Severe liver steatosis correlates with nitrosative and oxidative stress in rats

Little is known about nitric oxide (NO) metabolism and redox changes with hepatocyte adipocytic transformation. The aims of this study were to investigate the changes occurring in plasma and hepatic NO metabolites and redox balance in a rat experimental model of simple fatty liver, and to relate plasma with hepatic and mitochondrial changes at different degrees of steatosis.

Circulating and hepatic redox active and nitrogen regulating molecules thioredoxin, glutathione, protein thiols (PSH), mixed disulfides (PSSG), NO metabolites nitrosothiols, nitrite plus nitrate (NOx), and lipid peroxides (TBARs) were measured in rats fed a choline deprived (CD) diet for 30 days.

At histology, the CD diet resulted in hepatocellular steatosis (75% of liver weight at day 30) with no signs of necro-inflammation. In plasma, thioredoxin, nitrosothiols and NOx were unchanged, while TBARs levels increased significantly and were positively related with hepatic TBARs (r = 0.87, P < 0.001) and lipid content (r = 0.90, P < 0.001). In the liver, glutathione initially increased (day 3) and then decreased. From day 14, PSH decreased and NO derivatives increased. Thioredoxin 1 had initially increased (days 7-14) and then decreased. In the mitochondria, on day 14, nitrosothiols were inversely related to thioredoxin 2 (r = 0.988, P < 0.05); on day 30, PSH were decreased by 70%, PSSG were doubled and related with nitrosothiols levels (r = 0.925, P < 0.001).

Adipocytic transformation of hepatocytes is accompanied by major interrelated modifications of redox parameters and NO metabolism especially at mitochondrial level, suggesting an early adaptive protective response but also an increased predisposition towards pro-oxidant insults.