Association between albuminuria, kidney function, and inflammatory biomarker profile in CKD in CRIC

Inflammatory Cytokines as Uremic Toxins: "Ni Son Todos Los Que Estan, Ni Estan Todos Los Que Son"

Chronic kidney disease is among the fastest growing causes of death worldwide. An increased risk of all-cause and cardiovascular death is thought to depend on the accumulation of uremic toxins when glomerular filtration rate falls. In addition, the circulating levels of several markers of inflammation predict mortality in patients with chronic kidney disease. Indeed, a number of cytokines are listed in databases of uremic toxins and uremic retention solutes. They include inflammatory cytokines (IL-1β, IL-18, IL-6, TNFα), chemokines (IL-8), and adipokines (adiponectin, leptin and resistin), as well as anti-inflammatory cytokines (IL-10). We now critically review the cytokines that may be considered uremic toxins. We discuss the rationale to consider them uremic toxins (mechanisms underlying the increased serum levels and evidence supporting their contribution to CKD manifestations), identify gaps in knowledge, discuss potential therapeutic implications to be tested in clinical trials in order to make this knowledge useful for the practicing physician, and identify additional cytokines, cytokine receptors and chemokines that may fulfill the criteria to be considered uremic toxins, such as sIL-6R, sTNFR1, sTNFR2, IL-2, CXCL12, CX3CL1 and others. In addition, we suggest that IL-10, leptin, adiponectin and resistin should not be considered uremic toxins toxins based on insufficient or contradictory evidence of an association with adverse outcomes in humans or preclinical data not consistent with a causal association.

Higher plasma transforming growth factor (TGF)-β is associated with kidney disease in older community dwelling adults

Background

TGF-β is induced in the vasculature with aging suggesting that high plasma TGF-β levels may be a risk factor for chronic kidney disease (CKD) in older adults.

Methods

We conducted a cross-sectional analysis of the association between plasma TGF-β levels and CKD including data for 1722 older adults who had participated in the 1996/97 visit of the Cardiovascular Health Study (CHS). Prevalent CKD was defined as eGFR < 60 mL/min/1.73 m² or urinary albumin/creatinine ratio (ACR) ≥30 mg/g. We also evaluated whether baseline TGF-β levels predicted change in eGFR, cardiovascular (CV) events, or mortality in longitudinal analysis.

Results

Plasma TGF-β levels were significantly and independently associated with lower eGFR in cross-sectional analysis. Doubling of TGF-β was significantly associated with lower eGFR (β estimate after adjusting for CV risk factors = −1.18, 95% CI −2.03, −0.32). We observed no association with albuminuria. There was no association between baseline TGF-β and change in eGFR, but each doubling of TGF-β at baseline was associated with increased risk of a composite outcome of CV events and mortality, adjusted HR 1.10 (95% C.I. 1.02– 1.20, p = 0.006).

Conclusion

In this large cohort of community-dwelling older individuals, high plasma TGF-β levels are modestly, but independently associated with lower eGFR but not with albuminuria in cross-sectional analysis. In addition, TGF-β levels are associated with increased risk of CV events and mortality. Further research is needed to determine the direction of association between plasma TGF-β and the risk of CKD and CKD-associated morbidities in older adults.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-017-0509-6) contains supplementary material, which is available to authorized users.

Kidney dysfunction in patients with pulmonary arterial hypertension

Pulmonary arterial hypertension (PH) and chronic kidney disease (CKD) both profoundly impact patient outcomes, whether as primary disease states or as co-morbid conditions. PH is a common co-morbidity in CKD and vice versa. A growing body of literature describes the epidemiology of PH secondary to chronic kidney disease and end-stage renal disease (ESRD) (WHO group 5 PH). But, there are only limited data on the epidemiology of kidney disease in group 1 PH (pulmonary arterial hypertension [PAH]). The purpose of this review is to summarize the current data on epidemiology and discuss potential disease mechanisms and management implications of kidney dysfunction in PAH. Kidney dysfunction, determined by serum creatinine or estimated glomerular filtration rate, is a frequent co-morbidity in PAH and impaired kidney function is a strong and independent predictor of mortality. Potential mechanisms of PAH affecting the kidneys are increased venous congestion, decreased cardiac output, and neurohormonal activation. On a molecular level, increased TGF-β signaling and increased levels of circulating cytokines could have the potential to worsen kidney function. Nephrotoxicity does not seem to be a common side effect of PAH-targeted therapy. Treatment implications for kidney disease in PAH include glycemic control, lifestyle modification, and potentially Renin-Angiotensin-Aldosterone System (RAAS) blockade.

Circulating TNF Receptors 1 and 2 Predict Mortality in Patients with End-stage Renal Disease Undergoing Dialysis

Relatively high circulating levels of soluble tumor necrosis factor (TNF) receptors (TNFRs: TNFR1, TNFR2) have been associated with not only progression to end-stage renal disease but also mortality in patients with diabetes. It remains unknown whether elevated TNFR levels in haemodialysis patients are associated with mortality. We studied 319 patients receiving maintenance haemodialysis who were followed for a median of 53 months. Circulating markers of TNF pathway (TNFα and TNFRs) were measured with immunoassay. Strong positive correlations between TNFR1 and TNFR2 were observed (r = 0.81, P < 0.0001). During follow-up, 88 (27.6%) patients died of any cause (40 [45.5%] died of cardiovascular disease). In the Cox multivariate model, either TNFR but not TNFα remained a significant independent predictor of all-cause mortality (TNFR1: hazard ratio [HR] 2.34, 95% confidence interval [CI], 1.50–3.64; TNFR2: HR 2.13, 95% CI 1.38–3.29) after adjustment for age, prior cardiovascular disease, predialysis systolic blood pressure, and large systolic blood pressure decline during dialysis session. For cardiovascular mortality, significance was only observed in TNFR1 (TNFR1: HR 2.15, 95% CI 1.13–4.10). Elevated TNFRs levels were associated with the risk of cardiovascular and/or all-cause mortality independent of all relevant covariates in patients undergoing haemodialysis.

Research Article. Comparative Analysis of Hepcidin-25 and Inflammatory Markers in Patients with Chronic Kidney Disease with and without Anemia

Introduction: Hepcidin is a regulatory protein in iron metabolism; we do not know the role in chronic kidney disease anemia. Methods: 22 patients with CKD anemia and 15 patients with CKD without anemia were investigated. CKD anemia-inclusion criteria: over 18 years, hemoglobin ≤12 g/dl for women and ≤13 g/dl for men, no treatment for anemia 6 months before enrollment, glomerular filtration rate (eGFR) <60 ml/min/1.73m2 and stable creatinine three months before enrollment. Exclusion criteria: infection, bleeding, malignancy, systemic or liver disease, immunosuppression, renal replacement therapy. CKD without anemia-inclusion criteria: over 18 years, no anemia or treatment for anemia, CKD with stable creatinine values three months before enrollment. Exclusion criteria: medical conditions known to have a role in the development of polycythemia. Hepcidin-25 and ferritin were measured by ELISA method. Erythropoietin (EPO), tumor necrosis factor (TNF)-α, interleukin (IL)-6 were evaluated using chemiluminescent enzyme immunometric assays. Unpaired T test, Pearson correlation and multiple regression were used for statistical analysis. Results: Hemoglobin values were significantly lower in anemia group. There were no differences in terms of eGFR, age, body mass index, serum hepcidin, erythropoietin, fibrinogen, IL-6, and TNF-α between CKD patients with and without anemia. Serum hepcidin correlated positively with ferritin (r=0.45 p<0.05), TNF-α (r=0.54, p<0.05) and negatively with erythropoietin (r=-0.51, p<0.05). Multiple linear regression analysis demonstrated that TNF-α is an independent predictor of serum hepcidin in our patients (p=0.003, R=0.71). Conclusion: We found no differences in serum hepcidin, erythropoietin and inflammatory markers in non-dialysis CKD patients with and without anemia.

Markers of endothelial damage in patients with chronic kidney disease on hemodialysis

Patients with Stage 5 chronic kidney disease who are on hemodialysis (HD) remain in a chronic inflammatory state, characterized by the accumulation of uremic toxins that induce endothelial damage and cardiovascular disease (CVD). Our aim was to examine microvesicles (MVs), monocyte subpopulations, and angiopoietins (Ang) to identify prognostic markers in HD patients with or without diabetes mellitus (DM). A total of 160 prevalent HD patients from 10 centers across Spain were obtained from the Biobank of the Nephrology Renal Network (Madrid, Spain): 80 patients with DM and 80 patients without DM who were matched for clinical and demographic criteria. MVs from plasma and several monocyte subpopulations (CD14²⁺/CD16⁺, CD14⁺/CD16²⁺) were analyzed by flow cytometry, and the plasma concentrations of Ang1 and Ang2 were quantified by ELISA. Data on CVD were gathered over the 5.5 yr after these samples were obtained. MV level, monocyte subpopulations (CD14⁺/CD16²⁺ and CD14²⁺/CD16⁺), and Ang2-to-Ang1 ratios increased in HD patients with DM compared with non-DM patients. Moreover, MV level above the median (264 MVs/µl) was associated independently with greater mortality. MVs, monocyte subpopulations, and Ang2-to-Ang1 ratio can be used as predictors for CVD. In addition, MV level has a potential predictive value in the prevention of CVD in HD patients. These parameters undergo more extensive changes in patients with DM.

Clot Structure: A Potent Mortality Risk Factor in Patients on Hemodialysis

Patients with CKD on hemodialysis exhibit increased cardiovascular risk. Fibrin clot structure and clot lysis are crucially involved in development of cardiovascular events, but little is known about the influence of clot density on outcome in patients on hemodialysis. We determined fibrin clot structure parameters and effect on mortality in a prospective cohort of 171 patients on chronic hemodialysis (mean±SD age =59±11 years old; 54% men) using a validated turbidimetric assay. Kaplan-Meier analysis revealed that patients on hemodialysis with a denser clot structure had increased all-cause and cardiovascular mortality risks (log rank P=0.004 and P=0.003, respectively). Multivariate Cox regression models (adjusted for age, diabetes, sex, and duration of dialysis or fibrinogen, C-reactive protein, and complement C3) confirmed that denser clots are independently related to mortality risk. We also purified fibrinogen from healthy controls and patients on hemodialysis using the calcium-dependent IF-1 mAb against fibrinogen for additional investigation using mass spectrometric analysis and electron microscopy. Whereas purified fibrinogen from healthy controls displayed no post-translational modifications, fibrinogen from patients on hemodialysis was glycosylated and guanidinylated. Clots made of purified fibrinogen from patients on hemodialysis exhibited significantly thinner fibers compared with clots from fibrinogen of control individuals (mean±SD =63±2 and 77±2 nm, respectively; P<0.001). In vitro guanidinylation of fibrinogen from healthy subjects increased the formation of thinner fibers, suggesting that difference in fiber thickness might be at least partially due to post-translational modifications. Thus, in patients on hemodialysis, a denser clot structure may be a potent independent risk factor for mortality.

Relationship between plasma levels of zonulin, bacterial lipopolysaccharides, D-lactate and markers of inflammation in haemodialysis patients

BACKGROUND

Increased permeability of the intestinal wall and intestinal dysbiosis may contribute to chronic systemic inflammation, one of the causes of accelerated atherosclerosis and cardiovascular morbidity and mortality burden in patients with chronic kidney disease. The aim of this study was to evaluate the association between markers of intestinal permeability and inflammation in haemodialysis (HD) patients.

METHODS

Plasma concentration of zonulin, haptoglobin, TNFα, IL6, D-lactates and bacterial lipopolysaccharides (LPS) was assessed in blood samples obtained after overnight fast before midweek morning HD session in 150 stable, prevalent HD patients. Daily intake of energy and macronutrients was assessed on the basis of a food frequency questionnaire.

RESULTS

Serum hsCRP level was increased in over 70% of patients. Plasma levels of zonulin [11.6 (10.9-12.3) vs 6.8 (5.8-7.8) ng/mL], IL6 [6.2 (1.0-10.3) vs 1.3 (1.0-2.0) pg/mL] and TNFα [5.9 (2.9-11.8) vs 1.6 (1.3-1.8) pg/mL], but not LPS and D-lactates were significantly higher in HD than in healthy controls. D-lactates and LPS levels were weakly associated with IL6 (R = 0.175; p = 0.03, and R = 0.241; p = 0.003). There was a borderline correlation between plasma zonulin and serum hsCRP (R = 0.159; p = 0.07), but not with IL6, LPS and D-lactates. In multiple regression, both serum CRP and plasma IL6 variability were explained by LPS (β = 0.143; p = 0.08 and β = 0.171; p = 0.04, respectively), only.

CONCLUSION

The weak association between plasma D-lactate, LPS and IL6 levels indicates that intestinal flora overgrowth or increased intestinal permeability contributes very slightly to the chronic inflammation development in HD patients.

Inflammation and elevated levels of fibroblast growth factor 23 are independent risk factors for death in chronic kidney disease

Inflammation is a consequence of chronic kidney disease (CKD) and is associated with adverse outcomes in many clinical settings. Inflammation stimulates production of fibroblast growth factor 23 (FGF23), high levels of which are independently associated with mortality in CKD. Few large-scale prospective studies have examined inflammation and mortality in patients with CKD, and none tested the interrelationships among inflammation, FGF23, and risk of death. Therefore, we conducted a prospective investigation of 3875 participants in the Chronic Renal Insufficiency Cohort (CRIC) study with CKD stages 2 to 4 to test the associations of baseline plasma interleukin-6, high-sensitivity C-reactive protein, and FGF23 levels with all-cause mortality, censoring at the onset of end-stage renal disease. During a median follow-up of 6.9 years, 550 participants died (20.5/1000 person-years) prior to end-stage renal disease. In separate multivariable-adjusted analyses, higher levels of interleukin-6 (hazard ratio per one standard deviation increase of natural log-transformed levels) 1.35 (95% confidence interval, 1.25-1.46), C-reactive protein 1.28 (1.16-1.40), and FGF23 1.45 (1.32-1.60) were each independently associated with increased risk of death. With further adjustment for FGF23, the risks of death associated with interleukin-6 and C-reactive protein were minimally attenuated. Compared to participants in the lowest quartiles of inflammation and FGF23, the multivariable-adjusted hazard ratio of death among those in the highest quartiles of both biomarkers was 4.38 (2.65-7.23) for interleukin-6 and FGF23, and 5.54 (3.04-10.09) for C-reactive protein and FGF23. Thus, elevated levels of interleukin-6, C-reactive protein, and FGF23 are independent risk factors for mortality in CKD.

DASH dietary pattern and chronic kidney disease in elderly Korean adults

BACKGROUND/OBJECTIVES

Dietary patterns are linked to risk and outcomes in chronic kidney disease (CKD). Dietary intake varies by race, region and age. The relationship between a Dietary Approaches to Stop Hypertension (DASH) diet and CKD in elderly Koreans is unclear.

SUBJECTS/METHODS

We conducted cross-sectional analyses of 2408 community-dwelling elderly participants from the Korean National Health and Nutrition Examination Survey (2011-2012). DASH dietary patterns for six nutrients (protein, fiber, calcium, potassium, total fat and sodium) were collected by 24 h recall. DASH-US (based on the US recommendations) and DASH-KQ (Korean quartile) scores were generated by summing the scores for the six nutrients. Multivariate logistic regression analysis was used to calculate odds ratio (OR) for the association between a DASH diet and CKD.

RESULTS

Mean subject age was 72.4±5.1 years, 13.9% had CKD and 23.8% had diabetes. Protein, fiber, calcium and potassium intake was lower in CKD than non-CKD participants. In multivariate logistic regression analysis adjusted for age, sex, body mass index, comorbid conditions and other factors, a high DASH score was associated with a low odds for CKD based on DASH-US (OR=0.78, 95% confidence interval (CI), 0.65-0.94, P=0.009) and DASH-KQ (OR=0.95, 95% CI, 0.91-0.99, P=0.022). In six nutrients of DASH diet, high fiber intake showed a low odds for CKD in the DASH-KQ model (P for trend=0.010).

CONCLUSIONS

Our findings suggest that higher adherence to a DASH diet and higher fiber intake are associated with lower odds of CKD in elderly Koreans. These results should be corroborated through longitudinal studies of the association between a DASH diet and high-fiber diet on the risk of developing CKD.

Inflammatory Markers and Risk for Cognitive Decline in Chronic Kidney Disease: The CRIC Study

Introduction

Chronic kidney disease (CKD) is associated with an increased risk of cognitive decline, but the mechanisms remain poorly defined. We sought to determine the relation between serum inflammatory markers and risk of cognitive decline among adults with CKD.

Methods

We studied 757 adults aged ≥55 years with CKD participating in the Chronic Renal Insufficiency Cohort Cognitive study. We measured interleukin (IL)−1β, IL-1 receptor antagonist, IL-6, tumor necrosis factor (TNF)−α, high-sensitivity C-reactive protein (hs-CRP), and fibrinogen in baseline plasma samples. We assessed cognitive function at regular intervals in 4 domains and defined incident impairment as a follow-up score more than 1 SD poorer than the group mean.

Results

The mean age of the sample was 64.3 ± 5.6 years, and the mean follow-up was 6.2 ± 2.5 years. At baseline, higher levels of each inflammatory marker were associated with poorer age-adjusted performance. In analyses adjusted for baseline cognition, demographics, comorbid conditions, and kidney function, participants in the highest tertile of hs-CRP, the highest tertile of fibrinogen, and the highest tertile of IL-1β had an increased risk of impairment in attention compared to participants in the lowest tertile of each marker. Participants in the highest versus lowest tertile of TNF-α had a lower adjusted risk of impairment in executive function. There was no association between other inflammatory markers and change in cognitive function.

Discussion

Among adults with CKD, higher levels of hs-CRP, fibrinogen, and IL-1β were associated with a higher risk of impairment in attention. Higher levels of TNF-α were associated with a lower risk of impaired executive function.

Inflammation and Progression of CKD: The CRIC Study

BACKGROUND AND OBJECTIVES

CKD is a global public health problem with significant mortality and morbidity.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We examined the multivariable association of plasma levels of IL-1, IL-1 receptor antagonist, IL-6, TNF-α, TGF-β, high-sensitivity C-reactive protein, fibrinogen, and serum albumin with progression of CKD in 3430 Chronic Renal Insufficiency Cohort study participants.

RESULTS

Over a median follow-up time of 6.3 years, 899 participants reached the composite end point of ≥50% decline in eGFR from baseline or onset of ESRD. Elevated plasma levels of fibrinogen, IL-6, and TNF-α and lower serum albumin were associated with a greater decline in eGFR over time. After adjusting for demographics, BP, laboratory variables, medication use, and baseline eGFR, hazard ratios for the composite outcome were greater for the patients in the highest quartile of fibrinogen (hazard ratio, 2.05; 95% confidence interval, 1.64 to 2.55; P<0.001), IL-6 (hazard ratio, 1.44; 95% confidence interval, 1.17 to 1.77; P<0.01), and TNF-α (hazard ratio, 1.94; 95% confidence interval, 1.52 to 2.47; P<0.001) compared with those in the respective lowest quartiles. The hazard ratio was 3.48 (95% confidence interval, 2.88 to 4.21; P<0.001) for patients in the lowest serum albumin quartile relative to those in the highest quartile. When also adjusted for albuminuria, the associations of fibrinogen (hazard ratio, 1.49; 95% confidence interval, 1.20 to 1.86; P<0.001), serum albumin (hazard ratio, 1.52; 95% confidence interval, 1.24 to 1.87; P<0.001), and TNF-α (hazard ratio, 1.42; 95% confidence interval, 1.11 to 1.81; P<0.001) with outcome were attenuated but remained significant.

CONCLUSIONS

Elevated plasma levels of fibrinogen and TNF-α and decreased serum albumin are associated with rapid loss of kidney function in patients with CKD.

OLDER PEOPLE WITH CHRONIC KIDNEY DISEASE: DEFINITION, AND INFLUENCE OF BIOMARKERS AND MEDICATIONS UPON CARDIOVASCULAR AND RENAL OUTCOMES

BACKGROUND

Chronic kidney disease (CKD) is a global problem. With an ageing population the burden on the health services has increased due to the growing number of older people with CKD. This group of individuals is far different to the younger CKD population and their risk of cardiovascular death is far greater than the risk of progressing to end stage kidney disease (ESKD).

OBJECTIVE

In this review we explore the role of certain biomarkers and medications in predicting the risk of progression to ESKD and death in old people with CKD.

METHODS

An electronic literature search of EMBASE and MEDLINE databases was performed using Healthcare Databases Advanced Search (HDAS) in December 2014.

RESULTS

Albuminuria is a key biomarker in predicting the risk of death and progression to ESKD. Cystatin C appears to be superior in predicting the risk of cardiovascular and non-cardiovascular death compared to GFR or creatinine. Several inflammatory biomarkers can be used to predict the risk of death and progression to CKD but measuring and monitoring them in routine clinical practice will be expensive and impractical. The effects of long-term RAAS inhibition in older people are not well established. Older people especially those with CKD receive suboptimal secondary preventive measures. Due to multiple comorbidities older people with CKD are usually receiving a number of medications. This can potentially lead to significant adverse drug events (ADE) due to drug interactions.

CONCLUSION

Novel non-traditional risk factors like albuminuria, Cystatin C and inflammatory biomarkers play an important role in predicting their risk of death and progression to ESKD. The efficacy and safety of medications in older people with CKD is not well established and requires more extensive, focused study.

Pretransplant Immune- and Apoptosis-Related Gene Expression Is Associated with Kidney Allograft Function

Renal transplant candidates present immune dysregulation, caused by chronic uremia. The aim of the study was to investigate whether pretransplant peripheral blood gene expression of immune factors affects clinical outcome of renal allograft recipients. Methods. In a prospective study, we analyzed pretransplant peripheral blood gene expression in87 renal transplant candidates with real-time PCR on custom-designed low density arrays (TaqMan). Results. Immediate posttransplant graft function (14-day GFR) was influenced negatively by TGFB1 (P = 0.039) and positively by IL-2 gene expression (P = 0.040). Pretransplant blood mRNA expression of apoptosis-related genes (CASP3, FAS, and IL-18) and Th1-derived cytokine gene IFNG correlated positively with short- (6-month GFR CASP3: P = 0.027, FAS: P = 0.021, and IFNG: P = 0.029) and long-term graft function (24-month GFR CASP3: P = 0.003, FAS: P = 0.033, IL-18: P = 0.044, and IFNG: P = 0.04). Conclusion. Lowered pretransplant Th1-derived cytokine and apoptosis-related gene expressions were a hallmark of subsequent worse kidney function but not of acute rejection rate. The pretransplant IFNG and CASP3 and FAS and IL-18 genes' expression in the recipients' peripheral blood is the possible candidate for novel biomarker of short- and long-term allograft function.

Hepcidin Response to Iron Therapy in Patients with Non-Dialysis Dependent CKD: An Analysis of the FIND-CKD Trial

Hepcidin is the key regulator of iron homeostasis but data are limited regarding its temporal response to iron therapy, and response to intravenous versus oral iron. In the 56-week, open-label, multicenter, prospective, randomized FIND-CKD study, 626 anemic patients with non-dialysis dependent chronic kidney disease (ND-CKD) and iron deficiency not receiving an erythropoiesis stimulating agent were randomized (1:1:2) to intravenous ferric carboxymaltose (FCM), targeting higher (400-600μg/L) or lower (100-200μg/L) ferritin, or to oral iron. Serum hepcidin levels were measured centrally in a subset of 61 patients. Mean (SD) baseline hepcidin level was 4.0(3.5), 7.3(6.4) and 6.5(5.6) ng/mL in the high ferritin FCM (n = 17), low ferritin FCM (n = 16) and oral iron group (n = 28). The mean (SD) endpoint value (i.e. the last post-baseline value) was 26.0(9.1),15.7(7.7) and 16.3(11.0) ng/mL, respectively. The increase in hepcidin from baseline was significantly smaller with low ferritin FCM or oral iron vs high ferritin FCM at all time points up to week 52. Significant correlations were found between absolute hepcidin and ferritin values (r = 0.65, p<0.001) and between final post-baseline increases in both parameters (r = 0.70, p<0.001). The increase in hepcidin levels over the 12-month study generally mirrored the cumulative iron dose in each group. Hepcidin and transferrin saturation (TSAT) absolute values showed no correlation, although there was an association between final post-baseline increases (r = 0.42, p<0.001). Absolute values (r = 0.36, p = 0.004) and final post-baseline increases of hepcidin and hemoglobin (p = 0.30, p = 0.030) correlated weakly. Baseline hepcidin levels were not predictive of a hematopoietic response to iron therapy. In conclusion, hepcidin levels rose in response to either intravenous or oral iron therapy, but the speed and extent of the rise was greatest with intravenous iron targeting a higher ferritin level. However neither the baseline level nor the change in hepcidin was able to predict response to therapy in this cohort.

Role of Vitamin D in Cognitive Function in Chronic Kidney Disease

Both vitamin D deficiency and cognitive impairment are common in patients with chronic kidney disease (CKD). Vitamin D exerts neuroprotective and regulatory roles in the central nervous system. Hypovitaminosis D has been associated with muscle weakness and bone loss, cardiovascular diseases (hypertension, diabetes and hyperlipidemia), inflammation, oxidative stress, immune suppression and neurocognitive impairment. The combination of hypovitaminosis D and CKD can be even more debilitating, as cognitive impairment can develop and progress through vitamin D-associated and CKD-dependent/independent processes, leading to significant morbidity and mortality. Although an increasingly recognized comorbidity in CKD, cognitive impairment remains underdiagnosed and often undermanaged. Given the association of cognitive decline and hypovitaminosis D and their deleterious effects in CKD patients, determination of vitamin D status and when appropriate, supplementation, in conjunction with neuropsychological screening, should be considered integral to the clinical care of the CKD population.

Bariatric surgery is associated with improvement in kidney outcomes

Severe obesity is associated with increased risk of kidney disease. Whether bariatric surgery reduces the risk of adverse kidney outcomes is uncertain. To resolve this we compared the risk of estimated glomerular filtration rate (eGFR) decline of ≥30% and doubling of serum creatinine or end-stage renal disease (ESRD) in 985 patients who underwent bariatric surgery with 985 patients who did not undergo such surgery. Patients were matched on demographics, baseline body mass index, eGFR, comorbidities, and previous nutrition clinic use. Mean age was 45 years, 97% were white, 80% were female, and 33% had baseline eGFR <90 ml/min per 1.73 m(2). Mean 1-year weight loss was 40.4 kg in the surgery group compared with 1.4 kg in the matched cohort. Over a median follow-up of 4.4 years, 85 surgery patients had an eGFR decline of ≥30% (22 had doubling of serum creatinine/ESRD). Over a median follow-up of 3.8 years, 177 patients in the matched cohort had an eGFR decline of ≥30% (50 had doubling of serum creatinine/ESRD). In adjusted analysis, bariatric surgery patients had a significant 58% lower risk for an eGFR decline of ≥30% (hazard ratio 0.42, 95% confidence interval 0.32-0.55) and 57% lower risk of doubling of serum creatinine or ESRD (hazard ratio 0.43, 95% confidence interval: 0.26-0.71) compared with the matched cohort. Results were generally consistent among subgroups of patients with and without eGFR <90 ml/min per 1.73 m(2), hypertension, and diabetes. Thus, bariatric surgery may be an option to prevent kidney function decline in severely obese individuals.

Intestinal Dysbiosis, Barrier Dysfunction, and Bacterial Translocation Account for CKD-Related Systemic Inflammation

CKD associates with systemic inflammation, but the underlying cause is unknown. Here, we investigated the involvement of intestinal microbiota. We report that collagen type 4 α3-deficient mice with Alport syndrome-related progressive CKD displayed systemic inflammation, including increased plasma levels of pentraxin-2 and activated antigen-presenting cells, CD4 and CD8 T cells, and Th17- or IFNγ-producing T cells in the spleen as well as regulatory T cell suppression. CKD-related systemic inflammation in these mice associated with intestinal dysbiosis of proteobacterial blooms, translocation of living bacteria across the intestinal barrier into the liver, and increased serum levels of bacterial endotoxin. Uremia did not affect secretory IgA release into the ileum lumen or mucosal leukocyte subsets. To test for causation between dysbiosis and systemic inflammation in CKD, we eradicated facultative anaerobic microbiota with antibiotics. This eradication prevented bacterial translocation, significantly reduced serum endotoxin levels, and fully reversed all markers of systemic inflammation to the level of nonuremic controls. Therefore, we conclude that uremia associates with intestinal dysbiosis, intestinal barrier dysfunction, and bacterial translocation, which trigger the state of persistent systemic inflammation in CKD. Uremic dysbiosis and intestinal barrier dysfunction may be novel therapeutic targets for intervention to suppress CKD-related systemic inflammation and its consequences.

Role of Myeloperoxidase in Patients with Chronic Kidney Disease

Chronic kidney disease (CKD) is a worldwide public health problem. Patients with CKD have a number of disorders in the organism, and the presence of oxidative stress and systemic inflammation in these patients is the subject of numerous studies. Chronic inflammation joined with oxidative stress contributes to the development of numerous complications: accelerated atherosclerosis process and cardiovascular disease, emergence of Type 2 diabetes mellitus, development of malnutrition, anaemia, hyperparathyroidism, and so forth, affecting the prognosis and quality of life of patients with CKD. In this review we presented the potential role of the myeloperoxidase enzyme in the production of reactive/chlorinating intermediates and their role in oxidative damage to biomolecules in the body of patients with chronic kidney disease and end-stage renal disease. In addition, we discussed the role of modified lipoprotein particles under the influence of prooxidant MPO intermediates in the development of endothelial changes and cardiovascular complications in renal failure.

Impact of Continuous Erythropoietin Receptor Activator on Selected Biomarkers of Cardiovascular Disease and Left Ventricle Structure and Function in Chronic Kidney Disease

Background. Cardiovascular morbidity and mortality are very high in patients with chronic kidney disease (CKD). The purpose of this study is to evaluate the impact of continuous erythropoietin receptor activator (CERA) on selected biomarkers of cardiovascular disease, left ventricle structure, and function in CKD. Material and Methods. Peripheral blood was collected from 25 CKD patients before and after CERA treatment and 20 healthy subjects. In serum samples, we assessed inflammatory markers (IL-1β, TNF-RI, TNF-RII, sFas, sFasL, MMP-9, TIMP-1, and TGF-β1), endothelial dysfunction markers (sE-selectin, sICAM-1, and sVCAM-1), and volume-related marker (NT-proBNP). All subjects underwent echocardiography and were evaluated for selected biochemical parameters (Hb, creatinine, and CRP). Results. Evaluated biomarkers and echocardiographic parameters of left ventricle structure were significantly increased but left ventricle EF was significantly decreased in CKD patients compared to controls. After CERA treatment, we observed a significant increase of Hb and left ventricle EF and a significant decrease of NT-proBNP and MMP-9. There was a significant negative correlation between Hb and TNF-RI, sICAM-1, and IL-1β. Conclusions. Our results indicate that selected biomarkers related to cardiovascular risk are significantly increased in CKD patients compared to controls. CERA treatment has anti-inflammatory action, diminishes endothelial dysfunction, and improves left ventricle function in these patients.

Combined body mass index with high-sensitivity C-reactive protein as independent predictors for chronic kidney disease in a relatively healthy population in Taiwan

BACKGROUND/OBJECTIVES

Obesity, a chronic inflammatory state, increases risk of cardiovascular disease and insulin resistance, which are the leading cause of end-stage renal disease (ESRD). We evaluated the relationship between body mass index (BMI) and high-sensitivity C-reactive protein (hsCRP) level and impaired kidney function to determine the predictive value of both markers for estimating chronic kidney disease (CKD) risk in a healthy adult population in Taiwan.

SUBJECTS/METHODS

In a retrospective cross-sectional study of 4100 subjects ⩾18 years, a multivariate logistic regression model was used to assess the relationship among BMI, high hsCRP levels and CKD. Receiver-operating characteristic curve and Youden index were developed to define the discrimination power of combining BMI with hsCRP for CKD prediction and to determine the best predictive index.

RESULTS

Overweight/obese subjects with high hsCRP levels had the highest odds ratio for CKD (P=0.048). In females, combining BMI with hsCRP for CKD prediction was superior to that of males (0.890 vs 0.623, respectively; both P<0.001). For females, the Youden index was 25.65 kg/m(2) for BMI and 1.04 μg/ml for hsCRP.

CONCLUSIONS

Overweight/obesity with higher hsCRP levels is associated with reduced renal function and increased risk for CKD. BMI and hsCRP levels can be used as surrogate markers for CKD risk, especially for females.

Antioxidant therapy improves non-thyroidal illness syndrome in uremic rats

BACKGROUND

The roles of antioxidant therapy on non-thyroidal illness syndrome (NTIS) in uremic rats is still unclear.

MATERIALS AND METHODS

Twenty-four Sprague-Dawley (SD) rats were randomly divided into blank, 5/6 nephrectomy (Nx), pyrrolidine dithiocarbamate (PDTC, 10 mg/100 g), sodium bicarbonate (SB, 0.1 g/100 g), N-acetylcysteine (NAC, 80 mg/100 g) and thyroid hormones (TH, levothyroxine 2 μg/100 g) groups. The serum levels of malondialdehyde (MDA), superoxide dismutase (SOD), advanced oxidation protein products (AOPP), interleukin (IL)-1β, free triiodothyronine (FT3), and thyroid stimulating hormone (TSH) were detected in the sixth week. The expressions of IL-1β and deiodinase type 1 (DIO1) were assessed by western blotting. The nuclear factor kappa B (NF-κB) inflammatory signal pathway was confirmed by electrophoretic mobility shift assay (EMSA).

RESULTS

Compared with 5/6 Nx group, PDTC and NAC significantly reduced the levels (p < 0.01, respectively) of serum MDA, AOPP, TSH, and elevated levels of serum SOD (p < 0.01, respectively) and FT3 (p = 0.016 and p < 0.01). Neither had significant effects on serum IL-1β content (p = 0.612 and p = 0.582). PDTC and NAC markedly decreased the protein expression of IL-1β (p < 0.01) and increased the protein expression of DIO1 (p < 0.01), respectively. Both had been considerably blunted NF-κB activity (p < 0.01).

CONCLUSIONS

In uremic rat model, PDTC and NAC can effectively improve oxidative stress level and NTIS. In terms of improving oxidative stress level, NAC is probably superior to PDTC.

Mortality Outcomes of Patients with Chronic Kidney Disease and Chronic Obstructive Pulmonary Disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is associated with higher mortality in the general population. We studied the associations between COPD and death among chronic kidney disease (CKD) patients along with reporting cause-specific death data.

METHODS

We included 56,960 patients with stages 3 and 4 CKD who were followed in a large health care system. Associations between COPD and all-cause mortality and various causes of death (respiratory deaths, cardiovascular deaths, malignancy-related deaths and deaths due to other reasons) were studied using the Cox proportional hazards and competing risk models.

RESULTS

Out of 56,960 CKD patients, 4.7% (n = 2,667) had underlying COPD. Old age, presence of diabetes, hypertension, coronary artery disease, congestive heart failure, and smoking were associated with higher risk for COPD. During a median follow-up of 3.7 years, 15,969 patients died. After covariate adjustment, COPD was associated with a 41% increased risk (95% CI 1.31-1.52) for all-cause mortality, and fourfold increased risk (sub-hazard ratio 4.36, 95% CI 3.54-5.37) for respiratory-related deaths. In a sensitivity analysis that was performed by defining COPD as the use of relevant International Classification of Diseases-9 codes and medications used to treat COPD, similar results were noted.

CONCLUSIONS

COPD is associated with higher risk for death among those with CKD, and an underlying lung disease accounts for significant proportion of deaths. These data highlight the need for further prospective studies to understand the underlying mechanisms and potential interventions to improve outcomes in this population.

Interleukin-6 Is a Risk Factor for Atrial Fibrillation in Chronic Kidney Disease: Findings from the CRIC Study

Atrial fibrillation (AF) is the most common sustained arrhythmia in patients with chronic kidney disease (CKD). In this study, we examined the association between inflammation and AF in 3,762 adults with CKD, enrolled in the Chronic Renal Insufficiency Cohort (CRIC) study. AF was determined at baseline by self-report and electrocardiogram (ECG). Plasma concentrations of interleukin(IL)-1, IL-1 Receptor antagonist, IL-6, tumor necrosis factor (TNF)-α, transforming growth factor-β, high sensitivity C-Reactive protein, and fibrinogen, measured at baseline. At baseline, 642 subjects had history of AF, but only 44 had AF in ECG recording. During a mean follow-up of 3.7 years, 108 subjects developed new-onset AF. There was no significant association between inflammatory biomarkers and past history of AF. After adjustment for demographic characteristics, comorbid conditions, laboratory values, echocardiographic variables, and medication use, plasma IL-6 level was significantly associated with presence of AF at baseline (Odds ratio [OR], 1.61; 95% confidence interval [CI], 1.21 to 2.14; P = 0.001) and new-onset AF (OR, 1.25; 95% CI, 1.02 to 1.53; P = 0.03). To summarize, plasma IL-6 level is an independent and consistent predictor of AF in patients with CKD.

Macrophage Migration Inhibitory Factor in Clinical Kidney Disease

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine implicated in acute and chronic inflammatory conditions, including sepsis, autoimmune disease, atherogenesis, plaque instability, and pulmonary arterial hypertension. MIF in plasma and urine is significantly elevated in patients with acute kidney injury (AKI) and elevated MIF in serum is associated with markers of oxidative stress, endothelial dysfunction, arterial stiffness, and markers of myocardial damage in chronic kidney disease (CKD). Furthermore, MIF seems to be involved in vascular processes and cardiovascular disease associated with CKD, glomerulonephritis, autosomal dominant polycystic kidney disease, and possibly also in progression to renal failure. Moreover, in active anti-neutrophil cytoplasmatic antibody-associated vasculitis, plasma MIF levels have been shown to be significantly elevated as compared with samples from patients in remission. A significant difference in the genotype frequency of high production MIF -173 G/C genotype has been found in end-stage renal disease, compared to controls. Inhibition of MIF in a diabetic nephropathy model ameliorated blood glucose and albuminuria and in a model of adult polycystic kidney disease cyst growth was delayed. Preclinical studies support a potential therapeutic role for MIF in AKI and in a number of CKDs, whereas these data in human disease are still observational. Future interventional studies are needed to delineate the role of MIF as a treatment target in clinical kidney disease.

The Role of the Gut Microbiome on Chronic Kidney Disease

Chronic kidney disease (CKD) is estimated to affect nearly 500 million people worldwide and cardiovascular (CV) disease is a major cause of death in this population. However, therapeutic interventions targeting traditional CV risks are not effective at lowering the incidence of CV events or at delaying the progression of the disease in CKD patients. In recent years, disturbances of normal gut microbiome were recognized in the pathogenesis of diverse chronic diseases. Gut dysbiosis is being unraveled in CKD and pointed as a nontraditional risk factor for CV risk and CKD progression. The most often reported changes in gut microbiome in CKD are related to the lower levels of Bifidobacteriaceae and Lactobacillaceae and to higher levels of Enterobacteriaceae. Although metagenomics brought us an amplified vision on the microbial world that inhabits the human host, it still lacks the sensitivity to characterize the microbiome up to species level, not revealing alterations that occur within specific genus. Here, we review the current state-of-the-art concerning gut dysbiosis in CKD and its role in pathophysiological mechanisms in CKD, particularly in relation with CV risk. Also, the strategies towards prevention and treatment of gut dysbiosis in CKD progression will be discussed.

Therapeutics targeting persistent inflammation in chronic kidney disease

Systemic inflammation is a condition intrinsically linked to chronic kidney disease (CKD) and its other typical sequelae, such as acquired immune dysfunction, protein-energy wasting (PEW), and accelerated vascular aging that promote premature cardiovascular disease (CVD) and infections, the two leading causes of death in CKD patients. Inflammation is a major contributor to complications in CKD, and inflammatory markers, such as C-reactive protein and pro- and anti-inflammatory cytokines, correlate with underlying causes and consequences of the inflamed uremic phenotype, such as oxidative stress, endothelial dysfunction, CVD, PEW, and infections, and are sensitive and independent predictors of outcome in CKD. Therefore, inflammation appears to be a logical target for potential preventive and therapeutic interventions in patients with CKD. Putative anti-inflammatory therapy strategies aiming at preventing complications and improving outcomes in CKD span over several areas: (1) dealing with the source of inflammation (such as cardiovascular, gastrointestinal or periodontal disease and depression); (2) providing nonspecific immune modulatory effects by promoting healthy dietary habits and other lifestyle changes; (3) promoting increased use of recognized pharmacologic interventions that have pleiotropic effects; and, (4) introducing novel targeted anticytokine interventions. This review provides a brief update on inflammatory biomarkers and possible therapeutic approaches targeting inflammation and the uremic inflammatory milieu in patients with CKD.

Significance of Neutrophil Gelatinase-Associated Lipocalin Level-to-Serum Creatinine Ratio for Assessing Severity of Inflammation in Patients with Renal Dysfunction

The aim of this study was to assess the significance of the neutrophil gelatinase-associated lipocalin/serum creatinine ratio (NGAL/sCr ratio) in patients with renal dysfunction. The percent difference between plasma NGAL level and the NGAL/sCr ratio was 36.7% (95% CI, 18.4–83.7%) in patients with sCr level ≥ 1.2 mg/dL. In a multivariate analysis, high sensitivity C-reactive protein (hsCRP) was significantly associated with the NGAL/sCr ratio and plasma NGAL level (r = 0.526 and r = 0.453, resp., P < 0.001). In a receiver operating characteristics curve, the diagnostic ability of the NGAL/sCr ratio to identify hsCRP > 4.0 mg/dL was superior to that of NGAL [0.783 (95% CI, 0.674–0.892) versus 0.733 (95% CI, 0.615–0.852), P = 0.032]. The area under the curve of the NGAL/sCr ratio was larger than that of hsCRP to detect corrected erythrocyte sedimentation rate > 25 mm/h and the neutrophil-to-lymphocyte ratio >4.5 in renal dysfunction. In short, the NGAL/sCr ratio may offer useful information when screening patients with both systemic inflammation and renal dysfunction.

Inflammatory Markers and Procoagulants in Chronic Renal Disease Stages 1-4

Introduction:

Starting from the point that the chronic kidney disease (CKD) is chronic, inflammatory and hypercoagulable state characterized by an increase in procoagulant and inflammatory markers high cardiovascular morbidity and mortality in these patients could be explained.

Aim:

The aim of the research was to monitor inflammatory markers and procoagulants in various stages of kidney disease (stage 1-4).

Materials and Methods:

The research included 120 subjects older than 18 years with CKD stages 1-4 examined and monitored in Clinic of Nephrology, University Clinical Centre Sarajevo over a period of 24 months. The research included determining the following laboratory parameters: serum creatinine, serum albumin, C-reactive protein, leukocytes in the blood, plasma fibrinogen, D-dimer, antithrombin III, coagulation factors VII (FC VII) and coagulation factor VIII (FC VIII).

Results:

With the progression of kidney disease (CKD stages 1-4), there was a significant increase of inflammatory and procoagulant markers: CRP, fibrinogen and coagulation factor VIII, and an increase in the average values of leukocytes and a reduction in the value of antithrombin III, but without statistical significance. Also, there were no significant differences in the values of D-dimer and coagulation factor VII.

Conclusion:

The progression of kidney disease is significantly associated with inflammation, which could in the future be useful in prognostic and therapeutic purposes. Connection of CKD with inflammation and proven connection of inflammation with cardiovascular risk indicates the potential value of some biomarkers, which could in the future identify as predictors of outcome and could have the benefit in the early diagnosis and treatment of cardiovascular disease in CKD.

Gut microbiome in chronic kidney disease

NEW FINDINGS

What is the topic of this review? This review addresses the contribution of the altered gut microbiome to uraemic syndrome, with specific reference to gut microbiome-derived uraemic toxins. It also discusses the potential treatment options to normalize the disturbed microbiome in chronic kidney disease (CKD). What advances does it highlight? This review highlights the importance of the gut-kidney connection and how the altered microbial landscape in the intestine contributes to dysmetabolism and inflammation in CKD. Recent findings linking gut-derived uraemic toxins to progression of CKD, cardiovascular disease and mortality are also discussed. Finally, we briefly explain targeted therapies that have been studied to restore intestinal symbiosis in CKD. The human intestine is now recognized as an important metabolic organ powered by gut microbiota. This review addresses the alteration in the gut microbiome in patients with chronic kidney disease (CKD) and its consequence. We describe the major uraemic toxins, p-cresol sulfate, indoxyl sulfate and trimethylamine N-oxide, which are produced by the gut microbiome, and how these metabolites contribute to progression of CKD and associated cardiovascular disease. Translocation of endotoxin from the gut into the systemic circulation contributes to inflammation in CKD. Targeting the gut microbiome to restore symbiosis may prove to be a potent strategy in reducing inflammation and production of these uraemic toxins.

TLR4 mutant mice are protected from renal fibrosis and chronic kidney disease progression

Chronic kidney disease (CKD) is associated with persistent low-grade inflammation and immunosuppression. In this study we tested the role of Toll-like receptor 4, the main receptor for endotoxin (LPS), in a mouse model of renal fibrosis and in a model of progressive CKD that better resembles the human disease. C3HeJ (TLR4 mutant) mice have a missense point mutation in the TLR4 gene, rendering the receptor nonfunctional. In a model of renal fibrosis after folic acid injection, TLR4 mutant mice developed less interstititial fibrosis in comparison to wild-type (WT) mice. Furthermore, 4 weeks after 5/6 nephrectomy with continuous low-dose angiotensin II infusion, C3HeOuJ (TLR4 WT) mice developed progressive CKD with albuminuria, increased serum levels of BUN and creatinine, glomerulosclerosis, and interstitial fibrosis, whereas TLR4 mutant mice were significantly protected from CKD progression. TLR4 WT mice also developed low-grade systemic inflammation, splenocyte apoptosis and increased expression of the immune inhibitory receptor PD-1 in the spleen, which were not observed in TLR4 mutant mice. In vitro, endotoxin (LPS) directly upregulated NLRP3 inflammasome expression in renal epithelial cells via TLR4. In summary, TLR4 contributes to renal fibrosis and CKD progression, at least in part, via inflammasome activation in renal epithelial cells, and may also participate in the dysregulated immune response that is associated with CKD.

Probiotics and chronic kidney disease

Probiotics are the focus of a thorough investigation as a natural biotreatment due to their various health-promoting effects and inherent ability to fight specific diseases including chronic kidney disease (CKD). Indeed, intestinal microbiota has recently emerged as an important player in the progression and complications of CKD. Because many of the multifactorial physiological functions of probiotics are highly strain specific, preselection of appropriate probiotic strains based on their expression of functional biomarkers is critical. The interest in developing new research initiatives on probiotics in CKD have increased over the last decade with the goal of fully exploring their therapeutic potentials. The efficacy of probiotics to decrease uremic toxin production and to improve renal function has been investigated in in vitro models and in various animal and human CKD studies. However to date, the quality of intervention trials investigating this novel CKD therapy is still lacking. This review outlines potential mechanisms of action and efficacy of probiotics as a new CKD management tool, with a particular emphasis on uremic toxin production and inflammation.

Precision renal medicine: a roadmap towards targeted kidney fibrosis therapies

Based on extensive pre-clinical achievements over the past decades, it appears to be due time for a successful clinical translation in the renal fibrosis field-but what is the quickest road to get there? In light of the recent launch of the Precision Medicine Initiative and success of molecularly informed drugs in oncology, we here discuss what it may take to bring molecularly targeted anti-fibrotic to clinical use in chronic progressive kidney disease.

Aging and low-grade inflammation reduce renal function in middle-aged and older adults in Japan and the USA

The objective of this study was to investigate the effects of low-grade inflammation on age-related changes in glomerular filtration rate (GFR) in middle-aged and older white Americans, African-Americans, and Japanese adults. Serum creatinine, C-reactive protein (CRP), and interleukin-6 (IL-6) levels were determined for 1570 adult participants in two surveys of aging in the USA and Japan (N = 1188 and 382, respectively). Kidney function declined with age in both countries and was associated with IL-6 and CRP. IL-6 and CRP also influenced the extent of the arithmetic bias when calculating the GFR using the chronic kidney disease epidemiology (CKD-EPI) formula with just serum creatinine. Younger African-Americans initially had the highest GFR but showed a steep age-related decrement that was associated with elevated inflammation. Japanese adults had the lowest average GFR but evinced a large effect of increased inflammatory activity when over 70 years of age. Importantly, our results also indicate that low-grade inflammation is important to consider when evaluating kidney function solely from serum creatinine.

Key role of the kidney in the regulation of fibroblast growth factor 23

High circulating levels of fibroblast growth factor 23 (FGF23) have been demonstrated in kidney failure, but mechanisms of this are not well understood. Here we examined the impact of the kidney on the early regulation of intact FGF23 in acute uremia as induced by bilateral or unilateral nephrectomy (BNX and UNX, respectively) in the rat. BNX induced a significant increase in plasma intact FGF23 levels from 112 to 267 pg/ml within 15 min, which remained stable thereafter. UNX generated intact FGF23 levels between that seen in BNX and sham-operated rats. The intact to C-terminal FGF23 ratio was significantly increased in BNX rats. The rapid rise in FGF23 after BNX was independent of parathyroid hormone or FGF receptor signaling. No evidence of early stimulation of FGF23 gene expression in the bone was found. Furthermore, acute severe hyperphosphatemia or hypercalcemia had no impact on intact FGF23 levels in normal and BNX rats. The half-life of exogenous recombinant human FGF23 was significantly prolonged from 4.4 to 11.8 min in BNX rats. Measurements of plasma FGF23 in the renal artery and renal vein demonstrated a significant renal extraction. Thus the kidney is important in FGF23 homeostasis by regulation of its plasma level and metabolism.

Type of Renal Replacement Therapy (Hemodialysis versus Peritoneal Dialysis) Does Not Affect Cytokine Gene Expression or Clinical Parameters of Renal Transplant Candidates

Patients with renal failure suffer from immune disturbances, caused by uremic toxins and influenced by dialysis treatment. The aim of the present study was to reveal whether type of dialysis modality (hemodialysis, HD, versus peritoneal dialysis, PD) differentially affects the immunocompetence, particularly the expression of genes involved in the immune response. Material. 87 renal transplant candidates (66 HD, 21 PD) were included in the study. Methods. The peripheral blood RNA samples were obtained with the PAXgene Blood system just before transplantation. The gene expression of CASP3, FAS, TP53, FOXP3, IFNG, IL2, IL6, IL8, IL10, IL17, IL18, LCN2, TGFB1, and TNF was assessed with real-time PCR on custom-designed low density arrays (TaqMan). Gene expression data were analyzed in relation to pretransplant clinical parameters. Results. The mean expression of examined genes showed no significant differences between PD and HD with the exception of FAS, expression of which was 30% higher in PD patients compared to the HD group. There was nonsignificantly higher expression of proinflammatory cytokines in the PD group. The clinical inflammatory parameters (CRP, albumin, cholesterol, and hemoglobin levels) did not differ between the groups. Conclusion. Type of renal replacement therapy exerts no differential effect on cytokine gene expression or inflammatory clinical parameters.

Association of C-reactive protein, tumor necrosis factor-alpha, and interleukin-6 with chronic kidney disease

BACKGROUND

We studied the association of inflammatory biomarkers including C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) with chronic kidney disease (CKD).

METHODS

We conducted a case-control study among 201 CKD patients and 201 community-based controls in the greater New Orleans area. CKD was defined as estimated-glomerular filtration rate (eGFR) <60 mL/min/1.73 m(2) or albuminuria ≥30 mg/24-h. Serum CRP, TNF-α, and IL-6 were measured using standard methods. Multivariable regression models were used to examine associations between the inflammatory biomarkers and CKD adjusting for important CKD risk factors, history of cardiovascular disease, and use of antihypertensive, antidiabetic, and lipid-lowering agents and aspirin.

RESULTS

The multivariable-adjusted medians (interquartile-range) were 2.91 (1.47, 5.24) mg/L in patients with CKD vs. 1.91 (0.99, 3.79) mg/L in controls without CKD (p = 0.39 for group difference) for CRP; 1.86 (1.51, 2.63) pg/mL vs. 1.26 (1.01, 1.98) pg/mL (p < 0.0001) for TNF-α; and 2.53 (1.49, 4.42) pg/mL vs. 1.39 (0.95, 2.15) pg/mL (p = 0.04) for IL-6, respectively. Compared to the lowest tertile, the highest tertile of TNF-α (OR 7.1, 95% CI 3.2 to 15.5) and IL-6 (OR 2.5, 95% CI 1.1 to 5.5) were significantly associated with higher odds of CKD in multivariable-adjusted models. Additionally, higher TNF-α and IL-6 were independently and significantly associated with lower eGFR and higher albuminuria.

CONCLUSIONS

Our data suggest that TNF-α and IL-6, but not CRP, are associated with the prevalence and severity of CKD, independent from established CKD risk factors, history of cardiovascular disease, and use of antihypertensive, antidiabetic, and lipid-lowering agents and aspirin.

Differential Ly6C Expression after Renal Ischemia-Reperfusion Identifies Unique Macrophage Populations

Macrophages are a heterogeneous cell type implicated in injury, repair, and fibrosis after AKI, but the macrophage population associated with each phase is unclear. In this study, we used a renal bilateral ischemia-reperfusion injury mouse model to identify unique monocyte/macrophage populations by differential expression of Ly6C in CD11b(+) cells and to define the function of these cells in the pathophysiology of disease on the basis of microarray gene signatures and reduction strategies. Macrophage populations were isolated from kidney homogenates by fluorescence-activated cell sorting for whole genome microarray analysis. The CD11b(+)/Ly6C(high) population associated with the onset of renal injury and increase in proinflammatory cytokines, whereas the CD11b(+)/Ly6C(intermediate) population peaked during kidney repair. The CD11b(+)/Ly6C(low) population emerged with developing renal fibrosis. Principal component and hierarchical cluster analyses identified gene signatures unique to each population. The CD11b(+)/Ly6C(intermediate) population had a distinct phenotype of wound healing, confirmed by results of studies inhibiting the macrophage colony-stimulating factor 1 receptor,whereas the CD11b(+)/Ly6C(low) population had a profibrotic phenotype. All populations, including the CD11b(+)/Ly6C(high) population, carried differential inflammatory signatures. The expression of M2-specific markers was detected in both the CD11b(+)/Ly6C(intermediate) and CD11b(+)/Ly6C(low) populations, suggesting these in vivo populations do not fit into the traditional classifications defined by in vitro systems. Results of this study in a renal ischemia-reperfusion injury model allow phenotype and function to be assigned to CD11b(+)/Ly6C(+) monocyte/macrophage populations in the pathophysiology of disease after AKI.

Association between Inflammation and Cardiac Geometry in Chronic Kidney Disease: Findings from the CRIC Study

Background

Left ventricular hypertrophy (LVH) and myocardial contractile dysfunction are independent predictors of mortality in patients with chronic kidney disease (CKD). The association between inflammatory biomarkers and cardiac geometry has not yet been studied in a large cohort of CKD patients with a wide range of kidney function.

Methods

Plasma levels of interleukin (IL)-1β, IL-1 receptor antagonist (IL-1RA), IL-6, tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β, high-sensitivity C-Reactive protein (hs-CRP), fibrinogen and serum albumin were measured in 3,939 Chronic Renal Insufficiency Cohort study participants. Echocardiography was performed according to the recommendations of the American Society of Echocardiography and interpreted at a centralized core laboratory.

Results

LVH, systolic dysfunction and diastolic dysfunction were present in 52.3%, 11.8% and 76.3% of the study subjects, respectively. In logistic regression analysis adjusted for age, sex, race/ethnicity, diabetic status, current smoking status, systolic blood pressure, urinary albumin- creatinine ratio and estimated glomerular filtration rate, hs-CRP (OR 1.26 [95% CI 1.16, 1.37], p<0.001), IL-1RA (1.23 [1.13, 1.34], p<0.0001), IL-6 (1.25 [1.14, 1.36], p<0.001) and TNF-α (1.14 [1.04, 1.25], p = 0.004) were associated with LVH. The odds for systolic dysfunction were greater for subjects with elevated levels of hs-CRP (1.32 [1.18, 1.48], p<0.001) and IL-6 (1.34 [1.21, 1.49], p<0.001). Only hs-CRP was associated with diastolic dysfunction (1.14 [1.04, 1.26], p = 0.005).

Conclusion

In patients with CKD, elevated plasma levels of hs-CRP and IL-6 are associated with LVH and systolic dysfunction.

Circulating and urinary microRNA profile in focal segmental glomerulosclerosis: a pilot study

BACKGROUND

MicroRNAs (miRNAs) are noncoding RNA molecules that play important roles in the pathogenesis of various kidney diseases. We investigated whether patients with minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS) have distinct circulating and urinary miRNA expression profiles that could lead to potential development of noninvasive biomarkers of the disease.

MATERIALS AND METHODS

Exosome miRNAs were extracted from plasma and urine samples of patients with primary FSGS (n = 16) or MCD (n = 5) and healthy controls (n = 5). Differences in miRNA abundance were examined using Affymetrix GeneChip miRNA 3.0 arrays. QRT-PCR was used to validate the findings from the array.

RESULTS

Comparison analysis of FSGS versus MCD revealed 126 and 155 differentially expressed miRNAs in plasma and in urine, respectively. Only 38 of these miRNAs were previously cited, whereas the remaining miRNAs have not been described. Comparison analysis showed that a significant number of miRNAs were downregulated in both plasma and urine samples of patients with FSGS compared to those with MCD. Plasma levels of miR-30b, miR-30c, miR-34b, miR-34c and miR-342 and urine levels of mir-1225-5p were upregulated in patients with MCD compared to patients with FSGS and controls (P < 0.001). Urinary levels of mir-1915 and miR-663 were downregulated in patients with FSGS compared to MCD and controls (P < 0.001), whereas the urinary levels of miR-155 were upregulated in patients with FSGS when compared to patients with MCD and controls (P < 0.005).

CONCLUSIONS

Patients with FSGS and MCD have a unique circulating and urinary miRNA profile. The diagnostic and prognostic potential of miRNAs in FSGS and MCD warrants further studies.

Serum Fractalkine (CX3CL1) and Cardiovascular Outcomes and Diabetes: Findings From the Chronic Renal Insufficiency Cohort (CRIC) Study

BACKGROUND

Cardiometabolic disease is a major cause of morbidity and mortality in persons with chronic kidney disease (CKD). Fractalkine (CX3CL1) is a potential mediator of both atherosclerosis and metabolic disease. Studies of the relationship of CX3CL1 with risk of cardiovascular disease (CVD) events and metabolic traits are lacking, particularly in the high-risk setting of CKD.

STUDY DESIGN

Cross-sectional and longitudinal observational analysis.

SETTING & PARTICIPANTS

Adults with CKD from 7 US sites participating in the Chronic Renal Insufficiency Cohort (CRIC) Study.

PREDICTOR

Quartiles of plasma CX3CL1 levels at baseline.

OUTCOMES

Baseline estimated glomerular filtration rate from a creatinine and cystatin C-based equation, prevalent and incident CVD, diabetes, metabolic syndrome and its criteria, homeostatic model assessment of insulin resistance, hemoglobin A1c level, myocardial infarction, all-cause mortality, and the composite outcome of myocardial infarction/all-cause mortality.

RESULTS

Among 3,687 participants, baseline CX3CL1 levels were associated positively with several CVD risk factors and metabolic traits, lower estimated glomerular filtration rate, and higher levels of inflammatory cytokines, as well as prevalent CVD (OR, 1.09; 95% CI, 1.01-1.19; P=0.03). Higher CX3CL1 level also was associated with prevalent diabetes (OR, 1.26; 95% CI, 1.16-1.38; P<0.001) in adjusted models. During a mean follow-up of 6 years, there were 352 deaths, 176 myocardial infarctions, and 484 composite outcomes. In fully adjusted models, 1-SD higher CX3CL1 level increased the hazard for all-cause mortality (1.11; 95% CI, 1.00-1.22; P=0.02) and the composite outcome (1.09; 95% CI, 1.00-1.19; P=0.04).

LIMITATIONS

Study design did not allow evaluation of changes over time, correlation with progression of phenotypes, or determination of causality of effect.

CONCLUSIONS

Circulating CX3CL1 level may contribute to both atherosclerotic CVD and diabetes in a CKD cohort. Further studies are required to establish mechanisms through which CX3CL1 affects the pathogenesis of atherosclerosis and diabetes.

Effects of sevelamer carbonate on advanced glycation end products and antioxidant/pro-oxidant status in patients with diabetic kidney disease

BACKGROUND AND OBJECTIVES

The primary goals were to re-examine whether sevelamer carbonate (SC) reduces advanced glycation end products (AGEs) (methylglyoxal and carboxymethyllysine [CML]), increases antioxidant defenses, reduces pro-oxidants, and improves hemoglobin A1c (HbA1c) in patients with type 2 diabetes mellitus (T2DM) and diabetic kidney disease (DKD). Secondary goals examined albuminuria, age, race, sex, and metformin prescription.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This two-center, randomized, intention-to-treat, open-label study evaluated 117 patients with T2DM (HbA1c >6.5%) and stages 2-4 DKD (urinary albumin/creatinine ratio ≥200 mg/g) treated with SC (1600 mg) or calcium carbonate (1200 mg), three times a day, without changing medications or diet. Statistical analyses used linear mixed models adjusted for randomization levels. Preselected subgroup analyses of sex, race, age, and metformin were conducted.

RESULTS

SC lowered serum methylglyoxal (95% confidence interval [CI], -0.72 to -0.29; P<0.001), serum CML (95% CI, -5.08 to -1.35; P≤0.001), and intracellular CML (95% CI, -1.63 to -0.28; P=0.01). SC increased anti-inflammatory defenses, including nuclear factor like-2 (95% CI, 0.58 to 1.29; P=0.001), AGE receptor 1 (95% CI, 0.23 to 0.96; P=0.001), NAD-dependent deacetylase sirtuin-1 (95% CI, 0.20 to 0.86; P=0.002), and estrogen receptor α (95% CI, 1.38 to 2.73; P ≤0.001). SC also decreased proinflammatory factors such as TNF receptor 1 (95% CI, -1.56 to -0.72; P≤0.001) and the receptor for AGEs (95% CI, -0.58 to 1.53; P≤0.001). There were no differences in HbA1c, GFR, or albuminuria in the overall group. Subanalyses showed that SC lowered HbA1c in women (95% CI, -1.71 to -0.27; P=0.01, interaction P=0.002), and reduced albuminuria in those aged <65 years (95% CI, -1.15 to -0.07; P=0.03, interaction P=0.02) and non-Caucasians (95% CI, -1.11 to -0.22; P=0.003, interaction P≤0.001), whereas albuminuria increased after SC and calcium carbonate in Caucasians.

CONCLUSIONS

SC reduced circulating and cellular AGEs, increased antioxidants, and decreased pro-oxidants, but did not change HbA1c or the albumin/creatinine ratio overall in patients with T2DM and DKD. Because subanalyses revealed that SC may reduce HbA1c and albuminuria in some patients with T2DM with DKD, further studies may be warranted.

Update on inflammation in chronic kidney disease

BACKGROUND

Despite recent advances in chronic kidney disease (CKD) and end-stage renal disease (ESRD) management, morbidity and mortality in this population remain exceptionally high. Persistent, low-grade inflammation has been recognized as an important component of CKD, playing a unique role in its pathophysiology and being accountable in part for cardiovascular and all-cause mortality, as well as contributing to the development of protein-energy wasting.

SUMMARY

The variety of factors contribute to chronic inflammatory status in CKD, including increased production and decreased clearance of pro-inflammatory cytokines, oxidative stress and acidosis, chronic and recurrent infections, including those related to dialysis access, altered metabolism of adipose tissue, and intestinal dysbiosis. Inflammation directly correlates with the glomerular filtration rate (GFR) in CKD and culminates in dialysis patients, where extracorporeal factors, such as impurities in dialysis water, microbiological quality of the dialysate, and bioincompatible factors in the dialysis circuit play an additional role. Genetic and epigenetic influences contributing to inflammatory activation in CKD are currently being intensively investigated. A number of interventions have been proposed to target inflammation in CKD, including lifestyle modifications, pharmacological agents, and optimization of dialysis. Importantly, some of these therapies have been recently tested in randomized controlled trials.

KEY MESSAGES

Chronic inflammation should be regarded as a common comorbid condition in CKD and especially in dialysis patients. A number of interventions have been proven to be safe and effective in well-designed clinical studies. This includes such inexpensive approaches as modification of physical activity and dietary supplementation. Further investigations are needed to evaluate the effects of these interventions on hard outcomes, as well as to better understand the role of inflammation in selected CKD populations (e.g., in children).

Pro-inflammatory cytokines and leukocyte oxidative burst in chronic kidney disease: culprits or innocent bystanders?

BACKGROUND

Pro-inflammatory cytokines are elevated in chronic kidney disease (CKD), a condition characterized by microinflammation with oxidative stress as key feature. However, their role in the inflammatory response at uraemic concentrations has not yet been defined. In this study, the contribution of cytokines on induction of leukocyte oxidative stress was investigated.

METHODS

Whole blood from healthy donors was incubated with 20-1400 pg/mL TNFα, 5-102.8 pg/mL IL-6, 20-400 pg/mL IL-1β and 75-1200 pg/mL IL-18 separately or in combination. Oxidative burst was measured, at baseline and after stimulation with fMLP (Phagoburst™). The effect of the TNFα blocker, adalimumab (Ada), was evaluated on TNFα-induced ROS production. Finally, the association between TNFα and the composite end point all-cause mortality or first cardiovascular event was analysed in a CKD population stage 4-5 (n = 121).

RESULTS

While interleukin (IL)-6, IL-1β and IL-18 alone induced no ROS activation of normal leukocytes, irrespective of concentrations, TNFα induced ROS activation at baseline (P < 0.01) and after fMLP stimulation (P < 0.05), but only at uraemic concentrations in the high range (400 and 1400 pg/mL). A similar pattern was observed with all cytokines in combination, but already at intermediate uraemic concentrations (all P < 0.05, except for monocytes after fMLP stimulation: n.s.), suggesting synergism between cytokines. ROS production induced by TNFα (400 pg/mL) and the cytokine combination was blocked with Ada. Uraemia-related oxidative stress in leukocytes of haemodialysis patients was however not blocked by Ada. In patients, TNFα was not associated to adverse events (HR: 1.52, 95% CI 0.81-2.85, P = 0.13).

CONCLUSION

Among several pro-inflammatory cytokines, TNFα alone was pro-oxidative but only at high-range uraemic concentrations. Adding a TNFα blocker, Ada, blocked this ROS production, but not the oxidative stress in blood samples from haemodialysis patients, suggesting that other uraemic toxins than TNFα are more crucial in this process. However, the lack of association between TNFα and mortality suggests that the role of TNFα-linked oxidative stress is limited.

Association of a polymorphism of the interleukin 6 receptor gene with chronic kidney disease in Japanese individuals

AIM

Various loci and genes that confer susceptibility to coronary artery disease (CAD) have been identified in Caucasian populations by genome-wide association studies (GWASs). The aim of the present study was to examine a possible association of chronic kidney disease (CKD) with 29 polymorphisms previously identified as susceptibility loci for CAD by meta-analyses of GWASs.

METHODS

The study population comprised 2247 Japanese individuals, including 1588 subjects with CKD [estimated glomerular filtration rate (eGFR) of <60 mL min(-1) 1.73 m(-2) ] and 659 controls (eGFR of ≥90 mL min(-1) 1.73 m(-2) ). The genotypes for 29 polymorphisms of 28 candidate genes were determined.

RESULTS

The χ(2) test revealed that rs4845625 (T→C) of IL6R, rs4773144 (A→G) of COL4A1, rs9319428 (G→A) of FLT1, and rs46522 (T→C) of UBE2Z were significantly (P < 0.05) related to CKD. Multivariable logistic regression analysis with adjustment for age, sex, body mass index, and the prevalence of smoking, hypertension, diabetes mellitus, and dyslipidaemia revealed that rs4845625 of IL6R (P = 0.0008; dominant model; odds ratio, 1.49), rs4773144 of COL4A1 (P = 0.0252; dominant model; odds ratio, 1.28), and rs9319428 of FLT1 (P = 0.0260: additive model; odds ratio, 0.77) were significantly associated with CKD. The serum concentration of creatinine was significantly (P = 0.0065) greater and eGFR was significantly (P = 0.0009) lower in individuals with the TC or CC genotype of IL6R than in those with the TT genotype.

CONCLUSION

The rs4845625 of IL6R may be a susceptibility locus for CKD in Japanese individuals.