Short Term High Fat Diet Challenge Promotes Alternative Macrophage Polarization in Adipose Tissue via Natural Killer T Cells and Interleukin-4

Inflammation in adipose tissue plays an important role in the pathogenesis of obesity-associated complications. However, the detailed cellular events underlying the inflammatory changes at the onset of obesity have not been characterized. Here we show that an acute HFD challenge is unexpectedly associated with elevated alternative (M2) macrophage polarization in adipose tissue mediated by Natural Killer T (NKT) cells. Upon 4d HFD feeding, NKT cells are activated, promote M2 macrophage polarization and induce arginase 1 expression via interleukin (IL)-4 in adipose tissue, not in the liver. In NKT-deficient CD1d −/− mice, M2 macrophage polarization in adipose tissue is reduced while systemic glucose homeostasis and insulin tolerance are impaired upon 4d HFD challenge. Thus, our study demonstrate, for the first time to our knowledge, that acute HFD feeding is associated with remarkably pronounced and dynamic immune responses in adipose tissue, and adipose-resident NKT cells may link acute HFD feeding with inflammation. Background: Our understanding of immune responses at early stages of obesity is very limited. Results: Acute HFD feeding promotes alternative macrophage polarization in adipose tissue via NKT cells and IL-4. Conclusion: NKT cells in adipose tissue play important role in linking acute HFD feeding with adipose inflammation. Significance: Acute HFD feeding is unexpectedly associated with pronounced and dynamic immune responses in adipose tissue.