July 21, 1998 DALLAS, July 21 -- Drugs that lower blood cholesterol levels may work by increasing the amount of a chemical that relaxes blood vessels, helping them regain flexibility, according to a study reported today in an American Heart Association journal.
The chemical, nitric oxide, signals blood vessels to open and close in response to the body's changing need for increased or decreased blood flow. Individuals with elevated cholesterol have an impaired ability to relax, or dilate, their blood vessels, which researchers attribute to a problem in nitric oxide activation. In individuals whose cholesterol levels were lowered by the drug fluvastatin, more nitric oxide was produced, improving dilation.
"Cholesterol-lowering therapy has been associated with a decrease in deaths from heart disease, and this improvement in dilation may be one way that the drug works," says Roland Schmeider, M.D., professor of medicine, University of Erlangen-Nuremberg, Germany.
Researchers already know that cholesterol-lowering helps prevent fatty deposits that can clog blood vessels, triggering a heart attack or stroke. The new study published in Circulation: Journal of the American Heart Association finds that lowering cholesterol also improves dilation of blood vessels.
Schmeider believes that the other cholesterol-lowering or statin drugs improve vessel dilation. He goes on to say that in patients with very high cholesterol levels the same results can not be achieved by a reduced-fat diet without any drug treatment.
Testing the ability of vessels to dilate may be a new way to determine the need for cholesterol-lowering treatment, Schmeider says. "We know we have patients with high cholesterol levels, but which are the ones at highest risk to develop atherosclerosis? By developing a test to look at vessel function and dilation, it might help us determine who is in most need of this treatment."
In the study, 11 individuals were given a placebo (an inert substance) and 16 were given fluvastatin. The rate of blood flow in the arm, an indication of blood vessel dilation, was measured before and after treatment with fluvastatin.
In one of the experiments to determine the capacity for dilation, researchers injected a chemical called acetylcholine to dilate the participants' blood vessels, then measured any increase in the rate of blood flow. Before treatment, both groups (placebo and fluvastatin) had about the same increase in blood flow.
After treatment, the fluvastatin group had up to 75 percent (from a 2.07 milliliters per minute increase to 3.64 mL/min) more of an increase in blood flow, while the placebo group showed little or no effect. Participants in the study who took fluvastatin also showed a marked decrease in blood levels of total cholesterol and LDL (bad) cholesterol and an increase in HDL (good) cholesterol.
Co-authors are Stephan John, M.D.; Marakus Schlaich, M.D.; Matthias Langerfeld, M.D., Horst Weiprecht, M.D.; and Gerd Schmitz, M.D.
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