Journal Article

Increased Toll-Like Receptor (TLR) Activation and TLR Ligands in Recently Diagnosed Type 2 Diabetic Subjects

Devaraj, Sridevi, Jialal, Ishwarlal, Park, Samuel, Dasu, Mohan R

2010

Overview

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, Nε-(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-κB p65 expression in monocytes compared with control subjects. Furthermore, TLR-MyD88-NF-κB signaling resulted in elevated levels of cytokines (P < 0.05), but increased interleukin (IL)-1β, interferon (IFN)-γ, 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.

• Publisher: American Diabetes Association
• Subject: Adapter proteins / Adaptor Proteins, Vesicular Transport / Adaptor Proteins, Vesicular Transport - metabolism / Atherosclerosis / Blotting, Western / body mass index / Case-Control Studies / Chaperonin 60 / Chaperonin 60 - metabolism / Chronic illnesses / correlation / Diabetes / Diabetes Mellitus, Type 2 / Diabetes Mellitus, Type 2 - metabolism / E coli / Enzyme-Linked Immunosorbent Assay / flow cytometry / free fatty acids / genetics / glucose / HMGB1 Protein / HMGB1 Protein - metabolism / homeostasis / HSP72 Heat-Shock Proteins / HSP72 Heat-Shock Proteins - metabolism / Human subjects / Humans / Hyaluronic Acid / Hyaluronic Acid - metabolism / Hyperglycemia / Immune system / Immunoprecipitation / Inflammation / Insulin resistance / Interferon Regulatory Factor-3 / Interferon Regulatory Factor-3 - metabolism / Interferon-gamma / Interferon-gamma - metabolism / interferons / Interleukin-1 Receptor-Associated Kinases / Interleukin-1 Receptor-Associated Kinases - metabolism / Interleukin-1beta / Interleukin-1beta - metabolism / interleukins / lysine / Messenger RNA / metabolism / Molecular weight / monocytes / Monocytes - metabolism / Myeloid Differentiation Factor 88 / Myeloid Differentiation Factor 88 - metabolism / noninsulin-dependent diabetes mellitus / Original Research / patients / protein synthesis / receptors / Reverse Transcriptase Polymerase Chain Reaction / Rheumatoid arthritis / risk / Sample size / Studies / Toll-Like Receptor 2 / Toll-Like Receptor 2 - genetics / Toll-Like Receptor 2 - metabolism / Toll-Like Receptor 4 / Toll-Like Receptor 4 - genetics / Toll-Like Receptor 4 - metabolism / Toll-Like Receptors / Toll-Like Receptors - genetics / Toll-Like Receptors - metabolism / Transcription Factor RelA / Transcription Factor RelA - metabolism / Type 2 diabetes / Western blotting