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Dietary (n-9) Eicosatrienoic Acid from a Cultured Fungus Inhibits Leukotriene B₄ Synthesis in Rats and the Effect Is Modified by Dietary Linoleic Acid^1,2,

Leslie G. Cleland³, Robert A. Gibson^*, Mark A. Neumann^*, Tomohito Hamazaki, Kengo Akimoto^** and Michael J. James

Rheumatology Unit, Royal Adelaide Hospital, Adelaide, SA, Australia ^* Department of Paediatrics and Child Health, Flinders Medical Centre, Bedford Park, SA, Australia First Department of Internal Medicine, Toyama Medical and Pharmaceutical University, Toyama, Japan ^** Institute for Biomedical Research, Suntory Ltd., Mishima-Gun, Osaka, Japan

Eicosatrienoic acid (ETrA) is the (n-9) homologue of (n-6) arachidonic acid (AA) and (n-3) eicosapentaenoic acid (EPA). ETrA can be synthesized endogeneously, but tissue levels are normally undetectable except in essential fatty acid (EFA) deficiency. An ETrA-rich oil extracted from a cultured fungus was used to prepare diets which had varying levels of ETrA (0–8 g/kg diet) in combination with one of two levels of linoleic acid (LA, 2.2 or 9.5 g/kg diet). All diets were sufficient in essential fatty acids. Groups of rats were fed these diets for 4 wk after which leucocyte fatty acid content and leukotriene B₄ (LTB₄) synthesis were measured. The influence of dietary LA on ETrA accumulation in cells was studied and correlations with LTB₄ synthesis determined. ETrA was efficiently incorporated into peritoneal exudate cell (PEC) phospholipids with no evident saturation being observed with levels up to 10 mol/100 mol total fatty acids in peritoneal exudate cells. Cellular ETrA levels were lower (P < 0.001) in rats fed the higher level of LA. ETrA accumulation in peritoneal exudate cells correlated (r² = 0.63, P < 0.05) with reduced LTB₄ synthesis which was attributable to LTA hydrolase inhibition. Thus, dietary ETrA from a biological source can accumulate in leucocytes and suppress inflammatory eicosanoid synthesis. The findings justify further studies into the biochemical and anti-inflammatory effects of dietary ETrA, which could be incorporated into palatable food additives.

KEY WORDS: • (n-9) eicosatrienoic acid • linoleic acid • neutrophils • leukotriene B₄ • rats

¹ Supported by a project grant from the National Health and Medical Research Council of Australia.

² The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

³ To whom correspondence should be addressed.

Manuscript received 26 September 1995. Revision accepted 8 February 1996.