Antiulcerogenic and antiinflammatory actions of fatty acids on the gastrointestinal tract

Dietary polyunsaturated fatty acids improve histological and biochemical alterations in rats with experimental ulcerative colitis

The aim of the present study was to determine whether dietary intake of monounsaturated (MUFA) and/or polyunsaturated fatty acids (PUFA) of the (n- 3) and (n-6) series could improve intestinal damage and reduce inflammation in experimental ulcerative colitis (UC). Rats were treated with 80 mg/kg body of 2,4,6-trinitrobenzenesulfonic acid and fed for 1 or 2 wk diets enriched in olive oil (OO), fish oil (FO), or purified pig brain phospholipids (BPL), as sources of monounsaturated and PUFA of the (n-3) and (n-3) + (n-6) series. Evaluation of macroscopic and microscopic colonic damage was assessed. Ultrastructural and histologic changes were analyzed as well as plasma and colonic mucosa fatty acid profiles and some biochemical markers of injury and inflammation [alkaline phosphatase (AP), mieloperoxidase (MPO), prostaglandin E(2) (PGE(2)) and leukotriene B(4)]. Fatty acid profiles of both plasma and mucosa mostly reflected the dietary fatty acid composition. Plasma MUFA proportions were higher in UC animals fed the OO diet compared with FO or BPL groups 1 and 2 wk and (n-3) long chain PUFA (LC-PUFA) were higher in the FO than in the OO and BPL groups. At 1 wk, UC led to lower MUFA mucosa levels and (n-3)LC-PUFA were higher in the FO group compared with the OO and BPL groups. Rats with UC fed FO at 1 wk showed significantly less macroscopic and microscopic colonic damage. They also have lower AP and MPO activities and PGE(2) levels compared with the OO and BPL groups and showed enhanced histological repair, less necrotic areas within the mucosa, and more goblet cells with mature mucin granules. These results suggest that the use of balanced diets containing (n-3) LC-PUFA could ameliorate the inflammation and mucosal damage in UC.

Effect of dietary linoleate/alpha-linolenate balance on experimentally induced gastric injury in rats

Rats were fed diets containing different ratios of linoleate (18:2 n-6) to alpha-linolenate (18:3 n-3), and the severity of gastric injury induced by ethanol, ischemia/reperfusion and water-immersion stress was compared. On decreasing the 18:2 n-6/18:3 n-3 ratios in the diets, the proportion of arachidonic acid (20:4 n-6) decreased and that of eicosapentaenoic acid (20:5 n-3) increased in the phospholipids of the gastric mucosa, which was associated with decreased mucosal prostaglandin E2 content. Mucosal injury in all the three experimental models was exacerbated significantly in the diet group fed 18:2 n-6/18:3 n-3 ratio of 0.25 (perilla oil) as compared with the groups fed dietary oils with 18:2 n-6/18:3 n-3 ratios of 2.7 (mixture of perilla and safflower oils) and 127 (safflower oil). This adverse effect induced by perilla oil diet was not observed when rats were pretreated with a mild irritant (20% ethanol) prior to challenge with a strong irritant (absolute ethanol). Furthermore, an 18:2 n-6/18:3 n-3 ratio of as low as 1 was found to be in a safe range in the water-immersion stress ulcer model. Thus, oils with very low n-6/n-3 ratios, for example perilla oil, could be used without the risk of the observed adverse effects on experimental gastric injury in people of industrialized countries ingesting foods with n-6/n-3 ratios of above 4. A decrease in the n-6/n-3 ratios to 2 or below is still recommended for the prevention of chronic diseases in the elderly related to atherosclerosis and inflammation.

Effect of evening primrose oil on gastric ulceration and secretion induced by various ulcerogenic and necrotizing agents in rats

The evening primrose oil (EPO) commercially known as Callanish evening primrose oil (omega-6 polyunsaturated fatty acid) is linoleic acid (LA) and gamma-linolenic acid (GLA)-enriched oil obtained from the seeds of Oenothera biennis L. (Fam. Onagraceae). EPO was investigated for its ability to protect the gastric mucosa against injuries caused by pylorus ligation, non-steroidal anti-inflammatory drugs (NSAIDs; aspirin, indomethacin and phenylbutazone), hypothermic restraint stress and necrotizing agents [0.6 M HCl, 0.2 M NaOH, 25% NaCl or 80% (v/v) aqueous ethanol]. It was administered by gastric intubation at doses of 5 and 10 ml/kg body weight to rats fed standard chow diet. An additional group of animals was given the same amount of corn oil in each experimental model studied. The results showed that EPO at the doses of 5 and 10 ml/kg body weight provided significant protection in various experimental models used. It produced a significant inhibition of gastric mucosal damage induced by pylorus ligation, NSAIDs, or hypothermic restraint ulcers. EPO also had a marked cytoprotective effective effect against all necrotizing agents used in this study. The results suggest that EPO rich in LA and GLA possesses both antisecretory and anti-ulcerogenic effects.

Eicosanoids and the gastrointestinal tract

Determining the role of eicosanoids in gastrointestinal physiology and pathophysiology has been an active area of investigation over the past 20 years. The landmark discovery of prostaglandin endoperoxide synthase and other enzymes involved in the production of arachidonic acid products (lipoxygenases and epoxygenases) ushered in a new era of research. The goal of this review is to distill a large body of work pertaining to studies of eicosanoids in the gastrointestinal tract. This review has been organized according both to functional (secretion and motility) and disease-related (inflammation, mucosal injury, and neoplasia) effects. The aim of this article is to present a clear summary of this area of gastroenterology so that future research can be directed in a logical and productive manner.

Effect of acute administration of fish oil (omega-3 marine triglyceride) on gastric ulceration and secretion induced by various ulcerogenic and necrotizing agents in rats

The fish oil commercially known as Marine-25 (omega-3 marine triglyceride) is an eicosapentaenoic acid (EPA)-rich oil. It was investigated for its ability to inhibit gastric secretion and to protect the gastric mucosa against the injuries caused by pyloric ligation, non-steroidal anti-inflammatory drugs (NSAIDs--aspirin and indomethacin), reserpine, hypothermic restraint stress and necrotizing agents [0.6 M HCl 0.2 M NaOH or 80% (v/v) aqueous ethanol]. The results showed that the fish oil, at a dose of 5 or 10 ml/kg body weight, provided significant protection in the various experimental models used. It produced a significant inhibition of gastric mucosal damage induced by pyloric ligation, NSAIDs, reserpine or hypothermic restraint ulcers. Fish oil also exerted a significant inhibitory action on gastric mucosal lesions produced by various necrotizing agents. Our findings show that fish oil rich in eicosapentaenoic acid possesses both antisecretory and antiulcerogenic effects.