Association of genetic polymorphisms of ACADSB and COMT with human hypertension

Identification of biomarkers, pathways, and potential therapeutic targets for heart failure using next-generation sequencing data and bioinformatics analysis

BACKGROUND

Heart failure (HF) is the most common cardiovascular diseases and the leading cause of cardiovascular diseases related deaths. Increasing molecular targets have been discovered for HF prognosis and therapy. However, there is still an urgent need to identify novel biomarkers. Therefore, we evaluated biomarkers that might aid the diagnosis and treatment of HF.

METHODS

We searched next-generation sequencing (NGS) dataset (GSE161472) and identified differentially expressed genes (DEGs) by comparing 47 HF samples and 37 normal control samples using limma in R package. Gene ontology (GO) and pathway enrichment analyses of the DEGs were performed using the g: Profiler database. The protein-protein interaction (PPI) network was plotted with Human Integrated Protein-Protein Interaction rEference (HiPPIE) and visualized using Cytoscape. Module analysis of the PPI network was done using PEWCC1. Then, miRNA-hub gene regulatory network and TF-hub gene regulatory network were constructed by Cytoscape software. Finally, we performed receiver operating characteristic (ROC) curve analysis to predict the diagnostic effectiveness of the hub genes.

RESULTS

A total of 930 DEGs, 464 upregulated genes and 466 downregulated genes, were identified in HF. GO and REACTOME pathway enrichment results showed that DEGs mainly enriched in localization, small molecule metabolic process, SARS-CoV infections, and the citric acid tricarboxylic acid (TCA) cycle and respiratory electron transport. After combining the results of the PPI network miRNA-hub gene regulatory network and TF-hub gene regulatory network, 10 hub genes were selected, including heat shock protein 90 alpha family class A member 1 (HSP90AA1), arrestin beta 2 (ARRB2), myosin heavy chain 9 (MYH9), heat shock protein 90 alpha family class B member 1 (HSP90AB1), filamin A (FLNA), epidermal growth factor receptor (EGFR), phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1), cullin 4A (CUL4A), YEATS domain containing 4 (YEATS4), and lysine acetyltransferase 2B (KAT2B).

CONCLUSIONS

This discovery-driven study might be useful to provide a novel insight into the diagnosis and treatment of HF. However, more experiments are needed in the future to investigate the functional roles of these genes in HF.

Long-term monitoring for short/branched-chain acyl-CoA dehydrogenase deficiency: A single-center 4-year experience and open issues

INTRODUCTION

Short/branched-chain acyl-CoA dehydrogenase deficiency (SBCADD) is an inherited disorder of L-isoleucine metabolism due to mutations in the ACADSB gene. The role of current diagnostic biomarkers [i.e., blood 2-methylbutyrylcarnitine (C5) and urine 2-methylbutyrylglycine (2MBG)] in patient monitoring and the effects of proposed treatments remain uncertain as follow-data are lacking. This study presents first systematic longitudinal biochemical assessment in SBCADD patients.

METHODS

A retrospective, observational single-center study was conducted on newborns born between 2017 and 2020 and suspected with SBCADD. Biochemical, molecular, clinical and dietary data collected upon NBS recall and during the subsequent follow-up were recorded.

RESULTS

All enrolled subjects (n = 10) received adequate protein intake and L-carnitine supplementation. Nine subjects were diagnosed with SBCADD. During the follow-up [median: 20.5 (4-40) months] no patient developed symptoms related to SBCADD. No patient normalized serum C5 and urine 2MBG values. In 7/9 SBCADD patients mean serum C5 values decreased or stabilized compared to their first serum C5 value. A major increase in serum C5 values was observed in two patients after L-carnitine discontinuation and during intercurrent illness, respectively. Urine 2MBG values showed moderate intra-patient variability.

DISCUSSION

The relatively stable serum C5 values observed during L-carnitine supplementation together with C5 increase occurring upon L-carnitine discontinuation/intercurrent illness may support the value of serum C5 as a monitoring biomarker and the benefit of this treatment in SBCADD patients. The role of urine 2MBG in patient monitoring remains uncertain. As all patients were asymptomatic, no association between biochemical parameters and clinical phenotype could be investigated in this study.

Interleukin-1β enhances cell adhesion in human endothelial cells via microRNA-1914-5p suppression

Atherosclerosis is a chronic inflammatory disease and the underlying cause of most cardiovascular diseases. Interleukin (IL)-1β facilitates early atherogenic lesion formation by increasing monocyte adhesion to endothelial cells via upregulation of adhesion molecules, including intercellular adhesion molecule-1 (ICAM-1). MicroRNAs (miRNAs) have been shown to be associated with inflammatory conditions in the vascular system. The expression of circulating miR-1914-5p is reportedly downregulated in patients with cardiovascular diseases. However, the role of miR-1914-5p downregulation in IL-1β-induced endothelial cell dysfunction and the effect of miR-1914-5p on lesion formation remain unclear. Therefore, we investigated whether miR-1914-5p is associated with monocyte adhesion in human endothelial cells. IL-1β decreased miR-1914-5p expression in EA.hy926 cells. In addition, miR-1914-5p depletion enhanced ICAM-1 expression and monocyte adhesion in EA.hy926 cells. Moreover, miR-1914-5p mimic suppressed monocyte adhesion and ICAM-1 expression induced by IL-1β in endothelial cells. These results suggest that suppression of miR-1914-5p expression by IL-1β may be an important regulator in mediating monocyte adhesion in endothelial cells. Further investigation of miR-1914-5p may lead to the development of novel therapeutic strategies for atherosclerosis.

VAL158MET catechol O-methyltransferase polymorphism contributes to the development of preeclampsia

Objectives: Establishment of association between: (a) Val158Met COMT (G1947A) polymorphism and preeclampsia; (b) cytokines gene expression and COMT genotypes. Methods: 50 preeclampsia and 50 healthy pregnant women were enrolled. COMT genotyping was done by PCR/RFLP. TNF-α, IL-1β, and IL-6 mRNA levels were determined by Real-time PCR. Results: Variant (AA) homozygotes carried 3.7-fold increased preeclampsia odds, especially for severe (OR = 9.0, 95%CI (2.09-38.799)) and early forms (OR = 6.6, 95%CI (1.62-26.87)). AA homozygotes with PE had higher TNF-α levels compared to controls (P = 0.012). Conclusions: Val158Met COMT polymorphism increases preeclampsia risk. TNF-α expression and Val158Met COMT polymorphism have concomitant roles in PE pathogenesis.

Clinical, biochemical, and molecular spectrum of short/branched-chain acyl-CoA dehydrogenase deficiency: two new cases and review of literature

Background Short/branched-chain acyl-CoA dehydrogenase (SBCAD) deficiency is a rare inborn error of metabolism with uncertain clinical significance. As it leads to C5-carnitine (i.e. isovalerylcarnitine, 2methylbutyrilcarnitine, or pivaloylcarnitine) elevation, SBCAD deficiency is detectable at newborn screening, requiring differential diagnosis from isovaleric acidemia and pivalic acid administration. Increased urinary excretion of 2-methylbutyrylglycine (2MBG) is the hallmark of SBCAD deficiency. Methods We report two cases of SBCAD deficiency and provide a review of the available literature on this condition. Results Two siblings newly diagnosed with SBCAD deficiency are reported. Newborn screening allowed the early diagnosis in the second-born (C5=0.5 μmol/L, normal 0.05-0.3 μmol/L) and addressed selective screening in the 5-year asymptomatic brother (C5=1.9 μmol/L). Both patients showed increased urinary excretion of 2MBG and two mutations in the ACADSB gene (c.443C>T/c.1145C>T). Currently, both the patients are asymptomatic. Longitudinal biochemical monitoring of the two patients while on treatment with carnitine (100 mg/kg/day) was provided. Based on our experience and the literature review (162 patients), SBCAD deficiency is symptomatic in about 10% of reported patients. Clinical onset occurs in newborns or later in life with seizures, developmental delay, hypotonia, and failure to thrive. On longitudinal follow-up, epilepsy, developmental delay, microcephaly, and autism can develop. Acute metabolic decompensation due to catabolic stressors can occur, as observed in one newly reported patient. Fifteen mutations in the ACADSB gene are known, including the newly identified variant c.1145C>T (p.Thr382Met), variably associated to the phenotype. In the Hmong population, SBCAD deficiency is highly prevalent, mostly due to the founder mutation c.1165A>G, and is largely asymptomatic. Conclusions Although mostly asymptomatic, considering SBCAD deficiency as a non-disease in non-Hmong subjects appears unsafe. Catabolic situations can precipitate acute metabolic decompensation. Carnitine supplementation and valproate avoidance appear to be indicated. Providing an emergency protocol for the management of acute catabolic episodes seems reasonable in asymptomatic patients with SBCAD deficiency. Longitudinal follow-up is recommended.

The effect of short/branched chain acyl-coenzyme A dehydrogenase gene on triglyceride synthesis of bovine mammary epithelial cells

Abstract. Short/branched chain acyl-CoA dehydrogenase (ACADSB) is a member of the acyl-CoA dehydrogenase family of enzymes that catalyze the dehydrogenation of acyl-CoA derivatives in the metabolism of fatty acids. Our previous transcriptome analysis in dairy cattle showed that ACADSB was differentially expressed and was associated with milk fat metabolism. The aim of this study was to elucidate the background of this differential expression and to evaluate the role of ACADSB as a candidate for fat metabolism in dairy cattle. After analysis of ACADSB mRNA abundance by qRT-PCR and Western blot, overexpression and RNA interference (RNAi) vectors of ACADSB gene were constructed and then transfected into bovine mammary epithelial cells (bMECs) to examine the effects of ACADSB on milk fat synthesis. The results showed that the ACADSB was differentially expressed in mammary tissue of low and high milk fat dairy cattle. Overexpression of ACADSB gene could significantly increase the level of intracellular triglyceride (TG), while ACADSB gene knockdown could significantly reduce the TG synthesis in bMECs. This study suggested that the ACADSB was important in TG synthesis in bMECs, and it could be a candidate gene to regulate the metabolism of milk fat in dairy cattle.

The influence of dopamine-beta-hydroxylase and catechol O-methyltransferase gene polymorphism on the efficacy of insulin detemir therapy in patients with type 2 diabetes mellitus

BACKGROUND

Type II diabetes is an important health problem with a complex connection to obesity, leading to a broad range of cardiovascular complications. Insulin therapy often results in weight gain and does not always ensure adequate glycemic control. However, previous studies reported that insulin detemir is an efficient long-acting insulin with a weight sparing effect. The aim of this study was to determine the association of catechol O-methyltransferase (COMT) Val108/158Met and dopamine-beta-hydroxylase (DBH) 1021C/T polymorphisms with the effectiveness of insulin detemir in achieving glucose control and body weight control. Participants and methods: This 52-week observational study included 185 patients with inadequate glycemic control treated with premix insulin analogues, which were replaced with insulin aspart and insulin detemir, and 156 healthy controls. After DNA isolation from blood samples, genotyping of DBH-1021C/T polymorphism (rs1611115) and COMT Val108/158Met polymorphism (rs4680) was performed.

RESULTS

Our results confirmed that insulin detemir did not lead to weight gain. The most significant finding was that A carriers (the combined AG and AA genotype) of the COMT Val108/158Met achieved significantly better hemoglobin A1c (HbA1c) values compared to patients carrying GG genotype. No association between DBH-1021C/T genotypes and weight and/or glucose control was detected in diabetes patients or in healthy control subjects.

CONCLUSIONS

This study showed that the presence of one or two A allele of the COMT Val108/158Met was associated with improved glycemic response, and with a better response to insulin detemir therapy in patients with type II diabetes, separating them as best candidates for detemir therapy.

Catechol-O-methyltransferase Gene Polymorphism (Val158Met) and Development of Pre-eclampsia

OBJECTIVES

Catechol-O-methyltransferase (COMT) is a key enzyme in degradation pathways of estrogens and catecholamines. The present meta-analysis was done to elucidate the association of COMT Val158Met polymorphism with pre-eclampsia among pregnant women.

METHODS

A literature search was conducted in electronic databases including PubMed, Scopus, Elsevier, Springer and Google Scholar to find eligible studies. The pooled odds ratios (ORs) with 95% confidence intervals were calculated under dominant, recessive, co-dominant, and allelic models.

RESULTS

This meta-analysis included 6 eligible studies consisting 2596 cases and 4223 controls. The ORs for the COMT G472A polymorphism and pre-eclampsia were indicative of positive association under several genetic models. The results indicated that COMT Val158Met polymorphism was significantly associated with the increased risk of pre-eclampsia in recessive model (AA vs. AG + GG: OR = 1.522 [95% CI: 1.089-2.127]; p = 0.014), co-dominant model (AA vs. GG: OR = 1.605 [95% CI: 1.102-2.336]; p = 0.014), and allelic model (A vs. T: OR = 1.200 [95% CI: 1.021-1.402]; p = 0.021).

CONCLUSIONS

In summary, COMT Val158Met polymorphism is positively associated with the increased risk of pre-eclampsia among pregnant women, especially the homozygous carriers. It could be of value to investigate its association with pre-eclampsia in combination with additional risk factors. However, very large studies with different ethnic population are required to accurately demonstrate the role of this candidate gene in development of pre-eclampsia.

Pulse Pressure Magnifies the Effect of COMT Val(158)Met on 15 Years Episodic Memory Trajectories

We investigated whether a physiological marker of cardiovascular health, pulse pressure (PP), and age magnified the effect of the functional COMT Val(158)Met (rs4680) polymorphism on 15-years cognitive trajectories [episodic memory (EM), visuospatial ability, and semantic memory] using data from 1585 non-demented adults from the Betula study. A multiple-group latent growth curve model was specified to gauge individual differences in change, and average trends therein. The allelic variants showed negligible differences across the cognitive markers in average trends. The older portion of the sample selectively age-magnified the effects of Val(158)Met on EM changes, resulting in greater decline in Val compared to homozygote Met carriers. This effect was attenuated by statistical control for PP. Further, PP moderated the effects of COMT on 15-years EM trajectories, resulting in greater decline in Val carriers, even after accounting for the confounding effects of sex, education, cardiovascular diseases (diabetes, stroke, and hypertension), and chronological age, controlled for practice gains. The effect was still present after excluding individuals with a history of cardiovascular diseases. The effects of cognitive change were not moderated by any other covariates. This report underscores the importance of addressing synergistic effects in normal cognitive aging, as the addition thereof may place healthy individuals at greater risk for memory decline.

Meta-Analysis of the COMT Val158Met Polymorphism in Major Depressive Disorder: Effect of Ethnicity

The COMT (catechol-O-methyltransferase) Val158Met polymorphism (rs4680) is a potential susceptibility variant for major depressive disorder (MDD). Although many genetic studies have examined the association between MDD and this polymorphism, the results were inconclusive. In the present study, we conducted a series of meta-analyses of samples consisting of 2905 MDD cases and 2403 controls with the goal of determining whether this variant indeed has any effect on MDD. We revealed a significant association in the comparison of Val/Val + Val/Met vs. Met/Met (OR =1.180; 95 % CI = 1.019, 1.367; P = 0.027), Val/Met vs. Val/Val (OR =1.18; 95 % CI = 1.038, 1.361; P = 0.013), and Val/Met vs. Met/Met (OR =1.229; 95 % CI = 1.053, 1.435; P = 0.009). Further meta-analyses of samples with European ancestry demonstrated a significant association of this SNP with MDD susceptibility in Val/Val + Val/Met vs. Met/Met (OR =1.231, 95 % CI = 1.046, 1.449; P = 0.013) and Val/Met vs. Met/Met (OR =1.284, 95 % CI = 1.050, 1.484; P = 0.012). For the samples with East Asian ancestry, we found a significant association in both allelic (Val vs. Met: OR =0.835; 95 % CI = 0.714, 0.975; P = 0.023) and genotypic (Met/Met + Val/Met vs. Val/Val: OR =1.431, 95 % CI = 1.143, 1.791; P = 0.002; Val/Met vs. Val/Val: OR =1.482, 95 % CI = 1.171, 1.871; P = 0.001) analyses. No evidence of heterogeneity among studies or publication bias was observed. Together, our results indicate that the COMT Val158Met polymorphism is a vulnerability factor for MDD with distinct effects in different ethnic populations.

A case control association study of COMT gene polymorphism (I/D) with type 2 diabetes and its related factors in Pakistani Punjabi population

BACKGROUND

The Catechol-O-Methyl Transferase (COMT) gene polymorphism (I/D of C nucleotide at base position 900) has been previously implicated in the development of type 2 diabetes (T2D) and kidney disease. So, aim of this study was to find association of I/D polymorphism with T2D, and its associated factors like family history and nephropathy (End Stage Renal Disease, ESRD) patients in a cohort of Pakistani Punjabis.

METHODS

Genomic DNA was extracted from human subjects divided as four study groups: controls (n = 46), diabetics (n = 46), diabetics with nephropathy/ESRD (n = 53), and non-diabetics without nephropathy/ESRD (n = 43). The 900 I/D C polymorphism in the COMT gene was tested by PCR-RFLP method. Genotype and allele frequencies as well as Odds Ratios were calculated for these groups. Groups were compared statistically for the analysis of genotypes, alleles, biochemical parameters as well as disease status.

RESULTS

In comparison with control group (non-diabetic, non-nephropathy), there was no significant difference in rest of the three groups for allele or genotype frequencies of COMT gene. However, Chi square (χ(2)) analysis identified a significant (p = 0.02) correlation of the 900 I/D C polymorphism with family history of diabetes, as it was found that greater number (74%) of patients having I allele had a positive family history of T2D.

CONCLUSIONS

A significant correlation of the COMT polymorphism (900 I/D C) with the family history of T2D has been observed, which has not been previously reported in Pakistani Punjabi population, however, this preliminary finding requires further validation studies.

Association of COMT G675A and MTHFR C677T polymorphisms with hypertensive disorders of pregnancy in Mexican mestizo population

OBJECTIVE

To investigate the relationship between COMT G675A and MTHFR C677T polymorphisms and hypertension disorders of pregnancy (HDP) in a Mexican mestizo population.

DESIGN AND METHODS

This case-control study involved 194 HDP and 194 normoevolutive pregnant women. The polymorphisms were genotyped by real time PCR.

RESULTS

Our results showed that the COMT AA genotype increases the risk to HDP (OR: 2.67; 95% CI 1.33-5.35), preeclampsia (OR: 2.69; 95% CI 1.00-7.22) and gestational hypertension (OR: 3.87; 95% CI 1.25-12.0). Furthermore, the double mutant genotype (COMTAA/MTHFRTT) potency the risk to HDP more than two times (OR: 5.21; 95% CI 1.12-24.3, p=0.019).

CONCLUSION

Our work provides evidence that COMT 675AA genotype is a risk factor for HDP and that this risk is increased by the presence of MTHFR 677TT genotype in a Mexican mestizo population.

Association between Val158Met functional polymorphism in the COMT gene and risk of preeclampsia in a Chinese population

BACKGROUND AND AIMS

The catechol-O-methyltransferase (COMT) gene is a potential candidate in altering risk for preeclampsia due to the important enzymatic effects in the metabolism of steroid hormones. It contains a non-synonymous G-A base change at codon 158 in the membrane bound isoform, which leads to a valine-to-methionine amino acid substitution. In the soluble isoform the polymorphism rs4680 is located in codon 108. The variant allele is the Met (A) allele and the Val (G) allele is the wild type allele. Despite its previously reported association with preeclampsia in genotypes in three selected ethnic groups, further studies in other populations are required.

METHODS

We genotyped the Val158Met polymorphism in the COMT gene by polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) analysis in a Chinese population.

RESULTS

In the case-control study that included 187 patients with preeclampsia (cases) and 189 normal subjects (controls), the AA genotype and variant Met allele frequencies of Val158Met in the COMT gene were significantly higher in patients with preeclampsia than those in the control group (both p <0.05). The odds ratio for the risk of preeclampsia was 2.395 [95% confidence interval (CI): 1.061-5.408] in women homozygous for the variant COMT allele (χ(2) = 4.649, p = 0.031). Furthermore, it showed that obese women homozygous for the variant COMT allele (Met/Met) had higher diastolic blood pressure levels during pregnancy than wild-type homozygotes (Val/Val) (p = 0.034).

CONCLUSIONS

Our study provided evidence in favor of COMT being a candidate gene for conferring genetic susceptibility to preeclampsia in a South West Chinese population.

A Hypertension Gene: Are We There Yet?

Cardiovascular diseases are the leading cause of death worldwide. Essential hypertension is a major risk factor for the development of other cardiovascular diseases and is caused by a combination of environmental and genetic factors, with up to 50% of blood pressure variance currently attributed to an individual's genetic makeup. By studying genes that cause monogenic forms of hypertension and pathways relevant to blood pressure control, a number of polymorphisms have been identified that increase an individual's risk of developing high blood pressure. We report on candidate gene association studies and genome-wide association studies that have been performed to date in the field of hypertension research. It is becoming clear that for the majority of people there is no single gene polymorphism that causes hypertension, but rather a number of common genetic variants, each having a small effect. Using pharmacogenomics to personalize the treatment of hypertension holds promise for achieving and sustaining normotensive pressures quickly, while minimizing the risk of adverse reactions and unwanted side-effects. This will decrease the risk of stroke and myocardial infarction in individuals and lead to a reduced burden of disease upon society as a whole.

Association of the catechol-O-methyl transferase gene Val158Met polymorphism with blood pressure and prevalence of hypertension: interaction with dietary energy intake

BACKGROUND

Previous studies of a functional variant of the catechol-O-methyl transferase (COMT) gene, Val158Met, have provided inconsistent results with regard to blood pressure or hypertension. We examined the effect of this variant, the considering environmental factors of daily salt and energy intakes.

METHODS

A total of 735 Japanese men (mean age, 47 years) were recruited from two separate occupational cohorts from Kanagawa and Kyoto prefectures. Participants were genotyped for the presence of COMT Val158Met (rs4680, G/A). Daily salt and energy intakes were evaluated by the food frequency questionnaire (FFQ).

RESULTS

Met/Met carriers had higher adjusted systolic blood pressure (SBP) (+4.79 mm Hg, P < 0.001) and diastolic blood pressure (DBP) (+2.33 mm Hg, P = 0.001) than Met/Val or Val/Val carriers. There was a significant association between being a Met/Met carrier and having a higher prevalence of hypertension (odds ratio = 2.448, 95% confidence interval = 1.426-4.205, P = 0.001). When salt and energy intakes were dichotomized, the effect of Val158Met on hypertension was observed only in the high-energy intake group, and was equivalent between low- and high-salt groups.

CONCLUSION

The Met allele of COMT Val158Met is associated with higher blood pressure and higher prevalence of hypertension in Japanese men, and energy intake may interact with this effect.

The combined impact of 12 common variants on hypertension in Japanese men, considering GWAS results

Genome-wide association studies have identified several polymorphisms that appear to be on hypertension-susceptible regions. We performed the current replication study in order to evaluate the association of these loci with hypertension in healthy Japanese males and then examined the combined effect of 12 independent variants. Overall, 735 Japanese men from two independent cohorts were recruited. Association with hypertension was assessed in 16 polymorphisms on 12 genes and 12 were chosen to evaluate the combined impact. Polymorphisms on the COMT, ATP2B1, CYP11A1 and the CSK genes were confirmed to be associated with hypertension and blood pressure (BP). Current findings also replicated previous results for the CYP11B2 and PTGIS genes. Although there were no significant associations found for other variants, our results suggested there was a combined impact for 12 loci. Individuals carrying more risk alleles had a higher risk of hypertension (P for the slope=0.002). Blood pressures also increased in conjunction with an increasing risk allele score (P for trend=7.84 × 10(-6) and 1.85 × 10(-5) for SBP and DBP, respectively). Our results confirmed the associations between hypertension or blood pressure and four gene variants. We also found a significant combined effect of the 12 gene loci.

Systematic polymorphism discovery after genome-wide identification of potential susceptibility loci in a hereditary rodent model of human hypertension

Genetic strategies such as linkage analysis and quantitative trait locus (QTL) mapping have identified a multitude of loci implicated in the pathogenesis of hypertension in the spontaneously hypertensive rat (SHR). While several candidate genetic regions have been identified in the SHR and its control, the Wistar-Kyoto rat (WKY), systematic follow-up of candidate identification with polymorphism discovery has not been widespread. In the current report, we develop a data-mining strategy to identify candidate genes for hypertension in the SHR, and then sequence each gene in the SHR and WKY strains. We integrate blood pressure QTL data, microarray data and data-mining methods. First, we determined the set of genes differentially expressed in SHR and WKY adrenal glands. Next, the chromosomal position of all differentially expressed genes was compared with peak marker position of all reported SHR blood pressure QTLs. We also identified the set of differentially expressed genes with the most extreme fold-change. Finally, the QTL positional candidates and the genes with extreme differential expression were proposed as candidate genes if they had biologically plausible roles in hypertensive pathology. We identified seven candidate genes that merit resequencing (catechol-O-methyltransferase [Comt], chromogranin A [Chga], dopamine beta-hydroxylase [Dbh], electron transferring flavoprotein dehydrogenase [Etfdh], endothelin receptor type B [Ednrb], neuropeptide Y [Npy] and phenylethanolamine-N-methyltransferase [Pnmt]), and then discovered polymorphism in four of these seven candidate genes. Chga is proposed as the strongest candidate for additional functional investigation. Our method for candidate gene identification is portable and can be applied to microarray data from any tissue, in any disease model with a QTL database.

Promoter hypomethylation of COMT in human placenta is not associated with the development of pre-eclampsia

Disruption of the Catechol-O-methyltransferase (COMT) gene has been shown to be involved in pre-eclampsia (PE). To investigate whether two promoters of the COMT gene are differentially regulated by methylation in PE patients, we have analyzed the genomic DNA extracted from placenta (cases n = 16; controls n = 21), maternal peripheral blood (cases n = 4; controls n = 6) and umbilical cord blood (cases n = 8; controls n = 8) of women with PE and women with normal pregnancy. Bisulfite sequencing identified the predominantly unmethylated MB-COMT promoter in placenta, maternal peripheral blood and umbilical cord blood samples (PE and control). Subsequent quantitative MassArray data confirmed a significant tissue-specific hypomethylation of the S-COMT promoter in placenta (mean = 28.6%) when compared with its densely methylated patterns in blood samples (mean = 74.5%, P < 0.001), consistent with the sequencing data. However, no PE-specific methylation difference was found between cases and controls either in placenta or in blood samples. Moreover, none of the clinical characteristics had an effect on the methylation status of the S-COMT promoter. This study does not support a causal link between methylation regulation of COMT promoters and PE. However, the observed placenta-specific S-COMT promoter may be a potential marker for early prediction of PE in maternal plasma, although this remains to be further evaluated.

Low enzymatic activity haplotypes of the human catechol-O-methyltransferase gene: enrichment for marker SNPs

Catechol-O-methyltransferase (COMT) is an enzyme that plays a key role in the modulation of catechol-dependent functions such as cognition, cardiovascular function, and pain processing. Three common haplotypes of the human COMT gene, divergent in two synonymous and one nonsynonymous (val(158)met) position, designated as low (LPS), average (APS), and high pain sensitive (HPS), are associated with experimental pain sensitivity and risk of developing chronic musculoskeletal pain conditions. APS and HPS haplotypes produce significant functional effects, coding for 3- and 20-fold reductions in COMT enzymatic activity, respectively. In the present study, we investigated whether additional minor single nucleotide polymorphisms (SNPs), accruing in 1 to 5% of the population, situated in the COMT transcript region contribute to haplotype-dependent enzymatic activity. Computer analysis of COMT ESTs showed that one synonymous minor SNP (rs769224) is linked to the APS haplotype and three minor SNPs (two synonymous: rs6267, rs740602 and one nonsynonymous: rs8192488) are linked to the HPS haplotype. Results from in silico and in vitro experiments revealed that inclusion of allelic variants of these minor SNPs in APS or HPS haplotypes did not modify COMT function at the level of mRNA folding, RNA transcription, protein translation, or enzymatic activity. These data suggest that neutral variants are carried with APS and HPS haplotypes, while the high activity LPS haplotype displays less linked variation. Thus, both minor synonymous and nonsynonymous SNPs in the coding region are markers of functional APS and HPS haplotypes rather than independent contributors to COMT activity.

COMT genotype influences the effect of alcohol on blood pressure: results from the COMBINE study

BACKGROUND

Heavy drinking can cause chronic hypertension, possibly due to effects on the autonomic nervous system. Catechol- O-methyltransferase (COMT) inactivates catecholamines, and a G to A substitution in codon 108 in the soluble COMT mRNA (or codon 158 in the membrane-bound form) substitutes methionine for valine and alters enzyme activity.

METHODS

We evaluated the association of COMT genotype at this locus with blood pressure (BP) in 839 alcohol-dependent individuals before and during participation in an alcoholism treatment trial. Hierarchical linear models were used to account for within-subject correlation on repeated BP measurements, and findings were adjusted for age, gender, ethnicity, alcohol use, body mass index, current smoking, hypertension history, and study site.

RESULTS

Relative to those with the val-val genotype, those with the met-met genotype had higher adjusted systolic (+4.9 mm Hg, P < 0.01) and diastolic (+3.2 mm Hg, P < 0.01) BP at baseline. Those with the val-met genotype did not significantly differ from the val-val genotype. Changes in BP between baseline and 4 weeks of alcohol treatment also differed by genotype. Relative to the val-val genotype, the met-met genotype had a greater reduction in adjusted systolic pressure (-3.9 mm Hg, P < 0.01) and diastolic pressure (-2.8 mm Hg, P < 0.01). Corresponding relative reductions for the val-met genotype were -2.2 mm Hg systolic (P = 0.070) and -1.5 mm Hg diastolic (P < 0.05).

CONCLUSION

Findings suggest that alcohol-induced BP elevation may be related to the effects of catecholamines and their genetically determined inactivation.

Catechol O-methyltransferase val158-met polymorphism is associated with abdominal obesity and blood pressure in men

Catechol O-methyltransferase (COMT) degrades catecholamines and estrogens, both of which are of known importance for cardiovascular risk factors such as obesity and hypertension. The gene coding for COMT contains a val158-met polymorphism that exerts a considerable influence on enzymatic activity. We hypothesized that this polymorphism might influence risk factors for cardiovascular disease. Deoxyribonucleic acid samples and data regarding blood pressure and anthropometry were collected from 240 Swedish men, all 51 years old. Subjects homozygous for the low-activity allele (met) displayed higher blood pressure, heart rate, waist-to-hip ratio, and abdominal sagittal diameter as compared with heterozygous subjects, who in turn displayed higher blood pressure, heart rate, waist-to-hip ratio, and abdominal sagittal diameter than subjects homozygous for the high-activity allele (val). All measured variables were significantly correlated; however, the associations between COMT val158-met and cardiovascular variables, and the association between COMT val158-met and anthropometry, respectively, were partly independent of each other, as revealed by multiple linear regression.