Airway Lipid Mediators in Horses: Baseline Bronchoalveolar Lavage Fluid Profiles and Effects of EPA and DHA-rich Microalgae Oil Supplementation.

Overview

• This study examined how dietary supplementation with omega-3 fatty acids (EPA and DHA) from microalgae oil impacts airway inflammation and lipid mediator profiles in the lung fluid of healthy horses.
• Researchers measured lung immune cells, lipid mediators, and blood fatty acid levels before and after feeding horses an EPA- and DHA-enriched diet compared to controls.

Introduction and Background

• Airway inflammation in horses, such as equine asthma, is commonly marked by increased neutrophils (a type of immune cell) in the bronchoalveolar lavage fluid (BALF), which is obtained by washing the lung airways.
• Omega-3 polyunsaturated fatty acids (n-3 PUFAs), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are essential nutrients that help regulate inflammation.
• EPA and DHA are precursors to specialized pro-resolving mediators (SPMs), which help resolve inflammation and restore tissue health.
• Despite established roles in other species, the effects of EPA and DHA supplementation on equine airway inflammation and lung lipid mediator profiles had not been thoroughly characterized.

Study Design

• A prospective field trial was conducted over 7.5 weeks involving horses assigned to one of three diets: one enriched with EPA and DHA from microalgae oil and two control diets lacking the supplementation.
• Samples were collected from horses before and after the dietary intervention:
• Bronchoalveolar lavage fluid (BALF) was collected to assess airway inflammatory cells and lipid mediators.
• Blood samples were taken to measure red blood cell fatty acid composition.
• Advanced analytical techniques were applied:
• Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyzed the lipid mediator profiles in BALF.
• Gas chromatography of fatty acid methyl esters quantified the fatty acid composition in red blood cells.

Key Findings

• EPA and DHA supplementation led to a reduction in the percentage of neutrophils in the BALF, indicative of decreased airway inflammation.
• In un-supplemented control horses, BALF neutrophil percentages increased over time, showing worsening inflammation without omega-3 intervention.
• The supplemented horses showed increased levels of EPA and DHA in their red blood cells, confirming effective absorption and incorporation of these fatty acids.
• The ratio of n-3 to n-6 polyunsaturated fatty acids in red blood cells increased with supplementation, reflecting a more anti-inflammatory fatty acid profile systemically.
• This was one of the first studies to describe BALF lipid mediator profiles in clinically healthy horses using LC-MS/MS:
• DHA-derived lipid mediators and their biosynthetic pathway markers predominated in healthy horse airways.
• Supplementation tended to increase precursor fatty acid availability but did not significantly boost downstream specialized pro-resolving mediator (SPM) production.
• Seasonal variation seemingly influenced BALF levels of maresins, a class of DHA-derived SPMs, suggesting environmental or physiological changes across seasons affect lung mediator profiles.

Implications and Conclusions

• The results support that dietary EPA and DHA can beneficially modulate airway inflammation in horses, potentially through altering fatty acid pools and precursor availability rather than directly increasing SPM production in the lungs.
• The predominant presence of DHA-derived lipid mediators in healthy horse airways highlights their importance in maintaining pulmonary homeostasis.
• These findings could inform nutritional management strategies for equine asthma and other inflammatory airway diseases by leveraging omega-3 supplementation.
• Further studies may investigate the long-term impact of supplementation on clinical respiratory outcomes and the precise mechanisms regulating SPM biosynthesis in equine airways.