Oxidative stress, antioxidants, and assessment of oxidative stress in dogs and cats

Oxidative stress is an important contributor to morbidity for many diseases. Multiple factors influence the interplay between oxidative stress and disease progression. It is a challenge to predict the appropriate type and dosage of antioxidant needed to ameliorate the complex phenomenon of oxidative stress. Standardization of the assessment of damage attributable to oxidative stress and response to treatment is an essential first step for evaluating the success of clinical trials. Isoprostane, a product of ROS action on arachidonic acids, has been a good indicator of oxidative stress in several laboratory studies and clinical trials and offers the benefits of cost effectiveness and non-invasive testing. Because of the enormous complexity of oxidative stress, treatment that encompasses only 1 target is unlikely to yield substantial results. Currently, no single agent has been able to completely ameliorate oxidative stress. The best strategies will, in all likelihood, include a combination of treatments that target several steps in the oxidative stress pathway. Treatments that are promising in small animals include allopurinol administered to cats before oxidative stress and deferoxamine and dimethyl sulfoxide administered to dogs with experimentally created gastric dilatation-volvulus. Nutritional intervention is likely to be a popular method for delivery of antioxidants to pets in the future and offers the benefits of whole-food supplements that contain several synergistic antioxidants. Because oxidative stress is not detectable clinically it can be frustrating to monitor treatment. Obvious improvement in commonly measured variables is rarely evident after treatment with antioxidants. Objective improvement by use of standardized tests in several studies indicates the potential for the role of antioxidants in veterinary medicine. In addition, the lack of toxic effects reported with many of these supplements provides clinicians a greater sense of confidence when prescribing their use. A number of antioxidants (eg, SAMe and coenzyme Q10) have already appeared on the veterinary market. In addition, there are several additives for pet foods. It is likely that large-scale clinical trials will be performed to evaluate the potential beneficial effects of various antioxidants.