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

Introduction: 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 A_1c (HbA_1c) can negatively affect exercise parameters in PwCF and that reductions in oxidative stress can improve tissue oxygenation in individuals with elevated HbA_1c.

Methods: Twenty four PwCF were divided into two groups; normal HbA1c <5.7% (N-HbA_1c) and elevated HbA_1c >5.7% (E-HbA_1c). A maximal exercise test was conducted to obtain peak oxygen uptake (VO₂peak), VO₂ at ventilatory threshold (VT), ventilatory parameters (V_E/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-HbA_1cwere given an antioxidant cocktail (AOC) for 4 weeks to determine the effects on tissue oxygenation during exercise.

Results: A negative relationship between HbA_1c and VO₂peak at VT was observed (r = -0.511; p = 0.018). In addition, a positive relationship between HbA_1c and V_E/VCO₂ slope (r = 0.587;p = 0.005) and a negative relationship between HbA_1c and petCO₂ at maximal exercise (r = -0.472;p = 0.031) was observed. N-HbA_1c had greater VO₂peak (p = 0.021), VO₂ at VT (p = 0.004), petCO₂ (p = 0.002), and lower V_E/VCO₂ slope (p = 0.004) compared with E-HbA_1c. Muscle deoxygenated hemoglobin at VT was higher in N-HbA_1c vs. E-HbA_1c and 4 weeks of AOC improved skeletal muscle utilization of oxygen.

Conclusion: 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.