title: Global IRS-1 phosphorylation analysis in insulin resistance.
abstract: OBJECTIVE
  IRS-1 serine phosphorylation is often elevated in insulin resistance models, but confirmation in vivo in humans is lacking. We therefore analysed IRS-1 phosphorylation in human muscle in vivo.
  
  
  METHODS
  We used HPLC-electrospray ionisation (ESI)-MS/MS to quantify IRS-1 phosphorylation basally and after insulin infusion in vastus lateralis muscle from lean healthy, obese non-diabetic and type 2 diabetic volunteers.
  
  
  RESULTS
  Basal Ser323 phosphorylation was increased in type 2 diabetic patients (2.1 ± 0.43, p ≤ 0.05, fold change vs lean controls). Thr495 phosphorylation was decreased in type 2 diabetic patients (p ≤ 0.05). Insulin increased IRS-1 phosphorylation at Ser527 (1.4 ± 0.17, p ≤ 0.01, fold change, 60 min after insulin infusion vs basal) and Ser531 (1.3 ± 0.16, p ≤ 0.01, fold change, 60 min after insulin infusion vs basal) in the lean controls and suppressed phosphorylation at Ser348 (0.56 ± 0.11, p ≤ 0.01, fold change, 240 min after insulin infusion vs basal), Thr446 (0.64 ± 0.16, p ≤ 0.05, fold change, 60 min after insulin infusion vs basal), Ser1100 (0.77 ± 0.22, p ≤ 0.05, fold change, 240 min after insulin infusion vs basal) and Ser1142 (1.3 ± 0.2, p ≤ 0.05, fold change, 60 min after insulin infusion vs basal).
  
  
  CONCLUSIONS
  We conclude that, unlike some aspects of insulin signalling, the ability of insulin to increase or suppress certain IRS-1 phosphorylation sites is intact in insulin resistance. However, some IRS-1 phosphorylation sites do not respond to insulin, whereas other Ser/Thr phosphorylation sites are either increased or decreased in insulin resistance.
authors.affiliation: Center for Metabolic and Vascular Biology, School of Life Science, Arizona State University, ISTB1, 550 E. Orange St, Tempe, AZ 85287, USA.
authors.forename: P
authors.initials: P
authors.lastname: Langlais
authors.forename: Z
authors.initials: Z
authors.lastname: Yi
authors.forename: J
authors.initials: J
authors.lastname: Finlayson
authors.forename: M
authors.initials: M
authors.lastname: Luo
authors.forename: R
authors.initials: R
authors.lastname: Mapes
authors.forename: E
authors.initials: E
authors.lastname: De Filippis
authors.forename: C
authors.initials: C
authors.lastname: Meyer
authors.forename: E
authors.initials: E
authors.lastname: Plummer
authors.forename: P
authors.initials: P
authors.lastname: Tongchinsub
authors.forename: M
authors.initials: M
authors.lastname: Mattern
authors.forename: L J
authors.initials: LJ
authors.lastname: Mandarino
mesh_terms: D000328:Adult; D002851:Chromatography, High Pressure Liquid; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000378:metabolism*; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D007262:Infusions, Intravenous; D007328:Insulin / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D055504:Insulin Receptor Substrate Proteins / Q000737:chemistry / Q000378:metabolism*; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D052097:Quadriceps Muscle / Q000378:metabolism*; D012694:Serine / Q000737:chemistry / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry; D013912:Threonine / Q000737:chemistry / Q000378:metabolism
chemical_list: D007004:Hypoglycemic Agents; C526292:IRS1 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D013912:Threonine; D012694:Serine