Intermittent high glucose promotes expression of proinflammatory cytokines in monocytes

Objective and design The aim of this study was to examine expression of proinflammatory cytokines in monocytes under fluctuating glucose conditions. Material and treatment Monocytic cells (THP-1) were divided into four groups and cultured in the presence of 5 or 15 mmol/L glucose or in fluctuating conditions (12 h exposure to 15 mmol/L glucose or mannitol medium followed by 12 h exposure to 5 mmol/L glucose or mannitol medium) respectively. Methods Levels of interleukin (IL)-6 and tumor necrosis factor (TNF)-α in the supernatants and surface expression of CD11b in monocytes were measured after 72 h culture. Paired Student's t tests were used to compare two groups and ANOVA for multiple comparisons. Results Activation of monocytes was most pronounced in the fluctuating glucose conditions, as measured by concentrations of IL-6 and TNF-α in cultured supernatants and surface expression of CD11b in monocytes (P < 0.05). Fluctuating mannitol also induced a proinflammatory profile, but to a lesser extent than fluctuating glucose. Conclusions The results indicated that exposure to fluctuating glucose concentrations enhanced activation of monocytes compared with stable elevation of glucose concentrations. The effects were partly attributable to the inherent osmotic changes.