Study unlocks potential anti-inflammatory action of ETA omega-3

By Stephen Daniells

- Last updated on GMT

© Getty Images / gonin
© Getty Images / gonin
You’ve heard of EPA and DHA omega-3, but what about ETA? A new study from Canada indicates that ETA (eicosatetraenoic acid, 20:4) may convert into two novel compounds associated with inflammation management.

The results could have implications for SDA-rich oils, such as Buglossoides arvenis​ oil (Ahiflower oil) and Echium oil, because SDA (stearidonic acid, 18:4) is the immediate omega-3 metabolic precursor to ETA.

The novel metabolites were identified as 8‑hydroxy‑9,11,14,17-eicosatetraenoic acid (Δ17-8-HETE) and 8,15-dihydroxy-9,11,13,17-eicosatetraenoic acid (Δ17-8,15-diHETE) and were found to be produced and mediated through similar enzymes (called lipoxygenases) to those deriving from marine and algal oils rich in EPA and DHA.

“Current dietary sources of long-chain n-3 PUFAs are mainly of marine origin. However, diminishing fish stocks  have led to current efforts to identify sustainable and efficacious sources of n-3 PUFA,”​ wrote the researchers, led by Marc Surette and Kristine Gagnon from the University of Moncton, in the Prostaglandins, Leukotrienes and Essential Fatty Acids​.

“Such alternative sources include plant-derived oils that are rich in stearidonic acid (SDA, 18:4 n-3) whose consumption leads to increased tissue concentrations of 20-carbon n-3 PUFA including 20:4 n-3. The current study suggests that this n-3 PUFA is a precursor to compounds that possess anti-inflammatory properties.”

“Leading the way”

Ahiflower flower close up
Buglossoides arvensis. Image courtesy of Nature's Crop International

The study was funded by the Atlantic Innovation Fund program of the Atlantic Canada Opportunities Agency, the New Brunswick Innovation Foundation, and by Nature's Crop International (the exclusive producers of Ahiflower oil).

The commercially available oil reportedly offers the highest levels of non-GM omega-3 essential fatty acids among commercially available dietary plant oils, combining ALA (alpha linolenic acid) and high levels of SDA. It also offers GLA (gamma linolenic acid), an omega-6 essential fatty acid, and oleic acid, an omega-9 fatty acid, to complement the overall healthy profile of this plant oil.

The findings were welcomed by Greg Cumberford of Nature's Crops Incorporated, who expressed gratitude to Dr. Surette and his Canadian research colleagues “for delving deeply into the beneficial parallel role that plant-derived omegas like Ahiflower oil play in supporting natural anti-inflammatory response mechanisms, alongside marine omega sources.

“I personally believe that Ahiflower oil's uniquely high SDA and anti-inflammatory GLA combination will continue to 'cut new ice' in our understanding of anti-inflammatory response support mechanisms. The researchers from Moncton are leading the way globally.”

Study details

The University of Moncton researchers reported last year in Nutrients​ that consumption of Ahiflower oil may support the body's natural anti-inflammatory response, for example after strenuous exercise or immune challenge.

For their new study, they used a cellular model to discover that 5-lipoxygenase converts ETA to Δ17-8-HETE and Δ17-8,15-diHETE. The former has previously been identified by other researchers, said Gagnon and her co-authors, but Δ17-8,15-diHETE is novel.

They also found that Δ17-8,15-diHETE was able to inhibit inflammatory processes, such as neutrophil leukotriene stimulation and neutrophil chemotaxis, indicating an anti-inflammatory role for this novel compound.

“ETA content is typically not reported in human tissues because of its low abundance. However, with the recent emergence of [SDA]-containing dietary oils like Echium and Buglossoides oil, measurable quantities of ETA in human leukocytes, erythrocytes and plasma are measured after as little as 2–4 weeks of dietary supplementation as a result of the elongation of [SDA]. Thus, natural LTB4 receptor antagonists such as Δ17-8,15-diHETE may be released at inflammatory sites when the diet is supplemented with stearidonic acid and could be of benefit in individuals with inflammatory diseases,” ​wrote Gagnon and her co-authors.

“Moreover, metabolites of [ETA] could possibly possess anti-inflammatory or pro-resolving activities analogous to the well described EPA, DPA and DHA -derived resolvins, protectins and maresins. These latter compounds are products of dual lipoxygenase activities and it is likely that ETA is also a substrate for the generation of such metabolites.

“Given that the action of a single lipoxygenase can generate a compound with biological activity as shown in the present study, the investigation of other putative [ETA] metabolites and their biological activities is warranted.”

Source: Prostaglandins, Leukotrienes and Essential Fatty Acids
2018, Volume 138, Pages 33-44, doi: 10.1016/j.plefa.2018.10.005
“5-lipoxygenase-dependent biosynthesis of novel 20:4 n-3 metabolites with anti-inflammatory activity”
Authors: K.J. Gagnon et al.

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