Acute kidney injury in China

Assessing the predictive value of elevated postoperative syndecan-1 levels for progressive acute kidney injury and kidney replacement therapy necessity in adult cardiac surgery patients

BACKGROUND

The development of acute kidney injury (AKI) post-cardiac surgery significantly increases patient morbidity and healthcare costs. Prior researches have established Syndecan-1 (SDC-1) as a potential biomarker for endothelial injury and subsequent acute kidney injury development. This study assessed whether postoperative SDC-1 levels could further predict AKI requiring kidney replacement therapy (AKI-KRT) and AKI progression.

METHODS

In this prospective study, 122 adult cardiac surgery patients, who underwent valve or coronary artery bypass grafting (CABG) or a combination thereof and developed AKI within 48 h post-operation from May to September 2021, were monitored for the progression to stage 2-3 AKI or the need for KRT. We analyzed the predictive value of postoperative serum SDC-1 levels in relation to multiple endpoints.

RESULTS

In the study population, 110 patients (90.2%) underwent cardiopulmonary bypass, of which thirty received CABG or combined surgery. Fifteen patients (12.3%) required KRT, and thirty-eight (31.1%) developed progressive AKI, underscoring the severe AKI incidence. Multivariate logistic regression indicated that elevated SDC-1 levels were independent risk factors for progressive AKI (OR = 1.006) and AKI-KRT (OR = 1.011). The AUROC for SDC-1 levels in predicting AKI-KRT and AKI progression was 0.892 and 0.73, respectively, outperforming the inflammatory cytokines. Linear regression revealed a positive correlation between SDC-1 levels and both hospital (β = 0.014, p = 0.022) and ICU stays (β = 0.013, p < 0.001).

CONCLUSION

Elevated postoperative SDC-1 levels significantly predict AKI progression and AKI-KRT in patients following cardiac surgery. The study's findings support incorporating SDC-1 level monitoring into post-surgical care to improve early detection and intervention for severe AKI.

Renoprotective Effect of Pitavastatin against TAA-Induced Renal Injury: Involvement of the miR-93/PTEN/AKT/mTOR Pathway

This research investigated if pitavastatin (Pita) might protect rats' kidneys against thioacetamide (TAA). By altering the PTEN/AKT/mTOR pathway, pitavastatin may boost kidney antioxidant capacity and minimize oxidative damage. Statins have several benefits, including antioxidant and anti-inflammatory characteristics. The principal hypothesis of this study was that Pita can regulate the miR-93/PTEN/AKT/mTOR pathways, which is thought to be responsible for its renoprotective effects. The experiment divided male rats into four groups. Group 1 included untreated rats as the control. Group 2 included rats which received TAA (100 mg/kg intraperitoneally thrice a week for two weeks) to destroy their kidneys. Groups 3 and 4 included rats which received Pita orally at 0.4 and 0.8 mg/kg for 14 days after TAA injections. Renal injury increased BUN, creatinine, and MDA levels and decreased glutathione (GSH) levels. Pitavastatin prevented these alterations. TAA decreased PTEN and increased miR-93, Akt, p-Akt, mTOR, and Stat3 in the kidneys. Pitavastatin also regulated the associated culprit pathway, miR-93/PTEN/Akt/mTOR. In addition, TAA induced adverse effects on the kidney tissue, which were significantly ameliorated by pitavastatin treatment. The findings suggest that pitavastatin can attenuate renal injury, likely by regulating the miR-93/PTEN/Akt/mTOR pathway. This modulation of the pathway appears to contribute to the protective effects of pitavastatin against TAA-induced renal injury, adding to the growing evidence of the pleiotropic benefits of statins in renal health.

Complement C3 mediates podocyte injury through TLR4/NFΚB-P65 signaling during ischemia-reperfusion acute kidney injury and post-injury fibrosis

BACKGROUND

The aim of this study was to explore the mechanism of complement C3a mediating podocyte injury during ischemia-reperfusion acute kidney injury (IR-AKI) and post-injury fibrosis.

METHODS

Renal artery clamping was used to establish IR-AKI and post-injury fibrosis model. HE and Masson staining were performed to observe renal fibrosis. The protein abundance levels were measured along with inflammatory markers, renal complement C3. Podocytes were treated with C3a with or without Toll-like receptor 4(TLR4) inhibitor. The effects of TLR4 up-regulation by TLR4 plasmids were examined.

RESULTS

C3^-/- resulted in amelioration of renal dysfunction by reducing podocyte damage and renal fibrosis. Immunoblot with renal tissue homogenates from IR-AKI mice revealed that C3^-/- decreased TLR4/Nuclear Factor-κB (NFκB)-P65.

CONCLUSION

Our results indicate that modulating C3/TLR4/NFκB-P65 signaling pathway is a novel therapeutic target for the IR-AKI and post-injury fibrosis.

Proteinuria is a risk factor for acute kidney injury after cardiac surgery in patients with stages 3-4 chronic kidney disease: a case control study

BACKGROUND

Acute kidney injury (AKI) is a common complication after cardiac surgery, and preoperative renal dysfunction is an important risk factor. Proteinuria indicates renal structural damage, but there are few studies on proteinuria and the risk of AKI after cardiac surgery in patients with renal dysfunction. This study aimed to elucidate whether proteinuria can predict AKI after cardiac surgery in patients with renal dysfunction.

METHODS

Patients with stages 3-4 chronic kidney disease (CKD) who underwent cardiac surgery were included in this retrospective study. AKI was defined according to the KDIGO criteria. The association between proteinuria and AKI in patients with CKD stages 3-4 was investigated.

RESULTS

The incidence of AKI in the entire cohort (n = 1546) was 53.55%. The in-hospital mortality of patients with was higher than patients without AKI (AKI vs. no AKI, 4.7 vs. 0.8%, P < 0.001). Multivariate logistic regression analysis showed that proteinuria was an independent risk factor for AKI (trace to 1+ OR 2.37; 2+ -3+ OR 5.16) and AKI requiring renal replacement therapy (AKI-RRT) (trace to 1+ OR 3.64; 2+-3+ OR 5.71). Mild proteinuria (trace to 1+ OR 2.59) was also an independent risk factor for in-hospital death. In patients with diabetes mellitus, mild proteinuria (OR 1.925), instead of severe proteinuria (2-3+), was a risk factor of AKI in patients with kidney dysfunction and diabetes.

CONCLUSIONS

In the population of patients with renal dysfunction, the incidence of AKI was high, which significantly compromised renal and overall prognosis. As a simple and inexpensive routine test, preoperative proteinuria still has value in predicting AKI in patients with impaired renal function.

Predictive role of the neutrophil: lymphocyte ratio in acute kidney injury associated with off-pump coronary artery bypass grafting

OBJECTIVES

This study aims to investigate whether the ratios of cell types in peripheral blood could be used as reliable predictors of off-pump coronary artery bypass grafting (CABG)-associated acute kidney injury (AKI).

MATERIALS AND METHODS

We retrospectively reviewed patients (n = 420) undergoing off-pump CABG from January 1, 2021 to January 1, 2022 in Qilu Hospital of Shandong University. We used logistic regression analysis to identify the potential predictors of off-pump CABG-associated AKI and construct a predictive model. Receiver operating characteristic (ROC) curve analysis was used to evaluate the predictive ability of predictors and prediction models.

RESULTS

The prevalence of AKI associated with off-pump CABG was 20.95%. Patients in the AKI group had significantly higher ratios of peripheral blood cells on postoperative day (POD)1 than patients in the non-AKI group (P < 0.01). The area under the ROC curve (AUC) of the neutrophil:lymphocyte ratio (NLR) on POD1 for predicting off-pump CABG-associated AKI was 0.780 and the cutoff value was 20.07. Patients with high NLR on POD1 had a poor short-term prognosis. The AUC of the predictive model constructed by logistic regression analysis was 0.882. The sensitivity was 68.2% and the specificity was 93.1%.

CONCLUSION

The NLR on POD1 was a reliable predictive biomarker of off-pump CABG-associated AKI. And we successfully construct a prediction model, which contribute to the early recognition and management of off-pump CABG-associated AKI.

Selective Wnt/β-Catenin Pathway Activation Concomitant With Sustained Overexpression of miR-21 is Responsible for Aristolochic Acid-Induced AKI-to-CKD Transition

Acute kidney injury (AKI) is increasingly recognized as a cumulative risk factor for chronic kidney disease (CKD) progression. However, the underlying mechanisms remain unclear. Using an aristolochic acid (AA)-induced mouse model of AKI-to-CKD transition, we found that the development of tubulointerstitial fibrosis following AKI was accompanied with a strong activation of miR-21 and canonical Wnt signaling, whereas inhibition of miR-21 or selective silencing of Wnt ligands partially attenuated AKI-to-CKD transition. To explore the interaction between miR-21 and Wnt/β-catenin signaling, we examined the effects of genetic absence or pharmacologic inhibition of miR-21 on Wnt/β-catenin pathway expression. In miR-21^-/- mice and in wild-type mice treated with anti-miR21 oligos, Wnt1 and Wnt4 canonical signaling in the renal tissue was significantly reduced, with partial reversal of renal interstitial fibrosis. Although the renal abundance of miR-21 remained unchanged after inhibition or activation of Wnt/β-catenin signaling, early intervention with ICG-001, a β-catenin inhibitor, significantly attenuated renal interstitial fibrosis. Moreover, early (within 24 h), but not late β-catenin inhibition after AA administration attenuated AA-induced apoptosis and inflammation. In conclusion, inhibition of miR-21 or β-catenin signaling may be an effective approach to prevent AKI-to-CKD progression.

Lactoferrin Contributes a Renoprotective Effect in Acute Kidney Injury and Early Renal Fibrosis

Patients with acute kidney injury (AKI) who survive the acute stage are at notable risk for chronic kidney disease (CKD) progression. There is no single therapy that can effectively prevent the AKI to CKD transition. Autophagy is a cytoplasmic component degradation pathway and has complex functions in several diseases, such as renal fibrosis. Previous research has shown that lactoferrin has important functions in antioxidant defense and other defense systems, protecting kidneys against various injuries. The present study investigated the effect of lactoferrin in protecting against the AKI to CKD transition. We identified 62 consensus genes with two-fold changes in clinical kidney tissues from AKI and CKD patients. Among the 62 overlay genes, the mRNA levels of LTF were significantly upregulated in the kidney tissues of AKI and CKD patients. Lactoferrin induced autophagy via the activation of the AMPK and inhibition of Akt/mTOR pathway in human kidney proximal tubular cells. Lactoferrin suppressed oxidative stress-induced cell death and apoptosis by augmenting autophagy. Lactoferrin has an antifibrotic role in human kidney tubular cells. In a mouse model of folic acid-induced AKI to CKD transition, treatment with lactoferrin recovered renal function and further suppressed renal fibrosis through the inhibition of apoptosis and the induction of autophagy. These findings identify lactoferrin as a potential therapeutic target for the prevention of the AKI to CKD transition.

A mode of CVVH with regional citrate anticoagulation compared to no anticoagulation for acute kidney injury patients at high risk of bleeding

The study was designed to assess a practical mode of postdilution continuous venovenous hemofiltration (CVVH) with regional citrate anticoagulation (RCA) using a calcium-containing replacement solution, and to compare it with a CVVH mode with no anticoagulation (NA). Both methods were employed in our center for acute kidney injury (AKI) patients at high risk of bleeding. Fifty-six patients were equally allocated into the RCA-CVVH group and the NA-CVVH group. The study displayed no significant differences between groups involving baseline characteristics, severity level, blood gas analysis, hepatic/renal/coagulative functions, electrolytes, hemoglobin concentration, and platelet counts before or after continuous renal replacement therapy (CRRT). Compared to the NA-CVVH group, the RCA-CVVH group had a lower level of transfused packed red blood cells and platelet as well as a longer filter lifespan. The result showed no substantial differences between groups in terms of the mean supporting time and cost involving CRRT per person, the length of ICU and hospital stays, and the ICU survival. Homeostasis was basically preserved at a target range during the RCA post-CVVH procedure. Serious complications did not arise during the RCA process. RCA postdilutional CVVH is a safe and effective mode for application in AKI patients with a high risk of bleeding, and it can extend the filter lifespan and decrease blood loss, compared with the NA mode for CRRT. Further studies are needed to evaluate this mode for CRRT. (Retrospective Registration number ChiCTR1800016462, Registration date 2/6/2018)

The role of podocyte damage in the etiology of ischemia-reperfusion acute kidney injury and post-injury fibrosis

Background

To establish a model of chronic renal fibrosis following acute kidney injury (AKI) in BALB/c mice and to observe the effect of AKI on podocyte injury and chronic fibrosis of the kidney. Additional aims included using the model to explore the role of podocyte injury in AKI and post-injury fibrosis.

Methods

Fifty BALB/C mice were randomly divided into control group (Ctr), sham group (sham), AKI 20 group (renal ischemia, 20 min reperfusion), AKI 30 group (renal ischemia, 30 min reperfusion) and AKI 40 group (renal ischemia, 40 min reperfusion). Mice serum and 24-h urine were collected on the 8th, 9th, 10th, 14th, and 28th days for urinary protein, serum creatinine (Scr) and blood urea nitrogen (BUN) analysis. HE staining, transmission electron microscopy (TEM), Masson staining, Q-PCR, Western Blot and immunohistochemistry were applied.

Results

Serum Scr and BUN levels across all AKI groups at the 9th day were significantly higher (P < 0.05) than controls, with higher reperfusion groups maintaining that increase up to 28 days (P < 0.05). Compared with Ctr group, the urinary protein of the AKI 40 group significantly rose on the 9th day (P < 0.05), normalizing immediately on the 10th day (P < 0.05). In contrast, the AKI 30 group rose significantly on the 14th day (P < 0.05) maintaining elevated levels for two weeks (P < 0.05). HE staining demonstrated ischemia-dependent renal tissue damage was aggravated in the mild to aggravated AKI groups. Mesangial proliferation, glomerulosclerosis, and tubulointerstitial pathology were also significantly increased in these groups (P < 0.05). Masson staining further showed that glomerular, renal tubular, and interstitial collagen were increased by ischemia in a time-dependent manner. Transmission EM additionally that podocytes of the mild to severe AKI groups displayed extensive fusion, exfoliation and GBM exposure. Synaptopodin, Nephrin, and CD2AP mRNA and protein expression demonstrated ischemic time-dependent decreases, while the TRPC6 was increased. There was a significant difference in the levels of Synaptopodin, Nephrin, CD2AP, and TRPC6 between the mild and severe AKI groups (P < 0.05).

Conclusions

1) During the AKI process mice podocyte injury, proteinuria and the subsequent progression into chronic renal fibrosis is observed.2) Podocyte injury may be one of the causes of ischemia-reperfusion acute kidney injury and post-injury fibrosis.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1298-x) contains supplementary material, which is available to authorized users.

Association of urinary ionomic profiles and acute kidney injury and mortality in patients after cardiac surgery

OBJECTIVE

The rarity of sensitive biomarkers for acute kidney injury (AKI) has impeded the timely therapy of AKI. Emerging evidence suggests that ion homeostasis may play pertinent roles in AKI. We aimed to screen out representative urinary ions and build a cardiac surgery-associated AKI indication model.

METHODS

We performed urinary ionomic analysis from patients undergoing cardiac surgeries in Zhongshan Hospital, Fudan University, Shanghai, China (N = 261). By bioinformatics analysis, we identified differentially changed elements and established the AKI indication model we named the urinary ion index (UII). Follow-ups were performed to evaluate 30-day survival.

RESULTS

The concentrations of most ions dynamically changed whether a patient developed AKI or not. A significant number of differentially changed elements between AKI and non-AKI groups were detected, especially at 2 hours after cardiac surgery, based on which we generated UII, with the area under the curve of 0.815 ± 0.006 and a cut-off value of 1.24. UII was associated with need for renal replacement therapy, with an area under the curve of 0.83 at a cutoff value of 1.62. Kaplan-Meier and log-rank methods, as well as Cox proportional hazards model, reflected that patients in the UII > 1.24 group had significantly higher risk of mortality within 30 days after surgery (hazard ratio, 5.15; P = .0097 and hazard ratio, 3.56; P = .033) than the UII ≤ 1.24 group.

CONCLUSIONS

Our data demonstrate that UII appears to be a novel and valid index of early cardiac surgery-associated AKI. UII > 1.24 at 2 hours after surgery indicates high risk of AKI and less 30-day survival.

Validation of Four Prediction Scores for Cardiac Surgery-Associated Acute Kidney Injury in Chinese Patients

Objective

To assess the clinical value of four models for the prediction of cardiac surgery-associated acute kidney injury (CSA-AKI) and severe AKI which renal replacement therapy was needed (RRT-AKI) in Chinese patients.

Methods

1587 patients who underwent cardiac surgery in the department of cardiac surgery in the Zhongshan Hospital, Fudan University, between January 2013 and December 2013 were enrolled in this research. Evaluating the predicting value for cardiac surgery-associated AKI (AKICS score) and RRT-AKI (Cleveland score, SRI and Mehta score) by Hosmer-Lemeshow goodness-of-fit test for the calibration and area under receiver operating characteristic curve (AUROC) for the discrimination.

Results

Based on 2012 KDIGO (Kidney Disease: Improving Global Outcomes) AKI definition, the incidence of AKI and RRT-AKI was 37.4% (594/1587) and 1.1% (18/1587), respectively. The mortality of AKI and RRT-AKI was 6.1% (36/594) and 66.7% (12/18), respectively, while the total mortality was 2.8% (44/1587). The discrimination (AUROC=0.610) for the prediction of CSA-AKI of AKICS was low, while the calibration (x²=7.55, P=0.109) was fair. For the prediction of RRT-AKI, the discrimination of Cleveland score (AUROC=0.684), Mehta score (AUROC=0.708) and SRI (AUROC=0.622) were not good; while the calibration of them were fair (Cleveland score x²=1.918, P=0.166; Mehta score x²=9.209, P=0.238; SRI x²=2.976, P=0.271).

Conclusion

In our single-center study, based upon valve surgery dominant and less diabetes mellitus patients, according to KDIGO AKI definition, the predictive value of the four models, combining discrimination and calibration, for respective primary event, were not convincible.

The orphan nuclear receptor RORα is a potential endogenous protector in renal ischemia/reperfusion injury

Emerging evidence indicates that retinoid-related orphan receptor (ROR)α, a member of the ROR nuclear receptor subfamily, mediates key cellular adaptions to hypoxia and contributes to the pathophysiology of many disease states. However, the effects of RORα in renal ischemia/reperfusion (I/R) injury remain unclear. Wild-type (WT) C57 black 6 (C57BL/6) mice and RORα-deficient stagger [ROR(sg/sg)] mice and their WT littermates were used for in vivo studies. The renal I/R injury model was induced by bilateral renal pedicle clamping for 35 min. Human proximal tubule cell line cells were treated with hypoxia (1% oxygen) to establish the cell hypoxia/reoxygenation (H/R) model. We investigated the renal expression and biologic function of RORα, and we found that RORα was significantly down-regulated after renal I/R injury. ROR(sg/sg) mice displayed dramatically augmented renal dysfunction and morphologic damage compared with WT mice at 24 h post-I/R. Further study revealed that the detrimental effects of RORα deficiency were attributable to tubular epithelial cell apoptosis and, consequently, renal inflammation and oxidative stress. The proapoptotic effect of RORα deficiency was associated with aggravated mitochondrial dysfunction in renal tubular cells after I/R. However, pretreatment of C57BL/6 mice with the RORα agonist SR1078 ameliorated I/R-induced renal dysfunction and damage and elicited a concomitant decrease in tubular epithelial cell apoptosis. In summary, our study provides experimental evidence showing that RORα is a novel endogenous protector against renal I/R injury and that ROR-α activation is a promising therapeutic strategy for the prevention of acute kidney injury.-Cai, J., Jiao, X., Fang, Y., Yu, X., Ding, X. The orphan nuclear receptor RORα is a potential endogenous protector in renal ischemia/reperfusion injury.

Transforming growth factor-β1-overexpressing mesenchymal stromal cells induced local tolerance in rat renal ischemia/reperfusion injury

BACKGROUND

Regulatory T cells (Tregs) suppress excessive immune responses and play a crucial protective role in acute kidney injury (AKI). The aim of this study was to examine the therapeutic potential of transforming growth factor (TGF)-β1-overexpressing mesenchymal stromal cells (MSCs) in inducing local generation of Tregs in the kidney after ischemia/reperfusion (I/R) injury.

METHODS

MSCs were transduced with a lentiviral vector expressing the TGF-β1 gene; TGF-β1-overexpressing MSCs (designated TGF-β1/MSCs) were then transfused into the I/R-injured kidney via the renal artery.

RESULTS

MSCs genetically modified with TGF-β1 achieved overexpression of TGF-β1. Compared with green fluorescent protein (GFP)/MSCs, TGF-β1/MSCs markedly improved renal function after I/R injury and reduced epithelial apoptosis and subsequent inflammation. The enhanced immunosuppressive and therapeutic abilities of TGF-β1/MSCs were associated with increased generation of induced Tregs and improved intrarenal migration of the injected cells. Futhermore, the mechanism of TGF-β1/MSCs in attenuating renal I/R injury was not through a direct canonical TGF-β1/Smad pathway.

CONCLUSION

TGF-β1/MSCs can induce a local immunosuppressive effect in the I/R-injured kidney. The immunomodulatory activity of TGF-β1-modified MSCs appears to be a gateway to new therapeutic approaches to prevent renal I/R injury.

Remote Ischemic Preconditioning Ameliorates Acute Kidney Injury due to Contrast Exposure in Rats through Augmented O-GlcNAcylation

Remote ischemic preconditioning (RIPC) is an adaptive response, manifesting when local short-term ischemic preconditioning reduces damage to adjacent or distant tissues or organs. O-linked β-N-acetylglucosamine (O-GlcNAc) glycosylation of intracellular proteins denotes a type of posttranslational modification that influences multiple cytoplasmic and nuclear protein functions. Growing evidence indicates that stress can induce an acute increase in O-GlcNAc levels, which can be cytoprotective. The current study aimed to determine whether RIPC can provide renoprotection against contrast-induced acute kidney injury (CI-AKI) by augmenting O-GlcNAc signaling. We established a stable model of CI-AKI using 5/6 nephrectomized rats exposed to dehydration followed by iohexol injection via the tail vein. We found that RIPC increased UDP-GlcNAc levels through the hexosamine biosynthetic pathway as well as global renal O-GlcNAcylation. RIPC-induced elevation of O-GlcNAc signaling ameliorated CI-AKI based on the presence of less tubular damage and apoptosis and the amount of reactive oxygen species. In addition, the use of alloxan, an O-GlcNAc transferase inhibitor, and azaserine, a glutamine fructose-6-phosphate amidotransferase inhibitor, neutralized the protective effect of RIPC against oxidative stress and tubular apoptosis. In conclusion, RIPC attenuates local oxidative stress and tubular apoptosis induced by contrast exposure by enhancing O-GlcNAc glycosylation levels; this can be a potentially useful approach for lowering the risk of CI-AKI.

Utility of cystatin C-based equations in patients undergoing dialysis

Serum cystatin C (CysC) measurement is regarded as a simple and practical alternative to measure residual renal function for dialysis patients. Recent studies have shown that CysC has better diagnostic accuracy or at least equivalence to creatinine in predicting the early stages of renal damage, and is closely related to clinical outcomes of dialysis patients. Thus, the applicability of CysC-derived equations in patients undergoing dialysis should be paid attention. Here, we review the role of CysC in diagnosis, renal function evaluation, and prognosis outcomes for dialysis patients, so as to provide them with useful suggestions on evaluating renal function and predicting adverse outcomes in clinical practice.

Prolyl hydroxylase 2 (PHD2) inhibition protects human renal epithelial cells and mice kidney from hypoxia injury

Prolyl hydroxylase domain protein 2 (PHD2) is a key oxygen sensor, setting low steady-state level of hypoxia-inducible factor-α (HIF-α). Here, we showed that treatment of cobalt chloride (CoCl2), a hypoxia mimic, in HK-2 tubular epithelial cells induced PHD2 and HIF-1/2α expression as well as cell apoptosis and autophagy activation. Three methyladenine (3-MA), the autophagy inhibitor, blocked autophagy and protected HK-2 cells from CoCl2. Significantly, siRNA knockdown of PHD2 also protected HK-2 cells from CoCl2,possibly via increasing HIF-1α expression. Reversely, HIF-1α siRNA knockdown almost abolished cytoprotection by PHD2 siRNA in CoCl2-treated HK-2 cells. In vivo, pretreatment with a PHD inhibitor L-mimosine remarkably attenuated mice renal ischemia-reperfusion injuries. Molecularly, L-mimosine inhibited apoptosis and inflammatory responses in injured mice kidneys. Together, our results suggest that PHD2 silence or inhibition protects human renal epithelial cells and mice kidney from hypoxia injuries.

Risk Factor Analysis for AKI Including Laboratory Indicators: a Nationwide Multicenter Study of Hospitalized Patients

BACKGROUND/AIMS

Risk factor studies for acute kidney injury (AKI) in China are lacking, especially those regarding non-traditional risk factors, such as laboratory indicators.

METHODS

All adult patients admitted to 38 tertiary and 22 secondary hospitals in China in any one month between July and December 2014 were surveyed. AKI patients were screened according to the Kidney Disease: Improving Global Outcomes' definition of AKI. Logistic regression was used to analyze the risk factors for AKI, and Cox regression was used to analyze the risk of in-hospital mortality for AKI patients; additionally, a propensity score analysis was used to reconfirm the risk factors among laboratory indicators for mortality.

RESULTS

The morbidity of AKI was 0.97%. Independent risk factors for AKI were advancing age, male gender, hypertension, and chronic kidney disease. All-cause mortality was 16.5%. The predictors of mortality in AKI patients were advancing age, tumor, higher uric acid level and increases in Acute Physiologic Assessment and Chronic Health Evaluation II and Sequential Organ Failure Assessment scores. The hazard ratio (HR) for mortality with uric acid levels > 9.1 mg/dl compared with ≤ 5.2 mg/dl was 1.78 (95% CI: 1.23 to 2.58) for the AKI patients as a group, and was 1.73 (95% CI: 1.24 to 2.42) for a propensity score-matched set.

CONCLUSION

In addition to traditional risk factors, uric acid level is an independent predictor of all-cause mortality after AKI.

Renal replacement therapy practices for patients with acute kidney injury in China

Recent data indicate AKI is very common among hospitalized Chinese patients and continuous renal replacement therapy (CRRT) is increasingly offered for treatment. However, only anecdotal information regarding CRRT's use in relation to other modalities and the specific manner in which it is prescribed exists currently. This report summarizes the results of a comprehensive physician survey designed to characterize contemporary dialytic management of AKI patients in China, especially with respect to the utilization of CRRT. The survey queried both nephrologists and critical care physicians across a wide spectrum of hospitals about factors influencing initial RRT modality selection, especially patient clinical characteristics and willingness to receive RRT, treatment location, and institutional capabilities. For patients initially treated with CRRT, data related to indication, timing of treatment initiation, dose, anticoagulation technique, and duration of therapy were also collected. Among AKI patients considered RRT candidates, the survey indicated 15.1% (95% CI, 12.3%-17.9%) did not actually receive dialysis at Chinese hospitals. The finding was largely attributed to prohibitively high therapy costs in the view of patients or their families. The survey confirmed the dichotomy in RRT delivery in China, occurring both in the nephrology department (with nephrologists responsible) and the intensive care unit (with critical care physicians responsible). For all patients who were offered and received RRT, the survey participants reported 63.9% (56.4%-71.3%) were treated initially with CRRT and 24.8% (19.2%-30.3%) with intermittent hemodialysis (HD) (P<0.001). The mean percentage of patients considered hemodynamically unstable at RRT initiation was 36.2% (31.3%-41.1%), although this figure was two-fold higher in patients treated initially with CRRT (43.1%; 35.8%-50.4%) in comparison to those initially treated with HD (22.4%; 16.4%-28.4%)(P<0.001). An overwhelming majority of intensive care patients were treated initially with CRRT (86.6%; 79.8-93.4%) while it was the initial modality in only 44.6% (33.5-55.7%) of patients treated in a nephrology department (P<0.001). Approximately 70% of respondents overall reported prescribing a CRRT dose in the range of 20-30 mL/kg/hr while approximately 20% of prescriptions fell above this range. Daily prescribed therapy duration demonstrated a marked divergence from values reported in the literature and standard clinical practice. Overall, the most common average prescribed value (50% of respondents) fell in the 10-20 hr range, with only 18% in the 20-24 hr range. Moreover, 32% of respondents reported an average prescribed value of less than 10 hrs per day. While the percentages for the 10-20 hrs range were essentially the same for nephrology and ICU programs, a daily duration of less than 10 hrs was much more common in nephrology programs (48.0%; 38.3%-57.9%) versus ICU programs (16%; 10.0%-24.6%)(P<0.001). Our analysis demonstrates both similarities and differences between RRT practices for AKI in China and those in the developed world. While some differences are driven by non-medical factors, future studies should explore these issues further as Chinese RRT practices are harmonized with those in the rest of the world.

Augmented O-GlcNAc signaling via glucosamine attenuates oxidative stress and apoptosis following contrast-induced acute kidney injury in rats

Contrast-induced acute kidney injury (CI-AKI) is an iatrogenic renal injury and associated with substantial morbidity and mortality in susceptible individuals. Despite extensive study of a variety of agents for renal protection, limited strategies have been shown to be effective in the reduction of CI-AKI. O-linked β-N-acetylglucosamine (O-GlcNAc) is a post-translational regulatory modification of intracellular proteins and governs the function of numerous proteins, both cytosolic and nuclear. Increasing evidence suggests that O-GlcNAc levels are increased in response to stress and that acute augmentation of this reaction is cytoprotective. However, the underlying mechanisms by which augmented OGlcNAc signaling provides renoprotection against contrast media insults is still unknown. Here, we investigated the effect of augmented O-GlcNAc signaling via glucosamine on CI-AKI and explored the underlying molecular mechanisms, particularly its relationship with PI3-kinase (PI3K)/Akt signaling. We used a novel and reliable CI-AKI model consisting of 5/6 nephrectomized (NE) rats, and a low-osmolar contrast media (iohexol, 10mL/kg, 3.5gI) injected via the tail vein after dehydration for 48h. The results showed that augmented O-GlcNAc signaling by glucosamine prevented the kidneys against iohexol-induced injury characterized by the attenuation of renal dysfunction, tubular damage, apoptosis and oxidative stress. Furthermore, this renoprotection was blocked by treatment with alloxan, an O-GlcNAc transferase inhibitor. Augmented O-GlcNAc signaling also increased the protein expression levels of phospho-Akt (Ser473, but not Thr308 and Thr450), phospho-GSK-3β, Nrf2, and Bcl-2, and decreased the levels of Bax and cleaved caspase-3. Both alloxan and specific inhibitors of PI3K (Wortmannin and LY294002) blocked the protection of glucosamine via inhibiting Akt signaling pathway. We further identified O-GlcNAcylated Akt through immunoprecipitation and western blot. We confirmed that Akt was modified by O-GlcNAcylation, and glucosamine pretreatment increased the O-GlcNAcylation of Akt. Collectively, the results demonstrate that glucosamine induces renoprotection against CI-AKI through augmented O-GlcNAc and activation of PI3K/Akt signaling, making it a promising strategy for preventing CI-AKI.

Hyperuricemia increases the risk of acute kidney injury: a systematic review and meta-analysis

Background

Mounting evidence indicated that the elevated serum uric acid level was associated with an increased risk of acute kidney injury (AKI). Our goal was to systematically evaluate the correlation of serum uric acid (SUA) level and incidence of AKI by longitudinal cohort studies.

Methods

We searched electronic databases and the reference lists of relevant articles. 18 cohort studies with 75,200 patients were analyzed in this random-effect meta-analysis. Hyperuricemia was defined as SUA levels greater than 360-420 μmol/L (6–7 mg/dl), which was various according to different studies. Data including serum uric acid, serum creatinine, and incidence of AKI and hospital mortality were summarized using random-effects meta-analysis.

Results

The hyperuricemia group significantly exerted a higher risk of AKI compared to the controls (odds ratio OR 2.24, 95% CI 1.76-2.86, p < 0.01). Furthermore, there is less difference of the pooled rate of AKI after cardiac surgery between hyperuricemia and control group (34.3% vs 29.7%, OR 1.24, 95% CI 0.96-1.60, p = 0.10), while the rates after PCI were much higher in hyperuricemia group than that in control group (16.0% vs 5.3%, OR 3.24, 95% CI 1.93-5.45, p < 0.01). In addition, there were significant differences in baseline renal function at admission between hyperuricemia and control groups in most of the included studies. The relationship between hyperuricemia and hospital mortality was not significant. The pooled pre-operative SUA levels were higher in AKI group than that in the non-AKI group.

Conclusions

Elevated SUA level showed an increased risk for AKI in patients and measurements of SUA may help identify risks for AKI in these patients.

Dynamic Predictive Scores for Cardiac Surgery-Associated Acute Kidney Injury

Background

Cardiac surgery–associated acute kidney injury (CSA‐AKI) is a common complication with a poor prognosis. In order to identify modifiable perioperative risk factors for AKI, which existing risk scores are insufficient to predict, a dynamic clinical risk score to allow clinicians to estimate the risk of CSA‐AKI from preoperative to early postoperative periods is needed.

Methods and Results

A total of 7233 cardiac surgery patients in our institution from January 2010 to April 2013 were enrolled prospectively and distributed into 2 cohorts. Among the derivation cohort, logistic regression was used to analyze CSA‐AKI risk factors preoperatively, on the day of ICU admittance and 24 hours after ICU admittance. Sex, age, valve surgery combined with coronary artery bypass grafting, preoperative NYHA score >2, previous cardiac surgery, preoperative kidney (without renal replacement therapy) disease, intraoperative cardiopulmonary bypass application, intraoperative erythrocyte transfusions, and postoperative low cardiac output syndrome were identified to be associated with CSA‐AKI. Among the other 1152 patients who served as a validation cohort, the point scoring of risk factor combinations led to area under receiver operator characteristics curves (AUROC) values for CSA‐AKI prediction of 0.74 (preoperative), 0.75 (on the day of ICU admission), and 0.82 (postoperative), and Hosmer–Lemeshow goodness‐of‐fit tests revealed a good agreement of expected and observed CSA‐AKI rates.

Conclusions

The first dynamic predictive score system, with Kidney Disease: Improving Global Outcomes (KDIGO) AKI definition, was developed and predictive efficiency for CSA‐AKI was validated in cardiac surgery patients.