A novel promoter variant of the natriuretic peptide clearance receptor gene is associated with lower atrial natriuretic peptide and higher blood pressure in obese hypertensives

Role of Cardiac Natriuretic Peptides in Heart Structure and Function

Cardiac natriuretic peptides (NPs), atrial NP (ANP) and B-type NP (BNP) are true hormones produced and released by cardiomyocytes, exerting several systemic effects. Together with C-type NP (CNP), mainly expressed by endothelial cells, they also exert several paracrine and autocrine activities on the heart itself, contributing to cardiovascular (CV) health. In addition to their natriuretic, vasorelaxant, metabolic and antiproliferative systemic properties, NPs prevent cardiac hypertrophy, fibrosis, arrhythmias and cardiomyopathies, counteracting the development and progression of heart failure (HF). Moreover, recent studies revealed that a protein structurally similar to NPs mainly produced by skeletal muscles and osteoblasts called musclin/osteocrin is able to interact with the NPs clearance receptor, attenuating cardiac dysfunction and myocardial fibrosis and promoting heart protection during pathological overload. This narrative review is focused on the direct activities of this molecule family on the heart, reporting both experimental and human studies that are clinically relevant for physicians.

Edema in childhood nephrotic syndrome: possible genes-hormones interplay

Background

The role of atrial natriuretic peptide (ANP) in edema formation in idiopathic nephrotic syndrome (INS) was studied before with conflicting results reported; however, the possible contribution of genes regulating ANP expression and receptors was never explored.

Methods

One hundred children (60 with active INS and 40 in remission) were studied for plasma atrial natriuretic peptide (ANP), urinary sodium, ANP gene A2843G and ScaI polymorphisms, and natriuretic peptide receptor clearance C (-55) A polymorphism. For comparative purposes, 20 healthy controls were studied for ANP levels.

Results

ANP was higher in active compared to remission patients (p<0.001). ANP in the healthy control group was significantly lower than the ANP level of active INS (during edema) group (p=0.009) but did not show significant differences when compared to ANP levels of either active INS group after resolution of edema or remission group (p= 0.42 and 0.56, respectively). Urinary sodium levels in edematous patients were significantly lower while ANP levels were significantly higher during edema than after resolution (p< 0.001 for both). Genotypes’ frequencies of studied polymorphisms did not differ between active and remission groups. Patients with the A1A1 genotype of ScaI polymorphism had higher ANP levels compared to other genotypes (p =0.01).

Conclusions

During edema, ANP levels are elevated in INS children however this increment is not associated with natriuresis suggesting a blunted renal response to ANP. Polymorphisms of genes regulating ANP levels and receptors don’t seem to be implicated in edema formation except for the A1A1 genotype of ScaI polymorphism however, its possible role needs further evaluation.

Insulin: Trigger and Target of Renal Functions

Kidney function in metabolism is often underestimated. Although the word “clearance” is associated to “degradation”, at nephron level, proper balance between what is truly degraded and what is redirected to de novo utilization is crucial for the maintenance of electrolytic and acid–basic balance and energy conservation. Insulin is probably one of the best examples of how diverse and heterogeneous kidney response can be. Kidney has a primary role in the degradation of insulin released in the bloodstream, but it is also incredibly susceptible to insulin action throughout the nephron. Fluctuations in insulin levels during fast and fed state add another layer of complexity in the understanding of kidney fine-tuning. This review aims at revisiting renal insulin actions and clearance and to address the association of kidney dysmetabolism with hyperinsulinemia and insulin resistance, both highly prevalent phenomena in modern society.

The biological impact of blood pressure-associated genetic variants in the natriuretic peptide receptor C gene on human vascular smooth muscle

Elevated blood pressure (BP) is a major global risk factor for cardiovascular disease. Genome-wide association studies have identified several genetic variants at the NPR3 locus associated with BP, but the functional impact of these variants remains to be determined. Here we confirmed, by a genome-wide association study within UK Biobank, the existence of two independent BP-related signals within NPR3 locus. Using human primary vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) from different individuals, we found that the BP-elevating alleles within one linkage disequilibrium block identified by the sentinel variant rs1173771 was associated with lower endogenous NPR3 mRNA and protein levels in VSMCs, together with reduced levels in open chromatin and nuclear protein binding. The BP-elevating alleles also increased VSMC proliferation, angiotensin II-induced calcium flux and cell contraction. However, an analogous genotype-dependent association was not observed in vascular ECs. Our study identifies novel, putative mechanisms for BP-associated variants at the NPR3 locus to elevate BP, further strengthening the case for targeting NPR-C as a therapeutic approach for hypertension and cardiovascular disease prevention.

Inverse Correlation of Venous Brain Natriuretic Peptide Levels with Body Mass Index Is due to Decreased Production

OBJECTIVE

The aim of this paper was to study the association between body mass index (BMI) and coronary sinus (CS) brain natriuretic peptide (BNP) levels in patients with heart failure and reduced systolic function (HFrEF).

BACKGROUND

There is an inverse relationship between systemic venous BNP (V-BNP) levels and BMI in patients with HFrEF. It is unclear whether this finding is due to decreased production or due to an increased metabolism of BNP. Since CS-BNP levels reflect BNP production, we hypothesized that assessing the correlation of CS-BNP levels with BMI would provide insight into the mechanism of this inverse relationship of V-BNP and BMI.

METHODS

We prospectively enrolled 54 subjects with HFrEF who were to undergo cardiac resynchronization device implantation. CS-BNP, V-BNP, and arterial BNP (A-BNP) levels were measured during the implant procedure. Subjects were divided into 2 groups based on their BMI (group 1: BMI <30 and group 2: BMI ≥30).

RESULTS

The mean age of the overall study group was 64 ± 10 years. Average BMI for group 1 was 25.8 ± 2.8 and 36.8 ± 4.6 for group 2 (p < 0.03). A history of hypertension was present in 55% (n = 26) of the subjects, while diabetes was reported in 31% (n = 15). Serum creatinine was 1.0 ± 0.2 mg/dL and TSH 2.1 ± 1.4 mIU/L. 79% of the subjects were receiving β-blockers, while 94% were receiving angiotensin-converting enzyme inhibitors or angiotensin receptor blockers. The mean CS-BNP, V-BNP, and A-BNP levels in group 2 were significantly lower than in group 1 (286.2 ± 170.5 vs. 417.5 ± 247.5 pg/mL, p = 0.04; 126.6 ± 32.5 vs. 228 ± 96.4 pg/mL, p = 0.01; and 151.9 ± 28.6 vs. 242 ± 88.8 pg/mL, p = 0.04, respectively). Univariate analysis and multivariate regression adjusted for age, diabetes mellitus, sex, glomerular filtration rate, and left atrial size confirmed BMI as an independent predictor of CS-BNP levels (β = -0.372, p = 0. 03) in our study.

CONCLUSIONS

In this study, we demonstrate an inverse relationship between CS-BNP levels and BMI in patients with HFrEF. These findings suggest that the previously established inverse relationship between V-BNP and BMI is due to a decreased cardiac production of BNP in obese patients rather than from increased peripheral metabolism.

[Pathophysiology of hypertension secondary to obesity]

The obesity is a problem with a high morbidity and mortality all over the world. It has now been designated as a cardiovascular risk factor. It often predisposes the development of many diseases that reduce quality of life, such as hypertension, dyslipidaemia, and diabetes. These diseases are associated with some of the criteria that should be considered in the diagnosis of metabolic syndrome. During this review, explanations will be presented on the relationship between obesity, metabolic syndrome, and the development of hypertension from neurohumoral, biochemical and mechanical concepts.

Insulin resistance in chronic kidney disease: a systematic review

Insulin resistance (IR) is an early metabolic alteration in chronic kidney disease (CKD) patients, being apparent when the glomerular filtration rate is still within the normal range and becoming almost universal in those who reach the end stage of kidney failure. The skeletal muscle represents the primary site of IR in CKD, and alterations at sites beyond the insulin receptor are recognized as the main defect underlying IR in this condition. Estimates of IR based on fasting insulin concentration are easier and faster but may not be adequate in patients with CKD because renal insufficiency reduces insulin catabolism. The hyperinsulinemic euglycemic clamp is the gold standard for the assessment of insulin sensitivity because this technique allows a direct measure of skeletal muscle sensitivity to insulin. The etiology of IR in CKD is multifactorial in nature and may be secondary to disturbances that are prominent in renal diseases, including physical inactivity, chronic inflammation, oxidative stress, vitamin D deficiency, metabolic acidosis, anemia, adipokine derangement, and altered gut microbiome. IR contributes to the progression of renal disease by worsening renal hemodynamics by various mechanisms, including activation of the sympathetic nervous system, sodium retention, and downregulation of the natriuretic peptide system. IR has been solidly associated with intermediate mechanisms leading to cardiovascular (CV) disease in CKD including left ventricular hypertrophy, vascular dysfunction, and atherosclerosis. However, it remains unclear whether IR is an independent predictor of mortality and CV complications in CKD. Because IR is a modifiable risk factor and its reduction may lower CV morbidity and mortality, unveiling the molecular mechanisms responsible for the pathogenesis of CKD-related insulin resistance is of importance for the identification of novel therapeutic targets aimed at reducing the high CV risk of this condition.

Effects of Cardiac Hormones on Arterial Pressure and Sodium Excretion in NPRA Knockout Mice

These studies were designed to determine if the atria contains natriuretic substances that act through a non–natriuretic peptide type A (NPRA) receptor mechanism. C57BL/6 mice, either wild-type NPRA++ (WT) or NPRA —- knockout (KO), were anesthetized with pentobarbital. Catheters were placed in the trachea, carotid artery, jugular vein, and bladder. Urine was collected for six 30-min periods. Both groups received an iv injection of 100 ng of rat atrial natriuetic peptide (rANP) in 200 μl of saline after the first period (30 mins) and 200 μl of rat atrial extract after the fourth period (120 mins). ANP injection increased urine flow (UF) to 2.7 ± 0.5 μl/min in the WT versus 1.9 ± 0.2 in KO. Extract increased UF to 7.9 ± 1.5 μl/min in WT versus 2.7 ± 0.4 in KO (P < 0.01). ANP increased sodium excretion (ENa) to 0.47 ± 0.10 μmoles/min in WT versus 0.27 ± 0.04 in KO (P < 0.05). Extract increased ENa to 1.44 ± 0.47 μmoles/min in WT versus 0.26 ± 0.06 in KO (P < 0.05). Extract decreased mean arterial pressure (MAP) to 62 ± 3 mm Hg in the WT versus 81 ± 5 in KO (P < 0.01). ENa and MAP responses to extract in KO were not different from responses to 200 μl of saline. A constant 150-min infusion of rat atrial extract increased urine flow by 3-fold and ENa by 5-fold (both P < 0.05) in the WT mice but had no significant effect in the KO mice. Thus, acute renal and MAP responses to atrial extracts require the NPRA receptor.

Associations Between Genetic Variants of the Natriuretic Peptide System and Blood Pressure Response to Dietary Sodium Intervention: The GenSalt Study

BACKGROUND

The aim of this study was to comprehensively test the association of genetic variants in the natriuretic peptide (NP) system with blood pressure (BP) response to dietary sodium intervention in a Chinese population.

METHODS

We conducted a 7-day low-sodium intervention followed by a 7-day high-sodium intervention among 1,906 participants in rural China. BP measurements were obtained at baseline and each dietary intervention using a random-zero sphygmomanometer. Linear mixed-effect models were used to assess the associations of 48 single-nucleotide polymorphisms (SNPs) in 6 genes of NP system with BP response to dietary sodium intervention.

RESULTS

SNP rs5063 in the NPPA gene and SNP rs2077386 in the NPPC gene exhibited significant associations with BP response to low-sodium dietary intervention under recessive genetic model. For rs5063, absolute mean arterial pressure responses (95% confidence interval) to the low-sodium intervention were 1.31 (-1.08, 3.70) mm Hg for TT genotype and -3.74 (-4.01, -3.46) mm Hg for CC or TC genotype, respectively (P = 4.1 × 10(-5)). Individuals with at least one copy of the C allele of rs2077386 had significantly reduction in systolic BP during the low-sodium intervention compared to those with genotype GG with responses of -5.48 (-5.83, -5.14) vs. -2.76 (-3.52, -2.00) mm Hg, respectively (P = 1.9 × 10(-13)).

CONCLUSIONS

These novel findings suggested that genetic variants of NP system may contribute to the variation of BP response to sodium intervention in Chinese population. Certainly, replication of these results in other populations and further functional studies are warranted to clarify their role in the regulation of BP and hypertension.

Defective Natriuretic Peptide Receptor Signaling in Skeletal Muscle Links Obesity to Type 2 Diabetes

Circulating natriuretic peptide (NP) levels are reduced in obesity and predict the risk of type 2 diabetes (T2D). Since skeletal muscle was recently shown as a key target tissue of NP, we aimed to investigate muscle NP receptor (NPR) expression in the context of obesity and T2D. Muscle NPRA correlated positively with whole-body insulin sensitivity in humans and was strikingly downregulated in obese subjects and recovered in response to diet-induced weight loss. In addition, muscle NP clearance receptor (NPRC) increased in individuals with impaired glucose tolerance and T2D. Similar results were found in obese diabetic mice. Although no acute effect of brain NP (BNP) on insulin sensitivity was observed in lean mice, chronic BNP infusion improved blood glucose control and insulin sensitivity in skeletal muscle of obese and diabetic mice. This occurred in parallel with a reduced lipotoxic pressure in skeletal muscle due to an upregulation of lipid oxidative capacity. In addition, chronic NP treatment in human primary myotubes increased lipid oxidation in a PGC1α-dependent manner and reduced palmitate-induced lipotoxicity. Collectively, our data show that activation of NPRA signaling in skeletal muscle is important for the maintenance of long-term insulin sensitivity and has the potential to treat obesity-related metabolic disorders.

Metabolic actions of natriuretic peptides and therapeutic potential in the metabolic syndrome

Natriuretic peptides (NPs) are a group of peptide-hormones mainly secreted from the heart, signaling via c-GMP coupled receptors. NP are well known for their renal and cardiovascular actions, reducing arterial blood pressure as well as sodium reabsorption. Novel physiological functions have been discovered in recent years, including activation of lipolysis, lipid oxidation, and mitochondrial respiration. Together, these responses promote white adipose tissue browning, increase muscular oxidative capacity, particularly during physical exercise, and protect against diet-induced obesity and insulin resistance. Exaggerated NP release is a common finding in congestive heart failure. In contrast, NP deficiency is observed in obesity and in type-2 diabetes, pointing to an involvement of NP in the pathophysiology of metabolic disease. Based upon these findings, the NP system holds the potential to be amenable to therapeutical intervention against pandemic diseases such as obesity, insulin resistance, and arterial hypertension. Various therapeutic approaches are currently under development. This paper reviews the current knowledge on the metabolic effects of the NP system and discusses potential therapeutic applications.

A functional genetic variant (N521D) in natriuretic peptide receptor 3 is associated with diastolic dysfunction: the prevalence of asymptomatic ventricular dysfunction study

Objectives

To evaluate the impact of a functional genetic variant in the natriuretic peptide clearance receptor, NPR3, on circulating natriuretic peptides (NPs) and myocardial structure and function in the general community.

Background

NPR3 plays an important role in the clearance of NPs and through direct signaling mechanisms modulates smooth muscle cell function and cardiac fibroblast proliferation. A NPR3 nonsynonymous single nucleotide polymorphism (SNP) rs2270915, resulting in a N521D substitution in the intracellular catalytic domain that interacts with Gi could affect receptor function. Whether this SNP is associated with alterations in NPs levels and altered cardiac structure and function is unknown.

Methods

DNA samples of 1931 randomly selected residents of Olmsted County, Minnesota were genotyped. Plasma NT-proANP_1-98, ANP_1-28, proBNP_1-108, NT-proBNP_1-76, BNP_1-32 and BNP_3-32 levels were measured. All subjects underwent comprehensive echocardiography.

Results

Genotype frequencies for rs2270915 were as follows: (A/A 60%, A/G 36%, G/G 4%). All analyses performed were for homozygotes G/G versus wild type A/A plus the heterozygotes A/G. Diastolic dysfunction was significantly more common (p = 0.007) in the homozygotes G/G (43%) than the A/A+A/G (28%) group. Multivariate regression adjusted for age, sex, body mass index and hypertension demonstrated rs2270915 to be independently associated with diastolic dysfunction (odds ratio 1.94, p = 0.03). There was no significant difference in NPs levels between the 2 groups suggesting that the clearance function of the receptor was not affected.

Conclusions

A nonsynonymous NPR3 SNP is independently associated with diastolic dysfunction and this association does not appear to be related to alterations in circulating levels of natriuretic peptides.

Therapeutic interventions for hypertension in metabolic syndrome: a comprehensive approach

Hypertension is a major component of the metabolic syndrome and a major cardiovascular risk factor. Both disorders are rapidly increasing in frequency, with hypertension affecting nearly 60 million Americans and over 1 billion people worldwide, and metabolic syndrome affecting 44% of the US population above the age of 60 years. Sedentary lifestyle, together with obesity and aging of the population, are the major contributing factors for this growing epidemic. Hypertension in metabolic syndrome possesses unique pathophysiological aspects that have considerable implications on therapy of this disease. In this article, we review the pathophysiology and provide a rationale for the current therapeutic options in light of the most recent clinical trials in the field.

The pathophysiological relationship and clinical significance of left atrial function and left ventricular diastolic dysfunction in β-thalassemia major

Iron deposition in combination with inflammatory and immunogenetic factors is involved in the pathophysiology of cardiac dysfunction in β-thalassemia major. We investigated the mechanical and endocrine function of the left atrium and ventricle to identify early signs of dysfunction. We studied 90 patients (mean age: 29 ± 11 years) with β-thalassemia and normal left ventricular function and 90 age and sex-matched healthy controls. Patients and controls underwent a thorough cardiac echocardiographic study and measurements of the b-type (NT-proBNP) and atrial natriuretic peptides (proANP). Patients underwent 24-hr Holter recordings for arrhythmia monitoring. In the patient group, atria were affected early during the course of the disease, prior to diastolic and systolic left ventricular dysfunction. The E/E'ratio (E Doppler mitral fast inflow to the corresponding tissue Doppler E) continually increased with age (P < 0.05) and reached levels indicating left ventricular diastolic dysfunction (E/E' > 15) in the third decade whereas indexes of active and passive atrial function decreased gradually throughout life. In controls, the E/E' ratio continually increased with age but with later (fifth decade) appearance of diastolic dysfunction and a compensatory increase in atrial active function. Both natriuretic peptides were significantly increased in patients compared to controls (558 ± 141 and 2,580 ± 1,830 fmol/mL for NT-proBNP and proANP versus 332 ± 106 and 1,331 ± 1,134 fmol/mL, respectively). Atrial fibrillation was found in a subgroup of 23 (26%) patients, older in age with mild diastolic function and enlarged, depressed atria. In conclusion, atrial mechanical depression seems to be a very early sign of cardiac damage. It may become echocardiographically evident even before diastolic and systolic dysfunction and is associated to supraventricular arrhythmias.

The atrial natriuretic peptide genetic variant rs5068 is associated with a favorable cardiometabolic phenotype in a Mediterranean population

OBJECTIVE

We hypothesized that the minor allele of the atrial natriuretic peptide (ANP) genetic variant rs5068 is associated with a favorable cardiometabolic phenotype in a general Mediterranean population.

RESEARCH DESIGN AND METHODS

We genotyped a random sample of the residents of Ventimiglia di Sicilia, Sicily, for rs5068.

RESULTS

Genotype frequencies of rs5068 are AA, 93.5%; AG, 6.4%; and GG, 0.1%. All subsequent analyses are AA versus AG+GG. After adjusting for age and sex, the minor G allele is associated with lower BMI (estimate [SE]: -1.7 kg/m(2) [0.8], P = 0.04). In the AG+GG group, males with HDL cholesterol levels <40 mg/dL are less frequent (P = 0.05) and obesity tends to be less prevalent (P = 0.07). Importantly, the G allele is associated with a lower prevalence of metabolic syndrome (P = 0.02). After adjusting for BMI, the above associations were attenuated. Independently of age, sex, and BMI, the minor allele is also associated with lower systolic blood pressure (-6.0 mmHg [2.5], P = 0.02) and lower prevalence of hypertension (odds ratio 0.41 [95% CI 0.20-0.83], P = 0.01).

CONCLUSIONS

The association between the minor allele of rs5068 and a favorable cardiometabolic phenotype that we previously reported in a U.S. population is now replicated in a Mediterranean population in which the G allele of rs5068 is associated with lower blood pressure, BMI, and prevalence of hypertension and metabolic syndrome. These findings may lead to a diagnostic strategy to assess cardiometabolic risk and lay the foundation for the future development of an ANP or ANP-like therapy for metabolic syndrome.

Association of a single nucleotide polymorphism of the NPR3 gene promoter with early onset ischemic stroke in an Italian cohort

BACKGROUND

NPR3, located on human chromosome 5 (5p14-p13), encodes the natriuretic peptide receptor type C (NPR-C) that is mainly known as the natriuretic peptide clearance receptor. Involvement of NPR3 in susceptibility to cardiovascular diseases, i.e. hypertension, has been previously shown. With regard to stroke predisposition, evidence for a potential role of genetic variation within or nearby NPR3 has been suggested by a previous genome wide association study.

METHODS

We investigated the contribution to early-onset ischemic stroke susceptibility of the NPR3 -55 C>A transition by genotyping this variant in an Italian cohort of 368 cases and 335 controls.

RESULTS

In a multivariable logistic regression analysis adjusting for age, gender, hypertension, hypercholesterolemia, smoking habit and diabetes, a significant association of the -55 AA genotype with stroke was observed (OR=3.2, 95% CI 1.2-8.3, p=0.016). Remarkably, the polymorphism remained associated with stroke after adjusting for hypertensive status.

CONCLUSION

Our observation obtained in an Italian cohort of early onset ischemic strokes suggests that a NPR3 promoter gene variant could have a role on cerebrovascular disease susceptibility.

Natriuretic peptides and cGMP signaling control of energy homeostasis

Since the discovery of natriuretic peptides (NPs) by de Bold et al. in 1981, the cardiovascular community has been well aware that they exert potent effects on vessels, heart remodeling, kidney function, and the regulation of sodium and water balance. Who would have thought that NPs are also able to exert metabolic effects and contribute to an original cross talk between heart, adipose tissues, and skeletal muscle? The attention on the metabolic role of NPs was awakened in the year 2000 with the discovery that NPs exert potent lipolytic effects mediated by the NP receptor type A/cGMP pathway in human fat cells and that they contribute to lipid mobilization in vivo. In this review, we will discuss the biological effects of NPs on the main tissues involved in the regulation of energy metabolism (i.e., white and brown adipose tissues, skeletal muscle, liver, and pancreas). These recent results on NPs are opening a new chapter into the physiological properties and therapeutic usefulness of this family of hormones.

Natriuretic Peptide Clearance Receptor Alleles and Susceptibility to Abdominal Adiposity

OBJECTIVE

To test the association of the C(-55)A polymorphism of the natriuretic peptide clearance receptor (NPRC) with blood pressure (BP), overweight/obesity, and body fat distribution in a large male adult population.

RESEARCH METHODS AND PROCEDURES

The study population was from a cross-sectional and follow-up study of 787 untreated male participants in the 1994 to 1995 follow-up examination of the Olivetti Heart Study in Naples (356 of whom were examined previously in 1975). BP and anthropometric measures were taken, and biochemical assays were performed. The NPRC gene polymorphism C(-55)A was evaluated by polymerase chain reaction and HgaI digestion.

RESULTS

In the whole study population, there was no difference in BP, BMI, and biochemical tests among genotypes. Considering an A(-55) recessive model of inheritance, the AA subjects had lower BMI and waist circumference and lower prevalence of overweight, obesity, and abdominal adiposity as compared with the CC+CA subjects. On reviewing the characteristics of the subgroup previously examined in 1975, the AA subjects had already lower BMI, and their 20-year rate of overweight and obesity was lower than the CC+CA subjects; no difference was observed in the rate of hypertension.

DISCUSSION

Male subjects carrying the A(-55)A NPRC genotype had a significantly lower prevalence of overweight, obesity, and abdominal adiposity. They also had a lower 20-year rate of overweight compared with CC+CA individuals. These findings from a large unselected and untreated male population are in keeping with the recent evidence of a powerful lipolytic and lipomobilizing activity of natriuretic peptides.

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.

Relation of obesity to circulating B-type natriuretic peptide concentrations in blacks: the Jackson Heart Study

BACKGROUND

Lower plasma B-type natriuretic peptide (BNP) concentrations in obese individuals ("natriuretic handicap") may play a role in the pathogenesis of obesity-related hypertension. Whether this phenomenon may contribute to hypertension in blacks is unknown. We tested the hypothesis that body mass index is inversely related to BNP concentrations in blacks.

METHODS AND RESULTS

We examined the relation of plasma BNP to body mass index in 3742 Jackson Heart Study participants (mean age, 55 ± 13; 62% women) without heart failure using multivariable linear and logistic regression, adjusting for clinical and echocardiographic covariates. The multivariable-adjusted mean BNP was higher for lean participants compared with obese participants in both normotensive (P<0.0001) and hypertensive (P<0.0012) groups. In sex-specific analyses, the adjusted mean BNP was higher in lean hypertensive individuals compared with obese hypertensive individuals for both men (20.5 versus 10.9 pg/mL, respectively; P=0.0009) and women (20.0 versus 13.8 pg/mL; P=0.011). The differences between lean and obese participants were more pronounced in normotensive participants (men, 9.0 versus 4.4 pg/mL; P<0.0001; women, 12.8 versus 8.4 pg/mL; P=0.0005). For both hypertensive and normotensive individuals in the pooled sample, multivariable-adjusted BNP was significantly related to both continuous body mass index (P<0.05 and P<0.0001, respectively) and categorical body mass index (P for trend <0.006 and <0.0001, respectively).

CONCLUSION

Our cross-sectional study of a large community-based sample of blacks demonstrates that higher body mass index is associated with lower circulating BNP concentrations, thereby extending the concept of a natriuretic handicap in obese individuals observed in non-Hispanic whites to this high-risk population.

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.

Combined admixture mapping and association analysis identifies a novel blood pressure genetic locus on 5p13: contributions from the CARe consortium

Admixture mapping based on recently admixed populations is a powerful method to detect disease variants with substantial allele frequency differences in ancestral populations. We performed admixture mapping analysis for systolic blood pressure (SBP) and diastolic blood pressure (DBP), followed by trait-marker association analysis, in 6303 unrelated African-American participants of the Candidate Gene Association Resource (CARe) consortium. We identified five genomic regions (P< 0.001) harboring genetic variants contributing to inter-individual BP variation. In follow-up association analyses, correcting for all tests performed in this study, three loci were significantly associated with SBP and one significantly associated with DBP (P< 10(-5)). Further analyses suggested that six independent single-nucleotide polymorphisms (SNPs) contributed to the phenotypic variation observed in the admixture mapping analysis. These six SNPs were examined for replication in multiple, large, independent studies of African-Americans [Women's Health Initiative (WHI), Maywood, Genetic Epidemiology Network of Arteriopathy (GENOA) and Howard University Family Study (HUFS)] as well as one native African sample (Nigerian study), with a total replication sample size of 11 882. Meta-analysis of the replication set identified a novel variant (rs7726475) on chromosome 5 between the SUB1 and NPR3 genes, as being associated with SBP and DBP (P< 0.0015 for both); in meta-analyses combining the CARe samples with the replication data, we observed P-values of 4.45 × 10(-7) for SBP and 7.52 × 10(-7) for DBP for rs7726475 that were significant after accounting for all the tests performed. Our study highlights that admixture mapping analysis can help identify genetic variants missed by genome-wide association studies because of drastically reduced number of tests in the whole genome.

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.

Tyrosine hydroxylase polymorphism (C-824T) and hypertension: a population-based study

BACKGROUND

Sympathetic nervous system (SNS) overactivity is present in a large proportion of the hypertensive population and precedes the development of established hypertension. Variations in the proximal promoter of the tyrosine hydroxylase (TH) gene have been shown to influence biochemical and physiological traits in the SNS as well as hypertension.

METHODS

We investigated the relationship between a common single-nucleotide polymorphism (SNP) in the proximal TH promoter (C-824T) and blood pressure (BP) in a large general population sample, characterized by 24-h ambulatory BP (ABP) monitoring and office BP measurement.

RESULTS

The study population consisted of 1,221 women and 1,182 men, ages 41-71 years, without major cardiovascular diseases. Regarding the C-824T SNP, 32.4% had the C/C genotype, 50.0% the C/T genotype, and 17.6% the T/T genotype. The T/T genotype conferred an ~45% increase in relative risk of hypertension, defined by conventional criteria, compared with the C/C genotype, and participants with the T/T genotype had significantly higher mean (95% confidence interval (CI)) systolic BP (SBP) (138 (136-140) mm Hg vs. 135 (133-136)), diastolic BP (DBP) (88 (86-89) mm Hg vs. 85 (84-86)), and heart rate (68 (67-69) beats/min vs. 66 (65-67)) than participants with the C/C genotype (P < 0.05). BP, heart rate, and prevalence of hypertension were intermediate in participants with the C/T genotype. These effects were the same in women and men and whether BP was measured in the office or by 24-h ambulatory monitoring.

CONCLUSION

The C-824T SNP in the proximal TH promoter influences BP and prevalence of hypertension in the general population.

Natriuretic peptide pharmacogenetics: membrane metallo-endopeptidase (MME): common gene sequence variation, functional characterization and degradation

Membrane metallo-endopeptidase (MME), also known as neutral endopeptidase 24.11 (EC 3.4.24.11), is involved in the metabolism of natriuretic peptides that play a key role in modulating cardiac structure and function. Common genetic variation in MME has not been addressed by resequencing the gene using DNA from different ethnic populations. We set out to identify and functionally characterize common genetic variation in MME in three ethnic groups. DNA samples from 96 European-American, 96 African-American, and 96 Han Chinese-American healthy subjects were used to resequence MME. Ninety polymorphisms, 65 novel, were identified, including 8 nonsynonymous single nucleotide polymorphisms (nsSNPs). Expression constructs for the nsSNPs were created and COS-1 cells were transfected with constructs for wild type (WT) and variant allozymes. Recombinant proteins were analyzed by quantitative Western blot analysis and by a one-step fluorometric assay. A significant reduction in enzyme activity (21% of WT) and immunoreactive protein (29% of WT) for the Val73 variant allozyme was observed. Proteasome-mediated degradation and autophagy participated in the degradation of this variant allozyme. The chaperone proteins, BiP and GRP94, were upregulated after transfection with Val73 MME, suggesting protein misfolding, compatible with conclusions based on the MME X-ray crystal structure. Multiple novel polymorphisms of MME were identified in three ethnic groups. The Val73 variant allozyme displayed a significant decrease in MME protein quantity and activity, with degradation mediated by both proteasome and autophagy pathways. This polymorphism could have a significant effect on the metabolism of natriuretic peptides.

Natriuretic peptides: linking heart and adipose tissue in obesity and related conditions--a systematic review

The objective of this study was to investigate the association between natriuretic peptides, obesity and related comorbidities. A systematic review of the English language literature from 1996 to 2008 was performed with Pubmed/MEDLINE and the ISI Web of Knowledge. 'Natriuretic peptides', 'atrial natriuretic factor', 'brain natriuretic peptide', 'obesity', 'body mass index', 'lipolysis' and 'adipose tissue' were used as Mesh terms. We also conducted a handle search among the references of the original articles selected. Finally, seventy-five studies were considered eligible for inclusion in the review. Natriuretic peptides are widely known as body homeostasis regulators. Recently, their action as lipolytic agents has been identified. Obese patients, especially those with hypertension and metabolic risk factors, have reduced plasma levels of natriuretic peptides. Whether this precedes or follows obesity and its complications remains undefined. The lipolytic effect of natriuretic peptides indicates that they may be involved in the pathophysiology of obesity. In general, studies with obese patients support paradoxical reduced levels of natriuretic peptides. However, the selection of subjects and classification of obesity and heart failure varied among the reviewed studies, rendering comparison unreliable.

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.

Natriuretic peptide system gene variants are associated with ventricular dysfunction after coronary artery bypass grafting

BACKGROUND

Ventricular dysfunction (VnD) after primary coronary artery bypass grafting is associated with increased hospital stay and mortality. Natriuretic peptides have compensatory vasodilatory, natriuretic, and paracrine influences on myocardial failure and ischemia. The authors hypothesized that natriuretic peptide system gene variants independently predict risk of VnD after primary coronary artery bypass grafting.

METHODS

A total of 1,164 patients undergoing primary coronary artery bypass grafting with cardiopulmonary bypass at two institutions were prospectively enrolled. After prospectively defined exclusions, 697 patients of European descent (76 with VnD) were analyzed. VnD was defined as need for at least 2 new inotropes and/or new mechanical ventricular support after coronary artery bypass grafting. A total of 139 haplotype-tagging single nucleotide polymorphisms (SNPs) within 7 genes (NPPA, NPPB, NPPC, NPR1, NPR2, NPR3, CORIN) were genotyped. SNPs univariately associated with VnD were entered into logistic regression models adjusting for clinical covariates predictive of VnD. To control for multiple comparisons, permutation analyses were conducted for all SNP associations.

RESULTS

After adjusting for clinical covariates and multiple comparisons within each gene, seven NPPA/NPPB SNPs (rs632793, rs6668352, rs549596, rs198388, rs198389, rs6676300, rs1009592) were associated with decreased risk of postoperative VnD (additive model; odds ratios 0.44-0.55; P = 0.010- 0.036) and four NPR3 SNPs (rs700923, rs16890196, rs765199, rs700926) were associated with increased risk of postoperative VnD (recessive model; odds ratios 3.89-4.28; P = 0.007-0.034).

CONCLUSIONS

Genetic variation within the NPPA/NPPB and NPR3 genes is associated with risk of VnD after primary coronary artery bypass grafting. Knowledge of such genotypic predictors may result in better understanding of the molecular mechanisms underlying postoperative VnD.

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.

Influence of ScaI and Natriuretic Peptide (NP) Clearance Receptor Polymorphisms of the NP System on NP Concentration in Chronic Heart Failure

Background: Genetic variants related to the natriuretic peptide (NP) system [ScaI mutated allele (A1) of the atrial NP (ANP) gene and the C variant of the natriuretic peptide clearance receptor (NPRC) gene] have been identified as independent risk factors for cardiovascular morbidity and mortality. Despite the importance of NPs in heart failure (HF), the role of these polymorphisms in HF has not been evaluated.

Methods: We screened 124 HF patients [mean (SD), age 66 (12) years, 100 men, ejection fraction 32% (10%), New York Heart Association (NYHA) class I–II 65, III–IV 59] for NP concentrations [ANP, brain NP (BNP) and amino-terminal pro-BNP (NT-proBNP)] and for the ScaI and NPRC variants.

Results: ScaI polymorphism had no effect on NP concentration in the NYHA I–II subgroup. Conversely, in severe HF, A1 carriers had higher ANP (P ≤0.05), BNP (P &lt;0.01), and NT-proBNP (P &lt;0.01) than A2A2 patients. After multivariate adjustment, A1 presence remained an independent predictor for increased NP. Regarding NPRC polymorphism in mild HF, higher ANP (P &lt;0.05) and BNP (P &lt;0.05) were observed in CC than A allele carriers. After multivariate adjustment, however, this association did not remain significant. In severe HF, the NPRC polymorphism had no effect on NP.

Conclusions: The ScaI polymorphism of the ANP gene might be an important additive genetic factor influencing neurohormonal activation and disease progression in severe HF. The NPRC polymorphism is not an independent determinant of NP concentration in HF.

Angiotensin II stimulates and atrial natriuretic peptide inhibits human visceral adipocyte growth

OBJECTIVE

Cardiovascular peptides such as angiotensin II (Ang II) and atrial natriuretic peptide (ANP) have metabolic effects on adipose cells. These peptides might also regulate adipocyte proliferation and visceral adipose tissue (VAT) expansion. Well-differentiated and stabilized primary cultures of human visceral mature adipocytes (MA) and in vitro-differentiated preadipocytes (DPA) were used as a model to study regulation of VAT expansion.

METHODS

Adipocyte differentiation was evaluated by Oil Red O staining and antiperilipin antibodies. MA and DPA from intra- and retro-peritoneal depots were treated with increasing Ang II (with or without valsartan, a highly selective, competitive, 'surmountable' AT1 antagonist devoid of peroxisome proliferator-activated receptor gamma agonistic activity) or ANP concentrations. Cell counts and bromodeoxyuridine incorporation were used to evaluate proliferation. Apoptosis was evaluated by Hoechst 33342 staining. 8-Bromo cyclic guanosine monophosphate (8Br-cGMP) was used to investigate ANP effects, and real-time PCR to evaluate Ang II and ANP receptors' expression.

RESULTS

Cell proliferation was progressively stimulated by increasing Ang II concentrations (starting at 10-11 M) and inhibited by ANP (already at 10-13 M) in both MA and DPA. Co-incubation with increasing Ang II concentrations and valsartan indicated that Ang II effects were AT1-mediated. Indeed, AT2 receptors were not expressed. Valsartan alone slightly inhibited basal proliferation indicating an autocrine/paracrine growth factor-like effect of endogenous, adipocyte-derived Ang II. 8Br-cGMP experiments indicated that the effects of ANP were mediated by the guanylyl cyclase type A receptor.

CONCLUSION

A cell-culture model to study VAT growth showed stimulation by Ang II and inhibition by ANP at physiological concentrations. Because similar effects are likely to occur in vivo, Ang II and ANP might be important modulators of VAT expansion and associated metabolic and cardiovascular consequences.

Hypertension in people with diabetes and the metabolic syndrome: pathophysiologic insights and therapeutic update

Hypertension (HTN) and type 2 diabetes mellitus (T2DM) are emerging as epidemics of the 21st century and are important components of the metabolic syndrome (MS). Evidence demonstrates a relationship between HTN, T2DM, and several vascular and metabolic abnormalities that are components of the MS. HTN affects nearly 70 million Americans and over one billion worldwide; likewise, the MS affects 44% of the US population above the age of 60 years and is rapidly increasing. HTN associated with the MS has certain pathophysiologic characteristics that provide clinical challenges. There is growing evidence that tissue activation of the renin-angiotensin system contributes to endothelial dysfunction, microalbuminuria, insulin resistance, and subsequent increased risk for cardiovascular and chronic kidney disease. The notion that HTN is a metabolic as well as a vascular disease provides a new treatment paradigm.

The association of brain natriuretic peptide and insulin resistance in obesity-related hypertension

Hypertension is frequently associated with obesity and natriuretic peptide levels are reported to decrease in obese subjects. Both the lower brain natriuretic peptide (BNP) concentration and insulin resistance are suggested to be associated with hypertension. However, their involvement in obesity-related hypertension has not been clearly defined. Forty-four obese women (21 normotensive and 23 hypertensive) and 25 healthy women matched for age were included in the study. Anthropometrical parameters were determined. Serum BNP, fasting insulin and glucose concentrations, and lipid parameters were evaluated. Insulin resistance was calculated using Homeostasis Model Assessment (HOMA) and Quantative Insulin Sensitivity Check Index (QUICKI) formulations. Within the obese groups, HOMA and QUICKI reflected the increased insulin resistance in hypertensive obese subjects with a significant correlation to blood pressure. The decrease in BNP in the obese groups was in favour of the hypertensive obese subjects (31.43+/-6.43; 26.36+/-4.29; and 17.51+/-3.08 pg/ml, respectively) with a fractional statistical significance between the hypertensive obese group and the controls (P=0.047). Only for the obese hypertensive group, fasting glucose, HOMA and QUICKI were significantly correlated with BNP. Moreover, fasting plasma glucose (R(2)=0.22, P=0.007) and fasting plasma insulin (R(2)=0.39, P=0.03) were independently correlated with BNP only for the obese hypertensive group. It can be concluded that the decrease in BNP concentrations in the obese hypertensive subjects seem to be well correlated with the insulin resistance.

Salt sensitivity, a determinant of blood pressure, cardiovascular disease and survival

High dietary sodium has been adduced as a cause of hypertension and its target organ damage for millennia; yet careful observations using sophisticated techniques have revealed only a weak relationship between sodium intake/excretion and blood pressure in the general population. Further, studies of the effects of dietary sodium reduction on blood pressure have revealed minimal achieved reductions in blood pressure, no relationship between the magnitude of reduction in sodium intake/excretion and the blood pressure effect, and no evidence of an effect of sodium reduction on death or cardiovascular events. While blood pressure in the population as a whole is only modestly responsive to alterations in sodium intake, some individuals manifest large blood pressure changes in response to acute or chronic salt depletion or repletion, and are termed "salt sensitive". Salt sensitivity and resistance have a large variety of determinants, including genetic factors, race/ethnicity, age, body mass and diet (overall diet quality, macro- and micronutrient content), as well as associated disease states, e.g. hypertension, diabetes and renal dysfunction. Salt sensitivity can be modulated by improving the quality of the diet, e.g. the DASH diet reduced salt sensitivity by increasing the slope of the pressure-natriuresis curve. Mechanisms that appear to contribute to salt sensitivity include blunted activity of the renin-angiotensin-aldosterone system, deficiency in atrial natriuretic peptide expression, and blunted arterial baroreflex sensitivity. Salt sensitivity in both normotensive and hypertensive persons has been associated with increased cardiovascular disease events and reduced survival. Increased attention to strategies that reduce salt sensitivity, i.e. improvement in diet quality and weight loss, particularly in high risk persons, is urgently needed.

Cardiovascular and metabolic effects of natriuretic peptides

Natriuretic peptides (NP) are essential in mammals to regulate blood volume and pressure. The functional roles of NP are not limited to natriuresis and diuresis. Several peripheral and central actions of the peptides have been characterized. Studies on transgenic mice have revealed their key function in the regulation of cardiomyocyte growth. Plasma NP levels increase in patients with cardiovascular disorders and heart failure. They represent useful clinical markers for clinicians to diagnose heart diseases. The recent discovery of their potent lipolytic action in adipose tissue is a breakthrough in cardiovascular medicine. This new function of NP in the regulation of lipid metabolism offers interesting questions in the field of obesity, diabetes and cardiovascular diseases. This review will briefly describe the effects of NP on the cardiovascular system and lipid metabolism.

Hypertension, kidney, and transgenics: a fresh perspective

In this review, we outline the application and contribution of transgenic technology to establishing the genetic basis of blood pressure regulation and its dysfunction. Apart from a small number of examples where high blood pressure is the result of single gene mutation, essential hypertension is the sum of interactions between multiple environmental and genetic factors. Candidate genes can be identified by a variety of means including linkage analysis, quantitative trait locus analysis, association studies, and genome-wide scans. To test the validity of candidate genes, it is valuable to model hypertension in laboratory animals. Animal models generated through selective breeding strategies are often complex, and the underlying mechanism of hypertension is not clear. A complementary strategy has been the use of transgenic technology. Here one gene can be selectively, tissue specifically, or developmentally overexpressed, knocked down, or knocked out. Although resulting phenotypes may still be complicated, the underlying genetic perturbation is a starting point for identifying interactions that lead to hypertension. We recognize that the development and maintenance of hypertension may involve many systems including the vascular, cardiac, and central nervous systems. However, given the central role of the kidney in normal and abnormal blood pressure regulation, we intend to limit our review to models with a broadly renal perspective.

B-Type Natriuretic Peptide (BNP) and N-Terminal Pro-BNP in Obese Patients without Heart Failure: Relationship to Body Mass Index and Gastric Bypass Surgery

Background: Further investigations are warranted to better characterize variables that may confound the clinical interpretation of plasma natriuretic peptide measurements, which are increasingly recognized to have diagnostic and predictive importance.

Methods: Blood samples (EDTA plasma) from patients (n = 206) attending clinics for the medical treatment and follow-up of obesity were analyzed for B-type natriuretic peptide (BNP; Bayer assay) and the N-terminal segment of its prohormone (NT-proBNP; Roche assay). Natriuretic peptide concentration ranges were evaluated in those without diagnosis of congestive heart failure (CHF) or chronic kidney disease (CKD).

Results: BNP and NT-proBNP were directly correlated (r = 0.87; P = 0.01), with NT-proBNP concentrations higher relative to BNP. Of obese patients without CHF or CKD, 21.6% (40 of 185) had NT-proBNP concentrations greater than the published assay upper reference limit. Concentrations of both natriuretic peptides were higher in patients currently exposed to beta blockers, patients with the diagnosis of hypertension or type 2 diabetes, and patients with a history of gastric bypass surgery. An inverse relationship between body mass index (BMI) and both BNP and NT-proBNP was evident. According to the National Institutes of Health, National Heart, Lung, and Blood Institute classification, more than 95% of the participants sampled in this study were either obesity class 2 (35 kg/m2 &lt; BMI &lt; 39.9 kg/m2) or class 3 (BMI ≥40 kg/m2)

Conclusions: A substantial proportion of obese patients without CHF or CKD have concentrations greater than the upper reference limit for NT-proBNP but not for simultaneously measured BNP. A history of gastric bypass surgery appeared to be a significant predictor of increased natriuretic peptide concentrations when assessed in a population of patients with class 2 or 3 obesity.

An Unsuspected Metabolic Role for Atrial Natriuretic Peptides

In normal and obese humans, lipid mobilization and systemic nonesterified fatty acid levels are thought to be acutely controlled by catecholamines (ie, epinephrine and norepinephrine) and insulin. Natriuretic peptides (NPs) are known to play a key role in the regulation of salt and water balance and blood pressure homeostasis. They are involved in the pathophysiology of hypertension and heart failure. NPs have recently been found to exert potent lipolytic effects (ie, activating the breakdown of stored triacylglycerols) in isolated human fat cells and to promote lipid mobilization in vivo. Atrial natriuretic peptide increases the intracellular 3', 5'-cyclic guanosine monophosphate (cGMP) concentration which activates cGMP-dependent protein kinase leading to perilipin and hormone-sensitive lipase phosphorylation and lipolysis. NPs promote lipid mobilization when administered intravenously. NPs are also responsible for the residual lipid-mobilizing action observed under oral beta-blockade in subjects performing physical exercise. NPs are therefore novel factors which may open promising research pathways to explain the control of lipid mobilization in physiological and pathological conditions. The metabolic impact of altered production and circulation of NPs remains to be established. The potential influence of NPs on the development of lipid disorders, obesity-related cardiovascular events, and cardiac cachexia will be discussed in this review.

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

The gene for natriuretic peptides receptor C (NPRC), which is a candidate susceptibility gene for essential hypertension (EH) or obese hypertension, plays a key role in the regulation of plasma levels and biological effects of natriuretic peptides. The aims of the present study were to find new genetic markers in the 5'-flanking region of the NPRC gene and to assess relationships between variants and phenotypes of EH, including EH in obese patients. Using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis, we discovered a novel six-nucleotide repeat polymorphism located 4 base pairs (bp) upstream of the major transcriptional initiation site. We performed association analysis of this variable number of tandem repeat (VNTR) in 242 EH patients and 212 normotensive controls (NT). Although no significant difference in overall frequency of VNTR was found between NT and EH groups, the blood pressure level of EH patients with the 5/6 genotype was significantly higher in obese subjects. This suggests that the VNTR of the 5'-flanking region of the NPRC gene influences blood pressure levels in obesity-associated hypertension.

Effect of body mass index on natriuretic peptide levels in patients with acute congestive heart failure: a ProBNP Investigation of Dyspnea in the Emergency Department (PRIDE) substudy

BACKGROUND

Obesity is associated with lower B-type natriuretic peptide (BNP) levels in healthy individuals and patients with chronic congestive heart failure (CHF). Neither the mechanism of natriuretic peptide suppression in the obese patient nor whether obesity affects natriuretic peptide levels among patients with acute CHF is known.

METHODS

The associations of amino-terminal pro-BNP (NT-proBNP), BNP, and body mass index (BMI) were examined in 204 subjects with acute CHF. Multivariable regression analyses were performed to identify factors independently related to NT-proBNP and BNP levels.

RESULTS

Across clinical strata of normal (<25 kg/m2), overweight (25-29.9 kg/m2), and obese (> or =30 kg/m2) patients, median NT-proBNP and BNP levels decreased with increasing BMI (both P values < .001). In multivariable analyses adjusting for covariates known to affect BNP levels, the inverse relationship between BMI and both NT-proBNP and BNP remained ( P < .05 for both). Using a cut point of 900 pg/mL, NT-proBNP was falsely negative in up to 10% of CHF cases in overweight patients (25-29.9 kg/m2) and 15% in obese patients (> or =30 kg/m2). Using the standard cut point of 100 pg/mL, BNP testing was falsely negative in 20% of CHF cases in both overweight and obese patients. The assays for NT-proBNP and BNP exhibited similar overall sensitivity for the diagnosis of CHF.

CONCLUSIONS

When adjusted for relevant covariates, compared with normal counterparts, overweight and obese patients with acute CHF have lower circulating NT-proBNP and BNP levels, suggesting a BMI-related defect in natriuretic peptide secretion. NT-proBNP fell below the diagnostic cutoff for CHF less often than BNP in overweight and obese individuals; however, when used as a diagnostic tool to identify CHF in such patients, both markers may have reduced sensitivity.

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.