Three rare mutations lower blood pressure

updated 11:02 a.m. ET April 7, 2008

WASHINGTON - Up to 100 million people globally have genetic mutations that keep their blood pressure low and lower their risk of heart and kidney disease and stroke, U.S. researchers reported.

Their findings, published in the journal Nature Genetics, could help scientists design new and better blood pressure drugs. They also shed light on how the kidneys handle salt and in turn regulate blood pressure.

“We found that these mutation carriers have a 60 percent reduction in their risk of developing hypertension,” Richard Lifton, a Howard Hughes Medical Institute researcher at Yale University in Connecticut, said in a statement.

People with the mutations, in three genes, have the equivalent of their own, natural, blood-pressure-lowering medication, he added.

“We find that about two percent of the population has mutations in at least one of these three genes — although all of the identified mutations are individually very rare.”

Lifton’s team looked at the DNA of people taking part in the Framingham Heart Study, an ongoing study of people living in Framingham, Massachusetts, and their children, which started in 1948.

The researchers homed in on three genes known to cause rare recessive genetic diseases marked by dangerously low blood pressure. All affect how the kidneys handle salt.

High salt intake is known to cause high blood pressure, which affects an estimated 1 billion people globally and which is a major cause of stroke, heart disease and kidney failure.

But not everyone who eats too much salt develops high blood pressure.

People with two “bad” copies of the genes, called NCCT, NKCC2 and ROMK, have disease such as Gitelman and Bartter syndromes with extremely low blood pressure. Two of the most commonly used blood pressure medications known as diuretics target the functions of these genes.

“We used knowledge of the spectrum of mutations that cause Gitelman and Bartter syndromes to sort among the hundreds of sequence changes we observed,” Lifton said.

“The results show that nearly 2 percent of the (Framingham group) has a defective copy of one of these three genes,” Lifton said. “Unlike patients with Gitelman and Bartter syndromes, these subjects have only one defective copy, not two.”

These variations appear to keep blood pressure in check well into middle age, when most Americans begin to develop high blood pressure, defined as 140/90 or higher.

Lifton’s team has found other genetic mutations affecting blood pressure.

“Because these three genes comprise only a small fraction of those in which mutations are known to alter blood pressure, and because there are likely to be many more genes yet to be discovered, it seems probable that the combined effects of rare independent mutations will account for a substantial fraction of blood pressure variation in the population,” they concluded.

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