Effects of extract of leaves of <i>Newbouldia laevis</i> on the activities of some enzymes of hepatic glucose metabolism in diabetic rats

Abstract

In diabetes mellitus and insulin resistance, the activity of the enzymes involved in hepatic glucose homeostasis is disturbed. Promoting the physiologic functions of these enzymes and restoring homeostatic control by medicinal plants could be beneficial in the management of diabetes. This study investigates the effects of extract of leaves of Newbouldia laevis on some key enzymes of hepatic glucose metabolism in streptozotocin-induced diabetic rats. Diabetes was induced in rats by intravenous injection of streptozotocin. Diabetic rats were treated orally with N. laevis extract for four weeks. At the end of the treatment, the activities of hepatic glucokinase and glucose 6-phosphatase were evaluated. Effect of N. laevis extract on glucose 6-phosphatase activity was also assessed in vitro using enzyme obtained from rabbit liver. The levels of hepatic glycogen, pancreatic insulin and serum insulin were also determined. Treatment of diabetic rats with N. laevis extract resulted in a significant increase (P < 0.05) in the activity of hepatic glucokinase when compared with diabetic control. Extract of N. laevis showed significant inhibitory effect against the activity of glucose 6-phosphatase in both in vivo and in vitro studies. The level of hepatic glycogen in treated rats significantly increased (P < 0.05) compared to untreated diabetic rats. Although there was a slight increase in serum and pancreatic insulin levels of treated diabetic rats, the difference was not significant (P > 0.05) when compared to diabetic control. Based on the results of this study, we conclude that N. laevis leaf extract stimulates the activity of hepatic glucokinase and inhibits the activity of glucose 6-phosphatase in streptozotocin-induced diabetic rats. It could serve as a good alternative remedy in the management of diabetes mellitus.

Keywords: Liver, glucokinase, glucose 6-phosphatase, diabetes mellitus, Newbouldia laevis, glucose.

African Journal of Biotechnology, Vol 13(22) 2273-2281