Orally administered Streptococcus thermophilus YIT 2001 is a vehicle for the delivery of glutathione, a reactive reduced thiol, to the intestine.

Abstract

We aimed to analyze the behavior of cellular glutathione of Streptococcus thermophilus strain YIT 2001 (ST-1) in the gastrointestinal environment to understand how orally administered glutathione in ST-1 cells is delivered stably to the intestine in a reactive form, which is essential for its systemic bioavailability against lipid peroxidation. Intracellular glutathione was labeled with L-cysteine-containing stable isotopes. ST-1 cells from fresh culture or lyophilized powder were treated with simulated gastric and intestinal juices for 60 min each. The release of intracellular glutathione in digestive juices was quantified via LC-MS/MS. Most of the cellular glutathione was retained in the gastric environment and released in response to exposure to the gastrointestinal environment. During digestion, the membrane permeability of propidium iodide increased significantly, especially when cells were exposed to cholate, without change in the cell wall state. ST-1 cells act as vehicles to protect intracellular reactive components, such as glutathione, from digestive stress, and release them in the upper intestine owing to the disruption of membrane integrity induced by bile acid.