Hypoglycemic effect of Du-zhong (Eucommia ulmoides Oliv.) leaves in streptozotocin-induced diabetic rats

The current study investigated whether Du-zhong (Eucommia ulmoides Oliv.) leaves could improve the hyperglycemia in streptozotocin (STZ)-induced diabetic rats. Male Sprague-Dawley rats were divided into a non-diabetic group (NDM), diabetic group (DM), diabetic group supplemented with powdered Du-zhong leaves (DM-PDZ) and diabetic group supplemented with a water extract of the powdered Du-zhong leaves (DM-WDZ). Diabetes was induced by injecting STZ (70 mg/kg B.W., i.p.). The powdered Du-zhong leaves or its powdered water extract was add to a standard diet based on 1% dried Du-zhong leaves (1 g PDZ/100 g diet and 0.187 g WDZ/100 g diet, respectively) for 3 weeks. Body weight was significantly higher in both types of Du-zhong leaves supplemented groups than in the DM group. The blood glucose levels were significantly lower in the DM-PDZ and DM-WDZ groups than in the DM group (20.05 ± 0.88 and 18.96 ± 1.23 mmol/l versus 24.42 ± 1.07 mmol/l, P < 0.05), whereas the plasma insulin and C-peptide levels were significantly higher in the PDZ and WDZ supplemented groups than in the DM group (7.45 ± 0.27 and 7.62 ± 0.69 μl U/ml versus 3.75 ± 0.27 μl U/ml for the plasma insulin, and 224.52±14.6 and 239.76 ± 15.52 pmol/l versus 166.5 ± 10.4 pmol/l for the plasma C-peptide, respectively, P < 0.05). The supplementation of PDZ and WDZ also resulted in lower plasma urea nitrogen levels compared to the DM group. Du-zhong leaves supplement seemed to be helpful to preserve the normal histological appearance of pancreatic islets as well as to preserve insulin-positive β-cells but it did not reverse the effect of STZ to a great extent. Accordingly, the reduction in plasma glucose by the powdered Du-zhong leaves and its water extract is quite small but significant, nevertheless, this was occurred with simultaneous the increase in plasma insulin and C-peptide. They improved hyperglycemia and seemingly enhance the function of pancreatic β-cells in STZ-induced diabetic rats.