EFFECTS OF INTERMITTENT LOW DOSE CARBON MONOXIDE INHALATION ON BLOOD GLUCOSE REGULATION IN OVERWEIGHT ADULTS: A RANDOMIZED CONTROLLED CROSSOVER TRIAL

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PURPOSE: Low dose carbon monoxide (CO) inhalation upregulates several proteins important for glucose metabolism. However, it is not known whether CO’s ability to upregulate proteins associated with glucose metabolism has consequences for whole body glucose metabolism which could have implications for both research and clinical fields. We hypothesized that low dose CO inhalation would improve the glucose and insulin responses to ingestion of an oral glucose bolus in overweight humans. METHODS: Eleven young adults (5 male, 6 female; body mass index: 25-35 kg/m2) were included in this randomized, placebo-controlled, single blinded crossover study. Following screening, subjects completed two 7-day protocols, separated by at least 4 weeks. Prior to (24-hours) and following 5 consecutive days of either once daily CO (males: 1.2 mL kg-1 body mass; females: 1.0 mL kg-1 body mass) or placebo (room air) inhalation, subjects underwent two-hour oral glucose tolerance tests (OGTT). RESULTS: Although blood glucose was on average 5 mg/dl lower post-intervention compared to pre-intervention (p<0.001), there were no significant main effects or interactions across experimental conditions for any OGTT parameters (presented as overall average and [95% CI]), including fasting glucose (84.0 [78.8-89.2] mg/dL; intervention x pre/post interaction p=0.53), two hour post glucose (96.9 [87.2-107.0] mg/dL; p=0.71), fasting insulin (4.82 [2.63-7.00] μU/mL; p=0.33), the homeostatic model of insulin resistance (1.04 [0.53-1.55]; p=0.45) or the Matsuda Index (17.3 [6.24-28.3]; p=0.60). CONCLUSION: 5 days of low dose CO administration did not influence the glucose and insulin responses to an OGTT in overweight adults. Since low dose CO inhalation is used in the assessment of hemoglobin mass and other physiological parameters, these findings allow researchers to utilize these procedures without concern of altering glucose metabolism.