Genetic polymorphisms of L-type calcium channel alpha1C and alpha1D subunit genes are associated with sensitivity to the antihypertensive effects of L-type dihydropyridine calcium-channel blockers

Pharmacogenomic Study of Selected Genes Affecting Amlodipine Blood Pressure Response in Patients with Hypertension

Introduction

Despite the availability of various antihypertensive medications, the response to these medications varies among individuals. Understanding how individual genetic variations affect drugs treatment outcomes is a key area of focus in precision medicine. This study investigated the correlation between single nucleotide polymorphisms (SNPs) in selected genes (CACNA1C, CACNA1D, ABCB1, ACE, ADBR2, and NOS1AP) and the blood pressure (BP) control by amlodipine.

Methods

Four hundred individuals of Pashtun ethnicity undergoing amlodipine treatment for hypertension were included in the present study and divided into the controlled (BP less than 140/90 mmHg) and uncontrolled (BP greater than 140/90 mmHg) hypertension groups. Blood samples (3 mL) were collected from each participant, and DNA was extracted using the Kit method. Ten SNPs in amlodipine pharmacogenes were selected and genotyped using real-time PCR with the TaqMan® system. Logistic regression model was used to determine the association between SNPs and the amlodipine BP response.

Results

Notable association were observed between SNP rs2239050/CACNA1C and amlodipine blood pressure response, with GG genotype carriers demonstrating a better response (P=0.004) than individuals carrying CC or CG genotypes. SNP rs312481/CACNA1D also exhibited a positive pharmacogenetic association, Individuals with the GG genotype showing a considerable reduction in BP (P=0.021) compared to participants with AA or GA genotypes. In case of SNP rs429/ACE individuals carrying TA genotype were less likely to achieve BP control (P=0.002) than AA genotype carriers.

Conclusion

Our finding suggests that the SNPs rs2239050/CACNA1C, rs312481/CACNA1D and rs429/ACE influence amlodipine blood pressure response in patients with hypertension. It is recommended that prior knowledge of amlodipine associated pharmacogenetic variants is important that could improve its treatment outcomes in hypertensive patients.

CACNA1D Gene Polymorphisms Associate With Increased Blood Pressure and Salt Sensitivity of Blood Pressure in White Individuals

BACKGROUND

Disease-causing mutations in CACNA1D gene occur in aldosterone-producing adenomas and familial hyperaldosteronism. We determined whether single nucleotide polymorphisms in CACNA1D gene associate with higher aldosterone resulting in salt sensitivity of blood pressure (BP) and increased BP in men and women.

METHODS

Data were obtained from the HyperPATH (International Hypertension Pathotypes) cohort, where participants completed a cross-over intervention of liberal and restricted sodium diets. Multi-Ethnic Genotyping Array identified 104 CACNA1D single nucleotide polymorphisms that met quality control. Single nucleotide polymorphism is rs7612148 strongly associated with systolic BP and was selected for study in 521 White participants in 3 scenarios ([1] hypertensives; [2] normotensives; [3] total population=hypertensives+normotensives) using multivariate regression analysis.

RESULTS

In the total population and hypertensives, but not normotensives, risk allele carriers (CC, GC), as compared with nonrisk allele homozygotes (GG), exhibited higher salt sensitivity of BP and, on liberal sodium diet, higher systolic BP, lower baseline and angiotensin II-stimulated aldosterone, and lower plasma renin activity. On restricted sodium diet, BP was similar across genotypes, suggesting sodium restriction corrected/neutralized the genotype effect on BP. Because increased aldosterone did not seem to drive the increased salt sensitivity of BP and increased BP on liberal sodium diet, we assessed renal plasma flow. Renal plasma flow increase from restricted to liberal sodium diets was blunted in risk allele homozygotes in the total population and in hypertensives. A replication study in another cohort HyperPATH B (International Hypertension Pathotypes Cohort B) confirmed BP-genotype associations.

CONCLUSIONS

CACNA1D rs7612148 risk allele associated with increased BP and salt sensitivity of BP, likely due to an impaired ability to increase renal plasma flow in response to a liberal sodium diet and not to excess aldosterone.

CACNA1D-Related Channelopathies: From Hypertension to Autism

Tightly controlled Ca²⁺ influx through voltage-gated Ca²⁺ channels (Cavs) is indispensable for proper physiological function. Thus, it is not surprising that Cav loss and/or gain of function have been implicated in human pathology. Deficiency of Cav1.3 L-type Ca²⁺ channels (LTCCs) causes deafness and bradycardia, whereas several genetic variants of CACNA1D, the gene encoding the pore-forming α1 subunit of Cav1.3, have been linked to various disease phenotypes, such as hypertension, congenital hypoglycemia, or autism. These variants include not only common polymorphisms associated with an increased disease risk, but also rare de novo missense variants conferring high risk. This review provides a concise summary of disease-associated CACNA1D variants, whereas the main focus lies on de novo germline variants found in individuals with a neurodevelopmental disorder of variable severity. Electrophysiological recordings revealed activity-enhancing gating changes induced by these de novo variants, and tools to predict their pathogenicity and to study the resulting pathophysiological consequences will be discussed. Despite the low number of affected patients, potential phenotype-genotype correlations and factors that could impact the severity of symptoms will be covered. Since increased channel activity is assumed as the disease-underlying mechanism, pharmacological inhibition could be a treatment option. In the absence of Cav1.3-selective blockers, dihydropyridine LTCC inhibitors clinically approved for the treatment of hypertension may be used for personalized off-label trials. Findings from in vitro studies and treatment attempts in some of the patients seem promising as outlined. Taken together, due to advances in diagnostic sequencing techniques the number of reported CACNA1D variants in human diseases is constantly rising. Evidence from in silico, in vitro, and in vivo disease models can help to predict the pathogenic potential of such variants and to guide diagnosis and treatment in the clinical practice when confronted with patients harboring CACNA1D variants.

Single Nucleotide Polymorphisms in Amlodipine-Associated Genes and Their Correlation with Blood Pressure Control among South African Adults with Hypertension

Objective: This study describes the single nucleotide polymorphisms (SNPs) in amlodipine-associated genes and assesses their correlation with blood pressure control among South African adults with hypertension. Methods: In total, 304 hypertensive patients on amlodipine treatment belonging to the indigenous Swati, Xhosa and Zulu population groups of South Africa were recruited between June 2017 and June 2019. Participants were categorized into: controlled (blood pressure < 140/90 mmHg) and uncontrolled (blood pressure ≥ 140/90 mmHg) hypertension. Thirteen SNPs in amlodipine pharmacogenes with a high PharmGKB evidence base were selected and genotyped using MassArray (Agena BioscienceTM). Logistic regression was fitted to identify significant associations between the SNPs and blood pressure control with amlodipine. Results: The majority of the participants were females (76.6%), older than 45 years (89.1%) and had uncontrolled hypertension (52.3%). Of the 13 SNPs genotyped, five SNPs, rs1042713 (minor allele frequency = 45.9%), rs10494366 (minor allele frequency = 35.3%), rs2239050 (minor allele frequency = 28.7%), rs2246709 (minor allele frequency = 51.6%) and rs4291 (minor allele frequency = 34.4%), were detected among the Xhosa participants, while none were detected among the Swati and Zulu tribal groups. Variants rs1042713 and rs10494366 demonstrated an expression frequency of 97.5% and 79.5%, respectively. Variant TA genotype of rs4291 was significantly associated with uncontrolled hypertension. No association was established between blood pressure response to amlodipine and the remaining four SNPs. Conclusions: This study reports the discovery of five SNPs in amlodipine genes (rs2239050, rs2246709, rs4291, rs1042713 and rs10494366) among the indigenous Xhosa-speaking tribe of South Africa. In addition, the TA genotype of rs4291 was associated with blood pressure control in this cohort. These findings might open doors for more pharmacogenomic studies, which could inform innovations to personalised anti-hypertensive treatment in the ethnically diverse population of South Africa.

Genetic Contributors of Efficacy and Adverse Metabolic Effects of Chlorthalidone in African Americans from the Genetics of Hypertension Associated Treatments (GenHAT) Study

Hypertension is a leading risk factor for cardiovascular disease mortality. African Americans (AAs) have the highest prevalence of hypertension in the United States, and to alleviate the burden of hypertension in this population, better control of blood pressure (BP) is needed. Previous studies have shown considerable interpersonal differences in BP response to antihypertensive treatment, suggesting a genetic component. Utilizing data from 4297 AA participants randomized to chlorthalidone from the Genetics of Hypertension Associated Treatments (GenHAT) study, we aimed to identify variants associated with the efficacy of chlorthalidone. An additional aim was to find variants that contributed to changes in fasting glucose (FG) in these individuals. We performed genome-wide association analyses on the change of systolic and diastolic BP (SBP and DBP) over six months and FG levels over 24 months of treatment. We sought replication in the International Consortia of Pharmacogenomics Studies. We identified eight variants statistically associated with BP response and nine variants associated with FG response. One suggestive LINC02211-CDH9 intergenic variant was marginally replicated with the same direction of effect. Given the impact of hypertension in AAs, this study implies that understanding the genetic background for BP control and glucose changes during chlorthalidone treatment may help prevent adverse cardiovascular events in this population.

Polymorphisms in common antihypertensive targets: Pharmacogenomic implications for the treatment of cardiovascular disease

The idea of personalized medicine came to fruition with sequencing the human genome; however, aside from a few cases, the genetic revolution has yet to materialize. Cardiovascular diseases are the leading cause of death globally, and hypertension is a common prelude to nearly all cardiovascular diseases. Thus, hypertension is an ideal candidate disease to apply tenants of personalized medicine to lessen cardiovascular disease. Herein is a survey that visually depicts the polymorphisms in the top eight antihypertensive targets. Although there are numerous genome-wide association studies regarding cardiovascular disease, few studies look at the effects of receptor polymorphisms on drug treatment. With 17,000+ polymorphisms in the combined target proteins examined, it is expected that some of the clinical variability in the treatment of hypertension is due to polymorphisms in the drug targets. Recent advances in techniques and technology, such as high throughput examination of single mutations, structure prediction, computational power for modeling, and CRISPR models of point mutations, allow for a relatively rapid and comprehensive examination of the effects of known and future polymorphisms on drug affinity and effects. As hypertension is easy to measure and has a plethora of clinically viable ligands, hypertension makes an excellent disease to study pharmacogenomics in the lab and the clinic. If the promises of personalized medicine are to materialize, a concerted effort to examine the effects polymorphisms have on drugs is required. A clinician with the knowledge of a patient's genotype can then prescribe drugs that are optimal for treating that specific patient.

Dominant role of CACNA1D exon mutations for blood pressure regulation

BACKGROUND

CACNA1D gene, which encodes the α1 subunit of the Cav1.3 L-type calcium channel effectively regulates intracellular Ca2+ stability. In recent years, clinical studies have shown that the CACNA1D polymorphisms were associated with hypertension.

OBJECTIVE

The purpose of this study was to evaluate the effects of CACNA1D exon mutation on blood pressure (BP) in Sprague-Dawley rats.

METHODS

The rats with CACNA1D p.D307G, CACNA1D p.V936I or CACNA1D p.R1516Q were constructed using CRISPR-Cas9 technology. SBP measurements of rats were taken for 32 weeks. Tissue morphology of rats and vasoactive substances in serum was tested. Furthermore, the effects of L-type calcium channel blocker isradipine and endothelin-1 (ET-1) inhibitor BQ-123 on BP of double mutation rats (CACNA1D p.D307G/p.R1516Q) were tested. Then we examined the effects of CACNA1D gene mutation on gene expression in human umbilical vein endothelial cells (HUVECs) and vascular smooth muscle cells (VSMCs).

RESULTS

Elevated SBP and increased circulating ET-1 was observed in CACNA1D p.D307G mutant rats. Morphological assessments showed that the vascular, cardiac and renal remodeling could also be observed in rats with p.D307G mutant. Cav1.3 protein expression and calcineurin phosphatase activity in VSMCs of rats with CACNA1D p.D307G were increased in vitro, and the vascular ring tension test of mesenteric grade 3 arteries in CACNA1D p.D307G rats were increased in vivo. Furthermore, ET-1 expression were increased in isolated primary aortic endothelial cells in p.D307G mutant rats and transfected p.D307G mutant HUVECs. Finally, double heterozygosity rats with CACNA1D p.D307G/p.R1516Q or CACNA1D p.D307G/p.V936I further accelerated the rise of SBP compared with p.D307G mutation rats, and isradipine and BQ-123 reduced BP to the same extent in CACNA1D p.D307G/p.R1516Q rats.

CONCLUSION

CACNA1D gene is key players in the regulation of blood pressure. CACNA1D mutation rat may be a new hypertension animal model.

Use of Calcium Channel Blockers and the Risk of All-cause Mortality and Severe Illness in Patients With COVID-19: A Systematic Review and Meta-analysis

ABSTRACT

Owing to the reported safety concerns, we aimed to perform a systematic review and meta-analysis to determine the effect of preadmission/prediagnosis use of calcium channel blockers (CCBs) on the clinical outcomes in patients with COVID-19. A systematic literature search with no language restriction was conducted in electronic databases in July 2021 to identify eligible studies. The outcomes of interest were all-cause mortality and severe illness. A random-effects model was used to estimate the pooled summary measure for outcomes of interest with the preadmission/prediagnosis use of CCBs relative to nonuse CCBs, at 95% confidence intervals (CIs). The meta-analyses revealed no significant difference in the odds of all-cause mortality [pooled odds ratio (OR) = 0.82; 95% CI 0.68-1.00; n = 58,355] and in the odds of severe illness (pooled OR = 0.83; 95% CI 0.61-1.15; n = 46,091) respectively, with preadmission/prediagnosis use of CCBs relative to nonuse of CCBs. Nevertheless, subgroup analysis of studies originated from East Asia reported a significant reduction in the odds of all-cause mortality (pooled OR = 0.50; 95% CI 0.37-0.68) and the odds of severe illness (pooled OR = 0.51; 95% CI 0.33-0.78). There may not be safety concerns with the use of CCBs in patients with COVID-19, but their potential protective effects in the East Asian patients merit further investigations.

Pharmacogenomics of Hypertension Treatment

Hypertension is one of the strongest modifiable cardiovascular risk factors, affecting an increasing number of people worldwide. Apart from poor medication adherence, the low efficacy of some therapies could also be related to inter-individual genetic variability. Genetic studies of families revealed that heritability accounts for 30% to 50% of inter-individual variation in blood pressure (BP). Genetic factors not only affect blood pressure (BP) elevation but also contribute to inter-individual variability in response to antihypertensive treatment. This article reviews the recent pharmacogenomics literature concerning the key classes of antihypertensive drugs currently in use (i.e., diuretics, β-blockers, ACE inhibitors, ARB, and CCB). Due to the numerous studies on this topic and the sometimes-contradictory results within them, the presented data are limited to several selected SNPs that alter drug response. Genetic polymorphisms can influence drug responses through genes engaged in the pathogenesis of hypertension that are able to modify the effects of drugs, modifications in drug–gene mechanistic interactions, polymorphisms within drug-metabolizing enzymes, genes related to drug transporters, and genes participating in complex cascades and metabolic reactions. The results of numerous studies confirm that genotype-based antihypertension therapies are the most effective and may help to avoid the occurrence of major adverse events, as well as decrease the costs of treatment. However, the genetic heritability of drug response phenotypes seems to remain hidden in multigenic and multifactorial complex traits. Therefore, further studies are required to analyze all associations and formulate final genome-based treatment recommendations.

Pharmacogenomics of amlodipine and hydrochlorothiazide therapy and the quest for improved control of hypertension: a mini review

Blood pressure (BP) is a complex trait that is regulated by multiple physiological pathways and include but is not limited to extracellular fluid volume homeostasis, cardiac contractility, and vascular tone through renal, neural, or endocrine systems. Uncontrolled hypertension (HTN) has been associated with an increased mortality risk. Therefore, understanding the genetics that underpins and influence BP regulation will have a major impact on public health. Moreover, uncontrolled HTN has been linked to inter-individual variation in the drugs’ response and this has been associated with an individual’s genetics architecture. However, the identification of candidate genes that underpin the genetic basis of HTN remains a major challenge. To date, few variants associated with inter-individual BP regulation have been identified and replicated. Research in this field has accelerated over the past 5 years as a direct result of on-going genome-wide association studies (GWAS) and the progress in the identification of rare gene variants and mutations, epigenetic markers, and the regulatory pathways involved in the pathophysiology of BP. In this review we describe and enhance our current understanding of how genetic variants account for the observed variability in BP response in patients on first-line antihypertensive drugs, amlodipine and hydrochlorothiazide.

Pharmacogenomics And Hypertension: Current Insights

Hypertension is a multifactorial disease that affects approximately one billion subjects worldwide and is a major risk factor associated with cardiovascular events, including coronary heart disease and cerebrovascular accidents. Therefore, adequate blood pressure control is important to prevent these events, reducing premature mortality and disability. However, only one third of patients have the effective control of blood pressure, despite several classes of antihypertensive drugs available. These disappointing outcomes may be at least in part explained by interpatient variability in drug response due to genetic polymorphisms. To address the effects of genetic polymorphisms on blood pressure responses to the antihypertensive drug classes, studies have applied candidate genes and genome wide approaches. More recently, a third approach that considers gene-gene interactions has also been applied in hypertension pharmacogenomics. In this article, we carried out a comprehensive review of recent findings on the pharmacogenomics of antihypertensive drugs, including diuretics, β-blockers, angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers, and calcium channel blockers. We also discuss the limitations and inconsistences that have been found in hypertension pharmacogenomics and the challenges to implement this valuable approach in clinical practice.

Combined effects of the rs9810888 polymorphism in calcium voltage-gated channel subunit alpha1 D (CACNA1D) and lifestyle behaviors on blood pressure level among Chinese children

Backgrounds

A recent GWAS Study found a new locus (rs9810888 in CACNA1D) was associated with blood pressure (BP) in Chinese adults. But whether the association exists in children is unknown. Whether lifestyle behaviors could interact with rs9810888 on BP is not clear. This study aimed to identify the association between rs9810888 and BP in children, and also explore the gene-lifestyle interaction.

Methods

A case-control study was conducted among 2030 Chinese children aged 7 to 18 years. Genotyping was conducted by using the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Lifestyle behaviors were investigated with questionnaire.

Results

With adjustment for age, age square, sex, study group and body mass index (BMI), rs9810888 was significantly associated with diastolic BP (DBP) (b = 1.69, p = 0.021) and mean arterial BP (MAP) (b = 1.56, p = 0.010). Stratified analysis showed that the rs9810888 GG genotype carriers had higher DBP than GT/TT carriers (b = 3.78, p = 0.023) in the subgroup having protein intake (meat/fish/soybeans/egg) <twice/day, but not in the subgroup ≥twice/day. In addition, in the subgroup with screen time≥2h/day, the rs9810888 GG genotype carriers had higher DBP than GT/TT carriers (b = 5.49, p = 0.012), but not in the subgroup with screen time<2h/day. For MAP, in the subgroup having either fruits or vegetables < twice/day, the rs9810888 GG genotype carriers had higher MAP than GT/TT carriers (b = 2.64, p = 0.037), but not in the subgroup with both fruits and vegetables intake ≥twice/day. Additionally, in the subgroup with screen time≥2h/day, the rs9810888 GG genotype carriers had higher MAP than GT/TT carriers (b = 4.80, p = 0.017), but not in those with screen time<2h/day.

Conclusions

The CACNA1D rs9810888 polymorphism was significantly associated with DBP and MAP. In addition, unhealthy lifestyle behaviors and rs9810888 GG genotype had combined effects on BP level among Chinese children.

A Systematically Assembled Signature of Genes to be Deep-Sequenced for Their Associations with the Blood Pressure Response to Exercise

: Background: Exercise is one of the best nonpharmacologic therapies to treat hypertension. The blood pressure (BP) response to exercise is heritable. Yet, the genetic basis for the antihypertensive effects of exercise remains elusive. Methods: To assemble a prioritized gene signature, we performed a systematic review with a series of Boolean searches in PubMed (including Medline) from earliest coverage. The inclusion criteria were human genes in major BP regulatory pathways reported to be associated with: (1) the BP response to exercise; (2) hypertension in genome-wide association studies (GWAS); (3) the BP response to pharmacotherapy; (4a) physical activity and/or obesity in GWAS; and (4b) BP, physical activity, and/or obesity in non-GWAS. Included GWAS reports disclosed the statistically significant thresholds used for multiple testing. Results: The search yielded 1422 reports. Of these, 57 trials qualified from which we extracted 11 genes under criteria 1, 18 genes under criteria 2, 28 genes under criteria 3, 27 genes under criteria 4a, and 29 genes under criteria 4b. We also included 41 genes identified from our previous work. Conclusions: Deep-sequencing the exons of this systematically assembled signature of genes represents a cost and time efficient approach to investigate the genomic basis for the antihypertensive effects of exercise.

Association study of CACNA1C polymorphisms with large artery atherosclerotic stroke in Chinese Han population

Aims Ischemic stroke (IS) is one of the most common diseases of neurology and the main cause of death and disability in Chinese population. CACNA1C was considered to be involved in the process of atherosclerosis, but there was little information about the association between genotypic polymorphisms of CACNA1C and ischemic stroke. Our study was designed to elucidate the relationship between four single-nucleotide polymorphisms (SNPs) variants in CACNA1C gene and the risk of large-artery atherosclerotic (LAA) stroke patients. Methods A total of 384 subjects were enrolled in this study, including 192 LAA stroke cases and 192 healthy controls. And four SNPs variants in CNCNA1C gene were genotyped using in-house developed multiplex tagged-amplicon deep sequencing (TAm-Seq). Statistical analysis were conducted using χ2 test and binary logistic regression analysis. Results We found one variant was significantly associated with LAA stroke in the allele models (rs10848683, p = 0.036, OR = 1.371, 95%CI: 1.021-1.841). And rs10848683 was also found to associate with LAA stroke under recessive model (p = 0.027, OR = 0.618, 95% CI: 0.403-0.947) after adjustment for gender and age. We also found that significant difference existed between haplotypes (rs229961-rs215976-rs216008-rs10848683) and LAA stroke (C-T-C-C, p = 0.017, OR = 2.265, 95%CI: 1.136-4.518; G-C-C-C, p = 0.046, OR = 1.891, 95% CI: 1.003-3.565; C-T-C-T, p = 0.001, OR = 0.256, 95%CI: 0.101-0.645). Conclusion The results suggested that there was a potential association between CNCNA1C gene and the risk factor of LAA stroke in Chinese Han population.

Translational Systems Pharmacology Studies in Pregnant Women

Pregnancy involves rapid physiological adaptation and complex interplay between mother and fetus. New analytic technologies provide large amounts of genomic, proteomic, and metabolomics data. The integration of these data through bioinformatics, statistical, and systems pharmacology techniques can improve our understanding of the mechanisms of normal maternal physiologic changes and fetal development. New insights into the mechanisms of pregnancy‐related disorders, such as preterm birth (PTB), may lead to the development of new therapeutic interventions and novel biomarkers.

Associations of Variants in the CACNA1A and CACNA1C Genes With Longitudinal Blood Pressure Changes and Hypertension Incidence: The GenSalt Study

BACKGROUND

We aimed to examine the associations of voltage-dependent calcium-channel genes CACNA1A and CACNA1C with blood pressure (BP) changes and hypertension incidence in a longitudinal family study.

METHODS

A total of 1,768 Han Chinese participants from the Genetic Epidemiology Network of Salt Sensitivity (GenSalt) follow-up study were eligible for the current study. Nine BP measurements were obtained at baseline and each follow-up visit using a random-zero sphygmomanometer. Mixed-effect models were used to assess additive associations of 176 tag single-nucleotide polymorphisms (SNPs) in CACNA1A and CACNA1C with longitudinal BP changes and hypertension incidence. The truncated product method was used for gene-based analysis. The Bonferroni correction was used for adjustment of multiple testing.

RESULTS

During an average of 7.2 years of follow-up, 512 (32.1%) participants developed hypertension. CACNA1A SNP rs8182538 was significantly associated with longitudinal diastolic BP (DBP) change after Bonferroni correction ( Pinteraction = 9.90×10 -5 ), with mean DBP increases of 0.85, 1.03, and 1.19mm Hg per year for participants with genotypes C/C , C/T , and T/T , respectively. A similar trend was observed for the association of rs8182538 with systolic BP (SBP) change. In the gene-based analysis, CACNA1A and CACNA1C were significantly associated with DBP change ( P = 2.0×10 -5 ) and SBP change ( P = 1.4×10 -4 ) after Bonferroni correction, respectively. The gene-based associations remained significant after removing rs8182538 within CACNA1A and rs758116 within CACNA1C in sensitivity analysis.

CONCLUSIONS

Our findings indicated that CACNA1A and CACNA1C might contribute to BP changes over time in Han Chinese population. Further replication of these findings is warranted.

Is personalized medicine achievable in obstetrics?

Personalized medicine seeks to identify the right dose of the right drug for the right patient at the right time. Typically, individualization of therapy is based on the pharmacogenomic makeup of the individual and environmental factors that alter drug disposition and response. In addition to these factors, during pregnancy, a woman's body undergoes many changes that can impact the therapeutic efficacy of medications. Yet, there is minimal research regarding personalized medicine in obstetrics. Adoption of pharmacogenetic testing into the obstetrical care is dependent on evidence of analytical validity, clinical validity, and clinical utility. Here, we briefly present information regarding the potential utility of personalized medicine for treating the obstetric patient for pain with narcotics, hypertension, and preterm labor, and discuss the impediments of bringing personalized medicine to the obstetrical clinic.

A rare mutation of CACNA1C in a patient with bipolar disorder, and decreased gene expression associated with a bipolar-associated common SNP of CACNA1C in brain

Timothy Syndrome (TS) is caused by very rare exonic mutations of the CACNA1C gene that produce delayed inactivation of Cav1.2 voltage-gated calcium channels during cellular action potentials, with greatly increased influx of calcium into the activated cells. The major clinical feature of this syndrome is a long QT interval that results in cardiac arrhythmias. However, TS also includes cognitive impairment, autism and major developmental delays in many of the patients. We observed the appearance of bipolar disorder (BD) in a patient with a previously reported case of TS, who is one of the very few patients to survive childhood. This is most interesting because the common single-nucleotide polymorphism (SNP) most highly associated with BD is rs1006737, which we show here is a cis-expression quantitative trait locus for CACNA1C in human cerebellum, and the risk allele (A) is associated with decreased expression. To combine the CACNA1C perturbations in the presence of BD in this patient and in patients with the common CACNA1C SNP risk allele, we would propose that either increase or decrease in calcium influx in excitable cells can be associated with BD. In treatment of BD with calcium channel blocking drugs, we would predict better response in patients without the risk allele, because they have increased CACNA1C expression.

Pathways-driven sparse regression identifies pathways and genes associated with high-density lipoprotein cholesterol in two Asian cohorts

Standard approaches to data analysis in genome-wide association studies (GWAS) ignore any potential functional relationships between gene variants. In contrast gene pathways analysis uses prior information on functional structure within the genome to identify pathways associated with a trait of interest. In a second step, important single nucleotide polymorphisms (SNPs) or genes may be identified within associated pathways. The pathways approach is motivated by the fact that genes do not act alone, but instead have effects that are likely to be mediated through their interaction in gene pathways. Where this is the case, pathways approaches may reveal aspects of a trait's genetic architecture that would otherwise be missed when considering SNPs in isolation. Most pathways methods begin by testing SNPs one at a time, and so fail to capitalise on the potential advantages inherent in a multi-SNP, joint modelling approach. Here, we describe a dual-level, sparse regression model for the simultaneous identification of pathways and genes associated with a quantitative trait. Our method takes account of various factors specific to the joint modelling of pathways with genome-wide data, including widespread correlation between genetic predictors, and the fact that variants may overlap multiple pathways. We use a resampling strategy that exploits finite sample variability to provide robust rankings for pathways and genes. We test our method through simulation, and use it to perform pathways-driven gene selection in a search for pathways and genes associated with variation in serum high-density lipoprotein cholesterol levels in two separate GWAS cohorts of Asian adults. By comparing results from both cohorts we identify a number of candidate pathways including those associated with cardiomyopathy, and T cell receptor and PPAR signalling. Highlighted genes include those associated with the L-type calcium channel, adenylate cyclase, integrin, laminin, MAPK signalling and immune function.

EINVis: a visualization tool for analyzing and exploring genetic interactions in large-scale association studies

Epistasis (gene-gene interaction) detection in large-scale genetic association studies has recently drawn extensive research interests as many complex traits are likely caused by the joint effect of multiple genetic factors. The large number of possible interactions poses both statistical and computational challenges. A variety of approaches have been developed to address the analytical challenges in epistatic interaction detection. These methods usually output the identified genetic interactions and store them in flat file formats. It is highly desirable to develop an effective visualization tool to further investigate the detected interactions and unravel hidden interaction patterns. We have developed EINVis, a novel visualization tool that is specifically designed to analyze and explore genetic interactions. EINVis displays interactions among genetic markers as a network. It utilizes a circular layout (specially, a tree ring view) to simultaneously visualize the hierarchical interactions between single nucleotide polymorphisms (SNPs), genes, and chromosomes, and the network structure formed by these interactions. Using EINVis, the user can distinguish marginal effects from interactions, track interactions involving more than two markers, visualize interactions at different levels, and detect proxy SNPs based on linkage disequilibrium. EINVis is an effective and user-friendly free visualization tool for analyzing and exploring genetic interactions. It is publicly available with detailed documentation and online tutorial on the web at http://filer.case.edu/yxw407/einvis/.

The human L-type calcium channel Cav1.3 regulates insulin release and polymorphisms in CACNA1D associate with type 2 diabetes

AIMS/HYPOTHESIS

Voltage-gated calcium channels of the L-type have been shown to be essential for rodent pancreatic beta cell function, but data about their presence and regulation in humans are incomplete. We therefore sought to elucidate which L-type channel isoform is functionally important and its association with inherited diabetes-related phenotypes.

METHODS

Beta cells of human islets from cadaver donors were enriched using FACS to study the expression of the genes encoding voltage-gated calcium channel (Cav)1.2 and Cav1.3 by absolute quantitative PCR in whole human and rat islets, as well as in clonal cells. Single-cell exocytosis was monitored as increases in cell capacitance after treatment with small interfering (si)RNA against CACNA1D (which encodes Cav1.3). Three single nucleotide polymorphisms (SNPs) were genotyped in 8,987 non-diabetic and 2,830 type 2 diabetic individuals from Finland and Sweden and analysed for associations with type 2 diabetes and insulin phenotypes.

RESULTS

In FACS-enriched human beta cells, CACNA1D mRNA expression exceeded that of CACNA1C (which encodes Cav1.2) by approximately 60-fold and was decreased in islets from type 2 diabetes patients. The latter coincided with diminished secretion of insulin in vitro. CACNA1D siRNA reduced glucose-stimulated insulin release in INS-1 832/13 cells and exocytosis in human beta cells. Phenotype/genotype associations of three SNPs in the CACNA1D gene revealed an association between the C allele of the SNP rs312480 and reduced mRNA expression, as well as decreased insulin secretion in vivo, whereas both rs312486/G and rs9841978/G were associated with type 2 diabetes.

CONCLUSION/INTERPRETATION

We conclude that the L-type calcium channel Cav1.3 is important in human glucose-induced insulin secretion, and common variants in CACNA1D might contribute to type 2 diabetes.

Polygenic effects of common single-nucleotide polymorphisms on life span: when association meets causality

Recently we have shown that the human life span is influenced jointly by many common single-nucleotide polymorphisms (SNPs), each with a small individual effect. Here we investigate further the polygenic influence on life span and discuss its possible biological mechanisms. First we identified six sets of prolongevity SNP alleles in the Framingham Heart Study 550K SNPs data, using six different statistical procedures (normal linear, Cox, and logistic regressions; generalized estimation equation; mixed model; gene frequency method). We then estimated joint effects of these SNPs on human survival. We found that alleles in each set show significant additive influence on life span. Twenty-seven SNPs comprised the overlapping set of SNPs that influenced life span, regardless of the statistical procedure. The majority of these SNPs (74%) were within genes, compared to 40% of SNPs in the original 550K set. We then performed a review of current literature on functions of genes closest to these 27 SNPs. The review showed that the respective genes are largely involved in aging, cancer, and brain disorders. We concluded that polygenic effects can explain a substantial portion of genetic influence on life span. Composition of the set of prolongevity alleles depends on the statistical procedure used for the allele selection. At the same time, there is a core set of longevity alleles that are selected with all statistical procedures. Functional relevance of respective genes to aging and major diseases supports causal relationships between the identified SNPs and life span. The fact that genes found in our and other genetic association studies of aging/longevity have similar functions indicates high chances of true positive associations for corresponding genetic variants.

A genome-wide association study of hypertension-related phenotypes in a Japanese population

BACKGROUND

Large-scale genome-wide association studies (GWAS) have been successful in identifying genes that contribute to common diseases and phenotypes. A GWAS of hypertension-related phenotypes in a Japanese population was conducted in the current study.

METHODS AND RESULTS

A total of 936 participants were recruited from the Suita Study and a GWAS with 538,732 single nucleotide polymorphisms (SNP) was performed. The phenotypes included were systolic and diastolic blood pressure (SBP and DBP), body mass index (BMI), waist-to-hip ratio (WHR), plasma renin activity (PRA), plasma aldosterone concentration (PAC), plasma brain natriuretic peptide (BNP) concentration and alcohol consumption (AC). The SNP exceeding the genome-wide significance level were subjected to subsequent association studies using samples available from the Suita Study and Nomura Study. There is no master gene in the Japanese population that profoundly affects SBP, DBP, BMI, WHR, PRA and PAC. AC was influenced by the functional polymorphism in ALDH2, which affected BP levels in men. The BNP concentration was influenced by a polymorphism in the 3' region of the gene encoding for BNP. However, this polymorphism did not influence blood pressure (BP). Six SNP were identified to be associated with hypertension in both the Suita and Nomura studies.

CONCLUSIONS

Although several candidate SNP relevant to hypertension and those influencing AC and BNP were identified, our middle-sized GWAS indicated that there is no master gene in Japanese people that profoundly affects BP-related phenotypes.

Genetic variation in CACNA1C, a gene associated with bipolar disorder, influences brainstem rather than gray matter volume in healthy individuals

BACKGROUND

Genetic variation in CACNA1C has been repeatedly shown to increase risk for psychiatric disorders, with the strongest evidence for involvement in bipolar disorder. To elucidate the mechanisms by which such effects on psychiatric disease are brought about by genetic factors, we investigated the influence of CACNA1C polymorphisms on brain structure.

METHODS

In 585 healthy volunteers, for whom magnetic resonance imaging data at 1.5 T (n = 282) or 3 T (n = 304) were available, we tested 193 single nucleotide polymorphisms (SNPs) in or near CACNA1C for association with FSL FIRST-segmented subcortical brain structures and hippocampus as well as SPM5-derived total brain volume and global gray and white matter volume using PLINK.

RESULTS

A study-wide significant association of SNPs in intron 3 of the CACNA1C gene was found for brainstem volume (lowest p value = 3.62E-05) and was confirmed by voxel-based morphometry. An effect on gray matter volume of the bipolar disorder-associated SNP rs1006737, as reported earlier in a sample of 77 healthy adults, could not be confirmed.

CONCLUSIONS

Genetic variation in the pleiotropic psychiatric disease gene CACNA1C is associated with brainstem volume. Modulation of this structure, with its central control over motor, cognitive, affective, and arousal functions, constitutes an interesting novel potential mode of action of psychiatric risk factors.

Calcium channel blockers differentially modulate cytokine production by peripheral blood mononuclear cells

BACKGROUND

Calcium channel blockers (CCB) are known to modulate immune reactions, so the present study was performed to examine the effects of various CCBs that have shown different effects on transcription factors and on the production of pro-inflammatory cytokines by human peripheral blood mononuclear cells (PBMC).

METHODS AND RESULTS

PBMC from healthy volunteers were isolated by Ficoll-paque density centrifugation. To study the effect of CCBs, the PBMC were stimulated with lipopolysaccharide or concanavalin A. After 24 h of incubation, the supernatants were harvested and the interleukin (IL)-1alpha, -1beta, and -6, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma levels were determined by specific enzyme-linked immunosorbent assay. The production of IL-1alpha and -1beta stimulated with lipopolysaccharide was significantly increased in the presence of amlodipine. In contrast, nifedipine and verapamil suppressed the production of IL-1beta, TNF-alpha, and IFN-gamma. Amlodipine and diltiazem significantly increased production of IL-1alpha stimulated with concanavalin A. Nifedipine inhibited production of IL-1alpha, IL-6, and IFN-gamma. Verapamil suppressed production of IFN-gamma.

CONCLUSIONS

Differential modulation of cytokine production was seen with various CCBs, and the suppressive effect of nifedipine was most prominent.

CACNA1C gene polymorphisms, cardiovascular disease outcomes, and treatment response

BACKGROUND

The gene encoding the target of calcium channel blockers, the alpha1c-subunit of the L-type calcium channel (CACNA1C), has not been well characterized, and only small pharmacogenetic studies testing this gene have been published to date.

METHODS AND RESULTS

Resequencing of CACNA1C was performed followed by a nested case-control study of the INternational VErapamil SR/trandolapril STudy (INVEST) GENEtic Substudy (INVEST-GENES). Of 46 polymorphisms identified, 8 were assessed in the INVEST-GENES. Rs1051375 was found to have a significant interaction with treatment strategy (P=0.0001). Rs1051375 A/A genotype was associated with a 46% reduction in the primary outcome among those randomized to verapamil SR treatment, when compared with atenolol treatment (odds ratio 0.54 95% CI 0.32 to 0.92). In heterozygous A/G individuals, there was no difference in the occurrence of the primary outcome when randomized to verapamil SR versus atenolol treatment (odds ratio 1.47 95% CI 0.86 to 2.53), whereas homozygous G/G individuals had a greater than 4-fold increased risk of the primary outcome with verapamil treatment compared with those randomized to atenolol treatment (odds ratio 4.59 95% CI 1.67 to 12.67). We did not identify allelic expression imbalance or differences in mRNA expression in heart tissue by rs1051375 genotype.

CONCLUSIONS

Variation in CACNA1C is associated with treatment response among hypertensive patients with stable coronary artery disease. Our data suggest a genetically defined group of patients that benefit most from calcium channel blocker therapy, a group that benefits most from beta-blocker therapy, and a third group in which calcium channel blocker and beta-blocker therapy are equivalent.