Synthesis of arachidonic acid metabolites by Syrian hamster platelets and peritoneal cells

Supplementation of Ω-3 Fatty Acids in Parenteral Nutrition Beneficially Alters Phospholipid Fatty Acid Pattern

BACKGROUND

The clinical safety and the uptake of omega-3 polyunsaturated fatty acids (PUFA) into the serum phospholipids and erythrocyte membranes after administration of fish-oil-supplemented parenteral nutrition (PN) was investigated in colorectal surgical patients.

METHODS

Forty patients undergoing colorectal surgery (n = 40) and with an indication for PN were enrolled in a prospective, double-blind, randomized study to receive an omega-3 PUFA-supplemented 20% lipid emulsion (Lipoplus; B. Braun Melsungen, Melsungen, Germany; test group, n = 19) for 5 days postoperatively. The control group received a standard 20% fat emulsion (Lipofundin MCT/LCT, B. Braun Melsungen, Melsungen, Germany, control group, n = 21). Clinical outcome parameters and safety were assessed by means of adverse events recording clinical parameters and hematologic analyses. The contents of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as well as arachidonic acid (AA), in phospholipid fractions in plasma and in erythrocytes were analyzed preoperatively, on postoperative days 1, 6, and 10 using liquid gas chromatography.

RESULTS

Both fat emulsions were well tolerated, and none of the adverse events was considered to be related to treatment. Postoperative infectious complications occurred in 4 patients of the omega-3 PUFA group vs 7 patients in the control group. As compared with the control group, the omega-3 PUFA group had significantly increased levels of EPA in the membranes of the erythrocytes in postoperative day 6 (2.0% +/- 0.9% vs 0.8% +/- 0.5% fatty acid methyl esters, [FAME]) and postoperative day 10 (2.1% +/- 0.8% vs 0.9% +/- 0.7% FAME, p < .05). Also, the EPA levels in the serum phospholipids were significantly higher than in the control group on the same postoperative days (7.0% +/- 2.6% vs 1.3% +/- 0.8% and 3.6% +/- 1.0% vs 1.0% +/- 0.4% FAME, p < .05). The DHA levels in the serum phospholipids were significantly higher in the omega-3 PUFA group compared with the control on postoperative days 6 and 10 (11.8% +/- 1.9% vs 8.4% +/- 1.5% and 11.2% +/- 1.6% vs 8.5% +/- 1.4% FAME, p < .05). AA levels were not significantly different in the both groups.

CONCLUSIONS

Omega-3-fatty-acids-supplemented fat emulsions for parenteral administration are safe and very well tolerated. This study demonstrates that parenteral administration of omega-3-PUFA-enriched fat emulsions leads to increased incorporation of EPA and DHA into phospholipids in serum and erythrocytes, whereas AA levels remain unchanged. Thus, postoperative parenteral administration of omega-3-PUFA-enriched lipid emulsions could have an impact on the postoperative inflammatory response after abdominal surgery and could be used in standard postoperative care when PN is indicated.

The change in leukotrienes and lipoxins in activated mouse peritoneal macrophages

The aim of this study was to investigate to what extent the generation of leukotrienes (LTs) and lipoxins (LXs) was affected by the expression of definite levels of macrophage activation. We used a system of murine peritoneal macrophages at different states of activation consisting in resident macrophages and FCS-, thioglycollate- or Corynebacterium parvum-elicited macrophages. The profile of lipoxygenase metabolites in resident macrophages was characterized by the presence of high levels of 12-HETE, followed by 15-HETE, 5-HETE, LTB(4) and 6-trans-LTB(4), 6-trans-12-epi-LTB(4). A comparable pattern was also found in FCS-elicited macrophages which appeared not to be responsive to the challenge with interferon gamma plus LPS, as measured by the generation of NO and tumor necrosis factor alpha. Resident as well as FCS-elicited macrophages also generated appreciable quantities of LXs (A(4) and B(4)). Thioglycollate-elicited macrophages, which expressed a state of 'responsive' macrophages, showed a block of the LT and LX synthesis. This block was also present in C. parvum-elicited macrophages which expressed a fully 'activated' phenotype, reflected by their capacity of releasing NO and tumor necrosis factor alpha even though they were not challenged. These results provide the first evidence that the level of 'responsive' as well as 'activated' macrophages was associated with of a simultaneous block of LTB(4) and LXs.

Cloning, sequencing and expression of a 5-lipoxygenase from Syrian hamster embryo fibroblasts

The hamster ortholog of human and rat 5-lipoxygenase (5-LO) was cloned from a Syrian hamster embryo (SHE) cell line. A combination of polymerase chain reaction (PCR) and 5' and 3' RACE (rapid amplification of cDNA ends) was used to isolate the complete cDNA for this gene. The cDNA sequence demonstrates the extreme sequence conservation found in this gene family, with a deduced amino acid sequence 95% identical to the rat 5-LO, and 90% identical to the human enzyme. The hamster 5-LO was expressed in E. coli. The expressed protein was detected by an antibody to human 5-LO, and had an apparent molecular weight of 75-80 kD. The products of the action of this enzyme on arachidonic acid are 5-HETE and the diHETEs resulting from the breakdown of LTA4, in a pattern similar to that produced by the recombinant human 5-LO. No oxidation of linoleic acid by this enzyme was detected.

Dietary n - 3 polyunsaturated fatty acids modify Syrian hamster platelet and macrophage phospholipid fatty acyl composition and eicosanoid synthesis: a controlled study

The aim of this study was to determine the effects of varying intakes of dietary n - 3 polyunsaturated fatty acids (PUFA) on the fatty acyl composition and arachidonic acid metabolite synthesis of platelets and macrophages in Syrian hamsters consuming diets that were strictly controlled for n - 6 PUFA content. Animals consumed highly controlled diets which were not supplemented with n - 3 PUFA (control) or supplemented with 0.4%, 0.8% or 2% (w/w) n - 3 fatty acids. The content of n - 3 PUFA in cellular phospholipids increased progressively with the intake of n - 3 PUFA, while n - 6 PUFA, including arachidonic acid, decreased despite the constant intake of 18:2(n - 6); this latter effect was more substantial in macrophages than in platelets. The synthesis by stimulated macrophages of prostaglandin E2, 6-keto-prostaglandin F1 alpha, thromboxane B2 and 11- and 15-hydroxyeicosatetraenoic acids decreased with the intake of 0.8% n - 3 PUFA to 30-50% of the control values. Little effect of diets on platelet aggregation and eicosanoid synthesis was observed reflecting the limited effect on platelet arachidonic acid content. The synthesis of 12-hydroxyeicosapentaenoic acid by stimulated platelets increased with n - 3 PUFA consumption in a dose-dependent fashion. Circulating triacylglycerols and HDL-cholesterol were decreased only in animals consuming 2% n - 3 PUFA. The strict control of n - 6 PUFA intake allows the determination of the effects of n - 3 PUFA intake on the measured parameters without confounding effects of other dietary lipids.