COPDの喫煙者の末梢筋損傷

COPDの喫煙者の末梢筋損傷を生検で調査した論文を紹介します。

Orozco-Levi M, Coronell C, Ramírez-Sarmiento A, Lloreta J, Martínez-Llorens J, Galdiz JB, Gea J. Injury of peripheral muscles in smokers with chronic obstructive pulmonary disease. Ultrastruct Pathol. 2012 Aug;36(4):228-38.

COPD患者では筋力・筋持久力の低下を認めますが、その原因が何かを生検で調査しました。COPD患者と健常者で比較したところ、現在の喫煙とCOPDの存在（程度にかかわらず）が、末梢筋損傷の増加と関連していました。

これよりCOPDが軽度で、呼吸不全、高二酸化炭素血症、ステロイド使用、低体重、他の併存疾患がなくても、末梢筋損傷を認めるという結論です。

おそらくCOPDによる全身炎症・悪液質が関与していると考えます。ただ、禁煙が無効というわけではありません。現在の喫煙も末梢筋損傷に関連しているという結果ですので、COPDの有無にかかわらず、禁煙はサルコペニアの予防・治療に有効だと思われます。

Abstract
Muscle injury has clinical relevance in diseased individuals because it is associated with muscle dysfunction in terms of decreased strength and/or endurance. This study was aimed at answering three questions: whether the presence of chronic obstructive pulmonary disease (COPD) is associated with peripheral muscle injury; whether muscle injury is associated with some of the relevant functional impairment in the muscles; and whether muscle injury can be solely justified by deconditioning. Twenty-one male COPD patients were eligible for the study. Seven healthy volunteers recruited from the general population were included as controls. Function of the quadriceps muscle was assessed through specific single-leg exercise (strength and endurance). Cellular (light microscopy) and subcellular (electron microscopy) techniques were used to evaluate muscle injury on biopsies from the vastus lateralis muscle. Signs of injury were found in muscles from both control and COPD patients, not only in cases showing severe airflow obstruction but also in the mild or moderate stages of the disease. Current smoking and presence of COPD were significantly associated with increased injury of the muscle as assessed by light and electron microscopy techniques. The authors conclude that peripheral muscle injury is evident in mild, moderate, and severe stages of COPD even in the absence of respiratory failure, hypercapnia, chronic steroid treatment, low body weight, or some coexisting disease. These findings support the theory that systemic factors with deleterious effect are acting on peripheral muscles of smokers with COPD, increasing the susceptibility of the muscle fibers to membrane and sarcomere injury.