Date Published: April 30, 2019
Publisher: Public Library of Science
Author(s): Brianna K. Bruggeman, Katharine E. Storo, Haley M. Fair, Andrew J. Wommack, Colin R. Carriker, James M. Smoliga, Oliver Chen.
Glutathione is an endogenous antioxidant found in oxidized (GSSG) and reduced (GSH) forms. Glutathione depletion is indicative of oxidative stress and occurs in various pathological conditions and following extreme exercise activity. Raising blood glutathione concentration has potential to attenuate and prevent chronic disease and also to improve recovery from exercise. There are a number of challenges to achieving this through traditional dietary supplements, and thus there is a need to develop optimized delivery methods to improve blood glutathione status. This study evaluated the effect of a novel glutathione formulation on blood glutathione parameters in healthy individuals.
15 (8 male) healthy individuals (25±5y old, 78.0±14.6kg) participated in a single-blinded randomized placebo-controlled crossover study, with a minimum one-week washout period between treatments. Participants were overnight fasted and administered 1mL of a non-liposomal nano-size glutathione solution (NLNG) containing 200mg of glutathione or 1mL of placebo lacking glutathione. The solution was held in the mouth for 90 seconds before the remainder was swallowed. Blood was collected at baseline, 5, 10, 30, 60 and 120 minutes post-treatment. Protein-bound plasma and erythrocyte lysate concentrations of GSH and GSSG were measured at all time points using previously validated procedures. Linear mixed effects models were used to compare differences between baseline and post-treatment glutathione concentrations between NLNG and placebo for each parameter.
There was a significant main effect for treatment type, such that increases in GSH concentration in erythrocyte lysate were greater following NLNG than placebo (p = 0.001). Similar significant main effects for treatment were also found for total (protein bound + erythrocyte lysate) GSH (p = 0.015) and GSSG (p = 0.037) concentration, as well as total blood glutathione pool (GSH+GSSG, p = 0.006).
NLNG increased multiple blood glutathione parameters compared to placebo. Future research should examine whether NLNG can attenuate oxidative stress.
Glutathione is an endogenous antioxidant which is involved in numerous signaling pathways throughout various tissues in the body. Oxidized glutathione (GSSG) can be reduced by glutathione reductase . In its reduced state (GSH), glutathione serves to mediate oxidative stress and signaling by covalently scavenging various reactive species, such as hydrogen peroxide and superoxide, as a ubiquitous low-molecular-weight thiol . Glutathione synthesis can occur in most cells types, with the liver having the greatest role in synthesis and interorgan homeostasis , and thus it is not an essential nutrient. Nonetheless, GSH depletion can occur in various conditions associated with excessive formation of reactive oxygen and nitrogen species (RONS) . This excessive production of radical oxidants can occur in pathological states where mitochondrial function is impaired , as is common in numerous metabolic diseases [4–6], as well as infection.
This study demonstrated that NLNG acutely increased total blood glutathione concentration using proven spectrophotometric detection methods to quantify reactive thiol species. While the analytical protocol does not disambiguate the structure of the reactive thiol species, direct reaction of GSH or other GSH-derived compounds, such as γGlu-Cys and Cys-Gly, is reliably determined using this methodology . Fig 1 suggests that this increase in total glutathione pool appears to mostly result from increased GSH bound to plasma proteins, though GSH in erythrocyte lysate and GSSG bound to plasma proteins also contribute to this. The baseline values for glutathione parameters in this study are generally within the range reported in other studies [24, 25]. However, changes in GSH parameters within this study are not readily comparable to that of other studies attempting to alter blood glutathione pool due to differences in research methodology, including the specialized nanoformulation of glutathione utilized in this study.