Translational Study Provides Clues to Potassium’s Beneficial Effect on Hypertension

A nephrology-pharmacology researcher at the University of Miami Miller School of Medicine has identified how potassium can help regulate sodium balance in a groundbreaking hypertension study.

“Potassium-rich foods like bananas or orange juice are known to have a positive impact on high blood pressure, but the reason has remained a mystery,” said Richard A. Preston, M.D., M.S.P.H., M.B.A., professor of medicine, chief of the Division of Clinical Pharmacology, and director of the Clinical Pharmacology Phase I Research Unit (CPRU). “One possible way that potassium intake could reduce blood pressure is by increasing the amount of sodium excreted in the urine.”

The research team: Front row, from left, Eileen Alonso, M.D., APRN; Richard A. Preston, M.D., M.S.P.H., M.B.A. Second row: Evelyn V Caizapanta, M.D. Third row, Miriam Gonzalez-Sosa, M.D., Nadine Francois, M.A., Rolando Rodco, M.D.

Drawing on the resources of the CPRU – one of the few U.S. facilities to conduct complex physiology studies in humans – Dr. Preston and his team looked at the role of the sodium-chloride cotransporter (called the NCC) in regulating the sodium and potassium levels that affect blood pressure. “Our study characterizes the time, course, and magnitude of sodium excretion following a standard potassium intake in obese hypertensive humans,” he said. “We found that the impact of potassium in producing sodium excretion was comparable to thiazide, a medication that also increases the excretion of sodium and lowers blood pressure.”

Dr. Preston was the lead author of the study, “Thiazide-Sensitive NCC (Sodium-Chloride Cotransporter) in Human Metabolic Syndrome Sodium Sensitivity and Potassium-Induced Natriuresis,” published in January in the journal Hypertension. Miller School coauthors were David Afshartous, Ph.D.; Evelyn V. Caizapanta, M.D.; Barry J. Materson, M.D., M.B.A.; Rolando Rodco, M.D.; Eileen Alonso, M.D., APRN; and Alberto B. Alonso, M.D., P.A.

The 13-day inpatient study involved 19 obese hypertensive individuals with metabolic syndrome who were put on a special high-sodium diet. Blood and urine samples were taken regularly to determine how much sodium was cleared by the kidneys.

The study also looked at the impact of sodium on individuals with salt sensitivity, whose blood pressure increases significantly when provided a high salt diet. Prior research has found that genetic factors, as well as older age, obesity, and kidney disease, are associated with salt sensitivity. Further, hypertensive patients whose blood pressure is salt-sensitive tend to have worse outcomes than those who are salt-resistant.

“We tested the hypothesis that increased activity of the NCC was associated with salt sensitivity in humans with metabolic syndrome, but found no difference between sodium-sensitive and sodium-resistant participants,” said Dr. Preston. “But further translational studies of NCC are needed – especially following the clinically relevant finding of the positive impact of potassium.”

The NCC study was conducted as an investigator-originated project by the Division of Clinical Pharmacology, which is dedicated to studying the effects of new pharmacological agents and disease mechanisms in humans, and conducts phase I drug development studies for pharmaceutical companies across a wide range of therapeutic areas.

“The CPRU enjoys an international reputation as a premier study site for conducting phase I studies in special populations,” said Dr. Preston, who has conducted more than 340 studies as principal investigator, including 120 relating to renal impairment and 120 to hepatic impairment.

Tags: Clinical Pharmacology Research Unit, Division of Clinical Pharmacology, Dr. Richard Preston, Hypertension journal