Operation Everest II: plasma lipid and hormonal responses during a simulated ascent of Mt. Everest.
To examine the effect of hypobaric hypoxia on plasma lipid profiles, fasting blood samples were collected from six men (21-31 yr) at 760 Torr and periodically during a 40-day exposure to decreasing barometric pressure culminating in a final ambient pressure of 282 Torr. Preascent plasma total cholesterol concentration ([TC]) was decreased by 25% after the 40-day exposure (P less than 0.01). High-density lipoprotein concentrations ([HDL-C]) decreased 32% (P less than 0.001) with no alteration in the TC-to-HDL-C weight ratio. Plasma triglyceride concentration increased twofold during this period (P less than 0.01). There were no significant differences in fasting plasma free fatty acid concentrations or free fatty acid-to-albumin molar ratio throughout the study. Fasting plasma insulin levels were increased approximately twofold with no significant changes in glucagon concentration or the insulin-to-glucagon molar ratio. Plasma norepinephrine concentrations were increased threefold on reaching 282 Torr (P less than 0.01), with no significant changes in plasma epinephrine concentrations. Mean energy intake (kcal/day) decreased 42%, whereas mean body weights decreased by 8.9 +/- 0.8% (P less than 0.01) with exposure. Increased concentrations of insulin may lead to increased hepatic production of triglyceride-rich lipoproteins, thus eliciting metabolic changes independent of weight loss and dietary intake.
Young
P M
PM
US Army Research Institute of Environmental Medicine, Natick, Massachusetts 01760.
Rose
M S
MS
Sutton
J R
JR
Green
H J
HJ
Cymerman
A
A
Houston
C S
CS
D000328:Adult; D000531:Altitude; D001786:Blood Glucose / Q000032:analysis; D001823:Body Composition; D005215:Fasting; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005934:Glucagon / Q000097:blood; D005990:Glycerol / Q000097:blood; D013006:Growth Hormone / Q000097:blood; D006728:Hormones / Q000097:blood*; D006801:Humans; D000860:Hypoxia / Q000097:blood; D007328:Insulin / Q000097:blood; D008055:Lipids / Q000097:blood*; D008297:Male; D009638:Norepinephrine / Q000097:blood; D009752:Nutritional Status; D010101:Oxygen Consumption; D012016:Reference Values; D014280:Triglycerides / Q000097:blood; D015431:Weight Loss
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D006728:Hormones; D007328:Insulin; D008055:Lipids; D014280:Triglycerides; D013006:Growth Hormone; D005934:Glucagon; D005990:Glycerol; D009638:Norepinephrine