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Synthesis of erythrocyte glutathione in healthy adults consuming the safe amount of dietary protein

Record type: Article

Background: The finding that plasma glutathione turnover decreases as dietary protein intake decreases suggests that the safe amount of dietary protein, although sufficient for maintenance of nitrogen balance, may be insufficient for maintenance of cellular glutathione.
Objective: Our objective was to determine the effect of the safe protein intake on the erythrocyte glutathione synthesis rate and its relation with urinary 5-L-oxoproline excretion.
Design: Erythrocyte glutathione synthesis and urinary 5-L-oxoproline excretion were measured in young adults (6 men and 6 women) by using an infusion of [13C2]glycine on 3 occasions: initially during the subjects' habitual protein intake (1.13 g · kg–1 · d–1) and on days 3 and 10 of consumption of a diet providing the safe protein intake (0.75 g · kg–1 · d–1).
Results: Compared with baseline values, the fractional synthesis rate of erythrocyte glutathione was significantly lower (P < 0.05) on days 3 and 10 of the diet with the safe protein intake. Urinary 5-L-oxoproline excretion increased significantly (P < 0.05) above baseline by the third day of the diet with the safe protein intake and remained elevated. Erythrocyte glutathione concentrations and absolute synthesis rates decreased by day 3 but recovered to baseline values by day 10. Erythrocyte concentrations of cysteine, methionine, and serine remained unchanged, whereas erythrocyte concentrations of glycine, glutamic acid, and glutamine increased significantly by day 10.
Conclusion: During adaptation to the safe amount of dietary protein, there are changes in the concentration and kinetics of erythrocyte glutathione that suggest a reduced antioxidant capacity and possible increased susceptibility to oxidant stress.

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Citation

Jackson, Alan A., Gibson, Neil R., Lu, Yi and Jahoor, Farook (2004) Synthesis of erythrocyte glutathione in healthy adults consuming the safe amount of dietary protein American Journal of Clinical Nutrition, 80, (1), pp. 101-107.

More information

Published date: July 2004
Additional Information: Original research communication
Keywords: glutathione, glycine, safe amount of dietary protein, amino acids, nitrogen balance, 5-L-oxoproline

Identifiers

Local EPrints ID: 25659
URI: http://eprints.soton.ac.uk/id/eprint/25659
ISSN: 0002-9165
PURE UUID: 2804fd44-224f-4faa-8c6c-d9e5af100b40

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Date deposited: 20 Apr 2006
Last modified: 17 Jul 2017 16:09

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Contributors

Author: Alan A. Jackson
Author: Neil R. Gibson
Author: Yi Lu
Author: Farook Jahoor

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