The Equine Model to Study the Influence of Obesity and Insulin Resistance in Human Ovarian Function

Background: Understanding ovarian folliculogenesis is critical to the study of fertility and in the development of fertility techniques as well as contraception. Mares and women share striking similarities in ovarian folliculogenesis, and in insulin resistance and obesity syndromes. The effects of insulin resistance and obesity on follicular development and the surrounding endocrinology and genes in mares may shed light on the causes and effects of metabolic and reproductive disorders such as polycystic ovarian syndrome (PCOS) in women using an appropriate research model. Review: Studies in laboratory animals (e.g. mice and rats) have demonstrated that, in general, these animals are not good research models to study ovarian function in women because of the remarkable physiological differences in ovarian folliculogenesis and luteogenesis/luteolysis. Therefore, there is an urgent need for the development of in vivo (whole animal) research models using species (e.g. mare and cow) that have a similar physiological ovarian function to the woman. The use of such models will allow for an understanding of the causes and effects of different pathological reproductive processes involved in diseases. Several studies from our group and others have shown that nowadays the mare seems to be one, if not the best, animal model to study ovarian function in women. In addition, the recent elucidation of the equine genome has provided evidence of the high gene conservation and similar chromosomal order of this species to humans, reinforcing the importance of this species for comparative studies with humans. Conclusions: The use of farm animal models is also relevant for agricultural and biomedical research because this might help to improve reproductive efficiency and health in animals and humans, as well as the quality of products (e.g. oocytes, embryos, etc.). This review will focus on the potential use of the mare as a model to study the effects of obesity and insulin resistance syndromes on ovarian function in women.