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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

A substantial increase in blood glucose concentration changed the IL-1beta production, but not the production of other cytokines, in response to LPS stimulation.