After seven days of quarantine period, animals were induced with diabetes through a single intraperitoneal (i.p.) injection of 60 mg/kg of streptozotocin (Sigma-Aldrich, Germany) after 10 h fasting. streptozotocin was dissolved in 0.1 M citrate buffer solution (pH 4.5) and immediately injected. Normal control rats received the same amount of sodium citrate buffer. Three days after streptozotocin injection, a blood sample was drawn from the tail vein and plasma glucose concentration was checked using the Accu-Chek blood glucose test meter (Roche Diagnostic, Germany). Rats with blood sugar higher than 300 mg/dL (more than 90% of injected animals) were considered diabetics (DM type I). No exogenous insulin treatment was given (19 (link)).