The researchers, led by Stuart A. Lipton, of Children1s Hospital in Boston, and Jonathan S. Stamler, of Duke University, reported in the May 27 issue of the Proceedings of the National Academy of Sciences that a mild elevation of the amino acid homocysteine in the blood, called hyperhomocysteinemia, can be lethal to certain nerve cells. They found that even at low concentrations homocysteine was lethal to brain cells with a type of glutamate receptor known as NMDA. Homocysteine, in combination with glycine, overstimulates the NMDA receptor, allowing calcium into the cell and causing cell death.
According to Lipton, an associate professor of neurology at Harvard Medical School, a drug that blocks the activation of the NMDA receptor may have major benefits in treating and preventing strokes in people under 50 with hyperhomocysteinemia. Lipton is currently undertaking clinical trials with a drug called memantine, which may have these effects.
Epidemiological studies have previously shown that hyperhomocysteinemia is a major risk factor for stroke in people under 50. Other studies have shown that elevated homocysteine is a cause of arteriosclerosis and can lead to strokes. Up to 40 percent of the population may have these mild elevations of homocysteine. In addition, almost half the people with blockages in their arteries have homocysteine elevations.