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PEOPLE WHO MAKE long-haul aircraft trips are no strangers to jet lag, the delayed response of our bodies to different time zones around the world. Nor are travelers particularly fond of “airplane air,” that often overly-arid cabin atmosphere of reduced pressure. However, recent research has shown that this less-than-normal pressure may actually encourage the body to reset its circadian clock.
Commercial aircraft are typically pressurized to an equivalent altitude of 5200 to 8000 feet, akin to visits to Denver or Aspen, Colorado, respectively. This “cabin altitude” depends on the aircraft: An older Boeing 767’s is around 6900 ft; a sample of 747-400s showed a median cabin altitude of 5159 ft. The regulatory maximum cabin altitude set by the Federal Aircraft Administration is 8000 ft.
Researchers at the Weizmann Institute of Science in Rehovot, Israel, realized that light, food and temperature were known influences of a body’s time clock. They also knew that oxygen absorption varies in animals in accordance with these other influences.
Their research employed lab mice to study the relationship between oxygen levels and circadian rhythms. The mice were given a six-hour change in their light-dark cycles, a simulated jet lag that affected their eating, sleeping and running patterns.
Some of the mice were also given a 12-hour exposure to reduced oxygen level, in conditions similar to cabin altitude. These particular mice adapted to their new environment much quicker than the others.
The researchers knew that the HIF1α protein plays a role in cellular response to oxygen levels in mammals. To test the relationship of oxygen level and circadian rhythm, the researchers repeated the 12-hour oxygen reduction, this time with mice bred to be deficient in this HIF1α gene.
Unlike the control mice, these HIF1α-deficient counterparts suffered jet lag akin to their siblings that hadn’t had the 12-hour oxygen reduction.
The researchers also learned that a slight drop of oxygen level, only 3 percent, two hours after the six-hour time shift had the same beneficial effect on alleviating jet lag.
Perhaps only mice may benefit from this regime. The paper Rhythmic Oxygen Levels Reset Circadian Clocks Through HIF1α offers four conclusions: Oxygen levels exhibit daily rhythms in blood and tissue of rodents. Physiological oxygen rhythms reset clocks in cultured cells in HIF1α-dependent manner. Several core clock genes respond to changes in oxygen levels in HIF1α-dependent manner. And modulation of oxygen levels accelerates the recovery of mice in a jet lag protocol. A summary of the paper in the Cell Metabolism journal offers more details.
Further research on circadian rhythms and oxygen is needed to extend the result to humans, researchers note. However, “We conclude that oxygen, via HIF1α activation, is a resetting cue for circadian clocks and propose oxygen modulation as therapy for jet lag.” ds
© Dennis Simanaitis, SimanaitisSays.com, 2016