Relationship between exercise capacity and glucose tolerance in cystic fibrosis

Exercise performance in children and adolescents with cystic fibrosis with and without abnormal glucose tolerance: a single center cross-sectional study

BACKGROUND

Abnormal glucose tolerance (AGT) in cystic fibrosis (CF) affects lung function and clinical parameters, including aerobic fitness. However, its effects on physical activity level (PAL), anaerobic power (AP), and muscle strength (MS) in children and adolescents are unknown.

PURPOSE

To investigate aerobic fitness, PAL, AP, and MS in pediatric patients with mild-to-moderate CF and AGT.

METHODS

The study included children and adolescents with CF aged 10-18 years. Participants underwent a pulmonary function test, quadriceps, and handgrip MS measurement, vertical jump test to assess AP, and six-minute walk test (6MWT) to assess aerobic fitness. Bouchard's Three-Day Physical Activity record was used to determine PAL.

RESULTS

Height z-score (p = .006), 6MWT (p = .024), handgrip (p = .028), quadriceps MS (p = .044), and AP (p = .036) were significantly lower in AGT (n = 21) than normal glucose tolerance (NGT) (n = 19). In the AGT group, glycosylated hemoglobin (HbA1c) was significantly associated with forced expiratory volume in one second (FEV1) (p = .046). 6MWT distance (6MWD) was associated with height (p = .008), FEV1 (p = .001), forced vital capacity (FVC) (p = .001), forced expiratory flow from 25% to 75% (FEF25-75%) (p = .030), handgrip MS (p = .012), and PAL (p = .034). After adjusting for height and FEV1, the groups had similar 6MWD, MS, and AP (p > .05); also, insulin was associated with MS and AP but not with 6MWT or quadriceps MS.

CONCLUSION

Measures of aerobic fitness, MS, and AP are lower in AGT, but after adjusting for height and FEV1, aerobic fitness, MS, and AP do not show substantial differences. Insulin sensitivity and resistance are associated with MS and AP.

Cystic fibrosis related diabetes is not associated with maximal aerobic exercise capacity in cystic fibrosis: a cross-sectional analysis of an international multicenter trial

BACKGROUND

Previous studies have reported differences in aerobic exercise capacity, expressed as peak oxygen uptake (VO_2peak), between people with and without cystic fibrosis (CF) related diabetes (CFRD). However, none of the studies controlled for the potential influence of physical activity on VO_2peak. We investigated associations between CFRD and VO_2peak following rigorous control for confounders including objectively measured physical activity.

METHODS

Baseline data from the international multicenter trial ACTIVATE-CF with participants ≥12 years performing up to 4 h per week of vigorous physical activity were used for this project. Multivariable models were computed to study associations between CFRD and VO_2peak (mL.min^-1) adjusting for a set of pre-defined covariates: age, sex, weight, forced expiratory volume in 1 s (FEV₁), breathing reserve index, Pseudomonas aeruginosa infection, and physical activity (aerobic step counts from pedometry). Variables were selected based on their potential confounding effect on the association between VO_2peak and CFRD.

RESULTS

Among 117 randomized individuals, 103 (52% female) had a maximal exercise test and were included in the analysis. Participants with (n = 19) and without (n = 84) CFRD did not differ in FEV₁, physical activity, nutritional status, and other clinical characteristics. There were also no differences in VO_2peak (mL.min^-1 or mL.kg^-1.min^-1 or% predicted). In the final multivariable model, all pre-defined covariates were significant predictors of VO_2peak (mL.min^-1), however CFRD [coefficient 82.1, 95% CI -69.5 to 233.8, p = 0.28] was not.

CONCLUSIONS

This study suggests no meaningful differences in VO_2peak between people with and without CFRD given comparable levels of physical activity.

The Effect of Dysglycaemia on Changes in Pulmonary and Aerobic Function in Cystic Fibrosis

Cross-sectional studies have reported lower pulmonary and aerobic function during exercise in people with cystic fibrosis-related diabetes (CFRD) compared to non-CFRD counterparts. However, this association has yet to be longitudinally investigated. Therefore, this study examines these differences over time between people with cystic fibrosis (CF) of differing glycaemic status. Annual review data, including cardiopulmonary exercise tests and pulmonary function tests, were retrospectively analysed at baseline (T0, n = 82) and at a one-year follow-up (T1, n = 54). Data was analysed in three groups: normal glucose tolerance (NGT), impaired glucose tolerance (IGT), and CFRD. Further analyses were undertaken, with a dichotomous split of NGT and a combined IGT/CFRD group. At baseline, a significant reduction in the majority of variables, including forced expiratory volume in one second (FEV₁) and maximal oxygen uptake (VO_2max), was observed in the CFRD (n = 19) group compared to NGT (n = 58). At follow-up, no significant differences were observed, and no interaction effect between CFRD status and time was identified. FEV₁ and VO_2max presented with varying directions and magnitudes of change within patients. In summary, patients with CFRD have a reduced aerobic and pulmonary function compared to non-CFRD counterparts, although such changes disappeared at follow up. Varying responses for FEV₁ and VO_2max highlight the need to consider both variables as independent markers of function in CF.

Airway clearance and exercise for people with cystic fibrosis: Balancing longevity with life

Airway clearance has been an integral part of cystic fibrosis (CF) care for almost as long as CF has been identified as a condition. From diagnosis as a neonate through to end-of-life care, airway clearance is an everyday aspect of life, adding a considerable treatment burden to the lives of people with CF. There are many different techniques used for airway clearance which have evolved over time with an aim to improve effectiveness, support adherence and, more recently, to consider the impact of burden. A popular thought is whether airway clearance could be replaced by exercise. With new precision therapies in the form of CFTR modulators available, the CF landscape is rapidly changing, raising the question of whether certain treatments are needed at all. Depending on factors such as CFTR mutation, age, and pre-existing lung damage before starting a CFTR modulator, individuals with CF may need different levels of intensity and type of maintenance treatment. Precision medicine is likely to lead to the need for increased precision and individualized management around other maintenance therapies such as airway clearance.

Physiological predictors of cardiorespiratory fitness in children and adolescents with cystic fibrosis without ventilatory limitation

Objectives:

[1] To investigate the cardiorespiratory fitness (CRF) levels in children and adolescents with cystic fibrosis (CF) with no ventilatory limitation (ventilatory reserve ⩾ 15%) during exercise, and [2] to assess which physiological factors are related to CRF.

Methods:

A cross-sectional study design was used in 8- to 18-year-old children and adolescents with CF. Cardiopulmonary exercise testing was used to determine peak oxygen uptake normalized to body weight as a measure of CRF. Patients were defined as having ‘low CRF’ when CRF was less than 82%predicted. Physiological predictors used in this study were body mass index z-score, P. Aeruginosa lung infection, impaired glucose tolerance (IGT) including CF-related diabetes, CF-related liver disease, sweat chloride concentration, and self-reported physical activity. Backward likelihood ratio (LR) logistic regression analysis was used.

Results:

Sixty children and adolescents (51.7% boys) with a median age of 15.3 years (25th–75th percentile: 12.9–17.0 years) and a mean percentage predicted forced expiratory volume in 1 second of 88.5% (±16.9) participated. Mean percentage predicted CRF (ppVO_2peak/kg) was 81.4% (±12.4, range: 51%–105%). Thirty-three patients (55.0%) were classified as having ‘low CRF’. The final model that best predicted low CRF included IGT (p = 0.085; Exp(B) = 6.770) and P. Aeruginosa lung infection (p = 0.095; Exp(B) = 3.945). This model was able to explain between 26.7% and 35.6% of variance.

Conclusions:

CRF is reduced in over half of children and adolescents with CF with normal ventilatory reserve. Glucose intolerance and P. Aeruginosa lung infection seem to be associated to low CRF in children and adolescents with CF.

Short-Term Effects of Elexacaftor/Tezacaftor/Ivacaftor Combination on Glucose Tolerance in Young People With Cystic Fibrosis-An Observational Pilot Study

BACKGROUND

The effect of elexacaftor/tezacaftor/ivacaftor (ELX/TEZ/IVA) on glucose tolerance and/or cystic-fibrosis-related diabetes (CFRD) is not well understood. We performed an observational study on the short-term effects of ELX/TEZ/IVA on glucose tolerance.

METHODS

Sixteen adolescents with CF performed oral glucose tolerance tests (OGTT) before and 4-6 weeks after initiating ELX/TEZ/IVA therapy. A continuous glucose monitoring (CGM) system was used 3 days before until 7 days after starting ELX/TEZ/IVA treatment.

RESULTS

OGTT categories improved after initiating ELX/TEZ/IVA therapy (p = 0.02). Glucose levels of OGTT improved at 60, 90, and 120 min (p < 0.05), whereas fasting glucose and CGM measures did not change.

CONCLUSION

Shortly after initiating ELX/TEZ/IVA therapy, glucose tolerance measured by OGTT improved in people with CF. This pilot study indicates that ELX/TEZ/IVA treatment has beneficial effects on the endocrine pancreatic function and might prevent or at least postpone future CFRD.

Cystic fibrosis year in review 2018, part 2

Cystic fibrosis (CF) research and case reports were robust in the year 2018. This report summarizes publications related the multisystem effects of CF, pulmonary exacerbations, new and expanded therapies other than cystic fibrosis transmembrane conductance regulator modulator studies, and patient-reported priorities and outcomes.

Exercise as a therapeutic intervention for people with cystic fibrosis

INTRODUCTION

The complex multisystem nature of cystic fibrosis (CF) commonly results in reduced exercise tolerance, which is independently associated with poor clinical outcomes. Exercise is routinely recommended as part of the therapeutic regimen in CF to improve both respiratory and non-respiratory impairments. Areas covered: This article summarises the most recent evidence regarding the use of exercise as a therapeutic intervention in CF and discusses some of the practical considerations for exercise prescription in this setting. Clinical trials in progress and future research priorities are outlined. Expert opinion: On the balance of available evidence, exercise is likely to assist in improving physical fitness and health-related quality of life (HRQOL) and may be associated with a slower rate of decline in respiratory function in CF. Limitations to current studies include small sample sizes, study durations insufficient to achieve a training effect and difficulty distinguishing the effects of exercise training from that of other interventions implemented as part of a package of care. Larger, multi-centred trials are required to clarify the role of exercise in CF in improving physical fitness, respiratory function, HRQOL, as a substitute for traditional airway clearance techniques and in the management of common CF-related comorbidities.