Insulin resistance induced by a high-fat diet (HFD) is related to metabolic diseases, and sterol O-acyltransferase 1 (SOAT1) is a key enzyme for the biosynthesis of cholesteryl ester. In the present study, wild type (WT) mice and SOAT1-knockout (KO) mice with a C57BL6 background fed a HFD were used to explore the role of SOAT1 in the hypothalamus. The results show that the WT mice exhibited a significant increase in body weight as well as hepatic histologic changes; they also had a lower glucose and insulin tolerance than the WT mice fed a normal diet. However, the metabolic syndrome was attenuated in the SOAT1-KO HFD-fed mice. With regard to brain function, the SOAT1-KO HFD-fed mice showed improved cognitive function; they also manifested reduced levels of pro-inflammatory cytokines, including tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL:1 beta), and 1L-6, which would otherwise be raised by a HFD. In addition, the HFD led to the overexpression of GFAP and phosphorylated NF-kappa B in the hypothalamus, changes that were reversed in the SOAT1-KO HFD-fed mice. Moreover, SOAT1-KO mice improved HFD-caused defective hypothalamic insulin resistance, as evidenced by the upregulation of p-insulin receptor (INSR), p-AKT and p-glycogen synthase kinase (GSK)-3 beta, while the downregulation of p-AMP-activated protein kinase (AMPK)-alpha and p-acetyl-CoA carboxylase (ACC)-alpha. In addition, similar results were observed in high fructose (HFR)-stimulated astrocytes (ASTs) isolated from VVT or KO mice. These results suggest that SOAT1 plays an important role in hypothalamic insulin sensitivity, linked to cognitive impairment, in HFD-fed mice. (C) 2018 Published by Elsevier Inc.