Plasma lipids, lipoproteins and post-heparin lipases in ponies with hyperlipaemia.

This research investigates the metabolic origins of equine hyperlipaemia by analysing plasma lipoproteins in ponies affected by this condition, and suggests that overproduction of VLDL, not faulty catabolism, is the cause.

Objective and Methodology of the Research

• The research aimed to understand the origins of equine hyperlipaemia, a disorder where there is an excessive amount of lipids (fats) in the blood, by investigating the concentration and makeup of plasma lipoproteins in ponies with this condition.
• A total of 18 ponies with hyperlipaemia were analysed and compared against a control group of 18 healthy ponies.
• The metabolic components, including cholesterol, triglyceride, and very low-density lipoproteins (VLDL) levels, were measured and compared.

Findings

• A significant increase in mean concentrations of cholesterol, triglyceride, and VLDL levels were found in the ponies with hyperlipaemia.
• Among the observations, a new lipoprotein fraction, named VLDL1, was discovered to be prevalent in ponies with hyperlipaemia but absent in healthy ponies. This VLDL1 was found to be enriched in triglyceride and free cholesterol, but deficient in cholesteryl esters, phospholipid, and protein.
• The ratio of apoB-100 to apoB-48 particles was also different in VLDL1 than the normal ratio present in control VLDL, with more apoE present in the VLDL1.
• Despite the overproduction of VLDL particles, the liver had increased activities of lipoprotein lipase and hepatic lipase, the enzymes responsible for breaking down VLDL and its remnants, suggesting that the liver was trying to cope with the increased concentration of substrate.

Conclusion

• The findings led researchers to conclude that it was the overproduction of VLDL, not the faulty catabolism, causing the hyperlipaemia. This meant that it wasn’t that the body was unable to break down the lipids but that more VLDL than normal was being produced in the first place.
• The 17 out of 18 ponies with hyperlipaemia showed increased plasma free fatty acid (FFA) concentrations, leading the team to suggest that an increased FFA flux could be stimulating the liver to synthesise more triglyceride and secrete more VLDL.
• The researchers propose lipid-lowering agents as potential treatment options for managing hyperlipaemia in ponies. The agents would work by reducing VLDL synthesis, thus decreasing adipose lipolysis and FFA flux.