Colic Surgery? Protein Expression Test Could Help Guide Decision

Expression of a particular protein in fat tissue is positively associated with an increased rate of postoperative mortality in horses, researchers recently reported.

The research was led by Melissa Packer, BVetMed, MRCVS, who recently finished a three year clinical training program at the University of Liverpool, funded by The Horse Trust.

Packer collected abdominal fat samples from around 230 horses undergoing colic surgery. She then looked at the expression of various cytokine genes in the fat tissue to see which cytokines were being produced. Each of the 230 horses were then followed over the next two years, with data gathered on postoperative complications and survival following colic surgery.

After analysing fat samples from 78 horses, Packer found a significant and positive association between the expression of a cytokine called MCP-1 and an increased rate of postoperative mortality.

"The relationship between MCP-1 and mortality from colic opens up the possibility of using it as a diagnostic tool when examining horses," Packer said. "Such a test would be a useful additional tool for vets when dealing with horses that are seriously ill and where it is uncertain whether they would survive additional surgery, or whether it is better to consider euthanasia."

Packer found no relationship between postoperative mortality and the other cytokines she looked at, which included leptin, adiponectin, TNF, MIF, NGF and IL-6.

During her research, Packer also examined the relationship between various cytokines and the BMI of horses. Expression of equine leptin from retroperitoneal fat increased significantly with increasing BMI but was not associated with increased postoperative mortality.

She expected to find a higher genetic expression of MCP-1 in the fat tissue of obese horses as they would be expected to have a lower survival rate from colic surgery.

However, she found the opposite--that the expression of the MCP-1 genes was lower in obese horses. Packer hypothesises that this could be because obese horses already have the maximum level of MCP-1 in their blood, so are no longer producing the cytokine within their fat cells at the time of sampling.

Packer now hopes to look at MCP-1 levels in blood to confirm this theory. She has already collected and frozen blood samples from each of the 230 horses involved in the study, so hopes to analyze these samples in the near future.

Packer is currently applying for funding for a PhD to continue research into this area. "Obesity is a major health issue for horses, so it is vital that we have a better understanding of the impact obesity has on colic surgery survival rates," said Packer.

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