The stimulation of insulin secretion in a β-cell assay of Momordica charantia, an antidiabetic plant in traditional Dominican medicine

Momordica charantia (L.), Cucurbitaceae, is a widely-used diabetes treatment in the traditional medicine of the Dominican Republic and other cultures. Results from in vivo studies verify that the fruit of the domestic cultivar has antidiabetic activity as shown by its ability to lower blood glucose concentrations. However, the exact physiological mechanisms of such activity are largely unexplored. Therefore, we examined whether an ethanol extract of M. charantia fruit can directly stimulate insulin secretion from MIN6 β-cells, a mouse insulinoma β-cell line. We measured insulin secretion in response to incubation with the extract, as compared with a positive control of a high glucose (HG 27 mM) together with the insulin secretagogue, glipizide (50µM). MIN6 β-cells, grown in standard DMEM culture media, were washed with Krebs-Ringer buffer (KRB), and incubated with concentrations of M. charantia ranging from 25µg/ml to 2.5mg/ml, and HG plus glipizide in final concentrations in KRB. Aliquots of the treatment solution were collected at baseline, 15, and 60 minutes and assayed for insulin content by a mouse ELISA kit. The 25µg/ml concentration of M. charantia extract stimulated greater β-cell insulin secretion at 15 and 60 minutes (4.4X10^-07µg/cell and 1.2X10^-06µg/cell respectively), as compared to HG plus glipizide (2.9X10^-07µg/cell and 7.2X10^-07µg/cell, respectively). Preliminary observations also indicate that higher concentrations of M. charantia extract resulted in elevated insulin due to excess cytotoxicity and cell lysis as assessed by trypan blue staining. We intend to test purified compounds and fractions of M. charantia extract with insulin-secretagogue activity in in vivo mouse models of diabetes.

Acknowledgements: This research is supported in part by NIH/NCCAM fellowship 1F31AT004548–01.