Fructose reabsorption by rat proximal tubules: role of Na+-linked cotransporters and the effect of dietary fructose
| Autor: | Jessica Asirwatham, Nancy J. Hong, Fara Saez, Jeffrey L. Garvin, Pablo D. Cabral, Agustin Gonzalez-Vicente |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
0301 basic medicine
medicine.medical_specialty Kidney food.ingredient Physiology Chemistry Reabsorption Phlorizin Sodium chemistry.chemical_element Fructose 030204 cardiovascular system & hematology Sugar transport Corn syrup 03 medical and health sciences chemistry.chemical_compound 030104 developmental biology 0302 clinical medicine Endocrinology food medicine.anatomical_structure Internal medicine medicine Cotransporter |
| Zdroj: | American Journal of Physiology-Renal Physiology. 316:F473-F480 |
| ISSN: | 1522-1466 1931-857X |
| Popis: | Fructose consumption has increased because of widespread use of high-fructose corn syrup by the food industry. Renal proximal tubules are thought to reabsorb fructose. However, fructose reabsorption (Jfructose) by proximal tubules has not yet been directly demonstrated, nor the effects of dietary fructose on Jfructose. This segment expresses Na+- and glucose-linked transporters (SGLTs) 1, 2, 4, and 5 and glucose transporters (GLUTs) 2 and 5. SGLT4 and -5 transport fructose, but SGLT1 and -2 do not. Knocking out SGLT5 increases urinary fructose excretion. We hypothesize that Jfructosein the S2 portion of the proximal tubule is mediated by luminal entry via SGLT4/5 and basolateral exit by GLUT2 and that it is enhanced by a fructose-enriched diet. We measured Jfructoseby proximal straight tubules from rats consuming either tap water (Controls) or 20% fructose (FRU). Basal Jfructosein Controls was 14.1 ± 1.5 pmol·mm−1·min−1. SGLT inhibition with phlorizin reduced Jfructoseto 4.9 ± 1.4 pmol·mm−1·min−1( P < 0.008), whereas removal of Na+diminished Jfructoseby 86 ± 5% ( P < 0.0001). A fructose-enriched diet increased Jfructosefrom 12.8 ± 2.5 to 19.3 ± 0.5 pmol·mm−1·min−1, a 51% increase ( P < 0.03). Using immunofluorescence, we detected luminal SGLT4 and SGLT5 and basolateral GLUT2; GLUT5 was undetectable. The expression of apical transporters SGLT4 and SGLT5 was higher in FRU than in Controls [137 ± 10% ( P < 0.01) and 38 ± 14% ( P < 0.04), respectively]. GLUT2 was also elevated by 88 ± 27% ( P < 0.02) in FRU. We conclude that Jfructoseby proximal tubules occurs primarily via Na+-linked cotransport processes, and a fructose-enriched diet enhances reabsorption. Transport across luminal and basolateral membranes is likely mediated by SGLT4/5 and GLUT2, respectively. |
| Databáze: | OpenAIRE |
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