Prevalence and associations of 25-hydroxyvitamin D deficiency in US children: NHANES 2001-2004

OBJECTIVES

To determine the prevalence of 25-hydroxyvitamin D (25[OH]D) deficiency and associations between 25(OH)D deficiency and cardiovascular risk factors in children and adolescents.

METHODS

With a nationally representative sample of children aged 1 to 21 years in the National Health and Nutrition Examination Survey 2001-2004 (n = 6275), we measured serum 25(OH)D deficiency and insufficiency (25[OH]D <15 ng/mL and 15-29 ng/mL, respectively) and cardiovascular risk factors.

RESULTS

Overall, 9% of the pediatric population, representing 7.6 million US children and adolescents, were 25(OH)D deficient and 61%, representing 50.8 million US children and adolescents, were 25(OH)D insufficient. Only 4% had taken 400 IU of vitamin D per day for the past 30 days. After multivariable adjustment, those who were older (odds ratio [OR]: 1.16 [95% confidence interval (CI): 1.12 to 1.20] per year of age), girls (OR: 1.9 [1.6 to 2.4]), non-Hispanic black (OR: 21.9 [13.4 to 35.7]) or Mexican-American (OR: 3.5 [1.9 to 6.4]) compared with non-Hispanic white, obese (OR: 1.9 [1.5 to 2.5]), and those who drank milk less than once a week (OR: 2.9 [2.1 to 3.9]) or used >4 hours of television, video, or computers per day (OR: 1.6 [1.1 to 2.3]) were more likely to be 25(OH)D deficient. Those who used vitamin D supplementation were less likely (OR: 0.4 [0.2 to 0.8]) to be 25(OH)D deficient. Also, after multivariable adjustment, 25(OH)D deficiency was associated with elevated parathyroid hormone levels (OR: 3.6; [1.8 to 7.1]), higher systolic blood pressure (OR: 2.24 mmHg [0.98 to 3.50 mmHg]), and lower serum calcium (OR: -0.10 mg/dL [-0.15 to -0.04 mg/dL]) and high-density lipoprotein cholesterol (OR: -3.03 mg/dL [-5.02 to -1.04]) levels compared with those with 25(OH)D levels > or =30 ng/mL.

CONCLUSIONS

25(OH)D deficiency is common in the general US pediatric population and is associated with adverse cardiovascular risks.

Differential gene expression following early renal ischemia/reperfusion

BACKGROUND

Acute renal failure from ischemia/reperfusion injury is associated with tubule cell apoptosis, the molecular mechanisms of which remain under active investigation. The purpose of this study was to identify apoptosis-related genes that are differentially expressed in the early periods following renal ischemia.

METHODS

Mice underwent unilateral renal artery clamping for 45 minutes and were sacrificed at 0, 3, 12, or 24 hours of reperfusion. Tubule cell apoptosis was confirmed by DNA laddering and terminal deoxynucleotidyl transferase-mediated uridine triphosphate nick end labeling (TUNEL) assay. We employed cDNA microarrays to define global changes in renal gene expression. Semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry were used as confirmatory tools.

RESULTS

By microarray analysis, we identified consistent patterns of altered gene expression, including transcription factors, growth factors, signal transduction molecules, and apoptotic factors. Prominent among the last category included FADD, DAXX, BAD, BAK, and p53. Up-regulation of these proapoptotic genes was confirmed by semiquantitative RT-PCR and immunohistochemistry.

CONCLUSION

The results indicate that apoptosis may represent an important mechanism for the early loss of tubule cells following ischemia/reperfusion injury. Both the death receptor-dependent (FADD-DAXX) and mitochondrial (BAD-BAK) pathways are activated. The results also provide a molecular basis for the previous findings that significant intrarenal mechanisms exist to enable tubule cell repair and regeneration, as evidenced by the up-regulation of genes such as growth, proliferation, transcription, and cytoskeletal factors.

Design of the Nephrotic Syndrome Study Network (NEPTUNE) to evaluate primary glomerular nephropathy by a multidisciplinary approach

The Nephrotic Syndrome Study Network (NEPTUNE) is a North American multicenter collaborative consortium established to develop a translational research infrastructure for nephrotic syndrome. This includes a longitudinal observational cohort study, a pilot and ancillary study program, a training program, and a patient contact registry. NEPTUNE will enroll 450 adults and children with minimal change disease, focal segmental glomerulosclerosis, and membranous nephropathy for detailed clinical, histopathological, and molecular phenotyping at the time of clinically indicated renal biopsy. Initial visits will include an extensive clinical history, physical examination, collection of urine, blood and renal tissue samples, and assessments of quality of life and patient-reported outcomes. Follow-up history, physical measures, urine and blood samples, and questionnaires will be obtained every 4 months in the first year and biannually, thereafter. Molecular profiles and gene expression data will be linked to phenotypic, genetic, and digitalized histological data for comprehensive analyses using systems biology approaches. Analytical strategies were designed to transform descriptive information to mechanistic disease classification for nephrotic syndrome and to identify clinical, histological, and genomic disease predictors. Thus, understanding the complexity of the disease pathogenesis will guide further investigation for targeted therapeutic strategies.

Clinical trial of focal segmental glomerulosclerosis in children and young adults

This NIH-funded multicenter randomized study of focal segmental glomerulosclerosis (FSGS) treatment compared the efficacy of a 12-month course of cyclosporine to a combination of oral pulse dexamethasone and mycophenolate mofetil in children and adults with steroid-resistant primary FSGS. Of the 192 patients enrolled, 138 were randomized to cyclosporine (72) or to mycophenolate/dexamethasone (66). The primary analysis compared the levels of an ordinal variable measuring remission during the first year. The odds ratio (0.59) for achieving at least a partial remission with mycophenolate/dexamethasone compared to cyclosporine was not significant. Partial or complete remission was achieved in 22 mycophenolate/dexamethasone- and 33 cyclosporine-treated patients at 12 months. The main secondary outcome, preservation of remission for 26 weeks following cessation of treatment, was not significantly different between these two therapies. During the entire 78 weeks of study, 8 patients treated with cyclosporine and 7 with mycophenolate/dexamethasone died or developed kidney failure. Thus, our study did not find a difference in rates of proteinuria remission following 12 months of cyclosporine compared to mycophenolate/dexamethasone in patients with steroid-resistant FSGS. However, the small sample size might have prevented detection of a moderate treatment effect.

Effect of an oral Shiga toxin-binding agent on diarrhea-associated hemolytic uremic syndrome in children: a randomized controlled trial

CONTEXT

Diarrhea-associated hemolytic uremic syndrome (HUS) is the most common cause of acute renal failure in children. Most cases are caused by an intestinal infection with Shiga toxin-producing strains of Escherichia coli.

OBJECTIVE

To determine if administration of an oral agent that binds Shiga toxin could diminish the severity of diarrhea-associated HUS in pediatric patients.

DESIGN, SETTING, AND PATIENTS

Multicenter, randomized, double-blind, placebo-controlled clinical trial of 145 children (96 experimental and 49 placebo) aged 6 months to 18 years with diarrhea-associated HUS conducted between July 27, 1997, and April 14, 2001, at 26 tertiary care pediatric nephrology centers in the United States and Canada. Trial included 2 phases, the hospital course for treatment of the acute illness and a 60-day outpatient follow-up period after discharge from the hospital.

INTERVENTION

Patients were assigned to receive the binding agent, 500 mg/kg daily, or cornmeal placebo orally for 7 days in a 2:1 randomization scheme.

MAIN OUTCOME MEASURES

Combined frequency of death or serious extrarenal events and need for dialysis in the experimental vs placebo group.

RESULTS

A total of 62 patients (43%) were male and 123 (85%) were white. The median age of the patients was 4.2 years. Most patients (59%) were transferred from other hospitals to participating sites. The severity of disease at the time of randomization was comparable in the 2 groups. The prevalence of death or serious extrarenal events was 18% and 20% in the experimental and placebo groups, respectively (P =.82). Dialysis was required in 42% of experimental and 39% of placebo groups (P =.86).

CONCLUSIONS

Oral therapy with a Shiga toxin-binding agent failed to diminish the severity of disease in pediatric patients with diarrhea-associated HUS.

Activation of mitochondrial apoptotic pathways in human renal allografts after ischemiareperfusion injury

BACKGROUND

Ischemia-reperfusion injury in cadaveric (CAD) kidney allografts is associated with tubular cell injury, delayed graft function, and an increased incidence of acute and chronic rejection. We tested the hypothesis that activation of specific apoptotic pathways represents a mechanism for tubular cell death after CAD kidney transplantation.

METHODS

Serial tissue sections from paraffin-embedded needle biopsy specimens obtained at approximately 1 hr of reperfusion after transplantation of 13 CAD and 12 living-related donor (LRD) renal allografts were examined by using the terminal deoxynucleotide transferase-mediated dUTP nick-end labeling assay to detect apoptosis and by immunohistochemistry for expression of key pro-apoptotic molecules (Bax, Bak, tumor necrosis factor receptor [TNFR]-1, Fas, and cytochrome c).

RESULTS

Apoptosis was detected primarily in tubular cells, with a mean+/-standard deviation of 6.8+/-2.2 apoptotic cells per 100 cells examined in CAD renal allografts compared with 1.8+/-2.7 cells per 100 in LRD (P<0.001) renal allografts. There was a significant correlation between apoptosis rate and cold ischemia time in CAD (r=0.86, P<0.001) renal allografts. Bax was expressed in 100% of CAD versus 17% of LRD renal allografts (P<0.001), Bak in 92% of CAD versus 17% of LRD renal allografts (P<0.001), and TNFR-1 in 100% of CAD versus 58% of LRD renal allografts (P<0.05). Fas was expressed in only a small number of samples (23% of CAD and 17% of LRD renal allografts, P=not significant). Bax and Bak were expressed predominantly in apoptotic cells. Cytochrome c was detected as a mitochondrial pattern in LRD renal allografts, but in a diffuse cytosolic distribution in CAD renal allografts.

CONCLUSIONS

Ischemia-reperfusion injury in CAD kidney transplants is associated with a duration-dependent increase in tubular cell apoptosis, mediated at least in part by activation of mitochondrial pathways.

Association of glucocorticoid use and low 25-hydroxyvitamin D levels: results from the National Health and Nutrition Examination Survey (NHANES): 2001-2006

CONTEXT

In many disorders requiring steroid therapy, there is substantial decrease in bone mineral density. The association between steroid use and 25-hydroxyvitamin D [25(OH)D] deficiency has not been confirmed in large population-based studies, and currently there are no specific vitamin D recommendations for steroid users.

OBJECTIVE

The aim of the study was to evaluate the association of serum 25(OH)D deficiency [defined as 25(OH)D <10 ng/ml] with oral steroid use.

DESIGN

Cross-sectional analysis was performed using NHANES 2001-2006.

SETTING

We analyzed a nationally representative sample of U.S. children and adults.

PARTICIPANTS

The study sample consisted of children, adolescents, and adults from NHANES 2001-2006 (n = 22,650), representative of 286 million U.S. residents, with serum 25(OH)D levels and data on other potential confounders.

MAIN OUTCOME MEASURE

We measured serum 25(OH)D levels below 10 ng/ml.

RESULTS

A total of 181 individuals (0.9% of the population) used steroids within the past 30 d. Overall, 5% of the population had 25(OH)D levels below 10 ng/ml. Among steroid users, 11% had 25(OH)D levels below 10 ng/ml, compared to 5% among steroid nonusers (P = 0.009). The odds of having 25(OH)D deficiency were 2-fold higher in those who reported steroid use compared to those without steroid use [odds ratio (OR), 2.36; 95% confidence interval (CI), 1.25, 4.45]. This association remained after multivariable adjustment (OR, 2.21; 95% CI, 1.01, 4.85) and in a multivariable model using NHANES III data (OR, 1.88; 95% CI, 1.01, 3.48).

CONCLUSION

Steroid use is independently associated with 25(OH)D deficiency in this nationally representative cohort limited by cross-sectional data. It suggests the need for screening and repletion in patients on chronic steroids.

Association of histologic variants in FSGS clinical trial with presenting features and outcomes

BACKGROUND AND OBJECTIVES

FSGS histologic variants have correlated with outcomes in retrospective studies. The FSGS Clinical Trial provided a unique opportunity to study the clinical impact of histologic variants in a well defined prospective cohort with steroid-resistant primary FSGS.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Renal biopsies of 138 FSGS Clinical Trial participants aged 2-38 years enrolled from 2004 to 2008 were analyzed using the Columbia classification by core pathologists. This study assessed the distribution of histologic variants and examined their clinical and biopsy characteristics and relationships to patient outcomes.

RESULTS

The distribution of histologic variants was 68% (n=94) FSGS not otherwise specified, 12% (n=16) collapsing, 10% (n=14) tip, 7% (n=10) perihilar, and 3% (n=4) cellular. Individuals with not otherwise specified FSGS were more likely to have subnephrotic proteinuria (P=0.01); 33% of teenagers and adults had tip or collapsing variants compared with 10% of children, and subjects with these variants had greater proteinuria and hypoalbuminemia than not otherwise specified patients. Tip variant had the strongest association with white race (86%) and the lowest pathologic injury scores, baseline creatinine, and rate of progression. Collapsing variant had the strongest association with black race (63%, P=0.03) and the highest pathologic injury scores (P=0.003), baseline serum creatinine (P=0.003), and rate of progression. At 3 years, 47% of collapsing, 20% of not otherwise specified, and 7% of tip variant patients reached ESRD (P=0.005).

CONCLUSIONS

This is the first prospective study with protocol-defined immunomodulating therapies confirming poor renal survival in collapsing variant and showing better renal survival in tip variant among steroid-resistant patients.

Clinical Features and Histology of Apolipoprotein L1-Associated Nephropathy in the FSGS Clinical Trial

Genetic variants in apolipoprotein L1 (APOL1) confer risk for kidney disease. We sought to better define the phenotype of APOL1-associated nephropathy. The FSGS Clinical Trial involved 138 children and young adults who were randomized to cyclosporin or mycophenolate mofetil plus pulse oral dexamethasone with a primary outcome of proteinuria remission. DNA was available from 94 subjects who were genotyped for APOL1 renal risk variants, with two risk alleles comprising the risk genotype. Two APOL1 risk alleles were present in 27 subjects, of whom four subjects did not self-identify as African American, and 23 of 32 (72%) self-identified African Americans. Individuals with the APOL1 risk genotype tended to present at an older age and had significantly lower baseline eGFR, more segmental glomerulosclerosis and total glomerulosclerosis, and more tubular atrophy/interstitial fibrosis. There were differences in renal histology, particularly more collapsing variants in those with the risk genotype (P=0.02), although this association was confounded by age. APOL1 risk genotype did not affect response to either treatment regimen. Individuals with the risk genotype were more likely to progress to ESRD (P<0.01). In conclusion, APOL1 risk genotypes are common in African-American subjects with primary FSGS and may also be present in individuals who do not self-identify as African American. APOL1 risk status is associated with lower kidney function, more glomerulosclerosis and interstitial fibrosis, and greater propensity to progress to ESRD. The APOL1 risk genotype did not influence proteinuria responses to cyclosporin or mycophenolate mofetil/dexamethasone.

HNF1B and PAX2 mutations are a common cause of renal hypodysplasia in the CKiD cohort

Malformations of the kidney and lower urinary tract are the most frequent cause of end-stage renal disease in children. Mutations in HNF1Β and PAX2 commonly cause syndromic urinary tract malformation. We searched for mutations in HNF1Β and PAX2 in North American children with renal aplasia and hypodysplasia (RHD) enrolled in the Chronic Kidney Disease in Children Cohort Study (CKiD). We identified seven mutations in this multiethnic cohort (10% of patients). In HNF1Β, we identified a nonsense (p.R181X), a missense (p.S148L), and a frameshift (Y352fsX352) mutation, and one whole gene deletion. In PAX2, we identified one splice site (IVS4-1G>T), one missense (p.G24E), and one frameshift (G24fsX28) mutation. All mutations occurred in Caucasians, accounting for 14% of disease in this subgroup. The absence of mutations in other ethnicities is likely due to the limited sample size. There were no differences in clinical parameters (age, baseline eGFR, blood pressure, body mass index, progression) between patients with or without HNF1B and PAX2 mutations. A significant proportion of North American Caucasian patients with RHD carry mutations in HNF1Β or PAX2 genes. These patients should be evaluated for complications (e.g., diabetes for HNF1Β mutations, colobomas for PAX2) and referred for genetic counseling.

Pathophysiology of focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is a major cause of idiopathic steroid-resistant nephrotic syndrome (SRNS) and end-stage kidney disease (ESKD). In recent years, animal models and studies of familial forms of nephrotic syndrome helped elucidate some mechanisms of podocyte injury and disease progression in FSGS. This article reviews some of the experimental and clinical data on the pathophysiology of FSGS.

The association between abnormal birth history and growth in children with CKD

BACKGROUND AND OBJECTIVES

Poor linear growth is a well described complication of chronic kidney disease (CKD). This study evaluated whether abnormal birth history defined by low birth weight (LBW; <2500 g), prematurity (gestational age <36 weeks), small for gestational age (SGA; birth weight <10th percentile for gestational age), or intensive care unit (ICU) at birth were risk factors for poor growth outcomes in children with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Growth outcomes were quantified by age-sex-specific height and weight z-scores during 1393 visits from 426 participants of the Chronic Kidney Disease in Children Study, an observational cohort of children with CKD. Median baseline GFR was 42.9 ml/min per 1.73 m(2), 21% had a glomerular diagnosis, and 52% had CKD for ≥ 90% of their lifetime.

RESULTS

A high prevalence of LBW (17%), SGA (14%), prematurity (12%), and ICU after delivery (40%) was observed. Multivariate analyses demonstrated a negative effect of LBW (-0.43 ± 0.14; P < 0.01 for height and -0.37 ± 0.16; P = 0.02 for weight) and of SGA (-0.29 ± 0.16; P = 0.07 for height and -0.41 ± 0.19; P = 0.03 for weight) on current height and weight. In children with glomerular versus nonglomerular diagnoses, the effect of SGA (-1.08 versus -0.18; P = 0.029) on attained weight was more pronounced in children with a glomerular diagnosis.

CONCLUSIONS

LBW and SGA are novel risk factors for short stature and lower weight percentiles in children with mild to moderate CKD independent of kidney function.

Induction of renal tubular cell apoptosis in focal segmental glomerulosclerosis: roles of proteinuria and Fas-dependent pathways

The hypothesis that apoptosis represents a proximate mechanism by which tubule cells are damaged in FSGS was tested. Thirty kidney biopsy specimens from children with idiopathic early FSGS were studied retrospectively. Unexpected, apoptosis was evident in both proximal and distal tubule cells. There was a significant correlation between the degree of proteinuria and the number of apoptotic cells. Fas protein was detected predominantly in the tubule cells that underwent apoptosis. When compared with patients with other chronic proteinuric states, those with FSGS displayed a proliferation/apoptosis ratio in favor of proliferation in the glomerulus but dramatically in favor of apoptosis in the tubules. When both proteinuria and apoptosis were included in a stepwise logistic regression procedure, only apoptosis was found to predict independently the development of ESRD. Prolonged incubation of cultured Madin-Darby canine kidney (distal/collecting) cells with albumin also resulted in a dose- and duration-dependent induction of apoptosis and activation of the Fas pathway, lending support to the novel finding of distal tubule cell apoptosis in patients with FSGS. The results indicate that an elevated tubule cell apoptosis rate at the time of initial biopsy represents an independent predictor of progression to ESRD in patients with early FSGS.

Complete Remission in the Nephrotic Syndrome Study Network

BACKGROUND AND OBJECTIVES

This analysis from the Nephrotic Syndrome Study Network (NEPTUNE) assessed the phenotypic and pathology characteristics of proteinuric patients undergoing kidney biopsy and defined the frequency and factors associated with complete proteinuria remission (CRever).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We enrolled adults and children with proteinuria ≥0.5 g/d at the time of first clinically indicated renal biopsy at 21 sites in North America from April 2010 to June 2014 into a prospective cohort study. NEPTUNE central pathologists assigned participants to minimal-change disease (MCD), FSGS, membranous nephropathy, or other glomerulopathy cohorts. Outcome measures for this analysis were (1) CRever with urine protein-to-creatinine ratio (UPC) <0.3 g/g with preserved native kidney function and (2) ESRD. Continuous variables are reported as median and interquartile range (IQR; 25th, 75th percentile). Cox proportional hazards modeling was used to assess factors associated with CRever.

RESULTS

We enrolled 441 patients: 116 (27%) had MCD, 142 (32%) had FSGS, 66 (15%) had membranous nephropathy, and 117 (27%) had other glomerulopathy. The baseline UPC was 4.1 g/g (IQR, 1.9, 7.7) and the eGFR was 81 ml/min per 1.73 m(2) (IQR, 50, 105). Median duration of observation was 19 months (IQR, 11, 30). CRever occurred in 46% of patients, and 4.6% progressed to ESRD. Multivariate analysis demonstrated that higher prebiopsy proteinuria (hazard ratio, 0.3; 95% confidence interval, 0.2 to 0.5) and pathology diagnosis (FSGS versus MCD; hazard ratio, 0.2; 95% confidence interval, 0.1 to 0.5) were inversely associated with CRever. The effect of immunosuppressive therapy on remission varied by pathology diagnosis.

CONCLUSIONS

In NEPTUNE, the high frequency of other pathology in proteinuric patients affirms the value of the diagnostic kidney biopsy. Clinical factors, including level of proteinuria before biopsy, pathology diagnosis, and immunosuppression, are associated with complete remission.

Fetal-Not Maternal-APOL1 Genotype Associated with Risk for Preeclampsia in Those with African Ancestry

Black Americans are at increased risk for preeclampsia. Genetic variants in apolipoprotein L1 (APOL1) account for much of the increased risk for kidney disease in blacks. APOL1 is expressed in human placenta and transgenic mice expressing APOL1 develop preeclampsia. We evaluated the role of APOL1 variants in human preeclampsia. We determined maternal and fetal APOL1 genotypes in black women with preeclampsia in two populations. At Einstein Montefiore Center (EMC) Affiliated Hospitals, we studied 121 pregnancies in black women with preeclampsia. At University of Tennessee Health Science Center (UTHSC), we studied 93 pregnancies in black women with preeclampsia and 793 pregnancies without preeclampsia. We measured serum markers of preeclampsia soluble fms-like tyrosine kinase 1 (sFlt-1), placental growth factor (PlGF), and soluble endoglin (sEng). Fetal APOL1 high-risk (HR) genotype was associated with preeclampsia, with odds ratios at EMC and UTHSC of 1.84 (95% CI 1.11, 2.93) and 1.92 (95% CI 1.05, 3.49), respectively. Maternal APOL1 HR genotype was not associated with preeclampsia. Mothers with the fetal APOL1 HR genotype had more cerebral or visual disturbances (63% versus 37%, p = 0.04). In addition, fetal APOL1 HR genotype was associated with a higher sFLT-1/PlGF ratio at birth (p = 0.04). Fetal APOL1 high-risk genotype increases the risk for preeclampsia, likely by adversely affecting placental function. Further research is needed to assess whether APOL1 genetic testing can predict preeclampsia and improve pregnancy outcomes.

Effect of CsA on the expression of renin and angiotensin type 1 receptor genes in the rat kidney

To determine whether Cyclosporine A (CsA) alters the intrarenal expression of the renin and type 1 angiotensin II receptor genes, male adult Sprague-Dawley rats were given 25 mg/kg/day CsA s.c. for three weeks (CsA, N = 20) and were compared to pair-fed vehicle treated rats (Con, N = 20). The intrarenal distribution of renin and its mRNA was assessed by immunocytochemistry and in situ hybridization. In addition, kidney renin and type 1 angiotensin II (AT1) receptor mRNA levels were determined by Northern blot analysis. The percentage of juxtaglomerular apparatuses containing renin was higher in the CsA (84 +/- 5.5%) than in the Con (61 +/- 6.7%) group, (P < 0.05). The length of renin immunostaining along afferent arterioles was higher in the CsA (74 +/- 4.5 microns) than in the Con (37 +/- 5.1 microns) group, (P < 0.05). In contrast, neither renin mRNA levels nor its intrarenal distribution were altered by chronic CsA administration. Kidney AT1 receptor mRNA levels were lower in the CsA group than in the Con group. We conclude that chronic CsA: (1) induces recruitment of renin containing cells along the afferent arteriole, (2) causes no changes in intrarenal renin mRNA levels or distribution, suggesting that post-transcriptional events may be responsible for the persistence and/or uptake of renin by the preglomerular vasculature, (3) promotes a downregulation of AT1 receptor gene in the kidney, suggesting that local angiotensin II may control AT1 receptor gene expression by a negative feedback.

Precision nephrology identified tumor necrosis factor activation variability in minimal change disease and focal segmental glomerulosclerosis

The diagnosis of nephrotic syndrome relies on clinical presentation and descriptive patterns of injury on kidney biopsies, but not specific to underlying pathobiology. Consequently, there are variable rates of progression and response to therapy within diagnoses. Here, an unbiased transcriptomic-driven approach was used to identify molecular pathways which are shared by subgroups of patients with either minimal change disease (MCD) or focal segmental glomerulosclerosis (FSGS). Kidney tissue transcriptomic profile-based clustering identified three patient subgroups with shared molecular signatures across independent, North American, European, and African cohorts. One subgroup had significantly greater disease progression (Hazard Ratio 5.2) which persisted after adjusting for diagnosis and clinical measures (Hazard Ratio 3.8). Inclusion in this subgroup was retained even when clustering was limited to those with less than 25% interstitial fibrosis. The molecular profile of this subgroup was largely consistent with tumor necrosis factor (TNF) pathway activation. Two TNF pathway urine markers were identified, tissue inhibitor of metalloproteinases-1 (TIMP-1) and monocyte chemoattractant protein-1 (MCP-1), that could be used to predict an individual's TNF pathway activation score. Kidney organoids and single-nucleus RNA-sequencing of participant kidney biopsies, validated TNF-dependent increases in pathway activation score, transcript and protein levels of TIMP-1 and MCP-1, in resident kidney cells. Thus, molecular profiling identified a subgroup of patients with either MCD or FSGS who shared kidney TNF pathway activation and poor outcomes. A clinical trial testing targeted therapies in patients selected using urinary markers of TNF pathway activation is ongoing.

Urinary proteome of steroid-sensitive and steroid-resistant idiopathic nephrotic syndrome of childhood

The response to steroid therapy is used to characterize the idiopathic nephrotic syndrome (INS) of childhood as either steroid-sensitive (SSNS) or steroid-resistant (SRNS), a classification with a better prognostic capability than renal biopsy. The majority (approximately 80%) of INS is due to minimal change disease but the percentage of focal and segmental glomerulosclerosis is increasing. We applied a new technological platform to examine the urine proteome to determine if different urinary protein excretion profiles could differentiate patients with SSNS from those with SRNS. Twenty-five patients with INS and 17 control patients were studied. Mid-stream urines were analyzed using surface enhanced laser desorption and ionization mass spectrometry(SELDI-MS). Data were analyzed using multiple bioinformatic techniques. Patient classification was performed using Biomarker Pattern Software and a generalized form of Adaboost and predictive models were generated using a supervised algorithm with cross-validation. Urinary proteomic data distinguished INS patients from control patients, irrespective of steroid response, with a sensitivity of 92.3%, specificity of 93.7%, positive predictive value of 96% and a negative predictive value of 88.2%. Classification of patients as SSNS or SRNS was 100%. A protein of mass 4,144 daltons was identified as the single most important classifier in distinguishing SSNS from SRNS. SELDI-MS combined with bioinformatics can identify different proteomic patterns in INS. Characterization of the proteins of interest identified by this proteomic approach with prospective clinical validation may yield a valuable clinical tool for the non-invasive prediction of treatment response and prognosis.

APOL1-associated glomerular disease among African-American children: a collaboration of the Chronic Kidney Disease in Children (CKiD) and Nephrotic Syndrome Study Network (NEPTUNE) cohorts

Background

Individuals of African ancestry harboring two variant alleles within apolipoprotein L1 ( APOL1 ) are classified with a high-risk (HR) genotype. Adults with an HR genotype have increased risk of focal segmental glomerulosclerosis and chronic kidney disease compared with those with a low-risk (LR) genotype (0 or 1 variants). The role of APOL1 risk genotypes in children with glomerular disease is less well known.

Methods

This study characterized 104 African-American children with a glomerular disease by APOL1 genotype in two cohorts: the Chronic Kidney Disease in Children (CKiD) and Nephrotic Syndrome Study Network (NEPTUNE).

Results

Among these subjects, 46% had an HR genotype with a similar age at cohort enrollment. For APOL1 HR children, the median age of disease onset was older (CKiD: 4.5 versus 11.5 years for LR versus HR; NEPTUNE: 11 versus 14 years for LR versus HR, respectively) and preterm birth was more common [CKiD: 27 versus 4%; NEPTUNE: 26 versus 12%; combined odds ratio 4.6 (95% confidence interval: 1.4, 15.5)]. Within studies, HR children had lower initial estimated glomerular filtration rate (eGFR) (CKiD: 53 versus 69 mL/min/1.73 m 2 ; NEPTUNE: 74 versus 94 mL/min/1.73 m 2 ). Longitudinal eGFR decline was faster among HR children versus LR (CKiD: -18 versus -8% per year; NEPTUNE: -13 versus -3% per year).

Conclusions

Children with an HR genotype in CKiD and NEPTUNE seem to have a more aggressive form of glomerular disease, in part due to a higher prevalence of focal segmental glomerulosclerosis. These consistent findings across independent cohorts suggest a common natural history for children with APOL1 -associated glomerular disease. Further study is needed to determine the generalizability of these findings.

Medication adherence in the transition of adolescent kidney transplant recipients to the adult care

Non-adherence is common in adolescent and young adult kidney transplant recipients, leading to adverse graft outcomes. The aim of this study was to determine whether adherence to immunosuppressant medications changes during transition from a pediatric to an adult program within the same transplant center. Adherence was assessed for a period of two yr before and two yr after the transfer. Subtherapeutic trough levels of serum tacrolimus and level variability were used as measures of adherence. Twenty-five patients were transitioned between 1996 and 2011 at the median age of 22.3 [IQR 21.6-23.0] yr. Young adults 21-25 yr of age (n = 26) and non-transitioned adolescents 17-21 yr of age (currently followed in the program, n = 24 and those that lost their grafts prior to the transfer, 22) formed the comparison groups. In the transitioned group, adherence prior to the transfer was not significantly different from the adherence after the transfer (p = 0.53). The rate of non-adherence in the group of non-transitioned adolescents who lost their grafts (68%) was significantly higher than in the transitioned group (32%, p = 0.01). In the group of young adults, adherence was not significantly different from the transitioned group (p = 0.27). Thus, transition was not associated with differences in medication adherence in this single-center study. Large-scale studies are needed to evaluate the national data on medication adherence after transfer.

Decreased hepatic insulin-like growth factor (IGF)-I and increased IGF binding protein-1 and -2 gene expression in experimental uremia

The imbalance between normal insulin-like growth factor-I (IGF-I) and markedly increased IGF binding protein (IGFBP) plasma levels plays a pathogenic role for growth retardation and catabolism in children with chronic renal failure. To investigate the mechanism of these alterations, experiments were performed in an experimental model of uremia in rats (5/6 nephrectomy) and in pair-fed and ad libitum-fed sham-operated controls Using a specific solution hybridization/RNase protection assay, we observed a marked reduction of hepatic IGF-I messenger RNA (mRNA) abundance at steady state in uremic animals (37 +/- 5% of control) compared both with pair-fed (65 +/- 10%) and ad libitum-fed controls (100 +/- 11%) (P < 0.001). Reduced IGF-I gene expression was clearly organ-specific; it was most pronounced in liver (significant vs., pair-fed controls) and lung and muscle tissue (significant vs., ad libitum-fed controls); no change was observed in kidney and heart tissue. To determine a potential mechanism of reduced hepatic IGF-I gene expression in uremia, the hepatic GH receptor gene expression in the same experimental animals was analyzed by specific solution hybridization/RNase protection assay. Uremic animals had a 20-30% reduction of hepatic GH receptor mRNA abundance compared with controls. Hepatic GHBP expression in uremia was decreased in parallel. Despite the reduction of hepatic IGF-I mRNA abundance, plasma IGF-I levels in uremia were not different from ad libitum-fed controls. This discrepancy is explained by an increased concentration of IGFBPs in uremic plasma. By RIA, plasma IGFBP-1 levels in uremia were increased 4-fold; by Western immunoblot, plasma IGFBP-2 levels were increased 7-fold and plasma IGFBP-4 levels were increased 2-fold compared with both control groups. Intact IGFBP-3 (M(r), approximately 48 kDa) and low molecular IGFBP-3 fragments were not significantly different among the three groups. By Northern blot analysis, hepatic IGFBP-1 mRNA levels in uremia were 2-fold higher than in controls. IGFBP-2 mRNA abundance in liver tissue was increased 4-fold, whereas in kidney there was a significant reduction of IGFBP-2 mRNA (30% of control). IGFBP-4 mRNA was increased by 50% in kidney but not in liver. Plasma insulin and corticosterone levels were not different among the groups. Our study shows that hepatic IGF-I gene expression was specifically reduced in uremia, partially as the consequence of a reduced hepatic GH receptor gene expression. One of the mechanisms contributing to increased IGFBP levels in uremia is increased hepatic gene expression of IGFBP-1 and IGFBP-2. The imbalance between reduced hepatic IGF-I production and increased hepatic IGFBP-1 and 2 production is likely to play a pathogenic role for catabolism and growth failure in CRF.

Prevalence and correlates of 25-hydroxyvitamin D deficiency in the Chronic Kidney Disease in Children (CKiD) cohort

BACKGROUND

Vitamin D plays an important role in the mineral and bone disorder seen in chronic kidney disease (CKD). Deficiency of 25-hydroxyvitamin D (25OHD) is highly prevalent in the adult CKD population.

METHODS

The prevalence and determinants of 25OHD deficiency (defined as a level <20 ng/ml) were examined longitudinally in 506 children in the CKiD cohort. Predictors of secondary hyperparathyroidism and the determinants of 1,25-dihydroxyvitamin D (1,25(OH)2D) levels were also evaluated.

RESULTS

Deficiency of 25OHD was observed in 28 % of the cohort at enrollment. Significant predictors of 25OHD deficiency were older age, non-white race, higher body mass index, assessment during winter, less often than daily milk intake, non-use of nutritional vitamin D supplement and proteinuria. Lower values of glomerular filtration rate (GFR), serum 25OHD, calcium and higher levels of FGF23 were significant determinants of secondary hyperparathyroidism. Lower GFR, low serum 25OHD, nephrotic-range proteinuria, and high FGF23 levels were significant determinants of serum 1,25(OH)2 D levels.

CONCLUSIONS

Deficiency of 25OHD is prevalent in children with CKD and is associated with potentially modifiable risk factors such as milk intake, nutritional vitamin D supplement use, and proteinuria. 25OHD deficiency is a risk factor for secondary hyperparathyroidism and decreased serum 1,25(OH)2D in children with CKD.

Perceived appetite and clinical outcomes in children with chronic kidney disease

BACKGROUND

Children with chronic kidney disease (CKD) may have impaired caloric intake through a variety of mechanisms, with decreased appetite as a putative contributor. In adult CKD, decreased appetite has been associated with poor clinical outcomes. There is limited information about this relationship in pediatric CKD.

METHODS

A total of 879 participants of the Chronic Kidney Disease in Children (CKiD) study were studied. Self-reported appetite was assessed annually and categorized as very good, good, fair, or poor/very poor. The relationship between appetite and iohexol or estimated glomerular filtration rate (ieGFR), annual changes in anthropometrics z-scores, hospitalizations, emergency room visits, and quality of life were assessed.

RESULTS

An ieGFR < 30 ml/min per 1.73 m(2) was associated with a 4.46 greater odds (95 % confidence interval: 2.80, 7.09) of having a worse appetite than those with ieGFR >90. Appetite did not predict changes in height, weight, or BMI z-scores. Patients not reporting a very good appetite had more hospitalizations over the next year than those with a very good appetite. Worse appetite was significantly associated with lower parental and patient reported quality of life.

CONCLUSIONS

Self-reported appetite in children with CKD worsens with lower ieGFR and is correlated with clinical outcomes, including hospitalizations and quality of life.

Renal and Cardiovascular Morbidities Associated with APOL1 Status among African-American and Non-African-American Children with Focal Segmental Glomerulosclerosis

BACKGROUND AND OBJECTIVES

African-American (AA) children with focal segmental glomerulosclerosis (FSGS) have later onset disease that progresses more rapidly than in non-AA children. It is unclear how APOL1 genotypes contribute to kidney disease risk, progression, and cardiovascular morbidity in children.

DESIGN SETTING PARTICIPANTS AND MEASUREMENTS

We examined the prevalence of APOL1 genotypes and associated cardiovascular phenotypes among children with FSGS in the Chronic Kidney Disease in Children (CKiD) study; an ongoing multicenter prospective cohort study of children aged 1-16 years with mild to moderate kidney disease.

RESULTS

A total of 140 AA children in the CKiD study were genotyped. High risk (HR) APOL1 genotypes were present in 24% of AA children (33/140) and were associated with FSGS, p < 0.001. FSGS was the most common cause of glomerular disease in children with HR APOL1 (89%; 25/28). Of 32 AA children with FSGS, 25 (78%) had HR APOL1. Compared to children with low risk APOL1 and FSGS (comprising 36 non-AA and 7 AA), children with HR APOL1 developed FSGS at a later age, 12.0 (IQR: 9.5, 12.5) vs. 5.5 (2.5, 11.5) years, p = 0.004, had a higher prevalence of uncontrolled hypertension (52 vs. 33%, p = 0.13), left ventricular hypertrophy (LVH) (53 vs. 12%, p < 0.01), C-reactive protein > 3 mg/l (33 vs. 15%, p = 0.12), and obesity (48 vs. 19%, p = 0.01). There were no differences in glomerular filtration rate, hemoglobin, iPTH, or calcium-phosphate product.

CONCLUSION

AA children with HR APOL1 genotype and FSGS have increase prevalence of obesity and LVH despite a later age of FSGS onset, while adjusting for socioeconomic status. Treatment of obesity may be an important component of chronic kidney disease and LVH management in this population.