title: 4-Hydroxyisoleucine stimulates glucose uptake by increasing surface GLUT4 level in skeletal muscle cells via phosphatidylinositol-3-kinase-dependent pathway.
abstract: OBJECTIVE
  To determine the effect of 4-Hydroxyisoleucine (4-HIL), an unusual amino acid isolated from the seeds of Trigonella foenum-graecum, on glucose uptake and the translocation of glucose transporter 4 (GLUT4) to plasma membrane in skeletal muscle cells and to investigate the underlying mechanisms of action.
  
  
  METHODS
  Rat skeletal muscle cells (L6-GLUT4myc) were treated with 4-HIL, and the effect on glucose uptake was determined by measuring the incorporation of radio-labeled 2-deoxy-[(3)H]-D-glucose (2-DG) into the cell. Translocation of GLUT4myc to plasma membrane was measured by an antibody-coupled colorimetric assay.
  
  
  RESULTS
  The prolonged exposure (16 h) of L6-GLUT4myc myotubes to 4-HIL caused a substantial increase in the 2-DG uptake and GLUT4 translocation to the cell surface, without changing the total amount of GLUT4 and GLUT1. Cycloheximide treatment reversed the effect of 4-HIL on GLUT4 translocation to the basal level suggesting the requirement of new protein synthesis. The 4-HIL-induced increase in GLUT4 translocation was completely abolished by wortmannin, and 4-HIL significantly increased the basal phosphorylation of AKT (Ser-473), but did not change the mRNA expression of AKT, IRS-1, GLUT4, and GSK3β.
  
  
  CONCLUSIONS
  Results suggest that 4-HIL stimulates glucose uptake in L6-GLUT4myc myotubes by enhancing translocation of GLUT4 to the cell surface in a PI-3-kinase/AKT-dependent mechanism.
authors.affiliation: Division of Biochemistry, CSIR-Central Drug Research Institute, Lucknow, 226001, India.
authors.forename: Natasha
authors.initials: N
authors.lastname: Jaiswal
authors.forename: Chandan K
authors.initials: CK
authors.lastname: Maurya
authors.forename: K
authors.initials: K
authors.lastname: Venkateswarlu
authors.forename: P
authors.initials: P
authors.lastname: Sukanya
authors.forename: Arvind K
authors.initials: AK
authors.lastname: Srivastava
authors.forename: Tadigoppula
authors.initials: T
authors.lastname: Narender
authors.forename: Akhilesh K
authors.initials: AK
authors.lastname: Tamrakar
mesh_terms: D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects; D005786:Gene Expression Regulation; D005947:Glucose / Q000493:pharmacokinetics*; D051272:Glucose Transporter Type 1 / Q000235:genetics / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000235:genetics / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism; D007532:Isoleucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D010936:Plant Extracts / Q000494:pharmacology*; D021381:Protein Transport / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D012639:Seeds / Q000737:chemistry; D015398:Signal Transduction; D029910:Trigonella / Q000737:chemistry
chemical_list: C104672:4-hydroxyisoleucine; D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D007328:Insulin; D010936:Plant Extracts; D012333:RNA, Messenger; C495679:Slc2a1 protein, rat; C495694:Slc2a4 protein, rat; D007532:Isoleucine; D019869:Phosphatidylinositol 3-Kinases; D005947:Glucose