Beneficial effects of thymoquinone on hepatic key enzymes in streptozotocin-nicotinamide induced diabetic rats

Aims: The present study was designed to evaluate the antihyperglycemic potential of thymoquinone (TQ), major constituent of Nigella sativa seeds on the activities of key enzymes of carbohydrate metabolism in streptozotocin (STZ)-nicotinamide (NA)-induced diabetic rats. Main methods: Diabetes was induced in experimental rats weighing 180-220 g, by a single intraperitoneal (i.p) injection of STZ (45 mg/kg b.w), 15 min after the i.p administration of NA (110 mg/kg b.w). Diabetic rats were administered TQ intragastrically at 20, 40, 80 mg/kg b.w for 45 days. The levels of plasma glucose, insulin, glycated hemoglobin (HbA(1C)) and hemoglobin (Hb) were measured. The activities of hexokinase. glucose 6-phosphate dehydrogenase, glucose 6-phosphatase and fructose 1,6-bisphosphatase were assayed in liver homogenates. Key findings: Oral administration of TQ for 45 days, dose dependently improved the glycemic status in STZ-NA induced diabetic rats. The levels of insulin, Hb increased with significant decrease in glucose and HbA(1C) levels. The altered activities of carbohydrate metabolic enzymes were restored to near normal. No significant changes were noticed in normal rats treated with TQ. Significance: These results show that TQ at 80 mg/kg b.w is associated with beneficial changes in hepatic enzyme activities and thereby exerts potential anti hyperglycemic effects. (C) 2009 Elsevier Inc. All rights reserved.