Disruption of mitochondrial complex III in cap mesenchyme but not in ureteric progenitors results in defective nephrogenesis associated with amino acid deficiency.

Oxidative metabolism in mitochondria regulates cellular differentiation and gene expression through intermediary metabolites and reactive oxygen species. Its role in kidney development and pathogenesis is not completely understood. Here we inactivated ubiquinone-binding protein QPC, a subunit of mitochondrial complex III, in two types of kidney progenitor cells to investigate the role of mitochondrial electron transport in kidney homeostasis. Inactivation of QPC in sine oculis-related homeobox 2 (SIX2)-expressing cap mesenchyme progenitors, which give rise to podocytes and all nephron segments except collecting ducts, resulted in perinatal death from severe kidney dysplasia. This was characterized by decreased proliferation of SIX2 progenitors and their failure to differentiate into kidney epithelium. QPC inactivation in cap mesenchyme progenitors induced activating transcription factor 4-mediated nutritional stress responses and was associated with a reduction in kidney tricarboxylic acid cycle metabolites and amino acid levels, which negatively impacted purine and pyrimidine synthesis. In contrast, QPC inactivation in ureteric tree epithelial cells, which give rise to the kidney collecting system, did not inhibit ureteric differentiation, and resulted in the development of functional kidneys that were smaller in size. Thus, our data demonstrate that mitochondrial oxidative metabolism is critical for the formation of cap mesenchyme-derived nephron segments but dispensable for formation of the kidney collecting system. Hence, our studies reveal compartment-specific needs for metabolic reprogramming during kidney development.

CRISPR/Cas9 engineering of albino cystinuria Type A mice.

Cystinuria Type A is a relatively common genetic kidney disease occurring in 1 in 7,000 people worldwide that results from mutation of the cystine transporter rBAT encoded by Slc3a1. We used CRISPR/Cas9 technology to engineer cystinuria Type A mice via genome editing of the C57BL/6NHsd background. These mice are an improvement on currently available models as they are on a coisogenic genetic background and have a single defined mutation. In order to use albinism to track Cas9 activity, we co-injected gRNAs targeting Slc3a1 and tyrosinase (Tyr) with Cas9 expressing plasmid DNA into mouse embryos. Two different Slc3a1 mutational alleles were derived, with homozygous mice of both demonstrating elevated urinary cystine levels, cystine crystals, and bladder stones. We used whole genome sequencing to evaluate for potential off-target editing. No off-target indels were observed for the top 10 predicted off-targets for Slc3a1 or Tyr. Therefore, we used CRISPR/Cas9 to generate coisogenic albino cystinuria Type A mice that could be used for in vivo imaging, further study, or developing new treatments of cystinuria.

Global Prevalence of Protein-Energy Wasting in Kidney Disease: A Meta-analysis of Contemporary Observational Studies From the International Society of Renal Nutrition and Metabolism.

OBJECTIVE: To better define the prevalence of protein-energy wasting (PEW) in kidney disease is poorly defined. METHODS: We performed a meta-analysis of PEW prevalence from contemporary studies including more than 50 subjects with kidney disease, published during 2000-2014 and reporting on PEW prevalence by subjective global assessment or malnutrition-inflammation score. Data were reviewed throughout different strata: (1) acute kidney injury (AKI), (2) pediatric chronic kidney disease (CKD), (3) nondialyzed CKD 3-5, (4) maintenance dialysis, and (5) subjects undergoing kidney transplantation (Tx). Sample size, period of publication, reporting quality, methods, dialysis technique, country, geographical region, and gross national income were a priori considered factors influencing between-study variability. RESULTS: Two studies including 189 AKI patients reported a PEW prevalence of 60% and 82%. Five studies including 1776 patients with CKD stages 3-5 reported PEW prevalence ranging from 11% to 54%. Finally, 90 studies from 34 countries including 16,434 patients on maintenance dialysis were identified. The 25th-75th percentiles range in PEW prevalence among dialysis studies was 28-54%. Large variation in PEW prevalence across studies remained even when accounting for moderators. Mixed-effects meta-regression identified geographical region as the only significant moderator explaining 23% of the observed data heterogeneity. Finally, two studies including 1067 Tx patients reported a PEW prevalence of 28% and 52%, and no studies recruiting pediatric CKD patients were identified. CONCLUSION: By providing evidence-based ranges of PEW prevalence, we conclude that PEW is a common phenomenon across the spectrum of AKI and CKD. This, together with the well-documented impact of PEW on patient outcomes, justifies the need for increased medical attention.

Psoas Muscle Cross-sectional Area as a Measure of Whole-body Lean Muscle Mass in Maintenance Hemodialysis Patients.

OBJECTIVE: We investigate whether psoas or paraspinous muscle area measured on a single L4-L5 image is a useful measure of whole lean body mass (LBM) compared to dedicated midthigh magnetic resonance imaging (MRI). DESIGN: Observational study. SETTING: Outpatient dialysis units and a research clinic. SUBJECTS: One hundred five adult participants on maintenance hemodialysis. No control group was used. INTERVENTION: Psoas muscle area, paraspinous muscle area, and midthigh muscle area (MTMA) were measured by magnetic resonance imaging. MAIN OUTCOME MEASURE: LBM was measured by dual-energy absorptiometry scan. RESULTS: In separate multivariable linear regression models, psoas, paraspinous, and MTMA were associated with increase in LBM. In separate multivariate logistic regression models, C statistics for diagnosis of sarcopenia (defined as <25th percentile of LBM) were 0.69 for paraspinous muscle area, 0.81 for psoas muscle area, and 0.89 for MTMA. With sarcopenia defined as <10th percentile of LBM, the corresponding C statistics were 0.71, 0.92, and 0.94. CONCLUSIONS: We conclude that psoas muscle area provides a good measure of whole-body muscle mass, better than paraspinous muscle area but slightly inferior to midthigh measurement. Hence, in body composition studies a single axial MR image at the L4-L5 level can be used to provide information on both fat and muscle and may eliminate the need for time-consuming measurement of muscle area in the thigh.

Glycemic load is associated with oxidative stress among prevalent maintenance hemodialysis patients.

BACKGROUND: High glycemic index (GI) and glycemic load (GL) are associated with increased levels of oxidative stress and systemic inflammation in the general population. Maintenance hemodialysis (MHD) patients are known to have excessive oxidative stress burden and inflammation. In this study, we examined the relationship between dietary GI or GL and markers of oxidative stress or inflammation among prevalent MHD patients. METHODS: A registered dietitian obtained GI, GL and other dietary data from 58 MHD patients. Two separate 24-h diet recalls (a hemodialysis day and a non-hemodialysis day) were analyzed using the Nutrition Data System for Research (NDS-R) software. Plasma or serum concentrations of F2-isoprostanes, high sensitivity C-reactive protein (hsCRP), leptin and adiponectin (ADPN) were measured in fasting state. Fat mass was measured by dual-energy X-ray absorptiometry (DEXA). Cross-sectional associations between GI, GL and markers of interest were examined by multiple regression analysis with adjustment for potential covariates. RESULTS: Mean (±SD) age, body mass index (BMI) and total trunk fat were 47 ± 12 years, 29.5 ± 6.8 kg/m(2) and 16.4 ± 8.8 kg, respectively. Dietary GI was associated with trunk fat (r = -0.182, P = 0.05) but not with F2-isoprostanes and hsCRP. In contrast, GL was significantly associated with F2-isoprostanes (P = 0.002), in unadjusted analysis, which remained in adjusted analyses, adjusting for age and sex (P = 0.005), and after adjusting for BMI, trunk fat and waist/hip ratio (P = 0.004). Addition of leptin or ADPN did not alter the significance of the association. GL also correlated with hsCRP (P = 0.03), but this association was modified by BMI and trunk fat. CONCLUSIONS: Dietary GL is significantly associated with markers of oxidative stress and inflammation among prevalent MHD patients, independent of the body composition and adipocytokines. These data indicate the importance of the contents of dietary nutrient intake composition and its potential role in determining the metabolic disturbances in MHD patients.

Sodium activates human monocytes via the NADPH oxidase and isolevuglandin formation.

AIMS: Prior studies have focused on the role of the kidney and vasculature in salt-induced modulation of blood pressure; however, recent data indicate that sodium accumulates in tissues and can activate immune cells. We sought to examine mechanisms by which salt causes activation of human monocytes both in vivo and in vitro. METHODS AND RESULTS: To study the effect of salt in human monocytes, monocytes were isolated from volunteers to perform several in vitro experiments. Exposure of human monocytes to elevated Na+ex vivo caused a co-ordinated response involving isolevuglandin (IsoLG)-adduct formation, acquisition of a dendritic cell (DC)-like morphology, expression of activation markers CD83 and CD16, and increased production of pro-inflammatory cytokines tumour necrosis factor-α, interleukin (IL)-6, and IL-1ß. High salt also caused a marked change in monocyte gene expression as detected by RNA sequencing and enhanced monocyte migration to the chemokine CC motif chemokine ligand 5. NADPH-oxidase inhibition attenuated monocyte activation and IsoLG-adduct formation. The increase in IsoLG-adducts correlated with risk factors including body mass index, pulse pressure. Monocytes exposed to high salt stimulated IL-17A production from autologous CD4+ and CD8+ T cells. In addition, to evaluate the effect of salt in vivo, monocytes and T cells isolated from humans were adoptively transferred to immunodeficient NSG mice. Salt feeding of humanized mice caused monocyte-dependent activation of human T cells reflected by proliferation and accumulation of T cells in the bone marrow. Moreover, we performed a cross-sectional study in 70 prehypertensive subjects. Blood was collected for flow cytometric analysis and 23Na magnetic resonance imaging was performed for tissue sodium measurements. Monocytes from humans with high skin Na+ exhibited increased IsoLG-adduct accumulation and CD83 expression. CONCLUSION: Human monocytes exhibit co-ordinated increases in parameters of activation, conversion to a DC-like phenotype and ability to activate T cells upon both in vitro and in vivo sodium exposure. The ability of monocytes to be activated by sodium is related to in vivo cardiovascular disease risk factors. We therefore propose that in addition to the kidney and vasculature, immune cells like monocytes convey salt-induced cardiovascular risk in humans.

Optimal management of HIV- positive adults at risk for kidney disease in Nigeria (Renal Risk Reduction "R3" Trial): protocol and study design.

BACKGROUND: Individuals with two copies of the apolipoprotein-1 (APOL1) gene risk variants are at high risk (HR) for non-diabetic kidney disease. The presence of these risk variants is highest in West Africa, specifically in Nigeria. However, there is limited availability of dialysis and kidney transplantation in Nigeria, and most individuals will die soon after developing end-stage renal disease. Blocking the renin angiotensin aldosterone system with angiotensin-converting enzyme inhibitors (ACEi) is a well-recognized strategy to slow renal disease progression in patients with diabetes mellitus with chronic kidney disease (CKD) and in patients with HIV-associated nephropathy. We propose to determine whether presence of the APOL1 HR genotype alters or predicts responsiveness to conventional therapy to treat or prevent CKD and if addition of an ACEi to standard combination antiretroviral therapy (ART) reduces the risk of kidney complications among non-diabetic Nigerian adults. METHODS/DESIGN: We will screen 2600 HIV-positive adults who have received ART to (1) determine the prevalence of APOL1 risk variants and assess whether APOL1 HR status correlates with prevalent albuminuria, estimated glomerular filtration rate (eGFR), and/or prevalent CKD; (2) assess, via a randomized, placebo-controlled trial (RCT) in a subset of these participants with microalbuminura (n = 280) whether addition of the ACEi, lisinopril, compared to standard of care, significantly reduces the incidence or progression of albuminuria; and (3) determine whether the APOL1 HR genotype is associated with worse kidney outcomes (i.e. eGFR slope or regression of albuminuria) among participants in the RCT. CONCLUSIONS: This study will examine the increasing prevalence of kidney diseases in HIV-positive adults in a West African population, and the relationship between these diseases and the APOL1 high-risk genotype. By evaluating the addition of an ACEi to the care of individuals with HIV infection who have albuminuria, our trial will provide definitive evidence to guide strategies for management and clinical care in this population, with the goal of reducing HIV-related kidney complications. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03201939 . Registered on 26 August 2016.

Evaluation of two fatigability severity measures in elderly adults.

OBJECTIVES: To document the stability, concurrent validity, and clinical correlates of two fatigability severity measures as recommended by the American Geriatrics Society. DESIGN: Descriptive, cross-sectional. SETTING: Two independent living and one community senior centers. PARTICIPANTS: Forty-three participants, with an average age 85 ± 6. MEASUREMENTS: Perceived fatigability severity was quantified by directly asking participants to report change in energy after a standardized 10-minute walk at a self-selected pace. Performance fatigability severity was defined as a ratio of change in walking speed to total distance walked. The walk test was repeated within 2 weeks to assess stability. Total daily physical activity (PA) was measured over 7 consecutive days using a waist-worn accelerometer. Frailty was measured using the Vulnerable Elders Survey interview scale, and gait speed was measured using a standardized 25-feet walk test. RESULTS: The perceived and performance fatigability severity measures were significantly correlated (correlation coefficient (r) = 0.94, P < .001) and stable over two assessments (r = 0.82 and 0.85, P < .001). Both fatigability severity measures were significantly correlated with PA level (r = -0.42 and r = -0.44, respectively, P = .02), frailty (r = 0.47 and 0.53, respectively, P = .001) and gait speed (r = -0.45, P = .003 and r = -0.54, P = .001, respectively). CONCLUSION: The methodology described in this study permits the calculation of two highly correlated fatigability severity scores, which summarize the relationship between a person's change in self-reported tiredness or change in physical performance and concurrently measured PA. The fatigability severity scores are reproducible and correlated with clinical measures predictive of decline. The methods used to quantify fatigability severity can be implemented during a brief assessment (<15 minutes) and should be useful in the design and evaluation of interventions to increase PA in older adults at risk of functional decline.