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


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.
Dasu
Mohan R
MR
Laboratory for Atherosclerosis and Metabolic Research, University of California Davis Medical Center, Sacramento, California, USA. ravi.dasu@ucdmc.ucdavis.edu
Devaraj
Sridevi
S
Park
Samuel
S
Jialal
Ishwarlal
I
D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D015153:Blotting, Western; D016022:Case-Control Studies; D018834:Chaperonin 60 / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D024243:HMGB1 Protein / Q000378:metabolism; D050884:HSP72 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D006820:Hyaluronic Acid / Q000378:metabolism; D047468:Immunoprecipitation; D050838:Interferon Regulatory Factor-3 / Q000378:metabolism; D007371:Interferon-gamma / Q000378:metabolism; D053592:Interleukin-1 Receptor-Associated Kinases / Q000378:metabolism; D053583:Interleukin-1beta / Q000378:metabolism; D009000:Monocytes / Q000378:metabolism; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism; D051193:Toll-Like Receptors / Q000235:genetics / Q000378:metabolism*; D051996:Transcription Factor RelA / Q000378:metabolism
D033942:Adaptor Proteins, Vesicular Transport; D018834:Chaperonin 60; D024243:HMGB1 Protein; D050884:HSP72 Heat-Shock Proteins; D050838:Interferon Regulatory Factor-3; D053583:Interleukin-1beta; D053594:Myeloid Differentiation Factor 88; C470409:TICAM1 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D051996:Transcription Factor RelA; D007371:Interferon-gamma; D006820:Hyaluronic Acid; C507768:IRAK1 protein, human; D053592:Interleukin-1 Receptor-Associated Kinases