High fat intake induces a population of adipocytes to co-express TLR2 and TNFα in mice with insulin resistance

Cytokine production in fat tissue plays a key role in insulin resistance. The aim of study is to know the phenotypic changes of adipocytes with high fat-induced insulin resistance. High fat intake induced the expression of tumor necrosis factor α (TNFα) in visceral fat tissue as well as development of insulin resistance. Analysis of the gene expression profiles in adipocytes showed that high fat intake induced the expression of toll-like receptor 2 (TLR2) in addition to TNFα. Flow cytometry analysis revealed the presence of adipocytes co-expressing TLR2 and TNFα (TLR2/TNFα-adipocytes), and the number of TLR2/TNFα-adipocytes in visceral fat tissues was increased by high fat intake compared to that in subcutaneous fat tissues. Free fatty acids increased TNFα expression in 3T3-L1 adipocytes through TLR2 signals. These results indicate that TLR2/TNFα-adipocytes possibly cause the induction of TNFα expression in visceral fat tissues, being associated with the development of high fat-induced insulin resistance.