Insulin but not phlorizin treatment induces a transient increase in GLUT2 gene expression in the kidney of diabetic rats.
OBJECTIVE
Increases in the renal glucose transporter gene expression are involved in renal tubule-glomerular diseases. Here we investigate the GLUT2 gene expression changes in the kidney of diabetic rats, by using insulin or phlorizin treatment.


METHODS
Rats were rendered diabetic and studied 20 days later: 4-12 h after one single injection of insulin or phlorizin, and 1-6 days after insulin or phlorizin injection twice a day, comparing with diabetic rats injected with placebo. GLUT2 was investigated by Northern and Western analysis.


RESULTS
In 20-day diabetic rats, acute treatment with insulin lowered the plasma glucose and increased the GLUT2 mRNA ( approximately 100%, p < 0.001) without changes in the protein content, while phlorizin lowered the plasma glucose, but changed neither the GLUT2 mRNA nor the protein expression. Twenty-four hours of insulin treatment increased both GLUT2 mRNA ( approximately 100%, p < 0.001) and protein ( approximately 50%, p < 0.01), but no effects of phlorizin were observed. After 6 days, insulin and phlorizin similarly reduced glycemia, with opposite effects upon plasma insulin and urinary glucose, and both treatments decreased GLUT2 mRNA and protein (p < 0.05).


CONCLUSIONS
In kidney of diabetic rats, an initial and transient upregulation of GLUT2 was induced specifically by insulin only. The 6-day normalization of GLUT2, however, was induced by both insulin and phlorizin treatment, which seems to be related to the plasma glucose lowering.
Freitas
Helayne Soares
HS
Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil.
D'Agord Schaan
Beatriz
B
da Silva
Robinson Sabino
RS
Okamoto
Maristela Mitiko
MM
Oliveira-Souza
Maria
M
Machado
Ubiratan Fabres
UF
D000818:Animals; D003920:Diabetes Mellitus / Q000188:drug therapy* / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects*; D051273:Glucose Transporter Type 2 / Q000378:metabolism*; D007004:Hypoglycemic Agents / Q000008:administration & dosage; D007328:Insulin / Q000008:administration & dosage*; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010695:Phlorhizin / Q000008:administration & dosage*; D051381:Rats; D017208:Rats, Wistar
D051273:Glucose Transporter Type 2; D007004:Hypoglycemic Agents; D007328:Insulin; C495683:Slc2a2 protein, rat; D010695:Phlorhizin