A new study finds that a high-salt diet triggers brain inflammation that drives up blood pressure.
The research, led by McGill University scientist Masha Prager-Khoutorsky in collaboration with an interdisciplinary team at McGill and the Research Institute of the McGill University Health Centre, suggests the brain may be a missing link in certain forms of high blood pressure-or hypertension-traditionally attributed to the kidneys.
"This is new evidence that high blood pressure can originate in the brain, opening the door for developing treatments that act on the brain," said Prager-Khoutorsky, associate professor in McGill's Department of Physiology.
Hypertension affects two-thirds of people over 60 and contributes to 10 million deaths worldwide each year. Often symptomless, the condition increases the risk of heart disease, stroke and other serious health problems.
About one-third of patients don't respond to standard medications, which primarily target the blood vessels and kidneys based on the long-standing view that hypertension begins there. The study, published in the journal Neuron, suggests the brain may also be a key driver of the condition, particularly in treatment-resistant cases.
How salt disrupts the brain
To mimic human eating patterns, rats were given water containing two per cent salt, comparable to a daily diet high in fast food and items like bacon, instant noodles and processed cheese.
The high-salt diet activated immune cells in a specific brain region, causing inflammation and a surge in the hormone vasopressin, which raises blood pressure. Researchers tracked these changes using cutting-edge brain imaging and lab techniques that only recently became available.
"The brain's role in hypertension has largely been overlooked, in part because it's harder to study," Prager-Khoutorsky said. "But with new techniques, we're able to see these changes in action."
The researchers used rats instead of the more commonly studied mice because rats regulate salt and water more like humans. That makes the findings more likely to apply to people, noted Prager-Khoutorsky.
Next, the scientists plan to study whether similar processes are involved in other forms of hypertension.
A 3D reconstruction of a brain immune cell (purple) engulfing fragments of other brain cells (green and orange) after a high-salt diet. The images were captured using super-resolution microscopy and reconstructed with IMARIS software. (Source: Prager-Khoutorsky Lab)
About the study
"Microglia regulate neuronal activity via structural remodeling of astrocytes" by Ning Gu et al., was published in Neuron and supported by the Canadian Institutes of Health Research, Heart and Stroke Foundation of Canada and the Azrieli Foundation.
