Familial aggregation of renal disease in a population-based case-control study

The Minnesota attributable risk of kidney donation (MARKD) study: a retrospective cohort study of long-term (> 50 year) outcomes after kidney donation compared to well-matched healthy controls

BACKGROUND

There is uncertainty about the long-term risks of living kidney donation. Well-designed studies with controls well-matched on risk factors for kidney disease are needed to understand the attributable risks of kidney donation.

METHODS

The goal of the Minnesota Attributable Risk of Kidney Donation (MARKD) study is to compare the long-term (> 50 years) outcomes of living donors (LDs) to contemporary and geographically similar controls that are well-matched on health status. University of Minnesota (n = 4022; 1st transplant: 1963) and Mayo Clinic LDs (n = 3035; 1st transplant: 1963) will be matched to Rochester Epidemiology Project (REP) controls (approximately 4 controls to 1 donor) on the basis of age, sex, and race/ethnicity. The REP controls are a well-defined population, with detailed medical record data linked between all providers in Olmsted and surrounding counties, that come from the same geographic region and era (early 1960s to present) as the donors. Controls will be carefully selected to have health status acceptable for donation on the index date (date their matched donor donated). Further refinement of the control group will include confirmed kidney health (e.g., normal serum creatinine and/or no proteinuria) and matching (on index date) of body mass index, smoking history, family history of chronic kidney disease, and blood pressure. Outcomes will be ascertained from national registries (National Death Index and United States Renal Data System) and a new survey administered to both donors and controls; the data will be supplemented by prior surveys and medical record review of donors and REP controls. The outcomes to be compared are all-cause mortality, end-stage kidney disease, cardiovascular disease and mortality, estimated glomerular filtration rate (eGFR) trajectory and chronic kidney disease, pregnancy risks, and development of diseases that frequently lead to chronic kidney disease (e.g. hypertension, diabetes, and obesity). We will additionally evaluate whether the risk of donation differs based on baseline characteristics.

DISCUSSION

Our study will provide a comprehensive assessment of long-term living donor risk to inform candidate living donors, and to inform the follow-up and care of current living donors.

Association between familial aggregation of chronic kidney disease and its incidence and progression

This study aimed to examine the association between familial aggregation of chronic kidney disease (CKD) and risk of CKD development and its progression. This nationwide family study comprised 881,453 cases with newly diagnosed CKD between 2004 and 2017 and 881,453 controls without CKD matched by age and sex, using data from the Korean National Health Insurance Service with linkage to the family tree database. The risks of CKD development and disease progression, defined as an incident end-stage renal disease (ESRD), were evaluated. The presence of any affected family member with CKD was associated with a significantly higher risk of CKD with adjusted ORs (95% CI) of 1.42 (1.38-1.45), 1.50 (1.46-1.55), 1.70 (1.64-1.77), and 1.30 (1.27-1.33) for individuals with affected parents, offspring, siblings, and spouses, respectively. In Cox models conducted on patients with predialysis CKD, risk of incident ESRD was significantly higher in those with affected family members with ESRD. The corresponding HRs (95% CI) were 1.10 (1.05-1.15), 1.38 (1.32-1.46), 1.57 (1.49-1.65), and 1.14 (1.08-1.19) for individuals listed above, respectively. Familial aggregation of CKD was strongly associated with a higher risk of CKD development and disease progression to ESRD.

Long-term Medical Outcomes of Living Kidney Donors

Historically, to minimize risks, living kidney donors have been highly selected and healthy. Operative risks are well-defined, yet concern remains about long-term risks. In the general population, even a mild reduction in glomerular filtration rate (GFR) is associated with cardiovascular disease, chronic kidney disease, and end-stage kidney disease (ESKD). However, reduction in GFR in the general population is due to kidney or systemic disease. Retrospective studies comparing donors with matched general population controls have found no increased donor risk. Prospective studies comparing donors with controls (maximum follow-up, 9 years) have reported that donor GFR is stable or increases slightly, whereas GFR decreases in controls. However, these same studies identified metabolic and vascular donor abnormalities. There are a few retrospective studies comparing donors with controls. Each has limitations in selection of the control group, statistical analyses, and/or length of follow-up. One such study reported increased donor mortality; 2 reported a small increase in absolute risk of ESKD. Risk factors for donor ESKD are similar to those in the general population. Postdonation pregnancies are also associated with increased risk of hypertension and preeclampsia. There is a critical need for long-term follow-up studies comparing donors with controls from the same era, geographic area, and socioeconomic status who are healthy, with normal renal function on the date matching the date of donation, and are matched on demographic characteristics with the donors. These data are needed to optimize donor candidate counseling and informed consent.

Genome-Wide Association Study for eGFR in a Taiwanese Population

BACKGROUND AND OBJECTIVES

Chronic kidney disease (CKD) is a global public health issue associated with large economic burdens. CKD contributes to higher risks of cardiovascular complications, kidney failure, and mortality. The incidence and prevalence rates of kidney failure in Taiwan have remained the highest in the world.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Assessing genetic factors that influence kidney function in specific populations has substantial clinical relevance. We investigated associations of genetic variants with eGFR. The quality control filtering and genotype imputation resulted in 10,008 Taiwan Biobank participants and 6,553,511 variants for final analyses. We examined these loci with in silico replication in individuals of European and African ancestry.

RESULTS

Our results revealed one significant locus (4q21.1) and three suggestive significant loci (17q23.2, 22q13.2, and 3q29) for eGFR in the Taiwanese population. In total, four conditional-independent single nucleotide polymorphisms were identified as the most important variants within these regions, including rs55948430 (Coiled-Coil Domain Containing 158), rs1010269 (BCAS3), rs56108505 (MKL1), and rs34796810 (upstream of DLG1). By performing a meta-analysis, we found that the 4q21.1 and 17q23.2 loci were successfully replicated in the European population, whereas only the 17q23.2 locus was replicated in African ancestry. Therefore, these two loci are suggested to be transethnic loci, and the other two eGFR-associated loci (22q13.2 and 3q29) are likely population specific.

CONCLUSIONS

We identified four susceptibility loci on 4q21.1, 17q23.2, 22q13.2, and 3q29 that associated with kidney-related traits in a Taiwanese population. The 22q13.2 (MKL1) and 3q29 (DLG1) were prioritized as critical candidates. Functional analyses delineated novel pathways related to kidney physiology in Taiwanese and East Asian ancestries.

The Living Kidney Donor Safety Study: Protocol of a Prospective Cohort Study

Background

Living kidney donation is considered generally safe in healthy individuals; however, there is a need to better understand the long-term effects of donation on blood pressure and kidney function.

Objectives

To determine the risk of hypertension in healthy, normotensive adults who donate a kidney compared with healthy, normotensive non-donors with similar indicators of baseline health. We will also compare the 2 groups on the rate of decline in kidney function, the risk of albuminuria, and changes in health-related quality of life.

Design Participants and Setting

Prospective cohort study of 1042 living kidney donors recruited before surgery from 17 transplant centers (12 in Canada and 5 in Australia) between 2004 and 2014. Non-donor participants (n = 396) included relatives or friends of the donor, or donor candidates who were ineligible to donate due to blood group or cross-match incompatibility. Follow-up will continue until 2021, and the main analysis will be performed in 2022. The anticipated median (25th, 75th percentile, maximum) follow-up time after donation is 7 years (6, 8, 15).

Measurements

Donors and non-donors completed the same schedule of measurements at baseline and follow-up (non-donors were assigned a simulated nephrectomy date). Annual measurements were obtained for blood pressure, estimated glomerular filtration rate (eGFR), albuminuria, patient-reported health-related quality of life, and general health.

Outcomes

Incident hypertension (a systolic/diastolic blood pressure ≥ 140/90 mm Hg or receipt of anti-hypertensive medication) will be adjudicated by a physician blinded to the participant's donation status. We will assess the rate of change in eGFR starting from 12 months after the nephrectomy date and the proportion who develop an albumin-to-creatinine ratio ≥3 mg/mmol (≥30 mg/g) in follow-up. Health-related quality of life will be assessed using the 36-item RAND health survey and the Beck Anxiety and Depression inventories.

Limitations

Donation-attributable hypertension may not manifest until decades after donation.

Conclusion

This prospective cohort study will estimate the attributable risk of hypertension and other health outcomes after living kidney donation.

Rethinking Chronic Kidney Disease in the Aging Population

The process of aging population will inevitably increase age-related comorbidities including chronic kidney disease (CKD). In light of this demographic transition, the lack of an age-adjusted CKD classification may enormously increase the number of new diagnoses of CKD in old subjects with an indolent decline in kidney function. Overdiagnosis of CKD will inevitably lead to important clinical consequences and pronounced negative effects on the health-related quality of life of these patients. Based on these data, an appropriate workup for the diagnosis of CKD is critical in reducing the burden of CKD worldwide. Optimal management of CKD should be based on prevention and reduction of risk factors associated with kidney injury. Once the diagnosis of CKD has been made, an appropriate staging of kidney disease and timely prescriptions of promising nephroprotective drugs (e.g., RAAS, SGLT-2 inhibitors, finerenone) appear crucial to slow down the progression toward end-stage kidney disease (ESKD). The management of elderly, comorbid and frail patients also opens new questions on the appropriate renal replacement therapy for this subset of the population. The non-dialytic management of CKD in old subjects with short life expectancy features as a valid option in patient-centered care programs. Considering the multiple implications of CKD for global public health, this review examines the prevalence, diagnosis and principles of treatment of kidney disease in the aging population.

Harnessing the Full Potential of Multi-Omic Analyses to Advance the Study and Treatment of Chronic Kidney Disease

Chronic kidney disease (CKD) was the 12th leading cause of death globally in 2017 with the prevalence of CKD estimated at ~9%. Early detection and intervention for CKD may improve patient outcomes, but standard testing approaches even in developed countries do not facilitate identification of patients at high risk of developing CKD, nor those progressing to end-stage kidney disease (ESKD). Recent advances in CKD research are moving towards a more personalised approach for CKD. Heritability for CKD ranges from 30% to 75%, yet identified genetic risk factors account for only a small proportion of the inherited contribution to CKD. More in depth analysis of genomic sequencing data in large cohorts is revealing new genetic risk factors for common diagnoses of CKD and providing novel diagnoses for rare forms of CKD. Multi-omic approaches are now being harnessed to improve our understanding of CKD and explain some of the so-called 'missing heritability'. The most common omic analyses employed for CKD are genomics, epigenomics, transcriptomics, metabolomics, proteomics and phenomics. While each of these omics have been reviewed individually, considering integrated multi-omic analysis offers considerable scope to improve our understanding and treatment of CKD. This narrative review summarises current understanding of multi-omic research alongside recent experimental and analytical approaches, discusses current challenges and future perspectives, and offers new insights for CKD.

Evaluation of Genetic Kidney Diseases in Living Donor Kidney Transplantation: Towards Precision Genomic Medicine in Donor Risk Assessment

Purpose of Review

To provide a comprehensive update on the role of genetic testing for the evaluation of kidney transplant recipient and living donor candidates.

Recent Findings

The evaluation of candidates for living donor transplantation and their potential donors occurs within an ever-changing landscape impacted by new evidence and risk assessment techniques. Criteria that were once considered contraindications to living kidney donation are now viewed as standard of care, while new tools identify novel risk markers that were unrecognized in past decades. Recent work suggests that nearly 10% of a cohort of patients with chronic/end-stage kidney disease had an identifiable genetic etiology, many whose original cause of renal disease was either unknown or misdiagnosed. Some also had an incidentally found genetic variant, unrelated to their nephropathy, but medically actionable. These patterns illustrate the substantial potential for genetic testing to better guide the selection of living donors and recipients, but guidance on the proper application and interpretation of novel technologies is in its infancy. In this review, we examine the utility of genetic testing in various kidney conditions, and discuss risks and unresolved challenges. Suggested algorithms in the context of related and unrelated donation are offered.

Summary

Genetic testing is a rapidly evolving strategy for the evaluation of candidates for living donor transplantation and their potential donors that has potential to improve risk assessment and optimize the safety of donation.

Pathway Association Studies Reveal Gene Loci and Pathway Networks that Associated With Plasma Cystatin C Levels

As a marker for glomerular filtration, plasma cystatin C level is used to evaluate kidney function. To decipher genetic factors that control the plasma cystatin C level, we performed genome-wide association and pathway association studies using United Kingdom Biobank data. One hundred fifteen loci yielded p values less than 1 × 10⁻¹⁰⁰, three genes (clusters) showed the most significant associations, including the CST8-CST9 cluster on chromosome 20, the SH2B3-ATXN2 gene region on chromosome 12, and the SHROOM3-CCDC158 gene region on chromosome 4. In pathway association studies, forty significant pathways had FDR (false discovery rate) and or FWER (family-wise error rate) ≤ 0.001: spermatogenesis, leukocyte trans-endothelial migration, cell adhesion, glycoprotein, membrane lipid, steroid metabolic process, and insulin signaling pathways were among the most significant pathways that associated with the plasma cystatin C levels. We also performed Genome-wide association studies for eGFR, top associated genes were largely overlapped with those for cystatin C.

Family History is Important to Identify Patients with Monogenic Causes of Adult-Onset Chronic Kidney Disease

Monogenic causes of chronic kidney disease (CKD) are more prevalent in adults than previously thought, as causative gene variants are found in almost 10% of unselected patients with CKD. Even so, genetic testing in patients with adult-onset CKD is uncommon in clinical practice and the optimal criteria for patient selection remain unclear. A family history of kidney disease emerges as one marker associated with a high diagnostic yield of genetic testing. We present 3 cases of adult-onset CKD with underlying monogenic causes exemplifying different modes of inheritance. Case 1 is a 60-year-old male with slowly progressive CKD initially ascribed to hypertension and diabetes despite a family history with several affected first-degree relatives. A pathogenic MUC1 variant was found, and thus we identified the first Danish family of MUC1-associated autosomal dominant tubulointerstitial kidney disease. Case 2 is a 40-year-old female with nephrocalcinosis, nephrolithiasis, and unexplainable hypercalcemia consistent with vitamin D intoxication. The family history indicated autosomal recessive inheritance, and genetic testing revealed 2 pathogenic CYP24A1 variants in compound heterozygous form associated with idiopathic infantile hypercalcemia. Case 3 is a 50-year-old male with microscopic hematuria, proteinuria, and hearing loss. Electron microscopy of renal biopsy showed thin basal membrane syndrome, and the family history indicated X-linked inheritance. A novel missense variant in COL4A5 was identified, suggesting an atypical late-onset form of X-linked Alport syndrome. This case series illustrates the heterogeneous presentations of monogenic kidney disease in adults and emphasizes the importance of family history for initiating genetic testing to identify underlying monogenic causation. Moreover, we discuss the potential impact of genetic diagnostics on patient management and genetic family counseling.

Familial Contributions to the Association Between Low Birth Weight and Risk of CKD in Adult Life

Introduction

Previous studies have revealed that individuals with low birth weight (LBW) have higher risk of chronic kidney disease (CKD) and that LBW and CKD cluster in families. This study investigates how familial factors affect the association between birth-related risk markers and risk of CKD.

Methods

The Medical Birth Registry (MBR) of Norway has registered all births in Norway since 1967. Sibling data were available through the Norwegian Population Registry. The Norwegian Patient Registry has registered diagnostic codes for all admissions and outpatient visits to Norwegian hospitals since 2008. Data from these registries were linked. Risk of CKD according to whether the individual himself or at least one of his siblings had LBW was analyzed using logistic regression statistics.

Results

Of 1,847,565 individuals, 3336 had been diagnosed with CKD. Compared with individuals without LBW and no siblings with LBW, individuals without LBW but who had a sibling with LBW had adjusted odds ratio (aOR) of 1.33 (1.19–1.49), those with LBW but no siblings with LBW had aOR of 1.74 (1.55–1.95), and those with LBW and a sibling with LBW had aOR of 1.77 (1.54–2.04) for CKD. Similar results were found for LBW for gestational age, but preterm birth revealed weaker associations.

Conclusion

Individuals who have a sibling with LBW have an increased risk of CKD later in life, and individuals who themselves have LBW have an even higher risk. Our findings suggest that there are familial contributions to the nephron endowment in utero hypothesis.

Associations of Genetic Factors, Educational Attainment, and Their Interaction With Kidney Function Outcomes

Both genetic predisposition and low educational attainment (EA) are associated with higher risk of chronic kidney disease. We examined the interaction of EA and genetic risk in kidney function outcomes. We included 3,597 participants from the Prevention of Renal and Vascular End-Stage Disease Cohort Study, a longitudinal study in a community-based sample from Groningen, the Netherlands (median follow-up, 11 years; 1997–2012). Kidney function was approximated by obtaining estimated glomerular filtration rate (eGFR) from serum creatinine and cystatin C. Individual longitudinal linear eGFR trajectories were derived from linear mixed models. Genotype data on 63 single-nucleotide polymorphisms, with known associations with eGFR, were used to calculate an allele-weighted genetic score (WGS). EA was categorized into high, medium, and low. In ordinary least squares analysis, higher WGS and lower EA showed additive effects on reduced baseline eGFR; the interaction term was nonsignificant. In analysis of eGFR decline, the significant interaction term suggested amplification of genetic risk by low EA. Adjustment for known renal risk factors did not affect our results. This study presents the first evidence of gene-environment interaction between EA and a WGS for eGFR decline and provides population-level insights into the mechanisms underlying socioeconomic disparities in chronic kidney disease.

Familial Aggregation of CKD and Heritability of Kidney Biomarkers in the General Population: The Lifelines Cohort Study

RATIONALE & OBJECTIVE

Chronic kidney disease (CKD) has a heritable component. We aimed to quantify familial aggregation of CKD in the general population and assess the extent to which kidney traits could be explained by genetic and environmental factors.

STUDY DESIGN

Cross-sectional 3-generation family study.

SETTING & PARTICIPANTS

Data were collected at entry into the Lifelines Cohort Study from a sample of the general population of the northern Netherlands, composed predominantly of individuals of European ancestry.

EXPOSURE

Family history of CKD.

OUTCOMES

The primary outcome was CKD, defined as estimated glomerular filtration rate (eGFR)<60mL/min/1.73m², where GFR was estimated using the CKD Epidemiology Collaboration creatinine equation. Among a subsample for which urinary albumin concentration was available (n=59,943), urinary albumin excretion was expressed as the rate of urinary albumin excretion (UAE) per 24 hours or urinary albumin-creatinine ratio (UACR).

ANALYTICAL APPROACH

Familial aggregation of CKD was assessed by calculating the recurrence risk ratio (RRR), using adapted Cox proportional hazards models. Heritability of continuous kidney-related traits was estimated using linear mixed models and defined as the ratio of the additive genetic variance to total phenotypic variance. All models were adjusted for age, sex, and known risk factors for kidney disease.

RESULTS

Among 155,911 participants with available eGFR data, the prevalence of CKD was 1.19% (1,862 cases per 155,911). The risk of CKD in those with an affected first-degree relative was 3 timeshigher than the risk in the total sample (RRR, 3.04 [95% CI, 2.26-4.09). In those with an affected spouse, risk of CKD was also higher (RRR, 1.56 [95% CI, 1.20-1.96]), indicative of shared environmental factors and/or assortative mating. Heritability estimates of eGFR, UAE, and UACR were 44%, 20%, and 18%, respectively. For serum urea, creatinine, and uric acid, estimates were 31%, 37%, and 48%, respectively, whereas estimates for serum electrolytes ranged from 22% to 28%.

LIMITATIONS

Use of estimated rather than measured GFR. UAE data only available in a subsample.

CONCLUSIONS

In this large population-based family study, a positive family history was strongly associated with increased risk of CKD. We observed moderate to high heritability of kidney traits and related biomarkers. These results indicate an important role of genetic factors in CKD risk.

Evaluation of a genetic risk score based on creatinine-estimated glomerular filtration rate and its association with kidney outcomes

Background

Meta-analysis of cross-sectional genome-wide association studies (GWAS) on creatinine-estimated glomerular filtration rate (eGFRcrea) identified 53 single-nucleotide polymorphisms (SNPs). These SNP effects can be aggregated into a genetic risk score (GRS) for chronic kidney disease (CKD). To assess its clinical utility, we examined associations with creatinine-estimated kidney outcomes, both cross-sectionally and longitudinally. Additionally, we examined associations with cystatin C-estimated kidney outcomes to verify that a GRS based on eGFRcrea SNPs represents the genetics underlying kidney function.

Methods

In the community-based Prevention of REnal and Vascular ENdstage Disease (PREVEND) study, we assessed eGFRcrea and eGFRcysc at baseline and four follow-up examinations. The GRS comprised 53 SNPs for eGFRcrea weighted for reported effect-sizes. We adjusted for baseline demographics and renal risk factors.

Results

We included 3649 subjects (median age 49 years, 52% male, median follow-up 11 years, n = 85 baseline CKD, n = 154 incident CKD). At baseline, a higher GRS associated with lower eGFRcrea {adjusted B [95% confidence interval (CI)] = -2.05 (-2.45 to - 1.65) mL/min/1.73 m2, P < 0.001} and higher CKD prevalence [adjusted odds ratio (95% CI) = 1.41 (1.12-1.77), P = 0.002]. During follow-up, a higher GRS associated with higher CKD incidence [adjusted hazard ratio (95% CI) = 1.28 (1.09-1.50), P = 0.004], but no longer significantly after adjustment for baseline eGFR. No significant association with eGFRcrea decline was found. Associations with cystatin C-estimated outcomes were similar.

Conclusions

The GRS robustly associated with baseline CKD and eGFR, independent of known risk factors. Associations with incident CKD were likely due to low baseline eGFR, not accelerated eGFR decline. The GRS for eGFRcrea likely represents the genetics underlying kidney function, not creatinine metabolism or underlying aetiologies. To improve the clinical utility of GWAS results for CKD, these need to specifically address eGFR decline and CKD incidence.

The Effect of Donors' Demographic Characteristics in Renal Function Post-Living Kidney Donation. Analysis of a UK Single Centre Cohort

Introduction: There is a great need to increase the organ donor pool, particularly for living donors. This study analyses the difference in post-living donation kidney function according to pre-donation characteristics of age, genetic relationship with the recipient, sex, ethnicity, and Body Mass Index (BMI). Methods: Retrospective single centre analysis of the trajectory of estimated Glomerular Filtration Rate (eGFR) post-living kidney donation, as a measure of kidney function. Mean eGFR of the different groups was compared at 6 months and during the 60 months follow up. Results: Mean age was 46 ± 13 years, 57% were female, and 60% Caucasian. Mean BMI was 27 ± 5 kg/m², with more than a quarter of the cohort having a BMI > 30 (26%), and the majority of the donors genetically related to their recipients (56%). The higher decline rate in eGFR was at 6 months after donation, with female sex, non-Caucasian ethnicity, and age lower than 60 years being independently associated with higher recovery in kidney function (p < 0.05). In the 60 months follow up, older age, genetic relationship with the recipient, and male sex led to higher percentual difference in eGFR post-donation. Conclusion: In this study, with a high proportion of high BMI living kidney donors, female sex, age lower than 60 years, and non-genetic relationship with recipient were persistently associated with higher increase in post-donation kidney function. Ethnicity and BMI, per se, should not be a barrier to increasing the living donor kidney pool.

Genomic approaches in the search for molecular biomarkers in chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is recognised as a global public health problem, more prevalent in older persons and associated with multiple co-morbidities. Diabetes mellitus and hypertension are common aetiologies for CKD, but IgA glomerulonephritis, membranous glomerulonephritis, lupus nephritis and autosomal dominant polycystic kidney disease are also common causes of CKD.

MAIN BODY

Conventional biomarkers for CKD involving the use of estimated glomerular filtration rate (eGFR) derived from four variables (serum creatinine, age, gender and ethnicity) are recommended by clinical guidelines for the evaluation, classification, and stratification of CKD. However, these clinical biomarkers present some limitations, especially for early stages of CKD, elderly individuals, extreme body mass index values (serum creatinine), or are influenced by inflammation, steroid treatment and thyroid dysfunction (serum cystatin C). There is therefore a need to identify additional non-invasive biomarkers that are useful in clinical practice to help improve CKD diagnosis, inform prognosis and guide therapeutic management.

CONCLUSION

CKD is a multifactorial disease with associated genetic and environmental risk factors. Hence, many studies have employed genetic, epigenetic and transcriptomic approaches to identify biomarkers for kidney disease. In this review, we have summarised the most important studies in humans investigating genomic biomarkers for CKD in the last decade. Several genes, including UMOD, SHROOM3 and ELMO1 have been strongly associated with renal diseases, and some of their traits, such as eGFR and serum creatinine. The role of epigenetic and transcriptomic biomarkers in CKD and related diseases is still unclear. The combination of multiple biomarkers into classifiers, including genomic, and/or epigenomic, may give a more complete picture of kidney diseases.

Preliminary analysis of the effect of Stevia (Stevia rebaudiana) in patients with chronic kidney disease (stage I to stage III)

Background

Stevia, Stevia rebaudiana (Bertoni), has become an important economic plant for its commercial use as a sweetener. Stevia plays a significant role in the healthcare practice of different cultures and in population. Previous animal and clinical studies demonstrated the efficacy of Stevia against chronic diseases like diabetes and hypertension. This study aimed to investigate the beneficial effect of Stevia in chronic kidney disease (CKD) patients after three (3) months of treatment along with the conventional antihypertensive and anti diabetic medications.

Methods

A prospective, interventional, randomized, single-blind, placebo-controlled trial has been done with 97 participants. Stevia capsule (250 mg) or matching placebo was given to the participants twice daily along with Angiotensin-II Receptor Blocker (ARB) and/or Ca²⁺ Channel Blocker (CCB). First follow up visits were done after 3 months of the interval. Blood and urine samples were collected for the biochemical tests. A structured questionnaire was used for the baseline assessment. Informed consent was taken from each participant.

Results

Both hypertension and diabetes were found to be associated with CKD. Most of the participants (52.3%) of Stevia group were in CKD Stage II. Significant changes were found in Serum creatinine (p < 0.027), Serum Uric acid (p < 0.009), Fasting blood sugar (p < 0.041) and Postprandial blood sugar (p < 0.013) and Microalbumin (p < 0.041) level in the treatment group.

Conclusion

The initial result demonstrated that Stevia has the potential for a significant improvement of some biochemical parameters in CKD patients. After completion of the nine (9) months clinical trial, the constructive effect of Stevia can be confirmed in this group of patients.

APOL1 Nephropathy: A Population Genetics and Evolutionary Medicine Detective Story

Common DNA sequence variants rarely have a high-risk association with a common disease. When such associations do occur, evolutionary forces must be sought, such as in the association of apolipoprotein L1 (APOL1) gene risk variants with nondiabetic kidney diseases in populations of African ancestry. The variants originated in West Africa and provided pathogenic resistance in the heterozygous state that led to high allele frequencies owing to an adaptive evolutionary selective sweep. However, the homozygous state is disadvantageous and is associated with a markedly increased risk of a spectrum of kidney diseases encompassing hypertension-attributed kidney disease, focal segmental glomerulosclerosis, human immunodeficiency virus nephropathy, sickle cell nephropathy, and progressive lupus nephritis. This scientific success story emerged with the help of the tools developed over the past 2 decades in human genome sequencing and population genomic databases. In this introductory article to a timely issue dedicated to illuminating progress in this area, we describe this unique population genetics and evolutionary medicine detective story. We emphasize the paradox of the inheritance mode, the missing heritability, and unresolved associations, including cardiovascular risk and diabetic nephropathy. We also highlight how genetic epidemiology elucidates mechanisms and how the principles of evolution can be used to unravel conserved pathways affected by APOL1 that may lead to novel therapies. The APOL1 gene provides a compelling example of a common variant association with common forms of nondiabetic kidney disease occurring in a continental population isolate with subsequent global admixture. Scientific collaboration using multiple experimental model systems and approaches should further clarify pathomechanisms further, leading to novel therapies.

Causes and timing of end-stage renal disease after living kidney donation

End-stage renal disease (ESRD) is a risk after kidney donation. We sought, in a large cohort of kidney donors, to determine the causes of donor ESRD, the interval from donation to ESRD, the role of the donor/recipient relationship, and the trajectory of the estimated GFR (eGFR) from donation to ESRD. From 1/1/1963 thru 12/31/2015, 4030 individuals underwent living donor nephrectomy at our center, as well as ascertainment of ESRD status. Of these, 39 developed ESRD (mean age ± standard deviation [SD] at ESRD, 62.4 ± 14.1 years; mean interval between donation and ESRD, 27.1 ± 9.8 years). Donors developing ESRD were more likely to be male, as well as smokers, and younger at donation, and to have donated to a first-degree relative. Of donors with a known cause of ESRD (n = 25), 48% was due to diabetes and/or hypertension; only 2 from a disease that would have affected 1 kidney (cancer). Of those 25 with an ascertainable ESRD cause, 4 shared a similar etiology of ESRD with their recipient. Almost universally, thechange of eGFR over time was stable, until new-onset disease (kidney or systemic). Knowledge of factors contributing to ESRD after living kidney donation can improve donor selection and counseling, as well as long-term postdonation care.

GFR ≤25 years postdonation in living kidney donors with (vs. without) a first-degree relative with ESRD

An increased risk of ESRD has been reported for living kidney donors, and appears to be higher for those donating to a relative. The reasons for this are not clear. One possibility is that ESRD is due to the nephrectomy-related reduction in GFR, followed by an age-related decline that may be more rapid in related donors. Between 1/1/1990 and 12/31/2014, we did 2002 living donor nephrectomies. We compared long-term postdonation eGFR trajectory for donors with (n = 1245) vs. without (n = 757) a first-degree relative with ESRD. Linear mixed-effects models were used to model the longitudinal trajectory of eGFR. With all other variables held constant, we noted a steady average increase in eGFR until donors reached age 70: 1.12 (95% CI: 0.92-1.32) mL/min/1.73m^² /yr between 6 weeks and 5 years postdonation; 0.24 (0.00-0.49) mL/min/1.73m^² /yr between 5 and 10 years; and 0.07 (-0.10 to +0.25) mL/min/1.73m^² /yr between 10 and 20 years for donors with attained age less than 70. After age 70, eGFR declined. After we adjusted for predonation factors, the difference in eGFR slopes between related and unrelated donors was 0.20 mL/min/1.753 m² /year (0.07-0.33). Our data suggests that postdonation, kidney donor eGFR increases each year for a number of years and that eGFR trajectory does not explain any increase in ESRD after donation.

The Patterns, Risk Factors, and Prediction of Progression in Chronic Kidney Disease: A Narrative Review

Chronic kidney disease (CKD) is a global public health problem that is associated with excess morbidity, mortality, and health resource utilization. The progression of CKD is defined by a decrease in glomerular filtration rate and leads to a variety of metabolic abnormalities including acidosis, hypertension, anemia, and mineral bone disorder. Lower glomerular filtration rate also bears a strong relationship with an increased risk of cardiovascular events, end-stage renal disease, and death. Patterns of CKD progression include linear and nonlinear trajectories, but kidney function can remain stable for years in some individuals. Addressing modifiable risk factors for the progression of CKD is needed to attenuate its associated morbidity and mortality. Developing effective risk prediction models for CKD progression is critical to identify patients who are more likely to benefit from interventions and more intensive monitoring. Accurate risk-prediction algorithms permit systems to best align health care resources with risk to maximize their effects and efficiency while guiding overall decision making.

Albuminuria and Reduced Estimated Glomerular Filtration Rate among First-degree Relatives of Patients with Chronic Kidney Disease in Lagos, Southwest Nigeria

Screening of individuals at increased risk of developing chronic kidney disease (CKD) has been advocated by several guidelines. Among individuals at increased risk are first-degree relatives (FDRs) of patients with CKD. There is a paucity of data on the prevalence and risk of CKD in FDRs of patients with CKD in sub-Saharan African population. This study aimed to screen FDRs of patients with CKD for albuminuria and reduced estimated glomerular filtration rate (eGFR). A cross-sectional survey of 230 FDRs of patients with CKD and 230 individuals without family history of CKD was conducted. Urinary albumin: creatinine ratio (ACR) was determined from an early morning spot urine. Glomerular filtration rate was estimated from serum creatinine. Reduced eGFR was defined as eGFR <60 ml/min/1.73 m² and albuminuria defined as ACR ≥30 mg/g. A higher prevalence of albuminuria was found in the FDRs compared to the controls (37.0% vs. 22.2%; P < 0.01). Reduced eGFR was more prevalent among the FDRs compared with the controls (5.7% vs. 1.7%, P < 0.03). Hypertension (odds ratio [OR], 2.9) and reduced eGFR (OR, 9.1) were independent predictors of albuminuria while increasing age (OR, 6.7) and proteinuria (OR, 10.7) predicted reduced eGFR in FDRs. The odds of developing renal dysfunction were increased 2-fold in the FDRs of patients with CKD, OR 2.3, 95% confidence interval, 1.29–3.17. We concluded that albuminuria and reduced eGFR are more prevalent among the FDRs of patient with CKD and they are twice as likely to develop kidney dysfunction as healthy controls.

Diabetic Microvascular Disease: An Endocrine Society Scientific Statement

Both type 1 and type 2 diabetes adversely affect the microvasculature in multiple organs. Our understanding of the genesis of this injury and of potential interventions to prevent, limit, or reverse injury/dysfunction is continuously evolving. This statement reviews biochemical/cellular pathways involved in facilitating and abrogating microvascular injury. The statement summarizes the types of injury/dysfunction that occur in the three classical diabetes microvascular target tissues, the eye, the kidney, and the peripheral nervous system; the statement also reviews information on the effects of diabetes and insulin resistance on the microvasculature of skin, brain, adipose tissue, and cardiac and skeletal muscle. Despite extensive and intensive research, it is disappointing that microvascular complications of diabetes continue to compromise the quantity and quality of life for patients with diabetes. Hopefully, by understanding and building on current research findings, we will discover new approaches for prevention and treatment that will be effective for future generations.

Epigenome-wide association studies identify DNA methylation associated with kidney function

Chronic kidney disease (CKD) is defined by reduced estimated glomerular filtration rate (eGFR). Previous genetic studies have implicated regulatory mechanisms contributing to CKD. Here we present epigenome-wide association studies of eGFR and CKD using whole-blood DNA methylation of 2264 ARIC Study and 2595 Framingham Heart Study participants to identify epigenetic signatures of kidney function. Of 19 CpG sites significantly associated (P < 1e-07) with eGFR/CKD and replicated, five also associate with renal fibrosis in biopsies from CKD patients and show concordant DNA methylation changes in kidney cortex. Lead CpGs at PTPN6/PHB2, ANKRD11, and TNRC18 map to active enhancers in kidney cortex. At PTPN6/PHB2 cg19942083, methylation in kidney cortex associates with lower renal PTPN6 expression, higher eGFR, and less renal fibrosis. The regions containing the 243 eGFR-associated (P < 1e-05) CpGs are significantly enriched for transcription factor binding sites of EBF1, EP300, and CEBPB (P < 5e-6). Our findings highlight kidney function associated epigenetic variation.

Genome-wide association studies of kidney function show enrichment of associated genetic variants in regulatory regions. Here, the authors perform epigenome-wide association studies of kidney function and disease, identifying 19 CpG sites significantly associated with these.

Family Aggregation and Heritability of ESRD in Taiwan: A Population-Based Study

BACKGROUND

Aggregation of end-stage renal disease (ESRD) has been observed in families of European origin, as well as those of African origin. However, it is not well documented if this disease aggregates in Asian families. Furthermore, the contribution of genetic factors and shared environmental factors to family aggregation remains unclear.

STUDY DESIGN

Population-based cross-sectional cohort study.

SETTING & PARTICIPANTS

All 23,422,955 individuals registered in the Taiwan National Health Insurance Research Database in 2013. Among these, 47.45%, 57.45%, 47.29%, and 1.51% had a known parent, child, sibling, or twin, respectively. We identified 87,849 patients who had a diagnosis of ESRD.

PREDICTOR

Family history of ESRD.

OUTCOMES & MEASUREMENTS

ESRD and heritability defined as the proportion of phenotypic variance attributable to genetic factors.

RESULTS

Having an affected first-degree relative with ESRD was associated with an adjusted relative risk of 2.46 (95% CI, 2.32-2.62). Relative risks were 96.38 (95% CI, 48.3-192.34) for twins of patients with ESRD, 2.15 (95% CI, 2.02-2.29) for parents, 2.78 (95% CI, 2.53-3.05) for offspring, 4.96 (95% CI, 4.19-5.88) for siblings, and 1.66 (95% CI, 1.54-1.78) for spouses without genetic similarities. Heritability in this study was 31.1% to 11.4% for shared environmental factors and 57.5% for nonshared environmental factors.

LIMITATIONS

This was a registry database study and we did not have detailed information about clinical findings or the definite causes of ESRD.

CONCLUSIONS

This whole population-based family study in Asia confirmed, in a Taiwanese population, that a family history of ESRD is a strong risk factor for this disease. Moderate heritability was noted and environmental factors were related to disease. Family history of ESRD is an important piece of clinical information.

A Case-Based Analysis of Whether Living Related Donors Listed for Transplant Share ESRD Causes with Their Recipients

BACKGROUND AND OBJECTIVES

Two recent studies reported increased risk of ESRD after kidney donation. In both, the majority of ESRD was seen in those donating to a relative. Confounding this observation is that, in the absence of donation, relatives of those with ESRD are at increased risk for ESRD. Understanding the pathogenesis and risk factors for postdonation ESRD is critical for both donor selection and counseling.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We hypothesized that if familial relationship was an important consideration in pathogenesis, the donor and linked recipient would share ESRD etiology. We obtained information from the Organ Procurement and Transplantation Network (OPTN) on all living kidney donors subsequently waitlisted for a kidney transplant in the United States between January 1, 1996 and November 30, 2015, to determine (1) the donor-recipient relationship and (2) whether related donor-recipient pairs had similar causes of ESRD.

RESULTS

We found that a significant amount of information, potentially available at the time of listing, was not reported to the OPTN. Of 441 kidney donors listed for transplant, only 169 had information allowing determination of interval from donation to listing, and only 99 (22% of the total) had information on the donor-recipient relationship and ESRD etiology. Of the 99 donors, 87 were related to their recipient. Strikingly, of the 87, only a minority (23%) of donor-recipient pairs shared ESRD etiology. Excluding hypertension, only 8% shared etiology.

CONCLUSIONS

A better understanding of ESRD in donors requires complete and detailed data collection, as well as a method to capture all ESRD end points. This study highlights the absence of critical information that is urgently needed to provide a meaningful understanding of ESRD after kidney donation. We found that of living related donors listed for transplant, where both donor and recipient cause of ESRD is recorded, only a minority share ESRD etiology with their recipient.

The Impact of Kidney Development on the Life Course: A Consensus Document for Action

Hypertension and chronic kidney disease (CKD) have a significant impact on global morbidity and mortality. The Low Birth Weight and Nephron Number Working Group has prepared a consensus document aimed to address the relatively neglected issue for the developmental programming of hypertension and CKD. It emerged from a workshop held on April 2, 2016, including eminent internationally recognized experts in the field of obstetrics, neonatology, and nephrology. Through multidisciplinary engagement, the goal of the workshop was to highlight the association between fetal and childhood development and an increased risk of adult diseases, focusing on hypertension and CKD, and to suggest possible practical solutions for the future. The recommendations for action of the consensus workshop are the results of combined clinical experience, shared research expertise, and a review of the literature. They highlight the need to act early to prevent CKD and other related noncommunicable diseases later in life by reducing low birth weight, small for gestational age, prematurity, and low nephron numbers at birth through coordinated interventions. Meeting the current unmet needs would help to define the most cost-effective strategies and to optimize interventions to limit or interrupt the developmental programming cycle of CKD later in life, especially in the poorest part of the world.

Chronic kidney disease in children and the role of epigenetics: Future therapeutic trajectories

Global differences in the observed causes of chronic kidney disease (CKD) in children are well documented and are attributed to dissimilarities in clime, race, hereditary, and ancestry. Thus, familial clustering and disparities in CKD prevalence rates across ethnic and racial groups indicate that the progression of renal disease has a strong genetic component. Mammalian studies have demonstrated a feasible nexus between nutrition and non-genetic exposure (around the time of conception and in epigenetic changes) in the expression of major genes identified in renal organogenesis. The major consequence is a reduction in the number of nephrons, with subsequent predisposition to hypertension and CKD. Identifying these epigenetic changes is crucial (due to their potentially reversible nature), as they may serve as future therapeutic targets to prevent kidney fibrosis and CKD. Despite progress in the field of epigenetics in oncology, research in other subspecialties of medicine is largely experimental with few existing studies regarding the clinical implication of epigenetics in renal disease. Therapeutic trajectories for CKD in children based on the influence of epigenetics may eventually revolutionize the management of this disease. The aim of the current narrative review is to appraise the role of epigenetics in CKD, and highlight the potential future therapeutic pathways.

Genetic Considerations in Pediatric Chronic Kidney Disease

Chronic kidney disease (CKD) in children is an irreversible process that, in some cases, may lead to end-stage renal disease. The majority of children with CKD have a congenital disorder of the kidney or urological tract arising from birth. There is strong evidence for both a genetic and epigenetic component to progression of CKD. Utilization of gene-mapping strategies, ranging from genome-wide association studies to single-nucleotide polymorphism analysis, serves to identify potential genetic variants that may lend to disease variation. Genome-wide association studies evaluating population-based data have identified different loci associated with CKD progression. Analysis of single-nucleotide polymorphisms on an individual level suggests that secondary systemic sequelae of CKD are closely related to dysfunction of the cardiovascular-inflammatory axis and may lead to advanced cardiovascular disease through abnormal vascular calcification and activation of the renin-angiotensin system. Similarly, genetic variants affecting cytokine control, fibrosis, and parenchymal development may modulate CKD through development and acceleration of renal interstitial fibrosis. Epigenetic studies evaluate modification of the genome through DNA methylation, histone modification, or RNA interference, which may be directly influenced by external or environmental factors directing genomic expression. Lastly, improved understanding of the genetic and epigenetic contribution to CKD progression may allow providers to identify a population at accelerated risk for disease progression and apply novel therapies targeted at the genetic mechanism of disease.

Genetic loci associated with renal function measures and chronic kidney disease in children: the Pediatric Investigation for Genetic Factors Linked with Renal Progression Consortium

BACKGROUND

Chronic kidney disease (CKD) in children is characterized by rapid progression and a high incidence of end-stage renal disease and therefore constitutes an important health problem. While unbiased genetic screens have identified common risk variants influencing renal function and CKD in adults, the presence and identity of such variants in pediatric CKD are unknown.

METHODS

The international Pediatric Investigation for Genetic Factors Linked with Renal Progression (PediGFR) Consortium comprises three pediatric CKD cohorts: Chronic Kidney Disease in Children (CKiD), Effect of Strict Blood Pressure Control and ACE Inhibition on the Progression of CRF in Pediatric Patients (ESCAPE) and Cardiovascular Comorbidity in Children with CKD (4C). Clean genotype data from > 10 million genotyped or imputed single-nucleotide polymorphisms (SNPs) were available for 1136 patients with measurements of serum creatinine at study enrollment. Genome-wide association studies were conducted to relate the SNPs to creatinine-based estimated glomerular filtration rate (eGFR crea) and proteinuria (urinary albumin- or protein-to-creatinine ratio ≥ 300 and ≥ 500 mg/g, respectively). In addition, European-ancestry PediGFR patients (cases) were compared with 1347 European-ancestry children without kidney disease (controls) to identify genetic variants associated with the presence of CKD.

RESULTS

SNPs with suggestive association P-values < 1 × 10(-5) were identified in 10 regions for eGFR crea, four regions for proteinuria and six regions for CKD including some plausible biological candidates. No SNP was associated at genome-wide significance (P < 5 × 10(-8)). Investigation of the candidate genes for proteinuria in adults from the general population provided support for a region on chromosome 15 near RSL24D1/UNC13C/RAB27A. Conversely, targeted investigation of genes harboring GFR-associated variants in adults from the general population did not reveal significantly associated SNPs in children with CKD.

CONCLUSIONS

Our findings suggest that larger collaborative efforts will be needed to draw reliable conclusions about the presence and identity of common variants associated with eGFR, proteinuria and CKD in pediatric populations.

Familial Factors, Low Birth Weight, and Development of ESRD: A Nationwide Registry Study

BACKGROUND

Previous studies have demonstrated that low birth weight (LBW) is associated with higher risk for end-stage renal disease (ESRD). However, both LBW and ESRD cluster in families. The present study investigates whether familial factors explain the association between LBW and ESRD.

STUDY DESIGN

Retrospective registry-based cohort study.

SETTING & PARTICIPANTS

Since 1967, the Medical Birth Registry of Norway has recorded medical data for all births in the country. Sibling data are available through the Norwegian Population Registry. Since 1980, all patients with ESRD in Norway have been registered in the Norwegian Renal Registry. Individuals registered in the Medical Birth Registry with at least 1 registered sibling were included.

PREDICTOR

LBW in the participant and/or LBW in at least 1 sibling.

OUTCOME

ESRD.

RESULTS

Of 1,852,080 included individuals, 527 developed ESRD. Compared with individuals without LBW and with no siblings with LBW, individuals without LBW but with a sibling with LBW had an HR for ESRD of 1.20 (95% CI, 0.91-1.59), individuals with LBW but no siblings with LBW had an HR of 1.59 (95% CI, 1.18-2.14), and individuals with LBW and a sibling with LBW had an HR of 1.78 (95% CI, 1.26-2.53). Similar results were observed for individuals who were small for gestational age (SGA). Separate analyses for the association of age 18 to 42 years and noncongenital ESRD showed stronger associations for SGA than for LBW, and the associations were not statistically significant for age 18 to 42 years for LBW.

LIMITATIONS

Follow-up only until 42 years of age.

CONCLUSIONS

LBW and SGA are associated with higher risk for ESRD during the first 40 years of life, and the associations were not explained by familial factors. Our results support the hypothesis that impaired intrauterine nephron development may be a causal risk factor for progressive kidney disease.

Race, Relationship and Renal Diagnoses After Living Kidney Donation

BACKGROUND

In response to recent studies, a better understanding of the risks of renal complications among African American and biologically related living kidney donors is needed.

METHODS

We examined a database linking U.S. registry identifiers for living kidney donors (1987-2007) to billing claims from a private health insurer (2000-2007 claims) to identify renal condition diagnoses categorized by International Classification of Diseases 9th Revision coding. Cox regression with left and right censoring was used to estimate cumulative incidence of diagnoses after donation and associations (adjusted hazards ratios, aHR) with donor traits.

RESULTS

Among 4650 living donors, 13.1% were African American and 76.3% were white; 76.1% were first-degree relatives of their recipient. By 7 years post-donation, after adjustment for age and sex, greater proportions of African American compared with white donors had renal condition diagnoses: chronic kidney disease (12.6% vs 5.6%; aHR, 2.32; 95% confidence interval [95% CI], 1.48-3.62), proteinuria (5.7% vs 2.6%; aHR, 2.27; 95% CI, 1.32-3.89), nephrotic syndrome (1.3% vs 0.1%; aHR, 15.7; 95% CI, 2.97-83.0), and any renal condition (14.9% vs 9.0%; aHR, 1.72; 95% CI, 1.23-2.41). Although first-degree biological relationship to the recipient was not associated with renal risk, associations of African American race persisted for these conditions and included unspecified renal failure and reported disorders of kidney dysfunction after adjustment for biological donor-recipient relationship.

CONCLUSIONS

African Americans more commonly develop renal conditions after living kidney donation, independent of donor-recipient relationship. Continued research is needed to improve risk stratification for renal outcomes among African American living donors.

[Prevalence of kidney disease in asymptomatic children with family history of renal replacement therapy]

BACKGROUND

Having a first- or second-degree relative with chronic kidney disease (CKD) has been reported as a risk factor for CKD development. The aim of the study was to determine the prevalence of CKD in children with a first- or second-degree relative undergoing renal replacement therapy (hemodialysis or renal transplant).

METHODS

A screening study was performed in asymptomatic children with a family history of CKD in a first- or second-degree relative undergoing renal replacement therapy. Informed consent was obtained in all cases. A clinical examination was performed. Blood and urine samples were obtained for serum creatinine, serum electrolytes, urinalysis, and microalbumin/creatinine ratio.

RESULTS

There were 45 subjects included with a median age of 9.6 years; 24 (53%) were male. Urinary abnormality/CKD was observed in 11 subjects (24.4%). The most common urinary abnormalities were hematuria (6/11) and microalbuminuria (4/11). Stage 2 CKD was found in seven subjects and four subjects with stage 1 CKD.

CONCLUSIONS

The study of families of patients undergoing renal replacement therapy is useful to identify children in early stages of kidney disease.

Agregação familiar da doença renal crônica secundária à hipertensão arterial ou diabetes mellitus: estudo caso-controle

No Brasil, a hipertensão e o diabetes mellitus tipo 2 são responsáveis por 60% dos casos de doença renal crônica terminal em terapia renal substitutiva. Estudos americanos identificaram agregação familiar da doença renal crônica, predominante em afrodescendentes. Um único estudo brasileiro observou agregação familiar entre portadores de doença renal crônica quando comparados a indivíduos internados com função renal normal. O objetivo deste artigo é avaliar se existe agregação familiar da doença renal crônica em familiares de indivíduos em terapia renal substitutiva causada por hipertensão e/ou diabetes mellitus. Estudo caso-controle tendo como casos 336 pacientes em terapia renal substitutiva portadores de diabetes mellitus ou hipertensão há pelo menos 5 anos e controles amostra pareada de indivíduos com hipertensão ou diabetes mellitus e função renal normal (n = 389). Os indivíduos em terapia renal substitutiva (casos) apresentaram razão de chance de 2,35 (IC95% 1,42-3,89; p < 0,001) versus controles de terem familiares com doença renal crônica terminal, independente da raça ou doença de base. Existe agregação familiar da doença renal crônica na amostra estudada e esta predisposição independe da raça e da doença de base (hipertensão ou diabetes mellitus).

Parental history of premature cardiovascular disease, estimated GFR, and rate of estimated GFR decline: results from the Aerobics Center Longitudinal Study

BACKGROUND

Despite cardiovascular disease (CVD) and chronic kidney disease sharing similar causes and interplay, it is unknown if a broader relationship between these diseases exists across generations. We investigated the association between parental CVD history and estimated glomerular filtration rate (eGFR) in the community.

STUDY DESIGN

Cross-sectional and longitudinal analyses.

SETTING & PARTICIPANTS

13,241 community-based adults with serum creatinine measurement and follow-up visits (from 1-8 visits ~2 years apart) from the Aerobics Center Longitudinal Study.

PREDICTORS

Premature parental CVD history (before age 50 years).

OUTCOMES

eGFR, decreased eGFR (<60 mL/min/1.73 m(2)), and rate of eGFR decline.

MEASUREMENTS

Information for parental history was collected by protocol-standardized questionnaires. eGFR was assessed with serum creatinine.

RESULTS

3,339 (25.2%) participants reported a history of parental CVD. Individuals with parental CVD had significantly lower eGFRs compared with those without parental CVD (69.4 ± 12.9 vs 74.8 ± 14.2 mL/min/1.73 m(2); P<0.001). After multivariable adjustment, parental CVD was associated independently with higher odds of having decreased eGFR (adjusted OR, 1.68; 95% CI, 1.52-1.86). Random-coefficient models showed that individuals with parental CVD had a faster decline in eGFR compared with those without parental CVD (sex- and ethnicity-adjusted annual change of -0.47 vs -0.41 mL/min/1.73 m(2); P=0.06).

LIMITATIONS

~70% of participants did not attend a second examination.

CONCLUSIONS

Parental history of CVD was associated with lower baseline eGFR, higher odds of decreased eGFR, and a nominally faster rate of eGFR decline in the offspring. Such findings may imply previously unrecognized cross-generational links between both diseases and be of support in community screening programs.

Familial risks of kidney failure in Sweden: a nationwide family study

Background

The value of family history as a risk factor for kidney failure has not been determined in a nationwide setting.

Aim

This nationwide family study aimed to determine familial risks for kidney failure in Sweden.

Methods

The Swedish multi-generation register on 0–78-year-old subjects were linked to the Swedish patient register and the Cause of death register for 1987–2010. Individuals diagnosed with acute kidney failure (n = 10063), chronic kidney failure (n = 18668), or unspecified kidney failure (n = 3731) were included. Kidney failure patients with cystic kidney disease, congenital kidney and urinary tract malformations, urolithiasis, and rare inherited kidney syndromes, and hyperoxaluria were excluded. Standardized incidence ratios (SIRs) were calculated for individuals whose parents/siblings were diagnosed with kidney failure compared to those whose parents or siblings were not.

Results

The concordant (same disease) familial risks (sibling/parent history) were increased for chronic kidney failure SIR = 2.02 (95% confidence interval, CI 1.90–2.14) but not for acute kidney failure SIR = 1.08 (95% CI 0.94–1.22) and for unspecified kidney failure SIR = 1.25 (95% CI 0.94–1.63). However, the discordant (different disease) familial risk for acute kidney failure SIR = 1.19 (95% CI 1.06–1.32) and unspecified kidney failure SIR = 1.63 (95% CI 1.40–1.90) was significantly increased in individuals with a family history of chronic kidney failure. The familial risk for chronic kidney failure was similar for males SIR = 2.04 (95% CI 1.90–2.20) and females SIR = 1.97 (95% CI 1.78–2.17). Familial risks for chronic kidney failure were highest at age of 10–19 years SIR = 6.33 (95% CI 4.16–9.22).

Conclusions

The present study shows that family history is an important risk factor for chronic kidney failure but to a lower degree for acute kidney failure and unspecified kidney failure.

Disease burden and risk profile in referred patients with moderate chronic kidney disease: composition of the German Chronic Kidney Disease (GCKD) cohort

BACKGROUND

A main challenge for targeting chronic kidney disease (CKD) is the heterogeneity of its causes, co-morbidities and outcomes. Patients under nephrological care represent an important reference population, but knowledge about their characteristics is limited.

METHODS

We enrolled 5217 carefully phenotyped patients with moderate CKD [estimated glomerular filtration rate (eGFR) 30-60 mL/min per 1.73 m(2) or overt proteinuria at higher eGFR] under routine care of nephrologists into the German Chronic Kidney Disease (GCKD) study, thereby establishing the currently worldwide largest CKD cohort.

RESULTS

The cohort has 60% men, a mean age (±SD) of 60 ± 12 years, a mean eGFR of 47 ± 17 mL/min per 1.73 m(2) and a median (IQR) urinary albumin/creatinine ratio of 51 (9-392) mg/g. Assessment of causes of CKD revealed a high degree of uncertainty, with the leading cause unknown in 20% and frequent suspicion of multifactorial pathogenesis. Thirty-five per cent of patients had diabetes, but only 15% were considered to have diabetic nephropathy. Cardiovascular disease prevalence was high (32%, excluding hypertension); prevalent risk factors included smoking (59% current or former smokers) and obesity (43% with BMI >30). Despite widespread use of anti-hypertensive medication, only 52% of the cohort had an office blood pressure <140/90 mmHg. Family histories for cardiovascular events (39%) and renal disease (28%) suggest familial aggregation.

CONCLUSIONS

Patients with moderate CKD under specialist care have a high disease burden. Improved diagnostic accuracy, rigorous management of risk factors and unravelling of the genetic predisposition may represent strategies for improving prognosis.

Epigenetics of progression of chronic kidney disease: fact or fantasy?

Epigenetic modifications are important in the normal functioning of the cell, from regulating dynamic expression of essential genes and associated proteins to repressing those that are unneeded. Epigenetic changes are essential for development and functioning of the kidney, and aberrant methylation, histone modifications, and expression of microRNA could lead to chronic kidney disease (CKD). Here, epigenetic modifications modulate transforming growth factor β signaling, inflammation, profibrotic genes, and the epithelial-to-mesenchymal transition, promoting renal fibrosis and progression of CKD. Identification of these epigenetic changes is important because they are potentially reversible and may serve as therapeutic targets in the future to prevent subsequent renal fibrosis and CKD. In this review we discuss the different types of epigenetic control, methods to study epigenetic modifications, and how epigenetics promotes progression of CKD.

Association of relatives of hemodialysis patients with metabolic syndrome, albuminuria and Framingham Risk Score

BACKGROUND AND AIM

Metabolic syndrome (MetS), albuminuria, and the Framingham Risk Score (FRS) are significant predictors for cardiovascular disease (CVD). However, the relationship and clinical significance of these CVD predictors in individuals with a family history of end-stage renal disease (ESRD) are unclear. We investigated the association of relatives of hemodialysis (HD) patients with MetS, albuminuria, and the FRS.

METHODS

One hundred and sixty-six relatives of HD patients and 374 age- and sex- matched community controls were enrolled. MetS was defined using the Adult Treatment Panel III for Asians. Albuminuria was defined as urine albumin-to-creatinine ratio ≥ 30 mg/g. CVD risk was evaluated by the FRS.

RESULTS

A significantly higher prevalence of MetS (19.9% vs. 12.5%, P = 0.026), albuminuria (12.7% vs. 5.1%, P = 0.002) and high FRS risk ≥ 10% of 10-year risk (15.7% vs. 8.5%, P = 0.013) was found in relatives of HD patients compared to their counterpart controls. In multivariate analysis, being relatives of HD patients (vs. controls) was an independent determinant for MetS (odds ratio [OR], 1.785; 95% confidence interval [CI], 1.045 to 3.050), albuminuria (OR, 2.891; 95% CI, 1.431 to 5.841), and high FRS risk (OR, 1.863; 95% CI, 1.015 to 3.418). Higher low-density lipoprotein cholesterol (OR, 1.034; 95% CI, 1.017 to 1.052) and betel nut chewing (OR, 13.994; 95% CI, 3.384 to 57.871) were independent determinants for having a high FRS risk in relatives of HD patients.

CONCLUSIONS

Being relatives of HD patients was independently associated with MetS, albuminuria and high FRS risk, suggesting family members of ESRD patients may have higher CVD risks through the interactions of renal risk factors. Proactive surveillance of these CVD predictors and preventive strategies should be targeted to this high-risk population.

DNA methylation profile associated with rapid decline in kidney function: findings from the CRIC study

BACKGROUND

Epigenetic mechanisms may be important in the progression of chronic kidney disease (CKD).

METHODS

We studied the genome-wide DNA methylation pattern associated with rapid loss of kidney function using the Infinium HumanMethylation 450 K BeadChip in 40 Chronic Renal Insufficiency (CRIC) study participants (n = 3939) with the highest and lowest rates of decline in estimated glomerular filtration rate.

RESULTS

The mean eGFR slope was 2.2 (1.4) and -5.1 (1.2) mL/min/1.73 m(2) in the stable kidney function group and the rapid progression group, respectively. CpG islands in NPHP4, IQSEC1 and TCF3 were hypermethylated to a larger extent in subjects with stable kidney function (P-values of 7.8E-05 to 9.5E-05). These genes are involved in pathways known to promote the epithelial to mesenchymal transition and renal fibrosis. Other CKD-related genes that were differentially methylated are NOS3, NFKBIL2, CLU, NFKBIB, TGFB3 and TGFBI, which are involved in oxidative stress and inflammatory pathways (P-values of 4.5E-03 to 0.046). Pathway analysis using Ingenuity Pathway Analysis showed that gene networks related to cell signaling, carbohydrate metabolism and human behavior are epigenetically regulated in CKD.

CONCLUSIONS

Epigenetic modifications may be important in determining the rate of loss of kidney function in patients with established CKD.

Transplantation: Increased ESRD and mortality risk for kidney donors?

For most patients with end-stage renal disease (ESRD), a kidney transplant is the best treatment option. Compared with dialysis, a successful kidney transplant is associated with increased life expectancy and improved quality of life; a living donor transplant is associated with better long-term results than a deceased donor transplant.

Association between family members of dialysis patients and chronic kidney disease: a multicenter study in China

BACKGROUND

Family members of patients with end stage renal disease were reported to have an increased prevalence of chronic kidney disease (CKD). However, studies differentiated genetic and non-genetic family members are limited. We sought to investigate the prevalence of CKD among fist-degree relatives and spouses of dialysis patients in China.

METHODS

Seventeen dialysis facilities from 4 cities of China including 1062 first-degree relatives and 450 spouses of dialysis patients were enrolled. Sex- and age- matched controls were randomly selected from a representative sample of general population in Beijing. CKD was defined as decreased estimated glomerular (eGFR<60 mL/min/1.73 m2) or albuminuria.

RESULTS

The prevalence of eGFR less than 60 mL/min/1.73 m2, albuminuria and the overall prevalence of CKD in dialysis spouses were compared with their counterpart controls, which was 3.8% vs. 7.8% (P<0.01), 16.8% vs. 14.6% (P=0.29) and 18.4% vs. 19.8% (P=0.61), respectively. The prevalence of eGFR less than 60 mL/min/1.73 m2, albuminuria and the overall prevalence of CKD in dialysis relatives were also compared with their counterpart controls, which was 1.5% vs. 2.4% (P=0.12), 14.4% vs. 8.4% (P<0.01) and 14.6% vs. 10.5% (P<0.01), respectively. Multivariable Logistic regression analysis indicated that being spouses of dialysis patients is negatively associated with presence of low eGFR, and being relatives of dialysis patients is positively associated with presence of albuminuria.

CONCLUSIONS

The association between being family members of dialysis patients and presence of CKD is different between first-degree relatives and spouses. The underlying mechanisms deserve further investigation.

Genetic susceptibility to hypertensive renal disease

Hypertensive renal disease occurs at increased frequency among the relatives of patients with this disease compared to individuals who lack a family history of disease. This suggests a heritable risk in which genetic variation may play a role. These observations have motivated a search for genetic variation contributing to this risk in both experimental animal models and in human populations. Studies of animal models indicate the capacity of natural genetic variants to contribute to disease risk and have produced a few insights into the disease mechanism. In its current phase, human population genetic studies have sought to associate genetic variation with disease in large populations by testing genotypes at a large number of common genetic variations in the genome, expecting that common genetic variants contributing to renal disease risk will be identified. These genome-wide association studies (GWAS) have been productive and are a clear technical success; they have also identified narrowly defined loci and genes containing variation contributing to disease risk. Further extension and refinement of these GWAS are likely to extend this success. However, it is also clear that few additional variants with substantial effects accounting for the greatest part of heritability will be uncovered by GWAS. This raises an interesting biological question regarding where the remaining unaccounted heritable risk may be located. At present, much consideration is being given to this question and to the challenge of testing hypotheses that lead from the various alternative mechanisms under consideration. One result of the progress of GWAS is likely to be a renewed interest in mechanisms by which related individuals can share and transmit traits independently of Mendelian inheritance. This paper reviews the current progress in this area and considers other mechanisms by which familial aggregation of risk for renal disease may arise.

Increased susceptibility to hypertensive renal disease in streptozotocin-treated diabetic rats is not modulated by salt intake

AIMS/HYPOTHESIS

In early type 1 diabetes mellitus, renal salt handling is dysregulated, so that the glomerular filtration rate becomes inversely proportional to salt intake. The salt paradox occurs in both humans and rats and, with low salt intake, results in diabetic hyperfiltration. We tested whether increased salt intake could reduce the susceptibility to injury of non-clipped kidneys in diabetic rats with pre-existing Goldblatt hypertension.

METHODS

Male Long-Evans rats were made hypertensive and half were then made diabetic. Blood glucose was maintained at ~20-25 mmol/l by insulin implants. One half of each received only the salt in normal chow (1% by weight) and the other half received added salt in drinking water to equal 2.7% by weight of food intake. Weekly 24 h blood pressure records were acquired by telemetry during the 4-month experiment.

RESULTS

Systolic blood pressure was not affected by diabetes or increased salt intake, alone or together. Autoregulation was highly efficient in the non-clipped kidney of both intact and diabetic rats. Histological examination showed minor injury in the clipped kidney, which did not differ among groups. The non-clipped kidney showed extensive pressure-dependent glomerular and vascular injury in both intact and diabetic rats.

CONCLUSIONS/INTERPRETATION

The relationship between pressure and injury was shifted toward lower blood pressure in diabetic rats, indicating that diabetes increased the susceptibility of the kidney to injury despite preservation of autoregulation. The increased susceptibility was not affected by high salt intake in the diabetic rats, thus disproving the hypothesis.

Mendelian and trans-generational inheritance in hypertensive renal disease

Familial risk in hypertensive renal disease has stimulated a search for genetic variation contributing to this risk. The current phase of population genetic studies has sought to associate genetic variation with disease in large populations by testing genotypes at a large number of common genetic variations in the genome, expecting that common genetic variants contributing to renal disease risk will be identified. These genome-wide association studies (GWAS) have been productive and are a clear technical success. It is also clear that narrowly defined loci and genes containing variation contributing to disease risk have been identified. Further extension and refinement of these GWAS are likely to extend this success. However, it is also clear that few if any variants with substantial effects accounting for the greatest part of heritability will be uncovered by GWAS. This raises an interesting biological question regarding where the remaining heritable risk may be located. One result of the progress of GWAS is likely to be a renewed interest in mechanisms by which related individuals can share and transmit traits independently of Mendelian inheritance. This paper reviews current progress in this area and considers other mechanisms by which familial aggregation of risk for renal disease may arise.

Prevalence and risk factors of chronic kidney disease in first-degree relatives of chronic kidney disease patients in Southern China

AIM

The aim of this study was to estimate the prevalence and risk factors of chronic kidney disease (CKD) in first-degree relatives (FDRs) of CKD patients.

METHODS

A cross-section study of first-degree relatives of CKD patients was conducted between November 2007 and March 2009 in southern China. A total of 1187 first-degree relatives (494 male and 693 female; mean age 41.26 years) of 419 CKD patients (194 male and 225 female; mean age 32.10 years) were reviewed and tested for haematuria, albuminuria and reduced glomerular filtration rate. CKD risk factors, including age, gender, body mass index, hypertension and the causes of index case were also investigated. CKD was diagnosed according to the criteria of the National Kidney Foundation-Kidney Disease Outcomes Quality Initiative.

RESULTS

The prevalence of CKD in first-degree relatives of CKD patients was 29.7% (95% confidence interval [CI]: 27.1%-32.2%). After adjusting for all the potential confounders, older age, female gender, hypertension, hyperglycaemia, hyperuricaemia, hypertriglyceridemic, low level of high density lipoproteins, increased body mass index and nephrotoxic medications were independently associated with increased risk of CKD. Furthermore, relatives of index cases with chronic glomerulonephritis were at higher risk haematuria (ORs = 2.12, 95% CI: 1.45-3.10) compared with relatives of index cases with other kinds of renal diseases.

CONCLUSION

The first-degree relatives of CKD patients are at high risk of CKD, especially those relatives of CKD patients with chronic glomerulonephritis. Screening in this high risk population might help to identify early CKD patients and make a proper intervention strategy to prevent the disease from quick progression.

Performance of a genetic risk score for CKD stage 3 in the general population

BACKGROUND

Recent genome-wide association studies have identified multiple genetic loci that increase the risk of chronic kidney disease (CKD) in the general population. We hypothesized that knowledge of these loci might permit improved CKD risk prediction beyond that provided by traditional phenotypic risk factors.

STUDY DESIGN

Observational cohort study.

SETTING & PARTICIPANTS

Participants who attended the 15th (1977-1979) and 24th (1995-1998) examination cycles of the original cohort or the 6th (1995-1998) and 8th cycles (2005-2008) of the offspring cohort of the Framingham Heart Study (n = 2,489).

PREDICTORS

Single-nucleotide polymorphisms at 16 stage 3 CKD loci were genotyped and used to construct a genetic risk score. Standard clinical predictors of incident stage 3 CKD also were used.

OUTCOMES & MEASUREMENTS

Incident stage 3 CKD was defined as estimated glomerular filtration rate <60 mL/min/1.73 m(2) at follow-up. Participants with baseline stage 3 CKD were excluded. Logistic regression was used to generate C statistics, which measured the power of the genetic risk score to discriminate risk of incident CKD stage 3 with and without traditional risk factors.

RESULTS

There were 270 new stage 3 CKD cases during an average of 10.8 years of follow-up. Mean genetic risk score was 17.5 ± 2.8 (SD) for those who developed stage 3 CKD and 17.3 ± 2.6 for those who did not (P for genotype score difference = 0.2). The OR for stage 3 CKD was 1.06 (95% CI, 1.01-1.11; P = 0.03) per additional risk allele, adjusting for age and sex. In the age- and sex-adjusted model, the C statistic was 0.748 without the genotype score and 0.751 with the score (P difference = 0.3). The risk score was not statistically significant in a multivariable model adjusted for standard stage 3 CKD risk factors (P = 0.07).

LIMITATIONS

All participants were of European ancestry; the genotype score may not be valid in different ancestral groups.

CONCLUSIONS

A genetic score generated from 16 known CKD risk alleles did not predict new cases of stage 3 CKD in the community beyond knowledge of common clinical risk factors alone.