The preliminary results of a physiological and molecular study carried out
in the frame of the Pyramid project have been reported on the occasion of
the "International Seminars on Mountains" (Kathmandu, Nepal, March 2002).
For the first time some variables related to physical performance have
been investigated in Tibetan refugees, during the early phase of
reacclimatization to normoxia. Tibetans, the only population resident
permanently at high altitude since thousands of years, appear to be well
adapted to chronic hypoxia. Their major characteristics are: almost normal
red blood cells count, and lack of pulmonary hypertension, high altitude
mountain sickness and muscle atrophy. At peak exhaustive exercise, carried
out at altitude, heart rate, arterial oxygen saturation and maximal
aerobic power are greater in Tibetans than in acclimatized lowlanders. The
mechanisms underlying such a great tolerance to hypoxia are not known.
They may involve oxygen sensing and/or defence against cellular damage by
reactive oxygen species (ROS). Tibetans therefore may represent an
appropriate model to study paraphysiological (such as ageing) or
pathophysiological (chronic heart and/or lung failure, peripheral
arterial disease, etc.) conditions, characterized by muscle structure and
function deterioration similar to that found after high altitude exposure,
and possibly related to damage by ROS. The major results of the study
were: a) "lactate paradox" is not a permanent phenomenon in Tibetans as
well as in Caucasians, b) the energy cost of locomotion seems to be
similar in Tibetans and in lowlanders, c) whereas at high altitude
acclimatized lowlanders loose great fractions of their sea level maximal
aerobic power, Tibetans' maximal aerobic power is not altered either by
normoxia or hypoxia. Thanks to highly developed and time-consuming
techniques the expression of proteins in vastus lateralis muscle was
assessed in lowlanders and a reference standard protein map constructed
(the results of such a preliminary study were published on Electrophoresis
24: 286-295, 2003). A comparison between the Tibetan protein map and the
standard one, leads to finding of a greater expression of some proteins
involved in the removal of ROS. The preliminary results of the present
project support the hypothesis that Tibetans are well adapted to cope with
severe chronic hypoxia and to perform at altitude as we do at sea level.
The knowledge of the mechanisms underlying this unique feature may be
useful to understand the pathogenesis of muscle deterioration in some
clinical conditions as well as in ageing.
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