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Het kunnen (over)leven op grote hoogte is een aangeboren gave.*
Tibetanen die boven de 3500meter wonen hebben de mogelijkheid geërfd zich tegen het gebrek aan zuurstof te wapenen. Door het gebrek aan voldoende zuurstof op grote hoogte ontstaat vrije radicalen schade in hersenen, longen en spieren van “gewone” mensen. Tibetanen blijken wel 380% meer Glutathion, het enzym dat vrije radicalen schade tegengaat, te hebben dan gewone Nepalezen.
Tibetans who live at over 3,500 metres above sea
level have, at least in part, inherited a system of protection against the
effects of lack of oxygen on their muscle tissue, according to new research.
Oxygen deficiency, or hypoxia, not only affects the lungs and brains of
mountain climbers in the form of altitude sickness, but also affects their
muscles. Research carried out with members of two Swiss Everest expeditions in
the 1980s revealed that the number of mitochondria, the 'powerhouses' of
cells, declined in European climbers exposed to hypoxia, resulting in cell
damage in muscle tissue. This is because hypoxia leads to the formation of
free radicals, highly reactive atoms or molecules, which attack the
mitochondria.
Amazingly, however, the indigenous Tibetan Sherpas were immune to such muscle
damage. This led scientists to question whether their bodies had adapted to
hypoxia during the course of their lives, or whether they have become
genetically adapted to the extreme conditions after 15,000 years of
colonisation of the Tibetan plateau by their ancestors.
In order to try and find an answer, a joint Swiss-Italian team of researchers,
led by Professor Hans Hoppeler from the University of Bern, carried out a
comparative study with nine Tebtans residing at altitudes above 3,500 metres,
six Tibetans whose parents had emigrated to the lowlands (at approximately
1,500 metres), and a control group of nine Nepalese, also residing at 1,500
metres.
The results clearly showed that Tibetans have significantly higher levels of
an antioxidant enzyme known as glutathione S-transferase, which neutralises
free radicals in muscle tissues, compared with the Nepalese volunteers. Those
Tibetans living at altitude had levels around 380 per cent higher than the
control group, while the lowland Tibetans had up to 50 per cent more of these
enzymes.
'Thanks to this enzyme the Tibetans are presumably better equipped to
neutralise the free radicals produced as a result of hypoxia,' said Professor
Hoppeler. 'It is the results from the Tibetans who live in the lowlands that
prove the hereditary adaptation to life at high altitudes. If the phenomenon
was purely environmentally induced, these individuals should have shown no
difference from the control group,'
Aside from making an important discovery about the human body's ability to
adapt to extreme and inhospitable environments, the research results will have
more practical applications, Professor Hoppeler explained. 'These results add
weight to the argument that altitude is basically not good for you. Athletes
and climbers will need to limit their high altitude exposure to the absolute
minimum needed to achieve a defined level of adaptation,' he concluded. (maart
2004)