A Portulaca oleracea L. extract promotes insulin secretion. - GreenMedInfo Summary
AL. extract promotes insulin secretion via a Kchannel dependent pathway in INS-1 pancreaticβ-cells.
Nutr Res Pract. 2018 Jun ;12(3):183-190. Epub 2018 Apr 25. PMID: 29854323
Jae Eun Park
BACKGROUND/OBJECTIVE: This study was designed to investigate how aL. extract (POE) stimulates insulin secretion in INS-1 pancreaticβ-cells.
MATERIALS/METHOD: INS-1 pancreaticβ-cells were incubated in the presence of various glucose concentrations: 1.1 or 5.6, 16.7 mM glucose. The cells were treated with insulin secretagogues or insulin secretion inhibitor for insulin secretion assay using an insulin ELISA kit. In order to quantify intracellular influx of Cacaused by POE treatment, the effect of POE on intracellular Cain INS-1 pancreaticβ-cells was examined using Fluo-2 AM dye.
RESULTS: POE at 10 to 200µg/mL significantly increased insulin secretion dose-dependently as compared to the control. Experiments at three glucose concentrations (1.1, 5.6, and 16.7 mM) confirmed that POE significantly stimulated insulin secretion on its own as well as in a glucose-dependent manner. POE also exerted synergistic effects on insulin secretion with secretagogues, such as L-alanine, 3-isobutyl-1-methylxanthine, and especially tolbutamide, and at a depolarizing concentration of KCl. The insulin secretion caused by POE was significantly attenuated by treatment with diazoxide, an opener of the Kchannel (blocking insulin secretion) and by verapamil (a Cachannel blocker). The insulinotropic effect of POE was not observed under Ca-free conditions in INS-1 pancreaticβ-cells. When the cells were preincubated with a Cafluorescent dye, Fluo-2 (acetoxymethyl ester), the cells treated with POE showed changes in fluorescence in red, green, and blue tones, indicating a significant increase in intracellular Ca, which closely correlated with increases in the levels of insulin secretion.
CONCLUSIONS: These findings indicate that POE stimulates insulin secretion via a Kchannel-dependent pathway in INS-1 pancreaticβ-cells.