Mechanism of Thiazide Diuretic Arterial Pressure Reduction: The Search Continues

Effects of thiazides and new findings on kidney stones and dysglycemic side effects

Thiazide and thiazide-like diuretics (thiazides) belong to the most frequently prescribed drugs worldwide. By virtue of their natriuretic and vasodilating properties, thiazides effectively lower blood pressure and prevent adverse cardiovascular outcomes. In addition, through their unique characteristic of reducing urine calcium, thiazides are also widely employed for the prevention of kidney stone recurrence and reduction of bone fracture risk. Since their introduction into clinical medicine in the early 1960s, thiazides have been recognized for their association with metabolic side effects, particularly impaired glucose tolerance, and new-onset diabetes mellitus. Numerous hypotheses have been advanced to explain thiazide-induced glucose intolerance, yet underlying mechanisms remain poorly defined. Regrettably, the lack of understanding and unpredictability of these side effects has prompted numerous physicians to refrain from prescribing these effective, inexpensive, and widely accessible drugs. In this review, we outline the pharmacology and mechanism of action of thiazides, highlight recent advances in the understanding of thiazide-induced glucose intolerance, and provide an up-to-date discussion on the role of thiazides in kidney stone prevention.

Causes of Chronic Kidney Disease and Their Associations with Cardiovascular Risk and Disease in a Sub-Saharan Low-Income Population

Introduction

The causes of chronic kidney disease (CKD) in people living in Sub-Saharan Africa await identification. Also, whether cardiovascular risk and disease extent differ among patients with different CKD etiologies is uncertain.

Methods

In this prospective cross-sectional study, we examined the presumed causes of chronic kidney disease (CKD) and their relationships with cardiovascular risk and disease in 743 consecutive patients from a sub-Saharan low-income population.

Results

Hypertensive nephropathy (HNP) (60.2%), diabetic nephropathy (DNP) (24.4%), HIV associated CKD (20.0%) and glomerular disease (13.6%) comprised the major CKD etiologies upon enrolment at the hospital nephrology clinic. Pulse pressure was larger in patients with concurrent HNP and DNP than in those with HNP only (p<0.001). Pulse pressure and systolic blood pressure were larger in HNP or/and DNP patients than those with HIV associated CKD and glomerular disease (p=0.04 to <0.001). Cardiovascular disease was more prevalent in patients with HNP and concurrent HNP and DNP than those from other etiologic categories (p<0.05). HNP and DNP were associated with pulsatile pressures (pulse pressure and systolic blood pressure) independent of one another (p<0.01). In adjusted product of coefficient mediation analysis, mean arterial or distending pressure accounted fully for the potential impact of HNP on pulsatile pressures (103.9-115.7%) but not for that of DNP on the respective pressures (-2.0%-(-)7.5%).

Conclusion

HNP is by far the most prevalent presumed cause of CKD in this African population. Cardiovascular risk and disease differ markedly across CKD etiological categories.

Integrated metabolomics analysis reveals mechanistic insights into variability in blood pressure response to thiazide diuretics and beta blockers

Hypertensive patients with a higher proportion of genetic West African ancestry (%GWAA) have better blood pressure (BP) response to thiazide diuretics (TDs) and worse response to β-blockers (BBs) than those with lower %GWAA, associated with their lower plasma renin activity (PRA). TDs and BBs are suggested to reduce BP in the long term through vasodilation via incompletely understood mechanisms. This study aimed at identifying pathways underlying ancestral differences in PRA, which might reflect pathways underlying BP-lowering mechanisms of TDs and BBs. Among hypertensive participants enrolled in the Pharmacogenomics Evaluation of Antihypertensive Responses (PEAR) and PEAR-2 trials, we previously identified 8 metabolites associated with baseline PRA and 4 metabolic clusters (including 39 metabolites) that are different between those with GWAA <45% versus ≥45%. In the current study, using Ingenuity Pathway Analysis (IPA), we integrated these signals. Three overlapping metabolic signals within three significantly enriched pathways were identified as associated with both PRA and %GWAA: ceramide signaling, sphingosine 1- phosphate signaling, and endothelial nitric oxide synthase signaling. Literature indicates that the identified pathways are involved in the regulation of the Rho kinase cascade, production of the vasoactive agents nitric oxide, prostacyclin, thromboxane A2, and endothelin 1; the pathways proposed to underlie TD- and BB-induced vasodilatation. These findings may improve our understanding of the BP-lowering mechanisms of TDs and BBs. This might provide a possible step forward in personalizing antihypertensive therapy by identifying patients expected to have robust BP-lowering effects from these drugs.

Role of atrial natriuretic peptide in the dissociation between flow relations with ventricular mass and function in a community with volume-dependent hypertension

Background

Whether differential effects of volume load on left ventricular mass (LVM) and function occur in sustained volume-dependent primary hypertension, and the impact of atrial natriuretic peptide (ANP) on these effects, is unknown.

Methods

From aortic pressure, velocity and diameter measurements and echocardiography, we determined in an African community (n = 772), the impact of systemic flow-induced increases in central pulse pressure (PPc) and circulating ANP (ELISA) on LVM and indexes of function.

Results

Stroke volume (SV), but not aortic flow (Q), was associated with LVM and mean wall thickness (MWT) beyond stroke work and confounders (p < 0.0001). Adjustments for SV markedly decreased the relationships between PPc and LVMI or MWT. However, neither SV, nor Q were independently associated with either myocardial s', e', or E/e' (p > 0.14) and adjustments for neither SV nor Q modified relationships between PPc and s', e' or E/e' (p < 0.005 to <0.0001). SV was nevertheless strongly and independently associated with ANP (p < 0.0001) and ANP was similarly strikingly associated with s' (p < 0.0001) and e' (p < 0.0005), but not E/e', independent of confounders and several determinants of afterload. Importantly, ANP concentrations were inversely rather than positively associated with LV diastolic dysfunction (DD) (p < 0.005) and lower rather than higher ANP concentrations contributed markedly to the ability to detect DD in those with, but not without LV hypertrophy.

Conclusion

In populations with sustained volume-dependent hypertension, flow (SV)-related increases in PP have a major impact on LV structure, but not on function, an effect attributed to parallel striking beneficial actions of ANP on myocardial function.

Attenuated Relationships Between Indexes of Volume Overload and Atrial Natriuretic Peptide in Uncontrolled, Sustained Volume-Dependent Primary Hypertension

BACKGROUND

Whether systolic blood pressure (SBP) control in sustained volume-dependent primary hypertension is associated with blunted ANP (atrial natriuretic peptide) relationships with indexes of volume load is unknown.

METHODS

Systemic hemodynamics (central pressure, echocardiographic aortic velocity and diameter measurements in the outflow tract), circulating ANP concentrations (ELISA assays) and glomerular and tubular function (24-hour urine collections [n=519]) were determined in a community of African ancestry (n=772).

RESULTS

As compared with those with a controlled SBP, those with an uncontrolled SBP (n=198) showed lower ANP concentrations (P<0.005) despite higher stroke volume and cardiac output (P<0.0001) and renal differences consistent with enhanced fluid retention. In those with a controlled SBP, fractional Na⁺ excretion (FeNa⁺; P<0.0005) and creatinine clearance (glomerular filtration rate; P<0.005) were inversely associated with ANP concentrations independent of confounders. Moreover, in those with a controlled SBP, stroke volume and cardiac output (P<0.0001) were independently and positively associated with ANP concentrations. In addition, in those with a controlled SBP, ANP concentrations were independently and inversely associated with systemic vascular resistance (SVR; P<0.0001) and aortic characteristic impedance (Zc; P<0.005). By contrast, in those with uncontrolled SBP, no relationships between either stroke volume (P>0.25), cardiac output (P>0.29), FeNa⁺ (P>0.77), or glomerular filtration rate (P>0.47) and ANP concentrations were noted. Furthermore, in those with an uncontrolled SBP, no relationships between ANP concentrations and SVR or Zc were observed (P>0.34).

CONCLUSIONS

In a population where primary hypertension is strongly volume-dependent, those with an uncontrolled SBP have an attenuated relationship between ANP and both renal and hemodynamic indexes of volume overload and the vascular effects of ANP.

Mathematical modeling of antihypertensive therapy

Hypertension is a multifactorial disease arising from complex pathophysiological pathways. Individual characteristics of patients result in different responses to various classes of antihypertensive medications. Therefore, evaluating the efficacy of therapy based on in silico predictions is an important task. This study is a continuation of research on the modular agent-based model of the cardiovascular and renal systems (presented in the previously published article). In the current work, we included in the model equations simulating the response to antihypertensive therapies with different mechanisms of action. For this, we used the pharmacodynamic effects of the angiotensin II receptor blocker losartan, the calcium channel blocker amlodipine, the angiotensin-converting enzyme inhibitor enalapril, the direct renin inhibitor aliskiren, the thiazide diuretic hydrochlorothiazide, and the β-blocker bisoprolol. We fitted therapy parameters based on known clinical trials for all considered medications, and then tested the model's ability to show reasonable dynamics (expected by clinical observations) after treatment with individual drugs and their dual combinations in a group of virtual patients with hypertension. The extended model paves the way for the next step in personalized medicine that is adapting the model parameters to a real patient and predicting his response to antihypertensive therapy. The model is implemented in the BioUML software and is available at https://gitlab.sirius-web.org/virtual-patient/antihypertensive-treatment-modeling.

Thiazides in chronic kidney disease: "back to the future"

The thiazide class diuretics are first-line agents for managing hypertension either as monotherapy or as a fixed-dose combination with other antihypertensive drugs. However, despite the extensive experience with these drugs for >60 years, there is general reluctance to use these agents in patients with advanced chronic kidney disease (CKD) because of concerns about their efficacy and safety as kidney function declines. In this issue of Clinical Kidney Journal, Minutolo et al. performed an updated review of the pharmacological properties, efficacy and side effects and randomized controlled trials that tested these drugs in patients with CKD.

Congenital Heart Disease: The State-of-the-Art on Its Pharmacological Therapeutics

Congenital heart disease is one of the most common causes of death derived from malformations. Historically, its treatment has depended on timely diagnosis and early pharmacological and surgical interventions. Survival rates for patients with this disease have increased, primarily due to advancements in therapeutic choices, but mortality remains high. Since this disease is a time-sensitive pathology, pharmacological interventions are needed to improve clinical outcomes. Therefore, we analyzed the applications, dosage, and side effects of drugs currently used for treating congenital heart disease. Angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers, and potassium-sparing diuretics have shown a mortality benefit in most patients. Other therapies, such as endothelin receptor antagonists, phosphodiesterase-5 inhibitors, prostaglandins, and soluble guanylyl cyclase stimulators, have benefited patients with pulmonary artery hypertension. Likewise, the adjunctive symptomatic treatment of these patients has further improved the outcomes, since antiarrhythmics, digoxin, and non-steroidal anti-inflammatory drugs have shown their benefits in these cases. Conclusively, these drugs also carry the risk of troublesome adverse effects, such as electrolyte imbalances and hemodynamic compromise. However, their benefits for survival, symptom improvement, and stabilization outweigh the possible complications from their use. Thus, cases must be assessed individually to accurately identify interventions that would be most beneficial for patients.

Effect of drug interventions on cerebral hemodynamics in ischemic stroke patients

The ischemic penumbra is sensitive to alterations in cerebral perfusion. A myriad of drugs are used in acute ischemic stroke (AIS) management, yet their impact on cerebral hemodynamics is poorly understood. As part of the Cerebral Autoregulation Network led INFOMATAS project (Identifying New Targets for Management and Therapy in Acute Stroke), this paper reviews some of the most common drugs a patient with AIS will come across and their potential influence on cerebral hemodynamics with a particular focus being on cerebral autoregulation (CA). We first discuss how compounds that promote clot lysis and prevent clot formation could potentially impact cerebral hemodynamics, before focusing on how the different classes of antihypertensive drugs can influence cerebral hemodynamics. We discuss the different properties of each drug and their potential impact on cerebral perfusion and CA. With emerging interest in CA status of AIS patients, either during or soon after treatment when timely reperfusion and salvageable tissue is at its most critical, the properties of these pharmacological agents may be relevant for modelling cerebral perfusion accuracy and for setting individualised treatment strategies.

Independent relationships between renal mechanisms and systemic flow, but not resistance to flow in primary hypertension in Africa

AIMS

Whether renal mechanisms of hypertension primarily translate into increases in systemic vascular resistance (SVR) in all populations is uncertain. We determined whether renal mechanisms associate with either increases in SVR (and impedance to flow) or systemic flow in a community of African ancestry.

METHOD

In a South African community sampled across the full adult age range (n = 546), we assessed stroke volume (SV), peak aortic flow (Q), SVR, characteristic impedance (Zc) and total arterial compliance (TAC) from velocity and diameter measurements in the outflow tract (echocardiography) and central arterial pressures. Renal changes were determined from creatinine clearance (glomerular filtration rate, GFR) and fractional Na+ excretion (FeNa+) (derived from 24-h urine collections).

RESULTS

Independent of confounders (including MAP and pressures generated by the product of Q and Zc), SV (and hence cardiac output) (P < 0.0001) and Q (P < 0.01), but not SVR, Zc or TAC (P = 0.09-0.20) were independently associated with decreases in both GFR (index of nephron number) and FeNa+. Through an interactive effect (P < 0.0001), the impact of GFR on SV or Q was strongly determined by FeNa+ and vice versa. The relationship between the GFR-FeNa+ interaction and either SV or Q was noted in those above or below 50 years of age, although neither GFR, FeNa+ nor the interaction were independently associated with SVR, Zc or TAC at any age.

CONCLUSION

Across the full adult lifespan, in groups of African ancestry, renal mechanisms of hypertension translate into increases in systemic flow rather than into resistance or impedance to flow.

Thiazide and other Cl-benzenesulfonamide-bearing clinical drug affinities for human carbonic anhydrases

Twelve carbonic anhydrase (CA) isoforms catalyze carbon dioxide hydration to bicarbonate and acid protons and are responsible for many biological functions in human body. Despite their vital functions, they are also responsible for, or implicated in, numerous ailments and diseases such as glaucoma, high altitude sickness, and cancer. Because CA isoforms are highly homologous, clinical drugs designed to inhibit enzymatic activity of a particular isoform, can also bind to others with similar affinity causing toxic side effects. In this study, the affinities of twelve CA isoforms have been determined for nineteen clinically used drugs used to treat hypertension related diseases, i.e. thiazides, indapamide, and metolazone. Their affinities were determined using a fluorescent thermal shift assay. Stopped flow assay and isothermal titration calorimetry were also employed on a subset of compounds and proteins to confirm inhibition of CA enzymatic activity and verify the quantitative agreement between different assays. The findings of this study showed that pharmaceuticals could bind to human CA isoforms with variable affinities and inhibit their catalytic activity, even though the drug was intended to interact with a different (non-CA) protein target. Relatively minor structural changes of the compounds may cause significant changes in affinity and selectivity for a particular CA isoform.

Analysis of Global Oxidative Status Using Multimarker Scores Reveals a Specific Association Between Renal Dysfunction and Diuretic Therapy in Older Adults

Aging and chronic kidney disease (CKD) are important interrelated cardiovascular risk (CVR) factors linked to oxidative stress, but this relationship has not been well studied in older adults. We assessed the global oxidative status in an older population with normal to severely impaired renal function. We determined the oxidative status of 93 older adults (mean age 85 years) using multimarker scores. OxyScore was computed as index of systemic oxidative damage by analyzing carbonyl groups, oxidized low-density lipoprotein, 8-hydroxy-2'-deoxyguanosine, and xanthine oxidase activity. AntioxyScore was computed as index of antioxidant defense by analyzing catalase and superoxide dismutase (SOD) activity and total antioxidant capacity. OxyScore and AntioxyScore were higher in subjects with estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2 than in peers with eGFR >60 mL/min/1.73 m2, with protein carbonyls, catalase, and SOD activity as major drivers. Older adults with a recent cardiovascular event had similar OxyScore and AntioxyScore as peers with eGFR >60 mL/min/1.73 m2. Multivariate linear regression analysis revealed that both indices were associated with decreased eGFR independently of traditional CVR factors. Interestingly, AntioxyScore was also associated with diuretic treatment, and a more pronounced increase was seen in subjects receiving combination therapy. The associations of AntioxyScore with diuretic treatment and eGFR were mutually independent. In conclusion, eGFR is the major contributor to the imbalance in oxidative stress in this older population. Given the association between oxidative stress, CKD, and CVR, the inclusion of renal function parameters in CVR estimators for older populations, such as the SCORE-OP, might improve their modest performance.

Effects of firibastat in combination with enalapril and hydrochlorothiazide on blood pressure and vasopressin release in hypertensive DOCA-salt rats

In the brain, aminopeptidase A (APA) generates angiotensin III, one of the effector peptides of the brain renin-angiotensin system (RAS), exerting tonic stimulatory control over blood pressure (BP) in hypertensive rats. Oral administration of firibastat, an APA inhibitor prodrug, in hypertensive rats, inhibits brain APA activity, blocks brain angiotensin III formation and decreases BP. In this study, we evaluated the efficacy of firibastat in combination with enalapril, an angiotensin I-converting enzyme inhibitor, and hydrochlorothiazide (HCTZ), in conscious hypertensive deoxycorticosterone acetate (DOCA)-salt rats, which display high plasma arginine-vasopressin levels, low circulating renin levels and resistance to treatment by systemic RAS blockers. We determined mean arterial BP, heart rate, plasma arginine-vasopressin levels and renin activity in DOCA-salt rats orally treated with firibastat, enalapril or HCTZ administered alone or in combination. Acute oral firibastat administration (30 mg/kg) induced a significant decrease in BP, whereas enalapril (10 mg/kg) or HCTZ (10 mg/kg) administered alone induced no significant change in BP in conscious DOCA-salt rats. The BP decrease induced by acute and nine-day chronic tritherapy [Firibastat+Enalapril+HCTZ] was significantly greater than that observed after bitherapy [Enalapril+HCTZ]. Interestingly, the chronic administration of a combination of firibastat with [Enalapril+HCTZ] reduced plasma arginine-vasopressin levels by 62% relative to those measured in DOCA-salt rats receiving bitherapy. Our data show that tritherapy with firibastat, enalapril and HCTZ improves BP control and arginine-vasopressin release in an experimental salt-dependent model of hypertension, paving the way for the development of new treatments for patients with currently difficult-to-treat or resistant hypertension.

SGLT2 inhibitors and thiazide enhance excretion of DEHP toxic metabolites in subjects with type 2 diabetes: A randomized clinical trial

OBJECTIVE

Phthalates are non-persistent pollutants related to impaired metabolism and high cardiovascular risk. Their toxic metabolites are eliminated through urine and feces. Prevention policies are considered by the governments, although no therapeutic strategy to facilitate their elimination from the human body has been proposed so far. Aim of the present study was to verify, for the first time in humans, whether diuretics might be able to enhance phthalates' toxic metabolites urinary output.

DESIGN AND METHODS

We conducted a two-armed, parallel-design, randomized clinical trial. Thirty patients with type 2 diabetes and hypertension received a four week-treatment with Dapagliflozin 10 mg or Hydrochlorothiazide 12.5 mg. 24-hours urine were collected to measure urinary excretion of three major 2-ethylhexyl-phthalate (DEHP) metabolites, i.e. mono 2-ethylhexyl phthalate (MEHP), mono-2-ethyl-5-oxohexyl phthalate (MEOHP) and mono 2-ethyl-5-hydroxyhexyl phthalate (MEHHP).

RESULTS

24-h urinary excretion of DEHP and MEHP was increased (+44%, p = 0.036; +49%, p = 0.0016) while MEOHP e MEHHP showed only a positive trend (+25%, p = 0.016; +36%, p = 0.062). Irrespective of the specific treatment, induced variations of daily urinary eliminations of MEHP metabolites were related with the 24-h urinary sodium (r = 0.42, p = 0.0226) and potassium (r = 0.54, p = 0.0026) excretion. Also, DEHP and MEOHP were related to sodium (r = 0·43, p = 0.0205; r = 0·44, p = 0.0168 respectively) but not to potassium.

CONCLUSIONS

Urinary phthalates excretion seems to occur mainly through sodium- and potassium-related mechanisms, apparently independent from the different diuretic effect. Both thiazide diuretics and SLGT2 inhibitors are effective into the removal of phthalates metabolites from the human body, reducing the human tissues' exposure to their toxicity.

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).