In healthy people blood pressure dips at night, and rises again in the morning. This variation is controlled by a gene called Period 1.
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SYDNEY: The circadian clock gene 'Period 1' is crucial to controlling variations in blood pressure, scientists found, which may lead to new treatments for some types of heart attack or stroke.
During a 24-hour period, bodily functions such as heartbeat, body temperature, hormones, kidney blood flow, and blood pressure vary in a cyclical way. This is known as the circadian rhythm.
The expression of some genes is subject to circadian control, and a dysfunctional circadian rhythm has been implicated in many medical problems, including kidney and heart disease and even bi-polar disorder.
However, the molecules that link the cycle to blood pressure are not known. This study provides the first clues to the molecular link between circadian rhythm and blood pressure, and may be clinically significant. The finding was published in The Journal of Clinical Investigation.
Treating blood pressure disorders
“The results of our study could help explain clinical findings that link circadian rhythms to physiological processes, such as kidney salt handling and blood pressure,” said lead author Michelle Gumz, a molecular biologist at the University of Florida in Gainsville, USA. “Understanding these mechanism certainly has implications for the treatment of blood pressure disorders,” she said.
Gumz and colleagues found that a gene known as 'Period 1' – which in the brain provides feedback to our central, master circadian clock – also alters blood pressure, by controlling the amount of salt absorbed in our kidneys.
The action of the Period 1 gene was stopped in mouse kidney cells, which means less proteins was produced form the gene. The altered cells were less able to take up salt. Strikingly, the effect remained even when the cells were treated with the hormone aldosterone, which normally increases salt uptake.
Dips and surges in blood pressure
Taken together, along with previous studies, Gumz and her colleagues concluded that the hormone aldosterone stimulates the Period 1 gene, which in turn stimulates salt absorption in kidney cells. Higher salt absorption in the kidneys causes more fluid to be absorbed into the bloodstream – and it is this that raises blood pressure.
In healthy people blood pressure dips at night, and rises again in the morning. Heart attacks and strokes occur more often during this early morning blood pressure surge, while 'non-dippers' are more prone to heart attack or stroke overall.
Understanding the molecular processes involved may allow scientists to develop drugs targeting the dip.
Judith Whitworth, a medical researcher at the Australian National University in Canberra, also considers this an important finding. “Day-night variations in salt handling by the body and blood pressure are well established, but the mechanisms have not been well understood,” she said.
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