Introduction MicroRNAs (miRs) are small non-coding RNAs that regulate gene expression and have been implicated in the control of skeletal muscle phenotype. Our group has previously shown that muscle-specific miRs are altered, and correlate with physiological parameters in the quadriceps¹ and plasma² of COPD patients. MiRs may therefore have a mechanistic role in the development of skeletal muscle dysfunction in COPD.

We hypothesised that muscle-specific miRs are involved in skeletal muscle adaptation to exercise and that changes in quadriceps miR expression after acute exercise would differ between patients and controls.

Methods 20 COPD patients and 11 controls were studied. Fasted quadriceps biopsies were taken before and one hour after an incremental, symptom limited, cycle exercise test. Muscle-specific miR-1,-499,-133, and -206 as well as miR-181, a more widely expressed miR associated with inflammatory responses, were quantified using qPCR. Paired analyses were performed using paired T-test or paired Wilcoxon.

Results See table of characteristics (Table 1)

Muscle miR results:

MiR-1, -499, -133 did not change with exercise. MiR-181 increased x1.5 in the COPD patients only one hour after exercise (p = 0.017, controls p = 0.83). There was also a trend for miR-206 to increase in the COPD group only (p = 0.07).

Conclusions Muscle-specific miRs do not change one hour after an acute bout of exercise in COPD patients or controls. However, miR-181 increased in the quadriceps of COPD patients. MiR-181 is not restricted to, but functions in muscle, and in addition has been shown to be linked to inflammatory signalling. The difference in the response of miR-181 expression to exercise is consistent with COPD patients having a greater inflammatory response to exercise stimulus than controls.

References

1. Lewis A, et al Thorax 2012;67:26–34

2. Donaldson AVJ et al Thorax 2013: EPUB 28/06/2013