Inflammatory Genes Linked to Salt-Sensitive Hypertension

If sodium handling goes awry, study says blood pressure spike persists long after it should

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FRIDAY, Jan. 12, 2007 (HealthDay News) -- Genes related to inflammation may be a key to high blood pressure, according to researchers.

High blood pressure, or hypertension, affects almost one in three Americans. And more than half of those who are hypertensive have salt-sensitive hypertension, which means changing the amount of sodium in the diet affects blood pressure.

Researchers at the Medical College of Georgia's (MCG's) Georgia Prevention Institute are looking at how inflammation, which is an immune response, may help translate stress into high blood pressure.

"There is a concept that hypertension is an inflammatory condition," Haidong Zhu, a molecular geneticist at MCG, said in a prepared statement. She believes that stress, inflammation and hypertension are connected by the kidneys' ability to release sodium.

When stress activates the body's fight-or-flight mechanism, the body produces interleukin 6, a pro-inflammatory factor. In addition, stress prompts the body to hold onto sodium to temporarily raise blood pressure so you can deal with the situation, according to George Harshfield, the director of the institute.

Zhu and her colleagues are conducting research to see if mutations in four sets of stress-activated inflammatory genes -- interleukin 6, interleukin 6 receptor, cytokine signal transducer and C-reactive protein -- may cause sodium handling to go awry, causing the stress-induced high blood pressure to persist after the stressful situation has passed.

In their study, the MCG researchers are investigating genetic variations of the four genes in 500 teenagers aged 15 to 19 with normal blood pressure. The teens were put on a four-day diet to regulate their sodium intake, and then they were monitored for a few hours in the laboratory.

Pilot data indicate that black teens with normal blood pressure and a certain variation of the interleukin 6 gene have reduced sodium excretion in their urine following stress. In addition, following stress, circulating levels of interleukin 6 rise and are still up an hour after the stressor is gone.

"Our long-term goal is to be able to identify a subgroup of individuals with a certain genetic profile that has an increased risk of developing high blood pressure in a stressful environment," Zhu said.

The researchers hope that their work may lead to the identification of people who could benefit from targeted therapy, including a low-salt diet, physical activity and possibly anti-inflammatory drugs, Zhu said.

More information

The National Heart, Lung, and Blood Institute has more about high blood pressure.

SOURCE: Medical College of Georgia, news release, January 2007

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