August 3, 2009

Gene Variants Linked to Blood Pressure in African-Americans

Photo of an arm in a blood pressure cuff

Scientists have identified several genetic variants associated with blood pressure in African-Americans. The results of this new genome-wide study offer potential clues to treating and preventing chronic high blood pressure, or hypertension.

About one-third of adults nationwide has hypertension, a major risk factor for heart disease, stroke or kidney disease. The condition is especially common among African-Americans. About 39% of African-American men and 43% of women have high blood pressure. Although diet, physical activity and obesity all contribute to risk of hypertension, researchers believe that genetics also plays an important role.

In 2 earlier international studies, reported in May, scientists used genome-wide analyses to pinpoint 13 genetic variants associated with blood pressure and hypertension in primarily European and South Asian populations. A new study—published in the July 17, 2009, online edition of PLoS Genetics—is the first genome-wide association study to look for similar links in an African-American population.

A research team led by investigators at NIH's National Human Genome Research Institute (NHGRI) analyzed DNA samples from 1,017 African-American men and women, half of whom had hypertension. Partial funding for the work came from NIH's National Institute of General Medical Sciences (NIGMS) and National Center for Research Resources (NCRR), along with NHGRI.

In their analysis of more than 800,000 genetic markers called single-nucleotide polymorphisms (SNPs), the researchers identified 5 genetic regions with SNPs that were significantly associated with systolic blood pressure—the pressure when the heart beats while pumping blood. However, no genetic variants were significantly linked with diastolic blood pressure—the pressure in large arteries when the heart rests between beats—or with combined systolic/diastolic blood pressure.

Further analysis showed that the 5 implicated regions contained or were near genes that code for proteins already thought to affect blood pressure. Additional study revealed that all of the variants are likely involved in biological pathways and networks related to blood pressure and hypertension. An existing class of anti-hypertension drugs, called calcium channel blockers, already targets 1 of the genes. The additional genes may point to new avenues for treatment and prevention.

To follow up and expand on their findings, the researchers next scanned DNA samples from 980 West Africans with and without hypertension. The analysis showed that some of the genetic variants detected in African-Americans were also linked to blood pressure in West Africans.

“Although the effect of each individual genetic variant was modest, our findings extend the scope of what is known generally about the genetics of human hypertension,” says senior author Dr. Charles Rotimi of NHGRI.

“We hope these findings eventually will translate into better ways of helping the millions of African-Americans at risk for hypertension, as well as improved treatment options for other populations,” adds Dr. Eric Green, scientific director of NHGRI.

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