In patients with chronic obstructive pulmonary disease (COPD), body composition and lung function are associated with levels of serum sclerostin (SOST), according to study findings published in the journal Pulmonology.
SOST is a secreted glycoprotein linked to bone metabolism that also blocks the wingless/integrated [Wnt] pathway — a pathway that appears to be pathologically activated in COPD. SOST may play an important role in muscle-bone crosstalk via regulation of muscle mass and lung function and may also be involved in modification of body composition. Recognizing these features of SOST, the researchers sought to analyze the relationships between blood SOST and body composition, bone metabolism, pulmonary function, and clinical parameters in a well-characterized cohort of patients with COPD.
The researchers conducted an observational, prospective study in a hospital COPD outpatient clinic in Spain between November 2017 and October 2018. All study participants were adults at least 40 years of age with COPD (as defined by Global Initiative for Chronic Obstructive Lung Disease [GOLD] guidelines) who were consecutively recruited during their routine visits to the COPD outpatient clinic. Trained staff recorded participants’ clinical information and performed lung function tests. All participants underwent spirometry, measurement of diffusing capacity of the lung for carbon monoxide (DLCO), and 6-minute walking distance (6MWD) tests. Body composition was measured with use of a bioelectrical impedance device.
A total of 139 individuals with COPD were ultimately included in the current study. A majority of the participants were men (70.5%); the mean patient age was 65.0±8.4 years. A high prevalence of current smoking (41.7%) was reported in the study cohort. Most of the participants had moderate obstruction, along with a moderate decrease in DLCO levels. All of the participants were followed prospectively for 12 months after enrollment. During follow-up, moderate disease exacerbations and hospital admissions were recorded.
Results of the study showed that serum SOST levels were 23.98±7.6 pmol/L (men: 25.5±7.7 pmol/L; women: 20.3±5.9 pmol/L; P <.001). SOST demonstrated correlations with age (r=0.36), fat-free mass index (FFMI; r=0.38), forced expiratory volume in 1 second (r=0.27), DLCO (r=0.39), 6MWD (r=0.19), and COPD Assessment Test score (r = –0.24). Per multivariate linear regression analysis, only age (β=0.264) and FFMI (β=1.241) remained significant. SOST demonstrated a significant negative correlation with serum phosphorus levels (r = –0.29).
Based on Cox proportional risk analysis, patients in the lower tertile of SOST levels were at a significantly higher risk for moderate COPD exacerbation (hazard ratio [HR], 2.015; 95% CI, 1.136-3.577; P =.017) and hospitalization due to COPD (HR, 5.142; 95% CI, 1.380-19.158; P =.015) compared with the remainder of the patients.
Limitations of the study include its single-center design, the high rate of hypovitaminosis D in current study participants, and the inability to show causality.
The investigators concluded that “SOST levels are associated with body composition and lung function in patients with COPD. Furthermore, lower SOST levels predict a higher risk of exacerbations and hospitalization.” The investigators noted that further studies are needed to explore the potential therapeutic application of these findings.
Amado CA, García-Unzueta M, Agüero J, et al. Associations of serum sclerostin levels with body composition, pulmonary function, and exacerbations in COPD patients. Pulmonology. Published online August 10, 2022. doi:10.1016/j.pulmoe.2022.06.003