Serum sirtuin-1 is reduced in COPD

<b>Introduction and background.</b> The protein deacetylase sirtuin-1 (SIRT1) is and anti-ageing molecule that is decreased in the lung from patients with chronic obstructive pulmonary disease (COPD). Recently, SIRT1 has been detected in the serum and is increased in the asthmatic patients. <b>Aims and objectives.</b> To determine serum SIRT1 levels in the patients with COPD as a potential disease biomarker. <b>Methods.</b> Serum SIRT1 was measured by Western blotting, and relative ratio of band density in samples against that of positive control were calculated. <b>Results.</b> Several SIRT1 bands with differing molecular weights, including a 75kDa truncated form and 120kDa (actual size) were observed by Western blotting. The 120kDa serum SIRT1 was significantly decreased in the patients with COPD compared to the subjects without COPD (SIRT1 ratio in healthy: 0.90±0.34, vs COPD: 0.68±0.24; p=0.014), and positively correlated with the lung function (FEV₁/FVC; r=0.31; p=0.020) and severity of airflow obstruction represented by FEV₁ % predicted (r=0.29; p=0.029). The 120kDa serum SIRT1 also showed; 1) positive correlation with BMI (r=0.36; p=0.0078) and diffusing capacity of the lung per unit volume (KCO%; r=0.32; p=0.025); 2) the tendency to decrease in the presence of lung emphysematous change (without emphysema: 0.92±0.37 <i>vs</i> with emphysema: 0.71±0.24; p=0.026) and clinical history of frequent COPD exacerbations (infrequent: 0.76±0.20 <i>vs</i> frequent: 0.56±0.26; p=0.027). No reduction was seen in 75KDa SIRT1. <b>Conclusions.</b> Serum SIRT1 was decreased in the patients with COPD, and might be a potential biomarkers of COPD and particularly accelerated ageing.