May Desynchronize Body Clocks, Study Shows
August 14, 2002-- Imagine
a wall full of clocks with a large dominant clock controlling the
synchronization of the peripheral clocks. Now imagine the big clock
continuing to keep time, but, as it ages, its connecting signal
to the smaller clocks weakens. Some of the smaller clocks eventually
become desynchronized and some stop running.
weakening of the signal, rather than a problem with the central
timekeeper itself, apparently is the cause of alterations in the
biological timing system in aging mammals -- possibly including
humans -- according to a new University of Virginia study in the
current issue of the journal, Proceedings of the National Academy
may explain why older people experience sleep disorders -- the signal
from the master clock in the brain has weakened, even as it keeps
on ticking. This weakened output causes some of the peripheral clocks
in other organs to eventually stop oscillating or to fall out of
proper synch, causing sleep disruption and malaise.
of sleep can affect more than a person's level of alertness. In
the long term it can disrupt the body's metabolism, affect eating
cycles, lead to declining cognitive abilities and possibly a shortened
lifespan. Sleep disorders also are associated with Alzheimer's disease.
studies in our laboratory revealed that the electrical signal from
neurons in the brain's master clock is weaker in older animals,
which led us initially to believe that the central clock mechanism
deteriorates with age," said Gene D. Block, professor of biology
and one of the study's lead researchers.
new finding demonstrates that the molecular machinery of the master
clock continues to function normally. Taken together with our earlier
studies, this suggests that there may be an age-related failure
of the conversion of the clock's molecular rhythm into the electrical
or humoral signals that the brain uses for communication. These
weakened central signals may fail to keep some peripheral clocks
appropriately synchronized or, in some cases, even rhythmic."
scientists studied tissue from the brain and other organs of older
mice and measured the activity of a gene that is part of the biological
clock. They found that the central clock in the brain, the suprachiasmatic
nucleus, maintained proper periodicity and synchronization. Clocks
in some peripheral organs, such as the liver and kidney of older
animals, were either improperly synchronized or had lost rhythm
new knowledge could eventually lead to new therapies for age-related
desynchronization," Block said. "Arrhythmic or improperly
synchronized tissues of old animals could possibly be stimulated
by a treatment to oscillate normally."
researchers who conducted the study include lead Research Scientist
Shin Tamazaki, Block, Mike Menaker and Martin Straume. Hajimi Tai
and Y. Sakaki of the University of Tokyo also contributed.
Fariss Samarrai. (434) 924-3778