title: Amino acids potentiate insulin signaling in CHO-K1 at high glucose conditions.
abstract: OBJECTIVE
  Amino acids reportedly increase the glucose uptake under high glucose conditions. However, there are controversies in the role of amino acids in diabetes mellitus. The present study explores the insulin signaling pathway involved in glucose uptake mediated by amino acids in CHO-K1 cells.
  
  
  METHODS
  CHO-K1 cells were exposed to normal (7 mM) and high glucose (17 and 27 mM) with 100 nM insulin in the presence and absence of amino acid mixtures (AAM) in varying concentration (5 and 20 mM) followed by the assays, insulin receptor tyrosine kinase (IRTK) and phosphatidylinositol 3 kinase (PI3K) by autoradiography, protein kinase B (Akt) and glucose transporter (GLUT4) by Western blot and glycogen synthase (GS) by HPLC.
  
  
  RESULTS
  The addition of 5 and 20 mM AAM significantly increased IRTK and PI3K activity (ANOVA p = 0.025, p = 0.003, respectively) with increasing glucose concentration. Addition of 5 mM AAM in the presence of normal glucose significantly increased the levels of phosphorylated Akt Ser473 (p = 0.02) with no significant change at high glucose. At 20 mM AAM there was a significant decrease in Akt phosphorylation (p = 0.035) that was increased by high glucose concentration. GLUT4 protein levels were increased with AAM (5 mM) along with increase in glycogen synthase activity at all glucose concentrations (p <0.05).
  
  
  CONCLUSIONS
  Amino acids as a mixture is beneficial in augmenting insulin signaling pathway via IRTK/PI3K/GLUT4 pathway along with activation of GS in CHO-K1 cells, thereby ensuring increased intracellular glucose availability.
authors.affiliation: Department of Biochemistry and Cell Biology, Vision Research Foundation, Chennai, India.
authors.forename: Radhakrishnan
authors.initials: R
authors.lastname: Selvi
authors.forename: Renganathan
authors.initials: R
authors.lastname: Bhuvanasundar
authors.forename: Aluru Venkata
authors.initials: AV
authors.lastname: Saijyothi
authors.forename: Konerirajapuram Natarajan
authors.initials: KN
authors.lastname: Sulochana
authors.forename: Narayanasamy
authors.initials: N
authors.lastname: Angayarkanni
mesh_terms: D000596:Amino Acids / Q000494:pharmacology*; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D005947:Glucose / Q000494:pharmacology*; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D006006:Glycogen Synthase / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D000596:Amino Acids; D051275:Glucose Transporter Type 4; D007328:Insulin; D006006:Glycogen Synthase; C410467:insulin receptor tyrosine kinase; D058539:Phosphatidylinositol 3-Kinase; D011505:Protein-Tyrosine Kinases; D051057:Proto-Oncogene Proteins c-akt; D005947:Glucose