The renin-angiotensin system in essential hypertension: associations with cardiovascular risk

Effect of angiotensin-converting enzyme inhibitors versus that of angiotensin receptor blockers on survival in patients undergoing hemodialysis: a nationwide observational cohort study

BACKGROUND

This study aimed to evaluate the patient survival rates based on the use of angiotensin-converting enzyme inhibitor (ACEI) or angiotensin II receptor blocker (ARB) in a large cohort of patients undergoing maintenance hemodialysis (HD).

METHODS

Data from a national HD quality assessment program were used in this retrospective study. The patients were classified into four groups based on the use of renin-angiotensin system blockers (RASBs) as follows: No group, patients without a prescription of any anti-hypertensive drugs including RASBs; Other group, patients with a prescription of anti-hypertensive drugs excluding RASBs; ACEI group, patients with a prescription of an ACEI; and ARB group, patients with a prescription of an ARB.

RESULTS

The 5-year survival rates in the no, other, ACEI, and ARB groups were 68.6%, 67.8%, 70.6%, and 69.2%, respectively. The ACEI group had the best patient survival trend among the four groups. In multivariable Cox regression analyses, no differences were observed between the ACEI and ARB groups. Among young patients and patients without diabetes or heart disease, the ACEI group had the best patient survival among the four groups. However, among patients with DM or heart disease, the ARB group had the best patient survival.

CONCLUSIONS

Our study found that patients receiving ACEI and ARB had comparable survival. However, patients receiving ARB had better survival in the subgroups of patients with DM or heart disease, and patients receiving ACEI had better survival in the subgroup of young patients or patients without diabetes or heart disease.

Effect of exercise training on the renin-angiotensin-aldosterone system: a meta-analysis

Blood pressure (BP) management reduces the risk of cardiovascular disease (CVD). The renin-angiotensin-aldosterone system (RAAS) plays an important role in regulating and maintaining blood volume and pressure. This analysis aimed to investigate the effect of exercise training on plasma renin, angiotensin-II and aldosterone, epinephrine, norepinephrine, urinary sodium and potassium, BP and heart rate (HR). We systematically searched PubMed, Web of Science, and the Cochrane Library of Controlled Trials until 30 November 2022. The search strategy included RAAS key words in combination with exercise training terms and medical subject headings. Manual searching of reference lists from systematic reviews and eligible studies completed the search. A random effects meta-analysis model was used. Eighteen trials with a total of 803 participants were included. After exercise training, plasma angiotensin-II (SMD -0.71; 95% CI -1.24, -0.19; p = 0.008; n = 9 trials), aldosterone (SMD -0.37; 95% CI -0.65, -0.09; p = 0.009; n = 8 trials) and norepinephrine (SMD -0.82; 95% CI -1.18, -0.46; p < 0.001; n = 8 trials) were reduced. However, plasma renin activity, epinephrine, and 24-h urinary sodium and potassium excretion remained unchanged with exercise training. Systolic BP was reduced (MD -6.2 mmHg; 95% CI -9.9, -2.6; p = 0.001) as was diastolic BP (MD -4.5 mmHg; 95% CI -6.9, -2.1; p < 0.001) but not HR (MD -3.0 bpm; 95% CI -6.0, 0.4; p = 0.053). Exercise training may reduce some aspects of RAAS and sympathetic nervous system activity, and this explains some of the anti-hypertensive response.

Familial genetic and environmental risk profile and high blood pressure event: a prospective cohort of cardio-metabolic and genetic study

BACKGROUND AND AIMS

High blood pressure is the heritable risk factor for cardiovascular diseases. We investigated whether the presence of familial genetic and environmental risk factors are associated with increased risk of high blood pressure.

METHODS

A total of 4,559 individuals from 401 families were included in this study. Familial aggregation analysis was carried out on systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index (BMI) and waist circumference (WC), and heritability was estimated for SBP and DBP. The association between familial risk factors and blood pressure traits including, incidence of hypertension, SBP and DBP was estimated separately using regression-based two-level Haseman-Elston (HE) method, with individual and familial BMI and WC as environmental exposures and familial genetic profile of known variants as genetic risk factors in 210 index families (≥2 hypertensive cases). Models were adjusted for the two nested sets of covariates.

RESULTS

During a follow-up of 15 years, the SBP, DBP, BMI and WC were highly correlated in inter class of mother-offspring and intraclass of sister-sister with heritability of 30 and 25% for DBP and SBP, respectively. Among index families, those whose members with higher familial BMI or WC had significantly increased risk of hypertension and consistent, strong signals of rs2493134 (AGT) linked with SBP and DBP, rs976683 (NLGN1) linked with SBP and HTN, and epistasis of rs2021783 (TNXB) and known genetic variants linked with all blood pressure traits.

CONCLUSIONS

Findings from this study show that familial genetic and environmental risk profile increase risk for high blood pressure beyond the effect of the individuals' own risk factors.

Metabolomic study for essential hypertension patients based on dried blood spot mass spectrometry approach

Hypertension is an increasingly serious public-health challenge worldwide. The traditional blood pressure measurement method could easily and reliably detect blood pressure. However, the delayed symptom onset may influence the screening of essential hypertension (EH). In addition, EH is significantly associated to cardiovascular disease, stroke and kidney disease. Hence, it is urgent to define associated biomarkers with early diagnosis potential for EH. A dried blood spot method integrated with direct infusion mass spectrometry (MS) metabolomic analysis was applied for the detection of metabolites toward 87 EH patients and 91 healthy controls (HC). Multiple algorithms were run on training set (62 EH and 64 HC) for selecting differential metabolites as potential biomarkers. A test set (25 EH and 27 HC) was used to verify and evaluate selected potential biomarkers. A novel blood biomarker model based on Gly, Orn, C10, Orn/Cit, Phe/Tyr, and C5-OH/C8 exhibited potential to differentiate EH patients from HC individuals, with a sensitivity of 0.8400 and a specificity of 0.8889 in test set. The metabolomic analysis of EH is beneficial to the definition of disease-associated biomarkers and the development of new diagnostic approaches. © 2018 IUBMB Life, 70(8):777-785, 2018.

Essential hypertension: A filtered serum based metabolomics study

Despite the easy and reliable methods of blood pressure measurement, the screening of essential hypertension (EH) is usually ignored due to delayed onset of symptoms. A probe into the biochemical changes in hypertension would serve as a welcome asset to provide insight into the mechanistic aspects of EH. Filtered serum samples from 64 EH patients and 59 healthy controls (HC) were analysed using 800 MHz nuclear magnetic resonance (NMR) spectroscopy. Application of principal component analysis (PCA) and orthogonal partial least-squares discriminant analysis (OPLS-DA) following receiver operating characteristic (ROC) curve of NMR data reveals significantly perturbed metabolites: alanine, arginine, methionine, pyruvate, adenine, and uracil. This set of metabolites correctly classified 99% of cases from HC and also showed excellent correlation in both isolated elevated diastolic blood pressure (DBP) cases and combined elevated systolic-diastolic blood pressure cases. Proton NMR metabolomics of EH may prove helpful in defining associated biomarkers and serve as an alternate diagnostic tool with judicious clinical assessment.

Epidemiology of essential hypertension: the role of genetic polymorphism

Over the past 20 years, the interest of the scientific community was increasingly placed in the field of genetic epidemiology and molecular genetics of blood pressure control. This paper explores references related to essential hypertension, gene and genetic epidemiology indexed in the MedLine health science database during the period 1980-2001. A systematic literature search was performed using selected keywords, such as 'genetic', 'genome' or a combination of words. We considered the study heading and evaluated the time profile of published articles. A total number of 3116 publications was collected and analyzed. Allelic distribution for the most studied polymorphisms of the renin-angiotensin system in different world populations was reviewed and reported together with a detection of their frequency in Italy: essential hypertensive patients (n = 90), healthy unrelated subjects (n = 300). Molecular variants at angiotensinogen (M and T), angiotensin II type 1 receptor (A and C) and angiotensin-converting enzyme (D and I) genes were analyzed by amplified fragment length polymorphism. A significant association was detected by chi2 analysis for angiotensinogen and angiotensin II-type I receptor allele distribution in hypertensive patients, in accordance with previous reports. Genetic data and methods are contributing more and more to epidemiological studies of complex diseases, and their application is influenced by information availability and Genome Project results.

Highly selective hydrolysis of kinins by recombinant prolylcarboxypeptidase

We have previously cloned a cDNA encoding human prolylcarboxypeptidase (PRCP) and expressed the cDNA in the Schneider 2 (S2) drosophila cell line. Here, we further characterized this recombinant enzyme. Investigations were performed to determine whether recombinant PRCP (rPRCP) metabolizes kinins (BK 1-9 and BK 1-8). The metabolites of these kinins were identified by LC/MS. rPRCP metabolized BK 1-8 to BK 1-7, whereas rPRCP was ineffective in metabolizing BK 1-9. The hydrolysis of BK 1-8 by rPRCP was dose- and time-dependent. A homology model of PRCP was developed based upon the sequence of dipeptidyl-peptidase 7 (DPP7, PDB ID: 3JYH), and providentially, the structure of PRCP (PDB ID: 3N2Z) was characterized during the course of our investigation. Docking studies of bradykinin oligopeptides were performed both from the homology model, and from the crystal structure of PRCP. These docking studies may provide a better understanding of the contribution of specific residues involved in substrate selectivity of human PRCP.

Temperature and blood pressure following amlodipine overdose

The cardiovascular system participates in both blood pressure (BP) and temperature regulation. As a result, salt ingestion creates conflict between BP and temperature homeostasis, as vasodilatation that would promptly lower the BP would simultaneously increase cutaneous blood flow, thereby accelerating heat loss. If temperature homeostasis has precedence over blood pressure homeostasis, as postulated by the thermoregulatory-vascular remodeling (TVR) hypothesis, then in order to minimize heat loss, BP remains elevated following salt ingestion until the kidneys excrete the excess salt. A case of amlodipine overdose offered an opportunity to test a corollary of the TVR hypothesis: vasodilators should cause a drop in body temperature and/or an increase in the metabolic rate. Following the ingestion of 1000 mg of amlodipine, the temperature and BP of a single patient were monitored during the initial 36 hours and during the 13th day of hospitalization. The BP dropped markedly between the fifth and seventh hours postingestion, but then rose steadily and normalized by 28 hours postingestion. The temperature was normal at 7 hours postingestion, declined gradually between the seventh and 26th hours postingestion, stabilized between the 26th and 31st hours postingestion, then began to rise. During this case of amlodipine overdose, a modest temperature decline lagged behind a marked BP decline. As the BP rose, the temperature also rose, but lagged behind the BP increases. These findings suggest that there is a relationship between BP and temperature and are consistent with the TVR hypothesis.

Effects of salt loading and various therapies on cardiac hypertrophy and fibrosis in young spontaneously hypertensive rats

We investigated the effects of salt loading on blood pressure, cardiac hypertrophy and fibrosis as well as on the effectiveness of various antihypertensive therapies in young spontaneously hypertensive rats (SHR). Twenty-five male SHR were salt-stimulated by drinking 1% NaCl from 3 to 6 months of age. Eighteen of them were treated for the last 2 weeks of salt loading with either the angiotensin-converting enzyme inhibitor captopril, the beta-adrenergic receptor blocker propranolol or the calcium-channel antagonist verapamil. Age-matched male Wistar-Kyoto (WKY) rats and SHR drinking only water served as controls. At the age of 6 months, SHR had significantly elevated blood pressure that was unchanged by salt loading. Relative heart weight was increased in SHR without (3.3) and even more so with salt intake (3.6 vs. 2.4 in WKY). Left ventricular (LV) hypertrophy was accompanied by a 17-fold increase in the expression of mRNA for atrial natriuretic factor (ANF) both in untreated and salt-loaded SHR compared to WKY (p<0.001). Collagen I and III mRNA increased 1.7-1.8-fold in SHR without and with additional salt intake (p<0.01). None of the therapies significantly reduced blood pressure or hypertrophy. Although captopril had no antihypertensive effect, it reduced ANF, collagen I and III mRNA in LV to control level. Less pronounced effects were achieved with verapamil. These findings emphasize the cardioprotective role of captopril which may not be fully expressed in the presence of elevated salt intake.

Vasopressin mechanism-mediated pressor responses caused by central angiotensin II in the ovine fetus

AVP not only influences renal water excretion but also has profound cardiovascular effects in adults. Our recent studies have demonstrated that central angiotensin induced fetal pressor responses accompanied with AVP release. However, little is known of hormonal mechanisms in angiotensin-mediated fetal blood pressure (BP) changes. The present study determined AVP mechanisms in central angiotensin-mediated fetal pressor responses. The V1-receptor antagonist or V2-receptor antagonist was infused intravenously into the ovine fetus at 90% gestation. Angiotensin II (Ang II; 1.5 microg/kg) was then injected intracerebroventricularly into the chronically instrumented fetus. Ang II produced a significant increase in fetal systolic, diastolic, and mean arterial pressure adjusted to amniotic pressure (A-MAP). The enhanced fetal A-MAP was associated with intense c-fos expression in the central putative cardiovascular area: the paraventricular nuclei (PVN). Double labeling demonstrated that a number of the AVP-containing neurons in the PVN were expressing c-fos in response to central Ang II. Consistent with the activation of AVP neurons in the PVN, fetal plasma AVP was markedly enhanced. Fetal i.v. V1-receptor antagonist or V2-receptor antagonist had no effect on either fetal or maternal baseline BP. However, intracerebroventricular Ang II-increased BP was partially inhibited, although not completely abolished, by the V1-receptor blockade. In contrast, fetal i.v. infusion of V2-receptor antagonist had no effect on the pressor responses induced by central Ang II. The results suggest that the central Ang II-mediated pressor responses at the last third of gestation is mediated partially by the AVP mechanism via V1 not V2 receptors.

Role of angiotensin II AT1 receptor blockers in the treatment of arterial hypertension

Hypertension is a very common condition and the most important risk factor for the occurrence of cardiovascular events. The hyperactivity of the renin-angiotensin-aldosterone system is considered a cardiovascular risk factor in subjects with essential hypertension. The intrinsic vascular abnormality in which the renin-angiotensin-aldosterone system is clearly the milieu for the development of the pathologic changes in blood vessel walls is one of the causes of the establishment of hypertension. Many drugs with different mechanisms of action have been used for the treatment of hypertension and its vascular complications. Nevertheless, the utilities of many drugs are limited by their adverse effects. Continuous research in the search for new pharmacological agents for the treatment of hypertension has led to the development of angiotensin II receptor type AT1 blockers. The most important functions mediated by AT1 receptors include: vasoconstriction, induction of the production and release of aldosterone, renal reabsorption of sodium, cardiac cellular growth, proliferation of vascular smooth muscle, increase of peripheral noradrenergic action and the central activity of the sympathetic nervous system, stimulation of vasopressin release, and inhibition of renin release from the kidney. The angiotensin II receptor type AT1 blockers inhibit the interaction of angiotensin II with its AT1 receptor. These agents lower blood pressure without producing cough as a side effect since, unlike the angiotensin-converting enzyme inhibitors they do not influence the levels of bradykinin or substance P. Hence, these drugs are suitable for the treatment of hypertensive patients who require therapy with a drug blocking the effect of angiotensin-converting enzyme but cannot use angiotensin-converting enzyme inhibitors due to cough as a side effect.

Transforming growth factor beta in cardiovascular development and function

Transforming growth factor betas (TGFbetas) are pleiotropic cytokines involved in many biological processes. Genetic engineering and tissue explanation studies have revealed specific non-overlapping roles for TGFbeta ligands and their signaling molecules in development and in normal function of the cardiovascular system in the adult. In the embryo, TGFbetas appear to be involved in epithelial-mesenchymal transformations (EMT) during endocardial cushion formation, and in epicardial epithelial-mesenchymal transformations essential for coronary vasculature, ventricular myocardial development and compaction. In the adult, TGFbetas are involved in cardiac hypertrophy, vascular remodeling and regulation of the renal renin-angiotensin system. The evidence for TGFbeta activities during cardiovascular development and physiologic function will be given and areas which need further investigation will be discussed.

Altered renin synthesis and secretion in the kidneys of heterozygous mice with a null mutation in the TGF-beta(2) gene

Transforming growth factors beta (TGF-betas) are peptides involved in autocrine and paracrine control of cell growth and differentiation. In the kidneys, TGF-beta(2) has been shown to localize specifically in renin-producing cells in various conditions stimulating the renin response. To test in vivo the functional role of TGF-beta(2), the renin response was investigated in mice heterozygous for a null mutation of the TGF-beta(2) gene, which had a twofold reduction in the amount of TGF-beta(2) mRNA. Although the increase in plasma renin concentration triggered by dehydration was not different from wild-type mice, renal renin mRNA and protein levels were higher in mutant mice under hydrated or dehydrated conditions. These data suggest that TGF-beta(2) exerts an inhibitory effect on renin synthesis and release from the juxtaglomerular apparatuses.

Gene therapy of hypertensive vascular injury

Hypertension and vascular injury usually require prolonged treatment, and compliance is a key to efficacy for pharmacologically-based antihypertensive therapy. Gene therapy has the potential to be long lasting, with few side effects. Recent studies have provided promising results, in which hypertension can be treated by either augmentation of vasodilation or inhibition of vasoconstriction through gene transfer in experimental models. Gene transfer is also becoming useful for the study of mechanisms of physiologic and pathophysiologic conditions, including hypertension. In this mini-review, we summarize some recent studies in this area of research, and suggest some areas where progress is needed to advance the research toward gene therapy.