The role of the liver in the protection by elemental diets against experimental colon cancer.

This study investigates the mechanism whereby the elemental diet 'Vivonex' protects against experimental colon cancer. A total of 240 Wistar rats were randomly allocated to three dietary groups: (A) Vivonex HN, (B) Vivonex HN with 0.05% added cholesterol and (C) control standard powdered diet. All received a colon cancer-producing regimen of dimethylhydrazine (DMH) at a dose of 40 mg/kg BW, s.c., once weekly for 5 weeks. Ten weeks following the first DMH injection, then at 5 weekly intervals until the 40th week, 10 randomly selected rats from each dietary group were weighed, killed and necropsied. Total liver weights were recorded with samples kept for total lipid extraction and cholesterol and phospholipid assay. Each colon underwent macroscopic examination and all neoplasms were recorded. Results showed that control rats had a constant total liver lipid content over the 40 weeks and an increased incidence, number and development of colonic neoplasms with time. In contrast, Vivonex fed rats had significantly elevated total liver lipids, cholesterol and phospholipids over the 40 weeks compared to controls and a significantly reduced number and rate of development of colonic neoplasms. Rats fed on Vivonex + cholesterol had total liver lipids intermediate and significantly different from both the Vivonex and control groups and a similar result was seen in tumour development with time. This study shows that a Vivonex diet results in an increase in hepatic lipids, this effect being partially reversed with dietary cholesterol. The protective effect of Vivonex feeding in the DMH model of colon cancer may thus be mediated in part by the liver.(ABSTRACT TRUNCATED AT 250 WORDS)