Heritability of conventional and ambulatory blood pressures. A study in twins

Genetic and Epigenetic Mechanisms Regulating Blood Pressure and Kidney Dysfunction

The pioneering work of Dr Lewis K. Dahl established a relationship between kidney, salt, and high blood pressure (BP), which led to the major genetic-based experimental model of hypertension. BP, a heritable quantitative trait affected by numerous biological and environmental stimuli, is a major cause of morbidity and mortality worldwide and is considered to be a primary modifiable factor in renal, cardiovascular, and cerebrovascular diseases. Genome-wide association studies have identified monogenic and polygenic variants affecting BP in humans. Single nucleotide polymorphisms identified in genome-wide association studies have quantified the heritability of BP and the effect of genetics on hypertensive phenotype. Changes in the transcriptional program of genes may represent consequential determinants of BP, so understanding the mechanisms of the disease process has become a priority in the field. At the molecular level, the onset of hypertension is associated with reprogramming of gene expression influenced by epigenomics. This review highlights the specific genetic variants, mutations, and epigenetic factors associated with high BP and how these mechanisms affect the regulation of hypertension and kidney dysfunction.

Assessment of Medication Adherence Among Patients With Hypertension and Diabetes Mellitus in a Tertiary Healthcare Center: A Descriptive Study

Introduction Effective management of diabetes and hypertension requires a comprehensive approach, including dietary adjustments, physical activity, routine screening for complications, and adherence to medication. Proper adherence to pharmacotherapy is essential for maintaining glycemic control and managing blood pressure. Non-adherence can result in increased complications, higher healthcare costs, and greater morbidity and mortality. This study aimed to evaluate the sociodemographic profile and medication adherence among adults with diabetes and hypertension, focusing on those undergoing treatment. The objective was to determine the extent of adherence and identify factors that influence adherence among patients with type 2 diabetes mellitus (T2DM) and hypertension. Methods A community-based study was conducted on patients with T2DM and/or hypertension in both rural and urban areas of Bhopal, specifically those attending JK Hospital, Bhopal, Madhya Pradesh, India. Participants were selected using a simple random sampling method. Medication adherence was assessed using the eight-item Morisky Medication Adherence Scale (MMAS-8), a validated tool for measuring patient adherence behavior. Results The study included 300 participants, of whom 68% (n=204) were male and 32% (n=96) were female. The average age of the participants was 57.52±10.3 years. Among the 300 patients, 9% (n=27) had high adherence to medication, 24.7% (n=74) had moderate adherence, and 66.3% (n=199) had low adherence. Conclusions Effective strategies must include targeted patient education on medication costs, side effects, and the long-term benefits of adherence. Integrating technological aids like smartphone apps may enhance adherence. Patients who adhere closely to their regimens are more likely to achieve better control over blood pressure and glycated hemoglobin (HbA1c) levels, underscoring the critical importance of adherence in managing chronic conditions effectively.

Physiotherapy Screening for Referral of a Patient with Patent Foramen Ovale Presenting with Neck Pain as Primary Complaint: A Case Report

Neck pain is a common musculoskeletal disorder encountered by physiotherapists. However, it may be the early manifestation of more alarming conditions, such as cardiovascular diseases mimicking musculoskeletal pain. Patent foramen ovale (PFO) is a congenital heart defect consisting of a small opening between the right and the left atrium. A 56-year-old male presented with neck pain and head heaviness as primary complaints. The cardiovascular profile and the behavioral symptoms led the physiotherapist to find an exaggerated blood pressure response during exercise; in addition to subtle neurological signs, this prompted the physiotherapist to make an urgent referral. At the emergency department a PFO was diagnosed. To the best of the authors' knowledge, this is the first case to describe a rare clinical presentation of a PFO presenting neck pain as primary complaint. This case report emphasizes the importance for physiotherapists to be able to triage patients for conditions outside their scope suggestive of further medical investigation.

Evaluation of the Safety and Efficacy of Dual Therapy Perindopril/Amlodipine in the Management of Hypertension. A Systematic Review and Meta-Analysis

INTRODUCTION

Hypertension represent the commonest cause of death in 2017. Hypertension is classified into two types which are primary or essential hypertension and secondary hypertension. The perindopril-amlodipine combination showed a significant effect in reduction of the elevated BP and the cardiovascular complications.

AIM

To evaluate the efficacy and safety of a fixed-dose single-pill combination of perindopril-amlodipine in hypertensive patients.

METHODS

We searched PubMed, Medline, SCOPUS, and Web of Science for relevant clinical trials. Quality appraisal was evaluated according to GRADE and we assessed the risk of bias using Cochrane's risk of bias tool. We included the following outcomes: systolic blood pressure, diastolic blood pressure, pulse pressure, mean blood pressure, heart rate, cough, dizziness, headache, and peripheral edema. We performed the analysis of homogeneous data under the fixed-effects model, while analysis of heterogeneous data was analyzed under the random-effects model. We conducted a meta-regression according to the dose.

RESULTS

We included ten clinical trials. The pooled analysis showed that there was a significant reduction of the systolic blood pressure, diastolic blood pressure, pulse plessure, mean blood pressure, and heart rate after the the perindopril-amlodipine combination (MD = 18.96 [14.32, 23.60], P < 0.0001), (MD = 11.90 [8.45, 15.35], P < 0.0001), (MD = 8.44 [6.91, 9.97], P = 0.0001), (MD = 13.07 [5.86, 20.29], P = 0.0004), and (MD = 2.93 [0.89, 4.96], P = 0.005), respectively. The results of the meta-regression revealed that the efficacy is increased by increasing the dose (P < 0.001) CONCLUSION: The use of the perindopril-amlodipine combination had a significant effect on the reduction of SBP, DBP, mean blood pressure, pulse pressure, and HR.

Interactions between the intrarenal dopaminergic and the renin-angiotensin systems in the control of systemic arterial pressure

Systemic arterial hypertension is one of the leading causes of morbidity and mortality in the general population, being a risk factor for many cardiovascular diseases. Although its pathogenesis is complex and still poorly understood, some systems appear to play major roles in its development. This review aims to update the current knowledge on the interaction of the intrarenal renin-angiotensin system (RAS) and dopaminergic system in the development of hypertension, focusing on recent scientific hallmarks in the field. The intrarenal RAS, composed of several peptides and receptors, has a critical role in the regulation of blood pressure (BP) and, consequently, the development of hypertension. The RAS is divided into two main intercommunicating axes: the classical axis, composed of angiotensin-converting enzyme, angiotensin II, and angiotensin type 1 receptor, and the ACE2/angiotensin-(1-7)/Mas axis, which appears to modulate the effects of the classical axis. Dopamine and its receptors are also increasingly showing an important role in the pathogenesis of hypertension, as abnormalities in the intrarenal dopaminergic system impair the regulation of renal sodium transport, regardless of the affected dopamine receptor subtype. There are five dopamine receptors, which are divided into two major subtypes: the D1-like (D1R and D5R) and D2-like (D2R, D3R, and D4R) receptors. Mice deficient in any of the five dopamine receptor subtypes have increased BP. Intrarenal RAS and the dopaminergic system have complex interactions. The balance between both systems is essential to regulate the BP homeostasis, as alterations in the control of both can lead to hypertension.

Life-Course Associations between Blood Pressure-Related Polygenic Risk Scores and Hypertension in the Bogalusa Heart Study

Genetic information may help to identify individuals at increased risk for hypertension in early life, prior to the manifestation of elevated blood pressure (BP) values. We examined 369 Black and 832 White Bogalusa Heart Study (BHS) participants recruited in childhood and followed for approximately 37 years. The multi-ancestry genome-wide polygenic risk scores (PRSs) for systolic BP (SBP), diastolic BP (DBP), and hypertension were tested for an association with incident hypertension and stage 2 hypertension using Cox proportional hazards models. Race-stratified analyses were adjusted for baseline age, age2, sex, body mass index, genetic principal components, and BP. In Black participants, each standard deviation increase in SBP and DBP PRS conferred a 38% (p = 0.009) and 22% (p = 0.02) increased risk of hypertension and a 74% (p < 0.001) and 50% (p < 0.001) increased risk of stage 2 hypertension, respectively, while no association was observed with the hypertension PRSs. In Whites, each standard deviation increase in SBP, DBP, and hypertension PRS conferred a 24% (p < 0.05), 29% (p = 0.01), and 25% (p < 0.001) increased risk of hypertension, and a 27% (p = 0.08), 29% (0.01), and 42% (p < 0.001) increased risk of stage 2 hypertension, respectively. The addition of BP PRSs to the covariable-only models generally improved the C-statistics (p < 0.05). Multi-ancestry BP PRSs demonstrate the utility of genomic information in the early life prediction of hypertension.

Role of MicroRNAs and their corresponding ACE2/Apelin signaling pathways in hypertension

Hypertension is controlled via the alteration of microRNAs (miRNAs), their therapeutic targets angiotensin II type I receptor (AT1R) and cross talk of signaling pathways. The stimulation of the Ang II/AT1R pathway by deregulation of miRNAs, has also been linked to cardiac remodeling as well as the pathophysiology of high blood pressure. As miRNAs have been associated to ACE2/Apelin and Mitogen-activated protein kinases (MAPK) signaling, it has revealed an utmost protective impact over hypertension and cardiovascular system. The ACE2-coupled intermodulation between RAAS, Apelin system, MAPK signaling pathways, and miRNAs reveal the practicalities of high blood pressure. The research of miRNAs may ultimately lead to the expansion of an innovative treatment strategy for hypertension, which indicates the need to explore them further at the molecular level. Therefore, here we have focused on the mechanistic importance of miRNAs in hypertension, ACE2/Apelin signaling as well as their biological functions, with a focus on interplay and crosstalk between ACE2/Apelin signaling, miRNAs, and hypertension, and the progress in miRNA-based diagnostic techniques with the goal of facilitating the development of new hypertension-controlling therapeutics.

Hypertension genetics past, present and future applications

Essential hypertension is a complex trait where the underlying aetiology is not completely understood. Left untreated it increases the risk of severe health complications including cardiovascular and renal disease. It is almost 15 years since the first genome-wide association study for hypertension, and after a slow start there are now over 1000 blood pressure (BP) loci explaining ∼6% of the single nucleotide polymorphism-based heritability. Success in discovery of hypertension genes has provided new pathological insights and drug discovery opportunities and translated to the development of BP genetic risk scores (GRSs), facilitating population disease risk stratification. Comparing highest and lowest risk groups shows differences of 12.9 mm Hg in systolic-BP with significant differences in risk of hypertension, stroke, cardiovascular disease and myocardial infarction. GRSs are also being trialled in antihypertensive drug responses. Drug targets identified include NPR1, for which an agonist drug is currently in clinical trials. Identification of variants at the PHACTR1 locus provided insights into regulation of EDN1 in the endothelin pathway, which is aiding the development of endothelin receptor EDNRA antagonists. Drug re-purposing opportunities, including SLC5A1 and canagliflozin (a type-2 diabetes drug), are also being identified. In this review, we present key studies from the past, highlight current avenues of research and look to the future focusing on gene discovery, epigenetics, gene-environment interactions, GRSs and drug discovery. We evaluate limitations affecting BP genetics, including ancestry bias and discuss streamlining of drug target discovery and applications for treating and preventing hypertension, which will contribute to tailored precision medicine for patients.

Prevalence and risk factors of hypertension among college freshmen in China

Hypertension is the leading single contributor to all-cause death and disability worldwide. However, there is scarce evidence on the prevalence and risk factors of hypertension for Chinese youth. This study aimed to investigate the prevalence of hypertension among Chinese college freshmen and to identify the influencing factors. We conducted a cross-sectional study of all freshmen from 2015 to 2017 at a university in Wuhan, China by physical examination and standard-structured questionnaire. The Pearson chi-square test was used to compare categorical variables. Forward stepwise logistic regression method was used in the multivariate analysis to identify independent predictors of hypertension in youth. A total of 12,849 participants were included, and the prevalence of hypertension of Chinese college freshmen was 4.3% (7.9% in men and 1.6% in women). Men had a higher risk of hypertension than women (odds ratio [OR]: 5.358, 95% confidence interval [CI]: 4.345-6.607, P < 0.001). Obese people were more likely to develop hypertension than those with normal body mass index (OR: 10.465, 95% CI: 8.448-12.964, P < 0.001). People with elevated resting heart rate (RHR) had a higher prevalence of hypertension (OR: 4.987, 95% CI: 3.641-6.832, P < 0.001). Staying up late (OR: 2.957, 95% CI: 2.482-3.523, P < 0.001), physical inactivity (OR: 4.973, 95% CI: 4.141-5.972, P < 0.001), living in urban district (OR: 1.864, 95% CI: 1.493-2.329, P < 0.001) and family history of cardiovascular diseases (CVDs) (OR: 2.685, 95% CI: 2.108-3.421, P < 0.001) were related to higher prevalence of hypertension in youth. Male, obesity, elevated RHR, physical inactivity and family history of CVDs were identified as important risk factors of hypertension in youth. These risk factors should be given more attention when designing and implementing the interventional programs.

Referrals to, and characteristics of patients attending a specialist hypertension clinic

The management of hypertension is suboptimal in Ireland and internationally. The role of a specialist hypertension clinic is not always defined but an analysis of the reasons for referral are likely informative. Also, a description of the clinical characteristics of patients with hypertension will inform requirements for comprehensive hypertension management in the community and secondary care. Patients were recruited at consecutive hypertension clinics at St James Hospital, Dublin from July to September 2019. Reasons for referral, clinical characteristics of patients, their investigations and treatment were analyzed. 236 patients were included in the study. The majority of patients, 83%, were obese or overweight. A family history of hypertension was a frequent finding with 70.8% of patients reporting same. 26.7% of patients were under the age of 40. 78% of referrals were from primary care and the most referrals were to investigate secondary causes of hypertension or because the patient was ≤40 years of age. Calcium channel blockers were the treatment most frequently prescribed (51.7%). Clinic blood pressure for the cohort was 137/81 mmHg and this was replicated by their ambulatory BP. This insight into the contemporary management of hypertension highlights the frequency of obesity and a positive family history in those with hypertension. Most referrals were consistent with international guidance though deviations were evident. Findings suggest a national program for hypertension with greater focus on public health interventions and better resourcing of primary care is required.

Exploring human trainability: Design and rationale of Studies of Twin Responses to Understand Exercise as a Therapy (STRUETH) study

Background

Exercise confers myriad health benefits and physical inactivity is a modifiable risk factor for many non-communicable chronic diseases. However, individual responsiveness to guideline-based exercise programs is idiosyncratic for health and fitness outcomes. It is not known whether the response of individuals to distinct exercise modalities tend to be concordant or whether there is a genetic contribution to variation in exercise responsiveness.

Methods/design

Healthy, young adult (16-40yrs) monozygotic (MZ) and dizygotic (DZ) twin pairs were recruited and randomly assigned to 3 months of endurance or resistance exercise training. Twin pairs trained together. After 3 months of training in their randomly assigned mode, a washout period of 3 months was observed before twin pairs crossed over to complete 3 months of the alternate exercise intervention. Measures of cardiac morphology and function, cerebrovascular function, cognitive performance, peripheral artery function, biochemistry, blood pressure, body composition, skeletal muscle strength and cardiopulmonary fitness were collected before and after each exercise intervention (i.e. at weeks 0, 12, 24 and 36).

Discussion

We adopted exercise modalities that produce distinct haemodynamic and physiological stimuli for physiological adaptation and recruited MZ and DZ twin pairs to address questions such as; do individuals exhibit concordant responses to distinct exercise modalities? and what is the genetic contribution to adaptation resulting from distinct training modalities? The results of this study will provide insight into the genetic and environmental contribution to exercise response to distinct modes of training, with implications for determining the optimal approaches to exercise prescription.

A Social Determinant of Health May Modify Genetic Associations for Blood Pressure: Evidence From a SNP by Education Interaction in an African American Population

African Americans experience the highest burden of hypertension in the United States compared with other groups. Genetic contributions to this complex condition are now emerging in this as well as other populations through large-scale genome-wide association studies (GWAS) and meta-analyses. Despite these recent discovery efforts, relatively few large-scale studies of blood pressure have considered the joint influence of genetics and social determinants of health despite extensive evidence supporting their impact on hypertension. To identify these expected interactions, we accessed a subset of the Vanderbilt University Medical Center (VUMC) biorepository linked to de-identified electronic health records (EHRs) of adult African Americans genotyped using the Illumina Metabochip (n = 2,577). To examine potential interactions between education, a recognized social determinant of health, and genetic variants contributing to blood pressure, we used linear regression models to investigate two-way interactions for systolic and diastolic blood pressure (DBP). We identified a two-way interaction between rs6687976 and education affecting DBP (p = 0.052). Individuals homozygous for the minor allele and having less than a high school education had higher DBP compared with (1) individuals homozygous for the minor allele and high school education or greater and (2) individuals not homozygous for the minor allele and less than a high school education. To our knowledge, this is the first EHR -based study to suggest a gene-environment interaction for blood pressure in African Americans, supporting the hypothesis that genetic contributions to hypertension may be modulated by social factors.

Risk Factors for Ischemic Heart Disease

BACKGROUND

Several risk factors have been empirically linked to an increased risk of cardiovascular disease. Some of them are therapeutically amenable to modification; while others are not. Modifiable risk factors include physical inactivity, tobacco use, diet, "bad fats" in the blood, hypertension, and being overweight; while non-modifiable risk factors include the patient's family history, the presence versus absence of diabetes mellitus, and demographic characteristics like age, gender, ethnicity, and socio-economic status.

METHODS

In this article, we review those risk factors that are both clinically important and amenable to change.

CONCLUSION

To prevent cardiovascular disease, it is important to minimize modifiable risk factors, like LDL cholesterol.

2018 ESC/ESH Guidelines for the management of arterial hypertension: The Task Force for the management of arterial hypertension of the European Society of Cardiology and the European Society of Hypertension: The Task Force for the management of arterial hypertension of the European Society of Cardiology and the European Society of Hypertension

: Document reviewers: Guy De Backer (ESC Review Co-ordinator) (Belgium), Anthony M. Heagerty (ESH Review Co-ordinator) (UK), Stefan Agewall (Norway), Murielle Bochud (Switzerland), Claudio Borghi (Italy), Pierre Boutouyrie (France), Jana Brguljan (Slovenia), Héctor Bueno (Spain), Enrico G. Caiani (Italy), Bo Carlberg (Sweden), Neil Chapman (UK), Renata Cifkova (Czech Republic), John G. F. Cleland (UK), Jean-Philippe Collet (France), Ioan Mircea Coman (Romania), Peter W. de Leeuw (The Netherlands), Victoria Delgado (The Netherlands), Paul Dendale (Belgium), Hans-Christoph Diener (Germany), Maria Dorobantu (Romania), Robert Fagard (Belgium), Csaba Farsang (Hungary), Marc Ferrini (France), Ian M. Graham (Ireland), Guido Grassi (Italy), Hermann Haller (Germany), F. D. Richard Hobbs (UK), Bojan Jelakovic (Croatia), Catriona Jennings (UK), Hugo A. Katus (Germany), Abraham A. Kroon (The Netherlands), Christophe Leclercq (France), Dragan Lovic (Serbia), Empar Lurbe (Spain), Athanasios J. Manolis (Greece), Theresa A. McDonagh (UK), Franz Messerli (Switzerland), Maria Lorenza Muiesan (Italy), Uwe Nixdorff (Germany), Michael Hecht Olsen (Denmark), Gianfranco Parati (Italy), Joep Perk (Sweden), Massimo Francesco Piepoli (Italy), Jorge Polonia (Portugal), Piotr Ponikowski (Poland), Dimitrios J. Richter (Greece), Stefano F. Rimoldi (Switzerland), Marco Roffi (Switzerland), Naveed Sattar (UK), Petar M. Seferovic (Serbia), Iain A. Simpson (UK), Miguel Sousa-Uva (Portugal), Alice V. Stanton (Ireland), Philippe van de Borne (Belgium), Panos Vardas (Greece), Massimo Volpe (Italy), Sven Wassmann (Germany), Stephan Windecker (Switzerland), Jose Luis Zamorano (Spain).The disclosure forms of all experts involved in the development of these Guidelines are available on the ESC website www.escardio.org/guidelines.

Mild Hypothyroidism in Childhood: Who, When, and How Should Be Treated?

Mild hypothyroidism, also known as subclinical hypothyroidism (SH), is biochemically defined as serum TSH levels above the upper limit of the reference range, in the presence of normal serum concentrations of total T4 and free T4 (FT4). In the neonatal period, mild hypothyroidism can be defined by the presence of a TSH value between 6 and 20 mIU/L and normal FT4 levels. After the neonatal period, SH can be defined mild if TSH ranges between 4.5 and 10 mIU/L. The management of mild hypothyroidism in childhood is challenging. The major concern is to establish whether this condition should always be considered an expression of mild thyroid dysfunction. Indeed, the effects of untreated mild hypothyroidism are still not completely defined. In the neonatal period, concern exists about neurocognitive outcome; in children, although there is no clear evidence of alterations in growth or neurocognitive development, subtle cardiovascular abnormalities have been documented. Therefore, there is still uncertainty about the need of treatment across all ages, and the management should be based on the age of the child, the etiology, and the degree of TSH elevation, as well as on other patient factors. This review updates current evidences on diagnosis and management of mild hypothyroidism in childhood.

Hypertension

Systemic arterial hypertension is the most important modifiable risk factor for all-cause morbidity and mortality worldwide and is associated with an increased risk of cardiovascular disease (CVD). Fewer than half of those with hypertension are aware of their condition, and many others are aware but not treated or inadequately treated, although successful treatment of hypertension reduces the global burden of disease and mortality. The aetiology of hypertension involves the complex interplay of environmental and pathophysiological factors that affect multiple systems, as well as genetic predisposition. The evaluation of patients with hypertension includes accurate standardized blood pressure (BP) measurement, assessment of the patients' predicted risk of atherosclerotic CVD and evidence of target-organ damage, and detection of secondary causes of hypertension and presence of comorbidities (such as CVD and kidney disease). Lifestyle changes, including dietary modifications and increased physical activity, are effective in lowering BP and preventing hypertension and its CVD sequelae. Pharmacological therapy is very effective in lowering BP and in preventing CVD outcomes in most patients; first-line antihypertensive medications include angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, dihydropyridine calcium-channel blockers and thiazide diuretics.

Childhood-Onset Essential Hypertension and the Family Structure

The prevalence and effect of single-parent families in childhood-onset essential hypertension (EH) is unknown. Children with EH and age-, sex-, and ethnicity-matched controls were enrolled. Family structure data were obtained by in-person interview. A total of 148 families (76 hypertension probands, 72 control probands; median 14 years) were prospective-ly enrolled in the study. Single-parent status was seen in 42% of the families--with and without EH (38% vs 46%, P=.41; odds ratio, 0.7; 95% confidence interval, 0.4-1.4). After multivariable analysis, a statistically significant sociofamilial contributor to the development of childhood-onset EH was not identified. A significant number of single-parent families (42%), the majority with single mothers, were found in our pedigree study. Sociofamilial factors are known to contribute to the expression of adult-onset EH, but findings in our study suggest that they appear to contribute less in the expression of childhood-onset EH.

microRNAs in Essential Hypertension and Blood Pressure Regulation

Unravelling the complete genetic predisposition to high blood pressure (BP) has proven to be challenging. This puzzle and the fact that coding regions of the genome account for less than 2 % of the entire human DNA support the hypothesis that mechanisms besides coding genes are likely to contribute to BP regulation. Non-coding RNAs, especially microRNAs, are emerging as key players of transcription regulation in both health and disease states. They control basic functions in virtually all cell types relevant to the cardiovascular system and, thus, a direct involvement with BP regulation is highly probable. Here we review the literature about microRNAs associated with regulation of BP and hypertension, highlighting investigations, methodology and difficulties arising in the field. These molecules are being studied for exploitation in diagnostics, prognostics and therapeutics in many diseases. There have been some studies that examined biological fluid microRNAs as biomarkers for hypertension, but most remain inconclusive due to the small sample sizes and differences in methodological standardisation. Fewer studies have analysed tissue microRNA levels in vascular smooth muscle cells and the kidney. Others focused on the interaction between single nucleotide polymorphisms and microRNA binding sites. Studies in animals have shown that angiotensin II, high-salt diet and exercise change microRNA levels in hypertension. Treatment of spontaneously hypertensive rats with a miR-22 inhibitor and treatment of hypertensive Schlager BPH/2J mice with a miR-181a mimic decreased their BP. This supports the use of microRNAs as therapeutic targets in hypertension, and future studies should test the use of other microRNAs found in human association studies. In conclusion, there is a clear need of increased pace of human, animal and functional studies to help us understand the multifaceted roles of microRNAs as critical regulators of the development and physiology of BP.

Progress and future aspects in genetics of human hypertension

Hypertension has become a major global health burden due to its high prevalence and associated increase in risk of cardiovascular disease and premature death. It is well established that hypertension is determined by both genetic and environmental factors and their complex interactions. Recent large-scale meta-analyses of genome-wide association studies (GWAS) have successfully identified a total of 38 loci which achieved genome-wide significance (P < 5 × 10(-8)) for their association with blood pressure (BP). Although the heritability of BP explained by these loci is very limited, GWAS meta-analyses have elicited renewed optimism in hypertension genomics research, highlighting novel pathways influencing BP and elucidating genetic mechanisms underlying BP regulation. This review summarizes evolving progress in the rapidly moving field of hypertension genetics and highlights several promising approaches for dissecting the remaining heritability of BP. It also discusses the future translation of genetic findings to hypertension treatment and prevention.

A functional variant in the serine-threonine kinase coding gene is associated with hypertension: a case-control study in a Finnish population, the Tampere adult population cardiovascular risk study

OBJECTIVES

Hypertension raises the risk of cardiovascular consequences to two-fold or three-fold. The incidence of hypertension is increasing worldwide. Genetic causes of blood pressure are estimated to cause half of the hypertension effect, but the genes behind this are still fairly unclear. Polymorphisms in gene STK39 (serine/threonine kinase) have in some studies been associated with hypertension, but results have differed according to genetic population. We screened the STK39 polymorphism rs6749447 in a Finnish cohort to see if it was associated with hypertension.

METHODS

The study included 447 hypertensive cases and 771 controls. All participants were 50-year-old Finnish patients and the data was collected from the Tampere adult population cardiovascular risk study (TAMRISK). Genotypes were determined by polymerase chain reaction using DNAs extracted from buccal swabs.

RESULTS

The risk for hypertension among G-allele carriers was 1.4-fold compared with controls (P = 0.006, 95% CI = 1.10-1.79). The genetic effect of the G-allele was even more significant when the strong effect of BMI on hypertension was taken into account: for normal weight patients (BMI < 25) the risk was two-fold (P = 0.003, 95% CI 1.3-3.1) and for normal weight or slightly overweight patients (BMI < 30), the risk was 1.6-fold (P = 0.001, 95% CI 1.2-2.2).

CONCLUSION

In conclusion, there was a significant association between STK39 genetic variant rs6749447 and hypertension in a Finnish cohort.

Association of variants in NEDD4L with blood pressure response and adverse cardiovascular outcomes in hypertensive patients treated with thiazide diuretics

OBJECTIVE

Single-nucleotide polymorphisms (SNPs) in NEDD4L may influence the ability of the NEDD4L protein to reduce epithelial sodium channel expression. A variant in NEDD4L, rs4149601, was associated with antihypertensive response and cardiovascular outcomes during treatment with thiazide diuretics and β-blockers in a Swedish population. We sought to further evaluate associations between NEDD4L polymorphisms, blood pressure response and cardiovascular outcomes with thiazide diuretics and β-blockers.

METHODS

Four SNPs, rs4149601, rs292449, rs1008899 and rs75982813, were genotyped in 767 patients from the Pharmacogenomic Evaluation of Antihypertensive Responses (PEAR) clinical trial and association was assessed with blood pressure response to hydrochlorothiazide and atenolol. One SNP, rs4149601, was also genotyped in 1345 patients from the International Verapmil SR Trandolapril Study (INVEST), and association was examined with adverse cardiovascular outcomes relative to hydrochlorothiazide treatment.

RESULTS

Significant associations or trends were found between rs4149601, rs292449, rs75982813 and rs1008899 and decreases in blood pressure in whites on hydrochlorothiazide, and a significant association was observed with increasing copies of the GC rs4149601-rs292449 haplotype and greater blood pressure response to hydrochlorothiazide in whites (P = 0.0006 and 0.006, SBP and DBP, respectively). Significant associations were also seen with rs4149601 and an increased risk for adverse cardiovascular outcomes in whites not treated with hydrochlorothiazide [P = 0.022, odds ratio (95% confidence interval) = 10.65 (1.18-96.25)].

CONCLUSION

NEDD4L rs4149601, rs292449 and rs75982813 may be predictors for blood pressure response to hydrochlorothiazide in whites, and NEDD4L rs4149601 may be a predictor for adverse cardiovascular outcomes in whites not treated with hydrochlorothiazide.

Genetic and environmental influences on blood pressure variability: a study in twins

OBJECTIVES

Blood pressure variability (BPV) and its reduction in response to antihypertensive treatment are predictors of clinical outcomes; however, little is known about its heritability. In this study, we examined the relative influence of genetic and environmental sources of variance of BPV and the extent to which it may depend on race or sex in young twins.

METHODS

Twins were enrolled from two studies. One study included 703 white twins (308 pairs and 87 singletons) aged 18-34 years, whereas another study included 242 white twins (108 pairs and 26 singletons) and 188 black twins (79 pairs and 30 singletons) aged 12-30 years. BPV was calculated from 24-h ambulatory blood pressure recording.

RESULTS

Twin modeling showed similar results in the separate analysis in both twin studies and in the meta-analysis. Familial aggregation was identified for SBP variability (SBPV) and DBP variability (DBPV) with genetic factors and common environmental factors together accounting for 18-40% and 23-31% of the total variance of SBPV and DBPV, respectively. Unique environmental factors were the largest contributor explaining up to 82-77% of the total variance of SBPV and DBPV. No sex or race difference in BPV variance components was observed. The results remained the same after adjustment for 24-h blood pressure levels.

CONCLUSIONS

The variance in BPV is predominantly determined by unique environment in youth and young adults, although familial aggregation due to additive genetic and/or common environment influences was also identified explaining about 25% of the variance in BPV.

Associations of common variants at APLN and hypertension in Chinese subjects with and without diabetes

Background. Apelin, the endogenous ligand for the APJ receptor, has a potent hypotensive effect via a nitric oxide-dependent mechanism in vivo. The aim of the study was to investigate the association between the common variants of apelin gene (APLN) and hypertension, which was reported recently in a Chinese Han population with and without diabetes. Methods. Three single nucleotide polymorphisms (SNPs) on APLN were genotyped in 3156 diabetic patients and 3736 nondiabetic individuals. For non-diabetic subjects, 1779 were enrolled in stage 1 and 1757 were recruited for validation. A meta-analysis combining the two stages was carried out to obtain the overall effect. Results. In diabetic patients, no significant associations of the three SNPs with hypertension were observed. In contrast, we found that rs2235306 was associated with hypertension in non-diabetic males after adjusting for covariates (OR = 1.19, P = 0.039) while rs2235307 and rs3115759 displayed no evidence of association in both genders. One haplotype, C-C-A, also showed an association with hypertension (OR = 1.47, P = 0.032) only in men. However, analysis in stage 2 and meta-analysis did not support these findings. Conclusions. We conclude that common variants on APLN are not associated with the prevalence of hypertension in the Chinese.

Heritability of ambulatory and beat-to-beat office blood pressure in large multigenerational Arab pedigrees: the 'Oman Family study'

OBJECTIVE

To estimate the heritability of ambulatory blood pressure (BP), heart rate (HR), and beat-to-beat office BP and HR in an isolated, environmentally and genetically homogeneous Omani Arab population.

METHODS

Ambulatory BP measurements were recorded in 1,124 subjects with a mean age of 33.8 ± 16.2 years, using the auscultatory mode of the validated Schiller ambulatory BP Monitor. Beat-to-beat BP and HR were recorded by the Task Force Monitor. Heritability was estimated using quantitative genetic analysis. This was achieved by applying the maximum-likelihood-based variance decomposition method implemented in SOLAR software.

RESULTS

We detected statistically significant heritability estimates for office beat-to-beat, 24-hour, daytime, and sleep HR of 0.31, 0.21, 0.20, and 0.07, respectively. Heritability estimates in the above mentioned conditions for systolic BP (SBP)/diastolic BP (DBP)/mean BP (MBP)were all significant and estimated at 0.19/0.19/0.19, 0.30/0.44/0.41, 0.28/0.38/0.39, and 0.21/0.18/0.20,respectively. Heritability estimates for 24-hour and daytime ambulatory SBP, DBP, and MBP ranged from 0.28 to 0.44, and were higher than the heritability estimates for beat-to-beat recordings and sleep periods,which were estimated within a narrow range of 0.18-0.21.

CONCLUSION

In this cohort, because shared environments are common to all, the environmental influence that occurs is primarily due to the variation in non-shared environment that is unique to the individual. We demonstrated significant heritability estimates for both beat-to-beat office and ambulatory BP and HR recordings, but 24-hour and daytime ambulatory heritabilities are higher than those from beat-to-beat resting levels and ambulatory night-time recordings.

Heritability and Stability of Resting Blood Pressure

We examined the contribution of genetic and environmental influences to variation in resting systolic (SBP) and diastolic (DBP) blood pressure in participants from 4 twin studies carried out between 1986 and 2003. A total of 1577 subjects (682 males, 895 females) participated. There were 580 monozygotic twins, 664 dizygotic twins and 333 of their siblings. The 4 studies sampled subjects in different age groups (average age 17, 32, 37, 44 years), allowing for comparison of the relative contribution of genetic and environmental factors across the first part of the life span. Blood pressure was assessed under laboratory conditions in 3 studies and by ambulatory monitoring in 1 study. Univariate analyses of SBP and DBP showed significant heritability of blood pressure in all studies (SBP h2 48% to 60%, DBP h2 34% to 67%). Overall, there was little evidence for sex differences in blood pressure heritability, and no evidence for differences in heritability due to measurement strategy (laboratory vs. ambulatory). For 431 subjects there were data from 2 or more occasions that allowed us to assess the tracking of blood pressure over time and to estimate the genetic and environmental contributions to blood pressure tracking. Correlations over time across an average period of 7.1 years (tracking) were between .41 and .70. Multivariate genetic analyses showed that blood pressure tracking was entirely explained by the same genetic factors being expressed across time. It was concluded that whole genome scans for resting blood pressure can safely pool data from males and females, laboratory and ambulatory recordings, and different age cohorts.

Genome-wide association studies of hypertension: Achievements, difficulties and strategies

Estimated from family studies, the heritability of hypertension ranges from 31% to 68%. Linkage studies and candidate gene association studies were once widely used to investigate the genetic mechanisms of hypertension. However, results from these studies could only explain 1%-2% heritability. With the technological advances and subsequently the accomplishment of the Human Genome Project, genome-wide association studies (GWA studies) have been applied to find genome-wide significant signals for many common diseases. Current GWA studies of hypertension have identified dozens of hypertension or blood pressure associated variants. However, different GWA study identified different variants and the results could hardly be replicated in other studies. Therefore, a debate took place on whether GWA studies will unlock the genetic basis of hypertension and whether we shall continue throwing millions of dollars on GWA studies. This review gives a short introduction to the history of genetic study on hypertension and summarizes the current findings for GWA studies of hypertension or blood pressure. Finally, we will discuss that debate and try to find alternative strategies and technologies that may hold a greater chance to make progress in understanding the genetic risk factors of hypertension and blood pressure regulation.

The genetics of blood pressure and hypertension: the role of rare variation

The role of heredity in influencing blood pressure and risk of hypertension is well recognized. However, progress in identifying specific genetic variation that contributes to heritability is very limited. This is in spite of completion of the human genome sequence, the development of extraordinary amounts of information about genome sequence variation and the investigation of blood pressure inheritance in linkage analysis, candidate gene studies and, most recently genome-wide association studies. This paper considers the progress of this research and the obstacles that have been encountered. This work has made clear that the genetic architecture of blood pressure regulation in the population is not likely to be shaped by commonly occurring genetic variation in a discrete set of blood pressure-influencing genes. Rather heritability may be accounted for by rare variation that has its biggest impact within pedigrees rather than on the population at large. Rare variants in a wide range of genes are likely to be the focus of high blood pressure genetics for the next several years and the emerging strategies that can be applied to uncover this genetic variation and the problems that must confronted are considered.

Genetic influence on blood pressure measured in the office, under laboratory stress and during real life

To determine to what extent the genetic influences on blood pressure (BP) measured in the office, under psychologically stressful conditions in the laboratory and during real life are different from each other. Office BP, BP during a video game challenge and a social stressor interview, and 24-h ambulatory BP were measured in 238 European American and 186 African American twins. BP values across the two tasks were averaged to represent stress levels. Genetic model fitting showed no ethnic or gender differences for any of the measures. The model fitting resulted in heritability estimates of 63, 75 and 71% for office, stress and 24-h systolic BP (SBP) and 59, 67 and 69% for diastolic BP (DBP), respectively. Up to 81% of the heritability of office SBP and 71% of office DBP were attributed to genes that also influenced stress BP. However, only 45% of the heritability of 24-h SBP and 49% of 24-h DBP were attributed to genes that also influence office BP. Similarly, about 39% of the heritability of 24-h SBP and 42% of 24-h DBP were attributed to genes that also influence stress BP. Substantial overlap exists between genes that influence BP measured in the office, under laboratory stress and during real life. However, significant genetic components specific to each BP measurement also exist. These findings suggest that partly different genes or sets of genes contribute to BP regulation in different conditions.

Genome-wide association studies of hypertension: have they been fruitful?

Over the last two decades candidate gene association studies and genome-wide linkage scans have met with little success in characterizing risk variants for hypertension. Several factors could be responsible for the relative lack of success, although our understanding of the genetics has evolved to support the belief that there are multiple common risk variants, which are associated with hypertension with modest effect sizes. Genome-wide association studies (GWAS) have successfully identified risk loci for several complex polygenic disease states. Until recently, the productivity of GWAS with respect to identifying risk loci for hypertension was limited. In this paper we describe the recent success of GWAS of hypertension in identifying over a dozen loci associated with essential hypertension. We will review these findings, and place these results in the context of the future potential of pharmocogenetics of hypertension.

Genetic influences on daytime and night-time blood pressure: similarities and differences

OBJECTIVE

To examine whether the genetic influences on blood pressure (BP) during night-time are different from those during daytime and the extent to which they depend on ethnicity or sex.

METHODS

Ambulatory BP was measured in 240 European-American and 190 African-American twins (mean +/- SD age, 17.2 +/- 3.4). Individuals with night-time BP falls more than 10% of the daytime values were defined as dippers. A bivariate analysis of the daytime and the night-time BP levels, as well as a liability-threshold model of dippers vs. nondippers were used.

RESULTS

Bivariate model fitting showed no ethnic or sex differences for any of the measures, with heritabilities of 0.70 and 0.68 for SBP and 0.70 and 0.64 for DBP at daytime and at night-time. The genetic influences on daytime and night-time were not significantly different for SBP or DBP. The bivariate analysis also indicated that about 56 and 33% of the heritabilities of night-time SBP and DBP could be attributed to genes that also influenced daytime levels. The specific heritabilities due to genetic effects only influencing night-time values were 0.30 for SBP and 0.43 for DBP. The heritabilities of systolic and diastolic dipping were 0.59 and 0.81, respectively.

CONCLUSION

Independent of ethnicity and sex, an overlap exists between genes that influence daytime and night-time BP, as well as a significant genetic component that is specific to the night-time BP. These findings suggest that different genes or sets of genes contribute to BP regulation at daytime and night-time.

Heterogeneity of responses to orthostatic stress in homozygous twins

Early analysis into the role of genetics on cardiovascular regulation has been accomplished by comparing blood pressure and heart rate in homozygous twins during unstressed, resting physiological conditions. However, many variables, including cognitive and environmental factors, contribute to the regulation of cardiovascular hemodynamics. Therefore, the purpose of this study was to determine the hemodynamic response of identical twins to an orthostatic stress, ranging from supine rest to presyncope. Heart rate, arterial blood pressure, middle cerebral artery blood velocity, an index of cerebrovascular resistance, cardiac output, total peripheral resistance, and end-tidal carbon dioxide were measured in 16 healthy monozygotic twin pairs. Five minutes of supine resting baseline data were collected, followed by 5 min of 60 degrees head-up tilt. After 5 min of head-up tilt, lower body negative pressure was applied in increments of 10 mmHg every 3 min until the onset of presyncope, at which time the subject was returned to the supine position for a 5-min recovery period. The data indicate that cardiovascular regulation under orthostatic stress demonstrates a significant degree of variance between identical twins, despite similar orthostatic tolerance. As the level of stress increases, so does the difference in the cardiovascular response within a twin pair. The elevated variance with increasing stress may be due to an increase in the role of environmental factors, as the influential role of genetics nears a functional limit. Therefore, although orthostatic tolerance times were very similar between identical twins, the mechanism involved in sustaining cardiovascular function during increasing stress was different.

Genes, environment, and race: quantitative genetic approaches

Understanding the origins of racial health disparities is currently a central focus of health-oriented funding agencies and the health policy community. In particular, the role of genetics in the origin of racial health disparities is receiving growing attention and has been susceptible to considerable misinterpretation. In this article, the authors provide a basic discussion about the concept of genes and race, an introduction to quantitative genetics, and some examples of quantitative genetic analyses of health conditions in an underserved population. The intent is to outline the conceptual limitations of exclusivist views of either environmental or genetic determination and to emphasize the coaction and interaction of genes and environments in health.

Heritability of ambulatory and office blood pressure phenotypes in Swedish families

OBJECTIVE

The aim of this study was to estimate the heritability of 24-h ambulatory blood pressure and office blood pressure phenotypes in Swedish families.

METHODS

We measured ambulatory and office blood pressure in 260 siblings without antihypertensive treatment from 118 families. Blood pressure heritability was estimated using standard quantitative genetic variance component analysis implemented in the 'SOLAR' software package after adjustment for significant covariates.

RESULTS

Heritability values were significant for night-time systolic (37%), diastolic (32%) and mean (32%) ambulatory blood pressure (P < 0.05 for all). During daytime, systolic ambulatory blood pressure was significantly heritable (33%, P < 0.05). Twenty-four-hour systolic (30%) and diastolic (29%) ambulatory blood pressure also had significant values of heritability (P < 0.05). Pulse pressure ambulatory blood pressure was significantly heritable over 24 h (63%, P < 0.01), during daytime (53%, P < 0.01) and at night (34%, P < 0.05). None of the office blood pressure phenotypes had a significant heritability.

CONCLUSIONS

We conclude that ambulatory blood pressure, in particular at night, seems better than office blood pressure to capture the heritable part of blood pressure, suggesting that ambulatory blood pressure may be a more exact estimate of an individual's true blood pressure. Genetic studies using ambulatory blood pressure as the phenotype are likely to be more powerful than those using office blood pressure. The high heritability of pulse pressure ambulatory blood pressure indicates that variation in arterial stiffness in subjects free from antihypertensive medication is strongly affected by genetic factors.

Relative roles of heredity and physical activity in adolescence and adulthood on blood pressure

Part of the association between physical activity and low blood pressure (BP) may be a consequence of genetic selection. We investigated the association of genetic factors and physical activity in adolescence and adulthood with BP. BP was measured with a Finapres device in 71 monozygotic and 104 dizygotic male twin pairs using no antihypertensive medication. Subjects' mean age was 50.4 yr (range 40–72 yr). Subjects were interviewed about their lifetime exercise and other health habits. Exercise was classified as aerobic, power, or other, and these were further divided into adolescence (12–20 yr of age), the previous year, and lifetime. Genetic modeling was conducted to estimate genetic and environmental components of variance of systolic and diastolic BP. Aerobic exercise in adolescence and high-intensity aerobic exercise throughout the lifetime were associated with low diastolic BP in adulthood. Of the variance in diastolic BP, genetic factors accounted for 35% and aerobic exercise in adolescence for 5%. For systolic BP, genetic factors accounted for 39% of the variance. In turn, genetic factors accounted for 44% of the variance in aerobic exercise in adolescence. The genetic factors in part accounting for the variance in diastolic BP and those in part accounting for variance in aerobic exercise in adolescence were correlated. The association between aerobic exercise in adolescence and low diastolic BP in adulthood is a new finding, as is the observation that the factors partly share the same genes.

Influence of chorionicity on the heritability estimates of blood pressure: a study in twins

BACKGROUND

A basic assumption of the twin design is that environmental influences including prenatal experiences are equal across twin types. However, the intra-uterine environment may differ according to the chorionicity of the monozygotic twins, which may have biased previous heritability estimates of blood pressure.

OBJECTIVE

The aim of the present study was to assess whether the heritability of blood pressure, derived from measurements in monozygotic and dizygotic twins, differs according to the chorionicity of the monozygotic twins.

METHODS

Conventional and 24-h ambulatory blood pressures were measured in 125 dizygotic twin pairs and in 97 dichorionic and 128 monochorionic monozygotic twin pairs at the age of 18-34 years. The twin sample was drawn from the East Flanders Prospective Twin Survey, in which perinatal data were collected at birth. Intra-pair correlation coefficients were calculated and compared between both types of monozygotic twin pairs. Heritability was estimated from model-fitting and path analysis, based on the dizygotic twins and, respectively, all monozygotic twins and the two subtypes.

RESULTS

Intra-pair correlation coefficients for the various blood pressures, after adjustment for body mass index, ranged from 0.45 to 0.71 in the monozygotic twin pairs and did not differ significantly according to chorionicity. Heritability estimates of blood pressure were between 52 and 64%, and were similar when calculated from dizygotic twins and, respectively, dichorionic and monochorionic monozygotic twins.

CONCLUSIONS

Heritability estimates of conventional and ambulatory blood pressure do not differ significantly according to the chorionicity of the monozygotic twins.

Dissecting the genetic architecture of the cardiovascular and renal stress response

We review the evidence for a genetic basis of the cardiovascular and renal stress response. A bio-behavioral model of stress-induced hypertension is presented that explains how repeated exposure to stress in combination with genetic susceptibility might lead to the development of hypertension. In this model, we focus on three underlying physiological systems that mediate the stress response of the heart, vasculature and kidney: the sympathetic nervous system (SNS), the renin-angiotensin-aldosterone system (RAAS) and the endothelial system (ES). We then review the evidence for a genetic influence on cardiovascular reactivity to psychological stress and stress-induced sodium retention using data from twin and family studies and a limited number of candidate gene studies. Finally, by describing the underlying physiological systems of our model and their genetic underpinning we emphasize the importance of inclusion of genetic measurements in any future studies testing the reactivity hypothesis.

A comparison of ambulatory blood pressure patterns across populations

BACKGROUND

Black individuals are characterized by a blunted nocturnal decline (i.e. dipping) in blood pressure compared with whites. The resulting increase in cardiovascular load has been hypothesized to contribute to ethnic differences in hypertension and its sequelae.

OBJECTIVE

To examine data from two different locations and determine factors related to ethnic differences in ambulatory blood pressure pattern.

METHODS

Ambulatory blood pressure recordings were performed on 300 youths from Memphis, Tennessee and 195 youths from Augusta, Georgia, USA. Stepwise regressions were performed to determine the factors associated with daytime and night-time blood pressure and the nocturnal decline in blood pressure. The factors examined were recording location, ethnicity, gender, age, height, weight and genetic predisposition.

RESULTS

Significant factors in the model for the nocturnal decline in systolic blood pressure included location (R(2) = 0.031, P < 0.001), followed by ethnicity (R(2) change = 0.015, P < 0.006) and height (R(2) change = 0.009,P < 0.03). Significant factors in the model for the nocturnal decline in diastolic blood pressure included location ( R(2) = 0.176, P < 0.001), followed by ethnicity ( R(2) change = 0.016, P < 0.002) and height (R(2) change = 0.02, P < 0.001). The nocturnal decline was greater in the Augusta subjects because of higher daytime systolic (P < 0.002) and diastolic (P < 0.001) blood pressure. Weight contributed significantly to the models for resting blood pressure and daytime blood pressure. Gender was the only variable that contributed to the model for resting systolic blood pressure.

CONCLUSIONS

Both genetic and environmental factors contribute to individual differences in ambulatory blood pressure patterns. Much of the variance of ambulatory blood pressure levels and patterns remains, however, unexplained.

Sociocultural influences in genetic designs of aging: unexplored perspectives

As the aging population continues to become more diverse, there is growing interest in understanding the similar and unique aspects of aging within and across people of different ethnic groups. The impact of culture on the sources of variation identified in quantitative genetic approaches has not been well discussed in the literature. The purpose of this paper is to review previous research pertinent to the cultural aspects of quantitative genetic approaches and methodologies, and provide conceptual and statistical approaches for advancing the science. To meet this objective, results from previously published studies as well as preliminary data analyses from the Carolina African American Twin Study of Aging will be presented. There are three themes to draw from the issues discussed in this paper: (1) avoiding genetic reductionism, (2) interpreting differential heritabilities, and (3) modeling cultural influences.

Tobacco smoking as a chronic disease: notes on prevention and treatment

Tobacco use represents a rare confluence of interesting circumstances. Elements of inheritable risk combine with powerful neuropharmacology and a ubiquitous environmental exposure and result in an epidemic that claims over 430,000 lives and costs us over $100 billion annually. It is the single most important remediable public health problem in the United States. Most smokers want to quit smoking and a simple advice from a physician can increase the likelihood of doing so. Moreover, there are a number of pharmacologic and behavioral therapies that are proven to be effective in smoking cessation. Yet, there is an apparent reluctance among physicians to address smoking cessation, perhaps due to a sense of frustration or low self-efficacy. Physicians play an important role in smoking cessation, and intensive interventions are necessary to improve their participation and efficacy. Teaching practical smoking cessation techniques within medical school curricula, with an opportunity for standardized practice and self-evaluation, may be an effective strategy to improve physician practice in this area. Since most smokers try their first cigarette before the age of 18, and youth smoking is on the rise, targeted interventions aimed at preventing initiation and encouraging cessation of smoking among youth are needed. For all tobacco users, a better understanding of the pharmacology and physiology of nicotine addiction may translate into targeted and individualized treatment and prevention strategies, which may improve success rates dramatically. To better control this epidemic, and to meet the nation's public health goals for the year 2010 [145], local tobacco control interventions need to be multifaceted and well integrated into regional and national efforts [146]. Because of the physician's unique societal role with respect to tobacco, doctors may indeed find it possible to impact public opinion and significantly reduce the toll of tobacco by acting at the public health and public policy levels [147]. Those interested in engaging in the public health debate can do more than relay facts about tobacco and health. Involvement in tobacco-control issues provides the opportunity to impact the environmental influences promoting smoking among patients, and is likely to be synergistic with efforts to help smokers quit within the office. Physicians who take steps to engage in local public health initiatives are likely to magnify the effects of their efforts at the bedside [148, 149].

Repeated blood pressure measurements in a sample of Swedish twins: heritabilities and associations with polymorphisms in the renin-angiotensin-aldosterone system

BACKGROUND

Twin and family studies have shown that genetic effects explain a relatively high amount of the phenotypic variation in blood pressure. However, many studies have not been able to replicate findings of association between specific polymorphisms and diastolic and systolic blood pressure.

METHODS

In a structural equation-modelling framework the authors investigated longitudinal changes in repeated measures of blood pressures in a sample of 298 like-sexed twin pairs from the population-based Swedish Twin Registry. Also examined was the association between blood pressure and polymorphisms in the angiotensin-I converting enzyme and the angiotensin II receptor type 1 with the 'Fulker' test. Both linkage and association were tested simultaneously revealing whether the polymorphism is a Quantitative Trait Locus (QTL) or in linkage disequilibrium with the QTL.

RESULTS

Genetic influences explained up to 46% of the phenotypic variance in diastolic and 63% of the phenotypic variance in systolic blood pressure. Genetic influences were stable over time and contributed up to 78% of the phenotypic correlation in both diastolic and systolic blood pressure. Non-shared environmental effects were characterised by time specific influences and little transmission from one time point to the next. There was no significant linkage and association between the polymorphisms and blood pressure.

CONCLUSIONS

There is a considerable genetic stability in both diastolic and systolic blood pressure for a 6-year period of time in adult life. Non-shared environmental influences have a small long-term effect. Although associations with the polymorphisms could not be replicated, results should be interpreted with caution due to power considerations.