Genetics of familial combined hyperlipidemia

Patient experiences in receiving telegenetics care for inherited cardiovascular diseases

Telegenetics played an important role in providing genetic services to patients during the COVID-19 pandemic. In particular, at our institution, it enabled us to expand our genetic counseling and testing services to non-local family members of patients outside of our prior catchment area. However, as telegenetics continues to be utilized even as social distancing is no longer required, further information is needed regarding the impact of this modality on patient experience within cardiogenetics. This study qualitatively explored the experiences of 12 genotype positive individuals who underwent genetic counseling and testing via telegenetics during the first 22 months of the COVID-19 pandemic and compared the experiences of local vs. non-local patients. Both local and non-local participants discussed similar benefits and drawbacks to the use of technology in telegenetics and overall found the use of telegenetics and at-home genetic testing to be convenient. Both groups also noted having to make changes in their daily lives and future planning as a consequence of the positive genetic testing results. However, access to follow-up care differed between local and non-local participants, with more local participants having scheduled and attended appointments with the appropriate medical providers compared to non-local participants. Supplying non-local patients access to remote cardiogenetic testing may therefore require careful consideration in how to ensure proper follow-up care for genotype positive patients and may necessitate the involvement of national professional or patient-centered organizations to help streamline the referral process.

Performance of the enhanced Sampson-NIH equation for VLDL-C and LDL-C in a population with familial combined hyperlipidemia

INTRODUCTION

Low-density cholesterol (LDL-C) has long been estimated by the Friedewald formula (F-LDL-C); however, this method underestimates LDL-C in patients with hypertriglyceridemia (HTG) or low LDL-C levels. The Martin (M-LDL-C) and Sampson (S-LDL-C) formulas partially resolve these limitations. Recently, Sampson et al. developed a new equation (eS-VLDL-C) that includes ApoB. This new equation could be particularly useful in FCHL, which is characterized by the predominance of triglyceride-rich VLDL and a discordance between LDL-C and ApoB.

METHODS

Very low-density lipoproteins (VLDL-C) was measured in 336 patients with FCHL by sequential ultracentrifugation. LDL-C was estimated by subtracting VLDL-C, estimated by the different equations, from non-HDL cholesterol. Spearman correlations, R2, mean squared error (RMSE), and bias were used to compare the accuracy of the different equations. Concordance of the estimated LDL-C values with LDL-C thresholds and ApoB was also assessed by their kappa coefficients and ROC analysis.

RESULTS

Overall population had a mean age of 47 years, and 61.5% were women. 19.5% had type 2 diabetes, hypertension was present in 20.8%, and only 12.2% were on statin treatment. Both S-LDL-C and eS-LDL-C performed similarly, and better than M-LDL-C and F-LDL-C. In Bland-Altman analysis, eS-LDL-C showed the lowest bias, better performance in HTG, and better concordance with LDL-C treatment goals compared to other formulas (e.g. ρ: 0.87, 95% CI 0.84-0.89).

CONCLUSIONS

LDL-S and LDL-eS equations estimate the concentration of LDL-C with greater accuracy than other formulas. The LDL-eS has best performance in estimating LDL-C with lower RMSE than other formulas.

Network Pharmacological Analysis of a New Herbal Combination Targeting Hyperlipidemia and Efficacy Validation In Vitro

The network pharmacology (NP) approach is a valuable novel methodology for understanding the complex pharmacological mechanisms of medicinal herbs. In addition, various in silico analysis techniques combined with the NP can improve the understanding of various issues used in natural product research. This study assessed the therapeutic effects of Arum ternata (AT), Poria cocos (PC), and Zingiber officinale (ZO) on hyperlipidemia after network pharmacologic analysis. A protein-protein interaction (PPI) network of forty-one key targets was analyzed to discover core functional clusters of the herbal compounds. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway and gene ontology (GO) term enrichment analysis identified significant categories of hypolipidemic mechanisms. The STITCH database indicated a high connection with several statin drugs, deduced by the similarity in targets. AT, PC, and ZO regulated the genes related to the energy metabolism and lipogenesis in HepG2 cells loaded with free fatty acids (FFAs). Furthermore, the mixture of three herbs had a combinational effect. The herbal combination exerted superior efficacy compared to a single herb, particularly in regulating acetyl-CoA carboxylase (ACC) and carnitine palmitoyltransferase 1 (CPT-1). In conclusion, the network pharmacologic approach was used to assess potential targets of the herbal combination for treatment. Experimental data from FFA-induced HepG2 cells suggested that the combination of AT, PC, and ZO might attenuate hyperlipidemia and its associated hepatic steatosis.

The use of telemedicine in cardiogenetics clinical practice during the COVID-19 pandemic

Background

The COVID‐19 pandemic has necessitated the rapid and widespread adoption of novel mechanisms of service delivery, including the use of telemedicine. The aim of this study was to examine the impact of COVID‐19 on cardiogenetics practices.

Methods

We retrospectively analyzed the clinical characteristics of patients who were seen for cardiogenetics visits pre‐pandemic (1 April–23 December 2019) and during the pandemic (1 April–23 December 2020) at Columbia University Irving Medical Center.

Results

Six percent (n = 6) of visits in 2019 were remote telemedicine encounters, whereas 80% (n = 106) of visits in 2020 were telemedicine encounters. In 2019, only 18% (n = 19) of the patients seen for genetic counseling were family members of probands; this percentage increased to 34% in 2020 (n = 45; p = .01). In 2020, the geographic reach of genetic counseling also extended far beyond New York State, reaching a total of 11 states as well as one patient in Puerto Rico. Genetic testing results were similar in 2019 and 2020.

Conclusion

Despite the health‐care delivery barriers created by the COVID‐19 pandemic, the use of telemedicine allowed us to expand the reach of cardiovascular genetic counseling and testing.

Familial combined hyperlipidemia is a polygenic trait

PURPOSE OF REVIEW

: Familial combined hyperlipidemia (FCH), defined by concurrently elevated plasma triglyceride (TG) and low-density lipoprotein (LDL) cholesterol, has long been investigated to characterize its genetic basis. Despite almost half a century of searching, a single gene cause for the phenotype has not yet been identified.

RECENT FINDINGS

: Recent studies using next-generation genetic analytic methods confirm that FCH has a polygenic basis, with a clear large contribution from the accumulation of small-to-moderate effect common single nucleotide polymorphisms (SNPs) throughout the genome that is associated with raising TG, and probably also those raising LDL cholesterol. On the other hand, rare monogenic variants, such as those causing familial hypercholesterolemia, play a negligible role, if any. Genetic profiling suggests that patients with FCH and hypertriglyceridemia share a strong polygenic basis and show a similar profile of multiple TG-raising common SNPs.

SUMMARY

: Recent progress in genomics has shown that most if not all of the genetic susceptibility to FCH is polygenic in nature. Future research should include larger cohort studies, with wider ancestral diversity, ancestry-specific polygenic scores, and investigation of epigenetic and lifestyle factors to help further elucidate the causative agents at play in cases where the genetic etiology remains to be defined.

Genetics of Familial Combined Hyperlipidemia (FCHL) Disorder: An Update

Familial combined hyperlipidemia (FCHL) is one of the most common familial lipoprotein disorders of the lipoproteins, with a prevalence of 0.5% to 2% in different populations. About 10% of these patients suffer from cardiovascular disease and this number is increased by up to 11.3% in the young survivors of myocardial infarction and by 40% among all the survivors of myocardial infarction. Although initially thought to be that FCHL has an inheritance pattern of monogenic, the disease's etiology is still not fully understood and it appears that FCHL has a complex pattern related to genetic variants, environmental factors, and lifestyles. Two strategies have been used to identify its complex genetic background: candidate gene and the linkage approach, which have yielded an extensive list of genes associated with FCHL with a variable degree of scientific evidence. Until now, more than 30 different genetic variants have been identified related to FCHL. In this study, we aimed to review the individual genes that have been described in FCHL and how these genes and variants can be related to the current concept of metabolic pathways resulting in familial combined hyperlipidemia.

A novel variant in LPL gene is associated with familial combined hyperlipidemia

Familial combined hyperlipidemia (FCHL) is a common genetic disorder characterized by increased fasted serum cholesterol, triglycerides, and apolipoprotein B-100. Molecular genetic techniques such as next generation sequencing have been very successful methods for rare variants finding with a moderate-to large effect. In this study, we characterized a large pedigree from MASHAD study in northeast Iran with coinheritance of FCHL and early-onset coronary heart disease. In this family, we used whole-exome sequencing and Sanger sequencing to determine the disease-associated gene. We identified a novel variant in the LPL gene, leading to a substitution of an asparagine for aspartic acid at position 151. The D151N substitution cosegregated with these characters in all affected family members in the pedigree but it was absent in all unaffected members in this family. We speculated that the mutation D151N in LPL gene might be associated with FCHL and early-onset coronary heart disease in this family. However, the substantial mechanism requires further investigation.

Familial combined hyperlipidemia: An overview of the underlying molecular mechanisms and therapeutic strategies

Among different types of dyslipidemia, familial combined hyperlipidemia (FCHL) is the most common genetic disorder, which is characterized by at least two different forms of lipid abnormalities: hypercholesterolemia and hypertriglyceridemia. FCHL is an important cause of cardiovascular diseases. FCHL is a heterogeneous condition linked with some metabolic defects that are closely associated with FCHL. These metabolic features include dysfunctional adipose tissue, delayed clearance of triglyceride-rich lipoproteins, overproduction of very low-density lipoprotein and hepatic lipids, and defect in the clearance of low-density lipoprotein particles. There are also some genes associated with FCHL such as those affecting the metabolism and clearance of plasma lipoprotein particles. Due to the high prevalence of FCHL especially in cardiovascular patients, targeted treatment is ideal but this necessitates identification of the genetic background of patients. This review describes the metabolic pathways and associated genes that are implicated in FCHL pathogenesis. We also review existing and novel treatment options for FCHL. © 2019 IUBMB Life, 71(9):1221-1229, 2019.

The Regulation of Cbf1 by PAS Kinase Is a Pivotal Control Point for Lipogenesis vs. Respiration in Saccharomyces cerevisiae

PAS kinase 1 (Psk1) is a key regulator of respiration in Saccharomyces cerevisiae. Herein the molecular mechanisms of this regulation are explored through the characterization of its substrate, Centromere binding factor 1 (Cbf1). CBF1-deficient yeast displayed a significant decrease in cellular respiration, while PAS kinase-deficient yeast, or yeast harboring a Cbf1 phosphosite mutant (T211A) displayed a significant increase. Transmission electron micrographs showed an increased number of mitochondria in PAS kinase-deficient yeast consistent with the increase in respiration. Although the CBF1-deficient yeast did not appear to have an altered number of mitochondria, a mitochondrial proteomics study revealed significant differences in the mitochondrial composition of CBF1-deficient yeast including altered Atp3 levels, a subunit of the mitochondrial F₁-ATP synthase complex. Both beta-galactosidase reporter assays and western blot analysis confirmed direct transcriptional control of ATP3 by Cbf1. In addition, we confirmed the regulation of yeast lipid genes LAC1 and LAG1 by Cbf1. The human homolog of Cbf1, Upstream transcription factor 1 (USF1), is also known to be involved in lipid biogenesis. Herein, we provide the first evidence for a role of USF1 in respiration since it appeared to complement Cbf1in vivo as determined by respiration phenotypes. In addition, we confirmed USF1 as a substrate of human PAS kinase (hPASK) in vitro. Combined, our data supports a model in which Cbf1/USF1 functions to partition glucose toward respiration and away from lipid biogenesis, while PAS kinase inhibits respiration in part through the inhibition of Cbf1/USF1.

Per-Arnt-Sim Kinase (PASK) Deficiency Increases Cellular Respiration on a Standard Diet and Decreases Liver Triglyceride Accumulation on a Western High-Fat High-Sugar Diet

Diabetes and the related disease metabolic syndrome are epidemic in the United States, in part due to a shift in diet and decrease in physical exercise. PAS kinase is a sensory protein kinase associated with many of the phenotypes of these diseases, including hepatic triglyceride accumulation and metabolic dysregulation in male mice placed on a high-fat diet. Herein we provide the first characterization of the effects of western diet (high-fat high-sugar, HFHS) on Per-Arnt-Sim kinase mice (PASK^−/−) and the first characterization of both male and female PASK^−/− mice. Soleus muscle from the PASK^−/− male mice displayed a 2-fold higher oxidative phosphorylation capacity than wild type (WT) on the normal chow diet. PASK^−/− male mice were also resistant to hepatic triglyceride accumulation on the HFHS diet, displaying a 2.7-fold reduction in hepatic triglycerides compared to WT mice on the HFHS diet. These effects on male hepatic triglyceride were further explored through mass spectrometry-based lipidomics. The absence of PAS kinase was found to affect many of the 44 triglycerides analyzed, preventing hepatic triglyceride accumulation in response to the HFHS diet. In contrast, the female mice showed resistance to hepatic triglyceride accumulation on the HFHS diet regardless of genotype, suggesting the effects of PAS kinase may be masked.

Combined hyperlipidemia: familial but not (usually) monogenic

PURPOSE OF REVIEW

Combined hyperlipidemia (CHL) is a complex phenotype that is commonly encountered clinically and is often associated with the expression of early heart disease. The affixed adjective 'familial' gives the impression that the trait is monogenic, like familial hypercholesterolemia. But despite significant efforts, genetic studies have yielded little evidence of single gene determinants of CHL.

RECENT FINDINGS

Sophisticated linkage studies suggest that individual lipid components of the CHL phenotype - such as elevated LDL and triglyceride - each have several determinants that segregate independently in families. Furthermore, DNA sequencing shows that rare large-effect variants in genes such as LDL receptor (LDLR) and lipoprotein lipase are found in some CHL patients, explaining the elevated LDL cholesterol and triglyceride components, respectively. In addition, multiple common small-effect lipid-altering variants accumulate in an individual's genome, raising the LDL cholesterol and/or triglyceride components by multiple mechanisms. Finally, secondary factors, such as poor diet, obesity,fatty liver or diabetes further modulate the expression of the biochemically defined CHL phenotype.

SUMMARY

Given the current state of genetic understanding, CHL may be best conceptualized as a syndrome with common clinical presentation but multigenic causes, similar to other common conditions such as type 2 diabetes.

Association of Apolipoprotein A5 Gene Polymorphisms with Metabolic Syndrome in the Korean Population

AIMS

Functional defects of the ApoA5 protein have been identified as risk factors for hypertriglyceridemia, vascular diseases and susceptibility to metabolic syndrome (MetS). These associations are neither strong nor consistent in all populations studied. In this study, we investigated the association between the ApoA5 -1131T>C and -12,238T>C polymorphic loci in Korean patients with MetS.

METHODS

A total of 1074 subjects, including 415 patients with MetS and 659 healthy control subjects, were enrolled to investigate the affect of ApoA5 polymorphisms on risk of MetS. Genotyping of the ApoA5 polymorphisms was performed by polymerase chain reaction-restriction fragment length polymorphism techniques.

RESULTS

The CC genotype and the dominant (TT vs. TC+CC) and recessive (TT+TC vs. CC) models of the -1131T>C polymorphism were associated with increased MetS susceptibility (p < 0.001, p = 0.018, and p = 0.002, respectively). The association was male-specific when stratified by gender. With regard to the -12,238T>C polymorphism, the TC and CC genotypes and the dominant (TT vs. TC+CC) and recessive (TT+TC vs. CC) models were frequently found in the patient group, compared with the control group (p = 0.001, p < 0.001, p < 0.001, and p = 0.031, respectively). The T-C, C-T, and C-C haplotypes of the ApoA5 -1131T>C and -12,238T>C polymorphisms were associated with an increased risk for MetS (p < 0.001, p = 0.001, and p < 0.001, respectively). The variant of the ApoA5 -1131T>C polymorphism was also associated with increased triglyceride (TG) levels. Dominant models of ApoA5 -1131T>C and -12,238T>C polymorphisms were associated with the risk components of MetS by the stratification analysis.

CONCLUSION

The -1131C and -12,238C variants and the C-containing haplotypes of ApoA5 -1131T>C and -12,238T>C polymorphisms were associated with higher risk for MetS in the Korean population. The -1131C variant was also associated with the increased level of TG.

Recent advances in pharmacotherapy for hypertriglyceridemia

Elevated plasma triglyceride (TG) concentrations are associated with an increased risk of atherosclerotic cardiovascular disease (CVD), hepatic steatosis and pancreatitis. Existing pharmacotherapies, such as fibrates, n-3 polyunsaturated fatty acids (PUFAs) and niacin, are partially efficacious in correcting elevated plasma TG. However, several new TG-lowering agents are in development that can regulate the transport of triglyceride-rich lipoproteins (TRLs) by modulating key enzymes, receptors or ligands involved in their metabolism. Balanced dual peroxisome proliferator-activated receptor (PPAR) α/γ agonists, inhibitors of microsomal triglyceride transfer protein (MTTP) and acyl-CoA:diacylglycerol acyltransferase-1 (DGAT-1), incretin mimetics, and apolipoprotein (apo) B-targeted antisense oligonucleotides (ASOs) can all decrease the production and secretion of TRLs; inhibitors of cholesteryl ester transfer protein (CETP) and angiopoietin-like proteins (ANGPTLs) 3 and 4, monoclonal antibodies (Mabs) against proprotein convertase subtilisin/kexin type 9 (PCSK9), apoC-III-targeted ASOs, selective peroxisome proliferator-activated receptor modulators (SPPARMs), and lipoprotein lipase (LPL) gene replacement therapy (alipogene tiparvovec) enhance the catabolism and clearance of TRLs; dual PPAR-α/δ agonists and n-3 polyunsaturated fatty acids can lower plasma TG by regulating both TRL secretion and catabolism. Varying degrees of TG reduction have been reported with the use of these therapies, and for some agents such as CETP inhibitors and PCSK9 Mabs findings have not been consistent. Whether they reduce CVD events has not been established. Trials investigating the effect of CETP inhibitors (anacetrapib and evacetrapib) and PCSK9 Mabs (AMG-145 and REGN727/SAR236553) on CVD outcomes are currently in progress, although these agents also regulate LDL metabolism and, in the case of CETP inhibitors, HDL metabolism. Further to CVD risk reduction, these new treatments might also have a potential role in the management of diabetes and non-alcoholic fatty liver disease owing to their insulin-sensitizing action (PPAR-α/γ agonists) and potential capacity to decrease hepatic TG accumulation (PPAR-α/δ agonists and DGAT-1 inhibitors), but this needs to be tested in future trials. We summarize the clinical trial findings regarding the efficacy and safety of these novel therapies for hypertriglyceridemia.

A comprehensive protein-protein interactome for yeast PAS kinase 1 reveals direct inhibition of respiration through the phosphorylation of Cbf1

PAS kinase is a conserved sensory protein kinase required for glucose homeostasis. The interactome for yeast PAS kinase 1 (Psk1) is identified, revealing 93 binding partners. Evidence is provided for in vivo phosphorylation of Cbf1 and subsequent inhibition of respiration, supporting a role for Psk1 in partitioning glucose for cell growth.

Per-Arnt-Sim (PAS) kinase is a sensory protein kinase required for glucose homeostasis in yeast, mice, and humans, yet little is known about the molecular mechanisms of its function. Using both yeast two-hybrid and copurification approaches, we identified the protein–protein interactome for yeast PAS kinase 1 (Psk1), revealing 93 novel putative protein binding partners. Several of the Psk1 binding partners expand the role of PAS kinase in glucose homeostasis, including new pathways involved in mitochondrial metabolism. In addition, the interactome suggests novel roles for PAS kinase in cell growth (gene/protein expression, replication/cell division, and protein modification and degradation), vacuole function, and stress tolerance. In vitro kinase studies using a subset of 25 of these binding partners identified Mot3, Zds1, Utr1, and Cbf1 as substrates. Further evidence is provided for the in vivo phosphorylation of Cbf1 at T211/T212 and for the subsequent inhibition of respiration. This respiratory role of PAS kinase is consistent with the reported hypermetabolism of PAS kinase–deficient mice, identifying a possible molecular mechanism and solidifying the evolutionary importance of PAS kinase in the regulation of glucose homeostasis.

Potential Role of Upstream Stimulatory Factor 1 Gene Variant in Familial Combined Hyperlipidemia and Related Disorders

Objective—

Genetic studies implicated upstream stimulatory factor 1 (USF1) in familial combined hyperlipidemia because the rs2073658 minor allele was associated with reduced risk of familial combined hyperlipidemia and related disorders. The molecular mechanisms whereby rs2073658 influences trait expression have remained elusive.

Methods and Results—

Plasma lipids, rs2073658 genotypes (N=372), and hepatic transcript levels (N=96) of USF1 and genes involved in hepatic lipoprotein production were determined in obese subjects. The rs2073658 minor allele was associated with reduced plasma triglycerides (TGs) ( P <0.001), hepatic USF1 ( P <0.01), and microsomal TG transfer protein transcript levels ( P <0.05). Functional studies in human hepatocellular carcinoma cells showed that rs2073658 is located in a forkhead box A2 (FOXA2) binding site and that major allele constructs displayed higher transcriptional activity than minor allele constructs. Knockdown of FOXA2 reduced the activity of major, but not minor allele constructs. Furthermore, an interaction between hepatic FOXA2 transcript levels and rs2073658 minor allele carrier status on hepatic USF1 transcript levels was observed in vivo ( P <0.05). USF1 activated the transcription of FOXA2 and FOXA2 strongly activated the transcription of microsomal TG transfer protein.

Conclusion—

A feed-forward loop comprising activation of USF1 transcription by FOXA2 and activation of FOXA2 transcription by USF1 , driving microsomal TG transfer protein expression, is modulated by rs2073658. Hence, rs2073658 likely influences hepatic TG secretion.

Low-density lipoprotein cholesterol, apolipoprotein B, and risk of coronary heart disease: from familial hyperlipidemia to genomics

Coronary heart disease (CHD) affects 17 million people in the United States and accounts for over a million hospital stays each year. Technological advances, especially in genetics and genomics, have changed our understanding of the risk factors for developing CHD. The purpose of this article is to review low-density lipoprotein cholesterol (LDL-C), apolipoprotein B (apo B), and risk of CHD. The article focuses on five topics: (1) a description of lipoprotein classes, normal lipoprotein metabolism, and the biological mechanism of atherosclerosis; (2) a review of selected epidemiologic and clinical trial studies examining the associations between elevated LDL-C and apo B with CHD; (3) a brief review of the familial forms of hyperlipidemia; (4) a description of variants in genes that have been associated with higher LDL-C levels in candidate gene studies and genome-wide association studies (GWAS); and (5) nursing implications, including a discussion on how genetic tests are evaluated and the current clinical utility and validity of genetic tests for CHD.

Genetic determinants of plasma triglycerides

Plasma triglyceride (TG) concentration is reemerging as an important cardiovascular disease risk factor. More complete understanding of the genes and variants that modulate plasma TG should enable development of markers for risk prediction, diagnosis, prognosis, and response to therapies and might help specify new directions for therapeutic interventions. Recent genome-wide association studies (GWAS) have identified both known and novel loci associated with plasma TG concentration. However, genetic variation at these loci explains only ∼10% of overall TG variation within the population. As the GWAS approach may be reaching its limit for discovering genetic determinants of TG, alternative genetic strategies, such as rare variant sequencing studies and evaluation of animal models, may provide complementary information to flesh out knowledge of clinically and biologically important pathways in TG metabolism. Herein, we review genes recently implicated in TG metabolism and describe how some of these genes likely modulate plasma TG concentration. We also discuss lessons regarding plasma TG metabolism learned from various genomic and genetic experimental approaches. Treatment of patients with moderate to severe hypertriglyceridemia with existing therapies is often challenging; thus, gene products and pathways found in recent genetic research studies provide hope for development of more effective clinical strategies.

Familial combined hyperlipidemia is associated with alterations in the cholesterol synthesis pathway

OBJECTIVE

Familial combined hyperlipidemia (FCH) is a common familial lipid disorder characterized by increases in plasma total cholesterol, triglyceride, and apolipoprotein B-100 levels. In light of prior metabolic and genetic research, our purpose was to ascertain whether FCH cases had significant abnormalities of plasma markers of cholesterol synthesis and absorption as compared to unaffected kindred members.

METHODS AND RESULTS

Plasma levels of squalene, desmosterol, and lathosterol (cholesterol synthesis markers) and campesterol, sitosterol, and cholestanol (cholesterol absorption markers) were measured by gas-liquid chromatography in 103 FCH patients and 240 normolipidemic relatives (NLR). Squalene, desmosterol, and lathosterol levels were 6% (0.078), 31%, (P<0.001) and 51% (P<0.001) higher in FCH as compared to NLR, and these differences were especially pronounced in women. An interaction with obesity was also noted for a subset of these markers. We did not observe any apparent differences for the cholesterol absorption markers among FCH patients and NLR.

CONCLUSIONS

Our data indicate that both men and women with FCH have alterations in the cholesterol synthesis pathway, resulting in 51% higher levels of lathosterol (and additionally desmosterol in women). Plasma levels of the cholesterol precursor sterol squalene were only slightly increased (6%), suggesting enhanced conversion of squalene to lathosterol in this disorder.

Gene-gene interaction between APOA5 and USF1: two candidate genes for the metabolic syndrome

OBJECTIVE

The metabolic syndrome, a major cluster of risk factors for cardiovascular diseases, shows increasing prevalence worldwide. Several studies have established associations of both apolipoprotein A5 (APOA5) gene variants and upstream stimulatory factor 1 (USF1) gene variants with blood lipid levels and metabolic syndrome. USF1 is a transcription factor for APOA5.

METHODS

We investigated a possible interaction between these two genes on the risk for the metabolic syndrome, using data from the German population-based KORA survey 4 (1,622 men and women aged 55-74 years). Seven APOA5 single nucleotide polymorphisms (SNPs) were analyzed in combination with six USF1 SNPs, applying logistic regression in an additive model adjusting for age and sex and the definition for metabolic syndrome from the National Cholesterol Education Program's Adult Treatment Panel III (NCEP (AIII)) including medication.

RESULTS

The overall prevalence for metabolic syndrome was 41%. Two SNP combinations showed a nominal gene-gene interaction (p values 0.024 and 0.047). The effect of one SNP was modified by the other SNP, with a lower risk for the metabolic syndrome with odds ratios (ORs) between 0.33 (95% CI = 0.13-0.83) and 0.40 (95% CI = 0.15-1.12) when the other SNP was homozygous for the minor allele. Nevertheless, none of the associations remained significant after correction for multiple testing.

CONCLUSION

Thus, there is an indication of an interaction between APOA5 and USF1 on the risk for metabolic syndrome.

Association of common variants in the Joubert syndrome gene (AHI1) with autism

It has been suggested that autism, like other complex genetic disorders, may benefit from the study of rare or Mendelian variants associated with syndromic or non-syndromic forms of the disease. However, there are few examples in which common variation in genes causing a Mendelian neuropsychiatric disorder has been shown to contribute to disease susceptibility in an allied common condition. Joubert syndrome (JS) is a rare recessively inherited disorder, with mutations reported at several loci including the gene Abelson's Helper Integration 1 (AHI1). A significant proportion of patients with JS, in some studies up to 40%, have been diagnosed with autism spectrum disorder (ASD) and several linkage studies in ASD have nominally implicated the region on 6q where AHI1 resides. To evaluate AHI1 in ASD, we performed a three-stage analysis of AHI1 as an a priori candidate gene for autism. Re-sequencing was first used to screen AHI1, followed by two subsequent association studies, one limited and one covering the gene more completely, in Autism Genetic Resource Exchange (AGRE) families. In stage 3, we found evidence of an associated haplotype in AHI1 with ASD after correction for multiple comparisons, in a region of the gene that had been previously associated with schizophrenia. These data suggest a role for AHI1 in common disorders affecting human cognition and behavior.

Genetics of ischaemic stroke

Ischaemic stroke is a heterogeneous multifactorial disorder. Epidemiological data provide substantial evidence for a genetic component to the disease, but the extent of predisposition is unknown. Large progress has been made in single-gene disorders associated with ischaemic stroke. The identification of NOTCH3 mutations in patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL) has led to new insights on lacunar stroke and small-vessel disease. Studies of sickle-cell disease have drawn attention to the importance of modifier genes and of gene-gene interactions in determining stroke risk. They have further highlighted a potential role of genetics in predicting stroke risk. Little is known about the genes associated with complex multifactorial stroke. There are probably many alleles with small effect sizes. Genetic-association studies on a wide range of candidate pathways, such as the haemostatic and inflammatory system, homocysteine metabolism, and the renin-angiotensin aldosterone system, suggest a weak but significant effect for several at-risk alleles. Genome-wide linkage studies in extended pedigrees from Iceland led to the identification of PDE4D and ALOX5AP. Specific haplotypes in these genes have been shown to confer risk for ischaemic stroke in the Icelandic population, but their role in other populations is unclear. Advances in high-throughput genotyping and biostatistics have enabled new study designs, including genome-wide association studies. Their application to ischaemic stroke requires the collaborative efforts of multiple centres. This approach will contribute to the identification of additional genes, novel pathways, and eventually novel therapeutic approaches to ischaemic stroke.

APOA5 variants and metabolic syndrome in Caucasians

Apolipoprotein A5 (APOA5) gene variants were reported to be associated with two components of metabolic syndrome (MetS): higher TG levels and lower HDL levels. Moreover, a recent Japanese case-control study found variant -1131T>C associated with MetS itself. Thus, our study systematically analyzed the APOA5 gene for association with lipid parameters, any other features of MetS, including waist circumference, glucose-related parameters, blood pressure, uric acid, and MetS itself in Caucasians. Ten polymorphisms were analyzed in a large fasting sample of the population-based Cooperative Health Research in the Region of Augsburg (KORA) survey S4 (n = 1,354; southern Germany) and in a second fasting sample, the Salzburg Atherosclerosis Prevention Program in Subjects at High Individual Risk (SAPHIR) study (n = 1,770; Austria). Minor alleles of variants -1131T>C, -3A>G, c.56C>G, 476G>A, and 1259T>C were significantly associated with higher TG levels in single polymorphism (P < 0.001) and haplotype (P <or= 6.6 x 10(-6)) analysis. Besides associations with lower HDL levels in SAPHIR (P <or= 0.001), there were no significant findings with any other features of MetS. Variant c.56C>G was associated with higher risk for MetS [odds ratio (95% confidence interval) = 1.43 (1.04, 1.99), P = 0.03 for KORA and 1.48 (1.10, 1.99), P = 0.009 for SAPHIR). Our study confirms the association of the APOA5 locus with TG and HDL levels in humans. Furthermore, the data suggest a different mechanism of APOA5 impact on MetS in Caucasians, as variant c.56C>G (not analyzed in the Japanese study) and not -1131T>C, as in the Japanese subjects, was associated with MetS.

Genetic testing in cardiovascular disease

Genetic testing is increasingly becoming possible for diagnosis, susceptibility testing, and prognostication in cardiovascular medicine. The practicing cardiologist, therefore, needs to be familiar with the clinical utilities and limitations of genetic testing. This review explores the major approaches to genetic testing and issues in test interpretation. Specific applications to cardiovascular diseases, including coronary artery disease, cardiomyopathies, cardiac arrhythmias, and pulmonary arterial hypertension are discussed.

Predict, prevent and personalize: Genomic and proteomic approaches to cardiovascular medicine

Genomic and proteomic approaches to cardiovascular medicine promise to revolutionize our understanding of disease initiation and progression. This improved appreciation of pathophysiology may be translated into avenues of clinical utility. Gene-based presymptomatic prediction of illness, finer diagnostic subclassifications and improved risk assessment tools will permit earlier and more targeted intervention. Pharmacogenetics will guide our therapeutic decisions and monitor response to therapy. Personalized medicine will require the integration of clinical information, stable and dynamic genomics, and molecular phenotyping. Bioinformatics will be crucial in translating these data into useful applications, leading to improved diagnosis, prediction, prognostication and treatment. The present paper reviews the potential contributions of genomic and proteomic approaches in developing a more personalized approach to cardiovascular medicine.