Monday, June 5, 2017

Sherpa metabolic adaptations

The Sherpa ethnic group of the high Himalaya have long interested physiologists.  Along with being better at just generally living at altitude, with all that requires (try keeping up a good immune system and successfully gestating a fetus at 14,000 feet!), they have superior endurance abilities at altitude.  Some are counterintuitive- for example, they don't respond to increased altitude by producing way more red blood cells as flatlanders do- and some of these adaptations are understood to be evolutionary*.  That is, over the thousands of years that Sherpa have lived on the Tibetan plateau, natural selection has favored genes (well, phenotypes) that better support endurance activity at high altitude.  A recent study has identified several biological, evolutionary adaptations at the metabolic level, meaning the chemistry that provides energy for muscles.  Muscle biopsies were collected from Sherpa and lowlander mountaineers during a high-altitude trek and the Sherpa muscles showed some interesting differences: they utilize fat differently as fuel; their mitochondria are more efficient in their use of oxygen (oxidation is more "tightly coupled" to energy production); and there are differences in anaerobic energy production (anaerobic meaning without oxygen).

NPR story here:
research paper here:

*note that there are three other levels of adaptation:  1) Acclimation, the physiological responses that happen as soon as the body's homeostasis is distrupted. For example, increased breathing and heart rate at altitude, to compensate for less oxygen per breath. 2) Acclimatization, a longer-term (days/weeks/months) response to disrupted homeostasis.  For example, making more red blood cells to compensate for less oxygen at altitude. 3) Cultural/behavioral adaptation, meaning all the ways that people cope with the environment other than biologically.  For example, wearing lots of warm clothes in cold climates. Acclimation and acclimatization are often used interchangeably, which is confusing, but regardless the two adaptation types are distinct.

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