Influence of type 2 diabetes mellitus on the morphology and apoptosis of germ cells in male mice

Abstract:

Objective To investigate the influence of type 2 diabetes mellitus（T2DM） on testicular histomorphology，testosterone secretion，and spermatogenesis by establishing a male mouse model of T2DM.Methods A total of 24 male C57BL/6J mice，aged 8 weeks，were randomly divided into control group with 10 mice and T2DM group with 14 mice. The mice in the control group were fed a basal diet，and those in the T2DM group were fed a high-fat diet. After 8 weeks，the mice in the control group were given intraperitoneal injection of citrate buffer，and those in the T2DM group were given intraperitoneal injection of 60 mg/kg streptozotocin（STZ），for 5 consecutive days. The mice were sacrificed after 4 weeks of feeding，and the serum，testis，and epididymis of the male mice were isolated. Sperm count and testosterone level were measured to assess the spermatogenic function of germ cells in male mice；HE staining was used to observe the morphological changes of the testis；TUNEL staining was used to observe the apoptosis of testicular germ cells. ELISA was used to measure the serum levels of superoxide dismutase（SOD），malondialdehyde（MDA），and heme oxygenase-1（HO-1），and Western blot was used to measure the protein expression levels of B cell lymphoma/leukemia-2（Bcl-2），Bcl-2-associated X protein（BaX），and cysteinyl aspartate specific proteinase-3（caspase-3） in testicular tissue of male mice.Results Compared with the control group，the T2DM group had significant reductions in body weight [（26.00±2.85） g vs. （29.71±4.28） g，P=0.000]，sperm number [（4.15±1.01） ×10⁶/L vs. （5.56±0.70）×10⁶/L，P=0.009]，and testosterone level [（0.99±0.41） ng/mL vs. （19.85±10.23） ng/mL，P=0.041]. TUNEL staining showed that the T2DM group had varying degrees of apoptosis in spermatogenic cells at all levels of testicular seminiferous tubules，with a significant increase in the number of apoptotic cells（21.60±5.11，P=0.033）. ELISA showed that the T2DM group had significant increases in the expression levels of the serum oxidative stress markers SOD（4.42±0.47） pg/mL and HO-1（2 968.00±536.10） pg/mL（P=0.000 and 0.008）. Western blot showed significant increases in the protein expression levels of BaX（1.270±0.059） and caspase-3（1.94±0.47）（P=0.008 and 0.041） and BaX/Bcl-2 ratio.Conclusion Male mice with T2DM have a significant reduction in serum testosterone level，a significant increase in the apoptosis of spermatogenic cells，and a significant reduction in the number of mature spermatogenic cells，which affect reproductive capacity.