title: Influence of Fasting Status and Sample Preparation on Metabolic Biomarker Measurements in Postmenopausal Women.
abstract: BACKGROUND
  Epidemiologic data linking metabolic markers-such as insulin, insulin-like growth factors (IGFs)-and adipose tissue-derived factors with cancer are inconsistent. Between-study differences in blood collection protocols, in particular participant's fasting status, may influence measurements.
  
  
  METHODS
  We investigated the impact of fasting status and blood sample processing time on components of the insulin/IGF axis and in adipokines in a controlled feeding study of 45 healthy postmenopausal-women aged 50-75 years. Fasting blood samples were drawn (T0), after which subjects ate a standardized breakfast; subsequent blood draws were made at 1 hour (T1), 3 hours (T3), and 6 hours (T6) after breakfast. Serum samples were assayed for insulin, C-peptide, total- and free-IGF-I, IGF-binding protein [BP]-1 and -3, total and high molecular weight (HMW)-adiponectin, retinol binding protein-4, plasminogen activator inhibitor (PAI)-1, and resistin.
  
  
  RESULTS
  Insulin and C-peptide levels followed similar postprandial trajectories; intra-class correlation coefficients [ICC] for insulin = 0.75, (95%CI:0.64-0.97) and C-peptide (ICC = 0.66, 95%CI:0.54-0.77) were similarly correlated in fasting (Spearman correlation, r = 0.78, 95%CI:0.64-0.88) and postprandial states (T1, r = 0.77 (95%CI: 0.62-0.87); T3,r = 0.78 (95%CI: 0.63-0.87); T6,r = 0.77 (95%CI: 0.61-0.87)). Free-IGF-I and IGFBP-1 levels were also affected by fasting status, whereas total-IGF-I and IGFBP-3 levels remained unchanged. Levels of adipokines were largely insensitive to fasting status and blood sample processing delays.
  
  
  CONCLUSIONS
  Several components of the insulin/IGF axis were significantly impacted by fasting state and in particular, C-peptide levels were substantially altered postprandially and in a similar manner to insulin.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, London, United Kingdom.|International Agency for Research on Cancer, Lyon, France.
authors.forename: Neil
authors.initials: N
authors.lastname: Murphy
authors.affiliation: Division of Cancer Epidemiology and Genetics, Hormonal and Reproductive Epidemiology Branch, National Cancer Institute, Bethesda, Maryland, United States of America.
authors.forename: Roni T
authors.initials: RT
authors.lastname: Falk
authors.affiliation: The Rockefeller University Hospital, New York, New York, United States of America.
authors.forename: Diana B
authors.initials: DB
authors.lastname: Messinger
authors.affiliation: Department of Oncology, McGill University, Montreal, Quebec, Canada.
authors.forename: Michael
authors.initials: M
authors.lastname: Pollak
authors.affiliation: Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America.
authors.forename: Xiaonan
authors.initials: X
authors.lastname: Xue
authors.affiliation: Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America.
authors.forename: Juan
authors.initials: J
authors.lastname: Lin
authors.affiliation: Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America.
authors.forename: Robin
authors.initials: R
authors.lastname: Sgueglia
authors.affiliation: Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America.
authors.forename: Howard D
authors.initials: HD
authors.lastname: Strickler
authors.affiliation: Epidemiology Research Program, American Cancer Society, Atlanta, Georgia, United States of America.
authors.forename: Mia M
authors.initials: MM
authors.lastname: Gaudet
authors.affiliation: International Agency for Research on Cancer, Lyon, France.
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Gunter
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000378:metabolism*; D005215:Fasting; D005260:Female; D006801:Humans; D008660:Metabolism; D008875:Middle Aged; D017698:Postmenopause
chemical_list: D015415:Biomarkers