Abstract
The effects of acute exposure to high altitude hypoxia upon plasma levels of lipids
and lipoproteins were studied in 6 healthy subjects observed under strict dietary
control. Fasting and postprandial values, first measured at low altitude (< 300 m),
were compared to values measured 7 days after transfer by helicopter to the Observatoire
Vallot (4350 m) near Mont-Blanc. Plasma levels of catecholamines and thyroid hormones
were measured in parallel. Under normoxic conditions, a rise in plasma levels of cholesterol,
triglycerides and phospholipids was found 4 hr after the test-meal, whereas circulating
norepinephrine fell. Under hypoxic conditions, postprandial effects on lipid parameters
disappeared, lipemic responses to the test-meal were dramatically reduced and plasma
levels of norepinephrine increased. These effects were accompanied by a fall in triglyceride-rich
lipoproteins, generally associated with a slight elevation of HDL-cholesterol, especially
the less dense HDL2 fraction. When all results obtained in normoxic and hypoxic conditions
were analyzed together, a series of highly significant correlations were found between
the magnitude of postprandial lipidemia and various lipid parameters, in particular
HDL2-cholesterol which was negatively correlated. These observations strongly suggest
that high altitude hypoxia, independent of interfering variables such as exercise
training or cold exposure, induced a net stimulation of the lipolysis of plasma triglycerides.
Key words
Altitude hypoxia - postprandial - lipoproteins - plasma lipids
