Objective To investigate toil-like receptor 4 (TLR4) expression and activity in peripheral blood mononuclear cells(PBMCs) of obese patients.Methods PBMCs from 16 obese patients and 16 normal control subjects were collected.TLR4 and IκBα protein concentrations were measured in PBMCs by western blotting.TLR4 and interleukin-6 (IL-6) mRNA expression levels in PBMCs were measured by quantitative realtime PCR.The blood levels of glucose,insulin,free fatty acids (FFA),IL-6 and tmnor necrosis factor-α (TNF-α) were measured after an overnight fast.Results The levels of FFA,IL-6,TNF-α and homeostasis model assessment of insulin resistance index (HOMA-IR) in obese patients were higher than that of control group (FFA:(879 ± 64) μmol/L vs.(458 ± 48) μmol/L; IL-6:(2.20 ± 0.35) ng/L vs.(1.26 ± 0.25) ng/L; TNF-α:(1.96±0.32) ng/Lvs.(1.38 ±0.24) ng/L;HOMA-IR:(1.8±0.2) vs.(0.4±0.1) ;t=24.613,P=0.000;t =14.993,P =0.000;t =9.128,P =0.000;t =32.254,P =0.000).Increased TLR4 gene and protein expression were observed in PBMCs of obese patients compared with control group(TLR4 mRNA:(3.13±0.21) vs.(0.99 ± 0.03),t =54.758,P ＜ 0.05; TLR4 protein:(7.04 ± 0.42) vs.(2.53 ± 0.17),t =77.450,P ＜0.05).IκBα protein concentration in PBMCs of obese patients (2.52 ±0.16) was lower than in control group (4.00 ± 0.30,t =23.284,P ＜ 0.05),indicating elevated IKKβ/NF-κB signaling.The increase in TLR4 and NF-κB signaling was accompanied by elevated expression of the NFκB-regulated gene IL-6 ((2.55 ±0.15) vs.(1.03 ±0.11),t =53.981,P ＜0.05).Conclusion TLR4 expression and activity are increased in the PBMCs of patients with obesity and might involve in the development and progress of insulin resistance.