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Articles by S. E Humphries
Total Records ( 4 ) for S. E Humphries
  A Taylor , G Bayly , K Patel , L Yarram , M Williams , J Hamilton Shield , S. E Humphries and G. Norbury
 

Autosomal dominant hypercholesterolaemia is genetically heterogeneous, but most commonly (~93%) caused by mutations in low-density lipoprotein receptor (LDLR), where the disease is known as familial hypercholesterolaemia (FH), or apolipoprotein B-100 (APOB) (~5.5%), where the disease is known as familial defective APOB (FDB), while in ~2% of patients the mutation is in the proprotein convertase subtilisin/kexin type 9 gene. Homozygous FH having inheritance of two LDLR mutations is a rare but recognized syndrome associated with an extreme hypercholesterolaemia and early-onset coronary artery disease. We present a 15-year-old girl with untreated total cholesterol levels of 8.8 mmol/L who was heterozygous for both the LDLR p.Leu479Pro and APOB p.Arg3527Gln mutation. Cascade testing confirmed the paternal origin of the LDLR mutation and revealed a maternal diagnosis of FDB. This case provides further evidence that the combined effect of an LDLR and an APOB mutation give rise to a phenotype more severe than either mutation alone and is more severe than homozygous FDB, but less severe than homozygous FH. It also highlights the need to consider the presence of additional mutations in families where relatives have varying phenotypes.

  R Sofat , A. D Hingorani , L Smeeth , S. E Humphries , P. J Talmud , J Cooper , T Shah , M. S Sandhu , S. L Ricketts , S. M Boekholdt , N Wareham , K. T Khaw , M Kumari , M Kivimaki , M Marmot , F. W Asselbergs , P van der Harst , R. P.F Dullaart , G Navis , D. J van Veldhuisen , W. H Van Gilst , J. F Thompson , P McCaskie , L. J Palmer , M Arca , F Quagliarini , C Gaudio , F Cambien , V Nicaud , O Poirer , V Gudnason , A Isaacs , J. C.M Witteman , C. M van Duijn , M Pencina , R. S Vasan , R. B D'Agostino , J Ordovas , T. Y Li , S Kakko , H Kauma , M. J Savolainen , Y. A Kesaniemi , A Sandhofer , B Paulweber , J. V Sorli , A Goto , S Yokoyama , K Okumura , B. D Horne , C Packard , D Freeman , I Ford , N Sattar , V McCormack , D. A Lawlor , S Ebrahim , G. D Smith , J. J.P Kastelein , J Deanfield and J. P. Casas
 

Background— Cholesteryl ester transfer protein (CETP) inhibitors raise high-density lipoprotein (HDL) cholesterol, but torcetrapib, the first-in-class inhibitor tested in a large outcome trial, caused an unexpected blood pressure elevation and increased cardiovascular events. Whether the hypertensive effect resulted from CETP inhibition or an off-target action of torcetrapib has been debated. We hypothesized that common single-nucleotide polymorphisms in the CETP gene could help distinguish mechanism-based from off-target actions of CETP inhibitors to inform on the validity of CETP as a therapeutic target.

Methods and Results— We compared the effect of CETP single-nucleotide polymorphisms and torcetrapib treatment on lipid fractions, blood pressure, and electrolytes in up to 67 687 individuals from genetic studies and 17 911 from randomized trials. CETP single-nucleotide polymorphisms and torcetrapib treatment reduced CETP activity and had a directionally concordant effect on 8 lipid and lipoprotein traits (total, low-density lipoprotein, and HDL cholesterol; HDL2; HDL3; apolipoproteins A-I and B; and triglycerides), with the genetic effect on HDL cholesterol (0.13 mmol/L, 95% confidence interval [CI] 0.11 to 0.14 mmol/L) being consistent with that expected of a 10-mg dose of torcetrapib (0.13 mmol/L, 95% CI 0.10 to 0.15). In trials, 60 mg of torcetrapib elevated systolic and diastolic blood pressure by 4.47 mm Hg (95% CI 4.10 to 4.84 mm Hg) and 2.08 mm Hg (95% CI 1.84 to 2.31 mm Hg), respectively. However, the effect of CETP single-nucleotide polymorphisms on systolic blood pressure (0.16 mm Hg, 95% CI –0.28 to 0.60 mm Hg) and diastolic blood pressure (–0.04 mm Hg, 95% CI –0.36 to 0.28 mm Hg) was null and significantly different from that expected of 10 mg of torcetrapib.

Conclusions— Discordance in the effects of CETP single-nucleotide polymorphisms and torcetrapib treatment on blood pressure despite the concordant effects on lipids indicates the hypertensive action of torcetrapib is unlikely to be due to CETP inhibition or shared by chemically dissimilar CETP inhibitors. Genetic studies could find a place in drug-development programs as a new source of randomized evidence for drug-target validation in humans.

  S. E Humphries , R. D. G Neely , R. A Whittall , J. S Troutt , R. J Konrad , M Scartezini , K. W Li , J. A Cooper , J Acharya and A. Neil
 

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.

  F Drenos , P. J Talmud , J. P Casas , L Smeeth , J Palmen , S. E Humphries and A. D. Hingorani
 

Individuals at risk of coronary heart disease (CHD) show multiple correlations across blood biomarkers. Single nucleotide polymorphisms (SNPs) indexing biomarker differences could help distinguish causal from confounded associations because of their random allocation prior to disease. We examined the association of 948 SNPs in 122 candidate genes with 12 CHD-associated phenotypes in 2775 middle aged men (a genic scan). Of these, 140 SNPs indexed differences in HDL- and LDL-cholesterol, triglycerides, C-reactive protein, fibrinogen, factor VII, apolipoproteins AI and B, lipoprotein-associated phospholipase A2, homocysteine or folate, some with large effect sizes and highly significant P-values (e.g. 2.15 standard deviations at P = 9.2 x 10–140 for F7 rs6046 and FVII levels). Top ranking SNPs were then tested for association with additional biomarkers correlated with the index phenotype (phenome scan). Several SNPs (e.g. in APOE, CETP, LPL, APOB and LDLR) influenced multiple phenotypes, while others (e.g. in F7, CRP and FBB) showed restricted association to the index marker. SNPs influencing six blood proteins were used to evaluate the nature of the associations between correlated blood proteins utilizing Mendelian randomization. Multiple SNPs were associated with CHD-related quantitative traits, with some associations restricted to a single marker and others exerting a wider genetic ‘footprint’. SNPs indexing biomarkers provide new tools for investigating biological relationships and causal links with disease. Broader and deeper integrated analyses, linking genomic with transcriptomic, proteomic and metabolomic analysis, as well as clinical events could, in principle, better delineate CHD causing pathways amenable to treatment.

 
 
 
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