There's nothing like jet lag to throw off sleeping patterns. Researchers have been studying what drives the biological phenomena, and now a team led by Weizmann Institute of Science's Gad Asher is a step closer to unraveling the mystery after discovering that variations in oxygen levels can reset circadian clocks - in mice at least.

Currently, temperature, food and light levels are the best known cues that affect circadian rhythms. If the researchers are able to confirm their findings, which they published in the journal Cell Metabolism, they can work with airlines to set air pressure in cabins right to help passengers deal with and avoid jet lag altogether.

Asher and colleagues wanted to know if oxygen might be be used to direct circadian rhythms because oxygen absorption in animals has been observed to vary alongside changing temperatures and mealtime.

Based on their findings, the researchers observed that altering oxygen concentration within mouse cells twice a day by just 3 percent allowed for circadian rhythm synchronization. They suspect that the gene HIF1α was what was linking circadian rhythms and oxygen because it has a role in cell oxygen homeostasis. When cells are low in HIF1α, they are unable to synchronize with circadian clocks when oxygen levels were changed.

"It was extremely exciting to see that even small changes in oxygen levels were sufficient to efficiently reset the circadian clock," said Asher.

However, while the study was able to show that resetting circadian clocks depends on the gene, it was unable to identify fully how HIF1α is a part of a clock's entire circuitry.

In exploring how oxygen affects circadian rhythms, the researchers carried out jet lag experiments on mice. Mice are just like humans in that they are likely to suffer jet lag after daylight hours suddenly shift.

After being left to sleep, eat and run in air-controlled environments, the mice subjects didn't experience a change in their circadian clocks until they were subjected to a 6-hour jump in daylight hours, with varying levels of oxygen helping them adjust their sleeping, eating and running habits based on the new time.

The researchers also observed that a 1-minute drop in the levels of oxygen 12 hours prior to the 6-hour shift in daylight or 2 hours back helped the mice stabilize their circadian clocks faster, an outcome that was dependent as well on levels of the HIF1α gene.

In the future, the researchers are looking to take the opposite route and see how higher levels of oxygen can affect circadian clocks. Asher noted too that passengers may be more amenable to being told they need air high in oxygen to address jet lag.

Photo: Matthew Hurst | Flickr

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