title: Proteomic profiling of hepatic endoplasmic reticulum-associated proteins in an animal model of insulin resistance and metabolic dyslipidemia.
abstract: Hepatic insulin resistance and lipoprotein overproduction are common features of the metabolic syndrome and insulin-resistant states. A fructose-fed, insulin-resistant hamster model was recently developed to investigate mechanisms linking the development of hepatic insulin resistance and overproduction of atherogenic lipoproteins. Here we report a systematic analysis of protein expression profiles in the endoplasmic reticulum (ER) fractions isolated from livers of fructose-fed hamsters with the intention of identifying new candidate proteins involved in hepatic complications of insulin resistance and lipoprotein dysregulation. We have profiled hepatic ER-associated proteins from chow-fed (control) and fructose-fed (insulin-resistant) hamsters using two-dimensional gel electrophoresis and mass spectrometry. A total of 26 large scale two-dimensional gels of hepatic ER were used to identify 34 differentially expressed hepatic ER protein spots observed to be at least 2-fold differentially expressed with fructose feeding and the onset of insulin resistance. Differentially expressed proteins were identified by matrix-assisted laser desorption ionization-quadrupole time of flight (MALDI-Q-TOF), MALDI-TOF-postsource decay, and database mining using ProteinProspector MS-fit and MS-tag or the PROWL ProFound search engine using a focused rodent or mammalian search. Hepatic ER proteins ER60, ERp46, ERp29, glutamate dehydrogenase, and TAP1 were shown to be more than 2-fold down-regulated, whereas alpha-glucosidase, P-glycoprotein, fibrinogen, protein disulfide isomerase, GRP94, and apolipoprotein E were all found to be up-regulated in the hepatic ER of the fructose-fed hamster. Seven isoforms of ER60 in the hepatic ER were all shown to be down-regulated at least 2-fold in hepatocytes from fructosefed/insulin-resistant hamsters. Implications of the differential expression of positively identified protein factors in the development of hepatic insulin resistance and lipoprotein abnormalities are discussed.
authors.affiliation: Division of Clinical Biochemistry, and Structural Biology and Biochemistry, Department of Pediatric Laboratory Medicine, Research Institute, The Hospital for Sick Children and the University of Toronto, Toronto, Ontario, Canada.
authors.forename: Jean-Paul F
authors.initials: JP
authors.lastname: Morand
authors.forename: Joseph
authors.initials: J
authors.lastname: Macri
authors.forename: Khosrow
authors.initials: K
authors.lastname: Adeli
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D006224:Cricetinae; D004195:Disease Models, Animal; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D020869:Gene Expression Profiling / Q000379:methods*; D006360:Heat-Shock Proteins / Q000032:analysis / Q000235:genetics*; D006949:Hyperlipidemias / Q000235:genetics*; D007333:Insulin Resistance / Q000235:genetics*; D008099:Liver / Q000737:chemistry; D008297:Male; D008647:Mesocricetus; D008969:Molecular Sequence Data; D040901:Proteomics / Q000379:methods*; D013347:Subcellular Fractions / Q000737:chemistry / Q000378:metabolism
chemical_list: D006360:Heat-Shock Proteins