Freeze-Dried Ham Promotes Azoxymethane-Induced Mucin-Depleted Foci and Aberrant Crypt Foci in Rat Colon

Abstract

Processed and red meat consumption is associated with the risk of colorectal cancer. Meta-analyses have suggested that the risk associated with processed meat is higher. Most processed meats are cured and cooked, which leads to formation of free nitrosyl heme. We speculated that free nitrosyl heme is more toxic than native myoglobin. The promoting effect of a freeze-dried, cooked, cured ham diet was looked for in a 100-day study. Colon carcinogenesis endpoints were aberrant crypt foci and mucin depleted foci (MDF). A second study (14 days) was designed 1) to compare the effect of ham, hemoglobin, and hemin; and 2) to test the effect of sodium chloride, nitrite, and phosphate in diet on early biomarkers associated with heme-induced promotion. In the 100-day study, control and ham-fed rats had 3.5 and 8.5 MDF/colon, respectively (P < 0.0001). Promotion was associated with cytotoxicity and lipid peroxidation. In the short-term study, cytotoxicity and lipid peroxidation of fecal water, and the urinary marker of lipid peroxidation, increased dramatically in ham- and hemin-fed rat. In contrast, the hemoglobin diet, sodium chloride, nitrite, phosphate diet had no effect. Freeze-dried cooked ham can promote colon carcinogenesis in a rodent model. Hemin, but not hemoglobin, mimicked ham effect on early biochemical markers associated with carcinogenesis.

ACKNOWLEDGMENTS

We thank Xavier Blanc (UPAE) for the preparation of experimental diets, Raymond Gazel and Florence Blas Y Estrada for the care of the animals, and Michael Charton for the participation in the short-term study. The studies were supported in part by the INRA, by the DGER, and by a grant of the French region Midi-Pyrénées.

Notes

^a Low-calcium casein.

^b AIN76 mix, but 500 g/kg of dibasic calcium phosphate replaced by sucrose in mineral mix.

^aValues are means and SD; N = 10 rats/dietary group. A Student's test analysis of ACF data shown in Table 2 shows no significant difference (P = 0.14) because ACF counts from 2 readers have been grouped, which blurred the difference by increasing the variance. However, the two-way analysis of variance clearly showed the significant effect of diet on ACF number (P = 0.048).

^bDiets were based on a low calcium formula, as shown in Table 1.

^cSignificantly different from control group by 2-way analysis of variance (ACF, P < 0.05) and by Welsh's test (MDF, P < 0.0001).

^a Abbreviations are as follows: TBARS, thiobarbituric acid reactive substances; MDF, mucin-depleted foci; DHN-MA, 1,4-dihydroxynonane mercapturic acid. Values are means and SD.

^b Diets were based on a low-calcium formula. See Table 1 for precise composition.

^c Significantly different from control group by Student's t-test (P < 0.05).

^d Significantly different from control group by Tukey multiple comparison test (P < 0.05).

^e Significantly different from ham and hemin fed groups by Tukey multiple comparison test (P < 0.05).