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Alzheimer's f disease (AD) affects approximately 250,000 Ontarians, a number that is expected to double by 2040. The Ontario Neurodegenerative Disease Research Initiative has developed an in-province genetic test (ONDRISeq), which currently runs in Ontario in an experimental capacity. The aim of this study is to estimate the costs and health outcomes associated with ONDRISeq to diagnose AD relative to out-of-country (OOC) testing (status quo). A cost-utility analysis was developed for a hypothetical cohort of 65-year-olds at risk of AD in Ontario over a 25-year time horizon. Costs and health outcomes (quality-adjusted life years (QALYs)) were assessed from a healthcare payer perspective. Cost-effectiveness was assessed with a $50,000 cost-effectiveness threshold. Probabilistic sensitivity analyses were conducted to evaluate parameter uncertainty. ONDRISeq saved $54 per patient relative to OOC testing and led to a small QALY gain in the base case (0.0014 per patient). Results were most sensitive to testing costs, uptake rates, and treatment efficacy. ONDRISeq represented better value for money relative to OOC testing throughout 75% of 10,000 probabilistic iterations. Using ONDRISeq is expected to provide health system cost savings. Switching to ONDRISeq for AD genetic testing in Ontario would be dependent on the ability to accommodate the expected testing volumes. [ABSTRACT FROM AUTHOR]

Purpose of Review: We reviewed lipid-modifying therapies and the risk of stroke and other cerebrovascular outcomes, with a focus on newer therapies. Recent Findings: Statins and ezetimibe reduce ischemic stroke risk without increasing hemorrhagic stroke risk. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors similarly reduce ischemic stroke risk in statin-treated patients with atherosclerosis without increasing hemorrhagic stroke, even with very low achieved low-density lipoprotein cholesterol levels. Icosapent ethyl reduces the risk of total and first ischemic stroke in patients with established cardiovascular disease or diabetes mellitus. Clinical outcome trials are underway for newer lipid-modifying agents, including inclisiran, bempedoic acid, and pemafibrate. New biologic agents including evinacumab, pelacarsen, olpasiran, and SLN360 are also discussed. Summary: In addition to statins and ezetimibe, PCSK9 inhibitors and icosapent ethyl reduce the risk of ischemic stroke without increasing the risk of hemorrhagic stroke. These therapies dramatically expand options for reducing stroke in high-risk settings. [ABSTRACT FROM AUTHOR]

Purpose of Review: Common DNA variants with small effects work together to create susceptibility to polygenic hypercholesterolemia. Some clinicians wonder whether patients with polygenic hypercholesterolemia have less severe clinical features compared to patients with monogenic familial hypercholesterolemia (FH) caused by rare deleterious variants. Recent Findings: Studies performed in cohorts of patients with both monogenic and polygenic hypercholesterolemia have assessed lipid levels, non-invasive markers of atherosclerosis, and clinical end points, including major adverse cardiovascular events. The totality of data suggests a gradient across genotypes. Specifically, individuals with polygenic hypercholesterolemia have deleterious phenotypes that are intermediate in severity between those in patients with monogenic hypercholesterolemia and in control subjects. Summary: Although clinical variables in patients with polygenic hypercholesterolemia are less severe than in those with monogenic hypercholesterolemia, cardiovascular risk is still very high in these patients compared to controls. Patients with polygenic hypercholesterolemia must be treated assertively. [ABSTRACT FROM AUTHOR]

Introduction: Homozygous familial hypercholesterolaemia (HoFH) is characterised by extremely elevated levels of low-density lipoprotein cholesterol (LDL-C) and results from multiple mutations in genes affecting the LDL receptor pathway. Patients are at risk of premature atherosclerotic cardiovascular disease (ASCVD) and premature death. Lomitapide is a microsomal triglyceride transfer protein inhibitor developed to treat HoFH, but cardiovascular outcome data are lacking. Methods: We evaluated detailed data from five HoFH patients and one patient with heterozygous FH (HeFH) and a very severe phenotype. We also analysed confirmatory data from a further 8 HoFH cases. In total, we analysed data from patients in seven global centres in six countries who were all treated with lomitapide with long-term follow-up. Carotid intima-media thickness (CIMT) imaging was recorded on an ad hoc basis to monitor ASCVD in HoFH. Results: Lomitapide resulted in marked decreases in LDL-C of 56.8–93.9% [77.7–93.9% in the 6 initial cases (mean nadir 64.8 ± 30.1 mg/dL); 56.8–86.0% in the 8 confirmatory cases (mean nadir 131.4 ± 38.2 mg/dL)]. CIMT regressed in 50% of cases (mean follow-up 5.0 ± 3.1 years in initial six cases, and 4.4 ± 1.4 years in confirmatory cases). In the remaining patients, CIMT showed little further change. In patients where assessments of plaque area were available, regression or stabilisation in CIMT was accompanied by clinically significant regression of plaque area. Conclusions: Lomitapide reduces LDL-C levels in patients with HoFH and severe LDL-C phenotypes, and results in stabilisation and/or regression of CIMT, which is an established marker of ASCVD risk. Additional data are needed to determine if this confers a survival benefit in these very high-risk patients. [ABSTRACT FROM AUTHOR]

Neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), can be clinically heterogeneous which may be explained by the co-inheritance of multiple genetic variants that modify the clinical course. In this study we examine variants in three genes in a family with one individual presenting with ALS and lipodystrophy. Sequencing revealed a p.Gly602Ser variant in LMNA, and two additional variants, one each in SETX (g.intron10-13delCTT) and FUS (p.Gly167_Gly168del). These latter genes have been linked to ALS. All family members were genotyped and each variant, and each combination of variants detected, were functionally evaluated in vitro regarding effects on cell survival, expression patterns and cellular phenotype. Muscle biopsy retrieved from the individual with ALS showed leakage of chromatin from the nucleus, a phenotype that was recapitulated in vitro with expression of all three variants simultaneously. Individually expressed variants gave cellular phenotypes there were unremarkable. Interestingly the FUS variant appears to be protective against the effects of the SETX and the LMNA variants on cell viability and may indicate loss of interaction of FUS with SETX and/or R-loops. We conclude that these findings support genetic modifications as an explanation of the clinical heterogeneity observed in human disease. [ABSTRACT FROM AUTHOR]

Polygenic risk scores (PRSs), which often aggregate results from genome-wide association studies, can bridge the gap between initial discovery efforts and clinical applications for the estimation of disease risk using genetics. However, there is notable heterogeneity in the application and reporting of these risk scores, which hinders the translation of PRSs into clinical care. Here, in a collaboration between the Clinical Genome Resource (ClinGen) Complex Disease Working Group and the Polygenic Score (PGS) Catalog, we present the Polygenic Risk Score Reporting Standards (PRS-RS), in which we update the Genetic Risk Prediction Studies (GRIPS) Statement to reflect the present state of the field. Drawing on the input of experts in epidemiology, statistics, disease-specific applications, implementation and policy, this comprehensive reporting framework defines the minimal information that is needed to interpret and evaluate PRSs, especially with respect to downstream clinical applications. Items span detailed descriptions of study populations, statistical methods for the development and validation of PRSs and considerations for the potential limitations of these scores. In addition, we emphasize the need for data availability and transparency, and we encourage researchers to deposit and share PRSs through the PGS Catalog to facilitate reproducibility and comparative benchmarking. By providing these criteria in a structured format that builds on existing standards and ontologies, the use of this framework in publishing PRSs will facilitate translation into clinical care and progress towards defining best practice.An updated set of reporting standards for the development, interpretation and evaluation of polygenic risk scores is presented, which should aid the translation of these scores into clinical applications. [ABSTRACT FROM AUTHOR]

Hyperparathyroidism, commonly observed in asymptomatic middle-aged women, with mild hypercalcemia, is usually caused by a benign adenoma. Some cases present with more severe manifestation and greater hypercalcemia. Within this spectrum, several familial/genetic associations have been discovered. While the majority are caused by benign disease, adenomas, or hyperplasia, a small proportion (< 1%) are associated with malignant tumors and present with more severe symptoms. Although usually sporadic, recent reports document various gene mutations that strongly predispose to the development of parathyroid carcinoma. An increasing number of cases of hyperparathyroidism, benign or malignant, require and benefit from genetic analysis. We describe a 25-year-old male with hyperparathyroidism presenting with a pathological fracture, brown tumors, hypercalcemia, and markedly elevated parathyroid hormone levels. There was no family history of hyperparathyroidism or jaw tumors. Surgical removal revealed a single large tumor confirmed to be malignant. Immunohistochemical analysis revealed the absence of parafibromin and decreased APC (adenomatosis polyposis coli) expression. Genetic analysis revealed a rare germline nonsense mutation (R76X) in the parafibromin gene, HRPT2/CDC73. Parathyroid carcinoma should be suspected as a cause of hyperparathyroidism when clinical manifestations are severe, particularly in young individuals, < 59 years. Immunohistochemistry may lead to suspicion for a germline mutation as a significant contributor despite absence of a family history. The discovery of a germline mutation in parathyroid carcinoma alters the clinical management of the index case and that of family members. Long-term follow-up studies of such patients are necessary to develop evidence-based clinical guidelines. [ABSTRACT FROM AUTHOR]

Background: The gastrointestinal (GI) microbiome is recognized for potential clinical relevance in inflammatory bowel disease (IBD). Data suggest that there is a disease-dependent loss of microbial diversity in IBD. Trimethylamine-N-oxide (TMAO) is generated by GI anaerobes through the digestion of dietary phosphatidylcholine and carnitine in a microbial-mammalian co-metabolic pathway. IBD-related changes in the gut microbiome may result in disease-specific changes in TMAO plasma concentrations.Aim: To determine whether TMAO plasma levels in IBD are altered compared to controls and whether they correlate with disease presence or activity.Methods: Liquid chromatography-tandem mass spectrometry was used to measure TMAO, choline, and carnitine plasma levels in 479 subjects (373 non-IBD controls, 106 IBD). Subjects were also genotyped for the flavin monooxygenase (FMO)3 variants, E158K and E308G.Results: Plasma TMAO levels were 2.27 µM lower in the IBD population compared to the control population (p = 0.0001). Lower TMAO levels were similarly seen in active ulcerative colitis (UC) (1.56 µM) versus inactive disease (3.40 µM) (p = 0.002). No difference was seen in active Crohn's disease (CD) versus inactive CD. No intergroup variation existed in plasma TMAO levels based on FMO3 genotype. Choline levels were higher in IBD, while carnitine levels were similar between the two groups, suggesting that lower TMAO levels in IBD were not due to dietary differences.Conclusions: Decreased TMAO levels are seen in IBD compared to a non-IBD population. These data suggest that TMAO may have potential as a biomarker to support IBD diagnosis as well as to assess disease activity in UC. [ABSTRACT FROM AUTHOR]

Purpose of Review: Plasma triglycerides are routinely measured with a lipid profile, and elevated plasma triglycerides are commonly encountered in the clinic. The confounded nature of this trait, which is correlated with numerous other metabolic perturbations, including depressed high-density lipoprotein cholesterol (HDL-C), has thwarted efforts to directly implicate triglycerides as causal in atherogenesis. Human genetic approaches involving large-scale populations and high-throughput genomic assessment under a Mendelian randomization framework have undertaken to sort out questions of causality. Recent Findings: We review recent large-scale meta-analyses of cohorts and population-based sequencing studies designed to address whether common and rare variants in genes whose products are determinants of plasma triglycerides are also associated with clinical cardiovascular endpoints. The studied loci include genes encoding lipoprotein lipase and proteins that interact with it, such as apolipoprotein (apo) A-V, apo C-III and angiopoietin-like proteins 3 and 4, and common polymorphisms identified in genome-wide association studies. Summary: Triglyceride-raising variant alleles of these genes showed generally strong associations with clinical cardiovascular endpoints. However, in most cases, a second lipid disturbance-usually depressed HDL-C-was concurrently associated. While the findings collectively shift our understanding towards a potential causal role for triglycerides, we still cannot rule out the possibilities that triglycerides are a component of a joint phenotype with low HDL-C or that they are but markers of deeper causal metabolic disturbances that are not routinely measured in epidemiological-scale genetic studies. [ABSTRACT FROM AUTHOR]

Dyslipidaemia is characterized by increased blood levels of total or LDL cholesterol and triglycerides, or decreased HDL cholesterol levels, and is a risk factor for cardiovascular disease. Dyslipidaemia has a high worldwide prevalence, and many patients are turning to alternatives to pharmacotherapy to manage their lipid levels. Lifestyle modification should be emphasized in all patients to reduce cardiovascular risk and can be initiated before pharmacotherapy in primary prevention of cardiovascular disease. Many functional foods and natural health products have been investigated for potential lipid-lowering properties. Those with good evidence for a biochemical effect on plasma lipid levels include soy protein, green tea, plant sterols, probiotic yogurt, marine-derived omega-3 fatty acids and red yeast rice. Other products such as seaweed, berberine, hawthorn and garlic might confer some limited benefit in certain patient groups. Although none of these products can reduce lipid levels to the same extent as statins, most are safe to use in addition to other lifestyle modifications and pharmacotherapy. Natural health products marketed at individuals with dyslipidaemia, such as policosanol, guggulsterone and resveratrol, have minimal definitive evidence of a biochemical benefit. Additional research is required in this field, which should include large, high-quality randomized controlled trials with long follow-up periods to investigate associations with cardiovascular end points. [ABSTRACT FROM AUTHOR]

Genome-wide association studies (GWAS) have had a tremendous success in the identification of common DNA sequence variants associated with complex human diseases and traits. However, because of their design, GWAS are largely inappropriate to characterize the role of rare and low-frequency DNA variants on human phenotypic variation. Rarer genetic variation is geographically more restricted, supporting the need for local whole-genome sequencing (WGS) efforts to study these variants in specific populations. Here, we present the first large-scale low-pass WGS of the French-Canadian population. Specifically, we sequenced at ~5.6× coverage the whole genome of 1970 French Canadians recruited by the Montreal Heart Institute Biobank and identified 29 million bi-allelic variants (31 % novel), including 19 million variants with a minor allele frequency (MAF) <0.5 %. Genotypes from the WGS data are highly concordant with genotypes obtained by exome array on the same individuals (99.8 %), even when restricting this analysis to rare variants (MAF <0.5, 99.9 %) or heterozygous sites (98.9 %). To further validate our data set, we showed that we can effectively use it to replicate several genetic associations with myocardial infarction risk and blood lipid levels. Furthermore, we analyze the utility of our WGS data set to generate a French-Canadian-specific imputation reference panel and to infer population structure in the Province of Quebec. Our results illustrate the value of low-pass WGS to study the genetics of human diseases in the founder French-Canadian population. [ABSTRACT FROM AUTHOR]

Lipid-lowering medications, particularly statins, have been a popular target for pharmacogenetic studies. A handful of genes have shown promise for predicting response to therapy from the perspective of lipid lowering, as well as myopathy. A number of genes have been implicated and have biological plausibility based on their involvement with the pharmacokinetics or pharmacodynamics of statins or other lipid-lowering medications. The level of confidence and replication of these findings varies, although several associations are likely true. Novel classes of lipid-lowering therapy have opened up new possibilities in the treatment of severe inherited forms of dyslipidemia, making the identification of such mutations an important pharmacogenetic predictor of failure of standard therapy, with potential response to novel therapy. Advances in next-generation sequencing technology bring the application of pharmacogenetics even closer to routine clinical practice. [ABSTRACT FROM AUTHOR]

This Review discusses new developments in understanding the basis of chylomicronaemia--a challenging metabolic disorder for which there is an unmet clinical need. Chylomicronaemia presents in two distinct primary forms. The first form is very rare monogenic early-onset chylomicronaemia, which presents in childhood or adolescence and is often caused by homozygous mutations in the gene encoding lipoprotein lipase (LPL), its cofactors apolipoprotein C-II or apolipoprotein A-V, the LPL chaperone lipase maturation factor 1 or glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1. The second form, polygenic late-onset chylomicronaemia, which is caused by an accumulation of several genetic variants, can be exacerbated by secondary factors, such as poor diet, obesity, alcohol intake and uncontrolled type 1 or type 2 diabetes mellitus, and is more common than early-onset chylomicronaemia. Both forms of chylomicronaemia are associated with an increased risk of life-threatening pancreatitis; the polygenic form might also be associated with an increased risk of cardiovascular disease. Treatment of chylomicronaemia focuses on restriction of dietary fat and control of secondary factors, as available pharmacological therapies are only minimally effective. Emerging therapies that might prove more effective than existing agents include LPL gene therapy, inhibition of microsomal triglyceride transfer protein and diacylglycerol O-acyltransferase 1, and interference with the production and secretion of apoC-III and angiopoietin-like protein 3. [ABSTRACT FROM AUTHOR]

Several next generation sequencing platforms allow for a DNA-to-diagnosis protocol to identify the molecular basis of monogenic dyslipidemias. However, recent reports of the application of whole genome or whole exome sequencing in families with severe dyslipidemias have largely identified genetic variants in known lipid genes. To date, high-throughput DNA sequencing in families with previously uncharacterized monogenic dyslipidemias, have failed to reveal new genes for regulation of plasma lipids. This suggests that rather than sequencing whole genomes or exomes, most patients with monogenic dyslipidemias could be diagnosed using a more dedicated approach that focuses primarily on genes already known to act within lipoprotein metabolic pathways. [ABSTRACT FROM AUTHOR]

Niacin, or water-soluble vitamin B3, when given at pharmacologic doses, is a powerful lipid-altering agent. This drug, which lowers the levels of atherogenic, apolipoprotein-B-containing lipoproteins, is one of few medications that can raise the levels of atheroprotective HDL cholesterol. Niacin also has beneficial effects on other cardiovascular risk factors, including lipoprotein(a), C-reactive protein, platelet-activating factor acetylhydrolase, plasminogen activator inhibitor I and fibrinogen. Many clinical trials have confirmed the lipid effects of niacin treatment; however, its effects on cardiovascular outcomes have been called into question owing to the AIM-HIGH trial, which showed no benefit of niacin therapy on cardiovascular endpoints. Furthermore, use of niacin has historically been limited by tolerability issues. In addition to flushing, worsened hyperglycaemia among patients with diabetes mellitus has also been a concern with niacin therapy. This article reviews the utility of niacin including its mechanism of action, clinical trial data regarding cardiovascular outcomes, adverse effect profile and strategies to address these effects and improve compliance. [ABSTRACT FROM AUTHOR]

Demonstration of a direct relationship between plasma triglyceride (TG) concentration and atherosclerosis has proven difficult due to confounding variables that accompany elevated plasma TG, such as other dyslipidemias, obesity, and type 2 diabetes. However, human genetic studies have provided evidence suggesting a causal link between plasma TG and cardiovascular risk. Analyses in human patients with hypertriglyceridemia (HTG) also provides insight into the relationship between genetic variation, predisposition to elevated plasma TG, and risk of subsequent cardiovascular disease. Here, we review recent key studies that have contributed to our understanding of the genetic determinants of plasma TG concentration, including HTG susceptibility and phenotypic heterogeneity, and discuss our maturing model of the allelic and phenotypic spectrum of plasma TG. [ABSTRACT FROM AUTHOR]

Cholesterol ester transfer protein (CETP) exchanges lipids between circulating plasma lipoproteins and has been considered as an excellent drug target for raising plasma levels of high-density lipoprotein (HDL) cholesterol. However, HDL displays considerably more complexity than low-density lipoprotein (LDL) in terms of structure, proteomics, and several physiologic functions. After the discouraging results from clinical trials of torcetrapib (an early inhibitor of CETP that dramatically raised HDL cholesterol levels), there is renewed hope that dalcetrapib and anacetrapib are sufficiently different structurally and functionally to justify large-scale clinical end point studies. In fact, such trials are already underway in the case of dalcetrapib and are imminent in the case of anacetrapib. These end point trials will show whether CETP inhibition will live up to its promise for atheroprotection. [ABSTRACT FROM AUTHOR]

Here we report that the transcription factor cyclic AMP-responsive element-binding protein H (CREB-H, encoded by CREB3L3) is required for the maintenance of normal plasma triglyceride concentrations. CREB-H-deficient mice showed hypertriglyceridemia secondary to inefficient triglyceride clearance catalyzed by lipoprotein lipase (Lpl), partly due to defective expression of the Lpl coactivators Apoc2, Apoa4 and Apoa5 (encoding apolipoproteins C2, A4 and A5, respectively) and concurrent augmentation of the Lpl inhibitor Apoc3. We identified multiple nonsynonymous mutations in CREB3L3 that produced hypomorphic or nonfunctional CREB-H protein in humans with extreme hypertriglyceridemia, implying a crucial role for CREB-H in human triglyceride metabolism. [ABSTRACT FROM AUTHOR]

Protein kinases are one of the largest families of evolutionarily related proteins and comprise one of the most abundant gene families in humans. Here we survey kinase gene mutations from the perspective of human disease phenotypes and further analyse the structural features of mutant kinases, including mutational hotspots. Our evaluation of the genotype-phenotype relationship across 915 human kinase mutations - that underlie 67 single-gene diseases, mainly inherited developmental and metabolic disorders and also certain cancers - enhances our understanding of the role of kinases in development, kinase dysfunction in pathogenesis and kinases as potential targets for therapy. [ABSTRACT FROM AUTHOR]

Susceptibility to the growing global public health problem of cardiovascular disease is associated with levels of plasma lipids and lipoproteins. Several experimental strategies have helped us to clarify the genetic architecture of these complex traits, including classical studies of monogenic dyslipidaemias, resequencing, phenomic analysis and, more recently, genome-wide association studies and analysis of metabolic networks. The genetic basis of plasma lipoprotein levels can now be modelled as a mosaic of contributions from multiple DNA sequence variants, both rare and common, with varying effect sizes. In addition to filling gaps in our understanding of plasma lipoprotein metabolism, the recent genetic advances will improve our ability to classify, diagnose and treat dyslipidaemias. [ABSTRACT FROM AUTHOR]

Metabolic syndrome (MetS) is a common complex trait consisting of the clustering of abdominal obesity, hypertension, dyslipidemia, and dysglycemia. MetS is found in about 25% of the population in the United States and is associated with increased risk for type 2 diabetes and cardiovascular disease. Despite research into possible genetic influences for MetS, no consistently reproducible genetic markers have been obtained, partially due to lack of agreement on the definition of the phenotype. Because phenotypic precision is essential for genomic interrogation, the evolving discipline of clinical phenomics, which uses objective and systematic acquisition of phenotypic data (ie, “deep phenotyping”), may help evaluate the genetic influences of MetS. This article reviews evidence that MetS has a genetic component and the potential applicability of clinical phenomics for the genetic evaluation of MetS using the example of hierarchical cluster analysis of phenotypic components of lipodystrophy syndromes, which serve as monogenic models of MetS. [ABSTRACT FROM AUTHOR]

Metabolic syndrome (MetS) is a common phenotype, affecting about 24% of the US population. It is associated with an increased risk for type 2 diabetes and cardiovascular disease. Although there is no universally accepted definition for MetS, affected individuals commonly have a cluster of features, including abdominal obesity, hypertension, dyslipidemia, and dysglycemia. Recently, there has been extensive interest in potential genetic contributions to MetS. At present, no single gene or cluster of genes has been consistently replicated for MetS among different populations, likely due to the complex interplay between gene and environment necessary for expression of this phenotype. We review recent studies regarding the genetic contributions to MetS. [ABSTRACT FROM AUTHOR]

The dramatic failure of clinical trials evaluating the cholesterol ester transfer protein inhibitor torcetrapib has led to considerable doubt about the value of raising high-density lipoprotein cholesterol (HDL-C) as a treatment for cardiovascular disease. These results have underscored the intricacy of HDL metabolism, with functional quality perhaps being a more important consideration than the circulating quantity of HDL. As a result, HDL-based therapeutics that maintain or enhance HDL functionality warrant closer investigation. In this article, we review the complexity of HDL metabolism, discuss clinical-trial data for HDL-raising agents, including possible reasons for the failure of torcetrapib, and consider the potential for future HDL-based therapies. [ABSTRACT FROM AUTHOR]

The search for common genetic determinants of plasma lipoproteins began in the early 1980s. Despite some exceptions, these efforts have not yet yielded a set of biological markers that can be used in clinical practice. By contrast, successes in defining the molecular basis of rare single-gene disorders, such as familial hypoalphalipoproteinemia, have shown the value of experimental designs that focus on genomic analysis of individuals within the tails of Gaussian distributions of quantitative lipoprotein traits. For example, this strategy showed that a small but relevant proportion of individuals within the <5% tail of plasma HDL-cholesterol distribution have mutations in genes that cause familial hypoalphalipoproteinemia. The value of clinical testing for genomic variants as an adjunct to a biochemical measurement of plasma lipoproteins, however, is at best questionable. A more direct impact of genetic studies is that definitions of 'common' and 'large genetic effects' have become more tempered, reflecting perhaps the biological reality that plasma lipoproteins are probably determined by the aggregate of numerous modest and occasional large genetic effects in addition to environmental factors. Here, we review recent progress on genomic variants and cholesterol metabolism, and discuss the impact these genetic studies will have on clinical cardiology. [ABSTRACT FROM AUTHOR]

Hutchinson-Gilford progeria syndrome (HGPS; MIM 176670) is a rare disease characterized by accelerated aging. In this study, light and immunofluorescence microscopy were used to assess morphological changes, measures of cell growth kinetics and gene expression profiles in HGPS cells and normal fibroblasts in culture. A filtering strategy was developed based on differentially expressed transcripts seen consistently across three culture stages based on cell passage number. This filtering strategy produced a list of 66 unique differentially expressed genes, of which ∼40% were upregulated in HGPS cells compared to normal fibroblasts. The increased mRNA expression in HGPS cells that was seen for one gene defined using this strategy—namely ANK3— was validated using quantitative reverse-transcriptase amplification, Western analysis and immunofluorescence microscopy, all of which showed significantly increased ankyrin G expression. These findings demonstrate differences in morphology, growth kinetics and mRNA expression profiles in HGPS cells compared to normal fibroblasts in culture, including increased expression of ANK3/ankyrin G. Furthermore, other genes that co-clustered with ANK3 might provide mechanistic clues regarding senescence in cultured HGPS cells. [ABSTRACT FROM AUTHOR]

Cockayne syndrome is a rare autosomal recessive neurodegenerative disorder. It is considered to be a heterogeneous condition based on complementation in cell fusion studies, with two major forms, namely CS-A and CS-B. CKN1 is the gene responsible for CS-A, whose mutations disrupt the transcription-coupled repair system of the actively transcribed DNA. Mutation analysis of the CKN1 gene in eight typical CS-A Brazilian patients from six families showed a gene alteration in all of them. We found a total of five novel mutations that were absent from healthy control subjects. Six affected subjects were simple homozygotes and two affected siblings were each compound heterozygotes. While the findings extend the range of mutations in CS-A, there is no obvious genotype-phenotype correlation across the mutational spectrum. [ABSTRACT FROM AUTHOR]

Atherosclerosis is a complex disease with various intermediate phenotypes that are themselves complex and influenced by many factors. Through the use of carotid ultrasound techniques, the intermediate stages of vascular disease can be imaged and studied for association with potential genetic determinants. In this article we review the most recent available data (reports published since 2004) on the genetic determinants of atherosclerosis, as measured by one-, two-, and three-dimensional ultrasonography of the carotid arteries. In general, associations are disparate and modest. For intima-media thickness, promising associations have been found for both TNFRSFIA R92Q and PPARG P12A, but associations also differed in the same individuals depending on the specific ultrasound trait studied (eg, linear intima-media thickness versus total plaque volume in carotid arteries). Some of the challenging issues for future studies include accounting for gene-environment interactions, sex-specific associations, and the distinctiveness of different carotid ultrasound measures. [ABSTRACT FROM AUTHOR]

We previously determined sequenced the PNLIP gene encoding pancreatic lipase in cell lines of subjects with clinical deficiency of pancreatic lipase (MIM 246600) and found no putative disease-causing mutations. As part of the ongoing analysis of the genomic DNA of these subjects, we now report the development of genomic amplification primers to sequence the coding regions of CLPS, CEL, PLRP1, and PLRP2, encoding pancreatic co-lipase, carboxyl-ester lipase, and pancreatic-lipase-related proteins-1 and -2, respectively. Whereas we found no putative disease-causing missense or nonsense mutations in these samples, we discovered a total of 13 common polymorphisms (12 single nucleotide polymorphisms) in these four genes. Genotypes of these polymorphisms may be useful in future association analyses. [ABSTRACT FROM AUTHOR]

Hutchinson-Gilford progeria syndrome (HGPS; MIM 176670) is an extremely rare disease that is characterized by accelerated aging and early death, frequently from coronary artery disease. Wiedemann-Rautenstrauch syndrome (WRS; MIM 264090) is another extremely rare disease that is characterized by progeroid features from birth with multiple somatic anomalies and paucity of subcutaneous fat. Because mutations in LMNA, encoding nuclear lamin A/C, cause other lipodystrophy syndromes, we sequenced LMNA (MIM 150330) from the genomic DNAs of seven unrelated HGPS probands and two unrelated WRS probands. We found four novel LMNA coding sequence variants among the HGPS probands, namely R471C, R527C, G608S and c.2036C>T. All seven HGPS probands had at least one LMNA variant, which were found in none of the genomes of 100 normal subjects (P<4×10[SUP-11]). In contrast, neither of the WRS proband genomes had any LMNA sequence abnormality. The strong association of rare LMNA coding sequence mutations with HGPS implicates this syndrome as a laminopathy, while WRS is most probably due to mutations in another gene. [ABSTRACT FROM AUTHOR]

Hereditary cystathioninuria (MIM 219500) is presumed to be caused by deficiency of the activity of cystathionine gamma-lyase (cystathionase; CTH EC 4.4.1.1), which is normally required for the conversion of methionine into cysteine. To date, no mutations have been described among patients with cystathioninuria. From genomic DNA, we sequenced CTH in four unrelated probands with cystathioninuria. We found two nonsense mutations, namely exon 8 c.940–941delCT and exon 11 c.1220delC, and two missense mutations, namely exon 2 c.356C>T (T67I) and exon 7 c.874C>G (Q240E). All affected subjects were either simple homozygotes or compound heterozygotes. A common non-synonymous single nucleotide polymorphism in exon 12, namely c.1364G>T (S403I), was also identified and characterized in four ethnic groups. The reagents described in this report make the molecular diagnosis of cystathioninuria possible, allowing for studies of phenotype-genotype correlation. Also, the availability of a common non-synonymous SNP can allow for testing of association of the CTH gene with biochemical traits affected by trans-sulfuration, such as plasma concentrations of homocysteine or even cystathionine itself, in addition to more downstream clinical phenotypes, such as vascular disease. [ABSTRACT FROM AUTHOR]

The incidence of coronary heart disease (CHD) among aboriginal people in northern Ontario has tripled over the past 20 years. This is inextricably linked to the remarkably high prevalence of type 2 diabetes in these native communities. Approximately 40% of the Oji-Cree of northern Ontario have typical obesity-related type 2 diabetes, which represents a drastic increase from virtually unreportable levels 50 years ago. The Oji-Cree have a private mutation in the HNFIA gene, namely G319S, which is absent from other ethnic groups and aboriginal populations. The most compelling reasons that HNFIA S319 is a diabetes-susceptibility allele are its consistent statistical association with the presence and severity of diabetes. Also, HNFIA S319 has specificity and positive predictive values of 97% and 95%, respectively, for the development of diabetes in the Oji-Cree by 50 years of age. This makes the HNFIA G319S genotype the most specific predictive genetic test for diabetes in any human population. HNFIA S319 has all the attributes of a thrifty allele in the Oji-Cree. It is possible that the recent increase in CHD in the aboriginal people of northern Ontario is the result of the expression of diabetes susceptibility due to HNFIA S319 as a consequence of rapid changes in environment and lifestyle. [ABSTRACT FROM AUTHOR]

The common syndrome of insulin resistance is frequently seen in obese individuals, and is characterized by glucose intolerance, dyslipidemia, high blood pressure, and an increased risk of coronary heart disease. A rare genetic form of insulin resistance is Dunnigan-type familial partial lipodystrophy (FPLD; OMIM #151660), which is characterized by loss of subcutaneous fat from extremities, trunk, and gluteal region, and always by insulin resistance and hyperinsulinemia, often with hypertension, dyslipidemia, type-2 diabetes and early endpoints of atherosclerosis. FPLD was recently discovered to result from mutated LMNA (R482Q; OMIM #150330.0010), which is the gene encoding nuclear lamins A and C. Results from extended pedigrees indicate that dyslipidemia precedes the plasma glucose abnormalities in FPLD subjects with mutant LMNA, and that the hyperinsulinemia is present early in the course of the disease. Plasma leptin is also markedly reduced in subjects with FPLD due to mutant LMNA. Thus, rare mutations in a nuclear structural protein can be associated with markedly abnormal qualitative and quantitative phenotypes, indicating that a defect in the structure and function of the nuclear envelope can result in a phenotype that shares many aspects with the common syndrome of insulin resistance. [ABSTRACT FROM AUTHOR]

Antisense oligonucleotides have proven effective at preventing protein synthesis as a result of their on-target specificity. Recent data from several clinical trials including a phase I trial targeting Lp(a), published in The Lancet, highlight the therapeutic potential of antisense oligonucleotides in regulating plasma lipid levels. [ABSTRACT FROM AUTHOR]

Abstract Since adducin modulates cellular sodium retention, its follows that ADD1, which encodes the alpha-subunit of adducin, is an attractive candidate gene for blood pressure variation. Association studies examining the relationship between polymorphism at ADD1 codon 460 (G460W) and both hypertension and blood pressure, which were performed in a variety of human population samples derived from different genetic backgrounds, have given inconsistent results. We examined the association between the ADD1 G460W polymorphism and variation in blood pressure in a sample of non-diabetic, largely normotensive Canadian Oji-Cree from an isolated community in Northern Ontario. Among 481 Oji-Cree subjects, we measured blood pressure and related clinical phenotypes and determined genotypes of ADD1 G460W. We observed an allele frequency of 0.08 for the ADD1 W460 variant, which is among the lowest so far observed in human populations. We found significant associations between variation in both systolic and diastolic blood pressure and gender, age, body mass index (BMI), and treatment for hypertension. However, we found no association between the ADD1 W460 allele and increased blood pressure, nor did we observe a higher frequency of the W460 allele in a hypertensive subgroup compared with normotensive subjects. While the low sample frequency of ADD1 W460 is consistent with the low sample prevalence of hypertension, the absence of a specific association with both blood pressure and hypertension suggests that the ADD1 W460 variant is not an important determinant of blood pressure among individuals of this genetic background. [ABSTRACT FROM AUTHOR]

Although retrospective case-control studies continue to indicate that plasma lipoprotein(a) [Lp(a)] concentrations are associated with coronary heart disease (CHD), several large population-based prospective studies have failed to confirm that Lp(a) is an independent risk factor. However, evidence exists from several studies to suggest that elevated plasma Lp(a) increases the CHD risk associated with more traditional risk factors. Although identification of the functional role of Lp(a) in atherogenesis has been thwarted by the physical, chemical, and genetic complexity of Lp(a), the structural similarity of Lp(a) to both the fibrinolytic proenzyme plasminogen and low-density lipoprotein (LDL) has suggested a prothrombotic or atherogenic role (or both) for this lipoprotein. Because the clinical determination and application of plasma Lp(a) concentration poses several challenges, we cannot recommend its routine measurement at this time. Rather, plasma Lp(a) determinations should be limited to either patients at high risk for the development of CHD or patients at borderline risk for the development of CHD in whom uncertainty may exist about how aggressively to treat modifiable risk factors such as elevated LDL cholesterol. [ABSTRACT FROM AUTHOR]

The importance of environment and genetics working together to shape an individual's risk for atherosclerosis seems intuitively obvious. However, it is only recently that research strategies have begun to evolve that attempt to answer questions related to apportionment of risk that is due to specific environmental and genetic factors. These factors may impact upon risk either singly or, more likely, through a complex interaction that affects the metabolic history of the whole organism. Because the genetic bases of lipid and lipoprotein metabolism have been well-studied, and because of the epidemiologic and pathobiochemical associations between genetic disorders of lipid metabolism and atherosclerosis, researchers have searched for gene-environment interactions within animal and human systems in which the phenotype is defined by some index of lipoprotein metabolism. From work done in the lipoprotein area to this point a clear case can be made for: 1) the genetic influence over the phenotypic response to an environmental stimulus; 2) the environmental modulation of the phenotypic expression of severe genetic defects. In the realm of gene-environment interactions that affect lipoprotein phenotype, diet is the best-studied environmental factor. [ABSTRACT FROM AUTHOR]

The article offers information on Abetalipoproteinaemia or Bassen Kornzweig syndrome and its clinical utility. It says that Abetalipoproteinaemia is clinically distinguished by the lack of apolipoprotein (apo) B-containing lipoproteins with systemic manifestations. It mentions that the specificity of the disease rely on the age or family history. Moreover, it can be determined by prenatal, differential diagnostics, and predictive testing.

The article focuses on Familial hypobetalipoproteinaemia (APOB) disease, which is distinguished by the low level of plasma apoB-containing lipoproteins. It says that the common causes of hypobetalipoproteinaemia are illness, high-does statin therapy, and strict vegan diet. It also mentions that one among the 3000 births is estimated to possess apoB truncations. Moreover, the disease can be diagnosed by predictive testing, differential diagnostics, and prenatal check.

This article sets out the clinical context of the research presented by Samaha et al. in an accompanying article in this issue. Hyperlipidemia is a common and important risk factor for cardiovascular disease. Current lipid-lowering therapies, particularly statins, lead to substantial decreases in cardiovascular disease morbidity and mortality, but use has been limited by safety or efficacy issues. The way has, therefore, been paved for the pharmaceutical development and clinical investigation of new lipid-lowering therapies. The clinical trial by Samaha et al. examines the safety and efficacy of microsomal triglyceride transfer protein inhibition for lowering lipids. Joy and Hegele explore the difficulties of translating microsomal triglyceride transfer protein inhibition into clinical practice because of the trade-off between efficacy and potential adverse effects. They also stress the need for outcome studies, rather than biochemical or surrogate studies, as the final arbiter for the clinical use of this new treatment. [ABSTRACT FROM AUTHOR]

We found that a subject with Cockayne syndrome type A was a compound heterozygote for two new mutations in CKN1 (MIM 216400): a missense mutation (A205P) and a nonsense (E13X) mutation. We also identified and characterized a new common single nucleotide polymorphism in CKN1 in five groups. [ABSTRACT FROM AUTHOR]

Type 2 diabetes mellitus is a complex phenotype that is frequently associated with central obesity and insulin resistance. Recently, a protein named resistin, encoded by RSTN (OMIM #605565), was identified in adipose tissue. Serum resistin was elevated in obese and diabetic mice, and administration of resistin to normal mice was found to interfere with glucose tolerance and insulin action. Because of these functions, resistin is a candidate gene for diabetes and obesity. Through the use of DNA sequencing, we thus developed amplification primers for rapid screening of the RSTN gene that encodes resistin. No putative mutations were found, but two noncoding single-nucleotide polymorphisms (SNPs) were identified, and these were found to vary in frequency across various ethnic groups. The identification of amplification primers and SNPs provides tools to investigate resistin for association with other phenotypes. [ABSTRACT FROM AUTHOR]