GDF15 and Insulin resistance: Macrophage-specific Crif1 KO mice developed insulin resistance with M1 macrophage-like polarization, but GDF15 treatment upregulated the oxidative function of macrophages, leading to their polarization to an M2-like phenotype, which reversed insulin resistance in Crif1 KO mice fed an HFD, suggesting GDF15 improved glucose metabolism with altered macrophage polarization in the WAT [55].