In a study Ivy and the team at the University of Edinburgh, with funding from Kidney Research UK, have shown that studying changes in small blood vessels in the kidney in models during sleep could improve our understanding of heart and vessel health in kidney disease patients.
Jess Ivy, Georgios Krilis and Anastasiia Komolova in the lab
How does blood pressure change during sleep?
Usually, blood pressure is lower when asleep than when awake. This is part of the body’s natural rhythm. However, people with chronic kidney disease (CKD) are more likely to have blood pressure that doesn’t decrease during sleep, which is called non-dipping blood pressure. Non-dipping blood pressure is thought to be worse for heart and blood vessel health, and increases the risk of a cardiovascular event, such as a heart attack or stroke.
How could steroid hormones change blood pressure during sleep?
The body produces many naturally occurring hormones, this includes steroid hormones. Glucocorticoids are a steroid hormone essential for normal bodily functions and their levels vary throughout the day.
In laboratory models, altering the natural levels of glucocorticoids can trigger non-dipping blood pressure. Steroids, which are artificial versions of the body’s natural glucocorticoids, are widely used medicines to help reduce inflammation (part of the body’s defence system) in conditions where it is damaging the body’s own tissues. People living with long term conditions, such as diabetes, can also have changes to the body’s natural levels of glucocorticoids.
A closer look at glucocorticoids and kidney vessels
Jess and the team have been studying the effect of glucocorticoids on the small tubes which carry blood into the kidney, called the renal arteries. Widening and narrowing of the renal arteries controls the blood flow into the kidney, which is an important mechanism for helping the kidneys to control blood pressure.
To test the effect of glucocorticoids on the renal arteries, Jess and the team gave a laboratory model continuous glucocorticoids, to reduce its natural rhythm. They found that in this model the renal arteries lost their normal pattern of widening and narrowing while awake or asleep. They also found that different genes, which are small sections of DNA, were switched on and off in different rhythms. These changes to the widening and narrowing of the renal arteries, and the genes switched on and off, showed model renal arteries respond to rhythmic glucocorticoid levels, which could then influence blood pressure control by the kidney.
What could this mean for kidney patients?
By looking at the effect of glucocorticoid levels on the kidneys, we could increase understanding of the mechanisms behind blood pressure changes during sleep. This could lead to new ways of protecting the vessel health of kidney patients in the future and form a new approach to improving cardiovascular health.
David Crosby, chief research officer at Kidney Research UK commented: “We need to find new ways of protecting cardiovascular health in kidney patients who are at an increased risk of having an event such as a heart attack, heart failure or stroke. This new approach to better understand how blood pressure changes during sleep could potentially inform new ways of protecting cardiovascular health in kidney patients. More research is needed to develop this concept, and we look forward to the next steps.”
* This is an experimental study and no changes to medications should be made without advice from a healthcare professional.
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