Effects of fat, beef and fiber in diets on activities of sphingomyelinase, ceramidase and caspase-3 in rat colonic mucosa

Abstract

Objective: The present study investigates the activity changes of sphingomyelinase (SMase), ceramidase and caspase-3 in colonic mucosa of rats induced by high fat and red meat diets. Method: For a period of 3 weeks, rats were fed protein without fat (control), high fat only, high fat with beef, and high fat with fiber (cellulose) diets. The fat content (22.4%) was constant in the three high fat diets. Then, the colonic mucosae were scraped and homogenized and the activities of SMase, ceramidase and caspase-3 determined. Results: Compared to the control diet, the fat diet and fat with beef diet reduced intestinal alkaline SMase by 80 and 84%, respectively; ceramidase activity by 60 and 92%, respectively, and caspase-3 activity by 40 and 75%, respectively. The activities of acid and neutral SMases were also decreased by fat and fat with beef diets but to a smaller extent than those of alkaline SMase. Supplement of fiber in the fat diet had no effect on the changes of alkaline SMase activity but prevented fat-induced decreases in acid and neutral SMase activities and partially prevented those of ceramidase and caspase-3 activities. The activity of intestinal alkaline phosphatase was not changed by any of the diets. Conclusion: Fat, beef and fiber significantly affect the enzymes responsible for sphingomyelin metabolism and apoptosis in the colon. The effects may have implications in colonic tumorigenesis related to dietary factors. Copyright © 2002 S. Karger AG, Basel.