Moderate-intensity exercise training elevates serum and pancreatic zinc levels and pancreatic ZnT8 expression in streptozotocin-induced diabetic rats.

Diabetes mellitus is associated with disturbed zinc homeostasis and down-regulation of zinc transporter 8 (ZnT8); these changes contribute to the defective biosynthesis, storage, and secretion of insulin. Previous studies have reported an improvement in diabetic status and insulin levels in diabetic rats that underwent moderate exercise training, but the mechanisms underlying this effect remain unclear. Evidence shows that exercise training increases the zinc content in the muscle, liver, and kidney of diabetic rats and increases the expression of several types of zinc transporters in the rat hippocampus. We hypothesised that moderate exercise training may increase serum and pancreatic zinc levels, as well as pancreatic ZnT8 expression, in diabetic rats. Wistar rats were divided into 3 equally sized groups: sedentary normal control, sedentary diabetic, and exercise-trained diabetic groups. Diabetes was induced by an intraperitoneal injection of streptozotocin. The 6-week exercise training intervention involved 30 min of moderate-intensity running on a treadmill once daily (5 days/week). At the end of the study, the concentrations of serum and pancreatic zinc were determined using atomic absorptive spectrophotometry. Pancreatic ZnT8 expression was analysed by quantitative real-time RT-PCR. Diabetes caused reductions in the serum and pancreatic zinc levels and pancreatic ZnT8 expression. Following moderate exercise training, there was a significant increase in all of these parameters. The ability of moderate exercise training to ameliorate the reductions in serum and pancreatic zinc levels and pancreatic ZnT8 expression can partly explain the beneficial effects of exercise training in diabetes.