Monitoring and Managing Urinary Albumin Excretion: Practical Advice for Primary Care Clinicians

Association between Brachial-Ankle Pulse Wave Velocity and Microalbuminuria and to Predict the Risk for the Development of Microalbuminuria Using Brachial-Ankle Pulse Wave Velocity Measurement in Type 2 Diabetes Mellitus Patients

Brachial-ankle pulse wave velocity (baPWV) provides a useful means of assessing cardiovascular events and diabetic complications. However, the nature of associations between baPWV and microalbuminuria (MAU) and its presence in Type 2 diabetes mellitus (Type 2 DM) have rarely been investigated. This study aimed to examine the association between baPWV and MAU coupled with prediction of MAU using baPWV measurement among Type 2 DM patients. In this cross-sectional study, we enrolled 424 Type 2 DM patients who visited the cardiology and endocrinology department at a tertiary level health care facility, Republic of Korea between 1 January 2006 to 31 December 2008. Clinical and laboratory data were collected, and risk factors associated with MAU and prediction of risk for the development of MAU using baPWV measurement. The association between MAU and baPWV was examined using multivariable logistic regression analysis and predicted MAU by using receiver operating characteristic (ROC) curve analysis. Of the 424 Type 2 DM patients, 93 (21.9%) had MAU (20-200 μg/min). baPWV (cm/sec) was found to be significantly correlated with MAU levels (ug/min) (r = 0.791, p < 0.001). Further, baPWV was significantly associated MAU with higher odds ratio (adjusted odds ratio (AOR) 10.899; 95% confidence interval (CI) (4.518-26.292)). Similarly, smoking (AOR 10.899; 95% CI (4.518-26.292)), and low-density lipoprotein (LDL)-cholesterol (mg/dL) (AOR 1.017; 95% CI (1.001-1.033)) were also significantly associated with MAU. The appropriate cut-off value for baPWV to predict MAU 20 μg/min in our study was 1700 cm/sec (area under ROC curve = 0.976). This study shows that baPWV, cigarette smoking, and LDL-cholesterol are associated with MAU in Type 2 DM patients and suggests that a baPWV cut-off of 1700 cm/sec could be used to predict the presence of MAU (20 μg/min) in Type 2 DM patients in the Korean community.

Immune-unreactive urinary albumin as a predictor of cardiovascular events: the Hortega Study

BACKGROUND

We aimed to determine if immune-unreactive albumin excretion (IURAE) is associated with cardiovascular (CV) events in a representative sample of a general population from Spain.

METHODS

We included 1297 subjects (mean age ± standard error 48.0 ± 0.2 years, 48% females), who participated in the Hortega Follow-Up Study. The primary endpoint was incidence of fatal and non-fatal CV events. Urinary albumin excretion (UAE) was measured in spot voided urine, frozen at -80°C, by immunonephelometry [immune-reactive albumin excretion (IRAE)] and by high-performance liquid chromatography (HPLC) [total albumin excretion (AE)]. IURAE was calculated as the difference between HPLC measurements and IRAE. We estimated fully adjusted hazard ratios (HRs) of CV incidence by Cox regression for IRAE, IURAE and total AE.

RESULTS

After an average at-risk follow-up of 13 years, we observed 172 CV events. urinary albumin to creatinine ratio (UACR) of ≥30 mg/g assessed by IRAE, IURAE or total AE concentrations was observed in 74, 273 and 417 participants, respectively. Among discordant pairs, there were 49 events in those classified as micro- and macroalbuminuric by IURAE, but normoalbuminuric by IRAE. Only the IRAE was a significant independent factor for the incidence of CV events [HR (95% confidence interval) 1.15 (1.04-1.27)]. The association of UAE with CV events was mainly driven by heart failure (HF) [HR 1.33 (1.15-1.55) for IRAE; HR 1.38 (1.06-1.79) for IURAE; HR 1.62 (1.22-2.13) for total AE]. Those subjects who were micro- and macroalbuminuric by both IRAE and IURAE had a significant increase in risk for any CV event, and especially for HF.

CONCLUSIONS

IRAE, IURAE and AE were associated with an increased risk for CV events, but IRAE offered better prognostic assessment.

Intravital imaging of the kidney in a rat model of salt-sensitive hypertension

Hypertension is one of the most prevalent diseases worldwide and a major risk factor for renal failure and cardiovascular disease. The role of albuminuria, a common feature of hypertension and robust predictor of cardiorenal disorders, remains incompletely understood. The goal of this study was to investigate the mechanisms leading to albuminuria in the kidney of a rat model of hypertension, the Dahl salt-sensitive (SS) rat. To determine the relative contributions of the glomerulus and proximal tubule (PT) to albuminuria, we applied intravital two-photon-based imaging to investigate the complex renal physiological changes that occur during salt-induced hypertension. Following a high-salt diet, SS rats exhibited elevated blood pressure, increased glomerular sieving of albumin (GSC_alb = 0.0686), relative permeability to albumin (+Δ16%), and impaired volume hemodynamics (-Δ14%). Serum albumin but not serum globulins or creatinine concentration was decreased (-0.54 g/dl), which was concomitant with increased filtration of albumin (3.7 vs. 0.8 g/day normal diet). Pathologically, hypertensive animals had significant tubular damage, as indicated by increased prevalence of granular casts, expansion and necrosis of PT epithelial cells (+Δ2.20 score/image), progressive augmentation of red blood cell velocity (+Δ269 µm/s) and micro vessel diameter (+Δ4.3 µm), and increased vascular injury (+Δ0.61 leakage/image). Therefore, development of salt-induced hypertension can be triggered by fast and progressive pathogenic remodeling of PT epithelia, which can be associated with changes in albumin handling. Collectively, these results indicate that both the glomerulus and the PT contribute to albuminuria, and dual treatment of glomerular filtration and albumin reabsorption may represent an effective treatment of salt-sensitive hypertension.

The Role of Angiotensin II in Glomerular Volume Dynamics and Podocyte Calcium Handling

Podocytes are becoming a primary focus of research efforts due to their association with progressive glomeruli damage in disease states. Loss of podocytes can occur as a result of excessive intracellular calcium influx, and we have previously shown that angiotensin II (Ang II) via canonical transient receptor potential 6 (TRPC6) channels caused increased intracellular Ca2+ flux in podocytes. We showed here with patch-clamp electrophysiology that Ang II activates TRPC channels; then using confocal calcium imaging we demonstrated that Ang II-dependent stimulation of Ca2+ influx in the podocytes is precluded by blocking either AT1 or AT2 receptors (ATRs). Application of Ang(1-7) had no effect on intracellular calcium. Ang II-induced calcium flux was decreased upon inhibition of TRPC channels with SAR7334, SKF 96365, clemizole hydrochloride and La3+, but not ML204. Using a novel 3D whole-glomerulus imaging ex vivo assay, we revealed the involvement of both ATRs in controlling glomerular permeability; additionally, using specific inhibitors and activators of TRPC6, we showed that these channels are implicated in the regulation of glomerular volume dynamics. Therefore, we provide evidence demonstrating the critical role of Ang II/TRPC6 axis in the control of glomeruli function, which is likely important for the development of glomerular diseases.

Efficacy and safety of combined vs. single renin-angiotensin-aldosterone system blockade in chronic kidney disease: a meta-analysis

BACKGROUND

Although dual blockade of the renin-angiotensin-aldosterone system (RAAS) has gained popularity for the treatment of kidney disease, its benefits and potential risks have not been fully elucidated. We conducted a meta-analysis of all randomized controlled trials comparing the efficacy and safety of combined vs. single RAAS blockade therapy in chronic kidney disease (CKD).

METHODS

We performed a literature search using MEDLINE, the Cochrane Central Register of Controlled Trials, ClinicalTrials.gov, scientific abstracts from meetings, and bibliographies of retrieved articles. We used random-effects models to compute net changes and rate differences in variables.

RESULTS

Fifty-nine (25 crossover and 34 parallel-arm) randomized controlled trials (RCTs) comparing the efficacy and safety of combined vs. single RAAS blockade therapy in CKD were identified (4,975 patients). Combined RAAS blockade therapy was associated with a significant net decrease in glomerular filtration rate (GFR) (-1.8ml/min or ml/min/1.73 m(2); P = 0.005), albuminuria (-90mg/g of creatinine; P = 0.001 or -32mg/day; P = 0.03), and proteinuria (-291mg/g; P = 0.003 or -363mg/day; P < 0.001). Combined RAAS blockade therapy was associated with a 9.4% higher rate of regression to normoalbuminuria and a 5% higher rate of achieving the blood pressure (BP) goal (as defined in individual trials). However, combined RAAS blockade therapy was associated with a significant net increase in serum potassium level, a 3.4% higher rate of hyperkalemia, and a 4.6% higher rate of hypotension. There was no effect on doubling of the serum creatinine level, hospitalization, or mortality.

CONCLUSIONS

Although combined RAAS blockade therapy in CKD is associated with a decrease in albuminuria and proteinuria, it is associated with a decrease in GFR and a higher incidence of hyperkalemia and hypotension relative to monotherapy. The potential long-term kidney benefits of combined RAAS blockade therapy require further study.

Reducing cardiorenal risk through combination therapy with a direct renin inhibitor

Interruption of the renin-angiotensin-aldosterone system (RAAS) cascade with angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), or more recently direct renin inhibitors (DRIs) is a safe and effective antihypertensive strategy that is in routine clinical use. The clinical utility of these agents in cardiorenal end-organ protection is increasingly being recognized. Although both ACE inhibitors and ARBs demonstrate substantial benefit in patients with cardiovascular and/or renal disease, considerable evidence indicates that they only partially suppress the RAAS pathway due to feedback upregulation of plasma renin activity. With the goal of providing more comprehensive RAAS blockade, combination ACE inhibitor/ARB therapy has been evaluated. However, this approach has not shown the anticipated improvements in composite cardiovascular and renal outcomes and appears to be associated with significant toxicity. Due to a unique mechanism of action, the combination of a DRI with an ACE inhibitor or ARB may represent an effective end-organ-protective therapeutic strategy.

Renal protective effect of RAAS blockade across the renal continuum, with a review of the efficacy and safety of valsartan

Abstract Objective: The purpose of this report is to review key data on the angiotensin receptor blocker (ARB) valsartan, along with data from several pivotal studies with other ARBs and angiotensin-converting enzyme (ACE) inhibitors, to highlight the beneficial class effects of renin-angiotensin-aldosterone system (RAAS) blockade throughout the renal continuum.

METHODS

The selection of articles was based on a search of PubMed for clinical trials published between 1997 (the year in which valsartan was approved for sale in the US) and 2009 that involved valsartan and reported effects on renal function, plus a select range of articles on other agents acting on the RAAS, including key guidance documents issued during this time.

SUMMARY

Valsartan has been studied extensively and is widely used for the management of hypertension. Data from clinical studies involving valsartan and other ARBs and ACE inhibitors provide evidence of an additional renal protective effect. This renal protection apparently arises from hemodynamic, endothelial, and anti-inflammatory actions.

LIMITATIONS

Given the extent of the available literature on this topic, this review included only a subset of available publications. This report may reflect inherent heterogeneity between patient populations from these studies and also incorporate the limitations of these individual publications. The inclusion of guidance documents from several organizations may have resulted in apparent minor conflicts in the approaches of the different groups.