We reported previously that loss of the C-C chemokine receptor CCR5 prevents obesity-related insulin resistance independently of MCP-1-CCR2. Moreover, we found that hepatic expression of macrophage inflammatory protein 1α (MIP-1α), a CCR5 ligand, increases markedly in obese mice. To investigate the role of MIP-1α in lipotoxicity-induced hepatic insulin resistance and nonalcoholic steatohepatitis (NASH), the metabolic phenotypes of MIP-1α-/- mice and their littermates were compared by feeding them a high-cholesterol/high-fat (CL) diet for 16 weeks. Expression of MIP-1α mRNA increased significantly in the liver of wild-type (WT) mice fed the CL diet compared with that in chow fed WT mice (P < 0.01), particularly in the macrophage/Kupffer cell fraction. An immunofluorescence analysis of the liver revealed that MIP-1α was expressed by F4/80+ macrophages in CL fed mice. The excess hepatic lipid accumulation and peroxidation induced by the CL diet decreased in MIP-1α-/- mice compared with those in MIP-1α+/+ mice (P < 0.01). CL diet-induced glucose intolerance and hyperinsulinemia improved in MIP-1α-/- mice compared with those in MIP-1α+/+ mice. In addition, phosphorylation of IRβ and Akt was enhanced in the liver of MIP-1α-/- mice, accompanied by attenuated NF-kB and MAPK signaling, and decreased plasma TNFα levels (P < 0.05). Furthermore, CL diet-induced stellate cells activation and fibrogenesis decreased in the liver of MIP-1α-/- mice. A flow cytometry analysis demonstrated that MIP-1α-/- mice fed the CL diet had 37% fewer CD11c+CD206-(M1) macrophages but 59% more CD11c-CD206+ (M2) macrophages than those in MIP-1α+/+ mice, resulting in a predominance of M2 over the M1 population. Importantly, chimeric mice lacking MIP-1α only in myeloid cells (MIP-1α-/- into MIP-1α+/+ bone marrow transplant) were protected from CL diet-induced insulin resistance and NASH. Thus, MIP-1α deficiency prevented lipotoxicity-induced insulin resistance and NASH by polarizing M2 macrophages in the liver.