Regulation of glucose transporters in human peritoneal mesothelial cells.
BACKGROUND
Risk factors for peritoneal fibrosis and mesothelial cell (MsC) injury in CAPD are infections and bioincompatibility of the dialysate, including high glucose concentrations. To study a potential link between dialysate and glucose toxicity in MsC, we investigated the expression of facilitative glucose transporters (GLUT), which could contribute to glucose toxicity.


METHODS
After induction of cell differentiation, MsC were incubated in regular medium or medium with 60 mM D-glucose, 30 mM glucose plus 30 mM mannitol, 60 mM mannitol, PD effluent, or with a cytokine mix. Expression of GLUT1, GLUT3, SGLT and GAPDH/L32 was studied by RNase protection assay. MsC were incubated under identical conditions with 14C-fluoro-deoxy-glucose for 30 minutes and glucose uptake was measured. To estimate Vmax and Km, 14C-fluoro-deoxy-glucose uptake rates were determined over a range of 0.6 to 10 mM unlabeled glucose.


RESULTS
The cytokine mix significantly stimulated GLUT1 expression (3-fold) and GLUT3 (1.7-fold). There was a 1.4-fold increase in GLUT1 (p<0.05) and a 1.7-fold increase in GLUT3 (p<0.05) after incubation in high glucose but not in mannitol or PD-effluent controls. Glucose uptake studies confirmed this increase after incubation in 30 mM (p<0.05) and 60 mM glucose solutions. Kinetic studies showed the Km was approximately 3.7 mM for this transport.


CONCLUSIONS
GLUT mRNA expression and glucose uptake are induced by high ambient glucose concentrations and cytokines. Unlike many other cells, MsC are not able to protect themselves from increased glucose concentrations by downregulation of GLUTs. The intracellular glucose concentration may therefore increase during CAPD, affecting growth factor expression and glycosylation, and contributing to glucose toxicity.
Fischereder
Michael
M
Medical Policlinic, Ludwig-Maximilians-University, Munich, Germany. michael.fischereder@klinik.uni-regensburg.de
Schröppel
Bernd
B
Wiese
Patrick
P
Fink
Monika
M
Banas
Bernhard
B
Schmidbauer
Stefan
S
Schlöndorff
Detlef
D
D001693:Biological Transport, Active / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D004847:Epithelial Cells / Q000502:physiology; D005355:Fibrosis / Q000209:etiology / Q000473:pathology; D005947:Glucose / Q000494:pharmacology*; D051274:Glucose Transporter Type 3; D006801:Humans; D007676:Kidney Failure, Chronic / Q000628:therapy; D008353:Mannitol / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins; D010531:Peritoneal Dialysis, Continuous Ambulatory / Q000009:adverse effects; D010532:Peritoneal Diseases / Q000209:etiology / Q000473:pathology; D010537:Peritoneum / Q000166:cytology*; D011336:Probability; D012313:RNA / Q000032:analysis; D012680:Sensitivity and Specificity
D017077:Culture Media, Conditioned; D051274:Glucose Transporter Type 3; D008562:Membrane Glycoproteins; D009004:Monosaccharide Transport Proteins; D009419:Nerve Tissue Proteins; C495687:SLC2A3 protein, human; D008353:Mannitol; D012313:RNA; D005947:Glucose