Phospholipid fatty acid composition and protein kinase C activity in the large intestine of rats fed on butter and coconut-oil diets

Abstract

Protein kinase C (PKC) has been proposed to play an important role in the aetiology of colon cancer. Therefore, we investigated whether the amount and type of saturated fat could affect colonic PKC activity by modifying either mucosal phospholipid fatty acid composition or faecal diacylglycerol production. Male Wistar rats (n 13 per group) were fed on diets containing butter or coconut oil at energy levels of 10 % and 43 % for 4 weeks. The control group received a low-fat diet providing 10 % of energy from sunflowerseed oil. PKC activity was higher in the distal than the proximal colon but the quantity or type of fat did not alter PKC activity in either region of the colon. Saturated fats caused moderate changes in the fatty acid composition of caecal phospholipids, which were more obvious in the phosphatidylethanolamine than in the phosphatidylcholine fraction. A significant correlation was found between fatty acid composition of phosphatidylcholine and membrane PKC activity. In particular, there was a positive correlation between the proportion of saturated 14:0 and 18:0 and increased PKC activity while unsaturated 18:2n-6, 20:4n-6 and 16:1n-7 were inversely correlated with PKC activity. No relationship was found between phosphatidylethanolamine fatty acids and PKC activity. Concentration of faecal diacylglycerol was not affected by the diet. Overall the data suggest that diets high in saturated fat may not alter colonic PKC activity to a significant extent.