BACKGROUND: Boschniakia rossica is a well-known traditional Chinese medicine for tonifying kidney and improving impotence. Boschnaloside is the major iridoid glycoside in this herb but therapeutic benefits for diabetes remained to be evaluated. HYPOTHESIS/PURPOSE: The current investigation aims to study the antidiabetic effect and the underlying pharmacological mechanisms. STUDY DESIGN AND METHODS: Receptor binding, cAMP production, Ins secretion, glucagon-like peptide 1 (GLP-1) secretion, and dipeptidyl peptidase-4 activity assays were performed. Therapeutic benefits of orally administrated boschnaloside (150 and 300mg/kg/day) were evaluated using severely 12-week old female diabetic db/db mice (Hemoglobin A1c >10%). RESULTS: Oral treatment of boschnaloside for 4 weeks improved diabetic symptoms including fasting blood sugar, hemoglobin A1c, glucose intolerance, and Homeostatic Model Assessment of Ins Resistance, accompanied by circulating GLP-1active and adiponectin levels. In addition, bochnaloside treatment improved islet/beta cell function associated with an alteration of the pancreatic and duodenal homeobox 1 level. It was shown that boschnaloside interacted with the extracellular domain of GLP-1 receptor and enhanced glucose stimulated Ins secretion. Boschnaloside also augmented the insulinotropic effect of GLP-1. Finally, the presence of boschnaloside caused a reduction of dipeptidyl peptidase-4 activity while enhanced GLP-1 secretion from STC-1 cells. CONCLUSION: It appears that bochnaloside at oral dosage greater than 150mg/kg/day exerts antidiabetic effects in vivo through modulating the action of GLP-1.
