Stimulation of insulin secretion by Viscum album (mistletoe) leaf extract in streptozotocin-induced diabetic rats

Abstract

Twenty male white rats (250-300g) of Wistar strain were randomly divided into two batches, the normoglycaemic batch and the streptozotocin-induced diabetic batch of ten rats each. Animals in each batch were further divided into two groups of five rats per group. After an overnight fast (12hrs), animals in each group received D-glucose load (2.0g/kg.i.v) under pentobarbital anaesthesia, with or without the crude extract (100mg/kg/iv). Blood samples were collected intravenously at 15 min intervals for 3hrs. for analysis of glucose, insulin and glucagon levels. From the results, the extract (100mg/kg) did not appear to have any significant effect on the blood glucose level of normal rats, but produced about 35.3% decrease in the diabetic rats. Despite the apparent lack of action on glucose level of normal rats, the extract stimulated insulin secretion by about 92.9% (% control) in this group, and about 81.5% in the diabetic group (% control). The glucagon level was not altered by the extract in the normal rats. In the diabetic group, there was mild but significant suppression of glucagon level after the first 1hr. which lasted for about 50min. We suggest that this extract from V album leaves may possess antihyperglycaemic, insulinotropic, and possibly, mild glucagonostatic agent(s) and may therefore be a candidate for the anti-diabetic drugs.