Study points way to saliva test for diagnosing gastric ulcers in horses

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Protein changes in saliva can even distinguish between the two forms of gastric ulcer disease, researchers found.
File image by Mona Eendra

Protein changes in saliva can distinguish between horses with gastric ulcers and their healthy counterparts, scientists report.

Not only that, but the researchers found that they could distinguish between horses with equine glandular gastric disease, which affects the acid-producing lower portion of the stomach, and equine squamous gastric disease, which affects the upper non-acid-producing part of the stomach.

The proteins have potential to be used as biomarkers for the two conditions, they reported in the journal Animals.

Equine gastric ulcers are common in horses and can affect both welfare and performance

The syndrome has has nonspecific clinical signs and its mechanisms are not yet fully understood. The most common clinical signs include poor appetite, weight loss, yawning, teeth grinding or clenching, weight loss, salivation, abdominal discomfort, and reduced performance.

The only diagnostic method currently validated and considered as a gold standard is evaluation of the entire stomach using gastroscopy, which allows the vet to see the lesions and their locations.

Alberto Muñoz-Prieto and his fellow researchers set out to pinpoint salivary proteins with the potential to help diagnose stomach ulcers, using a molecular-based technique that allowed them to identify and quantify the different peptides present.

They used the technique to assess the salivary proteome in 12 horses with gastric ulcers. Half had equine glandular gastric disease and the other half had squamous gastric disease.

The results were compared to those from 10 healthy control horses. Serum was also analysed for comparative purposes.

The comparison between the horses with glandular gastric disease and the controls showed significant changes in 10 salivary proteins, they reported, whereas 36 salivary proteins were differently abundant between those with squamous gastric disease and the controls.

The most upregulated proteins in cases of glandular gastric ulcers were related to immune activation whereas, in horses with squamous gastric ulcers, the most significantly changed proteins were associated with squamous cell regulation and growth.

Compared to serum test results, saliva showed a higher number of proteins with significant changes and a different pattern of changes, the authors reported.

They noted that the number of differentially expressed proteins was more than three times higher in squamous disease than in glandular gastric disease.

Furthermore, the changes were not uniform when the horses with each form of gastric disease were independently compared with the healthy horses.

Many of the proteins with an increased abundance in saliva in horses with ulcers in the lower glandular portion of the stomach are involved in the regulation and activation of the immune system.

The changes in proteins in squamous disease point to an alteration of the squamous mucosa cells. This alteration has been found to be caused by acid and results in hyperkeratosis, erosions, and ulceration.

Many of the risks for the development of squamous disease relate to factors that allow or promote a more acidic gastric pH or increase the exposure of the squamous mucosa to this acid, they noted.

The authors said it is important to point out that their work should be considered a pilot study.

The most important thing, following large-scale validation of their results, should be the development of high throughput tests to quantify the potential biomarker proteins identified.

This large-scale validation should include a larger number of horses with gastric disease, as well as horses with other diseases, in order to determine the clinical sensitivity and specificity of these proteins, and to evaluate their possible use as biomarkers for diagnostic or monitoring purposes.

The proteins identified, in addition to providing new information about the mechanisms behind these diseases, have the potential to be novel biomarkers for diagnosing or monitoring either form of the disease, they wrote.

The protein differences identified in the study make it clear that glandular gastric disease and squamous gastric disease in horses have two different pathophysiological mechanisms, they said. This suggests they should be considered two different diseases instead of combining them into a single equine gastric ulcer syndrome.

The study team comprised Muñoz-Prieto, Maria Dolores Contreras-Aguilar, Jose Joaquín Cerón, Ignacio Ayala, Maria Martin-Cuervo, Juan Carlos Gonzalez-Sanchez, Stine Jacobsen, Josipa Kuleš, Anđelo Beletić, Ivana Rubić, Vladimir Mrljak, Fernando Tecles and Sanni Hansen, variously affiliated with the University of Zagreb in Croatia, the University of Murcia in Spain, the University of Extremadura, also in Spain, Heidelberg University in Germany, and the University of Copenhagen in Denmark.

Muñoz-Prieto, A.; Contreras-Aguilar, M.D.; Cerón, J.J.; Ayala, I.; Martin-Cuervo, M.; Gonzalez-Sanchez, J.C.; Jacobsen, S.; Kuleš, J.; Beletić, A.; Rubić, I.; Mrljak, V.; Tecles, F.; Hansen, S. Changes in Proteins in Saliva and Serum in Equine Gastric Ulcer Syndrome Using a Proteomic Approach. Animals 2022, 12, 1169. https://doi.org/10.3390/ani12091169

The study, published under a Creative Commons License, can be read here

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