A lifetime economic research of universal HLA-B*58:01 genotyping or febuxostat initiation therapy in Chinese gout patients with mild to moderate chronic kidney disease

OBJECTIVE

To evaluate Chinese long-term economic impact of universal human leukocyte antigen B (HLA-B)*58:01 genotyping-guided urate-lowering therapy or febuxostat initiation therapy for gout patients with mild to moderate chronic kidney disease (CKD) from perspective of healthcare system.

METHODS

A Markov model embedded in a decision tree was structured including four mutually exclusive health states (uncontrolled-on-therapy, controlled-on-therapy, uncontrolled-off-therapy, and death). Mainly based on Chinese real-world data, the incremental costs per quality-adjusted life years (QALYs) gained were evaluated from three groups (universal HLA-B*58:01 testing strategy, and no genotyping prior to allopurinol or febuxostat initiation therapy) at 25-year time horizon. All costs were adjusted to 2021 levels based on Chinese Consumer Price Index and were discounted by 5% annually. One-way and probability sensitivity analysis were performed.

RESULTS

Among these three groups, universal HLA-B*58:01 genotyping was the most cost-effective strategy in base-case analysis according to Chinese average willingness-to-pay threshold of $37 654.50 per QALY. The based incremental cost-effectiveness ratio was $31784.55 per QALY, associated with 0.046 additional QALYs and $1463.81 increment costs per patient at a 25-year time horizon compared with no genotyping prior to allopurinol initiation strategy. Sensitivity analysis showed 64.3% robustness of these results.

CONCLUSION

From Chinese perspective of healthcare system, HLA-B*58:01 genotyping strategy was cost-effective for gout patients with mild to moderate CKD in mainland China, especially in the most developed area, such as Beijing and Shanghai. Therefore, we suggest China's health authorities choose the genotyping strategy and make different recommendations according to the differences of local conditions.

Bayesian mixed model analysis uncovered 21 risk loci for chronic kidney disease in boxer dogs

Chronic kidney disease (CKD) affects 10% of the human population, with only a small fraction genetically defined. CKD is also common in dogs and has been diagnosed in nearly all breeds, but its genetic basis remains unclear. Here, we performed a Bayesian mixed model genome-wide association analysis for canine CKD in a boxer population of 117 canine cases and 137 controls, and identified 21 genetic regions associated with the disease. At the top markers from each CKD region, the cases carried an average of 20.2 risk alleles, significantly higher than controls (15.6 risk alleles). An ANOVA test showed that the 21 CKD regions together explained 57% of CKD phenotypic variation in the population. Based on whole genome sequencing data of 20 boxers, we identified 5,206 variants in LD with the top 50 BayesR markers. Following comparative analysis with human regulatory data, 17 putative regulatory variants were identified and tested with electrophoretic mobility shift assays. In total four variants, three intronic variants from the MAGI2 and GALNT18 genes, and one variant in an intergenic region on chr28, showed alternative binding ability for the risk and protective alleles in kidney cell lines. Many genes from the 21 CKD regions, RELN, MAGI2, FGFR2 and others, have been implicated in human kidney development or disease. The results from this study provide new information that may enlighten the etiology of CKD in both dogs and humans.

Chronic Kidney Disease: Combined Effects of Gene Polymorphisms of Tissue Inhibitors of Metalloproteinase 3, Total Urinary Arsenic, and Blood Lead Concentration

The tissue inhibitor of metalloproteinase 3 (TIMP3) is known to be an anti-fibrotic factor. Arsenic, lead, and cadmium exposure and selenium intake may affect TIMP3 expression. The downregulation of TIMP3 expression is related to kidney fibrosis. Genotypes of TIMP3 are related to hypertension and cardiovascular diseases. Therefore, this study explored whether TIMP3 polymorphism is associated with hypertension-related chronic kidney disease (CKD). In addition, the combined effects of TIMP3 polymorphism and total urinary arsenic, blood lead and cadmium, and plasma selenium concentrations on CKD, were investigated. This was a case-control study, with 213 CKD patients and 423 age- and sex-matched controls recruited. Polymerase chain reaction-restriction fragment length polymorphism was used to determine TIMP3 gene polymorphisms. The concentrations of urinary arsenic species, plasma selenium, and blood lead and cadmium were measured. The odds ratio (OR) of CKD in the TIMP3rs9609643 GA/AA genotype was higher than that of the GG genotype at high levels of total urinary arsenic and blood lead; the OR and 95% confidence interval (CI) were 0.57 (0.31-1.05) and 0.52 (0.30-0.93), respectively, after multivariate adjustment. High blood lead levels tended to interact with the TIMP3rs9609643 GG genotype to increase the OR of CKD, and gave the highest OR (95% CI) for CKD of 5.97 (2.60-13.67). Our study supports a possible role for the TIMP3rs9609643 risk genotype combined with high total urinary arsenic or with high blood lead concentration to increase the OR of CKD.

Causal Effects of Specific Gut Microbiota on Chronic Kidney Diseases and Renal Function-A Two-Sample Mendelian Randomization Study

BACKGROUND

Targeting the gut microbiota may become a new therapeutic to prevent and delay the progression of chronic kidney disease (CKD). Nonetheless, the causal relationship between specific intestinal flora and CKD is still unclear.

MATERIALS AND METHOD

To identify genetically predicted microbiota, we used summary data from genome-wide association studies on gut microbiota in 18340 participants from 24 cohorts. Furthermore, we genetically predicted the causal relationship between 211 gut microbiotas and six phenotypes (outcomes) (CKD, estimated glomerular filtration rate (eGFR), urine albumin to creatinine ratio (UACR), dialysis, rapid progress to CKD, and rapid decline of eGFR). Four Mendelian randomization (MR) methods, including inverse variance weighted (IVW), MR-Egger, weighted median, and weighted mode were used to investigate the casual relationship between gut microbiotas and various outcomes. The result of IVW was deemed as the primary result. Then, Cochrane's Q test, MR-Egger, and MR-PRESSO Global test were used to detect heterogeneity and pleiotropy. The leave-one method was used for testing the stability of MR results and Bonferroni-corrected was used to test the strength of the causal relationship between exposure and outcome.

RESULTS

Through the MR analysis of 211 microbiotas and six clinical phenotypes, a total of 36 intestinal microflora were found to be associated with various outcomes. Among them, Class Bacteroidia (=-0.005, 95% CI: -0.001 to -0.008, p = 0.002) has a strong causality with lower eGFR after the Bonferroni-corrected test, whereas phylum Actinobacteria (OR = 1.0009, 95%CI: 1.0003-1.0015, p = 0.0024) has a strong causal relationship with dialysis. The Cochrane's Q test reveals that there is no significant heterogeneity between various single nucleotide polymorphisms. In addition, no significant level of pleiotropy was found according to MR-Egger and MR-PRESSO Global tests.

CONCLUSIONS

Through the two-sample MR analysis, we identified the specific intestinal flora that has a causal relationship with the incidence and progression of CKD at the level of gene prediction, which may provide helpful biomarkers for early disease diagnosis and potential therapeutic targets for CKD.

Identification of Hub Genes Correlated with the Initiation and Development in Chronic Kidney Disease via Bioinformatics Analysis

INTRODUCTION

Chronic kidney disease (CKD) is a major public health issue worldwide, which is characterized by irreversible loss of nephron and renal function. However, the molecular mechanism of CKD remains underexplored.

METHODS

This study integrated three transcriptional profile datasets to investigate the molecular mechanism of CKD. The differentially expressed genes (DEGs) between Sham control (Con) and unilateral ureteral obstruction (UUO)-operated mice were analyzed by utilizing the limma package in R. The shared DEGs were analyzed by Gene Ontology and functional enrichment. Protein-protein interactions (PPIs) were constructed by utilizing the STRING database. Hub genes were analyzed by MCODE and Cytohubba. We further validated the gene expression by using the other dataset and mouse UUO model.

RESULTS

A total of 315 shared DEGs between Con and UUO samples were identified. Gene function and KEGG pathway enrichment revealed that DEGs were mainly enriched in inflammatory response, immune system process, and chemokine signaling pathway. Two modules were clustered based on PPI network analysis. Module 1 contained 13 genes related to macrophage activation, migration, and chemotaxis. Ten hub genes were identified by PPI network analysis. Subsequently, the expression levels of hub genes were validated with the other dataset. Finally, these four validated hub genes were further confirmed by our UUO mice. Three validated hub genes, Gng2, Pf4, and Ccl9, showed significant response to UUO.

CONCLUSION

Our study reveals the coordination of genes during UUO and provides a promising gene panel for CKD treatment. GNG2 and PF4 were identified as potential targets for developing CKD drugs.

Role of the Circadian Clock and Effect of Time-Restricted Feeding in Adenine-Induced Chronic Kidney Disease

Most physiological functions exhibit circadian rhythmicity that is partly regulated by the molecular circadian clock. Herein, we investigated the relationship between the circadian clock and chronic kidney disease (CKD). The role of the clock gene in adenine-induced CKD and the mechanisms of interaction were investigated in mice in which Bmal1, the master regulator of the clock gene, was knocked out, and Bmal1 knockout (KO) tubule cells. We also determined whether the renoprotective effect of time-restricted feeding (TRF), a dietary strategy to enhance circadian rhythm, is clock gene-dependent. The mice with CKD showed altered expression of the core clock genes with a loss of diurnal variations in renal functions and key tubular transporter gene expression. Bmal1 KO mice developed more severe fibrosis, and transcriptome profiling followed by gene ontology analysis suggested that genes associated with the cell cycle, inflammation, and fatty acid oxidation pathways were significantly affected in the mutant mice. Tubule-specific deletion of BMAL1 in HK-2 cells by CRISPR/Cas9 led to upregulation of p21 and tumor necrosis α and exacerbated epithelial-mesenchymal transition-related gene expression upon transforming growth factor β stimulation. Finally, TRF in the mice with CKD partially restored the disrupted oscillation of the kidney clock genes, accompanied by improved cell cycle arrest and inflammation, leading to decreased fibrosis. However, the renoprotective effect of TRF was abolished in Bmal1 KO mice, suggesting that TRF is partially dependent on the clock gene. Our data demonstrate that the molecular clock system plays an important role in CKD via cell cycle regulation and inflammation. Understanding the role of the circadian clock in kidney diseases can be a new research field for developing novel therapeutic targets.

RNA Seq and ceRNA Network Analysis of the Rat Model of Chronic Kidney Disease

BACKGROUND

Long non-coding RNAs (lncRNAs) containing microRNA (miRNA) response elements (MREs) can be used as competitive endogenous RNAs (ceRNAs) to regulate gene expression.

OBJECTIVE

The purpose of this study was to investigate the expression profile and role of mRNAs and lncRNAs in unilateral ureteral obstruction (UUO) model rats and to explore any associated competing endogenous (ceRNA) network.

METHODS

Using the UUO model, the obstructed kidney was collected on the 15th day after surgery. RNA Seq analysis was performed on renal tissues of four UUO rats and four sham rats. Four mRNAs and four lncRNAs of differentially expressed genes were randomly selected for real-time quantitative PCR (RT qPCR) analysis. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were analyzed, and bioinformatics was used to predict MREs. By screening for ceRNAs combined with target gene prediction, a related ceRNA network was constructed and verified by RT-qPCR.

RESULTS

We identified 649 up-regulated lncRNAs, 518 down-regulated lncRNAs, 924 downregulated mRNAs and 2029 up-regulated mRNAs. We identified 30 pathways with the highest enrichment in GO and KEGG. According to the RNA Seq results and the expression of Nr4a1, the network was constructed based on Nr4a1 and included two MREs and ten lncRNAs. Furthermore, lncNONRATT011668.2/miR-361-3p/Nr4a1 was identified and verified according to ceRNA sequencing and target gene prediction.

CONCLUSION

mRNAs and lncRNAs are differentially expressed in UUO model rats, which may be related to the pathogenesis of chronic kidney disease. The lncNONRATT011668.2/miR-361- 3p/Nr4a1 ceRNA network may be involved in the pathogenesis of chronic kidney disease.

Cardiac epigenetic changes in VEGF signaling genes associate with myocardial microvascular rarefaction in experimental chronic kidney disease

Chronic kidney disease (CKD) is common in patients with heart failure and often results in left ventricular diastolic dysfunction (LVDD). However, the mechanisms responsible for cardiac damage in CKD-LVDD remain to be elucidated. Epigenetic alterations may impose long-lasting effects on cellular transcription and function, but their exact role in CKD-LVDD is unknown. We investigate whether changes in cardiac site-specific DNA methylation profiles might be implicated in cardiac abnormalities in CKD-LVDD. CKD-LVDD and normal control pigs (n = 6 each) were studied for 14 wk. Renal and cardiac hemodynamics were quantified by multidetector CT and echocardiography. In randomly selected pigs (n = 3/group), cardiac site-specific 5-methylcytosine (5mC) immunoprecipitation (MeDIP)- and mRNA-sequencing (seq) were performed, followed by integrated (MeDiP-seq/mRNA-seq analysis), and confirmatory ex vivo studies. MeDIP-seq analysis revealed 261 genes with higher (fold change > 1.4; P < 0.05) and 162 genes with lower (fold change < 0.7; P < 0.05) 5mC levels in CKD-LVDD versus normal pigs, which were primarily implicated in vascular endothelial growth factor (VEGF)-related signaling and angiogenesis. Integrated MeDiP-seq/mRNA-seq analysis identified a select group of VEGF-related genes in which 5mC levels were higher, but mRNA expression was lower in CKD-LVDD versus normal pigs. Cardiac VEGF signaling gene and VEGF protein expression were blunted in CKD-LVDD compared with controls and were associated with decreased subendocardial microvascular density. Cardiac epigenetic changes in VEGF-related genes are associated with impaired angiogenesis and cardiac microvascular rarefaction in swine CKD-LVDD. These observations may assist in developing novel therapies to ameliorate cardiac damage in CKD-LVDD.NEW & NOTEWORTHY Chronic kidney disease (CKD) often leads to left ventricular diastolic dysfunction (LVDD) and heart failure. Using a novel translational swine model of CKD-LVDD, we characterize the cardiac epigenetic landscape, identifying site-specific 5-methylcytosine changes in vascular endothelial growth factor (VEGF)-related genes associated with impaired angiogenesis and cardiac microvascular rarefaction. These observations shed light on the mechanisms of cardiac microvascular damage in CKD-LVDD and may assist in developing novel therapies for these patients.

Causal associations between polyunsaturated fatty acids and kidney function: A bidirectional Mendelian randomization study

BACKGROUND

PUFAs were suggested to be beneficial for kidney function in observational studies. However, whether these associations are causal remains unclear.

OBJECTIVES

This study explores the causality between PUFAs and chronic kidney disease (CKD) or estimated glomerular filtration rate (eGFR) using bidirectional 2-sample Mendelian randomization (MR).

METHODS

Single nucleotide polymorphisms associated with PUFAs and kidney function were obtained from the largest and most recent genome-wide association studies with sample sizes of 13,544, 13,506, 13,499, 13,527, and 13,549 for omega-3 fatty acids, omega-6 fatty acids, DHA, LA, and other PUFAs than 18:2 (otPUFA), and 480,698 and 1,201,909 for CKD and eGFR, respectively. MR inverse-variance weighted (IVW) and pleiotropy residual sum and outlier test (MR-PRESSO) were used for data analysis, supplemented with a weighted median estimator, MR-Egger regression, and multivariable MR, giving β or OR and their 95% CIs.

RESULTS

There was suggestive evidence that higher omega-6 fatty acids were associated with increased eGFR using MR-PRESSO [β: 0.005 log(mL/min/1.73 m²) per SD increase in omega-6 fatty acids; 95% CI: 0.002, 0.008; P = 0.008]. Higher LA level was also associated with higher eGFR [β: 0.005 log(mL/min/1.73 m²) per SD increase in LA; 95% CI: 0.003, 0.007; P = 0.0007] using MR-PRESSO. Neither association of the other PUFAs, i.e., omega-3 fatty acids, DHA, and otPUFA, with CKD or eGFR nor the association of CKD and eGFR with PUFAs was found. Similar results were found in sensitivity analyses.

CONCLUSIONS

Our results suggest that higher omega-6 fatty acids and LA may increase eGFR levels. Although the estimated effects were relatively small, the results provide public health and research relevance, indicating the need for further longitudinal cohorts or randomized controlled trials on omega-6 fatty acids in improving kidney function.

Urinary MicroRNA Analysis Indicates an Epigenetic Regulation of Chronic Kidney Disease of Unknown Etiology in Sri Lanka

BACKGROUND

Chronic kidney disease of unknown etiology (CKDu) is reported among male paddy farmers in the dry zone of Sri Lanka. The exact cause of this disease remains undetermined. Genetic susceptibility is identified as a major risk factor for CKDu Objectives: In this study, small urinary RNAs were characterized in CKDu patients, healthy endemic and non-endemic controls. Differently expressed urinary miRNAs and their associated pathways were identified in the study population.

METHODS

Healthy and diseased male volunteers (n = 9) were recruited from Girandurukotte (endemic) and Mawanella (non-endemic) districts. Urinary small RNAs were purified and sequenced using Illumina MiSeqTM. The sequence trace files were assembled and analyzed. Differentially ex-pressed miRNAs among these three groups were identified and pathway analysis was conducted.

RESULTS

The urine samples contained 130,623 sequence reads identified as non-coding RNAs, PIWI-interacting RNAs (piRNA), and miRNAs. Approximately four percent of the total small RNA reads represented miRNA, and 29% represented piRNA. A total of 409 miRNA species were ex-pressed in urine. Interestingly, both diseased and endemic controls population showed significantly low expression of miRNA and piRNA. Regardless of the health status, the endemic population ex-pressed significantly low levels of miR-10a, miR-21, miR-148a, and miR-30a which have been linked with several environmental toxins Conclusion: Significant downregulation of miRNA and piRNA expression in both diseased and healthy endemic samples indicates an epigenetic regulation of CKDu involving genetic and environmental interaction. Further studies of specific miRNA species are required to develop a miRNA panel to identify individuals susceptible to CKDu.

Four missense genetic variants in CUBN are associated with higher levels of eGFR in non-diabetes but not in diabetes mellitus or its subtypes: A genetic association study in Europeans

AIM

Rare genetic variants in the CUBN gene encoding the main albumin-transporter in the proximal tubule of the kidneys have previously been associated with microalbuminuria and higher urine albumin levels, also in diabetes. Sequencing studies in isolated proteinuria suggest that these variants might not affect kidney function, despite proteinuria. However, the relation of these CUBN missense variants to the estimated glomerular filtration rate (eGFR) is largely unexplored. We hereby broadly examine the associations between four CUBN missense variants and eGFR_creatinine in Europeans with Type 1 (T1D) and Type 2 Diabetes (T2D). Furthermore, we sought to deepen our understanding of these variants in a range of single- and aggregate- variant analyses of other kidney-related traits in individuals with and without diabetes mellitus.

METHODS

We carried out a genetic association-based linear regression analysis between four CUBN missense variants (rs141640975, rs144360241, rs45551835, rs1801239) and eGFR_creatinine (ml/min/1.73 m², CKD-EPI_{creatinine(2012)}, natural log-transformed) in populations with T1D (n ~ 3,588) or T2D (n ~ 31,155) from multiple European studies and in individuals without diabetes from UK Biobank (UKBB, n ~ 370,061) with replication in deCODE (n = 127,090). Summary results of the diabetes-group were meta-analyzed using the fixed-effect inverse-variance method.

RESULTS

Albeit we did not observe associations between eGFR_creatinine and CUBN in the diabetes-group, we found significant positive associations between the minor alleles of all four variants and eGFR_creatinine in the UKBB individuals without diabetes with rs141640975 being the strongest (Effect=0.02, P_{eGFR_creatinine}=2.2 × 10^-9). We replicated the findings for rs141640975 in the Icelandic non-diabetes population (Effect=0.026, P_{eGFR_creatinine}=7.7 × 10^-4). For rs141640975, the eGFR_creatinine-association showed significant interaction with albuminuria levels (normo-, micro-, and macroalbuminuria; p = 0.03). An aggregated genetic risk score (GRS) was associated with higher urine albumin levels and eGFR_creatinine. The rs141640975 variant was also associated with higher levels of eGFR_{creatinine-cystatin C} (ml/min/1.73 m², CKD-EPI₂₀₂₁, natural log-transformed) and lower circulating cystatin C levels.

CONCLUSIONS

The positive associations between the four CUBN missense variants and eGFR in a large population without diabetes suggests a pleiotropic role of CUBN as a novel eGFR-locus in addition to it being a known albuminuria-locus. Additional associations with diverse renal function measures (lower cystatin C and higher eGFR_{creatinine-cystatin C} levels) and a CUBN-focused GRS further suggests an important role of CUBN in the future personalization of chronic kidney disease management in people without diabetes.

Assessment of Fibrinogen-like 2 (FGL2) in Human Chronic Kidney Disease through Transcriptomics Data Analysis

Fibrinogen-like 2 (FGL2) was recently found to be associated with fibrosis in a mouse model of kidney damage and was proposed as a potential therapeutic target in chronic kidney disease (CKD). We assessed the association of renal FGL2 mRNA expression with the disease outcome in two independent CKD cohorts (NEPTUNE and Innsbruck CKD cohort) using Kaplan Meier survival analysis. The regulation of FGL2 in kidney biopsies of CKD patients as compared to healthy controls was further assessed in 13 human CKD transcriptomics datasets. The FGL2 protein expression in human renal tissue sections was determined via immunohistochemistry. The regulators of FGL2 mRNA expression in renal tissue were identified in the co-expression and upstream regulator analysis of FGL2-positive renal cells via the use of single-cell RNA sequencing data from the kidney precision medicine project (KPMP). Higher renal FGL2 mRNA expression was positively associated with kidney fibrosis and negatively associated with eGFR. Renal FGL2 mRNA expression was upregulated in CKD as compared with healthy controls and associated with CKD progression in the Innsbruck CKD cohort (p-value = 0.0036) and NEPTUNE cohort (p-value = 0.0048). The highest abundance of FGL2 protein in renal tissue was detected in the thick ascending limb of the loop of Henle and macula densa, proximal tubular cells, as well as in glomerular endothelial cells. The upstream regulator analysis identified TNF, IL1B, IFNG, NFKB1, and SP1 as factors potentially inducing FGL2-co-expressed genes, whereas factors counterbalancing FGL2-co-expressed genes included GLI1, HNF1B, or PPARGC1A. In conclusion, renal FGL2 mRNA expression is elevated in human CKD, and higher FGL2 levels are associated with fibrosis and worse outcomes.

Molecular Pathology, Diagnostics, and Therapeutics of Nephropathy

Years of standing still have ended, and the field of nephrology has seen a plethora of clinical trials, changing the therapeutic landscape of chronic kidney disease (CKD) and immune-mediated kidney disease management [...].

Cyclin G1 induces maladaptive proximal tubule cell dedifferentiation and renal fibrosis through CDK5 activation

Acute kidney injury (AKI) occurs in approximately 13% of hospitalized patients and predisposes patients to chronic kidney disease (CKD) through the AKI-to-CKD transition. Studies from our laboratory and others have demonstrated that maladaptive repair of proximal tubule cells (PTCs), including induction of dedifferentiation, G2/M cell cycle arrest, senescence, and profibrotic cytokine secretion, is a key process promoting AKI-to-CKD transition, kidney fibrosis, and CKD progression. The molecular mechanisms governing maladaptive repair and the relative contribution of dedifferentiation, G2/M arrest, and senescence to CKD remain to be resolved. We identified cyclin G1 (CG1) as a factor upregulated in chronically injured and maladaptively repaired PTCs. We demonstrated that global deletion of CG1 inhibits G2/M arrest and fibrosis. Pharmacological induction of G2/M arrest in CG1-knockout mice, however, did not fully reverse the antifibrotic phenotype. Knockout of CG1 did not alter dedifferentiation and proliferation in the adaptive repair response following AKI. Instead, CG1 specifically promoted the prolonged dedifferentiation of kidney tubule epithelial cells observed in CKD. Mechanistically, CG1 promotes dedifferentiation through activation of cyclin-dependent kinase 5 (CDK5). Deletion of CDK5 in kidney tubule cells did not prevent G2/M arrest but did inhibit dedifferentiation and fibrosis. Thus, CG1 and CDK5 represent a unique pathway that regulates maladaptive, but not adaptive, dedifferentiation, suggesting they could be therapeutic targets for CKD.

sFlt-1 in Chronic Kidney Disease: Friend or Foe?

Placental growth factor (PlGF) and its receptor, fms-like tyrosine kinase-1 (Flt-1), are important regulators involved in angiogenesis, atherogenesis, and inflammation. This review article focuses on the function of PlGF/Flt-1 signaling and its regulation by soluble Flt-1 (sFlt-1) in chronic kidney disease (CKD). Elevation of circulating sFlt-1 and downregulation of sFlt-1 in the vascular endothelium by uremic toxins and oxidative stress both exacerbate heart failure and atherosclerosis. Circulating sFlt-1 is inconsistent with sFlt-1 synthesis, because levels of matrix-bound sFlt-1 are much higher than those of circulating sFlt-1, as verified by a heparin loading test, and are drastically reduced in CKD.

Machine learning for risk stratification in kidney disease

PURPOSE OF REVIEW

Risk stratification for chronic kidney is becoming increasingly important as a clinical tool for both treatment and prevention measures. The goal of this review is to identify how machine learning tools contribute and facilitate risk stratification in the clinical setting.

RECENT FINDINGS

The two key machine learning paradigms to predictively stratify kidney disease risk are genomics-based and electronic health record based approaches. These methods can provide both quantitative information such as relative risk and qualitative information such as characterizing risk by subphenotype.

SUMMARY

The four key methods to stratify chronic kidney disease risk are genomics, multiomics, supervised and unsupervised machine learning methods. Polygenic risk scores utilize whole genome sequencing data to generate an individual's relative risk compared with the population. Multiomic methods integrate information from multiple biomarkers to generate trajectories and prognostic different outcomes. Supervised machine learning methods can directly utilize the growing compendia of electronic health records such as laboratory results and notes to generate direct risk predictions, while unsupervised machine learning methods can cluster individuals with chronic kidney disease into subphenotypes with differing approaches to care.

The m6A demethylase FTO promotes renal epithelial-mesenchymal transition by reducing the m6A modification of lncRNA GAS5

BACKGROUND

Renal interstitial fibrosis (RIF) is the main pathological change of a variety of chronic kidney diseases (CKD). Epigenetic modifications of fibrosis-prone genes regulate RIF progression. This study aimed to investigate long non-coding RNA (lncRNA) N6-methyladenosine (m⁶A) modification and its role in regulating RIF progression.

METHODS

Unilateral ureteral occlusion (UUO) was employed to construct the RIF in vivo model; and TGF-β1-treated HK-2 and HKC-8 cells were used for in vitro experiments. The mRNA and protein expressions were assessed using qRT-PCR and western blot. The proliferation and migration were evaluated by EdU assay and transwell assay, respectively. In addition, levels of inflammatory cytokines were determined by ELISA assay and qRT-PCR. Moreover, lncRNA GAS5 m⁶A level was detected using Me-RIP assay. HE and Masson staining were employed to evaluate fibrotic lesions of the kidney.

RESULTS

FTO expression was elevated in HK-2 and HKC-8 cells after TGF-β1 treatment and mouse kidney tissue following UUO, and lncRNA GAS5 was downregulated. LncRNA GAS5 overexpression or FTO silencing suppressed TGF-β1-induced the increase of EMT-related proteins (Vimentin, Snail and N-cadherin) and inflammatory cytokines (IL-6, IL-1β and TNF-α) levels in HK-2 cells. FTO suppressed lncRNA GAS5 expression by reducing the m6A modification of lncRNA GAS5. Additionally, FTO knockdown could suppress EMT process and inflammation response induced by TGF-β1 and UUO in vitro and in vivo. As expected, FTO knockdown abrogated the promotion effects of lncRNA GAS5 silencing on TGF-β1-induced EMT process and inflammation response in HK-2 and HKC-8 cells.

CONCLUSION

FTO promoted EMT process and inflammation response through reducing the m⁶A modification of lncRNA GAS5.

Polygenic association of glomerular filtration rate decline in world trade center responders

BACKGROUND

The factors associated with estimated glomerular filtrate rate (eGFR) decline in low risk adults remain relatively unknown. We hypothesized that a polygenic risk score (PRS) will be associated with eGFR decline.

METHODS

We analyzed genetic data from 1,601 adult participants with European ancestry in the World Trade Center Health Program (baseline age 49.68 ± 8.79 years, 93% male, 23% hypertensive, 7% diabetic and 1% with cardiovascular disease) with ≥ three serial measures of serum creatinine. PRSs were calculated from an aggregation of single nucleotide polymorphisms (SNPs) from a recent, large-scale genome-wide association study (GWAS) of rapid eGFR decline. Generalized linear models were used to evaluate the association of PRS with renal outcomes: baseline eGFR and CKD stage, rate of change in eGFR, stable versus declining eGFR over a 3-5-year observation period. eGFR decline was defined in separate analyses as "clinical" (> -1.0 ml/min/1.73 m2/year) or "empirical" (lower most quartile of eGFR slopes).

RESULTS

The mean baseline eGFR was ~ 86 ml/min/1.73 m2. Subjects with decline in eGFR were more likely to be diabetic. PRS was significantly associated with lower baseline eGFR (B = -0.96, p = 0.002), higher CKD stage (OR = 1.17, p = 0.010), decline in eGFR (OR = 1.14, p = 0.036) relative to stable eGFR, and the lower quartile of eGFR slopes (OR = 1.21, p = 0.008), after adjusting for established risk factors for CKD.

CONCLUSION

Common genetic variants are associated with eGFR decline in middle-aged adults with relatively low comorbidity burdens.

Variant APOL1 protein in plasma associates with larger particles in humans and mouse models of kidney injury

BACKGROUND

Genetic variants in apolipoprotein L1 (APOL1), a protein that protects humans from infection with African trypanosomes, explain a substantial proportion of the excess risk of chronic kidney disease affecting individuals with sub-Saharan ancestry. The mechanisms by which risk variants damage kidney cells remain incompletely understood. In preclinical models, APOL1 expressed in podocytes can lead to significant kidney injury. In humans, studies in kidney transplant suggest that the effects of APOL1 variants are predominantly driven by donor genotype. Less attention has been paid to a possible role for circulating APOL1 in kidney injury.

METHODS

Using liquid chromatography-tandem mass spectrometry, the concentrations of APOL1 were measured in plasma and urine from participants in the Seattle Kidney Study. Asymmetric flow field-flow fractionation was used to evaluate the size of APOL1-containing lipoprotein particles in plasma. Transgenic mice that express wild-type or risk variant APOL1 from an albumin promoter were treated to cause kidney injury and evaluated for renal disease and pathology.

RESULTS

In human participants, urine concentrations of APOL1 were correlated with plasma concentrations and reduced kidney function. Risk variant APOL1 was enriched in larger particles. In mice, circulating risk variant APOL1-G1 promoted kidney damage and reduced podocyte density without renal expression of APOL1.

CONCLUSIONS

These results suggest that plasma APOL1 is dynamic and contributes to the progression of kidney disease in humans, which may have implications for treatment of APOL1-associated kidney disease and for kidney transplantation.

High risk APOL1 genotypes and kidney disease among treatment naïve HIV patients at Kano, Nigeria

Introduction

Racial disparities are known in the occurrence of kidney disease with excess risks found among people of African descent. Apolipoprotein L1 (APOL1) gene variants G1 and G2 are associated with kidney disease among HIV infected individuals of African descent in the USA as well as among black population in South Africa. We set out to investigate the prevalence of these high-risk variants and their effects on kidney disease among HIV infected patients in Northern Nigeria with hitherto limited information despite earlier reports of high population frequencies of these alleles from the Southern part of the country.

Methods

DNA samples obtained from the whole blood of 142 participants were genotyped for APOL1 G1 and G2 variants after initial baseline investigations including assessment of kidney function. Participants comprised 50 HIV positive patients with no evidence of kidney disease, 52 HIV negative individuals with no kidney disease and 40 HIV positive patients with chronic kidney disease (CKD) evidenced by persistent proteinuria and/or reduced eGFR, who also had a kidney biopsy. All the HIV positive patients were newly diagnosed and treatment naïve.

Results

The distribution of the APOL1 genotypes among the study participants revealed that 24.6% had a G1 risk allele and 19.0% a G2. The frequency of the High Risk Genotype (HRG) was 12.5% among those with CKD compared to 5.8% in the HIV negative group and zero in the HIV positive no CKD group. Having the HRG was associated with a higher odds for developing HIV Associated Nephropathy (HIVAN) (2 vs 0 risk alleles: OR 10.83, 95% CI 1.38–84.52; P = 0.023; 2 vs 0 or 1 risk alleles: OR 5.5, 95% CI 0.83–36.29; P = 0.07). The HRG was also associated with higher odds for Focal Segmental Glomerulosclerosis (FSGS) (2 vs 0 risk alleles: OR 13.0, 95% CI 2.06–81.91; P = 0.006 and 2 vs 0 or 1 risk alleles: OR 9.0, 95%CI 1.62–50.12; P = 0.01) when compared to the control group.

Conclusion

This study showed a high population frequency of the individual risk alleles of the APOL1 gene with higher frequencies noted among HIV positive patients with kidney disease. There is high association with the presence of kidney disease and especially FSGS and HIVAN among treatment naive HIV patients carrying two copies of the HRG.

Neat1 promotes acute kidney injury to chronic kidney disease by facilitating tubular epithelial cells apoptosis via sequestering miR-129-5p

Acute kidney injury (AKI) is increasingly identified as a crucial risk factor for progression to CKD. However, the factors governing AKI to CKD progression remain largely unknown. By high-throughput RNA sequencing, we found that Neat1_2, a transcript variant of Neat1, was upregulated in 40-min ischemia/reperfusion injury (IRI), which resulted in the development of renal fibrotic lesions. The upregulation of Neat1_2 in hypoxia-treated TECs was attributed to p53 transcriptional regulation. Gain- and loss-of-function studies, both in vitro and in vivo, demonstrated that Neat1_2 promoted apoptosis of injured TECs induced by IRI and caused tubulointerstitial inflammation and fibrosis. Mechanistically, Neat1_2 shares miRNA response elements with FADD, CASP-8, and CASP-3. Neat1_2 competitively binds to miR-129-5p and prevents miR-129-5p from decreasing the levels of FADD, CASP-8, and CASP-3, and ultimately facilitates TEC apoptosis. Increased expression of Neat1_2 associated with kidney injury and TEC apoptosis was recapitulated in human AKI, highlighting its clinical relevance. These findings suggest that preventing TEC apoptosis by hindering Neat1_2 expression may be a potential therapeutic strategy for AKI to CKD progression.

Cardiac micro-RNA and transcriptomic profile of a novel swine model of chronic kidney disease and left ventricular diastolic dysfunction

Chronic kidney disease (CKD) is an independent risk factor for the development of heart failure, but the underlying mechanisms remain unknown. Using a novel translational swine model of CKD and cardiac dysfunction, we hypothesize that CKD alters the cardiac miRNA and transcriptomic profile that associate with cardiac remodeling and metabolic processes implicated in the development of left ventricular diastolic dysfunction (CKD-LVDD). CKD-LVDD and normal control pigs (n = 6 each) were studied for 14 wk. Renal and cardiac hemodynamics were quantified by multidetector CT and echocardiography. In randomly selected pigs (n = 3/group), cardiac miRNA- and mRNA-sequencing (seq) was performed, validated (qPCR), and followed by confirmatory ex vivo studies. Differential expression analysis identified nine miRNAs and 125 mRNAs upregulated and 17 miRNAs and 172 mRNAs downregulated [fold-change ≥ 2, and false discovery rate (FDR) ≤ 0.05] in CKD-LVDD versus normal controls. Integrated miRNA-/mRNA-seq analysis identified 71 overlappings downregulated mRNA targets of miRNAs upregulated, and 39 overlappings upregulated mRNA targets of miRNAs downregulated in CKD-LVDD versus controls. Functional analysis showed that these genes were primarily implicated in processes associated with cardiac remodeling, including ubiquitination, ATP and fatty acid synthesis, and extracellular matrix remodeling. In agreement, hearts of CKD-LVDD pigs exhibited abnormal diastolic relaxation, mitochondrial injury, moderate LV fibrosis, and myocardial lipid accumulation. Our work comprehensively characterizes the cardiac micro-RNA and transcriptomic profile of a translational model of CKD-LVDD. Our data may set the foundation for new targeted studies to further elucidate LVDD pathophysiology and assist to develop therapeutic interventions.NEW & NOTEWORTHY Chronic kidney disease (CKD) is a progressive disorder in which more than 50% of deaths are attributed to cardiovascular disease. Using a swine model of CKD that develops left ventricular dysfunction (CKD-LVDD), we characterize the cardiac micro-RNA and transcriptomic profile, identifying dysregulated genes associated with cardiac remodeling and fatty acid metabolism that might be post-transcriptionally regulated early in the disease. These findings pinpointed pathological pathways that may open new avenues toward therapeutic research to reduce cardiovascular morbidity in CKD.

Apolipoprotein L1 Genotypes and the Association of Urinary Potassium Excretion with CKD Progression

BACKGROUND AND OBJECTIVES

Progressive CKD in Black individuals is strongly associated with polymorphisms in the APOL1 gene, but it is unknown whether dietary risk factors for CKD progression vary in high- versus low-risk APOL1 genotypes. We investigated if APOL1 genotypes modify associations of dietary potassium and sodium with CKD progression and death.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We analyzed 1399 self-identified Black participants enrolled in the Chronic Renal Insufficiency Cohort from April 2003 to September 2008. Exposures were calibrated 24-hour urine potassium and sodium excretion. The primary outcome was CKD progression defined as the time to 50% decline in eGFR or kidney failure. The secondary outcome was CKD progression or death. We tested for an interaction between urinary potassium and sodium excretion and APOL1 genotypes.

RESULTS

Median 24-hour urinary sodium and potassium excretions in Black participants were 150 mmol (interquartile range, 118-188) and 43 mmol (interquartile range, 35-54), respectively. Individuals with high- and low-risk APOL1 genotypes numbered 276 (20%) and 1104 (79%), respectively. After a median follow-up of 5.23 years, CKD progression events equaled 605, and after 7.29 years, CKD progression and death events equaled 868. There was significant interaction between APOL1 genotypes and urinary potassium excretion with CKD progression and CKD progression or death (P=0.003 and P=0.03, respectively). In those with high-risk APOL1 genotypes, higher urinary potassium excretion was associated with a lower risk of CKD progression (quartiles 2-4 versus 1: hazard ratio, 0.83; 95% confidence interval, 0.50 to 1.39; hazard ratio, 0.54; 95% confidence interval, 0.31 to 0.93; and hazard ratio, 0.50; 95% confidence interval, 0.27 to 0.93, respectively). In the low-risk APOL1 genotypes, higher urinary potassium excretion was associated with a higher risk of CKD progression (quartiles 2-4 versus 1: hazard ratio, 1.01; 95% confidence interval, 0.75 to 1.36; hazard ratio, 1.23; 95% confidence interval, 0.91 to 1.66; and hazard ratio, 1.53; 95% confidence interval, 1.12 to 2.09, respectively). We found no interaction between APOL1 genotypes and urinary sodium excretion with CKD outcomes.

CONCLUSIONS

Higher urinary potassium excretion was associated with lower versus higher risk of CKD progression in APOL1 high-risk and low-risk genotypes, respectively.

Race, Interleukin-6, TMPRSS6 Genotype, and Cardiovascular Disease in Patients With Chronic Kidney Disease

Background Differences in death rate and cardiovascular disease (CVD) between Black and White patients with chronic kidney disease is attributed to sociocultural factors, comorbidities, genetics, and inflammation. Methods and Results We examined the interaction of race, plasma IL-6 (interleukin-6), and TMPRSS6 genotype as determinants of CVD and mortality in 3031 Chronic Renal Insufficiency Cohort study participants. The primary outcomes were all-cause mortality and a composite of incident myocardial infarction, peripheral artery disease, stroke, and heart failure. During the median follow-up of 10 years, Black patients with chronic kidney disease experienced a significantly higher mortality (34% versus 26%) and CVD composite (41% versus 28%) compared with White patients. After adjustment, TMPRSS6 genotype did not associate with the outcomes. The adjusted hazard ratio for mortality (4.11 [2.48-6.80], P<0.001) and CVD composite (2.52 [1.96-3.24], P<0.001) were higher for the highest versus lowest IL-6 quintile. The adjusted hazards for death per 1-quintile increase in IL-6 in White and Black individuals were 1.53 (1.42-1.64) versus 1.29 (1.20-1.38) (P<0.001), respectively. For CVD composite they were 1.61 (1.50-1.74) versus 1.30 (1.22-1.39) (P<0.001), respectively. In Cox proportional hazard models that included IL-6, there was no longer a racial disparity for death (1.01 [0.87-1.16], P=0.92), but significant unexplained mediation remained for CVD (1.24 [1.07-1.43]; P=0.004). Path models that included IL-6, diabetes, and urine albumin to creatinine ratio were able to identify variables responsible for racial disparity in mortality and CVD. Conclusions Racial differences in mortality and CVD among patients with chronic kidney disease could be explained by good-fitting path models that include selected mediator variables including diabetes and plasma IL-6.

The Benefits of Family Screening in Rare Diseases: Genetic Testing Reveals 165 New Cases of Fabry Disease among At-Risk Family Members of 83 Index Patients

Background: Fabry disease (FD, OMIM #301500) is a rare, progressive, X-linked, inherited genetic disease caused by a functional deficiency of lysosomal α-galactosidase, leading to the accumulation of glycosphingolipids in virtually all of the body’s cell types and fluids. Patients with rare genetic diseases and non-specific symptoms often experience substantial diagnostic delays, which can negatively impact the prompt initiation of treatment. If FD is not treated specifically, end organ damage (such as chronic renal failure, hypertrophic cardiomyopathy with arrhythmia, and strokes) impairs quality of life and reduces life expectancy. Patients and Methods: For 83 consecutive patients with FD referred to the Russian reference center for lysosomal storage diseases, family trees were built and genetic testing (cascade genotyping) was offered to family members. Results: The pathogenic GLA variant associated with FD was identified for all 83 probands. Family testing using cascade genotyping enabled the identification of 165 additional cases of FD among the tested 331 at-risk family members. Discussion: This is the first study to have described family screening in a large Russian cohort of patients with FD and chronic kidney disease. Raising awareness of FD among clinicians is important for earlier diagnosis and specific treatment.

Genetics of Chronic Kidney Disease in Low-Resource Settings

Advances in kidney genomics in the past 20 years has opened the door for more precise diagnosis of kidney disease and identification of new and specific therapeutic agents. Despite these advances, an imbalance exists between low-resource and affluent regions of the world. Individuals of European ancestry from the United States, United Kingdom, and Iceland account for 16% of the world's population, but represent more than 80% of all genome-wide association studies. South Asia, Southeast Asia, Latin America, and Africa together account for 57% of the world population but less than 5% of genome-wide association studies. Implications of this difference include limitations in new variant discovery, inaccurate interpretation of the effect of genetic variants in non-European populations, and unequal access to genomic testing and novel therapies in resource-poor regions. It also further introduces ethical, legal, and social pitfalls, and ultimately may propagate global health inequities. Ongoing efforts to reduce the imbalance in low-resource regions include funding and capacity building, population-based genome sequencing, population-based genome registries, and genetic research networks. More funding, training, and capacity building for infrastructure and expertise is needed in resource-poor regions. Focusing on this will ensure multiple-fold returns on investments in genomic research and technology.

Increased PHOSPHO1 expression mediates cortical bone mineral density in renal osteodystrophy

Patients with advanced chronic kidney disease (CKD) often present with skeletal abnormalities, a condition known as renal osteodystrophy (ROD). While tissue non-specific alkaline phosphatase (TNAP) and PHOSPHO1 are critical for bone mineralization, their role in the etiology of ROD is unclear. To address this, ROD was induced in both WT and Phospho1 knockout (P1KO) mice through dietary adenine supplementation. The mice presented with hyperphosphatemia, hyperparathyroidism, and elevated levels of FGF23 and bone turnover markers. In particular, we noted that in CKD mice, bone mineral density (BMD) was increased in cortical bone (P < 0.05) but decreased in trabecular bone (P < 0.05). These changes were accompanied by decreased TNAP (P < 0.01) and increased PHOSPHO1 (P < 0.001) expression in WT CKD bones. In P1KO CKD mice, the cortical BMD phenotype was rescued, suggesting that the increased cortical BMD of CKD mice was driven by increased PHOSPHO1 expression. Other structural parameters were also improved in P1KO CKD mice. We further investigated the driver of the mineralization defects, by studying the effects of FGF23, PTH, and phosphate administration on PHOSPHO1 and TNAP expression by primary murine osteoblasts. We found both PHOSPHO1 and TNAP expressions to be downregulated in response to phosphate and PTH. The in vitro data suggest that the TNAP reduction in CKD-MBD is driven by the hyperphosphatemia and/or hyperparathyroidism noted in these mice, while the higher PHOSPHO1 expression may be a compensatory mechanism. Increased PHOSPHO1 expression in ROD may contribute to the disordered skeletal mineralization characteristic of this progressive disorder.

Association of Chronic Kidney Disease With Risk of Intracerebral Hemorrhage

Importance

The evidence linking chronic kidney disease (CKD) to spontaneous intracerebral hemorrhage (ICH) is inconclusive owing to possible confounding by comorbidities that frequently coexist in patients with these 2 diseases.

Objective

To determine whether there is an association between CKD and ICH risk.

Design, Setting, and Participants

A 3-stage study that combined observational and genetic analyses was conducted. First, the association between CKD and ICH risk was tested in the Ethnic/Racial Variations of Intracerebral Hemorrhage (ERICH) study, a multicenter case-control study in the US. All participants with available data on CKD from ERICH were included. Second, this analysis was replicated in the UK Biobank (UKB), an ongoing population study in the UK. All participants in the UKB were included in this study. Third, mendelian randomization analyses were implemented in the UKB using 27 CKD-related genetic variants to test for genetic associations. ERICH was conducted from August 1, 2010, to August 1, 2017, and observed participants for 1 year. The UKB enrolled participants between 2006 and 2010 and will continue to observe them for 30 years. Data analysis was performed from November 11, 2019, to May 10, 2022.

Exposures

CKD stages 1 to 5.

Main Outcomes and Measures

The outcome of interest was ICH, ascertained in ERICH via expert review of neuroimages and in the UKB via a combination of self-reported data and International Statistical Classification of Diseases, Tenth Revision, codes.

Results

In the ERICH study, a total of 2914 participants with ICH and 2954 controls who had available data on CKD were evaluated (mean [SD] age, 61.6 [14.0] years; 2433 female participants [41.5%]; 3435 male participants [58.5%]); CKD was found to be independently associated with higher risk of ICH (odds ratio [OR], 1.95; 95% CI, 1.35-2.89; P < .001). This association was not modified by race and ethnicity. Replication in the UKB with 1341 participants with ICH and 501 195 controls (mean [SD] age, 56.5 [8.1] years; 273 402 female participants [54.4%]; 229 134 male participants [45.6%]) confirmed this association (OR, 1.28; 95% CI, 1.01-1.62; P = .04). Mendelian randomization analyses indicated that genetically determined CKD was associated with ICH risk (OR, 1.56; 95% CI, 1.13-2.16; P = .007).

Conclusions and Relevance

In this 3-stage study that combined observational and genetic analyses among study participants enrolled in 2 large observational studies with different characteristics and study designs, CKD was consistently associated with higher risk of ICH. Mendelian randomization analyses suggest that this association was causal. Further studies are needed to identify the specific biological pathways that mediate this association.

Genetic Variants Associated With Mineral Metabolism Traits in Chronic Kidney Disease

CONTEXT

Chronic kidney disease (CKD) causes multiple interrelated disturbances in mineral metabolism. Genetic studies in the general population have identified common genetic variants associated with circulating phosphate, calcium, parathyroid hormone (PTH), and fibroblast growth factor 23 (FGF23).

OBJECTIVE

In this study we aimed to discover genetic variants associated with circulating mineral markers in CKD.

METHODS

We conducted candidate single-nucleotide variation (SNV) analysis in 3027 participants in the multiethnic Chronic Renal Insufficiency Cohort (CRIC) to determine the associations between SNVs and circulating levels of mineral markers.

RESULTS

SNVs adjacent to or within genes encoding the regulator of G protein-coupled signaling 14 (RGS14) and the calcium-sensing receptor (CASR) were associated with levels of mineral metabolites. The strongest associations (P < .001) were at rs4074995 (RGS14) for phosphate (0.09 mg/dL lower per minor allele) and FGF23 (8.6% lower), and at rs1801725 (CASR) for calcium (0.12 mg/dL higher). In addition, the prevalence of hyperparathyroidism differed by rs4074995 (RGS14) genotype (chi-square P < .0001). Differential inheritance by race was noted for the minor allele of RGS14. Expression quantitative loci (eQTL) analysis showed that rs4074995 was associated with lower RGS14 gene expression in glomeruli (P = 1.03 × 10-11) and tubules (P = 4.0 × 10-4).

CONCLUSION

We evaluated genetic variants associated with mineral metabolism markers in a CKD population. Participants with CKD and the minor allele of rs4074995 (RGS14) had lower phosphorus, lower plasma FGF23, and lower prevalence of hyperparathyroidism. The minor allele of RGS14 was also associated with lower gene expression in the kidney. Further studies are needed to elucidate the effect of rs4074995 on the pathogenesis of disordered mineral metabolism in CKD.

An intermediate-effect size variant in UMOD confers risk for chronic kidney disease

The kidney-specific gene UMOD encodes for uromodulin, the most abundant protein excreted in normal urine. Rare large-effect variants in UMOD cause autosomal dominant tubulointerstitial kidney disease (ADTKD), while common low-impact variants strongly associate with kidney function and the risk of chronic kidney disease (CKD) in the general population. It is unknown whether intermediate-effect variants in UMOD contribute to CKD. Here, candidate intermediate-effect UMOD variants were identified using large-population and ADTKD cohorts. Biological and phenotypical effects were investigated using cell models, in silico simulations, patient samples, and international databases and biobanks. Eight UMOD missense variants reported in ADTKD are present in the Genome Aggregation Database (gnomAD), with minor allele frequency (MAF) ranging from 10-5 to 10-3. Among them, the missense variant p.Thr62Pro is detected in ∼1/1,000 individuals of European ancestry, shows incomplete penetrance but a high genetic load in familial clusters of CKD, and is associated with kidney failure in the 100,000 Genomes Project (odds ratio [OR] = 3.99 [1.84 to 8.98]) and the UK Biobank (OR = 4.12 [1.32 to 12.85). Compared with canonical ADTKD mutations, the p.Thr62Pro carriers displayed reduced disease severity, with slower progression of CKD and an intermediate reduction of urinary uromodulin levels, in line with an intermediate trafficking defect in vitro and modest induction of endoplasmic reticulum (ER) stress. Identification of an intermediate-effect UMOD variant completes the spectrum of UMOD-associated kidney diseases and provides insights into the mechanisms of ADTKD and the genetic architecture of CKD.

RIPK3-MLKL signaling activates mitochondrial CaMKII and drives intrarenal extracellular matrix production during CKD

Intrarenal extracellular matrix production is a prevalent feature of all forms of chronic kidney disease (CKD). The transforming growth factor-beta (TGFβ) is believed to be a major driver of extracellular matrix production. Nevertheless, anti-TGFβ therapies have consistently failed to reduce extracellular matrix production in CKD patients indicating the need for novel therapeutic strategies. We have previously shown that necroinflammation contributes to acute kidney injury. Here, we show that chronic/persistent necroinflammation drives intrarenal extracellular matrix production during CKD. We found that renal expression of receptor-interacting protein kinase-1 (RIPK1), RIPK3, and mixed lineage kinase domain-like (MLKL) increases with the expansion of intrarenal extracellular matrix production and declined kidney function in both humans and mice. Furthermore, we found that TGFβ exposure induces the translocation of RIPK3 and MLKL to mitochondria resulting in mitochondrial dysfunction and ROS production. Mitochondrial ROS activates the serine-threonine kinase calcium/calmodulin-dependent protein kinases-II (CaMKII) that increases phosphorylation of Smad2/3 and subsequent production of alpha-smooth muscle actin (αSMA), collagen (Col) 1α1, etc. in response to TGFβ during the intrarenal extracellular matrix production. Consistent with this, deficiency or knockdown of RIPK3 or MLKL as well as pharmacological inhibition of RIPK1, RIPK3, and CaMKII prevents the intrarenal extracellular matrix production in oxalate-induced CKD and unilateral ureteral obstruction (UUO). Together, RIPK1, RIPK3, MLKL, CaMKII, and Smad2/3 are molecular targets to inhibit intrarenal extracellular matrix production and preserve kidney function during CKD.

Hepatocyte Nuclear Factor 1α Proinflammatory Effect Linked to the Overexpression of Liver Nuclear Factor–κB in Experimental Model of Chronic Kidney Disease

Chronic kidney disease (CKD) is associated with low-grade inflammation that activates nuclear factor–κB (NF–κB), which upregulates the expression of numerous NF–κB responsive genes, including the genes encoding IL-6, ICAM-1, VCAM-1, and MCP-1. Herein, we found the coordinated overexpression of genes encoding RelA/p65 (a subunit of NF–κB) and HNF1α in the livers of chronic renal failure (CRF) rats—an experimental model of CKD. The coordinated overexpression of RelA/p65 and HNF1α was associated with a significant increase in IL-6, ICAM-1, VCAM-1, and MCP-1 gene expressions. A positive correlation between liver RelA/p65 mRNA levels and a serum concentration of creatinine and BUN suggest that RelA/p65 gene transcription is tightly related to the progression of renal failure. The knockdown of HNF1α in the HepG2 cell line by siRNA led to a decrease in Rel A/p65 mRNA levels. This was associated with a decrease in IL-6, ICAM-1, VCAM-1, and MCP-1 gene expressions. The simultaneous repression of HNF-1α and RelA/p65 by clofibrate is tightly associated with the downregulation of IL-6, ICAM-1, VCAM-1, and MCP-1 gene expression. In conclusion, our findings suggest that NF–κB could be a downstream component of the HNF1α-initiated signaling pathway in the livers of CRF rats.

Association of Mitochondrial DNA Copy Number with Risk of Progression of Kidney Disease

BACKGROUND AND OBJECTIVES

Mitochondrial DNA copy number is a biomarker of mitochondrial function, which has been hypothesized to contribute to pathogenesis of CKD through podocyte injury, tubular epithelial cell damage, and endothelial dysfunction. The prospective association of mitochondrial DNA copy number with CKD progression has not been previously evaluated.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Chronic Renal Insufficiency Cohort study participants had serum levels of mitochondrial DNA copy number calculated from probe intensities of mitochondrial single nucleotide polymorphisms genotyped on the Illumina HumanOmni 1-Quad Array. CKD progression was defined as kidney failure or halving of eGFR from baseline. Cox proportional hazards models were used to calculate hazard ratios for mitochondrial DNA copy number and risk of CKD progression.

RESULTS

Among 2943 participants, mean age was 58 years, 45% were women, and 48% self-identified as Black. There were 1077 patients who experienced CKD progression over a median follow-up of 6.5 years. The incidence rate of CKD progression was highest for those in the lowest tertile of mitochondrial DNA copy number (tertile 1, 58.1; tertile 2, 50.8; tertile 3, 46.3 per 1000 person-years). Risk for CKD progression was higher for participants with lower levels of mitochondrial DNA copy number after adjustment for established risk factors (for tertile 1 versus 3, hazard ratio, 1.28 [95% confidence interval, 1.10 to 1.50]; for tertile 2 versus 3, hazard ratio, 0.99 [95% confidence interval, 0.85 to 1.16]; trend P=0.002). Similar results were seen among those with albuminuria (for tertile 1 versus 3, hazard ratio, 1.24; 95% confidence interval, 1.05 to 1.47), but there were no statistically significant associations among individuals without albuminuria (for tertile 1 versus 3, hazard ratio, 1.04; 95% confidence interval, 0.70 to 1.53; interaction P<0.001).

CONCLUSIONS

These findings suggest lower mitochondrial DNA copy number is associated with higher risk of CKD progression, independent of established risk factors among patients with CKD.

Genome-wide polygenic score to predict chronic kidney disease across ancestries

Chronic kidney disease (CKD) is a common complex condition associated with high morbidity and mortality. Polygenic prediction could enhance CKD screening and prevention; however, this approach has not been optimized for ancestrally diverse populations. By combining APOL1 risk genotypes with genome-wide association studies (GWAS) of kidney function, we designed, optimized and validated a genome-wide polygenic score (GPS) for CKD. The new GPS was tested in 15 independent cohorts, including 3 cohorts of European ancestry (n = 97,050), 6 cohorts of African ancestry (n = 14,544), 4 cohorts of Asian ancestry (n = 8,625) and 2 admixed Latinx cohorts (n = 3,625). We demonstrated score transferability with reproducible performance across all tested cohorts. The top 2% of the GPS was associated with nearly threefold increased risk of CKD across ancestries. In African ancestry cohorts, the APOL1 risk genotype and polygenic component of the GPS had additive effects on the risk of CKD.

Selected aspects of genetic disorders in chronic kidney disease

Chronic kidney disease (CKD) can be caused by many conditions. The most common reasons are diabetic nephropathy, hypertension - associated nephropathy, cardiovascular disease. Although there are different reasons of deterioration of kidney function, many of them have combined molecular mechanisms by modulating metabolic homeostasis, autophagy, apoptosis, oxidative stress, inflammation. The aim of this paper is to present known molecular bases of CKD development in the course of other selected diseases to research why different patients are more prone to the CKD than others with the same condition. Selected aspects of genetic conditions were conducted, such as gene polymorphism of sirtuins, APOL1 gene polymorphism, the role of reactive oxygen species. More research is needed to understand the genetics of CKD and its' affecting the process of diagnostics and treatment.

Genetic Risk Score for Plasma Uric Acid Levels Is Associated With Early Rapid Kidney Function Decline in Type 2 Diabetes

CONTEXT

Observational studies have shown that elevated uric acid (UA) is associated with chronic kidney disease (CKD). However, whether the relationship is causal remains unclear.

OBJECTIVE

To determine the association of plasma UA and incident CKD and the causal relationship between plasma UA and rapid decline in kidney function (RDKF) in patients with type 2 diabetes (T2D).

METHODS

Multivariable Cox regression was conducted to evaluate the hazard ratio (HR) between plasma UA and incident CKD among 1300 normoalbuminuric patients in 2 T2D study cohorts (DN, n = 402; SMART2D, n = 898). A weighted genetic risk score (wGRS) was calculated based on 10 single nucleotide polymorphism (SNPs) identified in genome-wide association studies of UA in East Asians. Mendelian randomization (MR) analysis was performed among 1146 Chinese T2D patients without CKD (estimated glomerular filtration rate [eGFR] > 60 mL/min/1.73m2) at baseline (DN, 478; SMART2D, 668). The wGRS and individual SNPs were used as genetic instruments and RDKF was defined as eGFR decline of 5 mL/min/1.73m2/year or greater.

RESULTS

During mean follow-up of 5.2 and 5.4 years, 81 (9%) and 46 (11%) participants in SMART2D and DN developed CKD, respectively. A 1-SD increment in plasma UA conferred higher risk of incident CKD (DN, adjusted-HR = 1.40 [95% CI, 1.02-1.91], P = 0.036; SMART2D, adjusted-HR = 1.31 [95% CI, 1.04-1.64], P = 0.018). Higher wGRS was associated with increased odds for RDKF (meta-adjusted odds ratio = 1.12 [95% CI, 1.01-1.24], P = 0.030, Phet = 0.606).

CONCLUSION

Elevated plasma UA is an independent risk factor for incident CKD. Furthermore, plasma UA potentially has a causal role in early eGFR loss in T2D patients.

Genome-wide studies reveal factors associated with circulating uromodulin and its relationships to complex diseases

Uromodulin (UMOD) is a major risk gene for monogenic and complex forms of kidney disease. The encoded kidney-specific protein uromodulin is highly abundant in urine and related to chronic kidney disease, hypertension, and pathogen defense. To gain insights into potential systemic roles, we performed genome-wide screens of circulating uromodulin using complementary antibody-based and aptamer-based assays. We detected 3 and 10 distinct significant loci, respectively. Integration of antibody-based results at the UMOD locus with functional genomics data (RNA-Seq, ATAC-Seq, Hi-C) of primary human kidney tissue highlighted an upstream variant with differential accessibility and transcription in uromodulin-synthesizing kidney cells as underlying the observed cis effect. Shared association patterns with complex traits, including chronic kidney disease and blood pressure, placed the PRKAG2 locus in the same pathway as UMOD. Experimental validation of the third antibody-based locus, B4GALNT2, showed that the p.Cys466Arg variant of the encoded N-acetylgalactosaminyltransferase had a loss-of-function effect leading to higher serum uromodulin levels. Aptamer-based results pointed to enzymes writing glycan marks present on uromodulin and to their receptors in the circulation, suggesting that this assay permits investigating uromodulin's complex glycosylation rather than its quantitative levels. Overall, our study provides insights into circulating uromodulin and its emerging functions.

Association between Vitamin Intake and Chronic Kidney Disease According to a Variant Located Upstream of the PTGS1 Gene: A Cross-Sectional Analysis of Shika Study

Chronic kidney disease (CKD) patients have been advised to take vitamins; however, the effects have been controversial. The individual differences in developing CKD might involve genetic variants of inflammation, including variant rs883484 located upstream of the prostaglandin-endoperoxide synthase 1 (PTGS1) gene. We aimed to identify whether the 12 dietary vitamin intake interacts with genotypes of the rs883484 on developing CKD. The population-based, cross-sectional study had 684 Japanese participants (≥40 years old). The study used a validated, brief, self-administered diet history questionnaire to estimate the intake of the dietary vitamins. CKD was defined as estimated glomerular filtration < 60 mL/min/1.73 m2. The study participants had an average age of 62.1 ± 10.8 years with 15.4% minor homozygotes of rs883484, and 114 subjects had CKD. In the fully adjusted model, the higher intake of vitamins, namely niacin (odds ratio (OR) = 0.74, 95% confidence interval (CI): 0.57−0.96, p = 0.024), α-tocopherol (OR = 0.49, 95% CI: 0.26−0.95, p = 0.034), and vitamin C (OR = 0.97, 95% CI: 0.95−1.00, p = 0.037), was independently associated with lower CKD tendency in the minor homozygotes of rs883484. The results suggested the importance of dietary vitamin intake in the prevention of CKD in middle-aged to older-aged Japanese with minor homozygous of rs883484 gene variant.

Association of Clonal Hematopoiesis of Indeterminate Potential with Worse Kidney Function and Anemia in Two Cohorts of Patients with Advanced Chronic Kidney Disease

BACKGROUND

Clonal hematopoiesis of indeterminate potential (CHIP) is an inflammatory premalignant disorder resulting from acquired genetic mutations in hematopoietic stem cells. This condition is common in aging populations and associated with cardiovascular morbidity and overall mortality, but its role in CKD is unknown.

METHODS

We performed targeted sequencing to detect CHIP mutations in two independent cohorts of 87 and 85 adults with an eGFR<60 ml/min per 1.73m2. We also assessed kidney function, hematologic, and mineral bone disease parameters cross-sectionally at baseline, and collected creatinine measurements over the following 5-year period.

RESULTS

At baseline, CHIP was detected in 18 of 87 (21%) and 25 of 85 (29%) cohort participants. Participants with CHIP were at higher risk of kidney failure, as predicted by the Kidney Failure Risk Equation (KFRE), compared with those without CHIP. Individuals with CHIP manifested a 2.2-fold increased risk of a 50% decline in eGFR or ESKD over 5 years of follow-up (hazard ratio 2.2; 95% confidence interval, 1.2 to 3.8) in a Cox proportional hazard model adjusted for age, sex, and baseline eGFR. The addition of CHIP to 2-year and 5-year calibrated KFRE risk models improved ESKD predictions. Those with CHIP also had lower hemoglobin, higher ferritin, and higher red blood cell mean corpuscular volume versus those without CHIP.

CONCLUSIONS

In this exploratory analysis of individuals with preexisting CKD, CHIP was associated with higher baseline KFRE scores, greater progression of CKD, and anemia. Further research is needed to define the nature of the relationship between CHIP and kidney disease progression.

The Association Between Plasma MicroRNA-451 Expression Levels and Chronic Kidney Disease in Children with β-Thalassemia Major

INTRODUCTION

Patients with β -thalassemia major (β -TM) had a high rate of glomerular dysfunction due to chronic anemia, iron overload, and chelation therapy. There is also evidence of proximal tubular damage, as almost all patients have various amounts of proteinuria. MicroRNAs are non-coding RNA molecules that regulate gene expression. In diabetes, a relative increase in renal microRNA-451 appeared to protect against diabetic kidney injury. This study aimed to investigate the association between miRNA-451 and the development of chronic kidney disease (CKD) in children with β-TM.

METHODS

This study included 60 pediatric patients with β-TM and 30 healthy children as controls. We categorized patients into two groups according to the presence of CKD. Complete blood and reticulocyte counts, serum levels of ferritin, creatinine and glucose, and urine albumin/creatinine ratio (ACR) were measured. Plasma miRNA-451 expression level was measured by real-time quantitative reversed transcription PCR in all included children.

RESULTS

miRNA-451 levels were significantly higher in β-TM (25.326 ± 12.191) as compared with controls (9.453 ± 5.753) (P < .001). Patients with β-TM and CKD had significantly lower miRNA-451 levels (19.72 ± 13.023) than those without CKD (30.933 ± 8.23). MiRNA-451 levels had significantly positive correlated with eGFR (r = 0.385 P < .05) and reticulocyte counts (r = 0.27, P < .05). Linear logistic regression analysis showed that low plasma microRNA-451 was a significant independent predictor of CKD.

CONCLUSION

miRNA-451 has a protective role against CKD development, and low plasma expression levels are associated with CKD in children with β-TM  DOI: 10.52547/ijkd.6756.

Rosmarinic acid ameliorates renal interstitial fibrosis by inhibiting the phosphorylated-AKT mediated epithelial-mesenchymal transition in vitro and in vivo

Indoxyl sulfate (IS), a uremic toxin, causes chronic kidney disease (CKD) progression via renal fibrosis. Epithelial-mesenchymal transition (EMT) is a crucial feature of renal fibrosis. Rosmarinic acid (RA) is an ester of caffeic acid and 3,4-dihydroxyphenylacetic acid with a wide range of desirable biological activities. In this study, we investigated whether RA exerted anti-renal fibrosis effects and its related mechanisms in a unilateral ureteral obstruction (UUO) mouse model. C57BL/6 mice were orally administered RA (10 and 20 mg kg-1 d-1) for 7 consecutive days before and after UUO surgery. The mice were then sacrificed to collect the blood and kidneys. Hematoxylin and eosin (H&E) and Masson's trichrome staining were used to evaluate the renal injury and function. Immunohistochemical analysis, reverse transcription-polymerase chain reaction (RT-PCR), and western blotting were used to detect the expression levels of EMT markers. In vitro studies were performed using the IS-stimulated NRK-52E cell line. Here, the pathological changes, collagen deposition, and mRNA and protein expression levels of profibrotic factors and fibrotic markers were found to be significantly elevated in the kidneys of UUO mice. We found that RA administration significantly ameliorated UUO-induced kidney damage by reversing abnormal serum creatinine and blood urea nitrogen levels. It was found that RA treatment decreased the expression levels of alpha-smooth muscle actin (α-SMA), collagen I, fibronectin, transforming growth factor (TGF)-β1, vimentin and phosphorylated AKT (p-AKT) while increasing the E-cadherin expression in both UUO kidneys and IS-treated NRK-52E cells. Our results demonstrate that RA may be a promising therapeutic agent for renal interstitial fibrosis.

Diagnostic yield of massively parallel sequencing in patients with chronic kidney disease of unknown etiology: rationale and design of a national prospective cohort study

INTRODUCTION

Chronic kidney disease (CKD) can be caused by a variety of systemic or primary renal diseases. The cause of CKD remains unexplained in approximately 20% of patients. Retrospective studies indicate that massively parallel sequencing (MPS)-based gene panel testing may lead to a genetic diagnosis in 12%-56% of patients with unexplained CKD, depending on patient profile. The diagnostic yield of MPS-based testing in a routine healthcare setting is unclear. Therefore, the primary aim of the VARIETY (Validation of algoRithms and IdEnTification of genes in Young patients with unexplained CKD) study is to prospectively address the diagnostic yield of MPS-based gene panel testing in patients with unexplained CKD and an estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m² before the age of 50 years in clinical practice.

METHODS AND ANALYSIS

The VARIETY study is an ongoing, prospective, nationwide observational cohort study to investigate the diagnostic yield of MPS-based testing in patients with unexplained CKD in a routine healthcare setting in the Netherlands. Patients are recruited from outpatient clinics in hospitals across the Netherlands. At least 282 patients will be included to meet the primary aim. Secondary analyses include subgroup analyses according to age and eGFR at first presentation, family history, and the presence of extrarenal symptoms.

ETHICS AND DISSEMINATION

Ethical approval for the study has been obtained from the institutional review board of the University Medical Center Groningen. Study findings should inform physicians and policymakers towards optimal implementation of MPS-based diagnostic testing in patients with unexplained CKD.

Genetics of osteopontin in patients with chronic kidney disease: The German Chronic Kidney Disease study

Osteopontin (OPN), encoded by SPP1, is a phosphorylated glycoprotein predominantly synthesized in kidney tissue. Increased OPN mRNA and protein expression correlates with proteinuria, reduced creatinine clearance, and kidney fibrosis in animal models of kidney disease. But its genetic underpinnings are incompletely understood. We therefore conducted a genome-wide association study (GWAS) of OPN in a European chronic kidney disease (CKD) population. Using data from participants of the German Chronic Kidney Disease (GCKD) study (N = 4,897), a GWAS (minor allele frequency [MAF]≥1%) and aggregated variant testing (AVT, MAF<1%) of ELISA-quantified serum OPN, adjusted for age, sex, estimated glomerular filtration rate (eGFR), and urinary albumin-to-creatinine ratio (UACR) was conducted. In the project, GCKD participants had a mean age of 60 years (SD 12), median eGFR of 46 mL/min/1.73m2 (p25: 37, p75: 57) and median UACR of 50 mg/g (p25: 9, p75: 383). GWAS revealed 3 loci (p<5.0E-08), two of which replicated in the population-based Young Finns Study (YFS) cohort (p<1.67E-03): rs10011284, upstream of SPP1 encoding the OPN protein and related to OPN production, and rs4253311, mapping into KLKB1 encoding prekallikrein (PK), which is processed to kallikrein (KAL) implicated through the kinin-kallikrein system (KKS) in blood pressure control, inflammation, blood coagulation, cancer, and cardiovascular disease. The SPP1 gene was also identified by AVT (p = 2.5E-8), comprising 7 splice-site and missense variants. Among others, downstream analyses revealed colocalization of the OPN association signal at SPP1 with expression in pancreas tissue, and at KLKB1 with various plasma proteins in trans, and with phenotypes (bone disorder, deep venous thrombosis) in human tissue. In summary, this GWAS of OPN levels revealed two replicated associations. The KLKB1 locus connects the function of OPN with PK, suggestive of possible further post-translation processing of OPN. Further studies are needed to elucidate the complex role of OPN within human (patho)physiology.

Trans-ethnic genome-wide association study of blood metabolites in the Chronic Renal Insufficiency Cohort (CRIC) study

Metabolomics genome wide association study (GWAS) help outline the genetic contribution to human metabolism. However, studies to date have focused on relatively healthy, population-based samples of White individuals. Here, we conducted a GWAS of 537 blood metabolites measured in the Chronic Renal Insufficiency Cohort (CRIC) Study, with separate analyses in 822 White and 687 Black study participants. Trans-ethnic meta-analysis was then applied to improve fine-mapping of potential causal variants. Mean estimated glomerular filtration rate was 44.4 and 41.5 mL/min/1.73m2 in the White and Black participants, respectively. There were 45 significant metabolite associations at 19 loci, including novel associations at PYROXD2, PHYHD1, FADS1-3, ACOT2, MYRF, FAAH, and LIPC. The strength of associations was unchanged in models additionally adjusted for estimated glomerular filtration rate and proteinuria, consistent with a direct biochemical effect of gene products on associated metabolites. At several loci, trans-ethnic meta-analysis, which leverages differences in linkage disequilibrium across populations, reduced the number and/or genomic interval spanned by potentially causal single nucleotide polymorphisms compared to fine-mapping in the White participant cohort alone. Across all validated associations, we found strong concordance in effect sizes of the potentially causal single nucleotide polymorphisms between White and Black study participants. Thus, our study identifies novel genetic determinants of blood metabolites in chronic kidney disease, demonstrates the value of diverse cohorts to improve causal inference in metabolomics GWAS, and underscores the shared genetic basis of metabolism across race.

Genetic Etiologies for Chronic Kidney Disease Revealed through Next-Generation Renal Gene Panel

INTRODUCTION

Chronic kidney disease (CKD) is a major public health issue in the USA. Identification of monogenic causes of CKD, which are present in ∼10% of adult cases, can impact prognosis and patient management. Broad gene panels can provide unbiased testing approaches, which are advantageous in phenotypically heterogeneous diseases. However, the use and yield of broad genetic panels by nephrologists in clinical practice is not yet well characterized.

METHODS

Renal genetic testing, ordered exclusively for clinical purposes, predominantly by general and transplant nephrologists within the USA, was performed on 1,007 consecutive unique patient samples. Testing was performed using a commercially available next-generation sequencing-based 382 gene kidney disease panel. Pathogenic (P) and likely pathogenic (LP) variants were reported. Positive findings included a monoallelic P/LP variant in an autosomal dominant or X-linked gene and biallelic P/LP variants in autosomal recessive genes.

RESULTS

Positive genetic findings were identified in 21.1% (212/1,007) of cases. A total of 220 positive results were identified across 48 genes. Positive results occurred most frequently in the PKD1 (34.1%), COL4A5 (10.9%), PKD2 (10.0%), COL4A4 (6.4%), COL4A3 (5.9%), and TTR (4.1%) genes. Variants identified in the remaining 42 genes comprised 28.6% of the total positive findings, including single positive results in 26 genes. Positive results in >1 gene were identified in 7.5% (16/212) of cases.

CONCLUSIONS

Use of broad panel genetic testing by clinical nephrologists had a high success rate, similar to results obtained by academic centers specializing in genetics.