The influence of high and low molecular weight chitosan on colonic cell proliferation and aberrant crypt foci development in CF1 mice

The effect of dietary chitosan, a fibre of animal origin, on the induction and development of colonic precursor lesions was determined in CFl mice. Over a 2-wk pretreatment period, one group of mice was given azoxymethane (four injections of 5 mg/kg body weight) and the other was treated with saline. Subsequent to carcinogen or saline pretreatment mice were randomized into one of three dietary groups: (i) control AIN-76 diet; (ii) control AIN-76 diet with 2% low molecular weight chitosan (LMWC); or (iii) control AIN-76 diet with 2% high molecular weight chitosan (HMWC). Mice were maintained on this diet for 6 wk. Mice fed diet containing HMWC had significant reductions in the number of aberrant crypt foci, cell proliferation, crypt height and crypt circumference in the colonic epithelium (P < 0.05). In mice given diet supplemented with LMWC there was a trend towards reduced numbers of aberrant crypts, as well as decreased crypt height and circumference. The results of this study indicate that dietary chitosan reduces the incidence of early preneoplastic markers of colon carcinogenesis, as indicated by aberrant crypts and mitotic figures and altered crypt morphometrics in the murine colon. Molecular range and viscosity of the chitosan may influence the efficacy of this activity.