Interestingly, the mean levels of systemic Act A were absolutely elevated in patients with COPD (13.12±3.87 vs. 7.28±2.06), whereas serum levels of TNF-α as an important inflammatory factor playing a central role in the pathophysiology in muscle atrophy were also upregulated in COPD patients when compared with controls (9.36±3.18 vs. 6.03±1.86) (Figure 1). Here, TNF is linked to chronic obstructive pulmonary disease.