility, decreased the number of spermatozoa with progressive movement, and increased the number of immotile sperm. Melatonin intake reduced serum testosterone levels similar to 29% in healthy 14-week-old and similar to 23% in 21-week-old rats and reduced daily testicular sperm production similar to 26% in the latter disease stage, but did not interfere in sperm reserves and transit time for both experimental periods. Exogenous melatonin prevented the serum testosterone decrease and damage to sperm motility in diabetic rats and attenuated reduction in sperm counts and transit time induced by 1-week diabetes but did not avoid this decrease at 2-month diabetes. Low doses of melatonin administered prior to and during experimental diabetes attenuated damage to testicular steroidogenic activity and preserved sperm motility, but not sperm reserves in the rat. Our data indicated a differential action of melatonin in normoglycemic and hyperglycemic conditions, particularly in sperm motility and testosterone production by Leydig cells.