BIFIDOBACTERIUM-LONGUM AND LACTULOSE SUPPRESS AZOXYMETHANE-INDUCED COLONIC ABERRANT CRYPT FOCI IN RATS

Bifidobacterium longum has been shown to afford protection against col on tumorigenesis. Lactulose, a keto analog of lactose, serves as a sub strate for preferential growth of Bifidobacterium, It is not known whe ther feeding lactulose along with B.longum will have any advantage ove r feeding of B.longum alone, To test this combination effect, 61 male Fisher 344 weanling rats were divided into four groups of 15 rats each (16 in the control group) and assigned to one of the following four d iets for 13 weeks: (i) AIN76A (control, C); (ii)C + 0.5% B.longum (C+B l, containing 1x10(8) viable cells/g feed); (iii) C + 2.5% lactulose ( C+L); (iv)C + 0.5% B.longum + 2.5% lactulose (C+Bl+L). All animals rec eived a s.c. injection of azoxymethane at 16 mg/kg body wt at 7 and 8 weeks of age, Colons of 10 rats from each dietary group were analyzed for aberrant crypt foci (ACF), which are preneoplastic markers, Coloni c mucosa and livers from five rats were analyzed for glutathione S-tra nsferase (GST, a Phase II enzyme marker), Results indicate that feedin g of lactulose and B.longum singly and in combination reduces the numb er of ACF (P = 0.0001) and the total number of aberrant crypts signifi cantly (P = 0.0005), The total number of ACF in diets C, C+Bl, C+L and C+Bl+L were 187 +/- 9, 143 +/- 9, 145 +/- 11 and 97 +/- 11 respective ly, There was no significant difference in weight gain among treatment s, Colonic mucosal GST levels were significantly (P = 0.05) higher in the Bl and L groups compared with group C, Initially there was a mild diarrhea in lactulose-fed rats, There was a positive correlation betwe en higher cecal pH and number of ACF. Results of the study indicate th at Bifidobacterium and lactulose exert an additive antitumorigenic eff ect in rat colon.