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.

Associations of MRI-derived kidney volume, kidney function, body composition and physical performance in ≈38 000 UK Biobank participants: a population-based observational study

Background

Kidney volume is used as a predictive and therapeutic marker for several clinical conditions. However, there is a lack of large-scale studies examining the relationship between kidney volume and various clinicodemographic factors, including kidney function, body composition and physical performance.

Methods

In this observational study, MRI-derived kidney volume measurements from 38 526 UK Biobank participants were analysed. Major kidney volume-related measures included body surface area (BSA)-adjusted total kidney volume (TKV) and the difference in bilateral kidneys. Multivariable-adjusted linear regression and cubic spline analyses were used to explore the association between kidney volume-related measures and clinicodemographic factors. Cox or logistic regression was used to identify the risks of death, non-kidney cancer, myocardial infarction, ischaemic stroke and chronic kidney disease (CKD).

Results

The median of BSA-adjusted TKV and the difference in kidney volume were 141.9 ml/m2 [interquartile range (IQR) 128.1-156.9] and 1.08-fold (IQR 1.04-1.15), respectively. Higher BSA-adjusted TKV was significantly associated with higher estimated glomerular filtration rate {eGFR; β = 0.43 [95% confidence interval (CI) 0.42-0.44]; P < .001}, greater muscle volume [β = 0.50 (95% CI 0.48-0.51); P < .001] and greater mean handgrip strength [β = 0.15 (95% CI 0.13-0.16); P < .001] but lower visceral adipose tissue volume [VAT; β = -0.09 (95% CI -0.11 to -0.07); P < .001] in adjusted models. A greater difference in bilateral kidney volumes was associated with lower eGFR, muscle volume and physical performance but with higher proteinuria and VAT. Higher BSA-adjusted TKV was significantly associated with a reduced risk of CKD [odds ratio (OR) 0.7 (95% CI 0.63-0.77); P < .001], while a greater difference in kidney volume was significantly associated with an increased risk of CKD [OR 1.13 (95% CI 1.07-1.20); P < .001].

Conclusion

Higher BSA-adjusted TKV and lower differences in bilateral kidney volumes are associated with higher kidney function, muscle volume and physical performance and a reduced risk of CKD.

Menopausal hormone therapy and risk for dementia in women with CKD: A nationwide observational cohort study

AIM

The risk for dementia is increased in postmenopausal women. The incidences of premature menopause and dementia have increased in patients with chronic kidney disease (CKD). The potential benefits of hormone replacement therapy (HRT) on cognitive function may be a more critical issue for patients with CKD.

METHODS

Women aged >40 years with or without HRT were identified using the 2009 National Health Screening Questionnaire. Women who were newly diagnosed with CKD between 2009 and 2013 were enrolled. HRT was used as an exposure variable, and participants were followed from the day CKD was diagnosed to December 2019. The hazard ratio (HR) for dementia was evaluated using Cox proportional hazards regression analysis.

RESULTS

We included 755 426 postmenopausal women with CKD. The median follow-up period was 7.3 (IQR, 5.8-8.7) years. All-cause dementia, Alzheimer's disease, and vascular dementia occurred in 107 848 (14.3%), 87 833 (11.6%), and 10 245 (1.4%) women, respectively. HRT was significantly associated with a lower risk for dementia in the adjusted Cox regression model (all-cause dementia: HR 0.80; 95% confidence interval [CI] 0.78-0.82; p < 0.001; Alzheimer's disease: HR 0.80; 95% CI 0.77-0.82; p < 0.001; vascular dementia: HR 0.80; 95% CI 0.74-0.87; p < 0.001).

CONCLUSIONS

HRT was significantly associated with a lower risk for CKD-related cognitive dysfunction in postmenopausal women. Prospective studies are needed to determine whether HRT lowers the risk for dementia in menopausal women with CKD.

Risk of mortality and cause of death according to kidney function parameters: a nationwide observational study in Korea

BACKGROUND

Further study is warranted to determine the association between estimated glomerular filtration rate (eGFR) or albuminuria and the risk of death from diverse causes.

METHODS

We screened >10 million general health screening examinees who received health examinations conducted in 2009 using the claims database of Korea. After the exclusion of those previously diagnosed with renal failure and those with missing data, 9,917,838 individuals with available baseline kidney function measurements were included. The primary outcome was mortality and cause-specific death between 2009 and 2019 identified through death certificates based on the diagnostic codes of International Classification of Diseases, 10th revision. Multivariable Cox regression analysis adjusted for various clinicodemographic and social characteristics was used to assess mortality risk.

RESULTS

The hazard ratio of death was significantly high in both the eGFR <60 mL/min/1.73 m2 and in the eGFR ≥120 mL/ min/1.73 m2 groups in univariable and multivariable regression analyses when compared to those within the reference range (eGFR of 90-120 mL/min/1.73 m2). The results were similar for death by cardiovascular, cancer, infection, endocrine, respiratory, and digestive causes. We also found that albuminuria was associated with higher risk of death regardless of eGFR range, and those in the higher categories of dipstick albuminuria showed higher risk.

CONCLUSION

We reconfirmed the significant association between eGFR, albuminuria, and mortality. Healthcare providers should keep in mind that albuminuria and decreased eGFR as well as kidney hyperfiltration are independent predictors of mortality.

Intradialytic hypotension and worse outcomes in patients with acute kidney injury requiring intermittent hemodialysis

Background

Intradialytic hypotension (IDH) is a critical complication related to worse outcomes in patients undergoing maintenance hemodialysis. Herein, we addressed the impact of IDH on mortality and other outcomes in patients with severe acute kidney injury (AKI) requiring intermittent hemodialysis.

Methods

We retrospectively reviewed 1,009 patients who underwent intermittent hemodialysis due to severe AKI. IDH was defined as either dialysis discontinuation due to hemodynamic instability or a decrease in systolic blood pressure (BP) of ≥30 mmHg, with or without a nadir systolic BP of <90 mmHg during the first session. The primary outcome was all-cause mortality, and transfer to the intensive care unit (ICU) due to unstable status was additionally analyzed. Hazard ratios (HRs) of outcomes were calculated using a Cox regression model after adjusting for multiple variables. Risk factors for IDH were evaluated using a logistic regression model.

Results

IDH occurred in 449 patients (44.5%) during the first hemodialysis session. Patients with IDH had a higher mortality rate than those without IDH (40% vs. 23%; HR, 1.30; 95% confidence interval [CI], 1.02-1.65). The rate of ICU transfer was higher in patients experiencing IDH than in those without IDH (17% vs. 11%; HR, 1.43; 95% CI, 1.02-2.02). Factors such as old age, high BP and pulse rate, active malignancy, cirrhosis, and hypoalbuminemia were associated with an increased risk of IDH episodes.

Conclusion

The occurrence of IDH is associated with worse outcomes in patients with AKI requiring intermittent hemodialysis. Therefore, careful monitoring and early intervention of IDH may be necessary in this patient subset.

Mortality associated with the neutrophil-lymphocyte ratio in septic acute kidney injury requiring continuous renal replacement therapy

Background

Sepsis is an important cause of acute kidney injury in intensive care unit patients, accounting for 15% to 20% of renal replacement therapy prescriptions. The neutrophil-lymphocyte ratio (NLR), a maker of systemic inflammation and immune response, was previously associated with the mortality rate in multiple conditions. Herein, we aimed to examine how the NLR relates to the mortality rate in septic acute kidney injury patients requiring continuous renal replacement therapy (CRRT).

Methods

The NLRs of 6 and 18 were used for dividing NLRs into three groups and, thus, were set higher than those in previous studies accounting for steroid use in sepsis. Cox proportional hazard models were used to calculate hazard ratios of mortality outcomes before and after matching their propensity scores.

Results

A total of 798 septic acute kidney injury patients requiring CRRT were classified into three NLR groups (low, <6 [n = 277]; medium, ≥6 and <18 [n = 115], and high, ≥18 [n = 406], respectively). The in-hospital mortality rates per group were 83.4%, 74.8%, and 70.4%, respectively (p < 0.001). Per the univariable Cox survival analysis after propensity score matching, a high NLR was related to approximately 24% reduced mortality. The survival benefit of the high NLR group compared with the other two groups remained consistent across all subgroups, showing any p for interactions of >0.05.

Conclusion

A high NLR is associated with better clinical outcomes, such as low mortality, in septic acute kidney injury patients undergoing CRRT.

Glomerular spatial transcriptomics of IgA nephropathy according to the presence of mesangial proliferation

Mesangial proliferation is a diagnostic feature and a prognostic predictor of immunoglobulin A nephropathy (IgAN). We aimed to investigate the gene expression profiles of IgAN glomerulus according to the presence of mesangial proliferation. We performed spatial-specific transcriptomic profiling on kidney biopsy tissues using the GeoMx Digital Spatial Profiler. Twelve cases with three glomeruli for each case were profiled using direct pathologic classification (4 M1-IgAN, 4 M0-IgAN, and 4 donor controls). The results of enriched glom-specific genes demonstrated that M1-IgAN could be distinguished from controls (77 upregulated and 55 downregulated DEGs), while some DEGs were identified between M1-IgAN and M0-IgAN cases (24 upregulated and 8 downregulated DEGs) or between M0 and controls (1 upregulated and 16 downregulated DEGs). TCF21, an early podocyte damage marker, was the only differentially expressed gene (DEG) consistently upregulated in both M1-IgAN and M0-IgAN patients, whereas ATF3, EGR1, DUSP1, FOS, JUNB, KLF2, NR4A1, RHOB, and ZFP36 were consistently downregulated in IgAN cases. Glomeruli from M1-IgAN cases were significantly enriched for cell surface/adhesion molecules and gene expressions associated with vascular development or the extracellular matrix. Spatial transcriptomic analysis may contribute to dissecting structure-specific pathophysiology and molecular changes in IgAN.

Associations of metabolic variabilities and cardiovascular outcomes according to estimated glomerular filtration rate in chronic kidney disease: a nationwide observational cohort study

Background

The impact of baseline estimated glomerular filtration rate (eGFR) on the risk of adverse outcomes according to metabolic parameter variabilities in chronic kidney disease has rarely been investigated.

Methods

We conducted a retrospective nationwide cohort study using the National Health Insurance System data in Korea from 2007 to 2013 to identify individuals with three or more health screenings. The metabolic components variability was defined as intraindividual variability between measurements using the variability independent of the mean. The metabolic variability score was defined as the total number of high-variability metabolic components. Multivariable-adjusted Cox regression analysis was conducted to evaluate the risks of all-cause mortality, myocardial infarction, and ischemic stroke.

Results

During a mean follow-up of 6.0 ± 0.7 years, 223,531 deaths, 107,140 myocardial infarctions, and 116,182 ischemic strokes were identified in 9,971,562 patients. Low eGFR categories and higher metabolic variability scores were associated with a higher risk of adverse outcomes. The degree of association between metabolic variability and adverse outcomes was significantly larger in those with low eGFR categories than in those with preserved eGFR (p for interaction < 0.001). Representatively, those with high metabolic variability in the eGFR of <15 mL/min/1.73 m2 group showed a prominently higher risk for all-cause mortality (adjusted hazard ratio [aHR], 5.28; 95% confidence interval [CI], 4.02-6.94) when the degree was compared to the findings in those with preserved (eGFR of ≥60 mL/min/1.73 m2) kidney function (aHR, 2.55; 95% CI, 2.41-2.69).

Conclusion

The degree of adverse association between metabolic variability and poor prognosis is accentuated in patients with impaired kidney function.

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.

Impact of albuminuria on early-onset type 2 diabetes mellitus: a nationwide population-based study

Background

Early-onset diabetes mellitus has a significant lifetime burden and is associated with higher morbidity and mortality. Since insulin resistance is one of the mechanisms of podocyte injury, we aimed to evaluate the effect of albuminuria on newly developed early-onset type 2 diabetes mellitus (T2DM).

Methods

We screened 6,891,399 subjects aged ≥20 and <40 years without a history of prediabetes or diabetes from the Korean National Health Insurance Service database between 2009 and 2012. A multivariate Cox proportional hazard model was used to identify the impact of albuminuria on early-onset T2DM.

Results

Among a total of 5,383,779 subjects, 62,148 subjects (1.2%) developed early-onset diabetes over 7.3 ± 1.2 years. Albuminuria was significantly associated with early-onset T2DM (adjusted hazard ratio [aHR], 1.62; 95% confidence interval [CI], 1.55-1.70) after adjustment for age, sex, anthropometric data, physical exercise status, serum glucose, and total cholesterol. The risk of early-onset T2DM increased more in subjects with more components of metabolic syndrome (MetS). Among each component of MetS, hypertriglyceridemia was prominently associated with early-onset T2DM (aHR, 2.02; 95% CI, 1.81-2.25) in subjects with albuminuria.

Conclusion

Dipstick albuminuria was significantly associated with early-onset T2DM in young adult populations. Close monitoring of albuminuria is warranted for disease risk modification, especially in subjects with MetS.

Cardiovascular and Mortality Risks in Young Health Screening Examinees With Marginal Estimated GFR

Introduction

Additional evidence is necessary to interpret kidney function parameters in young adults, particularly in those with marginal estimated glomerular filtration rate (eGFR) values. Therefore, we aimed to investigate the association between eGFR and adverse outcomes in general young adults.

Methods

We performed a nationwide retrospective cohort study using the health-screening database of South Korea. We included young adults aged 20-39 years without a history of major adverse cardiovascular events (MACE) or kidney failure, who underwent nationwide health screening in 2012. The study exposure was eGFR categorized into 15 ml/min per 1.73 m2 intervals. The risks of all-cause mortality and MACE were calculated using Cox regression analysis, adjusted for various clinicodemographic characteristics.

Results

In total, 3,132,409 young adults were included in this study. During a median follow-up of 7.3 years, marginal eGFR (60-75 ml/min per 1.73 m2) was not significantly associated with a higher risk of all-cause mortality (adjusted hazard ratio [aHR], 0.80 [0.74-0.87]). The results were similar for MACE outcomes (aHR, 0.94 [0.87-1.01]). Although the presence of dipstick albuminuria had a significant interaction with the association between eGFR categories and all-cause mortality (interaction term P = 0.028), the risks of all-cause mortality were not significantly higher (aHR, 0.98 [0.62, 1.55]) in those with albuminuria and eGFR 60-75 ml/min per 1.73 m2.

Conclusion

Marginal eGFR was not associated with higher risks of all-cause mortality and MACE in general young adults. Additional clinical investigations for incidentally found marginal eGFR values may be discouraged in general young adults.

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.

Real-time dual prediction of intradialytic hypotension and hypertension using an explainable deep learning model

Both intradialytic hypotension (IDH) and hypertension (IDHTN) are associated with poor outcomes in hemodialysis patients, but a model predicting dual outcomes in real-time has never been developed. Herein, we developed an explainable deep learning model with a sequence-to-sequence-based attention network to predict both of these events simultaneously. We retrieved 302,774 hemodialysis sessions from the electronic health records of 11,110 patients, and these sessions were split into training (70%), validation (10%), and test (20%) datasets through patient randomization. The outcomes were defined when nadir systolic blood pressure (BP) < 90 mmHg (termed IDH-1), a decrease in systolic BP ≥ 20 mmHg and/or a decrease in mean arterial pressure ≥ 10 mmHg (termed IDH-2), or an increase in systolic BP ≥ 10 mmHg (i.e., IDHTN) occurred within 1 h. We developed a temporal fusion transformer (TFT)-based model and compared its performance in the test dataset, including receiver operating characteristic curve (AUROC) and area under the precision-recall curves (AUPRC), with those of other machine learning models, such as recurrent neural network, light gradient boosting machine, random forest, and logistic regression. Among all models, the TFT-based model achieved the highest AUROCs of 0.953 (0.952-0.954), 0.892 (0.891-0.893), and 0.889 (0.888-0.890) in predicting IDH-1, IDH-2, and IDHTN, respectively. The AUPRCs in the TFT-based model for these outcomes were higher than the other models. The factors that contributed the most to the prediction were age and previous session, which were time-invariant variables, as well as systolic BP and elapsed time, which were time-varying variables. The present TFT-based model predicts both IDH and IDHTN in real time and offers explainable variable importance.

Urinary Metabolite Profile Predicting the Progression of CKD

Key Points

As a biomarker, urinary metabolites could bridge the gap between genetic abnormalities and phenotypes of diseases. We found that levels of betaine, choline, fumarate, citrate, and glucose were significantly correlated with kidney function and could predict kidney outcomes, providing prognostic biomarkers in CKD.

Background

Because CKD is caused by genetic and environmental factors, biomarker development through metabolomic analysis, which reflects gene-derived downstream effects and host adaptation to the environment, is warranted.

Methods

We measured the metabolites in urine samples collected from 789 patients at the time of kidney biopsy and from urine samples from 147 healthy participants using nuclear magnetic resonance. The composite outcome was defined as a 30% decline in eGFR, doubling of serum creatinine levels, or end-stage kidney disease.

Results

Among the 28 candidate metabolites, we identified seven metabolites showing (1 ) good discrimination between healthy controls and patients with stage 1 CKD and (2 ) a consistent change in pattern from controls to patients with advanced-stage CKD. Among the seven metabolites, betaine, choline, glucose, fumarate, and citrate showed significant associations with the composite outcome after adjustment for age, sex, eGFR, the urine protein–creatinine ratio, and diabetes. Furthermore, adding choline, glucose, or fumarate to traditional biomarkers, including eGFR and proteinuria, significantly improved the ability of the net reclassification improvement (P < 0.05) and integrated discrimination improvement (P < 0.05) to predict the composite outcome.

Conclusion

Urinary metabolites, including betaine, choline, fumarate, citrate, and glucose, were found to be significant predictors of the progression of CKD. As a signature of kidney injury–related metabolites, it would be warranted to monitor to predict the renal outcome.

The need for prophylactic hemodialysis to protect against nephrogenic systemic fibrosis in patients with end-stage renal disease receiving gadolinium-based contrast agents

BACKGROUND

The risk of gadolinium (Gd)-based contrast agent (GBCA)-induced nephrogenic systemic fibrosis (NSF) in patients with end-stage renal disease (ESRD) and the efficacy of prophylactic hemodialysis (HD) for protection against NSF are not well understood or summarized in the literature.

PURPOSE

To determine the risk for NSF related to frequency and time per dialysis session after Gd-magnetic resonance imaging (MRI) by emphasizing the safety of Gd-MRI in patients with ESRD.

MATERIAL AND METHODS

This retrospective observational study identified all GBCA injections for MRI examinations performed at two tertiary referral hospitals between 2005 and 2020. All clinical data, including dialysis records and medical history, were investigated for each patient through 2021. The end of follow-up coincided with the last hospital visit.

RESULTS

Overall, 1129 patients with ESRD underwent 1461 Gd-MRI scans (41.5% gadoterate, 39.4% gadobutrol, and 7.7% gadoxetate); a total of 958 patients with 1229 (84.1%) examinations underwent HD on the day of the MRI study, within 2.1 ± 2.0 h (range = 0.2-15.7 h) immediately after Gd exposure. In 53.4% of scans, frequent HD had been performed urgently and then twice more on consecutive days to prophylactically avoid NSF. No cases of NSF were identified during the follow-up period (mean = 81.7 ± 50.5 months) regardless of dose of HD.

CONCLUSION

No cases of NSF were reported in 1461 Gd-MRI examinations of 1129 inpatients with ESRD on HD. Our findings support the lack of benefit of frequent prophylactic HD being performed urgently within 4 h of the receipt of GBCA.

Mendelian randomization uncovers a protective effect of interleukin-1 receptor antagonist on kidney function

Interleukins (ILs), key cytokine family of inflammatory response, are closely associated with kidney function. However, the causal effect of various ILs on kidney function needs further investigation. Here we show two-sample summary-level Mendelian randomization (MR) analysis that examined the causality between serum IL levels and kidney function. Genetic variants with strong association with serum IL levels were obtained from a previous genome-wide association study meta-analysis. Summary-level data for estimated glomerular filtration rate (eGFR) were obtained from CKDGen database. As a main MR analysis, multiplicative random-effects inverse-variance weighted method was performed. Pleiotropy-robust MR analysis, including MR-Egger with bootstrapped error and weighted median methods, were also implemented. We tested the causal estimates from nine ILs on eGFR traits. Among the results, higher genetically predicted serum IL-1 receptor antagonist level was significantly associated with higher eGFR values in the meta-analysis of CKDGen and the UK Biobank data. In addition, the result was consistent towards eGFR decline phenotype of the outcome database. Otherwise, nonsignificant association was identified between other genetically predicted ILs and eGFR outcome. These findings support the clinical importance of IL-1 receptor antagonist-associated pathway in relation to kidney function in the general individuals, particularly highlighting the importance of IL-1 receptor antagonist.

Incident dementia in kidney transplantation recipients: a matched comparative nationwide cohort study in South Korea

BACKGROUND

Recent studies have shown that patients with end-stage renal disease (ESRD) are at elevated risk of dementia. However, whether kidney transplantation (KT) lowers the risk for incident dementia remains unclear.

METHODS

From the Korean National Health Insurance Service database, we identified incident KT recipients aged ≥40 years without any history of dementia between 2007 and 2015. We also established a pair of age-, sex-, and inclusion year-matched control cohorts of patients with incident dialysis-dependent ESRD and members of the general population (GP) without a history of dementia, respectively. Cases of incident all-cause dementia, including Alzheimer disease (AD), vascular dementia (VD), and other kinds of dementia, were obtained from baseline until December 31, 2017.

RESULTS

We followed 8,841 KT recipients, dialysis-dependent ESRD patients, and GP individuals for 48,371, 28,649, and 49,149 patient- years, respectively. Their mean age was 52.5 years, and 60.6% were male. Over the observation period, 55/43/19 KT recipients, 230/188/75 dialysis-dependent ESRD patients, and 38/32/14 GP individuals developed all-cause dementia/AD/VD. The risks of incident all-cause dementia, AD, and VD in KT recipients were similar to those in GP (hazard ratio: 0.74 [p = 0.20], 0.74 [p = 0.24], and 0.59 [p = 0.18], respectively) and significantly lower than those in dialysis-dependent ESRD patients (hazard ratio: 0.17 [p < 0.001], 0.16 [p < 0.001], and 0.16 [p < 0.001], respectively). Older age and diabetes mellitus at the time of KT were risk factors for incident all-cause dementia and AD in KT recipients.

CONCLUSION

This is the first study to show a beneficial impact of KT on incident dementia compared to dialysis dependency.

Genetic variations in HMGCR and PCSK9 and kidney function: a Mendelian randomization study

BACKGROUND

The genetically predicted lipid-lowering effect of HMGCR or PCSK9 variant can be used to assess drug proxy effects on kidney function.

METHODS

Mendelian randomization (MR) analysis-identified HMGCR and PCSK9 genetic variants were used to predict the low-density lipoprotein (LDL) cholesterol-lowering effects of medications targeting related molecules. Primary summary-level outcome data for log-estimated glomerular filtration rate (eGFR; creatinine) were provided by the CKDGen Consortium (n = 1,004,040 European) from a meta-analysis of CKDGen and UK Biobank data. We also conducted a separate investigation of summary-level data from CKDGen (n = 567,460, log-eGFR [creatinine]) and UK Biobank (n = 436,581, log-eGFR [cystatin C]) samples. Summary-level MRs using an inverse variance weighted method and pleiotropy-robust methods were performed.

RESULTS

Summary-level MR analysis indicated that the LDL-lowering effect predicted genetically by HMGCR variants (50-mg/dL decrease) was significantly associated with a decrease in eGFR (-1.67%; 95% confidence interval [CI], -2.20% to -1.13%). Similar significance was found in results from the pleiotropy-robust MR methods when the CKDGen and UK Biobank data were analyzed separately. However, the LDL-lowering effect predicted genetically by PCSK9 variants was significantly associated with an increase in eGFR (+1.17%; 95% CI, 0.10%-2.25%). The results were similarly supported by the weighted median method and in each CKDGen and UK Biobank dataset, but the significance obtained by MR-Egger regression was attenuated.

CONCLUSION

Genetically predicted HMG-CoA reductase inhibition was associated with low eGFR, while genetically predicted PCSK9 inhibition was associated with high eGFR. Clinicians should consider that the direct effect of different types of lipid-lowering medication on kidney function can vary.

Changes in socioeconomic status and patient outcomes in kidney transplantation recipients in South Korea

Background

Socioeconomic status is an important factor affecting the accessibility and prognosis of kidney transplantation. We aimed to investigate changes in kidney transplant recipients' socioeconomic status in South Korea and whether such changes were associated with patient prognosis.

Methods

This retrospective nationwide observational cohort study in South Korea included kidney transplant recipients between 2007 and 2016. South Korea provides a single-insurer health insurance service, and information on the socioeconomic status of the recipients is identifiable through the claims database. First, a generalized linear mixed model was used to investigate changes in recipients' socioeconomic status as an outcome. Second, the risk of graft failure was analyzed using Cox regression as another outcome to investigate whether changes in socioeconomic status were associated with patient prognosis.

Results

Among the 15,215 kidney transplant recipients included in the study, economic levels (defined based on insurance fee percentiles) and employment rates declined within the first 2 years after transplantation. Beyond 2 years, the employment rate increased significantly, while no significant changes were observed in economic status. Patients whose economic status did not improve 3 years after kidney transplantation showed a higher risk of death than those whose status improved. When compared to those who remained employed after kidney transplantation, unemployment was associated with a significantly higher risk of death-censored graft failure.

Conclusions

The socioeconomic status of kidney transplant recipients changed dynamically after kidney transplantation, and these changes were associated with patient prognosis.

Risk of ventricular tachycardia and its outcomes in patients undergoing continuous renal replacement therapy due to acute kidney injury

Background

Despite efforts to treat critically ill patients who require continuous renal replacement therapy (CRRT) due to acute kidney injury (AKI), their mortality risk remains high. This condition may be attributable to complications of CRRT, such as arrhythmias. Here, we addressed the occurrence of ventricular tachycardia (VT) during CRRT and its relationship with patient outcomes.

Methods

This study retrospectively enrolled 2,397 patients who started CRRT due to AKI from 2010 to 2020 at Seoul National University Hospital in Korea. The occurrence of VT was evaluated from the initiation of CRRT until weaning from CRRT. The odds ratios (ORs) of mortality outcomes were measured using logistic regression models after adjustment for multiple variables.

Results

VT occurred in 150 patients (6.3%) after starting CRRT. Among them, 95 cases were defined as sustained VT (i.e., lasting ≥30 seconds), and the other 55 cases were defined as non-sustained VT (i.e., lasting <30 seconds). The occurrence of sustained VT was associated with a higher mortality rate than a nonoccurrence (OR, 2.04 and 95% confidence interval [CI], 1.23-3.39 for the 30-day mortality; OR, 4.06 and 95% CI, 2.04-8.08 for the 90-day mortality). The mortality risk did not differ between patients with non-sustained VT and nonoccurrence. A history of myocardial infarction, vasopressor use, and certain trends of blood laboratory findings (such as acidosis and hyperkalemia) were associated with the subsequent risk of sustained VT.

Conclusion

Sustained VT occurrence after starting CRRT is associated with increased patient mortality. The monitoring of electrolytes and acid-base status during CRRT is essential because of its relationship with the risk of VT.

Gut Microbial Genes and Metabolism for Methionine and Branched-Chain Amino Acids in Diabetic Nephropathy

Diabetic mellitus nephropathy (DMN) is a serious complication of diabetes and a major health concern. Although the pathophysiology of diabetes mellitus (DM) leading to DMN is uncertain, recent evidence suggests the involvement of the gut microbiome. This study aimed to determine the relationships among gut microbial species, genes, and metabolites in DMN through an integrated clinical, taxonomic, genomic, and metabolomic analysis. Whole-metagenome shotgun sequencing and nuclear magnetic resonance metabolomic analyses were performed on stool samples from 15 patients with DMN and 22 healthy controls. Six bacterial species were identified to be significantly elevated in the DMN patients after adjusting for age, sex, body mass index, and estimated glomerular filtration rate (eGFR). Multivariate analysis found 216 microbial genes and 6 metabolites (higher valine, isoleucine, methionine, valerate, and phenylacetate levels in the DMN group and higher acetate levels in the control group) that were differentially present between the DMN and control groups. Integrated analysis of all of these parameters and clinical data using the random-forest model showed that methionine and branched-chain amino acids (BCAAs) were among the most significant features, next to the eGFR and proteinuria, in differentiating the DMN group from the control group. Metabolic pathway gene analysis of BCAAs and methionine also revealed that many genes involved in the biosynthesis of these metabolites were elevated in the six species that were more abundant in the DMN group. The suggested correlation among taxonomic, genetic, and metabolic features of the gut microbiome would expand our understanding of gut microbial involvement in the pathogenesis of DMN and may provide potential therapeutic targets for DMN. IMPORTANCE Whole metagenomic sequencing uncovered specific members of the gut microbiota associated with DMN. The gene families derived from the discovered species are involved in the metabolic pathways of methionine and branched-chain amino acids. Metabolomic analysis using stool samples showed increased methionine and branched-chain amino acids in DMN. These integrative omics results provide evidence of the gut microbiota-associated pathophysiology of DMN, which can be further studied for disease-modulating effects via prebiotics or probiotics.

Effect of hemodialysis on the pharmacokinetics and pharmacodynamics of evogliptin

AIM

To investigate the possible effect of hemodialysis (HD) on the pharmacokinetics (PKs) and pharmacodynamics (PDs) 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 and its 90% CIs for the maximum concentration (C_max ) and area under the concentration-time curve from time 0 to the last measurable timepoint (AUC_last ) of evogliptin when administered before HD compared to after HD were 0.7293 (0.6171-0.8620) and 0.9480 (0.8162-1.1010), respectively. The maximum DPP-4 inhibitory effect (E_max ), area under the DPP-4 inhibitory effect-time curve (AUEC_last ), and time duration of more than 80% DPP-4 inhibition (Fi80) were comparable when evogliptin was administered before and after HD. Compared to healthy subjects, the mean AUC_last 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 PKs and PDs of evogliptin was not clinically significant; therefore, dose adjustment according to HD status is not necessary. This article is protected by copyright. All rights reserved.

Consulting to nephrologist when starting continuous renal replacement therapy for acute kidney injury is associated with a survival benefit

BACKGROUND

Several studies suggest improved outcomes for patients with kidney disease who consult a nephrologist. However, it remains undetermined whether a consultation with a nephrologist is related to a survival benefit after starting continuous renal replacement therapy (CRRT) due to acute kidney injury (AKI).

METHODS

Data from 2,397 patients who started CRRT due to severe AKI at Seoul National University Hospital, Korea between 2010 and 2020 were retrospectively collected. The patients were divided into two groups according to whether they underwent a nephrology consultation regarding the initiation and maintenance of CRRT. The Cox proportional hazards model was used to calculate the hazard ratio (HR) of mortality during admission to the intensive care unit after adjusting for multiple variables.

RESULTS

A total of 2,153 patients (89.8%) were referred to nephrologists when starting CRRT. The patients who underwent a nephrology consultation had a lower mortality rate than those who did not have a consultation (HR = 0.47 [0.40-0.56]; P < 0.001). Subsequently, patients who had nephrology consultations were divided into two groups (i.e., early and late) according to the timing of the consultation. Both patients with early and late consultation had lower mortality rates than patients without consultations, with HRs of 0.45 (0.37-0.54) and 0.51 (0.42-0.61), respectively.

CONCLUSIONS

Consultation with a nephrologist may contribute to a survival benefit after starting CRRT for AKI.

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.

Impact of intradialytic hypotension on mortality following the transition from continuous renal replacement therapy to intermittent hemodialysis

BACKGROUND

The transition of dialysis modalities from continuous renal replacement therapy (CRRT) to intermittent hemodialysis (iHD) is frequently conducted during the recovery phase of critically ill patients with acute kidney injury. Herein, we addressed the occurrence of intradialytic hypotension (IDH) after this transition, and its association with the mortality risk.

METHODS

A total of 541 patients with acute kidney injury who attempted to transition from CRRT to iHD at Seoul National University Hospital, Korea from 2010 to 2020 were retrospectively collected. IDH was defined as a discontinuation of dialysis because of hemodynamic instability plus a nadir systolic blood pressure <90 mm Hg or a decrease in systolic blood pressure ≥30 mm Hg during the first session of iHD. Odds ratios (ORs) of outcomes, such as in-hospital mortality and weaning from RRT, were measured using a logistic regression model after adjusting for multiple variables.

RESULTS

IDH occurred in 197 patients (36%), and their mortality rate (44%) was higher than that of those without IDH (19%; OR, 2.64; 95% confidence interval [CI], 1.70-4.08). For patients exhibiting IDH, the iHD sessions delayed successful weaning from RRT (OR, 0.62; 95% CI, 0.43-0.90) compared with sessions on those without IDH. Factors such as low blood pressure, high pulse rate, low urine output, use of mechanical ventilations and vasopressors, and hypoalbuminemia were associated with IDH risk.

CONCLUSIONS

IDH occurrence following the transition from CRRT to iHD is associated with high mortality and delayed weaning from RRT.

Causal linkage of tobacco smoking with ageing: Mendelian randomization analysis towards telomere attrition and sarcopenia

BACKGROUND

Ageing traits and frailty are important health issues in modern medicine. Evidence supporting the causal effects of tobacco smoking on various ageing traits is required.

METHODS

This study performed Mendelian randomization (MR) analysis instrumenting 377 genetic variants associated with being an ever-smoker at a genome-wide significance level to test the causal estimates from tobacco smoking. The outcome data were obtained from 337 138 white British ancestry participants from the UK Biobank. Leucocyte telomere length, appendicular lean mass index, subjective walking pace, handgrip strength, and wristband accelerometry-determined physical activity degree were collected as ageing-related outcomes. Summary-level MR analysis was performed using the inverse variance-weighted method and pleiotropy-robust MR methods, including weighted median and MR-Egger. Observational association between the outcome traits and phenotypically being an ever-smoker was also investigated.

RESULTS

Summary-level MR analysis indicated that a higher genetic predisposition for tobacco smoking was significantly associated with shorter leucocyte telomere length (twofold increase in prevalence of smoking towards standardized Z-score, -0.041 [-0.054, -0.028]), lower appendicular lean mass index (-0.007 [-0.010, -0.005]), slower walking pace (ordinal category, -0.047 [-0.054, -0.033]) and lower time spent on moderate-to-vigorous physical activity (hours per week, -0.39 [-0.56, -0.23]). The causal estimates were non-significant towards handgrip strength phenotype (kg, 0.074 [-0.055, 0.204]). Pleiotropy-robust MR results generally supported the main causal estimates. The observational findings also showed significant association between being an ever-smoker and the ageing traits.

CONCLUSIONS

Genetically predicted and observational tobacco smoking status are significantly associated with poor ageing phenotypes. Healthcare providers may continue to reduce tobacco use, which may be helpful in reducing the burden of ageing and frailty.

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.

Genetically predicted body selenium concentration and eGFR: A Mendelian randomization study

Introduction

Selenium is a trace mineral that is commonly included in micronutrient supplements. The effect of selenium on kidney function remains unclear. A genetically predicted micronutrient and its association with estimated glomerular filtration rate (eGFR) can be used to assess the causal estimates by Mendelian randomization (MR).

Methods

In this MR study, we instrumented 11 genetic variants associated with blood or total selenium levels from a previous genome-wide association study (GWAS). The association between genetically predicted selenium concentration and eGFR was first assessed by summary-level MR in the chronic kidney disease(CKDGen) GWAS meta-analysis summary statistics, including 567,460 European samples. Inverse-variance weighted and pleiotropy-robust MR analyses were performed, in addition to multivariable MR adjusted for the effects of type 2 diabetes mellitus. Replication analysis was performed with individual-level UK Biobank data, including 337,318 White individuals of British ancestry.

Results

Summary-level MR analysis indicated that a genetically predicted 1 SD increase in selenium concentration was significantly associated with lower eGFR (-1.05 [-1.28, -0.82] %). The results were similarly reproduced by pleiotropy-robust MR analysis, including MR-Egger and weighted-median methods, and consistent even in the multivariable MR adjusted for diabetes. In the UK Biobank data, genetically predicted higher selenium concentration was also significantly associated with lower eGFR (- 0.36 [-0.52, -0.20] %), and the results were similar when body mass index, waist circumference, hypertension, and diabetes mellitus covariates were adjusted (-0.33 [-0.50, -0.17] %).

Conclusion

This MR study supports the hypothesis that higher genetically predicted body selenium is causally associated with lower eGFR.

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)-β, 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-β treatment, accompanied by increases in markers of inflammation, fibrosis, senescence, and apoptosis in hPMCs after induction of fibrosis with rTGF-β. Anti-CCL8 monoclonal antibody (mAb) treatment suppressed the rTGF-β-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.

Insufficient early renal recovery and progression to subsequent chronic kidney disease in living kidney donors

BACKGROUND/AIMS

Renal recovery of a kidney donor after undergoing nephrectomy though challenging is essential. We aimed to examine the effect of estimated glomerular filtration rate (eGFR) percent change at 1-month post-donation on insufficient kidney function after kidney donation.

METHODS

A total of 3,952 living kidney donors who underwent donor nephrectomy from 1982 to 2019 from eight different tertiary hospitals in Korea were initially screened. Percent changes in the eGFR from baseline to 1-month post-donation were calculated. The degree of percent changes was categorized by quartile, and the 1st quartile was regarded as the group with the lowest decreased eGFR at 1-month after donation. The remaining eGFR less than 60 mL/min/1.73 m2 was the end-point. The Cox proportional hazard model was used for evaluating the impact of initial eGFR and eGFR percent change at 1-month post-donation on the condition with remaining eGFR &lt; 60 mL/ min/1.73 m2. In the multivariate analysis, we used variables with a p &lt; 0.1 in the univariate analysis.

RESULTS

A total of 1,585 donors were included in the analysis. During 62.2 ± 49.3 months, 13.7% of donors showed renal insufficiency. The 4th (adjusted hazard ratio [aHR], 10.41; 95% confidence interval [CI], 5.15 to 21.04) and the 3rd (aHR, 4.29; 95% CI, 2.15 to 8.56) quartiles of percent change in eGFR and the pre-donation eGFR (aHR, 0.90; 95% CI, 0.88 to 0.92) were associated with the development of renal insufficiency.

CONCLUSION

The impact of worse initial renal recovery on renal insufficiency was pronounced in donors with lower pre-donation eGFRs. Additionally, worse initial renal recovery of remaining kidney affected the long-term development of renal insufficiency in kidney donors.

Serum bilirubin and kidney function: a Mendelian randomization study

Background

Further investigation is needed to determine the causal effects of serum bilirubin on the risk of chronic kidney disease (CKD).

Methods

This study is a Mendelian randomization (MR) analysis. Among the well-known single-nucleotide polymorphisms (SNPs) related to serum bilirubin levels, rs4149056 in the SLCO1B1 gene was selected as the genetic instrument for single-variant MR analysis, as it was found to be less related to possible confounders than other SNPs. The association between genetic predisposition for bilirubin levels and estimated glomerular filtration rate (eGFR) or CKD was assessed in 337 129 individuals of white British ancestry from the UK Biobank cohort. Two-sample MR based on summary-level data was also performed. SNPs related to total or direct bilirubin levels were collected from a previous genome-wide association study and confounder-associated SNPs were discarded. The independent CKDGen meta-analysis data for CKD were employed as the outcome summary statistics.

Results

The alleles of rs4149056 associated with higher bilirubin levels were associated with better kidney function in the UK Biobank data. In the summary-level MR, both of the genetically predicted total bilirubin {per 5 µmol/L increase; odds ratio [OR] 0.931 [95% confidence interval (CI) 0.871-0.995]} and direct bilirubin [per 1 µmol/L increase; OR 0.910 (95% CI 0.834-0.993)] levels were significantly associated with a lower risk of CKD, supported by the causal estimates from various MR sensitivity analyses.

Conclusion

Genetic predisposition for higher serum bilirubin levels is associated with better kidney function. This result suggests that higher serum bilirubin levels may have causal protective effects against kidney function impairment.

Perception regarding live kidney donation in the general population of South Korea

This study aimed to know how the general population recognizes live kidney donation in Korea. Participants were randomly selected from the general population after proportional allocation by region, sex, and age. Selected participants received a questionnaire that included demographic information, socioeconomic and marital statuses, prior recognition of live donor kidney transplantation, expected changes after donation, and the need for support after donor nephrectomy. Among the 1,000 participants from the web-based survey, 83.8% answered they fully understood living donor kidney transplantation, 81.1% knew about them, and 51.1% were willing to donate. Various complications after nephrectomy and deterioration in health after donation were the most significant reasons for those reluctant to donate. Most agreed that the government should provide social and economic support to living kidney donors, especially after exposure to the description of donor nephrectomy. Financial support, including surgery and regular medical check-up costs, was the most preferred government support. The Korean general population seemed aware of the value and safety of kidney donation, although only half of them were willing to donate due to concerns about possible complications. Most participants agreed on social and economic support for living kidney donors, especially surgery-related costs.

Mendelian randomization reveals causal effects of kidney function on various biochemical parameters

The kidney is a vital organ with diverse biological effects and the burden of kidney function impairment is increasing in modern medicine. As the effects from kidney function on diverse biochemical parameters are yet fully understood, additional investigation to reveal the causal effects is warranted. Here we show the causal estimates from kidney function parameter, estimated glomerular filtration rate (eGFR), on 60 biochemical parameters by performing two-sample Mendelian randomization (MR) study in 337,138 white British UK Biobank participants. A higher genetically predicted eGFR was significantly associated with higher lymphocyte percentage, HDL cholesterol, and alanine aminotransferase. The causal estimates indicated that a higher genetically predicted eGFR was associated with lower urea, urate, insulin growth factor-1, and triglycerides levels. The parameters with significant but non-linear causal estimates were hemoglobin concentration, calcium, vitamin D, and urine creatinine values, identified by non-linear MR. Healthcare providers should understand that changes in eGFR may affect the identified biochemical parameters in diverse patterns. Future study is warranted to expand the knowledge of the mechanisms and clinical implications of the causal effects of eGFR on various biochemical parameters.

System of integrating biosignals during hemodialysis: the CONTINUAL (Continuous mOnitoriNg viTal sIgN dUring hemodiALysis registry

Background

Appropriate monitoring of intradialytic biosignals is essential to minimize adverse outcomes because intradialytic hypotension and arrhythmia are associated with cardiovascular risk in hemodialysis patients. However, a continuous monitoring system for intradialytic biosignals has not yet been developed.

Methods

This study investigated a cloud system that hosted a prospective, open-source registry to monitor and collect intradialytic biosignals, which was named the CONTINUAL (Continuous mOnitoriNg viTal sIgN dUring hemodiALysis) registry. This registry was based on real-time multimodal data acquisition, such as blood pressure, heart rate, electrocardiogram, and photoplethysmogram results.

Results

We analyzed session information from this system for the initial 8 months, including data for some cases with hemodynamic complications such as intradialytic hypotension and arrhythmia.

Conclusion

This biosignal registry provides valuable data that can be applied to conduct epidemiological surveys on hemodynamic complications during hemodialysis and develop artificial intelligence models that predict biosignal changes which can improve patient outcomes.

Clinical Significances of Anti-Collagen Type I and Type III Antibodies in Antibody-Mediated Rejection

It is important to determine the clinical significance of non-human leukocyte antigen (HLA) antibodies and their association with antibody-mediated rejection (ABMR) of kidney allografts. We collected post-transplant sera from 68 ABMR patients, 67 T-cell mediated rejection (TCMR) patients, and 83 control subjects without rejection, and determined the titers of 39 non-HLA antibodies including antibodies for angiotensin II receptor type I and MICA. We compared all these non-HLA antibody titers among the study groups. Then, we investigated their association with the risk of death-censored graft failure in ABMR cases. Among the antibodies evaluated, anti-collagen type I (p = 0.001) and type III (p < 0.001) antibody titers were significantly higher in ABMR cases than in both TCMR cases and no-rejection controls. Both anti-collagen type I [per 1 standard deviation (SD), adjusted odds ratio (OR), 11.72 (2.73-76.30)] and type III [per 1 SD, adjusted OR, 6.22 (1.91-31.75)] antibodies were significantly associated with the presence of ABMR. Among ABMR cases, a higher level of anti-collagen type I [per 1 SD, adjusted hazard ratio (HR), 1.90 (1.32-2.75)] or type III per 1 SD, [adjusted HR, 1.57 (1.15-2.16)] antibody was associated with a higher risk of death-censored graft failure. In conclusion, post-transplant anti-collagen type I and type III antibodies may be novel non-HLA antibodies related to ABMR of kidney allografts.

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.

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.

Causal effects from non-alcoholic fatty liver disease on kidney function: A Mendelian randomization study

BACKGROUND AND AIMS

An observational association between nonalcoholic fatty liver disease (NAFLD) and kidney function impairment has been reported. We aimed to investigate the causal effects from NAFLD on estimated glomerular filtration rate (eGFR) by a Mendelian randomization (MR) study.

METHODS

We first performed single-variant MR with rs738409 as a genetic instrument for NAFLD. Another genetic instrument was developed from a genome-wide association study for biopsy-confirmed NAFLD among individuals of European ancestry (1483 cases and 17 781 controls). The eGFR outcome was assessed in individuals of white British ancestry from the UK Biobank (N = 321 405). The associations were reassessed in the negative control subgroup (body mass index < 30 kg/m² , absence of central obesity, and serum alanine aminotransferase level ≤ 20 IU/mL) with a low probability of developing NAFLD. As a replication analysis, a summary-level MR was performed with the European ancestry CKDGen dataset (N = 567 460).

RESULTS

In the UK Biobank, a genetic predisposition for NAFLD, determined either by the single SNP rs738409 or by the group of variants, was significantly associated with a reduced eGFR even with adjustment for metabolic disorders. Although the associations were not significant in the negative control subgroup with a low probability of developing NAFLD, they were significant in the subgroup with a remaining risk of NAFLD, suggesting the absence of a horizontal pleiotropic pathway. The summary-level MR from the CKDGen dataset supported the causal effects of NAFLD on reduced eGFR.

CONCLUSIONS

This MR analysis supports the causal reduction in kidney function by NAFLD.

Association between visit-to-visit blood pressure variability and risks of dementia in CKD patients: a nationwide observational cohort study

Background

The association between visit-to-visit blood pressure (BP) variability and dementia risk in chronic kidney disease (CKD) patients has rarely been studied.

Methods

In this retrospective observational study, individuals who received three or more general health screenings were identified in the nationwide database of Korea. Those with persistent non-dialysis-dependent CKD [estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m² or dipstick albuminuria ≥1+] were included. The study exposure was systolic or diastolic BP variability, calculated as the variation independent of the mean and categorized into quartiles (Q4: the highest quartile; Q1: the lowest quartile). The risks of all-cause dementia, including Alzheimer's disease and vascular dementia, were analyzed by Cox regression adjusted for various clinical characteristics, including baseline BP and eGFR values.

Results

We included 103 139 CKD patients and identified 7574 (7%) dementia events, including 5911 (6%) Alzheimer's disease cases, 886 (1%) vascular dementia events and 777 (1%) cases categorized as other types of dementia. Higher systolic BP variability was significantly associated with higher risks of all-cause dementia {[Q4 versus Q1], hazard ratio [HR] 1.173 [95% confidence interval (CI) 1.102-1.249], P for trend < .001}. The results were also significant for the risk of Alzheimer's disease [HR 1.162 (95% CI 1.083-1.248), P < .001] and vascular dementia [HR 1.282 (95% CI 1.064-1.545), P = .039]. The results were similar when diastolic BP variability was the exposure, as high diastolic BP variability was significantly associated with higher risks of all-cause dementia [HR 1.191 (95% CI 1.117,1.270), P < .001].

Conclusions

Higher visit-to-visit BP variability is significantly associated with a higher risk of dementia in CKD patients.

Relation of Poor Handgrip Strength or Slow Walking Pace to Risk of Myocardial Infarction and Fatality

We aimed to investigate a causal effect of functional sarcopenia status, including poor handgrip strength and slow walking pace, on cardiovascular diseases. This study was an observational cohort study including observational analysis and Mendelian randomization. We studied the UK Biobank prospective cohort (n = 324,486) for observational analysis with poor handgrip strength or self-reported slow walking pace as the exposures, investigating risk of myocardial infarction or mortality. Genetic instruments for the exposures were developed in 337,138 individuals of white British ancestries, and coronary artery disease outcome (60,801 cases/123,504 controls) from the independent CARDIoGRAMplustC4D cohort was studied by two-sample Mendelian randomization. The findings were replicated by one-sample analysis by polygenic risk score analysis within the UK Biobank. Both slow walking pace and poor handgrip strength were significantly associated with higher risks of incident myocardial infarction and mortality, particularly from cardiovascular deaths, in the observational investigation. Genetically predicted poor handgrip strength (odds ratio: 1.128 [1.041 to 1.222]) and slow walking pace (odds ratio: 1.171 [1.022 to 1.342]) showed causal effects on the coronary artery disease risks in the independent cohort. The results were again identified by the one-sample Mendelian randomization, as the higher polygenic risk score for poor handgrip strength and slow walking pace was associated with a higher risk of mortality. In conclusion, this study supports the causal effects of slow walking pace and poor handgrip strength on the risks of cardiovascular disease and mortality. The functional sarcopenia status are targetable causative factors for interventions aiming to reduce risks of cardiovascular disease or mortality.

Quantitative magnetic resonance imaging of chronic kidney disease: an experimental in vivo study using rat chronic kidney disease models

BACKGROUND

Recent advances in magnetic resonance imaging (MRI) may allow it to be an alternative emerging tool for the non-invasive evaluation of renal parenchymal disease.

PURPOSE

To validate the usefulness of quantitative multiparametric MRI protocols and suggest the suitable quantitative MR sequence protocol to evaluate parenchymal fibrosis using an animal model of chronic kidney disease (CKD) by long-term adenine intake.

MATERIAL AND METHODS

In this prospective animal study, 16 male Wistar rats were analyzed and categorized into three groups. Rats in the CKD groups underwent 0.25% adenine administration for three or six weeks. Quantitative MRI protocols, including diffusion-weighted imaging (DWI), T1ρ (T1 rho), and T2* mapping were performed using a 9.4-T animal MR scanner. A semi-quantitative histopathologic analysis for renal fibrosis was conducted. Quantitative MR values measured from anatomic regions of kidneys underwent intergroup comparative analyses.

RESULTS

The apparent diffusion coefficient (ADC) and T1 (T1 rho) values were significantly increased in all CKD groups. Values measured from the cortex and outer medulla showed significant intergroup differences. Total ADC values tended to increase according to periods, and T1ρ values increased in three weeks and decreased in six weeks.

CONCLUSION

Quantitative MRI protocols could be a non-invasive assessment modality in the diagnosis and evaluation of CKD. Particularly, T1ρ may be a suitable MR sequence to quantitatively assess renal parenchymal fibrosis.

Causal effects of atrial fibrillation on brain white and gray matter volume: a Mendelian randomization study

BACKGROUND

Atrial fibrillation (AF) and brain volume loss are prevalent in older individuals. We aimed to assess the causal effect of atrial fibrillation on brain volume phenotypes by Mendelian randomization (MR) analysis.

METHODS

The genetic instrument for AF was constructed from a previous genome-wide association study (GWAS) meta-analysis (15,993 AF patients and 113,719 controls of European ancestry). The outcome summary statistics for head-size-normalized white or gray matter volume measured by magnetic resonance imaging were provided by a previous GWAS of 33,224 white British participants in the UK Biobank. Two-sample MR by the inverse variance-weighted method was performed, supported by pleiotropy-robust MR sensitivity analysis. The causal estimates for the effect of AF on ischemic stroke were also investigated in a dataset that included the findings from the MEGASTROKE study (34,217 stroke patients and 406,111 controls of European ancestry). The direct effects of AF on brain volume phenotypes adjusted for the mediating effect of ischemic stroke were studied by multivariable MR.

RESULTS

A higher genetic predisposition for AF was significantly associated with lower grey matter volume [beta -0.040, standard error (SE) 0.017, P=0.017], supported by pleiotropy-robust MR sensitivity analysis. Significant causal estimates were identified for the effect of AF on ischemic stroke (beta 0.188, SE 0.026, P=1.03E-12). The total effect of AF on lower brain grey matter volume was attenuated by adjusting for the effect of ischemic stroke (direct effects, beta -0.022, SE 0.033, P=0.528), suggesting that ischemic stroke is a mediator of the identified causal pathway. The causal estimates were nonsignificant for effects on brain white matter volume as an outcome.

CONCLUSIONS

This study identified that genetic predisposition for AF is significantly associated with lower gray matter volume but not white matter volume. The results indicated that the identified total effect of AF on gray matter volume may be mediated by ischemic stroke.

Kidney VISTA prevents IFNγ-IL-9 axis-mediated tubulointerstitial fibrosis after acute glomerular injury

Severe glomerular injury ultimately leads to tubulointerstitial fibrosis that determines patient outcome, but the immunological molecules connecting these processes remain undetermined. The present study addressed whether V-domain Ig suppressor of T cell activation (VISTA), constitutively expressed in kidney macrophages, plays a protective role in tubulointerstitial fibrotic transformation after acute antibody-mediated glomerulonephritis. After acute glomerular injury using nephrotoxic serum, tubules in the VISTA-deficient (Vsir–/–) kidney suffered more damage than those in WT kidneys. When interstitial immune cells were examined, the contact frequency of macrophages with infiltrated T cells increased and the immunometabolic features of T cells changed to showing high oxidative phosphorylation and fatty acid metabolism and overproduction of IFN-γ. The Vsir–/– parenchymal tissue cells responded to this altered milieu of interstitial immune cells as more IL-9 was produced, which augmented tubulointerstitial fibrosis. Blocking antibodies against IFN-γ and IL-9 protected the above pathological process in VISTA-depleted conditions. In human samples with acute glomerular injury (e.g., antineutrophil cytoplasmic autoantibody vasculitis), high VISTA expression in tubulointerstitial immune cells was associated with low tubulointerstitial fibrosis and good prognosis. Therefore, VISTA is a sentinel protein expressed in kidney macrophages that prevents tubulointerstitial fibrosis via the IFN-γ/IL-9 axis after acute antibody-mediated glomerular injury.

Correction: Use of Deep Learning to Predict Acute Kidney Injury After Intravenous Contrast Media Administration: Prediction Model Development Study

[This corrects the article DOI: 10.2196/27177.].

Risk of active tuberculosis infection in kidney transplantation recipients: A matched comparative nationwide cohort study

Large-scale evidence comparing the risk of Mycobacterium tuberculosis (TB) between kidney transplant (KT) recipients and dialysis patients is warranted. This is a nationwide retrospective cohort study based on the claims database of South Korea where a moderate prevalence of TB is reported. We included incident KT recipients from 2011 to 2015 and compared their active TB risks with 1:1 matched dialysis and general population control groups, respectively. The risk of incident active TB was assessed by multivariable Cox regression. Associations between active TB and posttransplant death or death-censored graft failure were investigated. The number of matched subjects included in each of the study groups was 7462. The KT group showed a significantly higher risk of active TB than the general population group (hazard ratio [HR] 3.39 [1.88-6.10]), whereas it showed a similar risk to that of the dialysis group (HR 0.98 [0.73-1.31]). In KT patients, active TB was a significant risk factor for both death (HR 2.33 [1.24-4.39]) and death-censored graft failure (HR 2.26 [1.39-3.67]). Although KT recipients may not have to burden the additional risk of active TB when compared with dialysis patients in recent medicine, active TB should not be overlooked as it is associated with a worse prognosis in posttransplant patients.

Hyperchloremia is associated with poor renal outcome after coronary artery bypass grafting

Background

Hyperchloremia is associated with the risks of several morbidities and mortality. However, its relationship with acute kidney injury (AKI) and end-stage renal disease (ESRD) in patients undergoing coronary artery bypass grafting (CABG) remains unresolved.

Methods

A total of 2977 patients undergoing CABG between 2003 and 2015 were retrospectively reviewed from two tertiary hospitals. Patients were categorized by serum chloride levels into normochloremia (95–105 mmol/L), mild hyperchloremia (106–110 mmol/L), and severe hyperchloremia (> 110 mmol/L). The odds ratios (ORs) for AKI and hazard ratios (HRs) for ESRD were calculated after adjustment for multiple covariates. The death-adjusted risk of ESRD was additionally evaluated.

Results

Postoperative AKI occurred in 798 patients (26.5%). The hyperchloremia group had a higher risk of AKI than the normochloremia group, wherein the risk was incremental depending on the severity of hyperchloremia, as follows: ORs were 1.26 (1.06–1.51) and 1.95 (1.52–2.51) in the mild and severe hyperchloremia groups, respectively. During a median period of 7 years (maximum 15 years), 70 patients (2.3%) had ESRD. The severe hyperchloremia group was at an elevated risk of ESRD compared with the normochloremia group, with an HR of 2.43 (1.28–4.63). Even after adjusting for the competing risk of death, hyperchloremia was associated with the risk of ESRD.

Conclusions

Preoperative hyperchloremia is associated with poor renal outcomes such as AKI and ESRD after CABG. Accordingly, serum chloride should be monitored in patients undergoing CABG.

Use of Deep Learning to Predict Acute Kidney Injury After Intravenous Contrast Media Administration: Prediction Model Development Study

Background

Precise prediction of contrast media–induced acute kidney injury (CIAKI) is an important issue because of its relationship with poor outcomes.

Objective

Herein, we examined whether a deep learning algorithm could predict the risk of intravenous CIAKI better than other machine learning and logistic regression models in patients undergoing computed tomography (CT).

Methods

A total of 14,185 patients who were administered intravenous contrast media for CT at the preventive and monitoring facility in Seoul National University Hospital were reviewed. CIAKI was defined as an increase in serum creatinine of ≥0.3 mg/dL within 2 days or ≥50% within 7 days. Using both time-varying and time-invariant features, machine learning models, such as the recurrent neural network (RNN), light gradient boosting machine (LGM), extreme gradient boosting machine (XGB), random forest (RF), decision tree (DT), support vector machine (SVM), κ-nearest neighbors, and logistic regression, were developed using a training set, and their performance was compared using the area under the receiver operating characteristic curve (AUROC) in a test set.

Results

CIAKI developed in 261 cases (1.8%). The RNN model had the highest AUROC of 0.755 (0.708-0.802) for predicting CIAKI, which was superior to that obtained from other machine learning models. Although CIAKI was defined as an increase in serum creatinine of ≥0.5 mg/dL or ≥25% within 3 days, the highest performance was achieved in the RNN model with an AUROC of 0.716 (95% confidence interval [CI] 0.664-0.768). In feature ranking analysis, the albumin level was the most highly contributing factor to RNN performance, followed by time-varying kidney function.

Conclusions

Application of a deep learning algorithm improves the predictability of intravenous CIAKI after CT, representing a basis for future clinical alarming and preventive systems.

The Prognostic Significance of Body Mass Index and Metabolic Parameter Variabilities in Predialysis CKD: A Nationwide Observational Cohort Study

BACKGROUND

The association between variabilities in body mass index (BMI) or metabolic parameters and prognosis of patients with CKD has rarely been studied.

METHODS

In this retrospective observational study on the basis of South Korea's national health screening database, we identified individuals who received ≥3 health screenings, including those with persistent predialysis CKD (eGFR <60 ml/min per 1.73 m² or dipstick albuminuria ≥1). The study exposure was variability in BMI or metabolic parameters until baseline assessment, calculated as the variation independent of the mean and stratified into quartiles (with Q4 the highest quartile and Q1 the lowest). We used Cox regression adjusted for various clinical characteristics to analyze risks of all-cause mortality and incident myocardial infarction, stroke, and KRT.

RESULTS

The study included 84,636 patients with predialysis CKD. Comparing Q4 versus Q1, higher BMI variability was significantly associated with higher risks of all-cause mortality (hazard ratio [HR], 1.66; 95% confidence interval [95% CI], 1.53 to 1.81), P [for trend] <0.001), KRT (HR, 1.20; 95% CI, 1.09 to 1.33; P<0.001), myocardial infarction (HR, 1.19; 95% CI, 1.05 to 1.36, P=0.003), and stroke (HR, 1.19; 95% CI, 1.07 to 1.33, P=0.01). The results were similar in the subgroups divided according to positive or negative trends in BMI during the exposure assessment period. Variabilities in certain metabolic syndrome components (e.g., fasting blood glucose) also were significantly associated with prognosis of patients with predialysis CKD. Those with a higher number of metabolic syndrome components with high variability had a worse prognosis.

CONCLUSIONS

Higher variabilities in BMI and certain metabolic syndrome components are significantly associated with a worse prognosis in patients with predialysis CKD.

Atrial fibrillation and kidney function: a bidirectional Mendelian randomization study

AIMS

The aim of this study was to investigate the causal effects between atrial fibrillation (AF) and kidney function.

METHODS AND RESULTS

We performed a bidirectional summary-level Mendelian randomization (MR) analysis implementing the results from a large-scale genome-wide association study for estimated glomerular filtration rate (eGFR) by the CKDGen (N = 765 348) and AF (N = 588 190) to identify genetic instruments. The inverse variance weighted method was the main MR method used. For replication, an allele score-based MR was performed by individual-level data within a UK Biobank cohort of white British ancestry individuals (N = 337 138). A genetic predisposition to AF was significantly associated with decreased eGFR [for log-eGFR, beta -0.003 (standard error, 0.0005), P < 0.001] and increased risk of chronic kidney disease [beta 0.059 (0.0126), P < 0.001]. The significance remained in MR sensitivity analyses and the causal estimates were consistent when we limited the analysis to individuals of European ancestry. Genetically predicted eGFR did not show a significant association with the risk of AF [beta -0.366 (0.275), P = 0.183]. The results were similar in allele score-based MR, as allele score for AF was significantly associated with reduced eGFR [for continuous eGFR, beta -0.079 (0.021), P < 0.001], but allele score for eGFR did not show a significant association with risk of AF [beta -0.005 (0.008), P = 0.530].

CONCLUSIONS

Our study supports that AF is a causal risk factor for kidney function impairment. However, an effect of kidney function on AF was not identified in this study.

Machine learning model to predict hypotension after starting continuous renal replacement therapy

Hypotension after starting continuous renal replacement therapy (CRRT) is associated with worse outcomes compared with normotension, but it is difficult to predict because several factors have interactive and complex effects on the risk. The present study applied machine learning algorithms to develop models to predict hypotension after initiating CRRT. Among 2349 adult patients who started CRRT due to acute kidney injury, 70% and 30% were randomly assigned into the training and testing sets, respectively. Hypotension was defined as a reduction in mean arterial pressure (MAP) ≥ 20 mmHg from the initial value within 6 h. The area under the receiver operating characteristic curves (AUROCs) in machine learning models, such as support vector machine (SVM), deep neural network (DNN), light gradient boosting machine (LGBM), and extreme gradient boosting machine (XGB) were compared with those in disease-severity scores such as the Sequential Organ Failure Assessment and Acute Physiology and Chronic Health Evaluation II. The XGB model showed the highest AUROC (0.828 [0.796-0.861]), and the DNN and LGBM models followed with AUROCs of 0.822 (0.789-0.856) and 0.813 (0.780-0.847), respectively; all machine learning AUROC values were higher than those obtained from disease-severity scores (AUROCs < 0.6). Although other definitions of hypotension were used such as a reduction of MAP ≥ 30 mmHg or a reduction occurring within 1 h, the AUROCs of machine learning models were higher than those of disease-severity scores. Machine learning models successfully predict hypotension after starting CRRT and can serve as the basis of systems to predict hypotension before starting CRRT.