The loss of muscle mass and changes in muscle composition are important factors for assessing skeletal muscle dysfunction. The cross-sectional area (CSA) of muscle is usually used to assess skeletal muscle function. However, the CSA of skeletal muscle can be difficult for clinicians to measure because a specific 3D image analysis system for computed tomography (CT) scans is needed. Therefore, we conducted a study to develop a new method of easily assessing physical activity, in which the thickness of the erector spinae muscles (ESM_T) was measured by CT, and to compare ESM_T to the CSA of the erector spinae muscles (ESM_CSA) in patients with nontuberculous mycobacteria (NTM) pulmonary infections who underwent surgery after some preoperative examinations, such as laboratory tests, chest CT scans, spirometry, and 6-minute walk tests (6MWT). We retrospectively studied adult patients with NTM pulmonary infections who underwent a lobectomy at Fukujuji Hospital from April 2010 to March 2016. We assessed the correlations between ESM_T and different variables, including ESM_CSA. Sixty-one patients with NTM pulmonary infections were included. The median ESM_T and ESM_CSA were 1371 mm² (IQR 1178–1784 mm²) and 28.5 mm (IQR 25.4–31.7 mm), respectively, and a very strong linear correlation was observed between ESM_T and ESM_CSA (R = 0.858, P < .001). ESM_T and ESM_CSA were positively associated with body weight (ESM_T: R = 0.540, P < .001, ESM_CSA: R = 0.714, P < .001), body mass index (ESM_T: R = 0.421, P < .001, ESM_CSA: R = 0.560, P < .001), the 6MWT value (ESM_T: R = 0.413, P = .040, ESM_CSA: R = 0.503, P = .010), vital capacity (ESM_T: R = 0.527, P < .001, ESM_CSA: R = 0.577, P < .001), and the forced expiratory volume in 1 second (ESM_T: R = 0.460, P < .001, ESM_CSA: R = 0.532, P < .001). We demonstrated that compared to ESM_CSA, ESM_T is easily measured by CT and can be a useful parameter for clinically evaluating physical activity. Furthermore, ESM_T and ESM_CSA were related to physical activity, as measured by the 6MWT and spirometry.

Peroxiredoxin (Prx) 2 in red blood cells (RBCs) reacts with various reactive oxygen species and changes to hyperoxidized Prx2 (Prx2-SO_2/3). Therefore, Prx2 may serve as an indicator of oxidative stress in vivo. This study aimed to analyze Prx2-SO_2/3 levels in clinical samples to examine whether the oxidation state of Prx2 in human RBCs reflects the pathological condition of oxidative stress diseases. We first focused on obstructive sleep apnea (OSA), a hypoxic stress-induced disease of the respiratory system, and investigated the levels of Prx2-SO_2/3 accumulated in the RBCs of OSA patients. In measurements on a small number of OSA patients and healthy subjects, levels of Prx2-SO_2/3 accumulation in patients with OSA were clearly increased compared to those in healthy subjects. Hence, we proceeded to validate these findings with more samples collected from patients with OSA. The results revealed significantly higher levels of erythrocytic Prx2-SO_2/3 in patients with OSA than in healthy subjects, as well as a positive correlation between the severity of OSA and Prx2-SO_2/3 levels in the RBCs. Moreover, we performed a chromatographic study to show the structural changes of Prx2 due to hyperoxidation. Our findings demonstrated that the Prx2-SO_2/3 molecules in RBCs from patients with OSA were considerably more hydrophilic than the reduced form of Prx2. These results implicate Prx2-SO_2/3 as a promising candidate biomarker for OSA.

Background: Oxidative stress plays an important role in the pathophysiology of bronchial asthma (BA), chronic obstructive pulmonary disease (COPD), and asthma–COPD overlap (ACO), but its relevance has not been fully elucidated. The aim of this study was to measure the levels of oxidative stress and investigate its clinical significance in patients with BA, COPD, or ACO. Methods: We recruited 214 patients between June 2020 and May 2023 (109 patients with BA, 63 with COPD, and 42 with ACO). To assess clinical conditions, we evaluated patient characteristics, results of respiratory function tests and blood tests, and administered several questionnaires. We evaluated oxidative stress using the test for derivatives–reactive oxygen metabolites (d–ROMs) in serum. Results: The d–ROMs levels were significantly higher in patients with COPD or ACO than in patients with BA. There was no difference in serum d–ROMs levels between the COPD and ACO groups. In BA, d–ROMs levels were positively correlated with interleukin (IL)-6, IL-8, serum amyloid A (SAA), and C-reactive protein (CRP) levels; white blood cell (WBC) and neutrophil counts; and St. George’s Respiratory Questionnaire (SGRQ) scores, and they were negatively correlated with forced expiratory volume in 1 s (%FEV₁) and asthma control test (ACT) score. In COPD, d–ROMs levels were positively correlated with IL-6, SAA, and CRP levels; WBC, neutrophil, and eosinophil counts; and COPD assessment test (CAT) and SGRQ scores, and they were negatively correlated with forced vital capacity (%FVC), %FEV₁, and %FEV₁/FVC scores. In ACO, d–ROMs levels were positively correlated with IL-6, SAA, tumor necrosis factor alpha (TNF-α), and CRP levels; and CAT and SGRQ scores, and they were negatively correlated with %FVC and %FEV₁ scores. Conclusions: Serum d–ROMs levels may serve as a marker reflecting clinical conditions such as systemic inflammation, symptom severity, and airflow limitation in patients with BA, COPD, and ACO.