Alteration of Lipid Metabolism Related Proteins in Liver of High-Fat Fed Obese Mice

Obesity and being overweight are strongly associated with the development of metabolic disease such as diabetes, hypertension, dyslipidemia. High-fat diet (HFD) is one of the most important factors which cause obesity. In this study, C57BL/6 mice were treated with a HFD for 22 weeks in order to induce obesity and hyperglycemia. Twenty-two weeks later, body weight and plasma glucose level of the HFD group were significantly increased, compared with the normal diet (ND) group. Intra-peritoneal glucose tolerance test (IPGTT) showed glucose intolerance in the HFD group compared with the ND group. These results confirmed that a HFD induced obesity and hyperglycemia in C57BL/6 mice. Plasma levels of triglyceride (TG) and total cholesterol (TC) were increased in the HFD group compared with the ND group. Hepatic levels of TG and TC were also increased by a HFD. To investigate the alteration of lipid metabolism in liver, proteins which are related to lipid metabolism were observed. Among lipid synthesis related enzymes, fatty acid synthase (FAS) and glycerol phosphate acyl transferase (GPAT) were significantly increased in the HFD group. Apolipoprotein B (apoB) and microsomal triglyceride transport protein (MTP), which are related to lipid transport, were significantly increased in the HFD group. Interestingly, protein level and phosphorylation of AMP-activated protein kinase (AMPK), which is known as a metabolic regulator, were significantly increased in the HFD group compared with the ND group. In the present study we suggest that HFD may physiologically increase the proteins which are related with lipid synthesis and lipid transport, but that HFD may paradoxically induce the activation of AMPK.