Transforming growth factor (beta1) in testes of aged and diabetic rats: correlation with testicular function

This study was conducted to evaluate the expression of transforming growth factor-beta1 (TGF-beta1) in testis with aging and progress of diabetes mellitus (DM) and correlated this with testicular function. Zucker diabetic fatty rats (15, 40, and 75 weeks old) were used as models for non-insulin-dependent DM. The controls were age-matched nondiabetic Zucker fatty rats. Serum testosterone levels and daily sperm production were evaluated. Testicular tissue was immunostained with anti-TGF-beta1. Labeled cells were assessed and the staining intensity was estimated. The 15-week control and diabetic animals showed the lowest levels of staining intensity but this started to increase significantly in the older animals of both categories. However, the diabetic animals had significantly deeper intensities relative to controls at the different age groups. These changes in TGF-beta1 expression were negatively correlated with both testosterone and sperm production. Therefore, aging and DM enhanced the expression of TGF-beta1 in testis, and this was parallel with progress of both conditions, although DM seems to be predominant. These alterations in TGF-beta1 expression may be related to changes in testicular function associated with both conditions.