Dietary carbohydrate level as a modifying factor of 3'-methyl-4-dimethylaminoazobenzene liver carcinogenesis in rats

The effect of dietary carbohydrate (CHO) level on liver carcinogenesis induced by 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) was investigated in male Wistar rats. In the first experiment, three groups of 30 rats were maintained on liquid diets, which differed only in the level of CHO (sucrose); high-CHO (14.04 g/day), medium-CHO (9.72 g/day) and low-CHO (3.64 g/day). Half of the animals from each group were given 3'-Me-ADB added to their diet at the level of 10 mg/day/rat for 20 weeks, the remainder being maintained as carcinogen-free controls. Final body and liver weights of control rats decreased with decreasing dietary level of CHO, while carcinogen treatment increased the liver/body weight ratio with decreasing CHO level. Quantitative analysis showed that the number and area of liver tumors per unit area of liver sections increased with decreasing dietary sucrose level. Hepatocellular carcinomas were only observed in rats placed on the low-CHO diet (4 out of 15 rats). In the second experiment, where rats were given 3'-Me-DAB in a semisynthetic powder diet for 16 weeks, the number and area of gamma-glutamyltranspeptidase-positive foci were significantly higher in the low-CHO diet group, with decreasing values being associated with increase in sucrose level in the diet. Thus, the present experiments clearly showed that lowered CHO intake enhanced, whereas high intake reduced, 3'-Me-DAB liver carcinogenesis in rats.