Lowering Homocysteine May Not Help
Blood protein might just indicate kidney trouble, not cause it

(HealthDay News) -- Lowering levels of homocysteine in the blood apparently won't help people with serious kidney disease.

Researchers speculate that homocysteine, a protein linked to inflammation, may be simply a marker of kidney disease because even when participants in a study took extra folic acid, vitamin B6 and vitamin B12 to lower their levels of homocysteine, there was no change in their risk of death, heart attack, stroke, end-stage renal disease or in the risk of leg amputation.

"We had every expectation at the start of the study that lowering homocysteine would be beneficial," Dr. Rex Jamison, chairman and principal investigator for the Homocysteine Study of the Veterans Administration Cooperative Studies Program, told HealthDay . "But our results show that there was no difference in the number of people who died in the treatment group versus the placebo group, and there was no difference in heart attack, stroke or amputations due to vascular disease."

Results of the study were published in the Journal of the American Medical Association .

Homocysteine has been linked to a number of serious problems, such as heart attack and stroke. Because of its link to those conditions, researchers thought that the protein might also play a role in vascular disease. The fact that people with kidney disease have high rates of vascular disease and they also have high levels of homocysteine made the inflammatory protein seem all the more suspect.

But not everyone was convinced that homocysteine was causing problems. Some thought it was probably just a marker, or indicator, of the conditions.

If homocysteine was in fact causing any of the problems, then lowering levels of homocysteine should affect the rates of heart disease, stroke, amputations and vascular disease.

To test that theory, Jamison and his colleagues randomly assigned 2,000 veterans from across the country, all of whom had advanced kidney disease or renal failure, to take either a placebo or a capsule containing 40 milligrams (mg) of folic acid, 100 mg of vitamin B6 and 2 mg of B12 daily.

After five years, the researchers found that homocysteine levels had fallen dramatically -- by 26 percent in the treatment group. But, the lower levels didn't make a difference. The rates of death, amputation, heart attack and stroke were virtually the same between the two groups.

"In my field, this is very important," said Dr. Robert Provenzano, chief of nephrology at St. John Hospital and Medical Center in Detroit . "We've been trying to bring homocysteine down in our patients, hoping it would have a positive impact, but the decrease in homocysteine was quite profound in this study. If there were any benefit, we would have seen it."

Instead, Provenzano said, homocysteine looks "like it's nothing more than a marker for inflammation."

Jamison said that may be true, but he noted that the results might also have been related to the population they studied. "Another [possibility] is that the vascular burden in these patients may be too great," he said. "It may be that we started too late to make a difference in these patients."

On the Web

To learn more about chronic kidney disease, visit the National Kidney Foundation online.

SOURCES: HealthDay News ; Rex L. Jamison, M.D., chairman and principal investigator, Homocysteine Study, the Veterans Administration Cooperative Studies Program, and professor of medicine, emeritus, Stanford University School of Medicine, Palo Alto, Calif.; Robert Provenzano, M.D., chief of nephrology, St. John Hospital and Medical Center, Detroit; Sept. 12, 2007, Journal of the American Medical Association
Author: Serena Gordon
Publication Date: Sept. 30, 2008
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