Effect of dietary linolenic acid on endotoxin-induced thromboxane and prostacyclin production by equine peritoneal macrophages.

This research explored how feeding horses a diet with 8% linseed oil, which is high in alpha linolenic acid, for 8 weeks affects the response of their peritoneal macrophages, a type of immune cell, to endotoxin. The results showed that this diet significantly reduced the production of certain immune compounds, which suggests that linseed oil supplementation could help prevent endotoxemia in horses.

Research Background

• This study centred on evaluating how the diet of horses influenced their immune response, specifically the production of thromboxane A2 (TxA2) and prostacyclin (PGI2), by peritoneal macrophages when exposed to endotoxin. TxA2 and PGI2 are compounds involved in inflammation and blood clotting.
• The study builds on previous research in laboratory animals showing that the diet, particularly one rich in alpha linolenic acid or other n-3 series fatty acids, can cause significant changes in cell membrane composition and arachidonic acid metabolism.

Methodology

• Horses were fed a diet containing 8% linseed oil, a rich source of alpha linolenic acid, for 8 weeks.
• The peritoneal macrophages, immune cells that reside within the abdominal cavity, were then cultured in vitro (in a laboratory setting) and exposed to endotoxin (also known as lipopolysaccharide or LPS) or a calcium ionophore.
• The quantities of TxA2 and PGI2 produced by the macrophages in response to these agents were assessed at 6 and 24 hours.

Findings

• The horses fed with the alpha linolenic acid-enriched diet showed a reduced production of TxA2 by their macrophages in response to the endotoxin compared to their production prior to the change in diet.
• A similar reduction was noted in the production of PGI2 during 6-hour incubation with the endotoxin.
• Interestingly, the production of PGI2 by the macrophages during 24-hour incubation without any agents or with different concentrations of endotoxin, and after being exposed to the calcium ionophore, was higher than during the 6-hour incubation.

Implication

• The lower production of TxA2 and PGI2, compounds typically elevated in inflammation and blood clotting, suggests that an alpha linolenic acid-enriched diet could alter the immune response of horses.
• This reduced inflammatory response implies linseed oil supplementation could represent a preventative measure for conditions such as endotoxemia, which is a serious systemic immune reaction often seen in horses.