Absence of ClC5 in knockout mice leads to glycosuria, impaired renal glucose handling and low proximal tubule GLUT2 protein expression.

Abstract

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.

• Authors: Jackson Souza-Menezes, Marcelo M Morales, Deepali N Tukaye, Sandra E Guggino, William B Guggino
• Journal: Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology (Cell Physiol Biochem) Vol. 20 Issue 5 Pg. 455-64 ( 2007) ISSN: 1015-8987 [Print] Germany
• PMID: 17762172 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright (c) 2007 S. Karger AG, Basel.

Chemical References

• CLC5 protein, mouse
• Chloride Channels
• Glucose Transporter Type 2
• Insulin
• Low Density Lipoprotein Receptor-Related Protein-2
• Glucose

Topics

• Animals
• Chloride Channels (deficiency, genetics, metabolism)
• Glucose (metabolism)
• Glucose Tolerance Test
• Glucose Transporter Type 2 (metabolism)
• Glycosuria (genetics, metabolism)
• Insulin (metabolism)
• Insulin Secretion
• Low Density Lipoprotein Receptor-Related Protein-2 (metabolism)
• Mice
• Mice, Knockout