Oxidative biomarkers and lipid alterations in euthyroid and hypothyroid dogs

Redox status of biomarkers in serum of dogs with hypothyroidism and its treatment with levothyroxine sodium

Information regarding canine hypothyroidism in China remains limited, particularly regarding the redox status of affected dogs. Therefore, the objective of this study was to evaluate the redox status of dogs with hypothyroidism and observe how it changed after levothyroxine replacement therapy. A total of 10 healthy dogs (control group) and 10 dogs with hypothyroidism (treatment group) from China Agricultural University Veterinary Teaching Hospital were included in the study. The redox status was assessed in all 20 dogs. Thyroid profiles such as thyroxine (T4), free thyroxine (fT4), and thyroid-stimulating hormone (TSH) and biomarkers of oxidative stress, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-px), and malondialdehyde (MDA), were assessed on day 0 in all dogs and on days 14 and 45 post-levothyroxine sodium treatment in dogs with hypothyroidism. Dogs with hypothyroidism had decreased levels of serum T4 and fT4 and increased levels of serum TSH. Based on SOD, CAT, GSH-px, and MDA, dogs with hypothyroidism had oxidative stress. Following 45-day treatment with levothyroxine sodium (0.02 mg/kg orally twice daily), antioxidant parameters improved progressively: SOD increased from 60.2 to 76.7 U/mL (Day 0-14) and further to 83.3 U/mL (Day 45); CAT from 105.9 to 115.5 mU/mL (Day 0-14) reaching 132.9 mU/mL (Day 45); GSH-Px from 10.2 to 8.4 U/mL (Day 0-14) then 9.7 U/mL (Day 45), while MDA decreased from 8.2→6.8→4.4 μmol/L correspondingly. In conclusion, increased serum TSH and MDA concentrations, in addition to decreased serum T4 and fT4 concentrations and decreased SOD and CAT activities, indicated that there was oxidative stress in dogs with hypothyroidism. However, there were significant improvements in the redox status of biomarkers in the serum of dogs with hypothyroidism after treatment with levothyroxine sodium (0.02 mg/kg twice daily) for 45 days.

Malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels in canine serum: establishing reference intervals and influencing factors

BACKGROUND

Mounting evidence suggests that malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) are valuable biomarkers of lipid and nucleic acid oxidation in numerous canine diseases. However, their application in clinical settings is limited due to the absence of reference intervals (RI) and the analytical inconsistencies. Therefore, this study aimed to characterize serum MDA and 8-OHdG concentrations in dogs, to establish assay-specific RI, and to identify biological, haematological and biochemical factors influencing these markers.

METHODS

A total of 190 clinically healthy dogs were recruited, including pet dogs, working dogs and shelter dogs. Serum MDA concentration was measured by the Thiobarbituric Acid Reactive Substances (TBARS) assay, while 8-OHdG levels were determined by using a competitive ELISA. RI were established by non-parametric methods. Potential associations between oxidative stress (OS) biomarkers and multiple biological, haematological and biochemical factors were assessed using multivariate regression models.

RESULTS

RI for serum MDA (1.85-14.51 µM) and 8-OHdG (0.06-0.75 ng/mL) were established in the reference population (144 and 143 dogs, respectively). The multivariate regression model for MDA revealed a positive association with total cholesterol concentration, and a negative association with monocyte count. 8-OHdG level was positively associated with urea concentration. Notably, both models also revealed a significant association between MDA and 8-OHdG. Biological factors, including the age and size of the animals, did not exert a significant influence on the results.

CONCLUSIONS

This is the first study to establish serum RI for MDA and 8-OHdG in a large and diverse canine population. Additionally, the multivariate regression models identified relevant haematological and biochemical, but not biological factors that should be considered when interpreting the results. These findings could significantly enhance the application of MDA and 8-OHdG as biomarkers in clinical settings, and promote further exploration of their value in canine diseases.

Oxidative Stress in Canine Diseases: A Comprehensive Review

Oxidative stress (OS), defined as a disruption in redox balance favoring oxidants, has emerged as a major contributor to numerous diseases in human and veterinary medicine. While several reviews have explored the implication of OS in human pathology, an exhaustive review of the canine species is lacking. This comprehensive review aims to summarize the existing literature on the role of OS in canine diseases, highlighting its potentially detrimental effect on various organs and systems. Some inconsistencies among studies exist, likely due to varying biomarkers and sample types. However, there is substantial evidence supporting the involvement of OS in the development or progression of numerous canine disorders, such as cardiovascular, oncologic, endocrine, gastrointestinal, hematologic, renal, neurologic, infectious, and parasitic diseases, among others. Additionally, this review discusses the efficacy of antioxidant and pro-oxidant therapeutic agents for these conditions. Dietary interventions to counteract OS in dogs have gained significant attention in recent years, although further research on the topic is needed. This review aims to serve as a foundational resource for future investigations in this promising field.

Changes in biomarkers of the redox status in whole blood and red blood cell lysates in canine hypothyroidism

Hypothyroidism is the most commonly diagnosed endocrine disease in dogs. The objective of this study was to evaluate the changes in the redox status in canine hypothyroidism using whole blood (WB) and red blood cell (RBCs) lysates. For this purpose, a panel of five antioxidants and five oxidants biomarkers was measured in WB and RBCs lysates of 30 dogs with hypothyroidism, 26 dogs with non-thyroidal illnesses and 15 healthy dogs. The antioxidants measured were cupric reducing antioxidant capacity (CUPRAC), ferric reducing ability of plasma (FRAP), Trolox equivalent antioxidant capacity (TEAC), thiol and paraoxonase type-1 (PON-1). Oxidants measured include the total oxidant status (TOS), peroxide-activity (POX-Act), reactive oxygen-derived metabolites (d-ROMs), advanced oxidation protein products (AOPP) and thiobarbituric acid reactive substances (TBARS). WB showed a significant decrease of the antioxidants CUPRAC, TEAC and thiol, and also an increase in TBARS and a decrease in AOPP in dogs with hypothyroidism compared to healthy dogs. Meanwhile, RBCs lysates showed a significant increase in FRAP and PON-1 in dogs with hypothyroidism. The changes in the redox biomarkers in this study show that WB in canine hypothyroidism had a higher number of changes in biomarkers of the redox status than RBCs lysates, making it a promising sample type for the evaluation of the redox status in this disease. In addition, WB is easier and simpler to process than RBCs lysates and unlike serum, it does not have any hemolysis interference.

Spectrophotometric assays for evaluation of Reactive Oxygen Species (ROS) in serum: general concepts and applications in dogs and humans

Reactive oxygen species (ROS) are reactive compounds derived from oxygen. In biological systems, an excessive amount of ROS can cause oxidative damage to biological macromolecules being involved in different diseases. Several assays have been developed in the last 30 years for ROS evaluation. The objective of this article will be to provide an update about the spectrophotometric methods currently used in the assessment of ROS in serum. The chemical basis of four different techniques will be reviewed, and examples of their possible applications will be provided. A particular emphasis about the practical applications of these assays in the dog will be made, but selected information about their use in humans will also be presented for comparative purposes, following a One-Health approach. The information about the spectrophotometric assays presented in this paper should be interpreted with caution once limited information about them is available yet, and further studies should be performed to clarify what they measure and their clinical application. Ideally, when applied to evaluate a sample's oxidative status, they should be incorporated in a panel of analytes where other oxidants, antioxidants, and biomarkers of inflammation were also included.