Renin in hypertension: how important as a risk factor?

An analysis of the plasma renin levels in relation to the incidence of severe cardiovascular complications (coronary thrombosis, stroke, ruptured aortic aneurysm) was made in 325 patients with various types of hypertension. These patients had one to four measurements of plasma renin activity taken under standard conditions of sodium intake and posture in the period 1963-68. The follow-up was 5 to 10 years in the four groups of hypertensive patients (essential hypertension, malignant hypertension, hypertension secondary to renal parenchymatous disease and hypertension caused by, or associated with, renal artery obstruction). For all 325 patients, the incidence of such complications was 23.6, 20.4 and 44.7% in the low, normal and high renin groups. These findings are at variance with the claim that renin constitutes a serious risk factor in hypertensive patients, especially if it is isolated from other parameters such as the level of diastolic pressure, the adequacy of kidney function, the effectiveness of dietary and drug management of hypertension, and especially the presence or absence of atherosclerotic lesions of the large vessels at the time of the renin determination.     

Plasma norepinephrine concentrations: No differences among normal volunteers and low,high or normal renin hypertensive patients

Plasma norepinephrine concentrations were measured by a sensitive radioenzymatic method in 51 patients with essential hypertension and 26 age-matched normal volunteers under conditions of ad libitum sodium intake, after volume expansion by infusion of saline intravenously, and after volume contraction by administration of furosemide orally. The hypertensive patients were classified into low, normal and high renin groups both by renin-sodium indexing and by their renin response to furosemide and saline administration. Plasma norepinephrine concentrations were similar among normal volunteers and patients with low, normal or high renin hypertension while the people were either recumbent or after they stood for 5 min. These and other results do not support the hypothesis that abnormal activity of the sympathetic nervous system accounts for the low or high renin values seen in many hypertensive patients.     

Prolonged pseudoaldosteronism induced by glycyrrhizin.

We describe the natural recovery from the aggravated hypertension, hypokalemia and suppression of the renin-aldosterone axis after the glycyrrhizin discontinuation in two mild hypertensive women aged 71 and 68 years, who had been administered 273 to 546 mg glycyrrhizin daily for 1.5 and 6 months, respectively, for the treatment of liver disease. About one month after the glycyrrhizin discontinuation, acceleration of hypertension, hypokalemia and suppression of the renin-aldosterone system still continued in both patients. At this stage, sodium restriction resulted in the normalization of blood pressure with weight loss and the subsequent sodium repletion produced a rapid increase in blood pressure to hypertensive levels observed before sodium restriction, with weight gain. Plasma renin activity and plasma aldosterone were low and did not respond to sodium restriction. Inappropriately excessive amounts of potassium were also excreted in the presence of hypokalemia. About one and a half months later, the improvements of aggravated hypertension, hypokalemia and suppressed renin-aldosterone system gradually occurred in both patients. Sodium restriction performed about three months later in case 2 no longer produced the changes in blood pressure and body weight. Plasma renin activity and plasma aldosterone responded subnormally to sodium restriction. These results demonstrate that both patients had a prolongation of the syndrome resembling primary aldosteronism except the low plasma aldosterone level about one month after the glycyrrhizin discontinuation. The possible mechanisms by which this prolongation was caused are discussed.     

Sodium outflow rate through lymphocyte cell membranes, serum levels of sodium, potassium, aldosterone, total catecholamines, 6-keto- PGF2alpha and plasma renin activity in patients with primary arterial hypertension treated with captopril]

Sodium ions outflow rate through lymphocyte membranes, serum sodium, potassium, aldosterone, total catecholamines and 6-keto-PGE alpha levels, and plasma renin activity were studied in patients with mild hypertension associated with low and hugh plasma renin activity treated with captopril in a single dose of 12.3 mg and after the treatment with daily doses of 12.5 mg and 25 mg for 3 days. It was found, that captopril in hypertensive patients with high plasma renin activity decreases both systolic and diastolic blood pressure, decelerates heart rate, and decreases serum total catecholamines and plasma renin activity. Sodium ions outflow rate and serum sodium, potassium, aldosterone, and 6-keto-PGE alpha remain unchanged. Captopril in hypertensive patients with low plasma renin activity. The remaining parameters are unchanged. Moreover, it was noted that serum 6-keto-PGE alpha levels are lower in hypertensive patients with low plasma renin activity.     

Increased aldosterone/renin quotient in obese hypertensive women: a novel role for low-density lipoproteins?

Obesity, especially visceral obesity, is strongly associated with arterial hypertension. Indeed, obesity hypertension has to be considered as the most common form of essential hypertension. However, the exact nature of the relationship between obesity and increased blood pressure remains poorly understood. Involvement of renin-independent mechanisms has been suggested in adrenal stimulation of aldosterone secretion in obese patients. This investigation examined the plasma levels of renin, aldosterone, insulin, and HDL and LDL in obese hypertensive and obese normotensive women. The group of hypertensive obese women showed significantly reduced plasma levels of renin and increased aldosterone/renin quotient (ARQ) compared to obese normotensive women. Plasma aldosterone levels were not significantly different between hypertensive and normotensive obese women. In addition, plasma levels of LDL-cholesterol in the hypertensive obese group were significantly increased in comparison to the obese normotensive group. No differences were observed in HDL-cholesterol or total cholesterol/HDL-C ratios between the two groups. We therefore examined the effect of LDL on angiotensin II-stimulated aldosterone release from human adrenocortical H295R cells. Treatment of adrenocortical cells with LDL led to a sensitization towards stimulation by angiotensin II, dramatically increasing angiotensin II-induced aldosterone production, so the increased aldosterone/renin ratio observed in the hypertensive group may be due to the enhanced LDL levels in these patients and/or other adipocyte-derived mineralocorticoid-stimulating factors.     

Relevance of Salt,Water, and Renin to Hypertension in Chronic Renal Failure

Blood pressure control was examined in 75 patients with end-stage renal failure treated by regular twice-weekly haemodialysis. Dietary sodium was restricted and extracellular fluid was removed by ultrafiltration until blood pressure was normal or signs of salt depletion were observed. Failure of these measures constituted an indication for nephrectomy. Of the 75 patients, 18 were never hypertensive, 46 had hypertension which could be corrected by salt and water depletion, and 11 had persistent hypertension which could not be controlled in this way. Nine of these 11 patients underwent bilateral nephrectomy; in each of the seven in whom the post operative result could be evaluated the blood pressure returned rapidly to normal.Plasma renin activity, measured in 34 subjects, was raised above normal in six out of nine patients whose blood pressure could not be controlled by salt and water depletion and in one of the 11 patients whose blood pressure could be so controlled, but was within the normal range in all nine normotensive patients. The mean level of plasma renin activity in the first group was significantly higher than that of each of the other two groups.There was a significant correlation between hypertension during dialysis and after transplantation, suggesting that, in addition to renin, there is a non-renal factor which predisposes certain patients to hypertension in the presence of salt and water excess.     

Reduction in extracellular superoxide dismutase activity in African-American patients with hypertension

Superoxide anions react with nitric oxide to form peroxynitrite and hence reduce the bioavailability of nitric oxide in the arteries. Extracellular superoxide dismutase (EC-SOD) is a major superoxide scavenger in human plasma and vascular tissues. The objective of this study is to assess whether essential hypertension is associated with an alteration in EC-SOD activity. In this report, blood samples were obtained from hypertensive (n=39) and normotensive (n=37) African-Americans. Plasma EC-SOD activity was measured using in-gel activity staining and spectrophotometric assays, EC-SOD protein level was measured using Western blotting, nitrotyrosine was measured using slot blotting, 8-isoprostane was measured with an enzyme immunoassay, and plasma copper and zinc concentrations were measured using an atomic absorption assay. Our data demonstrate that the copper, zinc, and plasma EC-SOD protein concentrations in the hypertensive and normotensive subjects are indistinguishable. Compared to normotensive controls, hypertensive patients have significantly reduced plasma EC-SOD activity. Plasma nitrotyrosine and 8-isoprostane levels are significantly higher in the hypertensive patients than in normotensive controls. Results from this study suggest that a reduction in EC-SOD activity in hypertensive patients is not due to a down-regulation of the SOD3 gene (encoding EC-SOD) or deficiency in mineral cofactors. Furthermore, the reduced EC-SOD activity might be at least partially responsible for the increased oxidative stress, as reflected by increased plasma nitrotyrosine and 8-isoprostane, in hypertensive subjects.     

Cerebrovascular Diseases in West Central India

Cerebral angiographic findings in ischaemic stroke are described and discussed in detail. Though the Indian patients studied had altogether different social customs, living standards, and dietary habits from Western people, the relative incidence of various cerebral vascular lesions did not differ significantly. Irrespective of the poor nutritional status of the patients, thrombosis associated with atherosclerosis was chiefly responsible for a non-embolic cerebral infarction. Atherothrombosis in the young normotensive persons not showing any evidence of arteritis, diabetes mellitus, or hypercholesterolaemia was also identified.The grave risks involved in cerebral angiography in cases of acute stroke are re-emphasized.As to prognosis, the nutritional status, the type and territory of an ictal lesion, and the blood levels of sugar and cholesterol had no significant influence on the immediate survival-after a non-embolic cerebral infarction. However, a significantly greater number of deaths were encountered in the hypertensive patients. Female patients and patients with a large cerebral infarction had a poor prognosis.     

Trimethyllysine,vascular risk factors and outcome in acute ischemic stroke (MARK–STROKE)

Trimethyllysine (TML) is involved in the generation of the pro-atherogenic metabolite trimethylamine-N-oxide (TMAO) by gut microbiota. In clinical studies, elevated TML levels predicted major adverse cardiovascular events (MACE) in patients with acute or stable coronary artery disease (CAD). In contrast to cardiovascular patients, the role of TML in patients with acute cerebral ischemia is unknown. Here, we evaluated circulating TML levels in 374 stroke patients from the prospective biomarkers in stroke (MARK–STROKE) study. Compared with 167 matched healthy controls, acute ischemic stroke patients had lower median TML plasma concentrations, i.e. 0.71 vs. 0.47 µmol/L (p < 0.001) and this difference persisted after adjusting for age and sex. TML plasma concentrations were associated with age, serum creatinine, glucose, cholesterol and lysine. Patients with prevalent arterial hypertension, atrial fibrillation or a history of myocardial infarction had increased TML levels, but this observation was not independent of age, sex and GFR. In 274 patients, follow-up data were available. During a median follow-up of 284 [25th–75th percentile: 198, 431] days, TML was not associated with incident MACE (stroke, myocardial infarction, death). In summary, our data suggests a different role of TML in acute ischemic stroke compared with CAD patients.

     

Urine dopamine in starving obese subjects

In seven obese female subjects undergoing a period of therapeutic starvation, the excretion of sodium, potassium and dopamine and plasma levels of renin and aldosterone were measured. Sodium excretion increased during starvation and was maximal on the 2nd day. The urinary excretion of dopamine was significantly higher on day 4 and it remained elevated till the end of the study. Plasma renin activity and plasma aldosterone levels were also higher on the 4th-6th days of starvation. These findings suggest that dopamine may not play a significant role in the natriuresis of starvation.     

Association of GNB3 C825T polymorphism with plasma electrolyte balance and susceptibility to hypertension

The role of G-protein activation in cardiovascular disorders is well-known. G-protein β3 subunit (GNB3) C825T polymorphism is associated with increased intracellular signal transduction. We investigated the role of the variant in plasma sodium and potassium concentrations and association with hypertension. 345 healthy controls and 455 patients with essential hypertension were enrolled. Plasma renin activity and aldosterone concentration were measured. The variant, typed by SNaPshot, was analyzed on an ABI Prism 3100 Genetic Analyzer and GeneScan. The TT genotype and T allele were over-represented in the patients (p < 0.001, p < 0.0001). Multiple-logistic regression disclosed that the risk of hypertension was significantly greater for TT (p < 0.0001, OR = 6.1, CI = 2.9-12.7). One-way ANOVA revealed that hypertensive T-allele carriers (CT+TT), compared to non-carriers (CC), had a greater body mass index (BMI), mean arterial pressure (MAP) and PAC (p = 0.01, p = 0.01, p < 0.0001, respectively); while the patients with 825TT risk genotype showed higher plasma sodium and lower potassium (p < 0.0001, each). The results strongly emphasize, not only the role of C825T polymorphism by the induction of increased G-protein activity and enhancement of Na/h exchangers, but also the association with higher plasma sodium and lower potassium levels, high BMI and susceptibility to hypertension.     

Polymorphism of catalase and glutathione peroxidase genes in macrovascular complications in patients with non-insulin-dependent diabetes mellitus and hypertension

Allelic and genotypic distributions of the polymorphic markers C1167T and Pro197Leu of the genes of catalase (CAT) and glutathione peroxidase (GPX1), respectively, were studied in patients with non-insulin-dependent diabetes mellitus (NIDDM) and hypertension without complications (the control group, n = 52) and with complications: myocardial infarction (MI, n = 53) or stroke (n = 50). No significant differences were found between complicated and uncomplicated patients with respect to the allelic or phenotypic distribution. Thus, there were no association between these polymorphic regions and either MI or stroke in hypertensive NIDDM patients.     

Myocardial renin is neither necessary nor sufficient to initiate or maintain ventricular hypertrophy

We tested the hypothesis that the myocardial renin-angiotensin system (RAS) is both necessary and sufficient to initiate and maintain all classes of ventricular hypertrophy. Myocardial and plasma renin and angiotensinogen were measured in rats during initiation and maintenance of ventricular hypertrophy associated with DOCA implants and 1% NaCl drinking water, with and without the AT(1) ANG II receptor blocker losartan. Additional groups of rats were given a low-sodium diet (0.04%) for 3 wk. Ventricular hypertrophy was initiated within 7 days and maintained for 35 days in DOCA-treated rats despite significantly low myocardial and plasma renin, normal or low myocardial and plasma angiotensinogen, or the presence of losartan. Furthermore, there was no ventricular hypertrophy in low-salt diet-fed animals despite increased myocardial and plasma renin levels and normal angiotensinogen levels. Therefore, the myocardial RAS is not necessary to initiate or maintain cardiac hypertrophy in DOCA-treated rats and is not sufficient to initiate cardiac hypertrophy in low-salt diet-fed rats. Additionally, myocardial renin and angiotensinogen were significantly correlated with corresponding plasma levels.     

Hemodynamic and endocrine parameters in the anesthetized cynomolgus monkey: a primate model

Hemodynamic and endocrine parameters were determined in nine anesthetized adult male cynomolgus monkeys. Simultaneous phasic and mean pressures were measured in the right atrium, pulmonary artery, and abdominal aorta. Intermittent pulmonary artery wedge pressures and mean cardiac output measured by the thermal dilution method were used to calculate stroke volume, systemic vascular resistance, and pulmonary vascular resistance. Plasma adrenocorticotropic hormone (ACTH), cortisol, and plasma renin activity were measured throughout the procedure. Technical aspects, data in the anesthetized monkey, and comparison with previously reported data are presented.     

Plasma Renin Activity and Blood Pressure in 89 Patients Receiving Maintenance Haemodialysis Therapy

Blood pressure, plasma renin activity, plasma sodium concentration, plasma potassium concentration, dietary sodium intake, and duration of dialysis have been measured under standard conditions in 89 patients on maintenance haemodialysis. No significant relation was found between plasma renin activity and blood pressure. Statistically significant correlations were found between plasma renin activity and plasma sodium concentration and between plasma renin activity and dietary sodium intake.Only one patient was found to have uncontrollable hypertension associated with a markedly raised plasma renin activity. Reasons are given for not performing bilateral nephrectomy in this patient. We believe the low incidence of uncontrollable hypertension and hyperreninaemia in our patients to be due to their slow introduction to haemodialysis, thus preventing violent swings in body weight, blood pressure, and renin secretion.Although plasma renin activity did fall with duration of dialysis, all 15 patients who have been on maintenance dialysis for longer than five years have normal levels.     

Prevention of cardiovascular complications in manifest arteriosclerosis by the use of Micristine]

A long-term clinical trial in micristin-treated patients suffering from organic arterial circulatory disturbances is reported. Problems of therapy monitoring by determination of the ASA level in plasma and of control of platelet aggregation are discussed. Acute cardiovascular complications (myocardial infarction, stroke, acute vascular occlusion, amputation and angiographically demonstrated progression) were observed. The observation time did not suffice to establish statistically significant differences between micristin therapy anticoagulant treatment and basic cardiovascular therapy. The results are suggestive of a more beneficial effect of anticoagulant treatment.     

Acute effects of angiotensin-converting enzyme inhibitor on erythrocyte sodium ion transport in essential hypertension.

The acute effects of angiotensin-converting enzyme inhibitor, captopril, on sodium ion transport systems were investigated in essential hypertensive and normotensive subjects. The passive sodium efflux through the erythrocyte membrane was significantly higher and erythrocyte sodium-potassium cotransport was lower in patients with essential hypertension when compared with normal subjects. However, sodium-potassium pump activity and sodium-lithium countertransport did not differ significantly between the hypertensive patients and the normal subjects. Immediately after captopril administration, erythrocyte passive sodium efflux and sodium-potassium cotransport returned to normal levels in the hypertensive subjects. Although the plasma renin activity and plasma aldosterone concentration were altered by captopril, they did not correlate with changes in any sodium transport system. These results suggest that the changes in sodium transport systems which occur immediately after captopril administration may contribute, at least in part, to its antihypertensive action.     

Impaired Lignocaine metabolism in patients with myocardial infarction and cardiac failure.

Plasma concentrations of lignocaine were measured during and after infusion of lignocaine at 1.4 mg/min for 36-46 hours in 12 patients with myocardial infarction and one patient with cardiac failure due to uncontrolled ventricular tachycardia. In six patients without cardiac failure the plasma concentrations of lignocaine rose progressively during the infusion and the mean lignocaine half life was 4.3 hours compared with 1.4 hours in healthy subjects. Mean plasma lignocaine concentrations were significantly higher in seven patients with cardiac failure, and concentrations also rose during the infusion and the half life was considerably prolonged to 10.2 hours. Lignocaine concentrations rose rapidly to toxic levels when cardiogenic shock developed in one patient and did not fall when the infusion was stopped. The mean plasma antipyrine half life was moderately prolonged (19.4 hours) in a larger group of patients with myocardial infarction and cardiac failure but returned to normal during convalescence (13.2 hours). The metabolism of lignocaine is grossly abnormal in patients with cardiac failure and cardiogenic shock after myocardial infarction.     

Plasma desmoplakin I biomarker of vascular recurrence after ischemic stroke

Stroke patients have a high risk of vascular recurrence. Biomarkers related to vascular recurrence, however, remain to be identified. The aim of the study was to identify, through proteomic analysis, plasma biomarkers associated with vascular recurrence within one year after the first ischemic stroke. This is a substudy (n = 134) of a large prospective multicenter study of post-stroke patients with an ischemic stroke. Plasma samples were obtained at inclusion. Among the identified proteins, only plasma levels of desmoplakin I were associated with protection against a new vascular event (Odds ratio: 0.64; 95% CI: 0.46-0.89; p = 0.009) after adjustment for hypercholesterolemia, statins and previous atherothrombotic stroke subtype. A greater number of patients without vascular recurrence had been treated with statins within three months of the recent ischemic stroke. Only patients who had been taking statins for 3 months after the ischemic stroke and did not suffer vascular recurrence over a follow-up year, have higher levels of desmoplakin I at the time of inclusion (Odds ratio 0.49; 95% CI: 0.28-0.86; p = 0.013). Increased desmoplakin I levels, determined within 1-3 months of the first ischemic stroke, could be a biomarker for statin responsiveness against a new vascular event in post-ischemic stroke patients taking statins early (1-3 months) after the ischemic stroke.     

Structure-based design of aliskiren,a novel orally effective renin inhibitor

Hypertension is a major risk factor for cardiovascular diseases such as stroke, myocardial infarction, and heart failure, the leading causes of death in the Western world. Inhibitors of the renin-angiotensin system (RAS) have proven to be successful treatments for hypertension. As renin specifically catalyses the rate-limiting step of the RAS, it represents the optimal target for RAS inhibition. Several peptide-like renin inhibitors have been synthesized previously, but poor pharmacokinetic properties meant that these compounds were not clinically useful. We employed a combination of molecular modelling and crystallographic structure analysis to design renin inhibitors lacking the extended peptide-like backbone of earlier inhibitors, for improved pharmacokinetic properties. This led to the discovery of aliskiren, a highly potent and selective inhibitor of human renin in vitro, and in vivo; once-daily oral doses of aliskiren inhibit renin and lower blood pressure in sodium-depleted marmosets and hypertensive human patients. Aliskiren represents the first in a novel class of renin inhibitors with the potential for treatment of hypertension and related cardiovascular diseases.