A C-reactive protein promoter polymorphism is associated with type 2 diabetes mellitus in Pima Indians Johanna K. Wolford, * Jonathan D. Gruber, Victoria M. Ossowski, Barbora Vozarova, P. Antonio Tataranni, Clifton Bogardus, and Robert L. Hanson ClinicalDiabetesandNutritionSection,PhoenixEpidemiologyandResearchBranch,NationalInstituteofDiabetesandDigestiveandKidneyDiseases, National Institutes of Health, 4212 North 16th Street, Phoenix, AZ 85016, USA Received 1 November 2002; received in revised form 22 November 2002; accepted 26 November 2002 Abstract Linkage analysis has identified a susceptibility locus for type 2 diabetes mellitus (T2DM) on chromosome 1q21–q23 in several populations. Results from recent prospective studies indicate that increased levels of C-reactive protein (CRP), a marker of immune system activation, are predictive of diabetes, independent of adiposity. Because CRP is located on 1q21, we considered it a potential positional candidate gene for T2DM. We therefore evaluated CRP and the nearby serum amyloid P-component, APCS, which is structurally similar to CRP, as candidate diabetes susceptibility genes. Approximately 10.9 kb of the CRP-APCS locus was screened for polymorphisms using denaturing high performance liquid chromatography and direct sequencing. We identified 27 informative polymorphisms, including 26 single nucleotide polymorphisms (SNPs) and 1 insertion/deletion, which were divided into 7 linkage disequilibrium clusters. We genotyped representative SNPs in 1300 Pima samples and found a single variant in the CRP promoter (SNP 133552) that was associated with T2DM (P ¼ 0:014), as well as a common haplotype (CGCG) that was associated with both T2DM (P ¼ 0:029) and corrected insulin response, a surrogate measure of insulin secretion in non-diabetic subjects (P ¼ 0:050). Linkage analyses that adjusted for the effect of these polymorphisms indicated that they do not in themselves account for the observed linkage with T2DM on chromosome 1q. However, these findings suggest that variation within the CRP locus may play a role in diabetes susceptibility in Pima Indians. Ó 2003 Elsevier Science (USA). All rights reserved. Keywords: 1q21; Single nucleotide polymorphisms (SNPs); Association analyses; Candidate genes; Positional cloning; Complex disease; Chronic inflammation; C-reactive protein; Diabetes mellitus, type 2; Type 2 diabetes mellitus; Corrected insulin response Introduction Linkage to type 2 diabetes mellitus (T2DM) has been demonstrated for chromosome 1q21–q23 in a number of populations including Pima Indians [1], Utah Cauca- sians [2], French Caucasians [3], British Caucasians [4], and Chinese [5]. To date, however, the specific poly- morphism(s) responsible for the linkage findings have not been identified. The present study represents part of our ongoing effort to identify genetic determinants of T2DM susceptibility in the 1q21–q23 region in Pima Indians. These efforts include analysis of linkage dis- equilibrium between T2DM and single nucleotide polymorphisms (SNPs) 1 spaced densely throughout the linked region, and analysis of variants in candidate genes mapping to the 1q21–q23 interval. We considered the C-reactive protein gene (CRP) one of the strongest, as yet unexamined, candidates mapping to this interval. CRP is an acute-phase reactant, elevations of which are indicative of an inflammatory process. Several in- vestigators have recently proposed an etiologic role for chronic inflammation in the development of insulin re- sistance [6] and T2DM [6–8]. In support of this hy- Molecular Genetics and Metabolism 78 (2003) 136–144 www.elsevier.com/locate/ymgme * Corresponding author. Fax: +602-200-5335. E-mail address: jwolford@exchange.nih.gov (J.K. Wolford). 1 Abbreviations used: CRP, C-reactive protein; APCS, amyloid P component, serum; SNP, single nucleotide polymorphism; dHPLC, denaturing high performance liquid chromatography; 3 0 UTR, 3 0 untranslated region; CIR, corrected insulin response. 1096-7192/03/$ - see front matter Ó 2003 Elsevier Science (USA). All rights reserved. doi:10.1016/S1096-7192(02)00230-5