Abstract
A high-fat diet contributes to the etiology of metabolic diseases. As the liver plays a crucial role in metabolism, an insight into the hepatic proteomics will help to illustrate the physiological effect of a high-fat diet. Fourteen nine-week old male Syrian hamsters were maintained on either control (C) or high-fat (HF) diets (0.2% cholesterol +22% fat) for 8 weeks. Hamsters were chosen because they show close similarity to human lipid metabolism. At the end of study, blood and livers were collected for analysis. Liver proteins were fractionated by electrophoresis, digested by trypsin, and then separated by label-free nano-LC/MS/MS. The TurboSequest algorithm was used to identify the peptide sequences against the hamster database in Universal Proteins Resource Knowledgebase (UniProt). The results indicate that 1191 hepatic proteins were identified and 135 of them were expressed differentially in the high-fat group (p < 0.05). Some of these 135 proteins that involve in metabolic diseases were further validated by Western blotting. The animals maintained on the high-fat diet had significantly (p < 0.05) higher serum triglyceride, cholesterol, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and uric acid. Animals consuming a high-fat diet also had significantly (p < 0.05) more accumulation of triglyceride and cholesterol in livers. Xanthine dehydrogenase (XDH), which plays an important role in uric acid synthesis, was up-regulated by the high-fat diet (p < 0.05). The α-subunit of hydroxyacyl-CoA dehydrogenase/3-ketoacyl-CoA thiolase/enoyl-CoA hydratase (HADHA), which catalyzes the second and third reactions of β-oxidation, was down-regulated by the high-fat diet (p < 0.05). Aconitate hydratase 2 (ACO2), which catalyzes the conversion of citrate to isocitrate in TCA cycle, was down-regulated in animals of the high-fat group (p < 0.05). Inflammatory markers annexin A3 (ANXA3) and annexin A5 (ANXA5) were up-regulated by the high-fat diet (p < 0.05). Moreover, enzymes involved in the urea cycle were suppressed by high-fat diet, including carbamoyl phosphate synthase 1 (CPS1), ornithine transcarbamoylase (OTC), argininosuccinate synthase (ASS), argininosuccinate lyase (ASL), and arginase 1 (ARG 1). Post-translational modifications (PTM) of ANXA3, ANXA5, and XDH were also analyzed. A set of differentially expressed proteins were identified as molecular markers for elucidating the pathological mechanism of high-fat diet.