Insulinotropic effect of cinnamaldehyde on transcriptional regulation of pyruvate kinase, phosphoenolpyruvate carboxykinase, and GLUT4 translocation in experimental diabetic rats.

Diabetes mellitus is a chronic metabolic disorder affecting about 6% of population worldwide with its complications and is rapidly reaching epidemic scale. Cinnamomum zeylanicum is widely used in alternative system of medicine for treatment of diabetes. In the present study, we have performed bioassay guided fractionation of chloroform extract of C. zeylaniucm and identified cinnamaldehyde (CND) as an active principle against diabetes. In continuation to it, a detailed study was undertaken to elucidate its mode of antidiabetic action in STZ induced diabetic rats. Oral administration of CND (20 mg/kg bw) to diabetic rats for 2 months showed significant improvement (p<0.001) in muscle and hepatic glycogen content. In vitro incubation of pancreatic islets with CND enhanced the insulin release compared to glibenclamide. The insulinotropic effect of CND was found to increase the glucose uptake through glucose transporter (GLUT4) translocation in peripheral tissues. The treatment also showed a significant improvement in altered enzyme activities of pyruvate kinase (PK) and phosphoenolpyruvate carboxykinase (PEPCK) and their mRNA expression levels. Furthermore, the median lethal dose (LD(50)) of CND could not be obtained even at 20 times (0.4 g/kg bw) of its effective dose. With the high margin of safety of CND, it can be developed as a potential therapeutic candidate for the treatment of diabetes.

Preliminary studies on antihyperglycemic effect of aqueous extract of Brassica nigra (L.) Koch in streptozotocin induced diabetic rats.

In the streptozotocin induced diabetic rats treated separately with aqueous, ethanol, acetone and chloroform extracts of the seeds of B. nigra, the increase in serum glucose value between 0 and 1 hr of glucose tolerance test (GTT) was the least (29 mg/dl) in aqueous extract treated animals while it was 54, 44 and 44 mg/dl with chloroform, acetone and ethanol extracts respectively. In further studies carried out with aqueous extract, the effective dose was found to be 200 mg/kg body weight in GTT. Administration of 200 mg/kg body weight of aqueous extract to diabetic animals daily once for one month brought down fasting serum glucose (FSG) levels while in the untreated group FSG remained at a higher value. In the treated animals the increase in glycosylated hemoglobin (HbA1c) and serum lipids was much less when compared with the levels in untreated diabetic controls. These findings suggest that further studies with the aqueous extract of B. nigra seeds on its antidiabetic activity would be useful.