Microalbuminuria breakthrough under chronic renin-angiotensin-aldosterone system suppression

Prevention of cardiorenal damage: importance of albuminuria

Chronic kidney disease (CKD) is projected to become a leading global cause of death by 2040, and its early detection is critical for effective and timely management. The current definition of CKD identifies only advanced stages, when kidney injury has already destroyed >50% of functioning kidney mass as reflected by an estimated glomerular filtration rate <60 mL/min/1.73 m2 or a urinary albumin/creatinine ratio >six-fold higher than physiological levels (i.e. > 30 mg/g). An elevated urinary albumin-excretion rate is a known early predictor of future cardiovascular events. There is thus a ‘blind spot’ in the detection of CKD, when kidney injury is present but is undetectable by current diagnostic criteria, and no intervention is made before renal and cardiovascular damage occurs. The present review discusses the CKD ‘blind spot’ concept and how it may facilitate a holistic approach to CKD and cardiovascular disease prevention and implement the call for albuminuria screening implicit in current guidelines. Cardiorenal risk associated with albuminuria in the high-normal range, novel genetic and biochemical markers of elevated cardiorenal risk, and the role of heart and kidney protective drugs evaluated in recent clinical trials are also discussed. As albuminuria is a major risk factor for cardiovascular and renal disease, starting from levels not yet considered in the definition of CKD, the implementation of opportunistic or systematic albuminuria screening and therapy, possibly complemented with novel early biomarkers, has the potential to improve cardiorenal outcomes and mitigate the dismal 2040 projections for CKD and related cardiovascular burden.

Early renal and vascular damage within the normoalbuminuria condition

OBJECTIVE

A continuous association between albuminuria and cardiorenal risk exists further below moderately increased albuminuria ranges. If only based in albumin to creatinine ratio (ACR) higher than 30 mg/g, a significant percentage of individuals may be out of the scope for therapeutic management. Despite epidemiological outcomes, the identification of biochemical changes linked to early albuminuria is underexplored, and normoalbuminuric individuals are usually considered at no risk in clinical practice. Here, we aimed to identify early molecular alterations behind albuminuria development.

METHODS

Hypertensive patients under renin-angiotensin system (RAS) suppression were classified as control, (ACR < 10 mg/g) or high-normal (ACR = 10-30 mg/g). Urinary protein alterations were quantified and confirmed by untargeted and targeted mass spectrometry. Coordinated protein responses with biological significance in albuminuria development were investigated. Immunohistochemistry assays were performed in human kidney and arterial tissue to in situ evaluate the associated damage.

RESULTS

A total of 2663 identified proteins reflect inflammation, immune response, ion transport and lipids metabolism (P value ≤ 0.01). A1AT, VTDB and KNG1 varied in high-normal individuals (P value < 0.05), correlated with ACR and associated with the high-normal condition (odds ratio of 20.76, 6.00 and 7.04 were found, respectively (P value < 0.001)). After 12 months, protein variations persist and aggravate in progressors to moderately increased albuminuria. At tissue level, differential protein expression was found in kidney from individuals with moderately increased albuminuria and atherosclerotic aortas for the three proteins, confirming their capacity to reflect subclinical organ damage.

CONCLUSION

Early renal and vascular damage is molecularly evidenced within the normoalbuminuria condition.

TCA Cycle and Fatty Acids Oxidation Reflect Early Cardiorenal Damage in Normoalbuminuric Subjects with Controlled Hypertension

Moderately increased albuminuria, defined by an albumin to creatinine ratio (ACR) > 30 mg/g, is an indicator of subclinical organ damage associated with a higher risk of cardiovascular and renal disease. Normoalbuminuric subjects are considered at no cardiorenal risk in clinical practice, and molecular changes underlying early development are unclear. To decipher subjacent mechanisms, we stratified the normoalbuminuria condition. A total of 37 hypertensive patients under chronic renin–angiotensin system (RAS) suppression with ACR values in the normoalbuminuria range were included and classified as control (C) (ACR < 10 mg/g) and high-normal (HN) (ACR = 10–30 mg/g). Target metabolomic analysis was carried out by liquid chromatography and mass spectrometry to investigate the role of the cardiorenal risk urinary metabolites previously identified. Besides this, urinary free fatty acids (FFAs), fatty acid binding protein 1 (FABP1) and nephrin were analyzed by colorimetric and ELISA assays. A Mann–Whitney test was applied, ROC curves were calculated and Spearman correlation analysis was carried out. Nine metabolites showed significantly altered abundance in HN versus C, and urinary FFAs and FABP1 increased in HN group, pointing to dysregulation in the tricarboxylic acid cycle (TCA) cycle and fatty acids β-oxidation. We showed here how cardiorenal metabolites associate with albuminuria, already in the normoalbuminuric range, evidencing early renal damage at a tubular level and suggesting increased β-oxidation to potentially counteract fatty acids overload in the HN range.

Effects of antihypertensive medication and high-intensity interval training in hypertensive metabolic syndrome individuals

Pharmacological and non-pharmacological therapies are simultaneously prescribed when treating hypertensive individuals with elevated cardiovascular risk (ie, metabolic syndrome individuals). However, it is unknown if the interactions between antihypertensive medication (AHM) and lifestyle interventions (ie, exercise training) may result in a better ambulatory blood pressure (ABP) control. To test this hypothesis, 36 hypertensive individuals with metabolic syndrome (MetS) under long-term prescription with AHM targeting the renin-angiotensin-aldosterone system (RAAS) were recruited. Before and after 4 months of high-intensity interval training (HIIT), participants completed two trials in a double-blind, randomized order: (a) placebo trial consisting of AHM withdrawal for 3 days and (b) AHM trial where individuals held their habitual dose of AHM. In each trial, 24-h mean arterial pressure (MAP) was monitored and considered the primary study outcome. Secondary outcomes included plasma renin activity (PRA) and aldosterone concentration to confirm withdrawal effects on RAAS, along with the analysis of urine albumin-to-creatinine ratio (UACR) to assess kidney function. The results showed main effects from AHM and HIIT reducing 24-h MAP (-5.7 mmHg, p < 0.001 and -2.3 mmHg, p = 0.007, respectively). However, there was not interaction between AHM and HIIT on 24-h MAP (p = 0.240). There was a main effect of AHM increasing PRA (p < 0.001) but no effect on plasma aldosterone concentration (p = 0.368). HIIT did not significantly improve RAAS hormones or the UACR. In conclusion, AHM and HIIT have independent and additive effects in lowering ABP. These findings support the combination of habitual AHM with exercise training with the goal to reduce ABP in hypertensive MetS individuals.

Differential metabolic profile associated with the condition of normoalbuminuria in the hypertensive population

BACKGROUND AND AIM

Albuminuria is an indicator of sub-clinical organ damage and a marker of cardiovascular risk and renal disease. A percentage of hypertensive patients develop albuminuria despite being under chronic suppression of the renin-angiotensin system (RAS). We previously identified urinary metabolites associated with the development of albuminuria. In this study, we searched for metabolic alterations which reflect different levels within the condition of normoalbuminuria.

PATIENTS, MATERIALS AND METHODS

Urine from 48 hypertensive patients under chronic RAS suppression was analysed. They were classified according to the albumin/creatinine ratio (ACR) into 3groups: Normoalbuminuria (<10mg/g); high-normal (10-30mg/g in men, or 20-40mg/g in women); and moderately high albuminuria (microalbuminuria, 30-200mg/g or 40-300mg/g, respectively). The metabolome was analysed by mass spectrometry and a correlation analysis was performed between altered metabolite levels and ACR.

RESULTS

Oxaloacetate, 3-ureidopropionate, guanidoacetate and malate show significant variation between the normo and micro groups. Additionally, these metabolites are able to differentiate between patients in the normo and high-normal range. A significant correlation between metabolites and ACR was found. Observed variations point to alterations in the energy metabolism already in patients with albuminuria in the high-normal range.

CONCLUSIONS

The association between the molecular panel consisting of 3-ureidopropionate, oxaloacetate, malate and guanidoacetate and different levels of albuminuria is confirmed. A metabolic fingerprint was also identified showing variations within the condition of normoalbuminuria allowing an earlier molecular stratification of patients.

A Prospective Single-Blind Randomized Trial of Ramipril, Eplerenone and Their Combination in Type 2 Diabetic Nephropathy

<b><i>Introduction:</i></b> Angiotensin-converting enzyme inhibitors (ACEI) combined with mineralocorticoid receptor antagonists were found to have a beneficial effect on patients with chronic kidney disease. <b><i>Objective:</i></b> The aim of our clinical trial was to compare the antialbuminuric effect of ramipril monotherapy, eplerenone monotherapy and eplerenone/ramipril combination therapy in patients with stage 1 hypertension and type 2 diabetes mellitus. <b><i>Methods:</i></b> In a single-blind, randomized clinical trial, 75 hypertensive patients (stage 1 hypertension) with type 2 diabetes mellitus and microalbuminuria were randomized in a 1:1:1 ratio to 1 of 3 groups: ramipril 10 mg monotherapy (25 patients), eplerenone 50 mg monotherapy (25 patients) and combination therapy of eplerenone/ramipril 50/10 mg (25 patients) through a randomized clinical trial. Blood pressure, urinary albumin/creatinine ratio (UACR), serum creatinine, estimated glomerular filtration rate (eGFR) and serum K level were measured before randomization and after 24 weeks. <b><i>Results:</i></b> Ramipril and eplerenone monotherapy showed a significant lowering of UACR compared with baseline levels (<i>p</i> ≤ 0.0001). The eplerenone/ramipril combination group showed a more significant reduction of UACR compared with the ramipril and eplerenone monotherapy groups (<i>p</i> = 0.0001). There was a more significant lowering of systolic blood pressure in the combination group (<i>p</i> &#x3c; 0.0001). A nonsignificant change of serum potassium level, serum creatinine and eGFR was found among the 3 groups. <b><i>Conclusion:</i></b> Addition of eplerenone to ACEI shows an added antialbuminuric effect without significant change of the serum K level compared with eplerenone or ACEI.

The endless story of markers of renal function and cardiovascular risk

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Association between renal dysfunction and metalloproteinase (MMP)-9 activity in hypertensive patients

BACKGROUND AND OBJECTIVE

Matrix metalloproteinases (MMPs) are involved in deleterious tissue remodeling associated with target organ damage in renal disease. The aim of this study was to study the association between renal dysfunction and activity of the inflammatory metalloproteinase MMP-9 in hypertensive patients with mild-moderate chronic kidney disease (CKD).

MATERIAL AND METHODS

Plasmatic active MMP-9, total MMP-9, tissue inhibitor of MMP-9 (TIMP-1), MMP-9/TIMP-1 ratio and MMP-9-TIMP-1 interaction were analyzed in 37 hypertensive patients distributed by estimated glomerular filtration rate (eGFR) in 3 groups:>90, 90-60 y 60-30mL/min/1.73 m².

RESULTS

Total MMP-9 was not different as eGFR declines. TIMP-1 was significantly increased in hypertensive patients with eGFR 60-30mL/min/1.73 m² (P<.01 versus>90mL/min/1.73 m²). This relates to the significant decrease in the interaction between MMP-9-TIMP-1 observed in patients with eGFR 60-30mL/min/1.73 m² (P<.01 versus>90mL/min/1.73 m²). Despite the systemic elevation of TIMP-1, active MMP-9 was significantly increased in hypertensive patients with eGFR 60-30mL/min/1.73 m² (P<.05 and P<0.01 versus>90 and 90-60mL/min/1.73 m², respectively). TIMP-1, active MMP-9 and MMP-9-TIMP-1 interaction significantly correlate with the decline in renal function, which was not observed with total MMP-9.

CONCLUSIONS

The progression of CKD, even in stages where the decline of renal function is still moderate, is associated with an increase in MMP-9 activity, which could be considered as a potential therapeutic target.

Long-Term Effects of Spironolactone on Kidney Function and Hyperkalemia-Associated Hospitalization in Patients with Chronic Kidney Disease

Background: Spironolactone, a non-selective mineralocorticoid receptor antagonist, can protect against cardiac fibrosis and left ventricular dysfunction, and improve endothelial dysfunction and proteinuria. However, the safety and effects of spironolactone on patient-centered cardiovascular and renal endpoints remain unclear. Methods: We identified predialysis stage 3–4 chronic kidney disease (CKD) patients between 2000 and 2013 from the Longitudinal Health Insurance Database 2005 (LHID 2005). The outcomes of interest were end-stage renal disease (ESRD), major adverse cardiovascular events (MACE), hospitalization for heart failure (HHF), hyperkalemia-associated hospitalization (HKAH), all-cause mortality and cardiovascular mortality. The Fine and Gray sub-distribution hazards approach was adopted to adjust for the competing risk of death. Results: After the propensity score matching, 693 patients with stage 3–4 CKD were spironolactone users and 1386 were nonusers. During the follow-up period, spironolactone users had a lower incidence rate for ESRD than spironolactone non-users (39.2 vs. 53.69 per 1000 person-years) and a higher incidence rate for HKAH (54.79 vs. 18.57 per 1000 person-years). The adjusted hazard ratios for ESRD of spironolactone users versus non-users were 0.66 (95% CI, 0.51–0.84; p value < 0.001) and 3.17 (95% CI, 2.41–4.17; p value < 0.001) for HKAH. A dose-response relationship was found between spironolactone use and risk of ESRD and HKAH. There were no statistical differences in MACE, HHF, all-cause mortality and cardiovascular mortality between spironolactone users and non-users. Conclusion: Spironolactone represented a promising treatment option to retard CKD progression to ESRD amongst stage 3–4 CKD patients, but strategic treatments to prevent hyperkalemia should be enforced.

Urinary exosomes reveal protein signatures in hypertensive patients with albuminuria

Albuminuria is an indicator of cardiovascular risk and renal damage in hypertensive individuals. Chronic renin-angiotensin system (RAS) suppression facilitates blood pressure control and prevents development of new-onset-albuminuria. A significant number of patients, however, develop albuminuria despite chronic RAS blockade, and the physiopathological mechanisms are underexplored. Urinary exosomes reflect pathological changes taking place in the kidney. The objective of this work was to examine exosomal protein alterations in hypertensive patients with albuminuria in the presence of chronic RAS suppression, to find novel clues underlying its development. Patients were followed-up for three years and were classified as: a) patients with persistent normoalbuminuria; b) patients developing de novo albuminuria; and c) patients with maintained albuminuria. Exosomal protein alterations between groups were identified by isobaric tag quantitation (iTRAQ). Confirmation was approached by target analysis (SRM). In total, 487 proteins were identified with high confidence. Specifically, 48 proteins showed an altered pattern in response to hypertension and/or albuminuria. Out of them, 21 proteins interact together in three main functional clusters: glycosaminoglycan degradation, coagulation and complement system, and oxidative stress. The identified proteins constitute potential targets for drug development and may help to define therapeutic strategies to evade albuminuria progression in hypertensive patients chronically treated.

Translational science in albuminuria: a new view of de novo albuminuria under chronic RAS suppression

The development of de novo albuminuria during chronic renin–angiotensin system (RAS) suppression is a clinical entity that remains poorly recognized in the biomedical literature. It represents a clear increment in global cardiovascular (CV) and renal risk that cannot be counteracted by RAS suppression. Although not specifically considered, it is clear that this entity is present in most published and ongoing trials dealing with the different forms of CV and renal disease. In this review, we focus on the mechanisms promoting albuminuria, and the predictors and new markers of de novo albuminuria, as well as the potential treatment options to counteract the excretion of albumin. The increase in risk that accompanies de novo albuminuria supports the search for early markers and predictors that will allow practising physicians to assess and prevent the development of de novo albuminuria in their patients.

Kalirin and CHD7: novel endothelial dysfunction indicators in circulating extracellular vesicles from hypertensive patients with albuminuria

Despite of the great advances in anti-hypertensive therapies, many patients under Renin-Angiotensin- System (RAS) suppression develop albuminuria, which is a clear indicator of therapeutic inefficiency. Hence, indicators of vascular function are needed to assess patients’ condition and help deciding future therapies.

Proteomic analysis of circulating extracellular vesicles (EVs) showed two proteins, kalirin and chromodomain-helicase-DNA-binding protein 7 (CHD7), increased in albuminuric patients. A positive correlation of both with the expression of the endothelial activation marker E-selectin was found in EVs. In vitro analysis using TNFα-treated adult human endothelial cells proved their involvement in endothelial cell activation.

Hence, we propose protein levels of kalirin and CHD7 in circulating EVs as novel endothelial dysfunction markers to monitor vascular condition in hypertensive patients with albuminuria.

Immune system deregulation in hypertensive patients chronically RAS suppressed developing albuminuria

Albuminuria development in hypertensive patients is an indicator of higher cardiovascular (CV) risk and renal damage. Chronic renin-angiotensin system (RAS) suppression facilitates blood pressure control but it does not prevent from albuminuria development. We pursued the identification of protein indicators in urine behind albuminuria development in hypertensive patients under RAS suppression. Urine was collected from 100 patients classified in three groups according to albuminuria development: (a) patients with persistent normoalbuminuria; (b) patients developing de novo albuminuria; (c) patients with maintained albuminuria. Quantitative analysis was performed in a first discovery cohort by isobaric labeling methodology. Alterations of proteins of interest were confirmed by target mass spectrometry analysis in an independent cohort. A total of 2416 proteins and 1223 functional categories (coordinated protein responses) were identified. Immune response, adhesion of immune and blood cells, and phagocytosis were found significantly altered in patients with albuminuria compared to normoalbuminuric individuals. The complement system C3 increases, while Annexin A1, CD44, S100A8 and S100A9 proteins showed significant diminishment in their urinary levels when albuminuria is present. This study reveals specific links between immune response and controlled hypertension in patients who develop albuminuria, pointing to potential protein targets for novel and future therapeutic interventions.

Maximum renal responses to renin inhibition in healthy study participants: VTP-27999 versus aliskiren

BACKGROUND

Renin inhibition with aliskiren induced the largest increases in renal plasma flow (RPF) in salt-depleted healthy volunteers of all renin-angiotensin system (RAS) blockers. However, given its side-effects at doses higher than 300 mg, no maximum effect of renin inhibition could be established. We hypothesized that VTP-27999, a novel renin inhibitor without major side-effects at high doses, would allow us to establish this.

METHODS AND RESULTS

The effects of escalating VTP-27999 doses (75-600 mg) on RPF, glomerular filtration rate (GFR), and plasma RAS components were compared with those of 300 mg aliskiren in 22 normal volunteers on a low-sodium diet. VTP-27999 dose-dependently increased RPF and GFR; its effects on both parameters at 600 mg (increases of 18 ± 4 and 20 ± 4%, respectively) were equivalent to those at 300 mg, indicating that a maximum had been reached. The effects of 300 mg aliskiren (increases of 13 ± 5 and 8 ± 6%, respectively; P < 0.01 vs. 300 and 600 mg VTP-27999) resembled those of 150 mg VTP-27999. VTP-27999 dose-dependently increased renin, and lowered plasma renin activity and angiotensin II to detection limit levels. The effects of aliskiren on RAS components were best comparable to those of 150 mg VTP-27999.

CONCLUSION

Maximum renal renin blockade in healthy, salt-depleted volunteers, requires aliskiren doses higher than 300 mg, but can be established with 300 mg VTP-27999. To what degree such maximal effects (exceeding those of angiotensin-converting enzyme inhibitors and AT1-receptor blockers) are required in patients with renal disease, given the potential detrimental effects of excessive RAS blockade, remains to be determined.

Hypertensive patients exhibit an altered metabolism. A specific metabolite signature in urine is able to predict albuminuria progression

Hypertension (HTN) is increasing in prevalence, and albuminuria is a strong indicator of cardiovascular risk and renal damage progression. Despite blood pressure control with chronic treatment, a relevant subgroup of patients develop albuminuria. However, the biological factors responsible for albuminuria development and progression are underexplored. We aimed to identify key metabolic targets and biological pathways involved in the negative progression of cardiovascular and renal damage in hypertensives undergoing chronic treatment. A series of 1533 patients were followed for 5 years to investigate the evolution of albuminuria. Patients were classified as: (1) patients with persistent normoalbuminuria; (2) patients developing de novo albuminuria; and (3) patients with maintained albuminuria. At the end of follow-up, urine from 30 nonhypertensive subjects (control group) and a representative cohort of 118 patients was collected for metabolomic analysis. Metabolic patterns of interest were identified in a first discovery phase by nuclear magnetic resonance and further confirmed by liquid chromatography-mass spectrometry. Metabolites corresponding to HTN or albuminuria were measured in a prospective study carried out in 35 individuals still in normoalbuminuria, to evaluate their potential as predictors of albuminuria development. Nine metabolites were significantly altered, linking β-alanine metabolism, arginine and proline metabolism, and tricarboxylic acid cycle. The prospective study revealed a panel composed of guanidinoacetate, glutamate, and pantothenate, which was able to predict development of albuminuria. These metabolic signatures open new possibilities in hypertensive therapy and cardiovascular risk control, providing prompt and more efficient intervention, particularly in patients with worse cardiovascular prognosis.

Association Between High and Very High Albuminuria and Nighttime Blood Pressure: Influence of Diabetes and Chronic Kidney Disease

OBJECTIVE

Nighttime blood pressure (BP) and albuminuria are two important and independent predictors of cardiovascular morbidity and mortality. Here, we examined the quantitative differences in nighttime systolic BP (SBP) across albuminuria levels in patients with and without diabetes and chronic kidney disease.

RESEARCH DESIGN AND METHODS

A total of 16,546 patients from the Spanish Ambulatory Blood Pressure Monitoring Registry cohort (mean age 59.6 years, 54.9% men) were analyzed. Patients were classified according to estimated glomerular filtration rate (eGFR), as ≥60 or <60 mL/min/1.73 m(2) (low eGFR), and urine albumin-to-creatinine ratio, as normoalbuminuria (<30 mg/g), high albuminuria (30-300 mg/g), or very high albuminuria (>300 mg/g). Office and 24-h BP were determined with standardized methods and conditions.

RESULTS

High albuminuria was associated with a statistically significant and clinically substantial higher nighttime SBP (6.8 mmHg higher than with normoalbuminuria, P < 0.001). This association was particularly striking at very high albuminuria among patients with diabetes and low eGFR (16.5 mmHg, P < 0.001). Generalized linear models showed that after full adjustment for demographic, lifestyles, and clinical characteristics, nighttime SBP was 4.8 mmHg higher in patients with high albuminuria than in those with normoalbuminuria (P < 0.001), and patients with very high albuminuria had a 6.1 mmHg greater nighttime SBP than those with high albuminuria (P < 0.001). These differences were 3.8 and 3.1 mmHg, respectively, among patients without diabetes, and 6.5 and 8 mmHg among patients with diabetes (P < 0.001).

CONCLUSIONS

Albuminuria in hypertensive patients is accompanied by quantitatively striking higher nighttime SBP, particularly in those with diabetes with very high albuminuria and low eGFR.

Effect of mineralocorticoid receptor antagonists on proteinuria and progression of chronic kidney disease: a systematic review and meta-analysis

BACKGROUND

Hypertension and proteinuria are critically involved in the progression of chronic kidney disease. Despite treatment with renin angiotensin system inhibition, kidney function declines in many patients. Aldosterone excess is a risk factor for progression of kidney disease. Hyperkalaemia is a concern with the use of mineralocorticoid receptor antagonists. We aimed to determine whether the renal protective benefits of mineralocorticoid antagonists outweigh the risk of hyperkalaemia associated with this treatment in patients with chronic kidney disease.

METHODS

We conducted a meta-analysis investigating renoprotective effects and risk of hyperkalaemia in trials of mineralocorticoid receptor antagonists in chronic kidney disease. Trials were identified from MEDLINE (1966-2014), EMBASE (1947-2014) and the Cochrane Clinical Trials Database. Unpublished summary data were obtained from investigators. We included randomised controlled trials, and the first period of randomised cross over trials lasting ≥4 weeks in adults.

RESULTS

Nineteen trials (21 study groups, 1 646 patients) were included. In random effects meta-analysis, addition of mineralocorticoid receptor antagonists to renin angiotensin system inhibition resulted in a reduction from baseline in systolic blood pressure (-5.7 [-9.0, -2.3] mmHg), diastolic blood pressure (-1.7 [-3.4, -0.1] mmHg) and glomerular filtration rate (-3.2 [-5.4, -1.0] mL/min/1.73 m(2)). Mineralocorticoid receptor antagonism reduced weighted mean protein/albumin excretion by 38.7 % but with a threefold higher relative risk of withdrawing from the trial due to hyperkalaemia (3.21, [1.19, 8.71]). Death, cardiovascular events and hard renal end points were not reported in sufficient numbers to analyse.

CONCLUSIONS

Mineralocorticoid receptor antagonism reduces blood pressure and urinary protein/albumin excretion with a quantifiable risk of hyperkalaemia above predefined study upper limit.

Plasma Molecular Signatures in Hypertensive Patients With Renin–Angiotensin System Suppression

Albuminuria is a risk factor strongly associated with cardiovascular disease, the first cause of death in the general population. It is well established that renin–angiotensin system suppressors prevent the development of new-onset albuminuria in naïf hypertensive patients and diminish its excretion, but we cannot forget the percentage of hypertensive patients who develop de novo albuminuria. Here, we applied multiple proteomic strategy with the purpose to elucidate specific molecular pathways involved in the pathogenesis and provide predictors and chronic organ damage indicators. Briefly, 1143 patients were followed up for a minimum period of 3 years. One hundred and twenty-nine hypertensive patients chronically renin–angiotensin system suppressed were recruited, classified in 3 different groups depending on their albuminuria levels (normoalbuminuria, de novo albuminuria, and sustained albuminuria), and investigated by multiple proteomic strategies. Our strategy allowed us to perform one of the deepest plasma proteomic analysis to date, which has shown 2 proteomic signatures: (1) with predictive value of de novo albuminuria and (2) sustained albuminuria indicator proteins. These proteins are involved in inflammation, immune as well as in the proteasome activation occurring in situations of endoplasmic reticulum stress. Furthermore, these results open the possibility of a future strategy based on anti-immune therapy to treat hypertension which could help to prevent the development of albuminuria and, hence, the progression of kidney damage.

Development of albuminuria and enhancement of oxidative stress during chronic renin-angiotensin system suppression

OBJECTIVE

Albuminuria has been recently described in hypertensive patients under chronic renin-angiotensin system (RAS) suppression. We investigated whether this fact could be related to an increase in oxidative stress.

METHODS

We examined normoalbuminuric and albuminuric patients in stage 2 chronic kidney disease, both with more than 2 years of RAS blockade. The relationship between albuminuria and circulating biomarkers for both oxidative damage, that is carbonyl and malondialdehyde, as well as antioxidant defense, that is reduced glutathione, thiol groups, uric acid, bilirubin, or catalase, and superoxide scavenging activity, was assessed.

RESULTS

We found that only patients with albuminuria showed an important increase in carbonyls (P < 0.001) and malondialdehyde (P < 0.05) compared to normoalbuminuric patients. This increase in oxidative damage was also accompanied by a rise in catalase activity (P < 0.05) and low-molecular-weight antioxidants only when they were measured as total antioxidant capacity (P < 0.01). In order to establish the specific oxidative status of each group, new indexes of oxidative damage and antioxidant defense were calculated with all these markers following a mathematical and statistical approach. Although both pro-oxidant and antioxidant indexes were significantly increased in patients with albuminuria, only the oxidative damage index positively correlated with the increase of albumin/creatinine ratio (P = 0.0024).

CONCLUSIONS

We conclude that albuminuria is accompanied by an amplified oxidative damage in patients in early stages of chronic kidney disease. These results indicate that chronic RAS protection must be directed to avoid development of albuminuria and oxidative damage.

[Cardiovascular risk study in patients with renin-angiotensin system blockade by means of the proteone of circulating extracellular vesicles]

INTRODUCTION

Extracellular vesicles (EVs) are released to the bloodstream by certain cell types due to transport, activation and cell death processes. Blood count of EVs from platelet and endothelial origin has been proved to be a cardiovascular risk biomarker. Thus, EVs proteome might reflect the underlying cellular processes in hypertensive patients with albuminuria.

MATERIAL AND METHODS

Protein content of circulating EVs was analyzed by liquid chromatography coupled to mass spectrometry. EVs were isolated by an ultracentrifugation protocol optimized in order to avoid contamination by blood plasma proteins. Purity of the isolated fraction was verified by electronic and confocal microscopy, and by flow cytometry.

RESULTS

We hereby show a method to isolate circulating EVs from hypertensive patients with/without albuminuria with high yield and purity. Besides, we provide a reference proteome of the EVs of these patients, composed of 2,463 proteins, and prove that the proteins carried by these vesicles are associated with crucial processes involved in the inherent cardiovascular risk.

CONCLUSION

The proteome of circulating EVs is an interesting source of indicators in the evaluation of cardiovascular risk in hypertensive patients with renin-angiotensin system blockage.

Urinary alpha-1 antitrypsin and CD59 glycoprotein predict albuminuria development in hypertensive patients under chronic renin-angiotensin system suppression

BACKGROUND

Hypertension is a multi-factorial disease of increasing prevalence and a major risk factor for cardiovascular mortality even in the presence of adequate treatment. Progression of cardiovascular disease (CVD) occurs frequently during chronic renin-angiotensin-system (RAS) suppression, and albuminuria is a marker of CV risk. High prevalence of albuminuria in treated hypertensive patients has been demonstrated, but there are no available markers able to predict evolution. The aim of this study was the identification of novel indicators of albuminuria progression measurable in urine of diabetic and non-diabetic patients.

METHODS

1143 hypertensive patients under chronic treatment were followed for a minimum period of 3 years. Among them, 105 diabetic and non-diabetic patients were selected and classified in three groups according to albuminuria development during follow-up: (a) patients with persistent normoalbuminuria; (b) patients developing de novo albuminuria; (c) patients with maintained albuminuria. Differential urine analysis was performed by 2D gel electrophoresis (2D-DIGE) and further confirmed by liquid chromatography-mass spectrometry. Non-parametric statistical tests were applied.

RESULTS

CD59 glycoprotein and alpha-1 antitrypsin (AAT) resulted already altered in patients developing albuminuria de novo, with a similar response in those with maintained albuminuria. A prospective study in a sub-group of normoalbuminuric patients who were clinically followed up for at least 1 year from urine sampling, revealed CD59 and AAT proteins significantly varied in the urine collected from normoalbuminurics who will negatively progress, serving as predictors of future albuminuria development.

CONCLUSIONS

CD59 and AAT proteins are significantly altered in hypertensive patients developing albuminuria. Interestingly, CD59 and AAT are able to predict, in normoalbuminuric individuals, who will develop albuminuria in the future, being potential predictors of vascular damage and CV risk. These findings contribute to early identify patients at risk of developing albuminuria even when this classical predictor is still in the normal range, constituting a novel strategy towards a prompt and more efficient therapeutic intervention with better outcome.

Role of matrix metalloproteinase-9 in chronic kidney disease: a new biomarker of resistant albuminuria

Resistant albuminuria, developed under adequate chronic blockade of the renin-angiotensin system, is a clinical problem present in a small number of patients with chronic kidney disease (CKD). The mechanism underlying this resistant albuminuria remains unknown. Matrix metalloproteinases (MMPs) are involved in the pathophysiology of cardiovascular and renal diseases. In the present study we tested the role of MMPs in resistant albuminuria. First we evaluated gelatinase MMP-2 and MMP-9 activity by zymography in the Munich Wistar Frömter (MWF) rat, a model of progressive albuminuria, and subsequently in patients with resistant albuminuria. Markers of oxidative stress were observed in the kidneys of MWF rats, together with a significant increase in pro-MMP-2 and active MMP-9 forms. These changes were normalized together with reduced albuminuria in consomic MWF-8(SHR) rats, in which chromosome 8 of MWF was replaced with the respective chromosome from spontaneously hypertensive rats. The MMP-2 and MMP-9 protein levels were similar in patients with normal and resistant albuminuria; however, high circulating levels of collagen IV, a specific biomarker of tissue collagen IV degradation, were observed in patients with resistant albuminuria. These patients showed a significant increase in gelatinase MMP-2 and MMP-9 activity, but only a significant increase in the active MMP-9 form quantified by ELISA, which correlated significantly with the degree of albuminuria. Although the expression of the tissue inhibitor of MMP-9 (TIMP)-1 was similar, a novel AlphaLISA assay demonstrated that the MMP-9-TIMP-1 interaction was reduced in patients with resistant albuminuria. It is of interest that oxidized TIMP-1 expression was higher in patients with resistant albuminuria. Therefore, increased circulating MMP-9 activity is associated with resistant albuminuria and a deleterious oxidative stress environment appears to be the underlying mechanism. These changes might contribute to the progression of CKD in these patients.

Genetic predisposition to albuminuria is associated with increased arterial stiffness: role of elastin

BACKGROUND AND PURPOSE

The Munich Wistar Frömter (MWF) rat strain represents an experimental model to study cardiovascular alterations under conditions of progressive albuminuria. The aim of this study was to evaluate the association between genetic predisposition to albuminuria and the development of arterial stiffness and/or vascular remodelling.

EXPERIMENTAL APPROACH

Experiments were performed in mesenteric arteries from 12-week-old MWF, Wistar Kyoto (WKY) and consomic MWF-6(SHR) and MWF-8(SHR) rats in which chromosomes 6 or 8 associated with albuminuria from MWF were replaced by the respective chromosome from spontaneously hypertensive rats (SHR).

KEY RESULTS

Incremental distensibility, wall stress and strain were reduced, and arterial stiffness was significantly increased in albuminuric MWF compared with WKY. Albuminuria suppression in both consomic strains was associated with lower β-values in MWF-8(SHR) and MWF-6(SHR) compared with MWF. Moreover, elastin content was significantly lower in MWF external elastic lamina compared with WKY and both consomic strains. In addition, a reduction in arterial external and internal diameter and cross-sectional area was detected in MWF compared with WKY, thus exhibiting an inward hypotrophic remodelling. However, these alterations remained unchanged in both consomic strains.

CONCLUSION AND IMPLICATIONS

These data demonstrate that albuminuria in MWF is associated with increased arterial stiffness due to a reduction of elastin content in the external elastic lamina. Moreover, inward hypotrophic remodelling in MWF is not directly associated with albuminuria. In contrast, we demonstrated that two major genetic loci affect both the development of albuminuria and arterial stiffness, thus linking albuminuria and impairment of mechanical properties of resistance arteries.

The necessity and effectiveness of mineralocorticoid receptor antagonist in the treatment of diabetic nephropathy

Diabetes mellitus is a major cause of chronic kidney disease (CKD), and diabetic nephropathy is the most common primary disease necessitating dialysis treatment in the world including Japan. Major guidelines for treatment of hypertension in Japan, the United States and Europe recommend the use of angiotensin-converting enzyme inhibitors and angiotensin-receptor blockers, which suppress the renin-angiotensin system (RAS), as the antihypertensive drugs of first choice in patients with coexisting diabetes. However, even with the administration of RAS inhibitors, failure to achieve adequate anti-albuminuric, renoprotective effects and a reduction in cardiovascular events has also been reported. Inadequate blockade of aldosterone may be one of the reasons why long-term administration of RAS inhibitors may not be sufficiently effective in patients with diabetic nephropathy. This review focuses on treatment in diabetic nephropathy and discusses the significance of aldosterone blockade. In pre-nephropathy without overt nephropathy, a mineralocorticoid receptor antagonist can be used to enhance the blood pressure-lowering effects of RAS inhibitors, improve insulin resistance and prevent clinical progression of nephropathy. In CKD categories A2 and A3, the addition of a mineralocorticoid receptor antagonist to an RAS inhibitor can help to maintain 'long-term' antiproteinuric and anti-albuminuric effects. However, in category G3a and higher, sufficient attention must be paid to hyperkalemia. Mineralocorticoid receptor antagonists are not currently recommended as standard treatment in diabetic nephropathy. However, many studies have shown promise of better renoprotective effects if mineralocorticoid receptor antagonists are appropriately used.

Efficacy of single-pill perindopril/indapamide in patients with hypertension and type 2 diabetes

OBJECTIVE

Hypertension and type 2 diabetes in combination are associated with a significantly higher level of cardiovascular events. The aim of this prospective study was to evaluate the antihypertensive efficacy and tolerability of single-pill perindopril/indapamide in patients with hypertension and type 2 diabetes.

DESIGN AND METHODS

Patients with both hypertension and type 2 diabetes were enrolled in this multicenter, prospective, open clinical study. Single-pill perindopril/indapamide was either prescribed on its own (started or switched to from previous treatment) or added to previous therapy. Perindopril/indapamide dosage could be increased, from 5/1.25 mg to 10/2.5 mg once daily, if blood pressure (BP) was uncontrolled. BP and tolerability were assessed at 4 visits over a 6-month period. Microalbuminuria was assessed at baseline and 6 months in a subgroup.

RESULTS

397 patients were analyzed (age 57.6 ± 9.4 years, men 46 %). At baseline, systolic blood pressure (SBP) was 160.0 ± 14.3 mmHg, diastolic blood pressure (DBP) 95.2 ± 8.3 mmHg, and pulse pressure 64.8 ± 12.7 mmHg. Nearly half (45 %) of patients received perindopril/indapamide alone and 55 % added this single-pill combination to existing therapy. After 6 months, SBP fell by 30 mmHg, DBP by 14 mmHg, and pulse pressure by 16 mmHg (all p < 0.0001). SBP was normalized (<140 mmHg) in 84 % of patients who took perindopril/indapamide 5/1.25 mg alone and in 90 % of patients who took perindopril/indapamide 10/2.5 mg alone. Tolerability was rated "good" or "better" by nearly all (99 %) patients. In a microalbuminuria subgroup (n = 59; baseline microalbuminuria 20-200 mg/L; average age 60.5 ± 11.5 years; 28 men [47 %]), there was a significant decrease in SBP (from 160.5 ± 13.9 mmHg to 132.6 ± 12.0 mmHg) and DBP (from 95.3 ± 7.8 mmHg to 81.6 ± 8.4 mmHg) (p < 0.001). Target SBP was reached by 71 % of these patients. Microalbuminuria decreased in 75 % of the subgroup during the follow-up period; levels fell significantly from 45 mg/L (30-88 mg/L) to 30 mg/L (20-50 mg/L) (p < 0.0001).

CONCLUSION

Treatment with single-pill perindopril/indapamide 5/1.25 or 10/2.5 mg significantly reduced BP, improved BP control, and enhanced kidney protection in patients with hypertension and type 2 diabetes in everyday clinical practice.

Effect of aldosterone breakthrough on albuminuria during treatment with a direct renin inhibitor and combined effect with a mineralocorticoid receptor antagonist

We have reported observing aldosterone breakthrough in the course of relatively long-term treatment with renin-angiotensin (RA) system inhibitors, where the plasma aldosterone concentration (PAC) increased following an initial decrease. Aldosterone breakthrough has the potential to eliminate the organ-protective effects of RA system inhibitors. We therefore conducted a study in essential hypertensive patients to determine whether aldosterone breakthrough occurred during treatment with the direct renin inhibitor (DRI) aliskiren and to ascertain its clinical significance. The study included 40 essential hypertensive patients (18 men and 22 women) who had been treated for 12 months with aliskiren. Aliskiren significantly decreased blood pressure and plasma renin activity (PRA). The PAC was also decreased significantly at 3 and 6 months; however, the significant difference disappeared after 12 months. Aldosterone breakthrough was observed in 22 of the subjects (55%). Urinary albumin excretion differed depending on whether breakthrough occurred. For the subjects in whom aldosterone breakthrough was observed, eplerenone was added. A significant decrease in urinary albumin excretion was observed after 1 month, independent of changes in blood pressure. In conclusion, this study demonstrated that aldosterone breakthrough occurs in some patients undergoing DRI therapy. Aldosterone breakthrough affects the drug's ability to improve urinary albumin excretion, and combining a mineralocorticoid receptor antagonist with the DRI may be useful for decreasing urinary albumin excretion. When the objective is organ protection in hypertensive patients, a two-pronged approach using combination therapy to inhibit both the RA system and aldosterone may be highly effective.

Cardiorenal disease development under chronic renin–angiotensin–aldosterone system suppression

Drugs suppressing the renin-angiotensin-aldosterone system (RAAS) are now widely used to treat patients all along the cardiorenal continuum. It supposes that many patients, in particular those with arterial hypertension are treated with converting-enzyme inhibitors and angiotensin receptor blockers for years during which the development and prograssion of cardiorenal disease can be observed. The meaning of this progression in the presence of RAAS suppression requires to be clarified and to be treated in order to diminish the velocity of progression of cardiorenal disease.