Statuses of food-derived glutathione in intestine, blood, and liver of rat

Oral administration of glutathione has been demonstrated to reduce exercise-induced fatigue and improve liver function, although glutathione can be synthesized in the liver. However, little is known about the underlying mechanism of this effect. To address this, the status of food-derived glutathione in the intestine, blood, and liver was examined. Glutathione-1-C-13 or N-acetyl-cysteine-1-C-13 (NAC) was orally administered to rats (50mg/kg). Food-derived glutathione contents within tissues were estimated by subtracting endogenous glutathione-1-C-13 from the total glutathione-1-C-13. Food-derived glutathione was present in rat intestines and livers (approximately 60 and 300 mu mol/kg, respectively, 120min after ingestion) in electrochemically reduced form, while all food-derived glutathione in the blood plasma was conjugated with proteins and low-molecular-weight thiol compounds. However, no significant amounts of NAC-derived glutathione were detected in the blood plasma. These findings indicate that food-derived glutathione is directly absorbed in its electrochemically reduced form in the intestine, is then transported in the blood in bound forms, and is finally deposited into the liver in reduced form. Therefore, upon entering the bloodstream, food-derived glutathione binds to thiol compounds and releases hydrogen atom; subsequently, it does the reverse upon incorporation into the liver, which might impact the physiological redox condition. With respect to food-derived glutathione and cysteine-containing peptides, this study provides new insights on their modes of transportation and mechanisms of action. Dietary supplement: understand the benefits of glutathioneThough human body itself can synthesize glutathione, oral administration of the glutathione supplements was shown to be effective on whitening skin, reducing fatigue and improving liver function. To understand the mechanism of these benefits, Kenji Sato from Kyoto University and coworkers examined the circulation and conversion of food-derived glutathione. They found glutathione conjugated to thiol groups of protein and other low-molecular-weight compounds in blood plasma while ended up incorporating into the liver. They proposed this conversion between bound- and free-form glutathione released and received hydrogen atom and thiol compounds, which can activate the antioxidant enzymes and enhance the mitochondrial biogenesis, leading to these known beneficial effects. The present work may encourage further studies on the transportation and incorporation of food-derived glutathione and food proteins.