Increased Levels of Serum Granulocyte-Macrophage Colony-Stimulating Factor Is Associated with Activated Peripheral Dendritic Cells in Type 2 Diabetes Subjects (CURES-99)

Background: Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a pro-inflammatory cytokine with growth factor-like properties for monocytes and dendritic cells (DCs). In the present study, serum GM-CSF levels and the activation status of DCs were studied in type 2 diabetes mellitus (T2DM) subjects. Methods: Study subjects were recruited from the Chennai Urban Rural Epidemiology Study. Healthy controls (n = 45) and T2DM patients (n = 45) were included in the study. Serum levels of GM-CSF, interleukin-1 beta, interleukin-6, and tumor necrosis factor-alpha were measured. Enumeration of circulating DCs (myeloid [m] and plasmocytoid [p]) and its surface antigen expression were quantified by flow cytometry. Results: The serum GM-CSF levels were significantly higher among diabetes subjects compared with subjects without diabetes and showed a positive correlation with glycated hemoglobin (r = 0.208, P = 0.018). The serum GM-CSF levels were lower in subjects on combined insulin and oral hypoglycemic agents (OHA) treatment (1.09 pg/mL) compared with those taking OHA alone (1.9 pg/mL). The increased GM-CSF levels were associated with the activated phenotype of mDCs and pDCs, as determined by up-regulation of the lineage markers. Conclusion: The activated state of mDCs and pDCs seen among diabetes subjects might be due to the increased levels of GM-CSF and other pro-inflammatory cytokines.