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

Abstract

Objective: To determine the impact of a commercially available docosahexaeonic acid (DHA) supplement (DHA, methylslfonylmethane, and mushroom blend) on equine alveolar macrophage metabolism and lipid and protein profiles in bronchoalveolar lavage (BAL) supernatant.

Methods: This was a prospective, sequential, placebo-controlled study using 10 healthy adult horses. Bronchoalveolar lavage fluid was collected at baseline, following 45 days of oral placebo administration, and following 45 days of oral commercially available DHA supplement, with a 14-day washout. Whole blood was collected following placebo and DHA supplementation. Bronchoalveolar lavage samples were collected for airway cytology. Adherent cells were isolated from BAL cell pellets and used to measure alveolar macrophage oxygen consumption rate and extracellular acidification rate. Protein and lipid profiles were measured in BAL supernatant.

Results: 7 horses completed the study. The DHA supplementation significantly decreased the whole-blood ratio of omega-6 to omega-3 fatty acids and significantly increased the ratio of DHA to arachidonic acid. Following DHA supplementation, mean alveolar macrophage basal and maximal respiratory capacity increased, and protein and lipid profiles in BAL supernatant were altered. There was no significant change in BAL cytology during any study period.

Conclusions: Oral administration of a DHA supplement increased alveolar macrophage oxygen consumption rate and altered lipid and protein profiles in BAL supernatant. Changes in alveolar macrophage metabolism may indicate a greater population of M2 (anti-inflammatory) alveolar macrophages.

Clinical relevance: These findings suggest that oral DHA supplementation may promote an anti-inflammatory profile in the lower airway, which could be beneficial for horses with subclinical airway inflammation and horses routinely exposed to airway-triggering environments.