Effects of dietary corn oil and salmon oil on the oxidation of fatty acids and prostaglandin E2 in rat gastric mucosa.

The investigations previously carried out by Grataroli and colleagues (1) to elucidate the relationships between dietary fatty acids, lipid composition, prostaglandin E2 production and phospholipase A2 activity in the rat gastric mucosa are, here, extended. In the present investigations, fatty acid and prostaglandin E2 catabolizing enzymes were assayed in gastric mucosa from rats fed either a low fat diet (corn oil: 4.4% w/w) (referred as control group), a corn oil-enriched diet (17%) or a salmon oil-enriched diet (12.5%) supplemented with corn oil (4.5%) (referred as groups of treated animals) for eight weeks. Peroxisomal fatty acyl-CoA beta-oxidation was induced in the treated animals whereas the activities of catalase and mitochondrial tyramine oxidase were increased and normal, respectively. Mitochondrial acyl-CoA dehydrogenations occurred at higher rates and carnitine acyltransferase activities were enhanced. In addition, the induction of peroxisomal but not mitochondrial prostaglandoyl-E2-CoA beta-oxidation could be demonstrated. Induction of peroxisomal oxidation of fatty acids and prostaglandins is suggested to contribute to the decrease of prostaglandin E2 production in the treated animals, especially those receiving the salmon oil diet, that the above mentioned authors originally reported

Effects of Dietary N-6/n-3 Ratios On Lipid and Prostaglandin-e2 Metabolism in Rat Gastric-mucosa

The effects of increased dietary n - 3 polyunsaturated fatty acids on gastric mucosal lipid metabolism were studied in rats fed for 8 weeks with different combinations of fish and corn oils. Lipid composition, ex vivo prostaglandin E2 (PGE2) production and enzymatic activities involved in phospholipid metabolism and peroxisomal oxidative catabolism of fatty acids and PGE2 were examined. With dietary n - 6/n - 3 compositional ratios ranging between 75 and 3.3 it was observed that: (i) the arachidonic acid-to-eicosapentaenoic acid ratio (AA/EPA) fell from infinity to 3.1 and 5.1 in phosphatidylcholines (PC) and phosphatidylethanolamines (PE), respectively; (ii) ex vivo production of PGE2 was lowered by a factor of about 2; and (iii) gastric phospholipase A2 activity was enhanced by 32%. With dietary n - 6/n - 3 ratios lower than 3.3, stimulation of PGE2-CoA oxidase activity was observed whilst the PGE2 level remained constant. These data suggest that the fish oil-induced decrease in ex vivo PGE2 production is more closely related to a decrease in the membrane AA level than to an enhanced oxidative catabolism of PGE2

Effect of various n-3/n-6 fatty acid ratio contents of high fat diets on rat liver and heart peroxisomal and mitochondrial β-oxidation

The present work extends tissue investigations previously performed in rat gastric mucosa on lipid metabolism alterations caused by n - 3 and n - 6 fatty acid-enriched diets [13-15]. Liver and heart tissues are here studied and demonstrated to undergo, upon exposure to high fat diets with various n - 3/n - 6 fatty acid ratio contents, biochemical and morphological changes which may be enumerated as follows: (1) Rat liver peroxisomal prostaglandin E2, fatty acid but not bile acid beta-oxidation rates are enhanced, especially upon the diet with the higher n - 3/n - 6 fatty acid ratio. Mitochondrial beta-oxidation rates are little or not affected by the high fat diets. (2) Rat liver carnitine acyltransferases are stimulated by the high fat diets, the more rich the n - 3 fatty acid content, the more pronounced the stimulatory effect. (3) Rat heart peroxisomal and mitochondrial beta-oxidation rates were increased in animals receiving the n - 3 fatty acid-enriched diet. At a low n - 3/n - 6 fatty acid ratio content of the diet, these oxidizing rate values were in control range. The carnitine acyltransferase activities were increased in rat heart to different extents, depending on the n - 3/n - 6 fatty acid ratio content of the diet. (4) Ultrastructural examination and morphometric determinations on hepatocytes from rats receiving the diets with the lowest and the highest n - 3/n - 6 fatty acid ratio contents disclose that in the latter case the numbers and fractional volumes of peroxisomes and mitochondria are significantly higher than in the former case