Influence of Metabolic Status and Diet on Early Pregnant Equine Histotroph Proteome: Preliminary Findings

Insulin resistance (IR) is characterized by an increase in biomarkers of systemic inflammation and susceptibility to laminitis in horses. Impacts on reproduction include a lengthened interovulatory period in horses. Dietary omega-3 (docosahexaenoic acid [DHA]) promotes anti-inflammatory processes, has been implicated in health benefits, and can reduce cytokine secretion. This preliminary study investigated the impact of IR as well as the influence of dietary supplementation (DHA) on the uterine fluid proteome in early pregnant horses. Mares were artificially inseminated; uterine fluid and embryos were collected on d 12.5 after ovulation. Uterine fluid was pooled for metabolic and diet categories (n = 8; n = 2 per metabolic and dietary status) and concentrated, and the proteome was analyzed using tandem mass spectrometry (iTRAQ). Five proteins met differential abundance criteria (±1.5-fold change, P < .05) in all comparisons (Control C, IS vs. C, IR; C, IS vs. DHA, IS; C, IR vs. DHA, IR). Serum amyloid A, afamin, and serotransferrin were upregulated in C, IR mares but downregulated in DHA, IR mares when compared to C, IS and C, IR, respectively. Quantitative PCR supported mass spectrometry results. The presence of serum amyloid A and serotransferrin in histotroph of IR mares potentially indicates an inflammatory response not seen in IS counterparts. These preliminary findings provide novel evidence on the potential impact of insulin resistance and DHA supplementation on the secreted equine uterine proteome during early pregnancy.