Different antioxidants were described as useful

Different antioxidants were described as useful biomarkers in monitoring response to treatment in human and veterinary medicine [33,65,66]. In the same line, Thiol and TAC also proved to be useful biomarkers in monitoring the post-ovariohysterectomy period in queens with pyometra, since antioxidants were increased at day 10 post-surgery when compared with pre-treatment values in the queens that recovered from the disease, indicating an improvement of the antioxidant capacity of the affected cats. Results obtained in the correlation study between APP and antioxidants suggest that SecinH3 influences the oxidative status in queens with pyometra. Similar results were already described in dogs with leishmaniosis and ehrlichiosis [21,33]. However, this information should be interpreted with caution since differences were observed when different methodologies were used for TAC determinations, and because significant correlations between APP and TAC were only found when determined by the CUPRAC and TEAC2 methods. Older age was associated with higher concentrations of SAA (but not of other APP) in cats, which was suggested to be due to the higher incidence of subclinical diseases in geriatric cats [47]. Information regarding the influence of age in the oxidative status of cats is scarce, but apparently is more significant in males than in females [19]. In the present study, queens of the pyometra group were significantly older than queens of the control group. This difference is related with the fact that feline pyometra is more frequent in middle aged to older queens [2,67], while elective ovariohysterectomy is frequently performed at younger ages. However, the reported influence of age [19,47] is not sufficient to explain the magnitude of differences in concentrations of APP and antioxidants between diseased and control queens obtained in this study. Obesity proved to influence biomarkers of inflammation and oxidative stress in cats [31,68,69]. In the present study, significant differences in body weight were detected between diseased and control cats, which were also mainly related with the age of the animals studied. However, the magnitude of differences in concentrations of APP and antioxidants reported in feline obesity cases [31,68,69] are lower than those observed between diseased and healthy animals included in this study. The etiology of pyometra is multifactorial; repeated uterine exposure to endogenous progesterone and/or exogenous progestogens is considered to be the main factor implicated, however other factors, including uterine neoplasia have been suggested to be involved in pyometra development in queens [[70], [71], [72], [73], [74]]. In the present study, 15 queens of the pyometra group presented a concomitant endometrial adenocarcinoma. Serum amyloid A was reported to be a biomarker of uterine neoplasia in women [75,76]. In our study, SAA concentrations were higher in queens with pyometra and a concomitant endometrial adenocarcinoma than in female cats with pyometra without a concomitant endometrial neoplasia, however the differences were not significant. This fact could be attributed to the great variation in SAA concentrations in each group. Similarly, no significant differences in serum concentrations of Hp, albumin or antioxidants were detected between the two groups. These data suggest that inflammatory and oxidative stress processes occurring in feline pyometra are of similar magnitude regardless of origin, although further long scale studies should be required in order to confirm these observations.
Conclusions
Funding source This work was supported by the Program “Juan de la Cierva Incorporacion” of ‘Ministerio de Economia y Competitividad’, Spain, through a postdoctoral grant (AT); by The National Council for Scientific and Technological development (CNPq) of Brazil through a doctoral scholarship (CPR); and by the “Fundação para a Ciência e a Tecnologia (FCT)” of “Ministério da Ciência, Tecnologia e Ensino Superior”, Portugal, through the project UID/CVT/00772/2013 (HV, SM, MAP and ASF).