title: Cellular phospholipid and cholesterol efflux in high-density lipoprotein deficiency.
abstract: BACKGROUND
  Prospective studies have examined the relationship between coronary artery disease and low plasma levels of high-density lipoprotein cholesterol (HDL-C).
  
  
  RESULTS
  We investigated the causes of hypoalphalipoproteinemia (HypoA; HDL-C <5th percentile) in 64 subjects (12 women and 52 men). Apolipoprotein AI-mediated cellular cholesterol and phospholipid efflux were measured in fibroblasts from HypoA subjects, 9 controls, 2 patients with Tangier disease, and 5 patients with hyperalphalipoproteinemia. A phospholipid efflux defect was defined as <70% of controls. Mean HDL-C was 0.49+/-0.21 mmol/L. Cholesterol and phospholipid efflux correlated strongly (r=0.72, P<0.001). Phospholipid efflux and HDL-C (r=0.64, P<0.001) correlated in HypoA subjects. However, phospholipid or cholesterol efflux was no longer a determinant of HDL-C levels at higher levels (> approximately 1.0 mmol/L) of HDL-C. In HypoA subjects, 4 cases of Tangier disease and 6 of familial HDL deficiency (heterozygous Tangier disease) were identified (10 of 64; 16%). In the remaining 54 subjects, mean lipid efflux was not significantly different from controls and subjects with hyperalphalipoproteinemia. A phospholipid efflux defect was identified in 7 additional HypoA subjects, and a cholesterol efflux defect was detected in 11 subjects. In 2 of these subjects, the ABCA1 gene was ruled out as the cause of the efflux defect, while in 3, the low HDL-C trait segregated with the ABCA1 gene locus.
  
  
  CONCLUSIONS
  Lipidation of lipid-poor apolipoprotein AI may not be a major determinant of cholesterol accumulation within more mature HDL particles and increasing cholesterol or phospholipid efflux beyond normal levels may not lead to increase in plasma HDL-C levels. ABCA1 is essential in the initial steps of HDL formation but other plasma events are major modulators of HDL-C levels.
authors.affiliation: Department of Cardiovascular Genetics, McGill University Health Centre, Montréal, Canada.
authors.forename: Michel
authors.initials: M
authors.lastname: Marcil
authors.forename: Rachel
authors.initials: R
authors.lastname: Bissonnette
authors.forename: Jérôme
authors.initials: J
authors.lastname: Vincent
authors.forename: Larbi
authors.initials: L
authors.lastname: Krimbou
authors.forename: Jacques
authors.initials: J
authors.lastname: Genest
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000328:Adult; D001692:Biological Transport; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D008076:Cholesterol, HDL / Q000172:deficiency*; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010743:Phospholipids / Q000378:metabolism*; D013631:Tangier Disease / Q000097:blood / Q000235:genetics / Q000378:metabolism*
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D008076:Cholesterol, HDL; D010743:Phospholipids; D002784:Cholesterol