Mechanical stress and glucose concentration modulate glucose transport in cultured rat podocytes.
BACKGROUND
Recent studies show that mechanical stress modifies both morphology and protein expression in podocytes. Ambient glucose is another factor modulating protein synthesis in these cells. In diabetes, podocytes experience elevated glucose concentrations as well as mechanical strain generated by high intracapillary pressures. Both these factors are responsible for podocyte injury, leading to impairment of kidney glomerular function. In the present study, we examined the effects of glucose concentration and mechanical stress on glucose uptake in podocytes.


METHODS
Following a 24 h pre-incubation in low (2.5 mM, LG), normal (5.6 mM, NG) or high (30 mM, HG) glucose media, cultured rat podocytes were exposed to 4 h mechanical stress. We used the labelled glucose analogue, [3H]2-deoxy-D-glucose, to measure glucose uptake. The distribution of facilitative glucose transporters GLUT2 and GLUT4 was assessed by flow cytometry.


RESULTS
In the control (static) cells, glucose uptake was similar in the three glucose groups. In mechanically stressed podocytes, glucose uptake increased 2-fold in the LG and NG groups but increased 3-fold in the HG group. In the NG cells, mechanical load increased the membrane expression of GLUT2 and reduced the membrane-bound GLUT4. In stretched HG cells, the membrane expression of both GLUT2 and GLUT4 was decreased. High glucose decreased the plasma membrane GLUT2 content in the stretched cells, whereas both static and stretched podocytes showed an elevation in GLUT4.


CONCLUSIONS
Mechanical stress potentiated glucose uptake in podocytes and this effect was enhanced by high ambient glucose. The decreased expression of GLUT2 and GLUT4 on the surface of stretched cells suggests that the activity of other glucose transporters may be regulated by mechanical stress in podocytes.
Lewko
Barbara
B
Department of Immunopathology, Medical University of Gdansk, ul. Debinki 7, 80-952 Gdansk, Poland. blew@amedec.amg.gda.pl
Bryl
Ewa
E
Witkowski
Jacek M
JM
Latawiec
Elzbieta
E
Angielski
Stefan
S
Stepinski
Jan
J
D000818:Animals; D001692:Biological Transport; D002478:Cells, Cultured; D005260:Female; D005947:Glucose / Q000378:metabolism*; D051273:Glucose Transporter Type 2; D051275:Glucose Transporter Type 4; D007678:Kidney Glomerulus / Q000166:cytology / Q000502:physiology*; D007700:Kinetics; D009004:Monosaccharide Transport Proteins / Q000235:genetics; D009124:Muscle Proteins / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D013314:Stress, Mechanical
D051273:Glucose Transporter Type 2; D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495694:Slc2a4 protein, rat; D005947:Glucose