Increase In Angiotensinogen Research Articles

Role of Gut Microbiota in Dengue.

Dengue is a disease caused by a flavivirus (DENV) and transmitted by the bite of a mosquito, primarily the Aedes aegypti and Aedes albopictus species. Previous studies have demonstrated a relationship between the host gut microbiota and the evolution of dengue. It seems to be a bidirectional relationship, in which the DENV can affect the microbiota by inducing alterations related to intestinal permeability, leading to the release of molecules from microbiota dysbiosis that can influence the evolution of dengue. The role of angiotensin II (Ang II) in the microbiota/dengue relationship is not well understood, but it is known that the renin-angiotensin system (RAS) is present in the intestinal tract and interacts with the gut microbiota. The possible effect of Ang II on the microbiota/Ang II/dengue relationship can be summarised as follows: the presence of Ang II induced hypertension, the increase in angiotensinogen, chymase, and microRNAs during the disease, the induction of vascular dysfunction, the production of trimethylamine N-oxide and the brain/microbiota relationship, all of which are elements present in dengue that could be part of the microbiota/Ang II/dengue interactions. These findings suggest the potential use of Ang II synthesis blockers and the use of AT1 receptor antagonists as therapeutic drugs in dengue.

An Oral Contraceptive Containing Estetrol 15 MG and Drospirenone 3 MG Has Limited Effects on Endocrine and Metabolic Parameters

Background: Most combined oral contraceptives (COCs) contain ethinylestradiol (EE), an estrogen component known to increase the risk of venous thromboembolic events. Previous phase 2 trials have shown that Estetrol (E4), a naturally-occurring estrogen produced by the human fetal liver, in combination with Drospirenone (DRSP), inhibits ovulation and is associated with favorable vaginal bleeding, safety and tolerability profiles and high user satisfaction. When administered in doses up to 10 mg for less than 3 months, E4 either alone or in combination with DRSP showed limited effects on liver function as well as on metabolic and endocrine parameters. However, the impact of E4 15 mg/DRSP 3 mg, the selected dose for pregnancy prevention (hereafter referred to as E4/DRSP), on metabolic and endocrine parameters was never investigated. Methods: A randomized, open-label, controlled, three-arm parallel study was conducted in 101 healthy volunteers aged 18-50 years with a body mass index between 18.0 and 30.0 kg/m2. Of the randomized individuals, 98 subjects received either E4/DRSP (n=38), EE 30 µg/levonorgestrel (LNG) 150 µg (n=29) or EE 20 µg/DRSP 3 mg (n=31) COCs for six consecutive treatment cycles of 28 days. Endocrine and metabolic parameters were measured at baseline, cycle 3 and cycle 6. Results: FSH and LH decreased with both EE/LNG (-84% and -92%, respectively) and EE/DRSP (-64% and -90%, respectively), whereas E4/DRSP slightly increased FSH (31%) and had minor effect on LH (-8%). Total cortisol increased by more than 100% during treatment with EE/LNG (109%) and EE/DRSP (107%), while E4/DRSP only slightly increased total cortisol (26%). The effects of E4/DRSP, EE/LNG and EE/DRSP on other endocrine parameters including androstenedione (-31%, -49% and -40%) and free testosterone (-50%, -50% and -71%) were similar. Liver proteins, except CRP, increased from baseline in all treatment groups. The increase in angiotensinogen, CBG, and TBG levels was significantly lower for E4/DRSP (75%, 40% and 17%) in comparison with EE/LNG (170%, 152% and 37%) and EE/DRSP (207%, 140% and 70%). SHBG substantially increased for EE/DRSP (251%), while EE/LNG and E4/DRSP had limited effects on SHBG (74% and 55%, respectively). Triglycerides changed to a lesser extent for E4/DRSP (24%) compared to EE/DRSP (66%); EE/LNG increased triglycerides levels by 28%. Moreover, E4/DRSP had minimal impact on lipid parameters including HDL (4%), Apolipoprotein A1 (5%) and Apolipoprotein B (4%) compared to baseline, and no effects on carbohydrate metabolism. Conclusion: These data confirm that E4/DRSP has limited effects on liver proteins, lipid and carbohydrate metabolism, cortisol, and gonadotropins. The effect on other endocrine parameters, including suppression of ovarian steroids, was typical for a COC. In conclusion, combining E4 15 mg with DRSP 3 mg resulted in a different and potentially favorable metabolic profile.

Early diagnosis of acute renal injury in patients with acute decompensation of chronic heart failure.

To study the possibilities of previously diagnosing acute renal damage in patients with acute decompensation of chronic heart failure with reduced systolic function using biomarkers of acute renal injury. The study included 60 patients (62.0±11.1 years) with HADS (BNP >500 pg/ml) and a reduced left ventricular ejection fraction (LV 27.05% [23.25; 32.75], c FC III-IV NYHA). The level of creatinine, urea, uric acid, albumin in serum was determined in all patients, as well as a number of biomarkers: lipocalin associated with neutrophil gelatinase (NGAL) and cystatin C (CysC) in serum; kidney damage molecule-1 (KIM-1) and angiotensinogen (AGT) in the urine. AKI is determined based on changes in serum creatinine concentration or diuresis value. The results obtained indicate a high specificity and sensitivity of the use of biomarkers for the diagnosis of AKI in patients with ADHF. NGAL AUC - 0.833 (p<0.001), Se - 82.8%, Sp - 4.2%. CysC AUC - 0.823 (p<0.001), Se - 79.3%, Sp - 74.2%. KIM-1 AUC - 0.782 (p<0.001), Se - 75.9%, Sp - 74.2%. AGT AUC - 0.829 (p<0.001), Se - 82.8%, Sp - 77.4%. In a multifactorial regression analysis, it was found that with NGAL greater than 157.35 ng/ml, the risk of AKI increases 13.1 times (95% CI 1.365-126.431), with an increase in KIM-1, the risk of the development of AKI increases 20.6 times (95% CI 1.802-235.524), and with an increase in AGT more than 14.31 leng/ml, the risk of AKI increases 32.8 times (95% CI 2.752-390.110). Acute kidney injury develops in 48.3% of patients hospitalized with acute decompensation of chronic heart failure. Patients with acute decompensation of chronic heart failure and AKI have significantly higher serum NGAL and CysC, KIM-1 and AGT values in the urine compared with patients without impairing renal function. These biomarkers can serve both for the early diagnosis of acute kidney damage and the prediction of AKI in patients with acute decompensation of chronic heart failure.

Abstract P380: Inverse Circadian Pattern in the Renal Generation of Tumor Necrosis Factor-Alpha (TNFå) and Angiotensinogen (AGT) in Salt-Sensitive Hypertension (SSH) Induced by Angiotensin II (AngII) in Mice

Individuals with SSH show a non-dipping blood pressure (BP) during the inactive night period, a phenomenon which is significantly associated with enhanced cardiovascular morbidity and mortality. However, the pathophysiological mechanism for this phenomenon is not yet clearly understood. Chronic AngII administration in mice (reversed circadian rhythm) induced SSH with an increase in intra-renal AGT formation, a response that was exaggerated in TNFα receptor type 1 (TNFR1) knockout mice, indicating that renal AGT formation is suppressed by TNFR1 activation by TNFα. The present study examined the hypothesis that AngII-induced TNFα formation follows a circadian pattern with increases during the active period compared to the inactive period, that facilitates less AGT formation during the active period. Experiments were performed in mice chronically treated with or without AngII (25 ng/min; osmotic mini-pump) + high salt (4% NaCl) intake for 4 weeks that increased BP from 90±2 to 108±3 mmHg (tail-cuff method). Circadian rhythm in urinary parameters was assessed by 12 hour collections of urine using metabolic cages during the active night period (7PM to 7AM) and the inactive day period (7 AM to 7 PM). In normal mice (n=6), urinary excretion of TNFα (uTNFα) was higher (0.5±0.2 vs 0.13±0.08 pg/hour) but urinary excretion of AGT (uAGT) was lower (0.28±0.18 vs 0.46±0.14 ng/hour) during the active period compared to that during the inactive period. This inverse relationship between uTNFα and uAGT was exaggerated in AngII+HS treated mice (n=6). From the baseline (0 week) to the 2nd and 4 th week period, there were marked incremental changes in uTNFα during active periods (0.68±0.20 to 14.2±5.4 and 44.6±14.6 pg/hour) which were less during inactive periods (0.73±0.48 to 10.3±3.3 and 12.1±4.7 pg/hour). Interestingly, uAGT changed minimally during active periods (0.21±0.14 to 0.05±0.04 and 1.42±0.97 ng/hour) but increased significantly during inactive periods (0.32±0.14 to 1.57±0.71 and 3.98±1.67 ng/hour). These data suggest that an increase in TNFα generation suppresses intra-renal AGT formation during active periods but this phenomenon is inversed during inactive periods. The increase in AGT during the inactive period could lead to a non-dipping BP pattern in SSH.

Abstract P218: Downregulation of Renal Tumor Necrosis Factor-Alpha Production in Response to Hypotonic Stress Facilitates Adaptive Increases in Renal Cortical Angiotensinogen and Nkcc2b

We previously showed that diverse stimuli activate the thick ascending limb of Henle’s loop (TAL) to synthesize tumor necrosis factor-alpha (TNF), which subsequently acts as an endogenous inhibitor of the Na(+)-K(+)-2Cl(-) cotransporter (NKCC2). Moreover, renal-specific silencing of TNF unmasks salt-dependent increases in blood pressure via a mechanism involving NKCC2A. The objective of the present study was to determine the effects of TNF on NKCC2 isoform and angiotensinogen (AGT) expression in the renal cortex under conditions of hypotonic stress. Mice given a low salt (0.02% NaCl) diet (LS) for 7 days exhibited a 62±7.4% decrease (p<0.5, n=4) in TNF mRNA expression in the renal cortex, compared with mice ingesting a normal salt diet (NSD), which was associated with a concomitant 4-fold increase in renal cortical AGT mRNA accumulation (p<0.05, n=4). Mice ingesting LS also exhibited about a 63% increase (p<0.05, n=4) in cortical TAL phospho-NKCC2 (pNKCC2) expression and a 3-fold increase in NKCC2B mRNA abundance without a concurrent change in NKCC2A mRNA accumulation. The increases in AGT and NKCC2B mRNA abundance were increased by 6-fold (p<0.05, n=4 ) and 5-fold (p<0.05, n=4), respectively, in mice ingesting LS that also received an intrarenal injection of a lentivirus construct designed to specifically silence TNF in the kidney (U6-TNF-ex4) compared with mice injected with control lentivirus (U6). The effects of a single intrarenal injection of murine recombinant TNF (5ng/g body weight) or saline control for 24 hr on renal AGT and NKCC2 mRNA levels were then determined in mice that ingested LS for 7 days. Administration of TNF inhibited the increase of AGT and NKCC2B mRNA abundance by approximately 42±5.9% and 49±6.5% respectively, p<0.05, n=4 ) in mice exposed to hypotonic stress. Similarly, intrarenal injection of TNF inhibited the increase in pNKCC2 by approximately 54% (p<0.05, n=4 ) in renal cortex from mice given LS for 7 days. Collectively, these findings suggest that downregulation of renal TNF production in response to hypotonic conditions contributes to the regulation of sodium chloride reabsorption via adaptive increases in AGT as well as a selective effect on NKCC2B, which is exclusively expressed by macula densa cells in the renal cortex.

Evidence for intraventricular secretion of angiotensinogen and angiotensin by the subfornical organ using transgenic mice.

Direct intracerebroventricular injection of angiotensin II (ANG II) causes increases in blood pressure and salt and water intake, presumably mimicking an effect mediated by an endogenous mechanism. The subfornical organ (SFO) is a potential source of cerebrospinal fluid (CSF), ANG I, and ANG II, and thus we hypothesized that the SFO has a secretory function. Endogenous levels of angiotensinogen (AGT) and renin are very low in the brain. We therefore examined the immunohistochemical localization of angiotensin peptides and AGT in the SFO, and AGT in the CSF in two transgenic models that overexpress either human AGT (A+ mice), or both human AGT (hAGT) and human renin (SRA mice) in the brain. Measurements were made at baseline and following volumetric depletion of CSF. Ultrastructural analysis with immunoelectron microscopy revealed that superficially located ANG I/ANG II and AGT immunoreactive cells in the SFO were vacuolated and opened directly into the ventricle. Withdrawal of CSF produced an increase in AGT in the CSF that was accompanied by a large decline in AGT immunoreactivity within SFO cells. Our data provide support for the hypothesis that the SFO is a secretory organ that releases AGT and possibly ANG I/ANG II into the ventricle at least under conditions when genes that control the renin-angiotensin system are overexpressed in mice.

A novel role for miR-133a in centrally mediated activation of the renin-angiotensin system in congestive heart failure.

An activated renin-angiotensin system (RAS) within the central nervous system has been implicated in sympathoexcitation during various disease conditions including congestive heart failure (CHF). In particular, activation of the RAS in the paraventricular nucleus (PVN) of the hypothalamus has been recognized to augment sympathoexcitation in CHF. We observed a 2.6-fold increase in angiotensinogen (AGT) in the PVN of CHF. To elucidate the molecular mechanism for increased expression of AGT, we performed in silico analysis of the 3'-untranslated region (3'-UTR) of AGT and found a potential binding site for microRNA (miR)-133a. We hypothesized that decreased miR-133a might contribute to increased AGT in the PVN of CHF rats. Overexpression of miR-133a in NG108 cells resulted in 1.4- and 1.5-fold decreases in AGT and angiotensin type II (ANG II) type 1 receptor (AT1R) mRNA levels, respectively. A luciferase reporter assay performed on NG108 cells confirmed miR-133a binding to the 3'-UTR of AGT. Consistent with these in vitro data, we observed a 1.9-fold decrease in miR-133a expression with a concomitant increase in AGT and AT1R expression within the PVN of CHF rats. Furthermore, restoring the levels of miR-133a within the PVN of CHF rats with viral transduction resulted in a significant reduction of AGT (1.4-fold) and AT1R (1.5-fold) levels with a concomitant decrease in basal renal sympathetic nerve activity (RSNA). Restoration of miR-133a also abrogated the enhanced RSNA responses to microinjected ANG II within the PVN of CHF rats. These results reveal a novel and potentially unique role for miR-133a in the regulation of ANG II within the PVN of CHF rats, which may potentially contribute to the commonly observed sympathoexcitation in CHF.NEW & NOTEWORTHY Angiotensinogen (AGT) expression is upregulated in the paraventricular nucleus of the hypothalamus through posttranscriptional mechanism interceded by microRNA-133a in heart failure. Understanding the mechanism of increased expression of AGT in pathological conditions leading to increased sympathoexcitation may provide the basis for the possible development of new therapeutic agents with enhanced specificity.

Role of the renin-angiotensin system, renal sympathetic nerve system, and oxidative stress in chronic foot shock-induced hypertension in rats.

Objective: The renin-angiotensin system (RAS) and renal sympathetic nerve system (RSNS) are involved in the development of hypertension. The present study is designed to explore the possible roles of the RAS and the RSNS in foot shock-induced hypertension.Methods: Male Sprague-Dawley rats were divided into six groups: control, foot shock, RSNS denervation, denervation plus foot shock, Captopril (angiotensin I converting enzyme inhibitor, ACE inhibitor) plus foot shock, and Tempol (superoxide dismutase mimetic) plus foot shock. Rats received foot shock for 14 days. We measured the quantity of thiobarbituric acid reactive substances (TBARS), corticosterone, renin, and angiotensin II (Ang II) in plasma, the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and renal noradrenaline content. RAS component mRNA and protein levels were quantified in the cerebral cortex and hypothalamus.Results: The two week foot shock treatment significantly increased systolic blood pressure, which was accompanied by an increase in angiotensinogen, renin, ACE1, and AT1a mRNA and protein expression in the cerebral cortex and hypothalamus, an increase of the plasma concentrations of renin, Ang II, corticosterone, and TBARS, as well as a decrease in plasma SOD and GSH-Px activities. Systolic blood pressure increase was suppressed by denervation of the RSNS or treatment with Captopril or Tempol. Interestingly, denervation or Tempol treatment both decreased main RAS components not only in the circulatory system, but also in the central nervous system. In addition, decreased antioxidant levels and increased TBARS and corticosterone levels were also partially restored by denervation or treatment with Tempol or Captopril.Conclusions: RAS, RSNS and oxidative stress reciprocally potentiate to play important roles in the development of foot shock-induced hypertension.

Role of intrarenal (pro)renin receptor in ischemic acute kidney injury in rats.

(Pro)renin receptor [(P)RR], a trans-membrane receptor for renin and prorenin, is involved in the local activation of renin-angiotensin system (RAS) in the kidney. However, it remains to be determined whether (P)RR plays a role in the development of ischemic acute kidney injury (AKI). We examined the abundance of (P)RR, renin/prorenin, angiotensinogen (AGT), AT1 receptor (AT1R), phosphorylation of extracellular signal-regulated protein kinase 1/2 (ERK 1/2) and nuclear factor-κB (NF-κB) by Western blots at 6, 24 and 48 h, and at 7 days after 45-min ischemic injury in rats. Intrarenal angiotensin II (Ang II) levels were determined by radioimmunoassay. We then tested whether the beneficial effects of oral loading of saline solution (1.0 % NaCl) for 7 days prior to ischemic injury were associated with changes in RAS components and ERK 1/2 and NF-κB phosphorylation in the kidney. We also examined the effect of AT1R blocker, olmesartan, on ischemia-induced changes of (P)RR downstream such as AGT and phosphorylation of ERK 1/2. Renal ischemia increased the abundance of (P)RR protein at 24 h, and peaked at 48 h. (P)RR was mainly stained in the connecting tubules and collecting ducts in control rats, while ischemia increased its immunointensity in the damaged proximal tubules. Renal ischemia increased phosphorylation of ERK 1/2 and NF-κB proteins as early as at 6 h. There was a significant increase in AGT and Ang II levels at 24 and 48 h. Prior saline loading prevented the increase in serum creatinine at 48 h (5.36 ± 1.26 vs. 3.38 ± 1.74 mg/dL, p < 0.05), and suppressed the increases in renal (P)RR, AGT and Ang II contents. Saline drinking also significantly blocked the ischemia-induced increases in phosphorylation of ERK 1/2 and NF-κB. In contrast, although treatment with olmesartan (10 mg/kg/day) for 14 days suppressed an increase of intrarenal AGT, olmesartan did not alleviate ischemic AKI, along with no change of (P)RR and phosphorylated ERK 1/2. These findings suggest that increased (P)RR is associated with activation of RAS-independent downstream such as ERK 1/2 and NF-κB phosphorylation in the ischemic kidney.

Increased Insulin-Stimulated Expression of Arterial Angiotensinogen and Angiotensin Type 1 Receptor in Patients With Type 2 Diabetes Mellitus and Atheroma

Because inhibition of the renin-angiotensin system (RAS) reduces the onset of type 2 diabetes (T2D) and prevents atherosclerosis, we investigated the expression of RAS in the arterial wall of T2D and nondiabetic (CTR) patients. mRNA and protein levels of angiotensinogen (AGT), angiotensin-converting enzyme (ACE) and AT1 receptor (AT1R) were determined in carotid atheroma plaque, nearby macroscopically intact tissue (MIT), and in vascular smooth muscle cells (VSMCs) before and after insulin stimulation from 21 T2D and 22 CTR patients. AGT and ACE mRNA and their protein levels were 2- to 3-fold higher in atheroma and in MIT of T2D patients. VSMCs from T2D patients had respectively 2.5- and 5-fold higher AGT and AT1R mRNA and protein contents. Insulin induced an increase in AGT and AT1R mRNA with similar ED50. These responses were blocked by PD98059, an inhibitor of MAP-kinase in the two groups whereas wortmannin, an inhibitor of PI3-kinase, partially prevented the response in CTR patients. Phosphorylated ERK1-2 was 4-fold higher in MIT from T2D than from CTR patients. The arterial RAS is upregulated in T2D patients, which can be partly explained by an hyperactivation of the ERK1-2 pathway by insulin.

Regulation of the intrarenal renin‐angiotensin system in diabetic db/db mice

The rising prevalence of obesity in the US is paralleled by an increase in the prevalence of type II diabetes. Recent studies have highlighted the importance of blockade of the renin-angiotensin system (RAS) in protecting against end-organ kidney damage due to diabetes. The purpose of this study was to examine the intrarenal RAS in diabetic leptin receptor deficient db/db and control mice. In addition, we examined the effect of stimulation of the intrarenal RAS with a low salt (LS) diet in db/db and control mice. Control and db/db male mice fed normal chow were examined at 7 and 14 weeks of age. At 7 weeks, ACE mRNA expression was decreased by 2-fold in the kidney of db/db compared to control. In contrast, ACE2 mRNA expression was increased by 2-fold in kidneys from db/db compared to control. No changes in angiotensinogen or renin gene expression were detected. At 14 weeks, changes in ACE and ACE2 gene expression in the kidney of db/db mice were accompanied by an increase in angiotensinogen and renin mRNA expression. To determine if the kidney RAS responds appropriately to LS challenge in db/db mice, we fed control and db/db mice a LS diet from 7 to 14 weeks of age. Control mice fed a LS diet exhibited a robust increase in renin and ACE mRNA expression in the kidney. In contrast, mRNA expression of RAS components in kidneys from db/db mice fed a LS diet was similar to that of 14 week-old db/db mice fed the chow diet. However, marked kidney hypertrophy was present in db/db mice fed a LS diet. These results demonstrate a shift in the intrarenal RAS of diabetic mice from a renoprotective (7 weeks of age) to a detrimental phenotype (14 weeks of age). In addition, despite the inability to respond to LS challenge to further increase kidney renin expression in db/db mice, renal hypertrophy was apparent, suggesting a deleterious effect of LS diet in diabetic mice.

Midkine, a newly discovered regulator of the renin–angiotensin pathway in mouse aorta: Significance of the pleiotrophin/midkine developmental gene family in angiotensin II signaling

We previously demonstrated that pleiotrophin (PTN the protein, Ptn the gene) highly regulates the levels of expression of the genes encoding the proteins of the renin–angiotensin pathway in mouse aorta. We now demonstrate that the levels of expression of these same genes are significantly regulated in mouse aorta by the PTN family member midkine (MK the protein, Mk the gene); a 3-fold increase in expression of renin, an 82-fold increase in angiotensinogen, a 6-fold decrease in the angiotensin converting enzyme, and a 6.5-fold increase in the angiotensin II type 1 and a 9-fold increase in the angiotensin II type 2 receptor mRNAs were found in Mk−/− mouse aorta in comparison with the wild type (WT, +/+). The results in Mk−/− mice are remarkably similar to those previously reported in Ptn−/− mouse aorta, with the single exception of that the levels of the angiotensinogen gene expression in Ptn−/− mice are equal to those in WT+/+ mouse aorta, and thus, in contrast to Mk gene expression unaffected by levels of Ptn gene expression. The data indicate that MK and PTN share striking but not complete functional redundancy. These data support potentially high levels importance of MK and the MK/PTN developmental gene family in downstream signals initiated by angiotensin II either in development or in the many pathological conditions in which MK expression levels are increased, such as atherosclerosis and many human neoplasms that acquire constitutive endogenous Mk gene expression by mutation during tumor progression and potentially provide a target through the renin–angiotensin pathway to treat advanced malignancies.

A novel mechanism for angiotensin II formation in streptozotocin-diabetic rat glomeruli

Recent evidence suggests that the intrarenal renin-angiotensin system (RAS) may play an important role in the development of glomerular changes associated with diabetic nephropathy. In this study, the glomerular RAS was examined in male Sprague-Dawley rats made diabetic with streptozotocin (STZ), and the findings compared with those obtained in control nondiabetic rats. In diabetic rat glomerular extracts, angiotensinogen and angiotensin II (ANG II) levels were increased significantly by 2.2- and 1.9-fold, respectively, compared with nondiabetic controls. No significant differences in ANG I and angiotensin-converting enzyme (ACE) levels were observed between these groups. The HPLC analysis of the glomerular extracts demonstrated that exogenous ANG I was converted into various ANG peptides including ANG II, ANG1-9, and ANG1-7. A significant increase in formation of ANG II from exogenous ANG I was observed in STZ rats compared with control rats. Preincubation of glomerular extracts with captopril resulted in a 20-30% decrease in ANG II conversion from exogenous ANG I in diabetic and control rats. The possible role of ANG1-9 in formation of ANG II was examined by HPLC. Exogenous ANG1-9 in glomerular extracts was converted into ANG II, this conversion being significantly higher in STZ rats than in control rats. These findings provide new information that ANG1-9 is produced in rat glomerular extracts, can be converted to ANG II, and that this conversion is also stimulated in diabetic rat glomeruli. Thus this study demonstrates that in diabetic rats, glomerular ANG II levels are increased due to an increase in angiotensinogen and an increase in the formation of ANG II.

Association of angiotensinogen haplotypes with angiotensinogen levels but not with blood pressure or coronary artery disease: the Ludwigshafen Risk and Cardiovascular Health Study

Angiotensinogen and its cleaved forms angiotensin I and angiotensin II are important regulators of blood pressure. The gene for angiotensinogen (AGT) carries two common polymorphisms, T207M and M268T (previously described as T174M and M235T). To investigate the role of haplotypes formed by these polymorphisms for angiotensinogen levels we examined blood pressure, coronary artery disease (CAD), myocardial infarction (MI), and AGT genotypes and haplotypes in 2,575 patients with angiographically documented CAD and 731 individuals in whom CAD had been ruled out by angiography. Three haplotypes, designated as Hap1 (T207, M268), Hap2 (T207, T268) and Hap3 (M207, T268), accounted for more than 99% of alleles. The AGT Hap2 haplotype was significantly associated with angiotensinogen levels; one additional Hap2 allele accounted for an approx. 8% increase in angiotensinogen. This association was stronger than that of either single polymorphism. AGT genotypes or haplotypes were not related to hypertension, CAD or MI. We conclude that a common haplotype of the angiotensinogen gene is linked to angiotensinogen levels but has no major impact on blood pressure, hypertension, or cardiovascular risk.

Mechanism of increased angiotensin II levels in glomerular mesangial cells cultured in high glucose.

Previous studies have shown that glucose increases angiotensin II (AngII) levels in rat glomerular mesangial cells and that AngII mediates the inhibitory effects of high glucose on matrix degradation in these cells. The present study addresses the following questions: (1) What are the mechanisms for the generation of AngII in mesangial cells? (2) What are the effects of glucose on AngII generation by these mechanisms? Experiments employed primary mesangial cells from normal Sprague-Dawley rats. The levels of immunoreactive angiotensinogen (AGT), angiotensin I (AngI), and angiotensin II (AngII) were measured by ELISA. AGT mRNA expression was determined by Northern blot analysis. Incubation of cells for 24 h in high glucose (30 mM) increased AGT levels by 1.5-fold and increased AGT mRNA expression; this was accompanied by a 1.5-fold increment in AngI and 1.7-fold increment in AngII levels. Renin activity (measured as AngI generation in the presence of excess AGT) and ACE levels and activity were not altered by high glucose. In further experiments, the effect of high glucose on formation of Ang peptides from exogenous AngI in mesangial cell extracts was examined using HPLC. Exogenous AngI was converted into various Ang peptides, including AngII, Ang(1-9), Ang(1-7), and Ang(3-8). A significant increase in formation of AngII from AngI was observed in cells incubated in high glucose. In addition, AngII production from exogenous Ang(1-9) in cell extracts was also stimulated by high glucose. These findings demonstrate that glucose increases mesangial AngII levels via an increase in AGT and AngI. In addition, this study provides new information that Ang(1-9) is produced by mesangial cells, can be converted to AngII, and that this conversion is also stimulated under high-glucose conditions.

Activation of local renin-angiotensin system by chronic hypoxia in rat pancreas

Previous studies have provided evidence that several key elements of renin-angiotensin system (RAS) are present in the rat pancreas, notably angiotensinogen, which is mandatory for intracellular generation of physiologically active angiotensin II. The data support the existence of an intrinsic RAS, which may be important for pancreatic blood flow and ductal anion secretion. In the present study, the effect of chronic hypoxia on the expression of RAS components, particularly at the levels of its precursor angiotensinogen and its receptor subtypes AT 1 and AT 2, were investigated in the rat pancreas. Results from western blot and semi-quantitative reverse-transcription polymerase chain reaction (RT-PCR) analyses unequivocally showed that chronic hypoxia caused a marked increase in angiotensinogen both at the protein and gene levels when compared with that in the normoxic pancreas. However, results from RT-PCR showed that there was a differential effect of chronic hypoxia on the expression of AT 1 and AT 2 receptor subtypes, which exhibited subtype-specific changes in gene expression. For AT 1, chronic hypoxia did not cause a significant change in mRNA expression for AT 1a but a significant increase in mRNA expression for AT 1b. For AT 2, chronic hypoxia caused a marked increase in its mRNA expression. The increased expression of RAS component genes by chronic hypoxia and its significance of changes may be important for physiological and pathophysiological aspects of the pancreas.

Effects of estrogen replacement therapy on the renin-angiotensin system in postmenopausal women.

Oral estrogen replacement therapy (ERT) is known to stimulate the synthesis of angiotensinogen. The effects of such therapy on renin, ACE, and aldosterone are less clear. This seems noteworthy, however, since further activation of the system could be disadvantageous to postmenopausal women who replace estrogen in the context of heart failure, coronary artery disease, or hypertension. Estrogen status and components of the renin-angiotensin system were examined in a population-based sample of postmenopausal women and age-matched men. Renin was quantified immunoradiometrically, ie, independent of substrate abundance; aldosterone, angiotensinogen, and ACE activity were determined by standard methods. Renin levels were lower in women with ERT (n = 107; 12.0 +/- 0.7 mU/L) compared with women without ERT (n = 223; 16.6 +/- 0.9 mU/L; P = .001) or men (n = 342, 20.5 +/- 1.5 mU/L, P < .0001). In contrast, angiotensinogen was higher in women with ERT (1.36 +/- 0.08 mg/L) compared with women without ERT (1.03 +/- 0.02 mg/L; P < .0001) or compared with men (0.97 +/- 0.01 mg/L; P < .0001). Renin suppression was seen with either oral or transdermal estrogen replacement (-30% and -31%, respectively; both P < .001). In contrast, the increase of angiotensinogen was limited to women taking oral estrogens (+58%, P < .001). Multivariate analysis revealed that these estrogen effects were independent of age, body mass index, blood pressure, and/or antihypertensive medication. Finally, only marginal differences between groups were observed for serum ACE activity and aldosterone. Aside from a well-documented induction of angiotensinogen, ERT is related to a substantial suppression of renin, a phenomenon that might have received little attention because of widely used indirect measurements of the hormone.

Immunocytochemical localization of angiotensinogen in the fetal and neonatal rat brain.

The aim of this study was to define the temporal appearance and regional distribution of angiotensinogen in the fetal and neonatal rat brain. This was done by immunocytochemical localization of angiotensinogen in brains from embryonic day 16 to postnatal day 12. Immunostaining was first observed on embryonic day 18, and persisted to postnatal day 2, in the choroid plexus and ependymal cells lining the third ventricle. This initial expression of angiotensinogen at embryonic day 18 was followed at postnatal day 20 by a rapid progression of angiotensinogen staining appearing in astrocytes in the paraventricular nucleus, medial preoptic area, ventromedial and arcuate hypothalamic nuclei; these areas showed the highest astrocyte staining intensity in the brain. This was followed sequentially by staining in areas of the thalamus, midbrain, forebrain and brainstem. In general, neuroglial staining was higher in regions proximal to the cerebral ventricles and cerebral aqueduct. Neuronal angiotensinogen was observed at day postnatal day 0 and later. The most consistent immunopositive areas were in the forebrain and thalamus; in particular, the hippocampus, anterior and posterior cingulate cortex, basal and lateral amygdala, the caudate-putamen, globus pallidus, lateral septum, medial habenular nuclei and lateral thalamic nuclei. Most of the immunopositive cells in the hypothalamus and brainstem were astrocytes, while those in the cortex were almost exclusively neurons. Staining in thalamic regions was both neuronal and neuroglial. From the intensity of staining and cell density, it was determined that a rapid increase in angiotensinogen occurs between embryonic day 20 and postnatal day 0, followed by further, smaller increases postnatally. In conclusion, this study has shown that angiotensinogen, the protein from which angiotensin II is generated, is present in the rat fetal brain. The timing of its appearance supports the establishment of a renin-angiotensin system by late gestation. Its predominance in fetal hypothalamic nuclei and in thalamic, cerebellar and cortical neurons suggests major roles in prenatal fluid and electrolyte balance, in sensorimotor development and in brain maturation.

17β-Estradiol: oral or parenteral administration in hyperandrogenic women? Metabolic tolerance in association with cyproterone acetate

To compare the metabolic effects of two different administration routes of estrogen associated with cyproterone acetate (CPA) in young women. Randomized and prospective study. University medical and research center. Sixty-five premenopausal young women with clinical hyperandrogenism. A high dose of CPA was administered, associated with either transdermal (group T) or oral (group O) 17 beta-E2. Glucose tolerance, plasma lipid level, coagulation and fibrinolysis parameters, and angiotensinogen, before and at 6 and 12 months during treatment. At 12 months, fasting blood glucose and basal insulin levels were significantly lower in group O than in group T. The increase in angiotensinogen was greater in group O, however, without modification in arterial blood pressure. No significant difference between the two groups was observed in lipids, coagulation, and fibrinolysis. Natural estrogens associated with CPA have no patent deleterious metabolic effect. However, the choice of oral estrogen administration seems to be better among patients with disorders such as hyperandrogenism or obesity with potential hyperinsulinism.

Angiotensin II is the mediator of the increase in hepatic angiotensinogen synthesis after bilateral nephrectomy.

The present study investigated the hypothesis that the increase in plasma angiotensinogen after nephrectomy is mediated by endogenous renin and angiotensin (ANG) II. Rats were divided into control, nephrectomy, or nephrectomy plus adrenalectomy groups. In addition, similar cohorts were divided as just mentioned and then given either atenolol (selective beta 1-adrenoceptor inhibitor that prevents renin release) or Dup-753 [ANG II (AT1) receptor antagonist]. The plasma angiotensinogen levels increase approximately fivefold after 24 h in nephrectomized rats. Pretreatment with atenolol blunted this increase. A significant reduction was observed 4 h (P < 0.05) and 8 h (P < 0.005) after surgery. Dup-753 nearly abolished the increase in angiotensinogen plasma levels. After pretreatment with Dup-753, significantly higher angiotensinogen levels (P < 0.005) were found only after 24 h. Nephrectomy plus adrenalectomy also blunted the rise in plasma angiotensinogen. A significant increase in angiotensinogen plasma levels could only be observed after 8 h (P < 0.005) and 12 h (P < 0.005) but not after 24 h. Atenolol further reduced this increase. After atenolol pretreatment, significantly higher angiotensinogen levels could only be observed after 12 h (P < 0.05). Dup-753 completely abolished the increase of plasma angiotensinogen after nephrectomy plus adrenalectomy. In anesthetized control rats at time 0 the plasma ANG I levels were 0.7 nM. Pretreatment with atenolol decreased the ANG I values by 30%, whereas Dup-753 caused a sixfold increase in plasma ANG I levels in the control rats at time 0.(ABSTRACT TRUNCATED AT 250 WORDS)