Does bitter melon contain an activator of AMP-activated kinase?

Extracts of the unripe fruit of Momordica charantia - bitter melon, which flourishes throughout the tropics - appear to have utility in the management of type 2 diabetes. Rodent studies suggest that the thus-far-uncharacterized active components of such extracts enhance the efficiency of postprandial glucose storage in muscle and liver, and likely diminish excessive hepatic glucose output, while often down-regulating serum insulin effects comparable to those reported for metformin. Other parallels between the actions of metformin and bitter melon in rodents appear to include: analogous effects on the hepatic activity of certain enzymes of glucose metabolism; increased expression of GLUT4 in the plasma membrane of skeletal muscle; a tendency to prevent weight gain; favorable effects on serum lipids; and an anti-promotional impact on cancer induction. Inasmuch as the clinical efficacy of metformin has recently been traced to its ability to activate AMP-activated kinase, it would be of interest to determine whether bitter melon extracts contain activators of this enzyme. The fact that bitter melon has the potential to down-regulate insulin suggests that, beyond its likely utility in the management of diabetes, it may have preventive value with respect to a wide range of disorders in which hyperinsulinemia plays a pathogenic role - and possibly could even favorably impact the aging process. (C) 2004 Elsevier Ltd. All rights reserved.