Abstract
Purpose: :
Amino acids in the form of mixtures have been shown to significantly reduce the blood glucose levels in hyperglycemia as seen in our previous studies. We investigated the effect of a specific amino acids mixture (AAM) on the activity of IRTK (Insulin receptor tyrosine kinase), PI3K and GLUT4 in CHO-K1 cells exposed to high glucose.
Methods: :
CHO-K1 Cells were exposed to varying amounts of glucose (concentration: 7.0, 12.0 and 27.0 mM), and L-amino acids mixture (AAM concentration: 0.25, 1.0, 5.0 and 20 mM). At the end of 8 min of exposure, the cell lysate was subjected to IRTK and PI3K activity by radiolabelled 32P (ATP) incorporation using autoradiography. GLUT4 expression was done by FACS for two different amino acids compositions (I & II). The cell morphology was observed by phase contrast microscopy.
Results: :
CHO-K1 cells on exposure to 5 mM and 20 mM amino acids mixture showed a significant improvement in the activity of IRTK (p=0.03,0.05 respectively), when the glucose concentration was 7mM. At high glucose concentration of both 12 mM and 27 mM, the presence of 20 mM AAM showed a significant increase in the activity of IRTK (p=0.047 and p=0.037 respectively). The PI3K activity was also significantly increased in the presence of both 1.0 mM & 5 mM AAM (p=0.05), when glucose concentration was 7mM. At high concentration of glucose i.e., at 27 mM, the presence of 20 mM AAM significantly improved the activity (p=0.03). Concomitantly there was an increase in the GLUT4 expression in the presence of AAM composition I and II though it was comparatively higher in composition II. The morphology also showed the protective effect of the AAM in a dose depended manner depending upon the AAM concentration.
Conclusions: :
At high glucose concentration the presence of amino acids mixture significantly increases the specific activity of IRTK and PI3K depending on the concentration of AAM. The increase in GLUT4 expression was also seen in high glucose concentration which also varied with composition of AAM. Thus amino acids in terms of its concentration and composition may play a role in the glucose uptake and therefore in the glucose metabolism and energy production in hyperglycemia.
Keywords: signal transduction • diabetes • nutritional factors