Role of the CCL20/CCR6 axis in tubular epithelial cell injury: Kidney-specific translational insights from acute kidney injury to chronic kidney disease.

This study investigated the role of the axis involving chemokine receptor 6 (CCR6) and its ligand chemokine (C-C motif) ligand 20 (CCL20) in acute kidney disease (AKD) using an ischemia-reperfusion injury (IRI) model. The model was established by clamping the unilateral renal artery pedicle of C57BL/6 mice for 30 min, followed by evaluation of CCL20/CCR6 expression at 4 weeks post-IRI. In vitro studies were conducted to examine the effects of hypoxia and H2 O2 -induced oxidative stress on CCL20/CCR6 expression in kidney tissues of patients with AKD and chronic kidney disease (CKD). Tubular epithelial cell apoptosis was more severe in C57BL/6 mice than in CCL20 antibody-treated mice, and CCR6, NGAL mRNA, and IL-8 levels were higher under hypoxic conditions. CCL20 blockade ameliorated apoptotic damage in a dose-dependent manner under hypoxia and reactive oxygen species injury. CCR6 expression in IRI mice indicated that the disease severity was similar to that in patients with the AKD phenotype. Morphometry of CCL20/CCR6 expression revealed a higher likelihood of CCR6+ cell presence in CKD stage 3 patients than in stage 1-2 patients. Kidney tissues of patients with CKD frequently contained CCL20+ cells, which were positively correlated with interstitial inflammation. CCL20/CCR6 levels were increased in fibrotic kidneys at 4 and 8 weeks after 5/6 nephrectomy. These findings suggest that modulating the CCL20/CCR6 pathway is a potential therapeutic strategy for managing the progression of AKD to CKD.

Antibiotic-induced intestinal microbiota depletion can attenuate the acute kidney injury to chronic kidney disease transition via NADPH oxidase 2 and trimethylamine-N-oxide inhibition.

Intestinal microbiota and their metabolites affect systemic inflammation and kidney disease outcomes. Here, we investigated the key metabolites associated with the acute kidney injury (AKI)-to chronic kidney disease (CKD) transition and the effect of antibiotic-induced microbiota depletion (AIMD) on this transition. In 61 patients with AKI, 59 plasma metabolites were assessed to determine the risk of AKI-to-CKD transition. An AKI-to-CKD transition murine model was established four weeks after unilateral ischemia-reperfusion injury (IRI) to determine the effects of AIMD on the gut microbiome, metabolites, and pathological responses related to CKD transition. Human proximal tubular epithelial cells were challenged with CKD transition-related metabolites, and inhibitory effects of NADPH oxidase 2 (NOX2) signals were tested. Based on clinical metabolomics, plasma trimethylamine N-oxide (TMAO) was associated with a significantly increased risk for AKI-to-CKD transition [adjusted odds ratio 4.389 (95% confidence interval 1.106-17.416)]. In vivo, AIMD inhibited a unilateral IRI-induced increase in TMAO, along with a decrease in apoptosis, inflammation, and fibrosis. The expression of NOX2 and oxidative stress decreased after AIMD. In vitro, TMAO induced fibrosis with NOX2 activation and oxidative stress. NOX2 inhibition successfully attenuated apoptosis, inflammation, and fibrosis with suppression of G2/M arrest. NOX2 inhibition (in vivo) showed improvement in pathological changes with a decrease in oxidative stress without changes in TMAO levels. Thus, TMAO is a key metabolite associated with the AKI-to-CKD transition, and NOX2 activation was identified as a key regulator of TMAO-related AKI-to-CKD transition both in vivo and in vitro.

Glutamyl-prolyl-tRNA synthetase (EPRS1) drives tubulointerstitial nephritis-induced fibrosis by enhancing T cell proliferation and activity.

Toxin- and drug-induced tubulointerstitial nephritis (TIN), characterized by interstitial infiltration of immune cells, frequently necessitates dialysis for patients due to irreversible fibrosis. However, agents modulating interstitial immune cells are lacking. Here, we addressed whether the housekeeping enzyme glutamyl-prolyl-transfer RNA synthetase 1 (EPRS1), responsible for attaching glutamic acid and proline to transfer RNA, modulates immune cell activity during TIN and whether its pharmacological inhibition abrogates fibrotic transformation. The immunological feature following TIN induction by means of an adenine-mixed diet was infiltration of EPRS1high T cells, particularly proliferating T and γδ T cells. The proliferation capacity of both CD4+ and CD8+ T cells, along with interleukin-17 production of γδ T cells, was higher in the kidneys of TIN-induced Eprs1+/+ mice than in the kidneys of TIN-induced Eprs1+/- mice. This discrepancy contributed to the fibrotic amelioration observed in kidneys of Eprs1+/- mice. TIN-induced fibrosis was also reduced in Rag1-/- mice adoptively transferred with Eprs1+/- T cells compared to the Rag1-/- mice transferred with Eprs1+/+ T cells. The use of an EPRS1-targeting small molecule inhibitor (bersiporocin) under clinical trials to evaluate its therapeutic potential against idiopathic pulmonary fibrosis alleviated immunofibrotic aggravation in TIN. EPRS1 expression was also observed in human kidney tissues and blood-derived T cells, and high expression was associated with worse patient outcomes. Thus, EPRS1 may emerge as a therapeutic target in toxin- and drug-induced TIN, modulating the proliferation and activity of infiltrated T cells.

Inflammatory chemokine (C-C motif) ligand 8 inhibition ameliorates peritoneal fibrosis.

Peritoneal fibrosis (PF) is an irreversible complication of peritoneal dialysis (PD) that leads to loss of peritoneal membrane function. We investigated PD effluent and serum levels and the tissue expression of chemokine (C-C motif) ligand 8 (CCL8) in patients with PD. Additionally, we investigated their association with PF in a mouse model. Eighty-two end-stage renal disease (ESRD) patients with PD were examined. CCL8 levels were measured via enzyme-linked immunosorbent assays in PD effluents and serum and analyzed with peritoneal transport parameters. Human peritoneal mesothelial cells (hPMCs) were obtained from the PD effluents of 20 patients. Primary cultured hPMCs were treated with recombinant (r) transforming growth factor (TGF)-ß, and CCL8 expression was assessed via western blotting. As the duration of PD increased, the concentration of CCL8 in PD effluents significantly increased. Correlations between peritoneal transport parameters and dialysate CCL8 levels were observed. Western blotting analysis showed that CCL8 was upregulated via rTGF-ß treatment, accompanied by increases in markers of inflammation, fibrosis, senescence, and apoptosis in hPMCs after induction of fibrosis with rTGF-ß. Anti-CCL8 monoclonal antibody (mAb) treatment suppressed the rTGF-ß-induced increase in all analyzed markers. Immunohistochemical analysis revealed that CCL8 along with fibrosis- and inflammation-related markers were significantly increased in the PF mouse model. Functional blockade of CCL8 using a CCR8 inhibitor (R243) abrogated peritoneal inflammation and fibrosis in vivo. In conclusion, high CCL8 levels in PD effluents may be associated with an increased risk of PD failure, and the CCL8 pathway is associated with PF. CCL8 blockade can ameliorate peritoneal inflammation and fibrosis.

Oral phosphate binders and incident osteoporotic fracture in patients on dialysis.

BACKGROUND AND HYPOTHESIS: End-stage kidney disease (ESKD) has an elevated risk of osteoporotic fractures in relation to mineral and bone disorder (MBD) as well as conventional risks of osteoporosis. We investigated the association between oral phosphate binders, the mainstay of MBD treatment, and osteoporotic fracture in dialysis patients. METHODS: We obtained data from the National Health Insurance database for incident dialysis patients without a history of osteoporotic fractures. Participants were categorized into four groups based on their initial 1-year prescription profiles: calcium-based phosphate binder (CBPB), non-calcium-based phosphate binder (NCBPB), both calcium and non-calcium-based binders (Mixed), and non-phosphate binder (non-user) groups. The primary outcome was the occurrence of new-onset osteoporotic fractures after 1 year of dialysis. Secondary outcomes included cardiovascular events and mortality. RESULTS: Out of 69 368 incident dialysis patients, 22 326, 5020, 2853, and 39 169 were included in the CBPB, NCBPB, mixed, and non-user groups, respectively. The overall risk of osteoporotic fractures was lower in patients taking any phosphate binders compared to non-users. Specifically, only the CBPB group showed a reduced risk of vertebral (adjusted hazard ratio (aHR) 0.83 [0.76-0.92]), hip (aHR 0.81 [0.74-0.89]), and distal radius (aHR 0.88 [0.78-0.99]) fractures compared to non-users. This relationship was represented by a time-dependent manner with fracture risk reduction in patients taking CBPB for 3-6 months (aHR 0.9 [0.83-0.99]) and ≥ 6 months (aHR 0.83 [0.78-0.89]), compared to those using CBPB for less than 3 months. Additionally, only the CBPB group had a lower risk of MACE, cardiac arrest, and ventricular arrhythmia than non-users. All phosphorus binder groups showed a reduced mortality risk compared to non-users. CONCLUSIONS: Our findings indicate that the using phosphate binders in ESKD patients is lowers the risk of osteoporotic fractures. Notably, those taking CBPB had a reduced risk without increasing cardiovascular events or mortality compared to non-users.

Primary sclerosing cholangitis causally affects kidney function decline: A Mendelian randomization study.

BACKGROUND AND AIM: The causal linkage between primary sclerosing cholangitis (PSC) and kidney function is unexplored despite their potential for long-term detrimental effects on kidney function. METHODS: Two-sample summary-level Mendelian randomization (MR) study was conducted to identify the association between PSC and kidney function. The genetic variants were extracted from the PSC-specific multi-trait analyzed genome-wide association study (GWAS) of European ancestry. Summary-level data for kidney function traits, including estimated glomerular filtration rate (eGFR), annual eGFR decline, and chronic kidney disease (CKD), were obtained from the CKDGen consortium. Multiplicative random-effects inverse-variance weighted (MR-IVW), and a series of pleiotropy-robust analyses were performed to investigate the causal effects and ascertain their robustness. RESULTS: Significant causal associations between genetically predicted PSC and kidney function traits were identified. Genetically predicted PSC was associated with decreased log-transformed eGFR (MR-IVW; beta = -0.41%; standard error [SE] = 0.02%; P < 0.001), increased rate of annual eGFR decline (MR-IVW; beta = 2.43%; SE = 0.18%; P < 0.001), and higher risk of CKD (MR-IVW; odds ratio = 1.07; 95% confidence interval = 1.06-1.08; P < 0.001). The main findings were supported by pleiotropy-robust analysis, including MR-Egger with bootstrapped error and weighted median. CONCLUSIONS: Our study demonstrates that genetically predicted PSC is causally associated with kidney function impairment. Further studies are warranted to identify the underlying mechanisms.

Long-term ozone exposure and mortality in patients with chronic kidney disease: a large cohort study.

BACKGROUND: Epidemiologic studies on the effects of long-term exposure to ozone (O3) have shown inconclusive results. It is unclear whether to O3 has an effect on chronic kidney disease (CKD). We investigated the effects of O3 on mortality and renal outcome in CKD. METHODS: We included 61,073 participants and applied Cox proportional hazards models to examine the effects of ozone on the risk of end-stage renal disease (ESRD) and mortality in a two-pollutants model adjusted for socioeconomic status. We calculated the concentration of ozone exposure one year before enrollment and used inverse distance weighting (IDW) for interpolation, where the exposure was evenly distributed. RESULTS: In the single pollutant model, O3 was significantly associated with an increased risk of ESRD and all-cause mortality. Based on the O3 concentration from IDW interpolation, this moving O3 average was significantly associated with an increased risk of ESRD and all-cause mortality. In a two-pollutants model, even after we adjusted for other measured pollutants, nitrogen dioxide did not attenuate the result for O3. The hazard ratio (HR) value for the district-level assessment is 1.025 with a 95% confidence interval (CI) of 1.014-1.035, while for the point-level assessment, the HR value is 1.04 with a 95% CI of 1.035-1.045. The impact of ozone on ESRD, hazard ratio (HR) values are, 1.049(95%CI: 1.044-1.054) at the district unit and 1.04 (95%CI: 1.031-1.05) at the individual address of the exposure assessment. The ozone hazard ratio for all-cause mortality was 1.012 (95% confidence interval: 1.008-1.017) for administrative districts and 1.04 (95% confidence interval: 1.031-1.05) for individual addresses. CONCLUSIONS: This study suggests that long-term ambient O3 increases the risk of ESRD and mortality in CKD. The strategy to decrease O3 emissions will substantially benefit health and the environment.

Causal effects from tobacco smoking initiation on obesity-related traits: a Mendelian randomization study.

BACKGROUND: There is a widespread notion that tobacco smoking controls weight based on the appetite suppressive effect of nicotine. However, the causal relationship between smoking initiation and obesity-related traits in the general population are unclear. METHODS: This Mendelian randomization analysis utilized 378 genetic variants associated with tobacco smoking initiation (usually in adolescence or young adulthood) identified in a genome-wide association study (meta-analysis) of 1.2 million individuals. Outcome data for body mass index, waist circumference, hip circumference, and waist-to-hip ratio were extracted from the 337,138 white British-ancestry UK Biobank participants aged 40-69 years. Replication analyses were performed for genome-wide association study meta-analysis for body mass index, including the GERA/GIANT data including 364,487 samples from mostly European individuals. In addition, summary-level Mendelian randomization by inverse variance weighted method and pleiotropy-robust Mendelian randomization methods, including median-based and MR-Egger regression, was performed. RESULTS: Summary-level Mendelian randomization analysis indicated that genetically predicted smoking initiation is causally linked to higher body mass index [+0.28 (0.18-0.38) kg/m2], waist circumference [+0.88 (0.66-1.10) cm], hip circumference [+0.40 (0.23-0.57) cm], and waist-to-hip ratio [+0.006 (0.005-0.007)]. These results were consistent with those of the pleiotropy-robust Mendelian randomization analysis. Additionally, in replication analysis, genetically predicted smoking initiation was significantly associated with a higher body mass index [+0.03 (0.01, 0.05] kg/m2). CONCLUSION: Tobacco initiation may lead to worse obesity-related traits in the general 40- to 69-year-old individuals. Therefore, tobacco-use initiation as a long-term weight-control measure should be discouraged.

Metformin Use and Long-term Clinical Outcomes in Kidney Transplant Recipients.

RATIONALE & OBJECTIVE: Metformin has been recommended for some patients with advanced chronic kidney disease. However, the value of metformin in kidney transplant recipients (KTRs) with pretransplant diabetes mellitus (DM) or posttransplant DM is uncertain. We investigated the clinical effects of metformin in KTRs. STUDY DESIGN: Retrospective cohort study. SETTING & PARTICIPANTS: A total of 1,995 KTRs with diabetes from 6 tertiary referral centers in the Republic of Korea. EXPOSURE: Metformin usage was defined as the use of metformin for>90 days after kidney transplantation; 1,193 KTRs were metformin users, and 802 KTRs did not use metformin. Changing usage of metformin among those exposed for >90 days was also characterized. OUTCOME: Primary outcomes were all-cause mortality and death-censored graft failure (DCGF). Secondary outcomes were biopsy-proven acute rejection (BPAR) and lactic acidosis events. ANALYTICAL APPROACH: Survival analyses were conducted using multivariable Cox regression and competing risk analyses using Fine and Gray models. Changes in metformin use over time were modeled using a time-varying covariate. Metformin usage, mean daily dose, and hemoglobin A1c (HbA1c) changes were considered in the landmark analysis to address time-varying confounding. RESULTS: Metformin use was associated with a lower risk of DCGF (adjusted hazard ratio [AHR], 0.47 [95% CI, 0.23-0.96], P=0.038); there was no significant association with all-cause mortality (AHR, 0.94 [95% CI, 0.32-2.76], P=0.915) or BPAR (AHR 0.98 [95% CI, 0.62-1.54], P=0.942). In the subgroup analysis, metformin usage was associated with a reduced risk of all-cause mortality and a lower risk of DCGF for both pretransplantation DM and posttransplant DM groups. Metformin usage was associated with a lower risk of BPAR in the posttransplant DM group, although it was less effective in the pretransplantation DM group. There was no confirmed case of metformin-associated lactic acidosis (MALA) in the present cohort. A higher dose of metformin was correlated with lower risks of DCGF and BPAR. LIMITATIONS: Data on newer antidiabetic drugs such as SGLT2 inhibitors are limited, and there is potential limited generalizability to other populations. CONCLUSIONS: Metformin usage may benefit KTRs, as evidenced by its association with a reduced risk of DCGF and the absence of MALA events. Randomized controlled trials are needed to validate these observational findings.

De novo major cardiovascular events in kidney transplant recipients: a comparative matched cohort study.

BACKGROUND: Although cardiovascular disease is known to be one of the leading causes of death after kidney transplantation (KT), evidence on the risk difference of de novo major adverse cardiovascular events (MACEs) in kidney transplant recipients (KTRs) compared with that in dialysis patients or the general population (GP) remains rare. METHODS: We identified KTRs using the nationwide health insurance database in South Korea and then 1:1 matched them with the dialysis and GP controls without a pre-existing MACE. The primary endpoint was defined as de novo MACEs consisting of myocardial infarction, coronary revascularization and ischemic stroke. The secondary endpoints were all-cause mortality and death-censored graft failure (DCGF) in KTRs. RESULTS: We included 4156 individuals in each of the three groups and followed them up for 4.7 years. De novo MACEs occurred in 3.7, 21.7 and 2.5 individuals per 1000 person-years in the KTRs, dialysis controls and GP controls, respectively. KTRs showed a lower MACE risk {adjusted hazard ratio (aHR) 0.16 [95% confidence interval (CI) 0.12-0.20], P < .001} than dialysis controls, whereas a similar MACE risk to GP controls [aHR 0.81 (95% CI 0.52-1.27), P = .365]. In addition, KTRs showed a similar MACE risk compared with the GP group, regardless of age, sex and the presence of comorbidities, including hypertension, diabetes and dyslipidemia. Among KTRs, de novo MACEs were associated with an increased risk of all-cause mortality, but not with DCGF. CONCLUSIONS: De novo MACEs in KTRs were much lower than that in dialysis patients and had a similar risk to the GP, but once it occurred it caused elevated mortality risk in KTRs.

Effect of haemodialysis on the pharmacokinetics and pharmacodynamics of evogliptin.

AIM: To investigate the possible effect of haemodialysis (HD) on the pharmacokinetic (PK) and pharmacodynamic (PD) characteristics of evogliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor. METHODS: A single-dose, open-label, parallel-group study of eight end-stage renal disease (ESRD) patients and eight matched healthy subjects was conducted. ESRD patients received a single oral dose of evogliptin 5 mg after and before HD with a 2-week washout between each dose, and healthy subjects received a single oral dose of evogliptin 5 mg. Serial blood, dialysate, and urine samples were collected to assess the PK and PD profiles of evogliptin. To compare PK parameters before and after HD, geometric mean ratios (GMRs) and 90% confidence intervals (CIs) were calculated. RESULTS: The GMRs for the maximum concentration and area under the concentration-time curve from time 0 to the last measurable timepoint (AUClast ) of evogliptin when administered before HD compared with after HD were 0.7293 (90% CI 0.6171-0.8620) and 0.9480 (90% CI 0.8162-1.1010), respectively. The maximum DPP-4 inhibitory effect, area under the DPP-4 inhibitory effect-time curve, and time duration of more than 80% DPP-4 inhibition were comparable when evogliptin was administered before and after HD. Compared with healthy subjects, the mean AUClast of evogliptin was approximately 1.4-fold greater in ESRD patients, but the difference is unlikely to affect the safety and efficacy of evogliptin. CONCLUSION: The effect of HD on the PK and PD characteristics of evogliptin was not clinically significant; therefore, dose adjustment according to HD status is not necessary.

Multisample Mass Spectrometry-Based Approach for Discovering Injury Markers in Chronic Kidney Disease.

Urinary proteomics studies have primarily focused on identifying markers of chronic kidney disease (CKD) progression. Here, we aimed to determine urinary markers of CKD renal parenchymal injury through proteomics analysis in animal kidney tissues and cells and in the urine of patients with CKD. Label-free quantitative proteomics analysis based on liquid chromatography-tandem mass spectrometry was performed on urine samples obtained from 6 normal controls and 9, 11, and 10 patients with CKD stages 1, 3, and 5, respectively, and on kidney tissue samples from a rat CKD model by 5/6 nephrectomy. Tandem mass tag-based quantitative proteomics analysis was performed for glomerular endothelial cells (GECs) and proximal tubular epithelial cells (PTECs) before and after inducing 24-h hypoxia injury. Upon hierarchical clustering, out of 858 differentially expressed proteins (DEPs) in the urine of CKD patients, the levels of 416 decreased and 403 increased sequentially according to the disease stage, respectively. Among 2965 DEPs across 5/6 nephrectomized and sham-operated rat kidney tissues, 86 DEPs showed same expression patterns in the urine and kidney tissue. After cross-validation with two external animal proteome data sets, 38 DEPs were organized; only ten DEPs, including serotransferrin, gelsolin, poly ADP-ribose polymerase 1, neuroblast differentiation-associated protein AHNAK, microtubule-associated protein 4, galectin-1, protein S, thymosin beta-4, myristoylated alanine-rich C-kinase substrate, and vimentin, were finalized by screening human GECs and PTECs data. Among these ten potential candidates for universal CKD marker, validation analyses for protein S and galectin-1 were conducted. Galectin-1 was observed to have a significant inverse correlation with renal function as well as higher expression in glomerulus with chronic injury than protein S. This constitutes the first multisample proteomics study for identifying key renal-expressed proteins associated with CKD progression. The discovered proteins represent potential markers of chronic renal cell and tissue damage and candidate contributors to CKD pathophysiology.

Plasma Circulating Tumor Necrosis Factor Receptors at Multiple Time Points Can Predict the Outcome of Severe Acute Kidney Injury.

INTRODUCTION: This prospective cohort study investigated the clinical role of circulating tumor necrosis factor receptor (cTNFR) levels as prognostic biomarkers in severe acute kidney injury (AKI) patients requiring continuous renal replacement therapy (CRRT). METHODS: We enrolled 136 patients from 7 hospitals participating in the VENUS (VolumE maNagement Under body composition monitoring in critically ill patientS on CRRT) trial from July 2017 to October 2019. The levels of cTNFR1 and cTNFR2 were measured using plasma samples collected on days 0 (D0), 2 (D2), and 7 (D7). Patients were divided into high- and low-cTNFR groups based on their receptor concentrations. RESULTS: D0 concentrations of cTNFR1 and cTNFR2 were positively correlated with one another (R2 = 0.37, p < 0.001). The high-cTNFR1 group displayed a higher in-hospital mortality rate than the low-TNFR1 group (p = 0.002). Moreover, the mortality rate was significantly higher in the high-TNFR1 group than in the low-TNFR1 group after adjusting for age, sex, and acute physiology, and chronic health evaluation II scores (hazard ratio 1.82, 95% confidence interval 1.09-3.03, p = 0.025). D2 and D7 cTNFR1 levels were also associated with in-hospital mortality; contrastingly, cTNFR2 levels were not associated with this outcome. Additionally, patients were divided into three groups according to the change in cTNFR levels from D0 to D2 (ΔcTNFR). Those in the highest ΔcTNFR tertile had a higher mortality rate than the remaining patients (p = 0.033 for ΔcTNFR1; p = 0.025 for ΔcTNFR2). Patients who underwent AKI-to-chronic kidney disease transition had higher concentrations of cTNFR1 (p = 0.014). DISCUSSION/CONCLUSION: Plasma cTNFR1 concentrations at CRRT initiation and changes in cTNFR1 and 2 levels immediately following CRRT initiation are significant biomarkers for predicting the outcomes of patients with severe AKI.

Hyperlactatemia is a predictor of mortality in patients undergoing continuous renal replacement therapy for acute kidney injury.

BACKGROUND: Hyperlactatemia occurs frequently in critically ill patients, and this pathologic condition leads to worse outcomes in several disease subsets. Herein, we addressed whether hyperlactatemia is associated with the risk of mortality in patients undergoing continuous renal replacement therapy (CRRT) due to acute kidney injury. METHODS: A total of 1,661 patients who underwent CRRT for severe acute kidney injury were retrospectively reviewed between 2010 and 2020. The patients were categorized according to their serum lactate levels, such as high (≥ 7.6 mmol/l), moderate (2.1-7.5 mmol/l) and low (≤ 2 mmol/l), at the time of CRRT initiation. The hazard ratios (HRs) for the risk of in-hospital mortality were calculated with adjustment of multiple variables. The increase in the area under the receiver operating characteristic curve (AUROC) for the mortality risk was evaluated after adding serum lactate levels to the Sequential Organ Failure Assessment (SOFA) and the Acute Physiology and Chronic Health Evaluation (APACHE) II score-based models. RESULTS: A total of 802 (48.3%) and 542 (32.6%) patients had moderate and high lactate levels, respectively. The moderate and high lactate groups had a higher risk of mortality than the low lactate group, with HRs of 1.64 (1.22-2.20) and 4.18 (2.99-5.85), respectively. The lactate-enhanced models had higher AUROCs than the models without lactates (0.764 vs. 0.702 for SOFA score; 0.737 vs. 0.678 for APACHE II score). CONCLUSIONS: Hyperlactatemia is associated with mortality outcomes in patients undergoing CRRT for acute kidney injury. Serum lactate levels may need to be monitored in this patient subset.

Trajectory of AKI and hospital mortality among patients with COVID-19.

BACKGROUND: Acute kidney injury (AKI) in COVID-19 patients is associated with poor prognosis. Characterization of AKI by timing and trajectory and early prediction of AKI progression is required for better preventive management and the prediction of patient outcomes. METHODS: A total of 858 patients who were hospitalized due to coronavirus disease 2019 (COVID-19) were retrospectively enrolled from December 2020 to August 2021. The occurrence of AKI was evaluated throughout hospitalization. The hazard ratios (HRs) of mortality outcomes according to the trajectory of AKI were measured using Cox regression models after adjustment for multiple variables. RESULTS: Among 858 patients, 226 (26.3%) presented AKI at admission, and 44 (5.1%) developed AKI during hospitalization. Patients with AKI at admission or hospital-acquired AKI had a higher risk of mortality than those without AKI, with HRs of 9.87 (2.81-34.67) and 13.74 (3.57-52.84), respectively. Of 226 patients with AKI at admission, 104 (46.0%) recovered within 48 hr, 83 (36.7%) had AKI beyond 48 hr and recovered in 7 days, and 39 (17.3%) showed no recovery from AKI on Day 7. Delayed recovery and persistent AKI were significantly associated with an increased risk of mortality, with HRs of 4.39 (1.06-18.24) and 24.33 (7.10-83.36), respectively. CONCLUSIONS: The onset and progression of AKI was significantly associated with in-hospital mortality in patients with COVID-19. A thorough observation of the recovery trajectory of early AKI after infection is necessary.

Revisiting metformin therapy for the mitigation of diabetic foot ulcer in patients with diabetic kidney disease from real-world evidence.

Diabetic foot ulcer and diabetic kidney disease are diabetes-related chronic vascular complications that strongly correlate with high morbidity and mortality. Although metformin potentially confers a wound-healing advantage, no well-established clinical evidence supports the benefit of metformin for diabetic foot ulcer. Thus, this study investigated the effect of metformin on diabetic foot ulcer from a large diabetic kidney disease cohort for the first time. This retrospective cohort study enrolled 10 832 patients who visited the nephrology department more than twice at two South Korean tertiary-referral centers between 2001 and 2016. The primary outcome was diabetic foot ulcer events; secondary outcomes included hospitalization, amputation, a composite of amputation or vascular intervention, and Wagner Grade ≥ 3. Multivariate Cox analysis and propensity score matching (PSM) were used to balance baseline intergroup differences between metformin users and non-users. In total, 4748 patients were metformin users, and 6084 patients were metformin non-users. Over a follow-up period of 117.5 ± 66.9 months, the diabetic foot ulcer incidence was 5.2%. After PSM, metformin users showed a lower incidence of diabetic foot ulcer events than metformin non-users (adjusted hazard ratio 0.41; p < 0.001). In a sensitivity analysis of 563 patients with diabetic foot ulcer, metformin usage was associated with lower severity in all four secondary outcomes: hospitalization (adjusted hazard ratio 0.33; p < 0.001); amputation (adjusted hazard ratio 0.44; p = 0.001); composite of amputation or vascular intervention (adjusted hazard ratio 0.47; p < 0.001); and Wagner Grade ≥ 3 (adjusted hazard ratio 0.39; p < 0.001). In conclusion, metformin therapy in patients with diabetic kidney disease can lower diabetic foot ulcer incidence and progression.

RNA-seq profiling of tubulointerstitial tissue reveals a potential therapeutic role of dual anti-phosphatase 1 in glomerulonephritis.

Transcriptome profiling of tubulointerstitial tissue in glomerulonephritis may reveal a potential tubulointerstitial injury-related biomarker. We profiled manually microdissected tubulointerstitial tissue from biopsy cores of 65 glomerulonephritis cases, including 43 patients with IgA nephropathy, 3 with diabetes mellitus nephropathy, 3 with focal segmental glomerulosclerosis, 3 with lupus nephritis, 4 with membranous nephropathy and 9 with minimal change disease, and additional 22 nephrectomy controls by RNA sequencing. A potential biomarker was selected based on the false discovery rate, and experiments were performed in TNF-α-stimulated primary cultured human tubular epithelial cells (hTECs). We identified 3037 genes with low expression and 2852 genes with high expression in the disease samples compared to the controls. Dual-specificity phosphatase 1 (DUSP1) exhibited universal low expression in various diseases (log2 fold change, -3.87), with the lowest false discovery rate (7.03E-132). In further experimental validation study, DUSP1 overexpression ameliorated inflammatory markers related to MAP kinase pathways in hTECs, while pharmacologic inhibition of DUSP1 increased these markers. The combination of DUSP1 overexpression with low-concentration corticosteroid treatment resulted in more potent suppression of inflammation than high-concentration corticosteroid treatment alone. The profiled transcriptomes provide insights into the pathophysiology of tubulointerstitial injury in kidney diseases and may reveal a potential therapeutic biomarker.

Blockade of STAT3 signaling alleviates the progression of acute kidney injury to chronic kidney disease through antiapoptosis.

Signal transducer and activator of transcription 3 (STAT3) is a pivotal mediator of IL-6-type cytokine signaling. However, the roles of its full-length and truncated isoforms in acute kidney injury (AKI) and its transition to chronic kidney disease (CKD) remain elusive. Herein, the role of STAT3 isoforms in the AKI-to-CKD transition was characterized using an ischemia-reperfusion injury (IRI) mouse model. The STAT3 inhibitor Stattic was administered to C57BL/6 mice 3 h before IRI. Intrarenal cytokine expression was quantified using real-time PCR and FACS. The effect of Stattic on human tubular epithelial cells cultured under hypoxic conditions was also evaluated. Phosphorylated (p)STAT3 isoforms were detected by Western blot analysis. Stattic treatment attenuated IRI-induced tubular damage and inflammatory cytokine/chemokine expression while decreasing macrophage infiltration and fibrosis in mouse unilateral IRI and unilateral ureteral obstruction models. Similarly, in vitro STAT3 inhibition downregulated fibrosis and apoptosis in 72-h hypoxia-induced human tubular epithelial cells and reduced pSTAT3α-mediated inflammation. Moreover, pSTAT3 expression was increased in human acute tubular necrosis and CKD tissues. STAT3 activation is associated with IRI progression, and STAT3α may be a significant contributor. Hence, STAT3 may affect the AKI-to-CKD transition, suggesting a novel strategy for AKI management with STAT3 inhibitors.NEW & NOTEWORTHY We found that IRI increased expression of STAT3 in murine kidneys, along with inflammation markers. Through the investigation of the role of STAT3 in the AKI-to-CKD transition mechanism using mouse unilateral IRI and unilateral ureteral obstruction models and 24- or 72-h hypoxic induction of primary cultured human tubular epithelial cells, we found that STAT3 could affect the AKI-to-CKD transition. We also observed different degrees of expression in STAT3 isoforms in these processes.

Nonlinear causal effects of estimated glomerular filtration rate on myocardial infarction risks: Mendelian randomization study.

BACKGROUND: Previous observational studies suggested that a reduction in estimated glomerular filtration rate (eGFR) or a supranormal eGFR value was associated with adverse cardiovascular risks. However, a previous Mendelian randomization (MR) study under the linearity assumption reported null causal effects from eGFR on myocardial infarction (MI) risks. Further investigation of the nonlinear causal effect of kidney function assessed by eGFR on the risk of MI by nonlinear MR analysis is warranted. METHODS: In this MR study, genetic instruments for log-eGFR based on serum creatinine were developed from European samples included in the CKDGen genome-wide association study (GWAS) meta-analysis (N=567,460). Alternate instruments for log-eGFR based on cystatin C were developed from a GWAS of European individuals that included the CKDGen and UK Biobank data (N=460,826). Nonlinear MR analysis for the risk of MI was performed using the fractional polynomial method and the piecewise linear method on data from individuals of white British ancestry in the UK Biobank (N=321,024, with 12,205 MI cases). RESULTS: Nonlinear MR analysis demonstrated a U-shaped (quadratic P value < 0.001) association between MI risk and genetically predicted eGFR (creatinine) values, as MI risk increased as eGFR declined in the low eGFR range and the risk increased as eGFR increased in the high eGFR range. The results were similar even after adjustment for clinical covariates, such as blood pressure, diabetes mellitus, dyslipidemia, or urine microalbumin levels, or when genetically predicted eGFR (cystatin C) was included as the exposure. CONCLUSION: Genetically predicted eGFR is significantly associated with the risk of MI with a parabolic shape, suggesting that kidney function impairment, either by reduced or supranormal eGFR, may be causally linked to a higher MI risk.

Economic Impact of Donating a Kidney on Living Donors: A Korean Cohort Study.

RATIONALE & OBJECTIVE: Although existing studies have reported adverse health outcomes after kidney donation, its socioeconomic impact on living donors requires further study. STUDY DESIGN: A retrospective observational cohort study including a matched comparison group. SETTING & PARTICIPANTS: 1,285 living kidney donors from 7 tertiary hospitals between 2003 and 2016, and a matched comparison group consisting of the same number of health screening examinees with similar baseline clinical characteristics and socioeconomic status. All participants were receiving Korean national health insurance. EXPOSURE: Kidney donation as reflected in the Korean National Health Insurance System (NHIS) database. OUTCOME: Changes in household economic status estimated by Korean national health insurance fees and changes in employment status reflected in the NHIS database. ANALYTICAL APPROACH: The outcomes of the donor group and matched control group were compared annually using multivariable logistic regression analyses adjusted for clinical and demographic characteristics. RESULTS: The median ages of the donors and matched controls were 45 and 46 years, respectively; 44.6% of both groups were male. Compared to the comparison group, living donors were at higher risk of being unemployed or losing employment during the first 2 years after donation (eg, first-year loss of employment: odds ratio (OR), 2.27 [95% CI, 1.55-3.33]); however, this association did not persist. Donors also had a significantly lower odds of improvement in economic status (OR, 0.57 [95% CI, 0.47-0.71]) and a higher odds of deterioration in financial status (OR, 1.54 [95% CI, 1.23-1.93]) in the first year after transplantation and subsequently. LIMITATIONS: Unmeasured differences between donors and matched controls creating residual selection bias and confounding. CONCLUSIONS: Living kidney donors may suffer loss of employment and poor economic status after their voluntary donation. The socioeconomic impact on these donors should be considered in conjunction with the potential long-term adverse health outcomes after donation.