The Rat Model of Type 2 Diabetic Mellitus and Its Glycometabolism Characters

To develop a rat model of type 2 diabetic mellitus that simulated the common manifestation of the metabolic abnormalities and resembled the natural history of a certain type 2 diabetes in human population, male Sprague-Dawley rats (4 months old) were injected with low-dose (15 mg/kg) STZ after high fat diet (30% of calories as fat) for two months (L-STZ/2HF). The functional and histochemical changes in the pancreatic islets were examined. Insulin-glucose tolerance test, islet immunohistochemistry and other corresponding tests were performed and the data in L-STZ/2HF group were compared with that of other groups, such as the model of type 1 diabetes (given 50 mg/kg STZ) and the model of obesity (high fat diet). The body weight of rats in the group of rats given 15 mg/kg STZ after high fat diet for two months increased significantly more than that of rats in the group of rats given 50 mg/kg STZ (the model of type 1 diabetes) (595 +/- 33 g vs. 352 +/- 32 g, p<0.05). Fast blood glucose levels for L-STZ/2HF group were 16.92 +/- 1.68 mmol/l, versus 5.17 +/- 0.55 mmol/l in normal control and 5.59 +/- 0.61 mmol/l in rats given high fat diet only. Corresponding values for fast serum insulin were 0.66 +/- 0.15 ng/ml, 0.52 +/- 0.13 ng/ml, 0.29 +/- 0.11 ng/ml, respectively. Rats of type 2 diabetes (L-STZ/2HF) had elevated levels of triglyceride (TG, 3.82 +/- 0.88 mmol/l), and cholesterol(Ch, 2.38 +/- 0.55 mmol/l) compared with control (0.95 +/- 0.15 mmol/l and 1.31 +/- 0.3 mmol/l, respectively) (p<0.05). The islet morphology as examined by immunocytochemistry using insulin antibodies in the L-STZ/2HF group was affected and quantitative analysis showed the islet insulin content was higher than that of rats with type 1 diabetes (P<0.05). We concluded that the new rat model of type 2 diabetes established with conjunctive treatment of low dose of STZ and high fat diet was characterized by hyperglycemia and light impaired insulin secretion function accompanied by insulin resistance, which resembles the clinical manifestation of type 2 diabetes. Such a model, easily attainable and inexpensive, would help further elucidation of the underlying mechanisms of diabetes and its complications.