Insulin Induces an Increase in Cytosolic Glucose Levels in 3T3-L1 Cells with Inhibited Glycogen Synthase Activation

International Journal of Molecular Sciences

Helena H. Chowdhury¹  Marko Kreft¹  Jørgen Jensen²  Robert Zorec¹ 

[1]Celica, Biomedical, Tehnološki park 24, 1000 Ljubljana, Slovenia

[2] E-Mails:

[3]Department of Physical Performance, Norwegian School of Sports Sciences, P.O. Box N-4014 Ullevål Stadion, 0806 Oslo, Norway

[4] E-Mail:

关键词: glucose;    FRET;    nanosensor;    3T3-L1 fibroblast;    insulin;    glycogen;   

DOI  :  10.3390/ijms151017827

来源: mdpi

【 摘 要 】

Glucose is an important source of energy for mammalian cells and enters the cytosol via glucose transporters. It has been thought for a long time that glucose entering the cytosol is swiftly phosphorylated in most cell types; hence the levels of free glucose are very low, beyond the detection level. However, the introduction of new fluorescence resonance energy transfer-based glucose nanosensors has made it possible to measure intracellular glucose more accurately. Here, we used the fluorescent indicator protein (FLIPglu-600µ) to monitor cytosolic glucose dynamics in mouse 3T3-L1 cells in which glucose utilization for glycogen synthesis was inhibited. The results show that cells exhibit a low resting cytosolic glucose concentration. However, in cells with inhibited glycogen synthase activation, insulin induced a robust increase in cytosolic free glucose. The insulin-induced increase in cytosolic glucose in these cells is due to an imbalance between the glucose transported into the cytosol and the use of glucose in the cytosol. In untreated cells with sensitive glycogen synthase activation, insulin stimulation did not result in a change in the cytosolic glucose level. This is the first report of dynamic measurements of cytosolic glucose levels in cells devoid of the glycogen synthesis pathway.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.