The findings of increased arginase I activity in diabetes may limit other therapeutic approaches proposed for early endothelial dysfunction such as oral L-arginine supplementation, Drs. Thomas L. Luscher and Jan Steffel, of the University of Zurich Cardiovascular Research Institute write in an accompanying editorial. Although dietary L-arginine supplementation has been shown to exert vascular protective effects in certain clinical settings, this approach is unlikely to be effective in diabetes, if the results of this study can be confirmed by patients in vivo. In fact, the findings of Romera et al may provide a possible explanation for the unexpected neutral or even adverse effects of oral L-arginine in some clinical studies, in particular patients with coronary artery disease and infarction.
A short intravenous course of L-arginine may provide short-term improvement in blood vessel tone, Dr. Romero notes. However most of L-arginine ingested goes directly to the liver to be broken down, not the bloodstream where it can promote relaxation of blood vessels, Dr. Romero says.
Arginase also is associated with vascular problems related to aging, hypertension, sickle cell disease, atherosclerosis and erectile dysfunction, Dr. Romero says. L-citrulline already is taken by some sickle cell patients to reduce breath-taking fibrosis in their lungs. In addition to helping the body turn toxins into urea that can be safely eliminated from the body, arginase also helps in collagen formation and cell proliferation, but too much can be bad. In fact, Drs. Caldwell and Romero are pursuing studies of how increased arginase activity may harden blood vessel walls.
|Contact: Toni Baker|
Medical College of Georgia