title: The inflammatory biomarker YKL-40 decreases stepwise after exercise stress test.
abstract: Serum YKL-40 is an inflammatory biomarker associated with disease activity and mortality in diseases characterized by inflammation such as coronary artery disease (CAD). Exercise has a positive effect on CAD, possibly mediated by a decreased inflammatory activity. This study aimed to compare serial measurements of serum YKL-40 before and after exercise in patients with stable CAD versus controls.
  
  
  
  Eleven patients with stable CAD verified by coronary angiography (>70% stenosis) and 11 patients with a computer tomography angiography with no stenosis or calcification (calcium score=0) (controls) performed a standard clinical maximal exercise test. Serum YKL-40 was measured before exercise, immediately after exercise, and every hour for 6 h.
  
  
  
  Cardiovascular risk factors were more prevalent among the CAD patients compared with the controls. CAD patients had higher serum concentration of YKL-40 at baseline compared with controls, median (interquartile range) 94 (52-151) versus 57 (45-79) μg/l. Serum YKL-40 decreased stepwise after exercise, with a median decrease of 16 (13-39) μg/l for the CAD patients and 13 (10-22) μg/l for the controls from baseline to the lowest value. Thereafter, values increased again toward baseline level. Time after exercise was a significant factor for decrease in serum YKL-40 (P<0.0001), but no difference in YKL-40 decrease over time could be demonstrated between the groups (P=0.12).
  
  
  
  Serum YKL-40 is elevated in patients with documented CAD compared with controls, and it decreases stepwise after exercise in both groups, indicating an anti-inflammatory effect of exercise independent of the presence of coronary atherosclerosis.
authors.affiliation: Department of Cardiology, Copenhagen University Hospital Rigshospitalet.
authors.forename: Naja Dam
authors.initials: ND
authors.lastname: Mygind
authors.affiliation: Department of Cardiology, Copenhagen University Hospital Rigshospitalet; Department of Cardiology, Copenhagen University Hospital Hillerød; Departments of Cardiology.
authors.forename: Anna
authors.initials: A
authors.lastname: Axelsson
authors.affiliation: Department of Cardiology, Copenhagen University Hospital Bispebjerg, Copenhagen, Denmark.
authors.forename: Martin H
authors.initials: MH
authors.lastname: Ruwald
authors.affiliation: Departments of Cardiology.
authors.forename: Morten
authors.initials: M
authors.lastname: Dalsgaard
authors.affiliation: Department of Cardiology, Copenhagen University Hospital Hillerød.
authors.forename: Rolf
authors.initials: R
authors.lastname: Steffensen
authors.affiliation: Departments of Cardiology.
authors.forename: Kasper
authors.initials: K
authors.lastname: Iversen
authors.affiliation: Medicine and Oncology, Copenhagen University Hospital Herlev.
authors.forename: Julia S
authors.initials: JS
authors.lastname: Johansen
authors.affiliation: Department of Cardiology, Copenhagen University Hospital Rigshospitalet.
authors.forename: Jens
authors.initials: J
authors.lastname: Kastrup
keywords: biomarkers; coronary artery disease; exercise test; inflammation; serum YKL-40; stable angina pectoris