Insulin Resistance in Macrophages Alters Their Metabolism and Promotes an M2-Like Phenotype.

Obesity and insulin resistance influences metabolic processes， but whether it affects macrophage metabolism is not known. In this study， we demonstrate that chronic exposure of macrophages to insulin either in culture or in vivo in diet-induced， glucose-intolerant mice rendered them resistant to insulin signals marked by failure to induce Akt2 phosphorylation. Similarly， macrophages lacking Akt2 or IGF1 receptor were also resistant to insulin signals. Insulin-resistant macrophages had increased basal mTORC1 activity， possessed an M2-like phenotype， and reduced LPS responses. Moreover， they exhibited increased glycolysis and increased expression of key glycolytic enzymes. Inhibition of mTORC1 reversed the M2-like phenotype and suppressed glycolysis in insulin-resistant macrophages. In the context of polymicrobial sepsis， mice harboring insulin-resistant macrophages exhibited reduced sepsis-induced lung injury. Thus， macrophages obtain resistance to insulin characterized by increased glycolysis and a unique M2-like phenotype， termed M-insulin resistant， which accounts for obesity-related changes in macrophage responses and a state of trained immunity.