Genetic Variation at the ACE Gene Is Associated With Persistent Microalbuminuria and Severe Nephropathy in Type 1 Diabetes: The DCCT/EDIC Genetics Study

Andrew P. Boright 1 2 Andrew D. Paterson 0 1 Lucia Mirea 0 4 Shelley B. Bull 0 4 Alireza Mowjoodi 1 Stephen W. Scherer 1 Bernard Zinman 3 4 the DCCT/EDIC Research Group 5 0 Department of Public Health Sciences, University of Toronto , Toronto , Canada; the 1 Program in Genetics and Genomic Biology, Hospital for Sick Children , Toronto , Canada; the 2 Department of Medicine, University Health Network, University of Toronto , Toronto , Canada; the 3 Leadership Sinai Centre for Diabetes, Department of Medicine, Mount Sinai Hospital , Toronto , Canada. PhD, Department of Medicine, Division of Endocrinology, University Health Network , 200 Elizabeth St., Toronto, Ontario , Canada M5G 2C4 4 Samuel Lunenfeld Research Institute of Mount Sinai Hospital, Prosserman Center for Health Research, University of Toronto , Toronto , Canada; and the 5 A complete list of the individuals and institutions participating in the DCCT/EDIC Research Group appears in N Engl J Med 348:2294-2303, 2003. Additional information for this article can be found in an online appendix at http://diabetes.diabetesjournals.org. AER, albumin excretion rate; DCCT, Diabetes Control and Complications Trial; EDIC, Epidemiology of Diabetes Interventions and Complications; SNP, single nucleotide polymorphism. 2005 by the American Diabetes Association. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact The development and progression of microvascular complications have been extensively documented in a cohort of type 1 diabetic subjects enrolled in the Diabetes Control and Complications Trial (DCCT) and followed in the Epidemiology of Diabetes Interventions and Complications (EDIC) study. We describe the association of genetic variation in the ACE gene in 1,365 DCCT/EDIC subjects with incident persistent microalbuminuria (n 312) and severe nephropathy (n 115). We studied three markers (rs1800764, insertion/ deletion, and rs9896208) in the ACE gene that allowed us to capture genetic variation in the common haplotypes occurring at frequencies of >5% in Caucasians. Compared with the more frequent genotype (D/I) for the insertion/deletion polymorphism, in multivariate models, the I/I genotype conferred a lower risk for persistent microalbuminuria (hazard ratio [HR] 0.62 [95% CI 0.43- 0.89], P 0.009) and severe nephropathy (0.56 [0.32- 0.96], P 0.033). Variation at the two other markers, rs1800764 and rs9896208, were also associated with these renal outcomes. In addition, homozygosity for the common haplotype TIC (which corresponded to the T, insertion, and C alleles at the three markers, rs1800764, insertion/deletion, and rs9896208, respec- - tively) versus the CDT/TIC haplotype pair was associated with lower risk for development of persistent microalbuminuria (HR 0.49 [0.32 0.75], P 0.0009) and severe nephropathy (0.41 [0.22 0.78], P 0.006). Our findings in the DCCT/EDIC cohort provide strong evidence that genetic variation at the ACE gene is associated with the development of nephropathy in patients with type 1 diabetes. Diabetes 54:1238 1244, 2005 Mand mortality. The Diabetes Control and icrovascular and neurologic complications of type 1 diabetes result in significant morbidity Complications Trial (DCCT) demonstrated that intensive therapy aimed at reducing glycemic exposure reduced the development and progression of longterm complications by as much as 76% compared with conventional therapy (1). In addition to the importance of intensive diabetes management, it is clear that there are other factors, including genetic ones, that contribute to the development of these complications. Epidemiologic studies (2,3) conducted before the use of intensive therapy suggested that 30% of patients with type 1 diabetes developed diabetic nephropathy after 20 years of diabetes; however, modern diabetes care has markedly reduced the incidence of diabetic nephropathy to 1316% (4 6) after 20 years diabetes duration. A number of studies have documented familial clustering of diabetic nephropathy (79). In the DCCT, there was an increased risk of microalbuminuria (albumin excretion rate [AER] 28 g/min) in diabetic relatives of microalbuminuria-positive versus -negative DCCT subjects in the secondary intervention cohort (odds ratio 5.4 [95% CI 2.213.7], P 0.001) after adjustment for covariates (10). Given the evidence for familial clustering of diabetic nephropathy, we have begun a systematic study of candidate genes associated with the development of nephropathy in the DCCT subjects. ACE plays an important role in the renin-angiotensinaldosterone pathway and has been studied extensively as a putative mediator of diabetic nephropathy. This enzyme cleaves the COOH-terminal dipeptide of angiotensin I to produce angiotensin II and inactivates bradykinin by removal of COOH-terminal peptides. Increased ACE activity increases intraglomerular pressure (11) and can lead to glomerulosclerosis (12). Plasma ACE activity, a highly heritable trait, is encoded by one of the three known isozymes transcribed from the ACE gene, which is composed of 26 exons located on chromosome 17q23 (13). There are many biallelic single nucleotide polymorphisms (SNPs) within and flanking this gene (14) that are associated with ACE activity; however, the exact etiologic variant(s) is/are as yet undetermined, as these polymorphisms are in strong linkage disequilibrium with each other (15). The most extensively studied polymorphism is the insertion/deletion of a 287-bp Alu repeat in intron 16 (16). Since the initial report of the protective effect of the I/I insertion/deletion genotype in the development of diabetic nephropathy in type 1 diabetes (17), there have been many other studies of the association of this polymorphism with elevated urinary excretion of albumin and/or nephropathy in patients with type 1 and type 2 diabetes. Meta-analyses (18 20) have suggested that discrepant results among studies may be partially attributed to differences in study design, diabetes phenotype (type 1 diabetes versus type 2 diabetes), ethnic composition, methods of quantitation, and estimation of AER (e.g., single measures of AER versus sustained elevations in AER) and definitions of diabetic nephropathy (microalbuminuria versus macroalbuminuria). The DCCT and its long-term follow-up, the Epidemiology of Diabetes Interventions and Complications (EDIC) study, have measured renal function, albuminuria, and the development of nephropathy for up to 17 years using standardized methods. We have analyzed the association of the insertion/deletion polymorphism of the ACE gene with the time to development of persistent elevation of microalbuminuria and severe nephropathy in 1,365 Caucasian subjects in the DCCT/EDIC study. To capture the genetic variation in the most common Caucasian haplotypes at the ACE locus occu (...truncated)