We also assessed trans-eQTLs in four different tissues from the 86 morbidly obese individuals that underwent bariatric surgery. DNA was extracted from blood samples using the Chemagic Magnetic Separation Module 1 (Chemagen) integrated with a Multiprobe II Pipeting robot (PerkinElmer). All samples were genotyped using both Illumina HumanCytoSNP-12 BeadChips and Illumina HumanOmni1-Quad BeadChips (QC was identical as was applied to the peripheral blood samples). We imputed HapMap 2 genotypes using Impute version 2.0. In addition expression profiling was performed for four different tissues for each of these individuals using the Illumina HumanHT-12 arrays. Wedge biopsies of liver, visceral adipose tissue (VAT, omentum majus), subcutaneous adipose tissue (SAT, abdominal), and muscle (musculus rectus abdominis) were taken during surgery. RNA was isolated using the Qiagen Lipid Tissue Mini Kit (Qiagen, UK, 74804). Assessment of RNA quality and concentration was done with an Agilent Bioanalyzer (Agilent Technologies USA). Starting with 200 ng of RNA, the Ambion Illumina TotalPrep Amplification Kit was used for anti-sense RNA synthesis, amplification, and purification according to the protocol provided by the manufacturer (Ambion, USA). 750 ng of complementary
