A multi-trait GWAS identifies novel genes influencing albuminuria.

BACKGROUND: Albuminuria is common and associated with increased risks of end-stage kidney disease and cardiovascular diseases, yet its underlying mechanism remains obscure. Previous genome-wide association studies (GWAS) for albuminuria did not consider gene pleiotropy and primarily focused on European ancestry populations. This study adopted a multi-trait analysis of GWAS (MTAG) approach to jointly analyze two vital kidney traits, estimated glomerular filtration rate (eGFR) and urine albumin-to-creatinine ratio (UACR) to identify and prioritize the genes associated with UACR. METHODS: Data from the Taiwan Biobank from 2012 to 2023 were analyzed. GWAS of UACR and eGFR were performed separately and the summary statistics from these GWAS were jointly analyzed using MTAG. The polygenic risk scores (PRS) of UACR were constructed for validation. The UACR-associated loci were further fine-mapped and prioritized based on their deleteriousness, eQTL associations, and relatedness to Mendelian kidney diseases. RESULTS: MTAG analysis of the UACR revealed 15 genetic loci, including 12 novel loci. The PRS for UACR was significantly associated with urinary albumin level (P < 0.001) and microalbuminuria (P = 0.001 ∼ 0.045). A list of priority genes was generated. Twelve genes with high priority included the albumin endocytic receptor gene LRP2 and ciliary genes  IFT172. CONCLUSIONS: The findings of this multi-trait GWAS suggest that primary cilia play a role in sensing mechanical stimuli, leading to albumin endocytosis. The priority list of genes warrants further translational investigation to reduce albuminuria.

Clinical implications of frailty in peritoneal dialysis patients - A prospective observational study.

BACKGROUND: Frailty is an age-related condition that predicts adverse outcomes. The study was aimed to investigate the clinical implications of frailty evolution in patients undergoing peritoneal dialysis (PD). METHOD: In this prospective study, all new-onset (<6 months) and prevalent (≧6 months) PD patients completed frailty assessment at entry and 6 months by a semiautomated frailty index of 80 risk factors (FI80) which also contained the 5 components of Fried frailty phenotype. A score ≧13/80 (FI80 > 0.16) or ≧3/5 (frailty phenotype) was designated to define frailty. RESULT: 337 PD patients were recruited (new-onset 23.4%, prevalent 76.6%). Two hundred (59.3%) and 163 (48.4%) patients were frail by FI80 and frailty phenotype, respectively. Predictors for frailty were old age, dialysis, diabetes mellitus, gout and sleep disorder. New-onset patients aged <55 years displayed the best evolution of frailty over 6 months (stable or improved, n = 29/47, 61.7% by FI80, p = 0.0293), compared with other groups. Survival analysis found that frail patients exhibited the worse outcomes (overall death and hospitalization). Poisson regression showed frailty was associated with increased utilizations of outpatient and ER services; however multivariate Cox models identified only diabetes, gout and low body mass index (<19 kg/m2), but not frailty, predicted overall death and hospitalizations. CONCLUSION: Frailty is a common medical condition in PD patients, and the status of which can be stabilized or improved in new-onset, young patients at least over the short term. Compared with frailty, certain comorbidities (diabetes and gout) and undernutrition appeared to be more robust in the prediction of adverse outcomes.

Prospective Impacts of Social Participation Activities on Cognitive and Psychopathological Statuses in Community-Dwelling Older Adults.

OBJECTIVES: This study investigated the impact of social activities on cognitive functioning and psychopathological symptoms. METHODS: Participants aged 55 or older were enrolled through communities. Initial measures assessed demographic data, neuropsychological functioning, psychopathological state, and happiness. Social activities were evaluated using a modified 12-item tool, with 3-4 activities as the cutoff. Follow-up after 6-9 months included Mini-Mental State Examination (MMSE), Beck Depression Inventory - II (BDI-II), Beck Anxiety Inventory (BAI), Health Assessment Questionnaire (HAQ), and Patient Health Questionnaire-15 (PHQ-15) measurements. Predictive models for psychiatric and cognitive statuses were built using multiple linear regression, adjusting for baseline conditions. RESULTS: Initially, 516 older individuals enrolled, with 403 undergoing follow-up. During follow-up, the low participation group reported lower MMSE scores, higher BAI scores, and increased PHQ-15 risk. Negative correlations between social activity numbers and PHQ-15 results were found. Engagement in social clubs correlated positively with higher MMSE scores, while regular interactions with one's adult child(ren) were linked to decreased BAI scores. CONCLUSIONS: The quantity of social activities was associated with lower somatic distress. Social club engagement positively influenced cognition, and regular interactions with one's adult child(ren) mitigated anxiety among older individuals. CLINICAL IMPLICATIONS: Enough types of social activities, participating in social clubs, and adequate interactions with children protected against psychopathologies.

Effect of isotemporal substitution of sedentary behavior with different intensities of physical activity on the muscle function of older adults in the context of a medical center.

BACKGROUND: Engaging in physical activity and reducing sedentary time in daily life may enable older individuals to maintain muscle mass. This study aimed to investigate the effects of replacing sedentary behavior with light physical activity (LPA) or moderate-to-vigorous physical activity (MVPA) on the muscle function of older adults at a medical center in Taiwan. METHODS: We recruited 141 older adults (51.1% men; 81.1 ± 6.9 years old) and asked them to wear a triaxial accelerometer on the waist to measure their sedentary behavior and physical activity. Functional performance was assessed based on handgrip strength, Timed Up and Go (TUG) test, gait speed, and five-times-sit-to-stand test (5XSST). Isotemporal substitution analysis was performed to examine the effect of substituting 60 min of sedentary time with 60 min of LPA, MVPA, and combined LPA and MVPA in different proportions. RESULTS: Reallocating 60 min of sedentary behavior per day to LPA was associated with better handgrip strength (Beta [B] = 1.587, 95% confidence interval [CI] = 0.706, 2.468), TUG test findings (B = -1.415, 95% CI = -2.186, -0.643), and gait speed (B = 0.042, 95% CI = 0.007, 0.078). Reallocating 60 min of sedentary behavior per day to MVPA was associated with better gait speed (B = 0.105, 95% CI = 0.018, 0.193) and 5XSST findings (B = -0.060, 95% CI = -0.117, -0.003). In addition, each 5-min increment in MVPA in the total physical activity replacing 60 min of sedentary behavior per day resulted in greater gait speed. Replacing 60 min of sedentary behavior with 30-min of LPA and 30-min of MVPA per day significantly decreased the 5XSST test time. CONCLUSION: Our study indicates that introducing LPA and a combination of LPA and MVPA to specifically replace sedentary behavior may help maintain muscle function in older adults.

Prediction of adverse health outcomes using an electronic frailty index among nonfrail and prefrail community elders.

BACKGROUND: Early recognition of older people at risk of undesirable clinical outcomes is vital in preventing future disabling conditions. Here, we report the prognostic performance of an electronic frailty index (eFI) in comparison with traditional tools among nonfrail and prefrail community-dwelling older adults. The study is to investigate the predictive utility of a deficit-accumulation eFI in community elders without overt frailty. METHODS: Participants aged 65-80 years with a Clinical Frailty Scale of 1-3 points were recruited and followed for 2 years. The eFI score and Fried's frailty scale were determined by using a semiautomated platform of self-reported questionnaires and objective measurements which yielded cumulative deficits and physical phenotypes from 80 items of risk variables. Kaplan-Meier method and Cox proportional hazards regression were used to analyze the severity of frailty in relation to adverse outcomes of falls, emergency room (ER) visits and hospitalizations during 2 years' follow-up. RESULTS: A total of 427 older adults were evaluated and dichotomized by the median FI score. Two hundred and sixty (60.9%) and 167 (39.1%) elders were stratified into the low- (eFI ≤ 0.075) and the high-risk (eFI > 0.075) groups, respectively. During the follow-up, 77 (47.0%) individuals developed adverse events in the high-risk group, compared with 79 (30.5%) in the low-risk group (x2, p = 0.0006). In multivariable models adjusted for age and sex, the increased risk of all three events combined in the high- vs. low-risk group remained significant (adjusted hazard ratio (aHR) = 3.08, 95% confidence interval (CI): 1.87-5.07). For individual adverse event, the aHRs were 2.20 (CI: 1.44-3.36) for falls; 1.67 (CI: 1.03-2.70) for ER visits; and 2.84 (CI: 1.73-4.67) for hospitalizations. Compared with the traditional tools, the eFI stratification (high- vs. low-risk) showed better predictive performance than either CFS rating (managing well vs. fit to very fit; not discriminative in hospitalizations) or Fried's scale (prefrail to frail vs. nonfrail; not discriminative in ER visits). CONCLUSION: The eFI system is a useful frailty tool which effectively predicts the risk of adverse healthcare outcomes in nonfrail and/or prefrail older adults over a period of 2 years.

Muscle strength in ostensibly healthy non-diabetic subjects.

BACKGROUND/PURPOSE: Sarcopenia and decreased muscle strength (dynapenia) are emerging health issues. However, the study exploring muscle strength changes of both upper and lower limbs at the same time among all age groups is rare. This study aims to investigate the muscle strength and to establish a muscle strength norm of an ostensibly healthy non-diabetic Asian population. METHODS: From 2018 June to 2020 March, subjects (aged from 20 to <80 years old) undergoing health checkup in Good Liver Medical Examination Center and National Taiwan University Hospital Geriatrics and Gerontology Department were enrolled. A battery of muscle power examinations including handgrip strength (HGS), five times sit-to-stand test (5TSTS), and one-leg standing test (OLST) were performed. RESULTS: A total of 183 participants was enrolled, consisting of 92 females and 91 males. The finding shows the strongest HGS, best 5TSTS, and the longest OLST of both genders appeared in the 20-29-year-old group. Age, gender, and palm length are significantly related to HGS, whereas age is the only factor affecting 5TSTS and OLST. It revealed a progressive decline during ageing process, especially after age 60. Finally, Z-score and T-score norms of these were established. CONCLUSION: These data will be useful as normal controls for muscle strength of specific disease groups. The application of the cutoffs from these data and their comparisons with the recommended cutoffs from various guidelines worth further exploration.

A competing risk predictive model for kidney failure in patients with advanced chronic kidney disease.

BACKGROUND/PURPOSE: Predictive modeling aids in identifying patients at high risk of adverse events. Using routinely collected data, we report a competing risk prediction model for kidney failure. METHODS: A total of 5138 patients with CKD stages 3b-5 were included and randomized into the development and validation cohorts at a ratio of 7:3. The outcome was end-stage kidney disease, defined as the initiation of dialysis or kidney transplantation. All patients were followed-up until December 31, 2020. A Fine and Gray model was applied to estimate the sub-hazard ratio of kidney failure, with death as a competing event. RESULTS: In the development cohort, the mean age was 67.6 ± 13.9 years and 60 % were male. The mean index eGFR and median urinary protein-creatinine ratio (UPCR) were 26.5 ± 12.8 mL/min/1.73 m2 and 1051 mg/g, respectively. The median follow-up duration was 1051 days. The proportion of patients with kidney failure and death was 25.4 % and 14.1 %, respectively. Four models were applied, including eGFR, age, sex, UPCR, systolic and diastolic blood pressure, serum albumin, phosphate, uric acid, haemoglobin, and potassium levels had the best goodness of fit. All models had good discrimination with time-to-event c statistics of 0.89-0.95 in the development cohort and 0.86-0.95 in the validation cohort. The prediction models showed excellent and fairly good calibration at 2 and 5-year risk, respectively. CONCLUSION: Using real-world data, our competing risk model can accurately predict progression to kidney failure over 2 years in patients with advanced CKD.

Evaluation of the optimal cutoff number of types of social participation activities in older people.

INTRODUCTION: Social participation activities have a close association with health aging. However, the clinical significance of numbers of social participation activities and its cutoff value has not been defined. METHODS: We recruited 516 people aged ≥55 years. Twelve social participation behaviors modified according to Taiwanese culture were investigated, and the adequacy of cutoff number was determined by the area under the receiver operating characteristic curve (AUC) according to the results of cluster analysis of individual activities and scores of the Brief Symptom Rating Scale-5 (BSRS-5) and the Chinese Happiness Inventory (CHI). Demographic, BSRS-5 and CHI data were then compared according to the candidate cutoff numbers. RESULTS: The distribution of the numbers of social activities suggested that the highest partition of numbers of social activities was 3 in women and 4 in men. The AUC regarding the cluster of activity types was 0.917, with the highest Youden's J value located between 3 and 4. The AUC regarding the cluster of activity types and scores of the BSRS-5 and the CHI was 0.929, with similar cutoffs. If 3 and 4 were used as cutoffs, the between-group differences of both the CHI and the BSRS-5 were significant. More types of social activities had a different engaging frequency with the 3 and 4 cutoffs. CONCLUSION: Our findings found an adequate cutoff with better differential power in the psychopathology and happiness of older people that provided a basis for application in intervention and policy formation.

Multimorbidity and prior falls correlate with risk of 30-day hospital readmission in aged 80+: A prospective cohort study.

BACKGROUND/PURPOSE: Thirty-day hospital readmission rate significantly raised with advanced age. The performance of existing predictive models for readmission risk remained uncertain in the oldest population. We aimed to examine the effect of geriatric conditions and multimorbidity on readmission risk among older adults aged 80 and over. METHODS: This prospective cohort study enrolled patients aged 80 and older discharged from a geriatric ward at a tertiary hospital, with phone follow-up for 12 months. Demographics, multimorbidity, and geriatric conditions were assessed before hospital discharge. Logistic regression models were conducted to analyse risk factors for 30-day readmission. RESULTS: Patients readmitted had higher Charlson comorbidity index scores, and were more likely to have falls, frailty, and longer hospital stay, compared to those without 30-day readmission. Multivariate analysis revealed that higher Charlson comorbidity index score was associated with readmission risk. Older patients with a fall history within 12 months had a near 4-fold increase in readmission risk. Severe frailty status before index admission was associated with a higher 30-day readmission risk. Functional status at discharge was not associated with readmission risk. CONCLUSION: In addition to multimorbidity, history of falls and frailty were associated with higher hospital readmission risk in the oldest.

Humeral and cellular immune responses to SARS-CoV-2 vaccination in patients on peritoneal dialysis.

BACKGROUND: Patients with chronic kidney disease are at high risk for coronavirus disease 2019. Little is known about immune response to severe acute respiratory syndrome coronavirus 2 vaccination in patients on peritoneal dialysis (PD). METHOD: We prospectively enrolled 306 PD patients receiving two doses of vaccines (ChAdOx1-S: 283, mRNA-1273: 23) from July 2021 at a medical center. Humeral and cellular immune responses were assessed by anti-spike IgG concentration and blood T cell interferon-γ production 30 days after vaccination. Antibody ≥0.8 U/mL and interferon-γ ≥ 100 mIU/mL were defined as positive. Antibody was also measured in 604 non-dialysis volunteers (ChAdOx1-S: 244, mRNA-1273: 360) for comparison. RESULT: PD patients had less adverse events after vaccinations than volunteers. After the first dose of vaccine, the median antibody concentrations were 8.5 U/mL and 50.4 U/mL in ChAdOx1-S group and mRNA-1273 group of PD patients, and 66.6 U/mL and 195.3 U/mL in ChAdOx1-S group and mRNA-1273 group of volunteers, respectively. And after the second dose of vaccine, the median antibody concentrations were 344.8 U/mL and 9941.0 U/mL in ChAdOx1-S group and mRNA-1273 group of PD patients, and 620.3 U/mL and 3845.0 U/mL in ChAdOx1-S group and mRNA-1273 group of volunteers, respectively. The median IFN-γ concentration was 182.8 mIU/mL in ChAdOx1-S group, which was substantially lower than the median concentration 476.8 mIU/mL in mRNA-1273 group of PD patients. CONCLUSION: Both vaccines were safe and resulted in comparable antibody seroconversion in PD patients when compared with volunteers. However, mRNA-1273 vaccine induced significantly higher antibody and T cell response than ChAdOx1-S in PD patients. Booster doses are recommended for PD patients after two doses of ChAdOx1-S vaccination.

Can peripheral biomarkers reflect the psychological condition in geriatric populations? The influence of cardiovascular comorbidities.

BACKGROUND: Although previous studies indicated the association between peripheral biomarkers and psychological conditions, a higher prevalence of cardiovascular diseases (CVD) among geriatric populations may hinder the applicability of the biomarkers. The objective of this study was to assess the adequacy of the application of biomarkers to evaluate psychological conditions among geriatric populations. METHOD: We collected information on the demographics and history of CVD in all participants. All participants completed the Brief Symptom Rating Scale (BSRS-5) and the Chinese Happiness Inventory (CHI), which are the measurement of negative and positive psychological conditions, respectively. Four indicators of the peripheral biomarkers, including the standard deviation of normal to normal RR intervals (SDNN), finger temperature, skin conductance, and electromyogram were collected for each participant during a 5-min resting state. Multiple linear regression models were conducted to evaluate the association between the biomarkers and the psychological measurements (BSRS-5, CHI) with and without the inclusion of the participants with CVD. RESULTS: A total of 233 participants without CVD (non-CVD group) and 283 participants with CVD (CVD group) were included. The CVD group was older and with higher body mass index compared to the non-CVD group. In the multiple linear regression model with all participants, only BSRS-5 scores had a positive association with electromyogram. After the exclusion of the CVD group, the association between the BSRS-5 scores and electromyogram was more relevant, while CHI scores became positively associated with SDNN. CONCLUSIONS: A single measurement of the peripheral biomarker may be insufficient to depict psychological conditions among geriatric populations.

Angiopoietin-2 inhibition attenuates kidney fibrosis by hindering chemokine C-C motif ligand 2 expression and apoptosis of endothelial cells.

Plasma levels of angiopoietin-2 are increased in patients with chronic kidney disease (CKD). Moreover, mouse models of progressive kidney disease also demonstrate increased angiopoietin-2 in both plasmas and kidneys. The role of dysregulated angiopoietins in the progression of kidney disease has not been thoroughly investigated. Here, we found in a cohort of 319 patients with CKD that plasma angiopoietin-2 and angiopoietin-2/angiopoietin-1 ratios were positively associated with the development of kidney failure. In mice with progressive kidney disease induced by either ureteral obstruction or ischemia-reperfusion injury, overexpression of human angiopoietin-1 in the kidney tubules not only reduced macrophage infiltration in the initial stage post-injury but also attenuated endothelial cell apoptosis, microvascular rarefaction, and fibrosis in the advanced disease stage. Notably, angiopoietin-1 attenuated chemokine C-C motif ligand 2 (CCL2) expression in the endothelial cells of the fibrosing kidneys, and these protective effects led to attenuation of functional impairment. Mechanistically, angiopoietin-1 reduced CCL2-activated macrophage migration and protected endothelial cells against cell apoptosis induced by angiopoietin-2 and Wnt ligands. Based on this, we applied L1-10, an angiopoietin-2 inhibitor, to the mouse models of progressive kidney disease and found inhibitory effects on macrophage infiltration, microvascular rarefaction, and fibrosis. Thus, we defined the detrimental impact of increased angiopoietin-2 on kidney survival of patients with CKD which appears highlighted by angiopoietin-2 induced endothelial CCL2-activated macrophage infiltration and endothelial cell apoptosis in their kidneys undergoing fibrosis.

Validation of clinical frailty scale in Chinese translation.

BACKGROUND: Identification of frailty is crucial to guide patient care for the elderly. The Clinical Frailty Scale (CFS) is a reliable, synthesis and clinical judgment-based tool. However, a validated Chinese version of CFS (CFS-C) is lacking. The aim of this study is to describe the translation process of CFS into traditional Chinese and to evaluate its reliability and validity in a geriatric study population in Taiwan. METHODS: This cross-sectional study recruited 221 geriatric outpatients aged 65 years or older at a medical center in Taipei, Taiwan. The Chinese version of CFS was produced following Brislin's translation model. Weighted kappa for agreement and Kendall's tau for correlation were used to assess inter-rater reliability (a subgroup of 52 outpatients) between geriatricians and one research assistant, and validity tests (221 outpatients) by comparing CFS-C with Fried frailty phenotype and Frailty Index based on Comprehensive Geriatric Assessment (FI-CGA). Correlation between CFS-C and other geriatric conditions were also assessed. RESULTS: The inter-rater reliability revealed moderate agreement (weighted kappa = 0.60) and strong correlation (Kendall's tau = 0.67). For criterion validity, CFS-C categorisation showed fair agreement (weighted kappa = 0.37) and significant correlation (Kendall's tau = 0.46) with Fried frailty phenotype, and higher agreement (weighted kappa = 0.51) and correlation (Kendall's tau = 0.63) with FI-CGA categorisation. CFS-C was significantly correlated with various geriatric assessments, including functional disability, physical performance, hand grip, comorbidity, cognition, depression, and nutrition status. No significant correlation was found between CFS-C and appendicular muscle mass. CONCLUSIONS: The CFS-C demonstrated acceptable validity and reliability in Chinese older adults in Taiwan. Development of CFS-C enhanced consistency and accuracy of frailty assessment, both in research and clinical practice.

Trends in the incidence and prevalence of end-stage kidney disease requiring dialysis in Taiwan: 2010-2018.

BACKGROUND/PURPOSE: Taiwan has the highest incidence and prevalence of end-stage kidney disease (ESKD) worldwide. However, the epidemiologic features of ESKD requiring dialysis in Taiwan are unclear. METHODS: Our study population included all patients undergoing chronic dialysis (i.e., receiving dialysis treatment for at least three successive months) from the National Health Insurance Research Database from 2010 to 2018. Dialysis was defined using ICD-9-CM order codes for dialysis treatment. The age-standardized incidence and prevalence rates were calculated based on the World Health Organization standard population. RESULTS: The mean age was 47.7 ± 15.4 years at dialysis initiation. The incidence of ESKD requiring dialysis increased steadily during the study period, whereas the age-standardized incidence rate remained constant. The increased rate was particularly prevalent in men aged 65-74 and 75+ years. Additionally, the percentage of patients with estimated glomerular filtration rates > 10 mL/min/1.73 m2 at dialysis inception increased during the study period, especially in persons aged 75+ years. Most patients chose hemodialysis as the initial dialysis modality, including 86.8% in 2010 and 90.6% in 2018. The prevalence of dialysis increased substantially between 2010 and 2018, whereas the age-standardized prevalence of dialysis remained stable. The increasing trend was especially prominent in men aged ≥ 65 years. Among the patients on dialysis, the proportion of patients with mean dialysis times of more than 10 years has been increasing. CONCLUSION: The annual incidence and prevalence of dialysis increased steadily from 2010 to 2018, whereas the age-standardized incidence and prevalence of dialysis remained stable. The increased numbers of patients undergoing incident and prevalent dialysis were mostly elderly, especially men aged ≥65 years. Age-based prevention strategies and multidisciplinary care should be implemented to target the elderly population at risk of developing ESKD.

Spectrum of cancer patients receiving renal biopsy.

BACKGROUND: The frontier of onco-nephrology, particularly renal complications of cancer and treatment, remains unexplored. We revisit the fundamental tool of diagnosing kidney disease, renal biopsy, in cancer patients with renal manifestation. METHODS: Patients who received renal biopsy from July 2015 to July 2019 were analyzed. Primary outcomes included end-stage renal disease (ESRD), mortality, and catastrophic outcome defined as either ESRD or mortality. A Cox proportional hazards model and Kaplan-Meier technique were used to assess the association with outcome measurements and survival analyses. Immunosuppression after renal biopsy and response to the treatment were evaluated. RESULTS: Among the 77 patients, the median age was 66 years (interquartile range [IQR] 59-73 years) and 46 (59.7%) were male. At the time of renal biopsy, 57 patients (74%) had various degrees of renal insufficiency. Tubulointerstitial damage score, quantified by renal pathology, were associated with higher hazards of ESRD (hazard ratio [HR], 1.77; 95% confidence interval [95% CI], 1.20 to 2.61; P = 0.004) and catastrophic outcome (HR, 1.30; 95% CI, 0.99 to 1.70; P = 0.058). The response rate to immunosuppression was lower in those diagnosed with tubulointerstitial nephritis (1 of 4 patients, 25%) than those with glomerulopathy (10 of 20 patients, 50%). CONCLUSION: Renal biopsy may improve diagnostic accuracy and assist in treatment guidance of cancer patients with renal manifestation. Renal biopsy should be encouraged with clinical indication. Collaboration between oncologists and nephrologists is of paramount importance to provide more comprehensive care for caner patients.

Kidney pericyte hypoxia-inducible factor regulates erythropoiesis but not kidney fibrosis.

Prolyl hydroxylase domain enzyme (PHD) inhibitors are effective in the treatment of chronic kidney disease (CKD)-associated anemia by stabilizing hypoxia inducible factor (HIF), thereby increasing erythropoietin and consequently erythropoiesis. However, concern for CKD progression needs to be addressed in clinical trials. Although pre-clinical studies showed an anti-inflammatory effect in kidney disease models, the effect of PHD inhibitors on kidney fibrosis was inconsistent probably because the effects of HIF are cell type and context dependent. The major kidney erythropoietin-producing cells are pericytes that produce erythropoietin through HIF-2α-dependent gene transcription. The concern for the impact of HIF in pericytes on kidney fibrosis arises from the fact that pericytes are the major precursor cells of myofibroblasts in CKD. Since cells expressing Gli1 fulfill the morphologic and anatomic criteria for pericytes, we induced Gli1+ cell-specific HIF stabilization or knockout to study the impact of HIF in pericytes on kidney pathology of mice with or without fibrotic injury induced by unilateral ureteral obstruction. Compared with the littermate controls, mice with pericyte-specific HIF stabilization due to von Hippel-Lindau protein or PHD2 knockout showed increased serum erythropoietin and polycythemia rather than a discernible difference in kidney fibrosis. Compared with Gli1+ pericytes sorted from littermate controls, Gli1+ pericytes sorted from PHD2 knockout mice showed increased erythropoietin gene expression rather than discernible changes in Col1a1 or Acta2 expression. Furthermore, pericyte-specific knockout of HIF-1α or HIF-2α did not affect kidney fibrosis. Thus, our study supports the absence of negative effects of PHD inhibitors on kidney fibrosis of mice despite HIF stabilization in pericytes.

Transforming growth factor-ß1 decreases erythropoietin production through repressing hypoxia-inducible factor 2α in erythropoietin-producing cells.

BACKGROUND: Renal erythropoietin (EPO)-producing (REP) cells produce EPO through hypoxia-inducible factor (HIF) 2α-activated gene transcription. Insufficient EPO production leads to anemia in patients with chronic kidney disease. Although recombinant EPO is effective to improve anemia, no reliable REP cell lines limit further progress of research and development of novel treatment. METHODS: We screened Epo mRNA expression in mouse fibroblast cell lines. Small interfering RNA specific for HIF1α or HIF2α was transfected to study Epo expression in C3H10T1/2 cells. The effect of transforming growth factor-ß1 (TGF-ß1) on HIF-EPO axis was studied in C3H10T1/2 cells and mice. RESULTS: Similar to mouse REP pericytes, C3H10T1/2 cells differentiated to α-smooth muscle actin+ myofibroblasts after exposure to TGF-ß1. Specific HIF knockdown demonstrated the role of HIF2α in hypoxia-induced Epo expression. Sustained TGF-ß1 exposure increased neither DNA methyltransferase nor methylation of Epas1 and Epo genes. However, TGF-ß1 repressed HIF2α-encoding Epas1 promptly through activating activin receptor-like kinase-5 (ALK5), thereby decreasing Epo induction by hypoxia and prolyl hydroxylase domain inhibitor roxadustat. In mice with pro-fibrotic injury induced by ureteral obstruction, upregulation of Tgfb1 was accompanied with downregulation of Epas1 and Epo in injured kidneys and myofibroblasts, which were reversed by ALK5 inhibitor SB431542. CONCLUSION: C3H10T1/2 cells possessed the property of HIF2α-dependent Epo expression in REP pericytes. TGF-ß1 induced not only the transition to myofibroblasts but also a repressive effect on Epas1-Epo axis in C3H10T1/2 cells. The repressive effect of TGF-ß1 on Epas1-Epo axis was confirmed in REP pericytes in vivo. Inhibition of TGF-ß1-ALK5 signaling might provide a novel treatment to rescue EPO expression in REP pericytes of injured kidney.

Inflammatory macrophages switch to CCL17-expressing phenotype and promote peritoneal fibrosis.

Peritoneal fibrosis remains a problem in kidney failure patients treated with peritoneal dialysis. Severe peritoneal fibrosis with encapsulation or encapsulating peritoneal sclerosis is devastating and life-threatening. Although submesothelial fibroblasts as the major precursor of scar-producing myofibroblasts in animal models and M2 macrophage (Mϕ)-derived chemokines in peritoneal effluents of patients before diagnosis of encapsulating peritoneal sclerosis have been identified, attenuation of peritoneal fibrosis is an unmet medical need partly because the mechanism for cross talk between Mϕs and fibroblasts remains unclear. We use a sodium hypochlorite-induced mouse model akin to clinical encapsulated peritoneal sclerosis to study how the peritoneal Mϕs activate fibroblasts and fibrosis. Sodium hypochlorite induces the disappearance of CD11bhigh F4/80high resident Mϕs but accumulation of CD11bint F4/80int inflammatory Mϕs (InfMϕs) through recruiting blood monocytes and activating local cell proliferation. InfMϕs switch to express chemokine (C-C motif) ligand 17 (CCL17), CCL22, and arginase-1 from day 2 after hypochlorite injury. More than 75% of InfMϕs undergo genetic recombination by Csf1r-driven Cre recombinase, providing the possibility to reduce myofibroblasts and fibrosis by diphtheria toxin-induced Mϕ ablation from day 2 after injury. Furthermore, administration of antibody against CCL17 can reduce Mϕs, myofibroblasts, fibrosis, and improve peritoneal function after injury. Mechanistically, CCL17 stimulates migration and collagen production of submesothelial fibroblasts in culture. By breeding mice that are induced to express red fluorescent protein in Mϕs and green fluorescence protein (GFP) in Col1a1-expressing cells, we confirmed that Mϕs do not produce collagen in peritoneum before and after injury. However, small numbers of fibrocytes are found in fibrotic peritoneum of chimeric mice with bone marrow from Col1a1-GFP reporter mice, but they do not contribute to myofibroblasts. These data demonstrate that InfMϕs switch to pro-fibrotic phenotype and activate peritoneal fibroblasts through CCL17 after injury. CCL17 blockade in patients with peritoneal fibrosis may provide a novel therapy. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Accelerated versus standard initiation of renal replacement therapy for critically ill patients with acute kidney injury: a systematic review and meta-analysis of RCT studies.

BACKGROUND: Acute kidney injury (AKI) is a common yet possibly fatal complication among critically ill patients in intensive care units (ICU). Although renal replacement therapy (RRT) is an important supportive management for severe AKI patients, the optimal timing of RRT initiation for these patients is still unclear. METHODS: In this systematic review, we searched all relevant randomized controlled trials (RCTs) that directly compared accelerated with standard initiation of RRT from PUBMED, MEDLINE, EMBASE, and Cnki.net published prior to July, 20, 2020. We extracted study characteristics and outcomes of being free of dialysis, dialysis dependence and mortality. We rated the certainty of evidence according to Cochrane methods and the GRADE approach. RESULTS: We identified 56 published relevant studies from 1071 screened abstracts. Ten RCTs with 4753 critically ill AKI patients in intensive care unit (ICU) were included in this meta-analysis. In our study, accelerated and standard RRT group were not associated with all-cause mortality (log odds-ratio [OR]: - 0.04, 95% confidence intervals [CI] - 0.16 to 0.07, p = 0.46) and free of dialysis (log OR: - 0.03, 95% CI - 0.14 to 0.09, p = 0.65). In the subgroup analyses, accelerated RRT group was significantly associated with lower risk of all-cause mortality in the surgical ICU and for those who received continuous renal replacement therapy (CRRT). In addition, patients in these two subgroups had higher chances of being eventually dialysis-free. However, accelerated initiation of RRT augmented the risk of dialysis dependence in the subgroups of patients treated with non-CRRT modality and whose Sequential Organ Failure Assessment (SOFA) score were more than 11. CONCLUSIONS: In this meta-analysis, critically ill patients with severe AKI would benefit from accelerated RRT initiation regarding all-cause mortality and being eventually free of dialysis only if they were surgical ICU patients or if they underwent CRRT treatment. However, the risk of dialysis dependence was increased in the accelerated RRT group when those patients used non-CRRT modality or had high SOFA scores. All the literatures reviewed in this study were highly heterogeneous and potentially subject to biases. Trial registration CRD42020201466, Sep 07, 2020. https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=201466 .

The journey from erythropoietin to 2019 Nobel Prize: Focus on hypoxia-inducible factors in the kidney.

The 2019 Nobel Prize in Physiology or Medicine was awarded to William G. Kaelin Jr, Sir Peter J. Ratcliffe, and Gregg L. Semenza "for their discoveries of how cells sense and adapt to oxygen availability." The three pioneers discovered the hypoxia-inducible factor (HIF), elucidated the oxygen sensing mechanism of cells, and confirmed the critical role of HIF in hypoxic cellular responses. The broad and profound biological effects of HIF open up the possibilities for clinical translation. HIF stabilizers have been proven effective on anemia of chronic kidney disease in phase III clinical trials. HIF antagonists for cancer treatment are under phase II clinical trials. It is imperative to gain insight into the biology of HIF. In this article, the discovery of HIF and its oxygen-dependent enzymatic regulation will be introduced, based largely on the groundbreaking work of the three Nobel laureates. Next, the biology of HIF in the kidney will be reviewed. Studies on the HIF stabilizers in the context of kidney disease, as well as the manipulation of HIF in different renal cell types will be covered. Lastly, the clinical application of HIF stabilizers and HIF antagonists for the treatment of anemia and cancer, respectively, will be discussed.