Polymerized Whey Protein Concentrate-Based Glutathione Delivery System: Physicochemical Characterization, Bioavailability and Sub-Chronic Toxicity Evaluation

Abstract

Glutathione (GSH) is a powerful antioxidant, but its application is limited due to poor storage stability and low bioavailability. A novel nutrient encapsulation and delivery system, consisting of polymerized whey protein concentrate and GSH, was prepared and in vivo bioavailability, antioxidant capacity and toxicity were evaluated. Polymerized whey protein concentrate encapsulated GSH (PWPC-GSH) showed a diameter of roughly 1115 ± 7.07 nm (D₅₀) and zeta potential of 30.37 ± 0.75 mV. Differential scanning calorimetry (DSC) confirmed that GSH was successfully dispersed in PWPC particles. In vivo pharmacokinetics study suggested that PWPC-GSH displayed 2.5-times and 2.6-fold enhancement in maximum concentration (C_max) and area under the concentration-time curve (AUC) as compared to free GSH. Additionally, compared with plasma of mice gavage with free GSH, significantly increased antioxidant capacity of plasma in mice with PWPC-GSH was observed (p < 0.05). Sub-chronic toxicity evaluation indicated that no adverse toxicological reactions related to oral administration of PWPC-GSH were observed on male and female rats with a diet containing PWPC-GSH up to 4% (w/w). Data indicated that PWPC may be an effective carrier for GSH to improve bioavailability and antioxidant capacity.

Keywords: glutathione; pharmacokinetics; physicochemical properties; polymerized whey protein; toxicity.

Figure 1

(A) Particle size distribution, (B) zeta potential, (C) apparent viscosity of glutathione (GSH), polymerized whey protein concentrate (PWPC) and polymerized whey protein concentrate encapsulated GSH (PWPC-GSH). In Figure 1B, completely different lower-case letters between samples mean significant difference (p < 0.05).

Figure 2

(A) Differential scanning calorimetry (DSC), (B) FT-IR spectrum, (C) TEM image of PWPC and PWPC-GSH.

Figure 3

(A) GSH concentration (μM) in plasma of mice after oral administration of normal saline (control), PWPC, GSH, and PWPC-GSH. (B) In vivo antioxidant activity of plasma of mice after oral administration of normal saline (control), PWPC, GSH, and PWPC-GSH measured by an assay kit (ABTS method). In Figure 3B, completely different letter between samples at the same timepoint means significant difference (p < 0.05).

Figure 4

(A) Body weight and (B) food consumption curves of rats in a 28-day feeding test, 0%, 0.5%, 2% and 4% represent daily intake of 0% (w/w, control), 0.5% (w/w, low dose), 1% (w/w, medium dose) and 4% (w/w, high dose) of freeze-dried PWPC-GSH powder, respectively.

Figure 5

Microscopic examination results of organs for rats in the control and 4% groups. The values 0%, 4% represent daily intake of 0% (w/w, control), 4% (w/w, high dose) of freeze-dried PWPC-GSH powder. M and F represent male and female rats, respectively. For pictures of brain, black arrows represent vascular endothelium, yellow arrows represent the nucleus, red arrow are neurons and blue arrow are pyramidal cells. For picture of heart, black arrow represents the gap of cardiac muscle fiber bundle. For picture of liver, black arrows represent prototype vacuoles with regular shapes and yellow arrow represent red blood cells. For picture of testes, black arrows represent sperm cells.