Glucose Tolerance is Unchanged During Acute Normobaric Hypoxia

Abstract

Blood glucose regulation is critical to support metabolism, particularly in contexts of metabolic stressors (e.g., high altitude). Data regarding insulin sensitivity and glucose tolerance in hypoxia are scant and inconclusive. We aimed to characterize the interactive effects of acute normobaric hypoxia and glucose regulation following an oral glucose tolerance test (OGTT) compared to normoxia. Following 12 hours of fasting on two separate days, 28 healthy participants (21.8±0.3 yrs; BMI 22.8±0.48 kg/m2; 16 females) were randomly exposed to either normoxia (FIO2 0.21) or hypoxia (FIO2 0.148) in a normobaric hypoxia chamber. Blood glucose was tested from finger capillary samples via glucometer and sterile lancets. Following a 10-min baseline in normoxia or hypoxia, participants consumed an OGTT (75g, 300ml) and blood glucose was sampled every 10-min for 80-min. Peripheral oxygen saturation was lower at baseline in hypoxia (88.6±0.7 vs. 96.8±0.41%; P<0.0001), but fasted blood glucose was not different between trials (hypoxia=4.86±0.07 vs. normoxia=4.80±0.08 mmol/L; P=0.47). Blood glucose responses following OGTT were compared between oxygen conditions using a two-factor repeated measures ANOVA (2FRM-ANOVA; factors = oxygen condition x time) and area under the curve (AUC; paired t-test). Blood glucose responses were not different between trials (2FRM-ANOVA interaction, P=0.765; AUC normoxia vs. hypoxia, P=0.227). We conclude that glucose tolerance is unchanged with acute normobaric hypoxia, likely protecting the metabolic rate of organs that do not require insulin for uptake or storage (e.g., brain) during hypoxic stress. Funding Sources: NSERC Discovery, MRU Faculty of Science and Technology