Portulaca oleracea L. extracts enhance GLUT4 translocation to the surface of muscle cells in insulin dependent and independent fashion

Abstract

Portulaca oleracea L. is a grassy plant with a fleshy stem, succulent leaves, yellow or white small flowers and small black seeds. P. oleracea used as a medicinal plant in many countries, as a diuretic, febrifuge, vermifuge, antiseptic, anti-spasmodic, anti-bacterial, anti-inflammatory and anti-oxidant. It is in use also as anti-diabetic medicinal herb. The aim of this study was to evaluate the effect of the aerial parts of P. oleracea 50% ethanol/50% water and methanol based extracts on the glucose transporter-4 (GLUT4) translocation to the plasma membrane of muscle cells. Anti-diabetic activity of the extracts was examined by measuring the relative amount of GLUT4 translocation to the plasma membrane in the presence and absence of insulin. L6 muscle cells, stably expressing myc-tagged GLUT4, repeatedly shown to display insulin regulated GLUT4 traffic, were used as a model in this project. L6 myoblasts were pre-treated with increasing concentrations of P. oleracea extracts for 20 h, followed by 3 h serum-deprivation and insulin stimulation for 20 min and then GLUT4myc levels at the plasma membrane was determined. Toxicity of the extracts was determined by MTT assay and LDH leakage assay. Results obtained show no cytotoxic effects in cells treated for 24 h with 50% ethanol and methanol P. oleracea extract up to 1 mg/ml and 0.5 mg/ml extract respectively as measured with MTT and LDH-leakage assays. GLUT4 translocation to the plasma membrane was elevated by 2.6 and 4 folds (-/+ insulin) after treatment for 20 h with 1 mg/ml P. oleracea 50% ethanol extract and 1.7 and 3 folds (-/+ insulin) when treated with 0.5 mg/ml methanol extract. These results indicate that P. oleracea anti-diabetic proporties are mediated in part by increasing GLUT4 distribution in the muscle plasma membrane.

Keywords: Portulaca oleracea L., GLUT4 translocation, medicinal plants, diabetes.

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