The effect of equine metabolic syndrome on the ovarian follicular environment.
Authors: D. R. Sessions-Bresnahan, E. Carnevale
Journal: Journal of animal science
Summary
# Editorial Summary: Equine Metabolic Syndrome and Ovarian Function Metabolic dysfunction in mares may compromise fertility through alterations to the follicular microenvironment, but the cellular mechanisms underlying this reproductive impairment remain poorly characterised. Sessions-Bresnahan and Carnevale compared follicular fluid composition and granulosa cell gene expression between eight insulin-resistant mares (defined by RISQI <0.32 and MIRG >5.50) and twelve metabolically normal controls, collecting samples from preovulatory follicles approximately 24 hours after GnRH and hCG administration as part of assisted reproductive procedures. Mares with equine metabolic syndrome demonstrated significantly elevated serum and follicular fluid insulin and TNF-α, with reduced adiponectin concentrations relative to controls; additionally, granulosa cells from EMS-affected mares showed reduced epiregulin expression and elevated tissue inhibitor of matrix metalloproteinase-2. These findings suggest that the systemic inflammatory state and altered adipokine profile characteristic of EMS penetrates the follicular compartment, potentially disrupting the precise hormonal and growth factor signalling required for optimal oocyte and embryonic development. For practitioners managing breeding mares, this research reinforces the importance of metabolic assessment and weight management in the prebreeding period, though further investigation is needed to determine whether these follicular alterations translate to reduced conception rates, altered pregnancy loss, or downstream effects on offspring health.
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Practical Takeaways
- •Mares with equine metabolic syndrome have compromised fertility due to altered ovarian follicular environment; metabolic management should be a priority before breeding unsound mares
- •The intrafollicular inflammatory state in metabolic syndrome may impair both oocyte maturation and subsequent offspring viability—addressing insulin resistance through diet and exercise is critical for reproductive soundness
- •Consider screening breeding mares for insulin resistance using RISQI or MIRG proxies; metabolically compromised mares may benefit from pre-breeding metabolic stabilization protocols
Key Findings
- •Mares with EMS had significantly higher serum and follicular fluid insulin, leptin, and inflammatory cytokines (TNF-α, IL-1β) compared to controls
- •Adiponectin concentrations were significantly lower in both serum and follicular fluid of EMS mares versus controls
- •Gene expression for epiregulin was significantly elevated in granulosa cells of control mares, suggesting altered follicle maturation in EMS
- •Metabolic biomarkers in serum and follicular fluid were highly correlated (P<0.001), indicating systemic metabolic disease affects the ovarian microenvironment