Captopril pretreatment augments diabetogenic response to streptozotocin administration: experimental in vivo rat model

Streptozotocin (STZ) is a glucose analogue commonly used for inducing diabetes in experimental animals. This study is intended to investigate the ability of captopril (Cap) pretreatment to augment STZ-induced diabetogenic effect in an experimental rat model. If this hypothesis were proven, Cap administration to rats could reduce the dosage of STZ by augmenting its effect and resulting in a subsequent reduction in STZ cost. Forty-two adult male Wistar rats were randomly divided into seven groups: a control group that fed a normal diet, whereas the other six experimental groups were fed a high-fat diet (HFD). The six groups were then divided into STZ-30, STZ-30-Cap, STZ-40, STZ-40-Cap, STZ-50, and STZ-50-Cap. All Cap-received groups were supplemented with 50 mg/kg Cap orally one hour just before intraperitoneal (I.P.) injection of STZ. 30-STZ, 40-STZ, and 50-STZ-treated groups were injected once with STZ I.P. at doses of 30, 40, and 50 mg/kg, respectively. An intraperitoneal glucose tolerance test (IPGTT) was done. Pancreatic tissue was obtained to measure Tumor necrosis factor alpha (TNF-α), interleukin one beta (IL-1β), and nitric oxide (NO) by enzyme-linked immunosorbent assay (ELISA) and glucose transporter 2 (GLUT2) gene expression by reverse transcription polymerase chain reaction (RT-PCR). Pancreatic sections were examined by hematoxylin and eosin (H&E) stain, and immunohistochemical staining by anti-insulin and anti-TNF-α antibodies.

Results indicated that administration of Cap before STZ in different doses significantly augmented the hyperglycemic state that was evident by intraperitoneal glucose tolerance test, and markedly increased pancreatic pro-inflammatory markers. Histological analysis of islets of Langerhans indicated degeneration with extensive vacuolations associated with a significant decrease in mean area % of insulin immunoreactivity and an increase in optical density of TNF-α immunoreactivity.

These findings pointed to the ability of captopril pretreatment to augment the hyperglycemic state and the diabetogenic response that was induced secondary to STZ injection in an experimental rat model.