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Background: Cathepsin B (CTSB) and cystatin C (CYSC) are new biomarkers for several physiological and pathological processes as their activities increase with age. The aim of this study was to explore population-level associations between serum CTSB and CYSC with an age-related pulmonary subclinical state., Methods: We examined 401 healthy participants (aged 36-87 years, of which 44.3% were male) in northern Chinese cities. We used a standard spirometer to determine lung function. Serum CTSB and CYSC levels were measured by enzyme-linked immunosorbent assay (ELISA)., Results: For all participants, serum CTSB was related to maximum vital capacity (VC MAX), forced vital capacity (FVC), forced expiratory volume in 1 s, peak expiratory flow, forced expiratory flow at 25% of FVC, forced expiratory volume in 3 s (FEV3), and inspiratory vital capacity (VC IN). These associations were lost after full adjustment. CYSC remained significantly associated with inspiratory capacity (IC), breath frequency (BF; p  < 0.001), minute ventilation (MV), the ratio of FEV3 and FVC (FEV3%FVC), and expiratory reserve volume ( p  < 0.05) after adjusting for all other possible confounders. In males, serum CYSC levels exhibited significant and independent associations with FVC, FEV3 ( p  < 0.05), and IC ( p  < 0.001) and serum CTSB levels exhibited significant and independent associations with BF ( p  < 0.05)., Conclusions: Our results confirmed serum CYSC concentration associations with an age-related lung function in healthy people. However, the association between serum CTSB and lung function was not well confirmed. Serum measurements of CYSC may provide valuable predictors of pulmonary function in healthy people, especially healthy elderly adults. The reviews of this paper are available via the supplemental material section .

Context: Cathepsin B (CTSB) is an important enzyme for many physiological and pathological processes, and its activity increases with age. Here, we explored the association between serum CTSB and aging-related subclinical cardiovascular and renal status in a healthy Chinese population., Methods: The study included 369 healthy individuals aged 36-87 years. Cardiovascular structure and function were assessed by the left ventricular ejection fraction, the early-diastolic peak flow velocity to late-diastolic peak flow velocity ratio at the mitral leaflet tips, carotid intima-media thickness (IMT), the diameter of the bilateral common carotid artery (D), and blood systolic peak (SPV) and end diastolic velocities, which were measured by M-mode ultrasonography. Serum CTSB, insulin-like growth factor-1 (IGF-1), 1, 25-dihydroxy vitamin D3, and parathyroid hormone (PTH) were measured by enzyme-linked immunosorbent assay., Results: In men, serum CTSB was significantly related to IMT and IMT/D in the unadjusted model, and these associations were lost after age adjustment. In women, serum CTSB remained significantly associated with serum creatinine (SCr) (p=0.009), estimated glomerular filtration rate (p=0.048) and IMT/D (p=0.017) following full adjustment. PTH was independently associated with SCr. IGF-1 was significantly associated with SPV in women. CTSB was correlated with metabolic and endocrine biomarkers., Conclusion: Serum CTSB was associated with aging-related cardiovascular-renal parameters even in healthy people. Measurement of serum CTSB alone or in combination with metabolic and endocrine biomarkers can provide valuable information for predicting cardiovascular-renal function in healthy people, especially in elderly women., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)