Time related incorporation of (N-3) polyunsaturated fatty acids from seal oil or fish oil into rat tissue phospholipids

Bioavailability of docosahexaenoic acid 22:6(n-3) from enantiopure triacylglycerols and their regioisomeric counterpart in rats

Lack of synthetic enantiospecific triacylglycerols (TAGs) has hindered our understanding of the impact of TAG structure on the absorption and metabolic fate of fatty acids (FAs). In a five-day feeding trial with mildly (n-3) deficient rats, the bioavailability of docosahexaenoic acid [22:6(n-3), DHA] and stearic acid (18:0) from the two different enantiomers of TAG: sn-22:6(n-3)-18:0-18:0 and sn-18:0-18:0-22:6(n-3), and their regioisomeric TAG: sn-18:0-22:6(n-3)-18:0 was compared. Less secretion of fecal DHA was detected from the sn-2 position compared with the sn-1 and sn-3 positions, but no difference was found in DHA content of the fasting plasma or in the weight of the body or organs. 18:0 was lost to feces mainly as cleaved from the primary positions but also as glycerol-bound. The 5-day intervention in rats was long enough to modify the fatty acid profile of plasma phospholipids.

Bioavailability of marine n-3 fatty acid formulations

The use of marine n-3 polyunsaturated fatty acids (n-3 PUFA) as supplements has prompted the development of concentrated formulations to overcome compliance problems. The present study compares three concentrated preparations - ethyl esters, free fatty acids and re-esterified triglycerides - with placebo oil in a double-blinded design, and with fish body oil and cod liver oil in single-blinded arms. Seventy-two volunteers were given approximately 3.3g of eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) daily for 2 weeks. Increases in absolute amounts of EPA and DHA in fasting serum triglycerides, cholesterol esters and phospholipids were examined. Bioavailability of EPA+DHA from re-esterified triglycerides was superior (124%) compared with natural fish oil, whereas the bioavailability from ethyl esters was inferior (73%). Free fatty acid bioavailability (91%) did not differ significantly from natural triglycerides. The stereochemistry of fatty acid in acylglycerols did not influence the bioavailability of EPA and DHA.

Effects of long-term feeding of marine oils with different positional distribution of eicosapentaenoic and docosahexaenoic acids on lipid metabolism, eicosanoid production, and platelet aggregation in hypercholesterolemic rats

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were distributed mainly in the sn-1,3 positions of seal oil triglyceride and in the sn-2 position of squid oil triglyceride. Seal oil-rich or squid oil-rich fats having constant saturated/monounsaturated/polyunsaturated fatty acid (PUFA) and n-6/n-3 PUFA ratios were fed to exogenously hypercholesterolemic rats for 1 60 d. The control fat contained linoleic acid as the sole PUFA. Before starting the experimental diets, rats were orally treated with high doses of vitamin D for 4 d to accelerate atherogenesis. The percentage of arachidonic acid in phosphatidylcholine and phosphatidylethanolamine of liver, platelets, and aorta was lower in the marine oil groups than in the control group, seal oil being more effective than squid oil. Maximal platelet aggregation induced by collagen was significantly lower in both marine oil groups. Platelet thromboxane (TX) A2 production induced by collagen or thrombin was markedly reduced by feeding seal or squid oils, the reduction being more pronounced in the seal oil than in the squid oil group. Aortic prostacyclin (PGI2) production was the same among the three groups. The ratio of the productions of aortic PGI2 and platelet TXA2 was significantly higher in the seal oil than in the control group. Although there was no difference in intimal thickness among the three groups, the aortic cholesterol content was significantly lower in the marine oil groups than in the control group. These results showed that the main effects in rats of the different intramolecular distributions of EPA and DHA in dietary fats were on arachidonic acid content in tissue phospholipids and on platelet TXA2 production.

Lymphatic absorption of n - 3 polyunsaturated fatty acids from marine oils with different intramolecular fatty acid distributions

Male Wistar rats were given 0.5 ml of either fish oil or seal oil intragastrically. The intramolecular fatty acid distributions of the triacylglycerols administered were determined by non-specific Grignard degradation followed by isolation and analysis of the 2-monoacylglycerols. The n - 3 polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (20:5(n - 3)) and docosahexaenoic acid (22:6(n - 3)), were located in outer positions (sn-1/3) in the seal oil triacylglycerols whereas the sn-2 position of fish oil triacylglycerols was enriched in 20:5(n - 3) and 22:6(n - 3). The mesenteric lymph was collected over the following 24 h and the absorption patterns of n-3 PUFAs were determined. In the lymph, the n - 3 fatty acids characteristic of the marine oils rapidly increased both with regard to mole percentage and transport (micrograms/min). There were, however, no overall significant differences in the absorption patterns over a 24 h period. The ratio between mole percentage in the oil and mole percentage in the lymph calculated at the steady-state period was significantly greater for both 20:5(n - 3) and 22:6(n - 3) following fish oil administration compared with seal oil. Initially, the recovery of n - 3 PUFAs as a percentage of the total amount transported over the experimental period was higher following injection of fish oil than seal oil but seal oil resulted in greater recovery in the last two fractions at 8 and 24 h post injection, respectively. This indicated that n - 3 PUFAs from fish oil may have been better absorbed in the initial period of digestion but overall the structure of dietary triacylglycerols had negligible effects on the assimilation of n - 3 PUFAs when these were administered as native marine oils.