Eleanor M. Kellon, VMD
MMPs are matrix metalloproteinases – enzymes that break down connective tissue protein/collagen in the body. If you follow news releases and articles about equine laminitis, you have surely seen mention of MMP enzymes since the late 1990s. Turns out they are not the major players as was originally thought.
The basement membrane (BM) in the hoof is a thin layer of connective tissue lining the junction between the dead laminae of the hoof wall, and the live laminae of the inner hoof. This system locks the hoof wall to the tissues inside like Velcro.
In laminitis caused by things like colic/gut infections, black walnut shavings, grain, or experimental fructan overload, it was noted the basement membrane is damaged or destroyed and that the level of MMP enzymes is increased. This led to the theory that the activation of MMP is what causes laminitis.
These various causes of laminitis are also associated with inflammation. White blood cells invade the hoof and the body, in general, is in an inflammatory state. It didn’t take long for research to start showing inflammation was not a feature of endocrinopathic laminitis, which is caused by high insulin.
Basement membrane damage and high MMP levels are also not a feature of endocrinopathic laminitis. In fact Visser and Pollitt (2012), have also shown that most of the MMP present in fructan-induced laminitis is inactive, bringing into question what, if any, role it plays.
These differences are summarized in an article by Patterson-Kane, et al. (2017), which you can download for free here: https://www.researchgate.net/publication/321257027_Paradigm_shifts_in_understanding_equine_laminitis.
Since it is estimated that 90% of all laminitis cases are caused by high insulin, these findings have important indications. They explain why anti-inflammatories like phenylbutazone or fibrocoxib have limited effect in laminitis pain. They also mean you need to involve your veterinarian in a diagnostic plan that determines what type of hormonal disorder your horse has, and how to most effectively get insulin down, because that is the only thing that will relieve the pain.
Ancillary supplements to balance the diet and improve blood flow to the hoof also play an important role.
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Visser MB, Pollitt CC, The timeline of metalloprotease events during oligofructose induced equine laminitis development 23 June 2011; https://doi.org/10.1111/j.2042-3306.2011.00393.x
Patterson-Kane J, Karikoski N, Mcgowan CM, Paradigm shifts in understanding equine laminitis November 2017 The Veterinary Journal 231 DOI:10.1016/j.tvjl.2017.11.011
About ECIR Group Inc.
Started in 1999, the ECIR Group is the largest field-trial database for PPID and EMS 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/EMS 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 EMS.
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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