Sympathetic regulation of blood pressure in normotension and hypertension: when sex matters

Histone 3 modifications and blood pressure in the Beijing Truck Driver Air Pollution Study

CONTEXT

Histone modifications regulate gene expression; dysregulation has been linked with cardiovascular diseases. Associations between histone modification levels and blood pressure in humans are unclear.

OBJECTIVE

We examine the relationship between global histone concentrations and various markers of blood pressure.

MATERIALS AND METHODS

Using the Beijing Truck Driver Air Pollution Study, we investigated global peripheral white blood cell histone modifications (H3K9ac, H3K9me3, H3K27me3, and H3K36me3) associations with pre- and post-work measurements of systolic (SBP) and diastolic (DBP) blood pressure, mean arterial pressure (MAP), and pulse pressure (PP) using multivariable mixed-effect models.

RESULTS

H3K9ac was negatively associated with pre-work SBP and MAP; H3K9me3 was negatively associated with pre-work SBP, DBP, and MAP; and H3K27me3 was negatively associated with pre-work SBP. Among office workers, H3K9me3 was negatively associated with pre-work SBP, DBP, and MAP. Among truck drivers, H3K9ac and H3K27me were negatively associated with pre-work SBP, and H3K27me3 was positively associated with post-work PP.

DISCUSSION AND CONCLUSION

Epigenome-wide H3K9ac, H3K9me3, and H3K27me3 were negatively associated with multiple pre-work blood pressure measures. These associations substantially changed during the day, suggesting an influence of daily activities. Blood-based histone modification biomarkers are potential candidates for studies requiring estimations of morning/pre-work blood pressure.

A genetic variant in the catechol-O-methyl transferase (COMT) gene is related to age-dependent differences in the therapeutic effect of calcium-channel blockers

Hypertension is the leading risk factor for cardiovascular disease and one of the major health concerns worldwide. Genetic factors impact both the risk for hypertension and the therapeutic effect of antihypertensive drugs. Sex- and age-specific variances in the prevalence of hypertension are partly induced by estrogen. We investigated 6 single nucleotide polymorphisms in genes encoding enzymes involved in estrogen metabolism in relation to sex- and age-specific differences in the systolic and diastolic blood pressure (SBP and DBP) outcome under the treatment of diuretics, calcium-channel blockers (CCBs), angiotensin-converting-enzyme inhibitors, and angiotensin-receptor blockers (ARBs).We included 5064 subjects (age: 40-82) from the population-based CoLaus cohort. Participants were genotyped for the catechol-O-methyltransferase gene (COMT) variants rs4680, rs737865, and rs165599; the uridine-diphospho-glucuronosyltransferase 1A gene family (UGT1A) variants rs2070959 and rs887829; and the aromatase gene (CYP19A1) variant rs10046. Binomial and linear regression analyses were performed correcting for age, sex, body mass index, smoking, diabetes, and antihypertensive therapy to test whether the variants in focus are significantly associated with BP.All investigated COMT variants were strongly associated with the effect of diuretics, CCBs, and ARBs on SBP or DBP (P < .05), showing an additive effect when occurring in combination. After Bonferroni correction the polymorphism rs4680 (ValMet) in COMT was significantly associated with lower SBP in participants treated with CCBs (P = .009) with an especially strong impact in elderly individuals (age ≥ 70) alone (Δ = -14.08 mm Hg, P = .0005).These results underline the important role of estrogens and catecholamines in hypertension and the importance of genotype dependent, age-related adjustments of calcium-channel blocker treatment.

Sex differences in renin-angiotensin-aldosterone system affect extracellular volume in healthy subjects

Several studies reported sex differences in aldosterone. It is unknown whether these differences are associated with differences in volume regulation. Therefore we studied both aldosterone and extracellular volume in men and women on different sodium intakes. In healthy normotensive men ( n = 18) and premenopausal women ( n = 18) we investigated plasma aldosterone, blood pressure, and extracellular volume (¹²⁵I-iothalamate), during both low (target intake 50 mmol Na⁺/day) and high sodium intake (target intake 200 mmol Na⁺/day) in a crossover setup. Furthermore, we studied the adrenal response to angiotensin II infusion (0.3, 1.0, and 3.0 ng·kg^-1·min^-1 for 1 h) on both sodium intakes. Men had a significantly higher plasma aldosterone, extracellular volume, and systolic blood pressure than women during high sodium intake ( P < 0.05). During low sodium intake, extracellular volume and blood pressure were higher in men as well ( P < 0.05), whereas the difference in plasma aldosterone was no longer significant ( P = 0.252). The adrenal response to exogenous angiotensin II was significantly lower in men than in women on both sodium intakes. Constitutive sex differences in the regulation of aldosterone, characterized by a higher aldosterone and a lower adrenal response to exogenous angiotensin II infusion in men, are associated with a higher extracellular volume and blood pressure in men. These findings suggest that sex differences in the regulation of aldosterone contribute to differences in volume regulation between men and women.

Race and sex differences in ambulatory blood pressure measures among HIV+ adults

Ambulatory blood pressure monitoring (ABPM) can identify phenotypes that cannot be measured in the clinic. Determining race and sex disparities in ABPM measures among HIV+ individuals may improve strategies to diagnose and treat hypertension in this high-risk population. We compared ABPM measures between 24 African-American and 25 white HIV+ adults (36 men and 13 women). Awake systolic blood pressure (SBP) and diastolic blood pressure (DBP) were similar in African-Americans and whites. After multivariable adjustment, sleep SBP and DBP were 9.7 mm Hg (95% confidence interval [95% CI]: 4.7, 14.8) and 8.4 mm Hg (95% CI: 4.3, 12.5) higher, respectively, among African-Americans compared with whites. After multivariable adjustment, SBP and DBP dipping ratios were 5.2% (95% CI: 1.7%, 8.7%) and 6.1% (95% CI 2.0%, 10.3%) smaller among African-Americans compared with whites. After multivariable adjustment, awake and sleep SBP and DBP were higher in men compared to women. There was no difference in SBP or DBP dipping ratios comparing men and women. The prevalence of awake masked hypertension was 42% in men versus 17% in women, and the prevalence of sleep masked hypertension was 57% among African-Americans versus 18% among whites. These data suggest that ABPM measures differ by race and sex in HIV+ adults.

China Stroke Primary Prevention Trial: Visit-to-Visit Systolic Blood Pressure Variability Is an Independent Predictor of Primary Stroke in Hypertensive Patients

BACKGROUND

The optimal range of blood pressure variability remains unclear. We aimed to stratify the degree of risk of stroke based on visit-to-visit systolic blood pressure (SBP) variability in a large Chinese hypertensive population in 32 communities.

METHODS AND RESULTS

We retrospectively analyzed the data of 20 702 hypertensive patients from the China Stroke Primary Prevention Trial. The participants were randomized into 2 treatment groups to receive either enalapril or enalapril plus folic acid. Their blood pressures were measured every 3 months. The outcome was the first stroke. Three parameters of SBP variability were calculated: standard deviation, coefficient of variation, and average real variability. The records of first 4, 6, 8, 10 and 12 visits at which SBP was measured were used to calculate SBP variability and to predict subsequent stroke risk in adjusted Cox regression models. After median follow-up of 4.5 years, 597 patients had experienced stroke. Visit-to-visit SBP variability was an independent predictor of subsequent stroke (eg, the hazard ratio for the highest quintile of average real variability [22.67-61.07 mm Hg] over 6 visits was 1.55, 95% CI 1.07-2.25, P=0.021), independent of mean SBP over the follow-up period. Its value was more predictive when more blood pressure records were used.

CONCLUSIONS

Visit-to-visit SBP variability is an independent predictor of primary stroke in Chinese hypertensive patients. This predictive value depends on the number of blood pressure measurements used to calculate variability but is independent of mean SBP.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00794885.

Preoperative β-blockade and hypertension in the first hour of functional endoscopic sinus surgery

OBJECTIVES/HYPOTHESIS

Local anesthetic with epinephrine is commonly injected into the nasal mucosa during functional endoscopic sinus surgery (FESS). Systemic absorption of epinephrine following local injection may occur, resulting in a mild sympathetic response. This study seeks to determine whether an exaggerated sympathetic response to epinephrine is demonstrated in patients undergoing FESS treated preoperatively with established pharmacologic beta (β) adrenoceptor blockade.

STUDY DESIGN

A retrospective analysis of adult patients undergoing FESS at a tertiary care university hospital.

METHODS

The primary outcome was the occurrence of an exaggerated hypertensive response within the first hour of surgical time defined by a relative increase (>20%) in the first measured intraoperative systolic blood pressure (SBP) prior to induction of anesthesia, or a single SBP value above 200 mm Hg. A mixed effects logistic regression model was developed to identify independent predictors of an exaggerated hypertensive response and describe the variance in the outcome attributable to the surgeon and anesthesiologist.

RESULTS

There were 2,051 patients identified. Independent predictors of an exaggerated intraoperative hypertensive event included: preoperative β-blocker use (adjusted odds ratio [AOR]: 3.33), female gender (AOR: 1.92), body mass index (AOR: 1.03), lower baseline SBP (AOR: 0.93), and advanced age (AOR: 1.03). The C statistic for the model was 0.8881.

CONCLUSIONS

Preoperative β-blocker use is an independent predictor of an exaggerated hypertensive response within the first hour of operative time. An exaggerated hypertensive effect should be anticipated in patients presenting for FESS with established pharmacologic β-blockade, and caution should be applied to use of epinephrine-containing solutions.

LEVEL OF EVIDENCE

4. Laryngoscope, 127:1496-1505, 2017.

Sex differences in the physiology of exercise: an integrative perspective

Video slideshow introduction to the Symposium by Symposium Speaker A. William Sheel can be found here.