title: Serum apolipoprotein A-1 quantification by LC-MS with a SILAC internal standard reveals reduced levels in smokers.
abstract: BACKGROUND
  Absolute quantification of protein biomarkers such as serum apolipoprotein A1 by both immunoassays and LC-MS can provide misleading results.
  
  
  RESULTS
  Recombinant ApoA-1 internal standard was prepared using stable isotope labeling by amino acids in cell culture with [(13)C6(15)N2]-lysine and [(13)C9(15)N1]-tyrosine in human cells. A stable isotope dilution LC-MS method for serum ApoA-1 was validated and levels analyzed for 50 nonsmokers and 50 smokers.
  
  
  CONCLUSIONS
  The concentration of ApoA-1 in nonsmokers was 169.4 mg/dl with an 18.4% reduction to 138.2 mg/dl in smokers. The validated assay will have clinical utility for assessing effects of smoking cessation and therapeutic or dietary interventions in high-risk populations.
authors.affiliation: Center of Excellence in Environmental Toxicology & Penn SRP Center, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, USA.|Department of Systems Pharmacology & Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, USA.|Department of Pharmacology & Toxicology, Beijing Institute of Radiation Medicine, Beijing, 100850, China.
authors.forename: Qingqing
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Center of Excellence in Environmental Toxicology & Penn SRP Center, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, USA.|Department of Systems Pharmacology & Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, USA.
authors.forename: Suhong
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Center of Excellence in Environmental Toxicology & Penn SRP Center, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, USA.|Department of Systems Pharmacology & Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, USA.
authors.forename: Lili
authors.initials: L
authors.lastname: Guo
authors.affiliation: Center of Excellence in Environmental Toxicology & Penn SRP Center, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, USA.|Department of Systems Pharmacology & Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, USA.
authors.forename: Christine M
authors.initials: CM
authors.lastname: Busch
authors.affiliation: Janssen Research & Development, Johnson & Johnson, 1400 McKean Road, Spring House, PA 19477, USA.
authors.forename: Wenying
authors.initials: W
authors.lastname: Jian
authors.affiliation: Janssen Research & Development, Johnson & Johnson, 1400 McKean Road, Spring House, PA 19477, USA.
authors.forename: Naidong
authors.initials: N
authors.lastname: Weng
authors.affiliation: Center of Excellence in Environmental Toxicology & Penn SRP Center, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, USA.|Department of Systems Pharmacology & Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, USA.|AJ Drexel Autism Institute, Drexel University, Philadelphia, PA 19104, USA.
authors.forename: Nathaniel W
authors.initials: NW
authors.lastname: Snyder
authors.affiliation: Center of Excellence in Environmental Toxicology & Penn SRP Center, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, USA.|Department of Systems Pharmacology & Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, USA.|Metabolomics Facility, Centre for Cellular & Molecular Platforms, GKVK, Bellary Road, Bangalore 560065, India.
authors.forename: Kannan
authors.initials: K
authors.lastname: Rangiah
authors.affiliation: Center of Excellence in Environmental Toxicology & Penn SRP Center, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, USA.|Department of Systems Pharmacology & Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, USA.
authors.forename: Clementina
authors.initials: C
authors.lastname: Mesaros
authors.affiliation: Center of Excellence in Environmental Toxicology & Penn SRP Center, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, USA.|Department of Systems Pharmacology & Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA 19104, USA.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Blair
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000595:Amino Acid Sequence; D016632:Apolipoprotein A-I / Q000097:blood*; D016022:Case-Control Studies; D002853:Chromatography, Liquid / Q000379:methods*; D005260:Female; D006801:Humans; D007118:Immunoassay; D007553:Isotope Labeling / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D012907:Smoking / Q000503:physiopathology*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: C505693:APOA1 protein, human; D016632:Apolipoprotein A-I