Increased dependence on blood glucose after acclimatization to 4,300 m.
To evaluate the hypothesis that altitude exposure and acclimatization result in increased dependency on blood glucose as a fuel, seven healthy males (23 +/- 2 yr, 72.2 +/- 1.6 kg, mean +/- SE) on a controlled diet were studied in the postabsorptive condition at sea level (SL), on acute altitude exposure to 4,300 m (AA), and after 3 wk of chronic altitude exposure to 4,300 m (CA). Subjects received a primed continuous infusion of [6,6-2D]glucose and rested for a minimum of 90 min, followed immediately by 45 min of exercise at 101 +/- 3 W, which elicited 51.1 +/- 1% of the SL maximal O2 consumption (VO2 max; 65 +/- 2% of altitude VO2 max). At SL, resting arterial glucose concentration was 82.4 +/- 3.2 mg/dl and rose significantly to 91.2 +/- 3.2 mg/dl during exercise. Resting glucose appearance rate (Ra) was 1.79 +/- 0.02 mg.kg-1.min-1; this increased significantly during exercise at SL to 3.71 +/- 0.08 mg.kg-1.min-1. On AA, resting arterial glucose concentration (85.8 +/- 4.1 mg/dl) was not different from sea level, but Ra (2.11 +/- 0.14 mg.kg-1.min-1) rose significantly. During exercise on AA, glucose concentration rose to levels seen at SL (91.4 +/- 3.0 mg/dl), but Ra increased more than at SL (to 4.85 +/- 0.15 mg.kg-1.min-1; P less than 0.05). Resting arterial glucose was significantly depressed with CA (70.8 +/- 3.8 mg/dl), but resting Ra increased to 3.59 +/- 0.08 mg.kg-1.min-1, significantly exceeding SL and AA values.(ABSTRACT TRUNCATED AT 250 WORDS)
Brooks
G A
GA
University of California, Berkeley 94720.
Butterfield
G E
GE
Wolfe
R R
RR
Groves
B M
BM
Mazzeo
R S
RS
Sutton
J R
JR
Wolfel
E E
EE
Reeves
J T
JT
D000064:Acclimatization / Q000502:physiology*; D000328:Adult; D000531:Altitude; D001786:Blood Glucose / Q000378:metabolism*; D004837:Epinephrine / Q000097:blood; D015444:Exercise / Q000502:physiology; D006801:Humans; D007328:Insulin / Q000097:blood; D007700:Kinetics; D050356:Lipid Metabolism; D008297:Male; D009638:Norepinephrine / Q000097:blood; D010101:Oxygen Consumption
D001786:Blood Glucose; D007328:Insulin; D009638:Norepinephrine; D004837:Epinephrine