The adipose renin-angiotensin system: role in cardiovascular disease

Acetylcholine-loaded nanoparticles protect against doxorubicin-induced toxicity inin vitrocardiac spheroids

Doxorubicin (DOX) is widely used in chemotherapy, yet it significantly contributes to heart failure-associated death. Acetylcholine (ACh) is cardioprotective by enhancing heart rate variability and reducing mitochondrial dysfunction and inflammation. Nonetheless, the protective role of ACh in countering DOX-induced cardiotoxicity (DIC) remains underexplored as current approaches to increasing ACh levels are invasive and unsafe for patients. In this study, we explore the protective effects of ACh against DIC through three distinct ACh administration strategies: (i) freely-suspended 100µM ACh; (ii) ACh-producing cholinergic neurons (CNs); or (iii) ACh-loaded nanoparticles (ACh-NPs). These are tested inin vitrocardiac spheroids (CSs), which have previously been shown to approximate the complex DIC. We assess ACh's protective effects by measuring the toxicity ratio (cell death/viability), contractile activity, gene expression changes via qPCR and nitric oxide (NO) signaling. Our findings show that ACh effectively attenuates DOX-induced cell death and contractile dysfunction. ACh also counteracts the DOX-induced downregulation of genes controlling myocardial fibrosis, endothelial and cardiomyocyte dysfunction, and autonomic dysregulation. ACh cardioprotection against DOX is dependent on NO signaling in endothelial cells but not in cardiac myocytes or fibroblasts. Altogether, this study shows for the first time that elevating ACh levels showed a promising therapeutic approach for preventing DIC.

Predicting ART outcomes: The role of ovarian RAS and VEGF in follicular fluid of dominant follicles

As tissue and intracellular RAS have been reported in different organs and systems. there is local RAS in the ovary, called the ovarian renin-angiotensin system (OVRAS). In this study, we investigated the correlation between RAS (total renin, AngII, Ang1-7), vascular endothelial growth factor (VEGF) and E2 in dominant follicular fluid and ovarian reserve capacity and patient age. Moreover, we analyzed its predictive value for assisted reproductive technology (ART) related outcomes. We observed that the concentrations of VEGF in the follicular fluid of dominant follicles in the ≥ 38 year old group were markedly higher than those in the < 30 year old group (P < 0.05). Total renin and AngII levels were positively correlated with normal fertilization rate (P < 0.05). Ang1-7 levels were positively correlated with the number of mature oocytes, oocyte maturation rate and number of 2PN fertilized cells (P < 0.05). Expressions of VEGF were negatively correlated with number of 2PN fertilized cells, number of D3 embryos for blastocyst culture, number of blastocysts formed, number of available embryos and number of high-quality embryos (P < 0.05). Thus, the expressions of OVRAS (total renin, AngII, Ang1-7 and VEGF) in dominant follicular fluid are correlated with ART outcomes.

The interaction of BDNF with estrogen in the development of hypertension and obesity, particularly during menopause

The expression of BDNF in both neuronal and non-neuronal cells is influenced by various stimuli, including prenatal developmental factors and postnatal conditions such as estrogens, dietary habits, and lifestyle factors like obesity, blood pressure, and aging. Central BDNF plays a crucial role in modulating how target tissues respond to these stimuli, influencing the pathogenesis of hypertension, mitigating obesity, and protecting neurons from aging. Thus, BDNF serves as a dynamic mediator of environmental influences, reflecting an individual's unique history of exposure. Estrogens, on the other hand, regulate various processes to maintain overall physiological well-being. Through nuclear estrogen receptors (ERα, ERβ) and the membrane estrogen receptor (GPER1), estrogens modulate transcriptional processes and signaling events that regulate the expression of target genes, such as ERα, components of the renin-angiotensin system (RAS), and hormone-sensitive lipase. Estrogens are instrumental in maintaining the set point for blood pressure and energy balance. BDNF and estrogens work cooperatively to prevent obesity by favoring lipolysis, and counteractively regulate blood pressure to adapt to the environment. Estrogen deficiency leads to menopause in women with low central BDNF level. This review delves into the complex mechanisms involving BDNF and estrogen, especially in the context of hypertension and obesity, particularly among postmenopausal women. The insights gained aim to inform the development of comprehensive therapeutic strategies for these prevalent syndromes affecting approximately 68% of adults.

Comparison of the effects of renal denervation at early or advanced stages of hypertension on cardiac, renal, and adipose tissue pathology in Dahl salt-sensitive rats

Renal denervation (RDN) has emerged as a novel therapy for drug-resistant hypertension. We here examined the effects of RDN at early versus advanced stages of hypertension on blood pressure and organ pathology in rats with salt-sensitive hypertension. Dahl salt-sensitive (DahlS) rats fed an 8% NaCl diet from 6 weeks of age were subjected to RDN (surgical ablation and application of 10% phenol in ethanol) or sham surgery at 7 (early stage) or 9 (advanced stage) weeks and were studied at 12 weeks. RDN at early or advanced stages resulted in a moderate lowering of blood pressure. Although RDN at neither stage affected left ventricular (LV) and cardiomyocyte hypertrophy, it ameliorated LV diastolic dysfunction, fibrosis, and inflammation at both stages. Intervention at both stages also attenuated renal injury as well as downregulated the expression of angiotensinogen and angiotensin-converting enzyme (ACE) genes and angiotensin II type 1 receptor protein in the kidney. Furthermore, RDN at both stages inhibited proinflammatory gene expression in adipose tissue. The early intervention reduced both visceral fat mass and adipocyte size in association with downregulation of angiotensinogen and ACE gene expression. In contrast, the late intervention increased fat mass without affecting adipocyte size as well as attenuated angiotensinogen and ACE gene expression. Our results thus indicate that RDN at early or late stages after salt loading moderately alleviated hypertension and substantially ameliorated cardiac and renal injury and adipose tissue inflammation in DahlS rats. They also suggest that cross talk among the kidney, cardiovascular system, and adipose tissue may contribute to salt-sensitive hypertension. Supposed mechanism for the beneficial effects of RDN on hypertension and target organ damage in DahlS rats. RDN at early or late stages after salt loading moderately alleviated hypertension and substantially ameliorated renal injury in DahlS rats. Cross talk among the kidney, cardiovascular system, and adipose tissue possibly mediated by circulating RAS may contribute to salt-sensitive hypertension. LV; left ventricular, NE; norepinephrine, RAS; renin-angiotensin system, RDN; renal denervation.

Antiobesity Drug Discovery Research: In vitro Models for Shortening the Drug Discovery Pipeline

Obesity is a growing global health problem, leading to various chronic diseases. Despite standard treatment options, the prevalence of obesity continues to rise, emphasizing the need for new drugs. in vitro methods of drug discovery research provide a time and cost-saving platform to identify new antiobesity drugs. The review covers various aspects of obesity and drug discovery research using in vitro models. Besides discussing causes, diagnosis, prevention, and treatment, the review focuses on the advantages and limitations of in vitro studies and exhaustively covers models based on enzymes and cell lines from different animal species and humans. In contrast to conventional in vivo animal investigations, in vitro preclinical tests using enzyme- and cell line-based assays provide several advantages in development of antiobesity drugs. These methods are quick, affordable, and provide high-throughput screening. They can also yield insightful information about drug-target interactions, modes of action, and toxicity profiles. By shedding light on the factors that lead to obesity, in vitro tests can also present a chance for personalized therapy. Technology will continue to evolve, leading to the creation of more precise and trustworthy in vitro assays, which will become more and more crucial in the search for novel antiobesity medications.

The relationship between adipose tissue RAAS activity and the risk factors of prediabetes: a systematic review and meta-analysis

METHODS

This systematic review was developed in compliance with the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-2020) standards. This was accomplished by searching clinical MeSH categories in MEDLINE with full texts, EMBASE, Web of Science, PubMed, Cochrane Library, Academic Search Complete, ICTRP and ClinicalTrial.gov. Reviewers examined all the findings and selected the studies that satisfied the inclusion criteria. The Downs and Black Checklist was used to assess for bias, followed by a Review Manager v5. A Forrest plot was used for the meta-analysis and sensitivity analysis. The protocol for this review was registered with PROSPERO CRD42022320252.

RESULTS

The clinical studies (n = 2) comprised 1065 patients with prediabetes and 1103 normal controls. The RAAS measurements were completed in the adipose tissue. The RAAS components, renin and aldosterone were higher in the prediabetic (PD) compared to the control [mean difference (MD) = 0.16, 95% CI 0.16 (-0.13, 0.45), p = 0.25]. Furthermore, the PD group demonstrated higher triglycerides mean difference [MD = 7.84, 95% CI 7.84 (-9.84, 25.51), p = 0.38] and increased BMI [MD = 0.13, 95% CI 0.13 (-0.74, 0.99), p = 0.77] compared to the control. The overall quality of the studies was fair with a median score and range of 17 (16-18).

CONCLUSION

The current study highlights the relationship between increased BMI, RAAS and insulin resistance which is a predictor of prediabetes. The renin is slightly higher in the prediabetes group without any statistical significance, aldosterone is rather negatively associated with prediabetes which may be attributed to the use of anti-hypertensive treatment.

Fasting increases circulating angiotensin levels and brain Agtr1a expression in male rats

In addition to being recognised for involvement in cardiovascular control and hydromineral balance, the renin-angiotensin system (RAS) has also been associated with the neuroendocrine control of energy balance. One of the main brain sites for angiotensin II (ANG II)/type 1 receptor (AT1 R) signalling is the subfornical organ (SFO), a circumventricular organ related to the control of autonomic functions, motivated behaviours and energy metabolism. Thus, we hypothesised that circulating ANG II may act on the SFO AT1 R receptors to integrate metabolic and hydromineral balance. We evaluated whether food deprivation can modulate systemic RAS activity and Agrt1a brain expression, and if ANG II/AT1 R signalling influences the hypothalamic expression of mRNAs encoding neuropeptides and food and water ingestion in fed and fasted Wistar rats. We found a significant increase in both ANG I and ANG II plasma levels after 24 and 48 h of fasting. Expression of Agrt1a mRNA in the SFO and paraventricular nucleus (PVN) also increased after food deprivation for 48 h. Treatment of fasted rats with low doses of losartan in drinking water attenuated the decrease in glycemia and meal-associated water intake without changing the expression in PVN or arcuate nucleus of mRNAs encoding selected neuropeptides related to energy homeostasis control. These findings point to a possible role of peripheral ANG II/SFO-AT1 R signalling in the control of refeeding-induced thirst. On the other hand, intracerebroventricular losartan treatment decreased food and water intake over dark time in fed but not in fasted rats.

Perivascular Adipose Tissue Oxidative Stress in Obesity

Perivascular adipose tissue (PVAT) adheres to most systemic blood vessels in the body. Healthy PVAT exerts anticontractile effects on blood vessels and further protects against cardiovascular and metabolic diseases. Healthy PVAT regulates vascular homeostasis via secreting an array of adipokine, hormones, and growth factors. Normally, homeostatic reactive oxygen species (ROS) in PVAT act as secondary messengers in various signalling pathways and contribute to vascular tone regulation. Excessive ROS are eliminated by the antioxidant defence system in PVAT. Oxidative stress occurs when the production of ROS exceeds the endogenous antioxidant defence, leading to a redox imbalance. Oxidative stress is a pivotal pathophysiological process in cardiovascular and metabolic complications. In obesity, PVAT becomes dysfunctional and exerts detrimental effects on the blood vessels. Therefore, redox balance in PVAT emerges as a potential pathophysiological mechanism underlying obesity-induced cardiovascular diseases. In this review, we summarise new findings describing different ROS, the major sources of ROS and antioxidant defence in PVAT, as well as potential pharmacological intervention of PVAT oxidative stress in obesity.

Perindopril prevents development of obesity and hypertension in middle aged diet-induced obese rat models of metabolic syndrome

AIMS

The therapeutic properties of anti-hypertensive medications that extend beyond blood pressure lowering have started to become important clinical targets in recent years. This study aimed to assess the cardioprotective effects of perindopril in attenuating complications associated with metabolic syndrome in diet induced obese rats.

MAIN METHODS

Male Wistar-Kyoto (WKY) rats aged 16 weeks were fed either standard rat chow (SC) or given a high-fat-high-carbohydrate (HFHC) diet for 20 weeks. Perindopril treatment (1 mg/kg/day) was administered to a subset of WKY rats commencing at week 8 of the 20 week HFHC feeding period. Body weights, food, water and energy intakes, blood pressure, heart rate and glucose tolerance were measured throughout the treatment period. Oxidative stress and inflammatory markers, lipid levels, cardiac collagen deposition, vascular function, aortic and cardiac electrical function were examined after the treatment.

KEY FINDINGS

WKY rats developed metabolic syndrome after 20 weeks of HFHC feeding, evidenced by the presence of abdominal obesity, dyslipidaemia, glucose intolerance and hypertension. Perindopril treatment prevented the development of obesity and hypertension in WKY-HFHC. Perindopril improved blood lipid profiles in HFHC rats with decreases in LDL cholesterol, triglycerides and total cholesterol. Type I collagen levels were decreased in WKY-HFHC rats along with decreases in left ventricle mass. Perindopril treated rats also showed improved cardiac electrical function indicated by decreases in action potential at 90 % of repolarisation in WKY-HFHC rats.

SIGNIFICANCE

These results show that perindopril has a profound effect on preventing the development of metabolic syndrome in animals fed a HFHC diet.

Temporal patterns of alterations in obesity index, lipid profile, renal function and blood pressure during the development of hypertension in male, but not female, rats fed a moderately high-fat diet

CONTEXT

Male Sprague-Dawley rats consuming a moderately high-fat (MHF)-diet diverge into obesity-prone (OP) with hypertension and obesity-resistant.

OBJECTIVES

To study the temporal inter-relationships between body-weight, obesity-index, plasma lipid-profile, renal functional parameters and systolic-pressure alterations during 10-weeks feeding MHF or normal diet to male and female rats.

METHODS

Body-weight, obesity-index and systolic-pressure were measured weekly, while metabolic-cage and blood-sampling protocols were performed every other week. After 10-weeks, renal excretory responses to acute salt-loading and renal autoregulation were examined.

RESULTS

The male-OP group had progressively increased body-weight, plasma-triglyceride and systolic-pressure from Weeks 2, 4 and 5, respectively, lower renal sodium-excretion at weeks 4-8 and finally, delayed excretory response to salt-loading and rightward and downward shifts in renal autoregulatory curves compared to all other groups.

CONCLUSION

Feeding the MHF-diet in male-OP rats led to a greater weight-gain and adiposity followed by the development of atherogenic-hyperlipidaemia and persistently impaired pressure-natriuresis to induce hypertension.

Angiotensin II Inhibits Insulin Receptor Signaling in Adipose Cells

Angiotensin II (Ang II) is a critical regulator of insulin signaling in the cardiovascular system and metabolic tissues. However, in adipose cells, the regulatory role of Ang II on insulin actions remains to be elucidated. The effect of Ang II on insulin-induced insulin receptor (IR) phosphorylation, Akt activation, and glucose uptake was examined in 3T3-L1 adipocytes. In these cells, Ang II specifically inhibited insulin-stimulated IR and insulin receptor substrate-1 (IRS-1) tyrosine-phosphorylation, Akt activation, and glucose uptake in a time-dependent manner. These inhibitory actions were associated with increased phosphorylation of the IR at serine residues. Interestingly, Ang II-induced serine-phosphorylation of IRS was not detected, suggesting that Ang II-induced desensitization begins from IR regulation itself. PKC inhibition by BIM I restored the inhibitory effect of Ang II on insulin actions. We also found that Ang II promoted activation of several PKC isoforms, including PKCα/βI/βII/δ, and its association with the IR, particularly PKCβII, showed the highest interaction. Finally, we also found a similar regulatory effect of Ang II in isolated adipocytes, where insulin-induced Akt phosphorylation was inhibited by Ang II, an effect that was prevented by PKC inhibitors. These results suggest that Ang II may lead to insulin resistance through PKC activation in adipocytes.

CIHH protects the heart against left ventricular remodelling and myocardial fibrosis by balancing the renin-angiotensin system in SHR

AIM

The aim of our study was to clarify the cardioprotection of chronic intermittent hypobaric hypoxia (CIHH) and the underlying mechanism in spontaneously hypertensive rats (SHR).

MAIN METHODS

Adult male rats were divided into normal blood pressure Wistar-Kyoto rats (WKY) control (WKY-CON), WKY rats with CIHH treatment (WKY-CIHH), SHR control (SHR-CON) and SHR with CIHH treatment (SHR-CIHH) groups. SHR-CIHH and WKY-CIHH rats were subjected to hypobaric hypoxia simulating 4000-m altitude for 35 days, 5 h per day. Arterial blood pressure and cardiac function parameters, including ejection fraction, fractional shortening and left ventricular (LV) wall thickness, were evaluated. Cardiac pathomorphology and myocardial fibrosis were determined. The expression of angiotensin-converting enzyme (ACE), ACE2, Ang II, Ang1-7, AT1 receptor, Mas receptor, IL-6, TNF-α，IL-10, SOD and MDA were assayed in myocardium.

KEY FINDINGS

CIHH significantly decreased arterial blood pressure, alleviated LV hypertrophy, and improved cardiovascular function in SHR (P < 0.05-0.01). Also, CIHH protected SHR heart against morphological changes and fibrosis. In addition, CIHH significantly down-regulated the ACE/Ang II/AT1 receptor axis and up-regulated the ACE2/Ang1-7/Mas axis of renin-angiotensin system (RAS) in SHR (P < 0.05-0.01). CIHH significantly reduced IL-6, TNF-α, and MDA levels, but increased IL-10 and SOD in SHR myocardium (P < 0.05-0.01).

SIGNIFICANCE

The CIHH treatment protected the heart of SHR against LV remodelling and myocardial fibrosis, which might be carried out through a balance in the ACE/Ang II/AT1 axis and the ACE2/Ang1-7/Mas axis of the RAS to reduce inflammation, and inhibit oxidative stress.

Perivascular Adipose Tissue as a Target for Antioxidant Therapy for Cardiovascular Complications

Perivascular adipose tissue (PVAT) is the connective tissue surrounding most of the systemic blood vessels. PVAT is now recognized as an important endocrine tissue that maintains vascular homeostasis. Healthy PVAT has anticontractile, anti-inflammatory, and antioxidative roles. Vascular oxidative stress is an important pathophysiological event in cardiometabolic complications of obesity, type 2 diabetes, and hypertension. Accumulating data from both humans and experimental animal models suggests that PVAT dysfunction is potentially linked to cardiovascular diseases, and associated with augmented vascular inflammation, oxidative stress, and arterial remodeling. Reactive oxygen species produced from PVAT can be originated from mitochondria, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, and uncoupled endothelial nitric oxide synthase. PVAT can also sense vascular paracrine signals and response by secreting vasoactive adipokines. Therefore, PVAT may constitute a novel therapeutic target for the prevention and treatment of cardiovascular diseases. In this review, we summarize recent findings on PVAT functions, ROS production, and oxidative stress in different pathophysiological settings and discuss the potential antioxidant therapies for cardiovascular diseases by targeting PVAT.

Hyperuricemia Inhibition Protects SD Rats Against Fructose-Induced Obesity Hypertension Via Modulation of Inflammation and Renin-Angiotensin System in Adipose Tissue

OBJECTIVE

The present study was aimed to reveal the relationship between uric acid and fructose-induced obesity hypertension and its mechanisms.

METHODS

A rat model with obesity hypertension was induced by a high-fructose diet. In the experiment I, the rats were fed with fructose for 8 wks along with allopurinol or benzbromarone at the beginning. In the experiment II, the rats were fed with fructose for 8 wks firstly. And then, these rats were treated with allopurinol or benzbromarone for additional 6 wks.

RESULTS

Fructose-fed rats showed hyperuricemia, abdominal obesity hypertension and an activation in adipose renin-angiotensin system (RAS). Also, fructose-fed rats had higher levels of proinflammatory cytokines and more macrophages infiltrating in adipose tissue. In the experiment I, allopurinol and benzbromarone significantly reduced serum uric acid at 8 wk. Adipose RAS overactivation, adipose inflammatory responses and the development of obesity hypertension were all effectively prevented by hyperuricemia inhibition. In the experiment II, 6-wk treatment with allopurinol and benzbromarone significantly decreased serum uric acid, downregulated adipose RAS, abolished adipose inflammation and improved obesity hypertension.

CONCLUSION

In conclusion, urate-lowering therapy protects rats against fructose-induced obesity hypertension. The mechanisms appear to be via downregulated adipose RAS and reduced inflammation in adipose tissue.

Weight Loss and Hypertension in Obese Subjects

Arterial hypertension is strongly related to overweight and obesity. In obese subjects, several mechanisms may lead to hypertension such as insulin and leptin resistance, perivascular adipose tissue dysfunction, renal impairment, renin-angiotensin-aldosterone-system activation and sympathetic nervous system activity. Weight loss (WL) seems to have positive effects on blood pressure (BP). The aim of this review was to explain the mechanisms linking obesity and hypertension and to evaluate the main studies assessing the effect of WL on BP. We analysed studies published in the last 10 years (13 studies either interventional or observational) showing the effect of WL on BP. Different WL strategies were taken into account-diet and lifestyle modification, pharmacological intervention and bariatric surgery. Although a positive effect of WL could be identified in each study, the main difference seems to be the magnitude and the durability of BP reduction over time. Nevertheless, further follow-up data are needed: there is still a lack of evidence about long term effects of WL on hypertension. Hence, given the significant results obtained in several recent studies, weight management should always be pursued in obese patients with hypertension.

Losartan and isoproterenol promote alterations in the local renin-angiotensin system of rat salivary glands

Renin-angiotensin system (RAS) systemically or locally collaborates with tissue homeostasis, growth and development, which has been extensively studied for its pharmacological implications. This study was primarily aimed at finding and characterizing local RAS in rat parotid, sublingual and submandibular glands. It was also hypothesized that vasoactive drugs could affect the expression of RAS targets, as well as saliva flow and its composition. Therefore, another objective of this study was to compare the effects of losartan (angiotensin II receptor blocker) and isoproterenol (β-adrenergic receptor agonist). Forty-one Wistar rats were divided into three groups and administered a daily intraperitoneal dose of saline, losartan or isoproterenol solutions for one week. The following RAS targets were studied using qPCR: renin (REN), angiotensinogen (AGT), angiotensin converting enzyme (ACE), ACE-2, elastase-2 (ELA-2), AT1-a and MAS receptors, using RPL-13 as a reference gene. Morphology of glands was analyzed by immunohistochemistry using REN, ACE, ACE-2, AT1, AT2 and MAS antibodies. The volume and total protein content of saliva were measured. Our results revealed that ACE, ACE-2, AT1-a, AT2 and MAS receptors were expressed in all salivary gland samples, but REN and ELA-2 were absent. Losartan decreased mRNA expression of RAS targets in parotid (MAS) and submandibular glands (ACE and both AT receptors), without affecting morphological alterations, and significantly decreased saliva and total protein secretions. Isoproterenol treatment affected gene expression profiles in parotid (ACE, ACE-2, AT1-a, MAS, AGT), and submandibular (ACE, AT2, AGT) glands, thus promoting acinar hypertrophy in serous acini, without significant changes in salivary flow or total protein content. These drugs affected mainly acini, followed by duct systems and myoepithelial cells, whereas blood vessels were not affected. In conclusion, there is a local RAS in major rat salivary glands and losartan, an angiotensin II receptor blocker, affected not only the RAS-target gene expression but also decreased salivary flow and total protein content.

Obesity and its cardiovascular effects

Obesity is described in terms of body fat percentage or body mass index (BMI), despite the fact that these measures do not give full insight about the body fat distribution. It is presently a consistently growing universal challenge since it has tripled in the last 10 years, killing approximately 28 million people each year. In this review, we aim to clarify the different results of obesity on the working and physiology of the cardiovascular system and to reveal changes in the obesity "paradox"-a variety of cardiovascular outcomes in typical/overweight people. Central fat build-up in ordinary/overweight populaces has been related to expanded occurrences of myocardial infarction, heart failure, or all-cause mortality when contrasted with the obese populace. These discoveries are additionally clarified as the abundance and prolonged vulnerability to free fatty acids (FFAs) in obesity. This has been believed to cause the myocardial substrate to move from glucose to FFAs digestion, which causes lipid gathering in cardiomyocytes, spilling over to other lean tissues, and prompting a general atherogenic impact. This cardiomyocyte lipid aggregation has been demonstrated to cause insulin resistance and cardiovascular hypertrophy, and to lessen the heart functions in general. There is a proof backing the fact that fat tissue is not only an energy reservoir, it also coordinates hormones and proinflammatory cytokines and deals with the energy transition of the body by putting away abundant lipids in diverse tissues.

TLR2 and TLR4 mediate an activation of adipose tissue renin-angiotensin system induced by uric acid

Both hyperuricemia and adipose tissue renin-angiotensin system (RAS) are closely associated with multiple metabolic and cardiovascular diseases. We previously reported that uric acid could upregulate tissue RAS in adipocytes. In the present study, we aimed to reveal the involvement of toll-like receptors (TLRs) in uric acid-induced RAS activation in adipose tissue. A hyperuricemia rat model fed with a high-fructose diet and rat primary adipocytes were used in this study. Here, we inhibited TLR2 and TLR4 expression in adipose tissue and cultured adipocytes using small interfering RNA (siRNA). We found that high fructose-fed rats had hyperuricemia, higher body weight and greater adipose tissue content. We also found that hyperuricemia rats had raising blood pressure, higher expression levels of inflammatory cytokines and RAS components in adipose tissue, which could be prevented by TLR2/4-siRNA infection. In vitro study, uric acid caused a dose- and time-dependent increase in the mRNA expression of TLR2 and TLR4 in rat adipocytes. Uric acid could increase inflammatory cytokines and upregulate tissue RAS in rat adipocytes, which were both blocked with TLR2/4-siRNA infection. TNF-α and IL-6 could also result in an activation of tissue RAS expression in adipocytes. In conclusion, TLR2/4 mediated adipose inflammation plays a key role in RAS activation induced by uric acid in adipose tissue.

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.

Genetic knockdown of brain-derived neurotrophic factor in the nervous system attenuates angiotensin II-induced hypertension in mice

INTRODUCTION:

Brain-derived neurotropic factor (BDNF) is expressed throughout the central nervous system and peripheral organs involved in the regulation of blood pressure, but the systemic effects of BDNF in the control of blood pressure are not well elucidated.

MATERIALS AND METHODS:

We utilized loxP flanked BDNF male mice to cross with nestin-Cre female mice to generate nerve system BDNF knockdown mice, nestin-BDNF (+/-), or injected Cre adenovirus into the subfornical organ to create subfornical organ BDNF knockdown mice. Histochemistry was used to verify injection location. Radiotelemetry was employed to determine baseline blood pressure and pressor response to angiotensin II (1000 ng/kg/min). Real-time polymerase chain reaction was used to measure the expression of renin-angiotensin system components in the laminal terminalis and peripheral organs.

RESULTS:

Nestin-BDNF (+/-) mice had lower renin-angiotensin system expression in the laminal terminalis and peripheral organs including the gonadal fat pad, and a lower basal blood pressure. They exhibited an attenuated hypertensive response and a weak or similar modification of renin-angiotensin system component expression to angiotensin II infusion. Subfornical organ BDNF knockdown was sufficient for the attenuation of angiotensin II-induced hypertension.

CONCLUSION:

Central BDNF, especially subfornical organ BDNF is involved in the maintenance of basal blood pressure and in augmentation of hypertensive response to angiotensin II through systemic regulation of the expression of renin-angiotensin system molecules.

Mitochondrial oxidative stress in obesity: role of the mineralocorticoid receptor

Obesity is a multifaceted, chronic, low-grade inflammation disease characterized by excess accumulation of dysfunctional adipose tissue. It is often associated with the development of cardiovascular (CV) disorders, insulin resistance and diabetes. Under pathological conditions like in obesity, adipose tissue secretes bioactive molecules called 'adipokines', including cytokines, hormones and reactive oxygen species (ROS). There is evidence suggesting that oxidative stress, in particular, the ROS imbalance in adipose tissue, may be the mechanistic link between obesity and its associated CV and metabolic complications. Mitochondria in adipose tissue are an important source of ROS and their dysfunction contributes to the pathogenesis of obesity-related type 2 diabetes. Mitochondrial function is regulated by several factors in order to preserve mitochondria integrity and dynamics. Moreover, the renin-angiotensin-aldosterone system is over-activated in obesity. In this review, we focus on the pathophysiological role of the mineralocorticoid receptor in the adipose tissue and its contribution to obesity-associated metabolic and CV complications. More specifically, we discuss whether dysregulation of the mineralocorticoid system within the adipose tissue may be the upstream mechanism and one of the early events in the development of obesity, via induction of oxidative stress and mitochondrial dysfunction, thus impacting on systemic metabolism and the CV system.

Bmal1 in Perivascular Adipose Tissue Regulates Resting-Phase Blood Pressure Through Transcriptional Regulation of Angiotensinogen

BACKGROUND

The perivascular adipose tissue (PVAT) surrounding vessels constitutes a distinct functional integral layer of the vasculature required to preserve vascular tone under physiological conditions. However, there is little information on the relationship between PVAT and blood pressure regulation, including its potential contributions to circadian blood pressure variation.

METHODS

Using unique brown adipocyte-specific aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1) and angiotensinogen knockout mice, we determined the vasoactivity of homogenized PVAT in aortic rings and how brown adipocyte peripheral expression of Bmal1 and angiotensinogen in PVAT regulates the amplitude of diurnal change in blood pressure in mice.

RESULTS

We uncovered a peripheral clock in PVAT and demonstrated that loss of Bmal1 in PVAT reduces blood pressure in mice during the resting phase, leading to a superdipper phenotype. PVAT extracts from wild-type mice significantly induced contractility of isolated aortic rings in vitro in an endothelium-independent manner. This property was impaired in PVAT from brown adipocyte-selective Bmal1-deficient (BA-Bmal1-KO) mice. The PVAT contractile properties were mediated by local angiotensin II, operating through angiotensin II type 1 receptor-dependent signaling in the isolated vessels and linked to PVAT circadian regulation of angiotensinogen. Indeed, angiotensinogen mRNA and angiotensin II levels in PVAT of BA-Bmal1-KO mice were significantly reduced. Systemic infusion of angiotensin II, in turn, reduced Bmal1 expression in PVAT while eliminating the hypotensive phenotype during the resting phase in BA-Bmal1-KO mice. Angiotensinogen, highly expressed in PVAT, shows circadian expression in PVAT, and selective deletion of angiotensinogen in brown adipocytes recapitulates the phenotype of selective deletion of Bmal1 in brown adipocytes. Furthermore, angiotensinogen is a transcriptional target of Bmal1 in PVAT.

CONCLUSIONS

These data indicate that local Bmal1 in PVAT regulates angiotensinogen expression and the ensuing increase in angiotensin II, which acts on smooth muscle cells in the vessel walls to regulate vasoactivity and blood pressure in a circadian fashion during the resting phase. These findings will contribute to a better understanding of the cardiovascular complications of circadian disorders, alterations in the circadian dipping phenotype, and cross-talk between systemic and peripheral regulation of blood pressure.

Childhood adiposity, adult adiposity, and the ACE gene insertion/deletion polymorphism: evidence of gene-environment interaction effects on adult blood pressure and hypertension status in adulthood

BACKGROUND

Genetic variants may modify the associations of adiposity measures with blood pressure (BP) and hypertension. The insertion/deletion (I/D) polymorphism in the angiotensin-converting enzyme (ACE) gene is an attractive candidate.

AIMS

To examine interaction effects between I/D polymorphism and adiposity measures (BMI, waist circumference, waist-to-hip ratio, and skinfold thickness) during childhood and adulthood in relation to adult BP and hypertension.

METHODS

Data were available for 4835 participants from three prospective cohort studies. Multivariable linear regression models for adult SBP and DBP, and multivariable logistic regression models for hypertension were fit that included interaction effects between child or adult adiposity and I/D polymorphism.

RESULTS

Evidence for interaction effects on BP/hypertension were found across the three studies. Compared with childhood measures, the effect modification appeared to be more consistent when using adult adiposity. In particular, the adverse effects of greater adult waist circumference on increasing adult SBP and DBP appeared to be larger among carriers of ACE DD (or GG) [adjusted linear regression coefficients 0.26, 95% CI (0.21-0.31) and 0.28 (0.24-0.32) for SBP and DBP, respectively] and ID (or AG) genotypes [0.25 (0.21-0.29) and 0.25 (0.21-0.28), respectively], whereas those with II (or AA) genotypes had smaller effects [0.15 (0.09-0.21) and 0.19 (0.13-0.23)].

CONCLUSION

ACE genetic variation may modify the effect of adult adiposity on increasing BP and risk of hypertension in adulthood. Individuals with ACE DD (or GG) and/or ID (or AG) genotypes, compared with those with II (or AA) genotype, appear more vulnerable to the impact of excess adiposity.

Identifying treatment response to antihypertensives in patients with obesity-related hypertension

BACKGROUND

In patients with obesity-related hypertension (ORH), reaction to antihypertensive medication is likely influenced by patientcharacteristics.

METHODS

Effects of aliskiren, moxonidine and hydrochlorothiazide on 24-h blood pressure (BP) were compared to placebo. Linear mixed effect models were used to analyze the effect of patient characteristics on BP levels and treatment response.

RESULTS

Systolic BP response to aliskiren was higher in patients with a BMI > 30.7 kg/m2 compared to patients with a BMI ≤ 30.7 kg/m2 (-21 mmHg versus -4 mmHg). In patients with a hsCRP > 1.8 mg/L the systolic BP response to aliskiren was higher than in patients with a low hsCRP (-15 mmHg versus -7 mmHg). Hydrochlorothiazide (HCTZ) treatment effect on systolic BP was -13 mmHg when heart rate > 71 beats/min compared to -3 mmHg when heart rate was ≤ 71 beats/min.

CONCLUSION

In patients with ORH, BP response to aliskiren is positively related to BMI and hsCRP. Systolic BP response to HCTZ is positively related to heart rate and negatively to renin levels.

TRIAL REGISTRATION

NCT01138423. Registered June 4th, 2010.

Hepatic structural enhancement and insulin resistance amelioration due to AT1 receptor blockade

Over the last decade, the role of renin-angiotensin system (RAS) on the development of obesity and its comorbidities has been extensively addressed. Both circulating and local RAS components are up-regulated in obesity and involved in non-alcoholic fatty liver disease onset. Pharmacological manipulations of RAS are viable strategies to tackle metabolic impairments caused by the excessive body fat mass. Renin inhibitors rescue insulin resistance, but do not have marked effects on hepatic steatosis. However, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers (ARB) yield beneficial hepatic remodeling. ARBs elicit body mass loss and normalize insulin levels, tackling insulin resistance. Also, this drug class increases adiponectin levels, besides countering interleukin-6, tumoral necrosis factor-alpha, and transforming growth factor-beta 1. The latter is essential to prevent from liver fibrosis. When conjugated with peroxisome proliferator-activated receptor (PPAR)-alpha activation, ARB fully rescues fatty liver. These effects might be orchestrated by an indirect up-regulation of MAS receptor due to angiotensin II receptor type 1 (AT1R) blockade. These associations of ARB with PPAR activation and ACE2-angiotensin (ANG) (1-7)-MAS receptor axis deserve a better understanding. This editorial provides a brief overview of the current knowledge regarding AT1R blockade effects on sensitivity to insulin and hepatic structural alterations as well as the intersections of AT1R blockade with peroxisome proliferator-activated receptor activation and ACE2-ANG (1-7) - MAS receptor axis.

Alternative renin-angiotensin system pathways in adipose tissue and their role in the pathogenesis of obesity

Adipose tissue expresses all the renin-angiotensin system (RAS) components that play an important role in the adipogenesis, lipid and glucose metabolism regulation in an auto/paracrine manner. The classical RAS has been found to be over-activated during the adipose tissue enlargement, thus elevated generation of angiotensin II (Ang II) may contribute to the obesity pathogenesis. The contemporary view on the RAS has become more complex with the discovery of alternative pathways, including angiotensin-converting enzyme 2 (ACE2)/angiotensin (Ang)-(1-7)/Mas receptor, (pro)renin receptor, as well as angiotensin IV(Ang IV)/AT4 receptor. Ang-(1-7) via Mas receptor counteracts with most of the deleterious effects of the Ang II-mediated by AT1 receptor implying its beneficial role in the glucose and lipid metabolism, oxidative stress, inflammation, and insulin resistance. Pro(renin) receptor may play a role (at least partial) in the pathogenesis of the obesity by increasing the local production of Ang II in adipose tissue as well as triggering signal transduction independently of Ang II. In this review, modulation of alternative RAS pathways in adipose tissue during obesity is discussed and the involvement of Ang-(1-7), (pro)renin and AT4 receptors in the regulation of adipose tissue homeostasis and insulin resistance is summarized.

Adipocytes, aldosterone and obesity-related hypertension

Understanding the mechanisms linking obesity with hypertension is important in the current obesity epidemic as it may improve therapeutic interventions. Plasma aldosterone levels are positively correlated with body mass index and weight loss in obese patients is reported to be accompanied by decreased aldosterone levels. This suggests a relationship between adipose tissue and the production/secretion of aldosterone. Aldosterone is synthesized principally by the adrenal glands, but its production may be regulated by many factors, including factors secreted by adipocytes. In addition, studies have reported local synthesis of aldosterone in extra-adrenal tissues, including adipose tissue. Experimental studies have highlighted a role for adipocyte-secreted aldosterone in the pathogenesis of obesity-related cardiovascular complications via the mineralocorticoid receptor. This review focuses on how aldosterone secretion may be influenced by adipose tissue and the importance of these mechanisms in the context of obesity-related hypertension.

Adipocyte (Pro)Renin-Receptor Deficiency Induces Lipodystrophy, Liver Steatosis and Increases Blood Pressure in Male Mice

Adipose tissue dysfunction related to obesity is overwhelmingly associated with increased risk of developing cardiovascular diseases. In the setting of obesity, (pro)renin receptor (PRR) is increased in adipose tissue of mice. We sought to determine the physiological consequences of adipocyte-PRR deficiency using adiponectin-Cre mice. We report a unique model of adipocyte-PRR-deficient mice (PRR(Adi/Y)) with almost no detectable white adipose tissues. As a consequence, the livers of PRR(Adi/Y) mice were enlarged and demonstrated a marked accumulation of lipids. Adipocyte-specific deficiency of PRR increased systolic blood pressure and the concentration of soluble PRR in plasma. To determine whether adipocyte-PRR was involved in the development of obesity-induced hypertension, mice were fed a low-fat or a high-fat diet for 16 weeks. Adipocyte-PRR-deficient mice were resistant to diet-induced obesity. Both high-fat- and low-fat-fed PRR(Adi/Y) mice had elevated insulin levels. Interestingly, adipocyte-PRR deficiency improved glucose tolerance in high-fat-fed PRR(Adi/Y) mice. In response to feeding either low-fat or high-fat diets, systolic blood pressure was greater in PRR(Adi/Y) mice than in control mice. High-fat feeding elevated soluble PRR concentration in control and PRR(Adi/Y) mice. In vitro knockdown of PRR by siRNA significantly decreased mRNA abundance of PPARγ (peroxisome proliferator-activated receptor gamma), suggesting an important role for PRR in adipogenesis. Our data indicate that adipocyte-PRR is involved in lipid homeostasis and glucose and insulin homeostasis, and that soluble PRR may be a predictor of metabolic disturbances and play a role in systolic blood pressure regulation.

Prehypertension in adolescents with cardiovascular risk: a comparison between type 1 diabetic patients and overweight subjects

BACKGROUND

Adolescents with type 1 diabetes and obesity present higher cardiovascular risk and ambulatory blood pressure measurements (ABPM) has been shown to predict vascular events, especially by identifying the nondipper status. The aim of our observational cross-sectional study conducted in adolescents with type 1 diabetes, overweight subjects and healthy controls was to assess mean blood pressure parameters to identify subclinical cardiovascular risk.

METHODS

The study included adolescents patients with type 1 diabetes followed in our Pediatric Department in University of Catania between January 2011 and 2013. A total of 60 patients were enrolled, and 48 (32 male and 16 female) completed the study. For each subject we performed systolic and diastolic Ambulatory Blood Pressure Measurements (ABPM) during wakefulness and sleep recording blood pressure every 30 min for 24 h with the Tonoport V/2 GE CardioSoft V6.51 device. We compared the data of patients with those of overweight subjects and healthy controls.

RESULTS

ABPM revealed no significant difference between type 1 diabetic patients and overweight subjects in 24 h Systolic, 24 h Diastolic, Day-time Systolic, Night-time systolic and Day-time Diastolic blood pressure values but significantly different values in Night-time Diastolic blood pressure values (p < 0.001). We found significant differences between type 1 diabetic patients and healthy controls in all 24 h Systolic (p < 0.001), 24 h Diastolic (p < 0.01), Day-time Systolic (p < 0.01), Night-time Systolic (p < 0.001), Day-time Diastolic (p < 0.05) and Night-time Diastolic (p < 0.001) blood pressure values. We detected hypertension in 12/48 (25%) type 1 diabetic patients and in 10/48 overweight subjects (p = 0.62; OR 1.2; CI 0.48-3.29), whereas no-one of healthy controls presented hypertension (p < 0.001). We observed nondipper pattern in 40/48 (83.3%) type 1 diabetic patients, in 33/48 (68.8%) overweight subjects (p = 0.094; OR 2.27; CI 0.85-6.01), and in 16/48 (33.3%) of healthy controls (p < 0.001; OR 10; CI 3.79-26.3).

CONCLUSIONS

ABPM studies might help to define a subset of patients at increased risk for the development of hypertension. In evaluating blood pressure in type 1 diabetes and overweight subjects, ABPM should be used since a reduced dipping can indicate incipient hypertension.

Control of energy balance by the brain renin-angiotensin system

The renin-angiotensin system (RAS) exists as a circulating hormone system but it is also used by various tissues of the body, including the brain, as a paracrine signaling mechanism. The local brain version of the RAS is mechanistically involved in fluid balance and blood pressure control, and there is growing appreciation for a role of the brain RAS in the control of energy balance. Here, we review major evidence for the control of energy balance by the brain RAS; outline the current understanding of the RAS components, targets, and mechanisms involved; and highlight some major questions that currently face the field.

Mechanisms mediating renal sympathetic nerve activation in obesity-related hypertension

Excessive renal sympathetic nerve activation may be one of the mechanisms underlying obesity-related hypertension. Impaired baroreflex sensitivity, adipokine disorders-such as leptin, adiponectin, and resistin-activation of the renin-angiotensin system, hyperinsulinemia, insulin resistance, and renal sodium retention present in obesity increase renal sympathetic nerve activity, thus contributing to the development of hypertension. Renal sympathetic denervation reduces both renal sympathetic activity and blood pressure in patients with obesity-related hypertension.

Steroid biosynthesis in adipose tissue

Tissue-specific expression of steroidogenic enzymes allows the modulation of active steroid levels in a local manner. Thus, the measurement of local steroid concentrations, rather than the circulating levels, has been recognized as a more accurate indicator of the steroid action within a specific tissue. Adipose tissue, one of the largest endocrine tissues in the human body, has been established as an important site for steroid storage and metabolism. Locally produced steroids, through the enzymatic conversion from steroid precursors delivered to adipose tissue, have been proven to either functionally regulate adipose tissue metabolism, or quantitatively contribute to the whole body's steroid levels. Most recently, it has been suggested that adipose tissue may contain the steroidogenic machinery necessary for the initiation of steroid biosynthesis de novo from cholesterol. This review summarizes the evidence indicating the presence of the entire steroidogenic apparatus in adipose tissue and discusses the potential roles of local steroid products in modulating adipose tissue activity and other metabolic parameters.

RNA-Seq Analysis of Abdominal Fat in Genetically Fat and Lean Chickens Highlights a Divergence in Expression of Genes Controlling Adiposity, Hemostasis, and Lipid Metabolism

Genetic selection for enhanced growth rate in meat-type chickens (Gallus domesticus) is usually accompanied by excessive adiposity, which has negative impacts on both feed efficiency and carcass quality. Enhanced visceral fatness and several unique features of avian metabolism (i.e., fasting hyperglycemia and insulin insensitivity) mimic overt symptoms of obesity and related metabolic disorders in humans. Elucidation of the genetic and endocrine factors that contribute to excessive visceral fatness in chickens could also advance our understanding of human metabolic diseases. Here, RNA sequencing was used to examine differential gene expression in abdominal fat of genetically fat and lean chickens, which exhibit a 2.8-fold divergence in visceral fatness at 7 wk. Ingenuity Pathway Analysis revealed that many of 1687 differentially expressed genes are associated with hemostasis, endocrine function and metabolic syndrome in mammals. Among the highest expressed genes in abdominal fat, across both genotypes, were 25 differentially expressed genes associated with de novo synthesis and metabolism of lipids. Over-expression of numerous adipogenic and lipogenic genes in the FL chickens suggests that in situ lipogenesis in chickens could make a more substantial contribution to expansion of visceral fat mass than previously recognized. Distinguishing features of the abdominal fat transcriptome in lean chickens were high abundance of multiple hemostatic and vasoactive factors, transporters, and ectopic expression of several hormones/receptors, which could control local vasomotor tone and proteolytic processing of adipokines, hemostatic factors and novel endocrine factors. Over-expression of several thrombogenic genes in abdominal fat of lean chickens is quite opposite to the pro-thrombotic state found in obese humans. Clearly, divergent genetic selection for an extreme (2.5-2.8-fold) difference in visceral fatness provokes a number of novel regulatory responses that govern growth and metabolism of visceral fat in this unique avian model of juvenile-onset obesity and glucose-insulin imbalance.

Modulation of Immunity and Inflammation by the Mineralocorticoid Receptor and Aldosterone

The mineralocorticoid receptor (MR) is a ligand dependent transcription factor. MR has been traditionally associated with the control of water and electrolyte homeostasis in order to keep blood pressure through aldosterone activation. However, there is growing evidence indicating that MR expression is not restricted to vascular and renal tissues, as it can be also expressed by cells of the immune system, where it responds to stimulation or antagonism, controlling immune cell function. On the other hand, aldosterone also has been associated with proinflammatory immune effects, such as the release of proinflammatory cytokines, generating oxidative stress and inducing fibrosis. The inflammatory participation of MR and aldosterone in the cardiovascular disease suggests an association with alterations in the immune system. Hypertensive patients show higher levels of proinflammatory mediators that can be modulated by MR antagonism. Although these proinflammatory properties have been observed in other autoimmune and chronic inflammatory diseases, the cellular and molecular mechanisms that mediate these effects remain unknown. Here we review and discuss the scientific work aimed at determining the immunological role of MR and aldosterone in humans, as well as animal models.

Obesity-induced hypertension: interaction of neurohumoral and renal mechanisms

Excess weight gain, especially when associated with increased visceral adiposity, is a major cause of hypertension, accounting for 65% to 75% of the risk for human primary (essential) hypertension. Increased renal tubular sodium reabsorption impairs pressure natriuresis and plays an important role in initiating obesity hypertension. The mediators of abnormal kidney function and increased blood pressure during development of obesity hypertension include (1) physical compression of the kidneys by fat in and around the kidneys, (2) activation of the renin-angiotensin-aldosterone system, and (3) increased sympathetic nervous system activity. Activation of the renin-angiotensin-aldosterone system is likely due, in part, to renal compression, as well as sympathetic nervous system activation. However, obesity also causes mineralocorticoid receptor activation independent of aldosterone or angiotensin II. The mechanisms for sympathetic nervous system activation in obesity have not been fully elucidated but may require leptin and activation of the brain melanocortin system. With prolonged obesity and development of target organ injury, especially renal injury, obesity-associated hypertension becomes more difficult to control, often requiring multiple antihypertensive drugs and treatment of other risk factors, including dyslipidemia, insulin resistance and diabetes mellitus, and inflammation. Unless effective antiobesity drugs are developed, the effect of obesity on hypertension and related cardiovascular, renal and metabolic disorders is likely to become even more important in the future as the prevalence of obesity continues to increase.

Impact of obesity on kidney function and blood pressure in children

In recent years, obesity has become an increasingly important epidemic health problem in children and adolescents. The prevalence of the overweight status in children grew from 5% to 11% from 1960s to 1990s. The epidemic of obesity has been paralleled by an increase in the incidence of chronic kidney disease (CKD) and hypertension. Results of several studies have demonstrated that obesity and metabolic syndrome were independent predictors of renal injury. The pathophysiology of obesity related hypertension is complex, including activation of sympathetic nervous system, renin angiotensin aldosterone system, hyperinsulinemia and inflammation. These same mechanisms likely contribute to the development of increased blood pressure in children. This review summarizes the recent epidemiologic data linking obesity with CKD and hypertension in children, as well as the potential mechanisms.

Uric acid induces oxidative stress via an activation of the renin-angiotensin system in 3T3-L1 adipocytes

Hyperuricemia is recently reported involving in various obesity-related cardiovascular disorders, especially hypertension. However, the underlying mechanisms are not completely understood. In the present study, we investigated whether uric acid upregulates renin-angiotensin system (RAS) expression in adipocytes. We also examined whether RAS activation plays a role in uric acid-induced oxidative stress in adipocytes. The adipocytes of different phenotypes were incubated with uric acid for 48 h, respectively. Losartan (10(-4) M) or captopril (10(-4) M) was used to block adipose tissue RAS activation. mRNA expressions of angiotensinogen (AGT), angiotensin-converting enzyme-1 (ACE-1), renin, angiotensin type 1 receptor (AT1R), and angiotensin type 2 receptor (AT2R) were evaluated with real-time PCR. Angiotensin II concentrations in supernatant were measured by ELISA. Intracellular reactive species (ROS) levels were measured by fluorescent probe DCFH-DA, DHR, or NBT assay. The uric acid upregulated both RAS (AGT, ACE1, renin, AT1R, and AT2R) mRNA expressions and angiotensin II protein secretion and caused a significant increase in ROS production in 3T3-L1 adipocytes. These effects could be prevented by RAS inhibitors, either losartan or captopril. RAS activation has been causally implicated in oxidative stress induced by uric acid in 3T3-L1 adipocytes, suggesting a plausible mechanism through which hyperuricemia contributes to the pathogenesis of obesity-related cardiovascular diseases.

Angiotensin II and vascular injury

Vascular injury, characterized by endothelial dysfunction, structural remodelling, inflammation and fibrosis, plays an important role in cardiovascular diseases. Cellular processes underlying this include altered vascular smooth muscle cell (VSMC) growth/apoptosis, fibrosis, increased contractility and vascular calcification. Associated with these events is VSMC differentiation and phenotypic switching from a contractile to a proliferative/secretory phenotype. Inflammation, associated with macrophage infiltration and increased expression of redox-sensitive pro-inflammatory genes, also contributes to vascular remodelling. Among the many factors involved in vascular injury is Ang II. Ang II, previously thought to be the sole biologically active downstream peptide of the renin-angiotensin system (RAS), is converted to smaller peptides, [Ang III, Ang IV, Ang-(1-7)], that are functional and that modulate vascular tone and structure. The actions of Ang II are mediated via signalling pathways activated upon binding to AT1R and AT2R. AT1R activation induces effects through PLC-IP3-DAG, MAP kinases, tyrosine kinases, tyrosine phosphatases and RhoA/Rho kinase. Ang II elicits many of its (patho)physiological actions by stimulating reactive oxygen species (ROS) generation through activation of vascular NAD(P)H oxidase (Nox). ROS in turn influence redox-sensitive signalling molecules. Here we discuss the role of Ang II in vascular injury, focusing on molecular mechanisms and cellular processes. Implications in vascular remodelling, inflammation, calcification and atherosclerosis are highlighted.

Obesity-related hypertension: possible pathophysiological mechanisms

Hypertension is one of the major risk factors of cardiovascular diseases, but despite a century of clinical and basic research, the discrete etiology of this disease is still not fully understood. The same is true for obesity, which is recognized as a major global epidemic health problem nowadays. Obesity is associated with an increasing prevalence of the metabolic syndrome, a cluster of risk factors including hypertension, abdominal obesity, dyslipidemia, and hyperglycemia. Epidemiological studies have shown that excess weight gain predicts future development of hypertension, and the relationship between BMI and blood pressure (BP) appears to be almost linear in different populations. There is no doubt that obesity-related hypertension is a multifactorial and polygenic trait, and multiple potential pathogenetic mechanisms probably contribute to the development of higher BP in obese humans. These include hyperinsulinemia, activation of the renin-angiotensin-aldosterone system, sympathetic nervous system stimulation, abnormal levels of certain adipokines such as leptin, or cytokines acting at the vascular endothelial level. Moreover, some genetic and epigenetic mechanisms are also in play. Although the full manifestation of both hypertension and obesity occurs predominantly in adulthood, their roots can be traced back to early ontogeny. The detailed knowledge of alterations occurring in the organism of experimental animals during particular critical periods (developmental windows) could help to solve this phenomenon in humans and might facilitate the age-specific prevention of human obesity-related hypertension. In addition, better understanding of particular pathophysiological mechanisms might be useful in so-called personalized medicine.

Adipose tissue immune response: novel triggers and consequences for chronic inflammatory conditions

Adipose tissue inflammation mediates the association between excessive body fat accumulation and several chronic inflammatory diseases. A high prevalence of obesity-associated adipose tissue inflammation was observed not only in patients with cardiovascular conditions but also in patients with inflammatory bowel diseases, abdominal aortic aneurysm, or cardiorenal syndrome. In addition to excessive caloric intake, other triggers promote visceral adipose tissue inflammation followed by chronic, low-grade systemic inflammation. The infiltration and accumulation of immune cells in the inflamed and hypertrophied adipose tissue promote the production of inflammatory cytokines, contributing to target organ damages. This comorbidity seems to delimit subgroups of individuals with systemic adipose tissue inflammation and more severe chronic inflammatory diseases that are refractory to conventional treatment. This review highlights the association between adipose tissue immune response and the pathophysiology of visceral adiposity-related chronic inflammatory diseases, while suggesting several new therapeutic strategies.

Hypertension in children with obesity

The prevalence of obesity related hypertension has dramatically increased in children with the parallel increase in pediatric obesity. This pediatric health problem may adversely affect cardiovascular health in adult life. The pathogenesis of hypertension in obese children is not widely understood. We therefore undertake this review to raise public awareness. Early childhood parameters like birth weight and postnatal weight gain may play important roles in risk for obesity and obesity related hypertension later in childhood and adult life. Further information is required to confirm this origin of hypertension so that appropriate measures are taken in the peri-natal period. The role of sympathetic nervous system has now been well established as one of the principle mechanisms involved in obesity related hypertension. The Renin-Angiotensin system, insulin resistance due to obesity and as a part of metabolic syndrome along with imbalance in adipokines such as leptin and adiponectin, cause activation of the sympathetic system, vasoconstriction, endothelial dysfunction and sodium reabsorption among other perturbations. Multi-step interventions targeting these various mechanisms are required to break the cycle of obesity and metabolic syndrome. Vitamin D deficiency, sleep apnea due to airway obstruction and hyperuricemia may also play a significant role and should not be ignored in its early stages. Obesity is a risk factor for other co-morbid conditions like chronic kidney disease and fatty liver which further accentuate the risk of hypertension. Increased awareness is required to prevent, diagnose and treat obesity related hypertension among the pediatric population.

Pathophysiology of NASH: perspectives for a targeted treatment

Non alcoholic steatohepatitis (NASH) is the more severe form of nonalcoholic fatty liver disease. In NASH, fatty liver, hepatic inflammation, hepatocyte injury and fibrogenesis are associated, and this condition may eventually lead to cirrhosis. Current treatment of NASH relies on the reduction of body weight and increase in physical activity, but there is no pharmacologic treatment approved as yet. Emerging data indicate that NASH progression results from parallel events originating from the liver as well as from the adipose tissue, the gut and the gastrointestinal tract. Thus, dysfunction of the adipose tissue through enhanced flow of free fatty acids and release of adipocytokines, and alterations in the gut microbiome generate proinflammatory signals that underlie NASH progression. Additional 'extrahepatic hits' include dietary factors and gastrointestinal hormones. Within the liver, hepatocyte apoptosis, ER stress and oxidative stress are key contributors to hepatocellular injury. In addition, lipotoxic mediators and danger signals activate Kupffer cells which initiate and perpetuate the inflammatory response by releasing inflammatory mediators that contribute to inflammatory cell recruitment and development of fibrosis. Inflammatory and fibrogenic mediators include chemokines, the cannabinoid system, the inflammasome and activation of pattern-recognition receptors. Here we review the major mechanisms leading to appearance and progression of NASH, focusing on both extrahepatic signals and local inflammatory mechanisms, in an effort to identify the most promising molecular targets for the treatment of this condition.

Pathophysiology of NASH: perspectives for a targeted treatment

Non alcoholic steatohepatitis (NASH) is the more severe form of nonalcoholic fatty liver disease. In NASH, fatty liver, hepatic inflammation, hepatocyte injury and fibrogenesis are associated, and this condition may eventually lead to cirrhosis. Current treatment of NASH relies on the reduction of body weight and increase in physical activity, but there is no pharmacologic treatment approved as yet. Emerging data indicate that NASH progression results from parallel events originating from the liver as well as from the adipose tissue, the gut and the gastrointestinal tract. Thus, dysfunction of the adipose tissue through enhanced flow of free fatty acids and release of adipocytokines, and alterations in the gut microbiome generate proinflammatory signals that underlie NASH progression. Additional 'extrahepatic hits' include dietary factors and gastrointestinal hormones. Within the liver, hepatocyte apoptosis, ER stress and oxidative stress are key contributors to hepatocellular injury. In addition, lipotoxic mediators and danger signals activate Kupffer cells which initiate and perpetuate the inflammatory response by releasing inflammatory mediators that contribute to inflammatory cell recruitment and development of fibrosis. Inflammatory and fibrogenic mediators include chemokines, the cannabinoid system, the inflammasome and activation of pattern-recognition receptors. Here we review the major mechanisms leading to appearance and progression of NASH, focusing on both extrahepatic signals and local inflammatory mechanisms, in an effort to identify the most promising molecular targets for the treatment of this condition.

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.

Animal models in obesity and hypertension

Although obesity is a well-known risk factor for hypertension, the mechanisms by which hypertension develops in obese patients are not entirely clear. Animal models of obesity and their different susceptibilities to develop hypertension have revealed some of the mechanisms linking obesity and hypertension. Adipose tissue is an endocrine organ secreting hormones that impact blood pressure, such as elements of the renin-angiotensin system whose role in hypertension have been established. In addition, the appetite-suppressing adipokine leptin activates the sympathetic nervous system via the melanocortin system, and this activation, especially in the kidney, increases blood pressure. Leptin secretion from adipocytes is increased in most models of obesity due to leptin resistance, although the resistance is often selective to the anorexigenic effect, while the susceptibility to the hypertensive effect remains intact. Understanding the pathways by which obesity contributes to increased blood pressure will hopefully pave the way to and better define the appropriate treatment for obesity-induced hypertension.

Adipocytokines in relation to cardiovascular disease

Adipose tissue can be considered as a huge gland producing paracrine and endocrine hormones, the adipo(cyto)kines. There is growing evidence that these adipo(cyto)kines may link obesity to cardiovascular diseases. The excessive adipocyte hypertrophy in obesity induces hypoxia in adipose tissue. This leads to adiposopathy, the process that converts "healthy" adipose tissue to "sick" adipose tissue. This is accompanied by a change in profile of adipo(cyto)kines released, with less production of the "healthy" adipo(cyto)kines such as adiponectin and omentin and more release of the "unhealthy" adipo(cyto)kines, ultimately leading to the development of cardiovascular diseases. The present review provides a concise and general overview of the actual concepts of the role of adipo(cyto)kines in endothelial dysfunction, hypertension, atherosclerosis and heart diseases. The knowledge of these concepts may lead to new tools to improve health in the next generations.