Schematic representation of the proposed protective mechanisms of glycine in bile duct ligated mice. The effect of glycine on hepatocytes, mitochondria might play a major role in its mechanism of hepatoprotection in cholestasis.

Cholestasis is the stoppage of bile flow which could lead to serious clinical complications if not managed. Cytotoxic bile acids are involved in the pathogenesis of liver injury during cholestasis. There are no promising pharmacological interventions against cholestasis and its associated complications. This study examined the impact of glycine supplementation on liver mitochondria as a major target of bile acids-induced toxicity during cholestasis. Mice underwent BDL operation and received glycine (0.25% and 1% w:v in drinking water). Blood and liver samples were collected at scheduled time intervals (3, 7, and 14 days after BDL surgery). Plasma biomarkers of liver injury, along with markers of oxidative stress in the liver tissue were evaluated. Furthermore, liver mitochondria were isolated, and several mitochondrial indices were assessed. BDL-induced cholestasis was evident in mice as a significant elevation in plasma biomarkers of liver injury. Markers of oxidative stress were significantly increased in the liver of BDL animals. Liver injury was histopathologically evident by tissue necrosis, bile duct proliferation, hydropic changes, inflammation, and fibrosis. Furthermore, high level of reactive oxygen species, lipid peroxidation, depleted glutathione reservoirs, and impaired tissue antioxidant capacity were also detected in the liver of cholestatic mice. An assessment of liver mitochondrial function in BDL animals revealed an inhibition of mitochondrial dehydrogenases activity, collapse of mitochondrial membrane potential, mitochondrial swelling, and increase of reactive oxygen species (ROS), and lipid peroxidation (LPO). Furthermore, a significant decrease in mitochondrial ATP was detected in the liver mitochondria isolated from cholestatic animals. Glycine supplementation (0.25% and 1%) decreased mitochondrial swelling, ROS, and LPO. Moreover, glycine treatment improved mitochondrial membrane potential and restored liver mitochondrial ATP. On the other hand, it was found that glycine supplementation attenuated oxidative stress markers in the liver of BDL animals. Moreover, liver histopathological changes and collagen deposition were markedly mitigated by glycine treatment. The mechanisms for the beneficial effects of glycine administration in cholestatic animals might be linked to its ability for preserving cellular redox environment, preventing oxidative stress, and maintaining mitochondrial functionality.