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Glutathione Articles - Cardiovascular Disease
Diurnal variation in glutathione and cysteine redox states in human
plasma
Roberto A Blanco, Thomas R Ziegler, Bryce A
Carlson, Po-Yung Cheng, Youngja Park, George A Cotsonis, Carolyn Jonas
Accardi and Dean P Jones
Am J Clin Nutr 2007 Oct;86(4):1016–23.
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ABSTRACT
Background: Plasma
glutathione/glutathione disulfide (GSH/GSSG) and cysteine/cystine (Cys/CySS)
couples are oxidized in humans in association with oxidative stress and
cardiovascular disease risk. Animal studies show that both pools undergo
diurnal variations associated with dietary intake of sulfur amino acids.
Objective: The objective of this study was to determine whether the
redox state of GSH, Cys, GSH/GSSG, or Cys/CySS undergoes diurnal
variation in healthy adults.
Design: Plasma samples were collected every hour for 24 h from 63
persons aged 18–86 y who were consuming normal food (protein, 0.8 g ·
kg–1 · d–1; sulfur amino acids, 20 mg·kg–1·d–1) at standardized
mealtimes. Measurements of Cys, CySS, GSH, and GSSG were used with the
Nernst equation to calculate the redox states.
Results: Plasma Cys and GSH concentrations varied with the time of day.
The highest values for plasma Cys occurred 3 h after meals. Glutathione
was maximal 6 h after peak plasma Cys. The calculated redox states of
the GSH/GSSG and Cys/CySS couples varied in association with the
concentrations of the thiol forms. Maximal reduction and oxidation of
the Cys/CySS couple occurred at 2130 and 0630, whereas the respective
values for the GSH/GSSG couple occurred at 0330 and 1330. The mean
diurnal variation for Cys/CySS redox in persons aged 60 y was 1.8-fold
that in persons aged <40 y.
Conclusions: Cys/CySS and GSH/GSSG redox states in human plasma undergo
diurnal variation with an increased magnitude of variation in Cys/CySS
redox state in older persons. This variation could alter sensitivity to
oxidative stress over a course of hours.
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