Dietary sulfur amino acid effects on fasting plasma cysteine/cystine redox potential in humans

Abstract

Objective-Oxidation of plasma cysteine/cystine (Cys/CySS) redox potential (E h CySS) has been associated with risk factors for cardiovascular disease in humans. Cys and CySS are derived from dietary sulfur amino acids (SAA), but the specific effects of SAA depletion and repletion on Cys/ CySS redox indices are unknown. The present study examined the effect of dietary SAA intake level on free Cys, free CySS and E h CySS in human plasma under fasting conditions.Research Methods and Procedures-Healthy individuals aged 18-36 y (n=13) were equilibrated to foods providing the RDA for SAA and then fed chemically defined diets without SAA (0 mg·kg −1 ·d −1 ; n=13) followed by SAA at levels approximating the mean (56 mg·kg −1 ·d −1 ; n=8) or 99th percentile (117 mg·kg −1 ·d −1 ; n=5) intake levels of Americans. Fasting plasma samples were collected daily during 4-d study periods and analyzed for free Cys, free CySS and the E h CySS.Results-The SAA-free diet significantly (p<0.05) decreased plasma free Cys concentrations and oxidized E h CySS values after 4 days of SAA depletion. With SAA repletion at 56 mg·kg −1 ·d − 1 , plasma free Cys increased significantly and values for E h CySS became more reducing. Administration of a diet providing a higher dose of SAA (117 mg·kg −1 ·d −1 ) resulted in a significantly higher level of free Cys and a more reducing E h CySS.Conclusions-These results show that free Cys and Cys/CySS redox potential (E h CySS) in fasting plasma are affected by dietary SAA intake level in humans. Significant changes occur slowly over 4 days with insufficient SAA intake, but rapidly (after 1 day) with repletion.

Plasma Cysteine/Cystine Reduction Potential Correlates with Plasma Creatinine Levels in Chronic Kidney Disease

“…The plasma concentrations found for free Cys and free Cyss in healthy populations are highly variable among different papers. Our free Cys levels were approximately 4–5 times higher than those described by studies that employed fluorescence detection (table 1) [25,29,30], while our mean free Cyss concentration was lower than that found by these reports. Fluorescence detection of such thiols is very sensitive and reproducible but requires a derivatization step.…”

Physical training status determines oxidative stress and redox changes in response to an acute aerobic exercise

“…As mentioned before, glutathione couple GSH/GSSG is a critically important redox biomarker [38] which together with Cys/CySS participates in homeostasis of cellular redox [39]. For example, GSH/GSSG is involved in storage and transport of nitric oxide, reducing ribonucleotides to deoxyribonucleotides, processing of some proteins, interfering in redox signaling pathways, detoxification of xenobiotics [40], and finally protecting cells from oxidative stress [12].…”

Антиоксидантна Система Респіраторного Тракту Внутрішньоклітинний Антиоксидантний Захист У Респіраторному Тракті (Частина 2)

“…Глутатионовая система в антиоксидантной защите органов дыхания на данном этапе играет централь-ную роль. В зависимости от участия селена различа-ют селензависимые и селеннезависимые антиокси-дантные системы [9,23,36].…”