Transport of cycasin by the intestinal Na+/glucose cotransporter.
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| Abstract |
The medicinal and food use of seed from the cycad plant (Cycas spp.), which contains the neurotoxin cycasin, is a proposed etiological factor for amyotrophic lateral sclerosis/Parkinsonism dementia complex (ALS/PDC), a prototypical neurodegenerative disease found in the western Pacific. Cycasin, the beta-D-glucoside of methylazoxymethanol might enter neurons and other cells via a glucose transporter. Since the intestinal brush-border Na+/glucose cotransporter plays a major role in the absorption of monosaccharides, the following studies were conducted to determine if cycasin, the beta-D-glucoside of methylazoxymethanol, is a substrate for the transporter. We measured the ability of cycasin to (i) inhibit Na+/glucose uptake into rabbit intestinal brush-border membrane vesicles, and (ii) to generate current by the cloned Na+/glucose cotransporter (SGLT1) expressed in Xenopus laevis oocytes. The results show that cycasin inhibits Na(+)-dependent sugar transport in the vesicles, and cycasin generates phlorizin-sensitive currents in oocytes. We conclude that cycasin is a substrate for the intestinal brush-border Na+/glucose cotransporter, albeit with a lower affinity than D-glucose. This suggests that cycasin may be absorbed from the gut lumen by the cotransporter, and as a result either cycasin or the aglycone is presented to the blood-brain barrier for uptake into the brain.
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| Authors | B Hirayama, A Hazama, D F Loo, E M Wright, G E Kisby |
| Journal | Biochimica et biophysica acta (Biochim Biophys Acta) Vol. 1193 Issue 1 Pg. 151-4 (Jul 13 1994) ISSN: 0006-3002 [Print] Netherlands |
| PMID | 8038185 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.) |
| Chemical References |
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