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.

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.

Glomerular crescents are associated with the risk of type 2 diabetic kidney disease progression: a retrospective cohort study.

BACKGROUND: Diabetic kidney disease (DKD) stands as the predominant cause of chronic kidney disease and end-stage kidney disease. Its diverse range of manifestations complicates the treatment approach for patients. Although kidney biopsy is considered the gold standard for diagnosis, it lacks precision in predicting the progression of kidney dysfunction. Herein, we addressed whether the presence of glomerular crescents is linked to the outcomes in patients with biopsy-confirmed type 2 DKD. METHODS: We performed a retrospective evaluation, involving 327 patients diagnosed with biopsy-confirmed DKD in the context of type 2 diabetes, excluding cases with other glomerular diseases, from nine tertiary hospitals. Hazard ratios (HRs) were calculated using a Cox regression model to assess the risk of kidney disease progression, defined as either ≥ 50% decrease in estimated glomerular filtration rates or the development of end-stage kidney disease, based on the presence of glomerular crescents. RESULTS: Out of the 327 patients selected, ten patients had glomerular crescents observed in their biopsied tissues. Over the follow-up period (median of 19 months, with a maximum of 18 years), the crescent group exhibited a higher risk of kidney disease progression than the no crescent group, with an adjusted HR of 2.82 (1.32-6.06) (P = 0.008). The presence of heavy proteinuria was associated with an increased risk of developing glomerular crescents. CONCLUSION: The presence of glomerular crescents is indeed linked to the progression of type 2 DKD. Therefore, it is important to determine whether there is an additional immune-mediated glomerulonephritis requiring immunomodulation, and it may be prudent to monitor the histology and repeat a biopsy.

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.

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.

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.

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.

Causal effects of physical activity or sedentary behaviors on kidney function: an integrated population-scale observational analysis and Mendelian randomization study.

BACKGROUND: An investigation into the causality of the effects of physical activity and specific sedentary activities on kidney function in the general population is warranted. METHODS: In this observational cohort study, first, the clinical associations of the prevalence of stages 3-5 chronic kidney disease (CKD) and the estimated glomerular filtration rate (eGFR) with physical activity, determined by self-report or objective wrist-band accelerometer results, and sedentary activities (watching television, using a computer and driving) were investigated in 329 758 UK Biobank participants. To assess causality, a two-sample Mendelian randomization (MR) analysis was performed to investigate the associations of a genetic predisposition to physical activity and a sedentary lifestyle with the risk of kidney function impairment in an independent CKDGen genome-wide association study (N = 567 460). The findings were replicated with the 321 024 UK White British Biobank participants in the allele-score-based one-sample MR. RESULTS: A higher degree of self-reported or accelerometer-determined moderate-to-vigorous physical activity was associated with a higher eGFR, while a longer time spent watching television was significantly associated with a lower eGFR and a higher prevalence of CKD. The two-sample MR demonstrated that the genetic predisposition to a higher degree of physical activity was associated with a lower risk of CKD and a higher eGFR, while the genetically predicted television watching duration was associated with a higher risk of CKD and a lower eGFR. The other sedentary behaviors yielded inconsistent results. The findings were similarly replicated in the one-sample MR. CONCLUSION: Physical activity and television watching causally affect kidney function in the general population.

Longitudinal trajectory of acidosis and mortality in acute kidney injury requiring continuous renal replacement therapy.

BACKGROUND: Acidosis frequently occurs in severe acute kidney injury (AKI), and continuous renal replacement therapy (CRRT) can control this pathologic condition. Nevertheless, acidosis may be aggravated; thus, monitoring is essential after starting CRRT. Herein, we addressed the longitudinal trajectory of acidosis on CRRT and its relationship with worse outcomes. METHODS: The latent growth mixture model was applied to classify the trajectories of pH during the first 24 hours and those of C-reactive protein (CRP) after 24 hours on CRRT due to AKI (n = 1815). Cox proportional hazard models were used to calculate hazard ratios of all-cause mortality after adjusting multiple variables or matching their propensity scores. RESULTS: The patients could be classified into 5 clusters, including the normally maintained groups (1st cluster, pH = 7.4; and 2nd cluster, pH = 7.3), recovering group (3rd cluster with pH values from 7.2 to 7.3), aggravating group (4th cluster with pH values from 7.3 to 7.2), and ill-being group (5th cluster, pH < 7.2). The pH clusters had different trends of C-reactive protein (CRP) after 24 hours; the 1st and 2nd pH clusters had lower levels, but the 3rd to 5th pH clusters had an increasing trend of CRP. The 1st pH cluster had the best survival rates, and the 3rd to 5th pH clusters had the worst survival rates. This survival difference was significant despite adjusting for other variables or matching propensity scores. CONCLUSIONS: Initial trajectories of acidosis determine subsequent worse outcomes, such as mortality and inflammation, in patients undergoing CRRT due to AKI.

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.

Causal Effects of Positive Affect, Life Satisfaction, Depressive Symptoms, and Neuroticism on Kidney Function: A Mendelian Randomization Study.

BACKGROUND: Further investigation of the causal effects of psychologic wellbeing on kidney function is warranted. METHODS: In this Mendelian randomization (MR) study, genetic instruments for positive affect, life satisfaction, depressive symptoms, and neuroticism were introduced from a previous genome-wide association study meta-analysis of European individuals. Summary-level MR was performed using the CKDGen data of European ancestry (n=567,460), and additional allele score-based MR was performed in the individual-level data of White British UK Biobank participants (n=321,024). RESULTS: In summary-level MR with the CKDGen data, depressive symptoms were a significant causative factor for kidney function impairment (CKD OR, 1.45; 95% confidence interval, 1.07 to 1.96; eGFR change [%] beta -2.18; 95% confidence interval, -3.61 to -0.72) and pleiotropy-robust sensitivity analysis results supported the causal estimates. A genetic predisposition for positive affect was significantly associated with better kidney function (CKD OR, 0.69; 95% confidence interval, 0.52 to 0.91), eGFR change [%] beta 1.50; 95% confidence interval, 0.09 to 2.93) and sensitivity MR analysis results supported the finding for CKD outcome, but was nonsignificant for eGFR. Life satisfaction and neuroticism exposures showed nonsignificant causal estimates. In the UK Biobank with covariate-adjusted allele score MR analysis, allele scores for positive affect and life satisfaction were causally associated with reduced risk of CKD and higher eGFR. In contrast, neuroticism allele score was associated with increased risk of CKD and lower eGFR, and depressive symptoms allele score was associated with lower eGFR, but showed nonsignificant association with CKD. CONCLUSIONS: Health care providers in the nephrology field should be aware of the causal linkage between psychologic wellbeing and kidney function.

Automated Computational Detection of Interstitial Fibrosis, Tubular Atrophy, and Glomerulosclerosis.

BACKGROUND: Interstitial fibrosis, tubular atrophy (IFTA), and glomerulosclerosis are indicators of irrecoverable kidney injury. Modern machine learning (ML) tools have enabled robust, automated identification of image structures that can be comparable with analysis by human experts. ML algorithms were developed and tested for the ability to replicate the detection and quantification of IFTA and glomerulosclerosis that renal pathologists perform. METHODS: A renal pathologist annotated renal biopsy specimens from 116 whole-slide images (WSIs) for IFTA and glomerulosclerosis. A total of 79 WSIs were used for training different configurations of a convolutional neural network (CNN), and 17 and 20 WSIs were used as internal and external testing cases, respectively. The best model was compared against the input of four renal pathologists on 20 new testing slides. Further, for 87 testing biopsy specimens, IFTA and glomerulosclerosis measurements made by pathologists and the CNN were correlated to patient outcome using classic statistical tools. RESULTS: The best average performance across all image classes came from a DeepLab version 2 network trained at 40× magnification. IFTA and glomerulosclerosis percentages derived from this CNN achieved high levels of agreement with four renal pathologists. The pathologist- and CNN-based analyses of IFTA and glomerulosclerosis showed statistically significant and equivalent correlation with all patient-outcome variables. CONCLUSIONS: ML algorithms can be trained to replicate the IFTA and glomerulosclerosis assessment performed by renal pathologists. This suggests computational methods may be able to provide a standardized approach to evaluate the extent of chronic kidney injury in situations in which renal-pathologist time is restricted or unavailable.

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.

A Mendelian randomization study found causal linkage between telomere attrition and chronic kidney disease.

Chronic kidney disease (CKD) is highly prevalent in the elderly population. However, it is rarely investigated whether kidney function is causally linked to biological aging itself. In this Mendelian randomization study, genetic instruments for telomere attrition were applied to a CKDGen genome wide association study results for 41,395 cases of CKD among 480,698 individuals as summary-level Mendelian randomization. A replicative analysis was performed by polygenic score analysis using independent United Kingdom Biobank data for 8,118 cases of CKD among 321,024 white individuals of British ancestry. Reverse-direction Mendelian randomization analysis was performed utilizing genetic instruments for log-estimated glomerular filtration rate change with Z-standardized telomere length outcome data for 326,075 participants in the UK Biobank. Genetic predisposition toward telomere attrition (one Z score decrease in length) was found to be a causative factor for a higher CKD risk [Odds Ratio 1.20 (95% confidence interval 1.08‒1.33)], as supported by pleiotropy-robust Mendelian randomization sensitivity analyses implemented using the CKDGen data. Based on United Kingdom Biobank data, the polygenic score for telomere attrition was significantly associated with a higher risk of CKD [1.20 (1.04‒1.39)]. In reverse-direction Mendelian randomization, the genetically predicted kidney function decrease was significantly associated with a higher degree of telomere attrition [beta 0.039 (0.009‒0.069)]. Thus, our study supports the causal linkage between telomere attrition and kidney function impairment.

Kidney function and obstructive lung disease: a bidirectional Mendelian randomisation study.

BACKGROUND: Additional study is warranted to investigate the causal effects between kidney function and obstructive lung disease. METHODS: This study was a bidirectional two-sample Mendelian randomisation (MR) analysis. The Chronic Kidney Disease Genetics (CKDGen) genome-wide association study (GWAS) meta-analysis for estimated glomerular filtration rate (eGFR) including individuals of European ancestry (n=567 460) provided the genetic instrument for kidney function and outcome summary statistics. A GWAS for forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) including individuals of European ancestry from the UK Biobank (n=321 047) provided the genetic instrument for FEV1/FVC and outcome data. A polygenic score (PGS) analysis was performed to test the causal estimates from kidney function to binary obstructive lung disease outcomes, including COPD, asthma and FEV1/FVC <70%, and to perform nonlinear MR with individual-level UK Biobank data. RESULTS: The causal estimates by summary-level MR indicated that genetically predicted increased kidney function was significantly associated with increased FEV1/FVC z-scores (10% increase in eGFR; ß=0.055, 95% CI 0.024-0.086). The PGS for increased eGFR showed a significant association with a reduced risk of FEV1/FVC <70% (OR 0.93, 95% CI 0.87-0.99), COPD (OR 0.93, 95% CI 0.87-0.99) and late-onset (age ≥50 years) asthma (OR 0.93, 95% CI 0.88-0.99). The nonlinear MR demonstrated that the causal effect from eGFR to FEV1/FVC was apparent in eGFR ranges <60 mL·min-1·1.73 m-2. Conversely, genetically predicted FEV1/FVC showed nonsignificant causal estimates of eGFR change (ß=0.568%, 95% CI -0.458-1.605%). CONCLUSION: This study supports kidney function impairment as a causative factor for obstructive lung disease.

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.

Observational or Genetically Predicted Higher Vegetable Intake and Kidney Function Impairment: An Integrated Population-Scale Cross-Sectional Analysis and Mendelian Randomization Study.

BACKGROUND: Further exploration of the possible effects of vegetable intake on kidney function is warranted. OBJECTIVE: We aimed to study the causality of the association between vegetable intake and kidney function by implementing Mendelian randomization (MR) analysis. METHODS: This study comprised a cross-sectional dietary investigation using UK Biobank data and MR analysis. For the cross-sectional investigation, 432,732 participants aged 40-69 y from the UK Biobank cohort were included. Self-reported vegetable intake was the exposure, and the outcomes were the estimated glomerular filtration rate (eGFR) and chronic kidney disease (CKD). Next, we included 337,138 participants of white British ancestry in the UK Biobank, and a genome-wide association study (GWAS) was performed to generate a genetic instrument. For MR, we first performed polygenic score (PGS)-based 1-sample MR. In addition, 2-sample MR was performed with CKDGen GWAS for kidney function traits, and the inverse variance weighted method was the main MR method. RESULTS: Higher vegetable intake was cross-sectionally associated with a higher eGFR (per heaped tablespoon increase; ß: 0.154; 95% CI: 0.144, 0.165) and lower odds of CKD (OR: 0.975; 95% CI: 0.968, 0.982). A PGS for vegetable intake was significantly associated with a higher eGFR [per ordinal category increase (0, 1-3, 4-6, ≥7 tablespoons per day); ß: 4.435; 95% CI: 2.337, 6.533], but the association with CKD remained nonsignificant (OR: 0.468; 95% CI: 0.143, 1.535). In the 2-sample MR, the causal estimates indicated that a higher genetically predicted vegetable intake was associated with a higher eGFR (percent change; ß: 3.071; 95% CI: 0.602, 0.560) but nonsignificantly associated with the risk of CKD (OR: 0.560; 95% CI: 0.289, 1.083) in the European ancestry data from the CKDGen. CONCLUSIONS: This study suggests that higher vegetable intake may have a causal effect on higher eGFRs in the European population.

Renal outcomes in adult patients with horseshoe kidney.

BACKGROUND: Horseshoe kidney (HSK) is a congenital disorder that is usually asymptomatic, but that increases the risks of kidney stones and infectious disease. However, renal outcomes such as end-stage renal disease (ESRD) in patients with HSK remain unclear. METHODS: In total, 146 patients with HSK (age of ≥20 years) from two tertiary hospitals were included in this study. Control individuals who underwent medical check-ups were selected by matching for age, sex, serum creatinine level, hypertension and diabetes. The hazard ratios (HRs) for the risks of ESRD and all-cause mortality were calculated after adjustment for multiple variables. RESULTS: The proportions of HSK-related complications for obstruction, kidney stones, urinary tract infection and urogenital cancer were 26, 25, 19 and 4%, respectively. During the median follow-up period of 9 years (maximum 32 years), the incidence of ESRD was 2.6/10 000 person-years. The risk of ESRD in patients with HSK was higher than in control individuals [adjusted HR = 7.6; 95% confidence interval (CI) 1.14-50.47]. All-cause mortality did not differ between the two groups (adjusted HR = 0.6; 95% CI 0.08-4.29). CONCLUSIONS: Patients with HSK are at risk of ESRD, which may be attributable to the high prevalence of complications. Accordingly, these patients should be regarded as having chronic kidney disease and require regular monitoring of both kidney function and potential complications.

Cardiovascular risk of nonsteroidal anti-inflammatory drugs in dialysis patients: a nationwide population-based study.

BACKGROUND: Given the cardiovascular risk of nonsteroidal anti-inflammatory drugs (NSAIDs), it is essential to identify the relationship between NSAIDs and cardiovascular outcomes in dialysis patients who have elevated cardiovascular risk. METHODS: A case-crossover study was conducted to assess the association of NSAIDs with major adverse cardiac and cerebrovascular events (MACCEs) and mortality using the Korean Health Insurance dataset. The case period was defined as 1-30 days prior to the event date and the control periods were defined as 61-90 days and 91-120 days prior to the event date. RESULTS: There were 3433 and 8524 incident dialysis patients who experienced MACCEs and mortality, respectively, after exposure to NSAIDs within 120 days before each event. NSAIDs significantly increased the risk of MACCEs {adjusted odds ratio [aOR] 1.37 [95% confidence interval (CI) 1.26-1.50]} and mortality [aOR 1.29 (95% CI 1.22-1.36)]. Nonselective NSAIDs, but not selective cyclooxygenase-2 inhibitors, significantly increased the risk of MACCEs and mortality. However, the MACCE and mortality risk did not increase in a dose-dependent manner in the analysis according to the cumulative defined daily dosage of NSAIDs. The incidence of MACCEs in the case period tended to be more common in patients who had recent exposure to NSAIDs than in patients who did not have recent exposure to NSAIDs. CONCLUSIONS: Clinicians should be particularly cautious when prescribing NSAIDs to dialysis patients considering the associations of NSAIDs with cardiovascular outcomes and mortality, which might occur independent of the dose and duration of exposure.