A Functional Variant of NEDD4L Is Associated With Hypertension, Antihypertensive Response, and Orthostatic Hypotension

NEDD4L is a promoter for angiogenesis and cell proliferation in human umbilical vein endothelial cells

Dysregulated angiogenesis leads to neovascularization, which can promote or exacerbate various diseases. Previous studies have proved that NEDD4L plays an important role in hypertension and atherosclerosis. Hence, we hypothesized that NEDD4L may be a critical regulator of endothelial cell (EC) function. This study aimed to define the role of NEDD4L in regulating EC angiogenesis and elucidate their underlying mechanisms. Loss- and gain-of-function of NEDD4L detected the angiogenesis and mobility role in human umbilical vein endothelial cells (HUVECs) using Matrigel tube formation assay, cell proliferation and migration. Pharmacological pathway inhibitors and western blot were used to determine the underlying mechanism of NEDD4L-regulated endothelial functions. Knockdown of NEDD4L suppressed tube formation, cell proliferation and cell migration in HUVECs, whereas NEDD4L overexpression promoted these functions. Moreover, NEDD4L-regulated angiogenesis and cell progression are associated with the phosphorylation of Akt, Erk1/2 and eNOS and the expression of VEGFR2 and cyclin D1 and D3. Mechanically, further evidence was confirmed by using Akt blocker MK-2206, Erk1/2 blocker U0126 and eNOS blocker L-NAME. Overexpression NEDD4L-promoted angiogenesis, cell migration and cell proliferation were restrained by these inhibitors. In addition, overexpression NEDD4L-promoted cell cycle-related proteins cyclin D1 and D3 were also suppressed by Akt blocker MK-2206, Erk1/2 blocker U0126 and eNOS blocker L-NAME. Our results demonstrated a novel finding that NEDD4L promotes angiogenesis and cell progression by regulating the Akt/Erk/eNOS pathways.

Predicting the germline dependence of hematuria risk in prostate cancer radiotherapy patients

BACKGROUND AND PURPOSE

Late radiation-induced hematuria can develop in prostate cancer patients undergoing radiotherapy and can negatively impact the quality-of-life of survivors. If a genetic component of risk could be modeled, this could potentially be the basis for modifying treatment for high-risk patients. We therefore investigated whether a previously developed machine learning-based modeling method using genome-wide common single nucleotide polymorphisms (SNPs) can stratify patients in terms of the risk of radiation-induced hematuria.

MATERIALS AND METHODS

We applied a two-step machine learning algorithm that we previously developed for genome-wide association studies called pre-conditioned random forest regression (PRFR). PRFR includes a pre-conditioning step, producing adjusted outcomes, followed by random forest regression modeling. Data was from germline genome-wide SNPs for 668 prostate cancer patients treated with radiotherapy. The cohort was stratified only once, at the outset of the modeling process, into two groups: a training set (2/3 of samples) for modeling and a validation set (1/3 of samples). Post-modeling bioinformatics analysis was conducted to identify biological correlates plausibly associated with the risk of hematuria.

RESULTS

The PRFR method achieved significantly better predictive performance compared to other alternative methods (all p < 0.05). The odds ratio between the high and low risk groups, each of which consisted of 1/3 of samples in the validation set, was 2.87 (p = 0.029), implying a clinically useful level of discrimination. Bioinformatics analysis identified six key proteins encoded by CTNND2, GSK3B, KCNQ2, NEDD4L, PRKAA1, and TXNL1 genes as well as four statistically significant biological process networks previously shown to be associated with the bladder and urinary tract.

CONCLUSION

The risk of hematuria is significantly dependent on common genetic variants. The PRFR algorithm resulted in a stratification of prostate cancer patients at differential risk levels of post-radiotherapy hematuria. Bioinformatics analysis identified important biological processes involved in radiation-induced hematuria.

Pharmacogenetic association of the NR1H3 promoter variant with antihypertensive response among patients with hypertension: A longitudinal study

Background: The genetic factors in assessing therapeutic efficacy and predicting antihypertensive drug response are unclear. Therefore, this study aims to identify the associations between variants and antihypertensive drug response. Methods: A longitudinal study including 1837 hypertensive patients was conducted in Northern China and followed up for a median 2.24 years. The associations of 11 candidate variants with blood pressure changes in response to antihypertensive drugs and with the risk of cardiovascular events during the follow-up were examined. The dual-luciferase assay was carried out to assess the effect of genetic variants on gene transcriptional activity. Results: The variant rs11039149A>G in the promoter of nuclear receptor subfamily 1 group H member 3 (NR1H3) was associated with the change in systolic blood pressure (ΔSBP) in response to calcium channel blockers (CCBs) monotherapy. Patients carrying rs11039149AG genotype showed a significant increase of systolic blood pressure (SBP) at follow-up compared with AA carriers, and the difference of ΔSBP between AG and AA carriers was 5.94 mm Hg (95%CI: 2.09-9.78, p = 0.002). In 1,184 patients with CCBs therapy, SBP levels decreased in AA carriers, but increased in AG carriers, the difference of ΔSBP between AG and AA carriers was 8.04 mm Hg (95%CI: 3.28-12.81, p = 0.001). Further analysis in 359 patients with CCBs monotherapy, the difference of ΔSBP between AG and AA carriers was 15.25 mm Hg (95%CI: 6.48-24.02, p = 0.001). However, there was no significant difference in ΔSBP between AG and AA carriers with CCBs multitherapy. The rs11039149A>G was not associated with the cardiovascular events incidence during the follow-up. Additionally, transcriptional factor forkhead box C1 (FOXC1) bound to the NR1H3 promoter containing rs11039149A and significantly increased the transcriptional activity, while rs11039149 A to G change led to a loss-of-function and disabled FOXC1 binding. For the other 10 variants, associations with blood pressure changes or risk of cardiovascular events were not observed. Conclusion: Hypertensive patients with rs11039149AG genotype in the NR1H3 gene have a significant worse SBP control in response to CCBs monotherapy compared with AA carriers. Our findings suggest that the NR1H3 gene might act as a promising genetic factor to affect individual sensitivity to antihypertensive drugs.

Associations of genetic variations in NEDD4L with salt sensitivity, blood pressure changes and hypertension incidence in Chinese adults

Neural precursor cell expressed developmentally downregulated 4-like (NEDD4L), a member of the E3 ubiquitin-protein ligases, encoded by NEDD4L gene, was found to be involved in in salt sensitivity by regulating sodium reabsorption in salt-sensitive rats. The authors aimed to explore the associations of NEDD4L genetic variants with salt sensitivity, blood pressure (BP) changes and hypertension incidence in Chinese adults. Participants from 124 families in Northern China in the Baoji Salt-Sensitive Study Cohort in 2004, who received the chronic salt intake intervention, including a 7-day low-salt diet (3.0 g/day) and a 7-day high-salt diet (18 g/day), were analyzed. Besides, the development of hypertension over 14 years was evaluated. NEDD4L single nucleotide polymorphism (SNP) rs74408486 was shown to be significantly associated with systolic BP (SBP), diastolic BP (DBP) and mean arterial pressure (MAP) responses to low-salt diet, while SNPs rs292449 and rs2288775 were significantly associated with pulse pressure (PP) response to high-salt diet. In addition, SNP rs4149605, rs73450471, and rs482805 were significantly associated with the longitudinal changes in SBP, DBP, MAP, or PP at 14 years of follow-up. SNP rs292449 was significantly associated with hypertension incidence over the 14-year follow-up. Finally, this gene-based analysis found that NEDD4L was significantly associated with longitudinal BP changes and the incidence of hypertension over the 14-year follow-up. This study indicated that gene polymorphism in NEDD4L serve an important function in salt sensitivity, longitudinal BP change and development of hypertension in the Chinese population.

Function and Regulation of the Epithelial Na+ Channel ENaC

The Epithelial Na⁺ Channel, ENaC, comprised of 3 subunits (αβγ, or sometimes δβγENaC), plays a critical role in regulating salt and fluid homeostasis in the body. It regulates fluid reabsorption into the blood stream from the kidney to control blood volume and pressure, fluid absorption in the lung to control alveolar fluid clearance at birth and maintenance of normal airway surface liquid throughout life, and fluid absorption in the distal colon and other epithelial tissues. Moreover, recent studies have also revealed a role for sodium movement via ENaC in nonepithelial cells/tissues, such as endothelial cells in blood vessels and neurons. Over the past 25 years, major advances have been made in our understanding of ENaC structure, function, regulation, and role in human disease. These include the recently solved three-dimensional structure of ENaC, ENaC function in various tissues, and mutations in ENaC that cause a hereditary form of hypertension (Liddle syndrome), salt-wasting hypotension (PHA1), or polymorphism in ENaC that contributes to other diseases (such as cystic fibrosis). Moreover, great strides have been made in deciphering the regulation of ENaC by hormones (e.g., the mineralocorticoid aldosterone, glucocorticoids, vasopressin), ions (e.g., Na⁺ ), proteins (e.g., the ubiquitin-protein ligase NEDD4-2, the kinases SGK1, AKT, AMPK, WNKs & mTORC2, and proteases), and posttranslational modifications [e.g., (de)ubiquitylation, glycosylation, phosphorylation, acetylation, palmitoylation]. Characterization of ENaC structure, function, regulation, and role in human disease, including using animal models, are described in this article, with a special emphasis on recent advances in the field. © 2021 American Physiological Society. Compr Physiol 11:1-29, 2021.

The importance of the epithelial sodium channel in determining salt sensitivity in people of African origin

Hypertension is highly prevalent in Black Africans and has been found to be associated with worse blood pressure (BP) control and more cardiovascular disease. Black Africans are more salt sensitive with low renin and aldosterone levels. This can be explained in part by variants in the epithelial sodium channel (ENaC) causing an increase in channel activity resulting in sodium and water retention. These variants in the ENaC are increased in the Black African populations presumably due to selective pressure for sodium retention in traditionally low-salt diets. Furthermore, increased endothelial sodium channel activity contributes to the risk of vascular stiffness, which may also result in more difficult to control hypertension. Patients with increased activity of the ENaC are more likely to respond to amiloride (a selective sodium channel antagonist), which has implications for the management of severe and resistant hypertension in Black Africans. A large-scale controlled trial on the use of amiloride compared to usual care is warranted in Blacks with severe or resistant hypertension.

Role of the Ubiquitin Proteasome System in the Regulation of Blood Pressure: A Review

The kidney and the vasculature play crucial roles in regulating blood pressure. The ubiquitin proteasome system (UPS), a multienzyme process mediating covalent conjugation of the 76-amino acid polypeptide ubiquitin to a substrate protein followed by proteasomal degradation, is involved in multiple cellular processes by regulating protein turnover in various tissues. Increasing evidence demonstrates the roles of UPS in blood pressure regulation. In the kidney, filtered sodium is reabsorbed through diverse sodium transporters and channels along renal tubules, and studies conducted till date have provided insights into the complex molecular network through which ubiquitin ligases modulate sodium transport in different segments. Components of these pathways include ubiquitin ligase neuronal precursor cell-expressed developmentally downregulated 4-2, Cullin-3, and Kelch-like 3. Moreover, accumulating data indicate the roles of UPS in blood vessels, where it modulates nitric oxide bioavailability and vasoconstriction. Cullin-3 not only regulates renal salt reabsorption but also controls vascular tone using different adaptor proteins that target distinct substrates in vascular smooth muscle cells. In endothelial cells, UPS can also contribute to blood pressure regulation by modulating endothelial nitric oxide synthase. In this review, we summarize current knowledge regarding the role of UPS in blood pressure regulation, focusing on renal sodium reabsorption and vascular function.

Preparation of orally fast-dissolving tablets of etilefrine hydrochloride to achieve efficient absorption

Etilefrine hydrochloride (ET) is commonly used in the treatment of hypotension in dosage forms of oral tablets and parenteral injections. However, oral tablets only temporarily achieve high plasma levels and have low bioavailability (BA), while intravenous injections may cause pain and necrosis around administration sites. In an attempt to overcome these limitations, the buccal delivery of ET using oral droplets has been investigated. In this study, a buccal tablet as an alternative dosage form was developed for practical use. Buccal tablets were prepared by the direct compression method with sodium alginate (AL) and mannitol (MA) as excipients. Their disintegration and in vitro drug release were rapid (more than 50% being released after 3 min). Furthermore, effective plasma levels (> 5-7 ng/mL) were reached within 0.5 h of buccal administration in rats. The systemic absorption of these tablets was similar to that of buccal droplets. Therefore, the ET buccal tablets developed herein have potential as an alternative dosage form for hypotension therapy.

Pharmacogenomics of Hypertension Treatment

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

A Variant in the NEDD4L Gene Associates With Hypertension in Chronic Kidney Disease in the Southeastern Han Chinese Population

BACKGROUND

"Neuronal precursor cell expressed developmentally down-regulated 4-like" (NEDD4L) is considered a candidate gene for hypertension-both functionally and genetically-through the regulation of the ubiquitination of the epithelial sodium channel (ENaC). This study explores the relationship between genetic variation in NEDD4L and hypertension with chronic kidney disease (CKD) in the southeastern Han Chinese population.

METHODS

We recruited 623 CKD patients and measured ambulatory blood pressure monitoring (ABPM), and the rs4149601 and rs2288774 polymorphisms in NEDD4L were genotyped using quantitative polymerase chain reaction.

RESULTS

For rs4149601, significant differences in genotype frequencies in an additive model (GG vs. GA vs. AA) were observed between normotensive patients and hypertensive patients when hypertension was classified into ambulatory hypertension, clinical hypertension, and ambulatory systolic hypertension (P = 0.038, 0.005, and 0.006, respectively). In a recessive model (GG + GA vs. AA), the frequency of the AA genotype of rs4149601 in the hypertension groups was all higher than that in the normotensive groups. The genotype distribution of rs2288774 did not differ significantly between the normotensive and hypertensive patients. In both the full cohort and the propensity score matching (PSM) cohort, the AA genotype of rs4149601 (compared with the GG + GA genotype group) was independently correlated with ambulatory hypertension, clinical hypertension, and ambulatory systolic hypertension by multivariate logistic regression analysis.

CONCLUSIONS

The present study indicates that the AA genotype of rs4149601 associates with hypertension in CKD. Consequently, the rs4149601 A allele might be a risk factor for hypertension with CKD.

Pharmacogenomics And Hypertension: Current Insights

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

A multi-ancestry genome-wide study incorporating gene-smoking interactions identifies multiple new loci for pulse pressure and mean arterial pressure

Elevated blood pressure (BP), a leading cause of global morbidity and mortality, is influenced by both genetic and lifestyle factors. Cigarette smoking is one such lifestyle factor. Across five ancestries, we performed a genome-wide gene-smoking interaction study of mean arterial pressure (MAP) and pulse pressure (PP) in 129 913 individuals in stage 1 and follow-up analysis in 480 178 additional individuals in stage 2. We report here 136 loci significantly associated with MAP and/or PP. Of these, 61 were previously published through main-effect analysis of BP traits, 37 were recently reported by us for systolic BP and/or diastolic BP through gene-smoking interaction analysis and 38 were newly identified (P < 5 × 10-8, false discovery rate < 0.05). We also identified nine new signals near known loci. Of the 136 loci, 8 showed significant interaction with smoking status. They include CSMD1 previously reported for insulin resistance and BP in the spontaneously hypertensive rats. Many of the 38 new loci show biologic plausibility for a role in BP regulation. SLC26A7 encodes a chloride/bicarbonate exchanger expressed in the renal outer medullary collecting duct. AVPR1A is widely expressed, including in vascular smooth muscle cells, kidney, myocardium and brain. FHAD1 is a long non-coding RNA overexpressed in heart failure. TMEM51 was associated with contractile function in cardiomyocytes. CASP9 plays a central role in cardiomyocyte apoptosis. Identified only in African ancestry were 30 novel loci. Our findings highlight the value of multi-ancestry investigations, particularly in studies of interaction with lifestyle factors, where genomic and lifestyle differences may contribute to novel findings.

Genomics of Cardiovascular Measures of Autonomic Tone

The autonomic nervous system exerts broad control over the involuntary functions of the human body through complex equilibrium between sympathetic and parasympathetic tone. Imbalance in this equilibrium is associated with a multitude of cardiovascular outcomes, including mortality. The cardiovascular static state of this equilibrium can be quantified using physiological parameters such as heart rate (HR), blood pressure, and by spectral analysis of HR variability. Here, we review the current state of knowledge of the genetic background of cardiovascular measurements of autonomic tone. For most parameters of autonomic tone, a large portion of variability is explained by genetic heritability. Many of the static parameters of autonomic tone have also been studied through candidate-gene approach, yielding some insight into how genotypes of adrenergic receptors affect variables such as HR. Genome-wide approaches in large cohorts similarly exist for static variables such as HR and blood pressure but less is known about the genetic background of the dynamic and more specific measurements, such as HR variability. Furthermore, because most autonomic measures are likely polygenic, pathway analyses and modeling of polygenic effects are critical. Future work will hopefully explain the control of autonomic tone and guide individualized therapeutic interventions.

Genetics of Hypertension in African Americans and Others of African Descent

Hypertension is the leading cause of cardiovascular disease in the United States, affecting up to one-third of adults. When compared to other ethnic or racial groups in the United States, African Americans and other people of African descent show a higher incidence of hypertension and its related comorbidities; however, the genetics of hypertension in these populations has not been studied adequately. Several genes have been identified to play a role in the genetics of hypertension. They include genes regulating the renin-aldosterone-angiotensin system (RAAS), such as Sodium Channel Epithelial 1 Beta Subunit (SCNN1B), Armadillo Repeat Containing 5 (ARMC5), G Protein-Coupled Receptor Kinase 4 (GRK4), and Calcium Voltage-Gated Channel Subunit Alpha1 D (CACNA1D). In this review, we focus on recent genetic findings available in the public domain for potential differences between African Americans and other populations. We also cover some recent and relevant discoveries in the field of low-renin hypertension from our laboratory at the National Institutes of Health. Understanding the different genetics of hypertension among various groups is essential for effective precision-guided medical therapy of high blood pressure.

Patient-Centered Approach for Hypertension Management in End-Stage Kidney Disease: Art or Science?

Hypertension is present in most patients with end-stage kidney disease initiating dialysis and management of hypertension is a routine but challenging task in everyday dialysis care. End-stage kidney disease patients are uniquely heterogeneous individuals with significant variations in demographic characteristics, functional capacity, and presence of concomitant comorbid conditions and their severity. Therefore, these patients require personalized approaches in addressing not only hypertension but related illnesses, while also accounting for overall prognosis and projected longevity. There are only limited clinical trial data to guide individualized blood pressure management and current guidelines are based predominantly on observational evidence and expert opinions. Inthis review, we reflect on the shortcomings of peridialytic blood pressure recordings and discuss an important paradigm shift toward using out-of-dialysis blood pressure for evaluating hypertension control and for making treatment decisions. In addition, we provide our personal view on blood pressure goals and summarize nonpharmacologic and pharmacologic treatment options for individualized management of hypertension in end-stage kidney disease.

Personalized medicine-a modern approach for the diagnosis and management of hypertension

The main goal of treating hypertension is to reduce blood pressure to physiological levels and thereby prevent risk of cardiovascular disease and hypertension-associated target organ damage. Despite reductions in major risk factors and the availability of a plethora of effective antihypertensive drugs, the control of blood pressure to target values is still poor due to multiple factors including apparent drug resistance and lack of adherence. An explanation for this problem is related to the current reductionist and ‘trial-and-error’ approach in the management of hypertension, as we may oversimplify the complex nature of the disease and not pay enough attention to the heterogeneity of the pathophysiology and clinical presentation of the disorder. Taking into account specific risk factors, genetic phenotype, pharmacokinetic characteristics, and other particular features unique to each patient, would allow a personalized approach to managing the disease. Personalized medicine therefore represents the tailoring of medical approach and treatment to the individual characteristics of each patient and is expected to become the paradigm of future healthcare. The advancement of systems biology research and the rapid development of high-throughput technologies, as well as the characterization of different –omics, have contributed to a shift in modern biological and medical research from traditional hypothesis-driven designs toward data-driven studies and have facilitated the evolution of personalized or precision medicine for chronic diseases such as hypertension.

Association between health literacy and hypertension management in a Chinese community: a retrospective cohort study

Low health literacy is associated with poor clinical outcomes. The relationship between literacy and blood pressure (BP) has been inconsistent. We investigated the determinants of health literacy and the potential relationship between health literacy and hypertension management. We conducted a retrospective cohort trial of 360 hypertensive patients. Scale measurements, physical examination, and laboratory tests were performed based on a standard protocol. To determine factors associated with health literacy, multiple logistic regression analysis was performed and the discriminatory power of the scale score for hypertension control was assessed by the area under the receiver operating curve. After adjusting for potential confounders, our findings show that the level of education, home blood pressure measurement, regular medication, and systolic blood pressure are significantly associated with health literacy. Moreover, patients with high health literacy have better hypertension control, a lower risk of ischemic cardiovascular disease (ICVD), lower brachial ankle pulse wave velocity values, and better health-related quality of life. In addition, our study also demonstrates that we can identify the health literacy level of hypertensive patients using the Chinese Health Literacy Scale for Hypertension. At a cut-off value of 13.5, we predict that patients will achieve long-term hypertension control. Adequate health literacy is a contributing factor to better blood pressure (BP) control and better perceived quality of life in hypertensive patients. Low health literacy increases the 10-year risk of ICVD and incidence of artery stiffness in hypertensive patients. Improving health literacy should be considered an important part of the management of hypertension.

Personalized medicine and treatment approaches in hypertension: current perspectives

In the US, hypertension affects one in three adults. Current guideline-based treatment of hypertension involves little diagnostic testing. A more personalized approach to the treatment of hypertension might be of use. Several methods of personalized treatment have been proposed and vetted to varying degrees. The purpose of this narrative review is to discuss the rationale for personalized therapy in hypertension, barriers to its development and implementation, some influential examples of proposed personalization measures, and a view of future efforts.

TET2 and CSMD1 genes affect SBP response to hydrochlorothiazide in never-treated essential hypertensives

BACKGROUND

Thiazide diuretics have been recommended as a first-line antihypertensive treatment, although the choice of 'the right drug in the individual essential hypertensive patient' remains still empirical. Essential hypertension is a complex, polygenic disease derived from the interaction of patient's genetic background with the environment. Pharmacogenomics could be a useful tool to pinpoint gene variants involved in antihypertensive drug response, thus optimizing therapeutic advantages and minimizing side effects.

METHODS AND RESULTS

We looked for variants associated with blood pressure response to hydrochlorothiazide over an 8-week follow-up by means of a genome-wide association analysis in two Italian cohorts of never-treated essential hypertensive patients: 343 samples from Sardinia and 142 from Milan. TET2 and CSMD1 as plausible candidate genes to affect SBP response to hydrochlorothiazide were identified. The specificity of our findings for hydrochlorothiazide was confirmed in an independent cohort of essential hypertensive patients treated with losartan. Our best findings were also tested for replication in four independent hypertensive samples of European Ancestry, such as GENetics of drug RESponsiveness in essential hypertension, Genetic Epidemiology of Responses to Antihypertensives, NORdic DILtiazem intervention, Pharmacogenomics Evaluation of Antihypertensive Responses, and Campania Salute Network-StayOnDiur. We validated a polymorphism in CSMD1 and UGGT2.

CONCLUSION

This exploratory study reports two plausible loci associated with SBP response to hydrochlorothiazide: TET2, an aldosterone-responsive mediator of αENaC gene transcription; and CSMD1, previously described as associated with hypertension in a case-control study.

A Physiologic Approach to the Pharmacogenomics of Hypertension

Hypertension is a multifactorial condition with diverse physiological systems contributing to its pathogenesis. Individuals exhibit significant variation in their response to antihypertensive agents. Traditional markers, such as age, gender, diet, plasma renin level, and ethnicity, aid in drug selection. However, this review explores the contribution of genetics to facilitate antihypertensive agent selection and predict treatment efficacy. The findings, reproducibility, and limitations of published studies are examined, with emphasis placed on candidate genetic variants affecting drug metabolism, the renin-angiotensin system, adrenergic signalling, and renal sodium reabsorption. Single-nucleotide polymorphisms identified and replicated in unbiased genome-wide association studies of hypertension treatment are reviewed to illustrate the evolving understanding of the disease's complex and polygenic pathophysiology. Implementation efforts at academic centers seek to overcome barriers to the broad adoption of pharmacogenomics in the treatment of hypertension. The level of evidence required to support the implementation of pharmacogenomics in clinical practice is considered.

Mechanisms and pharmacogenetic signals underlying thiazide diuretics blood pressure response

Thiazide (TZD) diuretics are among the most commonly prescribed antihypertensives globally; however their chronic blood pressure (BP) lowering mechanism remains unclear. Herein we discuss the current evidence regarding specific mechanisms regulating the antihypertensive effects of TZDs, suggesting that TZDs act via multiple complex and interacting mechanisms, including natriuresis with short term use and direct vasodilatory effects chronically. Additionally, we review pharmacogenomics signals that have been associated with TZDs BP-response in several cohorts (i.e. NEDD4L, PRKCA, EDNRA-GNAS, and YEATS4) and discuss how these genes might be related to TZD BP-response mechanism. Understanding the association between these genes and TZD BP mechanism might facilitate the development of new drugs and therapeutic approaches based on a deeper understanding of the determinants of BP-response.

Hypertension pharmacogenomics: in search of personalized treatment approaches

Cardiovascular and renal diseases are associated with many risk factors, of which hypertension is one of the most prevalent. Worldwide, blood pressure control is only achieved in ∼50% of those treated for hypertension, despite the availability of a considerable number of antihypertensive drugs from different pharmacological classes. Although many reasons exist for poor blood pressure control, a likely contributor is the inability to predict to which antihypertensive drug an individual is most likely to respond. Hypertension pharmacogenomics and other 'omics' technologies have the potential to identify genetic signals that are predictive of response or adverse outcome to particular drugs, and guide selection of hypertension treatment for a given individual. Continued research in this field will enhance our understanding of how to maximally deploy the various antihypertensive drug classes to optimize blood pressure response at the individual level. This Review summarizes the available literature on the most convincing genetic signals associated with antihypertensive drug responses and adverse cardiovascular outcomes. Future research in this area will be facilitated by enhancing collaboration between research groups through consortia such as the International Consortium for Antihypertensives Pharmacogenomics Studies, with the goal of translating replicated findings into clinical implementation.

A Genome-wide study of blood pressure in African Americans accounting for gene-smoking interaction

Cigarette smoking has been shown to be a health hazard. In addition to being considered a negative lifestyle behavior, studies have shown that cigarette smoking has been linked to genetic underpinnings of hypertension. Because African Americans have the highest incidence and prevalence of hypertension, we examined the joint effect of genetics and cigarette smoking on health among this understudied population. The sample included African Americans from the genome wide association studies of HyperGEN (N = 1083, discovery sample) and GENOA (N = 1427, replication sample), both part of the FBPP. Results suggested that 2 SNPs located on chromosomes 14 (NEDD8; rs11158609; raw p = 9.80 × 10⁻⁹, genomic control-adjusted p = 2.09 × 10⁻⁷) and 17 (TTYH2; rs8078051; raw p = 6.28 × 10⁻⁸, genomic control-adjusted p = 9.65 × 10⁻⁷) were associated with SBP including the genetic interaction with cigarette smoking. These two SNPs were not associated with SBP in a main genetic effect only model. This study advances knowledge in the area of main and joint effects of genetics and cigarette smoking on hypertension among African Americans and offers a model to the reader for assessing these risks. More research is required to determine how these genes play a role in expression of hypertension.

Recent Advances in the Genetics of Hypertension

Hypertension is a silent killer worldwide, caused by both genetic and environmental factors. Until now, genetic and genomic association studies of hypertension are reporting different degree of association on hypertension. Hence, it is essential to gather all the available information on the reported genetic loci and to determine if any biomarker(s) is/are significantly associated with hypertension. Current review concluded the potential biomarkers for hypertension, with regards to electrolyte and fluid transports, as well as sodium/potassium ions homeostasis, which are supported by the results of case-controls and meta-analyses.

Arterial Stiffness, Central Pulsatile Hemodynamic Load, and Orthostatic Hypotension

The association between central pulsatile hemodynamic load, arterial stiffness, and orthostatic hypotension (OH) is unclear. The authors recruited 1099 participants from the community. Questionnaire, physical examination, and laboratory tests were performed. To assess the correlation between central pulsatile hemodynamic load, arterial stiffness, and OH, multiple logistic regression analysis was performed, and the discriminatory power was assessed by the area under the receiver operating curve. The prevalence of OH in this population was 5.6%. After adjusting for potential confounders, brachial-ankle pulse wave velocity (BaPWV) was significantly and positively correlated with OH in both the hypertension and nonhypertension groups (all P<.05), while central systolic blood pressure (CSBP) was only significantly associated with OH in the hypertension subgroup. In addition, BaPWV seemed to have a better discriminatory power than CSBP in both subgroups. BaPWV appears to be a better indicator of OH than CSBP in routine clinical practice.

Role of single nucleotide polymorphisms in pharmacogenomics and their association with human diseases

Global statistical data shed light on an alarming trend that every year thousands of people die due to adverse drug reactions as each individual responds in a different way to the same drug. Pharmacogenomics has come up as a promising field in drug development and clinical medication in the past few decades. It has emerged as a ray of hope in preventing patients from developing potentially fatal complications due to adverse drug reactions. Pharmacogenomics also minimizes the exposure to drugs that are less/non-effective and sometimes even found toxic for patients. It is well reported that drugs elicit different responses in different individuals due to variations in the nucleotide sequences of genes encoding for biologically important molecules (drug-metabolizing enzymes, drug targets and drug transporters). Single nucleotide polymorphisms (SNPs), the most common type of polymorphism found in the human genome is believed to be the main reason behind 90% of all types of genetic variations among the individuals. Therefore, pharmacogenomics may be helpful in answering the question as to how inherited differences in a single gene have a profound effect on the mobilization and biological action of a drug. In the present review, we have discussed clinically relevant examples of SNP in associated diseases that can be utilized as markers for "better management of complex diseases" and attempted to correlate the drug response with genetic variations. Attention is also given towards the therapeutic consequences of inherited differences at the chromosomal level and how associated drug disposition and/or drug targets differ in various diseases as well as among the individuals.

Genetics, ancestry, and hypertension: implications for targeted antihypertensive therapies

Hypertension is the most common chronic condition seen by physicians in ambulatory care and a condition for which life-long medications are commonly prescribed. There is evidence for genetic factors influencing blood pressure variation in populations and response to medications. This review summarizes recent genetic discoveries that surround blood pressure, hypertension, and antihypertensive drug response from genome-wide association studies, while highlighting ancestry-specific findings and any potential implication for drug therapy targets. Genome-wide association studies have identified several novel loci for inter-individual variation of blood pressure and hypertension risk in the general population. Evidence from pharmacogenetic studies suggests that genes influence the blood pressure response to antihypertensive drugs, although results are somewhat inconsistent across studies. There is still much work that remains to be done to identify genes both for efficacy and adverse events of antihypertensive medications.

NEDD4-2 (NEDD4L): the ubiquitin ligase for multiple membrane proteins

NEDD4-2 (also known as NEDD4L, neural precursor cell expressed developmentally down-regulated 4-like) is a ubiquitin protein ligase of the Nedd4 family which is known to bind and regulate a number of membrane proteins to aid in their internalization and turnover. Several of the NEDD4-2 substrates include ion channels, such as the epithelial and voltage-gated sodium channels. Given the critical function of NEDD4-2 in regulating membrane proteins, this ligase is essential for the maintenance of cellular homeostasis. In this article we review the biology and function of this important ubiquitin-protein ligase and discuss its pathophysiological significance.

The C-1021T polymorphism of dopamine β-hydroxylase is not associated with orthostatic hypotension in a Chinese population

To explore the association between the dopamine β-hydroxylase (DBH) gene C-1021T polymorphism and the occurrence of orthostatic hypotension (OH) in Chinese patients, the DBH C-1021T polymorphism was genotyped in 317 patients with OH and 664 age- and sex-matched controls with orthostatic normotension. All subjects underwent an upright posture study for the measurement of orthostatic blood pressure. OH was defined as a drop in blood pressure of 20/10 mm Hg or more within 3 min of assuming the upright posture. The allele frequency of the DBH C-1021T polymorphism in the orthostatic hypotensive group was similar to the orthostatic normotensive group (17.4 versus 14.9%, P>0.05). No statistical significant association was found between the distribution of the C-1021T genotypes and the risk of OH in both the orthostatic hypotensive and orthostatic normotensive groups even after adjustment for demographic parameters. Among the three different genotypes, blood pressure levels did not significantly differ in the general population in this study. The changes in orthostatic systolic or diastolic blood pressures among the different genotype groups were not detected (all P>0.05). The C-1021T polymorphism of the DBH was not associated with orthostatic hypotensive risk in a Chinese population.

Current concepts in orthostatic hypotension management

Orthostatic hypotension is a condition commonly affecting the elderly and is often accompanied by disabling presyncopal symptoms, syncope and impaired quality of life. The pathophysiology of orthostatic hypotension is linked to abnormal blood pressure regulatory mechanisms and autonomic insufficiency. As part of its diagnostic evaluation, a comprehensive history and medical examination focused on detecting symptoms and physical findings of autonomic neuropathy should be performed. In individuals with substantial falls in blood pressure upon standing, autonomic function tests are recommended to detect impairment of autonomic reflexes. Treatment should always follow a stepwise approach with initial use of nonpharmacologic interventions including avoidance of hypotensive medications, high-salt diet and physical counter maneuvers. If these measures are not sufficient, medications such as fludrocortisone and midodrine can be added. The goals of treatment are to improve symptoms and to make the patient as ambulatory as possible instead of targeting arbitrary blood pressure values.

Ubiquitylation of voltage-gated sodium channels

Ion channel proteins are regulated by different types of posttranslational modifications. The focus of this review is the regulation of voltage-gated sodium channels (Navs) upon their ubiquitylation. The amiloride-sensitive epithelial sodium channel (ENaC) was the first ion channel shown to be regulated upon ubiquitylation. This modification results from the binding of ubiquitin ligase from the Nedd4 family to a protein-protein interaction domain, known as the PY motif, in the ENaC subunits. Many of the Navs have similar PY motifs, which have been demonstrated to be targets of Nedd4-dependent ubiquitylation, tagging them for internalization from the cell surface. The role of Nedd4-dependent regulation of the Nav membrane density in physiology and disease remains poorly understood. Two recent studies have provided evidence that Nedd4-2 is downregulated in dorsal root ganglion (DRG) neurons in both rat and mouse models of nerve injury-induced neuropathic pain. Using two different mouse models, one with a specific knockout of Nedd4-2 in sensory neurons and another where Nedd4-2 was overexpressed with the use of viral vectors, it was demonstrated that the neuropathy-linked neuronal hyperexcitability was the result of Nav1.7 and Nav1.8 overexpression due to Nedd4-2 downregulation. These studies provided the first in vivo evidence of the role of Nedd4-2-dependent regulation of Nav channels in a disease state. This ubiquitylation pathway may be involved in the development of symptoms and diseases linked to Nav-dependent hyperexcitability, such as pain, cardiac arrhythmias, epilepsy, migraine, and myotonias.

Genome-wide association study of orthostatic hypotension and supine-standing blood pressure changes in two korean populations

Orthostatic hypotension (OH) is defined by a 20-mm Hg difference of systolic blood pressure (dtSBP) and/or a 10-mm Hg difference of diastolic blood pressure (dtDBP) between supine and standing, and OH is associated with a failure of the cardiovascular reflex to maintain blood pressure on standing from a supine position. To understand the underlying genetic factors for OH traits (OH, dtSBP, and dtDBP), genome-wide association studies (GWASs) using 333,651 single nucleotide polymorphisms (SNPs) were conducted separately for two population-based cohorts, Ansung (n = 3,173) and Ansan (n = 3,255). We identified 8 SNPs (5 SNPs for dtSBP and 3 SNPs for dtDBP) that were repeatedly associated in both the Ansung and Ansan cohorts and had p-values of <1 × 10^-5 in the meta-analysis. Unfortunately, the SNPs of the OH case control GWAS did not pass our p-value criteria. Four of 8 SNPs were located in the intergenic region of chromosome 2, and the nearest gene (CTNNA2) was located at 1 Mb of distance. CTNNA2 is a linker between cadherin adhesion receptors and the actin cytoskeleton and is essential for stabilizing dendritic spines in rodent hippocampal neurons. Although there is no report about the function in blood pressure regulation, hippocampal neurons interact primarily with the autonomic nervous system and might be related to OH. The remaining SNPs, rs7098785 of dtSBP trait and rs6892553, rs16887217, and rs4959677 of dtDBP trait were located in the PIK3AP1 intron, ACTBL2-3' flanking, STAR intron, and intergenic region, respectively, but there was no clear functional link to blood pressure regulation.

Orthostatic hypotension and incident heart failure in community-dwelling older adults

OBJECTIVES

To examine the association of orthostatic hypotension with incident heart failure (HF) in older adults.

METHODS

Of the 5,273 community-dwelling adults aged 65 years and older free of baseline prevalent HF in the Cardiovascular Health Study, 937 (18%) had orthostatic hypotension, defined as ≥20 mmHg drop in systolic or ≥10 mmHg drop in diastolic blood pressure from supine to standing position at 3 minutes. Of the 937, 184 (20%) had symptoms of dizziness upon standing and were considered to have symptomatic orthostatic hypotension. Propensity scores for orthostatic hypotension were estimated for each of the 5,273 participants and were used to assemble a cohort of 3,510 participants (883 participants with and 2,627 participants without orthostatic hypotension) who were balanced on 40 baseline characteristics. Cox regression models were used to estimate the association of orthostatic hypotension with centrally adjudicated incident HF and other outcomes during 13 years of follow-up.

RESULTS

Participants (n = 3,510) had a mean (±standard deviation) age of 74 (±6) years, 58% were women, and 15% nonwhite. Incident HF occurred in 25% and 21% of matched participants with and without orthostatic hypotension, respectively (hazard ratio, 1.24; 95% confidence interval, 1.06-1.45; p = .007). Among matched participants, hazard ratios for incident HF associated with symptomatic (n = 173) and asymptomatic (n = 710) orthostatic hypotension were 1.57 (95% confidence interval, 1.16-2.11; p = .003) and 1.17 (95% confidence interval, 0.99-1.39; p = .069), respectively.

CONCLUSIONS

Community-dwelling older adults with orthostatic hypotension have higher independent risk of developing new-onset HF, which appeared to be more pronounced in those with symptomatic orthostatic hypotension.

A functional variant of NEDD4L is associated with obesity and related phenotypes in a Han population of Southern China

NEDD4L is a candidate gene for hypertension, both functionally and genetically. Recently, studies showed evidence for the association of NEDD4L with obesity, a key intermediate phenotype in hypertension. To further investigate the relationship between NEDD4L and body mass-related phenotypes, we genotyped three common variants (rs2288774, rs3865418 and rs4149601) in a population-based study of 892 unrelated Han Cantonese using the Sequenom MALDI-TOF-MS platform. Allele frequencies and genotype distribution were calculated in lean controls and overweight/obese cases and analyzed for association by the Chi-squared test and Logistic regression. Linear regression analysis was used to analyze the effect of individual genotypes on quantitative traits. Multivariate analyses demonstrated that the minor allele of rs4149601(A = 20.9%) was associated with a 2.60 kg, 2.78 cm and 0.97 kg/m² decrease per allele copy in weight, waist and BMI, respectively. Carriers of this allele also had a significant lower risk of overweight/obesity (p < 0.0001, OR = 0.52, 95% CI: 0.37–0.74) as compared to non-carriers. However, no significant association between genotypes at rs2288774 and rs3865418 and covariate-adjusted overweight/obesity or any related phenotypes was observed. These results suggested that the functional variant of NEDD4L, rs4149601, may be associated with obesity and related phenotypes, and further genetic and functional studies are required to understand its role in the manifestation of obesity.

Lack of an association between TSC gene Arg904Gln polymorphisms and essential hypertension risk based on a meta-analysis

Although there have been several studies investigating a possible association between essential hypertension and TSC gene Arg904Gln polymorphisms, the results have been inconsistent. We conducted a meta-analysis of four case-control studies (one study in Europe and three studies in Asia), including 1811 essential hypertension cases and 1381 controls. The pooled results showed no significant associations between any of these polymorphisms and essential hypertension (allele Arg vs allele Gln: odds ratio (OR) = 0.94, 95% confidence interval (95%CI) = 0.70-1.27), additive genetic model (Arg/Arg vs Gln/Gln: OR = 0.98, 95%CI = 0.43-2.23), dominant genetic model (Arg/Arg + Arg/Gln vs Gln/ Gln: OR = 0.97, 95%CI = 0.43-2.21), and recessive genetic model (Arg/ Arg vs Arg/Gln + Gln/Gln: OR = 1.03, 95%CI = 0.45-2.35). Based on the results of our meta-analysis, we conclude that the TSC gene Arg904Gln polymorphism is not associated with essential hypertension risk.

A genome-wide association study of caffeine-related sleep disturbance: confirmation of a role for a common variant in the adenosine receptor

OBJECTIVES

To identify common genetic variants that predispose to caffeine-induced insomnia and to test whether genes whose expression changes in the presence of caffeine are enriched for association with caffeine-induced insomnia.

DESIGN

A hypothesis-free, genome-wide association study.

SETTING

Community-based sample of Australian twins from the Australian Twin Registry.

PARTICIPANTS

After removal of individuals who said that they do not drink coffee, a total of 2,402 individuals from 1,470 families in the Australian Twin Registry provided both phenotype and genotype information.

MEASUREMENTS AND RESULTS

A dichotomized scale based on whether participants reported ever or never experiencing caffeine-induced insomnia. A factor score based on responses to a number of questions regarding normal sleep habits was included as a covariate in the analysis. More than 2 million common single nucleotide polymorphisms (SNPs) were tested for association with caffeine-induced insomnia. No SNPs reached the genome-wide significance threshold. In the analysis that did not include the insomnia factor score as a covariate, the most significant SNP identified was an intronic SNP in the PRIMA1 gene (P = 1.4 × 10⁻⁶, odds ratio = 0.68 [0.53 - 0.89]). An intergenic SNP near the GBP4 gene on chromosome 1 was the most significant upon inclusion of the insomnia factor score into the model (P = 1.9 × 10⁻⁶, odds ratio = 0.70 [0.62 - 0.78]). A previously identified association with a polymorphism in the ADORA2A gene was replicated.

CONCLUSIONS

Several genes have been identified in the study as potentially influencing caffeine-induced insomnia. They will require replication in another sample. The results may have implications for understanding the biologic mechanisms underlying insomnia.

Nedd4-2 and the regulation of epithelial sodium transport

Nedd4-2 is a ubiquitin ligase previously demonstrated to regulate endocytosis and lysosomal degradation of the epithelial Na(+) channel (ENaC) and other ion channels and transporters. Recent studies using Nedd4-2 knockout mice specifically in kidney or lung epithelia has revealed a critical role for this E3 ubiquitin ligase in regulating salt and fluid transport in these tissues/organs and in maintaining homeostasis of body blood pressure. Interestingly, the primary targets for Nedd4-2 may differ in these two organs: in the lung Nedd4-2 targets ENaC, and loss of Nedd4-2 leads to excessive ENaC function and to cystic fibrosis - like lung disease, whereas in the kidney, Nedd4-2 targets the Na(+)/Cl(-) cotransporter (NCC) in addition to targeting ENaC. In accord, loss of Nedd4-2 in the distal nephron leads to increased NCC abundance and function. The aldosterone-responsive kinase, Sgk1, appears to be involved in the regulation of NCC by Nedd4-2 in the kidney, similar to its regulation of ENaC. Collectively, these new findings underscore the physiological importance of Nedd4-2 in regulating epithelial salt and fluid transport and balance.

Advancing management of hypertension through pharmacogenomics

Hypertension is the most common, chronic disease in the world, and there are many effective pharmacological agents available for its treatment. Despite the plethora of treatment options, data across the globe suggest that blood pressure control rates are < 50%, a fact likely influenced in part by the inability to predict the antihypertensive drug likely to be most effective for an individual patient. Pharmacogenomics in hypertension holds the promise of identifying genetic biomarkers for antihypertensive drug response, which might be used in the future in treatment selection. Research in the field is also likely to enhance our understanding of hypertension and the mechanisms by which the various drugs produce efficacy. There are several examples in the literature of genes with relatively strong data on associations of genetic polymorphisms with antihypertensive response; the data on ADRB1, CACNB2, and NEDD4L are detailed as examples. Substantial additional data in hypertension pharmacogenomics are expected to be forthcoming from recently completed genome-wide association studies. Increased collaboration among research groups will help insure successful discoveries from these large-scale studies. The next decade should clearly define the potential clinical implications of the research in hypertension pharmacogenomics that is currently in progress.

The association of an adenine insertion variant in the 5'UTR of the endothelin-1 gene with hypertension and orthostatic hypotension

INTRODUCTION

An adenine insertion polymorphism in the 5' untranslated region of the endothelin-1 gene is functional and increases the expression of endothelin mRNA and protein in the insertion homozygote. In the present study we hypothesized that this functional polymorphism might be associated with hypertension and/or orthostatic hypotension.

MATERIAL AND METHODS

The adenine insertion polymorphism was genotyped in 381 untreated hypertensive patients and 298 normotensive subjects, all of whom underwent an upright posture study for orthostatic blood pressure measurements. Orthostatic hypotension was defined as a drop in blood pressure of 20/10 mm Hg or more within 3 min of assuming the upright posture.

RESULTS

The allele frequency of the adenine insertion was similar in hypertensive and normotensive subjects (15.2% vs. 15.3%, p > 0.05). After adjustment for age, sex and body mass index, blood pressure levels did not differ significantly among the genotypes in both hypertensives and normotensives. No associations were found between the distribution of the adenine insertion genotypes and the risk of orthostatic hypotension in both hypertensive patients and normotensive subjects even after adjustment for demographic parameters and supine systolic or diastolic blood pressure. Neither hypertensive nor normotensive subjects showed significant differences in orthostatic systolic or diastolic blood pressure changes among the genotype groups (all p > 0.05).

CONCLUSIONS

We concluded that the functional adenine insertion polymorphism in the endothelin-1 gene is not associated with either hypertension or orthostatic hypotension risk in Chinese.

The association of genetic variants of type 2 diabetes with kidney function

Type 2 diabetes is highly prevalent and is the major cause of progressive chronic kidney disease in American Indians. Genome-wide association studies identified several loci associated with diabetes but their impact on susceptibility to diabetic complications is unknown. We studied the association of 18 type 2 diabetes genome-wide association single-nucleotide polymorphisms (SNPs) with estimated glomerular filtration rate (eGFR; MDRD equation) and urine albumin-to-creatinine ratio in 6958 Strong Heart Study family and cohort participants. Center-specific residuals of eGFR and log urine albumin-to-creatinine ratio, obtained from linear regression models adjusted for age, sex, and body mass index, were regressed onto SNP dosage using variance component models in family data and linear regression in unrelated individuals. Estimates were then combined across centers. Four diabetic loci were associated with eGFR and one locus with urine albumin-to-creatinine ratio. A SNP in the WFS1 gene (rs10010131) was associated with higher eGFR in younger individuals and with increased albuminuria. SNPs in the FTO, KCNJ11, and TCF7L2 genes were associated with lower eGFR, but not albuminuria, and were not significant in prospective analyses. Our findings suggest a shared genetic risk for type 2 diabetes and its kidney complications, and a potential role for WFS1 in early-onset diabetic nephropathy in American Indian populations.

Polymorphisms, hypertension and thiazide diuretics

It is 10 years since the discovery of the human genome; however, the study of the influence of genetic variants on drug effect - pharmacogenomics - has so far failed to create a major impact on day-to-day prescription practices. In the present article we analyze the main findings in candidate gene variants, gene combinations and whole-genome scans in relation to diuretic treatment. A critical analysis of the main reasons for some contrasting results will be discussed. The hypertension phases, in clinical trials dealing with genes and related pathophysiological mechanisms, may account for these inconsistent findings. The use of previously untreated versus treated patients is addressed. Finally, a positive study with a new genetic molecular strategy is described.

Association of intergenic polymorphism of organic anion transporter 1 and 3 genes with hypertension and blood pressure response to hydrochlorothiazide

BACKGROUND

Organic anion transporter (OAT) 1 and OAT3, encoded by a tightly linked gene pair, play a key role in renal secretion of diuretics. However, no study has yet examined the influence of OAT1 and OAT3 polymorphisms on high blood pressure (BP) and the response to thiazide diuretics. We hypothesized that intergenic polymorphisms between OAT1 and OAT3 might be associated with adult hypertension and the antihypertensive effects of hydrochlorothiazide (HCTZ).

METHODS

The association of an intergenic polymorphism (rs10792367) with hypertension risk was investigated in two independent case-control studies (n = 1,592 and 602), and then a combined analysis was performed for improving power (1,106 cases and 1,088 controls) with adjustment for geographic location. Two clinical trials (n = 542 and 274) were conducted in untreated hypertensive patients for the association of rs10792367 with antihypertensive responses to 4 and 8 weeks of HCTZ treatment.

RESULTS

No significant association was found between rs10792367 and hypertension after adjustment for conventional risk factors in either the two populations, respectively, or the combined two population. After adjustment for pretreatment BP and other confounders, HCTZ-induced reduction in systolic BP was 4.8 mm Hg (P = 0.006, first trial) and 6.1 mm Hg (P = 0.003, in second trial) lower, respectively, in C allele carriers than in GG carriers in the two clinical trials.

CONCLUSIONS

Intergenic polymorphism rs10792367 between OAT1 and OAT3 is not associated with hypertension, but appears to be involved in between-individual variations in antihypertensive responses to HCTZ.

Association between NEDD4L gene and sodium lithium countertransport

BACKGROUND

Sodium lithium countertransport (SLC) is an intermediate phenotype of essential hypertension. The aim of this study was to identify candidate genes for SLC by a strategy of combining gene expression profiling and linkage analysis, and to examine the association between the candidate gene and SLC as well as hypertension.

METHODS

In order to identify SLC-related genes, the top 1% of the genes that were differentially expressed between high- and low-SLC groups in a gene expression microarray were compared with published SLC/hypertension gene linkage maps so as to identify regions of overlap. The association between the genetic variation in the candidate gene and the SLC and blood pressure phenotypes were further assessed in the Rochester Family Heart Study (RFHS) involving 1,815 individuals of European ancestry, belonging to 252 pedigrees.

RESULTS

Based on gene expression profiling and evidence from genome-wide linkage analysis, and in the light of its potential biochemical function, E3 ubiquitin-protein ligase NEDD4-like (NEDD4L) was identified as being both a positional and a functional candidate gene for SLC. The difference in expressions of NEDD4L between the high- and low-SLC groups was confirmed by reverse transcription-PCR (RT-PCR) analysis. After adjusting for age, sex, and body mass index (BMI), four single-nucleotide polymorphisms (SNPs) in NEDD4L were found to be associated with SLC (P ≤ 0.05). Further, haplotype analysis revealed that, after correction for multiple testing, one of the haplotypes (H2) was still significantly (P = 0.006) associated with SLC.

CONCLUSIONS

The strategy of combining gene expression profiling and linkage analysis successfully guided us in identifying NEDD4L as a candidate gene involved in regulating SLC activity. Variations in the NEDD4L gene are associated with SLC activity.

Role of the ubiquitin system in regulating ion transport

Ion channels and transporters play a critical role in ion and fluid homeostasis and thus in normal animal physiology and pathology. Tight regulation of these transmembrane proteins is therefore essential. In recent years, many studies have focused their attention on the role of the ubiquitin system in regulating ion channels and transporters, initialed by the discoveries of the role of this system in processing of Cystic Fibrosis Transmembrane Regulator (CFTR), and in regulating endocytosis of the epithelial Na(+) channel (ENaC) by the Nedd4 family of ubiquitin ligases (mainly Nedd4-2). In this review, we discuss the role of the ubiquitin system in ER Associated Degradation (ERAD) of ion channels, and in the regulation of endocytosis and lysosomal sorting of ion channels and transporters, focusing primarily in mammalian cells. We also briefly discuss the role of ubiquitin like molecules (such as SUMO) in such regulation, for which much less is known so far.