Increased toll-like receptor (TLR) activation and TLR ligands in recently diagnosed type 2 diabetic subjects

Diabetes Care. 2010 Apr;33(4):861-8. doi: 10.2337/dc09-1799. Epub 2010 Jan 12.


Objective: Individuals with type 2 diabetes have a myriad of metabolic aberrations including increased inflammation, increasing their cardiovascular risk. Toll-like receptors (TLRs) and their ligands play a key role in insulin resistance and atherosclerosis. However, there is a paucity of data examining the expression and activity of TLRs in type 2 diabetes. Thus, in the present study, we examined TLR2 and TLR4 mRNA and protein expression, their ligands, and signaling in monocytes of recently diagnosed type 2 diabetic patients.

Research design and methods: TLR mRNA, protein expression, TLR ligands, and TLR signaling were measured in freshly isolated monocytes from healthy human control subjects (n = 23) and type 2 diabetic subjects (n = 23) using real-time RT-PCR, Western blot, and flow cytometric assays.

Results: Type 2 diabetic subjects had significantly increased TLR2, TLR4 mRNA, and protein in monocytes compared with control subjects (P < 0.05). Increased TLR2 and TLR4 expression correlated with BMI, homeostasis model assessment-insulin resistance (HOMA-IR), glucose, A1C, N(epsilon)-(carboxymethyl) lysine (CML), and free fatty acid (FFA). Ligands of TLR2 and TLR4, namely, HSP60, HSP70, HMGB1, endotoxin, and hyaluronan levels, were elevated in type 2 diabetic subjects and positively correlated with TLR2 and TLR4. Type 2 diabetic subjects showed increased MyD88, phosphorylated IRAK-1, Trif, TICAM-1, IRF-3, and NF-kappaB p65 expression in monocytes compared with control subjects. Furthermore, TLR-MyD88-NF-kappaB signaling resulted in elevated levels of cytokines (P < 0.05), but increased interleukin (IL)-1beta, interferon (IFN)-gamma, and endotoxin were not significant when adjusted for BMI.

Conclusions: In this comprehensive study, we make the novel observation that TLR2 and TLR4 expression and their ligands, signaling, and functional activation are increased in recently diagnosed type 2 diabetes and contribute to the proinflammatory state.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Vesicular Transport / metabolism
  • Blotting, Western
  • Case-Control Studies
  • Chaperonin 60 / metabolism
  • Diabetes Mellitus, Type 2 / metabolism*
  • Enzyme-Linked Immunosorbent Assay
  • HMGB1 Protein / metabolism
  • HSP72 Heat-Shock Proteins / metabolism
  • Humans
  • Hyaluronic Acid / metabolism
  • Immunoprecipitation
  • Interferon Regulatory Factor-3 / metabolism
  • Interferon-gamma / metabolism
  • Interleukin-1 Receptor-Associated Kinases / metabolism
  • Interleukin-1beta / metabolism
  • Monocytes / metabolism
  • Myeloid Differentiation Factor 88 / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Toll-Like Receptor 2 / genetics
  • Toll-Like Receptor 2 / metabolism
  • Toll-Like Receptor 4 / genetics
  • Toll-Like Receptor 4 / metabolism
  • Toll-Like Receptors / genetics
  • Toll-Like Receptors / metabolism*
  • Transcription Factor RelA / metabolism


  • Adaptor Proteins, Vesicular Transport
  • Chaperonin 60
  • HMGB1 Protein
  • HSP72 Heat-Shock Proteins
  • Interferon Regulatory Factor-3
  • Interleukin-1beta
  • Myeloid Differentiation Factor 88
  • TICAM1 protein, human
  • Toll-Like Receptor 2
  • Toll-Like Receptor 4
  • Toll-Like Receptors
  • Transcription Factor RelA
  • Interferon-gamma
  • Hyaluronic Acid
  • IRAK1 protein, human
  • Interleukin-1 Receptor-Associated Kinases