Activation Of Intrarenal Renin-angiotensin System Research Articles

Correlation between Urinary Angiotensinogen (AGT) and Albuminuria in Chronic Kidney Disease (CKD)

Chronic kidney disease (CKD) is a global health concern associated with significant morbidity and mortality. Albuminuria, a hallmark of kidney damage, is a strong predictor of CKD progression and adverse outcomes. Recent research has focused on understanding the correlation between urinary angiotensinogen (AGT) levels, a component of the renin-angiotensin system (RAS), and albuminuria in CKD patients. This review article synthesizes evidence from various studies exploring this correlation and elucidates its mechanistic insights and clinical implications. Clinical studies consistently demonstrate a positive correlation between urinary AGT levels and albuminuria in CKD patients. Elevated urinary AGT levels are associated with increased albuminuria, independent of traditional risk factors, suggesting a potential role for AGT in the pathogenesis of kidney damage and proteinuria in CKD. Mechanistic insights suggest that increased intrarenal RAS activity may lead to enhanced AGT production and secretion, contributing to glomerular hypertension, inflammation, and fibrosis, ultimately promoting albuminuria and CKD progression. The clinical implications of this correlation are profound. Elevated urinary AGT levels may serve as a non-invasive biomarker for assessing intrarenal RAS activity and predicting CKD progression and adverse outcomes. Furthermore, interventions targeting the RAS pathway, such as angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), may help reduce urinary AGT levels and mitigate albuminuria, offering promising therapeutic opportunities for improving patient outcomes in CKD. In conclusion, the correlation between urinary AGT and albuminuria in CKD represents a complex interplay between renal physiology, RAS activation, and kidney damage. By elucidating this correlation, we gain valuable insights into the pathogenesis of CKD and identify urinary AGT as a potential biomarker and therapeutic target for personalized CKD management. Further research is warranted to validate these findings, explore the clinical utility of urinary AGT measurement, and develop targeted interventions aimed at mitigating albuminuria and slowing CKD progression. Through continued investigation, we can strive to improve outcomes and quality of life for patients living with CKD.

Dapagliflozin attenuates renal fibrosis by suppressing angiotensin II/TGFβ signaling in diabetic mice

AimsDiabetic nephropathy (DN) complicates diabetes Mellitus and intimately relates to intrarenal renin–angiotensin system (RAS) activity. Dapagliflozin, a selective inhibitor of sodium-glucose cotransporter 2 (SGLT2), has been validated to improve renal outcomes in diabetic patients from clinical research by elusive mechanisms. This study explored the presumption that the eagerness activity of intrarenal RAS in DN generated oxidative stress to promote renal fibrosis, and the process can be interrupted by dapagliflozin. MethodsA streptozotocin-induced DN model was established in male C57BL/6J mice. Mice were treated with dapagliflozin or losartan for 14 weeks. Biochemical data, renal fibrosis, oxidative stress, and RAS were measured. ResultsDN mice were characterized by overtly low body weight, high levels of blood glucose, and renal injury. Interrupting SGLT2 and RAS significantly improved renal dysfunction and pathological lesions in DN mice. Consistent with these favorable effects, dapagliflozin revoked the local RAS/oxidative stress and the succeeding transforming growth factor beta (TGFβ) signaling. ConclusionsThis research clarifies that intrarenal RAS activity triggers renal injury in DN, and dapagliflozin attenuates renal fibrosis by suppressing Angiotensin II/TGFβ signaling. It unravels a novel insight into the role of prevention and treatment of SGLT2 inhibitors to DN.

Elevated urinary angiotensinogen excretion links central and renal hemodynamic alterations

Inappropriate activation of intrarenal renin–angiotensin system (RAS) may contribute to the pathogenesis of cardio-renal syndrome (CRS). We aimed to examine the cross-sectional associations of urinary angiotensinogen (AGT) excretion, a biomarker of intrarenal RAS activity, with central (aortic) and renal hemodynamic parameters in middle-aged and older adults, including patients with chronic kidney disease. Aortic and renal hemodynamic parameters were measured using applanation tonometry and duplex ultrasonography in 282 participants. Urinary AGT, liver-type fatty acid-binding protein (L-FABP), and plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels were measured for each participant. Multiple linear regression analyses demonstrated that urinary AGT levels were associated with aortic blood pressures, pulsatile measures of renal blood flow, plasma NT-proBNP and urinary L-FABP levels after adjusting for potential covariates, including age, sex, body mass index, estimated glomerular filtration rate (GFR), and medication use. Additionally, when classified based on GFR stages and urinary AGT levels, plasma NT-proBNP and urinary L-FABP levels increased in participants with lower GFR and higher AGT groups. Our findings suggest that urinary AGT excretion is a shared determinant of central (aortic) and renal hemodynamics in middle-aged and older adults, providing clinical evidence for the potential role of intrarenal RAS activity in the development of CRS.

#5289 INTRARENAL RENIN-ANGIOTENSIN SYSTEM ACTIVATION ALTERS RELATIONSHIP BETWEEN SYSTOLIC BLOOD PRESSURE AND PROGRESSION OF CHRONIC KIDNEY DISEASE

Abstract Background and Aims Elevated blood pressure (BP) and intrarenal renin-angiotensin system (RAS) activity are closely related to chronic kidney disease (CKD) progression. However, interrelationship between BP and intrarenal RAS activity on the risk of CKD progression is unknown. Method We analyzed 2,076 participants from the Korean Cohort Study for Outcomes in Patients With CKD. The main exposure was systolic BP (SBP). The urinary angiotensinogen-to-creatinine (u-AGT/Cr) ratio was stratified according to the median value (3.65 μg/gCr). The primary outcome was a composite kidney outcome of a ≥50% decline in estimated glomerular filtration rate from baseline measurement or initiation of kidney replacement therapy. Results During 10,550 person-years of follow-up (median, 5.2 years), the composite outcome occurred in 800 (38.5%) participants. In the multivariable cause-specific hazard model, higher SBP was associated with an increased risk of CKD progression. There was a significant interaction between SBP and u-AGT/Cr ratio on the risk of the primary outcome (P-for-interaction = 0.019). In patients with u-AGT/Cr <3.65 μg/gCr, the hazard ratios (HRs) (95% confidence intervals [CIs]) for SBP 120–129, 130–139, and ≥140 mmHg were 1.47 (1.08-2.01), 1.74 (1.26-2.39), and 2.43 (1.76-3.37), respectively, compared with SBP <120 mmHg. In addition, each 10 mmHg increase in SBP was associated with an 18% higher risk of CKD progression. Moreover, there was a greater decline in the estimated glomerular filtration rate among the higher SBP categories. However, these associations were not observed in patients with u-AGT/Cr ≥3.65 μg/gCr. Conclusion Urinary angiotensinogen levels may modify the association between SBP and adverse kidney outcomes.

Intrarenal Renin-Angiotensin System Activation Alters Relationship Between Systolic Blood Pressure and Progression of Chronic Kidney Disease.

Elevated blood pressure and intrarenal renin-angiotensin system activity are closely related to chronic kidney disease (CKD) progression. However, interrelationship between blood pressure and intrarenal renin-angiotensin system activity on the risk of CKD progression is unknown. We analyzed 2076 participants from the Korean Cohort Study for Outcomes in Patients With CKD. The main exposure was systolic blood pressure (SBP). The urinary angiotensinogen-to-creatinine ratio was stratified according to the median value (3.65 μg/gCr). The primary outcome was a composite kidney outcome of a ≥50% decline in estimated glomerular filtration rate from baseline measurement or initiation of kidney replacement therapy. During 10 550 person-years of follow-up (median, 5.2 years), the composite outcome occurred in 800 (38.5%) participants. In the multivariable cause-specific hazard model, higher SBP was associated with an increased risk of CKD progression. There was a significant interaction between SBP and urinary angiotensinogen-to-creatinine ratio on the risk of the primary outcome (P value for interaction=0.019). In patients with urinary angiotensinogen-to-creatinine <3.65 μg/gCr, the hazard ratios (95% CIs) for SBP 120 to 129, 130 to 139, and ≥140 mmHg were 1.46 (1.07-1.99), 1.71 (1.25-2.35), and 2.40 (1.73-3.32), respectively, compared with SBP <120 mmHg. However, these associations were not observed in patients with urinary angiotensinogen-to-creatinine ≥3.65 μg/gCr. In this prospective CKD cohort, higher SBP was associated with CKD progression when urinary angiotensinogen levels were low, while this association was not seen when urinary angiotensinogen levels were high. This finding suggests that intrarenal renin-angiotensin system activity may modify the relationship between SBP and adverse kidney outcome.

The intrarenal renin-angiotensin system in hypertension: insights from mathematical modelling.

The renin-angiotensin system (RAS) plays a pivotal role in the maintenance of volume homeostasis and blood pressure. In addition to the well-studied systemic RAS, local RAS have been documented in various tissues, including the kidney. Given the role of the intrarenal RAS in the pathogenesis of hypertension, a role established via various pharmacologic and genetic studies, substantial efforts have been made to unravel the processes that govern intrarenal RAS activity. In particular, several mechanisms have been proposed to explain the rise in intrarenal angiotensin II (Ang II) that accompanies Ang II infusion, including increased angiotensin type 1 receptor (AT1R)-mediated uptake of Ang II and enhanced intrarenal Ang II production. However, experimentally isolating their contribution to the intrarenal accumulation of Ang II in Ang II-induced hypertension is challenging, given that they are fundamentally connected. Computational modelling is advantageous because the feedback underlying each mechanism can be removed and the effect on intrarenal Ang II can be studied. In this work, the mechanisms governing the intrarenal accumulation of Ang II during Ang II infusion experiments are delineated and the role of the intrarenal RAS in Ang II-induced hypertension is studied. To accomplish this, a compartmental ODE model of the systemic and intrarenal RAS is developed and Ang II infusion experiments are simulated. Simulations indicate that AT1R-mediated uptake of Ang II is the primary mechanism by which Ang II accumulates in the kidney during Ang II infusion. Enhanced local Ang II production is unnecessary. The results demonstrate the role of the intrarenal RAS in the pathogenesis of Ang II-induced hypertension and consequently, clinical hypertension associated with an overactive RAS.

JS-HR-12: BASIC RESEARCH: ELUCIDATION OF “MOSAIC” PATHOGENESIS OF HYPERTENSION

Basic research plays critical roles in elucidating the “mosaic” pathogenesis of hypertension and developing its treatment. In the field of brain and autonomic nervous system, Chen et al. demonstrated that mild cold exposure elicits autonomic dysregulation, such as increased sympathetic activity and decreased baroreflex sensitivity, and poor sleep quality, causing blood pressure (BP) elevation in normotensive rats. This finding may have critical implications for the cardiovascular event occurrence with low ambient temperature. Domingos-Souza et al. showed that the ability of baroreflex activation to modulate hemodynamics and induce lasting vascular adaptation is critically dependent on the electrical parameters and duration of carotid sinus stimulation in spontaneously hypertensive rats (SHRs), proposing a rationale for improving baroreflex activation therapy in humans. In the kidney, Kasacka et al. showed that activity of Wnt/β-catenin pathway is increased in SHRs and 2K1C hypertensive rats, while it is inhibited in DOCA-salt rats. Intrarenal renin-angiotensin system (RAS) is involved in BP regulation. In renal damage with an impaired glomerular filtration barrier, liver-derived angiotensinogen filtered through damaged glomeruli regulates intrarenal RAS activity. Matsuyama et al. further showed that the glomerular filtration of liver-derived angiotensinogen depending on glomerular capillary pressure causes circadian rhythm of the intrarenal RAS. Otsuki et al. revealed that TWIST1, a transcription factor regulating mesodermal embryogenesis, transcriptionally upregulates complement 3, which has been demonstrated to activate intrarenal RAS, in the glomerular mesangial cells from SHRs. The RAS in the vascular system also contributes to BP regulation. Soring nexins (SNXs) are cellular sorting proteins and can regulate the expression and function of G protein-coupled receptors (GPCRs). Liu C et al. demonstrated that SNX1 knockout mice exhibit hypertension through vasoconstriction mediated by increased expression of GPCR AT1R within the arteries. Liu X et al. found that sirtuin 6 (SIRT6) expression is downregulated in the aortae of aged rats and showed that SIRT6 knockdown enhances angiotensin II-induced vascular adventitial aging by activating NF-κB pathway in vitro studies. The studies investigating extracellular vesicles (EVs) and gut microbiota have been increased. Ochiai-Homma et al. showed that pendrin in urinary EVs can be a useful biomarker for diagnosis and treatment of primary aldosteronism. Wu et al. demonstrated that captopril has the potential to rebalance the dysbiotic gut microbiota of DOCA-salt hypertensive rats. Several reports indicate the potential treatment for hypertension and the associated organ damages: rivaroxaban in cardiac hypertrophy; nebivolol, maximakinin, and Pinggan-Qianyang in hypertension; and melatonin and crocin in gestational hypertension.

Association of Novel Urinary Protein Biomarkers with Persistent Albuminuria in Patients with Sickle Cell Disease

Introduction: Standard assessments for kidney disease, albuminuria and decline in estimated glomerular filtration rate (eGFR), occur well after substantial functional and structural damage have ensued. Chronic kidney disease (CKD) is common in patients with sickle cell disease (SCD). With its association with increased morbidity and mortality, identification of novel biomarkers that could predict early development of CKD offers opportunities to modify risk factors in hopes of attenuating kidney function loss and decreasing mortality risk. Methods: The participants of this exploratory study represent a subset of patients with HbSS or HbSβ0 thalassemia enrolled in a prospective cohort study to assess the natural history of kidney disease in SCD. We excluded patients with diabetic nephropathy, cancer, connective tissue disease, other glomerular diseases, known infection with hepatitis (B or C) or HIV, end-stage kidney disease on dialysis and those who had undergone bone marrow transplantation. Participants were enrolled during routine clinic visits. Urine levels of clusterin [CLU; also referred to as apolipoprotein J], retinol-binding protein 4 [RBP4], alpha-1-microglobulin [A1M], interleukin-18 [IL-18], beta-2 microglobulin [B1M], insulin-like growth factor-binding protein 7 [IGFBP7], tissue inhibitor of metalloproteinases-2 [TIMP2], angiotensinogen [AGT], podocalyxin, and cysteine-rich with EGF-like domains 2 [CRELD2] were measured using quantitative ELISA assay. All values of urine biomarkers were normalized to urine creatinine. Persistent albuminuria (PA) was defined based on presence of at least 2 of 3 spot urine albumin/creatinine ratio (ACR) values ≥30 mg/g of creatinine or a single value ≥100 mg/g. Glomerular filtration rate was estimated using the 2009 creatinine-based Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula. Medians are presented with the interquartile range [IQR]. Associations between ACR and eGFR with each urine biomarker were assessed using linear regression. Levels of urinary biomarkers were compared using the Wilcoxon-Mann-Whitney test. Results: Thirty-seven subjects, 13 (35.2%) with PA (ACR - 147mg/g [IQR: 136.4, 223]), and 24 (64.9%) without PA (non-PA) (ACR - 12 mg/g [IQR: [6, 20]) were evaluated. Subjects with PA were older, had higher blood urea nitrogen (BUN), blood aspartate transaminase, and lower eGFR (Table 1). Urinary levels of CLU, RBP4, A1M, and AGT normalized to urine creatinine were significantly higher in subjects with PA vs. those with non-PA (Table 2). In univariate analysis, significant associations were identified between A1M and ACR (p=0.035) as well as between AGT and ACR (p<0.0001) (Table 2). In multivariable analyses, only AGT remained significantly associated with ACR (p=0.0003). Conclusion: The higher urinary levels of RBP4 and A1M, both low molecular weight proteins freely filtered in the glomerulus and reabsorbed by kidney proximal tubule cells, in subjects with PA suggests the presence of tubular injury. Higher levels of clusterin, a ubiquitously expressed glycoprotein that is rapidly upregulated upon acute kidney damage and present in de-differentiated kidney tubule cells, also indicates tubular injury in subjects with PA. Urinary AGT, the only precursor of all angiotensin peptides, is independently associated with ACR in this cohort. Higher levels of AGT indicates increased intrarenal renin-angiotensin system activity in subjects with PA. More studies are required to evaluate the association of these biomarkers with persistent albuminuria in SCD. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Augmented Urinary Excretion of Angiotensinogen Precedes Albuminuria in Human Young Adults with Overweight and Mice with High Fat Diet‐Induced Type 2 Diabetes

Obesity is linked to the development of hypertension and type 2 diabetes (T2D) and both causing chronic kidney disease (CKD). Increased body mass index (BMI) and high fat diet (HFD) contribute to activation systemic renin angiotensin system (RAS). In addition, activation of intrarenal and intratubular RAS has been associated with increased pressure (BP), CKD, and augmentation of urinary excretion of angiotensinogen (uAGT) during T2D. However, whether augmentation of uAGT reflect intrarenal/intratububular RAS activation in subjects with overweight, remains unclear. Here, we tested the hypothesis that increases in uAGT precedes renal dysfunction in mice and human subjects with overweight,MethodsC57BL/6 mice (N = 10) were fed either a normal fat diet (NFD) or HFD (45% Kcal from fat) for 28 weeks. During this period, metabolic phenotype along with urinary albumin, creatinine, reactive oxygen species (ROS) and AGT, were measured every 4 weeks. In addition, for evidence in humans (age 19‐22 years‐old), 11 individuals with overweight and 17 individuals with normal weight, were studied. In these subjects, anthropometric parameters, systolic and diastolic BP, fasting blood glucose (FBG), and urinary mRNA levels of AGT and kidney injury markers IL‐18 and connecting tissue growth factor, were determined. Patients with history of cardiac or cerebrovascular events and endocrine diseases, anti‐hypertensive treatment (ACE inhibitors, ARBs) and/or anti‐diabetic drugs, were excludedResultsIn mice with metabolic alterations overtime, systolic BP significantly increased after 18 weeks in HFD but not NFD mice. Intrarenal ROS increased in HFD mice. These changes paralleled the augmentation uAGT excretion, which occurred in the absence of overt albuminuria. In human subjects with overweight, systolic and diastolic BP, urinary transcripts levels of AGT, renin, and injury markers IL‐18 and CTGF were increased as compared to normal weight individuals. However, no significant changes were observed in proteinuria or albuminuria.ConclusionsOur results indicate that augmentation of uAGT precedes albuminuria in young human adults with overweight and mice during the development of HFD‐induced T2D. These findings emphasize the relevance of uAGT and indicator of intrarenal/intratubular RAS activations and its potential as early biomarker of kidney injury during metabolic diseases as obesity and diabetes.

Intrarenal Renin‐Angiotensin System and its Role in Angiotensin II‐Induced Hypertension: Insights from Computational Modelling

The kidney expresses all and independently regulates most elements of the renin‐angiotensin system (RAS). Importantly, the inappropriate activation of intrarenal RAS, as indicated by the local accumulation of angiotensin II (Ang II), has been linked to Ang II‐induced hypertension. Various Ang II and angiotensin type 1 receptor (AT1R)‐dependent positive feedback systems have been documented in the literature. However, their functional importance to the overactivation of the intrarenal RAS have yet to be lineated. The goal of this study is to identify the key mechanisms actuating the intrarenal accumulation of Ang II during hypertension induced by Ang II infusion. We hypothesize that the upregulation of tubular epithelial AT1Rs is the primary mediator of intrarenal RAS overactivation following Ang II infusion. To test this hypothesis, computational models of the intrarenal RAS and the AT1R‐blocker Losartan were created, coupled, and used to simulate Ang II‐infusion experiments in the absence and presence of this anti‐hypertensive therapy. Model simulations indicate that total renal Ang II concentrations rise once Ang II starts accumulating within tubular epithelial cells and that the upregulation of local AT1R expression, not Ang II production, is required to produce this effect. Indeed, the removal of this positive feedback and the administration of Losartan both prevented the intrarenal accumulation of Ang II. Since the simulated onset of Ang II accumulation in tubular epithelial cells coincides exactly with the experimental inception of Ang II‐dependent hypertension, we conclude that the stimulation of sodium reabsorption mediated by local Ang II is likely key to the development of Ang II‐induced hypertension.

POS-195 ROLE OF S1P-DERIVED SOLUBLE (PRO)RENIN RECEPTOR IN ALBUMIN OVERLOAD INDUCED NEPROPATHY IN 129/SV MICE

In albumin overload (AO) nephropathy model, PRR activation mediated activation of intrarenal renin-angiotensin system (RAS) and thus elevated inflammatory and fibrosis factors of the kidney. In the present study, our goal was to determine whether such action of PRR was mediated by PRR soluble form (sPRR), cleaved by site-1 protease (S1P), a serine protease in the Golgi.

Biomarkers for early diagnosis of diabetic kidney disease: still a long way to go.

Biomarkers for early diagnosis of diabetic kidney disease: still a long way to go.

Ренин-ангиотензиновая система в регуляции экскреторной функции почек при экспериментальном сахарном диабете

Целью исследования было изучение роли ренин-ангиотензиновой системы в нарушении экскреторной функции почек в динамике аллоксан-индуцированного экспериментального сахарного диабета. Материалы и методы. Исследования выполнены на 78 нелинейных половозрелых самцах белых крыс с 11-, 26- и 46-дневным экспериментальным сахарным диабетом, вызванным внутрибрюшинным введением аллоксана (160 мг/кг), на фоне фармакологической блокады внутрипочечной ренин-ангиотензиновой системы, индуцированной внутрибрюшинным введением каптоприла (10 мг/кг). Изучение экскреторной функции почек осуществляли клиренс-методом в условиях водного индуцированного 2-часового диуреза с определением клиренса эндогенного креатинина, скорости клубочковой фильтрации, относительной реабсорбции воды, содержания белка в моче, его экскреции. Результаты. Анализ изменений функции почек после фармакологической блокады ренин-ангиотензиновой системы у крыс на 11-й день аллоксанового диабета показал достоверное возрастание диуреза, скорости клубочковой фильтрации, концентрационного индекса эндогенного креатинина, а также экскреции белка. При этом фармакологическая блокада ренин-ангиотензиновой системы практически не влияла на интенсивность относительной реабсорбции воды у аллоксан-диабетических крыс. На 26-й день развития аллоксанового диабета после введения каптоприла наблюдалось незначительное уменьшение объема конечной мочи, интенсивности гломерулярной фильтрации, относительной реабсорбции воды, концентрационного индекса эндогенного креатинина. Вместе с тем каптоприл не вызывал антипротеинурического эффекта, а экскреция белка даже продемонстрировала тенденцию к увеличению. На 46-й день аллоксан-индуцированного диабета после введения каптоприла достоверно снижались диурез крыс, клиренс эндогенного креатинина и скорость клубочковой фильтрации, а также концентрация белка в моче и его экскреция. Выводы. Результаты исследования позволяют сделать вывод о том, что начальный этап формирования ренальных нарушений при аллоксан-индуцированном экспериментальным сахарным диабетом связан с гемодинамически-гиперперфузионным характером функционирования почек при сохранном почечном функциональном резерве и структуре клубочково-канальцевого аппарата почки, авторегуляторных механизмов. Указанные компенсаторно-функциональные изменения функций почек постепенно осложняются истощением почечного функционального резерва и патологической активацией внутрипочечной ренин-ангиотензиновой системы с последующим прогрессированием гиперперфузионно-ишемического поражения почек, уменьшением массы функционирующих нефронов.

Tetrahydrocurcumin Ameliorates Kidney Injury and High Systolic Blood Pressure in High-Fat Diet-Induced Type 2 Diabetic Mice.

BackgroundActivation of the intrarenal renin-angiotensin system (RAS) is implicated in the pathogenesis of kidney injury and hypertension. We aimed to investigate the protective effect of tetrahydrocurcumin (THU) on intrarenal RAS expression, kidney injury, and systolic blood pressure (SBP) in high-fat diet (HFD)-induced type 2 diabetic mice.MethodsEight-week-old male mice were fed a regular diet (RD) or HFD for 12 weeks, and THU (50 or 100 mg/kg/day) was intragastrically administered with HFD. Physiological and metabolic changes were monitored and the expression of RAS components and markers of kidney injury were assessed.ResultsHFD-fed mice exhibited hyperglycemia, insulin resistance, and dyslipidemia compared to those in the RD group (P<0.05). Kidney injury in these mice was indicated by an increase in the ratio of albumin to creatinine, glomerular hypertrophy, and the effacement of podocyte foot processes. Expression of intrarenal angiotensin-converting enzyme, angiotensin II type I receptor, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-4, and monocyte chemoattractant protein-1 was also markedly increased in HFD-fed mice. HFD-fed mice exhibited elevated SBP that was accompanied by an increase in the wall thickness and vascular cross-sectional area (P<0.05), 12 weeks post-HFD consumption. Treatment with THU (100 mg/kg/day) suppressed intrarenal RAS activation, improved insulin sensitivity, and reduced SBP, thus, attenuating kidney injury in these mice.ConclusionTHU alleviated kidney injury in mice with HFD-induced type 2 diabetes, possibly by blunting the activation of the intrarenal RAS/nicotinamide adenine dinucleotide phosphate oxidase IV (NOX4)/monocyte chemoattractant protein 1 (MCP-1) axis and by lowering the high SBP.

Urinary excretion of renin and angiotensinogen in hypertensive children and adolescents.

IntroductionIn recent years hypertension has become an emerging condition in the young population. It has been proposed that the renin–angiotensin system plays an important role in regulation of blood pressure. We assessed whether activation of the intrarenal renin-angiotensin system occurs in hypertensive children and adolescents and what better reflects its activity: urine angiotensinogen (AGT) or urine renin (REN).Material and methodsThe study was conducted on a sample of 58 subjects with primary hypertension (HT) and 29 normotensive children and adolescents. We measured urine REN and AGT excretion and assessed the values in relation to blood pressure (BP) and other clinical parameters. Both REN and AGT values were calculated by urine creatinine: REN/cr. and AGT/cr., respectively.ResultsWe observed higher urine REN/cr. values in hypertensive subjects in comparison to the reference group (6.99 vs. 2.93, p = 0.003). Hypertensive participants showed positive correlations between urine REN/cr. and diastolic 24-hour BP (r = 0.42, p = 0.002) as well as between urine REN/cr. and urine AGT/cr. (r = 0.266, p = 0.044, respectively).ConclusionsIncreased urine REN/cr. in hypertensive children and adolescents and its positive correlation with BP may indicate its important role in the pathogenesis of HT. Perhaps urine REN/cr. could be a marker of intrarenal renin-angiotensin system activity. Nevertheless, further research should be undertaken to confirm this observation.

Sex differences in soluble prorenin receptor in patients with type 2 diabetes

BackgroundThe soluble prorenin receptor (sPRR), a member of the renin-angiotensin system (RAS), is elevated in plasma of patients with preeclampsia, hypertension, chronic kidney disease (CKD), and type 2 diabetes. Our goal was to examine the relationship between sPRR and RAS activation to define whether sexual dimorphisms in sPRR might explain sex disparities in renal outcomes in patients with type 2 diabetes.MethodsTwo hundred sixty-nine participants were included in the study (mean age, 48 ± 16 years; 42% men, 58% women), including 173 controls and 96 subjects with type 2 diabetes. In plasma and urine, we measured sPRR, plasma renin activity (PRA), and prorenin. In the urine, we also measured angiotensinogen along with other biomarkers of renal dysfunction.ResultsPlasma sPRR and PRA were significantly higher in women with type 2 diabetes compared to men. In these women, plasma sPRR was positively correlated with PRA, age, and body mass index (BMI). In contrast, in men the sPRR in urine but not in plasma positively correlated with eGFR in urine, but negatively correlated with urine renin activity, plasma glucose, age, and BMI.ConclusionsIn patients with type 2 diabetes, sPRR contributes to RAS stimulation in a sex-dependent fashion. In diabetic women, increased plasma sPRR parallels the activation of systemic RAS; while in diabetic men, decreased sPRR in urine matches intrarenal RAS stimulation. sPRR might be a potential indicator of intrarenal RAS activation and renal dysfunction in men and women with type 2 diabetes.

ENHANCED PRODUCTIONS OF INTRARENAL NLRP-3 INFLAMMASOME AND ANGIOTENSINOGEN IN ANGIOTENSIN II-DEPENDENT HYPERTENSION ARE PREVENTED BY IMMUNOSUPPRESSANT TREATMENT

Objective: Activated inflammasomes enhance maturation of pro-inflammatory cytokines, which facilitates the development of kidney injury. NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3), one of major subunits in the inflammasome complex, plays a crucial role in innate immunity and inflammation. NLRP3 inflammasome is activated by ATP-P2X7 axis and reactive oxygen species. Expression of pro-NLRP3 is promoted by activated NF-κB by cytokines or PAMPs/DAMPs. In angiotensin II (Ang II)-dependent hypertension, there is augmentation of renal immune cells leading to enhanced production of cytokines and consequent activation of NF-κB. Therefore, we hypothesized that intrarenal NLRP3 levels are increased in Ang II-dependent hypertension in association with the kidney injury, and treatment with mycophenolate mofetil (MMF), an immunosuppressant, prevents the augmentation of NLRP3 and attenuates the consequent progression of kidney injury. Design and method: Ang II (80 ng/min) was infused with/without daily MMF administration (50 ng/kg) to male rats for 2 weeks. mRNA levels of intrarenal NLRP3 and AIM2, which forms another type of inflammasome complex by viral or bacterial infections, were measured by droplet digital PCR. Furthermore, levels of intrarenal angiotensinogen (AGT), a critical contributor to activation of intrarenal renin-angiotensin system leading to the development of hypertension and associated kidney injury, were evaluated. Histological analyses of kidney injury were also performed. Results: MMF prevented increases in intrarenal macrophage/monocyte and IL-6 levels induced by Ang II infusion, confirming immunosuppression by the drug. Ang II infusion significantly increased intrarenal NLRP3 levels (control group: 4.12 ± 1.1 copies/ng RNA vs. Ang II-infused group: 9.96 ± 1.8 copies). The elevated NLRP3 expression was attenuated by MMF (6.24 ± 1.4 copies). In contrast, intrarenal AIM2 levels were not altered by Ang II infusion or MMF. Urinary protein and AGT levels were elevated in Ang II-infused rats, which were prevented by MMF. Histological analyses showed mesangial expansion and tubulointerstitial fibrosis observed in Ang II-infused group, but these injury markers were in normal ranges in the group receiving Ang II + MMF. Conclusions: These results demonstrate activation of the NLRP3 inflammasome in Ang II dependent hypertension and indicate that immunosuppression by MMF mitigates the inflammasome activation, which contributes to attenuation of the kidney injury.

Baseline Urinary Angiotensinogen Excretion Predicts Deterioration of the Kidney Function in Patients with Chronic Kidney Disease.

Objective The intrarenal renin-angiotensin system (RAS) is activated in patients with chronic kidney disease (CKD), and urinary angiotensinogen (AGT) levels, a surrogate marker of the intrarenal RAS activation, are associated with blood pressure (BP) and urinary albumin excretion. In addition, it has been shown that changes in urinary AGT levels correlate with annual changes in the estimated glomerular filtration rate (eGFR) in patients with type 2 diabetes and that elevated levels of urinary AGT in type 2 diabetic patients with albuminuria are a high-risk factor for worsening renal and cardiovascular complications. However, whether or not baseline urinary AGT levels predict deterioration of the kidney function in all patients with CKD is unclear. Methods We recruited 62 patients with CKD whose eGFR was ＞15 mL/min/1.73 m2. We performed 24-hour ambulatory BP monitoring at 30-min intervals and daily urinary collection to examine the urinary AGT levels and albumin excretion and measured the levels of plasma angiotensin II (Ang II), a surrogate marker of circulating RAS. In addition, annual changes in the eGFR were followed up for 3.4±1.5 years. Results Annual changes in the eGFR were significantly and negatively associated with urinary AGT levels (r=-0.31, p=0.015) as well as the age, systolic BP, and urinary albumin levels. In contrast, annual changes in the eGFR were not correlated with plasma Ang II levels. Furthermore, when dividing patients into quartiles according to urinary AGT levels, patients with the highest urinary AGT levels showed a progressive decline in the eGFR. Conclusion These results suggest that elevated baseline urinary AGT levels can predict renal dysfunction in patients with CKD.

Circadian rhythm of the intrarenal renin-angiotensin system is caused by glomerular filtration of liver-derived angiotensinogen depending on glomerular capillary pressure in adriamycin nephropathy rats.

Circadian fluctuation disorder of the intrarenal renin-angiotensin system (RAS) causes that of blood pressure (BP) and renal damage. In renal damage with an impaired glomerular filtration barrier, liver-derived angiotensinogen (AGT) filtered through damaged glomeruli regulates intrarenal RAS activity. Furthermore, glomerular permeability is more strongly affected by glomerular hypertension than by systemic hypertension. Thus, we aimed to clarify whether the circadian rhythm of intrarenal RAS activity is influenced by AGT filtered through damaged glomeruli due to glomerular capillary pressure. Rats with adriamycin nephropathy and an impaired glomerular filtration barrier were compared with control rats. In adriamycin nephropathy rats, olmesartan medoxomil (an angiotensin II type 1 receptor blocker) or hydralazine (a vasodilator) was administered, and the levels of intrarenal RAS components in the active and rest phases were evaluated. Moreover, the diameter ratio of afferent to efferent arterioles (A/E ratio), an indicator of glomerular capillary pressure, and the glomerular sieving coefficient (GSC) based on multiphoton microscopy in vivo imaging, which reflects glomerular permeability, were determined. Mild renal dysfunction was induced, and the systemic BP increased, resulting in increased A/E ratios in the adriamycin nephropathy rats compared with the control rats. Fluctuations in intrarenal RAS activity occurred in parallel with circadian fluctuations in glomerular capillary pressure, which disappeared with olmesartan treatment and were maintained with hydralazine treatment. Furthermore, the GSCs for AGT also showed similar changes. In conclusion, intrarenal RAS activity is influenced by the filtration of liver-derived AGT from damaged glomeruli due to circadian fluctuation disorder of the glomerular capillary pressure.

Effect of Vitamin D on Urinary Angiotensinogen Level in Early Diabetic Nephropathy.

Background:Urinary angiotensinogen (UAGT) is supposed to be a marker of activation of the intrarenal renin– angiotensin system (RAS) system in early diabetic nnephropathy (EDN). Vitamin D has been studied as a negative regulator of the circulating and tissue RAS activity, so its supplementation may prevent the progression of diabetic nephropathy (DN). This study was planned to assess the RAS activation and effect of vitamin D supplementation in EDN progression by estimating the UAGT level.Methods:A total of 103 EDN subjects were randomized in two groups to receive either cholecalciferol (54) or matching placebo (49) in a double-blind manner. All were subjected to routine investigations, urinary albumin-to-creatinine ratio (UACR), UAGT, vitamin D, and intact parathyroid hormone (iPTH) at the 0 and 6 months. A total 40 healthy controls were also included for assessment of the same investigations at 0 month.Results:Significant reduction of UACR, UAGT, and iPTH level were corroborated with an increase in 25(OH) vitamin D level from 0 to 6 months (all four P < 0.001). After 6 months, the median [interquartile range (IQR)] of UAGT and UACR levels was significantly lower in the cholecalciferol group as compared to placebo group (p < 0.001 and P = 0.04, respectively). The median UAGT level was significantly higher in patients with EDN (cholecalciferol & placebo Group) than control group at 0 month (p = 0.001).Conclusion:Significantly higher UAGT levels in EDN supports the role of intrarenal RAS activation. A significant decrease in UAGT level in the cholecalciferol group supports the beneficial role of vitamin D supplementation in the progression of EDN.