Diets rich in phosphate additives, commonly found in processed foods, can increase blood pressure by triggering a brain signaling pathway and overactivating the sympathetic nervous system that regulates cardiovascular function, UT Southwestern researchers discovered. Their findings could lead to treatment strategies for patients with hypertension caused by overconsumption of foods containing high levels of phosphates.
“This research uncovers a previously unrecognized brain-mediated mechanism by which high dietary phosphate intake promotes hypertension and sympathetic overactivation, highlighting central fibroblast growth factor receptor signaling as a novel therapeutic target,” said the study’s first author, Han Kyul Kim, Ph.D., Assistant Professor of Internal Medicine in the Division of Cardiology at UT Southwestern.
Inorganic phosphate is often used as a preservative or flavor enhancer in packaged foods, processed meats, and other dietary staples. As a result, the study reports, the average adult in developed countries consumes phosphate far above the recommended daily allowance.
Following excessive phosphate intake, circulating fibroblast growth factor-23 (FGF23) can enter the brain and induce hypertension, Dr. Kim and his colleagues report in their study, published in Circulation. The research outlines a new paradigm for this previously unclear mechanism and identifies a potential target for developing treatment strategies.
Hypertension occurs when the pressure that pushes against a patient’s arterial walls is too high. Affecting nearly half of the U.S. population, according to the U.S. Centers for Disease Control and Prevention, hypertension increases the risk of life-threatening medical events such as heart attack and stroke.
UTSW researchers ran a series of tests that measured and compared FGF23 protein levels, mean arterial pressure, and renal sympathetic nerve activity in rats receiving a high (1.2%) phosphate diet and another group on a normal (0.6%) phosphate diet. The measurement was repeated during stress response to exercise by stimulation of the spinal cord.
Researchers found that those on the high phosphate diet showed increased levels of FGF23 protein in their serum, cerebrospinal fluid, and brain stem, and that FGF23 proteins were able to cross the blood-brain barrier, causing high blood pressure both at rest and during physical stress.
“FGF23 can cross into the brain and influence the brain stem centers that control blood pressure,” said senior corresponding author Wanpen Vongpatanasin, M.D., Professor of Internal Medicine at UT Southwestern and Director of the Hypertension Section in the Division of Cardiology and the Hypertension Fellowship Program.
Analysis also revealed that inhibiting fibroblast growth factor receptor 4 (FGFR4) during simulated exercise dampened the negative effects of a high phosphate diet, suggesting a connection between FGFR4 and overactivation. Inhibition of FGFR1 did not have the same effect.
Given these results, researchers explored the role of FGFR4 and found that activation of this receptor contributes to an exaggerated increase in blood pressure during simulated exercise. FGFR4 activation caused by an excess of dietary phosphate was accompanied by an increase in the protein calcineurin A and brain stem activity that may contribute to elevated blood pressure and overactivation of the sympathetic nervous system during simulated exercise.
