CLINICAL EPIDEMIOLOGY www.jasn.org Uromodulin Levels Associate with a Common UMOD Variant and Risk for Incident CKD ʈ ʈ Anna Ko¨ttgen,* Shih-Jen Hwang,†‡ Martin G. Larson,§ Jennifer E. Van Eyk, Qin Fu, Emelia J. Benjamin,†¶ Abbas Dehghan,** Nicole L. Glazer,†† W.H. Linda Kao,* ʈʈ Tamara B. Harris,‡‡ Vilmundur Gudnason,§§ Michael G. Shlipak,¶¶ Qiong Yang,§ Josef Coresh,* Daniel Levy,†‡ and Caroline S. Fox†‡*** *Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland; †Framingham Heart Study, Framingham, Massachusetts; ‡Center for Population Studies, National Heart, Lung, and Blood Institute, and ‡‡Laboratory of Epidemiology, Demography, and Biometry, Intramural Research Program, National Institute on Aging, National Institutes of Health, Bethesda, Maryland; Departments of §Biostatistics and ʈ ¶Epidemiology, Boston University School of Public Health, Boston, Massachusetts; Department of Medicine, Johns Hopkins University, Baltimore, Maryland; **Department of Epidemiology, Erasmus Medical Centre, Rotterdam, Netherlands; ††Cardiovascular Health Research Unit and Department of Medicine, University of Washington, Seattle, ʈʈ Washington; §§Icelandic Heart Association Research Institute, Kopavogur, Iceland; University of Iceland, Reykjavik, Iceland; ¶¶General Internal Medicine Division, San Francisco VA Medical Center, University of California, San Francisco, California; and ***Division of Endocrinology, Metabolism, and Diabetes, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts ABSTRACT Common variants in the region of the UMOD gene, which encodes uromodulin (Tamm-Horsfall protein), associate with chronic kidney disease (CKD) and estimated GFR (eGFR). Whether uromodulin levels associate with UMOD variants or with the risk for developing CKD is unknown. We conducted an age- and gender- matched case-control study (n ϭ 200) of incident CKD (eGFR Ͻ60 ml/min per 1.73 m2) within the Framingham Heart Study (FHS). Baseline urinary uromodulin concentrations were related to case-control status 9.9 yr later and to genotype at rs4293393. As a replication set, we tested the genotype association with uromodulin concentration in the Atherosclerosis Risk in Communities (ARIC) Study (n ϭ 42). Geometric means of uromodulin concentrations were 51% higher in case than in control subjects (P ϭ 0.016). The adjusted odds ratio of CKD per 1-SD higher concentration of uromodulin was 1.72 (95% confidence interval 1.07 to 2.77; P ϭ CLINICAL EPIDEMIOLOGY 0.03) after accounting for CKD risk factors and baseline eGFR. We observed lower urinary uromodulin concentrations per each copy of the C allele at rs4293393 in both cohorts. In summary, elevated uromodulin concentrations precede the onset of CKD and associate with a common polymorphism in the UMOD region. J Am Soc Nephrol 21: 337–344, 2010. doi: 10.1681/ASN.2009070725 Chronic kidney disease (CKD) constitutes a seri- In addition to major known risk factors for ous public health burden worldwide.1 CKD prev- CKD—hypertension and diabetes—multiple stud- alence increases with age and affects Ͼ10% of the ies have provided evidence for a genetic component US adult population2; estimates from the United 3 Kingdom and other European and Asian study Received July 15, 2009. Accepted October 13, 2009. populations are similar.1 CKD can progress to Published online ahead of print. Publication date available at ESRD that requires dialysis or transplantation www.jasn.org. and affects approximately 2 million individuals Correspondence: Dr. Caroline S. Fox, 73 Mount Wayte Avenue, 1 worldwide. In addition, CKD causes substantial Suite #2, Framingham, MA 01702. Phone: 508-935-3447; Fax: morbidity and is an independent risk factor for 508-626-1262; E-mail: [email protected] 4 5 cardiovascular disease and overall mortality. Copyright ᮊ 2010 by the American Society of Nephrology J Am Soc Nephrol 21: 337–344, 2010 ISSN : 1046-6673/2102-337 337 CLINICAL EPIDEMIOLOGY www.jasn.org to kidney disease.6 Identification of genetic risk variants for CKD women. Uromodulin concentrations ranged from 0.2 to may provide novel insights into underlying biologic mechanisms 70.9 ␮g/ml in case patients and 0.2 to 49.9 ␮g/ml in control and into CKD pathophysiology. We therefore recently conducted subjects. The overall geometric mean uromodulin concen- genome-wide association studies of CKD and estimated GFR tration was 4.5 ␮g/ml; mean values were similar in women (eGFR), a measure of kidney function, in 19,877 participants (5.1 ␮g/ml) and men (3.8 ␮g/ml; P ϭ 0.11). Log uromodu- from the Cohorts for Heart and Aging Research in Genomic Ep- lin concentrations were not associated with CKD risk fac- idemiology (CHARGE) Consortium. We identified common ge- tors in FHS (Table 2), with the exception of a negative cor- netic variants in the UMOD gene, including rs4293393, of minor relation with fasting glucose levels (P ϭ 0.05) and a positive allele frequency 0.18, in association with CKD and eGFR.7 correlation with log urinary albumin-to-creatinine ratio Rare mutations in UMOD have previously been described (UACR; P ϭ 0.008). as a cause of monogenetic forms of kidney disease.8 The UMOD gene is exclusively transcribed in the kidney,9 and its Uromodulin Levels in Case Patients and Control protein product is the Tamm-Horsfall protein (THP),10 also Subjects known as uromodulin.11 Although the protein was isolated The median (quartile 1, quartile 3) of uromodulin concentra- from urine almost 60 yr ago and is the most abundant urinary tions was 6.12 ␮g/ml (3.40, 12.55) in case patients and 4.97 protein in healthy individuals, the physiologic role of the pro- ␮g/ml (1.55, 9.12) in control subjects (Supplemental Figure 2). tein remains unclear,9 and its association with non-Mendelian, Baseline geometric mean concentrations of uromodulin were complex forms of CKD warrants further exploration. higher among case patients (5.58 ␮g/ml) than control subjects Our study had two objectives: First, to address whether uri- (3.71 ␮g/ml; paired t test P ϭ 0.016; Figure 1). Per 1-SD in- nary uromodulin concentrations are associated with incident crease in log uromodulin, the multivariable-adjusted odds ra- CKD in a community-based study, and, second, to determine tio for incident CKD was 1.72 (95% confidence interval [CI] whether a single-nucleotide polymorphism (SNP) in the 1.07 to 2.77; P ϭ 0.03; Table 3). Adding UACR to the model as UMOD region, rs4293393, is associated with urinary uro- an additional covariate did not materially change the results. modulin concentrations. We asked these questions in a nested When urinary uromodulin was indexed to urinary creatinine, case-control study of incident CKD in the Framingham Heart similar results were observed (odds ratio 1.69; P ϭ 0.04, fully Study (FHS). The association between genotype at rs4293393 adjusted model). Similar results were also observed in partici- and urinary uromodulin concentrations was examined in the pants free of diabetes and in older and younger participants FHS sample and confirmed in a subsample of Atherosclerosis (Table 3). Risk in Communities (ARIC) Study participants selected to represent equally the three genotypes at rs4293393. SNP rs4293393 and Log Uromodulin Concentrations The study sample characteristics by genotype are shown in RESULTS Supplemental Table 1. Genotype at rs4293393 was strongly associated with log uromodulin concentrations in FHS (P ϭ Baseline Study Characteristics 0.001; Figure 2): For each copy of the C allele at rs4293393, log By design, the mean age of the FHS case and control subjects uromodulin concentrations were significantly lower (geomet- was similar (63.8 yr; Table 1), and 60% of both groups were ric means 5.5, 3.1, and 1.5 ␮g/ml for zero, one, and two copies, Table 1. Baseline study sample characteristics by case-control status (FHS) and overall (ARIC) FHS Control Subjects Case Patients ARIC Characteristic (42 ؍ n) (100 ؍ n) (100 ؍ n) Baseline Follow-up Baseline Follow-up Age (yr; mean Ϯ SD) 63.8 Ϯ 7.3 74.0 Ϯ 7.0 63.8 Ϯ 7.2 73.4 Ϯ 7.4 68.8 Ϯ 3.1 Women (%) 60 60 60 60 0 BMI (kg/m2; mean Ϯ SD) 27.2 Ϯ 4.3 27.3 Ϯ 5.1 27.9 Ϯ 5.3 28.3 Ϯ 5.4 29.0 Ϯ 4.1 SBP (mmHg; mean Ϯ SD) 127 Ϯ 18 135 Ϯ 17 135 Ϯ 20 129 Ϯ 18 134 Ϯ 22 HDL cholesterol (mg/dl; mean Ϯ SD) 55 Ϯ 17 60 Ϯ 18 51 Ϯ 17 55 Ϯ 19 43 Ϯ 17 Diabetes (%) 5 15 11 22 19 Smoking (%) 10 7 11 3 7 Hypertension treatment (%) 23 49 50 77 55 Hypertension (%) 48 61 74 81 52 eGFR baseline (ml/min per 1.73 m2; 98.0 Ϯ 54.0 81.0 Ϯ 12.5 80.0 Ϯ 22.0 50.0 Ϯ 6.5 79.0 Ϯ 15.5 mean Ϯ SD) UACR (median ͓25th, 75th percentiles͔) 4.8 (2.2, 11.2) 8.1 (4.2, 16.0) 4.7 (2.3, 8.7) 8.2 (3.6, 16.8) 3.3 (1.4, 6.3) BMI, body mass index; SBP, systolic BP. 338 Journal of the American Society of Nephrology J Am Soc Nephrol 21: 337–344, 2010 www.jasn.org CLINICAL EPIDEMIOLOGY Table 2. Correlations between baseline log uromodulin ranged from 0.7 to 20.0 ␮g/ml, with an overall median concentrations and selected CKD risk factors in 200 FHS (25th, 75th percentile) of 3.3 (1.4, 6.3) ␮g/ml. For zero, one, participants and two copies of the C allele at rs4293393, geometric mean Pearson uromodulin concentrations on the basis of the immunoas- Characteristic P Correlation say were 6.6, 6.5, and 2.8 ␮g/ml (P ϭ 0.01 for trend; Figure Age 0.09 0.20 2).