Background 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. Methods 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. Results 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). Discussion NLNG increased multiple blood glutathione parameters compared to placebo. Future research should examine whether NLNG can attenuate oxidative stress.

Intro: Glutathione is endogenous within human plasma, erythrocyte lysate and is also bound to the protein within plasma. Glutathione mediates redox chemistry and prevents oxidative damage within and around cellular components via reduction of reactive species (e.g. reactive oxygen, nitrogen, or sulfur species). Polyphenols and antioxidants have been shown to improve NO bioavailability which may reduce long term incidence of endothelial dysfunction. Less is known about whether changes in antioxidant capacity augments the risk of developing hypertension. Hypothesis: We hypothesized that acute glutathione supplementation would decrease arterial stiffness and reduce both brachial (bBP) and central blood pressure (cBP) in healthy male and female volunteers. Methods: Six males and six females (25 ± 3 and 22 ± 1 years, respectively) participated in a randomized, double blind, placebo controlled, crossover protocol. On two visits separated by 1 week, following a 12-hour fast, participants consumed either a placebo or glutathione (negligible and 200 mg, respectively) supplement via 90 second sublingual absorption which was then swallowed. Concentrations of oxidized (GSSG) and reduced glutathione (GSH) were spectrophotometrically measured in plasma (protein-bound) and erythrocyte lysate using a kinetic, enzymatic assay. Arterial stiffness was measured via pulse wave velocity (PWV) using applanation tonometry, and cBP was determined non-invasively using pulse wave analysis. All data were recorded before supplementation (baseline) and at 10, 30, 60 and 120 minutes post-consumption. Results: Linear mixed effect models revealed a significant (p<0.01) increase in total glutathione (GSH+GSSG) in the supplement group compared to placebo across all post-supplementation time points with the greatest increase occurring at 120 minutes (mean 99.0; 95%CI: 7.9,190.1). At 120 minutes post-consumption, no difference was present between glutathione and placebo groups for PWV (5.86 ± 1.19 and 6.08 ± 1.25 m/s, respectively; p=0.43), resting heart rate (52.95 ± 3.55 and 55.83 ± 6.36, respectively; p=0.16), systolic bBP (123.05 ± 12.75 and 123.13 ± 14.52 mmHg; p=0.22), diastolic bBP (71.81 ± 7.87 and 74.21 ± 6.53; p=0.48), systolic cBP (108.05 ± 10.45 and 108.68 ± 11.14 mmHg, respectively; p=0.11) and diastolic cBP (72.03 ± 7.82 and 74.94 ± 6.42 mmHg, respectively; p=0.46). Conclusion: Young healthy males and females experienced an increase in circulating humoral antioxidants in response to glutathione supplementation. However, supplementation had minimal effects on resting hemodynamics. Future research should examine glutathione supplementation’s effect in participants with decreased antioxidant capacity and increased oxidative stress including patients with known disease such as hypertension or peripheral artery disease.

Introduction: Nitric oxide (NO) is a vasodilator that increases blood flow by promoting relaxation of endothelium. Dietary nitrate supplementation increases plasma nitrite, a marker of overall NO bioavailability. Previously, acute dietary nitrate supplementation has been shown to reduce oxygen consumption and improve tolerance during submaximal exercise in healthy populations. Less is known about the effect of dietary nitrate on oxygen consumption at rest. Hypothesis: We hypothesized that dietary nitrate supplementation would reduce resting metabolic rate (RMR) and oxidative stress (8-isoprostane) at rest, via enhanced NO bioavailability via the oxygen independent Nitrate-Nitrite-Nitric Oxide pathway in healthy, young males. Methods: In a randomized, double-blind, cross-over study, ten healthy, young males (21 ± 2 years) visited the laboratory on 5 separate occasions. Participants completed informed consent paperwork and underwent protocol familiarization during visit 1. Prior to visits 2 and 4, participants fasted for 12 hours and adhered to an NIH-approved low-nitrate diet for 48 hours. During visits 2 and 4, an initial blood draw was performed to analyze baseline plasma nitrite and 8-isoprostane. Participants then completed a 30-minute resting metabolic rate (RMR) test. Two hours prior to visits 3 and 5, participants consumed either a placebo or dietary nitrate supplement (negligible and 6.2 mmol nitrate, respectively). During visits 3 and 5, participants also had blood drawn for analysis of the previously stated measurements, and completed an RMR test. Visits 2 and 3 were on consecutive days, followed by a week-long washout period between visit 3 and visit 4, while visit 4 and 5 also occurred on consecutive days. Results: Plasma nitrite significantly increased following dietary nitrate consumption compared to baseline values (27.56 ± 7.58 and 1.25 ± 1.51 arbitrary units, respectively). No difference was present between nitrate and baseline measurements for 8-isoprostane (155.75 ± 57.01 and 198.42 ± 66.44 pg/mL, respectively; p=0.55) and RMR (2086.60 ± 202.23 and 2050.00 ± 209.23 kcal/day, respectively; p=0.13). Conclusion: Dietary nitrate supplementation increases plasma nitrite, but does not change resting metabolic rate following an acute dose of dietary nitrate in healthy males. Individuals consuming dietary nitrate as an ergogenic aid during exercise may not, however, experience similar changes in their resting metabolism. The lack of change in oxidative stress may have been associated with the overall health of the cohort examined. Future research should investigate the clinical implications of dietary nitrate in populations with decreased NO bioavailability and associated endothelial disfunction (and elevated oxidative stress). In such populations, dietary nitrate may provide benefit. However, in a healthy cohort, dietary nitrate exerts minimal effects.

Intro: Hypertension is a prominent risk factor for cardiovascular disease and arterial stiffness is a related predictor of both mortality and longitudinal onset of hypertension in normotensive individuals. Both vascular compliance and blood pressure have been shown to improve following dietary nitrate supplementation in some healthy and diseased individuals. Dietary nitrate supplementation increases plasma nitrite and may, therefore, enhance bioavailability of endothelium derived nitric oxide. Chronic increased flow mediated dilation (FMD) and reduction of pulse wave velocity (PWV) reduce a person’s long-term risk for developing endothelial dysfunction, atherosclerosis and hypertension. Hypothesis: We hypothesized that an acute dose of dietary nitrate would improve FMD, decrease PWV and reduce central blood pressure (cBP) in healthy, young females. Methods: Seven healthy, young (21 ± 2 years) females participated in a randomized, double blind, placebo controlled, crossover protocol. Participants had endothelial function measured via FMD, arterial stiffness via PWV and applanation tonometry, and cBP was determined non-invasively using pulse wave analysis following a 12-hour fasting period and 48-hour NIH approved low nitrate diet. Baseline values were measured the day before each treatment visit (placebo or nitrate-rich, separated by a 1-week washout period). Participants consumed either a placebo or nitrate-rich supplement (negligible and 6.2 mmol nitrate, respectively) 2 hours prior to their laboratory visit. Upon arrival, blood was drawn and participants assumed a supine position for 15 minutes. Then brachial artery FMD was assessed via high definition ultrasound imaging following 5 minutes of proximal forearm occlusion, followed by PWV and central blood pressure measurements. Results: Plasma nitrite was elevated following consumption of the nitrate rich supplement compared to placebo (26.33 ± 15.76 and 1.18 ± 0.96 arbitrary units, respectively; p<0.05). However, there was no difference between nitrate rich and placebo treatments for endothelial function as measured by FMD (10.33 ± 1.82 and 9.11 ± 5.43%, respectively; p=0.70). No difference was present between nitrate and placebo groups for PWV (5.99 ± 0.85 and 6.16 ± 0.80 m/s, respectively; p=0.90), systolic cBP (101.57 ± 9.29 and 96.90 ± 20.95 mmHg, respectively; p=0.40) and diastolic cBP (72.57 ± 7.67 and 73.20 ± 5.01 mmHg, respectively; p=0.97). Conclusion: While a single dose of dietary nitrate does increase plasma nitrite, supplementation has minimal effects on FMD, PWV and cBP in young healthy females. Future research should examine longer duration supplementation protocols as well as the changes in vascular health of patients with known disease such as hypertension or peripheral artery disease.