Plasma lipids and liver histochemistry of rats fed sea-lion or corn oil with or without cholesterol supplementation

Foraging behaviour of the South American sea lion (Otaria byronia) in two disparate ecosystems assessed through blubber fatty acid analysis

Fatty acids have been widely used as trophic biomarkers in marine mammals. However, for the South American sea lion, the most abundant otariid in the eastern South Pacific, there is no information about blubber fatty acids and their link to diet. Here, we compare fatty acid profiles of sea lions from two distinct oceanographic regions in northern and southern Chile. Their fatty acids vary greatly between regions, suggesting dietary differences at a spatial scale. The fatty acid C22:6ω3 was more abundant in sea lions from the northern region, likely associated with consumption of anchovy, cephalopods, and crustaceans, which are rich in that fatty acid, and have been reported as their main prey items. Sea lions from the southern region were richer in C22:1 and C20:1, characteristic of teleost fish, suggesting a piscivorous diet. Males displayed a more diverse fatty acid composition than females, suggesting a wider trophic niche. Few individual sea lions within the southern region had unusually high levels of C18:2ω6, commonly found in terrestrial environments. This suggests consumption of farmed salmon, whose diet is usually based on terrestrial sources. This demonstrates how human intervention is being reflected in the tissues of a top predator in a natural environment.

Effect of dietary oils, cholesterol and antioxidant vitamin supplementation on liver microsomal fluidity and xenobiotic-metabolizing enzymes in rats

This study was undertaken to compare the effects of four oils: corn (C), olive (O), hazelnut (H) or fish (F), and the intake of two supplements: cholesterol, 1% (Ch) or dl-alpha-tocopherol acetate, 500 mg/kg, and beta-carotene, 30 mg/kg (V), on liver microsomal fluidity, cyt P450 content and aniline hydroxylase (AH), aminopyrine-N-dimethylase (AND) and UDP-glucuronyltransferase (UDP-GT) activities. Male Sprague-Dawley rats (n = 6/group) were fed semipurified diets containing 15% oil, without or with Ch or V, for 20 days. Dietary intake and feed efficiency were lower in rats fed F. Relative liver weight was higher in animals fed F, similar in O and H, and lower in the group fed C. The intake of V increased feed intake in C+V group and decreased the relative liver weight of F+V group, which also decreased with the intake of F+Ch. Ch intake increased the relative liver weight in all groups consuming vegetable oils. Cyt P450 content was higher in rats fed F. Decreased cyt P450 content was observed in C+Ch and F+Ch groups, while it augmented in H+Ch group. Mixture V increased cyt P450 in rats fed C+V, F+V and O+V. The highest membrane fluidity was observed in rats fed F. Fluidity was also higher in group H versus O or C. The intake of Ch decreased microsomal fluidity in all groups, while V induced an increase in microsomal fluidity in group O+V. Rats fed F exhibited higher enzyme activities. AND activity increased with V only in rats fed H+V, while AH activity increased with V intake in groups F+V and O+V. In the C+V group, fluidity was not affected by V, while the cyt P450 content and UDP-GT activity increased. The O+V group exhibited lower UDP-GT activity and higher fluidity and cyt P450 content. The activity of AH decreased in groups F+Ch and C+Ch. UDP-GT activity was higher in rats fed F. It diminished after the intake of Ch in H+Ch and F+Ch. These results indicate that although AH and AND act in the same microsomal metabolic pathway, their localization into the membrane may be determinant of their activity and the response to dietary lipids. It is shown that F intake exerts the most significant effects upon liver microsomal properties, e.g. higher fluidity, cyt P450 content and enzymatic activities, an effect that prevails over the intake of the supplements tested.

Fat infiltration in liver of rats induced by different dietary plant oils: high oleic-, medium oleic- and high petroselinic acid-oils

Beneficial effects on health parameters by ingestion of plant oils having high levels of monounsaturated fatty acids such as oleic (cis-9-octadecenoic) acid have been described in several studies. Recently, we have shown that feeding of coriander oil containing high proportions of a positional isomer of oleic acid, i.e. petroselinic (cis-6-octadecenoic) acid, led to significantly decreasing proportions of arachidonic (all cis-5,8,11,14-eicosatetraenoic) acid in the cellular lipids. Here, we report histopathological findings in male Wistar rats fed isocaloric diets containing 2% corn oil and 12% (w/w), each, of different plant oils (high-oleic and conventional sunflower oil, olive oil, rapeseed oil as well as coriander oil) containing varying levels of monounsaturated fatty acids, i.e. oleic or petroselinic acids. One group of animals was fed a standard diet containing 4% (w/w) of fat as control. Liver, heart, aorta, stomach, and spleen were anatomically and histologically examined. Livers of animals from all the groups that had received high-fat diets-except the coriander oil group-showed moderate non-degenerative fat infiltrations of the hepatocytes beginning in the periportal fields. Marked to severe fat infiltration was observed in hepatocytes of animals fed coriander oil. In this experimental group the livers were found to contain fatty cysts in addition to hepatocytes with mixed-size lipid vesicles. Moreover, enlarged nuclei were observed in numerous hepatocytes without fat infiltration. Fat infiltration was not observed in livers of animals fed a rat standard diet. In the cells of all other organs and tissues studied, in particular heart and aorta, neither non-degenerative fat infiltrations nor other degenerative changes were observed for any group. Our results show that feeding of fat-rich diets containing varying proportions of C18 cis-monoenoic fatty acids induced different histopathological alterations in the livers of rats, depending on position of the double bond. Plant oils containing varying proportions of oleic acid lead exclusively to moderate fat infiltration in the hepatocytes, whereas in the animals fed high-petroselinic coriander oil degenerative alterations (fatty cysts) as well as -in several cases-enlarged nuclei were found that are likely due to a non-specific stimulation of the hepatocytes resulting from the cell degeneration observed.