title: Regional distribution and metabolic effect of PCSK9 insLEU and R46L gene mutations and apoE genotype.
abstract: BACKGROUND
  Natural loss-of-function mutations in the proprotein convertase subtilisin/kexin type-9 gene (PCSK9) are associated with lower cholesterol and cardiovascular risk. Because a founder effect exists in French Canadians for many lipid-related genes, we sought to investigate PCSK9 mutations and associated variables in this population. We also investigated the combined effect of PCSK9 mutations and the apolipoprotein E (apoE) polymorphism on metabolic variables.
  
  
  METHODS
  Gene sequencing and screening was carried out in 1745 healthy individuals ages 9, 13, and 16 years from a provincially representative population sample. In parallel, we measured related metabolic markers and used appropriate statistical methods.
  
  
  RESULTS
  We report herein that the carrier rates of the R46L single-nucleotide polymorphism were higher in the French Canadian population (4.8%) than previously seen in Caucasian individuals (2.4%). This is second to the most common variant, insertion of leucine, at a carrier rate of 24%, making it the most common PCSK9 loss-of-function mutation in French Canadian individuals. In R46L carriers, the contribution of the apoE genotype better explains the cholesterol phenotype than the R46L mutation alone. Patients, with both the R46L and apoE3/E2 genotype also showed a tendency toward insulin resistance as indicated by a 2-fold increase in insulin, homeostasis model assessment of insulin resistance, and leptin concentrations, compared with those without apoE3/E2.
  
  
  CONCLUSIONS
  R46L and insertion of leucine mutations were more frequent in French Canadian individuals and showed a specific geographic distribution. This might represent a gene selection to overcome clustering genes harbouring familial hypercholesterolemia and might suggest a founder effect. Subjects with the apoE3/E2 genotype and R46L have increased plasma insulin, homeostasis model assessment of insulin resistance, and leptin, an intriguing finding that warrants further investigation.
authors.affiliation: Institut de Recherches Cliniques (IRCM), Montréal, Québec, Canada.
authors.forename: Zuhier
authors.initials: Z
authors.lastname: Awan
authors.forename: Edgard E
authors.initials: EE
authors.lastname: Delvin
authors.forename: Emile
authors.initials: E
authors.lastname: Levy
authors.forename: Jacques
authors.initials: J
authors.lastname: Genest
authors.forename: Jean
authors.initials: J
authors.lastname: Davignon
authors.forename: Nabil G
authors.initials: NG
authors.lastname: Seidah
authors.forename: Alexis
authors.initials: A
authors.lastname: Baass
mesh_terms: D000293:Adolescent; D001057:Apolipoproteins E / Q000235:genetics*; D002170:Canada; D002648:Child; D005260:Female; D005602:France; D005838:Genotype; D006801:Humans; D007328:Insulin / Q000097:blood*; D007333:Insulin Resistance / Q000235:genetics*; D020738:Leptin / Q000097:blood*; D008055:Lipids / Q000097:blood* / Q000235:genetics; D008297:Male; D009154:Mutation; D010641:Phenotype; D011110:Polymorphism, Genetic; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases / Q000235:genetics*; D012307:Risk Factors; D017422:Sequence Analysis, DNA; D012697:Serine Endopeptidases / Q000235:genetics*
chemical_list: D001057:Apolipoproteins E; D007328:Insulin; D020738:Leptin; D008055:Lipids; C472125:PCSK9 protein, human; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D012697:Serine Endopeptidases