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Decreased expression of the vitamin C transporter SVCT1 by ascorbic acid in a human intestinal epithelial cell line

Published online by Cambridge University Press:  09 March 2007

Lauren MacDonald ,
Alfred E. Thumser  and
Paul Sharp
Lauren MacDonald
Affiliation:
Centre for Nutrition and Food Safety, School of Biomedical and Life Sciences, University of Surrey, Guildford GU2 7XH, UK
Alfred E. Thumser
Affiliation:
Centre for Nutrition and Food Safety, School of Biomedical and Life Sciences, University of Surrey, Guildford GU2 7XH, UK
Paul Sharp*
Affiliation:
Centre for Nutrition and Food Safety, School of Biomedical and Life Sciences, University of Surrey, Guildford GU2 7XH, UK
*
*Corresponding author: Dr Paul Sharp, fax +44 1483 576978, email [email protected]
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Abstract

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Vitamin C (ascorbic acid) is an essential nutrient that is involved in a number of cellular processes. However, unlike most mammals, man is unable to synthesize vitamin C and it must therefore be acquired from the diet. Absorption of vitamin C is achieved by two transporters, SVCT1 and SVCT2, recently cloned from rat and human kidney. SVCT1 is thought to be the predominant transporter in the intestine. Vitamin C supplements are increasingly common, thus contributing to an increased dietary load, and therefore the aim of the present study was to investigate the effect of high doses of ascorbic acid on SVCT1 expression. Using the Caco-2 TC7 cell model of small intestinal enterocytes, we measured the effects of ascorbic acid (4·5 mg/ml culture medium) on L-[14C]ascorbic acid uptake and SVCT1 expression (determined by reverse transcription-polymerase chain reaction). Ascorbic acid uptake was decreased significantly in Caco-2 TC7 cells exposed to ascorbate for 24 h (-50 %, P<0·0005). Expression of SVCT1 was also significantly reduced by exposure to elevated levels of ascorbate for 24 h (-77 %, P<0·005). Taken together these results suggest that high-dose supplements might not be the most efficient way of increasing the body pool of vitamin C.

Keywords

Ascorbic acidAbsorptionTransporterssupplements
Type
Short communication
Information
British Journal of Nutrition , Volume 87 , Issue 2 , February 2002 , pp. 97 - 100
Copyright
Copyright © The Nutrition Society 2002

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