Abstract
Fecal diacylglycerols (DAG) are known activators of protein kinase C (PKC), which in turn modulate colonic epithelial cell growth programs and, therefore, could play a role in the malignant transformation process. However, the effects of physiological modifiers such as diet and carcinogen on fecal DAG mass and composition have not been reported. We designed a 2 x 2 x 2 factorial study (2 fats: corn oil 'I and fish oil; 2 fibers: pectin and 'Cellulose; with and without carcinogen). Rats were provided with one of four semipurified diets for 5 weeks and either administered a carcinogen injection or a saline injection. At three weeks and 24 weeks after injection of azoxymethane, feces were collected from 10 rats/treatment (n = 80 total) and analyzed for DAG mass and fatty acyl composition by combined TLC and gas chromatography. Dietary fat had a significant effect on the mol % of fatty acyl composition of fecal DAG at both time points. Greater amounts of long chain n-3 polyunsaturated fatty acids (20:5n-3, 22:5n-3 and 22:6n-3) were detected in fecal DAG of fish oil-fed animals relative to corn oil(P<0.001). The most significant effect of fiber was on the total production (nmol excreted/day) of DAG at time point # 1, which was 2.5 times higher with cellulose than pectin supplementation. A significant interaction between fat and fiber was observed at both time points for nmols of 17:0 containing DAG, with fish oil/cellulose having the highest amount (P < 0.05). Fecal DAG was also examined as a possible diagnostic marker for colon cancer using multiple regression analysis. In the regression model, saturated fatty acids (14:0, 17:0, and 16:0) contributed to 50% of the model and had an inverse effect on colon cancer tumor development. These data show that fat, fiber and carcinogen can modulate the fatty acyl composition and mass of fecal DAG, and that DAG may have predictive value as a tumor diagnostic marker. Since the production of fecal DAG, an activator of protein kinase C, may alter colonic mucosal cell proliferation, our data offer insight into a mechanism by which diet may modify the risk of colon cancer development.
Pickering, Jennifer Sharon (1996). Effects of dietary fat, fiber and carcinogen on fecal diacylglcyerols in the rat. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1996 -THESIS -P534.