Page last updated at 19:00 GMT, Sunday, 13 December 2009

Body clock link to heart disease

Blood pressure reading
High blood pressure is linked to heart disease

Scientists have raised the possibility that cardiovascular disease is linked to disturbances in the body's 24-hour clock.

Working on mice, the Japanese team found a genetic risk factor for a form of high blood pressure is influenced by 24-hour or circadian rhythms.

The study appears online in the journal Nature Medicine.

Malfunctions in the body clock - which influences much of the body's chemistry - have been linked to many diseases.

We know that there is a strong correlation between time of day and cardiovascular events which often coincide with the early morning surge in blood pressure
Professor Bryan Williams
University of Leicester

And lead researcher Professor Hitoshi Okamura said the latest study was in line with data which suggested shift workers, long-distance flight crews and people with sleep disorders have a heightened risk of heart problems.

High blood pressure - known as hypertension - can lead to heart attack, stroke, kidney damage, and many other medical problems.

Many genes have been identified as being essential elements making up the circadian clock.

For example, mice lacking a pair of molecules known as cryptochromes have an abnormal circadian rhythm.

The latest study, by Kyoto University, found these mice were vulnerable to high blood pressure because of abnormally high levels of a hormone called aldosterone that prompts water retention in the kidneys.

Strong correlation

The researchers showed that the circadian clock directly controls a gene that plays a key role in production of the hormone.

The researchers say a similar gene is found in humans.

They stress more work is needed to determine whether a misfiring circadian clock can lead to high blood pressure in humans.

But Professor Okamura said the research raised the prospect of new ways to treat hypertension.

Professor Bryan Williams, an expert in hypertension at the University of Leicester, described the study as "fascinating".

He said: "We know that there is a strong correlation between time of day and cardiovascular events, which often coincide with the early morning surge in blood pressure.

"So this does provide some insights into the mechanism that might underpin blood pressure deregulation in some people."

Professor Williams said some people with high blood pressure were known to have high levels of aldosterone.

But he added: "What we don't know is how common this mutation might be in human hypertension."

Professor Jeremy Pearson, associate medical director at the British Heart Foundation, said: "Hypertension is common, but the genes controlling blood pressure are not well understood.

"Their identification will help design better treatments for high blood pressure."

But he also stressed more research was needed before it became clear whether the study had identified a potential target for new treatments.

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