Potential Novel Biomarkers for Diabetic Testicular Damage in Streptozotocin-Induced Diabetic Rats: Nerve Growth Factor Beta and Vascular Endothelial Growth Factor

Background . It is well known that diabetes mellitus may cause testicular damage. Vascular endothelial growth factor (VEGF) and nerve growth factor beta (NGF- β ) are important neurotrophic factors for male reproductive system. Objective . We aimed to investigate the correlation between testicular damage and testicular VEGF and NGF- β levels in diabetic rats. Methods . Diabetes was induced by streptozotocin (STZ, 45 mg/kg/i.p.) in adult rats. Five weeks later testicular tissue was removed; testicular VEGF and NGF- β levels were measured by ELISA. Testicular damage was detected by using hematoxylin and eosin staining and periodic acid-Schiff staining, and apoptosis was identified by terminal-deoxynucleotidyl-transferase-mediated dUTP nick end labeling (TUNEL). Seminiferous tubular sperm formation was evaluated using Johnsen's score. Results . In diabetic rats, seminiferous tubule diameter was found to be decreased; basement membrane was found to be thickened in seminiferous tubules and degenerated germ cells. Additionally, TUNEL-positive cells were increased in number of VEGF+ cells and levels of VEGF and NGF- β were decreased in diabetic testes. Correlation between VEGF and NGF- β levels was strong. Conclusion . These results suggest that the decrease of VEGF and NGF- β levels is associated with the increase of the apoptosis and testicular damage in diabetic rats. Testis VEGF and NGF- β levels could be potential novel biomarkers for diabetes induced testicular damage.