A collaborative research group by researchers from the National Rehabilitation Center for Persons with Disabilities (NRCD), Tohoku University, the National Cerebral and Cardiovascular Center, the University of Tokyo, Tokyo University of Agriculture and Technology, Kyushu University, International University of Health and Welfare (IUHW), Kwansei Gakuin University, Gunma University, Osaka University Graduate School of Medicine, Iwai Medical Foundation, Niigata University of Health and Welfare (NUHW), and Tokorozawa Heart Center performed an experiment in rats and a clinical study in adult humans, and they discovered a mechanism of moderate exercise inducing improvement in hypertension. The study was published in Nature Biomedical Engineering.
Previous research has reported that continuous exercise (20 m/min running, equivalent to light jogging in humans) in hypertensive rats is effective in improving hypertension and inhibiting sympathetic nerve activity. In another previous study, the research group reported that rats running at 20 m/min receive approximately 1G impact on the head at each forefoot landing.
In the current study, the study group demonstrated in anesthetized hypertensive rats that vertical head motion of twice per second generating 1G and rhythmically impacting the head induced interstitial-fluid flow in the brain which resulted in mechanical stimulation (shear stresses) on cells. When this head motion was repeated for 30 min/day for more than 2-3 weeks, a blood pressure lowering effect was observed. This effect was due to the reduced expression of the angiotensin receptor in astrocytes in a part of the medulla oblongata (rostral ventrolateral medulla) related to the pathology of hypertension. On the other hand, when interstitial-fluid flow movement was inhibited, the exercise or the passive vertical head motion did not exhibit neither the blood pressure lowering effect, the reduced expression of the angiotensin receptor in astrocytes, nor inhibition of sympathetic nerve activity.
The research group revealed that light jogging or brisk walking, which are typical examples of moderate exercise, also produce 1G vertical impact on the head at each foot landing. When study participants sat on a vertically oscillating chair designed to generate 1G vertical impact on the head, for 30 min/day, 3 days/week for 1 month, effects on improvement of hypertension and inhibition of sympathetic nerve activity were observed. The effect on improvement of hypertension continued for approximately 1 month after the end of the experiment of sitting on the vertically oscillating chair.
Hypertension is the largest risk factor for death globally. Although the effectiveness of moderate exercise on prevention and treatment of hypertension had already been reported, the mechanism of exercise improving hypertension was not well understood.
The current study clarified the underlying mechanism of exercise improving hypertension. It is statistically proven that the effect of moderate exercise not only has an effect on improving hypertension but also has effects on reducing and improving symptoms of many brain function-related diseases and disorders including dementia and depression. Therefore, the importance of the interstitial-fluid flow in the brain during exercise could also be relevant in those diseases.
The findings from this study may lead to finding a type and an amount of exercise (how much per day and per week) needed to maintain health, which may be a solution to a significant issue on prolonging healthy life expectancy. Based on the current study results, inducing moderate physical impact on the head through exercise may be of benefit to the brain and in maintaining physical health.
Journal Information
Publication: Nature Biomedical Engineering
Title: Interstitial-fluid shear stresses induced by vertically oscillating head motion lower blood pressure in hypertensive rats and humans
DOI: 10.1038/s41551-023-01061-x
This article has been translated by JST with permission from The Science News Ltd. (https://sci-news.co.jp/). Unauthorized reproduction of the article and photographs is prohibited.