Oral docosahexaenoic acid supplementation alters alveolar macrophage metabolism and protein and lipid profiles in the lower airway of healthy horses.

Overview

• This study investigated the effects of oral docosahexaenoic acid (DHA) supplementation on the metabolism and molecular composition of alveolar macrophages and airway fluids in healthy horses.
• The researchers found that DHA supplementation altered cellular metabolism and changed protein and lipid profiles in the lower airway, suggesting a potential anti-inflammatory benefit.

Study Design and Methods

• The study was prospective, sequential, and placebo-controlled, involving 10 healthy adult horses.
• Three sampling points were used: baseline, after 45 days of placebo administration, and after 45 days of oral DHA supplementation, with a 14-day washout period in between placebo and DHA phases.
• Samples collected included:
  • Bronchoalveolar lavage (BAL) fluid for airway cytology and to isolate alveolar macrophages.
  • Whole blood samples after placebo and DHA supplementation phases.
• Metabolic activity of alveolar macrophages was assessed by measuring:
  • Oxygen consumption rate (indicating mitochondrial respiration and energy production)
  • Extracellular acidification rate (related to glycolysis and metabolic changes)
• Protein and lipid compositions were analyzed in the BAL supernatant to determine molecular changes in the airway environment.

Key Findings

• Seven horses completed the entire study protocol.
• DHA supplementation significantly:
  • Decreased the omega-6 to omega-3 fatty acid ratio in whole blood, indicating a shift toward a more anti-inflammatory fatty acid profile.
  • Increased the DHA to arachidonic acid ratio, further showing elevated anti-inflammatory lipid mediators.
  • Raised basal and maximal respiratory capacities of alveolar macrophages, suggesting enhanced mitochondrial activity and possibly a shift in macrophage function.
  • Altered the protein and lipid profiles of the BAL supernatant, indicating changes in airway molecular environment after DHA intake.
• No significant changes were observed in BAL cytology, meaning that the number and types of airway cells did not change during the study period.

Interpretation of Results

• The increased oxygen consumption rate of alveolar macrophages may reflect a higher proportion of M2 macrophages, which are associated with anti-inflammatory and tissue repair functions.
• Changes in the lipid and protein composition of airway fluids support the idea that DHA supplementation modulates the local immune and inflammatory environment.
• The lack of changes in cell counts suggests that the effects are functional/metabolic rather than due to changes in cell population size.

Implications and Applications

• Oral DHA supplementation could be a strategy to promote an anti-inflammatory environment in the lower airways of horses.
• This may be particularly beneficial for horses with subclinical or low-grade airway inflammation that is not overtly obvious in routine cytology.
• Given that many horses are exposed to airway irritants such as dust or allergens, DHA supplementation might help mitigate inflammation and maintain respiratory health.
• Further research would be needed to evaluate the impact of DHA supplementation in horses with clinical respiratory disease or exposed to environmental airway triggers.