Glucocorticoid activation of anti-inflammatory macrophages protects against insulin resistance

Insulin resistance (IR) during obesity is linked to adipose tissue macrophage (ATM)-driven inflammation of adipose tissue. Whether anti-inflammatory glucocorticoids (GCs) at physiological levels modulate IR is unclear. Here, we report that deletion of the GC receptor (GR) in myeloid cells, including macrophages in mice, aggravates obesity-related IR by enhancing adipose tissue inflammation due to decreased anti-inflammatory ATM leading to exaggerated adipose tissue lipolysis and severe hepatic steatosis. In contrast, GR deletion in Kupffer cells alone does not alter IR. Co-culture experiments show that the absence of GR in macrophages directly causes reduced phospho-AKT and glucose uptake in adipocytes, suggesting an important function of GR in ATM. GR-deficient macrophages are refractory to alternative ATM-inducing IL-4 signaling, due to reduced STAT6 chromatin loading and diminished anti-inflammatory enhancer activation. We demonstrate that GR has an important function in macrophages during obesity by limiting adipose tissue inflammation and lipolysis to promote insulin sensitivity. Obesity and a high-fat diet can lead to insulin resistance in a process involving macrophage-mediated inflammation of adipose tissue. Here the authors show that glucocorticoid receptor-deficient macrophages have an elevated inflammatory response which aggravates insulin resistance implicating that glucocorticoids promote insulin-sensitizing actions via adipose tissue macrophages during obesity.

Automated summary

This study found that anti-inflammatory glucocorticoids can improve obesity-induced insulin resistance by regulating adipose tissue macrophages. Deletion of the glucocorticoid receptor in macrophages aggravates obesity-related insulin resistance, leading to increased adipose tissue inflammation, enhanced lipolysis, and severe hepatic steatosis. This suggests that glucocorticoids play an important role in macrophages by limiting adipose tissue inflammation and lipolysis to promote insulin sensitivity.