26/03/2010Posted : March 26, 2010
Protein in equine fat tissue linked to mortality from colic

A research project funded by The Horse Trust has discovered that the expression of a particular protein in fat tissue is positively associated with an increased rate of post-operative mortality in horses.
 
The research was led by Melissa Packer, who has recently finished a three year clinical training programme at the University of Liverpool funded by The Horse Trust.
 
Miss 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 post operative complications and survival following surgery.
 
After analysing fat samples from 78 horses, Miss Packer found a significant and positive association between the expression of a cytokine called MCP-1 and an increased rate of post-operative mortality.
 
She said: "The relationship between MCP-1 and mortality from colic, opens up the possibility of using it as a diagnostic tool when examining horses. 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."
 
Testing for the genetic expression of MCP-1 would take too long at present, as the DNA must first be amplified using a technique called polymerase chain reaction (PCR). However, further developments in designing a test to detect circulating levels of MCP-1 in the blood could be of great benefit, she claimed.
 
Miss Packer found no relationship between post-operative mortality and the other cytokines she looked at: leptin, adiponectin, TNF, MIF, NGF and IL-6. 
 
During her research, she also looked at the relationship between various cytokines and the Body Mass Index (BMI) of horses (calculated by using data on their age, species, breed, height and weight). Expression of equine leptin from retroperitoneal fat increased significantly with increasing BMI but was not associated with increased post operative mortality.
 
Miss Packer 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. Due to this, she 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. 
 
She now hopes to look at MCP-1 levels in blood to confirm this theory and has already collected and frozen blood samples from each of the 230 horses involved in the study, which she hopes to analyse in the near future.

Miss Packer is currently applying for funding for a PhD to continue research into this area. She said: "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."