Homocysteine—Potential Novel Diagnostic Indicator of Health and Disease in Horses

SIMPLE SUMMARY: Homocysteine is an organic compound that can be measured in the blood of humans and animals. High levels of homocysteine in human blood are associated with an increased risk of heart disease, diseases of blood vessels, formation of blood clots and brain damage. However, the role of homocysteine in the health and disease of domestic animals is poorly understood. This review critically appraises the literature concerning homocysteine in animals, focusing on horses. It aims to clearly define the existing knowledge gap to path an avenue for future research into homocysteine as a potential diagnostic marker of health and disease in this species. ABSTRACT: Homocysteine is an endogenous, non-protein sulfuric amino acid, an intermediate metabolite formed by the methionine transmethylation reaction. Its elevated serum concentration in humans, hyperhomocysteinemia, is a sensitive indicator and a risk factor for coagulation disorders, cardiovascular diseases and dementia. However, the role of homocysteine in veterinary species has not been unequivocally established. Although some research has been conducted in dogs, cats, cattle and pigs, relatively few studies on homocysteine have been conducted in horses. So far, it has been established in this species that homocysteine has an atherogenic effect, plays a role in early embryo mortality and is responsible for the induction of oxidative stress. These preliminary findings support establishing a reference range in a normal population of horses, including horses in training and merit further investigations into the role of this amino acid in health and disease in this species.