Scientists ID Gene Mutation That May Triple Alzheimer's Risk

WEDNESDAY, Nov. 14 (HealthDay News) -- A rare mutation in a gene called TREM2 appears to nearly triple the risk for Alzheimer's disease in adults, a new study finds.

This gene is involved in immune and inflammatory responses, and may be yet another piece of the mystery of the causes of Alzheimer's disease and a target for treatment, the researchers added.

"We found a mutation that confers a large risk for Alzheimer's disease," said lead researcher Dr. Kari Stefansson, the CEO of deCODE Genetics based in Reykjavik, Iceland.

Although only 1.2 percent of the population has the TREM2 mutation, when comparing adults aged 85 and older with and without it, those who do have it are almost seven times more likely to have Alzheimer's disease, he said.

Of course, having this mutation doesn't mean that one is destined to develop Alzheimer's disease. Alzheimer's is a complex disease and a person probably needs to have several risk factors that combine to produce the condition, Stefansson said.

"This has implications for treatment," he said. The mutation might be a target for new drugs that blunt the mutation's action, he said.

The report was published in the Nov. 14 online edition of the New England Journal of Medicine.

An Alzheimer's expert praised the new study.

"This shows the value of basic research," said William Thies, chief medical and scientific officer at the Alzheimer's Association. "This kind of science is very important, and can accelerate our finding better therapies for Alzheimer's disease."

Thies noted this finding doesn't mean people should run out and be tested for this mutation. The mutation might, in the future, be important for treatments, but that's a long way off, he said.

The need to develop treatments for Alzheimer's disease is a pressing issue, he added.

"The imperative for finding new therapies is obvious," Thies said. "When we get to 15 or 16 million people with the disease by the middle of the century, which is what the demographics would suggest, we can't take care of that many people and the dislocation in society is just going to be a mess."

For the study, Stefansson's group obtained gene sequences from more than 2,200 Icelanders. The researchers looked for gene variants in those with and without Alzheimer's disease.

To check their results, the researchers looked at other populations in the United States, Norway, the Netherlands and Germany, where they confirmed their findings.

Another expert noted that the inflammation finding is important.

"Inflammation is certainly part of the conventional wisdom in the pathogenesis of Alzheimer's," said Dr. Sam Gandy, associate director of the Mount Sinai Alzheimer's Disease Research Center in New York City.

What this study says is that inflammation is so important that imbalance in the inflammatory component can affect the risk for disease, he said.

"We don't have a new drug today, but TREM2 highlights potentially druggable steps in the pathogenesis of Alzheimer's that we might have never ever even studied were it not for this genetic information," Gandy said.

Another expert, Greg Cole, a neuroscientist at the Greater Los Angeles VA Healthcare System and associate director of the Alzheimer's Disease Research Center at the UCLA David Geffen School of Medicine, weighed in on the findings.

Cole said that "together with other discoveries of genetic variants in genes expressed in the same population of immune cells, this study adds to the now compelling data for a causal role for the brain's innate immune cells in the development of Alzheimer's disease, the most common dementia."

Understanding the role of genetic mutations "should help researchers devise drugs that achieve the opposite effect and modulate innate immune system function to reduce the risk," he said.

Another study in the same journal issue came to the same conclusion.

A team lead by John Hardy, at the University College London Institute of Neurology, and Andrew Singleton, at the U.S. National Institute on Aging (NIA), also found that the TREM2 mutation increased the risk for Alzheimer's disease.

"We have hypothesized for many years that a rare genetic variant can confer moderate risk for disease," Singleton said in an NIA statement. "These are the first studies to identify such a variant related to Alzheimer's disease."

More information

To learn more Alzheimer's disease, visit the Alzheimer's Association.

SOURCES: Kari Stefansson, M.D., Ph.D., CEO, deCODE genetics, Reykjavik, Iceland; William Thies, Ph.D., chief medical and scientific officer, Alzheimer's Association; Sam Gandy, M.D., Ph.D., associate director, Mount Sinai Alzheimer's Disease Research Center, New York City; Greg Cole, Ph.D., neuroscientist, Greater Los Angeles VA Healthcare System, and associate director, Alzheimer's Disease Research Center, University of California, Los Angeles, David Geffen School of Medicine; Nov. 14, 2012, news release, U.S. National Institute on Aging; Nov. 14, 2012, New England Journal of Medicine online

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