The Zuni Kidney Project

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Genetics of kidney disease and related cardiometabolic phenotypes in Zuni Indians: the Zuni Kidney Project

The objective of this study is to identify genetic factors associated with chronic kidney disease (CKD) and related cardiometabolic phenotypes among participants of the Genetics of Kidney Disease in Zuni Indians study. The study was conducted as a community-based participatory research project in the Zuni Indians, a small endogamous tribe in rural New Mexico. We recruited 998 members from 28 extended multigenerational families, ascertained through probands with CKD who had at least one sibling with CKD. We used the Illumina Infinium Human1M-Duo version 3.0 BeadChips to type 1.1 million single nucleotide polymorphisms (SNPs). Prevalence estimates for CKD, hyperuricemia, diabetes, and hypertension were 24%, 30%, 17% and 34%, respectively. We found a significant (p < 1.58 × 10-7) association for a SNP in a novel gene for serum creatinine (PTPLAD2). We replicated significant associations for genes with serum uric acid (SLC2A9), triglyceride levels (APOA1, BUD13, ZNF259), and total cholesterol (PVRL2). We found novel suggestive associations (p < 1.58 × 10-6) for SNPs in genes with systolic (OLFML2B), and diastolic blood pressure (NFIA). We identified a series of genes associated with CKD and related cardiometabolic phenotypes among Zuni Indians, a population with a high prevalence of kidney disease. Illuminating genetic variations that modulate the risk for these disorders may ultimately provide a basis for novel preventive strategies and therapeutic interventions

Genome-Wide Association and Trans-ethnic Meta-Analysis for Advanced Diabetic Kidney Disease: Family Investigation of Nephropathy and Diabetes (FIND)

Diabetic kidney disease (DKD) is the most common etiology of chronic kidney disease (CKD) in the industrialized world and accounts for much of the excess mortality in patients with diabetes mellitus. Approximately 45% of U.S. patients with incident end-stage kidney disease (ESKD) have DKD. Independent of glycemic control, DKD aggregates in families and has higher incidence rates in African, Mexican, and American Indian ancestral groups relative to European populations. The Family Investigation of Nephropathy and Diabetes (FIND) performed a genome-wide association study (GWAS) contrasting 6,197 unrelated individuals with advanced DKD with healthy and diabetic individuals lacking nephropathy of European American, African American, Mexican American, or American Indian ancestry. A large-scale replication and trans-ethnic meta-analysis included 7,539 additional European American, African American and American Indian DKD cases and non-nephropathy controls. Within ethnic group meta-analysis of discovery GWAS and replication set results identified genome-wide significant evidence for association between DKD and rs12523822 on chromosome 6q25.2 in American Indians (P = 5.74x10-9). The strongest signal of association in the trans-ethnic meta-analysis was with a SNP in strong linkage disequilibrium with rs12523822 (rs955333; P = 1.31x10-8), with directionally consistent results across ethnic groups. These 6q25.2 SNPs are located between the SCAF8 and CNKSR3 genes, a region with DKD relevant changes in gene expression and an eQTL with IPCEF1, a gene co-translated with CNKSR3. Several other SNPs demonstrated suggestive evidence of association with DKD, within and across populations. These data identify a novel DKD susceptibility locus with consistent directions of effect across diverse ancestral groups and provide insight into the genetic architecture of DKD

Troponin I and NT-proBNP and the Association of Systolic Blood&nbsp;Pressure With Outcomes in Incident Hemodialysis Patients: The&nbsp;Choices for Healthy Outcomes in Caring for ESRD&nbsp;(CHOICE)&nbsp;Study

Background: There is uncertainty regarding treatment of hypertension in hemodialysis patients due to the observed J-shaped association between blood pressure (BP) and death. We hypothesized that this association reflects confounding by cardiovascular disease (CVD) and that stratification by CVD biomarkers, cardiac troponin I (cTnI) and N-terminal fragment of prohormone brain natriuretic peptide (NT-proBNP), might change this association. Study Design: National prospective cohort study. Setting &amp; Participants: 446 incident hemodialysis patients. Predictor: Predialysis systolic BP. Outcomes: Mortality (all-cause and CVD) and first CVD event assessed using Cox regression adjusted for demographics, comorbid conditions, and clinical factors. Measurements: Participants with cTnI level ≥ 0.1 ng/mL or NT-proBNP level ≥ 9,252 pg/mL were classified as the high-biomarker group; remaining participants were included in the low-biomarker group. Results: Participants in the high-biomarker group (n = 138 [31%]) were older (61 vs 57 years) and had a higher prevalence of CVD (67% vs 23%), but similar baseline BPs (152 vs 153 mm Hg). There were 323 deaths (143 from CVD) and 271 CVD events. The high-biomarker group had a higher risk of mortality than the low-biomarker group (HR, 1.75; 95% CI, 1.37-2.24). The association between BP and outcomes differed between the 2 biomarker groups (P for interaction = 0.01, 0.2, and 0.07 for all-cause mortality, CVD mortality, and first CVD event, respectively). In the low-biomarker group, BP was associated with greater risk of outcomes: HR per 10 mm Hg higher BP was 1.07 (95% CI, 1.01-1.14), 1.10 (95% CI, 0.96-1.25), and 1.04 (95% CI, 0.96-1.13) for all-cause mortality, CVD mortality, and first CVD event, respectively. Importantly, lower BP was not associated with increased risk of outcomes in stratified models, including for those in high biomarker group. Limitations: BP measurements not standardized. Conclusions: The observed J-shaped association between BP and outcomes in hemodialysis patients is due to confounding by subclinical CVD. A stratification approach based on cTnI and NT-proBNP levels has the potential to inform BP treatment in hemodialysis patients. © 2014 National Kidney Foundation, Inc

Understanding the Recent Increase in Ferritin Levels in United States Dialysis Patients: Potential Impact of Changes in Intravenous Iron and Erythropoiesis-Stimulating Agent Dosing.

Background and objectivesAnemia management changed substantially among dialysis patients in the United States around the time of implementation of the new Centers for Medicare &amp; Medicaid Services bundled payment system and erythropoiesis-stimulating agent (ESA) label change in 2011. Among these, average ferritin levels increased dramatically and have remained high since; this study sought to gain understanding of this sustained rise in ferritin levels.Design, setting, participants, &amp; measurementsTrends in mean ferritin, hemoglobin, IV iron dose, and ESA dose from 2009 to 2013 were examined in 9735 patients from 91 United States Dialysis Outcomes and Practice Patterns Study facilities. Linear mixed models were used to assess the extent to which intravenous (IV) iron and ESA dose accounted for patients' changes in ferritin over time.ResultsMean ESA dose and hemoglobin levels declined throughout the study. Mean IV iron dose increased from 210 mg/mo in 2009-2010 to a peak of 280 mg/mo in 2011, then declined back to 200 mg/mo and remained stable from 2012 to 2013. Mean ferritin increased from 601 ng/ml in the third quarter of 2009 to 887 ng/ml in the first quarter of 2012; models suggest that higher IV iron dosing was a primary determinant during 2011, but lower ESA doses contributed to the sustained high ferritin levels thereafter. In a subset of 17 facilities that decreased IV iron dose in 2011, mean ferritin rose by 120 ng/ml to 764 ng/ml, which appeared to be primarily due to ESA reduction. Together, changes in IV iron and ESA doses accounted for 46% of the increase in ferritin over the study period.ConclusionsIn contrast to expectations, the rise in average IV iron dose did not persist beyond 2011. The sustained rise in ferritin levels in United States dialysis patients after policy changes in 2011, to average levels well in excess of 800 ng/ml, appeared to be partly due to reductions in ESA dosing and not solely IV iron dosing practices. The effect of these changes in ferritin on health outcomes requires further investigation

Age, Race, Diabetes, Blood Pressure, and Mortality among Hemodialysis Patients

Observational studies involving hemodialysis patients suggest a U-shaped relationship between BP and mortality, but the majority of these studies followed large, heterogeneous cohorts. To examine whether age, race, and diabetes status affect the association between systolic BP (SBP; predialysis) and mortality, we studied a cohort of 16,283 incident hemodialysis patients. We constructed a series of multivariate proportional hazards models, adding age and BP to the analyses as cubic polynomial splines to model potential nonlinear relationships with mortality. Overall, low SBP associated with increased mortality, and the association was more pronounced among older patients and those with diabetes. Higher SBP associated with increased mortality among younger patients, regardless of race or diabetes status. We observed a survival advantage for black patients primarily among older patients. Diabetes associated with increased mortality mainly among older patients with low BP. In conclusion, the design of randomized clinical trials to identify optimal BP targets for patients with ESRD should take age and diabetes status into consideration

Gender and left ventricular structural and functional differences in pulmonary hypertension among end stage renal disease patients on maintenance hemodialysis

Introduction: Pulmonary hypertension (PH) is prevalent in hemodialysis (HD). In the general population, more women than men have PH due to left ventricular (LV) disease with preserved ejection fraction (EF). Little is known about the gender-specific prevalence of PH and associated LV abnormalities in patients with end stage renal disease (ESRD) on HD. Our aim was to evaluate gender differences and LV structural and functional changes in PH among ESRD patients on HD. Methods: Ninety-four patients (ages 23-77 years) underwent echocardiography after HD. Patients were divided based on estimated pulmonary artery systolic pressure (PASP) (Group A PASP &lt; 40 mm Hg, Group B PASP &ge; 40 mm Hg). LV measurements included LV mass, LV internal dimensions, and LV ejection fraction (EF). LV diastolic function (LVDF) was assessed from mitral inflow deceleration time (DT) and E/A ratio. Results: Fifty-five patients (59%) had PH, including 32 of 49 men (65%) and 23 of 45 women (51%). LVEF was lower in Group B (46.4 &plusmn; 17.6 vs. 62.4 &plusmn; 14.4%, p &lt; 0.001). Men with PH had higher LVIDd, cm (5.52 &plusmn; 0.89 vs 4.78 &plusmn; 0.75, p &lt; 0.001), LVIDs, cm (3.75 &plusmn; 0.94 vs 3.14 &plusmn; 0.91, p = 0.03) LV mass, g (236 &plusmn; 74vs 189 &plusmn; 56, p = 0.02) and lower LVEF (40.0 &plusmn; 16.7 vs 52.0 &plusmn; 15.6, p = 0.008) than women. Conclusion: Patients on HD have a high prevalence of PH. PH was not associated with clear LV structural changes. There was a depression in LV systolic function without changes in LVDF. PH patients were more often men with hypertrophied LV with depressed LV systolic function.&nbsp