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This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: clinchem.2009.129759v1 55/12/2153    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Humphries, S. E. Articles by Neil, A. PubMed PubMed Citation Articles by Humphries, S. E. Articles by Neil, A.

Healthy Individuals Carrying the PCSK9 p.R46L Variant and Familial Hypercholesterolemia Patients Carrying PCSK9 p.D374Y Exhibit Lower Plasma Concentrations of PCSK9

¹ Centre for Cardiovascular Genetics, British Heart Foundation Laboratories, The Royal Free and University College London Medical School, London, UK; ² Department of Clinical Biochemistry, Royal Victoria Infirmary, Newcastle upon Tyne, UK; ³ Lilly Research Laboratories, Eli Lilly & Co., Indianapolis, IN; ⁴ Department of Medical Pathology, Federal University of Paraná, Paraná, Brazil; ⁵ Division of Public Health & Primary Health Care, University of Oxford, Oxford, UK.

^aAddress correspondence to this author at: Centre for Cardiovascular Genetics, British Heart Foundation Laboratories, The Rayne Building, Royal Free and University College London Medical School, London WC1E 6JJ, UK. Fax +44-020-7679-6212; e-mail rmhaseh{at}ucl.ac.uk.

Background: We measured plasma PCSK9 concentrations in healthy men with a PCSK9 (proprotein convertase subtilisin/kexin type 9) loss-of-function variant (p.R46L), in statin-treated patients with a clinical diagnosis of familial hypercholesterolemia (FH) and carrying a PCSK9 gain-of-function mutation (p.D374Y), and in statin-treated patients with FH due to different genetic causes.

Methods: PCSK9 was measured with a previously described ELISA.

Results: In 81 healthy middle-aged Caucasian men, the PCSK9 concentration was significantly associated with the concentrations of total cholesterol (r = 0.42; P < 0.0001), LDL cholesterol (r = 0.34; P = 0.01), and triglycerides (r = 0.25; P = 0.02). In p.R46L carriers, mean (SD) concentrations of PCSK9 were 15% lower than in RR individuals [65.5 µg/L (21.6 µg/L) vs 77.5 µg/L (18.2 µg/L); P = 0.03]. In patients with the p.D374Y variant (n = 7), the mean PCSK9 concentration was significantly lower than in the combined group of patients with an LDLR (low density lipoprotein receptor) mutation (n = 25), an APOB [apolipoprotein B (including Ag(x) antigen)] variant encoding p.R3527Q (n = 6), or no detectable mutation (n = 14) [96.4 µg/L (42.5 µg/L) vs 151.6 µg/L (69.6 µg/L); P = 0.02]. Two of the 14 patients with no mutation had PCSK9 concentrations below the mean for p.D374Y carriers; sequencing of the PCSK9 gene and promoter revealed no mutations. Among 409 FH patients, we identified 6 carriers of the promoter variant –287G>A (1.5%), a frequency similar to that (1.0%) previously reported for 2772 healthy men in the UK. In neither group was the –287G>A variant associated with differences in lipid traits.

Conclusions: The loss-of-function p.R46L variant is associated with the expected lower concentrations of circulating PCSK9; the gain-of-function p.D374Y mutation is also associated with lower concentrations, presumably because of the higher affinity of this variant for the LDL receptor and its more rapid clearance. In treated FH patients, a low plasma PCSK9 concentration does not appear to be a useful screening tool for identifying novel PCSK9 mutations.