Altered branched-chain α-keto acid metabolism is a feature of NAFLD in individuals with severe obesity.

Hepatic de novo lipogenesis is influenced by the branched-chain α-keto acid dehydrogenase (BCKDH) kinase (BCKDK). Here, we aimed to determine whether circulating levels of the immediate substrates of BCKDH, the branched-chain α-keto acids (BCKAs), and hepatic BCKDK expression are associated with the presence and severity of nonalcoholic fatty liver disease (NAFLD). Eighty metabolites (3 BCKAs, 14 amino acids, 43 acylcarnitines, 20 ceramides) were quantified in plasma from 288 patients with bariatric surgery with severe obesity and scored liver biopsy samples. Metabolite principal component analysis factors, BCKAs, branched-chain amino acids (BCAAs), and the BCKA/BCAA ratio were tested for associations with steatosis grade and presence of nonalcoholic steatohepatitis (NASH). Of all analytes tested, only the Val-derived BCKA, α-keto-isovalerate, and the BCKA/BCAA ratio were associated with both steatosis grade and NASH. Gene expression analysis in liver samples from 2 independent bariatric surgery cohorts showed that hepatic BCKDK mRNA expression correlates with steatosis, ballooning, and levels of the lipogenic transcription factor SREBP1. Experiments in AML12 hepatocytes showed that SREBP1 inhibition lowered BCKDK mRNA expression. These findings demonstrate that higher plasma levels of BCKA and hepatic expression of BCKDK are features of human NAFLD/NASH and identify SREBP1 as a transcriptional regulator of BCKDK.

Serum lipids are associated with nonalcoholic fatty liver disease: a pilot case-control study in Mexico.

BACKGROUND: Nonalcoholic fatty liver disease (NAFLD) is a leading cause of chronic liver disease and cirrhosis. NAFLD is mediated by changes in lipid metabolism and known risk factors include obesity, metabolic syndrome, and diabetes. The aim of this study was to better understand differences in the lipid composition of individuals with NAFLD compared to controls, by performing direct infusion lipidomics on serum biospecimens from a cohort study of adults in Mexico. METHODS: A nested case-control study was conducted with a sample of 98 NAFLD cases and 100 healthy controls who are participating in an on-going, longitudinal study in Mexico. NAFLD cases were clinically confirmed using elevated liver enzyme tests and liver ultrasound or liver ultrasound elastography, after excluding alcohol abuse, and 100 controls were identified as having at least two consecutive normal alanine aminotransferase (ALT) and aspartate aminotransferase (AST) (< 40 U/L) results in a 6-month period, and a normal liver ultrasound elastography result in January 2018. Samples were analyzed on the Sciex Lipidyzer Platform and quantified with normalization to serum volume. As many as 1100 lipid species can be identified using the Lipidyzer targeted multiple-reaction monitoring list. The association between serum lipids and NAFLD was investigated using analysis of covariance, random forest analysis, and by generating receiver operator characteristic (ROC) curves. RESULTS: NAFLD cases had differences in total amounts of serum cholesterol esters, lysophosphatidylcholines, sphingomyelins, and triacylglycerols (TAGs), however, other lipid subclasses were similar to controls. Analysis of individual TAG species revealed increased incorporation of saturated fatty acyl tails in serum of NAFLD cases. After adjusting for age, sex, body mass index, and PNPLA3 genotype, a combined panel of ten lipids predicted case or control status better than an area under the ROC curve of 0.83. CONCLUSIONS: These preliminary results indicate that the serum lipidome differs in patients with NAFLD, compared to healthy controls, and suggest that assessing the desaturation state of TAGs or a specific lipid panel may be useful clinical tools for the diagnosis of NAFLD.

Genome-Wide Association Study Identifies a Functional SIDT2 Variant Associated With HDL-C (High-Density Lipoprotein Cholesterol) Levels and Premature Coronary Artery Disease.

Objective: Low HDL-C (high-density lipoprotein cholesterol) is the most frequent dyslipidemia in Mexicans, but few studies have examined the underlying genetic basis. Our purpose was to identify genetic variants associated with HDL-C levels and cardiovascular risk in the Mexican population. Approach and Results: A genome-wide association studies for HDL-C levels in 2335 Mexicans, identified four loci associated with genome-wide significance: CETP, ABCA1, LIPC, and SIDT2. The SIDT2 missense Val636Ile variant was associated with HDL-C levels and was replicated in 3 independent cohorts (P=5.9×10−18 in the conjoint analysis). The SIDT2/Val636Ile variant is more frequent in Native American and derived populations than in other ethnic groups. This variant was also associated with increased ApoA1 and glycerophospholipid serum levels, decreased LDL-C (low-density lipoprotein cholesterol) and ApoB levels, and a lower risk of premature CAD. Because SIDT2 was previously identified as a protein involved in sterol transport, we tested whether the SIDT2/Ile636 protein affected this function using an in vitro site-directed mutagenesis approach. The SIDT2/Ile636 protein showed increased uptake of the cholesterol analog dehydroergosterol, suggesting this variant affects function. Finally, liver transcriptome data from humans and the Hybrid Mouse Diversity Panel are consistent with the involvement of SIDT2 in lipid and lipoprotein metabolism. Conclusions: This is the first genome-wide association study for HDL-C levels seeking associations with coronary artery disease in the Mexican population. Our findings provide new insight into the genetic architecture of HDL-C and highlight SIDT2 as a new player in cholesterol and lipoprotein metabolism in humans.

Transcriptional regulation of N6-methyladenosine orchestrates sex-dimorphic metabolic traits.

Males and females exhibit striking differences in the prevalence of metabolic traits including hepatic steatosis, a key driver of cardiometabolic morbidity and mortality. RNA methylation is a widespread regulatory mechanism of transcript turnover. Here, we show that presence of the RNA modification N6-methyladenosine (m6A) triages lipogenic transcripts for degradation and guards against hepatic triglyceride accumulation. In male but not female mice, this protective checkpoint stalls under lipid-rich conditions. Loss of m6A control in male livers increases hepatic triglyceride stores, leading to a more 'feminized' hepatic lipid composition. Crucially, liver-specific deletion of the m6A complex protein Mettl14 from male and female mice significantly diminishes sex-specific differences in steatosis. We further surmise that the m6A installing machinery is subject to transcriptional control by the sex-responsive BCL6-STAT5 axis in response to dietary conditions. These data show that m6A is essential for precise and synchronized control of lipogenic enzyme activity and provide insights into the molecular basis for the existence of sex-specific differences in hepatic lipid traits.

Liver Pyruvate Kinase Promotes NAFLD/NASH in Both Mice and Humans in a Sex-Specific Manner.

BACKGROUND & AIMS: The etiology of nonalcoholic fatty liver disease (NAFLD) is poorly understood, with males and certain populations exhibiting markedly increased susceptibility. Using a systems genetics approach involving multi-omic analysis of ∼100 diverse inbred strains of mice, we recently identified several candidate genes driving NAFLD. We investigated the role of one of these, liver pyruvate kinase (L-PK or Pklr), in NAFLD by using patient samples and mouse models. METHODS: We examined L-PK expression in mice of both sexes and in a cohort of bariatric surgery patients. We used liver-specific loss- and gain-of-function strategies in independent animal models of diet-induced steatosis and fibrosis. After treatment, we measured several metabolic phenotypes including obesity, insulin resistance, dyslipidemia, liver steatosis, and fibrosis. Liver tissues were used for gene expression and immunoblotting, and liver mitochondria bioenergetics was characterized. RESULTS: In both mice and humans, L-PK expression is up-regulated in males via testosterone and is strongly associated with NAFLD severity. In a steatosis model, L-PK silencing in male mice improved glucose tolerance, insulin sensitivity, and lactate/pyruvate tolerance compared with controls. Furthermore, these animals had reduced plasma cholesterol levels and intrahepatic triglyceride accumulation. Conversely, L-PK overexpression in male mice resulted in augmented disease phenotypes. In contrast, female mice overexpressing L-PK were unaffected. Mechanistically, L-PK altered mitochondrial pyruvate flux and its incorporation into citrate, and this, in turn, increased liver triglycerides via up-regulated de novo lipogenesis and increased PNPLA3 levels accompanied by mitochondrial dysfunction. Also, L-PK increased plasma cholesterol levels via increased PCSK9 levels. On the other hand, L-PK silencing reduced de novo lipogenesis and PNPLA3 and PCSK9 levels and improved mitochondrial function. Finally, in fibrosis model, we demonstrate that L-PK silencing in male mice reduced both liver steatosis and fibrosis, accompanied by reduced de novo lipogenesis and improved mitochondrial function. CONCLUSIONS: L-PK acts in a male-specific manner in the development of liver steatosis and fibrosis. Because NAFLD/nonalcoholic steatohepatitis exhibit sexual dimorphism, our results have important implications for the development of personalized therapeutics.

Relevance of Multi-Omics Studies in Cardiovascular Diseases.

Cardiovascular diseases are the leading cause of death around the world. Despite the larger number of genes and loci identified, the precise mechanisms by which these genes influence risk of cardiovascular disease is not well understood. Recent advances in the development and optimization of high-throughput technologies for the generation of "omics data" have provided a deeper understanding of the processes and dynamic interactions involved in human diseases. However, the integrative analysis of "omics" data is not straightforward and represents several logistic and computational challenges. In spite of these difficulties, several studies have successfully applied integrative genomics approaches for the investigation of novel mechanisms and plasma biomarkers involved in cardiovascular diseases. In this review, we summarized recent studies aimed to understand the molecular framework of these diseases using multi-omics data from mice and humans. We discuss examples of omics studies for cardiovascular diseases focused on the integration of genomics, epigenomics, transcriptomics, and proteomics. This review also describes current gaps in the study of complex diseases using systems genetics approaches as well as potential limitations and future directions of this emerging field.

Isoproterenol-Induced Cardiac Diastolic Dysfunction in Mice: A Systems Genetics Analysis.

We examined an isoproterenol heart failure model across a panel of diverse inbred strains of mice, the Hybrid Mouse Diversity Panel (HMDP), using left atrial (LA) and lung weights as well as echocardiogram parameters as surrogates for cardiac diastolic function. We identified gene transcripts that significantly correlated with diastolic function. In addition, we mapped echocardiographic parameters associated with diastolic function. We identified a locus near Tns3-Hus1 to be associated with baseline E/A ratio in mice (p = 1.65E-06), the syntenic region of which was recently associated with E/A ratio in a genome-wide association study (GWAS) meta-analysis of the EchoGen consortium in humans. We also identified a locus near Cdkn2a-Cdkn2b, which is a region syntenic to the human 9p21 locus, to be associated with week 3 A/E ratio (p = 2.15E-06). Our study is the first study to map diastolic dysfunction in mice, in which a locus was found to be shared with a recent human GWAS on diastolic function. Moreover, our cardiac transcriptome correlation and eQTL analysis generated hypotheses for future basic investigations. These results showed that, although technical and physiological challenges limit diastolic function assessment in mice and humans, future investigations examining the genetic architecture of diastolic function among a diverse mouse population, such as the HMDP, in controlled experimental settings, offer distinct advantages in understanding the genetic determinants of diastolic function.

Landscape of Intercellular Crosstalk in Healthy and NASH Liver Revealed by Single-Cell Secretome Gene Analysis.

Cell-cell communication via ligand-receptor signaling is a fundamental feature of complex organs. Despite this, the global landscape of intercellular signaling in mammalian liver has not been elucidated. Here we perform single-cell RNA sequencing on non-parenchymal cells isolated from healthy and NASH mouse livers. Secretome gene analysis revealed a highly connected network of intrahepatic signaling and disruption of vascular signaling in NASH. We uncovered the emergence of NASH-associated macrophages (NAMs), which are marked by high expression of triggering receptors expressed on myeloid cells 2 (Trem2), as a feature of mouse and human NASH that is linked to disease severity and highly responsive to pharmacological and dietary interventions. Finally, hepatic stellate cells (HSCs) serve as a hub of intrahepatic signaling via HSC-derived stellakines and their responsiveness to vasoactive hormones. These results provide unprecedented insights into the landscape of intercellular crosstalk and reprogramming of liver cells in health and disease.

Systems Genetics Approach to Biomarker Discovery: GPNMB and Heart Failure in Mice and Humans.

We describe a simple bioinformatics method for biomarker discovery that is based on the analysis of global transcript levels in a population of inbred mouse strains showing variation for disease-related traits. This method has advantages such as controlled environment and accessibility to heart and plasma tissue in the preclinical selection stage. We illustrate the approach by identifying candidate heart failure (HF) biomarkers by overlaying mouse transcriptome and clinical traits from 91 Hybrid Mouse Diversity Panel (HMDP) inbred strains and human HF transcriptome from the Myocardial Applied Genomics Network (MAGNet) consortium. We found that some of the top differentially expressed genes correlated with known human HF biomarkers, such as galectin-3 and tissue inhibitor of metalloproteinase 1. Using ELISA assays, we investigated one novel candidate, Glycoprotein NMB, in a mouse model of chronic ß-adrenergic stimulation by isoproterenol (ISO) induced HF. We observed significantly lower GPNMB plasma levels in the ISO model compared to the control group (p-value = 0.007). In addition, we assessed GPNMB plasma levels among 389 HF cases and controls from the METabolic Syndrome In Men (METSIM) study. Lower levels of GPNMB were also observed in patients with HF from the METSIM study compared to non-HF controls (p-value < 0.0001). In summary, we have identified several candidate biomarkers for HF using the cardiac transcriptome data in a population of mice that may be directly relevant and applicable to human populations.

Genetic Regulation of Fibroblast Activation and Proliferation in Cardiac Fibrosis.

BACKGROUND: Genetic diversity and the heterogeneous nature of cardiac fibroblasts (CFbs) have hindered characterization of the molecular mechanisms that regulate cardiac fibrosis. The Hybrid Mouse Diversity Panel offers a valuable tool to examine genetically diverse cardiac fibroblasts and their role in fibrosis. METHODS: Three strains of mice (C57BL/6J, C3H/HeJ, and KK/HlJ) were selected from the Hybrid Mouse Diversity Panel and treated with either isoproterenol (ISO) or saline by an intraperitoneally implanted osmotic pump. After 21 days, cardiac function and levels of fibrosis were measured by echocardiography and trichrome staining, respectively. Activation and proliferation of CFbs were measured by in vitro and in vivo assays under normal and injury conditions. RNA sequencing was done on isolated CFbs from each strain. Results were analyzed by Ingenuity Pathway Analysis and validated by reverse transcription-qPCR, immunohistochemistry, and ELISA. RESULTS: ISO treatment in C57BL/6J, C3H/HeJ, and KK/HlJ mice resulted in minimal, moderate, and extensive levels of fibrosis, respectively (n=7-8 hearts per condition). Isolated CFbs treated with ISO exhibited strain-specific increases in the levels of activation but showed comparable levels of proliferation. Similar results were found in vivo, with fibroblast activation, and not proliferation, correlating with the differential levels of cardiac fibrosis after ISO treatment. RNA sequencing revealed that CFbs from each strain exhibit unique gene expression changes in response to ISO. We identified Ltbp2 as a commonly upregulated gene after ISO treatment. Expression of LTBP2 was elevated and specifically localized in the fibrotic regions of the myocardium after injury in mice and in human heart failure patients. CONCLUSIONS: This study highlights the importance of genetic variation in cardiac fibrosis by using multiple inbred mouse strains to characterize CFbs and their response to ISO treatment. Our data suggest that, although fibroblast activation is a response that parallels the extent of scar formation, proliferation may not necessarily correlate with levels of fibrosis. In addition, by comparing CFbs from multiple strains, we identified pathways as potential therapeutic targets and LTBP2 as a marker for fibrosis, with relevance to patients with underlying myocardial fibrosis.

The Genetic Architecture of Diet-Induced Hepatic Fibrosis in Mice.

We report the genetic analysis of a "humanized" hyperlipidemic mouse model for progressive nonalcoholic steatohepatitis (NASH) and fibrosis. Mice carrying transgenes for human apolipoprotein E*3-Leiden and cholesteryl ester transfer protein and fed a "Western" diet were studied on the genetic backgrounds of over 100 inbred mouse strains. The mice developed hepatic inflammation and fibrosis that was highly dependent on genetic background, with vast differences in the degree of fibrosis. Histological analysis showed features characteristic of human NASH, including macrovesicular steatosis, hepatocellular ballooning, inflammatory foci, and pericellular collagen deposition. Time course experiments indicated that while hepatic triglyceride levels increased steadily on the diet, hepatic fibrosis occurred at about 12 weeks. We found that the genetic variation predisposing to NASH and fibrosis differs markedly from that predisposing to simple steatosis, consistent with a multistep model in which distinct genetic factors are involved. Moreover, genome-wide association identified distinct genetic loci contributing to steatosis and NASH. Finally, we used hepatic expression data from the mouse panel and from 68 bariatric surgery patients with normal liver, steatosis, or NASH to identify enriched biological pathways. Conclusion: The pathways showed substantial overlap between our mouse model and the human disease.

Genetic, dietary, and sex-specific regulation of hepatic ceramides and the relationship between hepatic ceramides and IR.

Elevated hepatic ceramide levels have been implicated in both insulin resistance (IR) and hepatic steatosis. To understand the factors contributing to hepatic ceramide levels in mice of both sexes, we have quantitated ceramides in a reference population of mice, the Hybrid Mouse Diversity Panel that has been previously characterized for a variety of metabolic syndrome traits. We observed significant positive correlations between Cer(d18:1/16:0) and IR/hepatic steatosis, consistent with previous findings, although the relationship broke down between sexes, as females were less insulin resistant, but had higher Cer(d18:1/16:0) levels than males. The sex difference was due in part to testosterone-mediated repression of ceramide synthase 6. One ceramide species, Cer(d18:1/20:0), was present at higher levels in males and was associated with IR only in males. Clear evidence of gene-by-sex and gene-by-diet interactions was observed, including sex-specific genome-wide association study results. Thus, our studies show clear differences in how hepatic ceramides are regulated between the sexes, which again suggests that the physiological roles of certain hepatic ceramides differ between the sexes.

An Amino Acid Signature Associated with Obesity Predicts 2-Year Risk of Hypertriglyceridemia in School-Age Children.

Childhood obesity is associated with a number of metabolic abnormalities leading to increased cardiovascular risk. Metabolites can be useful as early biomarkers and new targets to promote early intervention beginning in school age. Thus, we aimed to identify metabolomic profiles associated with obesity and obesity-related metabolic traits. We used data from the Obesity Research Study for Mexican children (ORSMEC) in Mexico City and included a case control (n = 1120), cross-sectional (n = 554) and a longitudinal study (n = 301) of 6-12-year-old children. Forty-two metabolites were measured using electrospray MS/MS and multivariate regression models were used to test associations of metabolomic profiles with anthropometric, clinical and biochemical parameters. Principal component analysis showed a serum amino acid signature composed of arginine, leucine/isoleucine, phenylalanine, tyrosine, valine and proline significantly associated with obesity (OR = 1.57; 95%CI 1.45-1.69, P = 3.84 × 10-31) and serum triglycerides (TG) (ß = 0.067, P = 4.5 × 10-21). These associations were validated in the cross-sectional study (P < 0.0001). In the longitudinal cohort, the amino acid signature was associated with serum TG and with the risk of hypertriglyceridemia after 2 years (OR = 1.19; 95%CI 1.03-1.39, P = 0.016). This study shows that an amino acid signature significantly associated with childhood obesity, is an independent risk factor of future hypertriglyceridemia in children.

A combined linkage and association strategy identifies a variant near the GSTP1 gene associated with BMI in the Mexican population.

Obesity is a major public health concern in Mexico and worldwide. Although the estimated heritability is high, common variants identified by genome-wide association studies explain only a small proportion of this heritability. A combination of linkage and association strategies could be a more robust and powerful approach to identify other obesity-susceptibility variants. We thus sought to identify novel genetic variants associated with obesity-related traits in the Mexican population by combining these methods. We performed a genome-wide linkage scan for body mass index (BMI) and other obesity-related phenotypes in 16 Mexican families using the Sequential Oligogenic Linkage Analysis Routines Program. Associated single-nucleotide polymorphisms (SNPs) were tested for associations in an independent cohort. Two suggestive BMI-linkage peaks (logarithm of odds ⩾1.5) were observed at chromosomal regions 11q13 and 13q22. Only rs614080 in the 11q13 region was significantly associated with BMI and related traits in these families. This association was also significant in an independent cohort of Mexican adults. Moreover, this variant was significantly associated with GSTP1 gene expression levels in adipose tissue. In conclusion, the rs614080 SNP near the GSTP1 gene was significantly associated with BMI and GSTP1 expression levels in the Mexican population.

Polymorphisms in the GNAS Gene as Predictors of Ventricular Tachyarrhythmias and Sudden Cardiac Death: Results From the DISCOVERY Trial and Oregon Sudden Unexpected Death Study.

BACKGROUND: Population-based studies suggest that genetic factors contribute to sudden cardiac death (SCD). METHODS AND RESULTS: In the first part of the present study (Diagnostic Data Influence on Disease Management and Relation of Genetic Polymorphisms to Ventricular Tachy-arrhythmia in ICD Patients [DISCOVERY] trial) Cox regression was done to determine if 7 single-nucleotide polymorphisms (SNPs) in 3 genes coding G-protein subunits (GNB3, GNAQ, GNAS) were associated with ventricular tachyarrhythmia (VT) in 1145 patients receiving an implantable cardioverter-defibrillator (ICD). In the second part of the study, SNPs significantly associated with VT were further investigated in 1335 subjects from the Oregon SUDS, a community-based study analyzing causes of SCD. In the DISCOVERY trial, genotypes of 2 SNPs in the GNAS gene were nominally significant in the prospective screening and significantly associated with VT when viewed as recessive traits in post hoc analyses (TT vs CC/CT in c.393C>T: HR 1.42 [CI 1.11-1.80], P=0.005; TT vs CC/CT in c.2273C>T: HR 1.57 [CI 1.18-2.09], P=0.002). TT genotype in either SNP was associated with a HR of 1.58 (CI 1.26-1.99) (P=0.0001). In the Oregon SUDS cohort significant evidence for association with SCD was observed for GNAS c.393C>T under the additive (P=0.039, OR=1.21 [CI 1.05-1.45]) and recessive (P=0.01, OR=1.52 [CI 1.10-2.13]) genetic models. CONCLUSIONS: GNAS harbors 2 SNPs that were associated with an increased risk for VT in ICD patients, of which 1 was successfully replicated in a community-based population of SCD cases. To the best of our knowledge, this is the first example of a gene variant identified by ICD VT monitoring as a surrogate parameter for SCD and also confirmed in the general population. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00478933.

Distinctive Clinical Profile of Blacks Versus Whites Presenting With Sudden Cardiac Arrest.

BACKGROUND: Sudden cardiac arrest (SCA) is a major contributor to mortality, but data are limited among nonwhites. Identification of differences in clinical profile based on race may provide opportunities for improved SCA prevention. METHODS AND RESULTS: In the ongoing Oregon Sudden Unexpected Death Study (SUDS), individuals experiencing SCA in the Portland, OR, metropolitan area were identified prospectively. Patient demographics, arrest circumstances, and pre-SCA clinical profile were compared by race among cases from 2002 to 2012 (for clinical history, n=126 blacks, n=1262 whites). Incidence rates were calculated for cases from the burden assessment phase (2002-2005; n=1077). Age-adjusted rates were 2-fold higher among black men and women (175 and 90 per 100 000, respectively) compared with white men and women (84 and 40 per 100 000, respectively). Compared with whites, blacks were >6 years younger at the time of SCA and had a higher prearrest prevalence of diabetes mellitus (52% versus 33%; P<0.0001), hypertension (77% versus 65%; P=0.006), and chronic renal insufficiency (34% versus 19%; P<0.0001). There were no racial differences in previously documented coronary artery disease or left ventricular dysfunction, but blacks had more prevalent congestive heart failure (43% versus 34%; P=0.04) and left ventricular hypertrophy (77% versus 58%; P=0.02) and a longer QTc interval (466±36 versus 453±41 milliseconds; P=0.03). CONCLUSIONS: In this US community, the burden of SCA was significantly higher in blacks compared with whites. Blacks with SCA had a higher prearrest prevalence of risk factors beyond established coronary artery disease, providing potential targets for race-specific prevention.

Cumulative effects of common genetic variants on risk of sudden cardiac death.

BACKGROUND: Genome-wide association studies and candidate-gene based approaches have identified multiple common variants associated with increased risk of sudden cardiac death (SCD). However, the independent contribution of these individual loci to disease risk is modest. OBJECTIVE: To investigate the cumulative effects of genetic variants previously associated with SCD risk. METHODS: A total of 966 SCD cases from the Oregon-Sudden Unexpected Death Study and 1,926 coronary artery disease controls from the Wellcome Trust Case-Control Consortium were investigated. We generated genetic risk scores (GRS) for each trait composed of variants previously associated with SCD or with abnormalities in specific electrocardiographic traits such as QRS duration, QTc interval and heart rate. GRSs were calculated using a weighted approach based on the number of risk alleles weighted by the beta coefficients derived from the original studies. We also compared the highest and lowest quintiles for the GRS composed of SCD SNPs. RESULTS: Increased cumulative risk was observed for a GRS composed of 14 SCD-SNPs (OR=1.17 [1.05-1.29], P = 0.002). The risk for SCD was 1.5 fold higher in the highest quintile when compared to the lowest quintile (OR = 1.46[1.11-1.92]). We did not observe significant associations with SCD for SNPs that determine electrocardiographic traits. CONCLUSIONS: A modest but significant effect on SCD risk was identified for a GRS composed of 14 previously associated SCD SNPs. While next generation sequencing methodology will continue to identify additional novel variants, these findings represent proof of concept for the additive effects of gene variants on SCD risk.

Sex hormone levels in patients with sudden cardiac arrest.

BACKGROUND: Sex hormones are known to have significant effects on the pathophysiology of cardiovascular disease. OBJECTIVE: The purpose of this study was to study the association between sex hormone levels and sudden cardiac arrest (SCA). METHODS: In the ongoing Oregon Sudden Unexpected Death Study (catchment population approximately 1 million), cases of SCA were compared with matched controls. Testosterone and estradiol levels were measured from blood samples drawn at the time of the SCA event in cases and during a routine visit in controls. RESULTS: Among cases (n = 149, age 64.1 ± 11.7 years, 73.2% male), compared to controls (n = 149, 64.2 ± 11.6 years, 72.5% male), median testosterone levels were significantly lower in males (4.4 vs 5.4 ng/mL, P = .01). Median estradiol levels were higher in male (68 vs 52 pg/mL, P <.001) and female cases (54 vs 36 pg/mL, P <.001). In multivariate analysis, higher testosterone levels were associated with lower SCA odds only in males (odds ratio [OR] 0.75, 95% confidence interval [CI] 0.58-0.96, P = .02). Higher estradiol levels were associated with higher SCA odds in both males (OR 2.0, 95% CI 1.5-2.6, P <.001) and females (OR 3.5, 95% CI 1.9-6.4, P <.001). A higher testosterone/estrogen ratio was associated with lower SCA odds in males only (OR 0.5, 95% CI 0.4-0.7, P <.001). In a canine model of SCA, plasma testosterone levels were not significantly altered by the cardiac arrest event. CONCLUSION: We observed significant differences in sex hormone levels in patients who suffered SCA, with potential mechanistic implications. The role of sex hormones in the genesis of fatal ventricular arrhythmias warrants further exploration.