Volume (weight) loss and blood pressure response following thiazide diuretics

Mechanisms of Antihypertensive Effect of Chlorthalidone in Advanced Chronic Kidney Disease: A Causal Mediation Analysis

Key Points

Chlorthalidone reduces the amount of fluid and the BP, but fluid volume reduction is not the cause of lowering of BP. It is not volume loss but the response to volume loss such as the synthesis of substances that lower BP is important.

Background

Chlorthalidone (CTD) in a chronic kidney disease randomized trial demonstrated a robust reduction in systolic BP in stage 4 CKD. In this study, we explore the mechanisms underlying the antihypertensive effect of CTD.

Methods

In this prespecified analysis, we analyzed the contributions of baseline levels of 24-hour urinary sodium and aldosterone and the changes from baseline to 4 weeks in the multiple mediators reflecting volume status in a causal mediation analysis framework. Baseline levels of these mediators served as covariates. No power calculation for this analysis was performed.

Results

Of the 160 patients randomized, 140 (87.5%) were included in this analysis. Compared with placebo, CTD within 4 weeks reduced weight −1.5% (95% confidence interval [CI], −2.2 to −0.7) and volume −1.4% (95% CI, −2.2 to −0.6), stimulated plasma renin 40.5% (95% CI, 25.4% to 57.4%) and serum aldosterone 40.2% (95% CI, 11.7% to 76%), and reduced plasma N -terminal pro-B-type natriuretic peptide levels −19.4% (95% CI, −33.8% to −1.9%). Mediation analysis revealed the following results: for weight change, the total effect on systolic BP was −10.8 mm Hg (95% CI, −16 to −5.7), of which weight change (indirect effect) accounted for −0.9 mm Hg (95% CI, −4.2 to 2.5) and BP change independent of weight (direct effect) accounted for −10 mm Hg (−15.7 to −4.2). Thus, the percent mediation was 8.1% (95% CI, −22.4 to 38.5). Baseline excretion of 24-hour sodium or aldosterone or any of the changes in the above mediators examined accounted for <2 mm Hg BP drop and were not significant for any of the mediators.

Conclusions

CTD improved BP control among patients with advanced CKD independent of baseline urinary sodium, aldosterone, weight loss, or changes in the renin-angiotensin system or N -terminal pro-B-type natriuretic peptide.

Clinical Trial registry name and registration number:

CTD in chronic kidney disease ClinicalTrials.gov number: NCT02841280 .

Predictors of weight reduction effectiveness of SGLT2 inhibitors in diabetes mellitus type 2 patients

Background

Sodium-glucose cotransporter-2 inhibitors (SGLT2i) are a novel medication for treating type 2 diabetes (T2DM), which have the pleiotropic effect of weight reduction. This study aimed to evaluate clinical and biochemical predictors of effective weight reduction in T2DM patients who use various types of SGLT2i.

Materials and methods

A retrospective study was conducted with 289 adults diagnosed with T2DM who were first prescribed SGLT2i either as monotherapy or add-on therapy. The primary outcome was the identification of clinical and biochemical factors that can potentially induce meaningful weight reduction (>3% in 1 year) in T2DM patients while using SGLT2 inhibitors. The relationship between predictors and significant weight loss was assessed using logistic regression analysis, including adjustment for confounding factors. Results are presented as odds ratios (ORs) with a 95% confidence interval (CI).

Results

Among the 289 patients, 45.6% had significant weight loss following SGLT2i use. The significant clinical predictors were age >70 years old (OR 3.26, 95% CI 1.39-7.6, p=0.006), body mass index >25 kg/m2 (OR 1.02, 95% CI 1.01-1.05, p=0.049), and the use of sulfonylureas (OR 2.41, 95% CI 1.15-5.09, p=0.020). Additionally, the use of HCTZ showed significantly decreased odds of weight loss (OR 0.35, 95% CI 0.13-0.96, p=0.043).

Conclusion

This research highlights multiple clinical factors that potentially can predict meaningful weight loss in patients with T2DM who are treated with SGLT2i. These findings could facilitate the identification of patients who might benefit from the weight loss effects of SGLT2i.

Screening and elucidation of fragmentations of 23 diuretics in dietary supplements using UHPLC-Q-Orbitrap

Diuretics are used to treat the edematous state in cases of renal insufficiency, nephrotic syndrome, liver cirrhosis, and heart failure. These compounds are used by athletes to lose weight and are included in the list of prohibited substances by the World Anti-Doping Agency. They are also used by obese and overweight people for losing weight, and there are a number of recent reports on the contamination of dietary supplements with diuretics. Due to the alluring online marketing and blogging, there is an extensive misuse of products that are illegally adulterated with diuretics, which has seriously increased health risks. Therefore, it is essential to develop an analytical method for the detection of adulterants in such substances. In this study, 23 diuretics, categorized into four groups, namely, thiazide diuretics (e.g., bendroflumethiazide), loop diuretics (e.g., bumetanide), potassium-sparing diuretics (e.g., amiloride), and carbonic anhydrase inhibitors (e.g., acetazolamide), were analyzed using ultrahigh-performance liquid chromatography-quadrupole orbitrap (UHPLC-Q-Orbitrap). Their fragmentation was elucidated based on the MS/MS data. The 124 products were screened by the UHPLC-Q-Orbitrap (LC-HRMS) method, and the confirmed compounds were quantitated by a previously established LC-MS/MS method. Approximately 5% of the samples were found to be illegally contaminated with diuretics at a concentration of 0.051-162 mg/g. The high selectivity and sensitivity of the UHPLC-Q-Orbitrap (LC-HRMS) method, in combination with the established fragmentation, offer a new approach for the rapid and accurate screening of diuretics in adulterated products, which would be ultimately beneficial for the public health.

Effect of diuretics on plasma renin activity in primary hypertension: A systematic review and meta-analysis

AIMS

Plasma renin activity (PRA) is regarded as a marker of sodium and fluid homeostasis in patients with primary hypertension. Whether effects of diuretics on PRA differ according to class of diuretic, whether diuretics lead to a sustained increase in PRA, and whether changes in PRA relate to those in blood pressure (BP) is unknown. We performed a systematic review and meta-analysis of trials investigating the antihypertensive effects of diuretic therapy in which PRA and/or other biomarkers of fluid homeostasis were measured before and after treatment.

METHODS

Three databases were searched: MEDLINE, EMBASE and The Cochrane Central Register of Controlled Trials. Titles were firstly screened by title and abstract for relevancy before full-text articles were assessed for eligibility according to a predefined inclusion/exclusion criteria.

RESULTS

A total of 1684 articles were retrieved of which 61 met the prespecified inclusion/exclusion criteria. PRA was measured in 30/61 studies. Diuretics led to a sustained increase in PRA which was similar for different classes of diuretic (standardised mean difference [95% confidence interval] 0.481 [0.362, 0.601], 0.729 [0.181, 1.28], 0.541 [0.253, 0.830] and 0.548 [0.159, 0.937] for thiazide, loop, mineralocorticoid receptor antagonists/potassium-sparing and combination diuretics respectively, Q = 0.897, P = .826), and did not relate to the average decrease in blood pressure.

CONCLUSION

In antihypertensive drug trials, diuretics lead to a sustained increase in average PRA, which is similar across different classes of diuretic and unrelated to the average reduction in blood pressure.

Contribution of systemic blood flow to untreated or inadequately controlled systolic--diastolic or isolated systolic hypertension in a community sample of African ancestry

AIMS

Age-related increases in systemic blood flow [stroke volume (SV), cardiac output (CO), and aortic flow (Q)] contribute substantially to untreated or inadequately controlled (uncontrolled) blood pressure (BP) in Africa. We aimed to identify the haemodynamic determinants of uncontrolled systolic--diastolic (Syst--diast HT) versus uncontrolled isolated systolic (ISH) or diastolic (IDH) hypertension.

METHODS

Using central arterial pressure and aortic outflow tract velocity and diameter measurements (echocardiography), the haemodynamic correlates of BP were determined in 725 community participants of African ancestry (19.6% uncontrolled Syst--diast HT, 9.2% uncontrolled ISH, 11.3% uncontrolled IDH).

RESULTS

Independent of confounders, compared with those with a normotensive BP, those with uncontrolled Syst--diast HT had increases in SV, CO, Q, systemic vascular resistance (SVR) and aortic characteristic impedance (Zc) and decreases in total arterial compliance (TAC) (P < 0.05--P < 0.0001). In multivariate regression models, uncontrolled Syst--diast HT was as strongly associated with Q, SV or CO as with SVR (P = 0.04--P = 0.20), Zc (P = 0.74--P < 0.0005) and TAC (P = 0.43--P < 0.005). Independent of confounders, compared with normotensive individuals those with uncontrolled ISH had increases in SV, CO, Q and Zc but not SVR, and decreases in TAC (P < 0.05-P < 0.0001), and those with IDH only had increases in SVR (P < 0.0001). Uncontrolled ISH was more strongly associated with Q, SV and CO than with SVR (P < 0.0005), but less than with TAC (P < 0.05--P < 0.0005).

CONCLUSION

In groups of African ancestry living in Africa, hypertension because of increases in either SBP or DBP is as strongly associated with increases in systemic flow (SV, Q) as with arterial and arteriolar effects (Zc, TAC, SVR).

Distinct Contribution of Systemic Blood Flow to Hypertension in an African Population Across the Adult Lifespan

Although hypertension in groups of African ancestry is volume-dependent, the relative impact of systemic flow (stroke volume, peak aortic flow [Q]) versus vascular mechanisms (systemic vascular resistance, aortic characteristic impedance [Zc], total arterial compliance) components of arterial load has not been evaluated across the adult age range. In participants of African ancestry (n=824, age=16–99 years, 68.3% female), using central arterial pressure and aortic velocity and diameter measurements in the outflow tract, we determined the hemodynamic correlates of age-related increases in blood pressure. Strong independent positive relations between age and stroke volume or peak aortic Q were noted ( P <0.0001), effects associated with ventricular end diastolic volume and aldosterone-to-renin ratios. Age-related increases in mean arterial pressure were associated with stroke volume and not systemic vascular resistance. Although age-Q relations began from early adulthood, initially an inverse association between age and aortic Zc ( P <0.0001) driven by increments in aortic root diameter ( P <0.0001) prevented an enhanced systolic blood pressure and pulse pressure. When Zc began to positively relate to age ( P <0.0001), age-Q relations translated into increases in forward wave pressures and hence systolic blood pressure and pulse pressure. Age relations with pulse pressure were as strongly determined by Q as by Zc or total arterial compliance (0.027±0.001 versus 0.028±0.001 and 0.032±0.003 mm Hg per yearly increase in pulse pressure produced by Q, Zc, and total arterial compliance; P <0.0001). Uncontrolled hypertension (confirmed with 24-hour blood pressure) was determined more by Q, Zc, and total arterial compliance than by increases in systemic vascular resistance ( P <0.0005 for comparison). In conclusion, relationships between age and systemic blood flow contribute markedly to hypertension in groups of African origins.

The Risks of Cardiovascular Disease and Mortality Following Weight Change in Adults with Diabetes: Results from ADVANCE

CONTEXT

Weight loss is strongly recommended for overweight and obese adults with type 2 diabetes. Unintentional weight loss is associated with increased risk of all-cause mortality, but few studies have examined its association with cardiovascular outcomes in patients with diabetes.

OBJECTIVE

To evaluate 2-year weight change and subsequent risk of cardiovascular events and mortality in established type 2 diabetes.

DESIGN AND SETTING

The Action in Diabetes and Vascular Disease: Preterax and Diamicron-MR Controlled Evaluation was an international, multisite 2×2 factorial trial of intensive glucose control and blood pressure control. We examined 5 categories of 2-year weight change: >10% loss, 4% to 10% loss, stable (±<4%), 4% to 10% gain, and >10% gain. We used Cox regression with follow-up time starting at 2 years, adjusting for intervention arm, demographics, cardiovascular risk factors, and diabetes medication use from the 2-year visit.

RESULTS

Among 10 081 participants with valid weight measurements, average age was 66 years. By the 2-year examination, 4.3% had >10% weight loss, 18.4% had 4% to 10% weight loss, and 5.3% had >10% weight gain. Over the following 3 years of the trial, >10% weight loss was strongly associated with major macrovascular events (hazard ratio [HR], 1.75; 95% confidence interval [CI], 1.26-2.44), cardiovascular mortality (HR, 2.76; 95% CI, 1.87-4.09), all-cause mortality (HR, 2.79; 95% CI, 2.10-3.71), but not major microvascular events (HR, 0.91; 95% CI, 0.61-1.36), compared with stable weight. There was no evidence of effect modification by baseline body mass index, age, or type of diabetes medication.

CONCLUSIONS

In the absence of substantial lifestyle changes, weight loss may be a warning sign of poor health meriting further workup in patients with type 2 diabetes.

Mechanism of Thiazide Diuretic Arterial Pressure Reduction: The Search Continues

Thiazide diuretic (TZD)-mediated chronic reduction of arterial pressure is thought to occur through decreased total peripheral vascular resistance. Further, the decreased peripheral vascular resistance is accomplished through TZD activation of an extrarenal target, resulting in inhibition of vascular constriction. However, despite greater than five decades of investigation, little progress has been made into the identification of the TZD extrarenal target. Proposed mechanisms range from direct inhibition of constrictor and activation of relaxant signaling pathways in the vascular smooth muscle to indirect inhibition through decreased neurogenic and hormonal regulatory pathways. Surprisingly, particularly in view of this lack of progress, comprehensive reviews of the subject are absent. Moreover, even though it is well recognized that 1) several types of hypertension are insensitive to TZD reduction of arterial pressure and, further, TZD fail to reduce arterial pressure in normotensive subjects and animals, and 2) different mechanisms underlie acute and chronic TZD, findings derived from these models and parameters remain largely undifferentiated. This review 1) comprehensively describes findings associated with TZD reduction of arterial pressure; 2) differentiates between observations in TZD-sensitive and TZD-insensitive hypertension, normotensive subjects/animals, and acute and chronic effects of TZD; 3) critically evaluates proposed TZD extrarenal targets; 4) proposes guiding parameters for relevant investigations into extrarenal TZD target identification; and 5) proposes a working model for TZD chronic reduction of arterial pressure through vascular dilation.

The Association between Antihypertensive Medication Use and Blood Pressure Is Influenced by Obesity

Introduction

One in three US adults is living with obesity or hypertension, and more than 75% of hypertensive individuals are using antihypertensive medications. Therefore, it is important to examine blood pressure (BP) differences in populations that are using these medications with differing obesity status.

Aim

We examined whether BP attained when using various antihypertensive medications varies amongst different body mass index (BMI) categories and whether antihypertensive medication use is associated with differences in other metabolic risk factors, independent of BMI.

Methods

Adults with hypertension from the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2014 were used (n=15,285). Linear regression analyses were used to examine the main effects and interaction between antihypertensive use and BMI.

Results

In general, users of antihypertensive medications had lower BP than those not taking BP medications (NoBPMed) (P < 0.05), whereby in women, the differences in systolic BP between angiotensin-converting-enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) users and NoBPMed were greater in those with obesity (ACE inhibitors: -14 ± 1 mmHg; ARB: -16 ± 1 mmHg) compared to normal weight individuals (ACE inhibitors: -9 ± 1 mmHg; ARB: -11 ± 1 mmHg) (P < 0.05). Diastolic BP differences between women ARB users and NoBPMed were also greatest in obesity (-5 ± 1 mmHg) (P < 0.05) whilst there were no differences in normal weight individuals (-1 ± 1 mmHg) (P>0.05). Furthermore, glucose levels and waist circumference in women were higher in those using ACE inhibitors compared to diuretics (P < 0.05).

Conclusion

ACE inhibitors and ARBs may be associated with more beneficial BP profiles in women with obesity, with no obesity-related BP differences for antihypertensive medication in men. However, there could be potential cardiometabolic effects for some antihypertensive medications that should be explored further.

Human genome evolution and development of cardiovascular risk factors through natural selection

Impressive advances in molecular genetic techniques allow to analyze the effects of natural selection on the development of human genome. For example, the trend towards blonde hair and blue eyes was documented. The approach to analyze possible effects of natural selection on the evolution of recent phenotypes with high risk of cardiovascular disease has not been described yet. A possible effect on the evolution of two main risk factors - hypercholesterolemia and hypertension - is presented. The close relationship of non-HDL cholesterol blood concentration to the proportion of pro-inflammatory macrophages in human visceral adipose tissue might be a result of long-lasting natural selection. Individuals with higher proportion of this phenotype might also display a higher ability to fight infection, which was very common in human setting from prehistory until Middle Ages. Successful battle against infections increased the probability to survive till reproductive age. Similar hypothesis was proposed to explain frequent hypertension in African Americans. A long-lasting selection for higher ability to conserve sodium during long-term adaptation to low sodium intake and hot weather was followed by a short-term (but very hard) natural selection of individuals during transatlantic slave transport. Only those with very high capability to retain sodium were able to survive. Natural selection of phenotypes with high plasma cholesterol concentration and/or high blood pressure is recently potentiated by high-fat high-sodium diet and overnutrition. This hypothesis is also supported by the advantage of familial hypercholesterolemia in the 19th century (at the time of high infection disease mortality) in contrast to the disadvantage of familial hypercholesterolemia during the actual period of high cardiovascular disease mortality.

The concept of crosstalk-directed embryological target mining and its application to essential hypertension treatment failures

This review aims to introduce the novel concept of embryological target mining applied to interorgan crosstalk network genesis, and applies embryological target mining to multidrug-resistant essential hypertension (a prototype, complex, undertreated, multiorgan systemic syndrome) to uncover new treatment targets and critique why existing strategies fail. Briefly, interorgan crosstalk pathways represent the next frontier for target mining in molecular medicine. This is because stereotyped stepwise organogenesis presents a unique opportunity to infer interorgan crosstalk pathways that may be crucial to discovering novel treatment targets. Insights gained from this review will be applied to patient management in a clinician-directed fashion.

Changes in selected metabolic parameters in patients over 65 receiving hydrochlorothiazide plus amiloride, atenolol or placebo in the MRC elderly trial

Background

Treatment of hypertension reduces incidence of stroke, myocardial infarction and heart failure perhaps partly by controlling different metabolic parameters. There is limited information regarding the changes in potassium, sodium, weight, cholesterol and glucose levels in patients using anti-hypertensives. This study aimed to determine changes in potassium, sodium, glucose, cholesterol, weight, urea and urate levels in patients using anti-hypertensives. Furthermore, to describe these changes and differences between the atenolol, hydrochlorothiazide plus amiloride and placebo arms of the Medical Research Council (MRC) elderly randomised controlled trial.

Methods

Patients were randomly allocated to one of the three treatment arms. Measurements were taken at baseline, end of year one and end of year two in 4396 subjects. Linear Mixed Models (LMM) were used to determine the longitudinal profiles of sodium, potassium, weight, cholesterol, glucose, urea and urate. Estimates of changes within groups and difference between groups were obtained.

Results

Patients randomised to receive hydrochlorothiazide + amiloride experienced a significantly greater mean reduction in potassium, sodium and weight compared to placebo at end of year one - mean differences in change −0.18 mmol/L, (95 % CI: −0.21, −0.15); −1.45 mmol/L, (95 % CI: −1.62, −1.29) and −0.46 kgs (95 % CI: −0.73, −0.20) respectively, and greater increases in cholesterol, urea and urate - mean differences in change 0.16 mmol/L, (95 % CI: 0.10,0.22); 0.77 mmol/L, (95 % CI: 0.68, 0.87) and 53.10 μmol/L, (95 % CI: 49.35, 56.85) respectively. Changes were in the same direction but smaller in the atenololarm except for potassium and weight (increases). No group differences in glucose were found.

Conclusion

Results were in line with expectation except for lack of change in glucose in the hydrochlorothiazide + amiloride arms.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-016-0368-2) contains supplementary material, which is available to authorized users.

How do thiazide and thiazide-like diuretics lower blood pressure?

Thiazide diuretics are widely used for the treatment of hypertension, but the mechanism by which these drugs lower blood pressure in the long term remains unknown. This article reviews current knowledge about the hypotensive actions of thiazides and thiazide-like diuretics and discusses possible mechanisms of action.

Approach to Antihypertensive Therapy

Antihypertensive agents are commonly prescribed by physicians to prevent the long-term mortality from chronic hypertension. They are also given to improve survival in a number of conditions (eg, heart failure, coronary artery disease), independent of the effect on blood pressure. Several classes of antihypertensives are available with unique pharmacologic characteristics and adverse effects. Not all agents in the same class have identical effects, and careful selection of drugs based on the comorbid conditions is recommended.

Sympathetic stimulation of thiazide-sensitive sodium chloride cotransport in the generation of salt-sensitive hypertension

Excessive renal efferent sympathetic nerve activity contributes to hypertension in many circumstances. Although both hemodynamic and tubular effects likely participate, most evidence supports a major role for α-adrenergic receptors in mediating the direct epithelial stimulation of sodium retention. Recently, it was reported, however, that norepinephrine activates the thiazide-sensitive NaCl cotransporter (NCC) by stimulating β-adrenergic receptors. Here, we confirmed this effect and developed an acute adrenergic stimulation model to study the signaling cascade. The results show that norepinephrine increases the abundance of phosphorylated NCC rapidly (161% increase), an effect largely dependent on β-adrenergic receptors. This effect is not mediated by the activation of angiotensin II receptors. We used immunodissected mouse distal convoluted tubule to show that distal convoluted tubule cells are especially enriched for β₁-adrenergic receptors, and that the effects of adrenergic stimulation can occur ex vivo (79% increase), suggesting they are direct. Because the 2 protein kinases, STE20p-related proline- and alanine-rich kinase (encoded by STK39) and oxidative stress-response kinase 1, phosphorylate and activate NCC, we examined their roles in norepinephrine effects. Surprisingly, norepinephrine did not affect STE20p-related proline- and alanine-rich kinase abundance or its localization in the distal convoluted tubule; instead, we observed a striking activation of oxidative stress-response kinase 1. We confirmed that STE20p-related proline- and alanine-rich kinase is not required for NCC activation, using STK39 knockout mice. Together, the data provide strong support for a signaling system involving β₁-receptors in the distal convoluted tubule that activates NCC, at least in part via oxidative stress-response kinase 1. The results have implications about device- and drug-based treatment of hypertension.

Antihypertensive and Metabolic Effects of Concomitant Administration of Terazosin and Methyclothiazide for the Treatment of Essential Hypertension

The efficacy and safety of once-daily 2.5- or 5.0-mg methyclothiazide (MCTZ) added to once-daily 5.0-mg terazosin (TRZ) versus 5.0-mg TRZ alone was evaluated in this double-blind, multicenter study. All patients received TRZ during a 6-week titration period. Hypertensive patients (222) (mean blood pressure of 159/104 mm Hg) were randomized to one of three treatment groups: TRZ alone (N = 76); TRZ+MCTZ-2.5 mg (N = 74); and TRZ+MCTZ-5.0 mg (N = 72) for the 8-week double-blind period. Changes in the supine and standing SBP/DBP from preTRZ period were: TRZ alone (-4.8/-8.1 and -2.6/-6.1 mm Hg); TRZ+MCTZ-2.5 mg (-17.3/-12.4 and -16.0/-11.2 mm Hg); and TRZ+MCTZ-5.0 mg (-20.6/-14.4 and -23.3/-14.6 mm Hg). Blood pressure changes in the combination groups were significantly greater than those in the TRZ alone group. However, there were no statistically significant differences between the TRZ+MCTZ-2.5-mg and TRZ+MCTZ-5.0-mg groups. The combination of TRZ and MCTZ tends to mitigate the adverse effects on serum glucose, uric, potassium and lipids usually associated with thiazide diuretics. Thus, combination treatment that begins with TRZ and adds MCTZ is effective in lowering blood pressure without any significant adverse metabolic effects.

Blood pressure-lowering efficacy of the fixed-dose combination of azilsartan medoxomil and chlorthalidone: a factorial study

This study compared the efficacy and safety of fixed-dose combinations (FDCs) of the angiotensin II receptor blocker azilsartan medoxomil (AZL-M) and the thiazide-like diuretic chlorthalidone (CLD) with the individual monotherapies in a double-blind factorial study. A total of 1714 patients with clinic systolic blood pressure (SBP) 160 mm Hg to 190 mm Hg inclusive were randomized to AZL-M 0 mg, 20 mg, 40 mg, or 80 mg and/or chlorthalidone 0 mg, 12.5 mg, or 25 mg. The primary efficacy end point was change from baseline to 8 weeks in trough (hour 22-24) SBP by ambulatory blood pressure (BP) monitoring (ABPM). Patients' mean age was 57 years; 47% were men and 20% were black. Baseline trough BP was approximately 165/95 mm Hg and 151/91 mm Hg by clinic and ABPM measurements, respectively. For the pooled AZL-M/CLD 40/25-mg and 80/25-mg FDC groups, SBP reduction by ABPM at trough was 28.9 mm Hg and exceeded AZL-M 80 mg and CLD 25 mg monotherapies by 13.8 mm Hg and 13 mm Hg, respectively (P<.001 for both comparisons). Discontinuation rates and elevations in serum creatinine were dose-dependent and occurred more often in the AZL-M/CLD groups. In patients with stage 2 hypertension, treatment with the combination of AZL-M and CLD resulted in substantially greater SBP reduction compared with either agent alone.

The effects of dietary patterns on plasma renin activity: results from the Dietary Approaches to Stop Hypertension trial

A diet rich in fruits, vegetables and low-fat dairy products, and reduced in saturated fat, total fat and cholesterol (the 'DASH' diet) significantly lowers blood pressure (BP). Previous studies have documented that certain therapies that lower BP increase plasma renin activity (PRA). Using data from the Dietary Approaches to Stop Hypertension (DASH) trial, we assessed the effects of dietary patterns on PRA and determined the relationship of change in PRA with change in BP on each diet. After eating a control diet for 3 weeks, participants were then randomized to receive for 8 weeks: the control diet, a diet rich in fruits and vegetables (F/V), or the DASH diet. Baseline and follow-up levels of PRA were available in 381 participants. Compared with the control diet, the DASH diet increased PRA by 0.37 ng ml(-1) h(-1) (P=0.01). In multivariable linear regression analyses, there was an inverse association of PRA change with systolic BP change on the control diet (slope=-0.35, P=0.001), but PRA did not differ by BP change on the F/V diet (slope=-0.002, P=0.98) or DASH diet (slope=-0.08, P=0.32). These data suggest that a blunted counter-regulatory response of the renin-angiotensin system is associated with the BP-lowering effect of the F/V and DASH diets.

Do thiazides worsen metabolic syndrome and renal disease? The pivotal roles for hyperuricemia and hypokalemia

PURPOSE OF REVIEW

The aims of this article are to review the current controversies related to the use of thiazide diuretics as first-line treatment of hypertension and to discuss the causal roles for hyperuricemia and hypokalemia on the adverse consequences of thiazide usage.

RECENT FINDINGS

Thiazides significantly reduce morbidity and mortality in hypertensive subjects. There remains, however, debate about thiazide usage as first-line treatment of hypertension. This negative impact of thiazides may be partially attributed to the ability of thiazides to exacerbate features of metabolic syndrome or increase the risk for developing diabetes. Several clinical trials suggest that thiazide-induced hyperuricemia and hypokalemia may account for some of these negative effects. Thiazide treatment is also associated with a decline of renal function in spite of a lowering blood pressure. In this review, we discuss the clinical and experimental evidence supporting a potential role of hyperuricemia and hypokalemia on the development of renal injury and worsening of the metabolic syndrome.

SUMMARY

Hyperuricemia and hypokalemia may have pivotal roles in the exacerbation of the metabolic syndrome in response to thiazides. We propose that controlling serum uric acid and serum potassium could improve thiazide efficacy and also reduce its risk for inducing metabolic syndrome or diabetes.

Dietary salt restriction and blood pressure in clinical trials

Dietary salt has long been recognized as a major factor affecting blood pressure such that sodium intake is a component of lifestyle modification guidelines for control of high blood pressure. These recommendations are based on results from epidemiologic observational studies and clinical trials of various sodium diets among normotensives and hypertensives. Nonetheless, results from the different studies vary such that specific recommendations regarding sodium intake are difficult to interpret. The results from several recent major trials indicated greater associations of blood pressure and sodium intake than earlier studies as well as meta-analyses of numerous clinical trials. The studies of sodium intake and blood pressures are complicated by measurements of intake, salt sensitivity, hypertension treatment, effects of sodium independent of blood pressure, and length of interventions. Limitations in the methodology of different studies have reduced the value of the results to provide specific and reliable sodium intake levels essential for clinical and lifestyle guidelines.

Titration of HCTZ to 50 mg daily in individuals with stage 2 systolic hypertension pretreated with an angiotensin receptor blocker

The authors studied the combination of hydrochlorothiazide (HCTZ) 50 mg/d plus olmesartan medoxomil (OM) 40 mg/d in stage 2 systolic hypertension during an extension phase of an open-label 12-week dose titration study. Subjects whose blood pressure remained above 120/80 mm Hg (n=105) on OM 40/HCTZ 25 mg/d subsequently received OM 40/HCTZ 50 mg/d for 4 weeks. Increasing HCTZ from 25 mg/d to 50 mg/d decreased systolic blood pressure by 3.6 mm Hg, increased BP control rates (<140/90 mm Hg) from 70.4% to 77.5%, and increased BP normalization rates (<120/80 mm Hg) from 15.4% to 27.8%. The combination was well tolerated. Compared with OM 40 mg/d monotherapy, neither dose of HCTZ affected serum potassium, but both increased serum glucose by about 5%. There was a dose-dependent increase in uric acid but no acute gout attacks. OM 40/HCTZ 50 mg/d is an effective strategy for managing stage 2 systolic hypertension.

Extracellular water: greater expansion with age in African Americans

Aging is associated with the onset of chronic diseases that lead to pathological expansion of the extracellular water (ECW) compartment. Healthy aging, in the absence of disease, is also reportedly accompanied by a relative expansion of the ECW compartment, although the studies on which this observation is based are few in number, applied different ECW measurement methods, included small ethnically homogeneous subject samples, and failed to adjust ECW for non-age-related influencing factors. The aim of the current study was to examine, in a large (n = 1,538) ethnically diverse [African American (AA), Asian, Caucasian, Hispanic] subject group the cross-sectional relationships between ECW and age after controlling first for other potential factors that may influence fluid distribution. ECW and intracellular water (ICW) were derived from measured total body water (isotope dilution) and potassium (40K whole body counting). The cross-sectional relationships between ECW, ICW, and ECW/ICW (E/I), and age were developed using multiple regression modelling methods. Body weight, weight squared, height, age, sex, race, and interactions were all significant ECW predictors. The slope of the observed race x age interaction was significantly greater in AA (beta = 0.0005, P = 0.005) than in the three other race groups. Race, sex, and age differences in fluid distribution persisted after adjusting for body composition in a subgroup (n = 994) with dual-energy X-ray absorptiometry lean soft tissue and fat measurements. A relative ECW expansion (i.e., E/I) was present with greater age in most sex-race groups, although the effect was not significantly larger in AA males (P > 0.05) compared with the other race groups, except Asians (P < 0.05). For females, a larger E/I-age effect was found in AA compared with the other race groups, but only the comparison against Hispanics was significant (P < 0.05). The ECW compartment and E/I are thus variably larger, according to race, in healthy older subjects independent of sex, lean soft tissue, and fat mass.

Hydrochlorothiazide versus chlorthalidone: evidence supporting their interchangeability

Thiazide diuretics are one of the preferred pharmacologic treatments for hypertension. Hydrochlorothiazide and chlorthalidone have been the 2 most commonly used diuretics in major clinical trials. Treatment guidelines and compendia often consider these 2 drugs interchangeable agents within the class of thiazide or thiazide-like diuretics. Many sources list them as equipotent. Despite these beliefs, there is some suggestion that cardiovascular outcomes are not necessarily the same with these 2 drugs. We conducted a literature search from 1960 to 2003 to identify studies that evaluated the pharmacokinetic and blood pressure-lowering effects of these 2 agents. There are significant pharmacokinetic and pharmacodynamic differences between these diuretics. Chlorthalidone is approximately 1.5 to 2.0 times as potent as hydrochlorothiazide, and the former has a much longer duration of action. Whether these pharmacokinetic and pharmacodynamic features cause differences in outcomes is not known.

Identification of hypertension-related QTLs in African American sib pairs

To link hypertension-related phenotypes with chromosomal loci, genome scans were performed in 150 African American sib pairs concordant for essential hypertension. Phenotypes included blood pressure, anthropomorphic measurements, and estimates of body fluid compartments as determined by impedance plethysmography. These phenotypes were also measured in 335 normotensive African Americans. Phenotypes with LOD scores >3.3 were further evaluated for significance by use of permutation procedures. Significant linkage was detected for body mass index (BMI) on chromosomes 1 and 8 and for the ratio of extracellular water to total body water (ECF/TBW) on chromosomes 3, 5, 6, and 7. Both BMI and ECF/TBW were greater in hypertensive sibs than in normotensive subjects (P<0.001). In a subset of hypertensive sibs and normotensive subjects, average 24-hour blood pressures were correlated with ECF/TBW (P<0.01). A region linked to BMI in the hypertensive sibs corresponds to a region of conserved synteny containing blood pressure-related QTLs in an F2 cross of Brown NorwayxDahl salt-sensitive rats. Focusing on hypertension-related phenotypes is a promising approach for identifying the genetic determinants of hypertension.

Multilevel integrative analyses of human behavior: social neuroscience and the complementing nature of social and biological approaches

Social and biological explanations traditionally have been cast as incompatible, but advances in recent years have revealed a new view synthesized from these 2 very different levels of analysis. The authors review evidence underscoring the complementing nature of social and biological levels of analysis and how the 2 together can foster understanding of the mechanisms underlying complex behavior and the mind. Specifically, they review the utility of considering social influences on biological processes that are often viewed as outside the social domain including genetic constitution, gene expression, disease, and autonomic, neuroendocrine, and immune activity. This research underscores the unity of psychology and the importance of retaining multilevel integrative research that spans molar and molecular levels of analysis. Especially needed in the coming years is more research on the mechanisms linking social and biological events and processes.

Pathophysiology and treatment implications of hypertension in the African-American population

Regardless of the etiology, hypertension remains a major public health problem in African-Americans and is associated with significant morbidity and mortality. Additional data on the pathophysiology of this disease in this population are needed, as are data on the best therapies to decrease the high complication rate. Because many of the large studies on hypertension have included few African-Americans, recruitment of this ethnic group into clinical trials should be promoted. Further studies into the genetic factors in the pathophysiology of racial differences in hypertension may shed more light on this complex issue.

Efficacy, tolerability, and quality of life of losartan, alone or with hydrochlorothiazide, versus nifedipine GITS in patients with essential hypertension

A randomized, double-masked, parallel-group, multicenter clinical trial was conducted to compare the efficacy, tolerability, and effects on quality of life associated with the angiotensin II receptor antagonist losartan, alone or with hydrochlorothiazide (HCTZ), and the dihydropyridine calcium channel blocker nifedipine gastrointestinal therapeutic system (GITS) in patients whose sitting diastolic blood pressure measurements were between 95 and 115 mm Hg, inclusive, while receiving placebo. Patients were randomized to receive either losartan or nifedipine GITS in a double-masked, double-dummy fashion. A 4-week placebo washout period established baseline untreated blood pressure measurements and was followed by a 12-week active treatment period. Patients receiving losartan (n = 110) were initially given 50 mg once a day (QD) and could be titrated to losartan/HCTZ 50 mg/12.5 mg QD after 4 weeks followed by losartan/HCTZ 50 mg/25 mg QD after 8 weeks, as necessary. Patients in the nifedipine GITS group (n = 113) received 30 mg QD, which could titrated to 60 mg QD after 4 weeks followed by 90 mg QD after 8 weeks. Medication was titrated upward as necessary to achieve a sitting trough diastolic blood pressure < 90 mm Hg. Efficacy, tolerability, and quality-of-life scores were assessed after 12 weeks of each therapy. Trough sitting diastolic blood pressure reductions after 4, 8, and 12 weeks of therapy were clinically comparable: losartan, -8.9, -11.6, and -12.7 mm Hg, respectively, and nifedipine GITS, -9.3, -11.0, and -11.1 mm Hg, respectively, with the mean reduction in sitting diastolic blood pressure at 12 weeks in the losartan group 1.6 mm Hg lower (95% confidence interval, 3.4 mm Hg lower to 0.3 mm Hg Higher) than the mean reduction in sitting diastolic blood pressure in the nifedipine GITS group. Similarly, reductions in systolic blood pressure between the two treatment groups were comparable at all time points. The percentage of patients reaching the goal trough sitting diastolic blood pressure was comparable for the two treatment groups, with 74% of patients in the losartan regimen and 68% of patients in the nifedipine GITS regimen reaching the goal. Of patients reporting adverse events in the two groups (75 patients receiving losartan and 69 receiving nifedipine GITS), there was significantly more edema in the nifedipine GITS group (15% vs 4%; P = 0.005). Fourteen (12%) patients in the nifedipine GITS group were withdrawn due to an adverse event (eight of these were for edema). Six patients (5%) in the losartan group were withdrawn due to an adverse event (none of these patients had edema). There were significant differences in the patient-reported quality-of-life symptom bother inventory with respect to edema, with nifedipine GITS therapy causing significantly more bother due to edema in patients, regardless of whether that symptom was present at baseline (27% vs 9%; P = 0.0004). No statistically significant differences for bother due to the other symptoms in the inventory were noted. Of note, while the incidence of patient-reported symptom bother due to edema in the nifedipine GITS group was 27%, the incidence of physician-reported drug-related edema was 12%. This difference points to the need for improved physician-patient communication regarding adverse effects and their impact of patients' quality of life. In conclusion, a regimen of losartan, when compared with a regimen of nifedipine GITS, provides comparable efficacy, and with respect to edema, superior tolerability, less bother to patients, and fewer therapy dropouts.

Race and hypertension. What is clinically relevant?

Hypertension, once considered rare in Africa, occurs frequently in most Black populations outside of the continent as well as within more urban areas of Africa. The frequency of hypertension in Black citizens of the US is among the highest in the world. Pathophysiological mechanisms suggest the frequency of salt-sensitive blood pressure is more common in Black patients. More Black than White patients initially present with volume expansion. However, in Black patients there appears to be no significant relationship between plasma renin activity, plasma volume and blood pressure. The syndrome of insulin resistance has also been reported in African Americans. Future studies should address this issue, both because it relates to identifying individuals at risk for development of high blood pressure and because it has implications for initial selection of antihypertensive therapy. Hypertensive kidney disease is prevalent in Black people. Lowering the blood pressure with diuretic-based therapies has not been shown to delay or prevent the loss of kidney function in patients with this condition, suggesting that this treatment approach may not be optimal. Lifestyle modifications remain the initial therapeutic regimen. Because diuretics and beta-blockers have been shown to reduce cardiovascular morbidity and mortality in controlled clinical trials, they are preferred therapies. The Hypertension Detection and Follow-up Program showed significant reductions in morbidity and mortality in Black patients using primarily diuretic-based therapies. However, controversy persists regarding use of diuretics since some investigators believe that greater reductions in overall cardiovascular risk may be achieved in Black patients using other agents. These agents may eventually be able to exert a beneficial cardiovascular effect in addition to and independent of their blood pressure-lowering effect. Long term data documenting reduced morbidity and mortality rates with other agents are needed for all populations, particularly in Black hypertensive patients.

Renal disease and black Americans: selected issues

Black Americans compared with their white counterparts are disproportionately hypertensive and have a greater incidence of end-stage renal disease (ESRD). Renal disease is a frequent end point of accelerated hypertension. The reasons why black Americans have a higher incidence of ESRD relative to white Americans are explored. As transplantation is a preferred mode of treatment for chronically ill ESRD patients, the paper examines some of the reasons why blacks are more reluctant than whites to donate their organs (e.g. kidneys) for transplantation. Although various reasons affect organ donation, altruism is explored as a possible factor that may influence the willingness of blacks to donate their organs.

Obesity as a determinant for response to antihypertensive treatment

OBJECTIVE

To test the hypothesis that beta blockers lower blood pressure more effectively than calcium entry blockers in obese hypertensive patients and that calcium entry blockers are more effective in lean patients.

DESIGN

Double blind, randomised controlled trial of treatment over six weeks.

SETTING

Tertiary referral centre.

SUBJECTS

42 white men with uncomplicated mild to moderate essential hypertension (World Health Organisation stage I or II); 36 completed the study.

INTERVENTION

Patients were randomised to metoprolol 50-100 mg twice daily or isradipine 2.5-5.0 mg twice daily for six weeks after a two week run in phase.

MAIN OUTCOME MEASURE

Blood pressure after six weeks of treatment.

RESULTS

When stratified according to treatment and presence of obesity (body mass index < or = 27 kg/m2), the mean (SD) fall in blood pressure in the beta blocker group was 24 (13)/18 (10) mm Hg in obese patients and 18 (19)/12 (13) mm Hg in lean patients. In the calcium entry blocker group, the fall in blood pressure was 21 (15)/17 (6) mm Hg in lean patients and 18 (11)/8 (10) mm Hg in obese patients. After taking age and blood pressure before treatment into account there was a significant interaction between obesity and drug therapy (p = 0.019) with a better diastolic blood pressure response to calcium entry blockers in lean patients and to beta blockers in obese hypertensive patients.

CONCLUSION

Obesity affects the efficacy of metoprolol and isradipine in reducing blood pressure.

Antihypertensive effects of low doses of hydrochlorothiazide in hypertensive black Zimbabweans

The antihypertensive effects of low doses of hydrochlorothiazide have not been examined in black African hypertensive patients although hydrochlorothiazide is commonly used as first-line therapy. The antihypertensive effects of hydrochlorothiazide in a daily dose of 6.25, 12.5, 25 and 50 mg were examined in 19 black Zimbabwean hypertensive patients in a double-blind, random order, placebo-controlled, cross-over trial. The mean systolic blood pressure on placebo was 170.2 mmHg (95% CI +/- 9.0 mmHg) and on daily doses of hydrochlorothiazide decreased to: 161.1 mmHg (95% CI + 10.0 mmHg) on 6.25 mg; 156.6 mmHg (95% CI +/- 8.6 mmHg) on 12.5 mg; 154.9 mmHg (95% CI +/- 8.5 mmHg) on 25 mg and 149.1 mmHg (95% CI +/- 9.2 mmHg) on 50 mg. The mean diastolic blood pressure on placebo was 101.4 mmHg (95% CI +/- 5.0 mmHg) and decreased to: 98.0 mmHg (95% CI +/- 5.7 mmHg) on 6.25 mg; 96.1 mmHg (95% CI +/- 4.5 mmHg) on 12.5 mg; 93.6 mmHg (95% CI +/- 5.3 mmHg) on 25 mg and 90.5 mmHg (95% CI +/- 3.9 mmHg) on 50 mg. Hydrochlorothiazide in doses of 25 mg and 50 mg decreased systolic and diastolic blood pressure and the 12.5 mg dose decreased systolic blood pressure significantly more than placebo. We conclude that in this population maximum antihypertensive effect is not seen with the lower doses of hydrochlorothiazide and 25 mg is an appropriate starting dose for most patients.

Evolving natural history of coronary artery disease in diabetes mellitus

White diabetic patients are at high risk of developing coronary artery disease (CAD). The natural history of CAD in insulin-dependent (ID) and noninsulin-dependent (NID) diabetes mellitus (DM) is reviewed to gain insight into the mechanisms responsible for the development of premature or accelerated atherosclerosis in diabetic patients. In both IDDM and NIDDM, the risk of CAD increases with lengthening duration of diabetes; the risk, however, does not grow as a constant multiple of the nondiabetic risk of CAD, suggesting that the cumulative exposure to diabetes plays a significant role as a risk factor for CAD only in a subset of patients. This is consistent with the hypothesis that the diabetic milieu has an impact on the progression of atherosclerotic lesions but not on their initiation. This hypothesis is corroborated further by the observation that CAD does not occur in diabetic patients in populations with a low risk of CAD among nondiabetic patients. The component of the diabetic milieu responsible for promotion of atherosclerotic lesions is unknown. There is evidence, however, of a direct or indirect role of hyperinsulinemia in this process.

Biohistory of slavery and blood pressure differences in blacks today. A hypothesis

Genetic factors are known to play an important role in the variations in blood pressure levels. However, genetic factors that explain the higher average blood pressure levels of western hemisphere blacks when compared with African blacks have not been seriously considered. Because the genetic makeup of a population is largely determined by biological and ecological forces in the past, an examination of the biohistory of blacks, specifically the slavery era, was conducted. An overview of the salient findings of that investigation is included in this article. The published historical evidence on the transatlantic slave trade and New World slavery (from the 16th century to the 19th century) reveals that conditions existed for "natural selection," and therefore, genetic changes were virtually inevitable in the slave populations. During this period of history, mortality was extremely high, and fertility (or reproductive success) was so low among the survivors that most plantation societies in the western hemisphere depended on a constant importation of captives (over 12 million) from Africa for the viability of the plantation communities. Because the major causes of death were salt-depletive diseases such as diarrhea, fevers, and vomiting, it is argued that individuals with an enhanced genetic-based ability to conserve salt had a distinct survival advantage over others and were, therefore, more likely to bequeath their genotype to subsequent generations of Western hemisphere blacks. Thus, it is predicted that blacks in the Americas have a greater frequency of individuals with an enhanced genetic-based ability to conserve salt than African blacks.(ABSTRACT TRUNCATED AT 250 WORDS)

Diuretics and the treatment of systemic hypertension

Diuretics are still among the most frequently used antihypertensive drugs in the treatment of hypertension. Their pharmacologic and hemodynamic properties are based on the water and salt metabolism in the pathophysiology of high blood pressure. Initially, there is a reduction of plasma and extracellular fluid volume; cardiac output also decreases. After this early phase, cardiac output returns to normal with an accompanying decrease in peripheral resistance so as to correct the underlying hemodynamic fault of the hypertensive state. Diuretics have a high therapeutic efficacy either as monotherapy or in combination with beta blockers, angiotensin-converting enzyme inhibitors or calcium antagonists. The main problem with the use of diuretics is related to their metabolic side effects, which are dose-related. Currently, there is a tendency to administer low-dose diuretics, which result in fewer clinical and metabolic side effects, but with a continued antihypertensive efficacy. Therefore, low doses of diuretics can be recommended as initial therapy in the stepped-care approach of hypertension.