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1.  Uromodulin concentrations are not associated with incident CKD among persons with coronary artery disease 
BMC Nephrology  2011;12:2.
A common variant of the UMOD gene was linked with prevalent chronic kidney disease (CKD) in large, genomics consortia. One community-based study found that urine concentrations of the uromodulin protein forecast risk of incident CKD. This study within persons with known coronary artery disease (CAD) evaluated whether uromodulin concentrations could distinguish CKD risk.
In the Heart and Soul Study, the UMOD snp (12917707) was genotyped in 879 individuals with baseline creatinine clearance (CrCl) measured from a 24-hour urine collection. Uromodulin protein was measured from stored urine specimens among a subset of 120 participants, balanced by genotype. Incident CKD cases (N = 102) were defined by an initial CrCl > 70 ml/min and a 5-year follow-up CrCl <60 ml/min; controls (N = 94) were matched on age, sex, and race.
Among 527 self-described White participants with DNA, 373 (71%) were homozygous for the dominant allele (G/G), 133 (25%) were heterozygous (G/T) and only 21 (4%) were homozygous for the minor allele (T/T). The T/T genotype had an approximately 11 ml/min higher CrCl than the other 2 groups, but this difference did not reach statistical significance (p = 0.20). The T/T genotype had significantly lower uromodulin levels than the common G/G genotype, and the G/T genotype had intermediate levels. However, uromodulin concentrations were similar between cases and controls (44 vs. 48 mg/dL, p = 0.88).
This study among a cohort of persons with established CAD found no association between urine uromodulin and incident CKD, although UMOD genotype was associated with urine uromodulin concentrations.
PMCID: PMC3031204  PMID: 21235779
2.  UMOD polymorphism rs12917707 is not associated with severe or stable IgA nephropathy in a large Caucasian cohort 
BMC Nephrology  2014;15:138.
Genetic factors are suspected in the pathogenesis of IgA nephropathy, as well as in the course of IgA nephropathy progression towards end stage renal failure. UMOD polymorphism rs12917707 is known to associate with end stage renal failure of mixed aetiologies.
We tested a large cohort of Caucasian patients for association of rs12917707 with IgA nephropathy showing a benign, stable course and with IgA nephropathy that progressed toward end stage renal failure.
No association was observed between either groups, and a non-significant trend was observed for more severe IgA nephropathy with the allele reported to protect against end stage renal failure of mixed aetiologies.
We conclude that UMOD is unlikely to play a role in IgA nephropathy pathogenesis nor progression to end stage renal failure, and suggest that UMOD effects are restricted to some causes of renal disease, e.g. diabetes or hypertension.
PMCID: PMC4236674  PMID: 25163389
3.  Genome-Wide Association Study of Blood Pressure Extremes Identifies Variant near UMOD Associated with Hypertension 
Padmanabhan, Sandosh | Melander, Olle | Johnson, Toby | Di Blasio, Anna Maria | Lee, Wai K. | Gentilini, Davide | Hastie, Claire E. | Menni, Cristina | Monti, Maria Cristina | Delles, Christian | Laing, Stewart | Corso, Barbara | Navis, Gerjan | Kwakernaak, Arjan J. | van der Harst, Pim | Bochud, Murielle | Maillard, Marc | Burnier, Michel | Hedner, Thomas | Kjeldsen, Sverre | Wahlstrand, Björn | Sjögren, Marketa | Fava, Cristiano | Montagnana, Martina | Danese, Elisa | Torffvit, Ole | Hedblad, Bo | Snieder, Harold | Connell, John M. C. | Brown, Morris | Samani, Nilesh J. | Farrall, Martin | Cesana, Giancarlo | Mancia, Giuseppe | Signorini, Stefano | Grassi, Guido | Eyheramendy, Susana | Wichmann, H. Erich | Laan, Maris | Strachan, David P. | Sever, Peter | Shields, Denis Colm | Stanton, Alice | Vollenweider, Peter | Teumer, Alexander | Völzke, Henry | Rettig, Rainer | Newton-Cheh, Christopher | Arora, Pankaj | Zhang, Feng | Soranzo, Nicole | Spector, Timothy D. | Lucas, Gavin | Kathiresan, Sekar | Siscovick, David S. | Luan, Jian'an | Loos, Ruth J. F. | Wareham, Nicholas J. | Penninx, Brenda W. | Nolte, Ilja M. | McBride, Martin | Miller, William H. | Nicklin, Stuart A. | Baker, Andrew H. | Graham, Delyth | McDonald, Robert A. | Pell, Jill P. | Sattar, Naveed | Welsh, Paul | Munroe, Patricia | Caulfield, Mark J. | Zanchetti, Alberto | Dominiczak, Anna F.
PLoS Genetics  2010;6(10):e1001177.
Hypertension is a heritable and major contributor to the global burden of disease. The sum of rare and common genetic variants robustly identified so far explain only 1%–2% of the population variation in BP and hypertension. This suggests the existence of more undiscovered common variants. We conducted a genome-wide association study in 1,621 hypertensive cases and 1,699 controls and follow-up validation analyses in 19,845 cases and 16,541 controls using an extreme case-control design. We identified a locus on chromosome 16 in the 5′ region of Uromodulin (UMOD; rs13333226, combined P value of 3.6×10−11). The minor G allele is associated with a lower risk of hypertension (OR [95%CI]: 0.87 [0.84–0.91]), reduced urinary uromodulin excretion, better renal function; and each copy of the G allele is associated with a 7.7% reduction in risk of CVD events after adjusting for age, sex, BMI, and smoking status (H.R. = 0.923, 95% CI 0.860–0.991; p = 0.027). In a subset of 13,446 individuals with estimated glomerular filtration rate (eGFR) measurements, we show that rs13333226 is independently associated with hypertension (unadjusted for eGFR: 0.89 [0.83–0.96], p = 0.004; after eGFR adjustment: 0.89 [0.83–0.96], p = 0.003). In clinical functional studies, we also consistently show the minor G allele is associated with lower urinary uromodulin excretion. The exclusive expression of uromodulin in the thick portion of the ascending limb of Henle suggests a putative role of this variant in hypertension through an effect on sodium homeostasis. The newly discovered UMOD locus for hypertension has the potential to give new insights into the role of uromodulin in BP regulation and to identify novel drugable targets for reducing cardiovascular risk.
Author Summary
Hypertension is the leading contributor to global mortality with a global prevalence of 26.4% in 2000, projected to increase to 29.2% by 2025. While 50%–60% of population variation in blood pressure can be attributable to additive genetic factors, all the genetic variants robustly identified so far explain only 1%–2% of the population variance indicating the presence of additional undiscovered risk variants. Using an extreme case-control strategy, we have discovered a SNP in the promoter region of the uromodulin gene (UMOD) to be associated with hypertension (minor allele protective against hypertension). We then validated this association using large-scale population and case-control studies, where similar extreme criteria for selection of cases and controls have been used (21,466 cases and 18,240 controls). As the locus was related to uromodulin, a protein exclusively expressed in the kidneys, we show that the association is independent of renal dysfunction. We also show preliminary evidence that the SNP allele which is protective against hypertension is also protective against cardiovascular events in 26,654 Swedish subjects followed-up for 12 years. The newly discovered UMOD locus for hypertension has the potential to give unique insights into the role of uromodulin in BP regulation and to identify novel drugable targets.
PMCID: PMC2965757  PMID: 21082022
4.  Uromodulin Upregulates TRPV5 by Impairing Caveolin-Mediated Endocytosis 
Kidney international  2013;84(1):130-137.
Uromodulin (UMOD) is synthesized in the thick ascending limb and secreted into urine as the most abundant protein. Association studies in humans suggest protective effects of UMOD against calcium-containing kidney stones. Mice carrying mutations of Umod found in human uromodulin-associated kidney disease (UAKD) and Umod deficient mice exhibit hypercalciuria. The mechanism for UMOD regulation of urinary Ca2+ excretion is incompletely understood. We examined if UMOD regulates TRPV5 and TRPV6, channels critical for renal transcellular Ca2+ reabsorption. Coexpression with UMOD increased whole-cell TRPV5 current density in HEK293 cells. In biotinylation studies UMOD increased TRPV5 cell-surface abundance. Extracellular application of purified UMOD upregulated TRPV5 current density within physiological relevant concentration ranges. UMOD exerted a similar effect on TRPV6. TRPV5 undergoes constitutive caveolin-mediated endocytosis. UMOD had no effect on TRPV5 in a caveolin-1 deficient cell line. Expression of recombinant caveolin-1 in these cells restored the ability of UMOD to upregulate TRPV5. Secretion of UAKD-mutant UMOD was markedly reduced and coexpression of mutant UMOD with TRPV5 failed to increase its current. Immunofluorescent studies demonstrated lower TRPV5 expression in Umod−/− mice compared to wild-type. UMOD upregulates TRPV5 by acting from extracellular and by decreasing endocytosis of TRPV5. The stimulation of Ca2+ reabsorption via TRPV5 by UMOD may contribute to protection against kidney stone formation.
PMCID: PMC3700562  PMID: 23466996
5.  CUBN as a Novel Locus for End-Stage Renal Disease: Insights from Renal Transplantation 
PLoS ONE  2012;7(5):e36512.
Chronic kidney disease (CKD) is a complex disorder. As genome-wide association studies identified cubilin gene CUBN as a locus for albuminuria, and urinary protein loss is a risk factor for progressive CKD, we tested the hypothesis that common genetic variants in CUBN are associated with end-stage renal disease (ESRD) and proteinuria. First, a total of 1142 patients with ESRD, admitted for renal transplantation, and 1186 donors were genotyped for SNPs rs7918972 and rs1801239 (case-control study). The rs7918972 minor allele frequency (MAF) was higher in ESRD patients comparing to kidney donors, implicating an increased risk for ESRD (OR 1.39, p = 0.0004) in native kidneys. Second, after transplantation recipients were followed for 5.8 [3.8–9.2] years (longitudinal study) documenting ESRD in transplanted kidneys – graft failure (GF). During post-transplant follow-up 92 (9.6%) cases of death-censored GF occurred. Donor rs7918972 MAF, representing genotype of the transplanted kidney, was 16.3% in GF vs 10.7% in cases with functioning graft. Consistently, a multivariate Cox regression analysis showed that donor rs7918972 is a predictor of GF, although statistical significance was not reached (HR 1.53, p = 0.055). There was no association of recipient rs7918972 with GF. Rs1801239 was not associated with ESRD or GF. In line with an association with the outcome, donor rs7918972 was associated with elevated proteinuria levels cross-sectionally at 1 year after transplantation. Thus, we identified CUBN rs7918972 as a novel risk variant for renal function loss in two independent settings: ESRD in native kidneys and GF in transplanted kidneys.
PMCID: PMC3344899  PMID: 22574174
6.  Association of eGFR-Related Loci Identified by GWAS with Incident CKD and ESRD 
PLoS Genetics  2011;7(9):e1002292.
Family studies suggest a genetic component to the etiology of chronic kidney disease (CKD) and end stage renal disease (ESRD). Previously, we identified 16 loci for eGFR in genome-wide association studies, but the associations of these single nucleotide polymorphisms (SNPs) for incident CKD or ESRD are unknown. We thus investigated the association of these loci with incident CKD in 26,308 individuals of European ancestry free of CKD at baseline drawn from eight population-based cohorts followed for a median of 7.2 years (including 2,122 incident CKD cases defined as eGFR <60ml/min/1.73m2 at follow-up) and with ESRD in four case-control studies in subjects of European ancestry (3,775 cases, 4,577 controls). SNPs at 11 of the 16 loci (UMOD, PRKAG2, ANXA9, DAB2, SHROOM3, DACH1, STC1, SLC34A1, ALMS1/NAT8, UBE2Q2, and GCKR) were associated with incident CKD; p-values ranged from p = 4.1e-9 in UMOD to p = 0.03 in GCKR. After adjusting for baseline eGFR, six of these loci remained significantly associated with incident CKD (UMOD, PRKAG2, ANXA9, DAB2, DACH1, and STC1). SNPs in UMOD (OR = 0.92, p = 0.04) and GCKR (OR = 0.93, p = 0.03) were nominally associated with ESRD. In summary, the majority of eGFR-related loci are either associated or show a strong trend towards association with incident CKD, but have modest associations with ESRD in individuals of European descent. Additional work is required to characterize the association of genetic determinants of CKD and ESRD at different stages of disease progression.
Author Summary
Chronic kidney disease (CKD) affects about 6%–11% of the general population, and progression to end stage renal disease (ESRD) has a significant public health impact. Family studies suggest that the risk for CKD and ESRD is heritable. Unraveling the genetic underpinning of risk for these diseases may lead to the identification of novel mechanisms and thus diagnostic and therapeutic tools. We have previously identified 16 genetic markers in association with kidney function and prevalent CKD in general population studies. However, little is known about the relevance of these SNPs to the initial development of CKD or to ESRD risk. Therefore, we have now analyzed the association of these markers with the initiation of CKD in more than 26,000 individuals from the general population using serial estimations of kidney function, and with ESRD in four case-control studies in subjects of European ancestry (3,775 cases, 4,577 controls). We show that many of the 16 markers are also associated or show a strong trend towards association with initiation of CKD, while only 2 markers are nominally associated with ESRD. Further work is required to characterize the association of genetic determinants of different stages of CKD progression.
PMCID: PMC3183079  PMID: 21980298
7.  Time to Renal Disease and End-Stage Renal Disease in PROFILE: A Multiethnic Lupus Cohort 
PLoS Medicine  2006;3(10):e396.
Renal involvement is a serious manifestation of systemic lupus erythematosus (SLE); it may portend a poor prognosis as it may lead to end-stage renal disease (ESRD). The purpose of this study was to determine the factors predicting the development of renal involvement and its progression to ESRD in a multi-ethnic SLE cohort (PROFILE).
Methods and Findings
PROFILE includes SLE patients from five different United States institutions. We examined at baseline the socioeconomic–demographic, clinical, and genetic variables associated with the development of renal involvement and its progression to ESRD by univariable and multivariable Cox proportional hazards regression analyses. Analyses of onset of renal involvement included only patients with renal involvement after SLE diagnosis (n = 229). Analyses of ESRD included all patients, regardless of whether renal involvement occurred before, at, or after SLE diagnosis (34 of 438 patients). In addition, we performed a multivariable logistic regression analysis of the variables associated with the development of renal involvement at any time during the course of SLE.
In the time-dependent multivariable analysis, patients developing renal involvement were more likely to have more American College of Rheumatology criteria for SLE, and to be younger, hypertensive, and of African-American or Hispanic (from Texas) ethnicity. Alternative regression models were consistent with these results. In addition to greater accrued disease damage (renal damage excluded), younger age, and Hispanic ethnicity (from Texas), homozygosity for the valine allele of FcγRIIIa (FCGR3A*GG) was a significant predictor of ESRD. Results from the multivariable logistic regression model that included all cases of renal involvement were consistent with those from the Cox model.
Fcγ receptor genotype is a risk factor for progression of renal disease to ESRD. Since the frequency distribution of FCGR3A alleles does not vary significantly among the ethnic groups studied, the additional factors underlying the ethnic disparities in renal disease progression remain to be elucidated.
Fcγ receptor genotype is a risk factor for progression of renal disease to ESRD but does not explain the ethnic disparities in renal disease progression.
Editors' Summary
Systemic lupus erythematosis (SLE, commonly known as “lupus”) is an illness of many manifestations that appear to result from the immune system attacking components of the body's own cells. One of the unfortunate effects of SLE is kidney damage, which can, in a minority of patients, progress to kidney failure (formally called “end-stage renal disease,” or ESRD). Compared to White Americans, other ethnic groups tend to develop renal complications of lupus more often and with worse outcomes.
Why Was This Study Done?
It is unclear why some people with lupus develop kidney problems. The purpose of this US-based study was to confirm the factors that increase the risk of kidney damage and kidney failure, particularly in racial and ethnic minority patients, and to determine which of these factors accelerate the pace of kidney disease. Knowing these risk factors could allow the development and targeting of interventions, such as screening tests and preventive treatments, to prevent long-term loss of kidney function in patients with lupus.
What Did the Researchers Do and Find?
The researchers measured a number of factors in a multi-ethnic group of 1,008 patients with lupus, almost half of whom had some degree of kidney involvement. They found that those who developed kidney damage after being diagnosed with lupus tended to be younger, to have had lupus for a longer time, and to have experienced more effects of lupus in general than those who did not have kidney involvement. Those who developed kidney problems were also more likely to have been unemployed, to have had fewer years of formal education, and to have had high blood pressure before developing kidney involvement. African-American and Texan Hispanic individuals with lupus were more likely to develop kidney involvement, and tended to develop it more rapidly, than White Americans or Puerto Rican Hispanic ethnicity. Actual kidney failure (ESRD requiring dialysis or kidney transplantation) was more likely to occur among Texan Hispanics with kidney involvement than in the other ethnic groups. Diabetes and high blood pressure were not found to predict ESRD, but people with a particular variant of a protein that helps antibodies bind to cells (know as Fc-gamma receptor IIIa, or FcγRIIIa) were found to be more likely to develop ESRD, and to develop it more quickly.
What Do These Findings Mean?
These results suggest that the emergence and progression of kidney disease in patients with lupus depends on medical, genetic, and socioeconomic factors. Because no single test or intervention can be expected to address all of these factors, those treating patients with lupus must remain aware of the complexity of their patients lives at a variety of levels. In particular, ethnic disparities in the risk of serious kidney disease remain to be addressed.
Additional Information.
Please access these Web sites via the online version of this summary at
MedlinePlus page on lupus
Lupus Foundation of America
American College of Rheumatology pages on lupus
Wikipedia entry on lupus (note: Wikipedia is a free Internet encyclopedia that anyone can edit)
PMCID: PMC1626549  PMID: 17076550
8.  Syndrome of rapid onset end stage renal disease in incident Mayo Clinic chronic hemodialysis patient 
Indian Journal of Nephrology  2014;24(2):75-81.
Despite decades of research, a full understanding of chronic kidney disease (CKD)-end stage renal disease (ESRD) progression remains elusive. The common consensus is a predictable, linear, progressive and time-dependent decline of CKD to ESRD. Acute kidney injury (AKI) on CKD is usually assumed to be transient, with recovery as the expected outcome. AKI-ESRD association in current nephrology literature is blamed on the so-called “residual confounding.” We had previously described a relationship between AKI events and rapid onset yet irreversible ESRD happening in a continuum in a high-risk CKD cohort. However, the contribution of the syndrome of rapid onset-ESRD (SORO-ESRD) to incident United States ESRD population remained conjectural. In this retrospective analysis, we analyzed serum creatinine trajectories of the last 100 consecutive ESRD patients in 4 Mayo Clinic chronic hemodialysis units to determine the incidence of SORO-ESRD. Excluding 9 patients, 31 (34%) patients, including two renal transplant recipients, had SORO-ESRD: 18 males and 13 females age 72 (range 50-92) years. Precipitating AKI followed pneumonia (8), acutely decompensated heart failure (7), pyelonephritis (4), post-operative (5), sepsis (3), contrast-induced nephropathy (2), and others (2). Time to dialysis was shortest following surgical procedures. Concurrent renin angiotensin aldosterone system blockade was higher with SORO-ESRD - 23% versus 5%, P = 0.0113. In conclusion, SORO-ESRD is not uncommon among the incident general US ESRD population. The implications for ESRD care planning, AV-fistula-first programs, general CKD care and any associations with renal ageing/senescence warrant further study.
PMCID: PMC3968613  PMID: 24701038
Acute kidney injury; chronic kidney disease; end stage renal disease; renal replacement therapy
9.  Investigation of known estimated glomerular filtration rate loci in patients with Type 2 diabetes 
Diabetic Medicine  2013;30(10):1230-1235.
To replicate the association of genetic variants with estimated glomerular filtration rate (GFR) and albuminuria, which has been found in recent genome-wide studies in patients with Type 2 diabetes.
We evaluated 16 candidate single nucleotide polymorphisms for estimated GFR in 3028 patients with Type 2 diabetes sampled from clinics across Tayside, Scotland, UK, who were included in the Genetics of Diabetes Audit and Research Tayside (GoDARTs) study. These single nucleotide polymorphisms were tested for their association with estimated GFR at entry to the study, with albuminuria, and with time to stage 3B chronic kidney disease (estimated GFR<45 ml/min/1.73 m2). We also stratified the effects on estimated GFR in patients with (n = 2096) and without albuminuria (n = 613).
rs1260326 in GCKR (β=1.30, P = 3.23E-03), rs17319721 in SHROOM3 (β = −1.28, P-value = 3.18E-03) and rs12917707 in UMOD (β = 2.0, P-value = 8.84E-04) were significantly associated with baseline estimated GFR. Analysis of effects on estimated GFR, stratified by albuminuria status, showed that in those without albuminuria (normoalbuminura; n = 613), UMOD had a significantly stronger effect on estimated GFR (βnormo = 4.03 ± 1.23 vs βalbuminuria = 1.72 ± 0.76, P = 0.002) compared with those with albuminuria, while GCKR (βnormo = 0.45 ± 0.89 vs βalbuminuria = 1.12 ± 0.55, P = 0.08) and SHROOM3 (βnormo = −0.07 ± 0.89 vs βalbuminuria = −1.43 ± 0.53, P = 0.003) had a stronger effect on estimated GFR in those with albuminuria. UMOD was also associated with a lower rate of transition to stage 3B chronic kidney disease (hazard ratio = 0.83[0.70, 0.99], P = 0.03).
The genetic variants that regulate estimated GFR in the general population tend to have similar effects in patients with Type 2 diabetes and in this latter population, it is important to adjust for albuminuria status while investigating the genetic determinants of renal function.
PMCID: PMC4204276  PMID: 23586973
10.  Standardized, Systemic Phenotypic Analysis of UmodC93F and UmodA227T Mutant Mice 
PLoS ONE  2013;8(10):e78337.
Uromodulin-associated kidney disease (UAKD) summarizes different clinical features of an autosomal dominant heritable disease syndrome in humans with a proven uromodulin (UMOD) mutation involved. It is often characterized by hyperuricemia, gout, alteration of urine concentrating ability, as well as a variable rate of disease progression inconstantly leading to renal failure and histological alterations of the kidneys. We recently established the two Umod mutant mouse lines UmodC93F and UmodA227T on the C3H inbred genetic background both showing kidney defects analogous to those found in human UAKD patients. In addition, disease symptoms were revealed that were not yet described in other published mouse models of UAKD. To examine if further organ systems and/or metabolic pathways are affected by Umod mutations as primary or secondary effects, we describe a standardized, systemic phenotypic analysis of the two mutant mouse lines UmodA227T and UmodC93F in the German Mouse Clinic. Different genotypes as well as different ages were tested. Beside the already published changes in body weight, body composition and bone metabolism, the influence of the Umod mutation on energy metabolism was confirmed. Hematological analysis revealed a moderate microcytic and erythropenic anemia in older Umod mutant mice. Data of the other analyses in 7-10 month-old mutant mice showed single small additional effects.
PMCID: PMC3813435  PMID: 24205203
11.  Association of Family History of ESRD, Prevalent Albuminuria, and Reduced GFR With Incident ESRD 
The contribution of albuminuria to the increased risk of incident end-stage renal disease (ESRD) in individuals with a family history of ESRD has not been well studied.
Study Design
Prospective cohort study.
Study Setting & Participants
We analyzed data for family history of ESRD collected from 19,409 participants of the Renal REGARDS (Reasons for Geographic and Racial Differences in Stroke) cohort study.
Family history of ESRD was ascertained by asking “Has anyone in your immediate family ever been told that he or she had kidney failure? This would be someone who is on or had been on dialysis or someone who had a kidney transplant.”
Study Outcomes
Incidence rate for ESRD.
Morning urine albumin-creatinine ratio (ACR) and estimated glomerular filtration rate (eGFR). Incident cases of ESRD were identified through the US Renal Data System.
A family history of ESRD was reported by 11.1% of participants. Mean eGFRs for those with and without a family history of ESRD were 87.5 ± 22.2 (SD) and 86.5 ± 19.3 mL/min/1.73 m2, respectively (P = 0.05) and the respective geometric mean ACRs were 12.2 and 9.7 mg/g (P < 0.001). ESRD incidence rates for those with and without a family history of ESRD were 244.3 and 106.1/100,000 person-years, respectively. After adjusting for age, sex, and race, the ESRD HR for those with versus those without a family history of ESRD was 2.13 (95% CI, 1.18-3.83). Adjustment for comorbid conditions and socioeconomic status attenuated this association (HR, 1.82; 95% CI, 1.00-3.28), and further adjustment for baseline eGFR and ACR completely attenuated the association between family history of ESRD and incident ESRD (HR, 1.12; 95% CI, 0.69-1.80).
The report of a family history of ESRD was not validated.
Family history of ESRD is common in older Americans and the increased risk of ESRD associated with a family history reflects lower GFR, higher albuminuria, and comorbid conditions.
PMCID: PMC3725825  PMID: 22078058
Race; albuminuria; end-stage renal disease; chronic kidney disease
12.  Epidemiology of Uromodulin-Associated Kidney Disease – Results from a Nation-Wide Survey 
Nephron Extra  2012;2(1):147-158.
Uromodulin-associated kidney disease (UAKD) is caused by uromodulin mutations and leads to end-stage renal disease. Our objective was to examine the epidemiology of UAKD.
Data from all UAKD families in Austria were collected. Patients included in the Austrian Dialysis and Transplantation Registry (OEDTR) with unclear diagnoses or genetic diseases were asked whether they had (1) a family history of kidney disease or (2) had suffered from gout. Patients with gout and autosomal dominant renal disease underwent mutational analysis. Kaplan-Meier and Cox analysis was employed to estimate time to renal failure.
Of the 6,210 patients in the OEDTR, 541 were approached with a questionnaire; 353 patients answered the questionnaire. Nineteen of them gave two affirmative answers. In 7 patients, an autosomal dominant renal disease was found; in 1 patient a UMOD mutation was identified. One family was diagnosed through increased awareness as a consequence of the study. At present, 14 UAKD patients from 5 families are living in Austria (1.67 cases per million), and 6 of them require renal replacement therapy (0.73 per 1,000 patients). Progression to renal failure was significantly associated with UMOD genotype.
UAKD patients can be identified by a simple questionnaire. UMOD genotype may affect disease progression.
PMCID: PMC3383240  PMID: 22740033
Clinical epidemiology; End-stage kidney disease; Genetic renal disease; Uromodulin
13.  Common noncoding UMOD gene variants induce salt-sensitive hypertension and kidney damage by increasing uromodulin expression 
Nature medicine  2013;19(12):10.1038/nm.3384.
Elevated blood pressure (BP) and chronic kidney disease (CKD) are complex traits representing major global health problems1,2. Multiple genome-wide association studies (GWAS) identified common variants giving independent susceptibility for CKD and hypertension in the promoter of the UMOD gene3-9, encoding uromodulin, the major protein secreted in the normal urine. Despite compelling genetic evidence, the underlying biological mechanism is not understood. Here, we demonstrate that UMOD risk variants directly increase UMOD expression in vitro and in vivo. We modeled this effect in transgenic mice and showed that uromodulin overexpression leads to salt-sensitive hypertension and to age-dependent renal lesions that are similarly observed in elderly subjects homozygous for UMOD risk variants. We demonstrate that the link between uromodulin and hypertension is caused by activation of the renal sodium co-transporter NKCC2. This very mechanism is relevant in humans, as pharmacological inhibition of NKCC2 is more effective in lowering BP in hypertensive patients homozygous for UMOD risk variants. Our findings establish a link between the genetic susceptibility to hypertension and CKD, the control of uromodulin expression and its role in a salt-reabsorbing tubular segment of the kidney. These data point to uromodulin as a novel therapeutic target to lower BP and preserve renal function.
PMCID: PMC3856354  PMID: 24185693
14.  Association of Variants at UMOD with Chronic Kidney Disease and Kidney Stones—Role of Age and Comorbid Diseases 
PLoS Genetics  2010;6(7):e1001039.
Chronic kidney disease (CKD) is a worldwide public health problem that is associated with substantial morbidity and mortality. To search for sequence variants that associate with CKD, we conducted a genome-wide association study (GWAS) that included a total of 3,203 Icelandic cases and 38,782 controls. We observed an association between CKD and a variant with 80% population frequency, rs4293393-T, positioned next to the UMOD gene (GeneID: 7369) on chromosome 16p12 (OR = 1.25, P = 4.1×10−10). This gene encodes uromodulin (Tamm-Horsfall protein), the most abundant protein in mammalian urine. The variant also associates significantly with serum creatinine concentration (SCr) in Icelandic subjects (N = 24,635, P = 1.3×10−23) but not in a smaller set of healthy Dutch controls (N = 1,819, P = 0.39). Our findings validate the association between the UMOD variant and both CKD and SCr recently discovered in a large GWAS. In the Icelandic dataset, we demonstrate that the effect on SCr increases substantially with both age (P = 3.0×10−17) and number of comorbid diseases (P = 0.008). The association with CKD is also stronger in the older age groups. These results suggest that the UMOD variant may influence the adaptation of the kidney to age-related risk factors of kidney disease such as hypertension and diabetes. The variant also associates with serum urea (P = 1.0×10−6), uric acid (P = 0.0064), and suggestively with gout. In contrast to CKD, the UMOD variant confers protection against kidney stones when studied in 3,617 Icelandic and Dutch kidney stone cases and 43,201 controls (OR = 0.88, P = 5.7×10−5).
Author Summary
Chronic kidney disease (CKD) is a common condition that is associated with substantial morbidity and mortality and has been recognized as a major public health problem worldwide. Common causes of CKD include hypertension, diabetes, and inflammatory disorders. Previous studies have shown a significant genetic contribution to kidney disease and a recent genome-wide association study yielded a variant in the UMOD gene that affects the risk of CKD. Here, we replicate the association between UMOD and CKD in an independent analysis. We also demonstrate for the first time an interaction between the UMOD variant and age that suggests that this variant may adversely affect the aging kidney and its adaptation to age-related risk factors of kidney disease, such as hypertension and diabetes. Furthermore, we show that the UMOD variant that affects risk of CKD also provides protection against kidney stone disease.
PMCID: PMC2912386  PMID: 20686651
15.  Marked Variation of the Association of ESRD Duration Before and After Wait Listing on Kidney Transplant Outcomes 
Numerous studies report a strong association between pretransplant end-stage renal disease (ESRD) duration and diminished transplant outcomes. However, cumulative waiting time may reflect distinct phases and processes related to patients’ physiological condition as well as pre-existing morbidity and access to care. The relative impact of pre- and postlisting ESRD durations on transplant outcomes is unknown. We examined the impact of these intervals from a national cohort of kidney transplant recipients from 1999 to 2008 (n = 112 249). Primary factors explaining prelisting ESRD duration were insurance and race, while primary factors explaining postlisting ESRD duration were blood type, PRA% and variation between centers. Extended time from ESRD to waitlisting had significant dose–response association with overall graft loss (AHR = 1.26 for deceased donors [DD], AHR = 1.32 for living donors [LD], p values < 0.001). Contrarily, time from waitlisting (after ESRD) to transplantation had negligible effects (p = 0.10[DD], p = 0.57[LD]). There were significant associations between pre- and postlisting ESRD time with posttransplant patient survival, however prelisting time had over sixfold greater effect. Prelisting ESRD time predominately explains the association of waiting time with transplant outcomes suggesting that factors associated with this interval should be prioritized for interventions and allocation policy. The degree to which the effect of prelisting ESRD time is a proxy for comorbid conditions, socioeconomic status or access to care requires further study.
PMCID: PMC3881969  PMID: 20645941
Access to care; African Americans; dialysis; ESRD; kidney transplantation; waiting list
16.  HLA Polymorphism and Susceptibility to End-Stage Renal Disease in Cantonese Patients Awaiting Kidney Transplantation 
PLoS ONE  2014;9(3):e90869.
End-Stage Renal Disease (ESRD) is a worldwide public health problem. Currently, many genome-wide association studies have suggested a potential association between human leukocyte antigen (HLA) and ESRD by uncovering a causal relationship between HLA and glomerulonephritis. However, previous studies, which investigated the HLA polymorphism and its association with ESRD, were performed with the modest data sets and thus might be limited. On the other hand, few researches were conducted to tackle the Chinese population with ESRD. Therefore, this study aims to detect the susceptibilities of HLA polymorphism to ESRD within the Cantonese community, a representative southern population of China.
From the same region, 4541 ESRD patients who were waiting for kidney transplantation and 3744 healthy volunteer bone marrow donors (controls) were randomly chosen for this study. Polymerase chain reaction-sequence specific primer method was used to analyze the HLA polymorphisms (including HLA-A, HLA-B and HLA-DRB1 loci) in both ESRD patients and controls. The frequencies of alleles at these loci and haplotypes were compared between ESRD patients and controls.
A total of 88 distinct HLA alleles and 1361 HLA A-B-DRB1 haplotypes were detected. The frequencies of five alleles, HLA-A*24, HLA-B*55, HLA-B*54, HLA-B*40(60), HLA-DRB1*04, and one haplotype (HLA-A*11-B*27-DRB1*04) in ESRD patients are significantly higher than those in the controls, respectively.
Five HLA alleles and one haplotype at the HLA-A, HLA-B and HLA-DRB1 loci appear to be associated with ESRD within the Cantonese population.
PMCID: PMC3946267  PMID: 24603486
17.  Urinary Uromodulin Excretion Predicts Progression of Chronic Kidney Disease Resulting from IgA Nephropathy 
PLoS ONE  2013;8(8):e71023.
Uromodulin, or Tamm-Horsfall protein, is the most abundant urinary protein in healthy individuals. Recent studies have suggested that uromodulin may play a role in chronic kidney diseases. We examined an IgA nephropathy cohort to determine whether uromodulin plays a role in the progression of IgA nephropathy.
A total of 344 IgA nephropathy patients were involved in this study. Morphological changes were evaluated with the Oxford classification of IgA nephropathy. Enzyme Linked Immunosorbent Assay (ELISA) measured the urinary uromodulin level on the renal biopsy day. Follow up was done regularly on 185 patients. Time-average blood pressure, time-average proteinuria, estimated glomerular filtration rate (eGFR) and eGFR decline rate were caculated. Association between the urinary uromodulin level and the eGFR decline rate was analyzed with SPSS 13.0.
We found that lower baseline urinary uromodulin levels (P = 0.03) and higher time-average proteinuria (P = 0.04) were risk factors for rapid eGFR decline in a follow-up subgroup of the IgA nephropathy cohort. Urinary uromodulin level was correlated with tubulointerstitial lesions (P = 0.016). Patients that had more tubular atrophy/interstitial fibrosis on the surface had lower urinary uromodulin levels (P = 0.02).
Urinary uromodulin level is associated with interstitial fibrosis/tubular atrophy and contributes to eGFR decline in IgA nephropathy.
PMCID: PMC3750049  PMID: 23990922
18.  Uromodulin is expressed in renal primary cilia and UMOD mutations result in decreased ciliary uromodulin expression 
Human Molecular Genetics  2010;19(10):1985-1997.
Uromodulin (UMOD) mutations are responsible for three autosomal dominant tubulo-interstitial nephropathies including medullary cystic kidney disease type 2 (MCKD2), familial juvenile hyperuricemic nephropathy and glomerulocystic kidney disease. Symptoms include renal salt wasting, hyperuricemia, gout, hypertension and end-stage renal disease. MCKD is part of the ‘nephronophthisis–MCKD complex’, a group of cystic kidney diseases. Both disorders have an indistinguishable histology and renal cysts are observed in either. For most genes mutated in cystic kidney disease, their proteins are expressed in the primary cilia/basal body complex. We identified seven novel UMOD mutations and were interested if UMOD protein was expressed in the primary renal cilia of human renal biopsies and if mutant UMOD would show a different expression pattern compared with that seen in control individuals. We demonstrate that UMOD is expressed in the primary cilia of renal tubules, using immunofluorescent studies in human kidney biopsy samples. The number of UMOD-positive primary cilia in UMOD patients is significantly decreased when compared with control samples. Additional immunofluorescence studies confirm ciliary expression of UMOD in cell culture. Ciliary expression of UMOD is also confirmed by electron microscopy. UMOD localization at the mitotic spindle poles and colocalization with other ciliary proteins such as nephrocystin-1 and kinesin family member 3A is demonstrated. Our data add UMOD to the group of proteins expressed in primary cilia, where mutations of the gene lead to cystic kidney disease.
PMCID: PMC2860893  PMID: 20172860
19.  Impact of MELD-Based Allocation on End-Stage Renal Disease after Liver Transplantation 
The proportion of patients undergoing liver transplantation (LT) with concomitant renal dysfunction markedly increased after allocation by the Model for End-stage Liver Disease (MELD) score was introduced. We examined the incidence of subsequent post-LT end-stage renal disease (ESRD) before and after the policy was implemented. Data on all adult deceased-donor LT recipients between 4/27/95 and 12/31/08 (n=59,242) from the Scientific Registry of Transplant Recipients were linked with Centers for Medicare & Medicaid Services ESRD data. Cox regression was used to (i) compare pre-MELD and MELD eras with respect to post-LT ESRD incidence (ii) determine the risk factors for post-LT ESRD (iii) quantify the association between ESRD incidence and mortality. Crude rates of post-LT ESRD were 12.8 and 14.5 per 1,000 patient-years in the pre-MELD and MELD eras, respectively. Covariate-adjusted post-LT ESRD risk was higher in the MELD era (hazard ratio [HR] =1.15; p=0.0049). African-American race, hepatitis C, pre-LT diabetes, higher creatinine, lower albumin, lower bilirubin and sodium>141 mMol/L at LT were also significant predictors of post-LT ESRD. Post-LT ESRD was associated with higher post-LT mortality (HR=3.32; p<0.0001). The risk of post-LT ESRD, a strong predictor of post-LT mortality, is 15% higher in the MELD era. This study identified potentially modifiable risk factors of post-LT ESRD. Early intervention and modification of these risk factors may reduce the burden of post-LT ESRD.
PMCID: PMC3203341  PMID: 21883908
End-stage renal disease; Liver transplant; Model for end-stage renal disease; Mortality; Scientific Registry of Transplant Recipients
20.  Common genetic variants of the human UMOD gene are functional on transcription and predict plasma uric acid in two distinct populations 
Kidney international  2013;83(4):733-740.
Uromodulin (UMOD) genetic variants cause familial juvenile hyperuricemic nephropathy, characterized by hyperuricemia, decreased renal excretion of UMOD and uric acid; such findings suggest a role for UMOD in the regulation of plasma uric acid. We screened common variants across the UMOD locus in two populations, one from a community-based Chinese population, the other from California twins and siblings. Transcriptional activity of promoter variants was estimated in luciferase reporter plasmids transfected into HEK293 cells and mlMCD3 cells. By variance components in twin pairs, uric acid concentration and excretion were heritable traits. In the primary population from Beijing, we identified that carriers of haplotype GCC displayed higher plasma uric acid, and 3 UMOD promoter variants associated with plasma uric acid. UMOD promoter variants displayed reciprocal effects on urine uric acid excretion and plasma uric acid concentration, suggesting a primary effect on renal tubular handling of urate. These UMOD genetic marker-on-trait associations for uric acid were replicated in an independent American population sample. Site-directed mutagenesis at trait-associated UMOD promoter variants altered promoter activity in transfected luciferase reporter plasmids. These results suggest that UMOD promoter variants seem to initiate a cascade of transcriptional and biochemical changes influencing UMOD secretion, eventuating in elevation of plasma uric acid.
PMCID: PMC3687544  PMID: 23344472
Uromodulin; uric acid; Tamm-Horsfall protein; UMOD
21.  Pediatric Renal Transplantation 
Although the number of children with end-stage renal disease (ESRD) in need for renal transplantation is small compared with adults, the problem associated with renal transplant in children are numerous, varied, and often peculiar. Pre-emptive transplantation has recently been growing in popularity as it avoids many of the associated long-term complications of ESRD and dialysis. Changes in immunosuppression to more potent agents over the years will have affected transplant outcome; there is also evidence that tacrolimus is more effective than cyclosporine. This review will discuss the short- and long-term complications such as acute and chronic rejection, hypertension, infections, and malignancies as well as factors related to long-term graft function.
Chronic allograft nephropathy is the leading cause of renal allograft loss in pediatric renal transplant recipients. It is likely that it reflects a combination of both immune and nonimmune injury occurring cumulatively over time so that the ultimate solution will rely on several approaches. Transplant and patient survival have shown a steady increase over the years. The major causes of death after transplantation are cardiovascular disease, infection and malignancy. Transplantation in special circumstances such as children with abnormal urinary tracts and children with diseases that have the potential to recur after transplantation will also be discussed in this review. Non-compliance with therapeutic regimen is a difficult problem to deal with and affects patients and families at all ages, but particularly so at adolescence. Growth may be severely impaired in children with ESRD which may result in major consequences on quality of life and self-esteem; a better height attainment at transplantation is recognized as one of the most important factors in final height achievement.
Although pediatric kidney transplantation is active in some parts of many developing countries, it is still inactive in many others and mostly relying on living donors. The lacking deceased programs in most of these countries is one of the main issues to be addressed to adequately respond to organ shortage.
In conclusion, transplantation is currently the best option for children with ESRD. Although improvement in immunosuppression demonstrated excellent results and has led to greater 1-year graft survival rates, chronic graft loss remains relatively unchanged and opportunistic infectious complications remain a problem
PMCID: PMC4089282  PMID: 25013625
Transplantation; Kidney; End-stage renal disease; Pediatrics
22.  Uromodulin Retention in Thick Ascending Limb of Henle's Loop Affects SCD1 in Neighboring Proximal Tubule: Renal Transcriptome Studies in Mouse Models of Uromodulin-Associated Kidney Disease 
PLoS ONE  2014;9(11):e113125.
Uromodulin-associated kidney disease (UAKD) is a hereditary progressive renal disease which can lead to renal failure and requires renal replacement therapy. UAKD belongs to the endoplasmic reticulum storage diseases due to maturation defect of mutant uromodulin and its retention in the enlarged endoplasmic reticulum in the cells of the thick ascending limb of Henle's loop (TALH). Dysfunction of TALH represents the key pathogenic mechanism of UAKD causing the clinical symptoms of this disease. However, the molecular alterations underlying UAKD are not well understood. In this study, transcriptome profiling of whole kidneys of two mouse models of UAKD, UmodA227T and UmodC93F, was performed. Genes differentially abundant in UAKD affected kidneys of both Umod mutant lines at different disease stages were identified and verified by RT-qPCR. Additionally, differential protein abundances of SCD1 and ANGPTL7 were validated by immunohistochemistry and Western blot analysis. ANGPTL7 expression was down-regulated in TALH cells of Umod mutant mice which is the site of the mutant uromodulin maturation defect. SCD1 was expressed selectively in the S3 segment of proximal tubule cells, and SCD1 abundance was increased in UAKD affected kidneys. This finding demonstrates that a cross talk between two functionally distinct tubular segments of the kidney, the TALH segment and the S3 segment of proximal tubule, exists.
PMCID: PMC4237372  PMID: 25409434
23.  Mutations of the UMOD gene are responsible for medullary cystic kidney disease 2 and familial juvenile hyperuricaemic nephropathy 
Journal of Medical Genetics  2002;39(12):882-892.
Introduction: Medullary cystic kidney disease 2 (MCKD2) and familial juvenile hyperuricaemic nephropathy (FJHN) are both autosomal dominant renal diseases characterised by juvenile onset of hyperuricaemia, gout, and progressive renal failure. Clinical features of both conditions vary in presence and severity. Often definitive diagnosis is possible only after significant pathology has occurred. Genetic linkage studies have localised genes for both conditions to overlapping regions of chromosome 16p11-p13. These clinical and genetic findings suggest that these conditions may be allelic.
Aim: To identify the gene and associated mutation(s) responsible for FJHN and MCKD2.
Methods: Two large, multigenerational families segregating FJHN were studied by genetic linkage and haplotype analyses to sublocalise the chromosome 16p FJHN gene locus. To permit refinement of the candidate interval and localisation of candidate genes, an integrated physical and genetic map of the candidate region was developed. DNA sequencing of candidate genes was performed to detect mutations in subjects affected with FJHN (three unrelated families) and MCKD2 (one family).
Results: We identified four novel uromodulin (UMOD) gene mutations that segregate with the disease phenotype in three families with FJHN and in one family with MCKD2.
Conclusion: These data provide the first direct evidence that MCKD2 and FJHN arise from mutation of the UMOD gene and are allelic disorders. UMOD is a GPI anchored glycoprotein and the most abundant protein in normal urine. We postulate that mutation of UMOD disrupts the tertiary structure of UMOD and is responsible for the clinical changes of interstitial renal disease, polyuria, and hyperuricaemia found in MCKD2 and FJHN.
PMCID: PMC1757206  PMID: 12471200
24.  Mutation analysis of the Uromodulin gene in 96 individuals with urinary tract anomalies (CAKUT) 
Uromodulin (UMOD) mutations were described in patients with medullary cystic kidney disease (MCKD2), familial juvenile hyperuricemic nephropathy (FJHN), and glomerulocystic kidney disease (GCKD). UMOD transcription is activated by the transcription factor HNF1B. Mutations in HNF1B cause a phenotype similar to FJHN/GCKD but also congenital anomalies of the kidney and the urinary tract (CAKUT). Moreover, we recently detected UMOD mutations in 2 patients with CAKUT. As HNF1B and UMOD act in the same pathway and cause similar phenotypes we here examined, whether UMOD mutations would be found in patients with CAKUT.
Mutation analysis of UMOD was performed in 96 individuals with CAKUT by direct sequencing of exons 4 and 5 and by heteroduplex analysis following CEL I digestion assay of the exons 3 and 6–12.
The mean age of patients was 11.4 years and in 36.4% of patients the family history was positive for CAKUT. In the CEL I assay 12 aberrant bands were detected in 103 of 960 PCR products and were sequenced. Two previously known and eight new SNPs were detected. As no UMOD mutations were identified in these 96 patients with CAKUT, UMOD mutations do not seem to be a significant cause of CAKUT in this cohort.
PMCID: PMC3155267  PMID: 18846391
Uromodulin; Tamm-Horsfall protein; urinary tract malformation; CAKUT; mutation analysis
25.  Kidney stones and kidney function loss: a cohort study 
Objective To investigate whether the presence of kidney stones increase the risk of end stage renal disease (ESRD) or other adverse renal outcomes.
Design A registry cohort study using validated algorithms based on claims and facility utilisation data. Median follow-up of 11 years.
Setting Alberta, Canada, between 1997 and 2009.
Participants 3 089 194 adult patients without ESRD at baseline or a history of pyelonephritis. Of these, 1 954 836 had outpatient serum creatinine measurements and were included in analyses of chronic kidney disease and doubling of serum creatinine level.
Exposure One or more kidney stones during follow-up.
Main outcome measures Incident ESRD, development of stage 3b–5 chronic kidney disease (estimated glomerular filtration rate <45 mL/min/1.73 m2), and sustained doubling of serum creatinine concentration from baseline.
Results 23 706 (0.8%) patients had at least one kidney stone, 5333 (0.2%) developed ESRD, 68 525 (4%) developed stage 3b–5 chronic kidney disease, and 6581 (0.3%) experienced sustained doubling of serum creatinine. Overall, one or more stone episodes during follow-up was associated with increased risk of ESRD (adjusted hazard ratio 2.16 (95% CI 1.79 to 2.62)), new stage 3b–5 chronic kidney disease (hazard ratio 1.74 (1.61 to 1.88)), and doubling of serum creatinine (hazard ratio 1.94 (1.56 to 2.43)), all compared with those without kidney stones during follow-up. The excess risk of adverse outcomes associated with at least one episode of stones seemed greater in women than in men, and in people aged <50 years than in those aged ≥50. However, the risks of all three adverse outcomes in those with at least one episode of stones were significantly higher than in those without stones in both sexes and age strata. The absolute increase in the rate of adverse renal outcomes associated with stones was small: the unadjusted rate of ESRD was 2.48 per million person days in people with one or more episodes of stones versus 0.52 per million person days in people without stones.
Conclusion Even a single kidney stone episode during follow-up was associated with a significant increase in the likelihood of adverse renal outcomes including ESRD. However, the increases were small in absolute terms.
PMCID: PMC3431443  PMID: 22936784

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