News / Health

Study Finds Gene That May Raise Alzheimer's Risk in US Blacks

Reuters
The largest study to date looking for genetic causes of Alzheimer's in African Americans may offer new clues about why blacks in the United States are twice as likely as whites to develop the deadly, brain-wasting disease.
       
The findings, published in the Journal of the American Medical Association on Tuesday, show that mutations in two genes that play a role in whites also contribute to Alzheimer's risk in blacks. One of those, known as ABCA7, may double the risk in blacks who have the mutation versus those who don't.
       
Although many genes have been found to raise the risk of Alzheimer's, most studies have been conducted in largely white populations, and few studies have looked specifically at genes that drive Alzheimer's in blacks. Part of that is because very few African Americans take part in gene studies looking at Alzheimer's risk.
       
The latest findings will need to be confirmed by other research teams, and critics say the study is incomplete until that work is done.
       
To get enough participants for the newly published study, researchers combined genetic information from 18 different Alzheimer's Disease Centers funded by the U.S. National Institutes of Health. They gathered information on 6,000 African Americans, 2,000 of whom had late-onset Alzheimer's disease, the most common form that occurs in older people.
       
The team then looked for genes that were most strongly associated with Alzheimer's. The strongest link was with a variant of a gene called apolipoprotein E or APOE, a gene that contains instructions for making a protein that carries cholesterol and is well-known risk factor for Alzheimer's.
       
The team found that a variant of this gene called APOE-e4 doubled the risk of Alzheimer's in blacks, in much the same way it does in whites.
       
But the study also turned up another gene that has only been weakly associated with Alzheimer's in whites. This gene, called ABCA7, which also plays a role in the production of cholesterol and fats, appears to have a much stronger effect in blacks.
       
"In whites, it increases risk by 10 to 20 percent, but in African Americans, it increases risk by about 70 to 80 percent.  It has a way larger effect size in African Americans,'' said Dr. Christiane Reitz of Columbia University Medical Center, who conducted the genetic analyses on the study.
       
ABCA7 is also involved in cholesterol metabolism, as are several of the genes which have been found in the past five years or so to be linked with Alzheimer's in whites.
       
"That seems to be a pathway that is involved in Alzheimer's disease,'' Reitz said.
       
Reitz said a variant form of APOE called APOE-e4 has the biggest effect, increasing the risk of Alzheimer's by about 200 percent. ABCA7 raised the risk by about 80 percent, and most other genes discovered so far increase risk by 10 to 20 percent.
       
Like other risk genes for the age-related form of Alzheimer's, the gene explains only part of the risk and likely will not lead to any new treatments soon. Reitz said it is clear that hundreds of genes are at work in Alzheimer's disease.
       
"ABCA7 and APOE are not the only genes involved in Alzheimer's disease in African Americans,'' Reitz said, adding that it would take tens of thousands of participants to detect some of the other risk genes. "What the study did show us is at least one gene which seems to have a major effect, and that's important to know.''
       
Representative Enough?
       
The next step is to study how the ABCA7 gene works in the brain, and the team still needs to validate the results of this study in another independent population of blacks, something that may be challenging.
       
According to Neil Buckholtz, director of the division of neuroscience at the National Institute on Aging, the study represented all of the well characterized genetic samples of blacks in the United States.

Dr. Allan Levey, director of Emory University's Alzheimer's Disease Research Center, said the study was significant for being the first large-scale genetic study done in African Americans. But he said a major limitation is that the study was not replicated in another population of blacks to confirm the findings, which is considered necessary to ensure its validity.
       
"Had this same study been done in whites, it would never have been published here,'' said Levey, referring to JAMA, a highly-regarded medical journal.
       
Troy Duster, a sociologist at the University of California, Berkeley and author of "Backdoor to Eugenics'' and contributor to "Whitewashing Race: The Myth of a Color-Blind Society,'' says the findings are too preliminary and the effect sizes too small to draw any definitive conclusions about differences in the risk of Alzheimer's between blacks and whites.
       
Without a replicating study in other groups who identify as African-American and as white, "it is impossible to interpret whether this small difference has significant meaning, or points to different etiologies (or the need for different treatments) in different groups,'' he said.
       
Heather Snyder, director of medical and scientific operations at the Alzheimer's Association, which funded two of the study authors, said the findings should spur new research into the potential reasons for this link between ABCA7 and Alzheimer's in African Americans.
       
"Really, that all requires more funding for Alzheimer's disease research,'' Snyder said.

You May Like

Nigeria Incumbent in Tight Spot as Poll Nears

Muhammadu Buhari is running a strong challenge to Goodluck Jonathan, amid a faltering economy and Boko Haram security worries More

Video Liberia's Almost Last Ebola Patient Grateful but Still Grieving

Beatrice Yardolo tells VOA that despite her fame, life is still a struggle as she waits for government's promise of support to arrive More

Video Cambodian Land Grabs Threaten Traditional Communities

At least seven different indigenous groups in Ratanakiri depend mainly on forest products for their survival, say they face loss of their land, traditional way of life More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Liberia's Almost Last Ebola Patient Grateful but Still Grievingi
X
Benno Muchler
March 26, 2015 3:41 PM
Beatrice Yardolo was to make history as Liberia’s last Ebola patient. Liberians recently started counting down 42 days, the period that has to go by without a single new infection until the World Health Organization can declare a country Ebola-free. That countdown stopped on March 20 when there was another new case of Ebola, making Yardolo’s story a reminder that Ebola is far from over. Benno Muchler reports from Monrovia.
Video

Video Liberia's Almost Last Ebola Patient Grateful but Still Grieving

Beatrice Yardolo was to make history as Liberia’s last Ebola patient. Liberians recently started counting down 42 days, the period that has to go by without a single new infection until the World Health Organization can declare a country Ebola-free. That countdown stopped on March 20 when there was another new case of Ebola, making Yardolo’s story a reminder that Ebola is far from over. Benno Muchler reports from Monrovia.
Video

Video Cambodian Land Grabs Threaten Traditional Communities

Indigenous communities in Cambodia's Ratanakiri province say the government’s economic land concession policy is taking away their land and traditional way of life, making many fear that their identity will soon be lost. Local authorities, though, have denied this is the case. VOA's Say Mony went to investigate and filed this report, narrated by Colin Lovett.
Video

Video US, South Korea Conduct Joint Military Exercises

The Eighth U.S. Army Division and the Eighth Republic of Korea Mechanized Infantry Division put on a well orchestrated show of force for the media this week during their joint military training exercises in South Korea. VOA’s Seoul correspondent Brian Padden was there and reports the soldiers were well disciplined both in conducting a complex live fire exercise and in staying on message with the press.
Video

Video Space Program Status Disappoints 'Last Man on the Moon'

One of the films that drew big crowds last week at the annual South by Southwest festival in Austin, Texas, tells the story of the last human being to stand on the moon, U.S. astronaut Eugene Cernan. It has been 42 years since Cernan returned from the moon and he laments that no one else has gone there since. VOA’s Greg Flakus reports.
Video

Video Young Filmmakers Shine Spotlight on Giving Back

A group of student filmmakers from across the United States joined President Barack Obama at the White House this month for the second annual White House Student Film Festival. Fifteen short films were officially selected from more than 1,500 entries by students aged 6 through 18. The filmmakers and their families then joined the president and a group of celebrities for a screening of their films. VOA’s Julie Taboh reports.
Video

Video VOA Exclusive: Interview with Afghan President Ashraf Ghani

Afghan President Ashraf Ghani, during his first visit as president to Washington, gave a one-on-one interview with VOA Afghan Service reporter Said Suleiman Ashna, about his request for a change in U.S. troop levels, the threat from the Islamic State, and repairing relations with the United States and Pakistan. The interview was held at Blair House, late Sunday, in Pashto.
Video

Video California Science Center Tells Story of Dead Sea Scrolls

The ancient manuscripts were uncovered in the mid-20th century, and they are still yielding clues about life and religious beliefs in ancient Israel. As VOA's Mike O'Sullivan reports, an exhibit in Los Angeles shows how modern science is bringing the history of these ancient documents to life.
Video

Video Angelina Jolie Takes Another Bold Step

Hollywood actress and filmmaker Angelina Jolie has revealed she had her ovaries and fallopian tubes removed to lower her odds of getting cancer. Doctors say the huge publicity over her decision will help raise awareness about the importance of cancer screening. VOA’s George Putic has more

All About America

Circumventing Censorship

An Internet Primer for Healthy Web Habits

As surveillance and censoring technologies advance, so, too, do new tools for your computer or mobile device that help protect your privacy and break through Internet censorship.
More