Muscle oxygen utilization and ventilatory parameters during exercise in people with cystic fibrosis: Role of HbA1c.

Abstract

Glycated hemoglobin can interfere with oxygen delivery and CO2 removal during exercise. Additionally, pancreatic insufficiency increases oxidative stress and exacerbates exercise intolerance in people with cystic fibrosis (PwCF). This investigation sought to test the hypotheses that elevated Hemoglobin A1c (HbA1c) can negatively affect exercise parameters in PwCF and that reductions in oxidative stress can improve tissue oxygenation in individuals with elevated HbA1c. Twenty four PwCF were divided into two groups; normal HbA1c <5.7% (N-HbA1c) and elevated HbA1c >5.7% (E-HbA1c). A maximal exercise test was conducted to obtain peak oxygen uptake (VO2peak), VO2 at ventilatory threshold (VT), ventilatory parameters (VE/VCO2 slope and end-tidal CO2 (petCO2)). Near-Infrared Spectroscopy (NIRS) was used to assess muscle oxygenated/deoxygenated hemoglobin during exercise. A subset of individuals with E-HbA1cwere given an antioxidant cocktail (AOC) for 4weeks to determine the effects on tissue oxygenation during exercise. A negative relationship between HbA1c and VO2peak at VT was observed (r = -0.511; p = 0.018). In addition, a positive relationship between HbA1c and VE/VCO2 slope (r = 0.587;p = 0.005) and a negative relationship between HbA1c and petCO2 at maximal exercise (r = -0.472;p = 0.031) was observed. N-HbA1c had greater VO2peak (p = 0.021), VO2 at VT (p = 0.004), petCO2 (p = 0.002), and lower VE/VCO2 slope (p = 0.004) compared with E-HbA1c. Muscle deoxygenated hemoglobin at VT was higher in N-HbA1c vs. E-HbA1c and 4weeks of AOC improved skeletal muscle utilization of oxygen. Findings demonstrate that glycated hemoglobin may lead to tissue oxygenation impairment and ventilation inefficiency during exercise in PwCF. In addition, antioxidant supplementation may lead to improved tissue oxygenation during exercise.