Impaired sodium excretion during mental stress in mild essential hypertension

The role of preterm birth in stress-induced sodium excretion in young adults

BACKGROUND

Early-life programming due to prematurity and very low birth weight (VLBW, <1500 g) is believed to contribute to development of hypertension, but the mechanisms remain unclear. Experimental data suggest that altered pressure natriuresis (increased renal perfusion pressure promoting sodium excretion) may be a contributing mechanism. We hypothesize that young adults born preterm will have a blunted pressure natriuresis response to mental stress compared with those born term.

METHODS

In this prospective cohort study of 190 individuals aged 18-23 years, 156 born preterm with VLBW and 34 controls born term with birth weight at least 2500 g, we measured urine sodium/creatinine before and after a mental stress test and continuous blood pressure before and during the stress test. Participants were stratified into groups by the trajectory at which mean arterial pressure (MAP) increased following the test. The group with the lowest MAP trajectory was the reference group. We used generalized linear models to assess poststress urine sodium/creatinine relative to the change in MAP trajectory and assessed the difference between groups by preterm birth status.

RESULTS

Participants' mean age was 19.8 years and 57% were women. Change in urine sodium/creatinine per unit increase in MAP when comparing middle trajectory group against the reference group was greater in those born preterm [β 5.4%, 95% confidence interval (95% CI) -11.4 to 5.3] than those born term (β 38.5%, 95% CI -0.04 to 92.0), interaction term P = 0.002.

CONCLUSION

We observed that, as blood pressure increased following mental stress, young adults born preterm exhibited decreased sodium excretion relative to term-born individuals.

Salty Subjects: Unpacking Racial Differences in Salt-Sensitive Hypertension

PURPOSE OF REVIEW

To review underlying mechanisms and environmental factors that may influence racial disparities in the development of salt-sensitive blood pressure.

RECENT FINDINGS

Our group and others have observed racial differences in diet and hydration, which may influence salt sensitivity. Dietary salt elicits negative alterations to the gut microbiota and immune system, which may increase hypertension risk, but little is known regarding potential racial differences in these physiological responses. Antioxidant supplementation and exercise offset vascular dysfunction following dietary salt, including in Black adults. Furthermore, recent work proposes the role of racial differences in exposure to social determinants of health, and differences in health behaviors that may influence risk of salt sensitivity. Physiological and environmental factors contribute to the mechanisms that manifest in racial differences in salt-sensitive blood pressure. Using this information, additional work is needed to develop strategies that can attenuate racial disparities in salt-sensitive blood pressure.

The influence of aircraft noise exposure on the systemic and renal haemodynamics

Aims

Epidemiological studies found a link between aircraft noise exposure and increased incidence of arterial hypertension and cardiovascular disease, but the underlying pathophysiological mechanisms are not fully understood. Clinical studies have shown that mental stress affects the systemic and renal haemodynamic, but no such study was performed with noise exposure as stress factor. We analysed systemic and renal effects of 25 min standardized aircraft noise in a sham controlled clinical study including 80 healthy men and 34 male patients with hypertension.

Methods and results

Systemic haemodynamic parameters were measured using electrocardiography and impedance cardiography. The renal haemodynamic was assessed using steady state input clearance with infusion of para-aminohippuric acid and inulin for glomerular filtration rate and renal plasma flow, respectively. In the systemic circulation of hypertensive patients, there was an increase in total peripheral resistance (TPR) (1420 ± 387 vs. 1640 ± 516 dyn·s·cm−5, P = 0.001) and a decrease in cardiac index (CI) (2.9 ± 0.8 vs. 2.6 ± 0.8 L/(min·m2, P &lt; 0.001) 25 min after the start of noise exposure, which was not present during sham procedure (P = 0.10, P = 0.86). In healthy individuals a procedure induced increase in TPR and decrease in CI was present after noise (TPR: 995 ± 239 vs. 1106 ± 308 dyn·s·cm−5, P = 0.001, CI: 3.6 ± 0.7 vs. 3.3 ± 0.9 L/(min·m2, P &lt; 0.001) and sham application (TPR: P = 0.002, CI: P &lt; 0.001). However, in healthy individuals changes in TPR (P = 0.450) and CI (P = 0.605) from baseline until 25 min after the start of the intervention did not differ between noise and sham exposure. In the renal circulation of hypertensive patients and healthy individuals the response did not differ between noise and sham procedure.

Conclusions

In hypertensive but not healthy men we observed a systemic vasoconstrictive response after aircraft noise exposure accompanied by a decrease in CI. No significant changes were observed in the renal circulation. Our results suggest that male hypertensive patients are more susceptible for noise-induced changes of vascular resistance in the systemic circulation.

The stress, salt excretion, and nighttime blood pressure (SABRE) study: Rationale and study design

Background

Abnormal diurnal patterns of blood pressure (BP) on ambulatory BP monitoring (ABPM), defined by reduced BP dipping or elevated nighttime BP, are associated with increased risk for adverse cardiovascular events. Psychological stress is associated with abnormal diurnal patterns of BP. Exposure to an acute stressor (e.g., mental stress task) normally increases urinary sodium excretion. However, some individuals have sodium retention after stress provocation, revealing substantial between-person variability in the degree of stress-induced sodium excretion. Prior research suggests urinary sodium excretion that does not occur during the daytime may shift toward the nighttime, accompanied by an increase in nighttime BP. Associations between psychological stress and the diurnal patterns of sodium excretion and BP are not yet fully understood.

Design

The study is conducted in both the laboratory and naturalistic environment with a multi-racial/ethnic sample of 211 healthy adults. In the laboratory, change in urinary sodium excretion in response to mental stress tasks is examined with pre-/post-stress assessments of sodium excretion. Changes in angiotensin-II, catecholamines, BP, heart rate, endothelin-1, and cortisol are also assessed. In the 24-hour naturalistic environment, the diurnal patterns of sodium excretion and systolic BP are assessed as daytime-to-nighttime ratio of sodium excretion and ABPM, respectively. Ecological momentary assessments of perceived stress are also collected.

Summary

The SABRE study investigates previously unexplored associations between stress-induced urinary excretion in the laboratory, diurnal patterns of sodium excretion and BP in the naturalistic environment, and ecological stress. It has high potential to advance our understanding of the role of psychological stress in hypertension.

Hypertension and childhood migration: a nationwide study of 2.7 million adolescents

OBJECTIVES

Immigration studies can shed light on hypertension development and reveal high-risk populations. To this end, we investigated the association between age at immigration and hypertension occurrence at adolescence among immigrants to Israel.

METHODS

We analyzed cross-sectional data on 2 681 294 adolescents assessed for mandatory military service at approximately 17 years of age between 1967 and 2016. The study population constituted of 410 488 immigrants with origins in Ethiopia, Middle East and North Africa, Former USSR and Western Countries. Age at immigration was categorized into 0-5, 6-11 and 12-19 years. Odds ratios (ORs) for hypertension were calculated according to age at immigration with Israel-born participants as controls. Models were made to account for possible confounders. Additionally, the study population was stratified by country of origin and each immigrant group referenced to Israel-born participants of the same origin.

RESULTS

In the fully-adjusted model, immigrants arriving until age 11 years had comparable ORs for hypertension to the Israeli-born reference group, whereas recent immigrants, arriving at age 12-19 years had a marked lower OR of 0.30 (95% CI 0.27-0.33; P < 0.001). The lower hypertension odds among recent immigrants persisted in all models and when the study sample was stratified by sex and origin, with all but those of Western origin showing a graded decrease with increasing age at migration categories.

CONCLUSION

Immigrants arriving earlier in childhood lose their protection against hypertension at adolescence relative to the Israeli-born, likely because of lifestyle acculturation. Prevention programs are needed, beginning upon arrival and placing emphasis on nutritional and physical activity habits.

Angiotensin II and the Natriuretic and Blood Pressure Response to Mental Stress in African Americans

Objective

To test the hypothesis that Angiotensin II (Ang II) is a contributing factor to the response pattern in African Americans (AAs) who retain rather than excrete sodium during mental stress.

Design/Study Participants

Double-blind, randomized, cross-over trial of 87 healthy AAs aged 18 to 50 years.

Interventions

The study participants received either a placebo or irbesartan, (150 mg PO), an Ang II receptor antagonist, for seven days prior to stress testing. Urinary sodium excretion (UNaV) and systolic blood pressure (SBP) were collected prior to and throughout a mental stress protocol (rest and stress period).

Setting

A southeastern university.

Main Outcome Measures

Ang II, SBP, and sodium retention.

Results

During the placebo condition, 62 participants showed the expected increase in UNaV (excreters) while 25 participants reduced UNaV during stress (retainers). Irbesartan retainers demonstrated a reversal in the direction of their natriuretic response, now increasing UNaV in response to stress (∆ UNaV of -.094 mmol/min with placebo vs .052 mmol/min on irbesartan; P<.001). In excreters, irbesartan reduced SBP levels during both rest (-2.36 mm Hg; P=.03) and stress (-4.59;P<.0001), and an even more pronounced reduction in SBP was demonstrated by retainers on treatment during both rest (-4.29 mm Hg; P=.03) and stress (-6.12; P<.001).

Conclusions

Ang II contributes to sodium retention in retainers. Furthermore, our findings indicate that suppression of Ang II has a beneficial effect on SBP during rest and stress in this population.

How far cardio metabolic and psychological factors affect salt sensitivity in normotensive adult population?

AIM

To evaluate the prevalence of salt sensitivity and the impact of cardiometabolic and psychological characteristics on salt sensitivity in normotensive population.

METHODS

Of all participants, anthropometric measurements and fasting venous blood samples were collected, and study questionnaires were completed. Salt Sensitivity was defined based on the difference in mean arterial pressure with infusion of 2 L of normal saline followed by a low sodium diet and administration of three doses of oral furosemide the day after.

RESULTS

Of 131 participants, 56 (42.7%) were diagnosed with salt sensitivity. Crude and age and sex adjusted regression analysis showed that low-density lipoprotein cholesterol and depression were positively associated with salt sensitivity (OR = 1.02, 95%CI: 1.01-1.04 and OR = 1.15, 95%CI: 1.00-1.34, respectively).

CONCLUSION

The high prevalence of salt sensitivity and its significant relation with prevalent risk factors necessitates considering its reduction actions at the population level and the need for further research.

Stress and salt sensitivity in primary hypertension

As the development of hypertension and target organ damage becomes more prevalent, it becomes exceedingly important to determine the underlying mechanisms through which this detrimental development occurs. Specifically, our studies and others have explored mechanisms through which stress elicits a salt-sensitive response in approximately 20-30 % of the population, resulting in the early development of hypertension and target organ damage. Data associated with this stress-induced cardiovascular response pattern have recently demonstrated additional effects across the body systems including factors contributing to the development of osteoporosis, obesity, autoimmune disease, and chronic inflammation. As each of these diseases become more prevalent in conjunction with hypertension, further research may discover stress and salt sensitivity to be at the "heart" of the matter for the development of many of today's most deadly conditions.

Interaction of stress and dietary NaCl intake in hypertension: renal neural mechanisms

A synthesizing concept of the development of primary hypertension is that it arises from an interaction of genetic and environmental factors. Of the environmental factors, dietary NaCl intake and mental stress are among the most thoroughly investigated. This review will focus on the interaction between genetic predisposition and the environmental influences of dietary NaCl intake and mental stress in the development of primary hypertension.

Reactive oxygen species and the central nervous system in salt-sensitive hypertension: possible relationship with obesity-induced hypertension

1. There are multiple and complex mechanisms of salt-induced hypertension; however, central sympathoexcitation plays an important role. In addition, the production of reactive oxygen species (ROS) is increased in salt-sensitive hypertensive humans and animals. Thus, we hypothesized that brain ROS overproduction may increase blood pressure (BP) by central sympathostimulation. 2. Recently, we demonstrated that ROS levels were elevated in the hypothalamus of salt-sensitive hypertensive animals. Moreover, intracerebroventricular anti-oxidants suppressed BP and renal sympathetic nerve activity more in salt-sensitive than non-salt-sensitive hypertensive rats. Thus, brain ROS overproduction increased BP through central sympathoexcitation in salt-sensitive hypertension. 3. Salt sensitivity of BP is enhanced in obesity and metabolic syndrome. Interestingly, it is also suggested that, in obesity-induced hypertension models, increases in BP are caused by brain ROS-induced central sympathoexcitation. 4. Recent studies suggest that increased ROS production in the brain and central sympathoexcitation may share a common pathway that increases BP in both salt- and obesity-induced hypertension.

Stress-induced sodium retention and hypertension: a review and hypothesis

Hypertension--an important health problem in industrialized nations--is particularly significant in blacks and obese individuals, in whom it is hypothesized to result from impaired renal sodium regulation. We reviewed studies that identified individuals with impaired sodium regulation by examining the natriuretic response to mental stress. A significant percentage of black and obese individuals retain or have a diminished natriuretic response to mental stress despite increased blood pressure (BP). This contributes a volume component to the normal resistance-mediated BP increase, and BP remains elevated after the stressor ceases until the volume expansion diminishes. The stress exposes these individuals to greater cardiovascular load. This response pattern has been linked to renin-angiotensin-aldosterone system activity, and is associated with premature target-organ damage. Assessing stress-induced sodium retention provides a method to identify patients with impaired sodium regulation without using a dietary protocol that poses adherence difficulties, or complicated laboratory assessments. Furthermore, research using this technique indicates the effectiveness of renin-angiotensin-aldosterone system blockers in correcting impaired sodium regulation and consequent hypertension in these individuals.

[Cardiovascular impact of psychological stress]

The cardiovascular impact of stress depends on, first individual perception of stress and second individual cardiovascular reactivity to a stressful stimulation. Psychological stressors are filtered by cognitive appraisal mechanisms before causing biological response so that, for the same strain, individual effects may differ. Therefore, due to complexity of stress personal management, a multilevel stress measurement strategy is needed. To measure stress cardiovascular impact, stress should be precisely quantified. Recently, questionnaires have been developed to score not only the strain but also the personal perception of the strain. Individual stress reactivity can be evaluated by hormone response (epinephrine, norepinephrine, steroids) or by cardiovascular reactivity to a stress test. Until now, all the studies found that stress was independently related to blood pressure especially in active people. Prospective studies are still ongoing to definitively prove that stress could explain hypertension in a subset of hypertensives.

Stress-induced renal alterations in normotensives offspring of hypertensives and in hypertensives

BACKGROUND

Scarce information is available on stress-induced renal behavior in humans, especially in normotensives offspring of hypertensives (HP) and in hypertensives (HT).

METHODS

Ten HP and 10 HT were compared to 10 normotensives with normotensive parents (NP). Systolic blood pressure (SBP) and renal functional parameters were determined during rest and stress periods.

RESULTS

The stress SBP reactivity was significantly (P < .05) higher in HP than in NP and HT. At rest, HP were characterized by a significantly (P < .05) higher glomerular filtration rate. Stress significantly reduced glomerular filtration rate (-14 +/- 4 mL/min/1.73 m2, P < .05) only in HT. Renal plasma flow significantly (P < .05) decreased during stress in NP (-35 +/- 16 mL/min/1.73 m2) and in HT (-49 +/- 25 mL/min/1.73 m2), whereas it did not change in HP. The resulting filtration fraction increased significantly during stress only in NP (1.5% +/- 0.6%, P < .05). Despite the increase in BP, stress induced a similar decrease in sodium excretion rate in NP (-52 +/- 26 micromol/min) and in HT (-56 +/- 24 micromol/min). The stress-induced sodium reabsorption occurred only in the proximal part of the tubules (lithium clearance). In HP, stress did not alter either sodium excretion rate or plasma renin activity.

CONCLUSIONS

The stress-induced renal modifications are characterized by an efferent vasoconstriction and a paradoxical increase in sodium reabsorption that occurred in the proximal part of the tubules in NP. In HP, genetically at risk of hypertension, basal renal alterations may explain a different stress-induced renal behavior. In HT, stress-induced increase in sodium reabsorption may be involved in the sustained BP level.