Exacerbation of diabetes-induced testicular apoptosis by zinc deficiency is most likely associated with oxidative stress, p38 MAPK activation, and p53 activation in mice

Since diabetes induces testicular oxidative damage and cell death, and zinc (Zn) plays an important role in the spermatogenesis, the objective of the present study was to define the effects of Zn deficiency on diabetes-induced testicular apoptosis and associated mechanisms. Zn deficiency was induced by chronic treatment of normal and diabetic mice with N,N,N′,N′-tetrakis (2-pyridylemethyl) ethylenediamine (TPEN) chelation. After diabetes onset, mice were given intraperitoneally TPEN at 5 mg/kg daily for four months, which, like diabetes, induced a significant decrease in testicular Zn level. TUNEL staining revealed that testicular apoptosis was significantly increased along with an increased Bax/Bcl-2 ratio, in diabetic mice and TPEN-treated normal mice. Zn deficiency significantly exacerbated diabetes-induced testicular apoptosis, along with significantly increased oxidative and nitrosative damage and down-regulation of antioxidant Nrf2 expression. Increased oxidative stress was associated with an increase in activation of p38 MAPK and p53 protein in diabetic testis, which was worsened in the testes of diabetic mice with Zn deficiency. Diabetes also induced a significant increase in endoplasmic reticulum stress and associated cell death, which was not affected by Zn deficiency. These results suggest that like diabetes, chronic depletion of Zn with TPEN induces testicular oxidative stress and damage, along with the activation of p38 MAPK and p53 signaling and mitochondria-related apoptotic cell death. Therefore, prevention of Zn deficiency for diabetic patients is important in order to avoid the exacerbation of diabetic effects on testicular cells death.