Calcium inhibits promotion by hot dog of 1,2-dimethylhydrazine-induced mucin-depleted foci in rat colon

Abstract

Epidemiology suggests that processed meat is associated with colorectal cancer risk, but few experimental studies support this association. We have shown that a model of cured meat made in a pilot workshop promotes preneoplastic lesions, mucin-depleted foci (MDF) in the colon of rats. This study had two aims: to check if real store-bought processed meats also promote MDF, and to test if calcium carbonate, which suppresses heme-induced promotion, can suppress promotion by processed meat. A 14-day study was done to test the effect of nine purchased cured meats on fecal and urinary biomarkers associated with heme-induced carcinogenesis promotion. Fecal water from rats given hot dog or fermented raw dry sausage was particularly cytotoxic. These two cured meats were thus given to rats pretreated with 1,2-dimethylhydrazine, to evaluate their effect on colorectal carcinogenesis. After a 100-days feeding period, fecal apparent total N-nitroso compounds (ATNC) were assayed and colons were scored for MDF. Hot dog diet increased fecal ATNC and the number of MDF per colon compared with the no-meat control diet (3.0 ± 1.7 vs. 1.2 ± 1.4, p < 0.05). In a third study, addition of calcium carbonate (150 µmol/g) to the hot dog diet decreased the number of MDF/colon and fecal ATNC compared with the hot dog diet without calcium carbonate (1.2 ± 1.1 vs. 2.3 ± 1.4, respectively, p < 0.05). This is the first experimental evidence that a widely consumed processed meat promotes colon carcinogenesis in rats. It also shows that dietary prevention of this detrimental effect is possible.

Keywords: calcium; colorectal cancer; preneoplastic lesions; prevention; processed meat.

Figure 1

(A) Effect of cured meat (hot dog, saucisson), and calcium carbonate (Ca), on mucin-depleted foci (MDF) in rat colon 99 d after the injection of 1,2-dimethylhydrazine, in two independent studies: Promotion study on the left, Protection study on the right. (B) Nitroso-compounds (ATNC) in feces of rats. Values are means and standard error of the mean (10 rats per group). Diets contained 40% and 50% processed meat (dry matter), full composition shown in Table 1. *: significantly different from control diet (left panel) or from hot dog diet (right panel)