Endotrophin as a Biomarker for Severe Acute Kidney Injury and Major Adverse Kidney Events.

BACKGROUND: The search for novel biomarkers in acute kidney injury (AKI) continues, both in terms of being able to predict adverse events in AKI but also in terms of confirming pathogenic pathways as potential therapeutic targets. Endotrophin (ETP) is an emerging biomarker in a number of fibroinflammatory diseases. We sought to test the association of ETP with the development of major adverse kidney events (MAKE) in critically ill adult patients. METHOD: Single-center prospective study of critically ill adult patients with stage 2-3 AKI and patients without AKI. Serum ETP was measured early in the first 3 days of critical care admission, 5-7 days later, and in some patients, 4-6 weeks later. The primary outcome was MAKE assessed at hospital discharge, a composite of mortality, kidney replacement therapy at discharge, and estimated glomerular filtration rate reduction of ≥ 25% from baseline. RESULTS: Among 121 patients evaluated in this study, serum ETP was significantly higher in patients with AKI vs. those without (p<0.05). In multivariable logistic regression analysis, higher tertiles of ETP were significantly associated with MAKE at discharge, controlled for relevant covariates. Further, sustained elevations in ETP 5-7 days later, as opposed to reductions towards normal, were also associated with MAKE. In patients seen in the clinic 4-6 weeks post-AKI, ETP remained elevated. In the acute period, ETP levels correlated most with TNF-α and neutrophil gelatinase-associated lipocalin. CONCLUSION: Higher levels of serum ETP early in the ICU admission, as well as sustained elevations of ETP within a 5-7 day period, are associated with MAKE at hospital discharge. ETP is a potential biomarker of AKI-related outcomes and a promising therapeutic target to minimize sequelae of AKI.

Serum Magnesium Levels and Cardiovascular Outcomes in Systolic Blood Pressure Intervention Trial Participants.

Rationale and Objective: Serum magnesium levels have been inversely yet inconsistently associated with cardiovascular (CV) outcomes. In this study, we examined the association of serum magnesium levels with CV outcomes in the Systolic Blood Pressure Intervention Trial (SPRINT) participants. Study Design: Case-control post hoc analysis of SPRINT. Setting & Participants: A total of 2,040 SPRINT participants with available serum samples at baseline level were included in this study. Case participants (n = 510) who experienced a CV event during the SPRINT observation period (median follow-up of 3.2 years) and control participants (n = 1,530) without CV events were sampled in a 1:3 ratio for measurements of serum magnesium level at baseline and 2-year follow-up. Predictors: Baseline serum magnesium levels and 2-year percentage change in serum magnesium levels (ΔSMg). Outcome: SPRINT primary composite CV outcome. Analytical Approach: Multivariable conditional logistic regression analysis, accounting for matching factors, was used to evaluate the association of baseline and ΔSMg with CV outcomes. Individual matching of cases and controls was based on the SPRINT treatment arm allocation (standard vs intensive) and prevalence of chronic kidney disease (CKD). Results: The median serum magnesium level at baseline was similar among the case and control groups. In a fully adjusted model, each standard deviation (SD) (0.18 mg/dL) higher of the baseline serum magnesium level was independently associated with a lower risk for composite CV outcomes in all study participants (adjusted odds ratio 95% CI, 0.79 [0.70-0.89]). This association was similar when serum magnesium levels were analyzed in quartiles but dissipated in the standard (vs intensive) arm of SPRINT (0.88 [0.76-1.02] vs 0.65 [0.53-0.79], respectively; Pinteraction = 0.06). The presence or absence of CKD at baseline did not modify this association. ΔSMg was not independently associated with CV outcomes occurring after 2 years. Limitations: ΔSMg was small in magnitude, limiting effect size. Conclusions: Higher baseline serum magnesium levels were independently associated with reduced risk for CV outcomes in all study participants, but ΔSMg was not associated with CV outcomes.

Risk Indicators of Sarcoidosis Evolution-Unified Protocol (RISE-UP): protocol for a multi-centre, longitudinal, observational study to identify clinical features that are predictive of sarcoidosis progression.

INTRODUCTION: Sarcoidosis is a pulmonary and systemic granulomatous disease with a wide range of potential outcomes, from spontaneous resolution to end-stage organ damage and death. Currently, clinicians have no easy-to-use risk stratification tools for important clinical outcomes in sarcoidosis, such as progressive lung disease. This study will address two clinical practice needs: (1) development of a risk calculator that provides an estimate of the likelihood of pulmonary progression in sarcoidosis patients during the follow-up period and (2) determine the optimal interval for serial clinical monitoring (eg, 6, 12, 18 months) using these risk prediction tools. METHODS AND ANALYSIS: The Risk Indicators of Sarcoidosis Evolution-Unified Protocol study is a National Institutes of Health-sponsored, longitudinal observational study of adults with pulmonary sarcoidosis who will be enrolled at five US tertiary care centres. Participants will be evaluated at approximately 6-month intervals for up to 60 months with collection of lung function, blood samples and clinical data. The target sample size is 557 and the primary objective is to determine which clinical features measured during a routine clinic visit carry the most prognostic information for predicting clinical progression of pulmonary sarcoidosis over the follow-up period. The primary outcome measure will be quantified by a clinically meaningful change in forced vital capacity, forced expiratory volume in 1 s or diffusing capacity of the lung for carbon monoxide. The secondary objective is to determine if blood biomarkers measured during a routine clinic visit can improve the risk assessment modelling for progression of pulmonary sarcoidosis over the follow-up period. ETHICS AND DISSEMINATION: The study protocol has been approved by the Institutional Review Boards at each centre and the reliance Institutional Review Board overseeing the study (WCG, Protocol #20222400). Participants will provide informed consent prior to enrolment. Results will be disseminated via publication in a relevant peer-reviewed journal. TRIAL REGISTRATION NUMBER: NCT05567133.

Serum renin and major adverse kidney events in critically ill patients: a multicenter prospective study.

BACKGROUND: Preliminary studies have suggested that the renin-angiotensin system is activated in critical illness and associated with mortality and kidney outcomes. We sought to assess in a larger, multicenter study the relationship between serum renin and Major Adverse Kidney Events (MAKE) in intensive care unit (ICU) patients. METHODS: Prospective, multicenter study at two institutions of patients with and without acute kidney injury (AKI). Blood samples were collected for renin measurement a median of 2 days into the index ICU admission and 5-7 days later. The primary outcome was MAKE at hospital discharge, a composite of mortality, kidney replacement therapy, or reduced estimated glomerular filtration rate to ≤ 75% of baseline. RESULTS: Patients in the highest renin tertile were more severely ill overall, including more AKI, vasopressor-dependence, and severity of illness. MAKE were significantly greater in the highest renin tertile compared to the first and second tertiles. In multivariable logistic regression, this initial measurement of renin remained significantly associated with both MAKE as well as the individual component of mortality. The association of renin with MAKE in survivors was not statistically significant. Renin measurements at the second time point were also higher in patients with MAKE. The trajectory of the renin measurements between time 1 and 2 was distinct when comparing death versus survival, but not when comparing MAKE versus those without. CONCLUSIONS: In a broad cohort of critically ill patients, serum renin measured early in the ICU admission is associated with MAKE at discharge, particularly mortality.

Spot urinary citrate-to-creatinine ratio is a marker for acid-base status in chronic kidney disease.

Due to multiple compensating mechanisms, the serum bicarbonate concentration is a relatively insensitive marker of acid-base status; especially in chronic kidney disease (CKD). This is a major drawback that impairs the ability to diagnose acid excess or monitor alkali therapy. We postulated that it is more logical to measure the compensatory defense mechanism(s) rather than the defended parameter, which remains normal if the compensation is successful. Therefore, a retrospective cross-sectional study was performed in 1733 stone formers along with a prospective cross-sectional study of 22 individuals with normal kidney function and 50 patients in different stages of CKD. While serum bicarbonate was flat and did not fall below the reference range until near CKD stage 5, citrate excretion (24-hour urinary citrate excretion rate; urinary citrate-to-creatinine ratio, in the retrospective analysis, and spot urinary citrate-to-creatinine ratio in the prospective study) progressively and significantly declined starting from CKD stage 2. Following an acute acid load in 25 participants with a wide range of estimated glomerular filtration rates, the urinary citrate-to-creatinine ratio inversely and significantly associated with acid accumulation, whereas serum bicarbonate did not. We compared changes in serum bicarbonate and urinary citrate-to-creatinine ratio in response to alkali therapy in patients with CKD stage 3 or 4 started on potassium citrate in our kidney stone database. With alkali therapy, there was no change in serum bicarbonate, but the urinary citrate-to-creatinine ratio rose consistently in all patients adherent to potassium citrate therapy. Thus, the urinary citrate-to-creatinine ratio (the defense mechanism) is a potential easily implementable, pragmatic, and a superior parameter to serum bicarbonate (the defended entity) to assess acid-base status, and monitor alkali therapy. Additional studies are needed before a clinical test can be devised.

Kidney Biomarkers and Major Adverse Kidney Events in Critically Ill Patients.

Background: Several biomarkers of AKI have been examined for their ability to predict AKI before serum creatinine. Few studies have focused on using kidney biomarkers to better predict major adverse kidney events (MAKE), an increasingly used composite outcome in critical care nephrology research. Methods: Single-center prospective study collecting blood and urine samples from critically ill patients with AKI Kidney Disease Improving Global Outcomes stage 2 or above, and matched controls from a single, tertiary care intensive care unit (ICU). Samples were collected at 24-48 hours after AKI diagnosis (patients) or ICU admission (controls), 5-7 days later, and 4-6 weeks after discharge for patients with AKI. The primary outcome of interest was MAKE at hospital discharge (MAKE-DC), consisting of the composite end point of death, RRT dependence, or a decrease in estimated glomerular filtration to <75% of baseline. Results: Serum/urinary neutrophil gelatinase-associated lipocalin (NGAL), serum/urinary cystatin C, and urinary kidney injury molecule-1 early in the AKI or ICU course were all significantly higher in patients with MAKE-DC compared with those not experiencing MAKE-DC. Additionally, serum/urinary NGAL and serum cystatin C measurements at the first time point remained significantly associated with MAKE events at 3, 6, and 12 months. Serum cystatin C, and to a lesser extent serum NGAL, significantly improved upon a logistic regression clinical prediction model of MAKE-DC (AUROC 0.94 and 0.87 versus 0.83; P=0.001 and P=0.02, respectively). Patients without MAKE-DC experienced a greater decline in serum NGAL from first to second measurement than those patients experiencing MAKE-DC. Conclusions: Early measures of kidney biomarkers in patients who are critically ill are associated with MAKE-DC. This relationship appears to be greatest with serum NGAL and cystatin C, which display additive utility to a clinical prediction model. Trending serum NGAL may also have utility in predicting MAKE-DC.

Performance of soluble Klotho assays in clinical samples of kidney disease.

BACKGROUND: Soluble Klotho has multiple systemic salutary effects. In animals, both acute and chronic kidney disease models display systemic Klotho deficiency. As such, there is considerable interest in investigating soluble Klotho as a biomarker in patients with different types and severity of kidney diseases. Unfortunately, there remains uncertainty regarding the best method to measure soluble Klotho in human serum samples. METHODS: Using human serum samples obtained from several clinical cohorts with a wide range of kidney function, we measured soluble Klotho using a commercial enzyme-linked immunosorbent assay (ELISA) as well as with an immunoprecipitation-immunoblot (IP-IB) assay utilizing a synthetic antibody with high affinity and specificity for Klotho. Recovery of spiking with a known amount of exogenous Klotho was tested. A subset of samples was analyzed with and without the addition of a protease inhibitor cocktail at the time of collection or after the first freeze-thaw cycle to determine if these maneuvers influenced performance. RESULTS: The IP-IB assay was superior to the ELISA at recovery of exogenous Klotho (81-115% versus 60-81%) across the spectrum of kidney function. Klotho measurements by IP-IB were highly correlated with estimated glomerular filtration rate (eGFR) (R = 0.80, P < 0.001) in comparison with the commercial ELISA, which exhibited minimal correlation with eGFR (R = 0.18, P = 0.12). Use of a protease inhibitor cocktail neither improved nor impaired performance of the IP-IB assay; however, subsequent freeze-thaw cycle resulted in a significant reduction in Klotho recovery and dissipated the correlation between Klotho levels and eGFR. With the ELISA, the use of protease inhibitor cocktail resulted in an increase in intrasubject variability. CONCLUSIONS: The IP-IB assay is preferable to the commercial ELISA to measure soluble Klotho concentrations in never-thawed serum samples of humans with varying severity of kidney disease. However, due to the labor-intensive nature of the IP-IB assay, further research is needed to secure an assay suitable for high-throughput work.

Continuous renal replacement therapy in critically ill patients with acute on chronic liver failure and acute kidney injury: A retrospective cohort study
.

BACKGROUND: Incident acute kidney injury (AKI) in critically ill patients with acute on chronic liver failure (ACLF) is associated with poor prognosis. The role of continuous renal replacement therapy (CRRT) is not well established for patients with ACLF and AKI. MATERIALS AND METHODS: We conducted a retrospective cohort study to examine clinical outcomes in 66 patients with ACLF and AKI requiring CRRT. RESULTS: All-cause hospital mortality was 89.4%. Five (7.6%) patients were listed for liver transplantation, of whom 1 (1.5%) was eventually subjected to transplantation. Etiology of AKI included type 1 hepatorenal syndrome (HRS) with or without some degree of acute tubular necrosis (ATN) in 20 (30.3%) patients, and primarily ATN in 46 (69.7%) patients. When evaluated at the time of CRRT initiation, Child-Pugh-Turcotte (CPT) and Model for End-stage Liver Disease (MELD) (area under the receiver operating characteristics curve (AUROC) 0.67 for both) had fair performance for prediction of mortality, whereas Sequential Organ Failure Assessment (SOFA) and Chronic Liver Failure (CLIF)-SOFA performed better for the prediction of mortality (AUROC 0.87 for both). SOFA and CLIF-SOFA also performed well when determined at the time of ICU admission (AUROC 0.86 and 0.85, respectively). Etiology of liver disease or AKI did not influence prognosis. CONCLUSION: Critically ill patients with ACLF and AKI requiring CRRT have poor hospital survival, even with provision of extracorporeal support therapy. SOFA and CLIF-SOFA are good prognostic tools of mortality in this susceptible population.

The role of vitamin D in sarcoidosis.

After the initial description of extrarenal synthesis of 1,25-dihydroxyvitamin D (1,25-(OH)2D) three decades ago, extensive progress has been made in unraveling the immunomodulatory roles of vitamin D in the pathogenesis of granulomatous disorders, including sarcoidosis. It has been shown that 1,25-(OH)2D has dual effects on the immune system, including upregulating innate immunity as well as downregulating the autoimmune response. The latter mechanism plays an important role in the pathogenesis and treatment of sarcoidosis. Vitamin D supplementation in patients with sarcoidosis has been hampered owing to concerns about the development of hypercalcemia and hypercalciuria given that extrarenal 1-α hydroxylase is substrate dependent. Recently, a few studies have cast doubt over the mechanisms underlying the development of hypercalcemia in this population. These studies demonstrated an inverse relationship between the level of vitamin D and severity of sarcoidosis. Consequently, clinical interest has been piqued in the use of vitamin D to attenuate the autoimmune response in this disorder. However, the development of hypercalcemia and the attendant detrimental effects are real possibilities. Although the average serum calcium concentration did not change following vitamin D supplementation, in two recent studies, hypercalciuria occurred in one out of 13 and two out of 16 patients. This review is a concise summary of the literature, outlining past work and newer developments in the use of vitamin D in sarcoidosis. We feel that larger-scale placebo-controlled randomized studies are needed in this population. Since the current first-line treatment of sarcoidosis is glucocorticoids, which confer many systemic adverse effects, and steroid-sparing immunosuppressant treatment options carry additional risks of adverse effects, adjunct management with vitamin D in combination with potent anti-osteoporotic medications could minimize the risk of glucocorticoid-induced osteoporosis and modulate the immune system to attenuate disease activity in sarcoidosis.

Adherence to reduced-polluting biomass fuel stoves improves respiratory and sleep symptoms in children.

BACKGROUND: Symptoms of sleep apnea are markedly increased in children exposed to smoke from biomass fuels and are reduced by kitchen stoves that improve indoor biomass pollution. However, the impact of adherence to the use of improved stoves has not been critically examined. METHODS: Sleep-related symptom questionnaires were obtained from children <15 years of age in 56 families residing in the communities of Lliupapuquio, Andahuaylas province in Peru before and 2 years after installation of less-polluting Inkawasi cooking stoves. RESULTS: 82 children with lifetime exposures to indoor fuel pollution were included. When compared to those alternating between both types of stoves or those using traditional stoves only, those children who exclusively used Inkawasi cooking stoves showed significant improvements in sleep and respiratory related symptoms, but some minor albeit significant improvements occurred when both stoves were concomitantly used. CONCLUSIONS: Improvements in respiratory and sleep-related symptoms associated with elevated indoor biomass pollution occur only following implementation and exclusive utilization of improved kitchen stoves.