Serum and liver lipid composition and lecithin: cholesterol acyltransferase in horses, Equus caballus.

This study explores the composition of lipids in the liver and serum of horses and investigates properties of a specific cholesterol-modifying enzyme in the serum, known as lecithin: cholesterol acyltransferase.

Lipid Composition of Serum and Liver

• The first focus was the composition of lipids in horse serum and liver. The researchers found that phospholipids and cholesterol were the main components of serum lipids in horses. On the other hand, triglycerides were present in significantly lower concentrations. In comparison to other mammals, the concentration of liver lipids in horses was found to be similar.

Fatty Acid Composition of Serum Cholesterol Ester

• The study delved into the fatty acid composition of serum cholesterol ester in horses, which appeared to mirror that of the lecithin at the 2-position, with the exception of one type of fatty acid, palmitic acid.

Activity of Serum Cholesterol Esterifying Enzyme

• The activity levels of the enzyme responsible for esterifying cholesterol in horse serum was between 0.03-0.09 mumol/hour per milliliter. When the enzyme was active, there was a noticeable equimolar decrease in both free cholesterol and lecithin. Changes in unsaturated fatty acids also matched well in these two components.

Cholesterol Esterification and Specificity of Acyl-Transferase

• In examining the process of cholesterol esterification, the study found that 5,5′-dithiobis-(2-nitrobenzoic acid) could inhibit the process, but this inhibition was reversible. The acyl-transferase (another enzyme involved in the process) was found to have a specific preference for linoleic acid, a common polyunsaturated omega-6 fatty acid.

In conclusion, these findings provide insight into the lipid composition and enzymatic activity related to lipid and cholesterol processing in horses. Understanding these processes may be helpful in assessing the metabolic health of horses and possibly other related animals.