Sherpa Resiliency at High Altitudes Begins on the Molecular Level

Researchers at the University of Cambridge found that levels of an energy source that kicks in when muscles crave fuel increased among Sherpa climbing Mount Everest, while decreasing in subjects from low-lying regions.

The heroic exploits of the Sherpas who have climbed Mt. Everest and other Himalayan peaks for millennia could hinge on their cells’ efficient use of oxygen compared to lowlanders, new research has found.

“Their performance is extraordinary at altitude,” said University of Cambridge Physiologist Andrew Murray, the senior author of the Sherpa study published today in the Proceedings of the National Academy of Sciences. “We’ll be huffing and puffing as we walk up an incline. They will breeze past you without effort.”

Highlighting the importance of understanding the Sherpas’ resiliency, the findings were published after an Australian and Slovakian climber perished on Sunday during their descent from the peak in the 27,500-feet “death zone” where the air is especially thin on the world’s highest mountain. 

Before, during, and after a 17,000-foot ascent followed by a two-month stay at the Mount Everest base camp, Murray and his team examined oxygen levels and other findings in blood and muscle biopsies from Sherpas and non-Sherpas, including Brits and others. The experiment was part of Xtreme Everest, a 10-year-old project seeking medical breakthroughs by studying human reactions to extreme altitudes.

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Sherpa resiliency thousands of feet in the clouds has been documented before. Geneticists have discovered, for example, that Sherpas likely adapted to their low-oxygen homeland as they evolved from folks who arrived in the region as late as 9,000 years ago.

But the University of Cambridge researchers showed how those genetic differences played out on the molecular and physiological levels, said Tatum Simonson, a geneticist at the University of California San Diego who did not participate in Murray’s study but has studied Sherpas.

“It’s an example of natural selection in humans, which is absolutely incredible,” said Simonson.

Sherpas burn less oxygen to create energy from fat, suggesting they burn sugars, a more efficient source of energy, Murray found. As they spent more time at the base camp, their levels of phosphocreatine, an energy source that kicks in when muscles crave fuel, increased while lowlanders’ levels decreased, he added. Lastly, Sherpa cells produced fewer free radicals, or damaging molecules that appear when cells are starving for oxygen.

Importantly, while the non-Sherpas in the experiment improved somewhat over the course of the study, the Sherpas’ advantages remained before and after the climb, suggesting they were born with them and weren’t simply more used to their surroundings.

“Our bodies adapt to some extent to become more Sherpa-like, but we are no match for their efficiency,” Murray said.

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The researchers couldn’t pinpoint exactly how much more efficient Sherpas’ bodies were on average versus lowlanders. Murray said he was now preparing to publish the results of a second batch of tests of Sherpas and non-Sherpas on exercise bikes that would help measure the differences between their metabolic activities.

But Murray isn’t pursuing his research solely to learn more about what makes Sherpas superhuman.

He’s hoping insights into the Sherpas’ efficient metabolism might help hospital patients cope with a lack of oxygen someday in the future. In the West, around 20 percent of patients in intensive care perish due to lack of the vital element, he said.

“If we have got one of these people who don't have the tolerance to low oxygen, is there a way to treat them and harness the mechanisms the Sherpas use?” he asked.

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