Oxidized ethyl linoleate induces mucosal hypertrophy of the large intestine and affects cecal fermentation of dietary fiber in rats.

Oxidized ethyl linoleate (OEL) was prepared by aeration at low temperature. Peroxide value (POV, mEq/kg lipid) of OEL was 1400; the major oxidized compounds were 9-hydroperoxy-cis, trans- and 13-hydroperoxy-trans, cis-octadecadienoate. Rats fed fiber-free or sugar-beet fiber (SBF, 100g/kg diet) diets were divided into three groups for each diet, and administered OEL (high OEL group), OEL diluted with ethyl linoleate (low OEL group, POV 700) and nonoxidized ethyl linoleate (EL group) through gastric tubes each day at 1400-1600 h (2.5 g/kg body wt) for 16 d. The relative wet weight, and DNA and protein contents of the cecal mucosa were higher in the high OEL groups than in the low OEL and EL groups in rats fed the fiber-free diet and in rats fed the SBF diet except for mucosal protein content. Spermidine concentration in cecal mucosa of rats fed the fiber-free diet was greater in the high OEL group than in the EL group. These results suggest that metabolism related to mucosal proliferation of the cecum was affected by the high dose of OEL. The total short-chain fatty acid (SCFA) concentration in the cecal contents of SBF-fed rats was 100% higher than the concentration in rats fed the fiber-free diet in the EL group, but the administration of low dose and high dose OEL lowered the SCFA concentration in fiber-fed rats to that of rats fed the fiber-free diet. Butyric acid concentration was markedly lowered by ingestion of OEL in a dose-dependent manner in rats fed the SBF diet. In contrast, the isobutyric acid concentration was higher in the OEL-treated groups than in the EL groups. We conclude that a low dose of OEL depresses cecal fermentation of dietary fiber with changes in SCFA composition, and that a high dose of OEL induces mucosal hypertrophy in the cecum. These data show that dietary oxidized lipids affect cecal metabolism and may be associated with colon cancer.