In a study by Samantha Steelman and Bhanu P. Chowdhary at the Veterinary Integrative Biosciences department of the College of Veterinary Medicine, Texas A and M University, the researchers examined the role of the anti-inflammatory protein APOA-IV in chronic equine laminitis.
Veterinarian performing a lameness exam
Results of a laminitis study support the hypothesis that localized laminar inflammation may be linked to systemic alterations in immune regulation, particularly in the gastrointestinal system.
Laminitis is a painful and debilitating disease of the equine foot. The specific molecular factors initiating laminitis are unknown, but it is often associated with insulin resistance and obesity and can be precipitated by diseases such as colic and diarrhea.
The acute phase of the disease is characterized by the onset of severe lameness and disintegration of the laminae, which connect the hoof wall to the underlying dermis and third phalanx. In many cases, the pathology progresses until the weight of the horse causes dorsopalmar rotation of the third phalanx, detaching it from the hoof wall. This condition is usually not reversible and euthanasia is often the only humane option.
In many instances, horses that survive an episode of acute laminitis are crippled for life. This stage of the disease is termed chronic laminitis or “founder”. Acute laminitis transitions to the chronic form of the disease in an estimated 75% of cases, leaving the majority of afflicted horses permanently lame.
Some evidence suggests that chronic laminar inflammation might be associated with alterations in the endocrine and immune systems. The researchers investigated this broad hypothesis by using DIGE to assess global differences in the plasma proteome between horses with chronic laminitis and controls.
The researchers identified 16 differentially expressed proteins; the majority of these were involved in the interrelated coagulation, clotting, and kininogen cascades. Clinical testing of functional coagulation parameters in foundered horses revealed a slight delay in prothrombin (PT) clotting time, although most other indices were within normal ranges. Upregulation of the intestinal apolipoprotein APOA-IV in horses with chronic laminitis was confirmed by western blot.
Conclusions
Results of the study support the hypothesis that localized laminar inflammation may be linked to systemic alterations in immune regulation, particularly in the gastrointestinal system. Gastrointestinal inflammation has been implicated in the development of acute laminitis but has not previously been associated with chronic laminitis.
Results of the study suggest that chronic equine laminitis is associated with specific changes in the plasma proteome, which might be reflective of alterations in the immune system that are not confined to the foot.
Specifically, the altered abundance of complement proteins and acute phase reactants suggests a chronic activation of the innate immune response.
These results provide a base upon which to build future studies with the ultimate goal of attenuating inflammation and reducing the pain associated with this devastating disease.
Read the Laminitis Study