Renin-angiotensin system genetic polymorphisms and salt sensitivity in essential hypertension

Epigenetic Regulation of Innate and Adaptive Immune Cells in Salt-Sensitive Hypertension

Access to excess dietary sodium has heightened the risk of cardiovascular diseases, particularly affecting individuals with salt sensitivity of blood pressure. Our research indicates that innate antigen-presenting immune cells contribute to rapid blood pressure increases in response to excess sodium intake. Emerging evidence suggests that epigenetic reprogramming, with subsequent transcriptional and metabolic changes, of innate immune cells allows these cells to have a sustained response to repetitive stimuli. Epigenetic mechanisms also steer T-cell differentiation in response to innate immune signaling. Immune cells respond to environmental and nutritional cues, such as salt, promoting epigenetic regulation changes. This article aims to identify and discuss the role of epigenetic mechanisms in the immune system contributing to salt-sensitive hypertension.

Recent Advances in Understanding Peripheral and Gut Immune Cell-Mediated Salt-Sensitive Hypertension and Nephropathy

Hypertension is the primary modifiable risk factor for cardiovascular, renal, and cerebrovascular diseases and is considered the main contributing factor to morbidity and mortality worldwide. Approximately 50% of hypertensive and 25% of normotensive people exhibit salt sensitivity of blood pressure, which is an independent risk factor for cardiovascular disease. Human and animal studies demonstrate that the immune system plays an important role in the etiology and pathogenesis of salt sensitivity of blood pressure, kidney damage, and vascular diseases. Antigen-presenting and adaptive immune cells are implicated in salt-sensitive hypertension and salt-induced renal and vascular injury. Elevated sodium activates antigen-presenting cells to release proinflammatory cytokines including IL (interleukin) 6, tumor necrosis factor-α, IL-1β, and accumulate isolevuglandin-protein adducts. In turn, these activate T cells release prohypertensive cytokines including IL-17A. Moreover, high-salt intake is associated with gut dysbiosis, leading to inflammation, oxidative stress, and blood pressure elevation but the mechanistic contribution to salt-sensitivity of blood pressure is not clearly understood. Here, we discuss recent advances in research investigating the cause, potential biomarkers, and therapeutic targets for salt-sensitive hypertension as they pertain to the gut microbiome, immunity, and inflammation.

Inflammation and oxidative stress in salt sensitive hypertension; The role of the NLRP3 inflammasome

Salt-sensitivity of blood pressure is an independent risk factor for cardiovascular disease and affects approximately half of the hypertensive population. While the precise mechanisms of salt-sensitivity remain unclear, recent findings on body sodium homeostasis and salt-induced immune cell activation provide new insights into the relationship between high salt intake, inflammation, and hypertension. The immune system, specifically antigen-presenting cells (APCs) and T cells, are directly implicated in salt-induced renal and vascular injury and hypertension. Emerging evidence suggests that oxidative stress and activation of the NLRP3 inflammasome drive high sodium-mediated activation of APCs and T cells and contribute to the development of renal and vascular inflammation and hypertension. In this review, we summarize the recent insights into our understanding of the mechanisms of salt-sensitive hypertension and discuss the role of inflammasome activation as a potential therapeutic target.

An update on angiotensin-converting enzyme 2 structure/functions, polymorphism, and duplicitous nature in the pathophysiology of coronavirus disease 2019: Implications for vascular and coagulation disease associated with severe acute respiratory syndrome coronavirus infection

It has been known for many years that the angiotensin-converting enzyme 2 (ACE2) is a cell surface enzyme involved in the regulation of blood pressure. More recently, it was proven that the severe acute respiratory syndrome coronavirus (SARS-CoV-2) interacts with ACE2 to enter susceptible human cells. This functional duality of ACE2 tends to explain why this molecule plays such an important role in the clinical manifestations of coronavirus disease 2019 (COVID-19). At the very start of the pandemic, a publication from our Institute (entitled "ACE2 receptor polymorphism: susceptibility to SARS-CoV-2, hypertension, multi-organ failure, and COVID-19 disease outcome"), was one of the first reviews linking COVID-19 to the duplicitous nature of ACE2. However, even given that COVID-19 pathophysiology may be driven by an imbalance in the renin-angiotensin system (RAS), we were still far from understanding the complexity of the mechanisms which are controlled by ACE2 in different cell types. To gain insight into the physiopathology of SARS-CoV-2 infection, it is essential to consider the polymorphism and expression levels of the ACE2 gene (including its alternative isoforms). Over the past 2 years, an impressive amount of new results have come to shed light on the role of ACE2 in the pathophysiology of COVID-19, requiring us to update our analysis. Genetic linkage studies have been reported that highlight a relationship between ACE2 genetic variants and the risk of developing hypertension. Currently, many research efforts are being undertaken to understand the links between ACE2 polymorphism and the severity of COVID-19. In this review, we update the state of knowledge on the polymorphism of ACE2 and its consequences on the susceptibility of individuals to SARS-CoV-2. We also discuss the link between the increase of angiotensin II levels among SARS-CoV-2-infected patients and the development of a cytokine storm associated microvascular injury and obstructive thrombo-inflammatory syndrome, which represent the primary causes of severe forms of COVID-19 and lethality. Finally, we summarize the therapeutic strategies aimed at preventing the severe forms of COVID-19 that target ACE2. Changing paradigms may help improve patients' therapy.

Dendritic Cell Epithelial Sodium Channel in Inflammation, Salt-Sensitive Hypertension, and Kidney Damage

Salt-sensitive hypertension is a major risk factor for cardiovascular morbidity and mortality. The pathophysiologic mechanisms leading to different individual BP responses to changes in dietary salt remain elusive. Research in the last two decades revealed that the immune system plays a critical role in the development of hypertension and related end organ damage. Moreover, sodium accumulates nonosmotically in human tissue, including the skin and muscle, shifting the dogma on body sodium balance and its regulation. Emerging evidence suggests that high concentrations of extracellular sodium can directly trigger an inflammatory response in antigen-presenting cells (APCs), leading to hypertension and vascular and renal injury. Importantly, sodium entry into APCs is mediated by the epithelial sodium channel (ENaC). Although the role of the ENaC in renal regulation of sodium excretion and BP is well established, these new findings imply that the ENaC may also exert BP modulatory effects in extrarenal tissue through an immune-dependent pathway. In this review, we discuss the recent advances in our understanding of the pathophysiology of salt-sensitive hypertension with a particular focus on the roles of APCs and the extrarenal ENaC.

Pathophysiology and genetics of salt-sensitive hypertension

Most hypertensive cases are primary and heavily associated with modifiable risk factors like salt intake. Evidence suggests that even small reductions in salt consumption reduce blood pressure in all age groups. In that regard, the ACC/AHA described a distinct set of individuals who exhibit salt-sensitivity, regardless of their hypertensive status. Data has shown that salt-sensitivity is an independent risk factor for cardiovascular events and mortality. However, despite extensive research, the pathogenesis of salt-sensitive hypertension is still unclear and tremendously challenged by its multifactorial etiology, complicated genetic influences, and the unavailability of a diagnostic tool. So far, the important roles of the renin-angiotensin-aldosterone system, sympathetic nervous system, and immune system in the pathogenesis of salt-sensitive hypertension have been studied. In the first part of this review, we focus on how the systems mentioned above are aberrantly regulated in salt-sensitive hypertension. We follow this with an emphasis on genetic variants in those systems that are associated with and/or increase predisposition to salt-sensitivity in humans.

Salt-Sensitivity of Blood Pressure and Insulin Resistance

Salt sensitivity of blood pressure (SSBP) is an independent risk factor for cardiovascular morbidity and mortality that is seen in both hypertensive and normotensive populations. Insulin resistance (IR) strongly correlates with SSBP and affects nearly 50% of salt sensitive people. While the precise mechanism by which IR and SSBP relate remains elusive, several common pathways are involved in the genesis of both processes, including vascular dysfunction and immune activation. Vascular dysfunction associated with insulin resistance is characterized by loss of nitric oxide (NO)-mediated vasodilation and heightened endothelin-1 induced vasoconstriction, as well as capillary rarefaction. It manifests with increased blood pressure (BP) in salt sensitive murine models. Another common denominator in the pathogenesis of insulin resistance, hypertension, and salt sensitivity (SS) is immune activation involving pro-inflammatory cytokines like tumor necrosis factor (TNF)-α, IL-1β, and IL-6. In the last decade, a new understanding of interstitial sodium storage in tissues such as skin and muscle has revolutionized traditional concepts of body sodium handling and pathogenesis of SS. We have shown that interstitial Na⁺ can trigger a T cell mediated inflammatory response through formation of isolevuglandin protein adducts in antigen presenting cells (APCs), and that this response is implicated in salt sensitive hypertension. The peroxisome proliferator-activated receptor γ (PPARγ) is a transcription factor that modulates both insulin sensitivity and BP. PPARγ agonists increase insulin sensitivity and ameliorate salt sensitivity, whereas deficiency of PPARγ results in severe insulin resistance and hypertension. These findings suggest that PPARγ plays a role in the common pathogenesis of insulin sensitivity and salt sensitivity, perhaps via effects on the immune system and vascular function. The goal of this review is to discuss those mechanisms that may play a role in both SSBP and in insulin resistance.

Early nutritional influences of cardiovascular health

INTRODUCTION

Increasing evidence shows that nutritional choices during children's formative years, including prenatally, impacts the development of adult onset cardiovascular diseases (CVDs), such as hypertension, myocardial infarction, or stroke.

AREAS COVERED

This literature review aims to synthesize the current body of evidence on nutritional factors, from conception through adolescence, which may influence a person's risk factors for future development of CVD.

EXPERT OPINION

Given the escalating healthcare costs associated with CVD, it is imperative that medical professionals and scientists remain steadfast in prioritizing and promoting early CVD prevention, even within the first few years of life. Though not the only contributing risk factor, diet is a modifiable risk factor and has been shown to have a profound impact on the reduction of cardiovascular morbidity and mortality in adult literature. Nutritional choices should be targeted on multiple levels: prenatally with the mother, individually with the patient, in conjunction with their family unit, and also within the broader community wherein they reside. Healthcare providers can play a key advocacy role for local and national food environment policy changes.

Candidate Gene Polymorphisms Influence the Susceptibility to Salt Sensitivity of Blood Pressure in a Han Chinese Population: Risk Factors as Mediators

Genome-wide association studies suggest that there is a significant genetic susceptibility to salt sensitivity of blood pressure (SSBP), but it still needs to be verified in varied and large sample populations. We attempted to verify the associations between single-nucleotide polymorphisms (SNPs) in candidate genes and SSBP and to estimate their interaction with potential risk factors. A total of 29 candidate SNPs were genotyped in the 2,057 northern Han Chinese population from the Systems Epidemiology Study on Salt Sensitivity. A modified Sullivan’s acute oral saline load and diuresis shrinkage test (MSAOSL-DST) was used to identify SSBP. A generalized linear model was conducted to analyze the association between SNPs and SSBP, and Bonferroni correction was used for multiple testing. Mediation analysis was utilized to explore the mediation effect of risk factors. Eleven SNPs in eight genes (PRKG1, CYBA, BCAT1, SLC8A1, AGTR1, SELE, CYP4A11, and VSNL1) were identified to be significantly associated with one or more SSBP phenotypes (P < 0.05). Four SNPs (PRKG1/rs1904694 and rs7897633, CYP4A11/rs1126742, and CYBA/rs4673) were still significantly associated after Bonferroni correction (P < 0.0007) adjusted for age, sex, fasting blood glucose, total cholesterol, salt-eating habit, physical activity, and hypertension. Stratified analysis showed that CYBA/rs4673 was significantly associated with SSBP in hypertensive subjects (P < 0.0015) and CYP4A11/rs1126742 was significantly associated with SSBP in normotensive subjects (P < 0.0015). Subjects carrying both CYBA/rs4673-AA and AGTR1/rs2638360-GG alleles have a higher genetic predisposition to salt sensitivity due to the potential gene co-expression interaction. Expression quantitative trait loci analysis (eQTL) suggested that the above positive four SNPs showed cis-eQTL effects on the gene expression levels. Mediation analysis suggested that several risk factors were mediators of the relation between SNP and SSBP. This study suggests that the genetic variants in eight genes might contribute to the susceptibility to SSBP, and other risk factors may be the mediators.

Effect of urinary angiotensinogen and high-salt diet on blood pressure in patients with chronic kidney disease: results from the Korean Cohort Study for Outcome in Patients with Chronic Kidney Disease (KNOW-CKD)

BACKGROUND/AIMS

This study aimed to investigate whether urinary angiotensinogen (UAGT) excretion was associated with elevated blood pressure in patients with chronic kidney disease (CKD) and to evaluate the relationship among blood pressure, intra-renal renin-angiotensin system (RAS) activity, and dietary sodium in patients with CKD.

METHODS

Participants from the Korean Cohort Study for Outcome in Patients with Chronic Kidney Disease (KNOW-CKD) were included. Of the total cohort of 2,238 individuals with CKD, we included 1,955 participants who underwent complete 24-hour urinary sodium (24-hour UNa) analysis. They were categorized into three groups according to three tertiles of their 24-hour UNa, reflecting daily salt intake. To measure intra-renal RAS activity, the UAGT excretion was assayed with an enzyme-linked immunosorbent assay.

RESULTS

Elevated 24-hour UNa levels, logarithm of UAGT-to-creatinine ratio (UAGT/Cr), increased waist-to-hip ratio, and decreased estimated glomerular filtration rate were the risk factors for increased systolic blood pressure. Systolic blood pressure showed a positive correlation with 24-hour UNa levels and logarithm of UAGT/Cr.

CONCLUSION

UAGT and urinary sodium excretion are independent determinants of systolic blood pressure in patients with CKD. These findings suggest that increased systolic blood pressure in CKD patients is associated with both increased dietary sodium levels and intra-renal RAS activity. The risk of elevated systolic blood pressure in the 3rd tertile of both the UAGT/Cr and 24-hour UNa groups was about 2.3 times higher than that in the reference group.

Diet-gene interaction: effects of polymorphisms in the ACE, AGT and BDKRB2 genes and the consumption of sodium, potassium, calcium, and magnesium on blood pressure of normotensive adult individuals

Functional variants in genes of the renin-angiotensin (RAS) and kallikrein-kinin (KKS) systems have already been implicated in blood pressure (BP) modulation, but few studies have focused on a nutrigenetics approach. Thus, the aim of this study is to verify the effects of the interaction between genetic polymorphisms (rs4340-ACE, rs699-AGT, and rs1799722-BDKRB2) and micronutrient consumption (sodium, potassium, calcium, and magnesium) on BP values of normotensive adult individuals. The study included 335 adults, men and women, 25.5 (6.6) years old. Biochemical, anthropometric, BP measurements, and food intake data were assessed for all participants. Gene-nutrient interaction on BP outcome was tested by multiple linear regression with manual backward stepwise modeling. Our results indicated that individuals with G allele for rs699 polymorphism, in the increase of sodium and magnesium consumption, both in the genotypic model (sodium, p = 0.035; magnesium, p = 0.016) and in the dominant model (sodium, p = 0.009; magnesium, p = 0.006) had higher systolic BP (SBP) levels compared to AA homozygotes (sodium, p = 0.001; magnesium, p < 0.001). Also, individuals with the T allele for the rs1799722 polymorphism, with higher calcium intake, had significantly higher levels of SBP and diastolic BP (DBP) when compared to CC homozygotes (p = 0.037). In conclusion, our findings pointed for significant interactions between genetic polymorphisms (rs699-AGT and rs1799722-BDKRB2) and the consumption of micronutrients (sodium, magnesium, and calcium) on the BP variation. These findings contribute to the understanding of the complex mechanisms involved in BP regulation, which probable include several gene-nutrition interactions.

The hypotensive effect of salt substitutes in stage 2 hypertension: a systematic review and meta-analysis

Background

Hypertension (HTN) is a ubiquitous risk factor for numerous non-communicable diseases, including cardiovascular disease and stroke. There are currently no wholly effective pharmacological therapies for subjects with HTN. However, salt substitutes have emerged as a potential therapy for the treatment of HTN. The aim of the present study was to assess the effect of salt substitutes on reducing systolic blood pressure (SBP) and diastolic BP (DBP), following a meta-analysis of randomized controlled trials.

Methods

Studies were found via systematic searches of the Pubmed/Medline, Scopus, Ovid, Google Scholar and Cochrane library. Ten studies, comprised of 11 trials and 1119 participants, were included in the meta-analysis.

Results

Pooled weighted mean differences showed significant reductions of SBP (WMD − 8.87 mmHg; 95% CI − 11.19, − 6.55, p < 0.001) and DBP (WMD − 4.04 mmHg; 95% CI − 5.70, − 2.39) with no statistically significant heterogeneity between the 11 included comparisons of SBPs and DBPs. The stratified analysis of trials based on the mean age of participants showed a significant reduction in the mean difference of SBP in both adults (< 65 years old) and elderly (≥65 years old). However, the DBP-lowering effect of salt substitutes was only observed in adult patients (WMD − 4.22 mmHg; 95% CI − 7.85, − 0.58), but not in the elderly subjects.

Conclusions

These findings suggest that salt-substitution strategies could be used for lowering SBP and DBP in patients with stage 2 HTN; providing a nutritional platform for the treatment, amelioration, and prevention of HTN.

ACE insertion/deletion genetic polymorphism, serum ACE levels and high dietary salt intake influence the risk of obesity development among the Saudi adult population

Introduction:

Angiotensin-converting enzyme (ACE), which contributes to adipocyte growth, differentiation and function, has recently been linked with both salt metabolism and obesity development. Therefore, this study has aimed to investigate the putative relationship between ACE genetic polymorphism, serum ACE levels and salt consumption on the risk of developing obesity in the Saudi population.

Materials and methods:

ACE genotype status of 267 adult Saudi volunteers (124 obese and 143 non-obese) was correlated with their serum ACE activity and dietary salt intake amounts.

Results:

Obesity was more prevalent in deletion-deletion genotype individuals (p<0.03), under dominant, co-dominant and monoallelic conditions (p<0.04). Deletion allele corresponds to serum ACE activity in obese patients (p<0.05). The amount of salt intake (<6 g/d) was significantly associated with obesity and particularly high in deletion-deletion and insertion-deletion genotype carriers (p<0.001). STITCH analysis underlined interactions of the ACE protein with sodium molecule, REN, ACE2, KNG1 and AGTR1 in a biological network.

Conclusions:

Our findings suggest the positive association between ACE deletion genotype, serum ACE activity and sodium intake with risk of obesity development in the Saudi population.

Lifestyle genomics and the metabolic syndrome: A review of genetic variants that influence response to diet and exercise interventions

Metabolic syndrome (MetS) comprises a cluster of risk factors that includes central obesity, dyslipidemia, impaired glucose homeostasis and hypertension. Individuals with MetS have elevated risk of type 2 diabetes and cardiovascular disease; thus placing significant burdens on social and healthcare systems. Lifestyle interventions (comprised of diet, exercise or a combination of both) are routinely recommended as the first line of treatment for MetS. Only a proportion of people respond, and it has been assumed that psychological and social aspects primarily account for these differences. However, the etiology of MetS is multifactorial and stems, in part, on a person's genetic make-up. Numerous single nucleotide polymorphisms (SNPs) are associated with the various components of MetS, and several of these SNPs have been shown to modify a person's response to lifestyle interventions. Consequently, genetic variants can influence the extent to which a person responds to changes in diet and/or exercise. The goal of this review is to highlight SNPs reported to influence the magnitude of change in body weight, dyslipidemia, glucose homeostasis and blood pressure during lifestyle interventions aimed at improving MetS components. Knowledge regarding these genetic variants and their ability to modulate a person's response will provide additional context for improving the effectiveness of personalized lifestyle interventions that aim to reduce the risks associated with MetS.

Precision Nutrition: A Review of Personalized Nutritional Approaches for the Prevention and Management of Metabolic Syndrome

The translation of the growing increase of findings emerging from basic nutritional science into meaningful and clinically relevant dietary advices represents nowadays one of the main challenges of clinical nutrition. From nutrigenomics to deep phenotyping, many factors need to be taken into account in designing personalized and unbiased nutritional solutions for individuals or population sub-groups. Likewise, a concerted effort among basic, clinical scientists and health professionals will be needed to establish a comprehensive framework allowing the implementation of these new findings at the population level. In a world characterized by an overwhelming increase in the prevalence of obesity and associated metabolic disturbances, such as type 2 diabetes and cardiovascular diseases, tailored nutrition prescription represents a promising approach for both the prevention and management of metabolic syndrome. This review aims to discuss recent works in the field of precision nutrition analyzing most relevant aspects affecting an individual response to lifestyle/nutritional interventions. Latest advances in the analysis and monitoring of dietary habits, food behaviors, physical activity/exercise and deep phenotyping will be discussed, as well as the relevance of novel applications of nutrigenomics, metabolomics and microbiota profiling. Recent findings in the development of precision nutrition are highlighted. Finally, results from published studies providing examples of new avenues to successfully implement innovative precision nutrition approaches will be reviewed.

Interaction of ACE genotype and salt intake on hypertension among Chinese Kazakhs: results from a population-based cross-sectional study

OBJECTIVES

To explore the effect of interaction between ACE genotype and salt intake on hypertension among Chinese Kazakhs, and to compare applications of interactions between logistic model and generalised partially linear tree-based regression (GPLTR) model.

DESIGN

Population-based cross-sectional study.

SETTING

Hong Dun, North Xinjiang, China.

PARTICIPANTS

Non-consanguineous Chinese Kazakh participants (n=916, 342 men and 574 women) aged ≥30 years.

MAIN OUTCOME MEASURES

Association between ACE genotype and hypertension, association between salt intake and hypertension, and interaction of ACE genotype and salt intake on hypertension in two models.

RESULTS

Associations between salt intake and hypertension were different in ACE genotype of II and ID+DD. Under the logistic models, main and interaction effects were not observed for men, but effects were present in opposite directions for women (main effect of ACE: OR=0.20, p=0.003; interaction effect: OR=1.07, p=0.027). Under the GPLTR model, Bayesian information criterion trees included both salt intake and ACE genotype as split variables. Individuals with a salt intake ≥19.5 g/day and ID+DD genotypes had a 3.99-fold (p=0.004) higher risk of hypertension compared with the II genotype for men, whereas salt intake <20.1 g/day and ID+DD genotypes had an OR=0.55 (p=0.014) compared with the II genotype for women.

CONCLUSIONS

An interaction of ACE genotype and salt intake on hypertension was observed among Chinese Kazakhs but in different ways according to sex. The GPLTR model appears to be more suitable for an exploration of interactions in complex diseases.

The High Blood Pressure-Malaria Protection Hypothesis

RATIONALE

A recently proposed hypothesis states that malaria may contribute to hypertension in endemic areas,¹ but the role of angiotensin II (Ang II), a major regulator of blood pressure, was not considered. Elevated levels of Ang II may confer protection against malaria morbidity and mortality, providing an alternative explanation for hypertension in malaria endemic areas.

OBJECTIVE

To discuss a possible alternative cause for hypertension in populations who have been under the selective pressure of malaria.

METHODS AND RESULTS

We reviewed published scientific literature for studies that could establish a link between Ang II and malaria. Both genetic and functional studies suggested that high levels of Ang II may confer protection against cerebral malaria by strengthening the integrity of the endothelial brain barrier. We also describe strong experimental evidence supporting our hypothesis through genetic, functional, and interventional studies.

CONCLUSIONS

A causal association between high levels of Ang II and protection from malaria pathogenesis can provide a likely explanation for the increased prevalence in hypertension observed in populations of African and South Asian origin. Furthermore, this potential causative connection might also direct unique approaches for the effective treatment of cerebral malaria.

Fast high-throughput screening of angiotensin-converting enzyme insertion/deletion polymorphism by variable programmed electric field strength-based microchip electrophoresis

An insertion (I)/deletion (D) polymorphism in angiotensin-converting enzyme (ACE) has been associated with susceptibility to various diseases in numerous studies. Traditionally, slab gel electrophoresis (SGE) after polymerase chain reaction (PCR) has been used to genotype this ACE I/D polymorphism. In this study, single- and multi-channel microchip electrophoresis (ME) methods based on variable programmed electric field strength (PEFS) (i.e., low constant, high constant, (+)/(-) staircase, and random electric field strengths) were developed for fast high-throughput screening of this specific polymorphism. The optimum PEFS conditions were set as 470V/cm for 0-9s, 129V/cm for 9-13s, 470V/cm for 13-13.9s, 294V/cm for 13.9-16s, and 470V/cm for 16-20s for single-channel ME, and 615V/cm for 0-22.5s, 231V/cm for 22.5-28.5s, and 615V/cm for 28.5-40s for multi-channel ME, respectively. In the multi-channel PEFS-ME, target ACE I/D polymorphism DNA fragments (D=190bp and I=490bp) were identified within 25s without loss of resolving power, which was ∼300 times faster than conventional SGE. In addition, PCR products of the ACE gene from human blood samples were detected after only 10 cycles by multi-channel PEFS-ME, but not by SGE. This parallel detection multichannel-based PEFS-ME method offers a powerful tool for fast high-throughput ACE I/D polymorphism screening with high sensitivity.

High salt intake as a multifaceted cardiovascular disease: new support from cellular and molecular evidence

Scientists worldwide have disseminated the idea that increased dietary salt increases blood pressure. Currently, salt intake in the general population is ten times higher than that consumed in the past and at least two times higher than the current recommendation. Indeed, a salt-rich diet increases cardiovascular morbidity and mortality. For a long time, however, the deleterious effects associated with high salt consumption were only related to the effect of salt on blood pressure. Currently, several other effects have been reported. In some cases, the deleterious effects of high salt consumption are independently associated with other common risk factors. In this article, we gather data on the effects of increased salt intake on the cardiovascular system, from infancy to adulthood, to describe the route by which increased salt intake leads to cardiovascular diseases. We have reviewed the cellular and molecular mechanisms through which a high intake of salt acts on the cardiovascular system to lead to the progressive failure of a healthy heart.

Differences in genotype frequencies of salt-sensitive genes between fishing and nonfishing communities in Japan

PURPOSE

To identify the differences in genotype frequencies of salt-sensitive genes between residents of fishing communities (FCs) and nonfishing communities (NFCs).

METHODS

The subjects included 18,156 individuals (8,043 males [44%] and 10,113 females [56%]; average age: 57.2±16.1 years) from the general population who were registered with large-scale genome banks and resided in 30 prefectures and 78 different regions in Japan. The measurement items were age, sex, blood pressure, presence or absence of hypertension, body mass index, alcohol consumption, and smoking habit. Furthermore, to analyze the genotype frequencies of salt-sensitive genes, α-adducin 1 (ADD1), angiotensinogen (AGT), angiotensin II receptor type 1 (AT1), and guanine nucleotide-binding protein β peptide 3 (GNB3) were measured. According to the 2004 government classification of municipalities (cities, towns, and villages), communities existing in areas bordering an ocean and with an ocean port were defined as FCs (28 areas). The others were defined as NFCs (50 areas). A logistic regression model was used for comparison of genotype frequencies between subjects residing in FCs and NFCs.

RESULTS

Of the included subjects, 4,916 (27.0%) and 13,240 (73.0%) resided in FCs and NFCs, respectively. In FCs, the mean age was 59.4±16.7 years and men accounted for 41.0% of the cohort (n=2,015). In NFCs, the mean age was 56.4±15.8 years and men accounted for 45.5% of the cohort (n=6,028). The adjusted odds ratios of the AA and AG genotypes compared with the GG genotype for AGT were 0.80 (95% confidence interval [CI]: 0.68-0.95) and 0.76 (95% CI: 0.64-0.91), respectively. The adjusted odds ratio of the CC genotype compared with AA for AT1 was 0.63 (95% CI: 0.40-0.93).

CONCLUSION

The incidence of the salt-sensitive genotypes AGT and AT1 in residents of FCs were significantly lower than in NFCs.

Influence of ACE I/D Polymorphism on Circulating Levels of Plasminogen Activator Inhibitor 1, D-Dimer, Ultrasensitive C-Reactive Protein and Transforming Growth Factor β1 in Patients Undergoing Hemodialysis

BACKGROUND

There is substantial evidence that chronic renal and cardiovascular diseases are associated with coagulation disorders, endothelial dysfunction, inflammation and fibrosis. Angiotensin-Converting Enzyme Insertion/Deletion polymorphism (ACE I/D polymorphism) has also be linked to cardiovascular diseases. Therefore, this study aimed to compare plasma levels of ultrassensible C-reactive protein (usCRP), PAI-1, D-dimer and TGF-β1 in patients undergoing HD with different ACE I/D polymorphisms.

METHODS

The study was performed in 138 patients at ESRD under hemodialysis therapy for more than six months. The patients were divided into three groups according to the genotype. Genomic DNA was extracted from blood cells (leukocytes). ACE I/D polymorphism was investigated by single polymerase chain reaction (PCR). Plasma levels of D-dimer, PAI-1 and TGF-β1 were measured by enzyme-linked immunosorbent assay (ELISA), and the determination of plasma levels of usCRP was performed by immunonephelometry. Data were analyzed by the software SigmaStat 2.03.

RESULTS

Clinical characteristics were similar in patients with these three ACE I/D polymorphisms, except for interdialytic weight gain. I allele could be associated with higher interdialytic weight gain (P = 0.017). Patients genotyped as DD and as ID had significantly higher levels of PAI-1 than those with II genotype. Other laboratory parameters did not significantly differ among the three subgroups (P = 0.033). Despite not reaching statistical significance, plasma levels of usCRP were higher in patients carrying the D allele.

CONCLUSION

ACE I/D polymorphisms could be associated with changes in the regulation of sodium, fibrinolytic system, and possibly, inflammation. Our data showed that high levels of PAI-1 are detected when D allele is present, whereas greater interdialytic gain is associated with the presence of I allele. However, further studies with different experimental designs are necessary to elucidate the mechanisms involved in these associations.

Polymorphisms of three genes (ACE, AGT and CYP11B2) in the renin-angiotensin-aldosterone system are not associated with blood pressure salt sensitivity: A systematic meta-analysis

Many studies have suggested that polymorphisms of three key genes (ACE, AGT and CYP11B2) in the renin-angiotensin-aldosterone system (RAAS) play important roles in the development of blood pressure (BP) salt sensitivity, but they have revealed inconsistent results. Thus, we performed a meta-analysis to clarify the association. PubMed and Embase databases were searched for eligible published articles. Fixed- or random-effect models were used to pool odds ratios and 95% confidence intervals based on whether there was significant heterogeneity between studies. In total, seven studies [237 salt-sensitive (SS) cases and 251 salt-resistant (SR) controls] for ACE gene I/D polymorphism, three studies (130 SS cases and 221 SR controls) for AGT gene M235T polymorphism and three studies (113 SS cases and 218 SR controls) for CYP11B2 gene C344T polymorphism were included in this meta-analysis. The results showed that there was no significant association between polymorphisms of these three polymorphisms in the RAAS and BP salt sensitivity under three genetic models (all p > 0.05). The meta-analysis suggested that three polymorphisms (ACE gene I/D, AGT gene M235T, CYP11B2 gene C344T) in the RAAS have no significant effect on BP salt sensitivity.

Salt Sensitivity and Hypertension: A Paradigm Shift from Kidney Malfunction to Vascular Endothelial Dysfunction

Hypertension is a complex trait determined by both genetic and environmental factors and is a major public health problem due to its high prevalence and concomitant increase in the risk for cardiovascular disease. With the recent large increase of dietary salt intake in most developed countries, the prevalence of hypertension increases tremendously which is about 30% of the world population. There is substantial evidence that suggests some people can effectively excrete high dietary salt intake without an increase in arterial BP, and another people cannot excrete effectively without an increase in arterial BP. Salt sensitivity of BP refers to the BP responses for changes in dietary salt intake to produce meaningful BP increases or decreases. The underlying mechanisms that promote salt sensitivity are complex and range from genetic to environmental influences. The phenotype of salt sensitivity is therefore heterogeneous with multiple mechanisms that potentially link high salt intake to increases in blood pressure. Moreover, excess salt intake has functional and pathological effects on the vasculature that are independent of blood pressure. Epidemiologic data demonstrate the role of high dietary salt intake in mediating cardiovascular and renal morbidity and mortality. Almost five decades ago, Guyton and Coleman proposed that whenever arterial pressure is elevated, pressure natriuresis enhances the excretion of sodium and water until blood volume is reduced sufficiently to return arterial pressure to control values. According to this hypothesis, hypertension can develop only when something impairs the excretory ability of sodium in the kidney. However, recent studies suggest that nonosmotic salt accumulation in the skin interstitium and the endothelial dysfunction which might be caused by the deterioration of vascular endothelial glycocalyx layer (EGL) and the epithelial sodium channel on the endothelial luminal surface (EnNaC) also play an important role in nonosmotic storage of salt. These new concepts emphasize that sodium homeostasis and salt sensitivity seem to be related not only to the kidney malfunction but also to the endothelial dysfunction. Further investigations will be needed to assess the extent to which changes in the sodium buffering capacity of the skin interstitium and develop the treatment strategy for modulating the endothelial dysfunction.

Disclosure of genetic information and change in dietary intake: a randomized controlled trial

BACKGROUND

Proponents of consumer genetic tests claim that the information can positively impact health behaviors and aid in chronic disease prevention. However, the effects of disclosing genetic information on dietary intake behavior are not clear.

METHODS

A double-blinded, parallel group, 2:1 online randomized controlled trial was conducted to determine the short- and long-term effects of disclosing nutrition-related genetic information for personalized nutrition on dietary intakes of caffeine, vitamin C, added sugars, and sodium. Participants were healthy men and women aged 20-35 years (n = 138). The intervention group (n = 92) received personalized DNA-based dietary advice for 12-months and the control group (n = 46) received general dietary recommendations with no genetic information for 12-months. Food frequency questionnaires were collected at baseline and 3- and 12-months after the intervention to assess dietary intakes. General linear models were used to compare changes in intakes between those receiving general dietary advice and those receiving DNA-based dietary advice.

RESULTS

Compared to the control group, no significant changes to dietary intakes of the nutrients were observed at 3-months. At 12-months, participants in the intervention group who possessed a risk version of the ACE gene, and were advised to limit their sodium intake, significantly reduced their sodium intake (mg/day) compared to the control group (-287.3 ± 114.1 vs. 129.8 ± 118.2, p = 0.008). Those who had the non-risk version of ACE did not significantly change their sodium intake compared to the control group (12-months: -244.2 ± 150.2, p = 0.11). Among those with the risk version of the ACE gene, the proportion who met the targeted recommendation of 1500 mg/day increased from 19% at baseline to 34% after 12 months (p = 0.06).

CONCLUSIONS

These findings demonstrate that disclosing genetic information for personalized nutrition results in greater changes in intake for some dietary components compared to general population-based dietary advice.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01353014.

Genetic variants of ACE (Insertion/Deletion) and AGT (M268T) genes in patients with diabetes and nephropathy

INTRODUCTION

Diabetes mellitus (DM) has been a growing epidemic worldwide and poses a major socio-economic challenge. The leading cause of DM death is nephropathy due to end-stage renal disease (ESRD). This study aims to identify the possible association of I/D variants of the ACE gene and M268T (rs699) of the AGT gene of renin-angiotensin-aldosterone system (RAAS).

MATERIALS AND METHODS

Study subjects include 115 patients with DM, 110 with diabetic nephropathy (DN) and 110 controls. Fasting blood samples were collected for biochemical analyses and PCR amplification of specific regions of the ACE and AGT genes using primers.

RESULTS

The distribution of ACE (I/D) II 28.8%, ID 35.6% and DD 35.6% while in DN II 24.5%, ID 41% and DD 34.5%. The AGT (M268T) genotypes were distributed in DM as TT 30.4%, MT 66.9% and MM 2.6% while in DN subjects TT 56.4%, MT 42.7% and MM 0.9%.

CONCLUSION

Significant differences were observed in the DD genotype and D allele of the ACE gene and the TT genotype and T allele of AGT genes between diabetic patients with and without nephropathy. The study may conclude that the D allele polymorphism in the ACE gene and the T allele polymorphism in AGT gene may be considered as genetic risk factors for the development of nephropathy in diabetes.

Hypertension in the elderly: unique challenges and management

Elderly individuals, worldwide, are on the rise, posing new challenges to care providers. Hypertension is highly prevalent in elderly individuals, and multiple challenges face care providers while managing it. In addition to treating hypertension, the physician must treat other modifiable cardiovascular risk factors in patients with or without diabetes mellitus or chronic kidney disease to reduce cardiovascular events and mortality. This review discusses some of the unique characteristics of high blood pressure in the elderly and provides an overview of the challenges facing care providers, as well as the current recommendations for management of hypertension in the elderly.

Hypertension in the teenager

Over the last two decades, essential hypertension has become common in adolescents, yet remains under-diagnosed in absence of symptoms. Diagnosis is based on normative percentiles that factor in age, sex and height. Evaluation is more similar to adult essential hypertension than childhood secondary hypertension. Modifiable risk factors such as obesity, sodium consumption and low exercise should be addressed first. Many anti-hypertensive medications now have specific regulatory approval for children. Sports participation need not be limited in mild or well-controlled cases. Primary care physicians play an important role in reduction of cardiovascular mortality by early detection and referral when needed.

Gene-environment interactions of selected pharmacogenes in arterial hypertension

Hypertension affects approximately 1 billion people worldwide. Owing to population aging, hypertension-related cardiovascular burden is expected to rise in the near future. In addition to genetic variants influencing the blood pressure response to antihypertensive drugs, several genes encoding for drug-metabolizing or -transporting enzymes have been associated with blood pressure and/or hypertension in humans (e.g., ACE, CYP1A2, CYP3A5, ABCB1 and MTHFR) regardless of drug treatment. These genes are also involved in the metabolism and transport of endogenous substances and their effects may be modified by selected environmental factors, such as diet or lifestyle. However, little is currently known on the complex interplay between environmental factors, endogenous factors, genetic variants and drugs on blood pressure control. This review will discuss the respective role of population-based primary prevention and personalized medicine for arterial hypertension, taking a pharmacogenomics' perspective focusing on selected pharmacogenes.

The role of the renin-angiotensin-aldosterone system in preeclampsia: genetic polymorphisms and microRNA

The compensatory alterations in the rennin-angiotensin-aldosterone system (RAAS) contribute to the salt-water balance and sufficient placental perfusion for the subsequent well-being of the mother and fetus during normal pregnancy and is characterized by an increase in almost all the components of RAAS. Preeclampsia, however, breaks homeostasis and leads to a disturbance of this delicate equilibrium in RAAS both for circulation and the uteroplacental unit. Despite being a major cause for maternal and neonatal morbidity and mortality, the pathogenesis of preeclampsia remains elusive, where RAAS has been long considered to be involved. Epidemiological studies have indicated that preeclampsia is a multifactorial disease with a strong familial predisposition regardless of variations in ethnic, socioeconomic, and geographic features. The heritable allelic variations, especially the genetic polymorphisms in RAAS, could be the foundation for the genetics of preeclampsia and hence are related to the development of preeclampsia. Furthermore, at a posttranscriptional level, miRNA can interact with the targeted site within the 3'-UTR of the RAAS gene and thereby might participate in the regulation of RAAS and the pathology of preeclampsia. In this review, we discuss the recent achievements of genetic polymorphisms, as well as the interactions between maternal and fetal genotypes, and miRNA posttranscriptional regulation associated with RAAS in preeclampsia. The results are controversial but utterly inspiring and attractive in terms of potential prognostic significance. Although many studies suggest positive associations with genetic mutations and increased risk for preeclampsia, more meticulously designed large-scale investigations are needed to avoid the interference from different variations.

Gender difference of serum angiotensin-converting enzyme (ACE) activity in DD genotype of ACE insertion/deletion polymorphism in elderly Chinese

INTRODUCTION

In this study we investigated the gender difference of serum angiotensin-converting enzyme (ACE) activity in a population of Hong Kong-dwelling elderly Chinese.

MATERIALS AND METHODS

A total of 1767 (843 male, 924 female) Hong Kong-dwelling elderly Chinese were recruited. ACE I/D genotypes were identified by polymerase chain reaction amplification and serum ACE activity was determined using a commercially available kinetic kit. ACE I/D genotype distribution was compared by chi-square test, the correlation between ACE I/D polymorphism and serum ACE activity was analysed by ANOVA test and gender difference of serum ACE activity of different genotypes was compared by independent sample t-test.

RESULTS

No statistically significant difference of genotype distribution between male and female subjects was found. Serum ACE activity was significantly correlated with ACE genotype. Overall, there was no gender difference of serum ACE activity; however, when sub-grouping the subjects by ACE I/D genotype, male subjects with DD genotype had higher serum ACE activity than female subjects with DD genotype.

CONCLUSIONS

No significant gender difference of genotype distribution was found in elderly Chinese. Serum ACE activity was significantly correlated with ACE I/D polymorphism in elderly Chinese. Male subjects with DD genotype had higher serum ACE activity than female subjects with DD genotype.

Genome-wide linkage and positional association study of blood pressure response to dietary sodium intervention: the GenSalt Study

The authors conducted a genome-wide linkage scan and positional association analysis to identify the genetic determinants of salt sensitivity of blood pressure (BP) in a large family-based, dietary-feeding study. The dietary intervention was conducted among 1,906 participants in rural China (2003-2005). A 7-day low-sodium intervention was followed by a 7-day high-sodium intervention. Salt sensitivity was defined as BP responses to low- and high-sodium interventions. Signals of the logarithm of the odds to the base 10 (LOD ≥ 3) were detected at 33-42 centimorgans of chromosome 2 (2p24.3-2p24.1), with a maximum LOD score of 3.33 for diastolic blood pressure responses to high-sodium intervention. LOD scores were 2.35-2.91 for mean arterial pressure (MAP) and 0.80-1.49 for systolic blood pressure responses in this region, respectively. Correcting for multiple tests, single nucleotide polymorphism (SNP) rs11674786 (2.7 kilobases upstream of the family with sequence similarity 84, member A, gene (FAM84A)) in the linkage region was significantly associated with diastolic blood pressure (P = 0.0007) and MAP responses (P = 0.0007), and SNP rs16983422 (2.8 kilobases upstream of the visinin-like 1 gene (VSNL1)) was marginally associated with diastolic blood pressure (P = 0.005) and MAP responses (P = 0.005). An additive interaction between SNPs rs11674786 and rs16983422 was observed, with P = 7.00 × 10(-5) and P = 7.23 × 10(-5) for diastolic blood pressure and MAP responses, respectively. The authors concluded that genetic region 2p24.3-2p24.1 might harbor functional variants for the salt sensitivity of BP.

Applying genomics to nutrition and lifestyle modification

Personalized nutrition aims to prevent the onset and development of chronic diseases by targeting dietary recommendations to an individual’s genetic profile. Gene–diet interactions that affect metabolic pathways relevant to disease risk are continuously being uncovered. Discoveries in the field of nutrigenomics demonstrate that some individuals may benefit from adhering to different dietary guidelines than others, depending on their genotype. Certain industries have already begun to capitalize on the anticipation that knowledge of genomic information could help prevent the risk of developing diseases. Although disclosure of genetic information has been associated with the adoption of positive health-related behaviors under certain circumstances, the effect of providing gene-based dietary advice on motivating adherence to favorable dietary changes is largely unknown.

The association between gene polymorphisms and leukocytosis with thrombotic complications in patients with essential thrombocythemia and polycythemia vera

Objective: Vascular events are a common complication in patients with polycythemia vera (PV) and essential thrombocythemia (ET). This study aimed to analyze the association between PAI-1 4G/5G and ACE I/D gene polymorphisms, and leukocytosis with thrombosis in patients with PV and ET.

Material and Methods: In total, 64 patients with ET and PV were evaluated. Arterial or venous thrombosis, such as cerebral transient ischemic attack, ischemic stroke, myocardial infarction, peripheral arterial thrombosis, deep venous thrombosis, and pulmonary embolism, were defined as a vascular event. DNA samples were screened for mutations via reverse hybridization strip assay.

Results: In terms of PAI-1 gene polymorphism, the frequency of the 4G and 5G allele was 48.5% and 51.5%, respectively. The ACE allele frequency was 51.2% and 48.8% for D and I, respectively. There wasn’t an association between occurrence of vascular events and the frequency of any allele. In terms of occurrence of vascular events, there weren’t any significance differences between the patients that were carrying the ACE D/D homozygous allele to ACE I/D and those that carried the I/I allele (P = 0.93). There wasn’t a significant difference in occurrence of vascular events between the PAI-1 5G/5G homozygote allele carriers, and the 4G/5G and 4G/4G allele carriers (P = 0.97). Vascular events were significantly more common in the patients with leukocytosis (leukocyte count >10 × 109 L–1) than in those without leukocytosis (leukocyte count ≤10 × 109 L–1) (P = 0.00). Age >60 years was also a significant risk factor for occurrence of vascular events(P = 0.008).

Conclusion: PAI-1 and ACE gene polymorphisms were not considered new risk factors for thrombosis in PV and ET patients. On the other hand, leukocytosis at diagnosis was associated with the occurrence of vascular events in the patients with ET and PV.

Top Three Pharmacogenomics and Personalized Medicine Applications at the Nexus of Renal Pathophysiology and Cardiovascular Medicine

Pharmacogenomics is a field with origins in the study of monogenic variations in drug metabolism in the 1950s. Perhaps because of these historical underpinnings, there has been an intensive investigation of 'hepatic pharmacogenes' such as CYP450s and liver drug metabolism using pharmacogenomics approaches over the past five decades. Surprisingly, kidney pathophysiology, attendant diseases and treatment outcomes have been vastly under-studied and under-theorized despite their central importance in maintenance of health, susceptibility to disease and rational personalized therapeutics. Indeed, chronic kidney disease (CKD) represents an increasing public health burden worldwide, both in developed and developing countries. Patients with CKD suffer from high cardiovascular morbidity and mortality, which is mainly attributable to cardiovascular events before reaching end-stage renal disease. In this paper, we focus our analyses on renal function before end-stage renal disease, as seen through the lens of pharmacogenomics and human genomic variation. We herein synthesize the recent evidence linking selected Very Important Pharmacogenes (VIP) to renal function, blood pressure and salt-sensitivity in humans, and ways in which these insights might inform rational personalized therapeutics. Notably, we highlight and present the rationale for three applications that we consider as important and actionable therapeutic and preventive focus areas in renal pharmacogenomics: 1) ACE inhibitors, as a confirmed application, 2) VDR agonists, as a promising application, and 3) moderate dietary salt intake, as a suggested novel application. Additionally, we emphasize the putative contributions of gene-environment interactions, discuss the implications of these findings to treat and prevent hypertension and CKD. Finally, we conclude with a strategic agenda and vision required to accelerate advances in this under-studied field of renal pharmacogenomics with vast significance for global public health.

Genetic correlation of blood pressure responses to dietary sodium and potassium intervention and cold pressor test in Chinese population

We examined the genetic association between blood pressure (BP) responses to dietary sodium and potassium intervention and to cold pressor test (CPT) in a large family-based dietary feeding study. The dietary intervention and CPT were conducted among 1906 participants in rural China. The dietary intervention included three 7-day periods of low-sodium feeding (51.3 mmol per day), high-sodium feeding (307.8 mmol per day) and high-sodium feeding plus potassium supplementation (60 mmol per day). BP responses to high-sodium intervention had strong genetic correlations (ρ(G)) with both BP responses to low sodium (ρ(G)=-0.43 to -0.54, P-values=0.0005 to 0.03) and to potassium supplementation (ρ(G)=-0.41 to -0.49, P-values=0.001 to 0.005) interventions. Most environmental correlations between BP responses to various dietary interventions were significant. The ρ(G) between BP responses to CPT and to high-sodium intervention and potassium supplementation were statistically significant. For example, the ρ(G) between maximum BP responses to CPT and BP responses to high-sodium intervention was 0.37 (P=0.006) for systolic BP (SBP) and 0.41 (P=0.002) for diastolic BP (DBP). The ρ(G) between maximum BP responses to CPT and BP responses to potassium intervention was -0.42 (P=0.001) for SBP and -0.46 (P=0.001) for SBP. Our study suggests that there are common genetic determinants that influence BP responses to dietary sodium and potassium interventions and to CPT.

Haplotype variation in the ACE gene in global populations, with special reference to India, and an alternative model of evolution of haplotypes

Angiotensin-I-converting enzyme (ACE) is known to be associated with human cardiovascular and psychiatric pathophysiology. We have undertaken a global survey of the haplotypes in ACE gene to study diversity and to draw inferences on the nature of selective forces that may be operating on this gene. We have investigated the haplotype profiles reconstructed using polymorphisms in the regulatory (rs4277405, rs4459609, rs1800764, rs4292, rs4291), exonic (rs4309, rs4331, rs4343), and intronic (rs4340; Alu [I/D]) regions covering 17.8 kb of the ACE gene. We genotyped these polymorphisms in a large number of individuals drawn from 15 Indian ethnic groups and estimated haplotype frequencies. We compared the Indian data with available data from other global populations. Globally, five major haplotypes were observed. High-frequency haplotypes comprising mismatching alleles at the loci considered were seen in all populations. The three most frequent haplotypes among Africans were distinct from the major haplotypes of other world populations. We have studied the evolution of the two major haplotypes (TATATTGIA and CCCTCCADG), one of which contains an Alu insertion (I) and the other a deletion (D), seen most frequently among Caucasians (68%), non-African HapMap populations (65-88%), and Indian populations (70-95%) in detail. The two major haplotypes among Caucasians are reported to represent two distinct clades A and B. Earlier studies have postulated that a third clade C (represented by the haplotypes TACATCADG and TACATCADA) arose from an ancestral recombination event between A and B. We find that a more parsimonious explanation is that clades A and B have arisen by recombination between haplotypes belonging to clade C and a high-frequency African haplotype CCCTTCGIA. The haplotypes, which according to our hypothesis are the putative non-recombinants (PuNR), are uncommon in all non-African populations (frequency range 0-12%). Conversely, the frequencies of the putative recombinant haplotypes (PuR) are very low in the Africans populations (2-8%), indicating that the recombination event is likely to be ancient and arose before, perhaps shortly prior to, the global dispersal of modern humans. The global frequency spectrum of the PuR and the PuNR is difficult to explain only by drift. It appears likely that the ACE gene has been undergoing a combination of different selective pressures.

ELECTRONIC SUPPLEMENTARY MATERIAL

The online version of this article (doi:10.1007/s11568-011-9153-6) contains supplementary material, which is available to authorized users.

Contribution of clinical, metabolic, and genetic factors on hypertension in obese children and adolescents

The role of ACE gene insertion (I) or deletion (D) polymorphism on blood pressure phenotype is not clear in children. The aim of this work is to examine the association between hypertension and ACE I/D polymorphism, as well as the contribution of clinical and metabolic parameters on blood pressure. The study participants were 199 obese children. Forty-four of them were hypertensive. The hypertensive subjects were older than the normotensive and most of them were pubertal. The prevalence of hypertension in obese subjects with II, ID, and DD genotype was similar. There was no difference between the hypertensive and the normotensive group according to ACE I/D genotype, BMISDS, sex, blood glucose level and total cholesterol levels. In obese children, high IR-HOMA values, puberty, presence of family history for hypertension, hypertriglyceridemia, and low HDL-cholesterol, high triglyceride/HDL-cholesterol ratio were found as increased risk factors of hypertension. In obese children and adolescents, blood pressure did not differ by ACE I/D genotype. The presence of family history, puberty, insulin resistance and hypertriglyceridemia constitute important risk factors for developing hypertension.

High-salt diet and hypertension: focus on the renin-angiotensin system

A high-salt diet is one of the major risk factors in the development and maintenance of hypertension. Numerous experimental and observational studies have confirmed the association of sodium intake with blood pressure levels. The effects of a high-salt diet are related to the function of the renin-angiotensin system, which is normally suppressed by a high-salt diet. Endothelial dysfunction probably plays an important role in the influence of high sodium intake on blood pressure, although the exact mechanisms remain elusive. Genetic factors are known to be very important, and various consomic and congenic rat strains as animal models have proven to be very useful in bringing us a step closer to understanding the interaction between salt intake and hypertension. In this article, experimental data obtained in studies on animals and humans, as well as epidemiological data are reviewed.

Angiotensin-Converting Enzyme Insertion/Deletion (ACE I/D) and Angiotensin II Type 1 Receptor (AT1R) Gene Polymorphism and Its Association with Preeclampsia in Chinese Women

OBJECTIVE

To investigate whether polymorphisms of angiotensin converting enzyme gene (ACE) and angiotensin II receptor type 1 gene (AT1R) are associated with etiology of preeclampsia and renal impact in women with preeclampsia.

METHODS

DNA was extracted from peripheral blood of 133 patients with preeclampsia and 105 healthy pregnant women. The I/D polymorphism of the ACE gene was assessed by polymerase chain reaction, and the A1166C polymorphism of the AT(1)R gene was additionally assessed by DdeI digestion. The level of proteinuria, fasting serum urea, creatinine and uric acid were investigated according to different genotypes of ACE and AT1R genes.

RESULTS

The frequency of genotypes of the ACE gene and the AT1R gene was similar in preeclampsia and normal pregnancy. DD and ID genotype predominated in patients with severe proteinuria, as well as increased serum urea and uric acid. Serum creatinine was also increased, but no significant difference was found among three genotypes. The level of proteinuria, serum uric acid, urea, and creatinine did not vary between different AT1R genotypes. Compared with patients without renal dysfunction, the frequency of DD and ID genotypes of ACE gene was much higher in those with renal dysfunction, but AC and CC genotypes of AT1R gene were not.

CONCLUSION

We found no association of the two gene polymorphisms with preeclampsia. However, ACE gene I/D polymorphisms were associated with the severe proteinuria and renal dysfunction seen in preeclampsia. Preeclampsia patients carrying the D allele may be susceptible to renal dysfunction.

Cellular mediators of renal vascular dysfunction in hypertension

The renal vasculature plays a major role in the regulation of renal blood flow and the ability of the kidney to control the plasma volume and blood pressure. Renal vascular dysfunction is associated with renal vasoconstriction, decreased renal blood flow, and consequent increase in plasma volume and has been demonstrated in several forms of hypertension (HTN), including genetic and salt-sensitive HTN. Several predisposing factors and cellular mediators have been implicated, but the relationship between their actions on the renal vasculature and the consequent effects on renal tubular function in the setting of HTN is not clearly defined. Gene mutations/defects in an ion channel, a membrane ion transporter, and/or a regulatory enzyme in the nephron and renal vasculature may be a primary cause of renal vascular dysfunction. Environmental risk factors, such as high dietary salt intake, vascular inflammation, and oxidative stress further promote renal vascular dysfunction. Renal endothelial cell dysfunction is manifested as a decrease in the release of vasodilatory mediators, such as nitric oxide, prostacyclin, and hyperpolarizing factors, and/or an increase in vasoconstrictive mediators, such as endothelin, angiotensin II, and thromboxane A(2). Also, an increase in the amount/activity of intracellular Ca(2+) concentration, protein kinase C, Rho kinase, and mitogen-activated protein kinase in vascular smooth muscle promotes renal vasoconstriction. Matrix metalloproteinases and their inhibitors could also modify the composition of the extracellular matrix and lead to renal vascular remodeling. Synergistic interactions between the genetic and environmental risk factors on the cellular mediators of renal vascular dysfunction cause persistent renal vasoconstriction, increased renal vascular resistance, and decreased renal blood flow, and, consequently, lead to a disturbance in the renal control mechanisms of water and electrolyte balance, increased plasma volume, and HTN. Targeting the underlying genetic defects, environmental risk factors, and the aberrant renal vascular mediators involved should provide complementary strategies in the management of HTN.

Angiotensin II type 1 receptor polymorphisms and susceptibility to hypertension: a HuGE review

The angiotensin II type 1 receptor (AGTR1) plays an integral role in blood pressure control, and is implicated in the pathogenesis of hypertension. Polymorphisms within this gene have been extensively studied in association with hypertension; however, findings are conflicting. To clarify these data, we conducted a systematic review of association studies of AGTR1 polymorphisms and hypertension, and performed a meta-analysis of the rs5186 variant. Results show that the currently available literature is too heterogeneous to draw meaningful conclusions. The definition of hypertension and gender composition of individual studies helps to explain this heterogeneity. Although the structure and splicing pattern of AGTR1 would suggest a likely effect of polymorphisms within the promoter region on gene function, few studies have been conducted thus far. In conclusion, there is insufficient evidence that polymorphisms in the AGTR1 gene are risk factors for hypertension. However, most studies are inadequately powered, and larger well-designed studies of haplotypes are warranted.