title: Methodological considerations to determine the effect of exercise on brain-derived neurotrophic factor levels.
abstract: OBJECTIVE
  Physical exercise up-regulates brain-derived neurotrophic factor (BDNF) in the brain and blood. However, there is yet no consensus about the adequate blood processing conditions to standardize its assessment. We aimed to find a reliable blood sample processing method to determine changes in BDNF due to exercise.
  
  
  METHODS
  Twelve healthy university students performed an incremental cycling test to exhaustion. At baseline, immediately after exercise, and 30 and 60 min of recovery, venous blood was drawn and processed under different conditions, i.e. whole blood, serum coagulated for 10 min and 24 h, total plasma, and platelet-free plasma. BDNF concentration was measured by ELISA.
  
  
  RESULTS
  Exercise increased BDNF in whole blood and in serum coagulated for 24 h when corrected by hemoconcentration. We did not find effects of exercise on BDNF in serum coagulated for 10 min or in plasma samples. Plasma shows heterogeneous BDNF values in response to exercise that are not prevented when platelets are eliminated while homogeneous BDNF levels were found in whole blood or serum coagulated for 24 hour samples.
  
  
  CONCLUSIONS
  In exercise studies, BDNF levels should be adjusted by hemoconcentration. Our data highlight the importance of blood sample selection since the differences between each one affect significantly the BDNF factor changes due to exercise.
authors.affiliation: Department of Physiology, School of Medicine, University of Valencia, INCLIVA, Valencia, Spain. Electronic address: helios.pareja@gmail.com.
authors.forename: Helios
authors.initials: H
authors.lastname: Pareja-Galeano
authors.affiliation: School of Medicine and Research Institute "Dr. Viña Giner", Molecular and Mitochondrial Medicine, Catholic University of Valencia San Vicente Mártir, Valencia, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: Alis
authors.affiliation: Department of Physiology, School of Medicine, University of Valencia, INCLIVA, Valencia, Spain.
authors.forename: Fabian
authors.initials: F
authors.lastname: Sanchis-Gomar
authors.affiliation: Department of Physiology, School of Medicine, University of Valencia, INCLIVA, Valencia, Spain.
authors.forename: Helena
authors.initials: H
authors.lastname: Cabo
authors.affiliation: Hospital La Fe., Valencia, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Cortell-Ballester
authors.affiliation: Department of Physiology, School of Medicine, University of Valencia, INCLIVA, Valencia, Spain.
authors.forename: Mari Carmen
authors.initials: MC
authors.lastname: Gomez-Cabrera
authors.affiliation: European University, Madrid, Spain; Research Institute of Hospital 12 de Octubre ('i+12'), Madrid, Spain.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Lucia
authors.affiliation: Department of Physiology, School of Medicine, University of Valencia, INCLIVA, Valencia, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Viña
mesh_terms: D000328:Adult; D001800:Blood Specimen Collection / Q000379:methods*; D019208:Brain-Derived Neurotrophic Factor / Q000097:blood*; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D044967:Serum / Q000378:metabolism; D011795:Surveys and Questionnaires
chemical_list: D019208:Brain-Derived Neurotrophic Factor
keywords: Enzyme-linked immunosorbent assay; Hemoconcentration; Plasma; Serum; Whole blood