Metabolic Reprogramming of Macrophages GLUCOSE TRANSPORTER 1 (GLUT1)-MEDIATED GLUCOSE METABOLISM DRIVES A PROINFLAMMATORY PHENOTYPE

Background: GLUT1 is the main glucose transporter in certain immune cells. Results: Overexpressing GLUT1 in macrophages results in increased glucose uptake and glucose utilization. Conclusion: Driving glucose uptake and metabolism through GLUT1 induces a proinflammatory response that is dependent upon glycolysis and reactive oxygen species. Significance: Understanding how macrophage substrate metabolism impacts inflammation is crucial to develop novel therapeutics for obesity and diabetes. Glucose is a critical component in the proinflammatory response of macrophages (M phi s). However, the contribution of glucose transporters (GLUTs) and the mechanisms regulating subsequent glucose metabolism in the inflammatory response are not well understood. Because M phi s contribute to obesity-induced inflammation, it is important to understand how substrate metabolism may alter inflammatory function. We report that GLUT1 (SLC2A1) is the primary rate-limiting glucose transporter on proinflammatory-polarized M phi s. Furthermore, in high fat diet-fed rodents, M phi s in crown-like structures and inflammatory loci in adipose and liver, respectively, stain positively for GLUT1. We hypothesized that metabolic reprogramming via increased glucose availability could modulate the M phi inflammatory response. To increase glucose uptake, we stably overexpressed the GLUT1 transporter in RAW264.7 M phi s (GLUT1-OE M phi s). Cellular bioenergetics analysis, metabolomics, and radiotracer studies demonstrated that GLUT1 overexpression resulted in elevated glucose uptake and metabolism, increased pentose phosphate pathway intermediates, with a complimentary reduction in cellular oxygen consumption rates. Gene expression and proteome profiling analysis revealed that GLUT1-OE M phi s demonstrated a hyperinflammatory state characterized by elevated secretion of inflammatory mediators and that this effect could be blunted by pharmacologic inhibition of glycolysis. Finally, reactive oxygen species production and evidence of oxidative stress were significantly enhanced in GLUT1-OE M phi s; antioxidant treatment blunted the expression of inflammatory mediators such as PAI-1 (plasminogen activator inhibitor 1), suggesting that glucose-mediated oxidative stress was driving the proinflammatory response. Our results indicate that increased utilization of glucose induced a ROS-driven proinflammatory phenotype in M phi s, which may play an integral role in the promotion of obesity-associated insulin resistance.