Oral supplementation with liposomal glutathione elevates body stores of glutathione and markers of immune function

Abstract

Background/objectives: Glutathione (GSH) is the most abundant endogenous antioxidant and a critical regulator of oxidative stress. Maintenance of optimal tissues for GSH levels may be an important strategy for the prevention of oxidative stress-related diseases. We investigated if oral administration of liposomal GSH is effective at enhancing GSH levels in vivo.

Subjects/methods: A 1-month pilot clinical study of oral liposomal GSH administration at two doses (500 and 1000 mg of GSH per day) was conducted in healthy adults. GSH levels in whole blood, erythrocytes, plasma and peripheral blood mononuclear cells (PBMCs) were assessed in 12 subjects at the baseline and after 1, 2 and 4 weeks of GSH administration.

Results: GSH levels were elevated after 1 week with maximum increases of 40% in whole blood, 25% in erythrocytes, 28% in plasma and 100% in PBMCs occurring after 2 weeks (P<0.05). GSH increases were accompanied by reductions in oxidative stress biomarkers, including decreases of 35% in plasma 8-isoprostane and 20% in oxidized:reduced GSH ratios (P<0.05). Enhancements in immune function markers were observed with liposomal GSH administration including Natural killer (NK) cell cytotoxicity, which was elevated by up to 400% by 2 weeks (P<0.05), and lymphocyte proliferation, which was elevated by up to 60% after 2 weeks (P<0.05). Overall, there were no differences observed between dose groups, but statistical power was limited due to the small sample size in this study.

Conclusions: Collectively, these preliminary findings support the effectiveness of daily liposomal GSH administration at elevating stores of GSH and impacting the immune function and levels of oxidative stress.

Figure 1:

Subject flowchart summary.

Figure 2:

Effect of liposomal glutathione supplementation on whole blood glutathione concentrations. Subjects were randomized to 500 or 1000 mg/d liposomal GSH for 4 weeks. Blood was collected at baseline and after 1, 2 and 4 weeks and free and protein-bound GSH was determined in whole blood (A & B) and in erythrocytes (C & D) as described in text. Whole blood levels are expressed as mmol/L (A) or percent change from baseline (B). Erythrocyte GSH levels are expressed as μmol/g hemoglobin (C) or percent change from baseline (D). Bars are mean ± SE. *Significantly different from baseline by repeated measures ANOVA, P<0.05.

Figure 3:

Effect of liposomal glutathione supplementation on plasma and PBMC glutathione concentrations. Subjects were randomized to 500 or 1000 mg/d liposomal GSH for 4 weeks. Blood was collected at baseline and after 1, 2 and 4 weeks and PBMCs were isolated and analyzed for GSH as described in text. Results are expressed as % changes from baseline in μmol/L of plasma (top panel) or μmol/10⁶ PBMCs (bottom panel). For plasma, baseline values ranged from 2.2 to 10.9 μmol/L (mean±SE: 4.57±0.62) for all subjects [low dose group: 2.2 to 10.9 (mean±SE: 4.63±1.29); high dose group: 3.94 to 5.15 (mean±SE: 4.51±0.17)]. For PBMCs, baseline values ranged from 0.23 to 1.34 μmol/10⁶ cells (mean±SE: 0.89±0.11) for all subjects [low dose group: 0.23 to 1.34 (mean±SE: 0.77±0.19); high dose group: 0.67 to 1.34 (mean±SE: 1.01±0.11)]. Bars are mean ± SE. *Significantly different from baseline by repeated measures ANOVA, P<0.05.

Figure 4:

Effect of liposomal glutathione supplementation on blood biomarkers of oxidative stress. Subjects were randomized to 500 or 1000 mg/d liposomal GSH for 4 weeks. Blood was collected at baseline and after 1, 2 and 4 weeks. Top panel: GSH and its major oxidized forms GSSG and GSSP were determined in whole blood as described in text. Baseline ratios ranged from 0.24 to 0.42 (mean±SE: 0.31±0.02) for all subjects [low dose group: 0.24 to 0.34 (mean±SE: 0.30±0.02); high dose group: 0.25 to 0.42 (mean±SE: 0.32±0.02)]. Bottom panel: plasma 8-isoprostane levels were measured by ELISA as described in text. Results are expressed as % changes in pg/ml from baseline. Baseline values ranged from 63.1 to 1170 pg/ml (mean±SE: 214±90.6) for all subjects [low dose group: 78.6 to 1170 (mean±SE: 331±123); high dose group: 63.1 to 181 (mean±SE: 97.7±12.8)]. Results are expressed as % of baseline and symbols and bars are mean ± SE. *Significantly different from baseline by repeated measures ANOVA, P<0.05.

Figure 5:

Effect of liposomal glutathione supplementation on lymphocyte proliferation and NK cell cytotoxicity. Subjects were randomized to 500 or 1000 mg/d liposomal GSH for 4 weeks. Blood was collected at baseline and after 1, 2 and 4 weeks and PBMCs were isolated. Top panel: Lymphocyte proliferation was assessed by measuring ³H-thymidine incorporation after incubation with PHA as described in the text. Results are expressed as % changes in CPM from baseline. Baseline values ranged from 20021 to 88197 CPM (mean±SE: 42105±6736) for all subjects [low dose group: 22270 to 40295 (mean±SE: 32596±1945); high dose group: 20021 to 88197 (mean±SE: 51613±8830)]. Bottom panel: NK cytotoxicity was assessed using ⁵¹Cr labeled human K562 cells as the target and measuring the percent of target cells lysed after incubation with lymphocytes for 4 hr at 37°C. Results are expressed as % changes in the extent of cell lysis from baseline. Baseline values ranged from 0.41 to 9.08% lysis (mean±SE: 4.04±0.82) for all subjects [low dose group: 0.41 to 7.73 (mean±SE: 3.89±0.89); high dose group: 1.41 to 9.08 (mean±SE: 4.19±0.83)]. Bars are mean ± SE. *Significantly different from baseline by repeated measures ANOVA, P<0.05.