Manon Dumont1, Julia van Heck1, Rick Meijer1, Cees Tack1, Rinke Stienstra1,2
1Department of Internal Medicine, Radboudumc, Nijmegen, 2Division of Human Nutrition and Health, Wageningen University, Wageningen
Background: Poor glucose control in diabetes increases the risk of developing complications. Glucose variability (GV) is believed to play an important role in complications through activation of innate immune cells, including macrophages. However, the exact mechanism by which high GV could trigger the immune response underlying diabetes-related complications is incompletely understood. The aim of this study is to elucidate underlying molecular mechanisms responsible for activation of the immune response by GV ex vivo.
Methods: Human primary monocytes were differentiated to macrophages and exposed to glucose fluctuations starting with 0.5 and ending with 29.5 mM glucose (F1) or the other way around (F2), with alternations every 24 hours for 4 days, or an averaged constant glucose (CG) of 15 mM. For each condition, we determined basal glycolysis and oxidative phosphorylation (OXPHOS). We also determined the subsequent metabolic and functional response after Toll-like receptor (TLR) stimulation following GV.
Results: After exposure to glucose fluctuations, ATP production through OXPHOS was increased with 65.5 pmol/min for F1 compared to CG (P<0.05, n=3), with a slighter increase for F2 with 29.4 pmol/min. A similar trend was observed for spare respiratory capacity. Basal glycolysis was decreased with 29.0 mpH/min for F1 and increased with 56.2 mpH/min for F2 compared to CG (n=15, P<0.001). Stimulation on TLR2 (n=6) resulted in an increase in glycolysis for F2 of 12.7 mpH/min compared to CG (P<0.01) and a 31.3% higher IL-6 production (P<0.05), identifying ending with low glucose as an important factor. Compared to CG, stimulation after glucose stabilisation resulted in apparent lower IL-6 (F1: -25.3%, F2: -21.1%) and IL-8 (F1: -11.8%, F2: -7.4%) production (n=3).
Discussion/Conclusion: The results indicate that glucose fluctuations alter metabolic and functional responses of macrophages, with apparent differences before and after glucose stabilisation. Based on these findings we will perform RNA sequencing, to elucidate changes in gene expression and use of cellular pathways related to the altered response.