The effects of ad libitum feeding of synthetic, low-protein diets on the incidence and number of gastric cancers induced by N-methyl-N′-nitro-N-nitrosoguanidine were investigated in Wistar rats. Rats were fed synthetic diets of equal calorie content containing 25% casein (normal protein diet), 10% casein (low-protein diet), or 5% casein (very-low-protein diet) after treatment with N-methyl-N′-nitro-N-nitrosoguanidine p.o. for 25 weeks. Administration p.o. of a very-low-protein diet containing 5% casein resulted in a significant increase in the incidence and number of gastric cancers in experimental Week 52. However, it did not affect the histology of the cancers. The very-low-protein diet also caused a significant increase in tissue norepinephrine concentration of the antral portion of the gastric wall and in the labeling index of the antral epithelial cells. These findings indicate that a very-low-protein diet enhances gastric carcinogenesis and that this effect may be related to its effect in increasing norepinephrine in the gastric wall and stimulating proliferation of antral epithelial cells.
This work was supported in part by a grant-in-aid from the Ministry of Health and Welfare, Japan, for a Comprehensive 10-year Strategy for Cancer Control.