Variable number of tandem repeat of the 5'-flanking region of type-C human natriuretic peptide receptor gene influences blood pressure levels in obesity-associated hypertension

Epstein-Barr virus-induced gene 3 (EBI3) single nucleotide polymorphisms and their association with central obesity and risk factors for cardiovascular disease: The GEA study

Obesity, a chronic low-grade inflammation metabolic abnormality, is related to high proinflammatory cytokines concentrations. Epstein-Barr virus-induced gene 3 (EBI3) encodes for the EBI3 beta subunit that constitutes interleukin (IL) 27 and 35. Our objective was to assess the association of three EBI3 single nucleotide polymorphisms (SNPs) with the presence of central obesity in a group of Mexican subjects. The rs428253, rs4740, and rs4905 EBI3 SNPs were genotyped in 1323 individuals (1092 central obese and 231 non-central obese). We also analyzed IL-6, IL-27, and IL-35 concentrations. Under different models, the rs4740 (OR = 0.384, P_recessive = 0.010; OR = 0.404, P_{codominant 2} = 0.019) and rs4905 (OR = 0.380, P_recessive = 0.009; OR = 0.404, P_{codominant 2} = 0.018) were related with a low risk of central obesity. In central obese subjects, the SNPs were related to lower risk of hypoalphalipoproteinemia (rs4740) and with high IL-6 concentrations (rs428253, rs4740, and rs4905), whereas in non-central obese individuals, the rs428253 was related with low risk of increased visceral abdominal fat and hypertriglyceridemia. Interleukin-6, IL-27 and IL-35 concentrations were similar in both groups and no relation was noticed with the studied genotypes. Our results suggest an association of EBI3 SNPs with a low risk of central obesity and with a few risk factors for cardiovascular disease in individuals with and without central obesity.

Association of NPR3 polymorphism with risk of essential hypertension in a Chinese population

WHAT IS KNOWN AND OBJECTIVE

Essential hypertension (EH) is a common disease exhibiting large individual difference in occurrence, development and treatment response. Genetic factors are implicated in the development and progression of EH. This study aimed to explore the association between NPR3 single nucleotide polymorphism rs2270915 (A/G, Asn521Asp) and the risk of EH in a Chinese Han population by a case-control study.

METHODS

The study was a single-centre, case-control trial, in which a total of 287 EH patients and 289 age- and sex-matched healthy controls were enrolled. The inclusion criteria were as follows: Han Chinese origin, male or female patients, systolic blood pressure (SBP) ≥140 mm Hg and/or diastolic blood pressure (DBP) ≥90 mm Hg. The healthy controls were subjects without histories of cardiovascular or cerebrovascular diseases. NPR3 rs2270915 polymorphism was genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). In addition, primary human umbilical vein endothelial cells (HUVECs) were isolated from 19 fresh human umbilical cords and cultured. Atrial natriuretic peptide (ANP) concentration in cell medium was determined by enzyme-linked immunosorbent assay (ELISA). NPR3 mRNA expression was determined by real-time semi-quantitative PCR.

RESULTS AND DISCUSSION

No significant difference in genotype distribution of NPR3 rs2270915 polymorphism was observed between cases and controls (P>.05). Patients carrying the rs2270915 G allele showed decreased SBP, and the difference was marginal. As compared with cells carrying the rs2270915 AA genotype, those with the AG genotype showed significantly lower NPR3 mRNA expression levels (P<.05) and lower medium ANP concentration (P<.001).

WHAT IS NEW AND CONCLUSION

This study suggested that NPR3 rs2270915 polymorphism was associated with decreased SBP level marginally in EH patients in a Chinese Han population, and the polymorphism may function through decreasing NPR3 mRNA expression and ANP level.

Body composition, resting energy expenditure and inflammatory markers: impact in users of depot medroxyprogesterone acetate after 12 months follow-up

OBJECTIVE

The aim of this study was to evaluate for 12 months the changes of body weight using Depot Medroxyprogesterone Acetate (DMPA) and if these changes are related to inflammatory markers.

SUBJECTS AND METHODS

Twenty women of childbearing age who chose the DMPA, without previous use of this method, BMI < 30 kg/m2, and 17 women using IUD TCu 380A, participated in the study. At the baseline and after one year, changes in weight gain, body composition by the bioimpedance electric method, resting energy expenditure (REE) by the indirect calorimetry method, inflammatory markers and HOMA-IR were assessed.

RESULTS

After 12 months of evaluation, we could observe a significant increase in the DMPA group in weight (3,01 kg) and BMI, while the IUD group's only significant increase was observed in the BMI. Relative to REE there was an increase of basal metabolic rate (BMR) in both groups after one year. The sub-group DMPA that gained < 3 kg had increased significant weight, BMI and body surface (BS) with respiratory quotient (RQ) reduction, while the sub-group that gained ≥ 3 kg had a significant increase in weight, BMI, BS, fat-free mass, fat mass, BMR, Leptin, HOMA-IR and waist circumference, with RQ significantly reduced.

CONCLUSION

Our study found significant changes in weight, body composition and metabolic profile of the population studied in the first 12 months of contraceptive use. These changes mainly increased body weight, leptin levels and HOMA-IR which can contribute to the development of some chronic complications, including obesity, insulin resistance and diabetes mellitus.

Arterial Stiffness and Decline in Kidney Function

BACKGROUND AND OBJECTIVES

The independent link between arterial stiffness and CKD remains unknown. We investigated the association of indicators of arterial stiffness with decline in kidney function.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We studied 3666 participants (mean age =65 years old; 58% women) from the Rotterdam Study. Pulse pressure (PP), carotid stiffness, and pulse wave velocity (PWV) were measured. We created genetic risk scores for PP and PWV. Annual declines in kidney function and incident CKD were assessed using eGFR. To put our findings in context of the literature, we performed a meta-analysis of the available population-based studies.

RESULTS

After a median (interquartile range) follow-up time of 11 (10.7-11.3) years, 601 participants with incident CKD were recognized. In the model adjusted for age, sex, mean arterial pressure, heart rate, and baseline GFR, each SD higher PP was associated with 0.15-ml/min per 1.73 m(2) steeper annual eGFR decline (95% confidence interval [95% CI], 0.10 to 0.20) and 11% higher risk of incident CKD (95% CI, 1.05 to 1.18). Each SD greater carotid stiffness was associated with 0.08-ml/min per 1.73 m(2) steeper annual eGFR decline (95% CI, 0.04 to 0.13) and 13% higher risk of incident CKD (95% CI, 1.05 to 1.22). Each SD higher PWV was associated with 7% higher risk of incident CKD (95% CI, 1.00 to 1.14). Incorporating our findings in a meta-analysis, each SD higher PP and PWV were associated with 16% (95% CI, 1.12 to 1.21) and 8% (95% CI, 1.03 to 1.14) higher risks of incident CKD. Each SD higher PP genetic risk score was associated with 0.06-ml/min per 1.73 m(2) steeper annual eGFR decline (95% CI, 0.01 to 0.10) and 8% higher risk of incident CKD (95% CI, 1.03 to 1.14). There was no association between PWV genetic risk score and kidney function decline.

CONCLUSIONS

Higher indices of arterial stiffness are associated with steeper decline in kidney function. This suggests that vascular stiffness could be considered as a target for delaying decline in kidney function.

Recombinant murine fibroblast growth factor 21 ameliorates obesity-related inflammation in monosodium glutamate-induced obesity rats

The aim of this study is to investigate the role of FGF21 in obesity-related inflammation in livers of monosodium glutamate (MSG)-induced obesity rats. The MSG rats were injected with recombinant murine fibroblast growth factor 21(FGF21) or equal volumes of vehicle. Metabolic parameters including body weight, Lee's index, food intake, visceral fat and liver weight, intraperitoneal glucose tolerance, glucose, and lipid levels were dynamically measured at specific time points. Liver function and routine blood test were also analyzed. Further, systemic inflammatory cytokines such as glucose transporter 1 (GLUT-1), leptin, TNF-α, and IL-6 mRNAs were determined by real-time PCR. FGF21 independently decreased body weight and whole-body fat mass without reducing food intake in the MSG rats. FGF21 reduced blood glucose level, Lee's index, visceral fat, and liver weight, and improved glucose tolerance, lipid metabolic spectrum, and hepatic steatosis in the MSG-obesity rats. Liver function parameters including AST, ALT, ALP, TP, T.Bili, and D.Bili levels significantly reduced in the FGF21-treated obesity rats compared to the controls. Further, FGF21 ameliorated the total and differential white blood cell (WBC) count, serum C-reactive protein (CRP), IL-6, and TNF-α levels in adipose tissues of the obesity rats, suggesting inflammation amelioration in the in the obesity rats by FGF21. FGF21 improves multiple metabolic disorders and ameliorates obesity-related inflammation in the MSG-induced obesity rats.

Endothelial C-type natriuretic peptide maintains vascular homeostasis

The endothelium plays a fundamental role in maintaining vascular homeostasis by releasing factors that regulate local blood flow, systemic blood pressure, and the reactivity of leukocytes and platelets. Accordingly, endothelial dysfunction underpins many cardiovascular diseases, including hypertension, myocardial infarction, and stroke. Herein, we evaluated mice with endothelial-specific deletion of Nppc, which encodes C-type natriuretic peptide (CNP), and determined that this mediator is essential for multiple aspects of vascular regulation. Specifically, disruption of CNP leads to endothelial dysfunction, hypertension, atherogenesis, and aneurysm. Moreover, we identified natriuretic peptide receptor-C (NPR-C) as the cognate receptor that primarily underlies CNP-dependent vasoprotective functions and developed small-molecule NPR-C agonists to target this pathway. Administration of NPR-C agonists promotes a vasorelaxation of isolated resistance arteries and a reduction in blood pressure in wild-type animals that is diminished in mice lacking NPR-C. This work provides a mechanistic explanation for genome-wide association studies that have linked the NPR-C (Npr3) locus with hypertension by demonstrating the importance of CNP/NPR-C signaling in preserving vascular homoeostasis. Furthermore, these results suggest that the CNP/NPR-C pathway has potential as a disease-modifying therapeutic target for cardiovascular disorders.

Association of natriuretic peptide receptor-C gene with ischemic stroke and hypertension in Chinese Han population

To investigate whether natriuretic peptide receptor-C (NPR3) gene polymorphisms were associated with ischemic stroke (IS) and hypertension (a conventional risk factor for stroke), we conducted a case-control study in Chinese Han population. We found that rs696831, located in intron 2, was associated with IS. In addition, we found that rs16890208 and rs700925, in linkage disequilibrium (LD) with each other in intron 3, were associated with hypertension. The A allele of the rs16890208, T allele of the rs700925, and the AT haplotype, derived from rs16890208 and rs700925, increased the risk of hypertension with odds ratios (ORs) of 1.74 (95% CI = 1.23-2.47), 1.72 (95% CI = 1.21-2.42), and 1.54 (95% CI = 1.14-2.08), respectively. Further, we found that rs11745562 and rs2270915, in LD with each other in intron 5 and exon 8, were associated with hypertension. The A allele of the rs11745562 and the G allele of the rs2270915 increased the risk of hypertension with ORs of 1.53 (95% CI = 1.07-2.19) and 1.55 (95% CI = 1.08-2.22), respectively. Therefore, we provided novel evidences that polymorphisms or haplotype in NPR3 gene may influence the risk of IS or hypertension independently in Chinese population.

Recent methods for polygenic analysis of genome-wide data implicate an important effect of common variants on cardiovascular disease risk

BACKGROUND

Traditional genome-wide association studies are generally limited in their ability explain a large portion of genetic risk for most common diseases. We sought to use both traditional GWAS methods, as well as more recently developed polygenic genome-wide analysis techniques to identify subsets of single-nucleotide polymorphisms (SNPs) that may be involved in risk of cardiovascular disease, as well as estimate the heritability explained by common SNPs.

METHODS

Using data from the Framingham SNP Health Association Resource (SHARe), three complimentary methods were applied to examine the genetic factors associated with the Framingham Risk Score, a widely accepted indicator of underlying cardiovascular disease risk. The first method adopted a traditional GWAS approach - independently testing each SNP for association with the Framingham Risk Score. The second two approaches involved polygenic methods with the intention of providing estimates of aggregate genetic risk and heritability.

RESULTS

While no SNPs were independently associated with the Framingham Risk Score based on the results of the traditional GWAS analysis, we were able to identify cardiovascular disease-related SNPs as reported by previous studies. A predictive polygenic analysis was only able to explain approximately 1% of the genetic variance when predicting the 10-year risk of general cardiovascular disease. However, 20% to 30% of the variation in the Framingham Risk Score was explained using a recently developed method that considers the joint effect of all SNPs simultaneously.

CONCLUSION

The results of this study imply that common SNPs explain a large amount of the variation in the Framingham Risk Score and suggest that future, better-powered genome-wide association studies, possibly informed by knowledge of gene-pathways, will uncover more risk variants that will help to elucidate the genetic architecture of cardiovascular disease.

The haplotype of the CACNA1B gene associated with cerebral infarction in a Japanese population

Cerebral infarction (CI) is thought to be a multifactorial disease that is affected by several environmental factors and genetic variants. N-type voltage-gated calcium channels (VGCCs), which are expressed primarily in the neurons, have various roles in neuronal functions and are especially involved with neurotransmitter release at the sympathetic nerve terminals. We considered the α1B subunit of the N-type voltage-gated calcium channel (CACNA1B) to be representative of the general characteristics of this channel type. The aim of the present study was to assess the association of the human CACNA1B gene with the occurrence of CI via a haplotype-based case-control study that used single nucleotide polymorphisms (SNPs) from the Japanese population. A total of 165 CI patients and 314 controls were enrolled in the case-controlled studies that examined three SNPs of the human CACNA1B gene (rs7042521, rs11137351, rs10780199). There were significant differences between the CI and control groups for the overall distribution of the genotypes and the presence of the recessive rs10780199. Multiple logistic regression analyses revealed that even after adjusting for confounding factors (odds ratio: 1.716), the frequencies of the A/G and G/G genotypes of rs10780199 in the CI group were significantly higher than those observed in the control group (p = 0.021). Furthermore, the C-C-G and G-G-G haplotypes of rs7042521-rs11137351-rs10780199 were significantly more frequent in the CI group than in the control group (p = 0.024 and p < 0.000). In conclusion, significant differences were noted between the CI and control patients for the specific SNPs and haplotypes in the CACNA1B gene. The results indicate that these polymorphisms and haplotypes might be genetic markers for CI.

Impact of natriuretic peptide clearance receptor (NPR3) gene variants on blood pressure in type 2 diabetes

OBJECTIVE

Hypertension in diabetes is characterized by abnormal sodium homeostasis, suggesting a particular role of natriuretic peptide pathway. Natriuretic peptides can affect blood pressure (BP) through their plasma concentrations, which are dependent on their receptor activities. We thus assessed the association between nine NPR3 gene polymorphisms and BP levels in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Nine single nucleotide polymorphisms (SNPs) tagging the haplotype structure of the NPR3 gene were genotyped in the 3,126 French Non-insulin-dependent Diabetes, Hypertension, Microalbuminuria or Proteinuria, Cardiovascular Events, and Ramipril (DIABHYCAR) trial participants. We then used a second population (Diabete de type 2, Nephropathie et Genetique [DIAB2NEPHROGENE]/Survie, Diabete de type 2 et Genetique [SURDIAGENE] study) of 2,452 patients for the purpose of replication. Finally, we separately investigated subjects selected according to their rs 2270915SNP genotypes for their BP response to salt restriction.

RESULTS

In DIABHYCAR patients, three SNPs (rs6889608, rs1173773, and rs2270915) were significantly associated with systolic BP (SBP). The effect of the rs2270915 was replicated in the second step population: AA homozygotes had a lower SBP than G carriers (137.4 ± 19.1 vs. 140.0 ± 20.2 mmHg, P = 0.004). The rs2270915 influenced the response of SBP to salt reduction, with AA homozygous patients showing greater reductions after restriction of salt intake compared with G carriers: -20 mmHg (-43 to -8) vs. -3 (-20 to +7); P = 0.006.

CONCLUSIONS

We found a consistent and significant association between the rs2270915 polymorphism of the NPR3 gene and SBP in diabetic patients. This genetic variation may affect pressure response to changes in dietary sodium.

Comorbidities of diabetes and hypertension: mechanisms and approach to target organ protection

Up to 75% of adults with diabetes also have hypertension, and patients with hypertension alone often show evidence of insulin resistance. Thus, hypertension and diabetes are common, intertwined conditions that share a significant overlap in underlying risk factors (including ethnicity, familial, dyslipidemia, and lifestyle determinants) and complications. These complications include microvascular and macrovascular disorders. The macrovascular complications, which are well recognized in patients with longstanding diabetes or hypertension, include coronary artery disease, myocardial infarction, stroke, congestive heart failure, and peripheral vascular disease. Although microvascular complications (retinopathy, nephropathy, and neuropathy) are conventionally linked to hyperglycemia, studies have shown that hypertension constitutes an important risk factor, especially for nephropathy. The familial predisposition to diabetes and hypertension appears to be polygenic in origin, which militates against the feasibility of a "gene therapy" approach to the control or prevention of these conditions. On the other hand, the shared lifestyle factors in the etiology of hypertension and diabetes provide ample opportunity for nonpharmacologic intervention. Thus, the initial approach to the management of both diabetes and hypertension must emphasize weight control, physical activity, and dietary modification. Interestingly, lifestyle intervention is remarkably effective in the primary prevention of diabetes and hypertension. These principles also are pertinent to the prevention of downstream macrovascular complications of the two disorders. In addition to lifestyle modification, most patients will require specific medications to achieve national treatment goals for hypertension and diabetes. Management of hyperglycemia, hypertension, dyslipidemia, and the underlying hypercoagulable and proinflammatory states requires the use of multiple medications in combination.

Association of genetic variation in the natriuretic peptide system with cardiovascular outcomes

Polymorphisms within individual natriuretic peptide genes have been associated with risk factors for cardiovascular disease, but their association with clinical outcomes was previously unknown. This study aimed to investigate the association between genetic variants in key genes of the natriuretic peptide system with cardiovascular outcomes in patients with coronary artery disease. Coronary disease patients (n=1810) were genotyped for polymorphisms within NPPA, NPPB, NPPC, NPR1 and NPR2. Clinical history, natriuretic peptide concentrations, echocardiography, all-cause mortality and cardiovascular hospital readmissions were recorded over a median 2.8 years. Minor alleles of NPPA rs5068, rs5065 and rs198358 were associated with less history of hypertension; minor alleles of NPPA rs5068 and rs198358 was also associated with higher circulating natriuretic peptide levels (p=0.003 to p=0.04). Minor alleles of NPPB rs198388, rs198389, and rs632793 were associated with higher circulating BNP and NT-proBNP (p=0.001 to p=0.03), and reduced E/E(1) (p=0.011), or LVESVI (p=0.001) and LVEDVI (p=0.004). Within NPPC, both rs11079028 and rs479651 were associated with higher NT-proBNP and CNP (p=0.01 to p=0.03), and rs479651 was associated with lower LVESVI (p=0.008) and LVEDVI (p=0.018). NPR2 rs10758325 was associated with smaller LVMI (p<0.02). A reduced rate of cardiovascular readmission was observed for minor alleles of NPPA rs5065 (p<0.0001), NPPB rs632793 (p<0.0001), rs198388 (p<0.0001), rs198389 (p<0.0001), and NPR2 rs10758325 (p<0.0001). There were no associations with all-cause mortality. In established cardiovascular disease, natriuretic peptide system polymorphisms were associated with natriuretic peptide levels, hypertension, echocardiographic indices and the incidence of hospital readmission for cardiovascular events.

Inflammation, a link between obesity and cardiovascular disease

Obesity, the most common nutritional disorder in industrialized countries, is associated with an increased mortality and morbidity of cardiovascular disease (CVD). Obesity is primarily considered to be a disorder of energy balance, and it has recently been suggested that some forms of obesity are associated with chronic low-grade inflammation. The present paper focuses on the current status of our knowledge regarding chronic inflammation, a link between obesity and CVDs, including heart diseases, vascular disease and atherosclerosis. The paper discusses the methods of body fat evaluation in humans, the endocrinology and distribution of adipose tissue in the genders, the pathophysiology of obesity, the relationship among obesity, inflammation, and CVD, and the adipose tissue-derived cytokines known to affect inflammation. Due to space limitations, this paper focuses on C-reactive protein, serum amyloid A, leptin, adiponectin, resistin, visfatin, chemerin, omentin, vaspin, apelin, and retinol binding protein 4 as adipokines.

Genetic Polymorphisms of the Natriuretic Peptide System in the Pathogenesis of Cardiovascular Disease: What Lies on the Horizon?

Background: The natriuretic peptide hormone family includes various proteins characterized by similar chemical structure and shared biological functions, with important effects on the cardiovascular system. Accordingly, these molecules are widely recognized as key clinical biomarkers in the diagnosis and monitoring of heart failure, hypertension, and coronary heart disease.

Content: Several single-nucleotide polymorphisms have been recently identified in genes associated with the natriuretic system. This review provides an overview of new insights into the functional role of these genetic variants, as well as their impact on cardiovascular physiopathology and drug response.

Conclusions: Noteworthy relationships between some specific polymorphisms and clinical correlates of cardiovascular disease have emerged. Nevertheless, future confirming studies are needed to substantiate the clinical relevance of such variants.

Haplotype-based case-control study of the human CYP4F2 gene and essential hypertension in Japanese subjects

CYP4F2 acts primarily as an enzyme that converts arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE), a metabolite involved in the regulation of blood pressure in humans. The aim of the present study was to assess the association between the human CYP4F2 gene and essential hypertension (EH) using a haplotype-based case-control study that included separate analysis of the two gender groups. The 249 EH patients and 238 age-matched controls were genotyped for 5 single-nucleotide polymorphisms (SNPs) of the human CYP4F2 gene (rs3093105, rs3093135, rs1558139, rs2108622, rs3093200). Data were analyzed for 3 separate groups: all subjects, and men and women separately. For the total population and for male subjects, the distribution of the dominant model of rs1558139 (CC vs. CT+TT) differed significantly between the EH patients and control subjects (p=0.037 and p=0.005, respectively), with a higher percentage of EH patients showing the CC genotype. Logistic regression showed that, for men, the CC genotype of rs1558139 was more prevalent in the EH patients than in the control subjects (p=0.026), while, for the total population, the difference disappeared (p=0.247). For men, the overall distribution of the haplotypes was significantly different between the EH patients and the control subjects (p=0.042), and the frequency of the T-T-G haplotype was also significantly lower for EH patients than for control subjects (p=0.009). In conclusion, the present results indicate that rs1558139 might be a genetic marker for EH and the T-T-G haplotype might be a protective genetic marker for EH in Japanese men.

Association of renin-angiotensin system and natriuretic peptide receptor A gene polymorphisms with hypertension in a Hellenic population

Introduction. Hypertension results from the interaction of genetic and environmental factors. Since the renin-angiotensin and the natriuretic peptide systems contribute to blood pressure regulation, variations in the relative genes are candidates for the development of hypertension.

Materials and methods. In 194 hypertensives and 304 controls of Hellenic origin, the possible association between the (CA)n repeat polymorphism of angiotensinogen (AGT), the 250 bp insertion/deletion (I/D) of angiotensin-converting enzyme (ACE), the tetranucleotide repeat polymorphism (TCTG)n of renin, and the (CT)n repeat polymorphism of the natriuretic peptide receptor A (NPRA) and hypertension was assessed.

Results. No association between AGT and NPRA polymorphisms and hypertension was observed. The presence of ID or DD genotype of ACE was associated with an increased risk for hypertension compared with the II genotype (OR: 1.782 [95% CI: 1.032—3.077]), whereas the LL genotype of the renin gene was associated with a decreased risk compared with the SS genotype (OR: 0.174 [95% CI: 0.044—0.689]). However, after adjustment for confounding factors only the latter association remained.

Conclusions. In the present study conducted in a homogeneous Hellenic population, no associations betweenAGT,ACE, and NPRA gene polymorphisms and hypertension were found. The presence of a significant negative association between the LL polymorphism of the renin gene and hypertension requires further confirmation.

Genetic variation in the natriuretic peptide system and heart failure

Heart failure (HF) is a modern epidemic and is one of the few cardiovascular diseases which is increasing in prevalence. The growing importance of the Natriuretic Peptide (NP) system in HF is well recognized. Laboratory tests for B-type Natriuretic Peptide (BNP) have proven value as diagnostic and prognostic tools in HF and are now part of routine clinical care. Furthermore, recombinant atrial natriuretic peptide (ANP) (carperitide) and BNP (nesiritide) and are approved HF therapies in Japan and the US, respectively and additional natriuretic peptides (e.g., CNP, urodilatin, and designer NPs) are under investigation for use in HF. Common genetic sequence variants are increasingly being recognized as determinants of disease risk or drug response and may help explain a portion of the inter-individual variation in the human NP system. This review describes current knowledge of NP system genetic variation as it pertains to HF as well as ongoing studies and where the field is expected to progress in the near future. To briefly summarize, NP system genetic variants have been associated with alterations in gene expression, NP levels, and cardiovascular disease. The next step forward will include specific investigations into how this genetic variation can advance 'Personalized Medicine', such as whether they impact the utility of diagnostic BNP testing or effectiveness of therapeutic NP infusion. This is already in progress, with pharmacogenetic studies of nesiritide currently underway. We expect that within 5 years there should be a reasonable idea of whether NP system genetic variation will have important clinical implications.

Renin-angiotensin system, natriuretic peptides, obesity, metabolic syndrome, and hypertension: an integrated view in humans

The obesity pandemic is closely related to hypertension and metabolic syndrome. Visceral adipose tissue plays a key role in the metabolic and cardiovascular complications of being overweight. The pathophysiological link between visceral adiposity and cardiometabolic complications focuses on insulin sensitivity, sympathetic nervous system, renin-angiotensin-aldosterone system (RAAS) and, only recently, on cardiac natriuretic peptide system (CNPS). RAAS and CNPS are endogenous antagonistic systems on sodium balance, cardiovascular system, and metabolism. The circulating RAAS is dysregulated in obese patients, and adipose tissue has a full local renin-angiotensin system that is active at local and systemic level. Adipocyte biology and metabolism are influenced by local renin-angiotensin system, with angiotensin II acting as a 'growth factor' for adipocytes. CNPS induces natriuresis and diuresis, reduces blood pressure, and, moreover, has powerful lipolytic and lipomobilizing activity in humans but not in rodents. In obesity, lower plasmatic natriuretic peptides levels with increasing BMI, waist circumference, and metabolic syndrome have been documented. Thus, reduced CNPS effects coupled with increased RAAS activity have a central role in obesity and its deadly complications. We propose herein an integrated view of the dysregulation of these two antagonistic systems in human obesity complicated with hypertension, metabolic syndrome, and increased cardiovascular risk.

A novel variable number of tandem repeat of the natriuretic peptide precursor B gene's 5'-flanking region is associated with essential hypertension among Japanese females

BACKGROUND

Brain natriuretic peptide (BNP) acts primarily as a cardiac hormone; it is produced by the ventricle and has both vasodilatory and natriuretic actions. Therefore, the BNP gene is thought to be a candidate gene for essential hypertension (EH). The present study identified variants in the 5'-flanking region of natriuretic peptide precursor B (NPPB) gene and assessed the relationship between gene variants and EH.

METHODS

The polymerase chain reaction-single strand conformation polymorphism method and nucleotide sequencing were used to identify variants.

RESULTS

A novel variable number of tandem repeat (VNTR) polymorphism in the 5'-flanking region (-1241 nucleotides from the major transcriptional initiation site) was discovered. This VNTR polymorphism is a tandem repeat of the 4-nucleotide sequence TTTC. There were 8 alleles, ranging from 9-repeat to 19-repeat. An association study was done involving 317 EH patients and 262 age-matched normotensive (NT) subjects. The 11-repeat allele was the most frequent (88.2%); the 16-repeat allele was the second most frequent (10.5%) in the NT group. The observed and expected genotypes were in agreement with the predicted Hardy-Weinberg equilibrium values (P=0.972). Among females, the overall distribution of genotypes was significantly different between the EH and NT groups (p=0.039). The frequency of the 16-repeat allele was significantly lower in the female EH group (6.5%) than in the female NT group (12.2%, p=0.046).

CONCLUSIONS

The 16-repeat allele of the VNTR in the 5'-flanking region of NPPB appears to be a useful genetic marker of EH in females.

Genetic variation in the B-type natiuretic peptide pathway affects BNP levels

PURPOSE

The importance of B-type natriuretic peptide (BNP) as a diagnostic and therapeutic modality in cardiovascular disease is well known. BNP levels correlate clinical and physiologic characteristics, as well as outcomes. We sought to investigate the influence of BNP pathway genetic variation on BNP levels after adjustment for clinical/physiologic factors.

MATERIALS AND METHODS

DNA was extracted from 147 patients undergoing elective cardiac catheterization. Patients with elevated troponin were excluded. Detailed clinical data was collected including standard demographic, laboratory, echocardiographic and catheterization data. Genotype was determined at 19 loci in five genes relevant to the BNP pathway. Multivariable linear regression models of logBNP, adjusted for clinical variables, were used to assess the incremental influence of the genetic variants.

RESULTS

Natriuretic peptide precursor B gene (NPPB) variants incrementally improved models of logBNP after inclusion of clinical/physiologic parameters. The NPPB -381 T > C genotype was significantly associated with logBNP in the model (p = 0.0005), with the model predicting 50% lower BNP levels in otherwise similar T/T vs. C/C subjects. The NPPB 777 G > A (3' flanking region) genotype was of borderline significance (p = 0.0078). None of the other genotypes examined were significant (all p > 0.2).

CONCLUSIONS

Genetic variation in NPPB significantly impacts BNP levels after adjustment for clinical/physiologic factors. The full linear regression model predicted up to a 50% relative difference in BNP levels between NPPB -381 T > C genotype groups. This suggests that NPPB sequence variants affect BNP physiology, possibly via transcriptional regulation. Further studies are needed to define whether these variants impact the clinical interpretation of BNP levels.

Genotyping of triallelic SNPs using TaqMan PCR

Methods for analysis of single nucleotide polymorphisms (SNP) are well developed. However, most ready-made SNP genotyping kits (e.g., those that use TaqMan PCR) are based on the assumption that the SNP is biallelic. Thus, most kits are unsuitable for triallelic SNPs. We have experienced difficulty genotyping an SNP using TaqMan PCR. In the present study, we developed a method of genotyping a triallelic SNP (rs3091244: alleles C, A and T) using TaqMan PCR. We used 2 different genotyping kits: one for C/A allele genotyping, and one for C/T allele genotyping. The results of these 2 kits were combined to complete the genotyping. The subjects were 320 essentially healthy elderly Japanese. The frequencies of the C, A and T alleles were 0.78, 0.155 and 0.065, respectively. This double-tube method using TaqMan SNP Genotyping Assays was very accurate and convenient, and it should be useful for genotyping in case-control association studies or linkage studies.

Relationship between the Thromboxane A2 Receptor Gene and Susceptibility to Cerebral Infarction

The risk of cerebral infarction (CI) in an individual is dependent on the interplay between genetic risk factors and environmental influences. Binding of thromboxane A2 (TXA2) to its receptor (TP) modulates thrombosis/hemostasis and plays a significant role in the pathogenesis of CI. The aim of the present study was to investigate the relationship between human TP gene single nucleotide polymorphisms (SNPs) and haplotypes and CI in a Japanese population. A genetic association study was performed in 194 CI patients and 365 non-CI subjects by specifically characterizing 6 SNPs in the human TP gene (rs2271875, rs768963, rs2238634, rs11085026, rs4523 and rs4806942). Analysis demonstrated that there were significant differences in the overall distribution of genotypes and dominant or recessive models of rs2271875 and rs768963 between the CI and the non-CI groups. Multiple logistic regression analysis revealed that the C allele of rs768963 was significantly associated with CI (p = 0.029), even after adjusting for confounding factors (odds ratio: 2.41). Further, the C-T-C haplotype of rs768963-rs2238634-rs4806942 was significantly more frequent in the CI group (23.0%) than in the non-CI group (17.7%). These results suggest that specific SNPs and haplotypes may have utility as genetic markers for the risk of CI and that TP or a neighboring gene is associated with the increased susceptibility to CI.

The genetic contribution of the natriuretic peptide system to cardiovascular diseases

Three types of natriuretic peptides (NP) have been isolated: atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). The NP family elicits a number of vascular, renal and endocrine effects that help to maintain blood pressure and extracellular fluid volume. These effects are mediated by the specific binding of NP to cell surface receptors that have been characterized, purified and cloned from cells of the vasculature, kidney, adrenal gland and brain. There are 3 subtypes of NP receptors: type A natriuretic peptide receptor (NPRA), type B natriuretic peptide receptor (NPRB), and type C natriuretic peptide receptor (NPRC). All 3 subtypes affect cellular second messenger activity. NPRA and NPRB are guanylyl cyclase receptors, and their activation increases cGMP levels. Activation of NPRC results in inhibition of adenylyl cyclase activity. Human NPRA has a high structural homology with human NPRB, and contains a highly-conserved guanylyl cyclase domain. ANP and BNP bind primarily to NPRA, which is found in the vasculature, causing vasodilation and inhibition of vascular smooth muscle cell proliferation. The present paper contains a review of NPs and their receptors and the genetic contribution of the NP system to cardiovascular diseases such as essential hypertension and myocardial infarction.