Changes in Oxidative Status Biomarkers in Saliva and Serum in the Equine Gastric Ulcer Syndrome and Colic of Intestinal Aetiology: A Pilot Study

Abstract

Changes in the oxidative status of the blood of horses suffering from gastric ulcers and colic of intestinal aetiology (CIE) have been reported. However, saliva can also be a source of biomarkers of oxidative status. Therefore, this study aims to validate automated assays for the measurement of oxidative status biomarkers (ferric reducing ability of saliva/serum—FRAS/FRAP, cupric reducing antioxidant capacity—CUPRAC, the Trolox equivalent antioxidant capacity—TEAC, uric acid, and advanced oxidation protein products—AOPP) in the saliva and serum of horses, to assess their changes in the different ulcer gastric diseases (squamous—ESGD and glandular—EGGD) and CIE, and to evaluate their relationship with serum amyloid A (SAA), adenosine deaminase (ADA), and the systemic inflammatory response syndrome (SIRS) status. The assays showed a low imprecision and good linearity with enough sensitivity in both fluids. In EGGD, higher levels of FRAS, uric acid, and AOPP in saliva were observed compared to the healthy group, correlating with the salivary ADA levels. Horses with CIE showed increases in uric acid concentrations in serum associated with their SIRS status and outcome of the disease. In conclusion, analytes related to the oxidative status can be measured in the saliva and serum from horses by automated assays, and some of them can potentially be assessed as biomarkers in horses with gastric ulcers and CIE.

Clinical insights: Clinicopathological parameters for diagnosing and predicting outcome of horses with colic

“…Across all causes of colic, the most useful novel marker was the serum ratio of advanced oxidation protein products (AOPP) to albumin concentration, as this was increased in cases of colic compared with healthy horses. 43 Horses with glandular gastric ulcer disease had higher concentrations of salivary uric acid, AOPP, and ferric reducing ability of saliva. Cases of colic of nongastric intestinal origin had a higher serum uric acid concentration compared with controls, and this value was also associated with SIRS and nonsurvival.…”

“…One recent study examined the concentrations of multiple oxidative status biomarkers in saliva and blood from healthy horses and horses with colic. 43 Horses presented for colic were grouped into those with equine gastric ulcer syndrome (either squamous, glandular or both) or all other intestinal causes of colic. Across all causes of colic, the most useful novel marker was the serum ratio of advanced oxidation protein products (AOPP) to albumin concentration, as this was increased in cases of colic compared with healthy horses.…”

“…Cases of colic of nongastric intestinal origin had a higher serum uric acid concentration compared with controls, and this value was also associated with SIRS and nonsurvival. 43 A previous study by the same group evaluated salivary alphaamylase (sAA) activity and concentration in healthy horses and horses with acute colic. 44 In humans, sAA is used as a marker of sympathetic nervous system stimulation, and as an alternative to measurement of serum catecholamine concentration.…”

“…Saliva is particularly attractive for its relatively noninvasive collection method, particularly as compared with peritoneal fluid. One recent study examined the concentrations of multiple oxidative status biomarkers in saliva and blood from healthy horses and horses with colic 43 . Horses presented for colic were grouped into those with equine gastric ulcer syndrome (either squamous, glandular or both) or all other intestinal causes of colic.…”

“…Horses presented for colic were grouped into those with equine gastric ulcer syndrome (either squamous, glandular or both) or all other intestinal causes of colic. Across all causes of colic, the most useful novel marker was the serum ratio of advanced oxidation protein products (AOPP) to albumin concentration, as this was increased in cases of colic compared with healthy horses 43 . Horses with glandular gastric ulcer disease had higher concentrations of salivary uric acid, AOPP, and ferric reducing ability of saliva.…”