title: Circulating endothelial cells in children: role of fitness, activity, and adiposity.
abstract: OBJECTIVE
  Circulating endothelial cells (CEC) are thought to be useful biomarkers of endothelial dysfunction and overall cardiovascular health. The extent to which CEC are influenced by fitness, physical activity, and adiposity in youth remains unknown, as they have seldom been examined in the pediatric population. This study assessed resting levels of CEC in boys and girls of different chronological and biological age and explored the relationship between these cells and aerobic fitness, physical activity, and adiposity.
  
  
  METHODS
  Seventy-five children (39 males; median [interquartile range], age = 14.4 [5.8]) completed two study visits. During the first visit, basic anthropometric data were collected and biological age was calculated. Peak mechanical power (Wpeak) was determined using the McMaster All-Out Continuous cycling test. Participants then wore an accelerometer over a 7-d period to assess habitual levels of moderate-to-vigorous physical activity. During visit 2, percent body fat (%BF) was assessed by dual-energy x-ray absorptiometry. A fasted blood sample was also collected from which concentrations of CEC, identified as CD31CD34CD45CD133, were quantified by flow cytometry.
  
  
  RESULTS
  No differences were seen in CEC by sex, chronological age, or biological age. The median (interquartile range) CEC concentration was 32.3 × 10 (63.0 × 10), representing 1.3% (2.7%) of collected peripheral blood mononuclear cells. CEC concentration was associated with Wpeak normalized to lean body mass (r = 0.36, P < 0.01) and time spent in moderate-to-vigorous physical activity (r = -0.27, P = 0.02). No relationship was observed between CEC and %BF.
  
  
  CONCLUSIONS
  Healthy children demonstrate relatively low concentrations of CECs. Because CEC represent a population of mature endothelial cells shed from the intima after irreversible damage, they may be more reflective of recent physical activity levels rather than fitness or level of adiposity.
authors.affiliation: Child Health & Exercise Medicine Program, Department of Pediatrics, McMaster University, Hamilton, ON, CANADA.
authors.forename: Joyce
authors.initials: J
authors.lastname: Obeid
authors.forename: Thanh
authors.initials: T
authors.lastname: Nguyen
authors.forename: Rachel G
authors.initials: RG
authors.lastname: Walker
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Gillis
authors.forename: Brian W
authors.initials: BW
authors.lastname: Timmons
mesh_terms: D050154:Adiposity / Q000502:physiology*; D000293:Adolescent; D000367:Age Factors; D002452:Cell Count; D002648:Child; D042783:Endothelial Cells / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D010809:Physical Fitness / Q000502:physiology*; D012016:Reference Values; D012737:Sex Factors