Regulation by glucocorticoids of angiotensinogen gene expression and secretion in adipose cells

JTT-654, an 11-beta hydroxysteroid dehydrogenase type 1 inhibitor, improves hypertension and diabetic kidney injury by suppressing angiotensinogen production

11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) plays an important role in regulating the expression of glucocorticoid actions in target tissues. Overexpression of 11β-HSD1 in mouse adipose tissue causes a metabolic syndrome-like phenotype, leading to hypertension. Although, many 11β-HSD1 inhibitors have been studied, few have shown a clear ameliorative effect against hypertension. We investigated whether JTT-654, a novel 11β-HSD1 inhibitor, ameliorated hypertension and elucidated the underlying mechanisms. JTT-654 showed inhibitory effects on angiotensinogen production in cortisone-treated 3T3-L1 adipocytes and in a rat model. JTT-654 improved hypertension not only in cortisone-treated rats and spontaneously hypertensive rats (SHR), but also in SHR/NDmcr-cp rats. In the SHR study, JTT-654 and losartan showed the same degree of antihypertensive efficacy. In addition, JTT-654 ameliorated diabetic nephropathy by suppressing renal angiotensinogen production in SHR/NDmcr-cp rats. These effects of JTT-654 were independent of its insulin-sensitizing effects, and similar effects were not observed for pioglitazone, an insulin sensitizer. Moreover, JTT-654 did not affect normotension or hypothalamus-pituitary-adrenal (HPA) axis function in normal Sprague-Dawley rats. Our results indicate that JTT-654 ameliorates hypertension and diabetic nephropathy by inhibiting 11β-HSD1 in the adipose tissue, liver, and kidney.

Conventional Vasopressor and Vasopressor-Sparing Strategies to Counteract the Blood Pressure-Lowering Effect of Small Interfering RNA Targeting Angiotensinogen

Background

A single dose of small interfering RNA (siRNA) targeting liver angiotensinogen eliminates hepatic angiotensinogen and lowers blood pressure. Angiotensinogen elimination raises concerns for clinical application because an angiotensin rise is needed to maintain perfusion pressure during hypovolemia. Here, we investigated whether conventional vasopressors can raise arterial pressure after angiotensinogen depletion.

Methods and Results

Spontaneously hypertensive rats on a low‐salt diet were treated with siRNA (10 mg/kg fortnightly) for 4 weeks, supplemented during the final 2 weeks with fludrocortisone (6 mg/kg per day), the α‐adrenergic agonist midodrine (4 mg/kg per day), or a high‐salt diet (all groups n=6–7). Pressor responsiveness to angiotensin II and norepinephrine was assessed before and after siRNA administration. Blood pressure was measured via radiotelemetry. Depletion of liver angiotensinogen by siRNA lowered plasma angiotensinogen concentrations by 99.2±0.1% and mean arterial pressure by 19 mm Hg. siRNA‐mediated blood pressure lowering was rapidly reversed by intravenous angiotensin II or norepinephrine, or gradually reversed by fludrocortisone or high salt intake. Midodrine had no effect. Unexpectedly, fludrocortisone partially restored plasma angiotensinogen concentrations in siRNA‐treated rats, and nearly abolished plasma renin concentrations. To investigate whether this angiotensinogen originated from nonhepatic sources, fludrocortisone was administered to mice lacking hepatic angiotensinogen. Fludrocortisone did not increase angiotensinogen in these mice, implying that the rise in angiotensinogen in the siRNA‐treated rats must have depended on the liver, most likely reflecting diminished cleavage by renin.

Conclusions

Intact pressor responsiveness to conventional vasopressors provides pharmacological means to regulate the blood pressure–lowering effect of angiotensinogen siRNA and may support future therapeutic implementation of siRNA.

Angiotensin Receptor Blocker is Associated with a Lower Fracture Risk: An Updated Systematic Review and Meta-Analysis

BACKGROUND

Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) are widely used in the treatment of hypertension. Hypertension is often accompanied by osteoporosis. However, the relationship between ACEI/ARB and fractures remains controversial. The purpose of this meta-analysis was to update the potential relationship between ACEI/ARB and fractures.

METHODS

This meta-analysis was identified through PubMed, EMBASE, Cochrane Library, and Web of Science. Related studies about ACEI/ARB with the risk of fracture were published from inception to June 2022.

RESULTS

Nine qualified prospective designed studies, involving 3,649,785 subjects, were included in this analysis. Overall, the RRs of ACEI compared with the nonusers were 0.98 (95% CI: 0.88, 1.10; P < 0.001) for composite fractures and 0.96 (95% CI: 0.87, 1.05; P=0.048) for hip fractures; the RRs of ARB compared to the nonusers were 0.82 (95% CI: 0.73, 0.91; P < 0.001) for composite fractures and 0.85 (95% CI: 0.74, 0.97; P=0.028) for hip fractures. Furthermore, in the subgroup analysis, male may benefit from ARB (RR = 0.65, 95% CI: 0.49, 0.89, P=0.028), and the European may also benefit from ARB (RR = 0.86, 95% CI: 0.80, 0.93, P=0.015).

CONCLUSIONS

ACEI usage will not decrease the risk of osteoporosis fracture. On the contrary, ARB usage can decrease the risk of total fracture and hip fracture, especially for males and Europeans. Compared with ACEI, for patients at higher risk of fracture in cardiovascular diseases such as hypertension, the protective effect of ARB should be considered.

The association between renin angiotensin aldosterone system blockers and future osteoporotic fractures in a hypertensive population - A population-based cohort study in Taiwan

Some cohort studies showed the possibility of renin-angiotensin-aldosterone system (RAAS) blockade in preventing future osteoporotic fractures. The study aimed to evaluate the association between angiotensin converting enzyme inhibitors (ACEIs), angiotensin II receptor blockers (ARBs), and future osteoporotic fracture in a hypertensive population. We queried the Taiwan Longitudinal Health Insurance Database between 2001 and 2012. We used propensity score matching and the total cohort was made up of 57,470 participants (28,735 matched-pairs using or not using RAAS blockers). The mean follow-up period was 6 years. The number of incident fractures was 3757. Hazard ratios (HRs) [95% confidence interval (CI)] of ACEIs and ARBs use with incident fractures were calculated. The incidence of future osteoporotic fracture was significantly lower in the ACEI and ARB user groups but not in the group using an ACEI plus ARB concomitantly, when compared with RAAS blocker nonusers. Comparing ACEI users with RAAS blocker non-users and ARB users with RAAS blocker non-users, the HRs for composite fractures were 0.70 (0.62-0.79) and 0.58 (0.51-0.65), respectively. Sensitivity analysis confirmed a lower incidence of future osteoporotic fracture in patients taking an ACEI for >55 cumulative defined daily doses (cDDDs) and those who received an ARB for >90 cDDDs. These results suggested a lower incidence of future osteoporotic fracture in a hypertensive population who were using an ACEI or ARB compared with RAAS blocker nonusers but not in the group taking an ACEI and ARB concomitantly.

Hydrogen peroxide and nitric oxide induce anticontractile effect of perivascular adipose tissue via renin angiotensin system activation

The perivascular adipose tissue (PVAT) is located around the adventitia, composed primarily by adipocytes, stromal cells, leukocytes, fibroblasts and capillaries. It is well described that PVAT is an important modulator of the vascular tone being considered a biologically active tissue, releasing both vasoconstrictor and vasodilators factors. The literature shows that the anti-contractile effect induced by PVAT may be due to activation of the renin-angiotensin system (RAS).

AIM

Investigate whether the renin-angiotensin system participates in the effect exerted by perivascular adipose tissue on the vascular tone.

METHODS AND RESULTS

For this study we used thoracic aorta from Balb/c mice and performed vascular reactivity, nitric oxide and hydrogen peroxide quantification using selective probes and fluorescence microscopy, immunofluorescence to locate receptors and enzymes involved in this response. Our results demonstrated that perivascular adipose tissue induces an anti-contractile effect in endothelium-independent manner and involves Mas and AT₂ receptors participation with subsequent PI3K/Akt pathway activation. This pathway culminated with nitric oxide and hydrogen peroxide production by neuronal nitric oxide synthase, being hydrogen peroxide most relevant for the anti-contractile effect of perivascular adipose tissue.

CONCLUSION

For the first time in the literature, our results show the presence of Mas and AT₂ receptors, as well as, nitric oxide synthase on perivascular adipose tissue. Furthermore, our results show the involvement of Mas and AT₂ receptors and consequently nitric oxide synthase activation in the anti-contractile effect exerted by perivascular adipose tissue.

Prenatal dexamethasone and postnatal high-fat diet have a synergistic effect of elevating blood pressure through a distinct programming mechanism of systemic and adipose renin-angiotensin systems

Background

Hypertension may result from high-fat (HF) diet induced-obesity and overexposure to glucocorticoids in utero. Recent studies demonstrated the potent contribution of adipose tissue’s renin-angiotensin system (RAS) to systemic RAS, which plays a key role in regulating blood pressure (BP). In this study, we investigated the effects of prenatal dexamethasone (DEX) exposure and postnatal HF diet on RAS of adipose tissue.

Methods

RAS and BP of 6-month old rats exposed to prenatal DEX and/or postnatal HF diet were examined.

Results

Prenatal DEX plus postnatal HF exerted a synergistic effect on systolic BP. Prenatal DEX exposure suppressed plasma angiotensin (ANG) I and ANG II, whereas postnatal HF suppressed plasma ANG-(1–7) level. Prenatal DEX increased prorenin receptor and renin levels, but suppressed angiotensinogen (AGT) and angiotensin-converting-enzyme 1 (ACE1) mRNA expressions in adipose tissue. Postnatal HF increased AGT mRNA expression, but suppressed prorenin receptor, renin, ACE2, ANG II type 2 receptor (AT2R), and Mas receptor (MasR) mRNA expression levels.

Conclusions

Prenatal GC exposure altered the ACE1/ANG II/ANG II type 1 receptor (AT1R) axis, whereas postnatal HF negatively impacted the ACE2/ANG-(1–7)/MasR axis. Prenatal DEX exposure and postnatal HF synergistically elevated BP through a distinct programming mechanism of systemic and adipose RAS. Adipose RAS might be a target for precise hypertension treatment.

Electronic supplementary material

The online version of this article (10.1186/s12944-018-0701-0) contains supplementary material, which is available to authorized users.

Exercise attenuates dexamethasone-induced hypertension through an improvement of baroreflex activity independently of the renin-angiotensin system

Dexamethasone-induced hypertension may be caused by baroreflex alterations or renin-angiotensin system (RAS) exacerbation. Aerobic training has been recommended for hypertension treatment, but the mechanisms responsible for reduction of arterial pressure (AP) in dexamethasone (DEX) treated rats are still inconclusive.This study evaluated whether mechanisms responsible for training-induced attenuation of hypertension involve changes in autonomic nervous system and in RAS components. Rats underwent aerobic training protocol on treadmill or were kept sedentary for 8 weeks. Additionally, animals were treated with DEX during the last 10 days of exercise. Body weight (BW), AP and baroreflex activity were analyzed. Tibialis anterior (TA), soleus (SOL) and left ventricle (LV) were collected for evaluation of RAS components gene expression and protein levels. Dexamethasone decreased BW (20%), caused TA atrophy (16%) and increased systolic AP (SAP, 16%) as well as decreased baroreflex activity. Training attenuated SAP increase and improved baroreflex activity, although it did not prevent DEX-induced BW reduction and muscle atrophy. Neither DEX nor training caused expressive changes in RAS components. In conclusion, exercise training was effective in attenuating hypertension induced by DEX and this response may be mediated by a better autonomic balance through an improvement of baroreflex activity rather than changes in RAS components.

Association between renin-angiotensin-aldosterone system blockade and future osteoporotic fracture risk in hypertensive population: A population-based cohort study in Taiwan

Tissue renin-angiotensin-aldosterone system (RAAS) activation in sites of osteoporosis had been demonstrated in animal studies; however, the possibility of RAAS blockade to prevent future osteoporotic fracture had rarely been verified in clinical studies. We Used the Taiwan Longitudinal Health insurance database 2000 to 2008, the cohort study comprised patients age over 40 with a recorded new diagnosis of hypertension between January 1, 2000 to December 31, 2008, in addition, patients who had diagnosis of osteoporosis before the date of cohort enter were excluded. After the definite diagnosis of hypertension, each patient was followed until osteoporotic fracture happened or the end of 2008. The occurrence of osteoporotic fracture was evaluated in patients who either were or without taking RAAS blockade agents. Cox proportional hazard regressions were used to evaluate the osteoporotic fracture incidence after adjusting for known confounding factors. In total, 57,132 hypertensive patients comprised the study cohort. Our study results showed that the incidence of osteoporosis fracture in the whole cohort was significantly higher in the RAAS blockade non-user group than the user group. This phenomenon was observed in both sex and all age categories. Sensitivity analysis further showed the concordant lower osteoporosis fracture risk in patients with various RAAS blockers usage durations; the risk of osteoporosis fracture was the lowest in those drug use >365 days when compared with the non-user cohort. In conclusion, our study result demonstrated the lower future osteoporotic fracture risk in hypertensive subjects who received long term RAAS blocker treatment.

Regulation and Functions of the Renin-Angiotensin System in White and Brown Adipose Tissue

The renin angiotensin system (RAS) is a major regulator of blood pressure, fluid, and electrolyte homeostasis. RAS precursor angiotensinogen (Agt) is cleaved into angiotensin I (Ang I) and II (Ang II) by renin and angiotensin converting enzyme (ACE), respectively. Major effects of Ang II, the main bioactive peptide of this system, is mediated by G protein coupled receptors, Angiotensin Type 1 (AGTR1, AT1R) and Type 2 (AGTR2, AT2R) receptors. Further, the discovery of additional RAS peptides such as Ang 1-7 generated by the action of another enzyme ACE2 identified novel functions of this complex system. In addition to the systemic RAS, several local RAS exist in organs such as the brain, kidney, pancreas, and adipose tissue. The expression and regulation of various components of RAS in adipose tissue prompted extensive research into the role of adipose RAS in metabolic diseases. Indeed, animal studies have shown that adipose-derived Agt contributes to circulating RAS, kidney, and blood pressure regulation. Further, mice overexpressing Agt have high blood pressure and increased adiposity characterized by inflammation, adipocyte hypertrophy, and insulin resistance, which can be reversed at least in part by RAS inhibition. These findings highlight the importance of this system in energy homeostasis, especially in the context of obesity. This overview article discusses the depot-specific functions of adipose RAS, genetic and pharmacological manipulations of RAS, and its applications to adipogenesis, thermogenesis, and overall energy homeostasis. © 2017 American Physiological Society. Compr Physiol 7:1137-1150, 2017.

The acute impact of polyphenols from Hibiscus sabdariffa in metabolic homeostasis: an approach combining metabolomics and gene-expression analyses

We explored the acute multifunctional effects of polyphenols from Hibiscus sabdariffa in humans to assess possible consequences on the host's health. The expected dynamic response was studied using a combination of transcriptomics and metabolomics to integrate specific functional pathways through network-based methods and to generate hypotheses established by acute metabolic effects and/or modifications in the expression of relevant genes. Data were obtained from healthy male volunteers after 3 hours of ingestion of an aqueous Hibiscus sabdariffa extract. The data were compared with data obtained prior to the ingestion, and the overall findings suggest that these particular polyphenols had a simultaneous role in mitochondrial function, energy homeostasis and protection of the cardiovascular system. These findings suggest beneficial actions in inflammation, endothelial dysfunction, and oxidation, which are interrelated mechanisms. Among other effects, the activation of the heme oxygenase-biliverdin reductase axis, the systemic inhibition of the renin-angiotensin system, the inhibition of the angiotensin-converting enzyme, and several actions mirroring those of the peroxisome proliferator-activated receptor agonists further support this notion. We also found concordant findings in the serum of the participants, which include a decrease in cortisol levels and a significant increase in the active vasodilator metabolite of bradykinin (des-Arg(9)-bradykinin). Therefore, our data support the view that polyphenols from Hibiscus sabdariffa play a regulatory role in metabolic health and in the maintenance of blood pressure, thus implying a multi-faceted impact in metabolic and cardiovascular diseases.

Dynamic regulation of the angiotensinogen gene by DNA methylation, which is influenced by various stimuli experienced in daily life

Angiotensinogen (AGT) has a central role in maintaining blood pressure and fluid balance. DNA methylation is an epigenomic modification maintaining a steady pattern in somatic cells. Herein we summarize the link between AGT regulation and DNA methylation. DNA methylation negatively regulates AGT expression and dynamically changes in response to continuous AGT promoter stimulation. High-salt intake and excess circulating aldosterone cause DNA demethylation around the CCAAT enhancer-binding protein-binding sites, thereby converting the phenotype of AGT expression from an inactive to an active state in visceral adipose tissue. Salt-dependent hypertension may be partially affected by increased adipose AGT expression. Because angiotensin II is a well-established aldosterone-releasing hormone, stimulation of adipose AGT by aldosterone creates a positive feedback loop. This effect is pathologically associated with obesity-related hypertension, although it would be physiologically favorable for humans to efficiently retain their body fluid. The clear difference in DNA demethylation patterns between aldosterone and cortisol indicates a difference in the respective target DNA-binding sites between mineralocorticoid and glucocorticoid receptors in the AGT promoter. Stimulation-induced interactions between transcription factors and target DNA-binding sites trigger DNA demethylation. Dynamic changes in DNA methylation occur in relaxed chromatin regions both where transcription factors actively interact and where transcription is initiated. In contrast to rapid histone modifications, DNA demethylation and remethylation will progress relatively slowly over days or years. A wide variety of stimuli in daily life will continue to slowly and dynamically change DNA methylation patterns throughout life. Wise choices of beneficial stimuli will improve health.

Dexamethasone promotes hypertension by allele-specific regulation of the human angiotensinogen gene

The human angiotensinogen (hAGT) gene has polymorphisms in its 2.5-kb promoter that form two haplotype (Hap) blocks: -6A/G (-1670A/G, -1562C/T, and -1561T/C) and -217A/G (-532T/C, -793A/G, -1074T/C, and -1178G/A). Hap -6A/-217A is associated with human hypertension, whereas Hap -6G/-217G reduces cardiovascular risk. Hap -6A/-217A has increased promoter activity with enhanced transcription factor binding, including to the glucocorticoid receptor (GR). Glucocorticoid therapy frequently causes hypertension, the mechanisms for which are incompletely understood. We have engineered double transgenic (TG) mice containing the human renin gene with either Hap of the hAGT gene and examined the physiological significance of glucocorticoid-mediated allele-specific regulation of the hAGT gene. We have also studied the consequential effects on the renin angiotensin system and blood pressure. TG mice with Hap -6A and -6G were treated with and without a low dose of a GR agonist, dexamethasone (2.5 μg/ml), for 72 h. We found greater chromatin-GR binding with increased GR agonist-induced hAGT expression in liver and renal tissues of Hap -6A mice. Additionally, dexamethasone treatment increased circulating hAGT and angiotensin II levels in Hap -6A mice, as compared with -6G mice. Importantly, GR agonist significantly increased blood pressure and redox markers in TG mice with Hap-6A of the hAGT gene. Taken together, our results show, for the first time, that glucocorticoids affect hAGT expression in a haplotype-dependent fashion with SNPs in Hap -6A favoring agonist-induced GR binding. This leads to increased expression of the hAGT, up-regulation of the renin angiotensin system, and increased blood pressure and oxidative stress in Hap -6A mice.

Genotypes of the renin-angiotensin system and glucocorticoid complications

BACKGROUND

Angiotensinogen (AGT) and angiotensin-converting enzyme (ACE) are recognized as important regulators of body mass index (BMI) and systemic blood pressure (BP). An association between these single nucleotide polymorphisms (SNP) of AGT and ACE genes and obesity or hypertension has been established. This study examined relationships between the molecular variants of the AGT and ACE genes and bodyweight or BP in children treated with glucocorticoids for nephrotic syndrome.

METHODS

Twenty Japanese children (male, n = 14; female, n = 6; age, 2-13 years) were genotyped for AGT polymorphisms (M235T and A-6G) and the ACE polymorphisms (insertion/deletion: I/D and rs4341). All of the children studied were treated with daily prednisolone 2 mg/kg for 4 weeks and thereafter alternate-day prednisolone for 8 weeks. BMI, BMI z-scores, blood lipids, renal function and BP in each group were evaluated during the study period.

RESULTS

BMI and BMI z-scores during the glucocorticoid therapy were significantly higher in the TT genotype of the AGT M235T polymorphisms and the AA genotype of the AGT A-6G polymorphisms compared to other genotypes (P < 0.05). In contrast, the molecular variant of ACE I/D and rs4341 genotypes did not change bodyweight during the glucocorticoid exposure. It was evident, however, that the BP and blood lipids and renal function were not significantly influenced by the AGT and ACE polymorphisms.

CONCLUSIONS

The TT genotype of the AGT M235T and the AA genotype of the A-6G polymorphisms may predispose children to bodyweight gain when initially treated with glucocorticoids for nephrotic syndrome.

Tissue Renin-Angiotensin systems: a unifying hypothesis of metabolic disease

The actions of angiotensin peptides are diverse and locally acting tissue renin-angiotensin systems (RAS) are present in almost all tissues of the body. An activated RAS strongly correlates to metabolic disease (e.g., diabetes) and its complications and blockers of RAS have been demonstrated to prevent diabetes in humans. Hyperglycemia, obesity, hypertension, and cortisol are well-known risk factors of metabolic disease and all stimulate tissue RAS whereas glucagon-like peptide-1, vitamin D, and aerobic exercise are inhibitors of tissue RAS and to some extent can prevent metabolic disease. Furthermore, an activated tissue RAS deteriorates the same risk factors creating a system with several positive feedback pathways. The primary effector hormone of the RAS, angiotensin II, stimulates reactive oxygen species, induces tissue damage, and can be associated to most diabetic complications. Based on these observations, we hypothesize that an activated tissue RAS is the principle cause of metabolic syndrome and type 2 diabetes, and additionally is mediating the majority of the metabolic complications. The involvement of positive feedback pathways may create a self-reinforcing state and explain why metabolic disease initiate and progress. The hypothesis plausibly unifies the major predictors of metabolic disease and places tissue RAS regulation in the center of metabolic control.

Dynamic CCAAT/enhancer binding protein-associated changes of DNA methylation in the angiotensinogen gene

DNA methylation patterns are maintained in adult somatic cells. Recent findings, however, suggest that all methylation patterns are not preserved. We demonstrate that stimulatory signals can change the DNA methylation status at a CCAAT/enhancer binding protein (CEBP) binding site and a transcription start site and activate expression of the angiotensinogen gene (AGT). A CEBP binding site in the human AGT promoter was hypomethylated in tissues with high expression of AGT, but not in those with low expression. The transcriptional activity of AGT promoter sequences cloned into a reporter plasmid depended on DNA methylation. In cultured human cells, interleukin 6 stimulation caused DNA demethylation around a CEBP binding site and a transcription start site; demethylation was accompanied by increased CEBP-β recruitment and chromatin accessibility of the AGT promoter. DNA methylation activity decreased in the nucleus. Excess circulating aldosterone upregulated AGT expression and was accompanied by DNA hypomethylation around a CEBP binding site and a transcription start site in human visceral adipose tissue. High salt intake led to upregulation of Agt expression, DNA hypomethylation around 2 CEBP binding sites and a transcription start site, and decreased DNA methylation activity in rat visceral adipose tissue. Taken together, CEBP binding initiates chromatin relaxation and transcription, which are followed by DNA demethylation around a CEBP binding site and a transcription start site in the AGT promoter. Decreased DNA methylation activity in the nucleus may play a role in DNA demethylation. DNA demethylation switches the phenotype of AGT expression from an inactive to an active state.

Evaluation of leptin and leptin receptor gene 3' UTR polymorphisms in essential hypertension

INTRODUCTION

Leptin and leptin receptor gene polymorphisms have been associated with obesity; however, their association with blood pressure has not been fully elucidated. The aim of this study was to examine the effect of tetranucleotide repeat polymorphism in the 3' flanking region of the leptin and leptin receptor gene on blood pressure in hypertensives with obesity.

METHODS

Two hundred and eighty hypertensives and 200 healthy controls were analyzed for a tetranucleotide repeat polymorphism of leptin and leptin receptor genes. Genotyping was done by amplifying DNA and determining the allele sizes using gel documentation system. Odds ratios were computed to predict the risk for hypertension caused by specific genotypes of leptin and leptin receptor genes and the effect of interaction between them on the development of hypertension was determined by MDR test.

RESULTS

Significant preponderance in the incidence of male sex, obese individuals and those with positive family history was observed with significant elevation in the mean levels of SBP, DBP, BMI and reduction of HDL levels in hypertensives as compared to controls. Class I/I genotypes of leptin showed significantly high risk for developing hypertension irrespective of obesity. Genotypes of leptin receptor did not confer any risk for hypertension and cohorts studied.

CONCLUSION

Homozygotes I/I were at greater risk for developing hypertension irrespective of obesity. When leptin and leptin receptor genes were considered together, synergistic interaction was observed between the two genes leading to hypertension, while the polymorphism at leptin gene and obesity was correlated.

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.

Periaortic adipose tissue-specific activation of the renin-angiotensin system contributes to atherosclerosis development in uninephrectomized apoE-/- mice

Chronic kidney disease (CKD) is an independent risk factor for the development of cardiovascular disease. The perivascular adipose tissue is closely implicated in the development of atherosclerosis; however, the contribution to CKD-associated atherogenesis remains undefined. Eight-week-old apoE-deficient mice were uninephrectomized and fed a high-cholesterol diet starting at 12 wk of age. The atherosclerotic lesion area in the thoracic aorta was comparable in 16-wk-old uninephrectomized (UNX) mice and sham control mice; however, the lesion area was markedly exaggerated in 20-wk-old UNX mice compared with the control (54%, P < 0.05). While the accumulation of monocytes/macrophages and the mRNA expression levels of inflammatory cytokines/chemokines in the thoracic periaortic adipose tissue (PAT) did not differ between the two groups, angiotensinogen (AGT) mRNA expression and the angiotensin II (ANG II) concentration in the PAT were significantly higher in 16-wk-old UNX mice than in the control (1.9- and 1.5-fold increases vs. control, respectively; P < 0.05). ANG II concentrations in both the plasma and epididymal white adipose tissue (WAT) were comparable between the two groups, suggesting that PAT-specific activation of the renin-angiotensin system (RAS) is primarily involved in CKD-associated atherogenesis. The homeostasis model assessment-insulin resistance (HOMA-IR) index and plasma insulin level after glucose loading were significantly elevated in 16-wk-old UNX mice. In vitro stimulation of preadipocytes with insulin exaggerated the AGT mRNA expression along with increased mRNA expression of PPARγ. These findings suggest that PAT-specific RAS activation probably primarily contributes in accelerating atherosclerotic development in UNX mice and could thus represent a therapeutic target for preventing CKD-associated atherogenesis.

Adipokine profile in glucocorticoid-treated patients: baseline plasma leptin level predicts occurrence of lipodystrophy

CONTEXT

Glucocorticoid therapy may result in adipose tissue redistribution of unknown pathophysiology.

OBJECTIVES

To evaluate the effects of glucocorticoids on adipokine levels and adipose tissue inflammation. To compare the results in patients with or without glucocorticoid-induced lipodystrophy (GIL) after 3 months of therapy.

DESIGN AND SETTING

Prospective monocentric study.

PATIENTS

Adult patients initiating systemic, high-dose prednisone therapy for at least 3 months. Blood samples and subcutaneous abdominal adipose tissue biopsies were collected at baseline and month 3. The presence of GIL after 3 months of therapy was assessed using standardized photography.

RESULTS

Thirty-two patients were enrolled. Blood samples and subcutaneous abdominal adipose tissue were available at baseline and month 3 for 30 patients [median age: 61 (38-79) years, 77% women]. Among those 30 patients, 15 were classified as GIL+ and 15 were GIL- at month 3. Between baseline and month 3, adiponectin and leptin levels increased in the overall population while the level of resistin remained unchanged. At baseline, leptin level was higher [19.3 (8.3-31.1) vs 4.5 (2.4-11.3) μg/l, P = 0.006] and resistin level lower [7.1 (6.3-12.4) vs 10.4 (8.0-21.7) μg/l, P = 0.05] in GIL+ than in GIL- patients. Baseline leptin level was predictive of GIL occurrence. Receiver operating characteristic curve analysis demonstrated that the best diagnostic accuracy was obtained with a baseline leptin cut-off of 5.9 μg/l (sensitivity: 93%, specificity: 60%). At month 3, leptin and adiponectin levels increased more in the GIL+ than in the GIL- group, as did the number of anti-inflammatory M2 macrophages in subcutaneous abdominal fat.

CONCLUSION

Glucocorticoid-induced lipodystrophy is associated with a different adipokine profile both before and after glucocorticoid therapy. Serum leptin level prior to glucocorticoid therapy is highly predictive of GIL occurrence.

Physiological, pathological and potential therapeutic roles of adipokines

Formerly regarded purely as passive energy storage, adipose tissue is now recognized as a vital endocrine organ. Adipocytes secrete diverse peptide hormones named adipokines, which act in a autocrine, paracrine or endocrine way to influence several biological functions. Adipokines comprise diverse bioactive substances, including cytokines, growth, and complement factors, which perform essential regulatory functions related to energy balance, satiety and immunity. Presently adipokines have been widely implicated in obesity, diabetes, hypertension and cardiovascular diseases. In this article we aim to present a brief description of the roles and potential therapeutic modulation of adipokines, such as leptin, resistin, adiponectin, apelin, visfatin, FABP-4, tumor necrosis factor-α (TNF-α), interleukin-6 and plasminogen activator inhibitor-1 (PAI-1).

Polymorphisms in the 3'UTR of the human leptin gene and their role in hypertension

Leptin is a protein hormone, mainly synthesized in adipocytes, that regulates the food intake and energy expenditure of the body. Rare mutations in the leptin gene cause obesity. Common polymorphisms of the leptin gene have been associated with obesity, however their association with arterial blood pressure has not been fully elucidated. The aim of the present study was to examine the effect of variants in the 3' flanking region of the leptin gene on blood pressure in hypertensive subjects with high (35.2 ± 5.12) and low (20.13 ± 1.3) body mass index (BMI). Microsatellite polymorphisms and the C538T SNP in the 3'UTR of the leptin gene were screened in 362 subjects, and different biochemical and anthropometric parameters were measured. The levels of serum urea, creatinine, glucose, cholesterol, triglyceride, leptin and angiotensin II were determined in all subjects. A strong association of microsatellite polymorphisms with essential hypertension was found in subjects with a high BMI, but this association was only slight in subjects with a normal BMI. The C538T variant was not found in this population. The frequency of the Class I/Class I and Class I/Class II genotype for tetranucleotide polymorphisms was also significantly higher in the hypertensive compared to the normotensive group (p ≤ 0.0001). In addition, a significant correlation was found between serum leptin and Class I/I and Class I/II genotypes. Linear regression analysis showed an independent correlation of leptinemia with BMI (p=0.019), while a notable correlation was found between serum leptin concentration and angiotensin II. The study confirmed that shorter alleles of microsatellites in the 3' flanking region of leptin are significantly associated with hypertension, however, the underlying mechanism remains unknown.

Adipokines and cardiovascular risk in Cushing's syndrome

Cushing's syndrome (CS) is associated with increased cardiovascular morbidity and mortality. Recent evidence also suggests that increased cardiovascular risk may persist even after long-term remission of CS. Increased central obesity, a typical feature of CS, is associated with altered production of adipokines, which contributes to the pathogenesis of several metabolic and cardiovascular complications observed in this condition. In vitro and in vivo studies have shown a relationship between cortisol and adipokines in several experimental settings. In patients with either active or 'cured' CS, an increase in leptin and resistin levels as well as the release of pro-inflammatory cytokines, such as tumor necrosis factor-α and interleukin-6, may be associated with increased cardiovascular risk. For other adipokines, including adiponectin, results are inconclusive. Studies are needed to further elucidate the interactions between clinical and subclinical increases in cortisol production and altered adipokine release in CS.

Expression of 11β-hydroxysteroid dehydrogenase type 1 in visceral and subcutaneous adipose tissues of patients with polycystic ovary syndrome is associated with adiposity

Polycystic ovary syndrome (PCOS) is characterized by insulin resistance (IR) and central obesity. The impact of adipose tissue cortisol reactivation by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) on markers of obesity and IR was assessed in PCOS patients. Eighty-five PCOS patients and 43 controls were enrolled for subcutaneous adipose tissue biopsy; 25/85 patients and 29/43 controls underwent also visceral adipose tissue biopsy. HSD11B1 gene expression and expression of lipid metabolism genes were measured in subcutaneous and visceral adipose tissues. Anthropometric and biochemical markers of IR and PCOS were also assessed. HSD11B1 expression in visceral and subcutaneous adipose tissue was increased in PCOS patients compared to controls (p<0.05). After BMI adjustment, the difference was no longer significant. In PCOS patients, visceral HSD11B1 expression correlated positively with waist circumference (p=0.001), BMI (p=0.002), plasma insulin (p<0.05), systolic blood pressure (p=0.003), and lipoprotein lipase (LPL), hormone-sensitive lipase (LIPE) and peroxisome-proliferator activated receptor γ gene expression. Subcutaneous HSD11B1 expression correlated positively with BMI, waist circumference (p<0.001 for both) and HOMA-IR (p=0.003), and negatively with LPL, LIPE, adiponectin and glucose transporter GLUT4 gene expression. HSD11B1 expression in both depots showed a negative correlation with plasma HDL-cholesterol (p<0.03) and a positive one with C-reactive protein (p<0.001). In multiple regression analysis, HSD11B1 expression in visceral adipose tissue was most prominently associated with waist circumference, and that in subcutaneous adipose tissue with BMI (p<0.001 for both). Our results show that PCOS is not associated with increased HSD11B1 expression once adiposity is controlled for. Increased expression of this gene correlates with markers of adiposity and predicts IR and an unfavorable metabolic profile, independently of PCOS.

The conflicting effects of maternal nutrient restriction and early-life obesity on renal health

Epidemiological and animal studies have demonstrated that early-life nutrition alters the metabolic responses and generates structural changes in complex tissues, such as the kidneys, which may lead to a reduction in the offspring lifespan. Independently, obesity induces a spontaneous low-grade chronic inflammatory response by modulating several of the major metabolic pathways that ultimately compromise long-term renal health. However, the combined effects of maternal nutrition and early-life obesity in the development of renal diseases are far from conclusive. Previous results, using the ovine model, demonstrated that the combination of a reduction in fetal nutrition and juvenile obesity induced a series of adaptations associated with severe metabolic syndrome in the heart and adipose tissue. Surprisingly, exposure to an obesogenic environment in the kidney of those offspring produced an apparent reduction in glomerulosclerosis in relation to age- and weight-matched controls. However, this reduction in cellular apoptosis was accompanied by a rise in glomerular filtration rate and blood pressure of equal intensity when compared with obese controls. The intention of this review is to explain the adaptive responses observed in this model, based on insights into the mechanism of renal fetal programming, and their potential interactions with some of the metabolic changes produced by obesity.

Transgenic mice with -6A haplotype of the human angiotensinogen gene have increased blood pressure compared with -6G haplotype

Hypertension is a serious risk factor for cardiovascular disease, and the angiotensinogen (AGT) gene locus is associated with human essential hypertension. The human AGT (hAGT) gene has an A/G polymorphism at -6, and the -6A allele is associated with increased blood pressure. However, transgenic mice containing 1.2 kb of the promoter with -6A of the hAGT gene show neither increased plasma AGT level nor increased blood pressure compared with -6G. We have found that the hAGT gene has three additional SNPs (A/G at -1670, C/G at -1562, and T/G at -1561). Variants -1670A, -1562C, and -1561T almost always occur with -6A, and variants -1670G, -1562G, and -1561G almost always occur with -6G. Therefore, the hAGT gene may be subdivided into either -6A or -6G haplotypes. We show that these polymorphisms affect the binding of HNF-1α and glucocorticoid receptor to the promoter, and a reporter construct containing a 1.8-kb hAGT gene promoter with -6A haplotype has 4-fold increased glucocorticoid-induced promoter activity as compared with -6G haplotype. In order to understand the physiological significance of these haplotypes in an in vivo situation, we have generated double transgenic mice containing either the -6A or -6G haplotype of the hAGT gene and the human renin gene. Our ChIP assay shows that HNF-1α and glucocorticoid receptor have stronger affinity for the chromatin obtained from the liver of transgenic mice containing -6A haplotype. Our studies also show that transgenic mice containing -6A haplotype have increased plasma AGT level and increased blood pressure as compared with -6G haplotype. Our studies explain the molecular mechanism involved in association of the -6A allele of the hAGT gene with hypertension.

Adipose tissue-specific regulation of angiotensinogen in obese humans and mice: impact of nutritional status and adipocyte hypertrophy

BACKGROUND

The adipose tissue renin-angiotensin system (RAS) has been implicated in the pathophysiology of obesity and dysfunction of adipose tissue. However, neither regulation of angiotensinogen (AGT) expression in adipose tissue nor secretion of adipose tissue-derived AGT has been fully elucidated in humans.

METHODS

Human subcutaneous abdominal adipose tissue (SAT) biopsies were performed for 46 subjects with a wide range of body mass index (BMI). Considering the mRNA level of AGT and indices of body fat mass, the amount of adipose tissue-derived AGT secretion (A-AGT-S) was estimated. Using a mouse model of obesity and weight reduction, plasma AGT levels were measured with a newly developed enzyme-linked immunosorbent assay (ELISA), and the contribution of A-AGT-S to plasma AGT levels was assessed.

RESULTS

A-AGT-S was substantially increased in obese humans and the value was correlated with the plasma AGT level in mice. A-AGT-S and plasma AGT were higher in obese mice, whereas lower in mice with weight reduction. However, the AGT mRNA levels in the liver, kidney, and aorta were not altered in the mouse models. In both humans and mice, the AGT mRNA levels in mature adipocytes (MAs) were comparable to those in stromal-vascular cells. Coulter Multisizer analyses revealed that AGT mRNA levels in the MAs were inversely correlated with the average size of mature adipocytes.

CONCLUSIONS

This study demonstrates that adipose tissue-derived AGT is substantially augmented in obese humans, which may contribute considerably to elevated levels of circulating AGT. Adipose tissue-specific regulation of AGT provides a novel insight into the clinical implications of adipose tissue RAS in human obesity.

The adipose renin-angiotensin system: role in cardiovascular disease

Several reviews have highlighted the importance of local tissue production of components of the renin-angiotensin system (RAS) [Bader, M., Ganten, D., 2008. Update on tissue renin-angiotensin systems. J. Mol. Med. 86, 615-621; Krop, M., Danser, A.H., 2008. Circulating versus tissue renin-angiotensin system: on the origin of (pro)renin. Curr. Hypertens. Rep. 10, 112-118; Paul, M., Poyan Mehr, A., Kreutz, R., 2006. Physiology of local renin-angiotensin systems. Physiol. Rev. 86, 747-803]. While the concept of tissue RAS is gaining more widespread acceptance, the concept of local angiotensin II (AngII) production, acting in coordinate or independently of the endocrine RAS, continues to be debated. The primary reasons that local AngII production has been studied by many investigators are that components of the RAS are expressed by multiple cell types, and that the endocrine RAS cannot fully explain all effects of AngII. Moreover, through the development and study of genetically altered models for over-expression or knockdown of individual RAS components within specific cell types, it is becoming increasingly more evident that local RAS contribute to effects of AngII in normal physiology and disease. The purpose of this review is to define the presence and physiological significance of a local RAS in adipose tissue in relation to cardiovascular disease.

Hypertension in rheumatoid arthritis

RA associates with an increased burden of cardiovascular disease, which is at least partially attributed to classical risk factors such as hypertension (HT) and dyslipidaemia. HT is highly prevalent, and seems to be under-diagnosed and under-treated among patients with RA. In this review, we discuss the mechanisms that may lead to increased blood pressure in such patients, paying particular attention to commonly used drugs for the treatment of RA. We also suggest screening strategies and management algorithms for HT, specific to the RA population, although it is clear that these need to be formally assessed in prospective randomized controlled trials designed specifically for the purpose, which, unfortunately, are currently lacking.

Metabolic action of peroxisome proliferator-activated receptor γ agonism in rats with exogenous hypercorticosteronemia

OBJECTIVE

The beneficial metabolic actions of peroxisome proliferator-activated receptor gamma (PPARgamma) agonism are associated with modifications in adipose tissue metabolism that include a reduction in local glucocorticoid (GC) production by 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1). This study aimed to assess the contribution of GC attenuation to PPARgamma agonism action on gene expression in visceral adipose tissue and global metabolic profile.

DESIGN

Rats were treated (2 weeks) with the PPARgamma agonist rosiglitazone (RSG, 10 mg/kg/day) with concomitant infusion of vehicle (cholesterol implant) or corticosterone (HiCORT, 75 mg/implant/week) to defeat PPARgamma-mediated GC attenuation.

MEASUREMENTS

mRNA levels of enzymes involved in lipid uptake (and lipoprotein lipase activity), storage, lipolysis, recycling, and oxidation in retroperitoneal white adipose tissue (RWAT). Serum glucose, insulin and lipids, and lipid content of oxidative tissues.

RESULTS

Whereas HiCORT did not alter RWAT mass, RSG increased the latter (+33%) independently of the corticosterone status. Both HiCORT and RSG increased lipoprotein lipase activity, the mRNA levels of the de novo lipogenesis enzyme fatty acid synthase, and that of the fatty acid retention-promoting enzyme acyl-CoA synthase 1, albeit in a nonadditive fashion. Expression level of the lipolysis enzyme adipose triglyceride lipase was increased additively by HiCORT and RSG. PPARgamma agonism increased mRNA of the fatty acid recycling enzymes glycerol kinase and cytosolic phosphoenolpyruvate carboxykinase and those of the fatty acid oxidation enzymes muscle-type carnitine palmitoyltransferase 1 and acyl-CoA oxidase, whereas HiCORT remained without effect. HiCORT resulted in liver steatosis and hyperinsulinemia, which were abrogated by RSG, whereas the HiCORT-induced elevation in serum nonesterified fatty acid levels was only partially prevented. The hypotriglyceridemic action of RSG was maintained in HiCORT rats.

CONCLUSION

The GC and PPARgamma pathways exert both congruent and opposite actions on specific aspects of adipose tissue metabolism. Both the modulation of adipose gene expression and the beneficial global metabolic actions of PPARgamma agonism are retained under imposed high ambient GC, and are therefore independent from PPARgamma effects on 11beta-HSD1-mediated GC production.

Angiotensin II increases adipose angiotensinogen expression

In addition to the well-defined contribution of the liver, adipose tissue has been recognized as an important source of angiotensinogen (AGT). The purpose of this study was to define the angiotensin II (ANG II) receptors involved in regulation of adipose AGT and the relationship of this control to systemic AGT and/or angiotensin peptide concentrations. In LDL receptor-deficient (LDLR(-/-)) male mice, adipose mRNA abundance of AGT was 68% of that in liver, and adipose mRNA abundance of the angiotensin type 1a (AT(1a)) receptor (AT(1a)R) was 38% of that in liver, whereas mRNA abundance of the angiotensin type 2 (AT(2)) receptor (AT(2)R) was 57% greater in adipose tissue than in liver. AGT and angiotensin peptide concentrations were decreased in plasma of AT(1a)R-deficient (AT(1a)R(-/-)) mice and were paralleled by reductions in AGT expression in liver. In contrast, adipose AGT mRNA abundance was unaltered in AT(1a)R(-/-) mice. AT(2)R(-/-) mice exhibited elevated plasma angiotensin peptide concentrations and marked elevations in adipose AGT and AT(1a)R mRNA abundance. Increases in adipose AGT mRNA abundance in AT(2)R(-/-) mice were abolished by losartan. In contrast, liver AGT and AT(1a)R mRNA abundance were unaltered in AT(2)R(-/-) mice. Infusion of ANG II for 28 days into LDLR(-/-) mice markedly increased adipose AGT and AT(1a)R mRNA but did not alter liver AGT and AT(1a)R mRNA. These results demonstrate that differential mRNA abundance of AT(1a)/AT(2) receptors in adipose tissue vs. liver contributes to tissue-specific ANG II-mediated regulation of AGT. Chronic infusion of ANG II robustly stimulated AT(1a)R and AGT mRNA abundance in adipose tissue, suggesting that adipose tissue serves as a primary contributor to the activated systemic renin-angiotensin system.

Angiotensin II, corticosteroids, type II diabetes and the metabolic syndrome

Syndrome X, the Metabolic Syndrome, and type II diabetes are closely related diseases that share risk factors and symptoms, notably insulin resistance. Several factors have been proposed either to mediate the disease(s) or to be their causes, and most converge on the endocrine/paracrine functions of the adipocyte. A common feature of such systems is their relative autonomy from systemic negative feedback regulation, for example by the HPA axis. We draw particular attention to two such mechanisms, both of which are associated with, and can cause, insulin resistance: the extra-adrenal production of corticosteroids, and the tissue renin angiotensin system of the adipocyte. These show another feature: the inter-regulation of glucocorticoid action and the RAS by positive feedback. Cortisol enhances the expression of 11 beta-HSD 1, and also of angiotensinogen and angiotensin type 1 receptors. In turn, angiotensin can stimulate further corticosteroid production, from the adrenal and perhaps from extra-adrenal sources. The instability inherent in such positive loops could account for the progressive nature of the disease(s), suggesting ways to break the circle.

Unravelling the roles of the apelin system: prospective therapeutic applications in heart failure and obesity

The apelin receptor was initially classed as an orphan G-protein-coupled receptor, and little was known about its physiological functions until apelin, the endogenous ligand, was identified. Similarities between the structure and anatomical distribution of apelin and its receptor and that of angiotensin II and the angiotensin AT1 receptor provide clues about the physiological functions of this novel signal-transduction system. Now, roles have been established for the apelin system in lowering blood pressure, as a potent cardiac inotrope, in modulating pituitary hormone release and food and water intake, in stress activation, and as a novel adipokine that is excreted from fat cells and regulates insulin. Given its broad array of physiological roles, apelin has attracted much interest as a target for novel therapeutic research and drug design.

11beta-Hydroxysteroid dehydrogenase type 1-driven cortisone reactivation regulates plasminogen activator inhibitor type 1 in adipose tissue of obese women

BACKGROUND

Plasminogen activator inhibitor type 1 (PAI-1) is the main inhibitor of the fibrinolytic system and contributes to an increased risk of atherothrombosis in insulin-resistant obese patients. In adipose tissue, we have shown that PAI-1 is synthesized mainly in the visceral stromal compartment and is positively regulated by glucocorticoids. We have demonstrated that adipose tissue expression of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD-1), an enzyme that catalyzes the conversion of inactive cortisone to active cortisol, is exaggerated in obese patients.

OBJECTIVES

We hypothesized that increased action of 11beta-HSD-1 in adipose tissue of obese subjects may contribute to PAI-1 overproduction.

PATIENTS AND METHODS

Using in situ hybridization, we studied the expression of the mRNAs coding for PAI-1 and 11beta-HSD-1 in the stromal compartment of visceral adipose tissue obtained from obese women. The regulation of PAI-1 secretion from in vitro incubated tissue explants was also investigated.

RESULTS

Regression analysis showed a significant positive linear relationship between PAI-1 and 11beta-HSD-1 mRNAs expression. In vitro incubation of adipose tissue explants demonstrated that cortisone stimulated PAI-1 gene expression and secretion, and that these effects were inhibited by co-incubation with the 11beta-HSD inhibitor, glycyrrhetinic acid.

CONCLUSIONS

Our data demonstrate that 11beta-HSD-1-driven cortisone reactivation regulates adipose PAI-1 synthesis and secretion. They suggest that the increased PAI-1 synthesis and secretion observed in obese patients can be also related, at least in part, to an increased local conversion of cortisone to cortisol. Therefore, local cortisol metabolism in adipose tissue may be involved in increasing the risk of cardiovascular disease in obese subjects.

A haplotype of angiotensinogen gene that is associated with essential hypertension increases its promoter activity in adipocytes

Obesity is associated with hypertension and other cardiovascular diseases especially in the African-American population. Human angiotensinogen (AGT) gene has seven single nucleotide polymorphisms (SNPs) in 1.2 kb region of its promoter. Recent studies have shown that variant -217A is associated with hypertension in African-American and Chinese population. Nucleotide sequence of the hAGT gene has shown that variant -217A almost always occurs with variants -532T, -793A and -1074T (forming haplotype AAT) and variant -217G almost always occurs with variants -532C, -793G and -1074G (forming haplotype GGG). Since hAGT gene is expressed in the adipose tissue and its expression in this tissue may play a role in hypertension, we have analyzed the role of haplotypes AAT and GGG on the expression of this gene in adipocytes. We show here that a reporter construct with haplotype AAT of the hAGT gene has increased promoter activity on transient transfection in pre-adipocytes and differentiated adipocytes as compared to the reporter construct containing GCGG haplotype. Increased expression of the AGT gene containing haplotype AAT in the liver and adipocytes may be a contributing factor for hypertension.

Regulation of apelin mRNA expression by insulin and glucocorticoids in mouse 3T3-L1 adipocytes

The novel 36-amino acid peptide, apelin, is the endogenous ligand for the orphan receptor APJ. Apelin may play important roles in the regulation of the cardiovascular system and the hypothalamic-pituitary axis. It is a potent hypotensive agent and one of the most potent stimulators of cardiac contractility. In this study, we investigated the roles of apelin derived from adipocytes in the regulation of cardiovascular homeostasis. We found that both apelin and APJ mRNAs were expressed in isolated mouse adipocytes and that apelin mRNA levels increased during the differentiation of 3T3-L1 cells to adipocytes. We also found that the administration of insulin (1 nM-100 nM) increased, while that of dexamethasone (0.1 nM-100 nM) decreased the apelin mRNA levels in 3T3-L1 adipocytes in a dose-dependent manner, suggesting that insulin and glucocorticoids regulate apelin gene expression in adipocytes. We speculate that high glucocorticoid levels suppress apelin production and stimulate angiotensin II production in adipocyte, decreasing the counter-regulatory activity of apelin against the pressor action of angiotensin II, which might partly be involved in the mechanism underlying the development of obesity-related hypertension.

[Adipose tissue, plastic and reconstructive surgery: come back to sources]

The adipose tissue represents a large amount of adult tissue. For long time, it was considered as a filling tissue and used in plastic and reconstructive surgery. It was always studied for its main involvement in energy metabolism and energy disorders as diabetes and obesity. More recently, its endocrine functions emerged and thus play a key role in many physiological functions as inflammation and immunity. The presence of preadipocytes throughout life was demonstrated using primary culture technology from cells derived from adipose tissue. In recent papers, cells derived from adipose tissue were used for haematopoiesis, vascularisation or skeletal muscle recovery. Differentiation into functional cardiomyocytes, osteoblasts and neural cells was obtained in vitro. These spectacular data, the fact that adipose tissue is easy to sample and the possibility to create cell or tissue banks open numerous and promising perspectives in regenerative medicine.

Glucocorticoid exposure in late gestation in the rat permanently programs gender-specific differences in adult cardiovascular and metabolic physiology

Glucocorticoid overexposure in utero may underlie the association between low birth weight and subsequent development of common cardiovascular and metabolic pathologies. Previously, we have shown that prenatal dexamethasone (DEX) exposure in rat reduces birth weight and programs the hypothalamic-pituitary axis and fasting and postprandial hyperglycemia in adult males and hypertension in adult males and females. This study aimed to determine 1) whether there were gender differences in prenatal DEX-programmed offspring, and 2) whether the renin-angiotensin system (RAS) plays a role in the programming of hypertension. Rats exposed to DEX in utero (100 microg.kg(-1).day(-1) from embryonic days 14-21) were of lower birth weight (by 12%, P < 0.01) and displayed full catch-up growth within the first month of postnatal life. DEX-treated male offspring in adulthood selectively displayed elevated plasma adrenocorticotropic hormone (by 221%) and corticosterone (by 188%, P < 0.05), postprandial insulin-glucose ratios (by 100%, P < 0.05), and hepatic expression of the gluconeogenic enzyme phosphoenolpyruvate carboxykinase (by 38%, P < 0.05). Conversely, DEX-programmed females were hypertensive (by 11%, P < 0.05), with elevated hepatic angiotensinogen mRNA expression (by 9%, P < 0.05), plasma angiotensinogen (by 61%, P < 0.05), and renin activity (by 88%, P < 0.05). These findings demonstrate that prenatal glucocorticoids program adulthood cardiovascular and metabolic physiology in a gender-specific pattern, and that an activated RAS may in part underlie the hypertension associated with prenatal DEX programming.

Human adipose angiotensinogen gene expression and secretion are stimulated by cyclic AMP via increased DNA cyclic AMP responsive element binding activity

Components of the adipose renin-angiotensin system (RAS) have been suggested as providing a potential path-way linking obesity to hypertension. In adipose cells, the biological responses to beta-adrenergic stimulation are mediated by an increase in intracellular cAMP. Because an association exists among body fat mass, hypertension, and increased sympathetic stimulation, we examined the influence of cAMP on angiotensinogen (ATG) expression and secretion in human adipose tissue and in parallel we studied the DNA binding activity of CRE transcriptional factors. A 24 h exposure to the cAMP analog 8Br-cAMP resulted in significant increases in ATG mRNA levels (+176+/-60%) and protein secretion (+40+/-27%). The ability of 8Br-cAMP to promote ATG gene expression was unaltered by H89, a protein kinase A inhibitor, because H89 per se was found to stimulate ATG mRNA levels and protein secretion. Moreover, 8Br-cAMP stimulated the specific CRE DNA binding activity (+115+/-14%) in human adipocyte nuclear extracts as assessed by electrophoretic mobility shift assays. These results indicate that cAMP upregulates in vitro ATG expression and secretion in human adipose tissue and that the induction in ATG mRNA levels appears to result, at least in part, from positive effects on the DNA binding activity of CRE transcription factors. Further studies are required to determine whether this regulatory pathway is activated in human obesity and to elucidate the importance of adipose ATG to the elevated blood pressure observed in this pathological state.

Adipose tissue as an endocrine organ? A review of recent data related to cardiovascular complications of endocrine dysfunctions

Clinical and experimental data obtained in the last few years have modified the concept of adipose tissue as one solely directed at energy storage and release. The adipose tissue is a target organ for glucocorticoids and several studies have been carried out on the function of hypothalamic-pituitary-adrenal axis in obese subjects without conclusive results. A recent and innovative finding is that adipose tissue can produce cortisol from its inactive precursor, cortisone. The identification of leptin, a hormone synthesised by fat tissue, has ushered in the modern view of this tissue as a true endocrine organ. Leptin is produced primarily by subcutaneous and to a lesser extent by visceral adipose tissue, and has a central role in controlling body weight and, especially in regulating fat stores. Leptin is also involved in several complex functions, including physiological processes associated with puberty. Another hormone of fat tissue is angiotensinogen, which is produced in larger amounts by visceral than subcutaneous fat. Human and animals adipose tissue express a whole renin-angiotensin system (RAS). Angiotensin II, the final effector of this system is probably produced locally by adipose tissue. The function of adipose RAS is not well known. RAS can participate together with other hormones and substances, in adipocyte differentiation and fat tissue growth, but could be also involved in the pathogenesis of complications of obesity including arterial hypertension.

cAMP-positive regulation of angiotensinogen gene expression and protein secretion in rat adipose tissue

The adipose renin-angiotensin system (RAS) has been assigned to participate in the control of adipose tissue development and in the pathogenesis of obesity-related hypertension. In adipose cells, the biological responses to beta-adrenergic stimulation are mediated by an increase in intracellular cAMP. Because cAMP is known to promote adipogenesis and because an association exists between body fat mass, hypertension, and increased sympathetic stimulation, we examined the influence of cAMP on angiotensinogen (ATG) expression and secretion in rat adipose tissue. Exposure of primary cultured differentiated preadipocytes to the cAMP analog 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) or cAMP-stimulating agents (forskolin and IBMX) results in a significant increase in ATG mRNA levels. In adipose tissue fragments, 8-BrcAMP also increases ATG mRNA levels and protein secretion, but not in the presence of the protein kinase A inhibitor H89. The addition of isoproterenol, known to stimulate the synthesis of intracellular cAMP via beta-adrenoreceptors, had the same stimulatory effect on ATG expression and secretion. These results indicate that cAMP in vitro upregulates ATG expression and secretion in rat adipose tissue via the protein kinase A-dependent pathway. Further studies are required to determine whether this regulatory pathway is activated in human obesity, where increased sympathetic tone is frequently observed, and to elucidate the importance of adipose ATG to the elevated blood pressure observed in this pathological state.

New paradigms in neuroendocrinology: relationships between obesity, systemic inflammation and the neuroendocrine system

Obesity may be an independent risk factor for coronary artery disease and contribute to a chronic state of systemic inflammation leading to atherosclerosis and metabolic abnormalities, such as diabetes, insulin resistance, dyslipidemia and hypertension. Visceral fat, in fact, may act as an endocrine organ, synthesizing and releasing atherogenic inflammatory cytokines, whose circulating levels depend on the individual's nutritional state, and the extent and anatomical location of fat stores. Unsuspected viral infections might also be involved in enhancing autocrine/paracrine mechanisms of cytokine release from omental fat. Elevated levels of blood cytokines may interact with the neuroendocrine system, autonomic nerves and peripheral lymphatic organs. This may lead to local inflammatory reactions in many body compartments, in particular in the heart tissue, possibly affecting the process of circulatory recovery in obese subjects, and predisposing these patients to a greater risk of myocardial inflammatory disease than individuals with normal body mass index. Circulating levels of inflammatory cytokines might be considered to determine risk categories for development of cardiovascular complications in obese subjects. In addition, their reduction with pharmacological antagonists might prevent and/or control acute cardiovascular events and increase energy expenditure in obese patients, especially after surgical treatment, through reduction of cytokine inhibition of the hypothalamic-pituitary-thyroid axis.

Transgenic amplification of glucocorticoid action in adipose tissue causes high blood pressure in mice

Obesity is closely associated with the metabolic syndrome, a combination of disorders including insulin resistance, diabetes, dyslipidemia, and hypertension. A role for local glucocorticoid reamplification in obesity and the metabolic syndrome has been suggested. The enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) regenerates active cortisol from inactive 11-keto forms, and aP2-HSD1 mice with relative transgenic overexpression of this enzyme in fat cells develop visceral obesity with insulin resistance and dyslipidemia. Here we report that aP2-HSD1 mice also have high arterial blood pressure (BP). The mice have increased sensitivity to dietary salt and increased plasma levels of angiotensinogen, angiotensin II, and aldosterone. This hypertension is abolished by selective angiotensin II receptor AT-1 antagonist at a low dose that does not affect BP in non-Tg littermates. These findings suggest that activation of the circulating renin-angiotensin system (RAS) develops in aP2-HSD1 mice. The long-term hypertension is further reflected by an appreciable hypertrophy and hyperplasia of the distal tubule epithelium of the nephron, resembling salt-sensitive or angiotensin II-mediated hypertension. Taken together, our findings suggest that overexpression of 11beta-HSD1 in fat is sufficient to cause salt-sensitive hypertension mediated by an activated RAS. The potential role of adipose 11beta-HSD1 in mediating critical features of the metabolic syndrome extends beyond obesity and metabolic complications to include the most central cardiovascular feature of this disorder.

The adipose-tissue renin-angiotensin-aldosterone system: role in the metabolic syndrome?

Overfeeding of rodents leads to increased local formation of angiotensin II due to increased secretion of angiotensinogen from adipocytes. Whereas angiotensin II promotes adipocyte growth and preadipocyte recruitment, increased secretion of angiotensinogen from adipocytes also directly contributes to the close relationship between adipose-tissue mass and blood pressure in mice. In contrast, angiotensin II acts as an antiadipogenic substance in human adipose tissue, and the total increase in adipose-tissue mass may be more important in determining human plasma angiotensinogen levels than changes within the single adipocyte. However, as increased local formation of angiotensin II in adipose tissue may be increased especially in obese hypertensive subjects, a contribution of the adipose-tissue renin-angiotensin system to the development of insulin resistance and hypertension is conceivable in humans, but not yet proven. Insulin resistance may be aggravated by the inhibition of preadipocyte recruitment, which results in the redistribution of triglycerides to the liver and skeletal muscle, and blood pressure may be influenced by local formation of angiotensin II in perivascular adipose tissue. Thus, although the mechanisms are still speculative, the beneficial effects of ACE-inhibition and angiotensin-receptor blockade on the development of type 2 diabetes in large clinical trials suggest a pathophysiological role of the adipose-tissue renin-angiotensin system in the metabolic syndrome.

Steroid responsiveness of renal epithelial cells. Dissociation of transrepression and transactivation

Glucocorticoids modulate cellular and inflammatory responses via stimulation or inhibition of gene transcription. Inhibition of cytokine gene expression is mediated via repression of transcription factors, including NF-kappaB. Previously we have shown that cytokine production by renal epithelial cells is insensitive to the inhibitory action of dexamethasone. In this study we demonstrate that dexamethasone is unable to inhibit NF-kappaB activation in the renal epithelial cell line HK-2, as measured by IkappaB-alpha degradation and DNA binding activity. Transfection of an NF-kappaB-inducible reporter gene demonstrated that non-stimulated HK-2 cells contain a high level of constitutively active NF-kappaB compared with the steroid-sensitive airway epithelial cell line A549, which was not blocked by dexamethasone. Expression and nuclear translocation of the glucocorticoid receptor (GR) was comparable in both cell types. In HK-2 cells, dexamethasone stimulated expression of two glucocorticoid-responsive genes, beta(2)-adrenoreceptors and angiotensinogen. The capacity of GR to transactivate the native angiotensinogen glucocorticoid-responsive element (GRE) using chromatin-IP was not impaired. Moreover, dexamethasone activation of a GRE-driven reporter construct appeared to be equally effective, although less sensitive compared with A549 cells. In conclusion, we provide evidence that glucocorticoids are unable to repress the activity of NF-kappaB in renal epithelial cells in the presence of an intact stimulatory pathway.

Leptin and the adipocyte endocrine system

Although adipose tissue has long been considered to be metabolically passive and primarily responsible for energy storage, recent scientific advances have dramatically altered our understanding of the function of this ubiquitous tissue. The fat cell is a transducer of energy supply for the changing metabolic needs of the body, modulating glucose homeostasis, hypothalamic function, sympathetic output, vascular tone, immune response, and reproduction. Through endocrine/autocrine and paracrine actions, adipocyte-derived molecules defend the body during periods of energy deficit and stress. With the development of obesity, maladaptive responses to adipose excess result in pathologic states of inflammation, coagulopathy, and altered insulin sensitivity.