One way diabetes is bad for your blood vessels is by creating too much competition for an amino acid that helps blood vessels relax, researchers say.
That amino acid, L-arginine, is broken down by the enzyme arginase to urea, which helps the body eliminate toxins resulting from the proteins we eat. Diabetics have a lot of arginase activity, which means they use a lot more L-arginine, says Dr. Maritza Romero, postdoctoral fellow at the Medical College of Georgia and lead author of the paper published in the current issue of Circulation Research.
It also means too little L-arginine is available to help nitric oxide synthase make nitric oxide, the powerful vasodilator that helps blood vessels relax, says Dr. Romero, who works in the lab of Dr. R. William Caldwell, chair of the MCG Department of Pharmacology and Toxicology and the studys corresponding author.
Researchers also found the amino acid, L-citrulline, as well as statins, compounds known to lower cholesterol, prevent elevation of arginase activity, restoring normal dilation abilities in animal models of type 1 diabetes. In fact, L-citrulline can be recycled into L-arginine.
Now they want to know specific factors and pathways involved in arginase activation and develop pharmaceutical agents to combat excessive arginase activity in diabetes. They also suggest clinical trials of L-citrulline as a supplemental therapy for diabetics with vascular problems.
Their findings also help explain why L-arginine supplement, marketed to treat hypertension, chest pain, heart failure and more, may not work long term. In the January 4, 2006 issue of the Journal of the American Medical Association, Johns Hopkins researchers reported that a clinical trial of patients taking an L-arginine supplement following a heart attack didnt improve in their vascular tone or their hearts ability to pump. In fact, more patients died who were taking L-arginine than placebo and the study was cl
|Contact: Toni Baker|
Medical College of Georgia