Journal of the American Society of Nephrology

Anemia is a common and disabling complication of chronic kidney disease (CKD). Current therapies can be burdensome, and full correction of anemia is limited by cardiovascular side effects. New approaches that may offer additional therapeutic options are needed. We explored the anti-anemic effects of erythroferrone, an erythroid hormone that induces iron mobilization by suppressing the master iron-regulatory hormone hepcidin. In a preclinical murine model of adenine-induced CKD, transgenic augmentation of erythroferrone mobilized iron, increased hemoglobin concentrations by approximately 2 g/dl, and modestly improved renal function without affecting systemic or renal inflammation, fibrosis, or markers of mineral metabolism. This study supports the concept that therapeutic augmentation of erythroferrone is a promising approach for alleviating CKD-associated anemia.

Background Acute kidney injury (AKI) is a major contributor to morbidity, mortality, and healthcare utilization among hospitalized adults. Long-standing racial and ethnic inequities in U.S. healthcare--including unequal access to care, neighborhood disadvantage, and other structural factors--are known to influence kidney health, yet national data describing how these inequities manifest in AKI remain limited. Methods We conducted a retrospective, cross-sectional analysis of the 2022 National Inpatient Sample. AKI was identified using ICD-10-CM codes N17.x, and race/ethnicity followed HCUP categories. Descriptive analyses compared characteristics across groups. Survey-weighted logistic regression estimated adjusted odds of developing AKI, in-hospital mortality among AKI patients, and dialysis use, adjusting for demographics, payer, and comorbidities. Age-specific predicted AKI probabilities were derived from the adjusted model. Results AKI prevalence ranged from 15% to 23% across racial and ethnic groups. After adjustment, Black (OR 1.34), Native American (OR 1.08), and Other patients (OR 1.07) had higher odds of AKI, whereas Asian/Pacific Islander (OR 0.94) and Hispanic (OR 0.98) had slightly lower or similar odds. Among AKI hospitalizations, mortality was modestly lower for Black and Hispanic patients relative to White patients and higher for Asian/Pacific Islander and Native American patients. All non-White groups had higher odds of dialysis use. Age-specific curves showed persistent risk differences across adulthood. Conclusions Substantial racial disparities in AKI incidence, mortality, and dialysis use persisted after adjustment, reflecting broader structural inequities. Addressing these gaps will require both targeted clinical strategies and policy interventions focused on upstream determinants.

AbstractLimiting progressive fibrosis in chronic kidney disease (CKD) is an ongoing therapeutic challenge that requires effective and safe inhibition of a broad inflammatory cell milieu that leads to irreversible organ damage. Asengeprast, an anti-fibrotic and anti-inflammatory small molecule, has shown promising efficacy in animal models of kidney disease, however its target and mechanism of action was unknown. Using in vitro assays, we showed that asengeprast modulates inflammatory and fibrotic responses through selective inhibition of G protein-coupled receptor 68 (GPR68), a proton sensor, expressed in tissue-resident and immune-infiltrating cells of the kidney. Transcriptomic analysis of kidney tissue from animal models of diabetic kidney disease (DKD) and CKD demonstrated that fibrotic and inflammatory pathways dysregulated in disease were reversed by asengeprast treatment. Differential expression analysis of upstream regulators showed that the major, distinct signaling networks reversed were centered on a key driver of fibroblast activation, transforming growth factor {beta}1, and associated signaling molecules. An asengeprast response gene signature derived from the CKD animal model when mapped onto gene expression profiles obtained from human kidney biopsies confirmed that the molecular pathways modulated by asengeprast were also dysregulated in human DKD and CKD. Further, this asengeprast response signature correlated with clinical markers of disease progression and tissue pathology. Overall, these findings provide evidence for targeted inhibition of GPR68 by asengeprast as a promising therapeutic strategy for treatment of CKD and potentially other fibrotic and inflammatory conditions. Translational StatementExisting therapeutic strategies for chronic kidney disease (CKD) do not directly target both inflammatory and fibrotic processes needed to slow or halt the progression of disease. Asengeprast is a Phase II candidate drug for CKD that blocks G protein-coupled receptor 68 in animal models to reverse inflammatory and fibrotic pathways, thereby improving kidney function. These same pathways were shown to be dysregulated in human CKD, providing strong evidence that the therapeutic effects observed in pre-clinical models will translate to the clinic. Using a novel mechanism of action, asengeprast has the potential to significantly improve the lives of patients with CKD.

Metabolic dysfunction-associated kidney disease (MDAKD) is closely linked to dietary excess, but models that capture early kidney injury without obesity are limited. We fed male C57BL/6J (6J) and C57BL/6N (6N) mice a high-fat, high-sodium (HF/HNa) or control diet for 16 weeks. HF/HNa feeding did not alter body weight, adiposity, or total food intake; however, it increased dietary energy and sodium exposure, kidney mass, water intake, and urine volume. GFR declined modestly in 6J mice, whereas 6N mice maintained or slightly increased GFR. Both substrains showed increased urinary albumin, creatinine, KIM-1, and NGAL, while cystatin C rose predominantly in 6N mice, indicating strain-dependent tubular injury. Whole-kidney trichrome staining revealed increased fibrotic area with HF/HNa, particularly in 6N mice, without significant changes in glomerular morphology. In isolated renal mitochondria, oxygen consumption was preserved, but ATP production and ATP:O ratios were reduced, with unchanged citrate synthase activity and OXPHOS protein abundance, consistent with early mitochondrial bioenergetic uncoupling. Exploratory urinary proteomics in 6J mice identified HF/HNa-associated changes in proteins linked to tubular stress and extracellular matrix remodeling. These findings define an early MDAKD-like renal phenotype with strain-specific functional responses, tubular injury, fibrosis, and impaired mitochondrial ATP efficiency. Translational StatementMetabolic Dysfunction-Associated Kidney Disease (MDAKD) is a leading driver of chronic kidney disease (CKD) in the world. In addition to obesity and related comorbidities, renal mitochondrial dysfunction is thought to be a key contributor to the development of CKD in patients with MDAKD; however, few models recapitulate the progression of MDAKD. We couple well-established mouse models of obesity, namely the C57Bl/6J and C57Bl/6N mouse lines, with a high-fat, high-salt diet to induce renal mitochondrial dysfunction, leading to early stages of MDAKD as indicated by widespread fibrosis and mild reduction in glomerular filtration rate, though these effects were strain-dependent. We identify diet-induced mitochondrial dysfunction as a common feature in both mouse strains, suggesting impairments in mitochondrial respiration and oxidative ATP production are indeed a contributing factor to the development of MDAKD. This study highlights the role of energetic impairments in the pathogenesis of MDAKD and may guide future therapies for CKD.

We investigated the risks of post-acute and chronic adverse kidney outcomes of SARS-CoV-2 infection in the pediatric population via a retrospective cohort study using data from the RECOVER program. We included 1,864,637 children and adolescents under 21 from 19 childrens hospitals and health institutions in the US with at least six months of follow-up time between March 2020 and May 2023. We divided the patients into three strata: patients with pre-existing chronic kidney disease (CKD), patients with acute kidney injury (AKI) during the acute phase (within 28 days) of SARS-CoV-2 infection, and patients without pre-existing CKD or AKI. We defined a set of adverse kidney outcomes for each stratum and examined the outcomes within the post-acute and chronic phases after SARS-CoV-2 infection. In each stratum, compared with the non-infected group, patients with COVID-19 had a higher risk of adverse kidney outcomes. For patients without pre-existing CKD, there were increased risks of CKD stage 2+ (HR 1.20; 95% CI: 1.13-1.28) and CKD stage 3+ (HR 1.35; 95% CI: 1.15-1.59) during the post-acute phase (28 days to 365 days) after SARS-CoV-2 infection. Within the post-acute phase of SARS-CoV-2 infection, children and adolescents with pre-existing CKD and those who experienced AKI were at increased risk of progression to a composite outcome defined by at least 50% decline in estimated glomerular filtration rate (eGFR), eGFR <15 mL/min/1.73m2, End Stage Kidney Disease diagnosis, dialysis, or transplant. Lay abstractThis study examined the impact of COVID-19 on kidney health in children and adolescents under 21 years old in the United States. Using data from the RECOVER program, we analyzed the health records of 1,864,637 young individuals from 19 hospitals and health institutions between March 2020 and May 2023. The study focused on three groups: those with pre-existing chronic kidney disease (CKD), those who experienced acute kidney injury (AKI) during the initial COVID-19 infection, and those without any prior kidney issues. The results showed that children and adolescents who had COVID-19 were at a higher risk of developing serious kidney problems later on, even if they had no previous kidney conditions. This research highlights the long-term effects of COVID-19 on kidney health in young people and underscores the importance of monitoring kidney function in pediatric COVID-19 patients.

Chronic kidney disease is a highly prevalent condition that remains a major clinical and biomedical challenge. Tubulo-interstitial fibrosis is the common pathological substrate for many causes that lead to chronic kidney disease. It is characterized by profound derangements in metabolic and inflammatory responses, whereby functional tissue is replaced with extracellular matrix, leading to the suppression of renal function. Perturbations in the circadian rhythm have been associated with many human pathologies, including renal disease. However, the role of the molecular clock in the instauration of fibrosis remains incompletely understood. We investigated the relationship between the molecular clock and renal damage in experimental models of injury and fibrosis (UUO, FAN and adenine toxicity), employing genetically-modified mice with selective deficiencies of the clock components Bmal1, Clock and Cry. We found that UUO induced a marked increase in the expression of Bmal1. In human tubular epithelial cells, the pro-fibrotic mediator, TGF-{beta}, significantly altered the expression of core clock components. We further observed that the absence of Cry drastically aggravated kidney fibrosis, while both Cry and Clock played a role in the neutrophil and macrophage mediated inflammatory response, respectively. Suppression of Cry1/2 was associated with a major shift in the expression of metabolism-related genes, underscoring the importance of metabolic dysfunction in fibrosis. These results support a reciprocal interaction between the circadian clock and the response to kidney injury. Translational statementChronic kidney disease (CKD) is a highly prevalent clinical syndrome that still poses major clinical challenges. Kidney fibrosis underlies many cases of CKD and therapies against it are of very limited efficacy. Alterations in circadian rhythms (CR) are relevant in patients with CKD, but very little is known about the relationship between CKD and CR. Our study shows that disruption of the molecular clock can impact kidney inflammation and fibrosis and that, reciprocally, kidney fibrosis can alter the expression of clock components. A better understanding of this crosstalk could open new therapeutic avenues for the prevention and treatment of CR-related CKD.

BackgroundChronic kidney disease (CKD) represents a leading non-communicable disease, significantly contributing to global morbidity and mortality. Mendelian randomization studies (MR) have been integral in providing robust evidence that increased body mass index (BMI) has a causal impact on CKD. However, dissecting which specific mechanisms are primarily responsible for disease development remains challenging. ObjectiveTo explore whether the effects of BMI to kidney function are driven primarily by brain-or adipose-tissue derived gene expression using tissue-partitioned Mendelian randomization (MR). MethodsWe employ two-sample univariable and multivariable MR methodology that segregates genetic variants associated with BMI based on colocalization with gene expression in either brain or subcutaneous adipose tissue. We utilize sets of adipose and brain expression quantitative trait loci (eQTLs) that demonstrated colocalization with BMI (86 and 140 loci respectively). We also use GWAS summary statistics of creatinine and cystatin C based eGFR (eGFRcrea and eGFRcys; N=460,826), blood urea nitrogen (BUN; N = 852,678), eGFR decline (N= 34,874 cases) and CKD (defined as eGFRcrea <60=ml=min-1 per 1.73=m2; N= 41,395) of European ancestry. ResultsUnivariable MR showed consistent positive associations between BMI and CKD (OR = 1.24, 95% CI: 1.2-1.3) and inverse associations with eGFRcys (beta = -0.05, 95% CI: -0.06 to -0.046). Both brain-and adipose-instrumented BMI showed similar effect sizes. However, in multivariable MR, neither brain-nor adipose-specific BMI variants showed clear independent effects on CKD (ORadipose= 1.24, 95% CIadipose= 0.87 to 1.65, ORbrain= 1.18, 95%CIbrain = 0.9 to 1.54) or other kidney function traits. ConclusionsWhile genetically predicted BMI was associated with kidney function, our tissue-partitioned MR analysis found no strong evidence that brain or subcutaneous adipose tissue derived gene expression independently drive this relationship. This suggests overlapping or additive mechanisms through which BMI influences kidney function.

Background: Patients with kidney failure undergoing maintenance hemodialysis suffer high rates of major adverse cardiovascular events(MACE) that are not accurately predicted by traditional cardiovascular risk models. There is an urgent need to identify novel, modifiable cardiovascular risk factors for these patients. Methods: We analyzed associations of 6287 circulating proteins with MACE among 1048 participants undergoing hemodialysis in the Chronic Renal Insufficiency Cohort(CRIC) (14-year follow-up) with validation in the Predictors of Arrhythmic and Cardiovascular Risk in End-Stage Renal Disease study(PACE) (7-year follow-up). In both cohorts, proteins were measured shortly after dialysis initiation and one year later. We compared protein-based risk models derived by elastic net regression to the Pooled Cohort Equations(PCE) optimized for these cohorts(Refit PCE), and to an Expanded Refit PCE that included Troponin T and N-terminal pro-B-type natriuretic peptide. Results: In CRIC, 149 proteins were associated with MACE at false discovery rate<0.05. Among 22 proteins significant at Bonferroni p<8x10-6, proteins that validated in PACE included Sushi von Willebrand factor type A EGF and pentraxin domain-containing protein 1(SVEP1), Complement component C7, R-spondin 4, Tenascin, Fibulin-3 and Fibulin-5. Complement pathways were prominent in network analyses. SVEP1 surpassed other markers by statistical significance, with CRIC HR per log2 1.8 (p=2.1x10-12) and HR per annual doubling 1.6 (p=6.8x10-6). For 2-year MACE, AUC(95%CI) for SVEP1 alone was 0.72(0.59, 0.84) in CRIC, and 0.73(0.63, 0.81) in PACE. SVEP1 surpassed the Expanded Refit PCE in CRIC (0.61 (0.48, 0.73)) (p=0.038). In the pooled CRIC + PACE cohort, SVEP1 AUC(95%CI) (0.79(0.70, 0.88)) surpassed Refit PCE (0.61(0.51, 0.72)) (p=0.004). Conclusions: SVEP1, a 390 kDa protein unlikely to be renally cleared, surpassed over 6000 other proteins and by itself outperformed traditional clinical risk models in predicting MACE in two populations of patients undergoing maintenance hemodialysis. Future studies should provide mechanistic insights behind these findings.

BackgroundCystic fibrosis (CF) is a chronic multisystem disease with features including recurrent pulmonary infection, bronchiectasis, malnutrition, and alterations in drug metabolism which may discourage referral and listing for kidney transplantation. Although no specific renal phenotype is identified in CF, chronic kidney disease (CKD) occurs in young people and adults with CF with greater frequency than in the general population. The characteristics and outcomes of kidney transplantation in the CF population have not been previously described. MethodsWe used de-identified data supplied by the US Renal Data System (USRDS) to compare persons with end stage kidney disease (ESKD) with first kidney transplant, who did and did not have a diagnosis of CF. We compared demographic and clinical characteristics, mortality, patient survival, and death-censored graft survival using linear and logistic regression, multivariable logistic regression models, and Kaplan-Meier and log-rank tests with stratification/binning by propensity scores. ResultsOf those with dual diagnoses of CF and ESKD, half received a first kidney transplant. CF was independently associated with higher odds of receiving a living donor transplant. Those with a kidney transplant were younger than both those who did not have CF and those with CF without transplant and had higher odds of being female. Those with dual diagnoses of CF and ESKD had disproportionately lower odds of being identified as Black or African American relative to their representation in the population of all with CF and ESKD. Diabetes was more frequently a diagnosis and primary cause of ESKD in people with CF, but was approximately half as frequently the primary cause of ESKD as in those without CF. Complications of transplantation, particularly lung, were the second most frequent etiology of ESKD in people with CF. Overall survival with ESKD was 21.1 years for those with CF and 31.8 for those without CF. The survival benefit associated with transplant was 17.2 years for those with CF and 24.8 years for those without CF. Death censored median graft survival was significantly longer for those with CF, 20.4 vs 13.7 years. ConclusionsCF is a chronic multisystem disease with features which may discourage referral and listing for kidney transplant. We used de-identified data from the USRDS datasets to describe the characteristics and outcomes of all unique individuals with the diagnosis of CF and first kidney transplant prevalent during the five-year period 2014 and 2018. Those with CF had similar odds to those without CF or receiving a first kidney transplant, and higher odds of receiving a living donor graft. Diabetes mellitus was significantly less frequently the primary cause of ESKD in those with CF and kidney transplant. Complications of solid organ transplant, particularly lung, were the second most frequent cause of ESKD in people with CF and kidney transplant. Median patient survival following the first kidney transplant was significantly shorter than for those who did not have CF, but was substantial, as was the survival advantage when compared to dialysis. Median graft survival was significantly longer for those with CF. It is our hope that this data will improve awareness of kidney disease in persons living with CF and their care teams, and encourage early referral to nephrology and transplant centers, and positive consideration of wait listing for kidney transplantation.

A variety of genetic diseases of the kidney tubule are amenable to correction via gene therapy. However, gene delivery to renal tubule epithelial cells mediated by viral vectors via the blood is inefficient due to the permselectivity of the glomerular barrier. We hypothesized that effacement of podocyte foot processes would disrupt typical glomerular limitations on filtration and make renal tubule epithelial cells susceptible to transduction from viral vectors delivered intravenously. We determined that adeno-associated virus serotype 8 (AAV8) transduced significantly more epithelial cells in the kidney under the conditions of LPS-induced proteinuria. Use of AAV1 in tandem with LPS-induced proteinuria yielded an ideal two-pronged effect of both partially detargeting the liver and transducing the kidney with a higher bioluminescent signal than AAV8 did, and at half of the dose. Using adenovirus serotype 5 (Ad5) in conjunction with LPS-induced proteinuria showed that kidney transduction was enhanced, but only in glomerular cells. These studies mechanistically test the efficacy of different viral vectors and demonstrate their capacity to transduce kidney epithelial cells. This is a fundamental step in designing future treatments for kidney gene therapy. Significance StatementThe slit diaphragms in the glomerulus of the kidney are too narrow to allow most solute from the blood to enter the nephron. As a result, large particles such as viral vectors generally cannot access tubule epithelial cells necessary to correct genetic disorders. In this study, mice are induced into a state of proteinuria and subsequently administered viral vectors intravenously. This group of mice had higher levels of transduced kidney epithelial cells than the control (non-proteinuria) group. The induction of transient proteinuria before intravenous viral vector administration is a novel approach that could make tubulopathies treatable via gene therapy in both animal models and humans.

BackgroundLymphatic abnormalities are observed in several types of kidney disease, but the relationship between the renal lymphatic system and renal function is unclear. The discovery of lymphatic-specific proteins, advances in microscopy, and available genetic mouse models provide the tools to help elucidate the role of renal lymphatics in physiology and disease. MethodsWe utilized a mouse model containing a missense mutation in Vegfr3 (dubbed Chy) that abrogates its kinase ability. Vegfr3Chy/+ mice were examined for developmental abnormalities and kidney-specific outcomes. Control and Vegfr3Chy/+ mice were subjected to cisplatin-mediated injury. We characterized renal lymphatics using a combination of tissue clearing, light-sheet microscopy and computational analyses. ResultsIn the kidney, we found Vegfr3 is expressed not only in lymphatic vessels, but also various blood vessels. Vegfr3Chy/+ mice had severely reduced renal lymphatics with 100% penetrance, but we found no abnormalities in blood pressure, renal function and histology. Similarly, there was no difference in the degree of renal injury after cisplatin, although Vegfr3Chy/+ mice developed more perivascular inflammation by histology. Control mice treated with cisplatin had a measurable increase in cortical lymphatic density despite no change in cortical lymphatic volume and length. ConclusionsWe demonstrate that Vegfr3 is required for development of renal lymphatics, but a reduction in lymphatic density does not alter renal function and induces only modest histological changes after injury. Our data suggests that an increase in lymphatic density after cisplatin injury may reflect the loss of cortical volume associated with chronic kidney disease rather than growth of lymphatic vessels. SIGNIFICANCE STATEMENTDefects in renal lymphatics occur in various kidney diseases, but their role in maintaining kidney structure and function is unknown. We combine tissue clearing, light-sheet microscopy and computational analysis to characterize lymphatics and find that mice with a heterozygous mutation in Vegfr3 (Vegfr3Chy/+) have severely reduced renal lymphatics. Strikingly, these mice have indistinguishable renal function and histology compared with controls. Even after cisplatin injury, there are no differences in renal function, although Vegfr3Chy/+ mice developed more perivascular inflammation. Our data present a novel method of lymphatic quantification and suggest that a normal complement of renal lymphatics is dispensable for renal structure and function.

BackgroundDietary fiber is important for a healthy diet, but intake is low in CKD patients and the impact this has on the manifestations of CKD-Mineral Bone Disorder (MBD) is unknown. MethodsThe Cy/+ rat with progressive CKD was fed a casein-based diet of 0.7% phosphate with 10% inulin (fermentable fiber) or cellulose (non-fermentable fiber) from 22 weeks to either 30 or 32 weeks of age (~30 and ~15 % of normal kidney function). We assessed CKD-MBD, cecal microbiota, and serum gut-derived uremic toxins. Two-way ANOVA was used to evaluate the effect of age and inulin diet, and their interaction. ResultsIn CKD animals, dietary inulin led to changes in microbiota alpha and beta diversity at 30 and 32 weeks, with higher relative abundance of several taxa, including Bifidobacterium and Bacteroides, and lower Lactobacillus. Inulin reduced serum levels of gut-derived uremic toxins, phosphate, and parathyroid hormone, but not fibroblast growth factor-23. Dietary inulin decreased aorta and cardiac calcification and reduced left ventricular mass index and cardiac fibrosis. Bone turnover and cortical bone parameters were improved with inulin; however, bone mechanical properties were not altered. ConclusionsThe addition of the fermentable fiber inulin to the diet of CKD rats led to changes in the gut microbiota composition, lowered gut-derived uremic toxins, and improved most parameters of CKD-MBD. Future studies should assess this fiber as an additive therapy to other pharmacologic and diet interventions in CKD. Significance StatementDietary fiber has well established beneficial health effects. However, the impact of fermentable dietary fiber on the intestinal microbiome and CKD-MBD is poorly understood. We used an animal model of progressive CKD and demonstrated that the addition of 10% of the fermentable fiber inulin to the diet altered the intestinal microbiota and lowered circulating gut-derived uremic toxins, phosphorus, and parathyroid hormone. These changes were associated with improved cortical bone parameters, lower vascular calcification, and reduced cardiac hypertrophy, fibrosis and calcification. Taken together, dietary fermentable fiber may be a novel additive intervention to traditional therapies of CKD-MBD.

Patients with End Stage Kidney Disease requiring dialysis are exceedingly vulnerable to SARS-CoV-2 infection with high hospitalization rates and mortality. Despite this risk, little is known about real world dialysis patient SARS-CoV-2 vaccination acceptance. Surveys of the general population suggest significant vaccine hesitancy and high potential for refusal. From January 27th to March 12th 2021, the University of Virginia (UVA) Health System, in partnership with the Virginia Department of Health / Blue Ridge Health District (BRHD) provided on-site mobile vaccination clinics at 12 UVA dialysis sites. We conducted a cross-sectional study to evaluate vaccine acceptance and evaluate factors associated with refusal. Of 859 dialysis patients with complete vaccination data, 80% received at least one dose of vaccine and 87% of these vaccinations were provided by the UVA/BRHD partnership. The overall patient refusal rate was low at 14%. Patients refusing SARS-CoV-2 vaccine were more likely to be female, younger and missing a documented flu vaccination during the 2020-2021 season. Attributes such as race or prior infection with SARS-CoV-2 were not significantly associated with vaccine refusal. In conclusion, dialysis patients in our program were surprisingly likely to accept vaccination for SARS-CoV-2. Identifying attributes associated with refusal may help target populations at high risk of vaccine refusal.

Background and ObjectiveChronic kidney disease (CKD) is associated with loss of muscle quality leading to mobility limitation and decreased independence. Identifying predictors of gait speed decline may help target rehabilitative therapies to those at highest risk of mobility impairment. Design, setting and participants, and measurementsThe current prospective cohort study recruited ambulatory patients with stage 1-4 CKD (eGFR 15-89 ml/min/1.73m2) from nephrology clinics. Predictors included demographic and clinical variables including GFR estimated using serum cystatin C. Outcomes were average change in gait speed (m/s) per year and inclusion in the top tertile of gait speed decline over 3 years. Linear mixed models and relative risk regression were used to estimate associations with annual gait speed changes and fastest tertile of decline. ResultsAmong 213 participants, 81% were male, 22% were black and 43% had diabetes. Mean age was 57{+/-}13 years, median follow-up 3.15 years, mean baseline eGFRcysc 47.9{+/-}21ml/min/1.73 m2, and median baseline gait speed 0.95m/s [IQR 0.81, 1.10]. Lower baseline eGFRcysc was associated with more rapid loss of gait speed (-0.029 m/s/year [95% CI -0.042, -0.015] per 30 ml/min/1.73 m2 lower eGFR; p<0.001). Diabetes was associated with -0.024m/s/year faster change (95% CI -0.042, -0.007; p=.007). Lower eGFRcysc was associated with a 49% greater risk of rapid gait speed decline (IRR 1.49; 95% CI 1.11, 2.00, p=.008) after adjustment. Prevalent cardiovascular disease and African American race were associated with a 45% greater (IRR 1.45; 95% CI 1.04, 2.01, p=.03) and 58% greater rate of rapid gait speed decline (IRR 1.58; 95% CI 1.09, 2.29, p=.02), respectively. ConclusionsAmong ambulatory, disability-free patients with CKD, lower eGFRcysc and diabetes status were associated with faster gait speed decline. Lower eGFRcysc, cardiovascular disease, and African American race were associated with rapid gait speed decline.

BackgroundDysregulation of phosphate homeostasis contributes to reduced longevity and vascular complications in chronic kidney disease and aging. This study investigates the role of TMEM174, a proximal tubule-specific protein, in regulating the phosphate co-transporter NPT2A and its subsequent impact on lifespan and vascular health. MethodsTMEM174 knockout (KO) mice (C57BL6/J and DBA/2J) were fed diets with varying phosphate concentrations (0.6% vs. 1.2%). In OKP cells, TIRF and FRET microscopy, alongside immunoprecipitation, were used to identify the TMEM174 protein regions essential for NPT2A binding and endocytosis. ResultsTMEM174 KO mice exhibited significantly shorter lifespans than wild-type controls. High phosphate diets exacerbated vascular calcification, stiffness, and mortality, while low phosphate diets rescued these phenotypes. In vitro, TMEM174 siRNA blocked PTH-induced NPT2A endocytosis, increasing its apical membrane retention. FRET and biochemical assays revealed that the C-terminal region of TMEM174 is essential for its association with NPT2A. While intact TMEM174 and N-terminal mutants (TMEM174{Delta}N) facilitated NPT2A degradation, C-terminal deletions (TMEM174{Delta}C) failed to associate with or degrade NPT2A. ConclusionsTMEM174 is a critical regulator of phosphate homeostasis and longevity. The C-terminal region of TMEM174 is specifically required for NPT2A endocytosis and degradation, identifying it as a potential therapeutic target for managing phosphate-related vascular complications.

Arteriolar hyalinosis in kidneys is an independent predictor of cardiovascular disease, the main cause of mortality in chronic kidney disease (CKD). The underlying molecular mechanisms of protein accumulation in the subendothelial space are not well understood. Using single cell transcriptomic data and whole slide images from kidney biopsies of patients with CKD and acute kidney injury in the Kidney Precision Medicine Project, the molecular signals associated with arteriolar hyalinosis were evaluated. Co-expression network analysis of the endothelial genes yielded three gene set modules as significantly associated with arteriolar hyalinosis. Pathway analysis of these modules showed enrichment of transforming growth factor beta / bone morphogenetic protein (TGF{beta} / BMP) and vascular endothelial growth factor (VEGF) signaling pathways in the endothelial cell signatures. Ligand-receptor analysis identified multiple integrins and cell adhesion receptors as over-expressed in arteriolar hyalinosis, suggesting a potential role of integrin-mediated TGF{beta} signaling. Further analysis of arteriolar hyalinosis associated endothelial module genes identified focal segmental glomerular sclerosis as an enriched term. On validation in gene expression profiles from the Nephrotic Syndrome Study Network cohort, one of the three modules was significantly associated with the composite endpoint (> 40% reduction in estimated glomerular filtration rate (eGFR) or kidney failure) independent of age, sex, race, and baseline eGFR, suggesting poor prognosis with elevated expression of genes in this module. Thus, integration of structural and single cell molecular features yielded biologically relevant gene sets, signaling pathways and ligand-receptor interactions, underlying arteriolar hyalinosis and putative targets for therapeutic intervention.

BackgroundParathyroid Ca2+-sensing receptor (CaSR) activation inhibits parathyroid hormone (PTH) release, while activation of CaSRs in kidneys and intestine attenuates local transepithelial Ca2+ transport. In patients with autosomal dominant hypocalcemia 1 (ADH1) due to activating CASR mutations, treatment of symptomatic hypocalcemia can be complicated by treatment-induced hypercalciuria, resulting in nephrocalcinosis and renal insufficiency. Although CaSRs throughout the body are activated by increased extracellular Ca2+ concentrations, it is not understood why some ADH1 patients have reduced PTH, but not hypercalciuria at presentation, despite CaSR expression in both kidney and parathyroid. MethodsActivation of the CaSR was studied in mouse models and a ADH1 patient. In vitro CaSR activation was studied in HEK293 cells. ResultsMice with a gain-of-function mutation in Casr are hypocalcemic with reduced plasma PTH levels. However, renal CaSRs are not activated as indicated by normal urinary calcium handling and unaltered renal Cldn14 expression. Activation of renal CaSRs only occurred after increasing plasma Ca2+ levels. Similarly, calcimimetic administration to wildtype mice induced hypocalcemia without activating renal CaSRs. Moreover, significant hypercalciuria was not observed in an ADH1 patient until blood Ca2+ was normalized. In vitro experiments suggest that increased CaSR levels in the parathyroid relative to the kidney contribute tissue-specific CaSR activation thresholds. ConclusionHere we delineate tissue-specific CaSR activation thresholds, where parathyroid CaSR overactivity can reduce plasma Ca2+ to levels insufficient to activate renal CaSRs, even with overactivating mutations. These findings may aid in the management of ADH1 patients.

BackgroundSodium-glucose cotransporter-2 inhibitors (SGLT2is) have been associated with lower risk of acute kidney injury (AKI), but existing studies rarely explore heterogeneous treatment effects or underlying causal pathways. We applied a comprehensive causal-learning framework to evaluate both overall and subgroup-specific effects of SGLT2i therapy on AKI. MethodsUsing a new-user, active-comparator target trial emulation in the OneFlorida+ data (2014-2023), we estimated individualized and average treatment effects with a doubly robust meta-learner, assessed heterogeneity via subgroup and decision-tree analyses, and used causal structure learning and mediation methods to identify mechanistic pathways linking treatment to AKI. ResultsSGLT2 inhibitors were associated with a significant reduction in AKI compared with other second-line glucose-lowering drugs, with an average individual treatment effect of -0.0039 (95% CI: -0.0065 to -0.0014). Kaplan-Meier curves demonstrated consistently lower cumulative AKI incidence among SGLT2i users. Subgroup analyses revealed substantial heterogeneity: protective effects were strongest in younger adults, males, and non-Hispanic Black patients, whereas benefits were attenuated in older adults, females, and those with baseline CKD. Decision tree-based heterogeneity modeling further identified atrial fibrillation, anemia, and antiparkinson agent use as key effect modifiers. Causal structure learning highlighted atrial fibrillation, anemia, chronic kidney disease, and eGFR as central intermediating nodes. Mediation analyses showed that most of the benefit operated through direct pathways (ADE {approx} -0.0034 to -0.0035), while anemia and heart failure contributed small but statistically significant indirect effects. ConclusionSGLT2 inhibitors reduce AKI risk, but effects vary meaningfully across clinical subgroups and are partially mediated through interconnected cardio-renal pathways. Causal-learning methods provide mechanistic insight beyond average associations and may support more individualized SGLT2i therapy for AKI prevention.

Genome-wide association studies (GWAS) have revealed numerous loci for kidney function (estimated glomerular filtration rate, eGFR). The relationship of polygenic predictors of eGFR, risk of incident adverse kidney outcomes, and the plasma proteome is not known. We developed a genome-wide polygenic risk score (PRS) using a weighted average of 1.2 million SNPs for eGFR using the LDpred algorithm, summary statistics generated by a European-ancestry (EA) meta-analysis of the CKDGen Consortium (N=558,423) and UK Biobank GWAS for eGFR (90% of the cohort; N=289,432), followed by best parameter selection using data from the remaining 10% of the UK Biobank (N=32,159). We then tested the association of the PRS among 8,886 EA participants in the Atherosclerosis Risk in Communities (ARIC) study (mean age: 54{+/-}6 years, 53% female) with incident chronic kidney disease (CKD), end stage kidney disease (ESKD), kidney failure (KF), and acute kidney injury (AKI). We also examined 4,877 plasma proteins measured at two time points (visit 3 (1993-95) and visit 5 (2011-13)) in relation to the PRS and compared associations between the proteome and eGFR itself. All models were adjusted for age, sex, center, and the first 10 principal components of ancestry. The developed PRS had an R2 for eGFR of 0.07 in ARIC. Over 30 years of follow up, the number of incident CKD, ESKD, KF, and AKI were 2,959, 137, 470, and 1,723, respectively. The PRS showed significant associations with all outcomes: hazard ratios (95% CI) per 1 SD lower PRS were 1.33 (1.28, 1.39), 1.20 (1.00, 1.42), 1.17 (1.06, 1.28), and 1.07 (1.02, 1.12) for incident CKD, ESKD, KF, and AKI respectively. The PRS was significantly associated (Bonferroni threshold P<1.02 x 10-5) with 108 proteins at both time points. The strongest associations were with cystatin-C (a marker of kidney function used in clinical practice), collagen alpha-1 (XV) chain, and desmocollin-2. All significant correlations with the PRS were negative, except those of testican-2 and angiostatin. Correlations of proteins with eGFR were much stronger than those with the PRS. Overall, we demonstrated that the PRS for eGFR is now sufficiently strong to capture risk for a spectrum of incident kidney diseases as well as broadly influence the plasma proteome.

BackgroundTransient receptor potential channel 5 (TRPC5) is a non-selective cationic ion channel expressed in brain, kidney and other organs where its activation underlies podocyte injury in chronic kidney diseases. Specifically, it has been suggested that a podocyte TRPC5 plasma membrane relocation and channel activation following injury results from activation of Rac-1, propagating podocyte dysfunction and proteinuria. However, previous TRPC5 transgenic mouse studies had questioned a pathogenic role for TRPC5 in podocytes. This investigation was designed to specifically evaluate podocyte Rac-1 activation in the context of functional TRPC5 or a TRPC5 pore mutant to assess effects on proteinuria. Materials and MethodsWe employed single cell patch-clamp studies of cultured podocytes and studied proteinuria in transgenic mouse models to characterize the effects of TRPC5 following podocyte Rac-1 activation. ResultsInhibition of TRPC5 by small molecules reportedly ameliorated proteinuria in murine models of proteinuric kidney diseases. In order to directly examine TRPC5 function following Rac-1-induced podocyte injury, we analyzed TRPC5 inhibition in podocyte specific Rac-1 (active) transgenic mice. In addition, we generated a double-transgenic mouse constitutively overexpressing either TRPC5 (TRPC5WT) or a TRPC5 dominant-negative pore mutant (TRPC5DN) in concert with podocyte specific and inducible activation of active Rac-1 (Rac-1Dtg). In electrophysiological experiments, active TRPC5 was detected in primary podocytes overexpressing TRPC5 but not in podocytes with endogenous TRPC5 expression, nor with Rac-1 overexpressing podocytes. TRPC5 inhibition did not change proteinuria in mice with active podocyte Rac-1, nor did an increase or loss of TRPC5 activity affected podocyte injury in Rac-1Dtg animals. Administration of TRPC5 inhibitors, ML204 and AC1903, did not alleviate podocyte Rac-1 induced proteinuria. ConclusionTRPC5 inhibition did not modify podocyte Rac-1 induced proteinuria in mice. Significance StatementTRPC5 is a calcium conducting ion channel involved in a plethora of biological functions in the brain, kidney and other organs. In proteinuric kidney diseases, others proposed a model that links activation of small GTPase Rac-1 in podocytes to activation of TRPC5 channels propagating cellular injury and eventually leading to progressive kidney disease. To test this hypothesis, we have developed a novel transgenic mouse model that employs podocyte Rac-1 activation in the presence or absence of a functional TRPC5 channel. Our data shows that transgenic mice with activated Rac-1 in podocytes did not enhance endogenous TRPC5 expression or its activity. Furthermore, TRPC5 blockade or activation did not modify Rac-1 induced proteinuria in mice.