Response to oral iron therapy in children with anemia of chronic kidney disease.

BACKGROUND: Anemia is a common complication of chronic kidney disease (CKD) and oral iron is recommended as initial therapy. However, response to iron therapy in children with non-dialysis CKD has not been formally assessed. METHODS: We reviewed medical records of pediatric patients with stages II-IV CKD followed in two New York metropolitan area medical centers between 2010 and 2020 and identified subjects who received oral iron therapy. Response to therapy at follow-up visits was assessed by improvement of hemoglobin, resolution of anemia by the 2012 KDIGO definition, and changes in iron status. Potential predictors of response were examined using regression analyses (adjusted for age, sex, eGFR, and center). RESULTS: Study criteria were met by 65 children (median age 12 years, 35 males) with a median time between visits of 81 days. Median eGFR was 44 mL/min/1.73 m2, and 40.7% had glomerular CKD etiology. Following iron therapy, hemoglobin improved from 10.2 to 10.8 g/dL (p < 0.001), hematocrit from 31.3 to 32.8% (p < 0.001), serum iron from 49 to 66 mcg/dL (p < 0.001), and transferrin saturation from 16 to 21.4% (p < 0.001). There was no significant change in serum ferritin (55.0 to 44.9 ng/mL). Anemia (defined according to KDIGO) resolved in 29.3% of children. No improvement in hemoglobin/hematocrit was seen in 35% of children, and no transferrin saturation improvement in 26.9%. There was no correlation between changes in hemoglobin and changes in transferrin saturation/serum iron, but there was an inverse correlation between changes in hemoglobin and changes in ferritin. The severity of anemia and alkaline phosphatase at baseline inversely correlated with treatment response. CONCLUSIONS: Anemia was resistant to 3 months of oral iron therapy in ~ 30% of children with CKD. Children with more severe anemia at baseline had better treatment response, calling for additional studies to refine approaches to iron therapy in children with anemia of CKD and to identify additional predictors of treatment response.

Skeletal muscle single fiber force production declines early in juvenile male mice with chronic kidney disease.

Children with chronic kidney disease (CKD) frequently exhibit delayed physical development and reduced physical performance, presumably due to skeletal muscle dysfunction. However, the cellular and molecular basis of skeletal muscle impairment in juvenile CKD remains poorly understood. Cellular (single fiber) and molecular (myosin-actin interactions and myofilament properties) function was examined ex vivo in slow (soleus) and fast (extensor digitorum longus) contracting muscles of juvenile male (6 weeks old) CKD and control mice. CKD was induced by 0.2% adenine diet for 3 weeks starting at 3 weeks of age. Specific tension (maximal isometric force divided by cross-sectional area) was reduced in larger myosin heavy chain (MHC) I and IIA fibers and in all IIB fibers in juvenile male mice with CKD due to fewer strongly bound myosin-actin cross-bridges. Fiber cross-sectional area in juvenile CKD mice was unchanged in MHC I and IIB fibers and increased in MHC IIA fibers, compared to controls. CKD slowed cross-bridge kinetics (slower rate of myosin force production and longer myosin attachment time, ton ) in MHC IIA fibers, and accelerated kinetics (shorter ton ) in MHC IIB fibers, which may indicate fiber type dependent shifts in contractile velocity in juvenile CKD. Overall, our findings show that single fiber myopathy is an early event during juvenile CKD, manifesting prior to the development of cellular atrophy as reduced force generation due to fewer strongly bound myosin heads. These results warrant clinical translation and call for early interventions to preserve physical function in children with CKD.

Urine-based multi-omic comparative analysis of COVID-19 and bacterial sepsis-induced ARDS.

BACKGROUND: Acute respiratory distress syndrome (ARDS), a life-threatening condition during critical illness, is a common complication of COVID-19. It can originate from various disease etiologies, including severe infections, major injury, or inhalation of irritants. ARDS poses substantial clinical challenges due to a lack of etiology-specific therapies, multisystem involvement, and heterogeneous, poor patient outcomes. A molecular comparison of ARDS groups holds the potential to reveal common and distinct mechanisms underlying ARDS pathogenesis. METHODS: We performed a comparative analysis of urine-based metabolomics and proteomics profiles from COVID-19 ARDS patients (n = 42) and bacterial sepsis-induced ARDS patients (n = 17). To this end, we used two different approaches, first we compared the molecular omics profiles between ARDS groups, and second, we correlated clinical manifestations within each group with the omics profiles. RESULTS: The comparison of the two ARDS etiologies identified 150 metabolites and 70 proteins that were differentially abundant between the two groups. Based on these findings, we interrogated the interplay of cell adhesion/extracellular matrix molecules, inflammation, and mitochondrial dysfunction in ARDS pathogenesis through a multi-omic network approach. Moreover, we identified a proteomic signature associated with mortality in COVID-19 ARDS patients, which contained several proteins that had previously been implicated in clinical manifestations frequently linked with ARDS pathogenesis. CONCLUSION: In summary, our results provide evidence for significant molecular differences in ARDS patients from different etiologies and a potential synergy of extracellular matrix molecules, inflammation, and mitochondrial dysfunction in ARDS pathogenesis. The proteomic mortality signature should be further investigated in future studies to develop prediction models for COVID-19 patient outcomes.

Iron therapy mitigates chronic kidney disease progression by regulating intracellular iron status of kidney macrophages.

Systemic iron metabolism is disrupted in chronic kidney disease (CKD). However, little is known about local kidney iron homeostasis and its role in kidney fibrosis. Kidney-specific effects of iron therapy in CKD also remain elusive. Here, we elucidate the role of macrophage iron status in kidney fibrosis and demonstrate that it is a potential therapeutic target. In CKD, kidney macrophages exhibited depletion of labile iron pool (LIP) and induction of transferrin receptor 1, indicating intracellular iron deficiency. Low LIP in kidney macrophages was associated with their defective antioxidant response and proinflammatory polarization. Repletion of LIP in kidney macrophages through knockout of ferritin heavy chain (Fth1) reduced oxidative stress and mitigated fibrosis. Similar to Fth1 knockout, iron dextran therapy, through replenishing macrophage LIP, reduced oxidative stress, decreased the production of proinflammatory cytokines, and alleviated kidney fibrosis. Interestingly, iron markedly decreased TGF-ß expression and suppressed TGF-ß-driven fibrotic response of macrophages. Iron dextran therapy and FtH suppression had an additive protective effect against fibrosis. Adoptive transfer of iron-loaded macrophages alleviated kidney fibrosis, validating the protective effect of iron-replete macrophages in CKD. Thus, targeting intracellular iron deficiency of kidney macrophages in CKD can serve as a therapeutic opportunity to mitigate disease progression.

Longitudinal Relationship Between Anemia and Statural Growth Impairment in Children and Adolescents With Nonglomerular CKD: Findings From the Chronic Kidney Disease in Children (CKiD) Study.

RATIONALE & OBJECTIVE: Anemia and statural growth impairment are both prevalent in children with nonglomerular chronic kidney disease (CKD) and are associated with poor quality of life and increased morbidity and mortality. However, to date no longitudinal studies have demonstrated a relationship between anemia and statural growth in this population. STUDY DESIGN: The CKD in Children (CKiD) study is a multicenter prospective cohort study with over 15 years of follow-up observation. SETTING & PARTICIPANTS: CKiD participants younger than 22 years with nonglomerular CKD who had not reached final adult height. EXPOSURE: Age-, sex-, and race-specific hemoglobin z score. OUTCOME: Age- and sex-specific height z score. ANALYTICAL APPROACH: The relationship between hemoglobin and height was quantified using (1) multivariable repeated measures paired person-visit analysis, and (2) multivariable repeated measures linear mixed model analysis. Both models were adjusted for age, sex, body mass index, estimated glomerular filtration rate, acidosis, and medication use. RESULTS: Overall, 67% of the 510 participants studied had declining hemoglobin z score trajectories over the follow-up period, which included 1,763 person-visits. Compared with average hemoglobin z scores of≥0, average hemoglobin z scores of less than -1.0 were independently associated with significant growth impairment at the subsequent study visit, with height z score decline ranging from 0.24 to 0.35. Importantly, in 50% of cases hemoglobin z scores of less than -1.0 corresponded to hemoglobin values higher than those used as cutoffs defining anemia in the KDIGO clinical practice guideline for anemia in CKD. When stratified by age, the magnitude of the association peaked in participants aged 9 years. In line with paired-visit analyses, our mixed model analysis demonstrated that in participants with baseline hemoglobin z score less than -1.0, a hemoglobin z score decline over the follow-up period was associated with a statistically significant concurrent decrease in height z score. LIMITATIONS: Limited ability to infer causality. CONCLUSIONS: Hemoglobin decline is associated with growth impairment over time in children with mild to moderate nonglomerular CKD, even before hemoglobin levels reach the cutoffs that are currently used to define anemia in this population.

Iron Supplementation Improves Skeletal Muscle Contractile Properties in Mice with CKD.

Background: Patients with chronic kidney disease (CKD) frequently have compromised physical performance, which increases their mortality; however, their skeletal muscle dysfunction has not been characterized at the single-fiber and molecular levels. Notably, interventions to mitigate CKD myopathy are scarce. Methods: The effect of CKD in the absence and presence of iron supplementation on the contractile function of individual skeletal muscle fibers from the soleus and extensor digitorum longus muscles was evaluated in 16-week-old mice. CKD was induced by the adenine diet, and iron supplementation was by weekly iron dextran injections. Results: Maximally activated and fatigued fiber force production was decreased 24%-52% in untreated CKD, independent of size, by reducing strongly bound myosin/actin cross-bridges and/or decreasing myofilament stiffness in myosin heavy chain (MHC) I, IIA, and IIB fibers. Additionally, myosin/actin interactions in untreated CKD were slower for MHC I and IIA fibers and unchanged or faster in MHC IIB fibers. Iron supplementation improved anemia and did not change overall muscle mass in CKD mice. Iron supplementation ameliorated CKD-induced myopathy by increasing strongly bound cross-bridges, leading to improved specific tension, and/or returning the rate of myosin/actin interactions toward or equivalent to control values in MHC IIA and IIB fibers. Conclusions: Skeletal muscle force production was significantly reduced in untreated CKD, independent of fiber size, indicating that compromised physical function in patients is not solely due to muscle mass loss. Iron supplementation improved multiple aspects of CKD-induced myopathy, suggesting that timely correction of iron imbalance may aid in ameliorating contractile deficits in CKD patients.

Urine-based multi-omic comparative analysis of COVID-19 and bacterial sepsis-induced ARDS.

Acute respiratory distress syndrome (ARDS), a life-threatening condition during critical illness, is a common complication of COVID-19. It can originate from various disease etiologies, including severe infections, major injury, or inhalation of irritants. ARDS poses substantial clinical challenges due to a lack of etiology-specific therapies, multisystem involvement, and heterogeneous, poor patient outcomes. A molecular comparison of ARDS groups holds the potential to reveal common and distinct mechanisms underlying ARDS pathogenesis. In this study, we performed a comparative analysis of urine-based metabolomics and proteomics profiles from COVID-19 ARDS patients (n = 42) and bacterial sepsis-induced ARDS patients (n = 17). The comparison of these ARDS etiologies identified 150 metabolites and 70 proteins that were differentially abundant between the two groups. Based on these findings, we interrogated the interplay of cell adhesion/extracellular matrix molecules, inflammation, and mitochondrial dysfunction in ARDS pathogenesis through a multi-omic network approach. Moreover, we identified a proteomic signature associated with mortality in COVID-19 ARDS patients, which contained several proteins that had previously been implicated in clinical manifestations frequently linked with ARDS pathogenesis. In summary, our results provide evidence for significant molecular differences in ARDS patients from different etiologies and a potential synergy of extracellular matrix molecules, inflammation, and mitochondrial dysfunction in ARDS pathogenesis. The proteomic mortality signature should be further investigated in future studies to develop prediction models for COVID-19 patient outcomes.

Erythropoiesis-independent effects of iron in chronic kidney disease.

Chronic kidney disease (CKD) leads to alterations of iron metabolism, which contribute to the development of anemia and necessitates iron supplementation in patients with CKD. Elevated hepcidin accounts for a significant iron redistribution in CKD. Recent data indicate that these alterations in iron homeostasis coupled with therapeutic iron supplementation have pleiotropic effects on many organ systems in patients with CKD, far beyond the traditional hematologic effects of iron; these include effects of iron on inflammation, oxidative stress, kidney fibrosis, cardiovascular disease, CKD-mineral and bone disorder, and skeletal growth in children. The effects of iron supplementation appear to be largely dependent on the route of administration and on the specific iron preparation. Iron-based phosphate binders exemplify the opportunity for using iron for both traditional (anemia) and novel (hyperphosphatemia) indications. Further optimization of iron therapy in patients with CKD may inform new approaches to the treatment of CKD complications and potentially allow modification of disease progression.

COVID-19 in Patients with CKD in New York City.

BACKGROUND: COVID-19 has affected millions of people, and several chronic medical conditions appear to increase the risk of severe COVID-19. However, our understanding of COVID-19 outcomes in patients with CKD remains limited. METHODS: This was a retrospective cohort study of patients with and without CKD consecutively admitted with COVID-19 to three affiliated hospitals in New York City. Pre-COVID-19 CKD diagnoses were identified by billing codes and verified by manual chart review. In-hospital mortality was compared between patients with and without underlying CKD. Logistic regression was used to adjust this analysis for confounders and to identify patient characteristics associated with mortality. RESULTS: We identified 280 patients with CKD, and 4098 patients without CKD hospitalized with COVID-19. The median age of the CKD group was 75 (65-84) years, and age of the non-CKD group 62 (48-75) years. Baseline (pre-COVID-19) serum creatinine in patients with CKD was 1.5 (1.2-2.2) mg/dl. In-hospital mortality was 30% in patients with CKD versus 20% in patients without CKD (P<0.001). The risk of in-hospital death in patients with CKD remained higher than in patients without CKD after adjustment for comorbidities (hypertension, diabetes mellitus, asthma, and chronic obstructive pulmonary disease), adjusted OR 1.4 (95% CI,1.1 to 1.9), P=0.01. When stratified by age, elderly patients with CKD (age >70 years) had higher mortality than their age-matched control patients without CKD. In patients with CKD, factors associated with in-hospital mortality were age (adjusted OR, 1.09 [95% CI, 1.06 to 1.12]), P<0.001, baseline and admission serum phosphorus (adjusted OR, 1.5 [95% CI, 1.03 to 2.1], P=0.03 and 1.4 [95% CI, 1.1 to 1.7], P=0.001), serum creatinine on admission >0.3 mg/dl above the baseline (adjusted OR 2.6 [95% CI, 1.2 to 5.4]P=0.01), and diagnosis of acute on chronic kidney injury during hospitalization (adjusted OR 4.6 [95% CI, 2.3 to 8.9], P<0.001). CONCLUSIONS: CKD is an independent risk factor for COVID-19-associated in-hospital mortality in elderly patients. Acute-on-chronic kidney injury increases the odds of in-hospital mortality in patients with CKD hospitalized with COVID-19.

Tumor necrosis factor-alpha is associated with mineral bone disorder and growth impairment in children with chronic kidney disease.

BACKGROUND: Mineral and bone disorder (MBD) and growth impairment are common complications of pediatric chronic kidney disease (CKD). Chronic inflammation detrimentally affects bone health and statural growth in non-CKD settings, but the impact of inflammation on CKD-MBD and growth in pediatric CKD remains poorly understood. This study assessed associations between inflammatory cytokines with biomarkers of CKD-MBD and statural growth in pediatric CKD. METHODS: This is a cross-sectional study of children with predialysis CKD stages II-V. Cytokines (IL-1b, IL-4, IL-6, IL-8, IL-10, IL-12, IL-13, TNF-α, interferon-γ), bone alkaline phosphatase (BAP), and procollagen type 1 N-terminal propeptide (P1NP) were measured at the same time as standard CKD-MBD biomarkers. Associations between cytokines, CKD-MBD biomarkers, and height z-score were assessed using linear regression analysis. RESULTS: Among 63 children, 52.4% had stage 3 CKD, 76.2% non-glomerular CKD etiology, and 21% short stature. TNF-α was the only cytokine associated with parathyroid hormone (PTH) independent of glomerular filtration rate. After stratification by low, medium, and high TNF-α tertiles, significant differences in PTH, serum phosphorus, alkaline phosphatase, BAP, P1NP, and height z-score were found. In a multivariate analysis, TNF-α positively associated with phosphorus, PTH, and alkaline phosphatase and inversely associated with height z-score, independent of kidney function, age, sex, and active vitamin D analogue use. CONCLUSIONS: TNF-α is positively associated with biomarkers of CKD-MBD and inversely associated with height z-score, indicating that inflammation likely contributes to the development of CKD-MBD and growth impairment in pediatric CKD. Prospective studies to definitively assess causative effects of inflammation on bone health and growth in children with CKD are warranted.

Carbonyl iron and iron dextran therapies cause adverse effects on bone health in juveniles with chronic kidney disease.

Anemia is a frequent complication of chronic kidney disease (CKD), related in part to the disruption of iron metabolism. Iron therapy is very common in children with CKD and excess iron has been shown to induce bone loss in non-CKD settings, but the impact of iron on bone health in CKD remains poorly understood. Here, we evaluated the effect of oral and parenteral iron therapy on bone transcriptome, bone histology and morphometry in two mouse models of juvenile CKD (adenine-induced and 5/6-nephrectomy). Both modalities of iron therapy effectively improved anemia in the mice with CKD, and lowered bone Fgf23 expression. At the same time, iron therapy suppressed genes implicated in bone formation and resulted in the loss of cortical and trabecular bone in the mice with CKD. Bone resorption was activated in untreated CKD, but iron therapy had no additional effect on this. Furthermore, we assessed the relationship between biomarkers of bone turnover and iron status in a cohort of children with CKD. Children treated with iron had lower levels of circulating biomarkers of bone formation (bone-specific alkaline phosphatase and the amino-terminal propeptide of type 1 procollagen), as well as fewer circulating osteoblast precursors, compared to children not treated with iron. These differences were independent of age, sex, and glomerular filtration rate. Thus, iron therapy adversely affected bone health in juvenile mice with CKD and was associated with low levels of bone formation biomarkers in children with CKD.

Mitophagy-dependent macrophage reprogramming protects against kidney fibrosis.

Mitophagy, by maintaining mitochondrial quality control, plays a key role in maintaining kidney function and is impaired in pathologic states. Macrophages are well known for their pathogenic role in kidney fibrosis. Here, we report that PINK1/Parkin-mediated mitophagy in macrophages is compromised in experimental and human kidney fibrosis. We demonstrate downregulation of mitophagy regulators mitofusin-2 (MFN2) and Parkin downstream of PINK1 in kidney fibrosis. Loss of either Pink1 or Prkn promoted renal extracellular matrix accumulation and frequency of profibrotic/M2 macrophages. Pink1-/- or Prkn-/- BM-derived macrophages (BMDMs) showed enhanced expression of rictor. Mitochondria from TGF-ß1-treated Pink1-/- BMDMs exhibited increased superoxide levels, along with reduced respiration and ATP production. In addition, mitophagy in macrophages involves PINK1-mediated phosphorylation of downstream MFN2, MFN2-facilitated recruitment of Parkin to damaged mitochondria, and macrophage-specific deletion of Mfn2 aggravates kidney fibrosis. Moreover, mitophagy regulators were downregulated in human CKD kidney and TGF-ß1-treated human renal macrophages, whereas Mdivi1 treatment suppressed mitophagy mediators and promoted fibrotic response. Taken together, our study is the first to our knowledge to demonstrate that macrophage mitophagy plays a protective role against kidney fibrosis via regulating the PINK1/MFN2/Parkin-mediated pathway.

Interleukin-6 Contributes to the Development of Anemia in Juvenile CKD.

INTRODUCTION: Anemia is a common complication of chronic kidney disease (CKD) in children; however, the role of inflammation in its pathogenesis remains incompletely understood. METHODS: To elucidate the role of interleukin (IL)-6 in renal anemia, we induced CKD by adenine diet in juvenile wild-type (WT) and IL-6 deficient (Il6KO) mice, and examined serum IL-6 and relevant parameters in children with CKD. RESULTS: WT-CKD mice developed anemia despite increases in serum erythropoietin and displayed low serum iron and elevated serum IL-6. IL-6 deficiency resulted in a significant improvement of red blood cell count and hemoglobin in CKD mice. This effect was associated with improvement of hypoferremia by Il6 deletion, likely mediated by hepcidin. However, correction of hypoferremia by oral iron supplementation in WT-CKD mice did not fully replicate the protective effects of Il6 deletion, suggesting an additional iron-independent role for IL-6 in CKD-anemia. Indeed, Il6 deletion mitigated the severity of renal fibrosis and alleviated relative erythropoietin insufficiency in CKD mice. Cytokine profiling in a pediatric CKD cohort demonstrated that of 10 cytokines (IL-1ß, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-13, tumor necrosis factor (TNF)-α, and interferon-γ), only IL-6 was significantly (inversely) associated with hemoglobin when adjusted for glomerular filtration rate (GFR). The association between IL-6 and hemoglobin in children with CKD remained significant after adjustment for CKD stage, iron therapy, and hepcidin. DISCUSSION: IL-6 contributes to development of anemia in juvenile CKD, through mechanisms that include induction of hypoferremia, aggravation of renal fibrosis, and alteration of the erythropoietin axis. IL-6 appears to be a promising therapeutic target in the management of CKD-anemia.

Chronic Kidney Disease and Dietary Measures to Improve Outcomes.

Chronic kidney disease is an ongoing deterioration of renal function that often progresses to end-stage renal disease. Management goals in children include slowing disease progression, prevention and treatment of complications, and optimizing growth, development, and quality of life. Nutritional management is critically important to achieve these goals. Control of blood pressure, proteinuria, and metabolic acidosis with dietary and pharmacologic measures may slow progression of chronic kidney disease. Although significant progress in management has been made, further research is required to resolve many outstanding controversies. We review recent developments in pediatric chronic kidney disease, focusing on dietary measures to improve outcomes.

RIPK3 promotes sepsis-induced acute kidney injury via mitochondrial dysfunction.

Sepsis causes acute kidney injury (AKI) in critically ill patients, although the pathophysiology remains unclear. The receptor-interacting protein kinase-3 (RIPK3), a cardinal regulator of necroptosis, has recently been implicated in the pathogenesis of human disease. In mice subjected to polymicrobial sepsis, we demonstrate that RIPK3 promotes sepsis-induced AKI. Utilizing genetic deletion and biochemical approaches in vitro and in vivo, we identify a potentially novel pathway by which RIPK3 aggravates kidney tubular injury independently of the classical mixed lineage kinase domain-like protein-dependent (MLKL-dependent) necroptosis pathway. In kidney tubular epithelial cells, we show that RIPK3 promotes oxidative stress and mitochondrial dysfunction involving upregulation of NADPH oxidase-4 (NOX4) and inhibition of mitochondrial complex I and -III, and that RIPK3 and NOX4 are critical for kidney tubular injury in vivo. Furthermore, we demonstrate that RIPK3 is required for increased mitochondrial translocation of NOX4 in response to proinflammatory stimuli, by a mechanism involving protein-protein interactions. Finally, we observed elevated urinary and plasma RIPK3 levels in human patients with sepsis-induced AKI, representing potential markers of this condition. In conclusion, we identify a pathway by which RIPK3 promotes kidney tubular injury via mitochondrial dysfunction, independently of MLKL, which may represent a promising therapeutic target in sepsis-induced AKI.

Approach to growth hormone therapy in children with chronic kidney disease varies across North America: the Midwest Pediatric Nephrology Consortium report.

BACKGROUND: Growth impairment remains common in children with chronic kidney disease (CKD). Available literature indicates low level of recombinant human growth hormone (rhGH) utilization in short children with CKD. Despite efforts at consensus guidelines, lack of high-level evidence continues to complicate rhGH therapy decision-making and the level of practice variability in rhGH treatment by pediatric nephrologists is unknown. METHODS: Cross-sectional online survey electronically distributed to pediatric nephrologists through the Midwest Pediatric Nephrology Consortium and American Society of Pediatric Nephrology. RESULTS: Seventy three pediatric nephrologists completed the survey. While the majority (52.1%) rarely involve endocrinology in rhGH management, 26.8% reported that endocrinology managed most aspects of rhGH treatment in their centers. The majority of centers (68.5%) have a dedicated renal dietitian, but 20.6% reported the nephrologist as the primary source of nutritional support for children with CKD. Children with growth failure did not receive rhGH most commonly because of family refusal. Differences in initial work-up for rhGH therapy include variable use of bone age (95%), thyroid function (58%), insulin-like growth factor-1 (40%), hip/knee X-ray (36%), and ophthalmologic evaluation (7%). Most pediatric nephrologists (95%) believe that rhGH treatment improves quality of life, but only 24% believe that it improves physical function; 44% indicated that rhGH improves lean body mass. CONCLUSIONS: There is substantial variation in pediatric nephrology practice in addressing short stature and rhGH utilization in children with CKD. Hence, there may be opportunities to standardize care to study and improve growth outcomes in short children with CKD.

Lack of hepcidin ameliorates anemia and improves growth in an adenine-induced mouse model of chronic kidney disease.

Growth delay is common in children with chronic kidney disease (CKD), often associated with poor quality of life. The role of anemia in uremic growth delay is poorly understood. Here we describe an induction of uremic growth retardation by a 0.2% adenine diet in wild-type (WT) and hepcidin gene (Hamp) knockout (KO) mice, compared with their respective littermates fed a regular diet. Experiments were started at weaning (3 wk). After 8 wk, blood was collected and mice were euthanized. Adenine-fed WT mice developed CKD (blood urea nitrogen 82.8 ± 11.6 mg/dl and creatinine 0.57 ± 0.07 mg/dl) and were 2.1 cm shorter compared with WT controls. WT adenine-fed mice were anemic and had low serum iron, elevated Hamp, and elevated IL6 and TNF-α. WT adenine-fed mice had advanced mineral bone disease (serum phosphorus 16.9 ± 3.1 mg/dl and FGF23 204.0 ± 115.0 ng/ml) with loss of cortical and trabecular bone volume seen on microcomputed tomography. Hamp disruption rescued the anemia phenotype resulting in improved growth rate in mice with CKD, thus providing direct experimental evidence of the relationship between Hamp pathway and growth impairment in CKD. Hamp disruption ameliorated CKD-induced growth hormone-insulin-like growth factor 1 axis derangements and growth plate alterations. Disruption of Hamp did not mitigate the development of uremia, inflammation, and mineral and bone disease in this model. Taken together, these results indicate that an adenine diet can be successfully used to study growth in mice with CKD. Hepcidin appears to be related to pathways of growth retardation in CKD suggesting that investigation of hepcidin-lowering therapies in juvenile CKD is warranted.

Partitioning-Defective 1a/b Depletion Impairs Glomerular and Proximal Tubule Development.

The kidney is a highly polarized epithelial organ that develops from undifferentiated mesenchyme, although the mechanisms that regulate the development of renal epithelial polarity are incompletely understood. Partitioning-defective 1 (Par1) proteins have been implicated in cell polarity and epithelial morphogenesis; however, the role of these proteins in the developing kidney has not been established. Therefore, we studied the contribution of Par1a/b to renal epithelial development. We examined the renal phenotype of newborn compound mutant mice carrying only one allele of Par1a or Par1b. Loss of three out of four Par1a/b alleles resulted in severe renal hypoplasia, associated with impaired ureteric bud branching. Compared with kidneys of newborn control littermates, kidneys of newborn mutant mice exhibited dilated proximal tubules and immature glomeruli, and the renal proximal tubular epithelia lacked proper localization of adhesion complexes. Furthermore, Par1a/b mutants expressed low levels of renal Notch ligand Jag1, activated Notch2, and Notch effecter Hes1. Together, these data demonstrate that Par1a/b has a key role in glomerular and proximal tubule development, likely via modulation of Notch signaling.

Update on inflammation in chronic kidney disease.

BACKGROUND: Despite recent advances in chronic kidney disease (CKD) and end-stage renal disease (ESRD) management, morbidity and mortality in this population remain exceptionally high. Persistent, low-grade inflammation has been recognized as an important component of CKD, playing a unique role in its pathophysiology and being accountable in part for cardiovascular and all-cause mortality, as well as contributing to the development of protein-energy wasting. SUMMARY: The variety of factors contribute to chronic inflammatory status in CKD, including increased production and decreased clearance of pro-inflammatory cytokines, oxidative stress and acidosis, chronic and recurrent infections, including those related to dialysis access, altered metabolism of adipose tissue, and intestinal dysbiosis. Inflammation directly correlates with the glomerular filtration rate (GFR) in CKD and culminates in dialysis patients, where extracorporeal factors, such as impurities in dialysis water, microbiological quality of the dialysate, and bioincompatible factors in the dialysis circuit play an additional role. Genetic and epigenetic influences contributing to inflammatory activation in CKD are currently being intensively investigated. A number of interventions have been proposed to target inflammation in CKD, including lifestyle modifications, pharmacological agents, and optimization of dialysis. Importantly, some of these therapies have been recently tested in randomized controlled trials. KEY MESSAGES: Chronic inflammation should be regarded as a common comorbid condition in CKD and especially in dialysis patients. A number of interventions have been proven to be safe and effective in well-designed clinical studies. This includes such inexpensive approaches as modification of physical activity and dietary supplementation. Further investigations are needed to evaluate the effects of these interventions on hard outcomes, as well as to better understand the role of inflammation in selected CKD populations (e.g., in children).