Decrease of subcutaneous adipose tissue lipolysis after exposure to hypoxia during a simulated ascent of Mt Everest

The purpose of this study was to examine the effects of prolonged hypoxia o n adipose tissue lipolysis, in relation to the weight loss usually observed at high altitude. Eight male subjects were exposed for 31 days to graduall y increasing hypobaric hypoxia up to the equivalent altitude of 8848 m (Mt Everest) in a decompression chamber, after 7 days at 4350 m for altitude pr e-acclimatization. A biopsy of subcutaneous adipose tissue was performed be fore and after hypoxic exposure, to study in vitro changes in adipose tissu e sensitivity. Fat mass, adipocyte volume and spontaneous lipolysis were no t impaired by the exposure to hypoxia. The in vitro lipolytic response to e pinephrine, isoproterenol, growth hormone (GH) and parathormone (PTH) decre ased significantly (P<0.01, P<0.05, P<0.01 and P<0.01 respectively), as did the plasma concentration of free fatty acid (P<0.01). The anti-lipolytic e ffect promoted by alpha 2-adrenergic receptor stimulation (epinephrine with propranolol) was greater after hypoxia (P<0.05), while the anti-lipolytic activity of insulin was decreased (P<0.01), In conclusion, prolonged exposu re to hypobaric hypoxia led to a potent reduction in lipid mobilization, th rough a decrease in the efficiency of beta-adrenergic, GPI and PTH lipolyti c pathways, as well as an increment in the alpha 2-adrenergic-receptor-medi ated anti-lipolytic effects.