Since 2014, the Korean Chip (K-CHIP), which includes 833,535 SNPs and uses an oligomer as a probe, has been developed by the Korea Biobank Array project as a low-cost customized chip that is optimized for genetic studies of diseases and complex traits in Koreans (Additional file : Table S1).
Since whole-genome sequencing requires very high calculation capacity and cost and commercial chips are designed for Western populations, whose genomic variants differ from Asian populations, the K-CHIP is more suitable for the discovery and identification of Korean population-specific SNPs related to disease occurrence .
Plasma ox-LDL was estimated using an enzyme immunoassay (Mercodia AB, Uppsala, Sweden), and the resulting color reaction was determined at 450 nm on a Wallac Victor2 multilabel counter (Perkin-Elmer Life Sciences, Boston, MA, USA).
A total of 2167 samples were genotyped according to the manufacturer’s protocol included in the Axiom® 2.0 Reagent Kit (Affymetrix Axiom® 2.0 Assay User Guide; Affymetrix, Santa Clara, CA, USA).
Waist to hip ratio values were obtained by dividing the waist circumference by the hip circumference.The serum fasting glucose level was measured using the hexokinase method with the GLU Kit (Roche, Mannheim, Germany), and the resulting color reaction was monitored with the Hitachi 7600 autoanalyzer (Hitachi, Tokyo, Japan).Serum fasting insulin was measured with an immunoradiometric assay using the Insulin IRMA Kit (DIAsource, Louvain, Belgium), and the resulting color reaction was monitored with an SR-300 system (Stratec, Birkenfeld, Germany).Systolic and diastolic BP were measured using a random-zero sphygmomanometer (HM-1101, Hico Medical Co., Ltd., Chiba, Japan) with appropriately sized cuffs after a rest period of at least 20 min in a seated position. The differences among the three systolic BP measurements were always less than 2 mm Hg.Participants were instructed not to smoke or drink alcohol for at least 30 min before each BP measurement.