Protective effects of Pycnogenol® on hyperglycemia-induced oxidative damage in the liver of type 2 diabetic rats

Abnormal regulation of glucose and impaired carbohydrate utilization that result from a defective or deficient insulin are the key pathogenic events in type 2 diabetes mellitus (T2DM). Experimental and clinical studies have shown the antidiabetic effects of Pycnogenol® (PYC). However, the protective effects of PYC on the liver, a major metabolic organ which primarily involves in glucose metabolism and maintains the normal blood glucose level in T2DM model have not been studied. The present study evaluated the beneficial effect of PYC, French maritime pine bark extract, on hyperglycemia and oxidative damage in normal and diabetic rats. Diabetes was induced by feeding rats with a high-fat diet (HFD; 40%) for 2 weeks followed by an intraperitoneal (IP) injection of streptozotocin (STZ; 40 mg/kg; body weight). An IP dose of 10 mg/kg PYC was given continually for 4 weeks after diabetes induction. At the end of the 4-week period, blood was drawn and the rats were then sacrificed, and their livers dissected for biochemical and histopathological assays. In the HFD/STZ group, levels of glycosylated hemoglobin (HbA1c), significantly increased, while hepatic glycogen level decreased. PYC supplementation significantly reversed these parameters. Moreover, supplementation with PYC significantly ameliorated thiobarbituric reactive substances, malonaldehyde, protein carbonyl, glutathione and antioxidant enzymes [glutathione-S-transferase, catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase] in the liver of HFD/STZ rats. These results were supported with histopathological examinations. Although detailed studies are required for the evaluation of the exact protective mechanism of PYC against diabetic complications, these preliminary experimental findings demonstrate that PYC exhibits antidiabetic effects in a rat model of type 2 DM by potentiating the antioxidant defense system. These finding supports the efficacy of PYC for diabetes management.