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

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.