Successive exposure to moderate hypoxia does not affect glucose metabolism and substrate oxidation in young healthy men

INTRODUCTION: Exposure to hypoxia has been suggested to acutely alter glucose regulation. However, the effects of successive exposure to moderate hypoxia on postprandial glucose regulation and substrate oxidation pattern after multiple meals have not been elucidated. PURPOSE: We examined the effects of successive exposure to moderate hypoxia on metabolic responses and substrate oxidation pattern. METHODS: Eight healthy men (21.0 ± 0.6 yrs, 173 ± 2.3 cm, 70.6 ± 5.0 kg, 23.4 ± 1.1 kg/m(2)) completed two experimental trials on separate days: a rest trial under normoxic conditions (FiO(2) = 20.9%) and a rest trial under hypoxic conditions (FiO(2) = 15.0%). Experimental trials were performed over 7 h in an environmental chamber. Blood and respiratory gas samples were collected over 7 h. Standard meals were provided 1 h (745 kcal) and 4 h (731 kcal) after entering the chamber. RESULTS: Although each meal significantly increased blood glucose and serum insulin concentrations (P < 0.05), these responses did not differ significantly between the trials. There were no significant differences in areas under the curves for glucose or insulin concentrations over 7 h between the trials. No significant differences were observed in blood lactate, serum cortisol, free fatty acid, or glycerol concentrations over 7 h between the trials. The oxygen consumption ( [Image: see text]) and carbon dioxide production ( [Image: see text]) 3 h after entering the chamber were significantly higher in the hypoxic trial than in the normoxic trial (P < 0.05). However, the differences did not affect respiratory exchange ratio (RER). The average values of [Image: see text], [Image: see text], and RER did not differ between the trials. CONCLUSION: Seven hours of moderate hypoxia did not alter postprandial glucose responses or substrate oxidation in young healthy men.