Hyperinsulinemia and the aldosterone and pressor responses to angiotensin II

Cardiovascular Sequelae of Bronchopulmonary Dysplasia in Preterm Neonates Born before 32 Weeks of Gestational Age: Impact of Associated Pulmonary and Systemic Hypertension

Bronchopulmonary dysplasia (BPD) remains the most common respiratory disorder of prematurity for infants born before 32 weeks of gestational age (GA). Early and prolonged exposure to chronic hypoxia and inflammation induces pulmonary hypertension (PH) with the characteristic features of a reduced number and increased muscularisation of the pulmonary arteries resulting in an increase in the pulmonary vascular resistance (PVR) and a fall in their compliance. BPD and BPD-associated pulmonary hypertension (BPD-PH) together with systemic hypertension (sHTN) are chronic cardiopulmonary disorders which result in an increased mortality and long-term problems for these infants. Previous studies have predominantly focused on the pulmonary circulation (right ventricle and its function) and developing management strategies accordingly for BPD-PH. However, recent work has drawn attention to the importance of the left-sided cardiac function and its impact on BPD in a subset of infants arising from a unique pathophysiology termed postcapillary PH. BPD infants may have a mechanistic link arising from chronic inflammation, cytokines, oxidative stress, catecholamines, and renin-angiotensin system activation along with systemic arterial stiffness, all of which contribute to the development of BPD-sHTN. The focus for the treatment of BPD-PH has been improvement of the right heart function through pulmonary vasodilators. BPD-sHTN and a subset of postcapillary PH may benefit from afterload reducing agents such as angiotensin converting enzyme inhibitors. Preterm infants with BPD-PH are at risk of later cardiac and respiratory morbidities as young adults. This paper reviews the current knowledge of the pathophysiology, diagnosis, and treatment of BPD-PH and BPD-sHTN. Current knowledge gaps and emerging new therapies will also be discussed.

Effect of the interaction between the visceral-to-subcutaneous fat ratio and aldosterone on cardiac function in patients with primary aldosteronism

Primary aldosteronism is the most frequent secondary hypertensive disease and is characterized by an elevated risk for cardiovascular disease. The current standard treatments are adrenalectomy and/or administration of mineralocorticoid receptor blockers, both of which are effective at ameliorating hypertension via intervention for hyperaldosteronism. However, both of these approaches have side effects and contraindications, and mineralocorticoid receptor blockers also have limited preventive efficacy against cardiovascular events. Recently, in vitro experiments have shown that aldosterone regulation is closely related to abdominal fat accumulation and that there is crosstalk between aldosterone and visceral fat tissue accumulation. We previously reported that this interaction was clinically significant in renal dysfunction; however, its effects on the heart remain unclear. Here, we analyzed data from 49 patients with primary aldosteronism and 29 patients with essential hypertension to examine the potential effect of the interaction between the ratio of visceral-to-subcutaneous fat tissue volume and the plasma aldosterone concentration on echocardiographic indices, including the tissue Doppler-derived E/e' ratio. A significant interaction was found in patients with primary aldosteronism (p < 0.05), indicating that patients with the combination of a high plasma aldosterone concentration and high visceral-to-subcutaneous fat ratio show an increased E/e' ratio, which is a well-known risk factor for future cardiovascular events. Our results confirm the clinical importance of the interaction between aldosterone and abdominal fat tissue, suggesting that an improvement in the visceral-to-subcutaneous fat ratio may be synergistically and complementarily effective in reducing the elevated risk of cardiovascular disease in patients with primary aldosteronism when combined with conventional therapies for reducing aldosterone activity. A significant effect of the interaction between plasma aldosterone concentration and the visceral-to-subcutaneous fat ratio on the tissue Doppler-derived E/e' ratio in patients with primary aldosteronism.

New Strategies for Volume Control in Patients with Diabetes Mellitus, a Narrative Review

Sodium is reabsorbed all along the renal tubules. The positive impacts of sodium-glucose cotransporter-2 inhibitors (SGLT2i), angiotensin receptor neprilysin inhibitor (ARNI) and mineralocorticoid receptor antagonists (MRA) on hard renal and/or cardiac endpoints calls for the role of diuretics in nephroprotection and cardioprotection in patients with diabetes mellitus to be reviewed. Here, we review: (a) the mechanisms of action of the available natriuretics; (b) the physiological adaptations to chronic loop diuretic usage that lead to increased sodium reabsorption in the proximal and distal convoluted tubules; (c) the physiology of sodium retention in patients with diabetes mellitus; and (d) the mechanisms of aldosterone breakthrough. We show the rationale for combined diuretics to target not only the loop of Henle, but also the proximal and distal convoluted tubules. Indeed, higher residual proteinuria in patients treated with renin-angiotensin-aldosterone system (RAAS) blockers portends poorer renal and cardiovascular outcomes. Diuretics are known to optimize the reduction of proteinuria, in addition to RAAS blockers, but may favor aldosterone breakthrough in the absence of MRA. The aim of our study is to support a combined diuretics strategy to improve the management of patients with diabetes mellitus and chronic kidney disease or heart failure.

Sirtuins-Mediated System-Level Regulation of Mammalian Tissues at the Interface between Metabolism and Cell Cycle: A Systematic Review

Sirtuins are a family of highly conserved NAD+-dependent proteins and this dependency links Sirtuins directly to metabolism. Sirtuins' activity has been shown to extend the lifespan of several organisms and mainly through the post-translational modification of their many target proteins, with deacetylation being the most common modification. The seven mammalian Sirtuins, SIRT1 through SIRT7, have been implicated in regulating physiological responses to metabolism and stress by acting as nutrient sensors, linking environmental and nutrient signals to mammalian metabolic homeostasis. Furthermore, mammalian Sirtuins have been implicated in playing major roles in mammalian pathophysiological conditions such as inflammation, obesity and cancer. Mammalian Sirtuins are expressed heterogeneously among different organs and tissues, and the same holds true for their substrates. Thus, the function of mammalian Sirtuins together with their substrates is expected to vary among tissues. Any therapy depending on Sirtuins could therefore have different local as well as systemic effects. Here, an introduction to processes relevant for the actions of Sirtuins, such as metabolism and cell cycle, will be followed by reasoning on the system-level function of Sirtuins and their substrates in different mammalian tissues. Their involvement in the healthy metabolism and metabolic disorders will be reviewed and critically discussed.

Tissue sodium content in patients with type 2 diabetes mellitus

BACKGROUND

Tissue sodium content by ²³Na magnetic resonance imaging (MRI) has been found to be increased in arterial hypertension. We analyzed whether tissue sodium content is increased in patients with type-2 diabetes (T2DM).

METHODS

Patients with T2DM were compared to those with primary hypertension. Patients with T2DM were off any antidiabetic and hypertensive patients off any antihypertensive therapy for at least 4 weeks. Skin and muscle sodium content was assessed non-invasively with a 3.0 T clinical MRI system (Magnetom Verio, Siemens Health Care, Erlangen, Germany) in each patient.

RESULTS

In patients with T2DM (N = 59) we observed significantly greater muscle sodium content (diabetes: 20.6 ± 3.5 vs hypertension: 16.3 ± 2.5 mmol/l, p < 0.001) and skin sodium content (diabetes: 24.5 ± 7.2 vs hypertension: 20.6 ± 5.7 mmol/l, p = 0.01) than in those with primary hypertension (N = 33). When potential confounders (age, body mass index, gender, systolic and diastolic blood pressure, estimated glomerular filtration rate) were entered in a covariance analysis, both skin sodium content (p = 0.037) and muscle sodium content (p < 0.001) were still clearly elevated.

CONCLUSION

Patients with T2DM have greater skin and muscle sodium content. These are the first known data to demonstrate increased tissue sodium content in patients with T2DM, measured by ²³Na magnetic resonance imaging. Since tissue sodium content is related to organ damage, therapeutic intervention should aim at reducing tissue sodium content.

ACE inhibition for severe bronchopulmonary dysplasia - an approach based on physiology

Premature infants have a high incidence of bronchopulmonary dysplasia (BPD). Systemic hypertension, arterial thickness and stiffness, and increased systemic afterload may all contribute to BPD pathophysiology by altering left ventricular (LV) function and increasing pulmonary venous congestion by lowering end-diastolic compliance. This case series studied the usefulness of angiotensin-converting enzyme (ACE) inhibition by measuring clinical and echocardiographic improvements in six consecutive infants with "severe" BPD unresponsive to conventional therapy. The range of gestation and birthweight were 23-29 weeks and 505-814 g, respectively. All required mechanical ventilation (including high-frequency oscillation) and all but one were administered postnatal corticosteroids. Other treatments including sildenafil and diuretics made no clinical improvements. Captopril was started for systemic hypertension after cardiac and vascular ultrasounds which were repeated 5 weeks later. A significant reduction in oxygen (55 ± 25 to 29 ± 3%, two-tailed P = 0.03) and ventilator requirements, and improved cardiovascular parameters were noted. This included a trend toward reduction in aorta intima media thickness [840 ± 94 to 740 ± 83 μm, P = 0.07] and an increased pulsatile diameter [36 ± 14 to 63 ± 25 μm, P = 0.04]). Improvements were observed for both systolic (increased LV output, 188 ± 13 to 208 ± 13 mL/kg/min, P = 0.046 and mean velocity of circumferential fiber shortening, 1.6 ± 0.2 to 2.5 ± 0.3 [circ/sec], P = 0.0004) and diastolic (decreased isovolumic relaxation time, 69.6 ± 8.2 to 59.4 ± 5 msec, P = 0.044) function which was accompanied by increased pulmonary vein flow. Right ventricular output increased accompanied by a significant lowering of pulmonary vascular resistance. These findings suggest that improving respiratory and cardiac indices (especially diastolic function) warrants further exploration of ACE inhibition in BPD infants unresponsive to conventional therapy.

Is high waist circumference and body weight associated with high blood pressure in Iranian primary school children?

INTRODUCTION AND OBJECTIVES

The prevalence of overweight, abdominal obesity and hypertension among children has increased worldwide including Iran over several decades. We carried out a study to provide current estimates of the prevalence and trends of hypertension, overweight and obesity along with the relationship between weight status and hypertension in Iranian school-children.

METHOD

This study was carried out among 1184 fifth-grade students, whose ages ranged from 11 to 14 years. Body weight, body mass index (BMI), height and waist circumference (WC), systolic (SBP) and diastolic blood pressure (DBP) were measured.

RESULTS

22.04 and 5.32 % of students were overweight and obese, respectively. The prevalence of overweight and obesity was significantly higher among girls than boys (all p = 0.02), whereas the prevalence of hypertension was significantly higher in boys than girls (p = 0.001). Although 27 % of boys and 24.32 % of girls had abdominal obesity, no significant associations were reported between abdominal obesity and sex (p = 0.12). The prevalence of hypertension in children with normal weight, overweight and obesity, was 3, 9.7 and 17.8 %, respectively (p < 0.01). We have obtained that the mean values of weight and WC were significantly higher in boys than girls. Based on linear regression, every 1 cm increase in abdominal circumference leads to an estimated DBP and SBP increase of 0.173 and 0.164 mmHg, respectively (p < 0.05).

CONCLUSIONS

This study showed a high prevalence of hypertension and obesity in a school-based population in Tehran, Iran, in which the prevalence of hypertension was significantly and positively correlated with weight and WC.

Review: Renin-angiotensin-aldosterone system intervention in the cardiometabolic syndrome and cardio-renal protection

The metabolic syndrome, also known as the cardiometabolic syndrome (CMS), is a state of metabolic and vascular dysregulation that is associated with activation of the renin-angiotensin-aldosterone system (RAAS). Clinical components of the CMS include central or visceral obesity, hypertension (HTN), dyslipidemia, insulin resistance/hyperinsulinemia, and microalbuminuria that collectively convey increases in oxidative stress, inflammation, and subsequent endothelial dysfunction. The cardio-renal inflammation and oxidative stress enhanced in the CMS increases the risk for cardiovascular disease (CVD) and renal disease end-points such as stroke, congestive heart failure, and chronic kidney disease (CKD). The development of proteinuria is known to herald progressive kidney disease (e.g. CKD) and both are now well accepted as CVD risk factors. Evidence suggests a role for visceral obesity, insulin resistance/hyperinsulinemia, HTN, and other components of the CMS lead to an increased risk for proteinuria and progressive loss of renal function. Intervention with agents that block the RAAS (e.g. ACE inhibitors and Angiotensin type 1 receptor blockers) have been shown to reduce proteinuria, CKD progression, and CVD events. Herein, we will examine the relationship between RAAS intervention and reductions in CKD and CVD events.

The incidental relationship between serum ferritin levels and hypertension

BACKGROUND AND OBJECTIVE

Although several studies have shown an association between ferritin level and hypertension, only a few studies have investigated the longitudinal relationship between them. Thus, we evaluated the incidental risk for hypertension according to baseline ferritin level.

PATIENTS AND METHODS

A total of 7104 healthy Korean men matched by a propensity score, who had participated in a medical health check-up program in 2005, were followed up from 2005 to 2010. They were divided into four groups according to baseline serum ferritin level (first quartile-fourth quartile). The incidence of hypertension was compared among the four groups, and the Cox-proportional hazard model was used to assess whether the development of hypertension was associated with higher baseline serum ferritin level.

RESULTS

A total of 1252 (17.6%) cases had newly developed hypertension during the 26,339.5 person-years of follow-up between 2006 and 2010. The adjusted hazard ratios (HRs) (95% confidence intervals, CIs) for incident hypertension were 1.00 (reference), 1.09 (0.91-1.30), 1.21 (1.01-1.45) and 1.28 (1.07-1.52), respectively (P for trend=0.003) through the quartiles of serum ferritin levels, respectively, after adjusting for multiple confounders. For the log-transformed serum ferritin levels as a continuous variable, adjusted HRs and 95% CIs for HTN were 1.15 (1.02-1.29).

CONCLUSIONS

Elevated serum ferritin level was independently associated with the incidental risk for hypertension in Korean men. This finding suggests the value of elevated ferritin level as an early predictor of hypertension.

Hypertension and left ventricular hypertrophy in autosomal dominant polycystic kidney disease

Hypertension is a common problem in patients with autosomal dominant polycystic kidney disease affecting both renal and patient survival. Activation of the renin-angiotensin-aldosterone system due to cyst expansion and local renal ischemia has been proposed to play an important role in the development of hypertension in autosomal dominant polycystic kidney disease. Left ventricular hypertrophy, a major cardiovascular risk factor, is also common in patients with autosomal dominant polycystic kidney disease. Both hypertension and the activation of the renin-angiotensin-aldosterone system play a role in the development of left ventricular hypertrophy in these patients. Prospective randomized results indicate that aggressive control of blood pressure is important for the optimal reversal of left ventricular hypertrophy, thereby diminishing a major risk factor for cardiovascular morbidity and mortality of patients with autosomal dominant polycystic kidney disease. There is also substantial epidemiological support for aggressive control of blood pressure in slowing renal disease progression in autosomal dominant polycystic kidney disease patients. Blockade of the renin-angiotensin-aldosterone system should be the initial approach in the treatment of hypertension in these patients.

Hypertension in metabolic syndrome: vascular pathophysiology

METABOLIC SYNDROME IS A CLUSTER OF METABOLIC AND CARDIOVASCULAR SYMPTOMS: insulin resistance (IR), obesity, dyslipemia. Hypertension and vascular disorders are central to this syndrome. After a brief historical review, we discuss the role of sympathetic tone. Subsequently, we examine the link between endothelial dysfunction and IR. NO is involved in the insulin-elicited capillary vasodilatation. The insulin-signaling pathways causing NO release are different to the classical. There is a vasodilatory pathway with activation of NO synthase through Akt, and a vasoconstrictor pathway that involves the release of endothelin-1 via MAPK. IR is associated with an imbalance between both pathways in favour of the vasoconstrictor one. We also consider the link between hypertension and IR: the insulin hypothesis of hypertension. Next we discuss the importance of perivascular adipose tissue and the role of adipokines that possess vasoactive properties. Finally, animal models used in the study of vascular function of metabolic syndrome are reviewed. In particular, the Zucker fatty rat and the spontaneously hypertensive obese rat (SHROB). This one suffers macro- and microvascular malfunction due to a failure in the NO system and an abnormally high release of vasoconstrictor prostaglandins, all this alleviated with glitazones used for metabolic syndrome therapy.

Oxidative stress in the cardiorenal metabolic syndrome

Excess visceral adiposity contributes to inappropriate activation of the renin-angiotensin-aldosterone system despite a state of volume expansion and of salt retention that contributes to subclinical elevations of pro-oxidant mechanisms. These adverse effects are mediated by excess generation of reactive oxygen species (ROS) and diminished antioxidant defense mechanisms. Excess tissue (i.e., skeletal muscle, liver, heart) free oxygen radicals contribute to impairments in the insulin-dependent metabolic signaling pathways that regulate glucose utilization/disposal and systemic insulin sensitivity. The generation of ROS is required for normal cell signaling and physiological responses. It is a loss of redox homeostasis that results in a proinflammatory/profibrotic milieu that promotes impairments in insulin metabolic signaling, reduced endothelial-mediated vasorelaxation, and associated cardiovascular and renal structural and functional abnormalities. These maladaptive processes are increasingly recognized as important in the progression of hypertension in the cardiorenal metabolic phenotype. There is increasing evidence to support a critical role for Ang II signaling through the AT(1)R and aldosterone actions through the MR in conjunction with an altered redox-mediating impaired endothelial, cardiac and renal function in this metabolic phenotype. There are emerging clinical data that indicate that therapies that target the renin angiotensin-aldosterone system (RAAS) also attenuate oxidative stress, and improve endothelial, cardiac and renal functions, which collectively contribute to reductions in hypertension.

Salt sensitivity is associated with insulin resistance, sympathetic overactivity, and decreased suppression of circulating renin activity in lean patients with essential hypertension

BACKGROUND

The mechanisms by which a derangement of glucose metabolism causes high blood pressure are not fully understood.

OBJECTIVES

This study aimed to clarify the relation between salt sensitivity of blood pressure and insulin resistance, which are important subcharacteristics of hypertension and impaired glucose metabolism, respectively. Effects on the renin-angiotensin and sympathetic nervous systems were also studied.

DESIGN

The state of glucose metabolism was assessed by a hyperinsulinemic euglycemic glucose clamp technique and a 75-g oral-glucose-tolerance test in 24 essential hypertensive patients who were lean and without diabetes or chronic kidney disease. The subjects were classified as salt-sensitive or salt-resistant on the basis of the difference (Delta mean blood pressure > or =5%) between 24-h ambulatory blood pressure monitoring results on the seventh day of low-salt (34 mmol/d) and high-salt (252 mmol/d) diets. Urine and blood samples were collected for analyses.

RESULTS

There was a robust inverse relation between the glucose infusion rate (GIR) and the salt sensitivity index. The GIR correlated directly with the change in urinary sodium excretion and was inversely related to the change in hematocrit when the salt diet was changed from low to high, which is indicative of salt and fluid retention in salt-sensitive subjects. The GIR also showed an inverse correlation compared with the changes in urinary norepinephrine excretion, plasma renin activity, and plasma aldosterone concentration.

CONCLUSIONS

Salt sensitivity of blood pressure is strongly associated with insulin resistance in lean, essential hypertensive patients. Hyperinsulinemia, sympathetic overactivation, and reduced suppression of the renin-angiotensin system may play a role in this relation.

Type 2 diabetic patients with resistant hypertension should be screened for primary aldosteronism

BP control in diabetic patients is often poor. The contribution of secondary hypertension due to undiagnosed PA in hypertensive type 2 diabetic patients is not well studied. We prospectively screened 100 consecutive Asian type 2 diabetic patients with difficult-to-control or resistant hypertension for PA. PAC (pmol/L) to PRA (ng/mL/h) ratio was measured; those with PAC-to-PRA ratio >550 (corresponding PAC >415) underwent intravenous 0.9% SLT. Patients with PAC >/=140 following SLT had CT adrenals and bilateral AVS. Thirteen patients (13%) were confirmed to have PA, and all had resistant hypertension. Eight had a surgically correctable form of PA. Patients with PA had higher mean (SD) systolic [159.0 (10.6) vs. 146.0 (10.7) mmHg, p=0.001] and diastolic BP [94.6 (6.0) vs. 87.6 (5.9) mmHg, p=0.001], lower serum potassium [3.5 (0.6) vs. 4.3 (0.5) mmol/L, p=0.001], and higher PAC [679.3 (291.0) vs. 239.5 (169.4) pmol/L, p=0.001]. Identification and institution of definitive treatment for PA resulted in better BP control and in a reduction in the use of antihypertensive medications. Our findings demonstrate a high prevalence of PA in type 2 diabetic patients with resistant hypertension. Systematic screening for PA in this select group is recommended, as targeted treatment improves BP control.

Cardiovascular abnormalities in autosomal-dominant polycystic kidney disease

Cardiovascular problems are a major cause of morbidity and mortality in patients with autosomal-dominant polycystic kidney disease (ADPKD). Hypertension is a common early symptom of ADPKD, and occurs in approximately 60% of patients before renal function has become impaired. Hypertension is associated with an increased rate of progression to end-stage renal disease and is the most important potentially treatable variable in ADPKD. Left ventricular hypertrophy, which is a powerful, independent risk factor for cardiovascular morbidity and mortality, also occurs frequently in patients with ADPKD. Both hypertension and left ventricular hypertrophy have important roles in cardiovascular complications in these individuals. Moreover, biventricular diastolic dysfunction, endothelial dysfunction, increased carotid intima-media thickness, and impaired coronary flow velocity reserve are present even in young patients with ADPKD who have normal blood pressure and well-preserved renal function. These findings suggest that cardiovascular involvement starts very early in the course of ADPKD. Intracranial and extracranial aneurysms and cardiac valvular defects are other potential cardiovascular problems in patients with ADPKD. Early diagnosis and treatment of hypertension, with drugs that block the renin-angiotensin-aldosterone system, has the potential to decrease the cardiovascular complications and slow the progression of renal disease in ADPKD.

The role of renin-angiotensin-aldosterone system-based therapy in diabetes prevention and cardiovascular and renal protection

Hypertension increases the risk of type 2 diabetes mellitus (T2DM) and cardiovascular disease. In addition to lowering blood pressure, blockade of the renin-angiotensin-aldosterone system (RAAS) reduces the risk of new-onset T2DM and offers renal protection. Using a MEDLINE search, we identified multiple trials that reported the incidence of T2DM in patients taking inhibitors of RAAS. In this review, we will discuss the RAAS as a potential target in diabetes prevention and the mechanisms through which inhibitors of this system achieve such an important effect. We will also shed light on the beneficial cardiovascular and renal effects of RAAS blockade. Although multiple studies have demonstrated that inhibitors of RAAS, especially angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, can reduce the incidence of T2DM, randomized controlled studies are still needed to further elucidate their exact role in diabetes prevention.

Low-dose spironolactone reduces reactive oxygen species generation and improves insulin-stimulated glucose transport in skeletal muscle in the TG(mRen2)27 rat

Renin-angiotensin-aldosterone system (RAAS) activation mediates increases in reactive oxygen species (ROS) and impaired insulin signaling. The transgenic Ren2 rat manifests increased tissue renin-angiotensin system activity, elevated serum aldosterone, hypertension, and insulin resistance. To explore the role of aldosterone in the pathogenesis of insulin resistance, we investigated the impact of in vivo treatment with a mineralocorticoid receptor (MR) antagonist on insulin sensitivity in Ren2 and aged-matched Sprague-Dawley (SD) control rats. Both groups (age 6-8 wk) were implanted with subcutaneous time-release pellets containing spironolactone (0.24 mg/day) or placebo over 21 days. Systolic blood pressure (SBP) and intraperitoneal glucose tolerance test were determined. Soleus muscle insulin receptor substrate-1 (IRS-1), tyrosine phosphorylated IRS-1, protein kinase B (Akt) phosphorylation, GLUT4 levels, and insulin-stimulated 2-deoxyglucose uptake were evaluated in relation to NADPH subunit expression/oxidase activity and ROS production (chemiluminescence and 4-hydroxy-2-nonenal immunostaining). Along with increased soleus muscle NADPH oxidase activity and ROS, there was systemic insulin resistance and reduced muscle IRS-1 tyrosine phosphorylation, Akt phosphorylation/activation, and GLUT4 expression in the Ren2 group (each P < 0.05). Despite not decreasing blood pressure, low-dose spironolactone treatment improved soleus muscle insulin signaling parameters and systemic insulin sensitivity in concert with reductions in NADPH oxidase subunit expression/activity and ROS production (each P < 0.05). Our findings suggest that aldosterone contributes to insulin resistance in the transgenic Ren2, in part, by increasing NADPH oxidase activity in skeletal muscle tissue.

Bayesian meta-analysis of tissue angiotensin-converting enzyme inhibitors for reduction of adverse cardiovascular events in patients with diabetes mellitus and preserved left ventricular function

The role of angiotensin-converting enzyme (ACE) inhibitors in diabetic patients with preserved ventricular function is uncertain. Tissue ACE inhibitors have been defined by increased lipophilicity and structural characteristics that result in greater tissue-specific ACE binding when compared with plasma ACE inhibitors. A Bayesian meta-analysis of randomized trials was conducted to evaluate tissue ACE inhibitors in prevention of cardiovascular disease among patients with diabetes mellitus and preserved left ventricular function. Four trials were selected that evaluated 2 different ACE inhibitors and included 10,328 patients (43,517 patient-years). The Perindopril Substudy in Coronary Artery Disease and Diabetes (PERSUADE) and the Perindopril Protection Against Recurrent Stroke Study (PROGRESS) compared the effects of perindopril vs a placebo, and the Heart Outcomes Prevention Evaluation (HOPE) and the Non-Insulin-Dependent Diabetes, Hypertension, Microalbuminuria, Proteinuria, Cardiovascular Events, and Ramipril (DIABHYCAR) study investigated the impact of ramipril vs a placebo. Bayesian meta-analysis of sequential trials and sensitivity analysis of therapeutic response were subsequently computed. Bayesian meta-analysis determined reduced risk of cardiovascular mortality (PB=.991), myocardial infarction (PB=.999), and the need for invasive coronary revascularization (PB=.995) when compared with placebo. Total mortality was also decreased (PB=.967), while the risk of stroke (PB=.907) and hospitalization for heart failure (PB=.923) were impacted. Bayesian meta-analysis of randomized trials suggests that tissue ACE inhibitors decrease the probability that diabetic patients with preserved left ventricular function will experience myocardial infarctions and cardiovascular death and reduce overall mortality.

Eplerenone improves prognosis in postmyocardial infarction diabetic patients with heart failure: results from EPHESUS

BACKGROUND

The Epleronone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival Study (EPHESUS) trial demonstrated that selective aldosterone blockade with eplerenone significantly reduced total mortality by 15%, combined cardiovascular (CV) mortality/CV hospitalization by 13%, CV mortality by 17% and sudden cardiac death by 21%, vs. placebo when added to standard care in patients with left ventricular systolic dysfunction (LVSD) and signs of congestive heart failure (CHF) following acute myocardial infarction (AMI). We retrospectively evaluated the effect of eplerenone vs. placebo in a subset of 1483 diabetic patients with LVSD and signs of CHF following AMI.

METHODS

Diabetic status was determined from medical histories at screening. Analyses were based on time to first occurrence of an event. Results were based on a Cox's proportional hazards regression model stratified by region with treatment, subgroup and treatment-by-subgroup interaction as factors. The 95% confidence intervals for the risk ratios were based on the Wald's test.

RESULTS

Treatment with eplerenone in diabetic patients with CHF following AMI reduced the risk of the primary endpoint, a composite of CV mortality or CV hospitalization, by 17% (p = 0.031). The absolute risk reduction of the primary endpoint was greater in the diabetic cohort (5.1%) than in the non-diabetic cohort (3%). Hyperkalaemia occurred more often with eplerenone than with placebo (5.6 vs. 3%, p = 0.015). Among the diabetic cohorts, the prespecified endpoint of 'any CV disorder' occurred in 28% of the eplerenone group and 35% of the placebo group (p = 0.007).

CONCLUSION

Eplerenone treatment may reduce adverse CV events in diabetic patients with LVSD and signs of CHF following AMI.

Fat intake and cardiovascular response

High dietary fat intake is a major risk factor for the development of obesity, which is frequently associated with diseases such as hypertension and diabetes and thus accelerated atherosclerosis. Angiotensin II and endothelin-1 are powerful growth factors and vasoconstrictors implicated in regulating vascular tone, vascular structure, and inflammation. Reduced bioactivity of nitric oxide and increased formation of reactive oxygen species (ROS) have been associated with obesity and high dietary fat intake. This article reviews the effects of high-fat diet on vascular functional changes in rodents and humans. Changes include alterations in vasoconstrictor function and receptor expression, and modulators of endothelium-dependent vascular tone (eg, nitric oxide- or endothelium-dependent contracting factor-mediated responses). Novel vasodilator effects of ROS and the anatomic heterogeneity of vascular responses are discussed. The beneficial effects of vasoactive mediators on vascular function could play a role for susceptibility to obesity-dependent hypertension, which is present in many, but not all, obese patients.

Hyperinsulinemic rats are normotensive but sensitized to angiotensin II

The effect of insulin on blood pressure (BP) is debated, and an involvement of an activated renin-angiotensin aldosterone system (RAAS) has been suggested. We studied the effect of chronic insulin infusion on telemetry BP and assessed sympathetic activity and dependence of the RAAS. Female Sprague-Dawley rats received insulin (2 units/day, INS group, n = 12) or insulin combined with losartan (30 mg·kg−1·day−1, INS+LOS group, n = 10), the angiotensin II receptor antagonist, for 6 wk. Losartan-treated (LOS group, n = 10) and untreated rats served as controls ( n = 11). We used telemetry to measure BP and heart rate (HR), and acute ganglion blockade and air-jet stress to investigate possible control of BP by the sympathetic nervous system. In addition, we used myograph technique to study vascular function ex vivo. The INS and INS+LOS groups developed euglycemic hyperinsulinemia. Insulin did not affect BP but increased HR (27 beats/min on average). Ganglion blockade reduced mean arterial pressure (MAP) similarly in all groups. Air-jet stress did not increase sympathetic reactivity but rather revealed possible blunting of the stress response in hyperinsulinemia. Chronic losartan markedly reduced 24-h-MAP in the INS+LOS group (−38 ± 1 mmHg P < 0.001) compared with the LOS group (−18 ± 1 mmHg, P ≤ 0.05). While insulin did not affect vascular function per se, losartan improved endothelial function in the aorta of insulin-treated rats. Our results raise doubt regarding the role of hyperinsulinemia in hypertension. Moreover, we found no evidence that insulin affects sympathetic nervous system activity. However, chronic losartan treatment revealed an important interaction between insulin and RAAS in BP control.

Developments in the management of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent life- threatening, hereditary disease. ADPKD is more common than sickle cell anemia, cystic fibrosis, muscular dystrophy, hemophilia, Down's syndrome, and Huntington's disease combined. ADPKD is a multisystemic disorder characterized by the progressive development of renal cysts and marked renal enlargement. Structural and functional renal deterioration occurs in ADPKD patients and is the fourth leading cause of end-stage renal disease (ESRD) in adults. Aside from the renal manifestations, extrarenal structural abnormalities, such as liver cysts, cardiovascular abnormalities, and intracranial aneurysms may lead to morbidity and mortality. Recent studies have identified prognostic factors for progressive renal impairment including gender, race, age, proteinuria, hematuria, hypertension and increased left ventricular mass index (LVMI). Early diagnosis and better understanding of the pathophysiology of the disease provides the opportunity to aggressivly treat hypertension with renin-angiotensin-aldosterone system inhibitors and thereby potentially reduce LVMI, prevent cardiovascular morbidity and mortality and slow progression of the renal disease.

Tissue angiotensin-converting enzyme inhibitors for the prevention of cardiovascular disease in patients with diabetes mellitus without left ventricular systolic dysfunction or clinical evidence of heart failure: a pooled meta-analysis of randomized placebo-controlled clinical trials

AIM

The aim of this study was to determine the role of tissue angiotensin-converting enzyme (ACE) inhibitors in the prevention of cardiovascular disease in patients with diabetes mellitus without left ventricular systolic dysfunction or clinical evidence of heart failure in randomized placebo-controlled clinical trials using pooled meta-analysis techniques.

METHODS

Randomized placebo-controlled clinical trials of at least 12 months duration in patients with diabetes mellitus without left ventricular systolic dysfunction or heart failure who had experienced a prior cardiovascular event or were at high cardiovascular risk were selected. A total of 10 328 patients (43 517 patient-years) from four selected trials were used for meta-analysis. Relative risk estimations were made using data pooled from the selected trials and statistical significance was determined using the Chi-squared test (two-sided alpha error <0.05). The number of patients needed to treat was also calculated.

RESULTS

Tissue ACE inhibitors significantly reduced the risk of cardiovascular mortality by 14.9% (p = 0.022), myocardial infarction by 20.8% (p = 0.002) and the need for invasive coronary revascularization by 14% (p = 0.015) when compared to placebo. The risk of all-cause mortality also tended to be lower among patients randomized to tissue ACE inhibitors, whereas the risks of stroke and hospitalization for heart failure were not significantly affected. Treating about 65 patients with tissue ACE inhibitors for about 4.2 years would prevent one myocardial infarction, whereas treating about 85 patients would prevent one cardiovascular death.

CONCLUSION

Pooled meta-analysis of randomized placebo-controlled trials suggests that tissue ACE inhibitors modestly reduce the risk of myocardial infarction and cardiovascular death and tend to reduce overall mortality in diabetic patients without left ventricular systolic dysfunction or heart failure.

Insulin resistance and hyperinsulinemia are related to plasma aldosterone levels in hypertensive patients

OBJECTIVE

An association between aldosterone and insulin resistance has been demonstrated in obesity and primary aldosteronism and in blacks with the metabolic syndrome. The aim of this study was to evaluate the relationship of plasma aldosterone with insulin sensitivity in white subjects.

RESEARCH DESIGN AND METHODS

In 356 patients with essential hypertension and 102 normotensive control subjects of comparable age and BMI, we measured, after discontinuation of treatment, plasma active renin, aldosterone, cortisol, glucose, insulin, and C-peptide levels and calculated markers of insulin sensitivity. Direct assessment of insulin sensitivity was obtained in a subset of 64 hypertensive patients by a hyperinsulinemic clamp.

RESULTS

Hypertensive patients had significantly greater fasting plasma insulin and C-peptide concentrations and homeostasis model assessment (HOMA) indexes than normotensive control subjects. A positive association with increasing plasma aldosterone concentrations was demonstrated for plasma glucose, insulin, C-peptides, and HOMA. Assessment of insulin sensitivity by clamp showed a significant decrease of the metabolic clearance rate of glucose with increasing aldosterone levels. Significant correlations were found between plasma aldosterone, plasma insulin, and C-peptide levels, HOMA, and glucose metabolic clearance rate. Blood pressure and plasma potassium, plasma cortisol, and renin levels, but not BMI, were also directly correlated with plasma aldosterone. Multiple regression analysis showed that HOMA, together with plasma potassium, cortisol, and renin levels, was independently correlated with plasma aldosterone.

CONCLUSIONS

This study demonstrates a direct relationship between aldosterone, insulin resistance, and hyperinsulinemia in white subjects. In patients with hypertension, this relationship might contribute to maintenance of high blood pressure and increased cardiovascular risk.

Reducing diabetes incidence through the inhibition of the renin–angiotensin system: a strategy for reducing cardiovascular mortality and morbidity?

The prevalence of type 2 diabetes is increasing worldwide, and prevention of the disease is a key objective. Several clinical trials reported a consistent reduction in the incidence of newly diagnosed diabetes in high-risk patients treated with renin-angiotensin system-inhibiting drugs. In all those trials, however, diabetes reduction was either a post-hoc analysis result or a secondary endpoint. Therefore, we need the results of ongoing specific prospectively designed trials, with new-onset diabetes as the principal endpoint.

Association of Adrenal Steroids With Hypertension and the Metabolic Syndrome in Blacks

Blacks have a high prevalence of hypertension and adrenal cortical adenomas/hyperplasia. We evaluated the hypothesis that adrenal steroids are associated with hypertension and the metabolic syndrome in blacks. Ambulatory blood pressures, anthropometric measurements, and measurements of plasma renin activity (PRA), aldosterone, fasting lipids, glucose, and insulin were obtained in 397 subjects (46% hypertensive and 50% female) after discontinuing antihypertensive and lipid-lowering medications. Hypertension was defined as average ambulatory blood pressure >130/85 mm Hg. Late-night and early morning salivary cortisol, 24-hour urine-free cortisol, and cortisone excretion were measured in a consecutive subsample of 97 subjects (40% hypertensive and 52% female). Compared with normotensive subjects, hypertensive subjects had greater waist circumference and unfavorable lipid profiles, were more insulin resistant, and had lower PRA and higher plasma aldosterone and both late-night and early morning salivary cortisol concentrations. Twenty-four-hour urine-free cortisol and cortisone did not differ. Overall, ambulatory blood pressure was positively correlated with plasma aldosterone (r=0.22; P<0.0001) and late-night salivary cortisol (r=0.23; P=0.03) and inversely correlated with PRA (r=-0.21; P<0.001). Plasma aldosterone correlated significantly with waist circumference, total cholesterol, triglycerides, insulin, and the insulin-resistance index. Based on Adult Treatment Panel III criteria, 17% of all of the subjects were classified as having the metabolic syndrome. Plasma aldosterone levels, but not PRA, were elevated in subjects with the metabolic syndrome (P=0.0002). The association of aldosterone with blood pressure, waist circumference, and insulin resistance suggests that aldosterone may contribute to obesity-related hypertension in blacks. In addition, we speculate that relatively high aldosterone and low PRA in these hypertensive individuals may reflect a mild variant of primary aldosteronism.

The antinatriuretic effect of insulin: an unappreciated mechanism for hypertension associated with insulin resistance?

Insulin resistance is proposed to be causally related to the metabolic syndrome disorders, but a direct cause-and-effect relationship between insulin resistance and hypertension was not originally obvious. Previous data suggested that insulin promotes sodium retention from the kidney, and thus research efforts focused on this action among several other possible pathways connecting insulin resistance and hyperinsulinemia with hypertension. A review of numerous studies provides evidence that this antinatriuretic effect of insulin is preserved in states of metabolic insulin resistance, representing a major mechanism for blood pressure elevation. More recent experimental and clinical studies have added data about the exact tubular sites of this insulin action, its relation with the respective insulin action on potassium handling, its possible role in the development of salt sensitivity in essential hypertension, as well as the involvement of oxidant stress in these associations. This review summarizes the current state of knowledge in this area and attempts to highlight an important but rather overlooked pathway for hypertension development in the metabolic syndrome, the influence of high insulin levels leading to volume expansion.

Insulin resistance, hyperinsulinemia, and renal injury: mechanisms and implications

Most of the basic components of the metabolic syndrome, namely type 2 diabetes mellitus, hypertension, obesity, or low high-density lipoprotein cholesterol levels, apart from being major risk factors for cardiovascular disease have been also associated with an increased risk of chronic kidney disease. However, several epidemiologic studies conducted over the past years suggest that the central component of the syndrome, insulin resistance, as well as compensatory hyperinsulinemia are independently associated with an increased prevalence of chronic kidney disease. In addition, background studies support the existence of several pathways linking insulin resistance and hyperinsulinemia with kidney damage. Insulin per se promotes the proliferation of renal cells and stimulates the production of other important growth factors such as insulin-like growth factor-1 and transforming growth factor beta. Insulin also upregulates the expression of angiotensin II type 1 receptor in mesangial cells, thus enhancing the deleterious effects of angiotensin II in the kidney, and stimulates production and renal action of endothelin-1. Moreover, insulin resistance and hyperinsulinemia are associated with decreased endothelial production of nitric oxide and increased oxidative stress which have been also implicated in the progression of diabetic nephropathy. This review analyzes the above and other potential mechanisms, through which insulin resistance and hyperinsulinemia can contribute to renal injury.

Biventricular diastolic dysfunction in patients with autosomal-dominant polycystic kidney disease

BACKGROUND

Left ventricular diastolic dysfunction has been shown in patients with autosomal-dominant polycystic kidney disease (ADPKD). However, there is no study evaluating right ventricular functions in these patients.

METHODS

In the present study, diastolic functions of both ventricles in normotensive and hypertensive ADPKD patients with well-preserved renal function were investigated. Fifteen hypertensive and 16 normotensive patients with ADPKD with well-preserved renal function, 16 patients with essential hypertension, and 24 healthy subjects were included in the study. Conventional left and right ventricular echocardiographic measurements were performed in all subjects. Left and right ventricular functions were investigated both by myocardial performance index (MPI) [calculated by dividing the sum of isovolumic contraction time and isovolumic relaxation time (IVRT) by ejection time] and by tissue Doppler imaging (TDI).

RESULTS

Left ventricular deceleration time and IVRT were significantly prolonged in hypertensive patients with ADPKD compared with patients with essential hypertension and even in normotensive patients with ADPKD compared with healthy subjects. Left and right MPIs were significantly higher in patients with ADPKD compared with healthy subjects, showing systolic and diastolic dysfunction. Moreover, by using TDI, the peak early diastolic mitral annular velocity (Em) to peak late diastolic mitral annular velocity (Am) ratio and the peak early diastolic tricuspid annular velocity (Et) to peak late diastolic tricuspid annular velocity (At) ratio were decreased in patients with ADPKD, suggesting biventricular diastolic dysfunction.

CONCLUSION

Both hypertensive and normotensive patients with ADPKD show significant biventricular diastolic dysfunction, suggesting cardiac involvement very early in the course of ADPKD.

Cardiometabolic Syndrome and Chronic Kidney Disease: What Is the Link?

The term metabolic syndrome or cardiometabolic syndrome describes the clustering of several cardiovascular and renal risk factors, including type 2 diabetes mellitus, central obesity, hypertension, and dyslipidemia. Over the past 15 years, several studies have examined the association between the metabolic/cardiometabolic syndrome or its central component, insulin resistance, with the presence of elevated urine albumin excretion. Intrarenal changes associated with the cardiometabolic syndrome result in elevated glomerular filtration rate, impaired pressure natriuresis, endothelial dysfunction related to changes in nitric oxide and, hence, impaired renal autoregulation and enhanced chronic inflammation. The aforementioned changes that occur in the cardiometabolic syndrome all contribute to the development of renal injury. While this review focuses on the epidemiology and mechanisms associated with vascular/renal injury, it must be remembered that prevention and treatment of kidney disease require a multifactorial approach. Weight loss through diet and exercise can reverse many of these pathophysiologic adaptations. Pharmacologic intervention should be aimed at achieving guideline goals and include insulin sensitizers to aid in tight glycemic control, lipid control, blockade of the renin-angiotensin-aldosterone system for blood pressure reduction, and anti-inflammatory therapies.

Obesity: prevalence, theories, medical consequences, management, and research directions

Obesity and its associated disorders are a growing epidemic across the world. Many genetic, physiological, and behavioral factors play a role in the etiology of obesity. Diet and exercise are known to play a valuable role in the treatment and prevention of obesity and associated disorders such as hypertension, heart disease, and diabetes. Therefore, the purpose of this review is to examine the prevalence, etiology, consequences, and treatment of obesity.

Angiotensin-converting enzyme inhibitors or angiotensin receptor blockers for prevention of type 2 diabetes: a meta-analysis of randomized clinical trials

OBJECTIVES

We sought to investigate the role of angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) in preventing the new onset of type 2 diabetes mellitus.

BACKGROUND

Diabetes is a public health problem of epidemic proportions and its prevalence is on the rise. The typical American born today has a one in three chance of developing type 2 diabetes. This diagnosis is associated with an adverse cardiovascular prognosis and is considered the risk equivalent of established coronary disease. Even in high-risk individuals, diabetes is a preventable disease. Several studies have shown that ACE inhibitors and ARBs decrease the incidence of new-onset type 2 diabetes. However, the exact role of these agents in diabetes prevention has not yet been fully elucidated.

METHODS

We conducted a meta-analysis of 12 randomized controlled clinical trials of ACE inhibitors or ARBs, identified through a MEDLINE search and a review of reports from scientific meetings, to study the efficacy of these medications in diabetes prevention.

RESULTS

This showed that ACE inhibitors and ARBs were associated with reductions in the incidence of newly diagnosed diabetes by 27% and 23%, respectively, and by 25% in the pooled analysis.

CONCLUSIONS

The use of an ACE inhibitor or ARB should be considered in patients with pre-diabetic conditions such as metabolic syndrome, hypertension, impaired fasting glucose, family history of diabetes, obesity, congestive heart failure, or coronary heart disease.

Rosiglitazone Reduces Insulin Requirement and C-Reactive Protein Levels in Type 2 Diabetic Patients Receiving Peritoneal Dialysis

BACKGROUND

Glycemic control is important in determining the outcome of patients with diabetes on dialysis therapy. However, the choice of oral hypoglycemia agent is limited in these patients. Very often, a high dose of insulin is required because of the uremia-associated insulin-resistant state. Rosiglitazone (RSG), a thiazolidinedione, can improve insulin resistance, and its excretion does not rely on renal function. Moreover, it has an anti-inflammatory effect that might be beneficial in patients with renal failure.

METHODS

An open-label randomized study was performed in which 52 patients with type 2 diabetes on peritoneal dialysis therapy administered a constant dosage of subcutaneous insulin with stable glycemic control were randomly assigned to the administration of either RSG (fixed dose, 4 mg) plus insulin or insulin alone. Insulin was titrated to maintain hemoglobin A1c (HbA1c) and blood glucose at pretreatment levels. Study duration was 24 weeks.

RESULTS

Both groups had similar baseline demographic characteristics, HbA1c and glucose levels, insulin requirement, and C-reactive protein (CRP) levels. Insulin requirement was decreased significantly in the RSG group (27.88 +/- 17.6 to 22.4 +/- 15.21 U/d; P < 0.001). There was a significantly greater decrease in insulin dosage in the RSG than control group (-21.5% versus +0.5%; P = 0.03), whereas glycemic control was similar between groups. At the end of the study, the RSG group also had significantly lower CRP levels than the control group (2.21 versus 8.59 mg/L; P = 0.03). No significant increase in such adverse effects as hypoglycemia, liver impairment, and fluid overload was observed in the RSG group. However, the RSG group was associated with more weight gain. Multivariate regression analysis (using decrease in HbA1c and lipid levels, change in insulin dosage, and treatment with RSG, with lipid-lowering agents) showed that only treatment with RSG was an independent predictor for posttreatment CRP level (P = 0.016).

CONCLUSION

RSG in combination with insulin is well tolerated and beneficial in the treatment of patients with type 2 diabetes on peritoneal dialysis therapy by improving insulin sensitivity and decreasing inflammatory response.

Obesidade visceral, hipertensão arterial e risco cárdio-renal: uma revisão

A maior parte da adversidade atribuída à obesidade é dada pelo risco cardiovascular/coronariano imputado à mesma, particularmente presente nos obesos com distribuição visceral de gordura corporal. O acúmulo de gordura visceral está sabidamente associado à maior prevalência de desarranjos metabólicos, hormonais, inflamatórios e hemodinâmicos, que no conjunto implicarão em maior acometimento da microvasculatura e impacto negativo sobre os órgãos-alvo, particularmente sobre o eixo cárdio-renal. Neste sentido, além da associação clássica com a doença coronariana, têm-se verificado uma associação maior da obesidade visceral com a hipertrofia ventricular esquerda e microalbuminúria, ambos fatores de risco cardiovascular e nefrológico reconhecidos. Assim, a abordagem terapêutica dos pacientes obesos, particularmente dos hipertensos, deve levar em conta a estratificação de risco baseada na distribuição de gordura corporal, o que permitirá uma terapêutica mais adequada, visando-se não só o controle dos fatores de risco como a monitorização do acometimento de órgãos-alvo nestas populações.

Daily exercise lowers blood pressure and reduces visceral adipose tissue areas in overweight Japanese men

OBJECTIVE

To investigate the link between a reduction in blood pressure (BP) and daily exercise.

DESIGN

Cross-sectional and longitudinal clinical intervention study with exercise education.

SUBJECTS

43 overweight Japanese men aged 32-59 years (BMI, 29.0+/-2.3 kg/m2) at baseline. Among the participants, a randomly selected 23 overweight men (BMI, 28.5+/-1.7) were further enrolled into the 10 months exercise program.

MEASUREMENTS

BP was measured every week and steps per day were also recorded every day throughout the observation period. Fat distribution was evaluated by visceral fat (V) and subcutaneous fat (S) areas measured with computed tomography (CT) scanning at umbilical level, at before, 5 months and after intervention. Anthropometric parameters were also measured at same point. Aerobic exercise level, muscle strength, flexibility and calorie intake and insulin resistance (HOMA index) were investigated at before and after the study.

RESULTS

In a cross sectional analysis, systolic BP (SBP) and diastolic BP (DBP) were significantly correlated with body composition. In a second longitudinal analysis, SBP was significantly reduced at 2 months and DBP was also reduced at 3 months, and almost maintained until the end of the observation period. Increasing daily walking was observed in 3 months and maintained until 10 months. Body composition, aerobic exercise level, muscle strength, flexibility and insulin resistance were significantly improved. There was positive correlation between DeltaDBP and Deltavisceral fat area (1-5, 5-10, 1-10 months). By stepwise multiple regression analysis, only Deltavisceral fat area was independently related to DeltaDBP at a significant level (1-10 months: DeltaDBP=-0.608+0.105Deltavisceral fat area, r2=0.227, P=0.0334).

CONCLUSION

The present study indicated daily exercise lowers BP and visceral fat area is the critical factor for BP change.

Obesity and hypertension

This article has discussed some of the mechanisms involved in the causal relation between obesity and hypertension. Obesity causes a constellation of maladaptive disorders that individually and synergistically contribute to hypertension, among other cardiovascular morbidities. Well-designed population-based studies are needed to assess the individual contribution of each of these disorders to the development of hypertension. In addition, because the control of obesity may eliminate 48% of the hypertension in whites and 28% in blacks, this article has offered an up-to-date on the management of this problem. It is hoped that this article will help scientists formulate a thorough understanding of obesity hypertension and form the basis for more research in this field, which has a huge impact on human life.

Low plasma aldosterone despite normal plasma renin activity in uncomplicated type 1 diabetes mellitus: effects of RAAS stimulation

BACKGROUND

Data on levels and responsiveness of PRA and aldosterone in type 1 diabetes mellitus are conflicting. Earlier studies were not standardized with respect to the type of diabetes mellitus, the presence of diabetic complications or sodium intake. Therefore, we studied plasma renin activity and plasma aldosterone in uncomplicated type 1 diabetes mellitus by evaluating the effects of endogenous (sodium restriction) and exogenous (angiotensin I infusion) stimulation.

DESIGN

Twenty-four type 1 diabetic patients and 24 matched healthy subjects were studied after 1 week of liberal sodium diet (200 mmol 24 h-1) and 1 week of low sodium diet (50 mmol 24 h-1). Angiotensin (Ang)I was infused at 4 and 8 ng kg-1 min-1 during both study days.

RESULTS

During liberal and low sodium intake, plasma aldosterone was lower in type 1 diabetic patients compared with healthy subjects both at 08:00 h (P < 0.05) and after a 2-h euglycaemic clamp (P < 0.05), despite similar PRA levels. The correlations between changes in PRA and changes in plasma aldosterone when shifting sodium intake were similar in both groups. During liberal sodium intake, the aldosterone levels after AngI infusion were lower in type 1 diabetic patients, whereas during low sodium they were not different.

CONCLUSIONS

Plasma aldosterone was deceased relative to PRA in uncomplicated type 1 diabetic patients, irrespective sodium intake. The responsiveness to sodium restriction was adequate and sodium restriction was able to overcome the decreased plasma aldosterone response to exogenous AngI, which was observed during liberal sodium in diabetic patients. The lower aldosterone is not secondary to diabetic complications and does not depend on the level of sodium intake.

The renin-angiotensin-aldosterone system: cardiorenal effects and implications for renal and cardiovascular disease states

The renin-angiotensin-aldosterone system (RAAS) plays an integral role in maintaining vascular tone, optimal salt and water homeostasis, and cardiac function in humans. However, it has been recognized in recent years that pathologic consequences may also result from overactivity of the RAAS. Clinical disease states such as renal artery stenosis, hypertension, diabetic and nondiabetic nephropathies, left ventricular hypertrophy, coronary atherosclerosis, myocardial infarction, and congestive heart failure (CHF) are examples. Part of the adverse cardiorenal effects of the RAAS may be related to the prominent role that this system plays in the activation of the sympathetic nervous system, the dysregulation of endothelial function and progression of atherosclerosis, as well as inhibition of the fibrinolytic system. Also, direct profibrotic actions of angiotensin II and aldosterone in the kidney and heart promote end organ injury. Current basic science and clinical research supports the use of inhibitors of the RAAS, including angiotensin converting enzyme inhibitors, angiotensin receptor blockers, and aldosterone antagonists in treating hypertension, improving diabetic nephropathy and other forms of chronic kidney disease, preventing or ameliorating CHF, and optimizing prognosis after myocardial infarction.

Insulin resistance is related to left ventricular hypertrophy in patients with polycystic kidney disease type 1

BACKGROUND

Left ventricular hypertrophy (LVH) is common in patients with autosomal dominant polycystic kidney disease (ADPKD). Although insulin resistance contributes to cardiac hypertrophy, the relationship between insulin resistance and LVH in patients with ADPKD has not been previously studied.

METHODS

We performed M-mode and color Doppler echocardiography on 176 family members (106 patients and 70 healthy relatives) from 16 families with polycystic kidney disease type 1 (PKD1). Left ventricular mass index (LVMI) was calculated using the Penn equation and corrected for body surface area. Fasting insulin and glucose concentrations were measured and insulin resistance was evaluated by means of the homeostasis model assessment.

RESULTS

In multivariate regression analysis, insulin resistance was significantly associated with LVMI in healthy relatives (P < 0.01) and patients with PKD1 (P < 0.05) independent of age, weight, systolic blood pressure, and albuminuria.

CONCLUSION

Insulin resistance is associated with LVMI in patients with PKD1 independently of other factors known to increase LVMI.

The renin-angiotensin-aldosterone system as a target in coronary disease

The renin-angiotensin-aldosterone system (RAAS) plays a fundamental role in the development of atherosclerosis and adverse cardiovascular events. Traditionally, the pathologic effects of the RAAS were assumed to result from vasoconstriction induced by angiotensin II, and salt and water retention due to aldosterone. However, these hormones also have powerful trophic effects, stimulating increased mass in both the arterial wall and left ventricle. In addition, angiotensin II and aldosterone predispose to vascular inflammation, thrombosis, oxidative stress, and sudden cardiac death. Therapy directed at RAAS overactivity is essential for normalizing the prognosis of most patients with atherosclerosis. An angiotensin-converting enzyme (ACE) inhibitor improves the prognosis of patients with atherosclerosis and/or diabetes even in the setting of normal baseline blood pressure. Angiotensin receptor blocking agents also improve cardiovascular structure and prognosis. Although these agents are better tolerated than ACE inhibitors, they do not appear to be as effective in reducing event rates. Aldosterone receptor blocking agents also improve cardiovascular structure, function, and prognosis. Aldosterone receptor blockers appear to provide additive benefit when used in conjunction with either an ACE inhibitor or an angiotensin receptor blocker.

Nitric oxide opposes glucose-induced hypertension by suppressing sympathetic activity

We have reported that glucose infusion in L-NAME-treated rats increased arterial pressure more than the additive responses to glucose and L-NAME alone. This suggested that nitric oxide synthesis inhibition potentiated the hypertensive response to chronic glucose infusion, and the heart rate data suggested an important role for the sympathetic nervous system. This study tested the role of the sympathetic nervous system by infusing glucose for 7 days in 4 groups of rats: L-NAME (L), L-NAME plus alpha- and beta-adrenergic receptor blockade (LB), vehicle, or vehicle plus adrenergic receptor blockade (blockers). Mean arterial pressure (MAP, 24 hours per day) increased significantly in both the vehicle and blockers groups, confirming our previous reports. Likewise, MAP increased significantly more during glucose infusion in the L rats, from 120+/-3 mm Hg to 158+/-4 mm Hg by day 7, which was >3 times the increase in the vehicle rats. Heart rate also increased significantly in the L rats, from 391+/-4 to 426+/-8 bpm, and that increase was prevented completely in the LB rats. However, although the increase in MAP in the LB rats was significantly less than in the L rats, the hypertension was not prevented completely. The explanation for that partial inhibition is not clear, but the overall effectiveness of adrenergic receptor blockade to attenuate the potentiated hypertensive and tachycardic responses to glucose infusion in the L-NAME-treated rats versus the normal rats suggests that nitric oxide may help protect against hypertension during glucose infusion through suppression of sympathetic activity.

Increasing daily walking lowers blood pressure in postmenopausal women

PURPOSE

The American College of Sports Medicine and the Centers for Disease Control and Prevention (ACSM-CDC) recommend 30 min of daily moderate-intensity physical activity for health; however, the effectiveness of this recommendation in lowering blood pressure (BP) in hypertensives is unclear. The present study tested the hypothesis that walking activity following the ACSM-CDC physical activity recommendation would lower BP in postmenopausal women with high BP.

METHODS

Resting BP was measured in 24 postmenopausal women with borderline to stage 1 hypertension at baseline, 12 wk, and 24 wk. Fifteen women in the exercise (EX) group walked 3 km.d-1 above their daily lifestyle walking, whereas 9 women in the control (CON) group did not change their activity. Walking activity was self-measured with a pedometer in both groups.

RESULTS

Resting systolic BP was reduced in the EX group after 12 wk by 6 mm Hg (P < 0.005) and was further reduced by 5 mm Hg at the end of 24 wk (P < 0.005). There was no change in diastolic BP with walking. The CON group experienced no change in BP at either 12 or 24 wk. Body mass was modestly reduced by 1.3 kg in the EX group after 24 wk (P < 0.05); however, it was not correlated with the change in BP. There were no changes in selected variables known to impact BP including percent body fat, fasting plasma insulin, or dietary intake.

CONCLUSION

In conclusion, a 24-wk walking program meeting the ACSM-CDC physical activity recommendation is effective in lowering systolic BP in postmenopausal women with borderline to stage 1 hypertension.

Significance of exaggerated natriuresis after angiotensin AT1 receptor blockade or angiotensin- converting enzyme inhibition in obese Zucker rats

1. Obese Zucker rats (OZR) were shown to be salt-sensitive in that they develop hypertension when placed on a high-salt diet. Because angiotensin (Ang) II is a major antinatriuretic factor, the present studies were undertaken to determine whether the characteristic of salt-sensitivity of OZR is associated with an enhanced antinatriuretic function of endogenous AngII. 2. The extent of AngII-mediated antinatriuresis was investigated in OZR and lean Zucker rats (LZR) using candesartan (100 microg/kg, i.v.), a selective angiotensin AT1 receptor antagonist, and ramipril (1 mg/kg, i.v.), an angiotensin-converting enzyme (ACE) inhibitor. The total number of AngII binding sites and their affinity were also assessed in renal cortical tubular membrane preparations of OZR and LZR using a specific radioligand-binding assay. Plasma renin activity was determined using a standard radioimmunoassay. 3. Both candesartan and ramipril produced substantially greater increases in urinary sodium excretion and urine flow in OZR and these effects were significantly greater than those observed in LZR. These observations suggest that basal antinatriuretic function of endogenous AngII is exaggerated in OZR. 4. The functional overexpression of AngII was not due to any alterations in the affinity or the total number of AngII binding sites in renal cortical tubular membranes. Higher plasma renin values in the OZR could have contributed to the phenomenon. 5. In conclusion, marked diuresis and natriuresis after AT1 receptor blockade and/or ACE inhibition suggest that the extent of endogenous AngII-mediated sodium transport under basal conditions is greatly augmented in OZR. It is proposed this phenomenon may be a contributing factor for the salt- sensitivity in the OZR.

Should an angiotensin-converting enzyme inhibitor be standard therapy for patients with atherosclerotic disease?

Angiotensin-converting enzyme (ACE) inhibitors appear to possess unique cardioprotective benefits, even when used in patients without high blood pressure or left ventricular dysfunction (the traditional indications for ACE inhibitor therapy). The ACE inhibitors improve endothelial function and regress both left ventricular hypertrophy and arterial mass better than other antihypertensive agents that lower blood pressure equally as well. These agents promote collateral vessel development and improve prognosis in patients who have had a coronary revascularization procedure (i.e., percutaneous transluminal coronary angioplasty and coronary artery bypass graft surgery). Insulin resistance, present not only in type 2 diabetes but also commonly in patients with hypertension or coronary artery disease, or both, sensitizes the vasculature to the trophic effects of angiotensin II and aldosterone. This may partly explain the improvement in prognosis noted when patients who have atherosclerosis or diabetes are treated with an ACE inhibitor. Therapy with ACE inhibitors has also been shown, in two large, randomized trials, to reduce the incidence of new-onset type 2 diabetes through largely unknown mechanisms. The ACE inhibitors are safe, well tolerated and affordable medications. The data suggest that most people with atherosclerosis should be considered candidates for ACE inhibitor therapy, unless they are intolerant to the medication, or have systolic blood pressures consistently <100 mm Hg. Patients who show evidence of insulin resistance (with or without overt type 2 diabetes) should also be considered as candidates for prophylactic ACE inhibitor therapy. Although angiotensin receptor blockers should not be considered equivalent to ACE inhibitors for this indication, they may be a reasonable alternative for patients intolerant of ACE inhibitors.