4-Hydroxyisoleucine stimulates glucose uptake by increasing surface GLUT4 level in skeletal muscle cells via phosphatidylinositol-3-kinase-dependent pathway

Eur J Nutr. 2012 Oct;51(7):893-8. doi: 10.1007/s00394-012-0374-9. Epub 2012 May 19.


Purpose: 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.

Conclusion: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cattle
  • Cell Membrane / drug effects
  • Gene Expression Regulation
  • Glucose / pharmacokinetics*
  • Glucose Transporter Type 1 / genetics
  • Glucose Transporter Type 1 / metabolism
  • Glucose Transporter Type 4 / genetics
  • Glucose Transporter Type 4 / metabolism*
  • Insulin / metabolism
  • Isoleucine / analogs & derivatives*
  • Isoleucine / pharmacology
  • Muscle Fibers, Skeletal / cytology
  • Muscle Fibers, Skeletal / drug effects*
  • Muscle Fibers, Skeletal / metabolism
  • Phosphatidylinositol 3-Kinases / genetics
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphorylation
  • Plant Extracts / pharmacology*
  • Protein Transport / drug effects
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Rats
  • Seeds / chemistry
  • Signal Transduction
  • Trigonella / chemistry


  • 4-hydroxyisoleucine
  • Glucose Transporter Type 1
  • Glucose Transporter Type 4
  • Insulin
  • Plant Extracts
  • RNA, Messenger
  • Slc2a1 protein, rat
  • Slc2a4 protein, rat
  • Isoleucine
  • Phosphatidylinositol 3-Kinases
  • Glucose