Genetic factors in end-stage renal disease

A targeted gene panel illuminates pathogenesis in young people with unexplained kidney failure

BACKGROUND

Kidney failure in young people is often unexplained and a significant proportion will have an underlying genetic diagnosis. National Health Service England pioneered a comprehensive genomic testing service for such circumstances accessible to clinicians working outside of genetics. This is the first review of patients using this novel service since October 2021, following its introduction into clinical practice.

METHODS

The 'Unexplained Young-Onset End-Stage Renal Disease' (test-code R257) gene panel uses targeted next generation sequencing to analyse 175 genes associated with renal disease in patients under 36 years of age. All tests undertaken between October 2021 and February 2022 were reviewed. Phenotypic data were extracted from request forms and referring clinicians contacted where additional details were required.

RESULTS

Seventy-one patients underwent R257 testing over the study period. Among them, 23/71 patients (32%) were confirmed to have a genetic diagnosis and 2/71 (3%) had a genetically suggestive variant. Nephronophthisis and Alport syndrome were the most common conditions identified, (4/23 (17%) with pathogenic variants in NPHP1 and 4/23 (17%) with pathogenic variants in COL4A3/COL4A4). Positive predictors of a genetic diagnosis included a family history of renal disease (60% of positive cases) and extra-renal disease manifestations (48% of positive cases).

CONCLUSION

This is the first study to evaluate the R257 gene panel in unexplained young-onset kidney failure, freely accessible to patients meeting testing criteria in England. A genetic diagnosis was identified in 32% of patients. This study highlights the essential and expanding role that genomic testing has for children and families affected by renal disease today.

Association between long-term exposure to low level air pollutants and incident end-stage kidney disease in the UK Biobank: A prospective cohort

BACKGROUND

Previous studies suggest that air pollution can increase the risk of incident chronic kidney disease (CKD). However, the association between end-stage kidney disease (ESKD) and co-exposure to relatively low-level air pollutants remains unclear.

METHODS

A prospective cohort was designed based on UK Biobank. From 1 January 2010 to 12 November 2021, 453,347 participants were followed up over a median of 11.87 years. Principal component analysis was used to identify major patterns of five air pollutants, including PM2.5, PM2.5-10, PM10, NO2, and NOx. Sub-distribution hazards models were used to estimate the associations between air pollution, individually or jointly, and incident ESKD, CKD, and all-cause death, respectively.

RESULTS

Principal component analysis identified two principal components, namely RC1 (PM2.5, NO2, and NOx) and RC2 (PM2.5-10 and PM10). An elevated risk of incident ESKD was associated with an interquartile range (IQR) increase in PM2.5 (hazard ratio: 1.11, 95% confidence interval: 1.02-1.22), NO2 (1.16, 1.04-1.30), NOx (1.08, 1.00-1.17), and RC1 (1.12, 1.02-1.23). An elevated risk of incident CKD was associated with an IQR increase in PM2.5 (1.05, 1.03-1.07), NO2 (1.04, 1.02-1.06), NOx (1.03, 1.02-1.05), and RC1 (1.04, 1.02-1.06). An increased risk of all-cause mortality was associated with an IQR increase in PM2.5 (1.02, 1.00-1.04). Restricted cubic spline analyses indicated a monotonic elevating association of PM2.5, NO2, NOx, and RC1 with ESKD incidence.

CONCLUSIONS

Long-term exposure to PM2.5, NO2, NOx, and their complex was associated with elevated ESKD incidence, even at relatively lower levels of air pollution.

Lithium and the living kidney donor: Science or stigma?

Nearly 10 000 people are removed from the kidney transplant waiting list each year either due to becoming too ill for transplant or due to death. Live donor kidney transplant (LDKT) provides superior outcomes and survival benefit relative to deceased donor transplant, but the number of LDKT has decreased over the past few years. Therefore, it is of paramount importance that transplant centers employ evaluation processes that safely maximize LDKT. Decisions about donor candidacy should be based on the best available data, rather than on processes prone to bias. Here, we examine the common practice of declining potential donors based solely on treatment with lithium. We conclude that the risk of end-stage renal disease related to lithium treatment is comparable to other generally accepted risks in LDKT. We present this viewpoint to specifically challenge the carte blanche exclusion of individuals taking lithium and highlight the importance of using the best available data relevant to any risk factor, rather than relying on biases, when evaluating potential living kidney donors.

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.

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.

Investigation of FADS Gene Cluster Single Nucleotide Polymorphisms in End-Stage Renal Disease Compared With Normal Controls

End-stage renal disease (ESRD) is a public health problem with a high burden. The condition is associated with abnormalities in lipid metabolism. The fatty acid desaturase (FADS) gene cluster includes three genes that are significantly correlated with a number of pathologic conditions related to abnormal lipid levels. In the current study, we genotyped rs174556, rs99780, and rs7115739 single nucleotide polymorphisms within the FADS cluster in a population of ESRD patients and healthy controls. The rs174556 of the FADS1 gene and rs99780 of the FADS2 gene were not associated with the risk of ESRD in any inheritance model. However, the rs7115739 of FADS3 was associated with the risk of ESRD in all models except for the recessive model. The T allele of this SNP was significantly less prevalent among cases compared with controls [odds ratio (OR) (95% CI) = 0.44 (0.25–0.77), P value = 0.004]. GT and TT genotypes has been shown to decrease the risk of ESRD in a codominant model [OR (95% CI) = 0.49 (0.26–0.92) and OR (95% CI) = 0.18 (0.02–1.6), respectively; P value = 0.019]. In the dominant model, GT + TT status was associated with lower risk of ESRD [OR (95% CI) = 0.45 (0.24–0.82), P value = 0.0078]. Assessment of association between this SNP and risk of ESRD in an overdominant model revealed that GT genotype decreases the risk of this condition [OR (95% CI) = 0.5 (0.27–0.94), P value = 0.029]. Taken together, the rs7115739 of FADS3 is suggested as a putative modulator of the risk of ESRD in the Iranian population.

Sept8/SEPTIN8 involvement in cellular structure and kidney damage is identified by genetic mapping and a novel human tubule hypoxic model

Chronic kidney disease (CKD), which can ultimately progress to kidney failure, is influenced by genetics and the environment. Genes identified in human genome wide association studies (GWAS) explain only a small proportion of the heritable variation and lack functional validation, indicating the need for additional model systems. Outbred heterogeneous stock (HS) rats have been used for genetic fine-mapping of complex traits, but have not previously been used for CKD traits. We performed GWAS for urinary protein excretion (UPE) and CKD related serum biochemistries in 245 male HS rats. Quantitative trait loci (QTL) were identified using a linear mixed effect model that tested for association with imputed genotypes. Candidate genes were identified using bioinformatics tools and targeted RNAseq followed by testing in a novel in vitro model of human tubule, hypoxia-induced damage. We identified two QTL for UPE and five for serum biochemistries. Protein modeling identified a missense variant within Septin 8 (Sept8) as a candidate for UPE. Sept8/SEPTIN8 expression increased in HS rats with elevated UPE and tubulointerstitial injury and in the in vitro hypoxia model. SEPTIN8 is detected within proximal tubule cells in human kidney samples and localizes with acetyl-alpha tubulin in the culture system. After hypoxia, SEPTIN8 staining becomes diffuse and appears to relocalize with actin. These data suggest a role of SEPTIN8 in cellular organization and structure in response to environmental stress. This study demonstrates that integration of a rat genetic model with an environmentally induced tubule damage system identifies Sept8/SEPTIN8 and informs novel aspects of the complex gene by environmental interactions contributing to CKD risk.

Meta-analysis of cognitive functioning in patients following kidney transplantation

Background

There is mixed evidence regarding the nature of cognitive function in patients who have undergone renal transplantation. The aim of this meta-analysis was to examine which cognitive domains are impacted following kidney transplantation and how performance compares with non-transplanted patients or healthy controls/normative data.

Method

A systematic search was conducted using keywords within three databases (Embase, MEDLINE and PsychINFO), yielding 458 unique studies, 10 of which met the inclusion criteria. Neuropsychological tests were grouped into nine cognitive domains and three separate analyses were undertaken within each domain: (i) within subjects pre- versus post-transplant, (ii) transplanted versus non-transplanted patients and (iii) transplanted versus healthy matched controls and standardized normative data.

Results

Transplanted patients showed moderate to large improvements in the domains of general cognitive status (g = 0.526), information and motor speed (g = 0.558), spatial reasoning (g = 0.376), verbal memory (g = 0.759) and visual memory (g = 0.690) when compared with their pre-operative scores. Test scores in the same five domains were significantly better in post-transplanted patients when compared with dialysis-dependant or conservatively managed chronic kidney disease patients. However, post-transplanted patients’ performance was significantly low compared with that of healthy controls (and standardized normative data) in the domains of executive functioning (g = −0.283), verbal fluency (g = −0.657) and language (g = −0.573).

Conclusions

Two key issues arise from this review. First, domain-specific cognitive improvement occurs in patients after successful transplantation. Nevertheless, transplanted patients still performed significantly below healthy controls in some domains. Second, there are important shortcomings in existing studies; the length of follow-up is typically short and only limited neuropsychological test batteries are employed. These factors are important in order to support the recovery of cognitive function among patients following renal transplant.

Black Ethnicity is Not a Risk Factor for Mortality or Graft Loss After Kidney Transplant in the United Kingdom

OBJECTIVES

There are conflicting reports in the literature regarding outcomes after kidney transplant for patients of black ethnicity. To investigate further, we compared outcomes for black versus white kidney transplant recipients in a single UK transplant center.

MATERIALS AND METHODS

We analyzed 1066 kidney transplant recipients (80 black patients, 986 white patients) within a single-center cohort (2007-2017) in the United Kingdom, with cumulative 4446 patient-year follow-up. Data were electronically extracted from the Department of Health Informatics database for every study recruit, with manual data linkage to the UK Transplant Registry (for graft survival, delayed graft function, and rejection data) and Office for National Statistics (for mortality data). Primary outcomes of interest were graft/patient survival.

RESULTS

Black recipients have increased baseline risk profiles with longer wait times, difficulty in matching, worse HLA matching, more socioeconomic deprivation, and lower rates of living kidney donors. Postoperatively, black versus white recipients had increased risk for delayed graft function (34.3% vs 10.2%; P < .001), increased 1-year rejection (16.7% vs 7.3%; P = .012), higher 1-year creatinine levels (166 vs 138 mmol/L; P = .003), and longer posttransplant length of stay (14.5 vs 9.5 days; P = .020). Although black recipients did not have increased risk of death versus white recipients (10.0% vs 11.0%, respectively; P = .486), they did have increased risk for death-censored graft loss (23.8% vs 11.1%; P = .002). However, in an adjusted Cox regression model, black ethnicity was not associated with increased risk for death-censored graft loss (hazard ratio of 1.209, 95% confidence interval, 0.660-2.216; P = .539).

CONCLUSIONS

Black kidney transplant recipients in the United Kingdom have increased risk of adverse graft-related outcomes due to high-risk baseline variables rather than their black ethnicity per se.

Characteristics and treatment of African-American and European-American patients with resistant hypertension identified using the electronic health record in an academic health centre: a case-control study

OBJECTIVE

To identify patients with hypertension with resistant and controlled blood pressure (BP) using electronic health records (EHRs) in order to elucidate practices in the real-world clinical treatment of hypertension and to enable future genetic studies.

DESIGN

Using EHRs, we developed and validated algorithms to identify patients with resistant and controlled hypertension.

SETTING

An academic medical centre in Nashville, Tennessee.

POPULATION

European-American (EA) and African-American (AA) patients with hypertension.

MAIN OUTCOME MEASURES

Demographic characteristics: race, age, gender, body mass index, outpatient BPs and the history of diabetes mellitus, chronic kidney disease stage 3, ischaemic heart disease, transient ischaemic attack, atrial fibrillation and sleep apnoea.

MEDICATION TREATMENT

All antihypertensive medication classes prescribed to a patient at the time of classification and ever prescribed following classification.

RESULTS

The algorithms had performance metrics exceeding 92%. The prevalence of resistant hypertension in the total hypertensive population was 7.3% in EA and 10.5% in AA. At diagnosis, AA were younger, heavier, more often female and had a higher incidence of type 2 diabetes and higher BPs than EA. AA with resistant hypertension were more likely to be treated with vasodilators, dihydropyridine calcium channel blockers and alpha-2 agonists while EA were more likely to be treated with angiotensin receptor blockers, renin inhibitors and beta blockers. Mineralocorticoid receptor antagonists use was increased in patients treated with more than four antihypertensive medications compared with patients treated with three (12.4% vs 2.6% in EA, p<0.001; 12.3% vs 2.8% in AA, p<0.001). The number of patients treated with a mineralocorticoid receptor antagonist increased to 37.4% in EA and 41.2% in AA over a mean follow-up period of 7.4 and 8.7 years, respectively.

CONCLUSIONS

Clinical treatment of resistant hypertension differs in EA and AA patients. These results demonstrate the feasibility of identifying resistant hypertension using an EHR.

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 single nucleotide polymorphism in the UMOD promoter is associated with end stage renal disease

BACKGROUND

Several genome-wide association studies revealed that several variants of UMOD gene were related to the estimated glomerular filtration rate (eGFR), CKD or hypertension. In this study, we investigated the association between a common variant rs13333226 in the promoter region of UMOD gene and end stage renal disease (ESRD).

METHODS

Variant rs13333226 of UMOD gene was genotyped by using the ABI Real time TaqMan allelic discrimination assay in a case-control study including 638 unrelated patients with ESRD and 366 controls.

RESULTS

The frequency of UMOD SNP rs13333226 GG/GA genotype was significantly higher (36.83% vs. 20.22%, P = 4.02 × 10^-8) and the frequency of G allele was much higher (19.04% vs. 11.20%, P = 4.00 × 10^-6) in the patients with ESRD than in the controls. The G allele was associated with an increased risk of ESRD (odds ratio 2.30, 95% confidence interval 1.70-3.11, P = 6.10 × 10^-8). And G allele (odds ratio 2.33, 95% confidence interval 1.32-4.13, P = 3.65 × 10^-3) was associated independently with ESRD.

CONCLUSIONS

A common variation rs13333226 in the promoter region of UMOD gene was independently associated with ESRD in Han Chinese.

Higher protein intake is associated with increased risk for incident end-stage renal disease among blacks with diabetes in the Southern Community Cohort Study

BACKGROUND AND AIMS

Diabetes, a risk factor for end-stage renal disease (ESRD), is associated with impaired protein metabolism. We investigated whether protein intake is associated with ESRD and whether the risk is higher among blacks with diabetes.

METHODS AND RESULTS

We conducted a nested case-control study of ESRD within the Southern Community Cohort Study, a prospective study of low-income blacks and whites in the southeastern US (2002-2009). Through 2012, 1057 incident ESRD cases were identified by linkage with the United States Renal Data System and matched to 3198 controls by age, sex, and race. Dietary intakes were assessed from a validated food frequency questionnaire at baseline. Odds ratios (ORs) and 95% confidence intervals (CIs) were computed from logistic regression models that included matching variables, BMI, education, income, hypertension, total energy intake, and percent energy from saturated and polyunsaturated fatty acids. Mean (±SD) daily energy intake from protein was higher among ESRD cases than controls (15.7 ± 3.3 vs. 15.1 ± 3.1%, P < 0.0001). For a 1% increase in percent energy intake from protein, the adjusted ORs (95% CIs) for ESRD were 1.06 (1.02-1.10) for blacks with diabetes, 1.02 (0.98-1.06) for blacks without diabetes, 0.99 (0.90-1.09) for whites with diabetes and 0.94 (0.84-1.06) for whites without diabetes. Protein intake in g/kg/day was also associated with ESRD (4th vs. 1st quartile OR = 1.76; 95% CI: 1.17-2.65).

CONCLUSION

Our results raise the possibility that among blacks with diabetes, increased dietary protein is associated with increased incidence of ESRD. Studies on how protein intake and metabolism affect ESRD are needed.

Genome-Wide Association of CKD Progression: The Chronic Renal Insufficiency Cohort Study

The rate of decline of renal function varies significantly among individuals with CKD. To understand better the contribution of genetics to CKD progression, we performed a genome-wide association study among participants in the Chronic Renal Insufficiency Cohort Study. Our outcome of interest was CKD progression measured as change in eGFR over time among 1331 blacks and 1476 whites with CKD. We stratified all analyses by race and subsequently, diabetes status. Single-nucleotide polymorphisms (SNPs) that surpassed a significance threshold of P<1×10^-6 for association with eGFR slope were selected as candidates for follow-up and secondarily tested for association with proteinuria and time to ESRD. We identified 12 such SNPs among black patients and six such SNPs among white patients. We were able to conduct follow-up analyses of three candidate SNPs in similar (replication) cohorts and eight candidate SNPs in phenotype-related (validation) cohorts. Among blacks without diabetes, rs653747 in LINC00923 replicated in the African American Study of Kidney Disease and Hypertension cohort (discovery P=5.42×10^-7; replication P=0.039; combined P=7.42×10^-9). This SNP also associated with ESRD (hazard ratio, 2.0 (95% confidence interval, 1.5 to 2.7); P=4.90×10^-6). Similarly, rs931891 in LINC00923 associated with eGFR decline (P=1.44×10^-4) in white patients without diabetes. In summary, SNPs in LINC00923, an RNA gene expressed in the kidney, significantly associated with CKD progression in individuals with nondiabetic CKD. However, the lack of equivalent cohorts hampered replication for most discovery loci. Further replication of our findings in comparable study populations is warranted.

Living Kidney Donors Who Develop Kidney Failure: Excerpts of Their Thoughts

BACKGROUND

Psychosocial data about living kidney donors have been collected for almost 5 decades now. To date, however, no study has provided any psychosocial follow-up of donors who developed a serious health problem such as end-stage renal disease (ESRD).

METHODS

Donors who developed ESRD were invited to participate in a qualitative interview if they met one or both of the inclusion criteria: (1) developed ESRD within 10 years of donating and/or (2) lacked health insurance at the time of donation. We contacted 38 individuals who met these criteria, and 22 participated (58%). Two were subsequently excluded from analysis.

RESULTS

Twenty qualitative interviews were analyzed. Five findings are described: (1) donors describe the decision-making process as spontaneous and fast; (2) donors describe lack of appreciation for the need for post-donation self-care; (3) donors do not regret donating despite the adverse outcome; (4) donors advise future donors to have in place emotional and physical support post donation; and (5) donors appreciate the opportunity to tell their story from being a living donor to living with ESRD, which virtually all perceive as 2 separate unrelated events.

CONCLUSIONS

Most donors are positive about their donation decision and experience and would donate again, despite developing ESRD themselves. They propose some important changes to the decision-making and informed-consent processes. Our data are reassuring regarding lack of donor regret, but highlight the need for living donor transplant programs to ensure that living donors understand their long-term risks and receive appropriate life-long follow-up care to minimize these risks.

Analytical Validation of a Personalized Medicine APOL1 Genotyping Assay for Nondiabetic Chronic Kidney Disease Risk Assessment

The incidence of chronic kidney disease (CKD) varies by ancestry, with African Americans (AA) having a threefold to fourfold higher rate than whites. Notably, two APOL1 alleles, termed G1 [c.(1072A>G; 1200T>G)] and G2 (c.1212_1217del6), are strongly associated with higher rates of nondiabetic CKD and an increased risk for hypertensive end-stage renal disease. This has prompted the opportunity to implement APOL1 testing to identify at-risk patients and modify other risk factors to reduce the progression of CKD to end-stage renal disease. We developed an APOL1 genotyping assay using multiplex allele-specific primer extension, and validated using 58 positive and negative controls. Genotyping results were completely concordant with Sanger sequencing, and both triplicate interrun and intrarun genotyping results were completely concordant. Multiethnic APOL1 allele frequencies were also determined by genotyping 7059 AA, Hispanic, and Asian individuals from the New York City metropolitan area. The AA, Hispanic, and Asian APOL1 G1 and G2 allele frequencies were 0.22 and 0.13, 0.037 and 0.025, and 0.013 and 0.004, respectively. Notably, approximately 14% of the AA population carried two risk alleles and are at increased risk for CKD, compared with <1% of the Hispanic and Asian populations. This novel APOL1 genotyping assay is robust and highly accurate, and represents one of the first personalized medicine clinical genetic tests for disease risk prediction.

Familial clustering of risk factors for cardiovascular disease among first-degree relatives of patients with chronic kidney disease in a sub-Saharan African population

Objective

To determine the prevalence of risk factors for cardiovascular disease (CVD) in first-degree relatives (FDRs) of patients with chronic kidney disease (CKD) in a sub-Saharan African population.

Methods

This was a cross-sectional survey of 460 subjects (230 FDRs of patients with CKD and 230 healthy controls). Anthropometrics and blood pressures were measured. Spot urine and fasting venous blood samples were obtained for biochemical analysis.

Results

The prevalence of hypertension, diabetes mellitus, obesity and dyslipidaemia were significantly higher in FDRs of patients with CKD compared with the controls: 56 (24.3%) vs 29 (12.6%), p = 0.01; 20 (8.7%) vs 6 (2.6%), p = 0.01; 40 (17.4%) vs 24 (10.4%), p = 0.03 and 171 (74.3%) vs 138 (60.0%), p = 0.01, respectively. Hypertension (OR, 1.65), dyslipidaemia (OR, 1.72) and albuminuria (OR, 1.61) were independently associated with being a FDR of patients with CKD.

Conclusion

In this sub-Saharan African population, risk factors for CVD were more prevalent in the FDRs of patients with CKD than in healthy controls.

Prevalence of persistent microalbuminuria and associated factors among HIV infected children attending a Tertiary Hospital in Northern Tanzania: a cross sectional, analytical study

INTRODUCTION

Human Immunodeficiency Virus (HIV) infection is a significant cause of paediatric morbidity and mortality especially in Sub-Saharan Africa. It affects the kidney by injuring the glomerular and tubular epithelial cells causing leakage of albumin in urine. Microalbuminuria is known to be an early indicator of kidney injury including HIVAN. The purpose of this study was to identify the prevalence and factors associated with microalbuminuria among HIV infected children receiving care and treatment at Kilimanjaro Christian Medical Centre (KCMC).

METHODS

We conducted a cross sectional hospital based analytical study at KCMC from December 2012 to April 2013. It involved children who are HIV infected attending child centred family care clinics (CCFCC). Patients' demographic and clinical characteristics were extracted from the file; physical examination performed. Urine samples were analysed for by HemoCue Albumin 201 system analyzer. Statistical package for social sciences (SPSS) version 16.0 was be used to process and analyze the data.

RESULTS

Three hundred thirty HIV-infected children under 18 years were recruited during the study period. Mean age was 119.4 (5-218) months. Prevalence of microalbuminuria by using HemoCue Albumin 201 analyzer was 28.8% (n = 95). Presence of microalbuminuria was significantly associated with severity of HIV disease progression according to WHO disease stage (p = 0.0015) and CD4 count less than 350 cells/µL (p = 0.044).

CONCLUSION

The study has shown that microalbuminuria is common in HIV infected children. Early screening and treatment of microalbuminuria is important to minimize the risk of developing end stage kidney disease. Children with advanced HIV disease and those with CD4 count less than 350 cells/µL should be given priority for urinary albumin screening in a setting without routine screening for microalbuminuria.

Analysis of human bradykinin receptor gene and endothelial nitric oxide synthase gene polymorphisms in end-stage renal disease among malaysians

The aim of this study was to determine the association of the c.894G>T; p.Glu298Asp polymorphism and the variable number tandem repeat (VNTR) polymorphism of the endothelial nitric oxide synthase (eNOS) gene and c.181C>T polymorphism of the bradykinin type 2 receptor gene (B2R) in Malaysian end-stage renal disease (ESRD) subjects. A total of 150 ESRD patients were recruited from the National Kidney Foundation's (NKF)dialysis centers in Malaysia and compared with 150 normal healthy individuals. Genomic DNA was extracted from buccal cells of all the subjects. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was carried out to amplify the products and the restricted fragments were separated by agarose gel electrophoresis. Statistical analyses were carried out using software where a level of p <0.05 was considered to be statistically significant. The genotypic and allelic frequencies of the B2R gene (c.181C>T, 4b/a) and eNOS gene (c.894G>T) polymorphisms were not statistically significant (p >0.05) when compared to the control subjects. The B2R and eNOS gene polymorphisms may not be considered as genetic susceptibility markers for Malaysian ESRD subjects.

Investigation of urinary abnormalities and risk factors for kidney disease in the World Kidney Day campaigns in Northeast Brazil

Objective: chronic kidney disease (CKD) is an increasing common problem in the world due to the exponential growth of diabetes mellitus, hypertension and other risk factors. The aim of this study is to investigate urinary abnormalities and risk factors for kidney disease in the general population. Methods: this study was performed from data collected during the annual World Kidney Day (WKD) campaigns, in Fortaleza, Ceará, Brazil, between 2009 and 2012. The population sought assistance spontaneously in stands placed in high people-traffic areas. Results: among 2,637 individuals interviewed, the mean age was 50.7±15.7 years and 53% were male. The main risk factors found were sedentarism (60.7%), obesity (22.7%) and smoking (19.8%). Blood pressure (BP) > 140x90 mmHg was found in 877 (33%). Increased BP was found for the first time in 527 cases (19.9%). Cardiovascular diseases were reported in 228 (8.6%). Diabetes was related by 343 (13%). Capillary blood glucose > 200 mg/dL was found in 127 (4.8%) and it was > 200 mg/dL for the first time in 30 (1.13%). Urinalysis was performed in 1,151 people and found proteinuria in 269 (23.3%). Proteinuria was most frequent in hypertension people (77.3% vs. 55.8%, p=0.0001), diabetes mellitus (22.7% vs. 15.2%, p=0.005) and elderly (42.1% vs. 30.7%, p=0.0007). Conclusion: risk factors for CKD are frequent in the general population. Many individuals had hypertension and diabetes and did not know this. It is important to regularly perform actions like WKD in order to early detect potential candidates for CKD.

Genetics of coronary heart disease with reference to ApoAI-CIII-AIV gene region

Cardiovascular diseases are affected by multiple factors like genetic as well as environmental hence they reveal factorial nature. The evidences that genetic factors are susceptible for developing cardiovascular diseases come from twin studies and familial aggregation. Different ethnic populations reveal differences in the prevalence coronary artery disease (CAD) pointing towards the genetic susceptibility. With progression in molecular techniques different developments have been made to comprehend the disease physiology. Molecular markers have also assisted to recognize genes that may provide evidences to evaluate the role of genetic factors in causation of susceptibility towards CAD. Numerous studies suggest the contribution of specific “candidate genes”, which correlate with various roles/pathways that are involved in the coronary heart disease. Different studies have revealed that there are large numbers of genes which are involved towards the predisposition of CAD. However, these reports are not consistent. One of the reasons could be weak contribution of genetic susceptibility of these genes. Genome wide associations show different chromosomal locations which dock, earlier unknown, genes which may attribute to CAD. In the present review different ApoAI-CIII-AIV gene clusters have been discussed.

Evaluation of living kidney donors: variables that affect donation

Approximately 10000 deceased donor organs are available yearly for 85 000 US patients awaiting kidney transplant. Living kidney donation is essential to close this gap and offers better survival rates. However, nationally, 80% of potential donors evaluated fail to donate. Nurse coordinators who perform predonation screening and education need additional insight into the large number of potential donors who fail to complete the donation process. Reasons for nondonation in donor candidates undergoing medical evaluation, and variables affecting nondonation at Vanderbilt University Medical Center between 2004 and 2009 are examined. Multivariable logistic regression models are used to test the effects of age and race on donation status and reasons for nondonation. Summary data are frequencies, percentages, and means (SD). The sample included 706 candidates (63% female, 80% white; mean age, 40 [SD, 12] years). Almost half (46%) received clearance to donate. Undiagnosed hypertension (14%), abnormal glucose tolerance (10%), and protein-urea (9%) were the most prevalent medical reasons for nondonation. About 13% of candidates changed their minds during evaluation. Analyses demonstrated an increased likelihood of older candidates (P < .001) and a decreased likelihood of white candidates (P = .007) being excluded from donation. Within the nondonation group, increased age was associated with undiagnosed hypertension and abnormal glucose tolerance (both race-adjusted, P = .01). Younger candidates (race-adjusted, P = .003) and African Americans (age-adjusted, P = .04) were more likely to decide against donation. The most prevalent medical reasons for nondonation could be identified through enhanced prescreening, and improved preevaluation education could decrease nondonation rates.

Prevalence of chronic kidney disease and its association with risk factors in disadvantageous population

The prevalence of kidney disease, particularly diabetic and hypertensive kidney disease is increasing rapidly specially in the disadvantageous group of population throughout the world. A cross sectional survey was carried out at certain selected slum areas of Mirpur in Dhaka city of Bangladesh over the period from July 2003 to June 2005, and a total of participants ranging from 15 to 65 years were studied. The analysis discovered that 4.1% of the participants were diabetic, 11.6% were hypertensive, and 7.7% had proteinuria. Based on MDRD equation, 13.1% of the participants were detected as having chronic kidney disease (CKD) while with Cockcroft-Gault equation 16% had CKD. Accordingly, the difference between the two equations was not significant. Association of sociodemographic factors with CKD was not significant except age more than 40 years and marital status. The association between CKD and risk factors like proteinuria, obese and overweight, use of tobacco, diabetes mellitus, and hypertension was highly significant. Combined prevalence of DM, hypertension, and proteinuria among CKD group was also demonstrated to be significantly higher (3.8% with Cockcroft-Gault equation and 5.3% with MDRD equation) than that of normal population. The survey data revealed that CKD and its risk factors like DM and hypertension are alarmingly high in disadvantageous population and adding further pressure to the existing burden of CKD.

Managing diabetes in Asia: overcoming obstacles and the role of DPP-IV inhibitors

Asia bears the world's greatest burden of type 2 diabetes (T2DM) and prevalence is increasing rapidly. Compared to other races, Asians develop T2DM younger, at a lower degree of obesity, suffer longer from its complications and die earlier. Curbing this epidemic requires an integrated, risk-based, and multidisciplinary approach. Inadequately managed T2DM has macrovascular and microvascular sequelae, Asians with T2DM being particularly susceptible to diabetic nephropathy. Earlier and more intensive monitoring and management of risk factors are required, especially for patients with, or at risk of, renal impairment. Particular challenges of T2DM management in Asia include: lack of access to specialist healthcare, insufficient clinical evaluation and delayed diagnosis. As in Caucasians, conventional treatment modalities are limited by deteriorating glycaemic control with disease progression and there is an unmet need for efficacious, safe, cost-effective and convenient pharmacotherapies for treating different stages of T2DM and preventing its complications, particularly in high-risk patients. There is a trend towards increasing use of DPP-IV inhibitors, which are no less efficacious and safe in Asians than Caucasians and may have some advantages over existing oral antidiabetic agents, particularly for certain high-risk groups. Such agents may play a significant future role in the management of T2DM.

Association of intercellular adhesion molecule 1 (ICAM1) with diabetes and diabetic nephropathy

Diabetes and diabetic nephropathy are complex diseases affected by genetic and environmental factors. Identification of the susceptibility genes and investigation of their roles may provide useful information for better understanding of the pathogenesis and for developing novel therapeutic approaches. Intercellular adhesion molecule 1 (ICAM1) is a cell surface glycoprotein expressed on endothelial cells and leukocytes in the immune system. The ICAM1 gene is located on chromosome 19p13 within the linkage region of diabetes. In the recent years, accumulating reports have implicated that genetic polymorphisms in the ICAM1 gene are associated with diabetes and diabetic nephropathy. Serum ICAM1 levels in diabetes patients and the icam1 gene expression in kidney tissues of diabetic animals are increased compared to the controls. Therefore, ICAM1 may play a role in the development of diabetes and diabetic nephropathy. In this review, we present genomic structure, variation, and regulation of the ICAM1 gene, summarized genetic and biological studies of this gene in diabetes and diabetic nephropathy and discussed about the potential application using ICAM1 as a biomarker and target for prediction and treatment of diabetes and diabetic nephropathy.

Clinical versus histological diagnosis of diabetic nephropathy--is renal biopsy required in type 2 diabetic patients with renal disease?

OBJECIVES

The clinical and histological diagnosis (gold standard) of diabetic nephropathy (dNP) and vascular nephropathy (vNP) were compared in type 2 diabetic patients with end-stage renal disease (ESRD).

AIM

The aim of the study was to investigate indication for renal biopsy in type 2 diabetic patients with renal disease.

DESIGN

Retrospective study in diabetic patients with clinical and histological diagnosis of renal disease.

PATIENTS AND METHODS

Eighty-four patients with type 2 diabetes and ESRD were investigated. Histological findings of the kidneys were available in all patients, 14 had undergone a renal biopsy before their first dialysis while a post-mortem kidney investigation was performed in 70 subjects. According to the histological findings, 66 patients had dNP and 18 subjects had vNP. The histological diagnosis was compared with the clinical diagnosis, and the sensitivity as well as the specificity of the clinical diagnosis of dNP and vNP were calculated.

RESULTS

The clinical diagnosis was not identical with the histological diagnosis in 10 cases. In the dNP group the diagnosis was 4 false positive and 3 false negative as in the vNP group 1 false positive and 2 false negative. The sensitivity of clinical diagnosis was 95% for dNP and 89% for vNP. Specificity was 78% for dNP and 97% for vNP.

CONCLUSION

The sensitivity of the clinical diagnosis is very high for dNP as well as vNP. A renal biopsy is not required in the majority of type 2 diabetic patients with ESRD, especially in patients who exhibit all criteria for clinical diagnosis.

Impact of nitric oxide synthase Glu298Asp polymorphism on the development of end-stage renal disease in type 2 diabetic Egyptian patients

BACKGROUND

Nitric oxide is an important regulator of renal hemodynamics. This study aimed to investigate the role of endothelial nitric oxide synthase (eNOS) gene polymorphism in type 2 diabetic patients with end-stage renal disease (ESRD) and to elucidate any alteration of nitric oxide synthase (NOS) activity caused by this polymorphism.

METHODS

The study included 80 patients with type 2 diabetes of >10 years duration (40 with diabetes-derived ESRD, 40 without nephropathy) and 20 healthy controls. Plasma nitrate/nitrite level, and serum NOS activity were measured and eNOS Glu298Asp genotypes were determined.

RESULTS

The frequency of Glu/Glu (GG) genotype in diabetics with ESRD was lower than controls. However, the frequency of Asp/Asp (TT) genotype was increased in diabetics with ESRD as compared to those without nephropathy and controls. Diabetics with ESRD had significantly lower nitrate/nitrite level and NOS activity than those without nephropathy. Diabetic patients with TT genotype are at a significant risk for ESRD. Moreover, subjects carrying TT genotype had lower nitrate/nitrite level and NOS activity than those carrying GG genotype. In diabetics with ESRD, creatinine clearance was positively correlated with both nitrate/nitrite level and NOS activity.

CONCLUSIONS

These results imply that TT genotype of eNOS may be associated with an increased risk of ESRD in Egyptian type 2 diabetics. It could represent a useful genetic marker to identify diabetics at high risk for the development of ESRD. However, larger future prospective studies are required to confirm the role of eNOS gene polymorphism in the progression of diabetic nephropathy to ESRD.

Etiopathology of chronic tubular, glomerular and renovascular nephropathies: clinical implications

Chronic kidney disease (CKD) comprises a group of pathologies in which the renal excretory function is chronically compromised. Most, but not all, forms of CKD are progressive and irreversible, pathological syndromes that start silently (i.e. no functional alterations are evident), continue through renal dysfunction and ends up in renal failure. At this point, kidney transplant or dialysis (renal replacement therapy, RRT) becomes necessary to prevent death derived from the inability of the kidneys to cleanse the blood and achieve hydroelectrolytic balance. Worldwide, nearly 1.5 million people need RRT, and the incidence of CKD has increased significantly over the last decades. Diabetes and hypertension are among the leading causes of end stage renal disease, although autoimmunity, renal atherosclerosis, certain infections, drugs and toxins, obstruction of the urinary tract, genetic alterations, and other insults may initiate the disease by damaging the glomerular, tubular, vascular or interstitial compartments of the kidneys. In all cases, CKD eventually compromises all these structures and gives rise to a similar phenotype regardless of etiology. This review describes with an integrative approach the pathophysiological process of tubulointerstitial, glomerular and renovascular diseases, and makes emphasis on the key cellular and molecular events involved. It further analyses the key mechanisms leading to a merging phenotype and pathophysiological scenario as etiologically distinct diseases progress. Finally clinical implications and future experimental and therapeutic perspectives are discussed.

Association of trypanolytic ApoL1 variants with kidney disease in African Americans

African Americans have higher rates of kidney disease than European Americans. Here, we show that, in African Americans, focal segmental glomerulosclerosis (FSGS) and hypertension-attributed end-stage kidney disease (H-ESKD) are associated with two independent sequence variants in the APOL1 gene on chromosome 22 {FSGS odds ratio = 10.5 [95% confidence interval (CI) 6.0 to 18.4]; H-ESKD odds ratio = 7.3 (95% CI 5.6 to 9.5)}. The two APOL1 variants are common in African chromosomes but absent from European chromosomes, and both reside within haplotypes that harbor signatures of positive selection. ApoL1 (apolipoprotein L-1) is a serum factor that lyses trypanosomes. In vitro assays revealed that only the kidney disease-associated ApoL1 variants lysed Trypanosoma brucei rhodesiense. We speculate that evolution of a critical survival factor in Africa may have contributed to the high rates of renal disease in African Americans.

Genetic contribution and associated pathophysiology in end-stage renal disease

End-stage renal disease (ESRD) or chronic kidney disease (CKD) is the terminal state of the kidney when its function has been permanently and irreversibly damaged. A wide variety of etiologies and pathological processes culminate in ESRD, and both environmental and genetic factors contribute to its development and progression. Various reports suggest that susceptibility to develop ESRD has a significant genetic component. These studies include familial aggregation studies, comparisons of incidence rates between different racial or ethnic populations, and segregation analysis. Genetic approaches have been used to identify genes that contribute to genetic susceptibility. Many studies have now been carried out assessing the contribution of specific “candidate genes”, which correlate with different functions that are involved in the renal pathogenesis. Independent studies for specific associated genes have frequently provided contradictory results. This may be due, in part, to the modest contribution to genetic susceptibility which these genes impart. With the availability of different genomewide association studies, chromosomal regions harboring novel, previously unrecognized, genes that may contribute to renal diseases have been recently reported. We have focused on different genetic studies conducted on ESRD and have discussed the strength and weaknesses of these studies. The nonmuscle myosin heavy chain 9 gene (MYH9) and renin–angiotensin system (RAS) have been discussed in detail.

Chromosome instability in patients with chronic renal failure

OBJECTIVE

The aim of this study was to investigate the frequency of sister chromatid exchanges (SCEs), the presence of cytostaticity, cytotoxicity, and therefore, the possible genetic instability in patients with chronic renal failure (CRF) in human cultured peripheral blood lymphocytes.

METHODS

Peripheral blood lymphocytes were cultured from 32 patients with CRF (average 55.2 years) and 18 healthy blood donors (average 44.6 years), and the SCE method was applied afterward. The increase in SCE frequency was evaluated as an immediate DNA damage index, while the reduction in the values of the proliferating rate indices was evaluated as a cytostatic index and the mitotic indices as a cytotoxic index was also measured.

RESULTS

A significant increase in the SCE frequencies along with a significant reduction in mitotic indices was observed in patients with CRF compared with the controls. It is notable that there was no significant difference in SCE levels among patients with CRF and cancer, and patients with CRF alone.

CONCLUSIONS

This study illustrates increased genetic instability in patients with CRF. These results could also be of a great importance in early diagnosis to prognosticate a possible generation of neoplasm in the future.

Prevalence of methylenetetrahydrofolate gene (MTHFR) C677T polymorphism among chronic hemodialysis patients and its association with cardiovascular disease: a cross-sectional analysis

INTRODUCTION

Cardiovascular disease (CVD) remains the main cause of morbidity and mortality in end stage renal disease (ESDR) patients. A common C-T mutation at nucleotide position 677 (C677T) has been identified in the gene coding for methylenetetrahydrofolate reductase (MTHFR), which is involved in the remethylation of homocysteine (Hcy). The C677T mutation decreases MTHFR activity, tends to increase Hcy concentrations in individuals who are homozygous for the T/T genotype, and may predispose to CVD. Recent reports suggested that the T/T genotype may predispose type 2 diabetic and hypertensive patients to the development of progressive renal insufficiency. The aim of this cross-sectional study is to analyze the prevalence of the MTHFR C677T gene polymorphism among a group of chronic dialysis patients in comparison to age- and gender-matched controls. We also examined the possible association between CVD and MTHFR gene mutation in this group of patients.

PATIENTS AND METHODS

Fifty chronic hemodialysis patients were included in the study. They were 29 males and 21 females with a mean age of 41.57 +/- 11.76 years. Three patients (6%) were diabetic (type 2). Mean duration of dialysis was 6.4 +/- 3.2 years (range 1-15 years). CVD was defined as being present if there was a medical history of coronary artery disease, cerebrovascular stroke or transient ischemic attacks. MTHFR C677T gene polymorphism was analyzed by PCR in order to discriminate between homozygous (C/C and T/T) and heterozygous (C/T) genotypes. We also measured serum vitamin B(12), folate, total plasma Hcy (tHcy), lipid profile and serum albumin concentrations in the study group. Thirty healthy subjects (16 males and 14 females with mean age of 37.42 +/- 7.63 years) served as healthy controls.

RESULTS

Thirteen patients (26%) experienced at least one cardiovascular event: two (4%) had a history of ischemic cerebrovascular disease, 13 (26%) had coronary artery disease, and one patient (2%) had myocardial infarction. The C677T mutation of MTHFR was not found to be different in hemodialysis patients and healthy controls. Thirty dialysis patients (60%) and 19 healthy subjects (63.33%) had only the wild-type allele (C/C), 16 dialysis patients (32%) and nine healthy controls (30%) had one T allele (C/T), and four dialysis patients (8%) and two healthy controls (6.67%) had two copies (T/T) of the T allele. There were no differences between patients with the three different MTHFR genotypes (C/C, C/T, T/T) regarding cardiovascular events or cardiovascular risk factors. Age, gender, percentages of diabetic and hypertensive patients, serum folate, vitamin B(12), lipid profile, and tHcy levels were not significantly different between the three groups (P > 0.05). Hemodialysis patients with CVD were significantly older compared to those without CVD (P = 0.02). Diabetes status was significantly associated with cardiovascular events (P = 0.01).

CONCLUSIONS

In the dialysis population that we studied, MTHFR C677T gene polymorphism occurred in a pattern similar to that seen for age- and gender-matched healthy controls. No significant association was detected between the T/T genotype and CVD in dialysis patients. Plasma total homocysteine levels were not affected by mutation of the gene coding for MTHFR, and this may be explained by the normal serum folate and vitamin B(12) levels found in the study group.

Functional ENTPD1 polymorphisms in African Americans with diabetes and end-stage renal disease

OBJECTIVE

The vascular ectonucleotidase ENTPD1 protects against renal injury and modulates glucose homeostasis in mouse models. We sought to determine whether human variation in ENTPD1 influences predisposition to diabetes or diabetic nephropathy.

RESEARCH DESIGN AND METHODS

We analyzed ENTPD1 single nucleotide polymorphisms (SNPs) in 363 African American control subjects, 380 subjects with type 2 diabetes and end-stage renal disease (DM-ESRD), and 326 subjects with ESRD unrelated to diabetes (non-DM-ESRD). Using human cell lines, we correlated disease-associated ENTPD1 haplotypes with ENTPD1 gene expression. Finally, we studied consequences of ENTPD1 deletion in a mouse model of type 2 diabetes (db/db).

RESULTS

A common ENTPD1 two-SNP haplotype was associated with increased risk for DM-ESRD (P = 0.0027), and an uncommon four-SNP haplotype was associated with protection against DM-ESRD (P = 0.004). These haplotypes correlated with ENTPD1 gene expression levels in human cell lines in vitro. Subjects with high ENTPD1-expressing haplotypes were enriched in the DM-ESRD group. By crossing ENTPD1-null mice with db mice, we show that ENTPD1 deletion has prominent effects on metabolic syndrome traits. Specifically, deletion of ENTPD1 lowered glucose levels in control (db/-) mice with one functional leptin receptor and dramatically lowered weights in db/db mice with no functional leptin receptors. Similar effects were seen in aged ENTPD1-null mice with normal leptin receptors.

CONCLUSIONS

ENTPD1 polymorphisms appear to influence susceptibility to type 2 diabetes and/or diabetic nephropathy in African Americans. Studies in human cell lines and in vivo mouse data support a potential role for ENTPD1 genetic variation in susceptibility to type 2 diabetes.

The use of stem cells in kidney disease

PURPOSE OF REVIEW

Acute and chronic kidney disease is a leading cause of morbidity and mortality worldwide with overall mortality rates between 50 and 80%. An acute shortage of compatible organs coupled with limited adaptability of current dialysis techniques has created a sense of urgency to investigate new alternatives, and the purpose of this review is to provide a concise overview of current stem cell-based strategies in renal repair following acute kidney injury.

RECENT FINDINGS

Bone marrow-derived mesenchymal stem cells hold therapeutic potential in repairing tubular injury, ameliorating renal function deficits, and prolonging survival in experimental models of acute kidney injury. These renoprotective effects are mediated mainly by paracrine mechanisms that act on surviving tubular cells by stimulating dedifferentiation, proliferation, migration, and eventually redifferentiation into mature epithelial cells as well as by stimulating expansion and differentiation of resident stem/progenitor cells. Mesenchymal stem cells are capable of immunosuppression as well as inducing protection against peritubular capillary changes following acute injury making them ideal for allogeneic cell therapy.

SUMMARY

Autologous transplantation of bone marrow-derived mesenchymal stem cells as well as adult renal stem/progenitor cells that can be easily harvested and expanded may be the solution to limited donor organ availability and chronic immunosuppressive therapy.

Ethnicity, age and incidence rates for renal replacement therapy (RRT) in Birmingham, UK: 1990-2004

BACKGROUND

Birmingham is a densely populated, industrial city with a high social deprivation index and large black (B) and Indo-Asian (I) populations. End stage renal failure is known to be more common in ethnic minorities and urban communities. Workforce planning requires accurate epidemiological data but most studies of the effect of ethnicity in the UK are from the early 1990s.

METHODS

RRT acceptance rates for adults (>16 years) in Birmingham were calculated for the 5-year periods 1990-5 and 1999-2004 using the 1991 and 2001 UK population census datasets and local programmes data.

RESULTS

The adult population of Birmingham Health Authority increased slightly (961,041 in 1991 v 977,099 in 2001) but the proportion of W fell (82.7% to 74.3%) while B (5.3% to 7.0%) and I (10.4% to 17.2%) both increased.Median age was lower for I (33.5 1991, 32.9 2001) than B(33.8 1991, 37.4 2001) and W (45.1 1991, 45.9 2001).Numbers of new patients increased by 29% in W, 98% in B and 109% in I. There was also a substantial increase in acceptance rates (W 92 to 129 pmp, I 175 to 243 pmp, B 191 to 278 pmp) but the proportional increase in I (26.9%) was less than in W (41.5%) or B (48.2%). This is because almost all the increase in RRT acceptance rates for all ethnic groups was seen in the over 55 age group (256 pmp 1991, 481 pmp 2001) but 85% of the population growth for I was in the under 55 age group. In all ethnic groups there was a striking increase in acceptance rates for the over 70's (W 177 to 440 pmp, I 536 to 1711 pmp, B 301 to 1858 pmp).

CONCLUSIONS

All acceptance rates were equivalent to the highest previously described in the UK. This may be due to local factors including social deprivation, availability of care and physicians attitudes. The increase in patient numbers was due to rising ethnic minority populations and increasing acceptance rates, especially in the elderly.The take-on rate is likely to rise disproportionately for I as the population ages over the next 10 years. This indicates that the future need for RRT in UK inner city areas, especially those with a large elderly ethnic population, will be greater than previously estimated.

Genetic predictors of renal failure

BACKGROUND

Both environmental and genetic factors contribute to the development and progression of chronic kidney disease. The completion of the human genome sequence and advances in genomic technology make possible identification of gene variants associated with renal failure.

OBJECTIVE

This review discusses the relevant genetic studies in chronic kidney disease, with particular emphasis on the most common causes of end stage renal failure, diabetic nephropathy and glomerulonephritis.

METHODS

Most of the studies presented were performed in recent years and employed association studies, both population-based and with candidate genes, as well as the genome-wide association and genome-wide scan approaches.

RESULTS/CONCLUSION

Increasing evidence supports an important role of genetic susceptibility in the development and progression of renal failure. Identification of disease genes will allow the identification of patients at high risk and the development of new strategies to prevent or delay the renal disease process.

Association of a CYP4A11 variant and blood pressure in black men

CYP4A11 arachidonic acid monooxygenase oxidizes endogenous arachidonic acid to 20-hydroxyeicosatetraenoic acid, a renal vasoconstrictor and natriuretic. Cyp4a deficiency causes hypertension in male mice, and a loss-of-function variant (T8590C) of CYP4A11 is associated with hypertension in white individuals. Hypertension and hypertensive renal disease are more common among black than white individuals, but the relationship between genetic variation at CYP4A11 and hypertension in black individuals is not known. This study tested the hypothesis that the CYP4A11 T8590C polymorphism is associated with higher BP or clinical outcomes in 732 black Americans with hypertensive renal disease participating in the African American Study of Kidney Disease (AASK). Men with the 8590CC genotype had significantly higher systolic BP (CC 156.5 +/- 22.6 versus 148.4 +/- 24.3 mmHg in CT and TT combined; P = 0.04) and pulse pressure (P = 0.04) at baseline; this association was not observed among women. In addition, this genotype was associated with higher systolic and diastolic BP at 36-mo follow-up among those randomly assigned to the lower BP arm of the AASK. Among all participants (or men but not women) with proteinuria, the 8590CC genotype was associated with an increased cumulative incidence of ESRD or death, controlling for randomization and clinical characteristics. In summary, the CYP4A11 8590CC genotype is associated with increased BP in black men with hypertensive nephrosclerosis and is associated with adverse clinical outcomes in those with baseline proteinuria. These data support a role for renal monooxygenases and 20-hydroxyeicosatetraenoic acid in the regulation of BP and renal function in men.

Mapping quantitative trait loci for proteinuria-induced renal collagen deposition

The progression of chronic kidney disease is a complex process influenced by genetic factors. Proteinuria is a predictor of functional deterioration and an accelerator of disease progression through renal parenchymal damage and interstitial fibrosis. To determine genetic components that might mediate renal fibrosis due to proteinuria, we mapped loci influencing the phenotype of two mouse strains differing in proteinuria-induced renal type I collagen (COLI) deposition. Collagen I deposition in 129S1/svImJ and C57BL/6J mice differs significantly among tested strains. We backcrossed 120 hemi-nephrectomized (129S1/svImJ x C57BL/6J) F1 x 129S1/svImJ backcrossed mice loaded with bovine serum albumin giving rise to proteinuria and renal COLI deposition. Quantitative trait loci (QTL) mapping was performed and our analysis identified one suggestive linkage for renal COLI deposition peaking at 87 cM near D2Mit224 (logarithm of odds: 2.41) on Chr 2. In silico analysis uncovered nine candidate genes. Hence, although more studies are needed, these QTL provide an initial cue to subsequent gene discovery, which might help unravel the genetics of renal fibrosis.

Cytokine gene polymorphism and progression of renal and cardiovascular diseases

Cytokines are important modulators of inflammation. The balance between pro- and anti-inflammatory cytokines determines whether the intensity of inflammatory response is within physiological limits or in the pathological range. The cytokine network is highly complex, containing interactive cascades of gene activation and suppression. Both chronic kidney disease (CKD) and end-stage renal disease (ESRD) are characterized by elevated levels of proinflammatory cytokines and markers of inflammation. Cytokines may modulate the risk for progression of renal disease and the susceptibility to cardiovascular disease (CVD). Polymorphisms of cytokine genes may influence gene transcription and cytokine secretion and thereby modulate the risk of progression of renal and CVDs. The observed inconsistencies in the data regarding associations between single-nucleotide gene polymorphisms (SNPs) and their presumed phenotypic expression emphasize the need to recognize several conceptual and methodological aspects such as haplotypic rather than single SNP variations and the influence of pathway genes with synergistic or antagonistic effects that ultimately determine the phenotype. It is conceivable that when a patient with a high-risk cytokine genotype develops CKD, the risk for CVD is increased. Early interventions in CKD patients with high-risk genotypes may slow the progression of renal disease and also decrease CV mortality and morbidity.

The vascular ectonucleotidase ENTPD1 is a novel renoprotective factor in diabetic nephropathy

Ectonucleoside triphosphate diphosphohydrolase 1 (ENTPD1) (also known as CD39) is the dominant vascular ectonucleotidase. By hydrolyzing ATP and ADP to AMP, ENTPD1 regulates ligand availability to a large family of P2 (purinergic) receptors. Modulation of extracellular nucleotide metabolism is an important factor in several acute and subacute models of vascular injury. We hypothesized that aberrant nucleotide signaling would promote chronic glomerular injury in diabetic nephropathy. Inducing diabetes in ENTPD1-null mice with streptozotocin resulted in increased proteinuria and more severe glomerular sclerosis compared with matched diabetic wild-type mice. Diabetic ENTPD1-null mice also had more glomerular fibrin deposition and glomerular plasminogen activator inhibitor-1 (PAI-1) staining than wild-type controls. In addition, ENTPD1-null mice showed increased glomerular inflammation, in association with higher levels of monocyte chemoattractant protein-1 (MCP-1) expression. Mesangial cell PAI-1 and MCP-1 mRNA expression were upregulated by ATP and UTP but not ADP or adenosine in vitro. The stable nucleotide analog ATPgammaS stimulated sustained expression of PAI-1 and MCP-1 in vitro, whereas the stable adenosine analog NECA [5'-(N-ethylcarboxamido)adenosine] downregulated expression of both genes. Extracellular nucleotide-stimulated upregulation of MCP-1 is, at least in part, protein kinase C dependent. We conclude that ENTPD1 is a vascular protective factor in diabetic nephropathy that modulates glomerular inflammation and thromboregulation.

Impact of glucose levels on advanced glycation end products in hemodialysis

The current obesity epidemic throughout the western world has resulted in a considerable increase in the condition Type II diabetes mellitus. Recently, the World Health Organization has predicted that the global prevalence of Type II will increase from 175 million patients in 2003 to over 350 million by 2030. One of the major consequences of this disorder is renal failure, which presents itself as chronic kidney disease, and can progress to end-stage renal disease. Once diagnosed, patients are generally treated using dialysis due to a shortage of kidney donors. The fundamental process of dialysis still requires improvement because the survival rate of these patients is relatively poor. This has resulted in considerable research into improvements in hemodialysis membranes, and the challenge to find more suitable marker(s) in assessing the efficacy of the dialysis process. A class of compounds highlighted as a possible accumulative toxin is advanced glycation end products or AGEs. This is an article regarding the impact of hemodialysis and hemodiafiltration on glucose and AGE levels within the body and the consequences of a chronic hyperglycemic condition. It also highlights the negative aspects of using dextrose in conventional dialysis solutions (an area that has already been identified by peritoneal dialysis clinicians as problematic). The review concludes by suggesting several possible topics of future research.

Interleukin-1beta and receptor antagonist (IL-1Ra) gene polymorphisms and the prediction of the risk of end-stage renal disease

Cytokines play an important role in the pathogenesis of kidney disease and its progression to end-stage renal disease (ESRD). Inflammation is regulated by the genes of the interleukin 1 (IL-1) gene cluster. Therefore, it was hypothesized that a polymorphism in this gene cluster may be associated with the risk of ESRD. Polymorphisms in the IL-1 gene cluster were examined in a cohort of 222 ESRD patients and 206 controls of similar ethnicity. These individuals were genotyped for IL-1 beta (promoter -511 and exon-5 +3953) genes and a variable number of tandem repeats (VNTR) in the IL-1 receptor antagonist gene (IL-1Ra). There was significant difference in genotype frequencies between ESRD patients and control group for IL-1beta (promoter region and exon-5) and IL-1Ra gene polymorphism (p < 0.001, 0.006 and < 0.001, respectively). A significant difference was observed in IL-1Ra for 1/1 (410/410) and 1/2 (410/240) genotypes, and the risk for ESRD was higher in those carrying the 1/1 genotype (p = 0.014, OR = 1.692, and p < 0.001, OR = 0.163). Also identified was a novel, rare allele of a single copy of 86 bp in ESRD patients as compared with the controls. The haplotype 'T-E2-1' frequency distribution between patients and controls revealed greater than threefold risk (p = 0.001, OR = 3.572, 95% CI = 1.589-8.032). Genetic linkage between the IL-1beta promoter region and exon-5 and between the IL-1beta promoter and IL-1Ra of IL-1 gene demonstrated a strong association among the variants in controls (D' = 0.42, p < 0.001, and D' = 0.39, p=0.001). Thus, the three polymorphisms within the IL-1 cluster are associated with ESRD. This finding is perhaps one of the strongest associations between genotype and ESRD reported, and it suggests that the IL-1 gene cluster affects the risk of development of ESRD.

Synergistic QTL interactions between Rf-1 and Rf-3 increase renal damage susceptibility in double congenic rats

The FHH (fawn-hooded hypertensive) rat is a model of hypertension-associated chronic kidney damage. Five interacting quantitative trait loci (QTLs), named Rf-1-Rf-5, determine the high renal susceptibility. The aim of the present study was to investigate a possible interaction between Rf-1 and Rf-3. Differences in renal susceptibility between ACI (August x Copenhagen Irish) controls, Rf-1A and Rf-3 single congenics, and Rf-1A+3 double congenic rats were assessed using four different treatments: two-kidney control (2K), 2K plus N(omega)-nitro-L-arginine methyl ester (L-NAME)-induced hypertension (2K+L-NAME), unilateral nephrectomy (UNX), and UNX plus L-NAME-induced hypertension (UNX+L-NAME). Proteinuria (UPV) and systolic blood pressure (SBP) were assessed after 6, 12, and 18 weeks, while the incidence of glomerulosclerosis (%FGS) was determined at the end of the experiment. In a separate experiment, renal autoregulation was assessed in 13-15-week old 2K rats of all four strains. Compared to ACI rats, small increases in renal susceptibility were found in Rf-1A and Rf-3 single congenics following 2K+L-NAME, UNX, and UNX+L-NAME treatments. However, in the Rf-1A+3 double congenics, a major increase in renal susceptibility was found with all four treatments. Both Rf-1A and Rf-1A+3 congenic rats had an impaired renal autoregulation. In contrast, the Rf-3 had a normal autoregulation, similar to that of the ACI rat. These findings indicate that Rf-1 and Rf-3 alone slightly increase the susceptibility to the development of renal damage. However, a synergistic interaction between these two QTLs markedly enhances renal susceptibility. In contrast to the Rf-1 region, the Rf-3 region does not carry genes influencing renal autoregulation.

Mechanisms of progression and regression of renal lesions of chronic nephropathies and diabetes

The incidence of chronic kidney diseases is increasing worldwide, and these conditions are emerging as a major public health problem. While genetic factors contribute to susceptibility and progression of renal disease, proteinuria has been claimed as an independent predictor of outcome. Reduction of urinary protein levels by various medications and a low-protein diet limits renal function decline in individuals with nondiabetic and diabetic nephropathies to the point that remission of the disease and regression of renal lesions have been observed in experimental animals and even in humans. In animal models, regression of glomerular structural changes is associated with remodeling of the glomerular architecture. Instrumental to this discovery were 3D reconstruction studies of the glomerular capillary tuft, which allowed the quantification of sclerosis volume reduction and capillary regeneration upon treatment. Regeneration of capillary segments might result from the contribution of resident cells, but progenitor cells of renal or extrarenal origin may also have a role. This review describes recent advances in our understanding of the mechanisms and mediators underlying renal tissue repair ultimately responsible for regression of renal injury.