title: The lipoprotein lipase gene in combined hyperlipidemia: evidence of a protective allele depletion.
abstract: BACKGROUND
  Lipoprotein Lipase (LPL), a key enzyme in lipid metabolism, catalyzes the hydrolysis of triglycerides (TG) from TG-rich lipoproteins, and serves a bridging function that enhances the cellular uptake of lipoproteins. Abnormalities in LPL function are associated with pathophysiological conditions, including familial combined hyperlipidemia (FCH). Whereas two LPL susceptibility alleles were found to co-segregate in a few FCH kindred, a role for common, protective alleles remains unexplored. The LPL Ser447Stop (S447X) allele is associated with anti-atherogenic lipid profiles and a modest reduction in risk for coronary disease. We hypothesize that significant depletion of the 447X allele exists in combined hyperlipidemia cases versus controls. A case-control design was employed. The polymorphism was assessed by restriction assay in 212 cases and 161 controls. Genotypic, allelic, and phenotypic associations were examined.
  
  
  RESULTS
  We found evidence of significant allelic (447Xcontrol: 0.130 vs. 447Xcase: 0.031, chi2 = 29.085; 1df; p < 0.001) and genotypic association (SS: 0.745 vs. 0.939, and SX+XX: 0.255 vs. 0.061) in controls and cases, respectively (chi2 = 26.09; 1df; p < 0.001). In cases, depletion of the 447X allele is associated with a significant elevation in very-low-density lipoprotein cholesterol (VLDL-C, p = 0.045). Consonant with previous studies of this polymorphism, regression models predict that carriers of the 447X allele displayed significantly lower TG, low-density lipoprotein cholesterol (LDL-C) and TG/high-density lipoprotein cholesterol (HDL-C) ratio.
  
  
  CONCLUSIONS
  These findings suggest a role for the S447X polymorphism in combined hyperlipidemia and demonstrate the importance of evaluating both susceptibility and protective genetic risk factors.
authors.affiliation: College of Nursing, University of Arizona, Tucson, AZ, USA. shufen@nursing.arizona.edu
authors.forename: Shu-Fen
authors.initials: SF
authors.lastname: Wung
authors.forename: Medha V
authors.initials: MV
authors.lastname: Kulkarni
authors.forename: Clive R
authors.initials: CR
authors.lastname: Pullinger
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Malloy
authors.forename: John P
authors.initials: JP
authors.lastname: Kane
authors.forename: Bradley E
authors.initials: BE
authors.lastname: Aouizerat
mesh_terms: D000328:Adult; D000368:Aged; D000483:Alleles; D005260:Female; D017353:Gene Deletion; D006801:Humans; D006950:Hyperlipidemia, Familial Combined / Q000235:genetics*; D008071:Lipoprotein Lipase / Q000235:genetics*; D008074:Lipoproteins / Q000097:blood; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide
chemical_list: D008074:Lipoproteins; D008071:Lipoprotein Lipase