Effect and Mechanisms of Momordica charantia Extract on Glucose Uptake in 3T3-L1 Adipocytes and L6 Myotubes

Bitter gourd (Momordica Charantia, BG) is a common tropical vegetable that has also been used in traditional medicine for treating diabetes. Numerous research in past decades have provided evidences supporint the hypoglycemic effect of BG. Insulin like polypeptide-p and triterpenoids from BG have been demonstrated for their hypoglycemic effect in vivo and in vitro. This study aims at examing the effects of BG water extract and its feactions on the glucose uptake of 3T3-L1 adipocytes and L6 myotute.
Lyophilized powder of wild bitter gourd (Hualian NO.4) was extracted with water (WE), treated with enzyme and extracted with ethyl acetate(We-E), and butanol (We-B). Small molecular weight fraction of WE (WES) was treated similarly and give rise to fractions Se-E and Se-B. Insulin-like peptide fraction (Pf) was isolated from WE. Cells, treated with various BG samples for 30min or 12 hr, were examined for their 3H-labeled 2-deoxyglucose uptake at basal or palmitate-induced insulin resistant state and in the presence or presence of insulin. In 3T3-L1 adipocytes, WE, WES, Se-E and Pf were increased glucose uptake in both basal and insulin resistant state (p<0.05), and also improved insulin resistance and amplified insulin action. Associated with these effects, 3T3-L1 adipocytes treated with BG WE and fractions for 12hr showed enhanced Akt phosphorylation, detected by western-blot analysis. In L6 myotubes, We-E, Se-E, and Pf increased glucose uptake after 30min treatment. Myotubes treated with Se-E for 12 hrs also showed higher glucose uptake. Most importantly, all BG samples prevented palmitate-induced inhibition of glucose uptake.
These datas suggested that the wild bitter gourd contains hypoglycemic components wihich increased adipocytes and myptubes uptake glucose. Among our BG fraction, Se-E might be the most effective fraction.