Effect of different dietary triglycerides on liver fatty acids and prostaglandin synthesis by mouse peritoneal cells

The effect of dietary triglycerides varying in fatty acid composition on the tissue fatty acids and prostaglandin synthesis was studied in mice. The dietary fats were medium-chain triglycerides (rich in C8:0 and C10:0), structured lipids (rich in 12:0), high oleic sunflower oil (rich in 18:1), corn oil (rich in n-6 polyunsaturated fatty acids), and menhaden oil (rich in n-3 polyunsaturated fatty acids) fed at 5% by weight in refined diets. The medium chain fatty acids C8 to C12 from medium-chain triglycerides and structured lipids did not accumulate in liver phospholipids. However, long-chain fatty acids from the dietary fats were incorporated into liver lipids, with n-3 polyunsaturated fatty acids replacing arachidonic acid. The synthesis of 6-keto-prostaglandin F1 alpha and prostaglandin E2 by peritoneal cells in response to intraperitoneal injection of zymosan decreased as the arachidonic acid levels were decreased. When the same dietary fats were added to the refined, fat-free diets, at 7.5 wt% levels, together with 2.5 wt% of safflower oil to provide essential fatty acids, only the long-chain fatty acids from the dietary fats were incorporated into the liver lipids. The arachidonic acid in liver lipids was enhanced after supplementation of diets with safflower oil. However, the reduction in prostaglandin synthesis by peritoneal cells in response to intraperitoneal injection of zymosan was similar to that observed when 5% fat was fed. The data suggest that dietary fats of defined composition, with or without added essential fatty acids, may be useful as alternate fat sources in parenteral nutrition in reducing inflammatory responses mediated via prostaglandins.