Early induction of TGF-beta1 through a fasting-re-feeding regimen promotes liver carcinogenesis by a sub-initiating dose of diethylnitrosamine.

We previously reported that a sub-necrogenic dose (20 mg/kg) of diethylnitrosamine (DENA) can induce the development of liver cancer when rats undergo a fasting-re-feeding regimen. The present study was undertaken to establish whether fasting followed by re-feeding builds up mechanisms able to trigger liver fibrosis, eventually leading to cirrhosis and cancer. Adult male rats, for fasted 4 days, were given 20 mg/kg of DENA after 1 day of re-feeding; in parallel, consistently fed animals receiving 20 mg/kg (sub-necrogenic) or 200 mg/kg (necrogenic dose) of DENA were used as negative and positive controls, respectively. All three groups were then subjected to the 2-acetylaminofluorene/carbon tetrachloride promoting regimen. Fasting induced moderate apoptosis in liver tissue, as evidenced by increased levels of transforming growth factor-beta1 (TGF-beta1) and Bax proteins and by a dramatic drop in the level of Bcl-2. Subsequent re-feeding caused all changes to revert except TGF-beta1 up-regulation. Histological findings of inflammation and fibrosis were consistently associated with increased production of TGF-beta1, the inflammatory cytokine with the most pronounced profibrogenic action. Thus, up-regulation of TGF-beta1 expression appears as a major mechanism by which the fasting-re-feeding regimen predisposes to initiation and promotion of liver carcinogenesis in rats. Avoiding fasting-re-feeding could be considered in the nutritional status of patients with liver fibrosis.