Inhibition of nitrosodiethylamine-induced hepatocarcinogenesis by dietary turmeric in rats

Turmeric, widely used in food and medicine has been shown to prevent benzo(a)pyrene [B(a)P] or dimethylbenz(a)anthracene (DMBA)-induced forestomach, skin and mammary tumors in mice and/or rats. In this study we examine the modulatory effects of turmeric on nitrosodiethylamine (NDEA)-induced hepatocarcinogenesis in rats. Female Wistar rats were administered NDEA (200 ppm) through drinking water (5 days per week) for 4 weeks. Control and/or NDEA-treated rats received 0, 0.2, 1.0 or 5.0% turmeric diet (w/w) either before (2 weeks), during (4 weeks) and after NDEA exposure (10 weeks) or starting from 24 h after NDEA exposure for 10 weeks. NDEA-treated rats receiving 1 or 5% turmeric before, during and after carcinogen exposure showed significant decrease in number of gamma glutamyl transpeptidase (GGT) positive foci measuring >500 or >1000 μm and decrease in the incidence of NDEA-induced focal dysplasia (FD) and hepatocellularcarcinomas. Decrease in the number of GGT positive foci measuring >1000 μm was also observed in NDEA-treated rats receiving 0.2% turmeric, although no decrease in tumor incidence was noted. On the other hand, similar levels of turmeric treatment (0.2, 1 and 5%) after exposure to NDEA did not show any protective effects. The underlying mechanism(s) of chemoprevention of NDEA-induced hepatocarcinogenesis need to be explored.