Pulmonary Obstruction and Age, Not Activity, Associate With Muscle Oxidative Impairment in Smokers With and Without...

Area of Science:

• Pulmonary Medicine
• Exercise Physiology
• Muscle Biology

Background:

• Low muscle oxidative capacity is a key extrapulmonary feature of chronic obstructive pulmonary disease (COPD).
• The exact causes of reduced muscle oxidative capacity in COPD remain unclear.
• This study investigates factors influencing locomotor muscle oxidative capacity in individuals with and without COPD.

Purpose of the Study:

• To characterize locomotor muscle oxidative capacity in never smokers and ever smokers with and without COPD.
• To identify clinical and behavioral factors associated with diminished muscle oxidative capacity.
• To explore the relationship between lung function, physical activity, and muscle oxidative function in COPD.

Main Methods:

• Observational study involving 243 adults from the Muscle Health Study (COPDGene ancillary study).
• Gastrocnemius oxidative capacity measured using near-infrared spectroscopy (muscle oxygen consumption recovery rate constant, k).
• Physical activity assessed via accelerometry; pulmonary function via spirometry (FEV1%predicted), DLCO, and CT scans. Multivariable linear regression used to identify associations.

Main Results:

• FEV1%predicted, age, and race were significantly associated with muscle oxidative capacity (k).
• A 10% decrease in FEV1%predicted corresponded to a 4.4% reduction in k; 10 years of aging corresponded to a 9.7% reduction in k.
• Physical activity levels and COPD radiographic features did not show significant associations with muscle oxidative capacity.

Conclusions:

• Muscle oxidative impairment in COPD is primarily associated with lung function (FEV1%predicted) and age.
• Physical activity and radiographic evidence of COPD were not significant predictors of reduced muscle oxidative capacity.
• These findings highlight the link between systemic health, lung function, and muscle energetics in COPD patients.