Years weaken signal of bodys
By Fariss Samarrai
a wall full of clocks with a large dominant clock controlling
the synchronization of the peripheral clocks. Now imagine the
big clock con-
tinuing to keep time, but, as time goes on, 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 U.Va. study in the current issue
of the Proceedings of the National Academy of Sciences.
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 persons level of alertness.
In the long term it can disrupt the bodys metabolism, affect
eating cycles, lead to declining cognitive abilities and possibly
a shortened lifespan. Sleep disorders also are associated with
studies in our laboratory revealed that the electrical signal
from neurons in the brains 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 studys 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 clocks 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, said Block, who is also U.Va.s
vice president and
provost. Arrhythmic or improperly synchronized tissues
of old animals could possibly be stimulated by a treatment to
researchers who conducted the study include lead scientist Shin
Tamazaki, Block, Michael Menaker and Martin Straume. Hajimi Tai
and Y. Sakaki of the University of Tokyo also contributed.