With 33% of domestic horses affected by obesity, there are concerns that resulting systemic inflammation might lead to development of osteoarthritis (OA) as occurs in humans. Over-production of inflammatory adipokines and cytokines is recognized in obese horses, with a suspected link between adiposity and inflammation that leads to laminitis. Researchers wanted to know if adiposity and related inflammation has effects on equine joint health, as well.
Synovial and plasma prostaglandin E (PGE) and glycosaminoglycan (GAG) are biomarkers used to predict inflammation and/or OA in horses. Canadian researchers sought to correlate these biomarkers to body fat using multi-frequency bioelectrical impedance analysis (mfBIA), a tool that provides an indirect estimate of percentage of body fat [Pearson, W.; Wood, K.; Stanley, S.; MacNicol, J. Exploring relationships between body condition score, body fat, activity level and inflammatory biomarkers. J Anim Physiol Anim Nutr Mar 2018; pp. 1-7].
The researchers used 54 horses of 11 different breeds to obtain body condition scores (BCS), synovial fluid samples and activity levels. BCS in this study positively correlated with body weight, fat mass, fat percentage, plasma PGE and lameness scores— values for obese horses were significantly higher than thin horses in all parameters.
Systemic (plasma PGE) inflammatory biomarkers correlated primarily with BCS, body weight and activity level. The report also mentioned that “BCS and plasma PGE levels appear to be partially mediated by activity level.” However, synovial PGE did not correlate with BCS, activity level or body weight. The authors suggested that, “A great many additional factors contribute to plasma PGE besides body fat.”
As a normal response to acute exercise, PGE is important for exercise adaptation and/or recovery through a number of physiologic responses: vasodilation, muscle hypertrophy and resolution of inflammation. NSAIDs block exercise-induced PGE production; such a blockade might increase oxidative stress and inhibit muscle protein synthesis. Still subject to further investigation is the interaction of exercise-induced PGE to the pro-inflammatory environment of an exercising but overweight horse.