Germ cell abnormalities in streptozotocin induced diabetic mice do not correlate with blood glucose level

To assess the effect of streptozotocin induced hyperglycemia on germ cell integrity, DNA ploidy and methylation status for a period of two spermatogenesis cycles in adult male Swiss albino mice.

Streptozotocin injected mice were monitored for hyperglycemia at a regular interval for a period of 36 and 72 days. The DNA integrity in epididymal spermatozoa was determined by the comet assay. Flow cytometric analysis was done in germ cells to assess the DNA ploidy. The global methylation analysis in germ cells was done by 5-methyl cytosine immunostaining.

Streptozotocin administration successfully resulted in hyperglycemic response which significantly affected serum testosterone level, sperm DNA integrity and DNA ploidy at the end of 36 days. However, no changes were observed in either epididymal sperm concentration or germ cell methylation status. In contrast, at the end of 76 days, although serum testosterone level, sperm DNA integrity and DNA ploidy status were unperturbed significantly in hyperglycemic group, the epididymal sperm concentration and methylation status of preleptotene/zygotene cells were significantly altered. Importantly, an attempt to find out the association between the blood glucose levels and the abnormalities in hyperglycemic group failed to demonstrate any correlation.

The germ cell abnormalities observed in hyperglycemic group could be interpreted as a primary effect of streptozotocin and not due to hyperglycemia. Our results call for further evaluation of streptozotocin before its application to study the hyperglycemic responses on male germ cells.