Augmented intrarenal and urinary angiotensinogen in hypertension and chronic kidney disease

Combination of Urinary Neutrophil Gelatinase-associated Lipocalin, Kidney Injury Molecular-1, and Angiotensinogen for the Early Diagnosis and Mortality Prediction of Septic Acute Kidney Injury

BACKGROUND

Acute kidney injury (AKI) is one of the most severe complications of sepsis. This study was conducted to analyze the role of urinary neutrophil gelatinase-associated lipocalin (uNGAL), urinary kidney injury molecular-1 (uKIM-1), and urinary angiotensinogen (uAGT) in the early diagnosis and mortality prediction of septic AKI.

METHODS

The prospective study enrolled 80 sepsis patients in the ICU and 100 healthy individuals and divided patients into an AKI group and a non-AKI group. uNGAL, uKIM-1, uAGT, serum creatinine/procalcitonin/C-reaction protein, and other indicators were determined, and clinical prediction scores were recorded. The sensitivity and specificity of uNGAL, uKIM-1, and uAGT in diagnosis and mortality prediction were analyzed by the receiver operator characteristic (ROC) curve and the area under the curve (AUC).

RESULTS

uNGAL, uKIM-1, and uAGT levels were higher in sepsis patients than healthy controls, higher in AKI patients than non-AKI patients, and higher in AKI-2 and AKI-3 patients than AKI-1 patients. At 0 h after admission, the combined efficacy of three indicators in septic AKI diagnosis (ROC-AUC: 0.770; sensitivity: 82.5%; specificity: 70.0%) was better than a single indicator. At 24 h, uNGAL, uKIM-1, and uAGT levels were higher in sepsis non-survivals than survivals and higher in septic AKI non-survivals than septic AKI survivals. The combined efficacy of three indicators in the prediction of sepsis/septic AKI mortality (ROC-AUC: 0.828/0.847; sensitivity: 71.4%/100.0%; specificity: 82.7%/66.7%) was better than a single indicator.

CONCLUSION

uNGAL, uKIM-1, and uAGT levels were increased in septic AKI, and their combination helped the early diagnosis and mortality prediction.

Intrarenal renin-angiotensin system activation and macrophage infiltrations in pediatric chronic glomerulonephritis

BACKGROUND

The current study tested the hypothesis that urinary angiotensinogen (UAGT) and urinary monocyte chemoattractant protein-1 (UMCP-1) levels provide a specific index of intrarenal renin-angiotensin system (RAS) status and the degree of infiltration of macrophages associated with RAS blockade and immunosuppressant treatment in pediatric patients with chronic glomerulonephritis.

METHODS

We measured baseline UAGT and UMCP-1 levels to examine the correlation between glomerular injury in 48 pediatric chronic glomerulonephritis patients before treatment. Furthermore, we performed immunohistochemical analysis of angiotensinogen (AGT) and CD68 in 27 pediatric chronic glomerulonephritis patients treated with RAS blockades and immunosuppressants for 2 years. Finally, we examined the effects of angiotensin II (Ang II) on monocyte chemoattractant protein-1 (MCP-1) expression in cultured human mesangial cells (MCs).

RESULTS

Baseline UAGT and UMCP-1 levels positively correlated with urinary protein levels, scores for mesangial hypercellularity, rate of crescentic formation, and expression levels of AGT and CD68 in renal tissues (p < 0.05). UAGT and UMCP-1 levels were significantly decreased after RAS blockade and immunosuppressant treatment (p < 0.01), which was accompanied by AGT and CD68 (p < 0.01), as well as the magnitude of glomerular injury. Cultured human MCs showed increased MCP-1 messenger ribonucleic acid and protein levels after Ang II treatment (p < 0.01).

CONCLUSIONS

The data indicates that UAGT and UMCP-1 are useful biomarkers of the degree of glomerular injury during RAS blockade and immunosuppressant treatment in pediatric patients with chronic glomerulonephritis.

Urinary Angiotensinogen and Progression of Chronic Kidney Disease: Results from KNOW-CKD Study

The prognostic value of urinary angiotensinogen (UAGT) in patients with chronic kidney disease (CKD) has not been completely evaluated, although the association of UAGT with renal outcomes has been suggested in specific subsets of CKD. In the present study, to investigate the association of UAGT with renal outcomes in patients with non-dialysis CKD irrespective of the primary cause, a total of 1688 subjects from the Korean Cohort Study for Outcomes in Patients With Chronic Kidney Disease (KNOW-CKD) were prospectively analyzed. The subjects were divided into the quintile by UAGT to urine creatinine ratio (UAGT/Cr) level. The primary outcomes of interest were composite renal event, which included decline in kidney function and onset of end-stage renal disease during follow-up periods. The median follow-up duration was 6.257 years. Cox regression model analysis unveiled that the risk of composite renal event was significantly higher in the fifth quintile (adjusted hazard ratio 1.528, 95% confidence interval 1.156 to 2.021) compared to that of the first quartile. The association between high UAGT/Cr level and adverse renal outcome remained consistent in sensitivity analyses, including the analysis of the cause-specific hazard model. Subgroup analyses revealed that the association of UAGT level with renal outcomes is modified by certain clinical contexts, such as BMI and albuminuria. In conclusion, high UAGT level is associated with adverse renal outcomes in patients with non-dialysis CKD. Further studies are warranted to elaborate and expand the predictive role of UAGT as a biomarker for renal outcomes in CKD.

Urinary angiotensin converting enzyme 2 and disease activity in pediatric IgA nephropathy

Background : Our previous studies demonstrated that the intrarenal renin-angiotensin system (RAS) status was activated in pediatric patients with chronic glomerulonephritis. In the present study, we tested the hypothesis that angiotensin-converting enzyme 2 (ACE2) expression in the kidney is associated with the development of pediatric IgA nephropathy. Methods : We analyzed urinary ACE2 levels and ACE2 expression in the kidney tissues of pediatric patients with IgA nephropathy treated with RAS blockade. Paired tests were used to analyze changes from the first to the second biopsy. Results : Urinary ACE2 levels were significantly decreased after RAS blockade treatment, accompanied by decreased ACE2 expression levels in kidney tissues, urinary protein levels and mesangial hypercellularity scores. Urinary ACE2 levels at the first biopsy were positively correlated with the ACE2 expression levels. Conclusions : These data suggest that urinary ACE2 is associated with ACE2 expression in the diseased kidney, which correlates with the pathogenesis of IgA nephropathy in pediatric patients. J. Med. Invest. 68 : 292-296, August, 2021.

Oncogenic mechanisms in renal insufficiency

The prevalence of both cancer and end-stage renal disease is increasing. In addition, medical advances have meant increased survival rates for both diseases. Many chemotherapeutics are renally excreted, and conversely, renal insufficiency promotes a pro-neoplastic state, including genitourinary and other cancers. Dialysis prolongs life while increasing cancer risk. Proposed oncogenic mechanisms include immune dysfunction, chronic inflammation, changes in gut microbiota and stimulation of the renin-angiotensin system. This review summarizes current concepts in the relationship between cancer and renal insufficiency.

Urinary angiotensinogen as a surrogate marker predicting the antiproteinuric effects of angiotensin receptor blockers in patients with overt proteinuria: a multicenter prospective study

BACKGROUND

Although urinary angiotensinogen (AGT) and renin reflect intrarenal renin-angiotensin system activity and are enhanced in proteinuric chronic kidney disease, the clinical value of urinary AGT and renin levels during antiproteinuric treatment has yet to be determined. We investigated the clinical usefulness of initial urinary AGT or renin to determine the antiproteinuric effects of angiotensin receptor blockers (ARBs).

METHODS

This multicenter, prospective, single-arm study included 205 patients with overt proteinuria (urinary protein/creatinine ratio [uPCR] ≥ 1 mg/mg) enrolled between April 2009 and December 2011. All patients were treated with valsartan. The urinary AGT/creatinine ratio (uAGT/Cr) was measured at the baseline and 24 weeks, and the renin/creatinine ratio (uR/Cr) was measured at the baseline. Fifty-six patients were followed-up for 5 years.

RESULTS

The mean age was 47.6 years and 51.2% were male. The mean uPCR was 2.32 mg/mg and the mean eGFR was 63.2 mL/min/1.73m². Natural logarithms (ln) (uAGT/Cr), ln(uR/Cr), and diabetes mellitus were associated with proteinuria decrement (decrease in uPCR ≥1 mg/mg). Ln(uAGT/Cr) was an independent predictor for proteinuria decrement (OR 1.372, 95% CI, 1.068-1.762, P = 0.013). Among the 56 patients followed-up for 5 years, Δln(uAGT/Cr) at 24 weeks was an independent predictor for uPCR < 1 mg/mg at 5 years (OR 0.379, 95% CI, 0.20-0.715, P = 0.003).

CONCLUSIONS

Our study demonstrates the potential role of both baseline urinary AGT and changes in urinary AGT during the initial 24 weeks as surrogate markers predicting the antiproteinuric effects of ARBs in patients with overt proteinuria.

Diabetes-induced upregulation of kallistatin levels exacerbates diabetic nephropathy via RAS activation

Kallistatin is an inhibitor of tissue kallikrein and also inhibits the Wnt pathway. Its role in diabetic nephropathy (DN) is uncertain. Here we reported that serum kallistatin levels were significantly increased in diabetic patients with DN compared to those in diabetic patients without DN and healthy controls, and positively correlated with urinary albumin excretion. In addition, renal kallistatin levels were significantly upregulated in mouse models of type 1 (Akita, OVE26) and type 2 diabetes (db/db). To unveil the effects of kallistatin on DN and its underlying mechanism, we crossed transgenic mice overexpressing kallistatin with OVE26 mice (KS‐tg/OVE). Kallistatin overexpression exacerbated albuminuria, renal fibrosis, inflammation, and oxidative stress in diabetes. Kallikrein activity was inhibited while the renin‐angiotensin system (RAS) upregulated in the kidney of KS‐tg/OVE mice compared to WT/OVE mice, suggesting a disturbed balance between the RAS and kallikrein‐kinin systems. As shown by immunostaining of endothelial makers, renal vascular densities were decreased accompanied by increased HIF‐1α and erythropoietin levels in the kidneys of KS‐tg/OVE mice. Taken together, high levels of kallistatin exacerbate DN at least partly by inducing RAS overactivation and hypoxia. The present study demonstrated a positive correlation between kallistatin levels and DN, suggesting a potential biomarker for prognosis of DN.

Novel Variants of Angiotensin Converting Enzyme-2 of Shorter Molecular Size to Target the Kidney Renin Angiotensin System

ACE2 is a monocarboxypeptidase which generates Angiotensin (1-7) from Angiotensin II (1-8). Attempts to target the kidney Renin Angiotensin System using native ACE2 to treat kidney disease are hampered by its large molecular size, 100 kDa, which precludes its glomerular filtration and subsequent tubular uptake. Here, we show that both urine and kidney lysates are capable of digesting native ACE2 into shorter proteins of ~60-75 kDa and then demonstrate that they are enzymatically very active. We then truncated the native ACE2 by design from the C-terminus to generate two short recombinant (r)ACE2 variants (1-605 and 1-619AA). These two truncates have a molecular size of ~70 kDa, as expected from the amino acid sequence and as shown by Western blot. ACE2 enzyme activity, measured using a specific substrate, was higher than that of the native rACE2 (1-740 AA). When infused to mice with genetic ACE2 deficiency, a single i.v. injection of 1-619 resulted in detectable ACE2 activity in urine, whereas infusion of the native ACE2 did not. Moreover, ACE2 activity was recovered in harvested kidneys from ACE2-deficient mice infused with 1-619, but not in controls (23.1 ± 4.3 RFU/µg creatinine/h and 1.96 ± 0.73 RFU/µg protein/hr, respectively). In addition, the kidneys of ACE2-null mice infused with 1-619 studied ex vivo formed more Ang (1-7) from exogenous Ang II than those infused with vehicle (AUC 8555 ± 1933 vs. 3439 ± 753 ng/mL, respectively, p < 0.05) further demonstrating the functional effect of increasing kidney ACE2 activity after the infusion of our short ACE2 1-619 variant. We conclude that our novel short recombinant ACE2 variants undergo glomerular filtration, which is associated with kidney uptake of enzymatically active proteins that can enhance the formation of Ang (1-7) from Ang II. These small ACE2 variants may offer a potentially useful approach to target kidney RAS overactivity to combat kidney injury.

Pharmacological Blockade of Soluble Epoxide Hydrolase Attenuates the Progression of Congestive Heart Failure Combined With Chronic Kidney Disease: Insights From Studies With Fawn-Hooded Hypertensive Rats

An association between congestive heart failure (CHF) and chronic kidney disease (CKD) results in extremely poor patient survival rates. Previous studies have shown that increasing kidney epoxyeicosatrienoic acids (EETs) by blocking soluble epoxide hydrolase (sEH), an enzyme responsible for EETs degradation, improves the survival rate in CHF induced by aorto-caval fistula (ACF) and attenuates CKD progression. This prompted us to examine if sEH inhibitor treatment would improve the outcome if both experimental conditions are combined. Fawn-hooded hypertensive (FHH) rats, a genetic model showing early CKD development was employed, and CHF was induced by ACF. Treatment with an sEH inhibitor was initiated 4 weeks after ACF creation, in FHH and in fawn-hooded low-pressure (FHL) rats, a control strain without renal damage. The follow-up period was 20 weeks. We found that ACF FHH rats exhibited substantially lower survival rates (all the animals died by week 14) as compared with the 64% survival rate observed in ACF FHL rats. The former group showed pronounced albuminuria (almost 30-fold higher than in FHL) and reduced intrarenal EET concentrations. The sEH inhibitor treatment improved survival rate and distinctly reduced increases in albuminuria in ACF FHH and in ACF FHL rats, however, all the beneficial actions were more pronounced in the hypertensive strain. These data indicate that pharmacological blockade of sEH could be a novel therapeutic approach for the treatment of CHF, particularly under conditions when it is associated with CKD.

Enhanced angiotensinogen expression in neonates during kidney development

BACKGROUND

We recently demonstrated that preterm neonates have higher urinary angiotensinogen (AGT) levels than full-term neonates. Here, we tested the hypothesis that enhanced neonatal AGT expression is associated with intrarenal renin-angiotensin system (RAS) status during kidney development.

METHODS

We prospectively recruited neonates born at our hospital and healthy children with minor glomerular abnormalities between April 2013 and March 2017. We measured neonatal plasma and urinary AGT levels at birth and 1 year later and assessed renal AGT expression in kidney tissues from neonates and healthy children using immunohistochemical (IHC) analysis.

RESULTS

Fifty-four neonates and eight children were enrolled. Although there were no changes in plasma AGT levels, urinary AGT levels were significantly decreased 1 year after birth. Urinary AGT levels at birth were inversely correlated with gestational age, and urinary AGT levels at birth and 1 year later were inversely correlated with estimated glomerular filtration rate 1 year after birth. IHC analysis showed that renal AGT expression in neonates was higher than that in healthy children and inversely correlated with gestational age.

CONCLUSIONS

Enhanced AGT expression and urinary AGT excretion may reflect intrarenal RAS activation associated with kidney development in utero.

Add-On Effect of Angiotensin Receptor Blockade (Candesartan) on Clinical Remission in Active IgA Nephropathy Patients Treated with Steroid Pulse Therapy and Tonsillectomy: a Randomized, Parallel-Group Comparison Trial

BACKGROUND/AIMS

Angiotensin receptor blockers (ARBs) may be beneficial for clinical remission during conventional therapy with tonsillectomy and steroid pulse (TSP) for active IgA nephropathy.

METHODS

Seventy-seven patients with active IgA nephropathy were randomly assigned to the control arm with conventional regimen (TSP followed by oral prednisolone) (n = 37) or the ARB arm with conventional regimen plus ARB candesartan for the first 6 months (n = 40). Patients not achieving proteinuria remission at 12 months in either arm were administered candesartan, which was titrated until the 24-month follow-up. The primary endpoints were remission of proteinuria (< 0.3 g/gCr) and hematuria at 12 months.

RESULTS

Baseline proteinuria (g/g Cr) were comparable between the control and ARB arm (1.02 vs. 0.97, P = 0.97). Similarly, cumulative remission rates at 6, 12, and 24 months were comparable between the control and ARB arms (37.8% vs. 35% [P = 0.80], 48.7% vs. 38.5% [P = 0.37], 71.4% vs. 51.3% [P = 0.08]). Proteinuria, which was slightly worse in the control arm than in the ARB arm at 6 months, was comparable afterwards (0.20 vs. 0.23 g/g Cr at 12 months; 0.12 vs. 0.13 g/g Cr at 24 months). Significant reductions observed in urinary angiotensinogen were almost comparable between the two treatment arms at both 6 and 12 months.

CONCLUSION

Early candesartan treatment combined with TSP may not benefit clinical remission regardless of the blood pressure. ARB titration later during the treatment might provide benefit for patients with active IgA nephropathy.

Plasma proteomic analysis reveals altered protein abundances in cardiovascular disease

BACKGROUND

Cardiovascular disease (CVD) describes the pathological conditions of the heart and blood vessels. Despite the large number of studies on CVD and its etiology, its key modulators remain largely unknown. To this end, we performed a comprehensive proteomic analysis of blood plasma, with the scope to identify disease-associated changes after placing them in the context of existing knowledge, and generate a well characterized dataset for further use in CVD multi-omics integrative analysis.

METHODS

LC-MS/MS was employed to analyze plasma from 32 subjects (19 cases of various CVD phenotypes and 13 controls) in two steps: discovery (13 cases and 8 controls) and test (6 cases and 5 controls) set analysis. Following label-free quantification, the detected proteins were correlated to existing plasma proteomics datasets (plasma proteome database; PPD) and functionally annotated (Cytoscape, Ingenuity Pathway Analysis). Differential expression was defined based on identification confidence (≥ 2 peptides per protein), statistical significance (Mann-Whitney p value ≤ 0.05) and a minimum of twofold change.

RESULTS

Peptides detected in at least 50% of samples per group were considered, resulting in a total of 3796 identified proteins (838 proteins based on ≥ 2 peptides). Pathway annotation confirmed the functional relevance of the findings (representation of complement cascade, fibrin clot formation, platelet degranulation, etc.). Correlation of the relative abundance of the proteins identified in the discovery set with their reported concentrations in the PPD was significant, confirming the validity of the quantification method. The discovery set analysis revealed 100 differentially expressed proteins between cases and controls, 39 of which were verified (≥ twofold change) in the test set. These included proteins already studied in the context of CVD (such as apolipoprotein B, alpha-2-macroglobulin), as well as novel findings (such as low density lipoprotein receptor related protein 2 [LRP2], protein SZT2) for which a mechanism of action is suggested.

CONCLUSIONS

This proteomic study provides a comprehensive dataset to be used for integrative and functional studies in the field. The observed protein changes reflect known CVD-related processes (e.g. lipid uptake, inflammation) but also novel hypotheses for further investigation including a potential pleiotropic role of LPR2 but also links of SZT2 to CVD.

Combined Inhibition of Soluble Epoxide Hydrolase and Renin-Angiotensin System Exhibits Superior Renoprotection to Renin-Angiotensin System Blockade in 5/6 Nephrectomized Ren-2 Transgenic Hypertensive Rats with Established Chronic Kidney Disease

BACKGROUND/AIMS

We found recently that increasing renal epoxyeicosatrienoic acids (EETs) levels by blocking soluble epoxide hydrolase (sEH), an enzyme responsible for EETs degradation, shows renoprotective actions and retards the progression of chronic kidney disease (CKD) in Ren-2 transgenic hypertensive rats (TGR) after 5/6 renal ablation (5/6 NX). This prompted us to examine if additional protection is provided when sEH inhibitor is added to the standard renin-angiotensin system (RAS) blockade, specifically in rats with established CKD.

METHODS

For RAS blockade, an angiotensin-converting enzyme inhibitor along with an angiotensin II type receptor blocker was used. RAS blockade was compared to sEH inhibition added to the RAS blockade. Treatments were initiated 6 weeks after 5/6 NX in TGR and the follow-up period was 60 weeks.

RESULTS

Combined RAS and sEH blockade exhibited additional positive impact on the rat survival rate, further reduced albuminuria, further reduced glomerular and tubulointerstitial injury, and attenuated the decline in creatinine clearance when compared to 5/6 NX TGR subjected to RAS blockade alone. These additional beneficial actions were associated with normalization of the intrarenal EETs deficient and a further reduction of urinary angiotensinogen excretion.

CONCLUSION

This study provides evidence that addition of pharmacological inhibition of sEH to RAS blockade in 5/6 NX TGR enhances renoprotection and retards progression of CKD, notably, when applied at an advanced stage.

Role of the intrarenal renin-angiotensin system in the progression of renal disease

The intrarenal renin-angiotensin system (RAS) has many well-documented pathophysiologic functions in both blood pressure regulation and renal disease development. Angiotensin II (Ang II) is the major bioactive product of the RAS. It induces inflammation, renal cell growth, mitogenesis, apoptosis, migration, and differentiation. In addition, Ang II regulates the gene expression of bioactive substances and activates multiple intracellular signaling pathways that are involved in renal damage. Activation of the Ang II type 1 (AT1) receptor pathway results in the production of proinflammatory mediators, intracellular formation of reactive oxygen species, cell proliferation, and extracellular matrix synthesis, which in turn facilities renal injury. Involvement of angiotensinogen (AGT) in intrarenal RAS activation and development of renal disease has previously been reported. Moreover, studies have demonstrated that the urinary excretion rates of AGT provide a specific index of the intrarenal RAS status. Enhanced intrarenal AGT levels have been observed in experimental models of renal disease, supporting the concept that AGT plays an important role in the development and progression of renal disease. In this review, we focus on the role of intrarenal RAS activation in the pathophysiology of renal disease. Additionally, we explored the potential of urinary AGT as a novel biomarker of intrarenal RAS status in renal disease.

The transcriptional regulation of the human angiotensinogen gene after high-fat diet is haplotype-dependent: Novel insights into the gene-regulatory networks and implications for human hypertension

Single nucleotide polymorphisms (SNPs) in the human angiotensinogen (hAGT) gene may modulate its transcription and affect the regulation of blood pressure via activation of the renin-angiotensin aldosterone system (RAAS). In this regard, we have identified polymorphisms in the 2.5 Kb promoter of the hAGT gene that form two haplotype (Hap) blocks: -6A/G (-1670A/G, -1562C/T, -1561T/C) and -217A/G (-532T/C, -793A/G, -1074T/C & -1178G/A). hAGT gene with Hap -6A/-217A (Hap I) is associated with increased blood pressure whereas, Hap -6G/-217G (Hap II) is associated with normal blood pressure in human subjects. Since RAAS over activity contributes to hypertension in obesity, we have made transgenic mice (TG) containing either Hap I or Hap II of the hAGT gene to understand the role of obesity on its transcriptional regulation. Although, a high-fat diet (60% Kcal from fat, 12 weeks) elevates hAGT and mAGT regardless of haplotype, this effect is significantly (p<0.05) accentuated in Hap I mice, in both adipose and liver tissues. Chromatin Immuno- precipitation (ChIP) assay shows an increased binding of transcription factors including, GR, CEBPβ and STAT3 to the chromatin of the Hap I TG mice after high-fat diet as compared to Hap II TG mice (p<0.05). Differential plasma levels of hAGT in Hap II and I mice, after high-fat diet, further corroborate the variable transcriptional regulation of the hAGT, governed by gene-haplotypes. Taken together, our results show that SNPs in the Hap-I of the hAGT gene promote high-fat diet-induced binding of transcription factors GR, CEBP-β and STAT3, which lead to elevated expression of the hAGT gene in hepatic and adipose tissues.

Blood pressure and phosphate level in diabetic and non-diabetic kidney disease: Results of the cross-sectional "Low Clearance Consultation" study

Highlights

A statistically significant and moderate positive correlation was verified between systolic blood pressure and plasma phosphate concentration in the whole sample (diabetic and non-diabetic), due to the diabetic chronic kidney disease group.A statistically significant and moderate positive correlation was verified between the diastolic blood pressure and plasma phosphate concentration in the whole sample (diabetic and non-diabetic), due to the diabetic chronic kidney disease group.A statistically significant and strong negative correlation was found between diastolic blood pressure and estimated glomerular filtration rate in the diabetic chronic kidney disease group, but there was no statistically significant correlation in the whole sample (diabetic and non-diabetic).

Abstract

Diabetic kidney disease features certain clinical and laboratorial characteristics that differ from chronic kidney disease of other etiologies. We performed a transversal study comparing some of these characteristics and assessed potential associations among blood pressure, plasma phosphate concentration and estimated glomerular filtration rate between patients with diabetic and non-diabetic chronic kidney disease.We found a positive correlation between both systolic and diastolic blood pressure and the plasma phosphate concentration in the diabetic kidney disease group, but not in the non-diabetic group. Also, diastolic blood pressure was negatively correlated with the estimated glomerular filtration rate in the diabetic group, yet not in the non-diabetic group.In conclusion, these data support the hypothesis of a close link between systolic and diastolic blood pressure and hyperphosphatemia, as well as between diastolic blood pressure and estimated glomerular filtration rate, in patients with diabetic kidney disease. Therapeutic approaches directed at these factors might prove to be important to delay the decline of renal function in the subgroup of patients with diabetic kidney disease.

Urinary Angiotensinogen Could Be a Prognostic Marker of the Renoprotection of Olmesartan in Metabolic Syndrome Patients

This study was performed to demonstrate urinary angiotensinogen as a potential prognostic marker of the albuminuria reduction effects of olmesartan in patients with metabolic syndrome. In 24 patients (eight women, 57.88 ± 2.00 years), 5-40 mg/day of olmesartan were given. Urinary concentrations of albumin and angiotensinogen (normalized by urinary concentrations of creatinine) and plasma renin activity were measured before and after the 12- and 24-week marks of olmesartan treatment. Olmesartan treatment increased plasma renin activity and decreased urinary albumin and urinary angiotensinogen significantly (p < 0.05). Based on the % change in urinary albumin, patients were divided into two groups, responders (<-50%) and non-responders (≥-50%), and a logistic analysis of urinary angiotensinogen before treatment showed the area under the curve as 0.694. When the cutoff value of urinary angiotensinogen before the treatment of 13.9 µg/g Cr was used, the maximum Youden index (0.500, specificity: 11/12 = 91.7% and sensitivity: 7/12 = 58.3%) was obtained. When all patients were re-divided into two groups, those with higher values of urinary angiotensinogen before the treatment (Group H, n = 16) and those with lower values, Group H showed significantly decreased urinary albumin (p < 0.05). Therefore, urinary angiotensinogen could be a prognostic marker of the albuminuria reduction effects of olmesartan in patients with metabolic syndrome.

Suppressing angiotensinogen synthesis attenuates kidney cyst formation in a Pkd1 mouse model

Activation of the intrarenal renin angiotensin system (RAS) is believed to play an important role in the development of hypertension and cystogenesis in autosomal dominant polycystic kidney disease (ADPKD). Results of clinical studies testing RAS inhibitors in slowing the progression of cystic disease in ADPKD are inconclusive, and we hypothesized that current RAS inhibitors do not adequately suppress intrarenal RAS. For this study, we compared a novel Gen 2 antisense oligonucleotide (ASO) that inhibits angiotensinogen (Agt) synthesis to lisinopril in adult conditional Pkd1 systemic-knockout mice, a model of ADPKD. Six weeks after Pkd1 global gene knockout, the mice were treated with Agt-ASO (66 mg/kg/wk), lisinopril (100 mg/kg/d), PBS (control), or scrambled ASO (66 mg/kg/wk) for 10 wk, followed by tissue collection. Agt ASO resulted in significant reduction in plasma, liver, and kidney Agt, and increased kidney renin compared with control treatments. Kidneys from Agt-ASO-treated mice were not as enlarged and showed reduced cystic volume compared with lisinopril or control treatments. Blood pressure was better controlled with lisinopril than with Agt-ASO. Agt-ASO suppressed cell proliferation in both cystic and noncystic cells compared with lisinopril and control treatments. However, Agt-ASO did not reduce cell proliferation in liver, which indicates that Agt-ASO targets cell signaling pathways that specifically suppresses cystogenesis in the kidney. These data suggest that Agt-ASO effectively attenuates intrarenal RAS and therefore can be a novel and effective agent for treating ADPKD.

Salt-Sensitive Hypertension: Perspectives on Intrarenal Mechanisms

Salt sensitive hypertension is characterized by increases in blood pressure in response to increases in dietary salt intake and is associated with an enhanced risk of cardiovascular and renal morbidity. Although researchers have sought for decades to understand how salt sensitivity develops in humans, the mechanisms responsible for the increases in blood pressure in response to high salt intake are complex and only partially understood. Until now, scientists have been unable to explain why some individuals are salt sensitive and others are salt resistant. Although a central role for the kidneys in the development of salt sensitivity and hypertension has been generally accepted, it is also recognized that hypertension is of multifactorial origin and a variety of factors can induce, or prevent, blood pressure responsiveness to the manipulation of salt intake. Excess salt intake in susceptible persons may also induce inappropriate central and sympathetic nervous system responses and increase the production of intrarenal angiotensin II, catecholamines and other factors such as oxidative stress and inflammatory cytokines. One key factor is the concomitant inappropriate or paradoxical activation of the intrarenal renin-angiotensin system, by high salt intake. This is reflected by the increases in urinary angiotensinogen during high salt intake in salt sensitive models. A complex interaction between neuroendocrine factors and the kidney may underlie the propensity for some individuals to retain salt and develop salt-dependent hypertension. In this review, we focus mainly on the renal contributions that provide the mechanistic links between chronic salt intake and the development of hypertension.

Changes in urinary angiotensinogen posttreatment in pediatric IgA nephropathy patients

BACKGROUND

Recently, we demonstrated that urinary angiotensinogen (AGT) levels are increased and reflect intrarenal renin-angiotensin system (RAS) status in pediatric patients with chronic glomerulonephritis. Therefore, this study was performed to test the hypothesis that urinary AGT (UAGT) levels provide a specific index of intrarenal RAS status associated with RAS blockade treatment in pediatric IgA nephropathy (IgAN) patients.

METHODS

We measured plasma and UAGT levels and urinary transforming growth factor beta (TGF-β) levels, after which we performed immunohistochemical analysis of AGT, angiotensin II (Ang II), and TGF-β in 24 pediatric IgAN patients treated with RAS blockades for 2 years. Paired tests were used to analyze the changes from baseline to study end.

RESULTS

Although there was no change in plasma AGT levels, UAGT and TGF-β levels were significantly decreased after RAS blockade, which was accompanied by the expression levels of AGT, Ang II, and TGF-β, as well as the magnitude of glomerular injury. Baseline UAGT levels positively correlated with diastolic blood pressure, urinary protein levels, scores for mesangial hypercellularity, and the expression levels of AGT, Ang II, and TGF-β in renal tissues.

CONCLUSIONS

These data indicate that UAGT is a useful biomarker of intrarenal RAS activation, which is associated with glomerular injury during RAS blockade in pediatric IgAN patients.

Urinary Angiotensinogen Could Be a Prognostic Marker of Renoprotective Effects of Alogliptin in Patients with Type 2 Diabetes

BACKGROUND

The aims of this study were (1) to examine the renoprotective effects of alogliptin and (2) to establish urinary angiotensinogen (AGT) as a prognostic marker of renoprotective effects of alogliptin in patients with type 2 diabetes (T2D).

METHODS

In 43 patients with T2D (18 women, 66.1 ± 1.71 years), 25 mg/day of alogliptin was added to the traditional hypoglycemic agents and/or nondrug treatments. Urinary concentrations of albumin (Alb) and AGT, normalized by urinary concentrations of creatinine (Cr) (UAlbCR and UAGTCR, respectively), were measured before and after the 12-week alogliptin treatment.

RESULTS

Alogliptin treatment tended to decrease UAlbCR (99.6 ± 26.8 versus 114.6 ± 36.0 mg/g Cr, P = 0.198). Based on % change in UAlbCR, patients were divided into two groups, responders (< -25%) and nonresponders (≥ -25%), and a logistic analysis of UAGTCR before treatment showed cutoff value of 20.8 µg/g Cr. When all patients were redivided into two groups, those with higher values of UAGTCR before the treatment (Group H, n = 20) and those with lower values (Group L), Group H showed significantly decreased UAlbCR in response to alogliptin (-14.6 ± 8.6 versus +22.8 ± 16.8%, P = 0.033).

CONCLUSION

Urinary AGT could be a prognostic marker of renoprotective effects of alogliptin in patients with T2D.

Up-regulation of intrarenal renin-agiotensin system contributes to renal damage in high-salt induced hypertension rats

BACKGROUND/AIMS

To investigate the change of intrarenal renin-agiotensin system (RAS) and its role in high-salt induced hypertension.

METHODS

Wistar rats were divided into normal-salt (NS), high-salt diet (HS) and high-salt diet with Losartan group (HS+L), for 6 weeks. Systolic blood pressure (SBP) was monitored. Blood and urine samples were collected every 2 weeks. Angiotensinogen (AGT) was measured by ELISA. AGT mRNA and protein were measured by real-time PCR and immunohistochemistry. Renin activity and angiotensin II (Ang II) were measured by radioimmunoassay.

RESULTS

HS versus NS group, SBP increased from 2(nd) week (P<0.05), urinary protein increased at 6(th) week (P<0.05). Although plasma renin, AGT and Ang II had no significant changes (P>0.05), renal cortex renin, AGT, and Ang II increased significantly in HS (P<0.05). In HS+L, Losartan failed to reduce SBP (P>0.05) but abolished the increase of proteinuria (P<0.01), renal cortex renin, AGT, Ang II and urinary AGT reduced (P<0.05) while plasma renin, AGT and Ang II enhanced (P<0.05) when compared with HS. Urinary AGT was positively correlated with renal AGT (r=0.592, P <0.01) and Ang II (r=0.726, P <0.01).

CONCLUSION

Inappropriate response of the renal RAS to a high salt diet may contribute to hypertension and renal damage, and urinary AGT could reflect intrarenal RAS activity.

Detailed localization of augmented angiotensinogen mRNA and protein in proximal tubule segments of diabetic kidneys in rats and humans

In the intrarenal renin-angiotensin system, angiotensinogen levels are well known to be increased in diabetes, and these enhanced intrarenal angiotensinogen levels may initiate the development and accelerate the progression of diabetic nephropathy. However, the specific localization of the augmented angiotensinogen in proximal tubule segments in diabetes is still unknown. We investigated the detailed localization of angiotensinogen in 3 proximal tubule segments in the diabetic Otsuka Long-Evans Tokushima fatty (OLETF) rats and the control Long-Evans Tokushima Otsuka (LETO) rats. We also prepared OLETF rats treated with angiotensin II type 1 receptor blocker, olmesartan or with a combination of vasodilator agents. Moreover, biopsied samples of human kidney cortex were used to confirm the results of animal studies. We examined the co-localization of angiotensinogen with segment-specific markers by double staining using fluorescence in situ hybridization and/or immunofluorescence. Angiotensinogen mRNA expression was barely detectable in segment 1. In segment 3, the area of angiotensinogen mRNA expression was augmented in the OLETF rats compared with the LETO rats. Angiotensinogen protein expression areas in segments 1 and 3 were also increased in the OLETF rats compared with the LETO rats. Chronic treatment with olmesartan ameliorated these areas of augmented angiotensinogen expression. Biopsied human kidney samples showed similar results. These data suggest that the augmented angiotensinogen mRNA levels in segment 3 and angiotensinogen protein levels in segments 1 and 3 may contribute to the progression of diabetic nephropathy.

Insulin treatment attenuates renal ADAM17 and ACE2 shedding in diabetic Akita mice

Angiotensin-converting enzyme 2 (ACE2) is located in several tissues and is highly expressed in renal proximal tubules, where it degrades the vasoconstrictor angiotensin II (ANG II) to ANG-(1-7). Accumulating evidence supports protective roles of ACE2 in several disease states, including diabetic nephropathy. A disintegrin and metalloprotease (ADAM) 17 is involved in the shedding of several transmembrane proteins, including ACE2. Our previous studies showed increased renal ACE2, ADAM17 expression, and urinary ACE2 in type 2 diabetic mice (Chodavarapu H, Grobe N, Somineni HK, Salem ES, Madhu M, Elased KM. PLoS One 8: e62833, 2013). The aim of the present study was to determine the effect of insulin on ACE2 shedding and ADAM17 in type 1 diabetic Akita mice. Results demonstrate increased renal ACE2 and ADAM17 expression and increased urinary ACE2 fragments (≈70 kDa) and albumin excretion in diabetic Akita mice. Immunostaining revealed colocalization of ACE2 with ADAM17 in renal tubules. Renal proximal tubular cells treated with ADAM17 inhibitor showed reduced ACE2 shedding into the media, confirming ADAM17-mediated shedding of ACE2. Treatment of Akita mice with insulin implants for 20 wk normalized hyperglycemia and decreased urinary ACE2 and albumin excretion. Insulin also normalized renal ACE2 and ADAM17 but had no effect on tissue inhibitor of metalloproteinase 3 (TIMP3) protein expression. There was a positive linear correlation between urinary ACE2 and albuminuria, blood glucose, plasma creatinine, glucagon, and triglycerides. This is the first report showing an association between hyperglycemia, cardiovascular risk factors, and increased shedding of urinary ACE2 in diabetic Akita mice. Urinary ACE2 could be used as a biomarker for diabetic nephropathy and as an index of intrarenal ACE2 status.

Insulin treatment attenuates renal ADAM17 and ACE2 shedding in diabetic Akita mice

Angiotensin-converting enzyme 2 (ACE2) is located in several tissues and is highly expressed in renal proximal tubules, where it degrades the vasoconstrictor angiotensin II (ANG II) to ANG-(1-7). Accumulating evidence supports protective roles of ACE2 in several disease states, including diabetic nephropathy. A disintegrin and metalloprotease (ADAM) 17 is involved in the shedding of several transmembrane proteins, including ACE2. Our previous studies showed increased renal ACE2, ADAM17 expression, and urinary ACE2 in type 2 diabetic mice (Chodavarapu H, Grobe N, Somineni HK, Salem ES, Madhu M, Elased KM. PLoS One 8: e62833, 2013). The aim of the present study was to determine the effect of insulin on ACE2 shedding and ADAM17 in type 1 diabetic Akita mice. Results demonstrate increased renal ACE2 and ADAM17 expression and increased urinary ACE2 fragments (≈70 kDa) and albumin excretion in diabetic Akita mice. Immunostaining revealed colocalization of ACE2 with ADAM17 in renal tubules. Renal proximal tubular cells treated with ADAM17 inhibitor showed reduced ACE2 shedding into the media, confirming ADAM17-mediated shedding of ACE2. Treatment of Akita mice with insulin implants for 20 wk normalized hyperglycemia and decreased urinary ACE2 and albumin excretion. Insulin also normalized renal ACE2 and ADAM17 but had no effect on tissue inhibitor of metalloproteinase 3 (TIMP3) protein expression. There was a positive linear correlation between urinary ACE2 and albuminuria, blood glucose, plasma creatinine, glucagon, and triglycerides. This is the first report showing an association between hyperglycemia, cardiovascular risk factors, and increased shedding of urinary ACE2 in diabetic Akita mice. Urinary ACE2 could be used as a biomarker for diabetic nephropathy and as an index of intrarenal ACE2 status.

Glomerular angiotensin-converting enzyme 2 in pediatric IgA nephropathy

BACKGROUND

Angiotensin-converting enzyme (ACE) 2 is a homolog of ACE and is thought to be a potent counter-regulator against ACE activity. However, the role of ACE2 has not been investigated in pediatric patients with IgA nephropathy (IgAN). This study was performed to examine the relationship between ACE2 expression and the development of pediatric IgAN.

METHODS

We performed immunohistochemical analysis of ACE2 and ACE in 39 patients with pediatric IgAN and 14 patients with minor glomerular abnormalities, and elucidated the effects of various cytokines on ACE2 expression in cultured human mesangial cells.

RESULTS

ACE2 expression levels in glomeruli and tubules were positively correlated with the mesangial hypercellularity score, while ACE expression levels in glomeruli and tubules are not. Multiple regression analysis showed that the mesangial hypercellularity score correlated with the ACE2 expression level in glomeruli and the urinary protein-creatinine ratio. In IgAN patients not treated with a renin-angiotensin system blocker, ACE2 expression levels in glomeruli were significantly increased compared to patients with minor glomerular abnormalities. IgAN patients treated with a renin-angiotensin system blocker did not show this increase in ACE2 expression. Furthermore, cultured human MC showed increased ACE2 mRNA and protein after treatment with IL-1β, a pro-inflammatory cytokine in IgAN. In fact, glomerular expressions of IL-1β were remarkably increased in patients with IgAN.

CONCLUSION

These data indicate that ACE2 expression in glomeruli is associated with mesangial hypercellularity in early lesions of pediatric IgAN.