Polygenic Contribution to Low-Density Lipoprotein Cholesterol Levels and Cardiovascular Risk in Monogenic Familial Hypercholesterolemia.

BACKGROUND: Familial hypercholesterolemia (FH) is a common autosomal codominant genetic disorder, which causes elevated levels of low-density lipoprotein cholesterol (LDL-C) and increased risk of premature atherosclerotic cardiovascular disease (ASCVD). Even among individuals with monogenic FH, there is substantial interindividual variability in LDL-C levels and risk of ASCVD. We assessed the influence of an LDL-C polygenic score on levels of LDL-C and risk of ASCVD for individuals with monogenic FH. METHODS: We constructed a weighted LDL-C polygenic score, composed of 28 single-nucleotide variants, for individuals with monogenic FH from the British Columbia FH (n=262); Nutrition, Metabolism and Atherosclerosis Clinic (n=552); and UK Biobank cohorts (n=306). We assessed the association between LDL-C polygenic score with LDL-C levels and ASCVD risk using linear regression and Cox-proportional hazard models, respectively. ASCVD was defined as myocardial infarction, coronary or carotid revascularization, transient ischemic attack, or stroke. The results from individual cohorts were combined in fixed-effect meta-analyses. RESULTS: Levels of LDL-C were significantly associated with LDL-C polygenic score in the Nutrition, Metabolism and Atherosclerosis Clinic cohort, UK Biobank cohort, and in the meta-analysis (ß [95% CI]=0.13 [0.072-0.19] per a 20% increase in LDL-C polygenic score percentile, P<0.0001). Additionally, an elevated LDL-C polygenic score (≥80th percentile) was associated with a trend towards increased ASCVD risk in all 3 cohorts individually. This association was statistically significant in the meta-analysis (hazard ratio [95% CI]=1.48 [1.02-2.14], P=0.04). CONCLUSIONS: Polygenic contributions to LDL-C explain some of the heterogeneity in clinical presentation and ASCVD risk for individuals with FH.

Six years' experience with LipidSeq: clinical and research learnings from a hybrid, targeted sequencing panel for dyslipidemias.

BACKGROUND: In 2013, our laboratory designed a targeted sequencing panel, "LipidSeq", to study the genetic determinants of dyslipidemia and metabolic disorders. Over the last 6 years, we have analyzed 3262 patient samples obtained from our own Lipid Genetics Clinic and international colleagues. Here, we highlight our findings and discuss research benefits and clinical implications of our panel. METHODS: LipidSeq targets 69 genes and 185 single-nucleotide polymorphisms (SNPs) either causally related or associated with dyslipidemia and metabolic disorders. This design allows us to simultaneously evaluate monogenic-caused by rare single-nucleotide variants (SNVs) or copy-number variants (CNVs)-and polygenic forms of dyslipidemia. Polygenic determinants were assessed using three polygenic scores, one each for low-density lipoprotein cholesterol, triglyceride, and high-density lipoprotein cholesterol. RESULTS: Among 3262 patient samples evaluated, the majority had hypertriglyceridemia (40.1%) and familial hypercholesterolemia (28.3%). Across all samples, we identified 24,931 unique SNVs, including 2205 rare variants predicted disruptive to protein function, and 77 unique CNVs. Considering our own 1466 clinic patients, LipidSeq results have helped in diagnosis and improving treatment options. CONCLUSIONS: Our LipidSeq design based on ontology of lipid disorders has enabled robust detection of variants underlying monogenic and polygenic dyslipidemias. In more than 50 publications related to LipidSeq, we have described novel variants, the polygenic nature of many dyslipidemias-some previously thought to be primarily monogenic-and have uncovered novel mechanisms of disease. We further demonstrate several tangible clinical benefits of its use.

Clinical Utility and Practical Considerations of a Coronary Artery Disease Genetic Risk Score.

BACKGROUND: Coronary artery disease (CAD) risk traditionally has been assessed using clinical risk factors. We evaluated whether molecular genetic markers for CAD risk could add information to traditional variables. METHODS: We developed a false discovery rate 267-marker genetic risk score (FDR267) from markers that were significantly associated with CAD in the UK Biobank cohort meta-analysis. FDR267 was tested in the Atherosclerosis Risk in Communities cohort using logistic regression and Cox proportional hazards analyses in the European and African American groups. RESULTS: Our genetic risk score (FDR267) was associated with a 1.45 (95% confidence interval, 1.39-1.51) increase in odds ratio and a 1.32 (95% confidence interval, 1.26-1.38) increase in hazard ratio per standard deviation of the score. The score modestly improved the area under the curve (AUC) statistic when added to a clinical model (ΔAUC = 0.0112, P = 0.0002). FDR267 predicted incident CAD (C-index = 0.60), although it did not improve on clinical risk factors (ΔAUC = 0.0159, P = 0.0965). Individuals in the top quintile of FDR267 genetic risk were at approximately 2-fold increased risk compared with the bottom quintile, which is comparable to risk associated with self-reported family history. The performance of FDR267 was less robust in the African American sample. CONCLUSIONS: FDR267 is significantly associated with CAD in the European sample, with an effect size comparable to self-reported family history. FDR267 discriminated between individuals with and without CAD, but did not improve CAD risk prediction over clinical variables. FDR267 was less predictive of CAD risk in African Americans.

INTRODUCTION: L'évaluation du risque de maladie coronarienne (MC) a traditionnellement reposé sur les facteurs de risque cliniques. Nous avons évalué si les marqueurs génétiques moléculaires de risque de MC pourraient servir de complément aux variables traditionnelles. MÉTHODES: Nous avons élaboré un taux de fausses découvertes (FDR pour false discovery rate) du score de risque génétique du marqueur 267 (FDR267) provenant des marqueurs qui étaient associés de manière significative à la MC dans la méta-analyse de cohortes de la UK Biobank. Le FDR267 a été testé dans la cohorte du Atherosclerosis Risk in Communities à l'aide de la régression logistique et des analyses selon le modèle à risques proportionnels de Cox dans des groupes européens et afro-américains. RÉSULTATS: Notre score de risque génétique (FDR267) a été associé à une augmentation de 1,45 (intervalle de confiance [IC] à 95 %, 1,39-1,51) du rapport des cotes et d'une augmentation de 1,32 (IC à 95 %, 1,26-1,38) du risque relatif par l'écart-type des scores. Le score a modestement amélioré l'aire sous la courbe (ASC) lorsqu'il a été ajouté à un modèle clinique (ΔASC = 0,0112, P = 0,0002). Le FDR267 a prédit les nouveaux cas de MC (C-index [indice de concordance] = 0,60), mais il n'a pas amélioré les facteurs de risque cliniques (ΔASC = 0,0159, P = 0,0965). Les individus dans le quintile supérieur du risque génétique du FDR267 ont montré un risque accru d'environ 2 fois par rapport au quintile inférieur, soit un risque comparable au risque associé aux antécédents familiaux auto-rapportés. La performance du FDR267 s'est révélée moins robuste chez les Afro-Américains. CONCLUSIONS: Le FDR267 est associé de manière significative à la MC dans l'échantillon d'Européens et a une taille de l'effet comparable aux antécédents familiaux auto-rapportés. Le FDR267 a fait la discrimination entre les individus atteints ou non atteints de MC, mais n'a pas amélioré la prédiction du risque de MC par rapport aux variables cliniques. Le FDR267 a moins bien prédit le risque de MC chez les Afro-Américains.

Efficacy of Evolocumab in Monogenic vs Polygenic Hypercholesterolemia.

BACKGROUND: Inhibitors of proprotein convertase subtilisin kexin 9 are indicated in Canada for treatment of patients with familial hypercholesterolemia (FH). Classically, FH is considered to be a monogenic condition caused by rare pathogenic mutations; however, some patients have hypercholesterolemia on a polygenic basis. Whether the effect of proprotein convertase subtilisin kexin 9 inhibitor treatment differs between patients with monogenic hypercholesterolemia and patients with polygenic hypercholesterolemia is unclear. METHODS: We performed retrospective chart reviews on patients treated with evolocumab 140 mg subcutaneously biweekly from the Lipid Genetics Clinic, London Health Sciences Centre. Evolocumab-treated patients with hypercholesterolemia were grouped into monogenic or polygenic categories on the basis of their genotype determined by targeted next-generation sequencing. Absolute and relative changes in low-density lipoprotein cholesterol (LDL-C) levels before and after evolocumab treatment were studied. RESULTS: In 32 patients with monogenic heterozygous FH and 7 patients with polygenic hypercholesterolemia treated with evolocumab, absolute incremental reductions in LDL-C were 2.94 ± 1.22 mmol/L and 3.15 ± 0.90 mmol/L, respectively (P = not significant), whereas percent reductions in LDL-C were 63.9% ± 16.0% and 67.7% ± 20.7%, respectively (P = not significant). CONCLUSION: Although the sample size is small, the findings suggest comparable biochemical responsiveness to evolocumab in both monogenic (heterozygous) and polygenic hypercholesterolemia.

INTRODUCTION: Au Canada, les inhibiteurs de la proprotéine convertase subtilisine/kexine de type 9 sont indiqués dans le traitement des patients atteints d'hypercholestérolémie familiale (HF). Traditionnellement, la HF est considérée comme une maladie monogénique causée par des mutations pathogènes rares. Toutefois, certains patients ont une hypercholestérolémie de forme polygénique. On ignore si les effets du traitement par inhibiteurs de la proprotéine convertase subtilisine/kexine de type 9 diffèrent entre les patients ayant une hypercholestérolémie monogénique et les patients ayant une hypercholestérolémie polygénique. MÉTHODES: Nous avons réalisé une revue rétrospective de dossiers de patients traités par évolocumab à raison de 140 mg par voie sous-cutanée 2 fois par semaine à la Lipid Genetics Clinic du London Health Sciences Centre. Les patients atteints d'hypercholestérolémie qui étaient traités par évolocumab ont été regroupés dans la catégorie de la forme monogénique et la catégorie de la forme polygénique en fonction de leur génotype déterminé par le séquençage ciblé de nouvelle génération. Nous avons étudié les changements absolus et relatifs des concentrations de cholestérol à lipoprotéines de faible densité (LDL-C) avant et après le traitement par évolocumab. RÉSULTATS: Chez 32 patients ayant une HF hétérozygote monogénique et 7 patients ayant une hypercholestérolémie polygénique traités par évolocumab, les réductions progressives absolues du LDL-C étaient respectivement de 2,94 ± 1,22 mmol/l et de 3,15 ± 0,90 mmol/l (P = non significatif), alors que les réductions du LDL-C en pourcentage étaient respectivement de 63,9 % ± 16,0 % et de 67,7 % ± 20,7 % (P = non significatif). CONCLUSION: Bien que la taille de l'échantillon soit petite, les résultats montrent une capacité de réponse biochimique comparable à l'évolocumab lors d'hypercholestérolémie (hétérozygote) monogénique et d'hypercholestérolémie polygénique.

Genetic Determinants of Myocardial Infarction Risk in Familial Hypercholesterolemia.

BACKGROUND: Familial hypercholesterolemia (FH) is an inherited condition of elevated serum low-density lipoprotein (LDL) cholesterol leading to premature coronary heart disease. We evaluated whether FH mutations are independently associated with the development of myocardial infarction (MI), after adjusting for LDL cholesterol level and clinical risk factors. METHODS: In 182 unrelated patients from different families referred with clinically suspected FH, targeted next-generation DNA sequencing was performed on 73 lipid-related genes and 178 single nucleotide polymorphisms, at 300-times mean read depth, to identify monogenic mutations and high-risk single nucleotide polymorphisms. RESULTS: Pathogenic FH mutations were identified in 27% of patients. Patients with mutations, compared with those without, were 12 years younger when referred to the lipid clinic (P < 0.001) and had higher baseline and post-treatment LDL cholesterol by 1.11 mmol/L (P < 0.001) and 0.62 mmol/L (P = 0.01), respectively. The hazard ratio for premature MI with respect to having an FH mutation, controlling for sex, hypertension, body mass index, diabetes, LDL cholesterol, and smoking, was 4.51 (P = 0.002). CONCLUSION: FH is a genetically diverse condition. FH mutations are independently associated with higher risk of premature MI in patients referred for hypercholesterolemia. Therefore, genotyping could guide cardiovascular risk stratification in the personalized treatment of FH.

INTRODUCTION: L'hypercholestérolémie familiale (HF) est une maladie héréditaire caractérisée par des concentrations élevées de lipoprotéines de faible densité (LDL) qui entraîne de manière précoce la maladie coronarienne. Nous avons évalué si les mutations propres à la HF sont indépendamment associées au développement de l'infarctus du myocarde (IM) après l'ajustement des concentrations de cholestérol LDL et des facteurs de risque cliniques. MÉTHODES: Chez les 182 patients non apparentés de différentes familles envoyés en consultation en raison d'une suspicion clinique de HF, nous avons réalisé le séquençage ciblé de l'ADN de nouvelle génération de 73 gènes du métabolisme des lipides et 178 polymorphismes mononucléotidiques, à une profondeur de lecture moyenne de 300 fois, pour déterminer les mutations monogènes et les polymorphismes mononucléotidiques à haut risque. RÉSULTATS: Nous avons déterminé les mutations pathogènes à l'origine de la HF de 27 % des patients. Comparativement aux patients qui ne présentaient pas de mutations, les patients qui en présentaient étaient 12 ans plus jeunes lorsqu'ils étaient envoyés en consultation à la clinique des lipides (P < 0,001) et avaient des concentrations respectives plus élevées de cholestérol LDL de 1,11 mmol/l (P < 0,001) et de 0,62 mmol/l (P = 0,01), au début et après le traitement. Le rapport de risque d'IM prématuré par rapport à la présence d'une mutation à l'origine de la HF, qui tient compte du sexe, de l'hypertension, de l'indice de masse corporelle, du diabète, du cholestérol LDL et de la consommation du tabac, était de 4,51 (P = 0,002). CONCLUSION: La HF est une maladie diversifiée sur le plan génétique. Les mutations à l'origine de la HF sont indépendamment associées à un risque plus élevé d'IM prématuré chez les patients envoyés en consultation en raison d'une hypercholestérolémie. Par conséquent, le génotypage pourrait être utile à la stratification du risque cardiovasculaire dans le traitement personnalisé de la HF.

Clinical and biochemical features of different molecular etiologies of familial chylomicronemia.

BACKGROUND: Familial chylomicronemia syndrome (FCS) is an ultra-rare phenotype that is usually caused by biallelic mutations in the LPL gene encoding lipoprotein lipase, or less often in APOC2, APOA5, LMF1, or GPIHBP1 genes encoding cofactors or interacting proteins. OBJECTIVES: We evaluated baseline phenotypes among FCS participants in a phase 3 randomized placebo-controlled trial of volanesorsen (NCT02211209). METHODS: Baseline clinical, fasting, and postfat load metabolic markers were assessed. Targeted next-generation DNA sequencing plus custom bioinformatics was used to genotype subjects. RESULTS: Among 52 FCS individuals, 41 had biallelic LPL gene mutations (LPL-FCS patients): 82%, 7%, and 11% were missense, nonsense, and splicing variants, respectively. Eleven individuals had non-LPL-FCS; 2 had mutations in APOA5, 5 in GPIHBP1, and 1 each in LMF1 and APOC2 genes, respectively. Two other individuals were double heterozygotes, each with 1 normal LPL allele. All subjects had extremely high triglycerides (TGs) and chylomicrons, but very low levels of other lipoproteins. Compared with LPL-FCS individuals, non-LPL-FCS individuals were very similar for most traits, but had significantly higher postheparin LPL activity, higher 4-hour postprandial insulin and C-peptide levels; and higher low-density lipoprotein cholesterol levels. In non-LPL-FCS individuals compared to those with LPL-FCS, there were also nonsignificant trends toward lower levels of total and chylomicron TGs, lower 4-hour postprandial chylomicron TG levels, and higher very-low-density lipoprotein TG levels. CONCLUSION: Thus, LPL FCS and non-LPL FCS are largely phenotypically similar. However, LPL FCS patients have lower postheparin LPL activity and a trend toward higher TGs, whereas low-density lipoprotein cholesterol was higher in non-LPL-FCS patients.

Polygenic determinants in extremes of high-density lipoprotein cholesterol.

HDL cholesterol (HDL-C) remains a superior biochemical predictor of CVD risk, but its genetic basis is incompletely defined. In patients with extreme HDL-C concentrations, we concurrently evaluated the contributions of multiple large- and small-effect genetic variants. In a discovery cohort of 255 unrelated lipid clinic patients with extreme HDL-C levels, we used a targeted next-generation sequencing panel to evaluate rare variants in known HDL metabolism genes, simultaneously with common variants bundled into a polygenic trait score. Two additional cohorts were used for validation and included 1,746 individuals from the Montréal Heart Institute Biobank and 1,048 individuals from the University of Pennsylvania. Findings were consistent between cohorts: we found rare heterozygous large-effect variants in 18.7% and 10.9% of low- and high-HDL-C patients, respectively. We also found common variant accumulation, indicated by extreme polygenic trait scores, in an additional 12.8% and 19.3% of overall cases of low- and high-HDL-C extremes, respectively. Thus, the genetic basis of extreme HDL-C concentrations encountered clinically is frequently polygenic, with contributions from both rare large-effect and common small-effect variants. Multiple types of genetic variants should be considered as contributing factors in patients with extreme dyslipidemia.

Polygenic Versus Monogenic Causes of Hypercholesterolemia Ascertained Clinically.

OBJECTIVE: Next-generation sequencing technology is transforming our understanding of heterozygous familial hypercholesterolemia, including revision of prevalence estimates and attribution of polygenic effects. Here, we examined the contributions of monogenic and polygenic factors in patients with severe hypercholesterolemia referred to a specialty clinic. APPROACH AND RESULTS: We applied targeted next-generation sequencing with custom annotation, coupled with evaluation of large-scale copy number variation and polygenic scores for raised low-density lipoprotein cholesterol in a cohort of 313 individuals with severe hypercholesterolemia, defined as low-density lipoprotein cholesterol >5.0 mmol/L (>194 mg/dL). We found that (1) monogenic familial hypercholesterolemia-causing mutations detected by targeted next-generation sequencing were present in 47.3% of individuals; (2) the percentage of individuals with monogenic mutations increased to 53.7% when copy number variations were included; (3) the percentage further increased to 67.1% when individuals with extreme polygenic scores were included; and (4) the percentage of individuals with an identified genetic component increased from 57.0% to 92.0% as low-density lipoprotein cholesterol level increased from 5.0 to >8.0 mmol/L (194 to >310 mg/dL). CONCLUSIONS: In a clinically ascertained sample with severe hypercholesterolemia, we found that most patients had a discrete genetic basis detected using a comprehensive screening approach that includes targeted next-generation sequencing, an assay for copy number variations, and polygenic trait scores.

Genetic Confirmation Rate in Clinically Suspected Maturity-Onset Diabetes of the Young.

OBJECTIVES: Maturity-onset diabetes of the young (MODY) is the most common form of monogenic diabetes, reportedly accounting for 2% to 5% of all cases of diabetes. In samples from Canadian patients referred for molecular genetic confirmation of a clinically suspected MODY, we determined the prevalence of likely disease-causing DNA variants in known MODY genes. METHODS: Between 1999 and 2015, our centre received requests from colleagues for DNA sequencing of 96 samples from unrelated Canadian patients with clinically suspected MODY. Prior to 2012, we used Sanger sequencing, and since 2012 we have used targeted next-generation sequencing. RESULTS: Of 96 samples received, 39 (40.6%) had a likely rare causal variant in 1 of 8 known MODY genes. Of these, 20 (51.3%) and 19 (48.7%) were diagnosed by Sanger and targeted next-generation sequencing, respectively. The 39 mutation-positive samples had 1 of 39 rare variants, of which the majority were in genes encoding either glucokinase (GCK, or MODY2) or hepatocyte nuclear factor 1-alpha (HNF1A, or MODY3). Furthermore, 12 (30.8%) of the detected rare variants had been unreported previously but were likely to have been clinically significant according to standard bioinformatic methods. An additional 6 samples had rare variants in MODY genes that were of uncertain clinical significance. CONCLUSIONS: The findings suggest that clinical suspicion for MODY has a diagnostic yield of ~40% at the molecular level. Confirmatory genetic testing in patients suspected to have MODY allows for definitive diagnoses which, in turn, may guide management and provide rationales for screening other family members presymptomatically.

Targeted exonic sequencing of GWAS loci in the high extremes of the plasma lipids distribution.

OBJECTIVE: Genome-wide association studies (GWAS) for plasma lipid levels have mapped numerous genomic loci, with each region often containing many protein-coding genes. Targeted re-sequencing of exons is a strategy to pinpoint causal variants and genes. METHODS: We performed solution-based hybrid selection of 9008 exons at 939 genes within 95 GWAS loci for plasma lipid levels and sequenced using next-generation sequencing technology individuals with extremely high as well as low to normal levels of low-density lipoprotein cholesterol (LDL-C, n = 311; mean low = 71 mg/dl versus high = 241 mg/dl), triglycerides (TG, n = 308; mean low = 75 mg/dl versus high = 1938 mg/dl), and high-density lipoprotein cholesterol (HDL-C, n = 684; mean low = 32 mg/dl versus high = 102 mg/dl). We identified 15,002 missense, nonsense, or splice site variants with a frequency <5%. We tested whether coding sequence variants, individually or aggregated within a gene, were associated with plasma lipid levels. To replicate findings, we performed sequencing in independent participants (n = 6424). RESULTS: Across discovery and replication sequencing, we found 6 variants with significant associations with plasma lipids. Of these, one was a novel association: p.Ser147Asn variant in APOA4 (14.3% frequency, TG OR = 0.49, P = 7.1 × 10(-4)) with TG. In gene-level association analyses where rare variants within each gene are collapsed, APOC3 (P = 2.1 × 10(-5)) and LDLR (P = 5.0 × 10(-12)) were associated with plasma lipids. CONCLUSIONS: After sequencing genes from 95 GWAS loci in participants with extremely high plasma lipid levels, we identified one new coding variant associated with TG. These results provide insight regarding design of similar sequencing studies with respect to sample size, follow-up, and analysis methodology.

Targeted next-generation sequencing in monogenic dyslipidemias.

PURPOSE OF REVIEW: To evaluate the potential clinical translation of high-throughput next-generation sequencing (NGS) methods in diagnosis and management of dyslipidemia. RECENT FINDINGS: Recent NGS experiments indicate that most causative genes for monogenic dyslipidemias are already known. Thus, monogenic dyslipidemias can now be diagnosed using targeted NGS. Targeting of dyslipidemia genes can be achieved by either: designing custom reagents for a dyslipidemia-specific NGS panel; or performing genome-wide NGS and focusing on genes of interest. Advantages of the former approach are lower cost and limited potential to detect incidental pathogenic variants unrelated to dyslipidemia. However, the latter approach is more flexible because masking criteria can be altered as knowledge advances, with no need for re-design of reagents or follow-up sequencing runs. Also, the cost of genome-wide analysis is decreasing and ethical concerns can likely be mitigated. DNA-based diagnosis is already part of the clinical diagnostic algorithms for familial hypercholesterolemia. Furthermore, DNA-based diagnosis is supplanting traditional biochemical methods to diagnose chylomicronemia caused by deficiency of lipoprotein lipase or its co-factors. SUMMARY: The increasing availability and decreasing cost of clinical NGS for dyslipidemia means that its potential benefits can now be evaluated on a larger scale.

G-protein estrogen receptor as a regulator of low-density lipoprotein cholesterol metabolism: cellular and population genetic studies.

OBJECTIVE: Estrogen deficiency is linked with increased low-density lipoprotein (LDL) cholesterol. The hormone receptor mediating this effect is unknown. G-protein estrogen receptor (GPER) is a recently recognized G-protein-coupled receptor that is activated by estrogens. We recently identified a common hypofunctional missense variant of GPER, namely P16L. However, the role of GPER in LDL metabolism is unknown. Therefore, we examined the association of the P16L genotype with plasma LDL cholesterol level. Furthermore, we studied the role of GPER in regulating expression of the LDL receptor and proprotein convertase subtilisin kexin type 9. APPROACH AND RESULTS: Our discovery cohort was a genetically isolated population of Northern European descent, and our validation cohort consisted of normal, healthy women aged 18 to 56 years from London, Ontario. In addition, we examined the effect of GPER on the regulation of proprotein convertase subtilisin kexin type 9 and LDL receptor expression by the treatment with the GPER agonist, G1. In the discovery cohort, GPER P16L genotype was associated with a significant increase in LDL cholesterol (mean±SEM): 3.18±0.05, 3.25±0.08, and 4.25±0.33 mmol/L, respectively, in subjects with CC (homozygous for P16), CT (heterozygotes), and TT (homozygous for L16) genotypes (P<0.05). In the validation cohort (n=339), the GPER P16L genotype was associated with a similar increase in LDL cholesterol: 2.17±0.05, 2.34±0.06, and 2.42±0.16 mmol/L, respectively, in subjects with CC, CT, and TT genotypes (P<0.05). In the human hepatic carcinoma cell line, the GPER agonist, G1, mediated a concentration-dependent increase in LDL receptor expression, blocked by either pretreatment with the GPER antagonist G15 or by shRNA-mediated GPER downregulation. G1 also mediated a GPER- and concentration-dependent decrease in proprotein convertase subtilisin kexin type 9 expression. CONCLUSIONS: GPER activation upregulates LDL receptor expression, probably at least, in part, via proprotein convertase subtilisin kexin type 9 downregulation. Furthermore, humans carrying the hypofunctional P16L genetic variant of GPER have increased plasma LDL cholesterol. In aggregate, these data suggest an important role of GPER in the regulation of LDL receptor expression and consequently LDL metabolism.

Common low-density lipoprotein receptor p.G116S variant has a large effect on plasma low-density lipoprotein cholesterol in circumpolar inuit populations.

BACKGROUND: Inuit are considered to be vulnerable to cardiovascular disease because their lifestyles are becoming more Westernized. During sequence analysis of Inuit individuals at extremes of lipid traits, we identified 2 nonsynonymous variants in low-density lipoprotein receptor (LDLR), namely p.G116S and p.R730W. METHODS AND RESULTS: Genotyping these variants in 3324 Inuit from Alaska, Canada, and Greenland showed they were common, with allele frequencies 10% to 15%. Only p.G116S was associated with dyslipidemia: the increase in LDL cholesterol was 0.54 mmol/L (20.9 mg/dL) per allele (P=5.6×10(-49)), which was >3× larger than the largest effect sizes seen with other common variants in other populations. Carriers of p.G116S had a 3.02-fold increased risk of hypercholesterolemia (95% confidence interval, 2.34-3.90; P=1.7×10(-17)), but did not have classical familial hypercholesterolemia. In vitro, p.G116S showed 60% reduced ligand-binding activity compared with wild-type receptor. In contrast, p.R730W was associated with neither LDL cholesterol level nor altered in vitro activity. CONCLUSIONS: LDLR p.G116S is thus unique: a common dysfunctional variant in Inuit whose large effect on LDL cholesterol may have public health implications.

The effect of infrequent low-dose rosuvastatin on the lipid profile.

We retrospectively studied 21 patients who had difficulty tolerating daily or alternating-day statins. Patients received rosuvastatin at a mean frequency of 1.7 doses per week, and a mean dose of 11.7 mg per week. We assessed lipid profiles at baseline and after at least 3 months of therapy. We found that total and low-density lipoprotein cholesterol were reduced by 2.03 ± 2.04 and 1.31 ± 0.83 mmol/L (27.9% and 31.5%), respectively, from baseline (both P < 0.001). Thus, in patients with statin intolerance, infrequent low-dose rosuvastatin significantly improved low-density lipoprotein cholesterol and was well tolerated over the long term.

A common hypofunctional genetic variant of GPER is associated with increased blood pressure in women.

AIMS: Activation of vascular GPER has been linked to vasodepressor effects in animals. However, the significance of GPER regulation on chronic blood pressure control in humans is unknown. METHODS: To examine this question we determined the functional significance of expression of a common missense single nucleotide variant of GPER, P16L in vascular smooth muscle cells, and its association with blood pressure in humans. Further, to validate the importance of carrying GPER P16L in the development of hypertension we assessed allele frequency in a cohort of hard-to-treat hypertensive patients referred to a tertiary care clinic. RESULTS: Expression of the GPER P16L variant (V) vs. wild type (WT) in rat aortic vascular smooth muscle cells, was associated with a significant decrease in G1 (1 µm, a GPER agonist)-mediated ERK phosphorylation (slope of the function of G1-stimulated ERK phosphorylation: GPER content WT: 16.2, 95% CI 9.9, 22.6; V: 5.0, 95% CI 1.0, 9.0; P < 0.005) and apoptosis (slope of the function of G1-stimulated apoptosis: GPER content: WT: 4.4, 95% CI: 3.4, 5.4; V: 2.5, 95% CI 1.6, 2.3 P < 0.005). Normotensive female subjects, but not male subjects, carrying this hypofunctional variant (allele frequency 22%) have increased blood pressure [mean arterial pressure: P16/P16: 80 ± 1 mmHg (n = 204) vs. P16L carriers: 82 ± 1 mmHg (n = 127), 95% CI for difference: 0.6, 4.0 mmHg, P < 0.05], [systolic blood pressure: P16/P16: 105 ± 1 mmHg vs. P16L carriers: 108 ± 1 mmHg, 95% CI for difference:1.0, 5.1 mmHg, P < 0.05], [diastolic blood pressure: P16/P16: 66 ± 0.5 mmHg vs. P16L carriers 68 ± 0.7, 95% CI for difference: 0.2, 3.6 mmHg, P < 0.05]. Further, the P16L allele frequency was almost two-fold higher in female vs. male hypertensive patients (31% vs. 16%, allele ratio 0.5, 95% CI 0.32, 0.76, P < 0.05). CONCLUSIONS: The common genetic variant, GPER P16L, is hypofunctional and female carriers of this allele have increased blood pressure. There was an increased prevalence in a population of hard-to-treat hypertensive female patients. Cumulatively, these data suggest that in females, impaired GPER function might be associated with increased blood pressure and risk of hypertension.

Inheritance of rare functional GCKR variants and their contribution to triglyceride levels in families.

Significant resources have been invested in sequencing studies to investigate the role of rare variants in complex disease etiology. However, the diagnostic interpretation of individual rare variants remains a major challenge, and may require accurate variant functional classification and the collection of large numbers of variant carriers. Utilizing sequence data from 458 individuals with hypertriglyceridemia and 333 controls with normal plasma triglyceride levels, we investigated these issues using GCKR, encoding glucokinase regulatory protein. Eighteen rare non-synonymous GCKR variants identified in these 791 individuals were comprehensively characterized by a range of biochemical and cell biological assays, including a novel high-throughput-screening-based approach capable of measuring all variant proteins simultaneously. Functionally deleterious variants were collectively associated with hypertriglyceridemia, but a range of in silico prediction algorithms showed little consistency between algorithms and poor agreement with functional data. We extended our study by obtaining sequence data on family members; however, functional variants did not co-segregate with triglyceride levels. Therefore, despite evidence for their collective functional and clinical relevance, our results emphasize the low predictive value of rare GCKR variants in individuals and the complex heritability of lipid traits.

Incremental lowering of low-density lipoprotein cholesterol with ezetimibe 20 mg vs 10 mg daily in patients receiving concomitant statin therapy.

BACKGROUND: Ezetimibe is typically administered at a dose of 10 mg daily, with few reports of use at other doses. We compared plasma concentrations of low-density lipoprotein (LDL) cholesterol and other lipid variables in patients with dyslipidemia who were receiving ezetimibe 10 mg and then 20 mg daily. METHODS: A retrospective chart review identified 27 patients who received ezetimibe 10 mg and then 20 mg daily at different times; 15 participants were receiving stable statin therapy and 12 were not receiving concomitant statins. Plasma concentrations of lipids, creatine kinase (CK), and aspartate transaminase (AST) were determined. Plasma concentrations of ezetimibe and ezetimibe glucuronide were measured in a second group of patients. RESULTS: Patients taking statins and ezetimibe 20 mg had further reductions in total and LDL cholesterol of 7.1% and 10.3%, respectively (both P < 0.05) than did those receiving the 10-mg dose. No difference between 20-mg and 10-mg dosing was seen among patients not receiving statins. Plasma concentrations of ezetimibe and its active metabolite were about 2-fold higher (P < 0.05) in patients taking ezetimibe 20 mg than in those receiving 10 mg daily. All patients tolerated ezetimibe 20 mg without side effects. CONCLUSIONS: Ezetimibe 20 mg daily reduced total and LDL cholesterol further in patients receiving statin therapy compared with 10 mg daily. Prospective studies are required to show whether the higher plasma levels of ezetimibe and its active metabolite in patients taking the 20-mg dose have any detrimental effects. Increasing the ezetimibe dose to 20 mg daily might be an interesting potential approach for patients who fail to reach lipid targets on ezetimibe 10 mg daily along with maximally tolerated doses of statin.

Western Database of Lipid Variants (WDLV): a catalogue of genetic variants in monogenic dyslipidemias.

BACKGROUND: Next-generation sequencing (NGS) is nearing routine clinical application, especially for diagnosis of rare monogenic cardiovascular diseases. But NGS uncovers so much variation in an individual genome that filtering steps are required to streamline data management. The first step is to determine whether a potential disease-causing variant has been observed previously in affected patients. METHODS: To facilitate this step for lipid disorders, we developed the Western Database of Lipid Variants (WDLV) of 2776 variants in 24 genes that cause monogenic dyslipoproteinemias, including conditions characterized primarily by either high or low low-density lipoprotein cholesterol, high or low high-density lipoprotein cholesterol, high triglyceride, and some miscellaneous disorders. We incorporated quality-control steps to maximize the likelihood that a listed mutation was disease causing. RESULTS: The details of each mutation found in a dyslipidemia, together with a mutation map of the causative genes, are shown in graphical display items. CONCLUSIONS: WDLV will help clinicians and researchers determine the potential pathogenicity of mutations discovered by DNA sequencing of patients or research participants with lipid disorders.

Efficacy and plasma drug concentrations with nondaily dosing of rosuvastatin.

BACKGROUND: Nondaily statin dosing is an alternative for patients unable to tolerate daily dosing. The higher potency and longer half-life of rosuvastatin lends itself to this regimen. The basis of this improved tolerability is not understood, but might be related to lower plasma drug concentrations. We examined the efficacy of nondaily rosuvastatin in previously statin-intolerant patients and determined plasma drug concentrations at various dose regimens. METHODS: A retrospective analysis at a specialty lipid clinic identified 58 patients eligible for evaluation after therapy with nondaily rosuvastatin. Plasma rosuvastatin levels were measured by liquid chromatography-mass spectrometry in 12 patients taking 10 mg nondaily rosuvastatin and in 11 and 12 age- and sex-matched patients taking 10 mg and 5 mg rosuvastatin daily, respectively. Whole body cholesterol synthesis was estimated from serum lathosterol measured by liquid chromatography-mass spectrometry. RESULTS: In patients with a previous history of statin intolerance, nondaily rosuvastatin (average of 29.4 mg per week) lowered low-density lipoprotein cholesterol by 34.4 ± 21.3% (P < 0.001). Serum lathosterol levels were significantly higher in patients on nondaily regimens, as expected. However, mean plasma rosuvastatin levels of patients taking 10 mg nondaily did not significantly differ from those taking 10 mg daily. CONCLUSIONS: In statin intolerant patients, nondaily rosuvastatin resulted in clinically relevant reductions in low-density lipoprotein cholesterol levels, with improved compliance. Whole body cholesterol synthesis was higher in patients taking nondaily rosuvastatin, but no differences in plasma drug concentrations were observed, suggesting that the improved tolerability was independent of plasma rosuvastatin levels.