L-Ascorbate Prevents Non-Alcoholic Steatohepatitis-Based Hepatocarcinogenesis in <em>Sod1</em>/<em>Prdx4</em> Double-Knockout Mice

Oxidative stress as well as endoplasmic reticulum (ER) stress are the major underlying factors that promote non-alcoholic steatohepatitis (NASH), which eventually leads to hepatocarcinogenesis. Knockout (KO) of superoxide dismutase 1 (Sod1) causes impaired lipid metabolism and an increase in hepatocarcinogenesis in aged mice whereas lipid overload alone neither induces NASH nor increases the incidence of tumor development in them. The double knockout (DKO) of Sod1 and peroxiredoxin 4 (Prdx4), a thiol oxidase that resides in the ER, causes NASH-mimicking symptoms even at younger ages. We found that in addition to high mortality, any surviving DKO mice develop hepatocellular carcinoma within the first year of life. The administration of a physiological dose of L-ascorbate (1.5 mg/ml) in drinking water decreased the rates of mortality and effectively prevented tumor development. Precancerous lesions showed higher reactivity to a ferroptosis-specific antibody compared with tumor lesions. Analyses of liver tissues from 8-month-old DKO mice revealed that upregulation in the metabolic pathways of amino acids were robustly suppressed by supplementation with L-ascorbate, which suggested a possible role in hepatocarcinogenesis. Iron-regulatory protein and aconitase activity were decreased in the DKO mice regardless of their ascorbate status. Given the dominant occurrence of ferroptosis in precancerous cells, it is conceivable that supplementation with ascorbate along with aberrant iron metabolism selectively induces the death of cells destined for tumorigenic proliferation at the precancerous stage. An adequate intake of ascorbate in daily life could ameliorate the tumorigenic processes that are promoted by the hepatic steatosis elicited by oxidative insult