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| June 26, 2010 | How our inner clock copes up with jet lag | | Washington: In a rodent study, researchers have shown how individual clock genes and the internal clocks of the different organs synchronise with the new external time in the case of jet lag. Travelling across different time zones makes our
internal body clocks go haywire. Scientists at the Max Planck Institute for Biophysical
Chemistry have now succeeded in demonstrating for mice, the clocks associated
with individual organs in the body adapt to the new time at different speeds.
Thus, the body's physiological processes are no longer coordinated. They found
that the adrenal gland plays a key role in this process. When the researchers
switched off the adrenal clock or manipulated the synthesis of corticosterone
by the adrenal gland with the help of metyrapone, the rodents adapted more quickly
to the altered circadian rhythm. These insights could pave the way for a new approach
to the hormonal treatment of the effects of jet lag and shift work. An entire
network of molecular clocks found in the different organs coordinate the body's
various physiological processes ranging from the heart beat, temperature, sleep
requirement and hormone balance to behaviour. All of these clocks are controlled
by the master pacemaker of the hypothalamic suprachiasmatic nuclei (SCN), which
synchronises all of the body's "peripheral" clocks with the outside world. At
molecular level, all of the clocks are based on a handful of "clock" genes and
proteins that regulate each other interactively and thus generate a molecular
time signal in the form of a circadian rhythm. Researchers have shown how individual
"clock" genes and the internal clocks of the different organs cope up with jet
lag. "The internal clocks and the 'clock' genes adapt to the altered external
influences at varying speeds. When an organism suffers from jet lag, it would
appear that the entire clock mechanism fails to tick at the right rhythm. As a
result, numerous physiological processes are no longer coordinated," said Gregor
Eichele, Director of the Institute's Genes and Behaviour Department. As the researchers
discovered, the adrenal clock plays a key role in the body's adaptation to a new
circadian rhythm. When the scientists switched off the adrenal clock in mice,
the rodents adapted their behaviour more quickly to the new time and made a more
rapid return to their laps on the wheel in synch with the new external time. Therefore,
a functioning adrenal clock keeps the organism in a temporally stable state and
halts the excessively rapid adaptation of the central clock in the SCN. It is
not necessary, however, to switch off the entire adrenal clock to enable the mice
to better recover from jet lag. When the scientists administered the active agent
metyrapone to the mice, their corticosterone rhythm changed as did their sleeping/waking
rhythm. "If the mice were given metyrapone at the right time, they adapted faster
to the disturbed circadian rhythm. While the 'sleep hormone' melatonin, which
is commonly used to treat jet lag, mainly acts by generating tiredness and is
therefore more suitable for use when flying east than west, with metyrapone, the
mice's internal clock can be turned both forwards and back," explained junior
scientist Silke Kiebling. The insights could produce an entirely new approach
to the treatment of jet lag in the future. The study is published in the Journal
of Clinical Investigation. | |
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