title: Quantification of HDL particle concentration by calibrated ion mobility analysis.
abstract: BACKGROUND
  It is critical to develop new metrics to determine whether HDL is cardioprotective in humans. One promising approach is HDL particle concentration (HDL-P), the size and concentration of HDL in plasma. However, the 2 methods currently used to determine HDL-P yield concentrations that differ >5-fold. We therefore developed and validated an improved approach to quantify HDL-P, termed calibrated ion mobility analysis (calibrated IMA).
  
  
  METHODS
  HDL was isolated from plasma by ultracentrifugation, introduced into the gas phase with electrospray ionization, separated by size, and quantified by particle counting. We used a calibration curve constructed with purified proteins to correct for the ionization efficiency of HDL particles.
  
  
  RESULTS
  The concentrations of gold nanoparticles and reconstituted HDLs measured by calibrated IMA were indistinguishable from concentrations determined by orthogonal methods. In plasma of control (n = 40) and cerebrovascular disease (n = 40) participants, 3 subspecies of HDL were reproducibility measured, with an estimated total HDL-P of 13.4 (2.4) μmol/L. HDL-C accounted for 48% of the variance in HDL-P. HDL-P was significantly lower in participants with cerebrovascular disease (P = 0.002), and this difference remained significant after adjustment for HDL cholesterol concentrations (P = 0.02).
  
  
  CONCLUSIONS
  Calibrated IMA accurately determined the concentration of gold nanoparticles and synthetic HDL, strongly suggesting that the method could accurately quantify HDL particle concentration. The estimated stoichiometry of apolipoprotein A-I determined by calibrated IMA was 3-4 per HDL particle, in agreement with current structural models. Furthermore, HDL-P was associated with cardiovascular disease status in a clinical population independently of HDL cholesterol.
authors.affiliation: Department of Medicine, University of Washington, Seattle, WA;
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Hutchins
authors.affiliation: Department of Medicine, University of Washington, Seattle, WA;
authors.forename: Graziella E
authors.initials: GE
authors.lastname: Ronsein
authors.affiliation: Department of Medicine, University of Washington, Seattle, WA;
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Monette
authors.affiliation: Department of Medicine, University of Washington, Seattle, WA;
authors.forename: Nathalie
authors.initials: N
authors.lastname: Pamir
authors.affiliation: Department of Medicine, University of Washington, Seattle, WA;
authors.forename: Jake
authors.initials: J
authors.lastname: Wimberger
authors.affiliation: Department of Medicine, University of Washington, Seattle, WA;
authors.forename: Yi
authors.initials: Y
authors.lastname: He
authors.affiliation: Atherosclerosis Unit, University of Alabama Medical Center, Birmingham, AL.
authors.forename: G M
authors.initials: GM
authors.lastname: Anantharamaiah
authors.affiliation: Department of Medicine, University of Washington, Seattle, WA;
authors.forename: Daniel Seung
authors.initials: DS
authors.lastname: Kim
authors.affiliation: Department of Medicine, University of Washington, Seattle, WA;
authors.forename: Jane E
authors.initials: JE
authors.lastname: Ranchalis
authors.affiliation: Department of Medicine, University of Washington, Seattle, WA;
authors.forename: Gail P
authors.initials: GP
authors.lastname: Jarvik
authors.affiliation: Department of Medicine, University of Washington, Seattle, WA;
authors.forename: Tomas
authors.initials: T
authors.lastname: Vaisar
authors.affiliation: Department of Medicine, University of Washington, Seattle, WA; heinecke@u.washington.edu.
authors.forename: Jay W
authors.initials: JW
authors.lastname: Heinecke
mesh_terms: D000367:Age Factors; D016632:Apolipoprotein A-I / Q000097:blood* / Q000302:isolation & purification; D002561:Cerebrovascular Disorders / Q000097:blood; D008076:Cholesterol, HDL / Q000097:blood* / Q000302:isolation & purification; D005260:Female; D006046:Gold / Q000737:chemistry; D006801:Humans; D007477:Ions / Q000737:chemistry; D008075:Lipoproteins, HDL / Q000097:blood* / Q000302:isolation & purification; D008297:Male; D053768:Metal Nanoparticles / Q000737:chemistry; D010316:Particle Size; D015203:Reproducibility of Results; D012737:Sex Factors; D014461:Ultracentrifugation
chemical_list: D016632:Apolipoprotein A-I; D008076:Cholesterol, HDL; D007477:Ions; D008075:Lipoproteins, HDL; D006046:Gold