Stevioside does not cause increased basal insulin secretion or β-cell desensitization as does the sulphonylurea, glibenclamide: Studies in vitro

Abstract

We have shown that stevioside (SVS) enhances insulin secretion and thus may have a potential role as antihyperglycemic agent in the treatment of type 2 diabetes mellitus. However, whether SVS stimulates basal insulin secretion (BIS) and/or cause desensitization of beta cells like sulphonylureas (SU), e.g. glibenclamide (GB), is not known. To explore and compare the effects of SVS pretreatment with those of GB and glucagon-like peptide-1 (GLP-1), we exposed isolated mouse islets to low or high glucose for 1 h after short-term (2 h) or long-term (24 h) pretreatment with SVS, GB or GLP-1, respectively. BIS at 3.3 or 5.5 mM glucose were not changed after short-term pretreatment with SVS (10 − 7 M), while it increased about three folds after pretreatment with GB (10 − 7 M). Glucose stimulated insulin secretion (GSIS) (16.7 mM) increased dose-dependently after long-term pretreatment with SVS at concentrations from 10 − 7 to 10 − 5 M. Pretreatment for 24 h with GB (10 − 7 M) increased the subsequent BIS (3.3 mM glucose) ( p < 0.001), but decreased GSIS (16.7 mM glucose) ( p < 0.001). In contrast SVS (10 − 7 M) and GLP-1 (10 − 7 M) did not stimulate BIS but both enhanced the subsequent GSIS (16.7 mM glucose) ( p < 0.05 and p < 0.05, respectively). While SVS pretreatment increased the intracellular insulin content, GB pretreatment decreased the insulin content. Our study suggests that SVS pretreatment does not cause a stimulation of BIS and does not desensitize β-cells, i.e. SVS seems to have advantageous characteristics to GB as a potential treatment of type 2 diabetes.