Background

Gentamicin, a well-known nephrotoxic drug, affects calcium and magnesium homeostasis. Although gentamicin induces urinary calcium and magnesium wasting immediately, it rarely causes significant hypocalcemia or hypomagnesemia clinically.

Methods

We conducted an animal study to investigate the renal adaptation in calcium and magnesium handling after gentamicin treatment and effects on the expression of calcium and magnesium transport molecules in distal tubule. Gentamicin (40 mg/kg) was injected daily in male Sprague-Dawley rats (220–250 g) for up to 7 days.

Results

This treatment did not affect serum creatinine, calcium, or magnesium levels. Gentamicin induced significant hypercalciuria (14-fold) and hypermagnesiuria (10-fold) in 6 h, which was associated with upregulation of TRPV5 (175 ± 3%), TRPV6 (170 ± 4%), TRPM6 (156 ± 4%) and calbindin-D28k (174 ± 3%; all p < 0.05 vs. control). This gene upregulation was maintained with daily injection of gentamicin for 7 days. The gentamicin-induced urinary calcium loss was reduced by 80% at days 3 and 7, while magnesium loss was reduced by 52 and 57% at days 3 and 7, respectively. On the other hand, urinary loss of potassium became worse on day 7 (2-fold), and phosphorus loss worse from day 3 to day 7 (3-fold).

Conclusion

There is a rapid adaptation to gentamicin-induced hypercalciuria and hypermagnesiuria. The upregulation of distal tubule transport molecules, TRPV5, TRPV6, TRPM6 and calbindin-D28k occurs within 6 h of gentamicin treatment. This renal adaptation prevents further mineral loss due to gentamicin treatment.

Background/Aims

Intravenous (IV) iron preparations are widely used in the management of anemia in ESRD populations. Recent changes in reimbursement policy have dramatically increased the use of IV iron to lower the use of costly erythropoiesis-stimulating agents. These preparations are frequently administered with insufficient attention to the total body iron stores or presence of inflammation which is aggravated by excess iron. Endothelial injury and dysfunction are critical steps in atherosclerosis, thrombosis and cardiovascular disease. IV iron preparations raise plasma non-transferrin-bound iron which can promote oxidative stress, endothelial damage and dysfunction. We explored the effect of an IV iron preparation on endothelial cells, monocytes and isolated arteries.

Methods

Primary cultures of human aortic endothelial cells (HAEC) were treated with pharmacologically relevant concentrations of iron sucrose (10–100 μg/ml) for 4–24 h. Endothelial cell morphology, viability, and monocyte adhesion were tested. Endothelial function was assessed by measuring the vasorelaxation response to acetylcholine in normal rat thoracic aorta rings preincubated with iron sucrose (200 μg/ml).

Results

In contrast to the control HAEC which showed normal cobblestone appearance, cells treated with iron sucrose (50–100 μg/ml) for 4 h showed loss of normal morphological characteristics, cellular fragmentation, shrinkage, detachment, monolayer disruption and nuclear condensation/fragmentation features signifying apoptosis. HAEC exposure to iron sucrose (10–100 μg/ml) increased monocyte adhesion 5- to 25-fold. Incubation in media containing 200 μg/ml iron sucrose for 3 h caused marked reduction in the acetylcholine-mediated relaxation in phenylephrine-precontracted rat aorta.

Conclusion

Pharmacologically relevant concentration of iron sucrose results in endothelial injury and dysfunction and marked increase in monocyte adhesion.

Background

Awareness of chronic kidney disease (CKD) is low. Efforts are underway to increase recognition of CKD among patients, assuming that such an increase will lead to better outcomes through greater adherence to proven therapies. Few studies have tested this assumption.

Methods

CKD awareness, defined by a ‘yes’ answer to ‘Have you ever been told by a healthcare provider you have weak or failing kidneys?’, was assessed among 2,404 adults with CKD stages 1–4, who participated in the 2003–2008 National Health and Nutrition Examination Surveys. Odds of blood pressure (BP) control, self-reported use of angiotensin-converting enzyme inhibitors (ACEI) or angiotensin receptor blockers (ARB), and glycemic control, were determined among those aware vs. unaware of their CKD.

Results

Optimal BP control, ACEI/ARB use and glycemic control were low in the US adult population with CKD, although there was a recent increase in attainment of guideline-concordant BP control. Odds of BP control and ACEI/ARB use were not different among individuals aware of their CKD compared to those unaware (adjusted odds ratio (AOR) 0.91; 95% CI 0.52–1.58 and AOR 0.75; 0.44–1.30, respectively). CKD awareness among diabetic participants was not associated with glycemic control (AOR 0.41; 95% CI 0.14–1.18).

Conclusion

Awareness of CKD is not associated with more optimal BP control, ACEI/ARB use or glycemic control. Future efforts in this area should further explore the measurement of CKD awareness and behaviors associated with CKD awareness.

Background

The relationship of routine postoperative troponin I (TnI) monitoring in kidney transplant recipients and in-hospital myocardial infarction (MI) is not known.

Methods

This observational study evaluated the prevalence of abnormal postoperative TnI (Ortho Clinical Diagnostics assay) in 376 consecutive kidney or kidney/pancreas transplant recipients. In-hospital MI was adjudicated using the universal definition. Rates of death and coronary revascularizations at 1 year were studied. Logistic regression analysis was performed to identify independent predictors of abnormal TnI.

Results

Ninety-five (25%) recipients had abnormal TnI (>0.04 ng/ml) following transplantation. Abnormal TnI levels were more common in older (mean age: 52.2 ± 13.4 vs. 48.3 ± 13.2 years, p = 0.01), diabetic (57.9 vs. 45.6%, p = 0.04), and prior coronary artery disease (31.6 vs. 20.3%, p = 0.02) patients. In-hospital MI occurred in 6 patients (1.6%). All subsequent in-hospital cardiovascular events occurred in the abnormal postoperative TnI group; most in those with TnI levels >1 ng/ml. Previous coronary artery disease was the only independent predictor of a postoperative TnI level >1 ng/ml in multivariate analysis (odds ratio 4.61, 95% confidence interval 1.49–14.32). At 1 year there was no significant difference in death (3.2 vs. 1.8%, p = 0.42) and borderline significant difference in coronary revascularization (5.3 vs. 1.4%, p = 0.049) in abnormal versus normal TnI groups.

Conclusions

In-hospital MI was infrequent, but abnormal TnI highly prevalent following renal transplantation. Normal TnI levels following renal transplantation had a high negative predictive value in excluding patients likely to develop subsequent postoperative MI. The role of a higher TnI cut-off for screening for postoperative MI in high-risk subgroups deserves future prospective evaluation.

Background

Inflammation is thought to play a role in ischemic acute kidney injury (AKI). We have demonstrated that macrophage and dendritic cell depletion, using liposome-encapsulated clodronate (LEC), is protective against ischemic AKI.

Methods

To determine whether macrophages or dendritic cells or both play a role in ischemic AKI, we performed ischemic AKI in CD11b-DTR mice that have a diphtheria toxin (DT)-induced depletion of CD11b cells (macrophages) and CD11c-DTR mice that have a DT-induced depletion of CD11c cells (dendritic cells).

Results

While LEC-treated animals had a significant functional protection from AKI, CD11b-DTR and CD11c-DTR mice were not protected against AKI despite a similar degree of renal macrophage and dendritic cell depletion. Proinflammatory cytokines are known to play a role in ischemic AKI. To determine the possible reasons for the lack of protection in CD11b-DTR and CD11c-DTR mice compared to LEC-treated mice, 32 cytokines/chemokines were measured in these mice. Of the cytokines/chemokines measured, IL-6, MCP-1, GMCSF, IL-1β and CXCL1 (also known as IL-8 in humans or KC in mice) showed significant differences in the LEC-treated, CD11b-DTR and CD11c-DTR mice. MCP-1 and CXCL1 (known mediators of AKI), and also GMCSF and IL-1β were increased in AKI and decreased in LEC-treated AKI but not AKI in CD11b-DTR or CD11c-DTR mice. Conclusions: These findings suggest that LEC-mediated protection from AKI is not simply mediated by depletion of renal macrophage or dendritic cell subpopulations. Protection against AKI in LEC-treated compared to CD11b-DTR or CD11c-DTR mice may be partially explained by differences in proinflammatory cytokine profiles.

Background

Chronic kidney disease (CKD) is a major public health problem, and despite continued research in the field, there is still a need to identify both biomarkers of risk and progression, as well as potential therapeutic targets. Structural equation modeling (SEM) is a family of statistical techniques that has been utilized in the fields of sociology and psychology for many years; however, its utilization in the biological sciences is relatively novel. SEM's ability to investigate complex relationships in an efficient, single model could be utilized to understand the progression of CKD, as well as to develop a predictive model to assess kidney status in the patient.

Methods

Fischer 344 rats were fed either an ad libitum diet or a calorically restricted diet, and a time-course study of kidney structure and function was performed. EQS, a SEM software package, was utilized to generate five CKD models of the Fisher 344 rat and identify relationships between measured variables and estimates of kidney damage and kidney function.

Results

All models identified strong relationships between a biomarker for CKD, kidney injury molecule-1 (Kim-1) and kidney damage, in the Fischer 344 rat CKD model. Models also indicate a strong relationship between age and renal damage and dysfunction.

Conclusion

SEM can be used to model CKD and could be useful to examine biomarkers in CKD patients.

Background

Several studies have shown an association between erythropoietin-stimulating agent (ESA) responsiveness and mortality in chronic kidney disease (CKD) patients. In our present study, we examined the association between prescribed ESA dose and mortality in peritoneal dialysis (PD) and hemodialysis (HD) patients. We hypothesized that PD patients received lower ESA dose for the same achieved hemoglobin compared to HD patients and that ESA dose-mortality associations were different between PD and HD patients.

Methods

We compared the prescribed doses of ESA between 139,103 HD and 10,527 PD patients treated in DaVita dialysis clinics from 7/2001 through 6/2006 using adjusted Poisson regression and examined mortality-predictability of prescribed ESA dose and ESA responsiveness index (ESA/hemoglobin) in PD and HD with follow-up through 6/2007 using Cox regression models.

Results

Poisson adjusted ratio of ESA dose of HD to PD was 3.6 (95% CI 3.5–3.7). In PD patients, adjusted all-cause death hazard ratios (HR) for ESA doses of 3,000–5,999, 6,000–8,999 and ≥9,000 U/week (reference <3,000 U/week) were 0.97 (0.87–1.07), 0.85 (0.76–0.95) and 1.08 (0.98–1.18), respectively; whereas in HD patients across commensurate ESA dose increments of 10,000–19,999, 20,000–29,999 and ≥30,000 U/week (reference <10,000 U/week) were 1.14 (1.11–1.17), 1.54 (1.50–1.58) and 2.15 (2.10–2.21), respectively. In PD and HD patients, the adjusted death HR of the 4th to 1st quartile of ESA responsiveness index were 1.14 (1.04–1.26) and 2.37 (2.31–2.43), respectively.

Conclusions

Between 2001 and 2006, most PD patients received substantially lower ESA dose for same achieved hemoglobin levels, and low ESA responsiveness was associated with higher mortality in both HD and PD patients.

Background

Low physical activity (PA) has been associated with higher rates of cardiovascular disease (CVD) and mortality in the general population. Despite the benefits of kidney transplantation, kidney transplant recipients (KTRs) remain at elevated risk for CVD and mortality compared to individuals without kidney disease.

Methods

A prospective cohort of 507 adult KTRs from three academic centers completed the Physical Activity Scale for the Elderly (PASE) at transplantation. PASE scores were divided into tertiles.

Results

PA was lower with older age, history of CVD, smoking, and diabetes. During the median 8-year follow-up period, 128 individuals died, among whom 101 had a functioning allograft. In multivariable Cox regression for all-cause mortality, greater PA was strongly associated with better survival (HR: 0.52 for most active vs. inactive tertiles, 95% CI: 0.31–0.87, p = 0.01). Secondary analyses, in which (1) death with a functioning graft was the primary outcome, and (2) PASE scores were converted to the metabolic equivalent of task, revealed similar results. We did not find an association between change of PA after transplantation and mortality.

Conclusions

PA at the time of kidney transplantation is a strong predictor of all-cause mortality and death with graft function. Evaluation of PA level among kidney transplant candidates may be a useful method to risk-stratify patients for survival after kidney transplantation. Kidney transplant candidates and recipients should also be encouraged to be physically active.

Background/Aims

Reduced renal L-arginine (L-Arg) synthesis/transport, induction of arginases and increased endogenous NOS inhibitor, asymmetric dimethylarginine (ADMA) will inhibit NO production. This study investigated pathways of L-Arg synthesis/uptake/utilization, ADMA degradation and oxidant/antioxidants in puromycin aminonucleoside (PAN) chronic kidney disease (CKD).

Methods

Rats were given low- (LD) or high-dose (HD) PAN and followed for 11 weeks for proteinuria. BP was measured and blood and tissues were harvested and analyzed for abundance of argininosuccinate synthase (ASS) and lyase (ASL), arginase, cationic amino acid transporter (CAT1) and dimethylargininedimethylaminohydrolase (DDAH) in kidney, cortex, aorta and liver. Arginase and DDAH activity, plasma L-Arg and ADMA, renal pathology and creatinine clearances were also measured.

Results

PAN caused dose-dependent kidney damage and hypertension and creatinine clearance fell in HD-PAN. Renal ASS fell in HD-PAN, renal cortex and aortic ASL and membrane CAT1 fell in both PAN groups. There was no activation of renal arginase, but aortic arginase increased in LD-PAN. Renal DDAH activity fell moderately in LD-PAN and markedly in HD-PAN where hepatic DDAH activity also fell. Plasma L-Arg was unchanged while ADMA rose moderately and dose-dependently with PAN. There were several indices of oxidative stress which was most prominent in HD-PAN.

Conclusion

Reduction in renal ASS/ASL and loss of renal cortex CAT1 compromises renal L-Arg synthesis and release. Loss of aortic CAT1 impairs L-Arg uptake. Increased plasma ADMA was associated with progressive loss of renal DDAH activity. However, loss of renal clearance and falls in hepatic DDAH activity in HD-PAN did not have additive effects on plasma ADMA.

Background and Aims

Cognitive impairment is a risk factor for death in dialysis patients and the general population. We sought to determine if cognitive impairment is associated with death in people with non-dialysis-dependent chronic kidney disease (CKD), and if so, whether this relationship is greater in the CKD population compared to the general population.

Methods

National Health and Nutrition Examination Survey-III participants older than 60 years were asked to subtract 3 from 20 five times and to perform immediate and delayed recall of three items. A cognitive score of 0–11 was assigned based on the number of correct responses. Participants were categorized according to cognitive score (11, 9–10, 6–9, and 0–5) and CKD status. Survival analyses were conducted using Cox models.

Results

Within the CKD subpopulation, those in the lowest cognitive score group had a twofold increased hazard of death compared to those with maximum score. Within the non-CKD subpopulation, those in the lowest cognitive score group had a 46% increased hazard of death compared to those with maximum score. However, the difference in the hazards of death in the CKD and non-CKD subpopulations with the lowest cognitive score was not significant (p = 0.99).

Conclusions

Low cognitive score is associated with an increased risk of death in elderly individuals with and without CKD; however, there was no interaction of CKD and low cognitive score in this analysis.

Background/Aims

Living donor nephrectomy can be associated with increases in blood pressure several years following the procedure, but the best method to assess blood pressure during the living donor evaluation process is unclear.

Methods

Living kidney donors underwent casual clinic and ambulatory blood pressure monitoring (ABPM) and measurement of central aortic pressures at baseline and 6 months following donor nephrectomy.

Results

There was a significant decline in clinic systolic blood pressure (SBP; p = 0.001) and central aortic systolic pressure (p = 0.011) during the study period. However, average ABPM was unchanged and other measures of central arterial pressures and Augmentation Index were unchanged at 6 months compared to baseline.

Conclusions

The remarkable differences between clinic SBP and ambulatory SBP prior to donation, and the disappearance of these differences 6 months later, suggest a substantial white coat effect on SBP associated with living kidney donor evaluation. Also, ABPM represents a better way to assess blood pressure prior to kidney donation.

Background/Aims

The mammalian target of rapamycin (mTOR) is a serine kinase that regulates phosphorylation (p) of its target ribosomal S6 kinase (S6K1), whose activation can lead to glomerular and proximal tubular cell (PTC) injury and associated proteinuria. Increased mTOR/S6K1 signaling regulates signaling pathways that target fibrosis through adherens junctions. Recent data indicate aldosterone signaling through the mineralocorticoid receptor (MR) can activate the mTOR pathway. Further, antagonism of the MR has beneficial effects on proteinuria that occur independent of hemodynamics.

Methods

Accordingly, hypertensive transgenic TG(mRen2)27 (Ren2) rats, with elevated serum aldosterone and proteinuria, and age-matched Sprague-Dawley rats were treated with either a low dose (1 mg/kg/day) or a conventional dose (30 mg/kg/day) of spironolactone (MR antagonist) or placebo for 3 weeks.

Results

Ren2 rats displayed increases in urine levels of the PTC brush border lysosomal enzyme N-acetyl-β-aminoglycosidase (β-NAG) in conjunction with reductions in PTC megalin, the apical membrane adherens protein T-cadherin and basolateral α-(E)-catenin, and fibrosis. In concert with these abnormalities, Ren2 renal cortical tissue also displayed increased Ser2448 (p)/activation of mTOR and Thr389 (p)-S6K1 and increased 3-nitrotyrosine (3-NT) content, a marker for peroxynitrite. Low-dose spironolactone had no effect on blood pressure but decreased proteinuria and β-NAG comparable to a conventional dose of this MR antagonist. Both doses of spironolactone attenuated ultrastructural maladaptive alterations and led to comparable reductions in (p)-mTOR/(p)-S6K1, 3-NT, fibrosis, and increased expression of α-(E)-catenin, T- and N-cadherin.

Conclusions

Thereby, MR antagonism improves proximal tubule integrity by targeting mTOR/S6K1 signaling and redox status independent of changes in blood pressure.

Background: Whether lipoprotein-associated phospholipase A2 (Lp-PLA2) levels are associated with kidney function decline has not been well studied. Methods: We investigated associations of Lp-PLA2 antigen and activity with kidney function decline and rapid decline over 5.7 years in the Cardiovascular Health Study (n = 4,359). We estimated kidney function by cystatin C (eGFRcys) in repeated measures, and defined rapid decline as ≥3 ml/min/1.73 m2 per year. We stratified by baseline preserved GFR (≥60 ml/min/1.73 m2). Results: Mean age was 72 ± 5 years. Average eGFRcys decline was −1.79 ml/min/1.73 m2 (SD = 2.60) per year. Among persons with preserved GFR, compared to the lowest quartile of Lp-PLA2 antigen, eGFRcys decline was faster among persons in the second, β −0.31 (95% CI −0.52, −0.10), third −0.19 (–0.41, 0.02) and fourth quartiles −0.26 (–0.48, −0.04) after full adjustment. Persons in the highest quartile of Lp-PLA2 antigen had increased odds of rapid decline 1.34 (1.03, 1.75), compared to the lowest. There was no significant association between levels of Lp-PLA2 activity and eGFRcys decline or rapid decline. Associations were not statistically significant among persons with low eGFR (<60 ml/min/1.73 m2) at baseline. Conclusion: Higher levels of Lp-PLA2 antigen but not activity were significantly associated with faster rates of kidney function decline. These findings may suggest a novel vascular pathway for kidney disease progression.

Background/Aims: In an antiglomerular basement membrane glomerulonephritis (GN) model, GN-resistant Lewis (LEW) rats naturally recover from early glomerular inflammation (days 21–23). We have previously identified a glomeruli-infiltrating CD8α+CD11highMHC II+ cell (GIL CD8α+ cell) in GN-prone Wistar Kyoto (WKY) rats, which terminates glomerular inflammation through inducing T cell apoptosis prior to glomerular fibrosis at days 35–40. We investigated if GIL CD8α+ cells were also associated with the recovery in LEW rats. Methods: GIL CD8α+ cells in LEW rats were characterized; their infiltration was observed in connection with T cell apoptosis in glomeruli. Results: An influx of GIL CD8α+ cells into inflamed glomeruli was confirmed in the immunized LEW rats at days 17–22, which was much earlier than days 28–35 in WKY rats. Notably, LEW rats had a GIL CD8α+CD11high subpopulation after day 17, while WKY rats lacked this population until after day 30. Analyses further revealed a large number of clustered apoptotic CD4+ or CD3+ T cells in the glomeruli during recovery (day 23) in LEW rats, as compared to day 35 (transition to fibrosis) in WKY rats. Thus, infiltration of GIL CD8α+ cells coincided with decline of glomerular inflammation and T cell apoptosis during recovery in LEW rats. Isolated GIL CD8α+ cells were able to infiltrate glomeruli in both WKY and LEW rats at day 20. Conclusion: Our data revealed a strong association between GIL CD8a+ cells and recovery from early glomerular inflammation. It raises a possibility of involvement of GIL CD8a+ cells in the recovery.

Introduction

Alemtuzumab and rabbit antithymocyte globulin (rATG) are being used with increasing frequency as induction agents in kidney transplantation. Using the US Renal Data Base System, we analyzed the safety profile of these agents in the elderly.

Methods

In a cohort of patients transplanted from January 2000 to July 2009 and followed through 2009, we assessed the effect of induction on allograft loss and death among elderly recipients. Recipients were censored at dates of allograft loss, death or the end of study. Independent associations between induction agents and allograft loss or death were examined using multivariate analysis with forward stepwise Cox regression.

Results

Among 130,402 patients with first transplants, 14,907 were age 65 years or older. 4,466 (30%), 3,049 (20.5%), 1,501 (10.1%), and 999 (6.7%) were induced with thymoglobulin, basiliximab, daclizumab, and alemtuzumab, respectively. After adjusting for baseline differences, induction with alemtuzumab was associated with an increased risk of graft loss and death, with an adjusted hazard ratio (AHR) of 1.26 (95% CI 1.08–1.48). Risk was also present at other age cutoffs [age >60 (AHR 1.16; 95% CI 1.03–1.31; p = 0.014), age >70 (AHR 1.43; 95% CI 1.13–1.81; p = 0.003) and age >75 (AHR 1.68; 95% CI 1.07–2.63; p = 0.024)].

Conclusions

In the elderly, alemtuzumab is associated with an escalating risk of death and graft loss in recipients of kidney transplantations.

Background/Aims

Currently available clinical indicators of kidney disease lack the sensitivity and/or specificity to identify early-stage diabetic nephropathy (DN). Quantitative diffusion magnetic resonance imaging (MRI), specifically diffusion tensor imaging (DTI), has been used to quantify pathophysiologic changes in other organs but has not been well studied in kidney diseases, including DN. The goal of this pilot study was to examine differences in kidney DTI parameters in diabetic subjects versus healthy controls.

Methods

16 diabetic and 5 healthy control subjects were recruited for this institutional review board-approved/Health Insurance Portability and Accountability Act-compliant study. Kidneys were scanned using DTI to generate apparent diffusion coefficient (ADC) and fractional anisotropy (FA) data. Mean cortical and medullary ADC and FA values were calculated by selecting multiple regions of interest. Diabetics were stratified by estimated glomerular filtration rate (eGFR) into 2 groups: eGFR ≥60 (n = 10) and eGFR <60 (n = 6) ml/min/1.73 m2. Mean diffusion parameters and eGFRs were compared between these groups of diabetic subjects and healthy controls.

Results

Medullary FA, ADC and cortical ADC values were significantly lower in diabetics with eGFR <60 compared to controls. Notably, both mean medullary FA and ADC were significantly lower in diabetics with eGFR ≥60 compared to controls (p = 0.001 and p = 0.042, respectively). For the study subjects in aggregate, medullary FA correlated significantly with eGFR (R = 0.69, p < 0.01); the other diffusion parameters showed no significant correlations.

Conclusions

This pilot study suggests that changes in medullary DTI assessments may serve as indicators of early DN. Further studies are needed to determine if these findings could serve as biomarkers to identify diabetics at risk of DN progression.

Background

Early detection of individuals at high risk for chronic kidney disease (CKD) may aid prevention. Urinary levels of trefoil factor 3 (TFF3) are associated with acute kidney injury in animal models, but the association of TFF3 levels with incident CKD in humans is unknown.

Methods

We conducted a case-control study nested within the Atherosclerosis Risk in Communities (ARIC) Study and the ARIC Carotid MRI Study to determine whether urinary TFF3 levels predict incident CKD over 8.6 years of follow-up. A total of 143 participants with incident CKD (eGFR decreasing by ≥25% to <60 ml/min/1.73 m2) were matched on age, sex and race to 143 non-cases.

Results

Higher TFF3 levels at baseline were strongly associated with Black race, diabetes (both p = 0.002), and antihypertensive medication use (p = 0.02). Compared to participants with TFF3 levels in the lowest quartile, the odds ratio (OR) of incident CKD was 1.84 (95% confidence interval (CI): 0.80, 4.22) for individuals with TFF3 levels in the second quartile, 2.43 (95% CI: 1.06, 5.53) for the third quartile, and 2.77 (95% CI: 1.22, 6.28) for the fourth quartile (p trend = 0.02). Adjustment for covariates, including urinary albumin: creatinine ratio, did not markedly change the associations. Twofold higher TFF3 levels were strongly associated with incident CKD after adjustment for CKD risk factors (adjusted OR = 1.35; 95% CI: 1.11, 1.64).

Conclusions

Higher urinary TFF3 levels may indicate ongoing repair of damage in the kidney. Additional studies are needed to confirm whether TFF3 can be useful as a marker of increased risk for CKD.

Background

Infection, bacteremia and sepsis are major sources of morbidity and mortality in patients with end-stage renal disease. This study sought to determine the association between predialysis chronic kidney disease (CKD) and infection-related mortality.

Methods

We analyzed participants in the Third National Health and Nutrition Examination Survey (NHANES III). The study included adults ≥45- years-old without end-stage renal disease. Estimated glomerular filtration rate (eGFR) was categorized as ≥60, 45–59.9 and <45 ml/min per 1.73 m2, and urinary albumin-to-creatinine ratio (ACR) as <30, 30–299.9 and ≥300 mg/g. The study identified infection-related mortality, including septicemia, respiratory, abdominal and gastrointestinal, cardiac, kidney and genitourinary, neurologic, and other infections over a median of 13 years using the National Death Index.

Results

Of 7,400 participants included in the study, 206 died from infections. Compared to individuals with eGFR ≥60 ml/min per 1.73 m2, infection-related mortality was higher for those with lower eGFR [adjusted HR = 1.36 (95% CI: 0.81, 2.30) and 2.36 (1.04, 5.38) for eGFR of 45–59.9 and <45 ml/min per 1.73 m2, respectively; p trend = 0.06]. Compared to individuals with ACR <30 mg/g, infection-related mortality was higher for ACR levels of 30–299 and ≥300 mg/g [adjusted HR = 1.68 (95% CI: 0.97, 2.92) and 2.84 (0.92, 8.74), p trend = 0.02].

Conclusions

Reduced eGFR and albuminuria are associated with increased risk for infection-related mortality. Efforts are needed to reduce its incidence and mitigate the effects of infections among individuals with CKD.

Background/Aims

The formation of advanced glycation end products (AGEs) is accelerated in patients with diabetic nephropathy. The aim of this study was to ascertain if the urinary excretion of proteins modified by advanced glycation can be used as biomarkers for albuminuria in individuals with type 1 or type 2 diabetes.

Methods

Community-based patients with type 1 (n = 68) or type 2 diabetes (n = 216) attending a diabetes clinic of a tertiary referral hospital were classified as having normoalbuminuria (Normo, albumin excretion rate (AER) <20 μg/min), microalbuminuria (Micro, AER 20–200 μg/min) or macroalbuminuria (Macro, AER ≥200 μg/min). Serum and urine AGE-modified proteins were measured.

Results

In patients with both type 1 diabetes and type 2 diabetes, there was a clear association between the degree of albuminuria and urinary AGE-modified proteins (p < 0.0001). Exclusive to patients with type 1 diabetes, urinary excretion of the AGE carboxymethyllysine correlated with AER, whereas patients with type 2 diabetes and macroalbuminuria had an increase in urinary methylglyoxal, an AGE intermediate. These changes were independent of isotopic glomerular filtration rate levels. Serum concentrations of AGEs or soluble receptor for AGEs were not consistently associated with albuminuria in either type 1 or type 2 diabetes.

Conclusions

Urinary excretion of proteins modified by AGEs may be useful biomarkers of albuminuria in individuals with type 1 and type 2 diabetes, warranting prospective investigation in larger diabetic cohorts.

Background

The epidemiology of hypertension among hemodialysis (HD) patients is difficult to describe accurately because of difficulties in the assessment of blood pressure (BP).

Methods

Using 44-hour interdialytic ambulatory BP measurements, we describe the epidemiology of hypertension in a cohort of 369 patients. To seek correlates of hypertension control, antihypertensive agents were withdrawn among patients with controlled hypertension and ambulatory BP monitoring was repeated.

Results

Hypertension (defined as an average ambulatory systolic BP ≥135 mm Hg or diastolic BP ≥85 mm Hg, or the use of antihypertensive medications) was prevalent in 82% of the patients and independently associated with epoetin use, lower body mass index and fewer years on dialysis. Although 89% of the patients were being treated, hypertension was controlled adequately in only 38%. Poor control was independently associated with greater antihypertensive drug use. Inferior vena cava (IVC) diameter in expiration was associated with increased risk of poorly controlled hypertension both in cross-sectional analysis and after withdrawal of antihypertensive drugs.

Conclusions

Interdialytic hypertension is highly prevalent and difficult to control among HD patients. End-expiration IVC diameter is associated with poor control of hypertension in cross-sectional analyses as well as after washout of antihypertensive drugs. Among HD patients, an attractive target for improving hypertension control appears to be the reduction of extracellular fluid volume.

Background/Aims

Studies have shown that kidney injury molecule-1 (KIM-1) is upregulated in damaged renal proximal tubules. In this study, we examined KIM-1 expression in glomerular epithelial cells in diabetic glomerulopathy.

Methods

Renal histology, immunostaining and Western blot for protein level, and real-time PCR for mRNA expression of KIM-1 and podocyte markers were evaluated in untreated or losartan-treated Zucker lean (Fa/+) and Zucker diabetic fatty (Fa/Fa) rats.

Results

The diabetic rats showed an increased glomerular expression of KIM-1. KIM-1 staining was localized primarily in the hyperplastic parietal epithelium of Bowman's capsule in the early stages of diabetes with subsequent increase in KIM-1-positive cells in the glomerular tuft in the more advanced stages. The increase in glomerular KIM-1 was associated with a decrease in podocytes in Fa/Fa rats. Antiproteinuric treatment with losartan attenuated podocytopenia and decreased renal expression of KIM-1 in treated diabetic rats. In an in vitro study, albumin overload increased KIM-1 protein in the primary cultures of rat glomerular epithelial cells.

Conclusion

These results show that glomerular KIM-1 expression was increased, in proportion to the extent of proteinuria and podocytopenia in the diabetic animals, supporting that KIM-1 could be used as a potential biomarker for glomerular injury in proteinuric kidney disease.

Background/Aims

Angiotensin (Ang) II contributes to tubulointerstitial fibrosis. Recent data highlight mammalian target of rapamycin (mTOR)/S6 kinase 1 (S6K1) signaling in tubulointerstitial fibrosis; however, the mechanisms remain unclear. Thereby, we investigated the role of Ang II on mTOR/S6K1-dependent proximal tubule (PT) injury, remodeling, and fibrosis.

Methods

We utilized young transgenic Ren2 rats (R2-T) and Sprague-Dawley rats (SD-T) treated with the Ang type 1 receptor (AT1R) blocker telmisartan (2 mg · kg−1 · day−1) or vehicle (R2-C; SD-C) for 3 weeks to examine PT structure and function.

Results

Ren2 rats displayed increased systolic blood pressure, proteinuria and increased PT oxidant stress and remodeling. There were parallel increases in kidney injury molecule-1 and reductions in neprilysin and megalin with associated ultrastructural findings of decreased clathrin-coated pits, endosomes, and vacuoles. Ren2 rats displayed increased Serine2448 phosphorylation of mTOR and downstream S6K1, in concert with ultrastructural basement membrane thickening, tubulointerstitial fibrosis and loss of the adhesion molecule N-cadherin. Telmisartan treatment attenuated proteinuria as well as the biochemical and tubulointerstitial structural abnormalities seen in the Ren2 rats.

Conclusions

Our observations suggest that Ang II activation of the AT1R contributes to PT brush border injury and remodeling, in part, due to enhanced mTOR/S6K1 signaling which promotes tubulointerstitial fibrosis through loss of N-cadherin.

Background

The relationship between stage of chronic kidney disease (CKD) and incident heart failure (HF) remains unclear.

Methods

Of the 5,795 community-dwelling adults ≥65 years in the Cardiovascular Health Study, 5,450 were free of prevalent HF and had baseline estimated glomerular filtration rate (eGFR: ml/min/1.73 m2) data. Of these, 898 (16%) had CKD 3A (eGFR 45–59 ml/min/1.73 m2) and 242 (4%) had CKD stage ≥3B (eGFR <45 ml/min/1.73 m2). Data on baseline proteinuria were not available and 4,310 (79%) individuals with eGFR ≥60 ml/min/1.73 m2 were considered to have no CKD. Propensity scores estimated separately for CKD 3A and ≥3B were used to assemble two cohorts of 1,714 (857 pairs with CKD 3A and no CKD) and 557 participants (148 CKD ≥3B and 409 no CKD), respectively, balanced on 50 baseline characteristics.

Results

During 13 years of follow-up, centrally-adjudicated incident HF occurred in 19, 24 and 38% of pre-match participants without CKD (reference), with CKD 3A [unadjusted hazard ratio (HR) 1.40; 95% confidence interval (CI) 1.20–1.63; p < 0.001] and with CKD ≥3B (HR 3.37; 95% CI 2.71–4.18; p < 0.001), respectively. In contrast, among matched participants, incident HF occurred in 23 and 23% of those with CKD 3A and no CKD, respectively (HR 1.03; 95% CI 0.85–1.26; p = 0.746), and 36 and 28% of those with CKD ≥3B and no CKD, respectively (HR 1.44; 95% CI 1.04–2.00; p = 0.027).

Conclusions

Among community-dwelling older adults, CKD is a marker of incident HF regardless of stage; however, CKD ≥3B, not CKD 3A, has a modest independent association with incident HF.

Background

Elevated serum uric acid has been associated with cognitive dysfunction and vascular cognitive impairment in the elderly. Serum uric acid is also commonly elevated in chronic kidney disease (CKD), but its relationship with cognitive function in these patients has not been addressed.

Methods

Subjects with CKD (defined as eGFR <60/ml/min/1.73 m2) were evaluated for cognitive dysfunction using the validated Standardized Mini-Mental State Examination (SMMSE). Individuals with dementia, depression or other psychiatric disorders were excluded, as were subjects on uric acid-lowering therapy or with serious illnesses such as severe anemia or active or ongoing cardiovascular or cerebrovascular disease.

Results

247 subjects were enrolled. SMMSE scores showed stepwise deterioration with increasing quartile of serum uric acid (26.4; 26.1; 25.5; 25.3, score range 20–30, p = 0.019). Post-hoc analysis demonstrated that there was no linear trend and only groups 1 and 4 were different with respect to SMMSE scores (p = 0.025). Stepwise multivariate linear regression revealed that age, educational status, presence of cerebrovascular disease, and serum uric acid were independently related to SMMSE scores.

Conclusion

Serum uric acid levels are independently and inversely associated with mild cognitive dysfunction in subjects with CKD.

Background/Aims

Percutaneous kidney biopsy (PKB) is the primary diagnostic tool for kidney disease. Outpatient ‘day surgery’ (ODS) following PKB in low-risk patients has previously been described as a safe alternative to inpatient observation (IO). This study aims to determine if ODS is less costly compared to IO while accounting for all institutional costs (IC) associated with post-PKB complications, including death.

Methods

A cost minimization study was performed using decision analysis methodology which models relative costs in relation to outcome probabilities yielding an optimum decision. The potential outcomes included major complications (bleeding requiring blood transfusion or advanced intervention), minor complications (bleeding or pain requiring additional observation), and death. Probabilities were obtained from the published literature and a base case was selected. IC were obtained for all complications from institutional activity-based cost estimates. The base case assumed a complication rate of 10% with major bleeding occurring in 2.5% of patients (for both arms) and death in 0.1 and 0.15% of IO and ODS patients, respectively.

Results

ODS costs USD 1,394 per biopsy compared to USD 1,800 for IO inclusive of all complications. IC for ODS remain less when overall complications <20%, major complications <5.5%, and IC per death

Conclusion

Outpatient management after PKB for low-risk patients costs less from the institutional perspective compared to IO, inclusive of complications and death. ODS should be considered for low-risk patients undergoing native kidney biopsy.