Changes in sodium or glucose filtration rate modulate expression of glucose transporters in renal proximal tubular cells of rat

Abstract

Renal glucose reabsorption is mediated by luminal sodium-glucose cotransporters (SGLTs) and basolateral facilitative glucose transporters (GLUTs). The modulators of these transporters are not known, and their substrates glucose and Na+ are potential candidates. In this study we examined the role of glucose and Na+ filtration rate on gene expression of glucose transporters in renal proximal tubule. SGLT1, SGLT2, GLUT1 and GLUT2 mRNAs were assessed by Northern blotting; and GLUT1 and GLUT2 proteins were assessed by Western blotting. Renal cortex and medulla samples from control rats (C), diabetic rats (D) with glycosuria, and insulin-resistant 15-month old rats (I) without glycosuria; and from normal (NS), low (LS), and high (HS) Na+-diet fed rats were studied. Compared to C and I rats, D rats increased (P < 0.05) gene expression of SGLT2 by approximately 36%, SGLT1 by approximately 20%, and GLUT2 by approximately 100%, and reduced (P < 0.05) gene expression of GLUT1 by more than 50%. Compared to NS rats, HS rats increased (P < 0.05) SGLT2, GLUT2, and GLUT1 expression by approximately 100%, with no change in SGLT1 mRNA expression, and LS rats increased (P < 0.05) GLUT1 gene expression by approximately 150%, with no changes in other transporters. In summary, the results showed that changes in glucose or Na+ filtrated rate modulate the glucose transporters gene expression in epithelial cells of the renal proximal tubule.