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Vitamin A Can Reset Blood Vessel Rhythm

Finding could allow fine tuning of body functions

MONDAY, July 2, 2001 (HealthDayNews) -- Time may wait for no man, but you can tinker with it, say University of Pennsylvania scientists who have discovered that vitamin A has the potential to alter the daily rhythms of blood vessel activities.

Bodily functions are known to be affected by the 24-hour cycle called the circadian clock. The incidence of heart attacks and strokes is higher in the morning, for instance, when blood pressure is at its highest of the day.

But Penn scientists have discovered a new mechanism by which doctors someday might manipulate body rhythms for medicinal or other health reasons.

In laboratory experiments testing how vitamin A hooks up with certain proteins, doctors found that the vitamin bonded with a protein linked to the brain's so-called "master clock" that regulates the body's cycles in relation to the environment. They discovered that bonding altered the rhythms of the genes that affect blood vessels.

"This is the first study to show findings of the circadian clock in blood vessels," says lead study author Peter McNamara of Penn's Center for Experimental Therapeutics. "Two or three years ago people thought the only circadian clock was in the brain and that it drove all the rhythms in the body. Now [we're finding] that lots of peripheral organs have their own clocks . . . and the question is what are the signals and how do they synchronize with the master clock."

More experiments will pinpoint how the varying rhythms affect the blood vessels and hopefully will lead to ways to alter the timing of blood vessel activity, McNamara says.

"The more we know about how to modulate the body's timing, the better we will be able to design drug treatments that will be more effective, depending on a person's body clock," he says. "Further, it would be really beneficial to be able to discreetly modify the circadian clock for people facing transatlantic travel [or for those] changing work schedules from night to day."

In the study, McNamara and his colleagues found that vitamin A, in the form of retinoic acid, bonded with a protein called MOP4, which is very similar to the protein that is known to activate the brain's master clock. When bonded with the retinoic acid, the MOP4 protein changed the rhythm of the genes that controlled blood vessels in mice. Genes basically turn on and off at different times, and McNamara says the researchers could see that the vitamin A/protein combination altered the way the genes turned on and off.

McNamara says the next step is to "look to identify all the genes in the blood vessels that are under the control of the clock," then to see what characteristics of the blood vessels are changed, from blood pressure to the size of the vessels.

The study was sponsored by the National Institutes of Health and reported in the June 29 Journal Cell.

Michael Menaker, a biology professor at the University of Virginia, says the findings are "very exciting." He says, "If these conclusions are correct, then what the testing procedure has discovered is one of what is bound to be a very large number of signals that connect the oscillators in the body."

What To Do: The field of chronobiology is a new and tantalizing one. Read an excerpt from the book The Body Clock to find out if you are a morning or night person and how knowing this can affect your health. Northwestern University also has information on the subject.

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