Increased Toll-like Receptor activation and TLR ligands in Recently Diagnosed Type 2 diabetes Subjects

Abstract

Objective: Individuals with Type 2 diabetes (T2DM) have a myriad of metabolic aberrations including increased inflammation that increase 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 T2DM. Thus, in the present study, we examined TLR2 and TLR4 mRNA and protein expression, their ligands, and signaling in monocytes of recently diagnosed T2DM patients.

Research Design & Methods: TLR mRNA, protein expression, TLR ligands and TLR signaling were measured in freshly isolated monocytes from healthy human controls (n=23) and T2DM subjects (n=23) using real time RT PCR, Western blot, and Flow cytometric assays.

Results: T2DM subjects had significantly increased TLR2, TLR4 mRNA and protein in monocytes compared to controls (P<0.05). Increased TLR2 and TLR4 expression correlated with BMI, HOMA-IR, glucose, HbA1c, CML, and FFA. Ligands of TLR2 and TLR4 namely, HSP60, HSP70, HMGB1, endotoxin, and hyaluronan levels were elevated in T2DM subjects and positively correlated with TLR2 and TLR4. T2DM subjects showed increased MyD88, phosphorylated IRAK-1, Trif, TICAM-1, IRF-3, and NF-κB p65 expression in monocytes compared to controls. Furthermore, TLR-MyD88-NF-κB signaling resulted in elevated levels of cytokines (P<0.05), but increased IL-1β, 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, their ligands, signaling, and functional activation are increased in recently diagnosed T2DM and contribute to the proinflammatory state.