Hypoglycaemic activity and molecular mechanisms of Caesalpinia ferrea Martius bark extract on streptozotocin-induced diabetes in Wistar rats

The tea from the stem bark of Caesalpinia ferrea Martius (Leguminosae) has been popularly used in the treatment of diabetes in Brazil. To investigate the hypoglycaemic properties and to elucidate the mechanisms by which the aqueous extract of the stem bark of Caesalpinia ferrea reduces blood glucose levels in streptozotocin-induced diabetic rats via the enzymatic pathways of protein kinase B (PKB/Akt), AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC). The aqueous extract of the stem bark of Caesalpinia ferrea (300 and 450mg/kg/day), vehicle and metformin (500mg/kg/day) were administered orally to STZ-diabetic rats (n=7/group) for 4 weeks. Changes in body weight, food and water intake, fasting glucose levels and oral glucose tolerance were evaluated. Phosphorylation (P) and the expression of Akt, AMPK and ACC in the liver and skeletal muscle were determined using Western blot. The aqueous extract of the stem bark of Caesalpinia ferrea reduced blood glucose levels and improved the metabolic state of the animals. P-Akt was increased in the liver and skeletal muscle of the treated animals, P-AMPK was reduced only in the skeletal muscle of these animals and P-ACC was reduced in both when compared with untreated rats. The results indicate that the aqueous extract of the stem bark of Caesalpinia ferrea has hypoglycaemic properties and possibly acts to regulate glucose uptake in liver and muscles by way of Akt activation, restoring the intracellular energy balance confirmed by inhibition of AMPK activation.