Inflammatory processes may contribute to type 2 diabetes (T2D), but there is limited information about genetic associations with circulating levels of inflammatory cytokines. We performed a genome-wide association study (GWAS) of cytokines in 1061 nondiabetic Southwestern Native Americans (500 women; 561 men).

Fasting serum concentrations of interleukin-6 (IL-6), plasminogen activator inhibitor-1 (PAI-1) and tumor necrosis factor-α (TNF-α) were measured using EMD Millipore assays. Genotypic data on 496,190 single-nucleotide polymorphisms (SNPs) with minor allele frequency >1% were derived from an Affymetrix Axiom array designed to capture common variation in Pima Indians. Data were normalized and analyzed for associations using a mixed model accounting for familial relationships, adjusted for age, sex and genetic principal components 1-5.

The strongest associations were on chromosome 3 near A4GNT with IL-6 levels (rs2724711 p=4.2×10-6), and on chromosome 7 with PAI-1 levels (rs1608488 (p=8.3×10-7). An association of genome-wide statistical significance (rs1862840; p=1.2×10-8) was observed on chromosome 16 near WWOX with TNF-α levels. Each copy of the G allele (frequency=0.12) confers a 0.41-SD increase in TNF-α levels. In a larger cohort of Southwestern Native Americans, rs1862840 was not associated with T2D (N=7,659; p=0.17). Among 3,983 nondiabetic subjects it did associate with 2 hour corrected insulin response (β=0.06-SD decrease per G allele copy, p=0.011). Among 300 normal glucose tolerant subjects it associated with the acute insulin response to intravenous glucose (β=20% decrease per G allele copy, p=0.045).

This study identified a novel association for TNF-α levels at WWOX (a gene previously implicated in T2D and insulin secretion in Han Chinese study populations) and suggests potential genetic links between inflammation and insulin secretion.

Disclosure

L.E. Wedekind: None. M. Walter: None. S. Kobes: None. P. Chen: None. W. Hsueh: None. R. Nelson: None. L. Baier: None. W.C. Knowler: None. R.L. Hanson: None.

Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. More information is available at http://www.diabetesjournals.org/content/license.