Blood leucocyte cytokine production after LPS stimulation at different concentrations of glucose and/or insulin

Abstract

Previous studies have indicated that alterations in blood glucose and/or insulin levels modify the inflammatory response. The purpose of this study was to elucidate whether increased levels of glucose and/or insulin influence the activation pattern of blood leucocytes and their production of cytokines in vitro. Venous blood was obtained from eight healthy male volunteers after an overnight fast. Glucose and/or insulin were added to aliquots of whole blood to increase the blood glucose concentration by 5 or 20 mmol/l and/or the insulin concentration by 6 or 30 nmol/l, respectively, before stimulation with E. coli lipopolysaccharide (LPS) at concentrations of 10, 100 or 1000 ng/ml. The samples were subsequently incubated at 37 degrees C for 6 h before cytokine measurements. After centrifugation the levels of interleukins (IL)-1beta, IL-6, IL-8, IL-10 and tumour necrosis factor (TNF)-alpha were measured in plasma using enzyme-linked immuno-sorbent assays. The results were compared with cytokine levels in parallel control samples to which only identical amounts of LPS were added. The LPS-stimulated production of IL-1beta was significantly reduced by on average 26% in samples to which glucose 20 mmol/l was added; addition of insulin and/or glucose 5 mmol/l had no apparent effect on the IL-1beta production at any LPS concentration. The levels of IL-6, IL-8, IL-10 and TNF-alpha were not manifestly altered by addition of glucose and/or insulin at any LPS concentration. A substantial increase in blood glucose concentration changed the IL-1beta production, but not the production of other cytokines, in response to LPS stimulation.