Serum levels of interleukin 6, C-reactive protein, vascular cell adhesion molecule 1, and monocyte chemotactic protein 1 in relation to insulin resistance and glucose intolerance-the Chennai Urban Rural Epidemiology Study (CURES)

Abstract

The aim of this cross-sectional study was to assess the association of insulin resistance (IR) with inflammatory molecules C-reactive protein (CRP), interleukin 6 (IL-6), vascular cell adhesion molecule 1 (VCAM-1), and monocyte chemotactic protein 1 (MCP-1) in urban South Indian subjects. The following groups were selected from the population-based Chennai Urban Rural Epidemiology Study: group 1 composed of 50 healthy subjects with normal glucose tolerance without IR; group 2 consisted of 50 normal glucose-tolerant subjects with IR as defined by homeostasis model assessment of IR (HOMA-IR); group 3 consisted of 50 subjects with impaired glucose tolerance (IGT); and groups 4 and 5 each comprised 50 newly diagnosed and known type 2 diabetic subjects, respectively. The inclusion criteria included nonsmokers; normal resting 12-lead electrocardiogram; and absence of angina, myocardial infarction, or history of any known vascular, infectious, or inflammatory diseases, and not on statins or aspirin. Normal glucose tolerance without IR had the lowest values of CRP, IL-6, and VCAM-1 (CRP, 1.32 mg/L; IL-6, 12.56 pg/mL; VCAM-1, 277 pg/mL) followed by normal glucose tolerance with IR (CRP, 2.25 mg/L; IL-6, 20.97 pg/mL; VCAM-1, 289 pg/mL), impaired glucose tolerance (CRP, 2.37 mg/L; IL-6, 22.11 pg/mL; VCAM-1, 335 pg/mL), newly diagnosed diabetic subjects (CRP, 3.24 mg/L; IL-6, 23.21 pg/mL; VCAM-1, 568 pg/mL), and the highest levels were in the known diabetic subjects (CRP, 4.08 mg/L; IL-6, 29.44 pg/mL; VCAM-1, 577 pg/mL). This trend was statistically significant (P < .001). However, monocyte chemotactic protein 1 did not show such a trend and did not differ significantly between groups. In nondiabetic subjects, Pearson correlation analysis revealed that CRP (r = 0.299; P < .001) and IL-6 (r = 0.180, P = .025) had a significant correlation with HOMA-IR. Monocyte chemotactic protein 1 did not show any correlation with HOMA-IR. Multiple linear regression analysis revealed CRP to be significantly associated with HOMA-IR (β = .229; P < .001) and this was unaltered by the addition of waist and IL-6 into the model (β = .158; P = .028). In conclusion, this study shows that in Asian Indians, inflammatory markers (CRP, IL-6, and VCAM-1) increase with increasing degrees of glucose intolerance.