title: Reduced expression of ATP-binding cassette transporter G1 increases cholesterol accumulation in macrophages of patients with type 2 diabetes mellitus.
abstract: BACKGROUND
  Patients with type 2 diabetes mellitus are at increased risk for the development of atherosclerosis. A pivotal event in the development of atherosclerosis is macrophage foam cell formation. The ATP-binding cassette (ABC) transporters ABCA1 and ABCG1 regulate macrophage cholesterol efflux and hence play a vital role in macrophage foam cell formation. We have previously found that chronic elevated glucose reduces ABCG1 expression. In the present study, we examined whether patients with type 2 diabetes mellitus had decreased ABCG1 and/or ABCA1, impaired cholesterol efflux, and increased macrophage foam cell formation.
  
  
  RESULTS
  Blood was collected from patients with and without type 2 diabetes mellitus. Peripheral blood monocytes were differentiated into macrophages, and cholesterol efflux assays, immunoblots, histological analysis, and intracellular cholesteryl ester measurements were performed. Macrophages from patients with type 2 diabetes mellitus had a 30% reduction in cholesterol efflux with a corresponding 60% increase in cholesterol accumulation relative to control subjects. ABCG1 was present in macrophages from control subjects but was undetectable in macrophages from patients with type 2 diabetes mellitus. In contrast, ABCA1 expression in macrophages was similar in both control subjects and patients with type 2 diabetes mellitus. Macrophage expression of ABCG1 in both patients and control subjects was induced by treatment with the liver X receptor agonist TO-901317. Upregulation of liver X receptor dramatically reduced foam cell formation in macrophages from patients with type 2 diabetes mellitus.
  
  
  CONCLUSIONS
  ABCG1 expression and cholesterol efflux are reduced in patients with type 2 diabetes mellitus. This impaired ABCG1-mediated cholesterol efflux significantly correlates with increased intracellular cholesterol accumulation. Strategies to upregulate ABCG1 expression and function in type 2 diabetes mellitus could have therapeutic potential for limiting the accelerated vascular disease observed in patients with type 2 diabetes mellitus.
authors.affiliation: Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Jeremy P
authors.initials: JP
authors.lastname: Mauldin
authors.forename: Melissa H
authors.initials: MH
authors.lastname: Nagelin
authors.forename: Allison J
authors.initials: AJ
authors.lastname: Wojcik
authors.forename: Suseela
authors.initials: S
authors.lastname: Srinivasan
authors.forename: Marcus D
authors.initials: MD
authors.lastname: Skaflen
authors.forename: Carlos R
authors.initials: CR
authors.lastname: Ayers
authors.forename: Coleen A
authors.initials: CA
authors.lastname: McNamara
authors.forename: Catherine C
authors.initials: CC
authors.lastname: Hedrick
mesh_terms: D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics* / Q000378:metabolism*; D050197:Atherosclerosis / Q000378:metabolism / Q000503:physiopathology; D002454:Cell Differentiation / Q000276:immunology; D002478:Cells, Cultured; D002788:Cholesterol Esters / Q000378:metabolism; D008076:Cholesterol, HDL / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism* / Q000503:physiopathology*; D003925:Diabetic Angiopathies / Q000378:metabolism / Q000503:physiopathology; D005260:Female; D015870:Gene Expression; D006801:Humans; D006845:Hydrocarbons, Fluorinated / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D005466:Fluorocarbons; D000096926:Benzenesulfonamides
chemical_list: D000070998:ATP Binding Cassette Transporter, Subfamily G, Member 1; D018528:ATP-Binding Cassette Transporters; D002788:Cholesterol Esters; D008076:Cholesterol, HDL; D006845:Hydrocarbons, Fluorinated; D013449:Sulfonamides; C419353:ABCG1 protein, human; C423915:T0901317; D005466:Fluorocarbons; D000096926:Benzenesulfonamides