Human islet DNA samples obtained from 53 donors (see Supplementary Table 1 online for clinical characteristics), using the DNeasy Blood & Tissue Kit (QIAGEN, Hilden, Germany) as previously described (51), were genotyped for SNPs rs4502156, rs7172432, and rs7163757. The rs7172432 locus was amplified by semi-nested PCR using primers TAG GTA TCT TGG AGC TGA GG and CCA CAC TTC ACA GAA TCA GG for the first round amplification and then CAG GTC AAG TGA GCA CTT GC and CCA CAC TTC ACA GAA TCA GG for the second round. The amplicons were then digested with SspI and genotyped based on the resulting restriction fragment length polymorphism.