Unique Associations of DNA Methylation Regions With 24-Hour Blood Pressure Phenotypes in Black Participants.

BACKGROUND: Epigenetic marks (eg, DNA methylation) may capture the effect of gene-environment interactions. DNA methylation is involved in blood pressure (BP) regulation and hypertension development; however, no studies have evaluated its relationship with 24-hour BP phenotypes (daytime, nighttime, and 24-hour average BPs). METHODS: We examined the association of whole blood DNA methylation with 24-hour BP phenotypes and clinic BPs in a discovery cohort of 281 Blacks participants using reduced representation bisulfite sequencing. We developed a deep and region-specific methylation sequencing method, Bisulfite ULtrapLEx Targeted Sequencing and utilized it to validate our findings in a separate validation cohort (n=117). RESULTS: Analysis of 38 215 DNA methylation regions (MRs), derived from 1 549 368 CpG sites across the genome, identified up to 72 regions that were significantly associated with 24-hour BP phenotypes. No MR was significantly associated with clinic BP. Two to 3 MRs were significantly associated with various 24-hour BP phenotypes after adjustment for age, sex, and body mass index. Together, these MRs explained up to 16.5% of the variance of 24-hour average BP, while age, sex, and BMI explained up to 11.0% of the variance. Analysis of one of the MRs in an independent cohort using Bisulfite ULtrapLEx Targeted Sequencing confirmed its association with 24-hour average BP phenotype. CONCLUSIONS: We identified several MRs that explain a substantial portion of variances in 24-hour BP phenotypes, which might be excellent markers of cumulative effect of factors influencing 24-hour BP levels. The Bisulfite ULtrapLEx Targeted Sequencing workflow has potential to be suitable for clinical testing and population screenings on a large scale.

Dietary Sodium Restriction Results in Tissue-Specific Changes in DNA Methylation in Humans.

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Team Science: American Heart Association's Hypertension Strategically Focused Research Network Experience.

In 2015, the American Heart Association awarded 4-year funding for a Strategically Focused Research Network focused on hypertension composed of 4 Centers: Cincinnati Children's Hospital, Medical College of Wisconsin, University of Alabama at Birmingham, and University of Iowa. Each center proposed 3 integrated (basic, clinical, and population science) projects around a single area of focus relevant to hypertension. Along with scientific progress, the American Heart Association put a significant emphasis on training of next-generation hypertension researchers by sponsoring 3 postdoctoral fellows per center over 4 years. With the center projects being spread across the continuum of basic, clinical, and population sciences, postdoctoral fellows were expected to garner experience in various types of research methodologies. The American Heart Association also provided a number of leadership development opportunities for fellows and investigators in these centers. In addition, collaboration was highly encouraged among the centers (both within and outside the network) with the American Heart Association providing multiple opportunities for meeting and expanding associations. The area of focus for the Cincinnati Children's Hospital Center was hypertension and target organ damage in children utilizing ambulatory blood pressure measurements. The Medical College of Wisconsin Center focused on epigenetic modifications and their role in pathogenesis of hypertension using human and animal studies. The University of Alabama at Birmingham Center's areas of research were diurnal blood pressure patterns and clock genes. The University of Iowa Center evaluated copeptin as a possible early biomarker for preeclampsia and vascular endothelial function during pregnancy. In this review, challenges faced and successes achieved by the investigators of each of the centers are presented.

SARS-CoV-2 Receptor ACE2 Gene Is Associated with Hypertension and Severity of COVID 19: Interaction with Sex, Obesity, and Smoking.

BACKGROUND: Angiotensin-converting enzyme 2 (ACE2) has been identified as the entry receptor for coronaviruses into human cells, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes coronavirus disease 2019 (COVID-19). Since hypertension (HT) is a leading comorbidity in non-survivors of COVID-19, we tested for association between ACE2 gene and HT in interaction with specific pre-existing conditions known to be associated with COVID-19 severity. METHODS: Genetic analysis of ACE2 gene was conducted in French-Canadian (FC) and British populations. RESULTS: In FC individuals, the T allele of the single nucleotide polymorphism rs2074192 of ACE2 gene was a risk factor for HT in adult obese males [odds ratio (OR) = 1.39, 95% confidence interval (CI) 1.06-1.83)] and even more so in obese males who smoked (OR = 1.67, CI: 1.24-2.55), but not in lean males, non-smoker males or females. The T allele was significantly associated with severity of HT and with earlier penetrance of HT in obese smoking males. Significant interaction between the T allele and obesity was present in both sexes. The association of ACE2 (rs233575) genotype with blood pressure was also seen in adolescents but the interaction with obesity was present only in females. Several variants in ACE2 gene were found to be associated with HT in obese, smoking males in British individuals of the UK Biobank. In addition, we observed more severe outcomes to COVID-19 in association with ACE2 risk alleles in obese, smoking males. CONCLUSIONS: This is the first report that ACE2 variants are associated with earlier penetrance and more severe HT and with more severe outcomes of COVID-19 in obese smoking males.

Epigenetic Modifications in T Cells: The Role of DNA Methylation in Salt-Sensitive Hypertension.

The SS (Dahl salt sensitive) rat is an established model of hypertension and renal damage that is accompanied with immune system activation in response to a high-salt diet. Investigations into the effects of sodium-independent and dependent components of the diet were shown to affect the disease phenotype with SS/MCW (JrHsdMcwi) rats maintained on a purified diet (AIN-76A) presenting with a more severe phenotype relative to grain-fed SS/CRL (JrHsdMcwiCrl) rats. Since contributions of the immune system, environment, and diet are documented to alter this phenotype, this present study examined the epigenetic profile of T cells isolated from the periphery and the kidney from these colonies. T cells isolated from kidneys of the 2 colonies revealed that transcriptomic and functional differences may contribute to the susceptibility of hypertension and renal damage. In response to high-salt challenge, the methylome of T cells isolated from the kidney of SS/MCW exhibit a significant increase in differentially methylated regions with a preference for hypermethylation compared with the SS/CRL kidney T cells. Circulating T cells exhibited similar methylation profiles between colonies. Utilizing transcriptomic data from T cells isolated from the same animals upon which the DNA methylation analysis was performed, a predominant negative correlation was observed between gene expression and DNA methylation in all groups. Lastly, inhibition of DNA methyltransferases blunted salt-induced hypertension and renal damage in the SS/MCW rats providing a functional role for methylation. This study demonstrated the influence of epigenetic modifications to immune cell function, highlighting the need for further investigations.

Dietary Effects on Dahl Salt-Sensitive Hypertension, Renal Damage, and the T Lymphocyte Transcriptome.

The Dahl salt-sensitive (SS) rat is an established model of SS hypertension and renal damage. In addition to salt, other dietary components were shown to be important determinants of hypertension in SS rats. With previous work eliminating the involvement of genetic differences, grain-fed SS rats from Charles River Laboratories (SS/CRL; 5L2F/5L79) were less susceptible to salt-induced hypertension and renal damage compared with purified diet-fed SS rats bred at the Medical College of Wisconsin (SS/MCW; 0.4% NaCl, AIN-76A). With the known role of immunity in hypertension, the present study characterized the immune cells infiltrating SS/MCW and SS/CRL kidneys via flow cytometry and RNA sequencing in T-cells isolated from the blood and kidneys of rats maintained on their respective parental diet or on 3 weeks of high salt (4.0% NaCl, AIN-76A). SS/CRL rats were protected from salt-induced hypertension (116.5±1.2 versus 141.9±14.4 mm Hg), albuminuria (21.7±3.5 versus 162.9±22.2 mg/d), and renal immune cell infiltration compared with SS/MCW. RNA-seq revealed >50% of all annotated genes in the entire transcriptome to be significantly differentially expressed in T-cells isolated from blood versus kidney, regardless of colony or chow. Pathway analysis of significantly differentially expressed genes between low and high salt conditions demonstrated changes related to inflammation in SS/MCW renal T-cells compared with metabolism-related pathways in SS/CRL renal T-cells. These functional and transcriptomic T-cell differences between SS/MCW and SS/CRL show that dietary components in addition to salt may influence immunity and the infiltration of immune cells into the kidney, ultimately impacting susceptibility to salt-induced hypertension and renal damage.

Stability of global methylation profiles of whole blood and extracted DNA under different storage durations and conditions.

AIM: To test whether DNA samples stored for a prolonged period (20 years) under various storage conditions could be used for comparative methylation studies using reduced representation bisulfite sequencing. PATIENTS & METHODS: Five groups of human blood DNA samples (n = 5-6/group) were compared. The groupings were based on the anticoagulant used and storage temperature and duration. RESULTS: Methylation profiles of defined genomic regions in the DNA or blood samples archived for 20 years were similar across all storage temperatures, including 4°C. The level of intersample similarity in archived samples was not significantly different than that in recently collected samples. CONCLUSION: Archived samples, including DNA stored at 4°C for 20 years, are suitable for comparative studies of DNA methylation.

Role of sodium restriction and diuretic therapy for "resistant" hypertension in chronic kidney disease.

In patients with chronic kidney disease, an impaired capacity of the kidney to excrete sodium is a major contributor to hypertension. We discuss the role of sodium restriction and diuretic therapy for resistant hypertension in chronic kidney disease. Independent of increasing blood pressure, a sustained high sodium intake also may affect the progression of renal disease adversely. Consequently, dietary sodium restriction and appropriate diuretic therapy are the foundation for the treatment of resistant hypertension. Thiazide-like diuretics have decreasing effectiveness in patients with advancing renal disease; however, they may augment the effectiveness of the more potent loop diuretics. Increasing evidence suggests that spironolactone is an effective adjunct for the treatment of resistant hypertension. Inclusion of other classes of antihypertensive agents to the treatment regimen generally is necessary to counterbalance other mechanisms contributing to resistant hypertension. The effectiveness of these agents is enhanced by dietary sodium restriction and diuretic therapy.

Developing hypertension guidelines: an evolving process.

Hypertension guidelines provide up-to-date information and recommendations for hypertension management to healthcare providers, and they facilitate translation of new knowledge into clinical practice. Guidelines represent consensus statements by expert panels, and the process of guideline development has inherent vulnerabilities. Between 1977 and 2003, under the direction of the National Institutes of Health (NIH), the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure (JNC) issued 7 reports. The evolution of the JNC recommendations reflects the acquisition of observational and clinical trial data and the availability of newer antihypertensive drugs. Despite 5 years in preparation, NIH did not release a JNC 8 report and recently made the decision to withdraw from issuing guidelines. The responsibility for issuing hypertension-related guidelines was transferred to the American Heart Association (AHA) and the American College of Cardiology. Without the endorsement of the NIH or the AHA, JNC 8 committee members recently published their guideline report. Notably, there have been discrepancies of JNC recommendations over time as well as discrepancies with recommendations of other professional organizations. The Institute of Medicine recently recommended criteria for "trustworthy" guidelines. Criticisms of the guideline process, and of the guidelines themselves, should not obscure their likely contribution to improved hypertension control and to decreases of mortality rates of stroke and cardiovascular disease over the past several decades. Nevertheless, translation of guidelines into clinical practice remains a challenge.

Epigenomics of hypertension.

Multiple genes and pathways are involved in the pathogenesis of hypertension. Epigenomic studies of hypertension are beginning to emerge and hold great promise of providing novel insights into the mechanisms underlying hypertension. Epigenetic marks or mediators including DNA methylation, histone modifications, and noncoding RNA can be studied at a genome or near-genome scale using epigenomic approaches. At the single gene level, several studies have identified changes in epigenetic modifications in genes expressed in the kidney that correlate with the development of hypertension. Systematic analysis and integration of epigenetic marks at the genome-wide scale, demonstration of cellular and physiological roles of specific epigenetic modifications, and investigation of inheritance are among the major challenges and opportunities for future epigenomic and epigenetic studies of hypertension.

Treatment of hypertension in obese patients.

Obesity is a global pandemic and with its rise, its associated co-morbidities are increasing in prevalence, particularly uncontrolled hypertension. Lifestyle changes should be an anchor for the management of obesity-related hypertension; however, they are difficult to sustain. Drug therapy is often necessary to achieve blood pressure control. Diuretics, inhibitors of the renin-angiotensin system, and dihydropyridine calcium channel blockers are often used as first trio, with subsequent additions of mineralocorticoid receptor antagonists and/or dual alpha/beta blocking agents. While a number of agents are currently available, 50 % of hypertensive patients remain uncontrolled. A number of novel drug and invasive therapies are in development and hold significant potential for the effective management of obesity-related hypertension.