Our findings demonstrate increased splenic metabolic activity after ACS and its association with proinflammatory remodeling of circulating leukocytes. Moreover, we observed that metabolic activity of the spleen independently predicted risk of subsequent CVD events. Collectively, these findings provide evidence of a cardiosplenic axis in humans similar to that shown in pre-clinical studies.

Objective While it is accepted that macrophage glycolysis is up-regulated under hypoxic conditions, it is not known whether this is linked to a similar increase in macrophage pro-inflammatory activation and whether specific energy demands regulate cell viability in the atheromatous plaque. Approach and Results We studied the interplay between macrophage energy metabolism, polarization and viability in the context of atherosclerosis. Cultured human and murine macrophages and an in vivo murine model of atherosclerosis were used to evaluate the mechanisms underlying metabolic and inflammatory activity of macrophages in the different atherosclerotic conditions analyzed. We observed that macrophage energetics and inflammatory activation are closely and linearly related, resulting in dynamic calibration of glycolysis to keep pace with inflammatory activity. Additionally, we show that macrophage glycolysis and proinflammatory activation mainly depend on hypoxia-inducible factor (HIF) and on its impact on glucose uptake, and on the expression of hexokinase II and ubiquitous 6-phosphofructo-2-kinase (PFKFB3). As a consequence, hypoxia potentiates inflammation and glycolysis mainly via these pathways. Moreover, when macrophages’ ability to increase glycolysis through PFKFB3 is experimentally attenuated, cell viability is reduced if subjected to proinflammatory and/or hypoxic conditions, but unaffected under control conditions. In addition to this, GM-CSF enhances anaerobic glycolysis while exerting a mild pro-inflammatory activation. Conclusions These findings, in human and murine cells and in an animal model, show that hypoxia potentiates macrophage glycolytic flux in concert with a proportional up-regulation of pro-inflammatory activity, in a manner that is dependent on both HIF-1α and PFKFB3.