DOI: 10.2337/db06-0640
Variants in ARHGEF11, a Candidate Gene for the Linkage to Type 2 Diabetes Mellitus on Chromosome 1q, Are Nominally Associated With Insulin Resistance and Type 2 Diabetes Mellitus in Pima Indians
1Diabetes Molecular Genetics Section, Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, DHHS, Phoenix, AZ 85004 Correspondence: lbaier{at}phx.niddk.nih.gov
A prior genome-wide linkage scan in Pima Indians indicated a young-onset (age<45 years) type 2 diabetes mellitus (T2DM) susceptibility locus on chromosome 1q21-q23. ARHGEF11, which encodes the Rho guanine nucleotide exchange factor 11, was analyzed as a positional candidate gene for this linkage because this protein may stimulate Rho-dependent signals, such as the insulin signaling cascade. The ARHGEF11 gene, and two adjacent genes NTRK1 and INSRR, were sequenced in 24 Pima Indians who were not first-degree relatives. Sequencing of the coding regions, 5'and 3' UTR's and putative promoter regions of these genes, identified 28 variants in ARHGEF11, 11 variants in NTRK1 and 8 variants in INSSR. These 47 variants, as well as 84 additional public database variants within/between these genes, were genotyped for association analysis in the same group of Pima Indians who had participated in the linkage study (N=1228). An R1467H in ARHGEF11, and several additional non-coding variants that were in high linkage disequilibrium with this variant, were nominally associated with young-onset T2DM (P=0.01, OR=3.39) after adjusting for sex, family membership and Pima heritage. The risk allele H had a frequency of 0.10. In a subgroup of 262 on-diabetic full-heritage Pima Indians who had undergone detailed metabolic testing, the risk allele H was also associated with a lower mean insulin-mediated glucose disposal rate and a lower mean non-oxidative glucose storage rate after adjusting for age, sex, nuclear family membership, and percentage of body fat (P
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