Is there a rationale for angiotensin blockade in the management of obesity hypertension?

Obesity in Heart Failure with Reduced Ejection Fraction: Time to Address the Elephant in the Room

Obesity has been long recognized as a risk factor for the development of heart failure, but recent evidence suggests obesity is more typically associated with heart failure with preserved ejection fraction as opposed to heart failure with reduced ejection fraction (HFrEF). Nevertheless, numerous studies have found that obesity modulates the presentation and progression of HFrEF and may contribute to the development of HFrEF in some patients. Although obesity has definite negative effects in HFrEF patients, the effects of intentional weight loss in HFrEF patients with obesity have been poorly studied.

High Systolic Blood Pressure of High-Income African American Children

BACKGROUND

According to the Minorities' Diminished Returns (MDRs) theory, racism may reduce the health returns of family socioeconomic status (SEP) resources such as family income for racial minorities, particularly African Americans, compared to Whites. However, we are unaware of any previous studies on racial variation in the protective effects of family income on children's blood pressure.

AIM

We conducted this study to compare the overall effects of family income on pre-adolescents' systolic and diastolic blood pressure, test racial variation in this effect, and investigate whether racial variation in this regard is due to racial differences in body mass index.

METHODS

In this cross-sectional study, we analyzed data from 4007 racially diverse US children 9-10 years old. The independent variable was family income measured as a three-level categorical variable: less than $50 K USD, 50-100 K USD, and 100 + K USD. The primary outcomes were systolic and diastolic blood pressure measured up to three times at 1-min time intervals. Body mass index was the mediator. Mixed-effects regression models were used for data analysis to adjust for data nested to the centers, families, and individuals. Age, gender, parental education, family structure, and Latino ethnicity were covariates.

RESULTS

In the pooled sample and in the absence of interaction terms in the model, family income did not show an inverse association with children's systolic (for 100 + K USD family income: β =  - 0.71, p = 0.233 and for 50-100 K USD family income: β = 0.01, p = 0.989) or diastolic blood pressure (for 100 + K USD family income: β =  - 0.66, p = 0.172 and for 50-100 K USD family income: β = 0.23, p = 0.600). However, race showed a significant interaction with family income on systolic blood pressure (for 50-100 K USD × African American: β = 2.75, p = 0.034), suggesting higher systolic blood pressure of African American adolescents from high-income backgrounds. Racial variation in the protective effect of family income on systolic BP was no more significant (for 50-100 K USD × African American: β = 2.14, p = 0.149) after we controlled for body mass index (BMI), which was higher for African American than White adolescents.

CONCLUSION

The association between high family income and reduced systolic blood pressure in pre-adolescence might be weaker for African Americans compared to Whites, a difference that African American adolescents' higher body mass index can explain.

Obesity in Heart Failure with Reduced Ejection Fraction: Time to Address the Elephant in the Room

Obesity has been long recognized as a risk factor for the development of heart failure, but recent evidence suggests obesity is more typically associated with heart failure with preserved ejection fraction as opposed to heart failure with reduced ejection fraction (HFrEF). Nevertheless, numerous studies have found that obesity modulates the presentation and progression of HFrEF and may contribute to the development of HFrEF in some patients. Although obesity has definite negative effects in HFrEF patients, the effects of intentional weight loss in HFrEF patients with obesity have been poorly studied.

Association between obesity and mortality in critically ill COVID-19 patients requiring invasive mechanical ventilation: a multicenter retrospective observational study

This study aimed to determine whether obesity and disease outcomes are associated in patients with critically-ill coronavirus disease 2019 (COVID-19) requiring invasive mechanical ventilation (IMV). This retrospective observational study using Japanese multicenter registry data included COVID-19 patients who required IMV and were discharged between January and September 2020. The patients were divided into the obese (body mass index [BMI] ≥ 25 kg/m²) and nonobese (BMI < 25 kg/m²) groups. Logistic regression models were used to analyze the association between obesity and disease outcomes. The primary outcome was in-hospital mortality; the secondary outcome was venovenous extracorporeal membrane oxygenation (VV-ECMO) implementation. Altogether, 477 patients were enrolled (obese, n = 235, median BMI, 28.2 kg/m²; nonobese, n = 242, median BMI, 22.4 kg/m²). Obesity was significantly associated with lower in-hospital mortality in the unadjusted logistic regression model (odds ratio 0.63; 95% confidence interval, 0.42-0.97; p = 0.033), but not with mortality in the adjusted logistic regression model using age, sex, and Charlson Comorbidity Index as covariates (p = 0.564). Obesity was not associated with VV-ECMO implementation in both unadjusted and adjusted models (unadjusted, p = 0.074; adjusted, p = 0.695). Obesity was not associated with outcomes in COVID-19 patients requiring IMV. Obesity may not be a risk factor for poor outcomes in these patients.

Predicting hypertension by obesity- and lipid-related indices in mid-aged and elderly Chinese: a nationwide cohort study from the China Health and Retirement Longitudinal Study

BACKGROUND

Currently, the study outcomes of anthropometric markers to predict the risk of hypertension are still inconsistent due to the effect of racial disparities. This study aims to investigate the most effective predictors for screening and prediction of hypertension (HTN) in the Chinese middle-aged and more elderly adult population and to predict hypertension using obesity and lipid-related markers in Chinese middle-aged and older people.

METHODS

The data for the cohort study came from the China Health and Retirement Longitudinal Study (CHARLS), including 4423 middle-aged and elderly people aged 45 years or above. We examined 13 obesity- and lipid-related indices, including waist circumference (WC), body mass index (BMI), waist-height ratio (WHtR), visceral adiposity index (VAI), a body shape index (ABSI), body roundness index (BRI), lipid accumulation product index (LAP), conicity index (CI), Chinese visceral adiposity index (CVAI), triglyceride-glucose index (TyG-index) and their combined indices (TyG-BMI, TyG-WC, TyG-WHtR). To compare the capacity of each measure to forecast the probability of developing HTN, the receiver operating characteristic curve (ROC) was used to determine the usefulness of anthropometric indices for screening for HTN in the elderly and determining their cut-off value, sensitivity, specificity, and area under the curve (AUC). Association analysis of 13 obesity-related anthropometric indicators with HTN was performed using binary logistic regression analysis.

RESULTS

During the four years, the incident rates of HTN in middle-aged and elderly men and women in China were 22.08% and 17.82%, respectively. All the above 13 indicators show a modest predictive power (AUC > 0.5), which is significant for predicting HTN in adults (middle-aged and elderly people) in China (P < 0.05). In addition, when WHtR = 0.501 (with an AUC of 0.593, and sensitivity and specificity of 63.60% and 52.60% respectively) or TYg-WHtR = 4.335 (with an AUC of 0.601, and sensitivity and specificity of 58.20% and 59.30% respectively), the effect of predicting the incidence risk of men is the best. And when WHtR = 0.548 (with an AUC of 0.609, and sensitivity and specificity of 59.50% and 56.50% respectively) or TYg-WHtR = 4.781(with an AUC of 0.617, and sensitivity and specificity of 58.10% and 60.80% respectively), the effect of predicting the incidence risk of women is the best.

CONCLUSIONS

The 13 obesity- and lipid-related indices in this study have modest significance for predicting HTN in Chinese middle-aged and elderly patients. WHtR and Tyg-WHtR are the most cost-effective indicators with moderate predictive value of the development of HTN.

Associations of long-term exposure to ambient ozone with hypertension, blood pressure, and the mediation effects of body mass index: A national cross-sectional study of middle-aged and older adults in China

BACKGROUND

The associations between long-term exposure to ozone (O₃) and respiratory diseases are well established. However, its association with cardiovascular disease (CVD) remains controversial. In this study, we examined the associations between O₃ and the prevalence of hypertension and blood pressure, and the mediation effects of body mass index (BMI) in Chinese middle-aged and older adults.

METHODS

In this national cross-sectional study, we estimated the O₃ exposure of 12,028 middle-aged and older adults from 126 county-level cities in China, using satellite-based spatiotemporal models. Generalized linear mixed models were used to evaluate the associations of long-term exposure to O₃ with hypertension and blood pressure, including systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and pulse pressure (PP). Mediation effect models were applied to examine the mediation effects of BMI among O₃-induced hypertension and elevated blood pressure.

RESULTS

Each 10 μg/m³ increase in O₃ concentration was significantly associated with an increase of 13.7% (95% confidence interval (CI): 4.8%, 23.3%) in the prevalence of hypertension, an increase of 1.128 mmHg (95% CI: 0.248, 2.005), 0.679 mmHg (95% CI: 0.059, 1.298), 0.820 mmHg (95%CI: 0.245, 1.358) in SBP, DBP, and MAP, respectively. Mediation effect models showed that BMI played 40.08%, 37.25%, 39.95%, and 33.51% mediation roles in the effects of long-term exposure to O₃ on hypertension, SBP, DBP, and MAP, respectively.

CONCLUSIONS

Long-term exposure to O₃ can increase the prevalence of hypertension and blood pressure levels of middle-aged and older adults, and an increase of BMI would be an important modification effect for O₃-induced hypertension and blood pressure increase.

Diet-induced prediabetes: Effects on the activity of the renin-angiotensin-aldosterone system (RAAS) in selected organs

Derangements often observed with type 2 diabetes (T2D) are associated with disturbances in renin-angiotensin-aldosterone system (RAAS) activity. A positive correlation between local RAAS activity and the complications observed in T2D has been noted. However, the detrimental ramifications due to moderate hyperglycemia noted in prediabetes and the affected organ system and mechanistic pathways are not elucidated. Hence, this study investigated the effects of diet-induced prediabetes on RAAS in various organs.

MATERIALS AND METHODS

Male Sprague-Dawley rats were separated into two groups: non-pre-diabetic (NPD) through exposure to standard rat chow and diet-induced prediabetic (PD) group by exposure to a high-fat high carbohydrate diet for 32 weeks. RAAS activity in the skeletal muscle, adipose tissue, liver, pancreas and heart was determined through the analysis of RAAS components such as; renin, angiotensinogen, angiotensin-converting enzyme (ACE) and angiotensin II type 1 receptor (AT1R) via PCR as well as the quantification of angiotensin II and aldosterone concentration. Furthermore, NADPH oxidase, SOD and GPx1 concentrations were determined in the skeletal muscle, pancreas and heart in addition to the hepatic triglycerides.

RESULTS

The RAAS components were elevated in the PD group when compared to the NPD. This was further accompanied by increased NADPH oxidase and reduced SOD and GPx1 concentrations in the selected organs, in addition to the elevated hepatic triglycerides concentration in the PD by comparison to NPD.

CONCLUSION

Due to these observed changes, we suggest that local RAAS activity in the prediabetic state in selected organs elicits the derangements noted in T2D.

Oxidative Stress, Plant Natural Antioxidants, and Obesity

Oxidative stress is important in the pathophysiology of obesity, altering regulatory factors of mitochondrial activity, modifying the concentration of inflammation mediators associated with a large number and size of adipocytes, promoting lipogenesis, stimulating differentiation of preadipocytes to mature adipocytes, and regulating the energy balance in hypothalamic neurons that control appetite. This review discusses the participation of oxidative stress in obesity and the important groups of compounds found in plants with antioxidant properties, which include (a) polyphenols such as phenolic acids, stilbenes, flavonoids (flavonols, flavanols, anthocyanins, flavanones, flavones, flavanonols, and isoflavones), and curcuminoids (b) carotenoids, (c) capsaicinoids and casinoids, (d) isothiocyanates, (e) catechins, and (f) vitamins. Examples are analyzed, such as resveratrol, quercetin, curcumin, ferulic acid, phloretin, green tea, Hibiscus Sabdariffa, and garlic. The antioxidant activities of these compounds depend on their activities as reactive oxygen species (ROS) scavengers and on their capacity to prevent the activation of NF-κB (nuclear factor κ-light-chain-enhancer of activated B cells), and reduce the expression of target genes, including those participating in inflammation. We conclude that natural compounds have therapeutic potential for diseases mediated by oxidative stress, particularly obesity. Controlled and well-designed clinical trials are still necessary to better know the effects of these compounds.

Acute chemoradiotherapy toxicity in cervical cancer patients

During radiotherapy treatment for cervical cancer, up to 84% of patients exhibit some form of acute radiation toxicity (ART). The primary aim of this clinical study is to determine the impact of angiotensin-converting enzyme (ACE) inhibitors, β-blockers and other risk factors such as the patient’s anatomical characteristics on ART emergence in patients with locally advanced cervical cancer treated by chemoradiotherapy. This is a combination of two nested case–control studies within the cohort of patients with locally advanced cervical cancer based on the analysis of potential risk factors for the onset of ART in patients treated with 3D conformal radiotherapy (3D-CRT) and 2D conventional radiotherapy (2D-RT), prospectively followed up from January 2017 to September 2018 in a tertiary care hospital. The ACE inhibitors and bladder volume were identified as factors that significantly affect the occurrence of ART in patients treated with 3D-CRT. In patients treated with 2D-RT, the factors that significantly affect the occurrence of ART were ACE inhibitors, body mass index (BMI), brachytherapy rectal and bladder dose. This study has shown that BMI, radiation dose received by the bladder and rectum are of exceptional importance for the occurrence of the ART and also that therapy with ACE inhibitors was associated with the decreased chances of the ART.

Obesity and Mortality Among Patients Diagnosed With COVID-19: Results From an Integrated Health Care Organization

BACKGROUND

Obesity, race/ethnicity, and other correlated characteristics have emerged as high-profile risk factors for adverse coronavirus disease 2019 (COVID-19)-associated outcomes, yet studies have not adequately disentangled their effects.

OBJECTIVE

To determine the adjusted effect of body mass index (BMI), associated comorbidities, time, neighborhood-level sociodemographic factors, and other factors on risk for death due to COVID-19.

DESIGN

Retrospective cohort study.

SETTING

Kaiser Permanente Southern California, a large integrated health care organization.

PATIENTS

Kaiser Permanente Southern California members diagnosed with COVID-19 from 13 February to 2 May 2020.

MEASUREMENTS

Multivariable Poisson regression estimated the adjusted effect of BMI and other factors on risk for death at 21 days; models were also stratified by age and sex.

RESULTS

Among 6916 patients with COVID-19, there was a J-shaped association between BMI and risk for death, even after adjustment for obesity-related comorbidities. Compared with patients with a BMI of 18.5 to 24 kg/m², those with BMIs of 40 to 44 kg/m² and greater than 45 kg/m² had relative risks of 2.68 (95% CI, 1.43 to 5.04) and 4.18 (CI, 2.12 to 8.26), respectively. This risk was most striking among those aged 60 years or younger and men. Increased risk for death associated with Black or Latino race/ethnicity or other sociodemographic characteristics was not detected.

LIMITATION

Deaths occurring outside a health care setting and not captured in membership files may have been missed.

CONCLUSION

Obesity plays a profound role in risk for death from COVID-19, particularly in male patients and younger populations. Our capitated system with more equalized health care access may explain the absence of effect of racial/ethnic and socioeconomic disparities on death. Our data highlight the leading role of severe obesity over correlated risk factors, providing a target for early intervention.

PRIMARY FUNDING SOURCE

Roche-Genentech.

Central blood pressure in morbid obesity and after bariatric surgery

Various mechanisms are related to arterial hypertension in obesity. Central blood pressure (BP) seems to correlate more than peripheral BP with future cardiovascular risk. Bariatric surgery is an effective method to reduce BP along with weight loss in patients with morbid obesity. The study of the relationship between weight modification after bariatric surgery and ambulatory BP measurement, not only peripheral BP, but also central BP, could provide information regarding the mechanisms of organic damage associated with elevated BP in obesity. In this review we analyze the available evidence regarding the association between central BP with obesity and its modifications after bariatric surgery.

Regulation of alternative splicing in obesity-induced hypertension

Obesity is the result of genetics which predisposes an individual to obesity and environmental factors, resulting in excessive weight gain. A well-established linear relationship exists between hypertension and obesity. The combined burden of hypertension and obesity poses significant health and economic challenges. Many environmental factors and genetic traits interact to contribute to obesity-linked hypertension. These include excess sodium re-absorption or secretion by the kidneys, a hypertensive shift of renal-pressure and activation of the sympathetic nervous system. Most individuals suffering from hypertension need drugs in order to treat their raised blood pressure, and while a number of antihypertensive therapeutic agents are currently available, 50% of cases remain uncontrolled. In order to develop new and effective therapeutic agents combating obesity-induced hypertension, a thorough understanding of the molecular events leading to adipogenesis is critical. With the advent of whole genome and exome sequencing techniques, new genes and variants which can be used as markers for obesity and hypertension are being identified. This review examines the role played by alternative splicing (AS) as a contributing factor to the metabolic regulation of obesity-induced hypertension. Splicing mutations constitute at least 14% of the disease-causing mutations, thus implicating polymorphisms that effect splicing as indicators of disease susceptibility. The unique transcripts resulting from the alternate splicing of mRNA encoding proteins that play a key role in contributing to obesity would be vital to gain a proper understanding of the genetic causes of obesity. A greater knowledge of the genetic basis for obesity-linked hypertension will assist in the development of appropriate diagnostic tests as well as the identification of new personalized therapeutic targets against obesity-induced hypertension.

Obesity and hypertension

Obesity and in particular the excessive visceral fat distribution is accompanied by several alterations at hormonal, inflammatory and endothelial level. These alterations induce a stimulation of several other mechanisms that contribute to the hypertensive state and on the other side to increase the cardiovascular morbidity. In these chapter we will examine the main mechanisms of obesity and obesity-related hypertension and in particular the role of sympathetic nervous system, the alterations of the renal function and at the microvascular level. We will also depict the role of insulin resistance as factor stimulating and potentiating the other mechanisms. The second part will be focalized on the major target organ damage linked with obesity and obesity-related hypertension. We will finally describe the management and treatment of obesity and the antihypertensive drug therapies more effective in hypertensive obeses.

Inhibitory effect of leaves extracts of Ocimum basilicum and Ocimum gratissimum on two key enzymes involved in obesity and hypertension in vitro

Aim:

To evaluate the phenolics composition and inhibitory effect of the leaves extracts of Ocimum basilicum and Ocimum gratissimum on two key enzymes (pancreatic lipase [PL] and angiotensin 1-converting enzyme [ACE]) involved in obesity and hypertension in vitro.

Materials and Methods:

The phenolics (flavonoids and phenolic acids) were quantified using high-performance liquid chromatography coupled with diode array detection. PL and ACE inhibitory effects; DPPH* and ABTS*⁺ scavenging activities of the extracts were tested using spectrophotometric methods.

Results:

O. basilicum had the following major phenolics: Rutin, quercetin, and quercitrin (flavonoids); caffeic, chlorogenic, and gallic acids (phenolic acids); while O. gratissimum had the following major phenolics: Rutin, quercitrin, and luteolin (flavonoids); ellagic and chlorogenic acids (phenolic acids). “Extracts of both plants inhibited PL and ACE; scavenged DPPH* in a dose-dependent manner”. O. gratissimum extract was more potent in inhibiting PL (IC_50: 20.69 µg/mL) and ACE (IC_50: 29.44 µg/mL) than O. basilicum (IC_50: 52.14 µg/mL and IC_50: 64.99 µg/mL, against PL and ACE, respectively). O. gratissimum also scavenged DPPH* and ABTS*⁺ more than O. basilicum.

Conclusion:

O. basilicum and O. gratissimum leaves could be used as functional foods for the management of obesity and obesity-related hypertension. However, O. gratissimum may be more effective than O. basilicum.

Review: The metabolic syndrome as an endocrine disease: is there an effective pharmacotherapeutic strategy optimally targeting the pathogenesis?

The metabolic syndrome (MetS) represents a combination of cardiovascular risk determinants such as obesity, insulin resistance and lipid abnormalities such as hypertriglyceridemia, increased free fatty acids, low high-density-cholesterol and hypertension. As a multiple component condition it imparts a doubling of relative risk for atherosclerotic cardiovascular disease (ASCVD). It is currently controversial which component of the syndrome carries what weight. There is even a considerable debate whether the risk for ASCVD is greater in patients diagnosed with MetS than that by the individual risk factors. At present, no unifying pathogenetic mechanism can explain the metabolic syndrome and there is no unique treatment for it. This review summarizes and critically reviews the currently available clinical and scientific evidence for the concept that the MetS is causally an endocrine disease and discusses pharmacotherapeutic strategies targeting the pathogenesis rather than single symptoms of the cluster.

Impact of renin-angiotensin-aldosterone system genes on the treatment response of patients with hypertension and metabolic syndrome

Objective. To evaluate the influence of clinical, biochemical and genetic markers on the response to antihypertensive treatment in patients with essential hypertension and the metabolic syndrome (MetS).

Methods. Measurements of anthropometric indices, blood pressure (BP), and metabolic parameters were obtained from the medical records of 132 (77 women) newly diagnosed, untreated hypertensive patients. Renin-angiotensin-aldosterone system (RAAS) genes polymorphisms (including ACE I/D, angiotensinogen M235T, angiotensin II type 1 receptor [AT1-receptor] A1166C) were determined. Response to treatment was defined as BP less than 140/90 mmHg.

Results. Patients with MetS (n=60) had higher systolic BP and pulse pressure and a more atherogenic lipid profile than patients without MetS.The frequencies of the ACE and the AT1-receptor gene polymorphisms were similar between patients with and without MetS. Response to treatment was positively associated with pulse pressure, and the presence of the C allele as well as the AC genotype of the AT1-receptor gene and inversely with age after adjustment for confounding factors.

Conclusions. RAAS genes distribution does not differ between hypertensive patients with and without the MetS. Higher baseline pulse pressure levels, the presence of the C allele and/or the AC genotype may be in favour of a better response to structured antihypertensive treatment in patients with MetS. However, these findings need to be evaluated in future studies.

Review: Potential protective effects of telmisartan on renal function deterioration

Experimental and clinical evidence is now available that antagonism of angiotensin II (Ang II) with both angiotensin-converting enzyme inhibitors and Ang II receptor antagonists (AIIAs) is effective in slowing the rate of renal functional loss in patients affected by proteinuric kidney diseases.Among AIIAs, telmisartan has been shown to be characterised by a potent and long lasting antihypertensive effect that may be associated with another specific effect of this molecule, the partial agonism of the peroxisome-activated receptor-gamma.Although this action has also been observed with other AIIAs, telmisartan seems to exert a more effective and specific action as in such a way to influence beneficially adipocyte metabolism, diabetes onset and insulin resistance. Recently, we have demonstrated, at the experimental and clinical level, that sustained blockade of Ang II biological activity with this class of compounds can potentially reduce the progression of renal dysfunction and in some circumstances induce the regression of renal functional and structural changes. In this review we analyse available experimental and clinical data that suggest that blocking Ang II with telmisartan may effectively ameliorate renal dysfunction in patients affected by the now frequently observed condition termed metabolic syndrome.

Obesity and renovascular disease

Obesity remains a prominent public health concern. Obesity not only contributes greatly to cardiovascular events but has also been identified to initiate and affect the progression of preexisting chronic kidney disease. The prevalence of renal artery stenosis is growing world-wide, especially in the elderly population and in individuals with atherosclerotic risk factors such as obesity. Prolonged renovascular disease causes inflammation and microvascular remodeling within the post-stenotic kidney, which promote tissue scarring and may account for irreversible renal damage. Obesity has been shown to aggravate kidney damage via several pathways, including exacerbation of microvascular regression and renal cell injury mediated by adipocytes and insulin resistance, thereby worsening the structural and functional outcomes of the kidney in renovascular disease. Dietary modification and inhibition of the renin-angiotensin-aldosterone system have been shown to alleviate obesity-induced tissue injury and remodeling. Possibly, angiogenic factors may boost microvascular repair in the ischemic kidney in the obesity milieu. Novel therapeutic interventions targeting deleterious pathways that are activated by obesity and responsible for kidney damage need to be explored in future studies.

The pathophysiology of hypertension in patients with obesity

The combination of obesity and hypertension is associated with high morbidity and mortality because it leads to cardiovascular and kidney disease. Potential mechanisms linking obesity to hypertension include dietary factors, metabolic, endothelial and vascular dysfunction, neuroendocrine imbalances, sodium retention, glomerular hyperfiltration, proteinuria, and maladaptive immune and inflammatory responses. Visceral adipose tissue also becomes resistant to insulin and leptin and is the site of altered secretion of molecules and hormones such as adiponectin, leptin, resistin, TNF and IL-6, which exacerbate obesity-associated cardiovascular disease. Accumulating evidence also suggests that the gut microbiome is important for modulating these mechanisms. Uric acid and altered incretin or dipeptidyl peptidase 4 activity further contribute to the development of hypertension in obesity. The pathophysiology of obesity-related hypertension is especially relevant to premenopausal women with obesity and type 2 diabetes mellitus who are at high risk of developing arterial stiffness and endothelial dysfunction. In this Review we discuss the relationship between obesity and hypertension with special emphasis on potential mechanisms and therapeutic targeting that might be used in a clinical setting.

Microvascular dysfunction in the course of metabolic syndrome induced by high-fat diet

Background

Metabolic syndrome (MetS) is associated with increased risk of cardiovascular disease (CVD). One important feature underlying the pathophysiology of many types of CVD is microvascular dysfunction. Although components of MetS are themselves CVD risk factors, the risk is increased when the syndrome is considered as one entity. We aimed to characterize microvascular function and some of its influencing factors in the course of MetS development.

Methods

Development of MetS in C57BL/6 mice on a high-fat diet (HFD, 51% of energy from fat) was studied. The initial phase of MetS (I-MetS) was defined as the first 2 weeks of HFD feeding, with the fully developed phase occurring after 8 weeks of HFD. We characterized these phases by assessing changes in adiposity, blood pressure, and microvascular function. All data are presented as mean ± standard error (SEM). Differences between cumulative dose–response curves of myograph experiments were calculated using non-linear regression analysis. In other experiments, comparisons between two groups were made with Student’s t-test. Comparisons between more than two groups were made using one-way ANOVA with Tukey post-hoc test. A probability value <0.05 was considered statistically significant.

Results

I-MetS mice presented with weight gain, blood pressure elevation, and microvascular dysfunction characterized by augmented vasoconstriction. This finding, contrary to those in mice with fully developed MetS, was not associated with endothelial dysfunction, insulin resistance, or systemic inflammation. In the initial phase, perivascular adipose tissue showed no sign of inflammation and had no influence on the pattern of vasoconstriction. These findings suggest that the onset of hypertension in MetS is strongly influenced by vascular smooth muscle cell dysfunction and independent of important factors known to influence microvascular function and consequently blood pressure levels.

Conclusion

We identified in I-MetS the occurrence of isolated augmented vasoconstriction along with blood pressure elevation, but not the presence of classical MetS components known to influence microvascular function. These findings increase our understanding of the pathophysiology of CVD risk associated with MetS.

Renal (tissue) kallikrein-kinin system in the kidney and novel potential drugs for salt-sensitive hypertension

A large variety of antihypertensive drugs, such as angiotensin converting enzyme inhibitors, diuretics, and others, are prescribed to hypertensive patients, with good control of the condition. In addition, all individuals are generally believed to be salt sensitive and, thus, severe restriction of salt intake is recommended to all. Nevertheless, the physiological defense mechanisms in the kidney against excess salt intake have not been well clarified. The present review article demonstrated that the renal (tissue) kallikrein-kinin system (KKS) is ideally situated within the nephrons of the kidney, where it functions to inhibit the reabsorption of NaCl through the activation of bradykinin (BK)-B2 receptors localized along the epithelial cells of the collecting ducts (CD). Kinins generated in the CD are immediately inactivated by two kidney-specific kinin-inactivating enzymes (kininases), carboxypeptidase Y-like exopeptidase (CPY), and neutral endopeptidase (NEP). Our work demonstrated that ebelactone B and poststatin are selective inhibitors of these kininases. The reduced secretion of the urinary kallikrein is linked to the development of salt-sensitive hypertension, whereas potassium ions and ATP-sensitive potassium channel blockers ameliorate salt-sensitive hypertension by accelerating the release of renal kallikrein. On the other hand, ebelactone B and poststatin prolong the life of kinins in the CD after excess salt intake, thereby leading to the augmentation of natriuresis and diuresis, and the ensuing suppression of salt-sensitive hypertension. In conclusion, accelerators of the renal kallikrein release and selective renal kininase inhibitors are both novel types of antihypertensive agents that may be useful for treatment of salt-sensitive hypertension.

Adiposity has unique influence on the renin-aldosterone axis and blood pressure in black children

OBJECTIVE

To comparatively examine the effects of adiposity on the levels of plasma renin activity (PRA), plasma aldosterone concentration (PAC), and aldosterone-renin ratio (ARR) in young black and white children.

STUDY DESIGN

We prospectively assessed 248 black and 345 white children and adolescents. A novel analytical technique was used to assess the concurrent influences of age and body mass index (BMI) on PRA, PAC, and ARR. The estimated effects were depicted by colored contour plots.

RESULTS

In contrast to whites, blacks had lower PRA (2.76 vs 3.36 ng/mL/h; P < .001) and lower PAC (9.01 vs 14.59 ng/dL; P < .001). In blacks, BMI was negatively associated with PRA (P = .001), consistent with an association with a more expanded plasma volume; there was no association with PAC. In whites, BMI was positively associated with PAC (P = .005); we did not detect a BMI-PRA association. The effects of BMI on ARR were directionally similar in the two race groups but more pronounced in blacks. Mean systolic blood pressure was greater in blacks with lower PRA (P < .01), higher PAC (P = .015), and higher ARR (P = .49).

CONCLUSIONS

An increase in adiposity was associated with a suppressed PRA in blacks and an increase in PAC in whites. The unique relationship between adiposity and renin-aldosterone axis in blacks suggests the possible existence of a population-specific mechanism characterized by volume expansion, which could in turn enhance the influences of adiposity on blood pressure in black children and adolescents.

Redox-inflammatory synergy in the metabolic syndrome

Metabolic syndrome (MetS) comprises interrelated disease states including obesity, insulin resistance and type 2 diabetes (T2DM), dyslipidemia, and hypertension. Essential to normal physiological function, and yet massively damaging in excess, oxidative stress and inflammation are pivotal common threads among the pathologies of MetS. Increasing evidence indicates that redox and inflammatory dysregulation parallels the syndrome's physiological, biochemical, and anthropometric features, leading many to consider the pro-oxidative, pro-inflammatory milieu an unofficial criterion in itself. Left unchecked, cross-promotion of oxidative stress and inflammation creates a feed-forward cycle that can initiate and advance disease progression. Such redox-inflammatory integration is evident in the pathogenesis of obesity, insulin resistance and T2DM, atherogenic dyslipidemia, and hypertension, and is thus hypothesized to be the "common soil" from which they develop. The present review highlights the synergistic contributions of redox-inflammatory processes to each of the components of the MetS.

Exercise, insulin resistance, and hypertension: a complex relationship

More than 300,000 deaths occur annually in the United States alone as a result of obesity, poor dietary habits, or physical inactivity. Obesity is now an increasingly recognized independent risk factor for cardiovascular disease and leads to numerous other comorbidities. The causal relationships between obesity and both insulin resistance and hypertension have been consistently demonstrated in numerous studies. The relationships consist of cascading events involving insulin, leptin, adiponectin, and other hormones that often precipitate the development of metabolic syndrome. As we learn more about the metabolic activity of the adipose tissue, we can better identify the mechanisms that associate weight reduction with a decrease in health risks. Evidence suggests that exercise produces a positive effect on weight reduction, insulin sensitivity, and blood pressure. Therefore, weight reduction and therapeutic changes in lifestyle should be encouraged in all overweight and obese patients. It is imperative to increase the awareness of the obesity epidemic and to emphasize the importance of exercise as both treatment and prevention of metabolic disease.

Effects of Irbesartan on the Growth and Differentiation of Adipocytes in Obese Zucker Rats

OBJECTIVE

The aim of this study was to evaluate the effects of the selective angiotensin receptor 1 antagonist irbesartan on the growth and differentiation of the adipocytes in obese Zucker fa/fa rats.

RESEARCH METHODS AND PROCEDURES

Obese Zucker fa/fa rats were treated by oral route for 3 weeks with irbesartan at doses of 3-10-30 mg/kg per day. The adipocyte differentiation was evaluated by analyzing tissue samples of white (retroperitoneal) or brown (interscapular) adipose tissue for the presence of peroxisome proliferator activated receptor gamma, leptin, and the activity of glycerol-3-phosphate dehydrogenase.

RESULTS

This study showed that the treatment of obese Zucker fa/fa with irbesartan effectively reduced the differentiation of adipocytes within brown (interscapular) and white (retroperitoneal) adipose tissue. In fact, irbesartan significantly (p < 0.01) and dose-dependently reduced the tissue levels of leptin, peroxisome proliferator activated receptor gamma, and the activity of the enzyme glycerol-3-phoshate dehydrogenase accepted markers of adipocyte differentiation. None of the tested doses of irbesartan affected these markers in non-obese rats.

DISCUSSION

The antagonism of the angiotensin receptor 1 receptors with irbesartan reduces the adipogenic activity of angiotensin II in obese Zucker rats, with the endpoint being reduction of the growth and differentiation of the adipocytes within the adipose tissue.

Renal hyperfiltration related to diabetes mellitus and obesity in human disease

High intraglomerular pressure is associated with renal hyperfiltration, leading to the initiation and progression of kidney disease in experimental models of diabetes mellitus (DM). In humans, hyperfiltration is observed in patients with type 1 and type 2 DM, and is also seen in patients with pre-diabetic conditions, such as the metabolic syndrome. From a mechanistic perspective, both vascular and tubular factors likely contribute to the pathogenesis of hyperfiltration. Until now, human studies have primarily focused on the use of medications that inhibit the renin angiotensin system to reduce efferent vasoconstriction and thereby improve hyperfiltration. More recent advances in the development of investigational adenosine antagonists and inhibitors of sodium glucose co-transport may help to elucidate tubular factors that contribute to afferent vasodilatation. In this review, we summarize available data from experimental and human studies of type 1 and type 2 DM and obesity to provide an overview of factors that contribute to the hyperfiltration state. We have focused on the renin angiotensin system, cyclooxygenase-2 system, nitric oxide, protein kinase C and endothelin as vascular determinants of hyperfiltration. We also discuss relevant tubular factors, since experimental models have suggested that inhibition of sodium-glucose cotransport may be renoprotective.

The renin-angiotensin system: a target of and contributor to dyslipidemias, altered glucose homeostasis, and hypertension of the metabolic syndrome

The renin-angiotensin system (RAS) is an important therapeutic target in the treatment of hypertension. Obesity has emerged as a primary contributor to essential hypertension in the United States and clusters with other metabolic disorders (hyperglycemia, hypertension, high triglycerides, low HDL cholesterol) defined within the metabolic syndrome. In addition to hypertension, RAS blockade may also serve as an effective treatment strategy to control impaired glucose and insulin tolerance and dyslipidemias in patients with the metabolic syndrome. Hyperglycemia, insulin resistance, and/or specific cholesterol metabolites have been demonstrated to activate components required for the synthesis [angiotensinogen, renin, angiotensin-converting enzyme (ACE)], degradation (ACE2), or responsiveness (angiotensin II type 1 receptors, Mas receptors) to angiotensin peptides in cell types (e.g., pancreatic islet cells, adipocytes, macrophages) that mediate specific disorders of the metabolic syndrome. An activated local RAS in these cell types may contribute to dysregulated function by promoting oxidative stress, apoptosis, and inflammation. This review will discuss data demonstrating the regulation of components of the RAS by cholesterol and its metabolites, glucose, and/or insulin in cell types implicated in disorders of the metabolic syndrome. In addition, we discuss data supporting a role for an activated local RAS in dyslipidemias and glucose intolerance/insulin resistance and the development of hypertension in the metabolic syndrome. Identification of an activated RAS as a common thread contributing to several disorders of the metabolic syndrome makes the use of angiotensin receptor blockers and ACE inhibitors an intriguing and novel option for multisymptom treatment.

Effect of Inhibition of Angiotensin-Converting Enzyme and/or Neutral Endopeptidase on Neuropathy in High-Fat-Fed C57Bl/6J Mice

We have demonstrated that treating diet-induced obese (DIO) mice with the vasopeptidase inhibitor ilepatril improved neural function. Vasopeptidase inhibitors block angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP) activity. We propose that increased activity of ACE and NEP contributes to pathophysiology of DIO. To address this issue C57Bl/6J mice or mice deficient in NEP were fed a high-fat diet and treated with ilepatril, enalapril, ACE inhibitor, or candoxatril, NEP inhibitor, using both prevention and intervention protocols. Endpoints included glucose utilization and neural function determination. In the prevention study glucose tolerance was impaired in DIO C57Bl/6J mice and improved with ilepatril or enalapril. Sensory nerve conduction velocity, thermal nociception, and intraepidermal nerve fiber density were impaired in DIO C57Bl/6J mice and improved with ilepatril or candoxatril. In the intervention study only enalapril improved glucose tolerance. Sensory nerve conduction velocity and intraepidermal nerve fiber density were improved by all three treatments, whereas thermal nociception was improved by ilepatril or candoxatril. In NEP-deficient mice DIO impaired glucose utilization and this was improved with enalapril. Nerve function was not impaired by DIO in NEP-deficient mice. These studies suggest that ACE and NEP play a role in pathophysiology associated with DIO.

Obesity and cardiovascular risk in children and adolescents

The global prevalence of overweight and obesity in children and adolescents has increased substantially over the past several decades. These trends are also visible in developing economies like India. Childhood obesity impacts all the major organ systems of the body and is well known to result in significant morbidity and mortality. Obesity in childhood and adolescence is associated with established risk factors for cardiovascular diseases and accelerated atherosclerotic processes, including elevated blood pressure (BP), atherogenic dyslipidemia, atherosclerosis, metabolic syndrome, type II diabetes mellitus, cardiac structural and functional changes and obstructive sleep apnea. Probable mechanisms of obesity-related hypertension include insulin resistance, sodium retention, increased sympathetic nervous system activity, activation of the renin-angiotensin-aldosterone system and altered vascular function. Adiposity promotes cardiovascular risk clustering during childhood and adolescence. Insulin resistance has a strong association with childhood obesity. A variety of proinflammatory mediators that are associated with cardiometabolic dysfunction are also known to be influenced by obesity levels. Obesity in early life promotes atherosclerotic disease in vascular structures such as the aorta and the coronary arteries. Childhood and adolescent adiposity has strong influences on the structure and function of the heart, predominantly of the left ventricle. Obesity compromises pulmonary function and increases the risk of sleep-disordered breathing and obstructive sleep apnea. Neglecting childhood and adolescent obesity will compromise the cardiovascular health of the pediatric population and is likely to result in a serious public health crisis in future.

Efficacy and tolerability of telmisartan plus amlodipine in added-risk hypertensive patients

OBJECTIVES

Added-risk hypertensive patients with co-morbidities such as diabetes and metabolic syndrome often require two or more antihypertensives to achieve blood pressure (BP) targets. The aim of this sub-analysis was to determine the efficacy and safety of telmisartan 40 or 80 mg plus amlodipine 5 or 10 mg in patients with hypertension, stratified according to certain criteria such as type 2 diabetes mellitus and metabolic syndrome.

METHODS

Patients were treated for 8 weeks with telmisartan 20-80 mg plus amlodipine 2.5-10 mg. This post-hoc analysis included patients treated with higher doses, and stratified according to a number of sub-populations (age, race, diabetes, obesity, metabolic syndrome, elevated baseline systolic BP (SBP), renal impairment).

RESULTS

Eight weeks' treatment with telmisartan plus amlodipine combinations provided consistent reductions in mean SBP/diastolic BP (DBP) across the different sub-populations, similar to the overall population. SBP/DBP reductions ranged from -13.5 to -34.7/-12.6 to -26.1 mmHg and BP goal rates (<140/90 mmHg) ranged from 29.8-100% for the four key dose combinations of telmisartan plus amlodipine. For the highest dose combination of telmisartan 80 mg plus amlodipine 10 mg, SBP/DBP reduction ranged from -19.1 to -34.7/-16.4 to -22.8 mmHg and goal attainment rate from 66.7% to 87.0%. Across the sub-populations, high SBP and DBP response rates were seen with combination treatment (83.3-97.7% and 75.0-95.7%, respectively, with telmisartan 80 mg plus amlodipine 10 mg). The combination was safe and well tolerated across all sub-populations and the incidence of peripheral oedema with telmisartan 40-80 mg plus amlodipine 10 mg was generally lower than with A10 monotherapy.

CONCLUSIONS

Despite small patient numbers in some sub-populations and the post-hoc nature of the analysis, this does show that the combination of telmisartan plus amlodipine provides an effective, safe and well-tolerated antihypertensive treatment for added-risk hypertensive patients.

Cardiovascular-renal and metabolic characterization of a rat model of polycystic ovary syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is the most common reproductive dysfunction in premenopausal women. PCOS is also associated with increased risk of cardiovascular disease when PCOS first occurs and later in life. Hypertension, a common finding in women with PCOS, is a leading risk factor for cardiovascular disease. The mechanisms responsible for hypertension in women with PCOS have not been elucidated.

OBJECTIVE

This study characterized the cardiovascular-renal consequences of hyperandrogenemia in a female rat model.

METHODS

Female Sprague-Dawley rats (aged 4-6 weeks) were implanted with dihydrotestosterone or placebo pellets lasting 90 days. After 10 to 12 weeks, blood pressure (by radiotelemetry), renal function (glomerular filtration rate, morphology, protein, and albumin excretion), metabolic parameters (plasma insulin, glucose, leptin, cholesterol, and oral glucose tolerance test), inflammation (plasma tumor necrosis factor-α), oxidative stress (mRNA expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits, p22(phox), p47(phox), gp91(phox), and NOX4), nitrate/nitrite excretion and mRNA expression of components of the renin-angiotensin system (angiotensinogen, angiotensin-I-converting enzyme [ACE], and AT1 receptor) were determined.

RESULTS

Plasma dihydrotestosterone increased 3-fold in hyperandrogenemic female (HAF) rats, whereas plasma estradiol levels did not differ compared with control females. HAF rats exhibited estrus cycle dysfunction. They also had increased food intake and body weight, increased visceral fat, glomerular filtration rate, renal injury, insulin resistance and metabolic dysfunction, oxidative stress, and increased expression of angiotensinogen and ACE and reduced AT1 receptor expression.

CONCLUSIONS

The HAF rat is a unique model that exhibits many of the characteristics of PCOS in women and is a useful model to study the mechanisms responsible for PCOS-mediated hypertension.

Angiotensin II Type 1 Receptors and Systemic Hemodynamic and Renal Responses to Stress and Altered Blood Volume in Conscious Rabbits

We examined how systemic blockade of type 1 angiotensin (AT(1)-) receptors affects reflex control of the circulation and the kidney. In conscious rabbits, the effects of candesartan on responses of systemic and renal hemodynamics and renal excretory function to acute hypoxia, mild hemorrhage, and plasma volume expansion were tested. Candesartan reduced resting mean arterial pressure (MAP, -8 ± 2%) without significantly altering cardiac output (CO), increased renal blood flow (RBF, +38 ± 9%) and reduced renal vascular resistance (RVR, -32 ± 6%). Glomerular filtration rate (GFR) was not significantly altered but sodium excretion (U(Na+)V) increased fourfold. After vehicle treatment, hypoxia (10% inspired O(2) for 30 min) did not significantly alter MAP or CO, but reduced heart rate (HR, -17 ± 6%), increased RVR (+33 ± 16%) and reduced GFR (-46 ± 16%) and U(Na+)V (-41 ± 17%). Candesartan did not significantly alter these responses. After vehicle treatment, plasma volume expansion increased CO (+35 ± 7%), reduced total peripheral resistance (TPR, -26 ± 5%), increased RBF (+62 ± 23%) and reduced RVR (-32 ± 9%), but did not significantly alter MAP or HR. It also increased U(Na+)V (803 ± 184%) yet reduced GFR (-47 ± 9%). Candesartan did not significantly alter these responses. After vehicle treatment, mild hemorrhage did not significantly alter MAP but increased HR (+16 ± 3%), reduced CO (-16 ± 4%) and RBF (-18 ± 6%), increased TPR (+18 ± 4%) and tended to increase RVR (+18 ± 9%, P = 0.1), but had little effect on GFR or U(Na+)V. But after candesartan treatment MAP fell during hemorrhage (-19 ± 1%), while neither TPR nor RVR increased, and GFR (-64 ± 18%) and U(Na+)V (-83 ± 10%) fell. AT(1)-receptor activation supports MAP and GFR during hypovolemia. But AT(1)-receptors appear to play little role in the renal vasoconstriction, hypofiltration, and antinatriuresis accompanying hypoxia, or the systemic and renal vasodilatation and natriuresis accompanying plasma volume expansion.

Drug mechanisms to help in managing resistant hypertension in obesity

Obesity is a major risk factor for the development of hypertension. Because the prevalence of obesity is increasing worldwide, the prevalence of obesity hypertension is also increasing. Importantly, hypertension in obesity is commonly complicated by dyslipidemia and type 2 diabetes mellitus and hence imposes a high cardiovascular disease risk. Furthermore, obesity is strongly associated with resistant hypertension. Activation of the sympathetic nervous system and the renin-angiotensin system, leading to renal sodium and water retention, links obesity with hypertension. There is also evidence for the release of factors by visceral adipose tissue promoting excessive aldosterone production, and a more central role of aldosterone in obesity hypertension is emerging. Randomized studies evaluating the effect of different classes of antihypertensive agents in obesity hypertension are scarce, short-lasting, and small. Considering the emerging role of aldosterone in the pathogenesis of obesity hypertension, mineralocorticoid receptor antagonism may play a more central role in the pharmacologic treatment of obesity hypertension in the near future.

Effect of Treatment of Sprague Dawley Rats with AVE7688, Enalapril, or Candoxatril on Diet-Induced Obesity

The objective of this study was to determine the effect of AVE7688, a drug that inhibits both angiotensin converting enzyme (ACE) and neutral endopeptidase (NEP) activity, on neural and vascular defects caused by diet induced obesity (DIO). Rats at 12 weeks of age were fed a standard or high fat diet with or without AVE7688 for 24 weeks. DIO rats had impaired glucose tolerance and developed sensory neuropathy. Vascular relaxation to acetylcholine and calcitonin gene-related peptide was decreased in epineurial arterioles of DIO rats. Rats fed a high fat diet containing AVE7688 did not become obese and vascular and sensory nerve dysfunction and impaired glucose tolerance were improved. DIO is associated with increased expression of NEP in epineurial arterioles. NEP degrades vasoactive peptides which may explain the decrease in neurovascular function in DIO.

Obesity-related hypertension: epidemiology, pathophysiology, and clinical management

The prevalence of obesity, including childhood obesity, is increasing worldwide. Weight gain is associated with increases in arterial pressure, and it has been estimated that 60-70% of hypertension in adults is attributable to adiposity. Centrally located body fat, associated with insulin resistance and dyslipidemia, is a more potent determinant of blood pressure elevation than peripheral body fat. Obesity-related hypertension may be a distinct hypertensive phenotype with distinct genetic determinants. Mechanisms of obesity-related hypertension include insulin resistance, sodium retention, increased sympathetic nervous system activity, activation of renin-angiotensin-aldosterone, and altered vascular function. In overweight individuals, weight loss results in a reduction of blood pressure, however, this effect may be attenuated in the long term. An increasing number of community-based programs (including school programs and worksite programs) are being developed for the prevention and treatment of obesity. Assessment and treatment of the obese hypertensive patient should address overall cardiovascular disease (CVD) risk. There are no compelling clinical trial data to indicate that any one class of antihypertensive agents is superior to others, and in general the principles of pharmacotherapy for obese hypertensive patients are not different from nonobese patients. Future research directions might include: (i) development of effective, culturally sensitive strategies for the prevention and treatment of obesity; (ii) clinical trials to identify the most effective drug therapies for reducing CVD in obese, hypertensive patients; (iii) continued search for the genetic determinants of the obese, hypertensive phenotype.

The RAAS in the pathogenesis and treatment of diabetic nephropathy

Angiotensin II and other components of the renin-angiotensin-aldosterone system (RAAS) have a central role in the pathogenesis and progression of diabetic renal disease. A study in patients with type 1 diabetes and overt nephropathy found that RAAS inhibition with angiotensin-converting-enzyme (ACE) inhibitors was associated with a reduced risk of progression to end-stage renal disease and mortality compared with non-RAAS-inhibiting drugs. Blood-pressure control was similar between groups and proteinuria reduction was responsible for a large part of the renoprotective and cardioprotective effect. ACE inhibitors can also prevent microalbuminuria in patients with type 2 diabetes who are hypertensive and normoalbuminuric; in addition, ACE inhibitors are cardioprotective even in the early stages of diabetic renal disease. Angiotensin-II-receptor blockers (ARBs) are renoprotective (but not cardioprotective) in patients with type 2 diabetes and overt nephropathy or microalbuminuria. Studies have evaluated the renoprotective effect of other RAAS inhibitors, such as aldosterone antagonists and renin inhibitors, administered either alone or in combination with ACE inhibitors or ARBs. An important task for the future will be identifying which combination of agents achieves the best renoprotection (and cardioprotection) at the lowest cost. Such findings will have major implications, particularly in settings where money and facilities are limited and in settings where renal replacement therapy is not available and the prevention of kidney failure is life saving.

Progression of cardiovascular damage: the role of renin-angiotensin system blockade

The renin-angiotensin system (RAS) plays key roles throughout the cardiovascular continuum, and blockade of this system--either through angiotensin-converting enzyme (ACE) inhibition or through angiotensin II type 1 (AT(1)) receptor antagonism--now occupies a central place in the management of cardiovascular disease (CVD). Understanding of the RAS has expanded in recent years with the identification of new pathways for formation of angiotensin II and novel effector peptides, such as angiotensin-(1-7), which may constitute new therapeutic targets. A substantial proportion of the benefits of ACE inhibitors, including vasodilation, improvements in endothelial function, and inhibition of cell proliferation, appear to be attributable to decreases in angiotensin II and increases in bradykinin. In addition, however, there is evidence that other mechanisms, such as modulation of ACE signaling, may also contribute. Angiotensin receptor blockers (ARBs) selectively block AT(1) receptors and allow unopposed stimulation of AT(2) receptors, with potentially beneficial vasodilatory, anti-inflammatory, and antiproliferative effects. As a result, these agents share many of the clinical benefits of ACE inhibitors. Both ACE inhibitors and ARBs have been shown to exert multiple antiatherogenic actions, and to reduce clinical events in high-risk participants; their use is recommended in current guidelines for the secondary prevention of CVD.

Metabolic effects of low dose angiotensin converting enzyme inhibitor in dietary obesity in the rat

BACKGROUND AND AIMS

Given the recent observation of a local renin-angiotensin system (RAS) in adipose tissue, and its association with obesity-related hypertension, the metabolic effects of treatment with a low dose angiotensin converting enzyme inhibitor (ACEI) were investigated in a rodent model of diet-induced obesity.

METHODS AND RESULTS

Male Sprague Dawley rats were exposed to either standard laboratory chow (12% calories as fat) or palatable high fat (30% calories as fat) diet for 12 weeks. A subset from both dietary groups was given low dose ACEI in drinking water (perindopril, 0.3 mg/kg/day) throughout the study. The high fat diet increased body weight, adiposity, circulating leptin and insulin and in the liver we observed fat accumulation and increased tissue ACE activity. Treatment with perindopril decreased food intake and circulating insulin in both diet groups, and hepatic ACE activity in high fat fed animals only. Decreased plasma leptin concentration with ACE inhibition was only evident in chow fed animals. These effects were independent of any blood pressure lowering effect of ACE inhibition.

CONCLUSION

Chronic low dose ACEI treatment reduced circulating insulin and leptin levels with some reduction in food intake in chow fed rats. Fewer beneficial effects were observed in obesity, and further work is required to investigate higher ACEI doses. Our data suggest a reduction in hepatic ACE activity may affect lipid accumulation and other inflammatory responses, as well as improving insulin resistance. Our findings may have implications for maximizing the clinical benefit of ACEI in patients without overt cardiovascular complications.

Is kidney ischemia the central mechanism in parallel activation of the renin and sympathetic system?

In chronic kidney disease simultaneous activation of the renin-angiotensin and sympathetic systems occurs. Kidney ischemia seems to play a key role in the pathogenesis. This review firstly summarizes experimental and clinical evidence in chronic kidney disease supporting this idea and addresses the possibility that this mechanism is also relevant in some other disease conditions.

Tempol or candesartan prevents high-fat diet-induced hypertension and renal damage in spontaneously hypertensive rats

BACKGROUND

Obesity has been strongly associated with the development and aggravation of hypertension and chronic kidney disease. To date, the systemic renin-angiotensin system (RAS) has been known to involve in obesity-induced tissue damage and hypertension. However, the intrarenal mechanism whereby obesity induces and aggravates hypertension and renal disease remains poorly understood. Therefore, we investigated the role of intrarenal RAS and oxidative stress in diet-induced hypertension and renal inflammation in spontaneously hypertensive rats (SHR) fed a high-fat diet.

METHODS

Male SHR and Wistar-Kyoto rats (WKY) were divided into eight groups: normal-fat diet-fed WKY (WKY-NF), high-fat diet-fed WKY (WKY-HF), high-fat diet-fed tempol-treated WKY (WKY-HF/T), high-fat diet-fed candesartan-treated WKY (WKY-HF/C), normal-fat diet-fed SHR (SHR-NF), high-fat diet-fed SHR (SHR-HF), high-fat diet-fed tempol-treated SHR (SHR-HF/T) and high-fat diet-fed candesartan-treated SHR (SHR-HF/C). After 12 weeks of treatment, haemodynamic measurements and histological assessment of the kidney were performed.

RESULTS

At the end of week 12, the high-fat fed SHR gained more body weight, their systolic blood pressure was further elevated and glucose intolerance induced. There was no significant difference in the insulin resistance index, serum lipid profile, plasma renin activity and serum aldosterone levels according to diet. However, the high-fat diet resulted in increases in immunohistochemical stains of renin and angiotensin II in the kidney. The real-time PCR also demonstrated significant increases in mRNA levels of renin, angiotensinogen and angiotensin-converting enzyme in the kidney, reflecting enhanced activation of the intrarenal RAS, which findings were also shown by Western blot analysis for renin and angiotensin II type 1 receptor. The expression of ED-1, osteopontin and TGF-beta1 in the renal cortex were prominently enhanced in the SHR-HF group with the increased intrarenal lipid concentrations and oxidative stress. Administration of tempol or candesartan in the high-fat diet-induced SHR inhibited the elevation of the systolic blood pressure, intrarenal lipid concentrations, oxidative stress and the degree of renal inflammation to the levels of, or more than, the SHR-NF with no differences in the body weight and periepididymal fat weight, compared to those in the SHR-HF group without such treatment.

CONCLUSIONS

Our study suggests that a high-fat diet induces fatty kidneys, aggravation of blood pressure and renal inflammation in the SHR. Blockade of oxidative stress by tempol or of RAS by candesartan ameliorates the increase in blood pressure and renal inflammation and improves intrarenal lipid accumulation. Therefore, antioxidants or angiotensin receptor blockers can prevent diet-induced hypertension and renal inflammation in hypertensive rats.