Alterations of Renal Epithelial Glucose and Uric Acid Transporters in Fructose Induced Metabolic Syndrome.

BACKGROUND/AIMS: Hyperglycemia and hyperuricemia are two major disorders of Metabolic syndrome. Kidney plays a crucial role in maintaining the homeostasis of uric acid and glucose. The aim of the study was to examine the changes of renal glucose and uric acid transporters in animals with metabolic syndrome.

METHODS: Sprague-Dawley rats were fed with high fructose diet (60%) for 3 months (FR-3) and 5 months (FR-5). At the end study, serum and urine biochemical data were compared. Gene expression and protein abundance of renal GLUT1, GLUT2, GLUT9, SGLT1, SGLT2, UAT and URAT1 was investigated by using RT-PCR and immunohistochemical staining.

RESULTS: Metabolic syndrome was induced by high-fructose diet. Systolic blood pressure and proteinuria was significantly increased in FR-5 animals. In kidney tissue, gene expression of GLUT2 and SGLT2 increased significantly in a time dependent manner. GLUT9, SGLT1 and UAT were also significantly upregulated in FR-5. Immunohistochemical study showed a significant increase of SGLT1 in both FR-3 (413.5 ± 88.3% of control, p< 0.001) and FR-5 (677.6 ± 26.5% of control, p< 0.001). Also, SGLT2 protein was increased in both FR-3 (643.1 ± 41.3% of control, p< 0.001) and FR-5 (563.3 ± 21.7% of control, p< 0.001). Fructose rich food also induced increase of UAT by nearly 5-fold in both FR-3 and FR-5 (both p< 0.05) and more than 3-fold of GLUT-9 in FR-3 and FR-5 (both p< 0.05).

CONCLUSION: Long term high fructose diet induced metabolic syndrome with increased blood pressure and proteinuria in rats. Metabolic syndrome was associated with dual increase in renal glucose and uric acid transporters, including SGLT1, SGLT2, GLUT2, GLUT9 and UAT.