A genome scan for all-cause end-stage renal disease in African Americans.

BACKGROUND: In an attempt to map the genes predisposing to the common, complex aetiologies of end-stage renal disease (ESRD), we performed a genome-wide scan in 1023 individuals with chronic kidney disease (946 dialysis dependent and 77 with advanced chronic renal failure) from 483 African American families. METHODS: The study sample comprised 563 ESRD-affected sibling pairs, with nephropathy attributed to diabetes mellitus, chronic glomerular disease or hypertension. Multipoint non-parametric linkage (NPL) analysis methods were employed. RESULTS: NPL regression provided modest evidence of linkage to 13q33.3 near D13S796 [log of the odds (LOD) = 1.72], 9q34.3 near D9S1826 (LOD = 1.22), 4p15.32 near D4S2639 (LOD = 1.11) and 1q25.1 near D1S1589 (LOD = 1.01). Adjusting for the evidence of linkage at the other loci using NPL regression analysis provided evidence for linkage to 4p15.32, 9q34.3 and 13q33.3. NPL regression interaction and ordered subset analysis (OSA) suggested that the evidence for linkage to ESRD significantly increased with higher body mass index (BMI) at 13q33.3 (LOD = 4.94 in 61% of families with the highest BMI). Additionally, OSA suggested that linkage significantly improved in the 13% of families with earliest age at ESRD onset (LOD = 3.05 at 2q32.1) and in the 16% of families with latest age at ESRD onset (LOD = 2.47 at 10q26.3). CONCLUSIONS: Multipoint single-locus linkage analysis provided modest evidence of linkage to all-cause ESRD in African Americans on 13q33.3, and NPL regression and OSA suggested that evidence for linkage in this region markedly increased in obese families. This region, as well as 9q34.3, 4p15.32 and 1q25.1, should receive priority in the search for loci contributing to ESRD susceptibility in African Americans.     

Linkage heterogeneity of end-stage renal disease on human chromosome 10

BACKGROUND: The human syntenic region of the rodent renal failure-1 gene (Rf1), an attractive candidate region for end-stage renal disease (ESRD) susceptibility, is located on chromosome 10q24-q26. In an attempt to assess for linkage between markers on human chromosome 10 and ESRD, we performed a linkage analysis in 356 African American sib pairs concordant for ESRD [199 sib pairs concordant for non-diabetic etiologies (hypertension-associated, chronic glomerulonephritis and unknown) and 157 sib pairs concordant for diabetic ESRD]. METHODS: Linkage was tested between 30 polymorphic markers spanning chromosome 10 and ESRD using GeneHunter software. RESULTS: In all 356 sib pairs, the maximum likelihood ratio z-score (Zlr) occurred near locus D10S677 (Zlr = 3.33, P = 0.0004, lod = 3.40), with a lesser peak near D10S1435 (Zlr = 1.77, P = 0.04, lod = 1.42). The locus at D10S677 contributed significantly to both diabetic ESRD (Zlr = 2.39, P = 0.008, lod = 2.08) and non-diabetic ESRD (Zlr = 2.35, P = 0.009, lod = 2.03). Additionally, the D10S677 peak was observed in both early onset (< or =50 years) and late onset (>50 years) ESRD (Zlr = 2.96, P = 0.002, lod = 2.82 in early onset and Zlr = 1.96, P = 0.03, lod = 1.60 in late onset ESRD families, respectively). The lesser peak at D10S1435 was observed in families with non-diabetic etiologies of ESRD (Zlr = 1.94, P = 0.02, lod = 1.58) and in those with early onset ESRD (Zlr = 1.89, P = 0.03, lod = 1.53). CONCLUSIONS: These results suggest that the region near D10S677, adjacent to the human homolog of the Rf1 gene, contributes to ESRD susceptibility in African Americans. They confirm that the region on 10p, near D10S1435, appears to be involved in early onset, non-diabetic etiologies of ESRD in African Americans.     

Geographic, ethnic, age-related and temporal variation in the incidence of end-stage renal disease in Europe, Canada and the Asia-Pacific region, 1998-2002.

BACKGROUND: Only unbiased estimates of end-stage renal disease (ESRD) incidence and trends are useful for disease control-identification of risk factors and measuring the effect of intervention. METHODS: Age- and sex-standardized incidences (with trends) were calculated for all-cause and diabetic/non-diabetic ESRD for persons aged 0-14, 15-29, 30-44 and 45-64 years in 13 populations identified geographically, and six populations identified by ethnicity. RESULTS: The incidence of ESRD varied most with age, ethnicity and prevalence of diabetes. All non-Europid populations had excess ESRD, chiefly due to rates of type 2 diabetic ESRD that were greater than accounted for by community prevalences of diabetes. Their rates of non-diabetic ESRD also were raised, with contributions from most common primary renal diseases except type 1 diabetic nephropathy and polycystic kidney disease. The ESRD rates generally were low, and more similar than different, in Europid populations, except for variable contributions from type 1 (high in Finland, Sweden, Denmark and Canada) and type 2 (high in Austria and Canada) diabetes. In Europid populations during 1998-2002, all-cause ESRD declined by 2% per year in persons aged 0-44 years, and all non-diabetic ESRD by a similar amount in persons aged 45-64 years, in whom diabetic ESRD had increased by 3% per year. CONCLUSIONS: Increased susceptibility to type 2 diabetes and to kidney disease progression characterizes excess ESRD in non-Europid peoples. The decline in all-cause ESRD in young persons, and non-diabetic ESRD in the middle-aged, probably reflects improving management of progressive renal disease.     

Sickle cell trait is not independently associated with susceptibility to end-stage renal disease in African Americans

Conflicting reports exist as to whether sickle cell trait is a risk factor for the progression of nephropathy. In order to determine whether African Americans with sickle cell trait are at increased risk for kidney disease, we assessed the genetic association between sickle cell trait and end-stage renal disease (ESRD). Hemoglobin S, non-muscle myosin heavy chain 9 (MYH9), and apolipoprotein L1 (APOL1) risk variants were genotyped in 3258 unrelated African Americans: 1085 with non-diabetic ESRD, 996 with type 2 diabetes-associated ESRD, and 1177 controls. Since APOL1 is strongly associated with ESRD in African Americans, interactions between APOL1 and MYH9 risk variants and hemoglobin S were assessed using case-only and case-control centered two-way logistic regression interaction analyses. The sickle cell trait genotype frequencies were 8.7% in non-diabetic ESRD, 7.1% in type 2 diabetes-ESRD, and 7.2% in controls. There was no age-, gender-, and admixture-adjusted significance for sickle cell trait association with non-diabetic ESRD (odds ratio 1.16); type 2 diabetes-ESRD (odds ratio 1.01); or all-cause ESRD (combined non-diabetic and type 2 diabetic-ESRD patients compared to the controls; odds ratio 1.05) in dominant models. In addition, no evidence of APOL1 or MYH9 interactions with sickle cell trait was detected. Hence, sickle cell trait is not associated with diabetic or non-diabetic ESRD in a large sample of African Americans.     

A genome scan for ESRD in black families enriched for nondiabetic nephropathy

Nephropathy is a complex disorder, with predisposition influenced by the interplay of both genetic and environmental factors. As part of an effort to map genes that predispose to ESRD, a genome scan was performed in 264 black pedigrees that contained 296 ESRD-affected sibling pairs using multipoint nonparametric linkage analysis methods. The cause of ESRD in index cases was consistent with hypertension-associated ESRD. Nonparametric linkage (NPL) regression provided modest evidence of linkage to 9p21.3 near D9S1121 (logarithm of odds [LOD] = 2.03), 1q25.1 near D1S1589 (LOD = 1.62), and 13q33.3 near D13S796 (LOD = 1.02). Adjusting for the evidence of linkage at the other loci through the NPL regression analysis provided evidence for linkage to 1q25.1, 6p23, and 9p21.3. The NPL regression and ordered subset analyses suggest that the evidence for linkage significantly increased with early onset of ESRD (2q32.1 LOD = 3.89, 13q13.1 LOD = 3.90), increased BMI (8p22 LOD = 3.37, 13q33.3 LOD = 5.20, 18p11.3 LOD = 2.38), early onset of hypertension (14q21.1 LOD = 3.19, 20q13.2 LOD = 2.32), and late onset of hypertension (4q13.1 LOD = 3.44, 5p15.33 LOD = 2.82). Multipoint single-locus linkage analysis provided modest evidence of linkage to nondiabetic ESRD on 9p21.3, 1q25.1 (in the region of the podocin gene), and 13q33.3. NPL regression and ordered subset analyses also identified loci on 13q13.1 and 13q33.3 as contributing to early-onset ESRD and ESRD in the presence of increased BMI, respectively. These regions should receive priority in the search for loci that contribute susceptibility to nondiabetic nephropathy.     

A genome-wide association study for diabetic nephropathy genes in African Americans

A genome-wide association study was performed using the Affymetrix 6.0 chip to identify genes associated with diabetic nephropathy in African Americans. Association analysis was performed adjusting for admixture in 965 type 2 diabetic African American patients with end-stage renal disease (ESRD) and in 1029 African Americans without type 2 diabetes or kidney disease as controls. The top 724 single nucleotide polymorphisms (SNPs) with evidence of association to diabetic nephropathy were then genotyped in a replication sample of an additional 709 type 2 diabetes-ESRD patients and 690 controls. SNPs with evidence of association in both the original and replication studies were tested in additional African American cohorts consisting of 1246 patients with type 2 diabetes without kidney disease and 1216 with non-diabetic ESRD to differentiate candidate loci for type 2 diabetes-ESRD, type 2 diabetes, and/or all-cause ESRD. Twenty-five SNPs were significantly associated with type 2 diabetes-ESRD in the genome-wide association and initial replication. Although genome-wide significance with type 2 diabetes was not found for any of these 25 SNPs, several genes, including RPS12, LIMK2, and SFI1 are strong candidates for diabetic nephropathy. A combined analysis of all 2890 patients with ESRD showed significant association SNPs in LIMK2 and SFI1 suggesting that they also contribute to all-cause ESRD. Thus, our results suggest that multiple loci underlie susceptibility to kidney disease in African Americans with type 2 diabetes and some may also contribute to all-cause ESRD.     

Candidate Gene Analysis in African Americans with Renal Failure

A search for renal failure genes is being conducted in African American sib pairs concordant for end-stage renal disease (ESRD) recruited predominantly from the dialysis population in the Southeastern United States. Family history data is being collected in patients from more than 250 individual dialysis units. Patients with polycystic kidney disease, Alport's Syndrome and confirmed urologic disease are excluded. The study employs a candidate gene strategy initially, followed by a genome-wide search for linkage between polymorphic markers and the phenotype “ESRD.”     

Patterns of end-stage renal disease in US African-Americans

Summary: Although African-Americans constitute only about 12.4% of the population of the United States of America (USA), they comprise over 30% of the end-stage renal disease (ESRD) patient population. Diabetes mellitus (predominantly type 2) is the most frequently reported cause of ESRD in all racial and ethnic groups in the USA. However, hypertensive renal disease is reported as the dominant cause of ESRD in African-Americans. In general, all racial and ethnic minority groups in the USA have greater incidence and prevalence rates of ESRD than Caucasians. However, survival probabilities in all ESRD patients, dialysis patients, and cadaveric renal allograft recipients are greater in African-Americans than in Caucasians. the suggested reasons for these racial and ethnic disparities are discussed.     

Endothelial nitric oxide synthase gene intron 4 polymorphism in patients with end-stage renal disease.

BACKGROUND: Nitric oxide (NO) synthesized by endothelial cell NO synthase (ecNOS) is a potent regulator of intrarenal haemodynamics. A polymorphism in intron 4 of the ecNOS gene is a candidate gene in cardiovascular and renal diseases. We investigated a potential involvement of this polymorphism in chronic renal failure. METHODS: We performed a case-control study involving 706 patients with end-stage renal disease (ESRD) and 321 healthy controls. All subjects were genotyped for the ecNOS4 polymorphism by the polymerase chain reaction followed by agarose gel electrophoresis. RESULTS: The analysis revealed that the frequencies of the ecNOS4 genotypes were significantly different in ESRD patients, both diabetic and non-diabetic, than in controls. In all dialysis patients for aa, ab and bb genotypes the frequencies were, respectively, 6.5, 35 and 58.5% in the patient group, and 1, 25 and 74% in control subjects. The a allele carriers (aa + ab) were more frequent among ESRD patients than in controls (OR 1.95; 95% CI 1.13-3.4; P = 0.0031). No significant association was found when hypertensive ESRD patients were compared with normotensive patients. The distribution of genotypes was similar in both subgroups (P = 0.21). CONCLUSION: There was a significantly higher frequency of the ecNOS4a allele carriers among ESRD patients, both diabetic and non-diabetic, than in control subjects. This suggests that the ecNOS gene polymorphism may be associated with an increased risk of chronic renal failure.     

Trends in incidence of treated end-stage renal disease, overall and by primary renal disease, in persons aged 20-64 years in Europe, Canada and the Asia-Pacific region, 1998-2002

AIMS: To determine if rates of diabetic and non-diabetic end-stage renal disease (ESRD), which had been rising in young and middle-aged adults in all populations up to the mid-1990s, had started to decline, and if so, whether improvement had occurred in respect of each of the principal primary renal diseases causing ESRD. METHODS: Poisson regression of age- and sex-standardized incidence of ESRD for persons aged 20-64 years in 18 populations from Europe, Canada and the Asia-Pacific region, for 1998-2002. RESULTS: In persons from 12 European descent (Europid) populations combined, there was a small downward trend in all-cause ESRD (-1.7% per year, P = 0.001), with type 1 diabetic ESRD falling by 7.8% per year (P < 0.001), glomerulonephritic ESRD by 3.1% per year (P = 0.001), and 'all other non-diabetic' ESRD by 2.5% per year (P = 0.02). The reductions in ESRD attributed to hypertensive (-2.2% per year) and polycystic renal disease (-1.5% per year) and unknown diagnosis (-0.2% per year) were not statistically significant. On the other hand, the incidence of type 2 diabetic ESRD rose by 9.9% per year (P < 0.001) in the combined Europid population, although that of (principally type 2) diabetic ESRD remained unchanged in the pooled data from the four non-Europid populations. CONCLUSION: Recent preventive strategies, probably chiefly modern renoprotective treatment, appear to have been effective for tertiary prevention of ESRD caused by the proteinuric nephropathies other than type 2 diabetic nephropathy, for which the continuing increase in Europid populations represents a failure of prevention and/or a change in the nephropathic potential of type 2 diabetes.     

Racial and ethnic disparities in end-stage kidney failure-survival paradoxes in African-Americans

The risk of death is nearly 45% lower in African-Americans than Caucasians undergoing chronic hemodialysis. In light of the higher mortality rate in African-Americans in the general US population, this paradox requires explanation and further investigation. Factors that may contribute to this survival advantage include a younger age at which African-Americans arrive at end-stage renal disease (ESRD) and the slightly higher body mass index. On the other hand, factors, such as lower residual renal function, lower mean hemoglobin and hematocrit, increased prevalence of hypertension, a higher prevalence of catheter use for initial dialysis, and generally lower dose of dialysis should put African-Americans on dialysis at a higher risk of death. This survival advantage seems to be completely annulled with a successful renal transplant. Finally, it should be noted that ESRD carries with it a very high mortality rate in all racial and ethnic groups. A successful renal transplant improves but does not restore the expected remaining life times. Therefore, aggressive approach is required in investigating the factors that confer such high mortality risk on ESRD patients.     

Impact of Nitric Oxide Synthase Glu298Asp Polymorphism on the Development of End-Stage Renal Disease in Type 2 Diabetic Egyptian Patients

Abstract

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.     

Autosomal dominant medullary cystic kidney disease: evidence of gene locus heterogeneity

Autosomal dominant medullary cystic kidney disease (ADMCKD; synonym: medullary cystic disease, MCD) is an autosomal dominant kidney disorder, sharing morphological and clinical features with recessive juvenile nephronophthisis (NPH), such as reduced urinary concentration ability and multiple renal cysts at the corticomedullary junction. While in NPH end-stage renal disease (ESRD) occurs in adolescence, ADMCKD leads to ESRD in adulthood. Recently a gene locus for ADMCKD has been localized to chromosome 1q21 in two large Cypriot families. This prompted us to examine linkage in three ADMCKD-families, using the same set of polymorphic microsatellite markers spanning the critical region on chromosome 1q21. Haplotype analysis revealed that none of the three families showed linkage to this locus, thus demonstrating evidence for genetic locus heterogeneity. Additional linkage analysis studies need to be performed in order to identify further gene loci cosegregating with this autosomal dominant kidney disorder.     

Relevance of the ACTN4 Gene in African-Americans with Non-Diabetic End-Stage Renal Disease

Background: African-Americans (AAs) are predisposed to non-diabetic (non-DM) end-stage renal disease (ESRD), and studies have shown a genetic component to this risk. Rare mutations in ACTN4 (α-actinin-4), an actin-binding protein expressed in podocytes, cause familial focal segmental glomerulosclerosis. Methods: We assessed the contribution of coding variants in ACTN4 to non-DM ESRD risk in AAs. Nineteen exons, 2,800 bases of the promoter and 392 bases of the 3' untranslated region of ACTN4 were sequenced in 96 AA non-DM ESRD cases and 96 non-nephropathy controls (384 chromosomes). Sixty-seven single-nucleotide polymorphisms (SNPs) including 51 novel SNPs were identified. The SNPs comprised 33 intronic, 21 promoter, 12 exonic, and one 3' variant. Sixty-two of the SNPs were genotyped in 296 AA non-DM ESRD cases and 358 non-nephropathy controls. Results: One SNP, rs10404257, was associated with non-DM ESRD (p < 1.0E-4, odds ratio, OR = 0.76; confidence interval, CI = 0.59-0.98; additive model). Forty-seven SNPs had minor allele frequencies <5%. These SNPs were segregated into risk and protective SNPs, and each category was collapsed into a single marker, designated by the presence or absence of any rare allele. The presence of any rare allele at a risk SNP was significantly associated with non-DM ESRD (p = 0.001, dominant model). The SNPs with the strongest evidence for association (n = 20) were genotyped in an independent set of 467 non-DM ESRD cases and 279 controls. Although rs10404257 was not associated in this replication sample, when the samples were combined, rs10404257 was modestly associated (p = 0.032, OR = 0.78, CI = 0.63-0.98; dominant model). SNPs were tested for interaction with markers in the APOL1 gene, previously associated with non-DM ESRD in AAs, and rs10404257 was modestly associated (p = 0.0261, additive model). Conclusions: This detailed evaluation of ACTN4 variation revealed limited evidence of association with non-DM ESRD in AAs.     

High-density single nucleotide polymorphism genome-wide linkage scan for susceptibility genes for diabetic nephropathy in type 1 diabetes: discordant sibpair approach

OBJECTIVE— Epidemiological and family studies have demonstrated that susceptibility genes play an important role in the etiology of diabetic nephropathy, defined as persistent proteinuria or end-stage renal disease (ESRD) in type 1 diabetes.RESEARCH DESIGN AND METHODS— To efficiently search for genomic regions harboring diabetic nephropathy genes, we conducted a scan using 5,382 informative single nucleotide polymorphisms on 100 sibpairs concordant for type 1 diabetes but discordant for diabetic nephropathy. In addition to being powerful for detecting linkage to diabetic nephropathy, this design allows linkage analysis on type 1 diabetes via traditional affected sibpair (ASP) analysis. In weighing the evidence for linkage, we considered maximum logarithm of odds score (maximum likelihood score [MLS]) values and corresponding allelic sharing patterns, calculated and viewed graphically using the software package SPLAT.RESULTS— Our primary finding for diabetic nephropathy, broadly defined, is on chromosome 19q (MLS = 3.1), and a secondary peak exists on chromosome 2q (MLS = 2.1). Stratification of discordant sibpairs based on whether disease had progressed to ESRD suggested four tertiary peaks on chromosome 1q (ESRD only), chromosome 20p (proteinuria only), and chromosome 3q (two loci 58 cm apart, one for ESRD only and another for proteinuria only). Additionally, analysis of 130 ASPs for type 1 diabetes confirmed the linkage to the HLA region on chromosome 6p (MLS = 9.2) and IDDM15 on chromosome 6q (MLS = 3.1).CONCLUSIONS— This study identified several novel loci as candidates for diabetic nephropathy, none of which appear to be the sole genetic determinant of diabetic nephropathy in type 1 diabetes. In addition, this study confirms two previously reported type 1 diabetes loci.Diabetic nephropathy is the major complication of type 1 diabetes. Clinically, diabetic nephropathy is manifested as persistent proteinuria that frequently progresses to end-stage renal disease (ESRD) (1). While hyperglycemia plays a major role in diabetic nephropathy (1), genetic predisposition has become apparent. Familial aggregation of diabetic nephropathy has been observed in all family studies with multiple type 1 diabetic siblings (2–6). The most comprehensive study, conducted at the Joslin Clinic (4), demonstrated that in comparison with a lifetime diabetic nephropathy risk of 35% among unrelated patients with type 1 diabetes, the risk to a second diabetic sibling increases to 72% or decreases to 25%, depending on whether the first diabetic sibling had diabetic nephropathy. Since familial clustering of glycemic control could not account for this large disparity, a major gene effect was proposed as a plausible explanation (4). To map such a gene, we showed that discordant sibpairs (DSPs) for diabetic nephropathy would be four times as efficient as affected sibpairs (ASPs) (7).Previously, we applied the DSP strategy to a collection of 66 DSPs to test for linkage with genes of the renin-angiotensin system (8). Manual genotyping of microsatellites did not identify any evidence for linkage with AGT (chromosome 1q) and ACE (chromosome 17q); however, we obtained suggestive evidence for linkage with the region on chromosome 3q containing ATR1 (8). Subsequent sequencing of this gene and association studies, however, excluded this gene (8). This report features a larger sample size (100 DSPs from 83 families) and a more stringent definition of diabetic nephropathy.     

Identification of podocin (NPHS2) gene mutations in African Americans with nondiabetic end-stage renal disease

BACKGROUND: Podocin, encoded by NPHS2 and mapped to 1q25.2, is an integral membrane protein exclusively expressed in glomerular podocytes. Mutations in the NPHS2 gene cause autosomal-recessive nephrotic syndrome and have been associated with proteinuria in several populations. Evidence for linkage of end-stage renal disease (ESRD) to chromosome 1q25-31 in the region of NPHS2 has been identified in a genome-wide scan in African American (AA) siblings. METHODS: To investigate the potential role of this gene in ESRD, we sequenced all coding regions and approximately 2 kb of upstream promoter sequence of NPHS2 in 96 unrelated AA nondiabetic ESRD cases and 96 healthy population-based AA controls, and assessed several single nucleotide polymorphisms (SNPs) for association in a larger case-control sample. RESULTS: Fifty-five variants were identified with minor allele frequencies ranging from <1% to 44%. Twenty-three polymorphisms were located in the promoter region, 11 were exonic, 13 were intronic, and 8 were in the 5' and 3'- untranslated regions. Two novel nonsynonymous coding SNPs were identified (A44E and A61V). An insertion polymorphism in intron 3, IVS3+9insA, was detected in 6 ESRD patients and in no controls. This variant, and 4 other common SNPs, were evaluated in a larger sample of 288 AA ESRD cases and 278 AA controls. The overall minor allele frequencies for the insertion allele were 0.018 in cases and 0.002 in controls. Significant evidence of association of IVS3+9insA was observed (P= 0.012), and the haplotype containing the insertion allele in cases was also associated. CONCLUSION: These results suggest that uncommon variants of the NPHS2 gene may play a role in the development of nondiabetic ESRD in AAs.     

Association of an IL-1A 3'UTR polymorphism with end-stage renal disease and IL-1 alpha expression

BACKGROUND: We evaluated polymorphisms in the interleukin-1 alpha 3'-untranslated region (IL-1A 3'[UTR]) for association with type 2 diabetes-associated (DM) and nondiabetic-associated (non-DM) end-stage renal disease (ESRD) in two ethnic groups. METHODS: IL-1A 3'UTR polymorphisms were identified by alignment of overlapping human expressed sequence tags (ESTs). Sequence ambiguities were experimentally confirmed and variants genotyped to test for association with ESRD in 75 unrelated Caucasians with DM ESRD, 95 unrelated Caucasian controls and, in a parallel study, 92 unrelated African Americans with type 2 DM ESRD, 95 unrelated African Americans with non-DM ESRD, and 86 unrelated African American controls. IL-1A 3' UTR genotype and lipopolysaccharide (LPS)-stimulated IL-1 alpha protein levels were measured in healthy Caucasians (N = 112) and African Americans (N = 101) to evaluate association between genotype and protein level. RESULTS: A polymorphism in the 3' UTR of the human IL-1A gene was associated with ESRD and IL-1 alpha protein expression. The polymorphism consists of two single nucleotide polymorphisms (SNPs) and an insertion/deletion generating four different haplotypes: TN7TTCAA, AN7TTCAA, TN7TTCAG and an allele deleted for four internal bases, TN7(delTTCA)A. The 4 bp deletion allele, TN7(delTTCA)A, was significantly less common among Caucasian DM ESRD and African American non-DM ESRD patients (recessive model; P = 0.0364 and P = 0.0293, respectively). In vitro, this polymorphism is associated with the amount of IL-1 alpha protein synthesized in LPS-stimulated lymphocytes from healthy subjects (P = 0.0013, additive model), with the TN7(delTTCA)A haplotype associated with higher levels of stimulated IL-1 alpha. CONCLUSION: The association of the TN7(delTTCA)A haplotype with higher levels of IL-1 alpha expression and reduced risk for ESRD is consistent with involvement of cytokines in risk for developing nephropathy.     

Renin-Angiotensin System Polymorphisms: A Risk Factor for Progression to End-Stage Renal Disease in Vesicoureteral Reflux Patients

Aim. Renin-angiotensin system (RAS) gene mutations have been implicated as a risk factor for the presence and progression of renal disease in vesicoureteral reflux (VUR). However, the results are contradictory, and the effects of RAS polymorphisms in VUR patients with end-stage renal disease (ESRD) have not been defined yet. This study was designed to evaluate the angiotensin-converting enzyme insertion/deletion (ACE-I/D), angiotensinogen (AGT) M235T, and angiotensin II receptor type 1 (ATR1) A1166C and type 2 (ATR2) C3123A gene polymorphisms as risk factors for progression to ESRD in patients with VUR. Methods. ACE-I/D, AGT-M235T, ATR1-A1166C, and ATR2-C3123A were identified in 161 ESRD patients (52 female, 109 male; 77 renal transplant, 84 dialysis; age: 34.4 ± 11.2 years). VUR was the ESRD etiology in 40 patients. Genetic polymorphisms of the ACE gene I/D, AGT gene M235T, ATR1 gene A1166C, and ATR2 gene C3123A were identified in all of the patients. Results. We detected no linkage between genetic polymorphisms of ATR1-, ATR2-, AGT-, and VUR-related ESRD. When ACE gene was considered, VUR(+) patients had 63.6% DD, 36.4% ID, and no II alleles, whereas VUR(?) patients had 48.6% DD, 43.2% ID, and 8.1% II alleles. Conclusion. A striking feature of VUR-related ESRD patients was the absence of II alleles, so the DD genotype may be accepted as a genetic susceptibility factor for progression to ESRD in VUR patients.     

Association of the tissue kallikrein gene promoter with ESRD and hypertension

BACKGROUND: Kallikreins have long been implicated in human essential hypertension and associated complications. In particular, low urinary kallikrein excretion has been associated with hypertension and renal disease in African Americans. In an effort to identify the source of differential kallikrein excretion, we investigated the promoter of KLK1, the tissue kallikrein gene. The KLK1 promoter is uniquely polymorphic with a poly-G length polymorphism coupled with multiple single base substitutions. In this report, we genetically evaluated the association of KLK1 gene promoter alleles with end-stage renal disease (ESRD) in African Americans. METHODS: A total of 15 haplotypes were identified in the KLK1 promoter region through detailed DNA sequence analysis. This polymorphic region was then genetically evaluated for association with ESRD in African Americans with diabetic and non-diabetic etiologies of ESRD. RESULTS: The complex polymorphic nature of the promoter presents challenges to determining the alleles. We have redefined the region as six separate loci: five substitution loci and one length locus. The length locus was defined as G repeats starting at position -130 and ending at -121 on the gene. Among four relevant substitution loci for this study, one at position -131, just outside the G repeats, is an A-to-G substitution. The other three variant positions are -129, -128, and -127, all G-to-C substitutions within the G repeats. This region was genotyped in African American subjects with and without ESRD using semiautomated sequencing. Four different G repeat alleles ranging from 11.8% for 12 Gs to 52.3% for 10 Gs were observed in 86 control subjects. The C substitution of Gs ranges from 2.9% at position -127 to 8.2% at -129. When affected probands from each of 76 hypertensive ESRD families were genotyped, an association for the 12 G allele, the longest of the length locus alleles, was detected (allele specific P = 0.004 and locus total P = 0.02). When all ESRD affected individuals with hypertension from each family (107 patients in total) were used in the analysis, an even stronger association was observed for this allele (allele specific P = 0.003, locus total P = 0.01). This allele was more frequent in the hypertensive (non-diabetic) patients (0.20 in probands and 0.19 in all ESRD cases) than in the controls (0.12). No evidence of association in diabetic ESRD patients was observed (P = 0.93). CONCLUSIONS: The KLK1 promoter is uniquely polymorphic. The observed genetic association suggests an etiologic effect of the KLK1 promoter on hypertension and/or hypertension associated ESRD.     

The role of anemia management in improving outcomes for African-Americans with chronic kidney disease

Chronic kidney disease (CKD) is a serious threat to African-American public health. In this population CKD progresses to end-stage renal disease (ESRD) at quadruple the rate in Caucasians. Factors fueling progression to ESRD include diabetes and hypertension, which show high prevalences and accelerated renal damage in African- Americans, as well as possible nutritional, socioeconomic, and genetic factors. Anemia, a common and deleterious complication of CKD, is more prevalent and severe in African-American than Caucasian patients at each stage of the disease. Proactive management of diabetes, hypertension, anemia, and other complications throughout the course of CKD can prevent or delay disease progression and alleviate the burden of ESRD for the African-American community. Currently, African-Americans with CKD are less likely than Caucasian patients to receive anemia treatment before and after the onset of dialysis. Although African-Americans often require higher doses of erythropoiesis-stimulating agents, this may result from late treatment initiation, lower hemoglobin levels, or the presence of comorbidities such as diabetes and inflammation, although racial differences in response cannot be excluded. This review explores racial-specific challenges and potential solutions in renal anemia management to improve outcomes in African-American patients.