Absence of ClC5 in Knockout Mice Leads to Glycosuria, Impaired Renal Glucose Handling and Low Proximal Tubule GLUT2 Protein Expression

• Published in: Cellular physiology and biochemistry Vol. 20; no. 5; pp. 455 - 464
• Main Authors: Souza-Menezes, Jackson, Morales, Marcelo, Tukaye, Deepali, Guggino, Sandra, Guggino, William
• Format: Journal Article
• Language: English
• Published: Basel, Switzerland 01.01.2007
• Subjects: Animals; Chloride Channels - deficiency; Chloride Channels - genetics; Chloride Channels - metabolism; Glucose - metabolism; Glucose Tolerance Test; Glucose Transporter Type 2 - metabolism; Glycosuria - genetics; Glycosuria - metabolism; Insulin - metabolism; Insulin Secretion; Low Density Lipoprotein Receptor-Related Protein-2 - metabolism; Mice; Mice, Knockout; Original Paper; ClC-5; Proximal tubule; Glucose transporters and insulin; Glucose homeostasis; Megalin
• ISSN: 1015-8987; 1421-9778
• DOI: 10.1159/000107529

Glycosuria is one of the well-documented characteristics in ClC-5 knockout (KO) mice and patients with Dent’s disease. However, the underlying pathophysiology of its occurrence is unknown. In this study, we have compared ClC-5 KO mice with age and gender matched wild-type (WT) control mice to investigate if the underlying cause of manifested glycosuria is an impairment of glucose homeostasis and/or an alteration in expression levels of proximal tubule (PT) glucose transporters. We observed that, the blood glucose concentration (n=12, p<0.01) and the fractional excretion of glucose and insulin (n=6, p<0.05) were higher in KO mice. In contrast, the fasting blood glucose levels (n=7) were not significantly different in the two groups. Plasma glucose increased to a greater extent in KO mice (n=7, p<0.05) when challenged by an intraperitoneal injection of glucose. However, no peripheral tissue insulin resistance was observed following an intraperitoneal injection of insulin (n=9) in the KO mice. ELISA analysis demonstrated low plasma insulin concentrations after a 12 hour fasting period and also following glucose injection in KO mice. The total insulin released during a 2 hour period following glucose challenge was significantly lower in KO mice (n=6, p<0.05). By western blot, we observed a significant decrease in GLUT2 protein expression levels in isolated PT ((n=10, p<0.01)) of KO mice. This decrease in protein levels was corroborated by a significant decrease in GLUT2 mRNA levels estimated semi quantitatively by RT-PCR in isolated PT (n=10, p<0.01). No significant changes in mRNA expression levels of SGLT2, SGLT1 and GLUT1, as analyzed by RT-PCR, could be detected in the isolated PT (n=10). Also, we have shown by western blot analysis that expression of megalin is lower in the renal cortex of KO mice when compared to WT mice (n=3, p<0.05). Our results suggest that low plasma insulin concentration together with renal function changes observed in KO mice significantly contribute towards the glucose intolerance and documented glycosuria observed in this animal.