[PHNUTR-L] Genetic test accurate for salt-related high blood pressure

[Kathrynne Holden, MS, RD]

Colleagues, the following is FYI and does not necessarily reflect my own
opinion. I have no further knowledge of the topic. If you do not wish to
receive these posts, set your email filter to filter out any messages
coming from   @nutritionucanlivewith.com    and the program will remove
anything coming from me.
---------------------------------------------------------
Public release date: 22-Feb-2006
http://www.eurekalert.org/pub_releases/2006-02/uovh-gta022206.php

Contact: Mary Jane Gore
mjgore at virginia.edu
434-924-9241
University of Virginia Health System

Genetic test accurate for salt-related high blood pressure

Researchers led by UVa Health System pathologist Robin Felder, Ph.D., 
have demonstrated that looking for several variations of genes that 
control blood pressure can predict the risk for high blood pressure 
caused by high levels of salt. Once it is fully developed, this 
effective diagnostic test will be the first of its kind, says Dr. 
Felder, whose work will be published in the Feb. 23 issue of the journal 
Clinical Chemistry. When a subject had three or more variations in these 
genes, the new genetic test correctly predicted risk for salt-induced 
high blood pressure in 94 percent of cases. Health is adversely affected 
by high salt intake in up to half of Americans.

In a separate finding, two genes at most were necessary to predict with 
a 78 percent accuracy which people with high blood pressure 
(hypertension) had a low renin levels, a substance that is currently 
measured to help establish the diagnosis of salt (sodium chloride) 
sensitivity. Thus, the researchers found different genetic bases for low 
renin in the blood and for salt sensitivity. Salt sensitivity is defined 
as a greater than 10 percent increase in blood pressure following a 
high-salt meal.

The researchers also determined that the increase in subjects' blood 
pressure and inability to eliminate excess salt from their systems was 
directly related to how many variations were found in the participants' 
salt regulating genes, a phenomenon called a gene dosing effect. The 
more gene variants, the bigger the health problems.

"A genetic test for high blood pressure and/or salt sensitivity will be 
instrumental in motivating Americans to adopt heart healthy lifestyles 
and help to improve their overall health and quality of life," Dr. 
Felder said. "In addition, because the treatment of hypertension costs 
the U.S. health system more than $13 billion per year, this test could 
result in significant cost savings as well."

"Diagnostic genetic tests with this high level of predictive value for 
hypertension simply don't exist at this time," said Dr. Hironobu Sanada, 
M.D., Ph.D., Fukushima Medical University, who led the clinical trials 
of the diagnostic genetic panel with Japanese subjects. Dr. Sanada is a 
former UVa pathology fellow who studied and worked with Dr. Felder.

Performing extended studies among people with different ethnic origins, 
the research group hopes to demonstrate the effectiveness of this test 
in particular among African Americans, who have a higher incidence of 
salt-sensitive hypertension than other races. While 98 million Americans 
suffer from either high blood pressure or sensitivity to dietary salt 
(or both), until now no genetic test had been created that could predict 
who may develop these diseases. Salt sensitivity, with or without high 
blood pressure, has the same deleterious consequences as high blood 
pressure. Left undiagnosed, high blood pressure and/or salt sensitivity 
can lead to devastating consequences such as stroke, blindness, heart 
attack and kidney failure.

The studies were conducted by a team of collaborators including Pedro A. 
Jose, M.D., Ph.D., at Georgetown University School of Medicine 
(Washington D.C.), Hironobu Sanada, M.D., Ph.D., Fukushima Medical 
University (Fukushima, Japan), and Scott Williams, Ph.D., Vanderbilt 
University (Nashville, TN). Funding for these studies was provided in 
part by a $10.2 million grant from the National Heart, Lung and Blood 
Institute.

The grant will allow this group of collaborating investigators, 
including Dr. Robert M. Carey, M.D. (University of Virginia) to extend 
their studies on the genetic bases for high blood pressure and salt 
sensitivity and their mechanisms in subjects from many different ethnic 
backgrounds, which could influence the predictive value of the 
diagnostic test. The team's work will examine the normal mechanisms 
associated with sodium (salt) management by the kidney and how the 
failure of these mechanisms contributes to high blood pressure.

Dr. Carey will recruit an additional 3,000 volunteers who will receive 
genetic screens to identify gene variants that contribute to elevated 
blood pressure. Dr. Jose's research will determine how dopamine 
receptors and angiotensin II receptors regulate each other. The 
information from these studies will provide new insights into how 
hypertension develops, how it can be tested and how it can be treated.

Right now, no definitive diagnostic test exists for salt sensitivity, 
except for a protocol in which diet is controlled rigorously over a 
two-week period. "Through these grant funds, we wish to stimulate 
broader research in the area of cardiovascular disease, hypertension and 
salt sensitivity," said Dr. Felder. "It's important because 
cardiovascular diseases, including stroke, account for more disability 
and death than the next top five causes combined."
-- 
Kathrynne Holden, MS, RD < fivestar at nutritionucanlivewith.com >
"Ask the Parkinson Dietitian"  http://www.parkinson.org/
"Eat well, stay well with Parkinson's disease"
"Parkinson's disease: Guidelines for Medical Nutrition Therapy"
http://www.nutritionucanlivewith.com/