Weight loss and the renin-angiotensin-aldosterone system

Metabolic syndrome prevalence in psoriasis: a cross-sectional study in the Italian population

BACKGROUND

The pathogenesis of psoriasis is complex, with a significant role suggested for pro-inflammatory mediators. There is strong evidence of an association between psoriasis and the metabolic syndrome (MetS), a cluster of cardiovascular risk factors, which impose a substantial disease burden.

OBJECTIVE

This study aimed to evaluate the prevalence of MetS and to examine the implications of disease severity, type 2 diabetes mellitus, and cardiovascular disease in a large cohort of Italian psoriatic patients representative of the whole population.

METHODS

This was a cross-sectional study involving 13 dermatological clinics in Italy. The primary study endpoint was a comparison of the prevalence of MetS between psoriatic patients and a non-psoriatic control group; secondary endpoints included the influence of psoriasis severity on the prevalence of MetS, and the relative prevalence and risk of type 2 diabetes mellitus and cardiovascular disorders.

RESULTS

A total of 720 patients were enrolled (n = 360 per group). The prevalence of MetS was 26.84% in the psoriatic population and 15.16% in the control population (p = 0.0001; adjusted odds ratio 1.96). MetS was associated with a greater degree of psoriasis severity, and the prevalence and risk of diabetes tended to be higher in psoriatic patients than in the control group.

CONCLUSION

In the Italian population, the prevalence of MetS and associated comorbidities is elevated in patients with psoriasis compared with non-psoriatic subjects, as has been demonstrated in other countries. Our findings reinforce the importance of considering the implications of metabolic comorbidities in treating patients with psoriasis.

Aberrant Rac1-mineralocorticoid receptor pathways in salt-sensitive hypertension

According to Guyton's model, impaired renal sodium excretion plays a key role in the increased salt sensitivity of blood pressure (BP). Several factors contribute to impaired renal sodium excretion, including the sympathetic nervous system, the renin-angiotensin system and aldosterone. Accumulating evidence suggests that abnormalities in aldosterone and its receptor (i.e. the mineralocorticoid receptor (MR)) are involved in the development of salt-sensitive (SS) hypertension. Patients with metabolic syndrome often exhibit hyperaldosteronism and are susceptible to SS hypertension. Aldosterone secretion from the adrenal glands is not suppressed in obese hypertensive rats fed a high-salt diet because of the abundant production of adipocyte-derived aldosterone-releasing factors, which are independent of the negative feedback regulation of aldosterone secretion by the renin-angiotensin-aldosterone system. Increased plasma aldosterone levels lead to SS hypertension via MR activation in the kidney. Renal MR activity is increased in Dahl salt-sensitive rats fed a high-salt diet, despite the appropriate suppression of plasma aldosterone levels. In this rat strain, activation of MR in the distal nephron causes salt-induced hypertension. This paradoxical response of the MR to salt loading can be attributed to activation of Rac1, a small GTPase. In the presence of aldosterone, activated Rac1 synergistically and directly activates MR in a ligand-independent manner. Thus, Rac1 activation in the kidney determines the salt sensitivity of BP. Together, the available evidence suggests that the aberrant Rac1-MR pathway plays a key role in the development of SS hypertension.

AT1 receptor blockade alters nutritional and biometric development in obesity-resistant and obesity-prone rats submitted to a high fat diet

Obesity is a chronic metabolic condition with important public health implications associated with numerous co-morbidities including cardiovascular disease, insulin resistance, and hypertension. The renin angiotensin system (RAS), best known for its involvement in cardiovascular control and body fluid homeostasis has, more recently, been implicated in regulation of energy balance. Interference with the RAS (genetically or pharmacologically) has been shown to influence body weight gain. In this study we investigated the effects of systemic AT₁ receptor blockade using losartan on ingestive behaviors and weight gain in diet induced obese (DIO) rats. Prior to losartan administration (30 mg/kg/day) body weight gain remained constant within the DIO animals (3.6 ± 0.3 g/day, n = 8), diet resistant (DR) animals (2.1 ± 0.6 g/day, n = 8) and in the age-matched chow fed control (CHOW) animals (2.8 ± 0.3 g/day, n = 8), Losartan administration abolished body weight gain in animals fed a high fat diet (DIO: -0.4 ± 0.7 g/day, n = 8; and DR: -0.8 ± 0.3 g/day, n = 8) while chow fed animals continued to gain weight (2.2 ± 0.3 g/day, n = 8) as they had previously to oral administration of losartan. This decrease in daily body weight gain was accompanied by a decrease in food intake in the HFD fed animals. Following the removal of losartan, both the DIO and DR animals again showed daily increases in body weight gain and food intake which were similar to control values. Our data demonstrate that oral losartan administration attenuates body weight gain in animals fed a HFD whether the animal is obese (DIO) or not DR while having no effect on body weight gain in age-matched chow fed animals suggesting a protective effect of losartan against body weight gain while on a HFD.

Elevated serum uric acid is associated with angiotensinogen in obese patients with untreated hypertension

This study investigated the correlation between elevated serum uric acid (SUA) and angiotensinogen in obesity patients with hypertension. A total of 162 obese and 162 nonobese men with hypertension were recruited in this study. Plasma angiotensinogen levels were measured by enzyme-linked immunosorbent assay. Fasting insulin (FINS) was evaluated by radioimmunoassay. Compared with nonobese patients, obese patients exhibited higher levels of angiotensinogen, FINS, and homeostasis model assessment index-insulin resistance (HOMA-IR) (P<.001 for all). Moreover, these indexes significantly increased in obese patients in the highest tertile of SUA when compared with those in the lowest tertile of SUA (P<.001, P=.002, P=.007, respectively). In the obese group, SUA levels were significantly related to angiotensinogen, FINS, and HOMA-IR, respectively. Furthermore, it was demonstrated that obesity × uric acid was an independent contributor to angiotensinogen (β=0.257, P<.001). In conclusion, elevated SUA is strongly related to angiotensinogen in an obesity-dependent manner in hypertension.

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.

Longitudinal changes of blood pressure after weight loss: factors involved

BACKGROUND

The combination of obesity and hypertension (HT) places patients at a higher risk for adverse cardiovascular outcomes and raises the need to establish the pathogenic mechanisms of this relationship. The aim of this study was to assess the effects of important weight loss on longitudinal changes in blood pressure (BP) and investigate the pathogenic factors associated with these changes.

METHODS

We performed a prospective, open-label study including 37 obese hypertensive patients (28 females, mean age 52±8 yr) undergoing BS. Before BS, and at 4 and 12 months postoperatively, the body mass index (BMI), 24-h ambulatory BP, renin-angiotensin-aldosterone system (RAAS: plasma rennin activity, aldosterone, angiotensin II, and angiotensin converting enzyme), sympathetic nervous system (SNS: metanephrines, normetanephrines, and norepinephrine) components, leptin, insulin, and abdominal fat were measured.

RESULTS

Before BS, HT-duration was 6±6 years, the BMI 45±5 kg/m2 and excess weight (EBW) was 53±12 kg. At 12 months, the excess BMI loss was 14 kg/m2 and the EBW loss was 70 %; HT remission was observed in 70%; 24-h (systolic 19±13/diastolic 7±9 mm Hg), day and night BP levels and aldosterone, norepinephrine, leptin, insulin, subcutaneous and visceral abdominal fat (VAT) significantly decreased (P<.05). Mixed models for repeated measures revealed that HT-duration, baseline BP, BMI, and VAT area were the main variables associated with longitudinal changes in BP.

CONCLUSION

These results demonstrate that the hypotensive response after weight loss in severely hypertensive obese patients is mainly regulated by HT-duration, baseline BP, BMI and VAT area, independently of suppression of hyperinsulinemia or changes in RAAS and SNS components.

In utero exposure to the endocrine disruptor di-(2-ethylhexyl) phthalate promotes local adipose and systemic inflammation in adult male offspring

Background:

Di-(2-ethylhexyl) phthalate (DEHP) is a plasticizer used to increase the flexibility of polyvinyl chloride. DEHP and its active metabolite mono-(2-ethylhexyl) phthalate are detected in many biological fluids during fetal and postnatal life. In rodent models, in utero DEHP exposure has been shown to alter sexual organ development, decrease testosterone and aldosterone production, increase body and epididymal adipose tissue weight, and raise serum lipids and glucose levels in male offspring.

Objectives:

The objective of this study is to characterize the effects of in utero DEHP exposure on adipose tissue development and function in male offspring.

Methods:

Sprague–Dawley pregnant dams were gavaged 1, 20, 50 or 300 mg DEHP per kg per day from gestational day 14 until birth.

Results:

Global gene expression analyses of postnatal day 60 male offspring that were exposed in utero to 300 mg DEHP per kg per day revealed increased expression of immune response and inflammation markers, and increased expression of differentiation pathway genes in the epididymal whole-adipose tissue and isolated stromal vascular fraction. C-reactive protein and tumor necrosis factor (TNF) serum levels were increased in the 300 mg DEHP in utero-exposed offspring. TNF levels in adipose tissue homogenates were increased in the 50 and 300 mg DEHP in utero-exposed offspring. Immunofluorescence studies revealed focal macrophage infiltration in whole-adipose tissue confirmed by increased CD163 tissue content.

Conclusions:

In utero DEHP exposure promotes local adipose tissue inflammation and chronic low-grade systemic inflammation. Moreover, evidence is presented, suggesting that DEHP increases the differentiation capacity of the pre-adipocytes of male offspring without affecting total body weight.

Increased aldosterone: mechanism of hypertension in obesity

The prevalence of both obesity and hypertension are increasing worldwide. Hypertension is a common consequence of obesity. Increased central adiposity is associated with increased aldosterone levels and blood pressure in human beings. A number of small studies have shown an association between obesity-mediated hypertension and mechanisms directly linked to increased levels of aldosterone. These studies have shown a trend toward relatively greater blood pressure reduction using aldosterone-receptor blockers compared with other classes of antihypertensive agents. Other than treatment for weight loss, treatment of hypertension with specific antihypertensive medications that block or reduce aldosterone action are appropriate in obese patients. Further research is needed to understand the exact role of the adipocyte in obesity-mediated hypertension.

The renin-angiotensin-aldosterone system in adolescent offspring born prematurely to mothers with preeclampsia

HYPOTHESIS/INTRODUCTION

Preeclampsia is associated with alterations in the maternal renin-angiotensin-aldosterone system (RAAS), increased blood pressure (BP), and cardiovascular risk in the offspring. We hypothesized that preeclampsia is associated with alterations in the RAAS in the offspring that persist into adolescence.

MATERIALS AND METHODS

We compared components of the circulating (n = 111) and renal (n = 160) RAAS in adolescents born prematurely with very low birth weight (VLBW) of preeclamptic (PreE) and normotensive (NoHTN) pregnancies. Multivariable linear regression was used to evaluate potential confounding and intermediate variables. Analyses were stratified by sex.

RESULTS

Adjusting for race and antenatal steroid exposure, male offspring of PreE mothers had higher circulating aldosterone than those of NoHTN mothers (adjusted mean difference = 109; 95% confidence limits: -9, 227 pmol/L). Further adjustment for current BMI attenuated this difference (adjusted mean difference: 93; 95% confidence limits: -30, 215 pmol/L).

CONCLUSION

Among male preterm VLBW infants, maternal preeclampsia is associated with increased circulating aldosterone level in adolescence, which appears to be mediated in part by higher BMI.

A comprehensive review on metabolic syndrome

Metabolic syndrome is defined by a constellation of interconnected physiological, biochemical, clinical, and metabolic factors that directly increases the risk of cardiovascular disease, type 2 diabetes mellitus, and all cause mortality. Insulin resistance, visceral adiposity, atherogenic dyslipidemia, endothelial dysfunction, genetic susceptibility, elevated blood pressure, hypercoagulable state, and chronic stress are the several factors which constitute the syndrome. Chronic inflammation is known to be associated with visceral obesity and insulin resistance which is characterized by production of abnormal adipocytokines such as tumor necrosis factor α , interleukin-1 (IL-1), IL-6, leptin, and adiponectin. The interaction between components of the clinical phenotype of the syndrome with its biological phenotype (insulin resistance, dyslipidemia, etc.) contributes to the development of a proinflammatory state and further a chronic, subclinical vascular inflammation which modulates and results in atherosclerotic processes. Lifestyle modification remains the initial intervention of choice for such population. Modern lifestyle modification therapy combines specific recommendations on diet and exercise with behavioural strategies. Pharmacological treatment should be considered for those whose risk factors are not adequately reduced with lifestyle changes. This review provides summary of literature related to the syndrome's definition, epidemiology, underlying pathogenesis, and treatment approaches of each of the risk factors comprising metabolic syndrome.

Low serum potassium level is associated with nonalcoholic fatty liver disease and its related metabolic disorders

CONTEXT

Subjects with nonalcoholic fatty liver disease (NAFLD) have a high risk of developing type 2 diabetes and cardiovascular diseases. Low serum potassium concentration or low dietary potassium intake can result in metabolic disorders.

OBJECTIVE

Our objective was to evaluate the association between low serum potassium level and prevalence of NAFLD in a Chinese population.

DESIGN

A population-based cross-sectional study.

PATIENTS

We conducted a community-based study in 8592 subjects to investigate the association of serum potassium with the risk of prevalent NAFLD. NAFLD was diagnosed by hepatic ultrasonography.

RESULTS

The prevalence rate of NAFLD was 30·3% in this population and gradually decreased across serum potassium quartiles. With the reduction in serum potassium level, participants have larger waist circumference (WC) and more severe insulin resistance. The correlations hold also in multivariate linear regression analysis. In logistic regression analysis, compared with subjects in the highest quartile of serum potassium level, the adjusted odds ratios (ORs) in the lowest quartile was 1·33 [95% confidence interval (CI), 1·11-1·60] for NAFLD, 1·81 (95% CI, 1·49-2·19) for insulin resistance and 1·58 (95% CI, 1·30-1·93) for central obesity. In subgroup analysis after multiple adjustments, significant relation between serum potassium level and prevalent NAFLD was detected in women, younger subjects, those with insulin resistance and those with central obesity, respectively.

CONCLUSION

Low serum potassium level significantly associated with prevalence of NAFLD in middle-aged and elderly Chinese.

Effects of angiotensin converting enzyme inhibition on adiponectin levels and lipid profile in the ovariectomized-aged rats

Objective:

To investigate the relationship between angiotensin converting enzyme (ACE) and adiponectin and lipid profile in the ovariectomized-aged rats.

Materials and Methods:

Wistar albino rats were first divided into two groups; control (C) and ovariectomized (OVX). Bilateral ovariectomy were carried out on rats (n = 30) except control group (n = 10). After 6 weeks from ovariectomy, ovariectomized rats were subdivided into three groups; one group received no treatment (OVX), two groups received low dose (OVX + Cap5; 5 mg/kg/day) and high dose (OVX + Cap20; 20 mg/kg/day) captopril (Cap). Body weights were monitored weekly. Adiponectin, triglyceride, cholesterol, high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), and very low density lipoprotein cholesterol (VLDL-C) levels were measured at the end of the 6 weeks.

Results:

In the OVX group, body weights increased (P < 0.001). In the OVX + Cap20 group, body weights significantly decreased compared with the OVX group during weeks 5 and 6 (P < 0.05). While adiponectin levels increased in the OVX + Cap5 group (P = 0.014), triglyceride and cholesterol levels decreased in the OVX + Cap20 group (P = 0.016 and P < 0.001, respectively) compared to the OVX group. HDL-C and VLDL-C levels decreased only in OVX + Cap20 group (P < 0.005).

Conclusions:

ACE inhibitors may be decreasing the ovariectomy-induced weight gain by increasing adiponectin levels, and by affecting lipid profiles. The adipose tissue renin-angiotensin system (RAS) may be playing an important role in the development of adiposity.

Pioglitazone upregulates angiotensin converting enzyme 2 expression in insulin-sensitive tissues in rats with high-fat diet-induced nonalcoholic steatohepatitis

Background and Aim. Thiazolidinediones (TZDs) can improve hepatic steatosis in nonalcoholic steatohepatitis (NASH). Angiotensin (Ang) II, the primary effector of renin-angiotensin system (RAS), plays vital roles in the development and progression of NASH. And some AngII-mediated effects can be regulated by TZDs. Angiotensin-converting enzyme (ACE) 2, a new component of RAS, can degrade Ang II to attenuate its subsequent physiological actions. We aimed to evaluate the effects of TZDs on ACE2 expression in insulin-sensitive tissues in NASH rats. Methods. Forty rats were divided into the normal control, high-fat diet (HFD), pioglitazone control, and HFD plus pioglitazone groups. After 24 weeks of treatment, we evaluated changes in liver histology and tissue-specific ACE2 expression. Results. ACE2 gene and protein expression was significantly greater in liver and adipose tissue in the HFD group compared with normal control group, while was significantly reduced in skeletal muscle. Pioglitazone significantly reduced the degree of hepatic steatosis compared with the HFD group. Pioglitazone significantly increased ACE2 protein expression in liver, adipose tissue, and skeletal muscle compared with the HFD group. Conclusions. Pioglitazone improves hepatic steatosis in the rats with HFD-induced NASH and upregulates ACE2 expression in insulin-sensitive tissues.

Adiposopathy: how do diet, exercise and weight loss drug therapies improve metabolic disease in overweight patients?

An increase in bodyweight is generally associated with an increased risk of excessive fat-related metabolic diseases (EFRMD), including Type 2 diabetes mellitus, hypertension and dyslipidemia. However, not all patients who are overweight have EFRMD, and not all patients with EFRMD are significantly overweight. The adipocentric paradigm provides the basis for a unifying, pathophysiological process whereby fat gain in susceptible patients leads to fat dysfunction ('sick fat'), and wherein pathological abnormalities in fat function (adiposopathy) are more directly related to the onset of EFRMD than increases in fat mass (adiposity) alone. But just as worsening fat function worsens EFRMD, improved fat function improves EFRMD. Peroxisome proliferator-activated receptor-gamma agonists increase the recruitment, proliferation and differentiation of preadipocytes ('healthy fat') and cause apoptosis of hypertrophic and dysfunctional (including visceral) adipocytes resulting in improved fat function and improved metabolic parameters associated with EFRMD. Weight loss interventions, such as a hypocaloric diet and physical exercise, in addition to agents such as orlistat, sibutramine and cannabinoid receptor antagonists, may have favorable effects upon fat storage (lipogenesis and fat distribution), nutrient metabolism (such as free fatty acids), favorable effects upon adipose tissue factors involved in metabolic processes and inflammation, and enhanced 'cross-talk' with other major organ systems. In some cases, weight loss therapeutic agents may even affect metabolic parameters and adipocyte function independently of weight loss alone, suggesting that the benefit of these agents in improving EFRMD may go beyond their efficacy in weight reduction. This review describes how adiposopathy interventions may affect fat function, and thus improve EFRMD.

Association between retinol-binding protein 4 and polycystic ovary syndrome: a meta-analysis

Studies have examined the association between retinol-binding protein 4 (RBP4) and polycystic ovary syndrome (PCOS). However, the results have been inconsistent. To investigate the association between RBP4 and PCOS, we performed a meta-analysis. The Cochrane Library, MEDLINE, the ISI Web of Science, and EMBASE were searched to identify all of the studies that examined the relationship between circulating RBP4 levels and PCOS. Standard mean difference (SMD) values and 95% confidence interval (CI) were estimated and pooled using meta-analysis methodology. A total of seven studies were involved in the meta-analysis, which included a total of 636 subjects (260 controls and 376 patients with PCOS). The RBP4 level was higher in PCOS patients than in non-PCOS patients (random effects MD (95% CI)=0.69, [0.20, 1.18], P=0.006). However, the RBP4 level was not higher in nonobese PCOS patients than in nonobese controls (random effects MD (95% CI)=0.38, [-0.21, 0.98], P=0.20). The effect size revealed that the RBP4 level was higher in overweight or obese PCOS patients than weight-matched controls (fixed effects MD (95% CI)=7.95, [5.96, 9.93], P<0.05). In the subgroup analysis by region, the RBP4 level was higher in PCOS patients in Asia than controls (random effects MD (95% CI)=0.85, [0.54, 1.15], P<0.05), but not in European PCOS patients compared with controls (random effects MD (95% CI)=0.34, [-1.12, 1.80], P=0.65). This subgroup analysis also showed that nonobese PCOS patients have higher RBP4 levels than controls in Asia. Our meta-analysis results indicated that RBP4 might be a useful tool for identifying PCOS women.

Obesity associated hypertension: new insights into mechanism

With excess nutrition, the burden of obesity is a growing problem worldwide. The imbalance between energy intake and expenditure leads to variable disorders as all major risk factors for cardiovascular disease. There are many hypothetical mechanisms to explain obesity-associated hypertension. Activation of the RAAS is a key contributing factor in obesity. Particularly, the RAAS in adipose tissue plays a crucial role in adipose tissue dysfunction and obesity-induced inflammation. The phenotypic changes of adipocytes occur into hypertrophy and an inflammatory response in an autocrine and paracrine manner to impair adipocyte function, including insulin signaling pathway. Adipose tissue produce and secretes several molecules such as leptin, resistin, adiponectin, and visfatin, as well as cytokines such as TNF-α, IL-6, MCP-1, and IL-1. These adipokines are stimulated via the intracellular signaling pathways that regulate inflammation of adipose tissue. Inflammation and oxidative stress in adipose tissue are important to interact with the microvascular endothelium in the mechanisms of obesity-associated hypertension. Increased microvascular resistance raises blood pressure. Therefore, a regulatory link between microvascular and perivascular adipose tissue inflammation and adipokine synthesis are provided to explain the mechanism of obesity-associated hypertension.

Effects of blocking of angiotensin system on the prevalence of metabolic syndrome in type 2 diabetic patients

OBJECTIVE

To evaluate prevalence of metabolic syndrome in hypertensive type 2 diabetic patients treated with antihypertensive drugs that inhibit renin angiotensin system.

METHODOLOGY

Two groups of patients were included in this study. The first group involved 130 hypertensive type 2 diabetic patients taking enalapril, captopril (Converting Enzyme inhibitors), valsartan or telmisartan (Angiotensin II receptor blockers) as monotherapy whereas group 2 involved 92 type 2 diabetic patients with normal blood pressure. Metabolic syndrome was diagnosed according to criteria made by the US National Cholesterol Education Program Adult Treatment Panel III. Serum glucose concentration, serum triglycerides and HDL-cholesterol were measured by using special kits.

RESULTS

The percentage of patients having metabolic syndrome was lower in group 1 (58.47%) as compared with group 2 (73%). Waist circumferences, triglycerides and FBS were significantly lower in group 1 as compared with group 2. BP and HDL-cholesterol were significantly higher in group 1 as compared with group 2.

CONCLUSION

Inhibition of RAS by converting enzyme inhibitors or angiotensin II receptor blockers captopril, enalapril, valsartan or telmisartan produce beneficial effects on the markers of metabolic syndrome and can reduce the frequency of metabolic syndrome in type 2 diabetic patients.

Renal hemodynamic effect of sodium-glucose cotransporter 2 inhibition in patients with type 1 diabetes mellitus

BACKGROUND

The primary objective of this mechanistic open-label, stratified clinical trial was to determine the effect of 8 weeks' sodium glucose cotransporter 2 inhibition with empagliflozin 25 mg QD on renal hyperfiltration in subjects with type 1 diabetes mellitus (T1D).

METHODS AND RESULTS

Inulin (glomerular filtration rate; GFR) and paraaminohippurate (effective renal plasma flow) clearances were measured in individuals stratified based on having hyperfiltration (T1D-H, GFR ≥ 135 mL/min/1.73m(2), n=27) or normal GFR (T1D-N, GFR 90-134 mL/min/1.73m(2), n=13) at baseline. Renal function and circulating levels of renin-angiotensin-aldosterone system mediators and NO were measured under clamped euglycemic (4-6 mmol/L) and hyperglycemic (9-11 mmol/L) conditions at baseline and end of treatment. During clamped euglycemia, hyperfiltration was attenuated by -33 mL/min/1.73m(2) with empagliflozin in T1D-H, (GFR 172±23-139±25 mL/min/1.73 m(2), P<0.01). This effect was accompanied by declines in plasma NO and effective renal plasma flow and an increase in renal vascular resistance (all P<0.01). Similar significant effects on GFR and renal function parameters were observed during clamped hyperglycemia. In T1D-N, GFR, other renal function parameters, and plasma NO were not altered by empagliflozin. Empagliflozin reduced hemoglobin A1c significantly in both groups, despite lower insulin doses in each group (P≤0.04).

CONCLUSIONS

In conclusion, short-term treatment with the sodium glucose cotransporter 2 inhibitor empagliflozin attenuated renal hyperfiltration in subjects with T1D, likely by affecting tubular-glomerular feedback mechanisms.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT01392560.

The renin-angiotensin system in adipose tissue and its metabolic consequences during obesity

Obesity is a worldwide disease that is accompanied by several metabolic abnormalities such as hypertension, hyperglycemia and dyslipidemia. The accelerated adipose tissue growth and fat cell hypertrophy during the onset of obesity precedes adipocyte dysfunction. One of the features of adipocyte dysfunction is dysregulated adipokine secretion, which leads to an imbalance of pro-inflammatory, pro-atherogenic versus anti-inflammatory, insulin-sensitizing adipokines. The production of renin-angiotensin system (RAS) components by adipocytes is exacerbated during obesity, contributing to the systemic RAS and its consequences. Increased adipose tissue RAS has been described in various models of diet-induced obesity (DIO) including fructose and high-fat feeding. Up-regulation of the adipose RAS by DIO promotes inflammation, lipogenesis and reactive oxygen species generation and impairs insulin signaling, all of which worsen the adipose environment. Consequently, the increase of circulating RAS, for which adipose tissue is partially responsible, represents a link between hypertension, insulin resistance in diabetes and inflammation during obesity. However, other nutrients and food components such as soy protein attenuate adipose RAS, decrease adiposity, and improve adipocyte functionality. Here, we review the molecular mechanisms by which adipose RAS modulates systemic RAS and how it is enhanced in obesity, which will explain the simultaneous development of metabolic syndrome alterations. Finally, dietary interventions that prevent obesity and adipocyte dysfunction will maintain normal RAS concentrations and effects, thus preventing metabolic diseases that are associated with RAS enhancement.

Mineralocorticoid receptors modulate vascular endothelial function in human obesity

Obesity increases linearly with age and is associated with impaired vascular endothelial function and increased risk of cardiovascular disease. MRs (mineralocorticoid receptors) contribute to impaired vascular endothelial function in cardiovascular disease; however, their role in uncomplicated human obesity is unknown. Because plasma aldosterone levels are elevated in obesity and adipocytes may be a source of aldosterone, we hypothesized that MRs modulate vascular endothelial function in older adults in an adiposity-dependent manner. To test this hypothesis, we administered MR blockade (eplerenone; 100 mg/day) for 1 month in a balanced randomized double-blind placebo-controlled cross-over study to 22 older adults (ten men, 55-79 years) varying widely in adiposity [BMI (body mass index): 20-45 kg/m²], but who were free from overt cardiovascular disease. We evaluated vascular endothelial function [brachial artery FMD (flow-mediated dilation)] via ultrasonography) and oxidative stress (plasma F2-isoprostanes and vascular endothelial cell protein expression of nitrotyrosine and NADPH oxidase p47phox) during placebo and MR blockade. In the whole group, oxidative stress (P>0.05) and FMD did not change with MR blockade (6.39 ± 0.67 compared with 6.23 ± 0.73%; P=0.7). However, individual improvements in FMD in response to eplerenone were associated with higher total body fat (BMI: r=0.45, P=0.02; and dual-energy X-ray absorptiometry-derived percentage body fat: r=0.50, P=0.009) and abdominal fat (total: r=0.61, P=0.005; visceral: r=0.67, P=0.002; and subcutaneous: r=0.48, P=0.03). In addition, greater improvements in FMD with eplerenone were related to higher baseline fasting glucose (r=0.53, P=0.01). MRs influence vascular endothelial function in an adiposity-dependent manner in healthy older adults.

Changes in serum aldosterone are associated with changes in obesity-related factors in normotensive overweight and obese young adults

Recent data suggest excess circulating aldosterone promotes cardiometabolic decline. Weight loss may lower aldosterone levels, but little longitudinal data is available in normotensive adults. We aimed to determine whether, independent of changes in sodium excretion, reductions in serum aldosterone are associated with favorable changes in obesity-related factors in normotensive overweight/obese young adults. We studied 285 overweight/obese young adult participants (body mass index ≥ 25 and<40 kg m⁻², age 20-45 years) in a clinical trial examining the effects of a 1-year diet and physical activity intervention with or without sodium restriction on vascular health. Body weight, serum aldosterone, 24-h sodium and potassium excretion and obesity-related factors were measured at baseline, 6, 12 and 24 months. Weight loss was significant at 6 (7%), 12 (6%) and 24 months (4%; all P<0.0001). Decreases in aldosterone were associated with decreases in C-reactive protein, leptin, insulin, homeostasis assessment of insulin resistance, heart rate, tonic cardiac sympathovagal balance and increases in adiponectin (all P<0.05) in models adjusting for baseline age, sex, race, intervention arm, time since baseline, and sodium and potassium excretion. Weight loss and reductions in thigh intermuscular fat (intermuscular adipose tissue area; IMAT) were associated with decreases in aldosterone in the subgroup (n=98) with metabolic syndrome (MetS) at baseline (MetS × weight loss, P=0.04; MetS × change in IMAT, P=0.04). Favorable changes in obesity-related factors are associated with reductions in aldosterone in young adults with no risk factors besides excess weight, an important finding, given aldosterone's emergence as an important cardiometabolic risk factor.

Angiotensin converting enzyme insertion/deletion polymorphism is associated with increased adiposity and blood pressure in obese children and adolescents

BACKGROUND

The insertion/deletion polymorphism in the gene encoding the angiotensin-converting enzyme (ACE I/D) was associated with arterial hypertension and obesity in adults, but the data in children are scarce and yielded contrasting results. We assessed the impact of the ACE I/D on blood pressure and obesity related traits in a Brazilian cohort of obese children and adolescents.

METHODS AND RESULTS

ACE I/D was genotyped in 320 obese children and adolescents (64% of girls) aged 7-16years, referred for a weight-loss program. We observed an association of the D-allele with blood pressure and with pre-hypertension/hypertension in boys (odds ratio 2.44, 95% C.I. 1.34-4.68, p=0.005 for a codominant model). The D-allele, insulin resistance and body fat mass had independent and additive effects and explained 14% of the variance of pre-hypertension/hypertension. The BMI, waist circumference, and body fat mass were significantly higher in DD/ID boys than in II boys (p<0.005). Allelic associations with obesity related traits were independent of the association with blood pressure. No genotype associations were observed in girls.

CONCLUSIONS

The D-allele of the ACE I/D polymorphism was associated with arterial hypertension and with obesity related traits in boys, but not in girls, in a cohort of obese children and adolescents. These associations were independent of each other, as well as of the effects of other confounding traits such as insulin secretion, insulin sensitivity and glucose tolerance. Our results are in agreement with experimental evidences suggesting that the renin-angiotensin system plays a role in the regulation of visceral adipose tissue accumulation.

Adipose tissue renin-angiotensin-aldosterone system (RAAS) and progression of insulin resistance

This review focuses on the expression of the key components of the renin-angiotensin-aldosterone axis in fat tissue. At the center of this report is the role of RAAS in normal and excessive fat mass enlargement, the leading etiology of insulin resistance. Understanding the expression and regulation of RAAS components in various fat depots allows insight not only into the processes by which these complex patterns are modified by the enlargement of adipose tissue, but also into their impact on local and systemic response to insulin.

Effects of weight on blood pressure at rest and during exercise

Body weight (BW) and blood pressure (BP) have a close relationship, which has been accounted for by hormonal changes. No previous study has evaluated the effect of wearing an external weight vest on BP to determine whether there is a simple mechanism between BW and BP. Seventeen healthy volunteers underwent weight reduction (WR) through caloric restriction. Before and after WR, BW, body fat percentage and BP at rest and during exercise were measured. Before and after WR, exercise testing was performed twice with the random allocation of a weight vest (10 kg) during one of the tests. Linear regression was used to detect independent associations between BP and the weight vest, BW and body fat percentage. BW decreased from 89.4 ± 15.4 kg to 79.1 ± 14.0 kg following WR (P<0.001). WR led to significant decreases in BP at rest (from 130.0/85.9 mm Hg to 112.5/77.8 mm Hg, P<0.001 for systolic and diastolic BPs) and during exercise. The weight vest significantly increased BP at rest (to 136.1/90.7 mm Hg before and 125.8/84.6 mm Hg after WR) and during exercise. Linear regression analysis identified an independent association between the weight vest and BP (P=0.006 for systolic BP and P=0.009 for diastolic BP at rest). This study demonstrates that wearing an external weight vest has immediate effects on BP at rest and during exercise independent of BW or body fat. More research is needed to understand the physiological mechanisms between weight and BP.

The role of the renin-angiotensin-aldosterone system in obesity-related renal diseases

Obesity is an independent risk factor for the development and progression of chronic kidney disease and one of the emerging reasons for end-stage renal disease owing to its dramatic increase worldwide. Among the potential underlying pathophysiologic mechanisms, activation of the renin-angiotensin-aldosterone-system (RAAS) plays a central role. Increased angiotensin II (AngII) levels also are central in hypertension, dyslipidemia, and insulin resistance, which, taken together with obesity, represent the metabolic syndrome. Increased AngII levels contribute to hyperfiltration, glomerulomegaly, and subsequent focal glomerulosclerosis by altering renal hemodynamics via afferent arteriolar dilation, together with efferent renal arteriolar vasoconstriction as well as by its endocrine and paracrine properties linking the intrarenal and the systemic RAAS, adipose tissue dysfunction, as well as insulin resistance and hypertension. The imbalance between increased AngII levels and the angiotensin converting enzyme 2/Ang (1-7)/Mas receptor axis additionally contributes to renal injury in obesity and its concomitant metabolic disturbances. As shown in several large trials and experimental studies, treatment of obesity by weight loss is associated with an improvement of kidney disease because it also is beneficial in dyslipidemia, hypertension, and diabetes. The most promising data have been seen by RAAS blockade, pointing to the central position of RAAS within obesity, kidney disease, and the metabolic syndrome.

The adipose tissue as an endocrine organ

During the past 2 decades, results of both basic science and clinical studies have changed the physicians' views about adipocyte pathophysiology. Since leptin was discovered in 1994, white adipose tissue was recognized as an endocrine organ and an important source of biologically active substances with local and/or systemic action called adipokines. Inappropriate secretion of several adipokines by the excessive amount of white adipose tissue seems to participate in the pathogenesis of obesity-related pathologic processes including endothelial dysfunction, inflammation, atherosclerosis, diabetes mellitus, and chronic kidney disease. In this review endocrine action of selected adipokines (mainly leptin and adiponectin) in the context of kidney diseases is discussed. Specifically, the role of these adipokines in malnutrition, chronic kidney disease progression, and pathogenesis of cardiovascular complications is presented.

The renin angiotensin aldosterone system and insulin resistance in humans

Alterations in the renin angiotensin aldosterone system (RAAS) contribute to the underlying pathophysiology of insulin resistance in humans; however, individual differences in the treatment response of insulin resistance to RAAS blockade persist. Thus, understanding inter-individual differences in the relationship between the RAAS and insulin resistance may provide insights into improved personalized treatments and improved outcomes. The effects of the systemic RAAS on blood pressure regulation and glucose metabolism have been studied extensively; however, recent discoveries on the influence of local tissue RAAS in the skeletal muscle, heart, vasculature, adipocytes, and pancreas have led to an improved understanding of how activated tissue RAAS influences the development of insulin resistance and diabetes in humans. Angiotensin II (ANGII) is the predominant RAAS component contributing to insulin resistance; however, other players such as aldosterone, renin, and ACE2 are also involved. This review examines the role of local ANGII activity on insulin resistance development in skeletal muscle, adipocytes, and pancreas, followed by a discussion of the other RAAS components implicated in insulin resistance, including ACE2, Ang1-7, renin, and aldosterone.

AMPK couples plasma renin to cellular metabolism by phosphorylation of ACC1

Salt reabsorption is the major energy-requiring process in the kidney, and AMP-activated protein kinase (AMPK) is an important regulator of cellular metabolism. Mice with targeted deletion of the β1-subunit of AMPK (AMPK-β1(-/-) mice) had significantly increased urinary Na(+) excretion on a normal salt diet. This was associated with reduced expression of the β-subunit of the epithelial Na(+) channel (ENaC) and increased subapical tubular expression of kidney-specific Na(+)-K(+)-2Cl(-) cotransporter 2 (NKCC2) in the medullary thick ascending limb of Henle. AMPK-β1(-/-) mice fed a salt-deficient diet were able to conserve Na(+), but renin secretion increased 180% compared with control mice. Cyclooxygenase-2 mRNA also increased in the kidney cortex, indicating greater signaling through the macula densa tubular salt-sensing pathway. To determine whether the increase in renin secretion was due to a change in regulation of fatty acid metabolism by AMPK, mice with a mutation of the inhibitory AMPK phosphosite in acetyl-CoA carboxylase 1 [ACC1-knockin (KI)(S79A) mice] were examined. ACC1-KI(S79A) mice on a normal salt diet had no increase in salt loss or renin secretion, and expression of NKCC2, Na(+)-Cl(-) cotransporter, and ENaC-β were similar to those in control mice. When mice were placed on a salt-deficient diet, however, renin secretion and cortical expression of cyclooxygenase-2 mRNA increased significantly in ACC1-KI(S79A) mice compared with control mice. In summary, our data suggest that renin synthesis and secretion are regulated by AMPK and coupled to metabolism by phosphorylation of ACC1.

Oral formulation of angiotensin-(1-7) improves lipid metabolism and prevents high-fat diet-induced hepatic steatosis and inflammation in mice

Angiotensin (Ang)-(1-7) has been described as an important tool on treating and preventing metabolic disorders. In this study, we aimed to evaluate the effect of an oral formulation of Ang-(1-7) included in hydroxypropylβ-cyclodextrin (HPβCD/Ang-[1-7]) on hepatic function, steatosis, and on liver inflammatory markers expression in mice treated with a high-fat diet. Male FVB/N mice were divided into 4 groups and fed for 60 days, with each group receiving 1 of the following diets: standard diet+HPβCD, standard diet+Ang-(1-7)/HPβCD, high-fat diet+HPβCD, or high-fat diet+Ang-[1-7]/HPβCD. Body weight, food intake, and blood parameters, such as total cholesterol, triglyceride, alaninetransaminases, and aspartate transaminases, were evaluated. Immunohistochemical analyses were performed for inflammatory markers tumor necrosis factor-α and interleukin-6. Expression of angiotensin converting enzyme, angiotensin-converting enzyme-2, interleukin-1β, tumor necrosis factor-α, interleukin-6, transforming growth factor-β, acetyl-CoA carboxylase, carbohydrate-responsive element-binding protein, peroxisome proliferator-activated receptor-γ, and sterol regulatory element-binding proteins-1c was evaluated by quantitative real-time polymerase chain reaction. The major findings of our study included reduced liver fat mass and weight, decreased plasma total cholesterol, triglyceride, and alaninetransaminase enzyme levels in the oral Ang-(1-7)-treated groups compared with the control groups. These results were accompanied by a significant reduction in tumor necrosis factor-α and interleukin-6 mRNA expression in the liver. Analyses of liver adipogenesis-related genes by quantitative real-time polymerase chain reaction showed that acetyl-CoA carboxylase, peroxisome proliferator-activated receptor-γ, and sterol regulatory element-binding proteins-1c mRNA expression were significantly suppressed. In conclusion, we observed that treatment with Ang-(1-7) improved metabolism and decreased proinflammatory profile and fat deposition in liver of mice.

A critical review of the evidence supporting aldosterone in the etiology and its blockade in the treatment of obesity-associated hypertension

Obesity is epidemic and is associated with increased blood pressure, which often manifests as treatment-resistant hypertension. Mineralocorticoids have been hypothesized to have a pathogenic role in human obesity-associated hypertension. In this review, we critically appraise the existing data regarding aldosterone in the pathophysiology and treatment of obesity-associated hypertension. We begin by reviewing the mechanisms by which obesity may increase mineralocorticoid activity. We then discuss human studies of plasma and urine aldosterone in obesity and with weight loss. From these studies, we conclude that aldosterone is often, but not always, mildly increased in obesity. Further study is needed to define circumstances in which aldosterone is increased in obesity. We discuss clinical studies in which measures of body size or weight were evaluated as potential predictors of response to mineralocorticoid receptor antagonists. In addition, we review three randomized, controlled clinical trials that exemplify a rigorous approach to determining the role of mineralocorticoid activity in a human disease. We propose that a similar clinical trial is warranted in order to definitively clarify the role of inappropriate mineralocorticoid activity in the etiology of human obesity-associated hypertension. Finally, we conclude that additional research is needed into the possible role of non-aldosterone mineralocorticoids in human obesity-associated hypertension.

Progressive cardiovascular autonomic dysfunction in rats with evolving metabolic syndrome

Metabolic syndrome is linked to increased cardiovascular mortality, which may be partially attributed to cardiac sympatho-vagal imbalance. However, autonomic changes were not evaluated during the metabolic syndrome development in a monosodium glutamate-induced animal model. We evaluate temporal changes in cardiovascular autonomic modulation in an animal model of metabolic syndrome. Eighteen neonate male spontaneously hypertensive rats (SHR) were treated with monosodium glutamate (MetS), and compared with Wistar-Kyoto (C) and saline-treated SHR (H). Lee index, insulin resistance and autonomic control (spectral analysis) were evaluated at 3 (3-mo), 6 (6-mo) and 9 (9-mo) months of age (compared by two-way ANOVA, p<0.05). Weight of visceral fat, Lee index and arterial pressure were higher in the MetS vs. C and H groups (p<0.001) at all ages. Heart rate variability (HRV) was decreased in the MetS and H groups at 3-mo and 9-mo vs. C. The LF component of HRV was reduced in the MetS group at 3-mo vs. C (p=0.032), and higher vs. C and H at 9-mo (p<0.001, all comparisons). H and MetS rats had a higher LF/HF index vs. C at 9-mo (p=0.001, all comparisons). The VLF component of systolic arterial pressure variability of the MetS was higher earlier (6-mo) than that of the H group. A reduction of 70%, 98% and 54% in αLF index of H and MetS rats vs. C, was observed at 3, 6 and 9 months, respectively. Metabolic syndrome and hypertension in rats evolve with progressive autonomic dysfunction (worst at 9 months), with specific derangements occurring very early.

Role of Rac1-mineralocorticoid-receptor signalling in renal and cardiac disease

The Rho-family small GTPase, Ras-related C3 botulinum toxin substrate 1 (Rac1), has been implicated in renal and cardiac disease. Rac1 activation in podocytes has been shown in several models of proteinuric kidney disease and a concept involving motile podocytes has been proposed. Evidence also exists for a critical role of Rac1-mediated oxidative stress in cardiac hypertrophy, cardiomyopathy and arrhythmia, and of the aldosterone-mineralocorticoid-receptor system in proteinuria and cardiac disorders. However, plasma aldosterone concentrations are not always increased in these conditions and the mechanisms of mineralocorticoid-receptor overactivation are difficult to determine. Using knockout mice, we identified a novel mechanism of Rac1-mediated podocyte impairment; Rac1 potentiates the activity of the mineralocorticoid receptor, thereby accelerating podocyte injury. We subsequently demonstrated that the Rac1-mineralocorticoid-receptor pathway contributes to ligand-independent mineralocorticoid-receptor activation in several animal models of kidney and cardiac injury. Hyperkalaemia is a major concern associated with the use of mineralocorticoid-receptor antagonists; however, agents that modulate the activity of the Rac1-mineralocorticoid-receptor pathway in target cells, such as cell-type-specific Rac inhibitors and selective mineralocorticoid-receptor modulators, could potentially be novel therapeutic candidates with high efficacy and a low risk of adverse effects in patients with renal and cardiac diseases.

Angiotensinogen gene silencing reduces markers of lipid accumulation and inflammation in cultured adipocytes

Inflammatory adipokines secreted from adipose tissue are major contributors to obesity-associated inflammation and other metabolic dysfunctions. We and others have recently documented the contribution of adipose tissue renin-angiotensin system to the pathogenesis of obesity, inflammation, and insulin resistance. We hypothesized that adipocyte-derived angiotensinogen (Agt) plays a critical role in adipogenesis and/or lipogenesis as well as inflammation. This was tested using 3T3-L1 adipocytes, stably transfected with Agt-shRNA or scrambled Sc-shRNA as a control. Transfected preadipocytes were differentiated and used to investigate the role of adipose Agt through microarray and PCR analyses and adipokine profiling. As expected, Agt gene silencing significantly reduced the expression of Agt and its hormone product angiotensin II (Ang II), as well as lipid accumulation in 3T3-L1 adipocytes. Microarray studies identified several genes involved in lipid metabolism and inflammatory pathways which were down-regulated by Agt gene inactivation, such as glycerol-3-phosphate dehydrogenase 1 (Gpd1), serum amyloid A 3 (Saa3), nucleotide-binding oligomerization domain containing 1 (Nod1), and signal transducer and activator of transcription 1 (Stat1). Mouse adipogenesis PCR arrays revealed lower expression levels of adipogenic/lipogenic genes such as peroxisome proliferator activated receptor gamma (PPARγ), sterol regulatory element binding transcription factor 1 (Srebf1), adipogenin (Adig), and fatty acid binding protein 4 (Fabp4). Further, silencing of Agt gene significantly lowered expression of pro-inflammatory adipokines including interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and monocyte chemotactic protein-1 (MCP-1). In conclusion, this study directly demonstrates critical effects of Agt in adipocyte metabolism and inflammation and further support a potential role for adipose Agt in the pathogenesis of obesity-associated metabolic alterations.

Obesity-related hypertension: pathogenesis, cardiovascular risk, and treatment--a position paper of the The Obesity Society and The American Society of Hypertension

In light of the worldwide epidemic of obesity, and in recognition of hypertension as a major factor in the cardiovascular morbidity and mortality associated with obesity, The Obesity Society and The American Society of Hypertension agreed to jointly sponsor a position paper on obesity-related hypertension to be published jointly in the journals of each society. The purpose is to inform the members of both societies, as well as practicing clinicians, with a timely review of the association between obesity and high blood pressure, the risk that this association entails, and the options for rational, evidenced-based treatment. The position paper is divided into six sections plus a summary as follows: pathophysiology, epidemiology and cardiovascular risk, the metabolic syndrome, lifestyle management in prevention and treatment, pharmacologic treatment of hypertension in the obese, and the medical and surgical treatment of obesity in obese hypertensive patients.

Obesity-related hypertension: pathogenesis, cardiovascular risk, and treatment: a position paper of The Obesity Society and the American Society of Hypertension

In light of the worldwide epidemic of obesity, and in recognition of hypertension as a major factor in the cardiovascular morbidity and mortality associated with obesity, The Obesity Society and the American Society of Hypertension agreed to jointly sponsor a position paper on obesity-related hypertension to be published jointly in the journals of each society. The purpose is to inform the members of both societies, as well as practicing clinicians, with a timely review of the association between obesity and high blood pressure, the risk that this association entails, and the options for rational, evidenced-based treatment. The position paper is divided into six sections plus a summary as follows: pathophysiology, epidemiology and cardiovascular risk, the metabolic syndrome, lifestyle management in prevention and treatment, pharmacologic treatment of hypertension in the obese, and the medical and surgical treatment of obesity in obese hypertensive patients.

Obesity-related hypertension and its remission following gastric bypass surgery - a review of the mechanisms and predictive factors

It is well established that hypertension and obesity appear to be associated. The exact mechanism by which they are linked is unclear and remains a topic of a great deal of research. Current NICE guidelines recommend that patients with a BMI in excess of 35 kg/m(2) should be considered for bariatric surgery if they have a concomitant obesity-associated condition, of which hypertension is one. The commonest bariatric procedure in the UK is the Roux-en-Y gastric bypass, which has been shown to result in long-standing remission of hypertension in up to 93% of patients. This paper summarizes the existing literature on the main theories as to how obesity leads to hypertension as well as the literature concerning the effects of gastric bypass surgery on hypertension.

Blood pressure response to angiotensin II is enhanced in obese Zucker rats and is attributed to an aldosterone-dependent mechanism

BACKGROUND AND PURPOSE

Plasma aldosterone levels correlate positively with obesity, suggesting a link between the hypertension associated with obesity and increased mineralocorticoid levels. We tested the hypothesis that aldosterone is involved in the BP response to angiotensin II (AngII) in obese rats.

EXPERIMENTAL APPROACH

Lean (LZR) and obese (OZR) Zucker rats were treated with AngII (9 µg·h(-1) ; 4 weeks), and BP and plasma AngII and aldosterone were determined.

KEY RESULTS

Chronic AngII increased the BP in OZR markedly more so than in LZR. Plasma AngII levels in LZR and OZR were similar after AngII treatment. The AngII stimulated a rise in plasma aldosterone that was sixfold more in OZR than in LZR. The thickness of the zona glomerulosa of the adrenal glands was selectively increased by AngII in OZR. Adrenal mRNA levels of CYP11B2 aldosterone synthase and the AT(1B) receptor were selectively increased in AngII-treated OZR. The BP response to chronic AngII stimulation was diminished in OZR after adrenalectomy when plasma aldosterone was absent. Acute bolus injections of AngII did not increase the BP response or aldosterone release in OZR.

CONCLUSIONS AND IMPLICATIONS

The AngII-induced BP response is enhanced in obesity and this is associated with a specific increase in circulating aldosterone. Due to the AngII-induced growth of the zona glomerulosa in OZR, the AT(1B) receptors and aldosterone synthase may be selectively enhanced in obesity under concomitant AngII stimulation, increasing the adrenal synthesis of aldosterone. Our results confirm functionally that aldosterone plays a major role in obesity-related hypertension.

Adipocyte deficiency of angiotensinogen prevents obesity-induced hypertension in male mice

Previous studies demonstrated that diet-induced obesity increased plasma angiotensin II concentrations and elevated systolic blood pressures in male mice. Adipocytes express angiotensinogen and secrete angiotensin peptides. We hypothesize that adipocyte-derived angiotensin II mediates obesity-induced increases in systolic blood pressure in male high fat-fed C57BL/6 mice. Systolic blood pressure was measured by radiotelemetry during week 16 of low-fat or high-fat feeding in Agt(fl/fl) and adipocyte angiotensinogen-deficient mice (Agt(aP2)). Adipocyte angiotensinogen deficiency had no effect on diet-induced obesity. Basal 24-hour systolic blood pressure was not different in low fat-fed Agt(fl/fl) compared with Agt(aP2) mice (124 ± 3 versus 128 ± 3 mm Hg, respectively). In Agt(fl/fl) mice, high-fat feeding significantly increased systolic blood pressure (24 hours; 134 ± 2 mm Hg; P<0.05). In contrast, high fat-fed Agt(aP2) mice did not exhibit an increase in systolic blood pressure (126 ± 2 mm Hg). Plasma angiotensin II concentrations were increased by high-fat feeding in Agt(fl/fl) mice (low fat, 32 ± 14; high fat, 219 ± 58 pg/mL; P<0.05). In contrast, high fat-fed Agt(aP2) mice did not exhibit elevated plasma angiotensin II concentrations (high fat, 18 ± 7 pg/mL). Similarly, adipose tissue concentrations of angiotensin II were significantly decreased in low fat- and high fat-fed Agt(aP2) mice compared with controls. In conclusion, adipocyte angiotensinogen deficiency prevented high fat-induced elevations in plasma angiotensin II concentrations and systolic blood pressure. These results suggest that adipose tissue serves as a major source of angiotensin II in the development of obesity hypertension.

Brain renin-angiotensin system in the nexus of hypertension and aging

Aging is associated with an imbalance in sympathetic and parasympathetic outflow to cardiovascular effector organs. This autonomic imbalance contributes to the decline in cardiovagal baroreceptor reflex function during aging, which allows for unrestrained activation of the sympathetic nervous system to negatively impact resting systolic blood pressure and its variability. Further, impaired baroreflex function can contribute to the development of insulin resistance and other features of the metabolic syndrome during aging through overlap in autonomic neural pathways that regulate both cardiovascular and metabolic functions. Increasing evidence supports a widespread influence of the renin-angiotensin system (RAS) on both sympathetic and parasympathetic activity through receptors distributed to peripheral and central sites of action. Indeed, therapeutic interventions to block the RAS are well established for the treatment of hypertension in elderly patients, and reduce the incidence of new-onset diabetes in clinical trials. Further, RAS blockade increases lifespan and improves numerous age-related pathologies in rodents, often independent of blood pressure. The beneficial effects of these interventions are at least in part attributed to suppression of angiotensin II formed locally within the brain. In particular, recent insights from transgenic rodents provide evidence that long-term alteration in the brain RAS modulates the balance between angiotensin II and angiotensin-(1-7), and related intracellular signaling pathways, to influence cardiovascular and metabolic function in the context of hypertension and aging.

The adipose tissue renin-angiotensin system and metabolic disorders: a review of molecular mechanisms

The renin-angiotensin system (RAS) is classically known for its role in regulation of blood pressure, fluid and electrolyte balance. In this system, angiotensinogen (Agt), the obligate precursor of all bioactive angiotensin peptides, undergoes two enzymatic cleavages by renin and angiotensin converting enzyme (ACE) to produce angiotensin I (Ang I) and angiotensin II (Ang II), respectively. The contemporary view of RAS has become more complex with the discovery of additional angiotensin degradation pathways such as ACE2. All components of the RAS are expressed in and have independent regulation of adipose tissue. This local adipose RAS exerts important auto/paracrine functions in modulating lipogenesis, lipolysis, adipogenesis as well as systemic and adipose tissue inflammation. Mice with adipose-specific Agt overproduction have a 30% increase in plasma Agt levels and develop hypertension and insulin resistance, while mice with adipose-specific Agt knockout have a 25% reduction in Agt plasma levels, demonstrating endocrine actions of adipose RAS. Emerging evidence also points towards a role of RAS in regulation of energy balance. Because adipose RAS is overactivated in many obesity conditions, it is considered a potential candidate linking obesity to hypertension, insulin resistance and other metabolic derangements.

Effects of aerobic exercise training on cardiac renin-angiotensin system in an obese Zucker rat strain

Objective

Obesity and renin angiotensin system (RAS) hyperactivity are profoundly involved in cardiovascular diseases, however aerobic exercise training (EXT) can prevent obesity and cardiac RAS activation. The study hypothesis was to investigate whether obesity and its association with EXT alter the systemic and cardiac RAS components in an obese Zucker rat strain.

Methods

The rats were divided into the following groups: Lean Zucker rats (LZR); lean Zucker rats plus EXT (LZR+EXT); obese Zucker rats (OZR) and obese Zucker rats plus EXT (OZR+EXT). EXT consisted of 10 weeks of 60-min swimming sessions, 5 days/week. At the end of the training protocol heart rate (HR), systolic blood pressure (SBP), cardiac hypertrophy (CH) and function, local and systemic components of RAS were evaluated. Also, systemic glucose, triglycerides, total cholesterol and its LDL and HDL fractions were measured.

Results

The resting HR decreased (∼12%) for both LZR+EXT and OZR+EXT. However, only the LZR+EXT reached significance (p<0.05), while a tendency was found for OZR versus OZR+EXT (p = 0.07). In addition, exercise reduced (57%) triglycerides and (61%) LDL in the OZR+EXT. The systemic angiotensin I-converting enzyme (ACE) activity did not differ regardless of obesity and EXT, however, the OZR and OZR+EXT showed (66%) and (42%), respectively, less angiotensin II (Ang II) plasma concentration when compared with LZR. Furthermore, the results showed that EXT in the OZR prevented increase in CH, cardiac ACE activity, Ang II and AT2 receptor caused by obesity. In addition, exercise augmented cardiac ACE2 in both training groups.

Conclusion

Despite the unchanged ACE and lower systemic Ang II levels in obesity, the cardiac RAS was increased in OZR and EXT in obese Zucker rats reduced some of the cardiac RAS components and prevented obesity-related CH. These results show that EXT prevented the heart RAS hyperactivity and cardiac maladaptive morphological alterations in obese Zucker rats.

Effects of Losartan vs. Enalapril on the Markers of Metabolic Syndrome

OBJECTIVE

To compare the effects of losartan and enalapril on the markers of metabolic syndrome.

METHODS

One hundred and twenty six newly diagnosed hypertensive patients having other markers of metabolic syndrome participated in this study. The study was performed in the department of pharmacology, college of medicine at Ibn-Sina Teaching Hospital in Mosul city, Iraq, during the period between December 2007 and June 2009. The patients were divided into 2 main groups: 1) Losartan group: consisted of 60 patients, and 2) enalapril group: Consisted of 66 patients. Waist circumference, weight, Body mass index, blood pressure, serum glucose concentration, triglyceride and HDL-cholestrol were measured before and after administration of therapy. The effects of therapy were assessed by statistically comparing the results before and after the drug administration.

RESULTS

Comparison of waist circumference, blood pressure, FSG, triglycerides of the patients before drug administration (baseline data), with those of the controls showed a significant elevation, while HDL-cholesterol showed a significant reduction. A significant reduction of waist circumference, BP, FSG and a significant elevation of HDL-cholesterol were also noted after therapy with both losartan and enalapril.

CONCLUSION

Both losartan and enalapril produced a significant reduction of markers of metabolic syndrome and may be regarded as effective drugs for treatment of hypertension in patients with markers of metabolic syndrome.

Does it matter how blood pressure is lowered in patients with metabolic risk factors?

Abdominal obesity is an important cardiovascular risk factor. It is a primary driver of the metabolic syndrome, the cluster of metabolic risk factors that includes insulin resistance and dyslipidemia, and often occurs in association with hypertension. The aim of antihypertensive therapy in patients with metabolic risk factors is to reduce cardiovascular risk, but some antihypertensive agents can exert adverse metabolic effects. For example, beta-blockers produce significant weight gain, and are associated with an increased incidence of diabetes. By contrast, agents that inhibit the renin-angiotensin system (RAS), such as angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), have been shown to be associated with a decreased risk of new-onset diabetes. This reflects the finding that increased activation of the RAS in obese individuals can contribute to the development of the metabolic syndrome. The ARB telmisartan has been shown to act as a selective peroxisome proliferator-activated receptor (PPAR)-gamma modulator. It is known that PPAR-gamma plays a role in the regulation of multiple genes affecting carbohydrate and lipid metabolism; however, the clinical significance of this remains to be established. The potential metabolic effects of RAS blockade should be considered in the choice of antihypertensive therapy for patients with metabolic risk factors, including obesity.

Valsartan Improves Insulin Sensitivity without Altering Vascular Function in Healthy Overweight Adults without the Metabolic Syndrome

Background. We investigated hyperactivity of the renin-angiotensin system (RAS) as a cause of endothelial dysfunction in obese humans. Methods. Thirty five healthy overweight (BMI = 33.6 +/- 6.6 kg m (2)) adults (33 +/- 10 years old) without cardiovascular risk factors received valsartan (160 mg) orally daily or a matching placebo for 6 weeks each. Results. Baseline flow-mediated dilatation (FMD) and nitroglycerin-mediated dilatation (NMD) were not altered by placebo or valsartan. However, fasting plasma insulin was significantly decreased by valsartan compared to placebo (-4.6 +/- 16.0 muUmL(1) versus -0.4 +/- 11.6 muUmL(1), P = 0.032) with no changes in glucose. A secondary analysis in patients with elevated waist to hip ratios (ÿ0.85, n = 18) showed an increase in FMD with valsartan. Conclusions. Our findings suggest that angiotensin 2 receptor blockade may aid in the prevention of diabetes even at the earliest stages of risk due solely to uncomplicated obesity. The lack of an improvement in FMD does not support a central role of RAS-hyperactivity in the etiology of the vascular dysfunction due solely to obesity. However, it is possible that obese patients with central adiposity may improve FMD with RAS blockade, and future investigation is warranted in this subgroup.

Joint statement of the European Association for the Study of Obesity and the European Society of Hypertension: obesity and difficult to treat arterial hypertension

Obese patients are prone to arterial hypertension, require more antihypertensive medications, and have an increased risk of treatment-resistant arterial hypertension. Obesity-induced neurohumoral activation appears to be involved. The association between obesity and hypertension shows large inter-individual variability, likely through genetic mechanisms. Obesity affects overall cardiovascular and metabolic risk; yet, the relationship between obesity and cardiovascular risk is complex and not sufficiently addressed in clinical guidelines. The epidemiological observation that obesity may be protective in patients with established cardiovascular disease is difficult to translate into clinical experience and practice. Weight loss is often recommended as a means to lower blood pressure. However, current hypertension guidelines do not provide evidence-based guidance on how to institute weight loss. In fact, weight loss influences on blood pressure may be overestimated. Nevertheless, weight loss through bariatric surgery appears to decrease cardiovascular risk in severely obese patients. Eventually, most obese hypertensive patients will require antihypertensive medications. Data from large-scale studies with hard clinical endpoints on antihypertensive medications specifically addressing obese patients are lacking and the morbidity from the growing population of severely obese patients is poorly recognized or addressed. Because of their broad spectrum of beneficial effects, renin-angiotensin system inhibitors are considered to be the most appropriate drugs for antihypertensive treatment of obese patients. Most obese hypertensive patients require two or more antihypertensive drugs. Finally, how to combine weight loss strategies and antihypertensive treatment to achieve an optimal clinical outcome is unresolved.

Targeting hypertension in patients with cardiorenal metabolic syndrome

Diabetes mellitus coexisting with hypertension is greater than chance alone would predict. Hypertensive patients have been shown to have altered composition of skeletal muscle tissue, decreased blood flow to skeletal muscle and post-receptor signaling alterations in the IRS insulin pathway, all inducing insulin resistance states, which partially explains why blood pressure goals in DM patients are lower than in normoglycemic patients. Although optimal first-step antihypertensive drug therapy in type 2 DM or impaired fasting glucose levels (IFG) should be individualized for each patient, converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs) have been demonstrated in some but not all studies to decrease the rate of development of proteinuria and diabetic renal disease. According to the ACCF/AHA 2011 Expert Consensus, elderly persons with diabetes, hypertension, and nephropathy should be initially treated with ACEIs or ARBs, although the choice of a specific antihypertensive may also depend on other associated comorbidities.