Objective: An association between type 2 diabetes mellitus and inflammation has been described in several studies. The aim of this study was to search for the presence of low-grade inflammation in a special group of insulin-treated patients with type 2 diabetes, and to investigate a possible correlation between inflammation and obesity, glucose homeostasis and insulin requirement (IU insulin/kg body weight, BW).
Methods: We studied 85 subjects with type 2 diabetes that were receiving insulin treatment (group A) and 32 receiving sulfonylurea treatment (group B), and 57 subjects without diabetes (group C). Interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-alpha), and the soluble TNF-alpha receptors sTNFR-60 and sTNFR-80 were measured in serum samples taken from all patients.
Results: The mean serum cytokine levels in group A vs. group B were: IL-6, 8.54+/-11 vs. 2.71+/-1.9 pg/ml (p=0.000); TNF-alpha, 14.33+/-24 vs. 5.12+/-15 pg/ml (p=0.016); sTNFR60, 3.9+/-2.8 vs. 2.36+/-1.4 ng/ml (p=0.000); and sTNFR80, 11.9+/-7 vs. 9.4+/-6 ng/ml (p=0.080). The mean serum cytokine levels in group A vs. group C were: IL-6, 8.54+/-11 vs. 4.74+/-7 pg/ml (p=0.017); TNF-alpha, 14.33+/-24 vs. 5.94+/-3.4 pg/ml (p=0.003); sTNFR60, 3.9+/-2.8 vs. 2.54+/-1.4 ng/ml (p=0.000); and sTNFR80, 11.9+/-7 vs. 10.85+/-8 ng/ml (p=0.470). A positive association between waist circumference and IL-6 (r=0.165, p=0.030) and sTNFR-60 (r=0.276, p=0.000) was detected. A significant correlation coefficient was observed between haemoglobin A1c (HbA1c) and both IL-6 (r=0.278, p=0.000) and sTNFR-60 (r=0.293, p=0.000), when the groups were studied as one. No correlation between inflammation and units of insulin/kg BW was found. In conclusion, low-grade chronic inflammation, as estimated by the relative levels of inflammatory cytokines, was present in patients with type 2 diabetes that were receiving insulin treatment, with significantly higher cytokine levels recorded compared to sulfonylurea-treated patients. In addition, an association between inflammation and both obesity and glucose homeostasis was detected.