title: AMPD1 regulates mTORC1-p70 S6 kinase axis in the control of insulin sensitivity in skeletal muscle.
abstract: BACKGROUND
  Insulin resistance triggered by excess fat is a key pathogenic factor that promotes type 2 diabetes. Understanding molecular mechanisms of insulin resistance may lead to the identification of a novel therapeutic target for type 2 diabetes. AMPD1, an isoform of AMP deaminase (AMPD), is suggested to play roles in the regulation of glucose metabolism through controlling AMP-activated protein kinase (AMPK) activation. We reported that the diet-induced insulin resistance was improved in AMPD1-deficient mice compared to wild type mice. To further delineate this observation, we studied changes of insulin signaling in skeletal muscle of wild type (WT) and AMPD1-deficient mice.
  
  
  METHODS
  Phosphorylation levels of kinases and expression levels of mTOR components were quantified by immunoblotting using protein extracts from tissues. The interaction between mTOR and Raptor was determined by immunoblotting of mTOR immunoprecipitates with anti-Raptor antibody. Gene expression was studied by quantitative PCR using RNA extracted from tissues.
  
  
  RESULTS
  Phosphorylation levels of AMPK, Akt and p70 S6 kinase in skeletal muscle were higher in AMPD1-deficient mice compared to WT mice after high fat diet challenge, while they did not show such difference in normal chow diet. Also, no significant changes in phosphorylation levels of AMPK, Akt or p70 S6 kinase were observed in liver and white adipose tissue between WT and AMPD1-deficient mice. The expression levels of mTOR, Raptor and Rictor tended to be increased by AMPD1 deficiency compared to WT after high fat diet challenge. AMPD1 deficiency increased Raptor-bound mTOR in skeletal muscle compared to WT after high fat diet challenge. Gene expression of peroxisome proliferator-activated receptor-γ coactivator 1α and β, downstream targets of p70 S6 kinase, in skeletal muscles was not changed significantly by AMPD1 deficiency compared to the wild type after high fat diet challenge.
  
  
  CONCLUSIONS
  These data suggest that AMPD1 deficiency activates AMPK/Akt/mTORC1/p70 S6 kinase axis in skeletal muscle after high fat diet challenge, but not in normal chow diet. These changes may contribute to improve insulin resistance.
authors.affiliation: Department of Bioscience and Genetics, National Cerebral and Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Suita, Osaka, 565-8565, Japan. andreas@ri.ncvc.go.jp.|Department of Molecular Imaging in Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka, Japan. andreas@ri.ncvc.go.jp.
authors.forename: Andreas A K
authors.initials: AA
authors.lastname: Tandelilin
authors.affiliation: Department of Bioscience and Genetics, National Cerebral and Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Suita, Osaka, 565-8565, Japan. hirase@ri.ncvc.go.jp.
authors.forename: Tetsuaki
authors.initials: T
authors.lastname: Hirase
authors.affiliation: Department of Bioscience and Genetics, National Cerebral and Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Suita, Osaka, 565-8565, Japan. athanasius_wrin@yahoo.com.|Department of Molecular Imaging in Cardiovascular Medicine, Osaka University Graduate School of Medicine, Suita, Osaka, Japan. athanasius_wrin@yahoo.com.
authors.forename: Athanasius W
authors.initials: AW
authors.lastname: Hudoyo
authors.affiliation: Department of Bioscience and Genetics, National Cerebral and Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Suita, Osaka, 565-8565, Japan. jidongcheng36@hotmail.com.|Present address: Department of Internal Medicine, The First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong, 515031, P R China. jidongcheng36@hotmail.com.
authors.forename: Jidong
authors.initials: J
authors.lastname: Cheng
authors.affiliation: Department of Bioscience and Genetics, National Cerebral and Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Suita, Osaka, 565-8565, Japan. ktoyama2@plum.ocn.ne.jp.|Department of Molecular Pathophysiology, Osaka University Graduate School of Pharmaceutical Sciences, Suita, Osaka, Japan. ktoyama2@plum.ocn.ne.jp.
authors.forename: Keiko
authors.initials: K
authors.lastname: Toyama
authors.affiliation: Department of Bioscience and Genetics, National Cerebral and Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Suita, Osaka, 565-8565, Japan. hirokom@ri.ncvc.go.jp.|Department of Molecular Pathophysiology, Osaka University Graduate School of Pharmaceutical Sciences, Suita, Osaka, Japan. hirokom@ri.ncvc.go.jp.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Morisaki
authors.affiliation: Department of Bioscience and Genetics, National Cerebral and Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Suita, Osaka, 565-8565, Japan. morisaki@ri.ncvc.go.jp.|Department of Molecular Pathophysiology, Osaka University Graduate School of Pharmaceutical Sciences, Suita, Osaka, Japan. morisaki@ri.ncvc.go.jp.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Morisaki
mesh_terms: D000659:AMP Deaminase / Q000235:genetics* / Q000378:metabolism; D000263:Adenylate Kinase / Q000378:metabolism; D052436:Adipose Tissue, White / Q000378:metabolism; D000818:Animals; D059305:Diet, High-Fat; D020869:Gene Expression Profiling; D007333:Insulin Resistance / Q000235:genetics*; D008099:Liver / Q000378:metabolism; D000076222:Mechanistic Target of Rapamycin Complex 1; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D046912:Multiprotein Complexes / Q000235:genetics* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D009765:Obesity / Q000378:metabolism; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D046912:Multiprotein Complexes; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; C485290:Ppargc1a protein, mouse; D012333:RNA, Messenger; D014157:Transcription Factors; D000076222:Mechanistic Target of Rapamycin Complex 1; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D000263:Adenylate Kinase; D000659:AMP Deaminase; C577245:AMPD1 protein, mouse