March 7, 2022

High Blood Pressure

Rick Johnson, M.D. on the relationship between salt & blood pressure

Read Time 3 minutes

This video clip is taken from  Podcast #194 – How Fructose Drives Metabolic Disease with Rick Johnson, M.D. Rick Johnson is a Professor of Nephrology at the University of Colorado.


Show Notes

Mechanisms that drive high blood pressure

  • The first issue was known is that salt is important in blood pressure 
    • In animals that are sensitive to high blood pressure, one can make blood pressure a lot worse by giving them salt.
    • Studies from 1900 showed that if you took people with high blood pressure and you put them on a salt restriction, this lowered blood pressure
    • This has led to recommendations to restrict salt in people with high blood pressure
  • Not everybody is sensitive to salt
    • Lot of people when they’re young can eat all the salt they want and they don’t seem to have so much of a problem
  • But as we get older, we become more and more sensitive to the effects of salt on blood pressure
    • Why is this?
    • For years, it was thought the problem is the kidneys in people with high blood pressure can’t excrete salt as easily or as well as normal people
      • And so it was thought that there was some defect in the kidney
    • To make a long story short, over a decade of studying this revealed that people with high blood pressure have inflammation in their kidneys
      • This low grade inflammation in the kidneys is due to T-cells and macrophages
      • This inflammation tends to be in the main part of the kidney where the tubules are and around the little blood vessels
    • Studies were able to prove that the inflammation was actually maintaining the kidney in a state where it couldn’t get rid of salt very well
    • This occurs by creating reduced blood flow to the kidney
  • People with high blood pressure, they all have reduced blood flow to their kidneys
    • When the blood flow is reduced, this affects the ability of the kidney to excrete salt, and triggers the retention of salt
  • Studies revealed that high blood pressure is an inflammatory disease that is driven by inflammation
    • But then the question is, what is driving the inflammation?
  • He found that many things could drive inflammation in the kidneys
    • Some drugs are very vasoconstrictive;  cocaine, for example, and other things that constrict the renal arteries 
    • Activation of the renin angiotensin system, for example, can cause ischemia to the kidneys and bring in this inflammation
    • But one thing that seems to drive it is a level of high uric acid
  • He did studies in adolescents who were overweight
  • He did some studies in animals and saw that when they raised uric acid, the animals developed high blood pressure
  • He thought maybe the uric acid could be playing a role in blood pressure in humans
  • He did a study, done by Dan Feig (published it in JAMA) where they randomized adolescents with high blood pressure to drugs to lower uric acid or not
    • This is a study of kids with newly discovered hypertension; they’ve never been on any kind of drug at all
    • He put them on allopurinol, a drug that can lower uric acid
    • The results were remarkable, 90% of them normalized their blood pressure when their uric acid levels were lowered
    • There was a 5-8 mm drop in ambulatory blood pressure
Rick Johnson, M.D.

Richard Johnson is a professor of medicine in the Department of Nephrology at the University of Colorado since 2008 and he’s spent the last 19 years being a division chief across three very prestigious medical schools. An unbelievably prolific author, Rick has well over 700 publications in JAMA, New England Journal of Medicine, Science, et Cetera. He’s lectured across 40 countries, authored two books, including The Fat Switch, and has been funded extensively by the National Institute of Health (NIH). His primary focus in research has been on the mechanisms causing kidney disease, but it was in doing this that he became really interested in the connection between fructose (and fructose metabolism) and obesity, diabetes, heart disease, hypertension, and metabolic disease.

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