Suppressive Effect of Insulin Infusion on Chemokines and Chemokine Receptors

In view of the previously described anti-inflammatory effects of insulin, we investigated the potential suppressive effect of insulin on plasma concentrations and expression of the chemokines, monocyte chemoattractant protein-1 (MCP-1) and regulated on activation normal T-cell expressed and secreted (RANTES) and their receptors, chemokine receptor (CCR)-2 and CCR-5, in mononuclear cells (MNCs). We also investigated the effect of insulin on other chemokines.Ten obese type 2 diabetic patients were infused with insulin (2 units/h with 100 ml of 5% dextrose/h) for 4 h. Another 8 and 6 type 2 diabetic patients were infused with 100 ml of 5% dextrose/h or saline for 4 h, respectively, and served as control subjects. Blood samples were obtained at 0, 2, 4, and 6 h.Insulin infusion significantly suppressed the plasma concentrations of MCP-1, eotaxin, and RANTES and the expression of RANTES, macrophage inflammatory protein (MIP)-1beta, CCR-2, and CCR-5 in MNCs at 2 and 4 h. Dextrose and saline infusions did not alter these indexes.A low-dose infusion of insulin suppresses the plasma concentration of key chemokines, MCP-1, and RANTES, and the expression of their respective receptors, CCR-2 and CCR-5, in MNCs. Insulin also suppresses the expression of RANTES and MIP-1beta in MNCs. These actions probably contribute to the comprehensive anti-inflammatory effect of insulin.