Alleviation of dimethylnitrosamine-induced liver injury and fibrosis by betaine supplementation in rats

Previous studies suggested that betaine intake might antagonize the induction of oxidative stress-mediated acute liver injury through regulation of the sulfur–amino acid metabolism. In this study we examined the protective effects of betaine on chronic liver injury and fibrosis induced by dimethylnitrosamine (DMN). Male rats were supplemented with betaine (1%, w/v) in drinking water from 2 weeks prior to the initiation of DMN treatment (10 mg/(kg day), i.p., 3 days/week, for 1, 2, or 4 weeks) until sacrifice. Induction of liver injury was determined by quantifying serum alanine aminotransferase, aspartate aminotransferase activities, bilirubin levels, hepatic xenobiotic-metabolizing capacity, histopathological changes and 4-hydroxyproline levels. Development of oxidative injury was estimated by malondialdehyde (MDA) levels and total oxyradical scavenging capacity (TOSC) of liver and serum toward hydroxyl, peroxyl radicals, and peroxynitrite. Progressive changes in the parameters of liver injury and fibrosis were evident in the rats challenged with DMN. Elevation of MDA levels in liver was significant before the onset of a change in any parameters determined in this study. Betaine supplementation markedly attenuated the induction of hepatotoxicity and fibrosis by DMN. Elevation of MDA and the reduction of TOSC were also depressed significantly. Development of liver injury corresponded well with the induction of oxidative stress in rats treated with DMN, both of which are inhibited effectively by betaine supplementation. It is suggested that betaine may protect liver from fibrogenesis by maintaining the cellular antioxidant capacity.