Of mice and men

We all know it as "jet lag" - that sick, sagging feeling after a long-haul flight. But in medicine, it's called "desynchronosis" - a physiological condition in which the body is out of sync with a new time zone. It's a disruption of the circadian system - the rhythmic biological cycles recurring at approximately 24-hour intervals. Light, in a complex interaction with genes, is significant in naturally resetting the inner clock of most plants and animals to adjust to external time.

But with jet lag, it's not just one clock that is out of whack in a new time-zone, said Gregor Eichele of the Max Planck Institute of Biophysical Chemistry in Goettingen, Germany.

"Jet lag is a complete mix-up of all the body's clocks," Eichele told Deutsche Welle.

Separate circadian clocks exists in all the organs and cells of the body, and though the brain constantly works at synchronizing them, some organs can be re-set faster than others to adjust to a new time zone, Eichele said about his study just published in the Journal of Clinical Investigation.

One organ asleep, the other awake

The brain itself may adjust to the new time zone within 24 hours, but the kidneys or pancreas can take longer. Some parts of the body are still back in the old time zone, in the light/dark-wake/sleep patterns of that location.

When the clocks are out of sync, bodily functions that depend on chemical communication can become disturbed, and could possibly be an explanation for jet leg symptoms such as insomnia, nausea, low spirits and gastrointestinal issues.

"In our new research, we found that the clocks consist of a network of genes that regulate each other - half a dozen different genes are important for making the clocks work - and even in the different organs, the clock genes are desynchronized in a different way," Eichele said.

Eichele and his colleagues examined mice, which have internal clocks similar to those of humans, to glean more about jet lag and how to combat it. Specifically, they focused on the adrenal glands, the triangular-shaped endocrine glands that sit on top of the kidneys and which release cortisol (in response to stress), adrenaline and other hormones.

By "knocking out" or manipulating those glands, the scientists found that the mice adjusted to jet lag, or time-zone changes, faster, thereby pinpointing the importance of the adrenal glands in helping to re-set the body's internal clock as a whole.

A pill to reset the clocks

One theory extrapolated from the new research is that perhaps, one day down the line, a person could take a pill a day or two before traveling to a new time zone "that would alter one's cortisol profile closer to what it has to be at the new destination," Eichele explained. In other words, that hormone would be pre-adjusted to the future site in a very short amount of time.

But those are all just ideas, Eichele warned. "No trials have been done on humans and I would not recommend it."

It will be a while, then, before anyone could pop a pill for a quick fix to reset the body's internal clock. The best method still to combat it is a day of rest for every time zone crossed.

Still, the research is significant, Eichele said, "because any successful anti-jet lag medication, which doesn't really exist at this point, would have to work on the principles that we elucidated in our research."

Tinkering with nature

Studies have also shown that aircraft crew who suffer from chronic jet leg are affected in various ways: their brains tend to shrink, they produce more stress hormones and women's menstrual cycles are disrupted. And you don't have to be up in the sky to feel the effects. Rotating work shifts - think doctors, police officers or journalists - has been linked to severe health problems such as cancer and heart disease, and even a shorter life span.

So the knowledge drawn from this new research could also potentially be applied to those on rotating shift work, whose body clocks constantly have to tick to a different beat.

Kei Cho, a University of Bristol, U.K. neuroscientist, said tinkering with the body's inner clocks, by deactivating the adrenal glands, for example, could do more harm than good.

"Cortisol is produced as a defense mechanism - it's a method of survival," he pointed out to Deutsche Welle. Altering the adrenal gland system, then, could be problematic.

"It's important to understand how and why all these clock systems function," he noted, so Eichele's research is significant. "But we have no idea what the side effects could be if we were to manipulate those clocks."

Author: Louisa Schaefer
Editor: Mark Mattox