Analysis of inflammatory cytokine and TLR expression levels in Type 2 Diabetes with complications

Abstract

The pathogenesis and complications of type 2 diabetes (T2DM) are closely linked with defective glucose metabolism, obesity, cardiovascular disease and an inability to mount an effective immune response to certain pathogenic organisms. Perturbations in key innate immune receptors known as Toll-like receptors (TLRs) and inflammatory mediators such as IL-6, TNFα and IL-1β have been linked with T2DM. Herein, we sought to establish whether patients with T2DM and underlying complications exhibit perturbations in cytokine and TLR expression. Serum cytokine and mRNA levels of cytokines/TLRs in monocytes (M) and neutrophils (N) were measured in a cohort of 112 diabetic patients: good glycaemic control without complications (GC), good glycaemic control with complications (GCC), poor glycaemic control without complications (PC) and poor glycaemic control with complications (PCC) and compared them with 34 non-diabetic volunteers (NGT). Serum cytokine levels were normal in all study participants. In the GC group, cytokine and TLR gene expression were enhanced compared to NGT. In contrast, suppressed cytokine and TLR gene expression were evident in PC, GCC & PCC groups when compared to the GC. In conclusion, whereas serum pro-inflammatory cytokine levels are unaltered in T2DM patients, differences in inflammatory gene profiles exist among the T2DM patient groups.

Figure 1

Levels of cytokines in sera from NGT and T2DM patients. TNF-α (A), IL-6 (B), IL-1β (C), IFN-β (D), IL-10 (E), Rantes (F), IL-8 (G) IL-12 (H) and IFNγ (I) levels in NGT (n = 34), GC (n = 27), GCC (n = 32), PC (n = 21) and PCC (n = 32) patient groups. *p < 0.05, **p < 0.01, ***p < 0.001 vs. NGT.

Figure 2

Gene expression of TNFα, IL-6, IL-1β, IFN-β and Rantes in monocytes and neutrophils from NGT and T2DM patients. Analysis of TNFα (A,F), IL-6 (B,G), IL-1β (C,H), IFN-β (D,I) and RANTES (E,J) gene expression in monocytes (A–E) and neutrophils (F–J) from NGT and T2DM patients (n = 8 per group). Top and bottom horizontal lines of the boxplots indicate 25th and 75^th percentiles respectively; lines within the box indicate median values. *p < 0.05, **p < 0.01, ***p < 0.001 vs NGT.

Figure 3

Gene expression of TLR1-10 in monocytes and neutrophils from NGT and T2DM patients. Analysis of TLR1 (A,K), TLR2 (B,L), TLR3 (C,M), TLR4 (D,N), TLR5 (E,O), TLR6 (F,P), TLR7 (G,Q), TLR8 (H,R), TLR9 (I,S), TLR10 (J,T) gene expression in monocytes (A–J) and neutrophils (K–T) from NGT and T2DM patients (n = 8 per group). Top and bottom horizontal lines of the boxplots indicate 25th and 75^th percentiles respectively; lines within the box indicate median values. *p < 0.05, **p < 0.01, ***p < 0.001 vs NGT.