Role of interleukin-6 levels in cardiovascular autonomic dysfunction in type 2 diabetic patients

Abstract

Increased serum interleukin-6 (IL-6) levels are associated with an increased risk of cardiovascular disease, and cardiovascular autonomic dysfunction is associated with high mortality in type 2 diabetic patients. However, the relationship between IL-6 levels and cardiovascular autonomic dysfunction has not been fully elucidated. The aim of this study was to determine whether serum IL-6 levels are associated with cardiovascular autonomic dysfunction in type 2 diabetic patients. Eighty type 2 diabetic patients who did not have organic heart disease were categorized into a high IL-6 group (>2.5 pg/ml, n = 40, age 59 +/- 12 years) or a non-high IL-6 group (<2.5 pg/ml, n = 40, 61 +/- 12 years). Cardiac autonomic function was assessed by baroreflex sensitivity, heart rate variability, plasma norepinephrine concentrations and (123)I-metaiodobenzylguanidine (MIBG) scintigraphy. The body mass index values (BMI), fasting insulin levels and homeostasis model assessment index values were higher in the high IL-6 group than in the non-high IL-6 group (p < 0.01). Early and delayed (123)I-MIBG myocardial uptake values were lower (p < 0.01), and the percent washout rate of (123)I-MIBG was higher (p < 0.05) in the high IL-6 group than in the non-high IL-6 group. Furthermore, multiple regression analysis revealed that the IL-6 level was independently predicted by the BMI and the myocardial uptake of (123)I-MIBG during the delayed phase. The results indicate that elevated IL-6 levels are associated with depressed cardiovascular autonomic function and obesity in type 2 diabetic patients.