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Blame it on your brain: Salt and hypertension

  • Posted by Milton Bertrand
  • January 23, 2015 12:03 AM EST
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  • 4,374 views
Excessive salt intake "reprograms" the brain, interfering with a natural safety mechanism that normally prevents the body's arterial blood pressure from rising, researchers have discovered.

An international research team led by scientists at McGill University has found that excessive salt intake "reprograms" the brain, interfering with a natural safety mechanism that normally prevents the body's arterial blood pressure from rising.

While the link between salt and hypertension is well known, scientists until now haven't understood how high salt intake increased blood pressure. By studying the brains of rats, a team led by Prof. Charles Bourque of McGill's Faculty of Medicine discovered that ingesting large amounts of dietary salt causes changes in key brain circuits.

"We found that a period of high dietary salt intake in rats causes a biochemical change in the neurons that release vasopressin (VP) into the systemic circulation," says Bourque who is also a researcher at the The Research Institute of the McGill University Health Centre (RI-MUHC).

Vasopressin is also called antidiuretic hormone; it is a hormone that plays a key role in maintaining osmolality (the concentration of dissolved particles, such as salts and glucose, in the serum) and therefore in maintaining the volume of water in the extracellular fluid (the fluid space that surrounds cells). This hormone is necessary to protect cells from sudden increases or decreases in water content, which are capable of interfering with proper cell function. Normal serum osmolality ranges from about 285 to 300 milliosmoles per kilogram (mOsm/kg) in healthy people. Vasopressin and a hormone called oxytocin evolved from a single primordial neurohypophyseal hormone called vasotocin, which is present in lower vertebrates (http://www.britannica.com/science/vasopressin).

"This change, which involves a neurotrophic molecule called BDNF (brain-derived neurotrophic factor), prevents the inhibition of these particular neurons by other cells."

The team's findings, published in the journal Neuron, found that high salt intake prevents the inhibition of VP neurons by the body's arterial pressure detection circuit. The disabling of this natural safety mechanism allows blood pressure to rise when a high amount of salt is ingested over a long period of time.

While the team's discovery advances the understanding of the link between salt intake and blood pressure, more work is needed to define new targets that could potentially be explored for therapeutic intervention. Among the questions for further research: Does the same reprogramming effect hold true for humans? If so, how might it be reversed?

In the meantime, Bourque says, the message remains: limit dietary salt.

 

Story Source:

The above story is based on materials provided by McGill UniversityNote: Materials may be edited for content and length.


Journal Reference:

  1. Katrina Y. Choe, Su Y. Han, Perrine Gaub, Brent Shell, Daniel L. Voisin, Blayne A. Knapp, Philip A. Barker, Colin H. Brown, J. Thomas Cunningham, Charles W. Bourque. High Salt Intake Increases Blood Pressure via BDNF-Mediated Downregulation of KCC2 and Impaired Baroreflex Inhibition of Vasopressin NeuronsNeuron, 2015; DOI: 10.1016/j.neuron.2014.12.048

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