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    Does A 'Food Clock' In The Brain Supercede Circadian Rhythm?
    By News Staff | May 22nd 2008 06:00 AM | 5 comments | Print | E-mail | Track Comments
    In investigating the intricacies of the body’s biological rhythms, scientists at Beth Israel Deaconess Medical Center (BIDMC) have discovered the existence of a “food-related clock” which can supercede the “light-based” master clock that serves as the body’s primary timekeeper.

    The findings, which appear in the May 23 issue of Science, help explain how animals adapt their circadian rhythms in order to avoid starvation, and suggest that by adjusting eating schedules, humans too can better cope with changes in time zones and nighttime schedules that leave them feeling groggy and jet-lagged.

    “For a small mammal, finding food on a daily basis is a critical mission,” explains the study’s senior author Clifford Saper, MD, PhD, Chairman of the Department of Neurology at BIDMC and James Jackson Putnam Professor of Neurology at Harvard Medical School. “Even a few days of starvation is a common threat in natural environments and may result in the animal’s death.”

    The suprachiasmatic nucleus (SCN), a group of cells in the brain’s hypothalamus, serves as the body’s primary biological clock. The SCN receives signals about the light-dark cycle through the visual system, and passes that information along to another cell group in the hypothalamus known as the dorsomedial nucleus (DMH). The DMH then organizes sleep-wake cycles, as well as cycles of activity, feeding and hormones.

    “When food is readily available,” explains Saper, “this system works extremely well. Light signals from the retina help establish the animals’ circadian rhythms to the standard day-night cycle.” But, if food is not available during the normal wake period, animals need to be able to adapt to food that is available when they are ordinarily asleep.

    In order to survive, animals appear to have developed a secondary “food-related” master clock. “This new timepiece enables animals to switch their sleep and wake schedules in order to maximize their opportunity of finding food,” notes Saper, who together with lead author Patrick Fuller, PhD, HMS Instructor in Neurology and coauthor Jun Lu, MD, PhD, HMS Assistant Professor of Neurology, set out to determine exactly where this clock was located.

    “In addition to the oscillator cells in the SCN, there are other oscillator cells in the brain as well as in peripheral tissues like the stomach and liver that contribute to the development of animals’ food-based circadian rhythms,” says Saper. “Dissecting this large intertwined system posed a challenge.”

    To overcome this obstacle, the authors used a genetically arrhythmic mouse in which one of the key genes for the biological clock, BMAL1, was disabled. They next placed the gene for BMAL1 into a viral vector which enabled them to restore a functional biological clock to only one spot in the brain at a time. Through this step-by-step analysis, the authors uncovered the feeding entrained clock in the DMH.

    “We discovered that a single cycle of starvation followed by refeeding turns on the clock, so that it effectively overrides the suprachiasmatic nucleus and hijacks all of the circadian rhythms onto a new time zone that corresponds with food availability,” says Saper. And, he adds, the implications for travelers and shift workers are promising.

    “Modern day humans may be able to use these findings in an adaptive way. If, for example, you are traveling from the U.S. to Japan, you are forced to adjust to an 11-hour time difference,” he notes. “Because the body’s biological clock can only shift a small amount each day, it takes the average person about a week to adjust to the new time zone. And, by then, it’s often time to turn around and come home.”

    But, he adds, by adapting eating schedules, a traveler might be able to engage his second “feeding” clock and adjust more quickly to the new time zone.

    “A period of fasting with no food at all for about 16 hours is enough to engage this new clock,” says Saper. “So, in this case, simply avoiding any food on the plane, and then eating as soon as you land, should help you to adjust – and avoid some of the uncomfortable feelings of jet lag.”

    This research was supported by grants from the U.S. Public Health Service.

    Comments

    It sure is a new idea to be explored further, and since it was published in a "peer-reviewed journal" I have little doubt about the quality of the research work within the constraints of the animal-experiment. But it may be grossly erroneous to advise it as a measure to prevent jet-lag in humans - through public media, or, common press.

    Starving yourself also impairs your immune function. Combine that with breathing in the same confined space for 11 hours of flight with often 400 plus individuals - I'm not sure - if that is a safe measure to prevent jet-lag. I wish, I could find out some scientific studies about risk of contacting influenza, or other airborne infections, during long flights!

    If the above is true, then why there are people with delayed Circadian Rhythm? I, my father, sister and a few uncles have this delay in their Body clock; there was one uncle whose CR had been a bit advanced. Accordingly, I , my father and uncle, for example, always had our breakfasts at 10 O'Clock in the morning. We slept late at around 2 in the morning, too.

    Eat breakfast when you wake up, don't eat after bedtime, and don't go to bed hungry is what I get from this. I'm really good at #3!

    If you are afraid of starving impairing immune function, they stop eating a day before you travel. Then eat on the airplane according to the new time.

    If you are afraid of starving impairing immune function, they stop eating a day before you travel. Then eat on the airplane according to the new time.