Objective: Visceral fat obesity is located upstream of metabolic syndrome and atherosclerotic diseases. Accumulating evidences indicate that several immunocytes including macrophages infiltrate into adipose tissue and induce chronic low-grade inflammation. We recently analyzed the association between visceral fat adiposity and the gene expression profile in peripheral blood cells in human subjects and demonstrated the close relationship of visceral fat adiposity and disturbance of circadian rhythm in peripheral blood cells. In a series of studies, we herein investigated the association of visceral fat adiposity and mRNA levels relating to inflammatory genes in peripheral blood cells. Approach and Results: Microarray analysis was performed in peripheral blood cells from 28 obese subjects. Reverse transcription-polymerase chain reaction (RT-PCR) was conducted by using blood cells from 57 obese subjects. Obesity was defined as body mass index (BMI) greater than 25 kg/m(2) according to the Japanese criteria. Gene expression profile analysis was carried out with Agilent whole human genome 4 x 44K oligo-DNA microarray. Gene ontology (GO) analysis showed that 14 genes were significantly associated with visceral fat adiposity among 239 genes relating to inflammation. Among 14 genes, RT-PCR demonstrated that S100A8, S100A9, and S100A12 positively correlated with visceral fat adiposity in 57 subjects. Stepwise multiple regression analysis showed that S100A8 and S100A12 mRNA levels were closely associated with HOMA-IR and S100A9 mRNA was significantly related to adiponectin and CRP. Conclusions: Peripheral blood mRNA levels of S100 family were closely associated with insulin resistance and inflammation. (C) 2013 Elsevier Inc. All rights reserved.