Exercise oxidative skeletal muscle metabolism in adolescents with cystic fibrosis

Abstract

Introduction Patients with Cystic Fibrosis (CF) are reported to have limited exercise capacity. There is no consensus about a possible abnormality in skeletal muscle oxidative metabolism in CF. Our aim is to test the hypothesis that abnormalities in oxygenation and/or muscle oxidative metabolism contribute to exercise intolerance in adolescents with mild CF. Methods Ten adolescents with CF (12–18 years of age, FEV1>80%pred, resting oxygen saturation > 94%) and ten healthy age-matched controls (HC) were tested with supine cycle ergometry using near-infrared spectroscopy (NIRS) and 31Phosphorus magnetic resonance spectroscopy (31P MRS) to study skeletal muscle oxygenation and oxidative metabolism during rest, exercise and recovery. Results No statistically significant (p>0.1) differences in peak workload and peak oxygen uptake per kilogram lean body mass were found between CF and HC. No differences were found between CF and HC in bulk changes of quadriceps phosphocreatine (PCr) (p = .550) and inorganic phosphate (Pi) (p = .896) content and pH (p = .512) during symptom limited exercise. Furthermore, we found statistically identical kinetics for PCr resynthesis during recovery for CF and HC (p = .53). No statistically significant difference in peak exercise arbitrary unit for total haemoglobin content (tHb_AU) was found between CF and HC (p = .66). Discussion The results of this study provide evidence that in patients with mild CF and a stable clinical status (without signs of systemic inflammation and/or chronic PA colonisation), no intrinsic metabolic constraints and/or abnormalities in oxygenation and/or muscle oxidative metabolism contribute to exercise intolerance.

Rebuttal from Erik H. J. Hulzebos, Jeroen A. L. Jeneson, Cornelis K. van der Ent, Maarten S. Werkman and Tim Takken

“…Furthermore, our recent report of a normal oxidative capacity of leg muscles in adolescents with CF (Werkman et al . ) was corroborated independently by the findings reported by Decorte and coworkers (Gruet et al . ; Decorte et al .…”

CrossTalk opposing view: Skeletal muscle oxidative capacity is not altered in cystic fibrosis patients

“…Werkman et al . () found no differences between adolescent subjects with CF and age‐, gender‐ and habitual physical activity‐matched healthy controls with regard to resting quadriceps PCr concentration, the magnitude of changes in quadriceps PCr, P i and pH during in‐magnet bicycle exercise, or post‐exercise recovery kinetics of PCr and P i , respectively. Decorte et al .…”

“…Indeed, two recent in vivo 31 P‐MRS studies also failed to find any evidence for impaired mitochondrial function in subjects with CF (Werkman et al . ; Decorte et al . ).…”

“…In active patients with mild to moderate CF, normal phosphorous metabolite degradation and preserved oxidative capacity in limb skeletal muscles have been described (Werkman et al . ; Decorte et al . ).…”

Rebuttal from Paula Rodriguez‐Miguelez, Melissa L. Erickson, Kevin K. McCully and Ryan A. Harris

“…It is likely that the disparity in findings can be explained by inclusion of a younger, healthier CF population (Werkman et al . ) and/or the evaluation of different muscle groups that are composed of different fibre‐type proportions (Decorte et al . ).…”