Eleanor M. Kellon, VMD
You have probably read more than one thing which claims inflammation causes EMS, or vice versa. Is there really a connection?
In people, the prevailing theory is that it starts with obesity and the rupture of overfilled fat cells causing an inflammatory reaction. As obesity develops in people, so does a clear picture of higher inflammatory cytokines circulating in their blood and increasing insulin levels reflecting insulin resistance. This does not hold true for horses.
Banse, et al., [2016] found that markers of inflammation in skeletal muscle were actually lower in horses that were obese, and lowest of all in obese horses with elevated insulin – the exact opposite of what would be expected in a human.
What about obesity causing high insulin and equine metabolic syndrome? Nope. Lindase, et al., [2016] induced obesity in horses that already had moderately elevated insulin by feeding additional fat, but the resultant 10% weight gain did not worsen insulin resistance. Similarly, Bamford, et al., [2016] studied normal horses and induced obesity by feeding excess fat with or without a once-daily high simple carbohydrate meal. Again, the weight gain did not result in insulin resistance in either group. Contrary to expectations, the horses receiving the high carb meals actually had better insulin sensitivity. This has also been reported in earlier studies and represents an adaptation to the higher carbohydrate feeding in normal horses.
It’s also true that you will find a higher percentage of obese horses with abnormally high insulin than in horses of normal weight. However, the reason for this is probably that horses with insulin resistance gain weight more easily, not because the weight gain causes EMS – a good reminder that association is not causation.
Endocrinopathic/metabolic laminitis is not inflammatory either. Wray, et al., [2013] found chronically laminitic ponies had lower adiponectin than normal but no further differences in nine other markers or mediators of inflammation. Metabolic laminitis also does not show the early influx of neutrophils [a white blood cell] that is seen in other types of laminitis.
Any time there is tissue damage there will be an inflammatory response triggered to clean it up but inflammation is not a root cause of metabolic laminitis which is why NSAIDs typically do such a poor job of controlling the pain.
Antiinflammatory diets or supplements will not control or prevent EMS and laminitis. The only way to do that is to control insulin.
References:
Banse HE, Holbrook TC, Frank N, McFarlane D, Relationship of skeletal muscle inflammation with obesity and obesity-associated hyperinsulinemia in horses Can J Vet Res 2016 Jul; 80(3): 217-24. PMID: 27408335 PMCID: PMC4924556
Lindåse SS, Nostell KE, Müller CE, Jensen-Waern M, Bröjer JT. Effects of diet-induced weight gain and turnout to pasture on insulin sensitivity in moderately insulin resistant horses. Am J Vet Res. 2016 Mar;77(3):300-9.
Bamford NJ, Potter SJ, Harris PA, Bailey SR. Effect of increased adiposity on insulin sensitivity and adipokine concentrations in horses and ponies fed a high fat diet, with or without a once daily high glycaemic meal. Equine Vet J. 2016 May;48(3):368-73. doi: 10.1111 evj.12434. Epub 2015 May 13.
Wray H, Elliott J, Bailey SR, Harris PA, Menzies‐Gow NJ. Plasma concentrations of inflammatory markers in previously laminitic ponies. EqVet Jour December 2012.
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About ECIR Group Inc. Started in 1999, the ECIR Group is the largest field-trial database for PPID and IR in the world and provides the latest research, diagnosis, and treatment information, in addition to dietary recommendations, for horses with these conditions. Even universities do not and cannot compile and follow long term as many in-depth case histories of PPID/IR horses as the ECIR Group.
In 2013 the Equine Cushing’s and Insulin Resistance Group Inc., an Arizona nonprofit corporation, was approved as a 501(c)3 public charity. Tax deductible contributions and grants support ongoing research, education, and awareness of Equine Cushing’s Disease/PPID and Insulin Resistance.
THE MISSION of the ECIR Group Inc. is to improve the welfare of equines with metabolic disorders via a unique interface between basic research and real-life clinical experience. Prevention of laminitis is the ultimate goal. The ECIR Group serves the scientific community, practicing clinicians, and owners by focusing on investigations most likely to quickly, immediately, and significantly benefit the welfare of the horse.
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