[Serum myostatin levels and malnutrition in patients with chronic obstructive pulmonary disease]

To investigate the prevalence and severity of malnutrition in patients with stable chronic obstructive pulmonary disease (COPD), analyze serum levels of myostatin, tumor necrosis factor alpha (TNFα) and C reactive protein (CRP), and investigate the relationship between serum myostatin and malnutrition in COPD.

Seventy-one patients with stable COPD and 60 age-matched healthy volunteers were recruited in this study. Pulmonary function was tested in all of the subjects and the severity of malnutrition was evaluated by a multiple-parameter malnutritional index (MNI). Based on the MNI scores, patients with COPD were divided into group I (MNI ≥ 5 score) and group II (MNI < 5 score), the former represents the patients with severe or very severe malnutrition while the latter represents the patients with mild or without malnutrition. Serum concentration of myostatin, TNFα and CRP were measured by enzyme-linked immunosorbent assay.

The MNI score was significantly elevated in patients with COPD [(7.75 ± 3.86) score] compared with the controls [(1.13 ± 0.96) score; P < 0.001], and 55 patients (77%) in COPD group I showed MNI ≥ 5 (9.30 ± 3.01) score. Serum myostatin concentration was significantly elevated in COPD group I [(12.18 ± 4.76) µg/L] than in COPD group II [(9.73 ± 2.85) µg/L] and controls [(7.93 ± 2.35) µg/L], with each P < 0.001. Serum TNFα concentration was also significantly elevated in patients with COPD compared with the controls (P < 0.001). Pearson correlation analysis showed that serum myostatin levels were significantly correlated with MNI scores (r = 0.438, P = 0.000) and TNFα levels (r = 0.234, P = 0.041) in COPD group (combined group I and II) while MNI scores were correlated inversely with BMI in COPD group (r = -0.530, P = 0.000). After stratified with subgroups, the correlation between myostatin levels and MNI scores was more significant and the correlation coefficient was higher (r = 0.464, P = 0.000) in COPD group I patients. Moreover, myostatin levels were inversely correlated with BMI (r = -0.287, P = 0.034) and forced expiratory volume in one second of the predicted value (r = -0.264, P = 0.049) in COPD group I patients.

Malnutrition commonly and substantially exists in patients with COPD; serum myostatin concentration is significantly elevated and is correlated with the severity of malnutrition in the patients. The elevation of serum myostatin may contribute to malnutrition in COPD patients.