Gender and skeletal muscle characteristics in subjects with chronic obstructive pulmonary disease.

BACKGROUND: The influence of gender in the clinical expression of COPD has received important attention. Limited information exists regarding gender differences in the skeletal muscle characteristics in COPD subjects. The present study was aimed to determine the differences in the skeletal muscle characteristics in men and women with and without COPD. METHODS: For comparison we studied 24 female (61 ± 9 years) and 30 male (65 ± 8 years) COPD patients with similar disease severity. In addition healthy subjects, 17 women (58 ± 8 years), and 9 men (57 ± 8 years) were studied. Pulmonary function, health status, six minute walk distance test (6MWD) and vastus lateralis muscle biopsy were assessed. Fiber type proportion, fiber type cross sectional area (CSA), capillary counts, and activity of citrate synthase (CS), 3-hydroxyacyl-CoA-dehydrogenase (HAD) and lactate-dehydrogenase (LDH) were determined. RESULTS: Pulmonary function, health status and 6MWD were similar in male and female COPD patients. Fiber type distribution was similar between women (I = 42 ± 9%, IIA = 39 ± 13%, IIX = 19 ± 7%) and men (I = 39 ± 13%, IIA = 38 ± 9%, IIX = 29 ± 10%) with COPD, as well as CSA, capillarity and enzymes (CS 8.59 ± 1.6 vs.9.74 ± 2.6, HAD 9.03 ± 1.9 vs. 9.84 ± 2.5, LDH 124 ± 48 vs. 151 ± 68 µmol min(-1) g(-1)). In normal subjects a decrease in type IIX fibers CSA was found in women compared with men (3703 ± 1478 vs. 5426 ± 1386 µm(2), respectively). CONCLUSIONS: Female and male with COPD have similar skeletal muscle characteristics; it is possible that the disease blurs the gender differences. On the other hand, there seems to be fewer differences in muscle characteristics between older men and women, perhaps due to lower male testosterone levels and physical inactivity.

Peripheral muscle composition and health status in patients with COPD.

STUDY OBJECTIVE: The present study evaluated the relationship between health status (HS) and peripheral muscle histochemical characteristics in chronic obstructive pulmonary disease (COPD), and identified selected independent respiratory and extrapulmonary variables that predicted the HS of these patients. DESIGN: Cross-sectional study. SETTING: Outpatient respiratory clinic of a university hospital. PATIENTS AND METHODS: We studied 29 patients (63+/-10 yrs) with a forced expiratory volume in 1s (FEV1) of 39+/-12%. All patients underwent vastus lateralis muscle biopsies for histochemical analysis. They also had spirometry, arterial blood gas analysis, body mass index (BMI), dyspnea determined with the MMRC scale and responded to the St. George's Respiratory Questionnaire (SGRQ) for HS assessment. RESULTS: SGRQ total score correlated with fiber type distribution. A stepwise multiple regression identified three independent predictors of SGRQ total score: type I fiber proportion, BMI, and FEV1; r = 0.78 and r2 = 0.61. CONCLUSIONS: These results indicate that impaired HS in COPD is related to the peripheral muscle changes characterized by less type I fibers proportion. The findings argue in favor of an important contribution of the systemic consequences on the HS in COPD independently from the airflow limitation severity, and help to explain the observation of the poor correlation between the degree of airflow limitation and SGRQ total score.