Tohoku J. Exp. Med., 2015 July, 236(3)

Augmented Carbohydrate Oxidation under Moderate Hypobaric Hypoxia Equivalent to Simulated Altitude of 2500 m

KAZUSHIGE GOTO,¹ TAKUMA MORISHIMA,¹ KAZUMICHI KUROBE,² ZHONG HUANG³ and FUTOSHI OGITA⁴

¹Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan
²Faculty of Business, Sports Management Course, Hannan University, Matsubara, Osaka, Japan
³Department of Sports Sciences, Japan Institute of Sports Sciences, Tokyo, Japan
⁴Department of Sports and Life Science, National Institute of Fitness and Sports in Kanoya, Kanoya, Kagoshima, Japan

Hypoxia itself stimulates glucose uptake mediated by a mechanism independent of insulin. However, whether moderate hypoxia causes similar metabolic effect in humans remains unclear. The present study aimed to determine glycemic regulation following glucose load at a simulated moderate altitude of 2,500 m. Eight healthy young males (mean ± standard error: 24 ± 1 years; 171.3 ± 1.6 cm; 66.9 ± 3.7 kg; 22.8 ± 1.0 kg/m²) consumed 75 g of glucose solution under either hypobaric condition (560 mmHg) or normobaric condition (745 mmHg). In the hypobaric chamber, the oxygen partial pressure is proportionally reduced with a reduction of atmospheric pressure, consequently leading to the hypoxic condition. Plasma glucose and serum insulin concentrations increased significantly following glucose load in both conditions (P < 0.05). However, no significant interaction (condition × time) or main effect for condition was observed. There were no significant differences in serum glycerol, plasma epinephrine, or plasma norepinephrine concentrations between the two conditions. No significant differences between the conditions were observed in changes in VO₂ or VCO₂. However, the hypobaric condition showed significantly higher respiratory exchange ratio (VCO₂/VO₂) at 90 and 120 min following glucose load (P < 0.05 vs. normobaric condition), suggesting that carbohydrate oxidation following glucose load was enhanced in moderate hypobaric hypoxia. In conclusion, acute exposure to moderate hypobaric hypoxia significantly augmented carbohydrate oxidation following the glucose load, without affecting glucose or insulin responses. Thus, a short-time exposure to moderate hypobaric hypoxia may be beneficial for people with impaired glucose tolerance.

keywords —— Keywords: carbohydrate oxidation; hypoxia; oral glucose tolerance test; respiratory exchange ratio; substrate metabolism

© 2015 Tohoku University Medical Press

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Tohoku J. Exp. Med., 2015, 236, 163-168

Correspondence: Kazushige Goto, Ph.D., Faculty of Sport and Health Science, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan.

e-mail: kagoto@fc.ritsumei.ac.jp