b'ENDOCRINOPATHIC LAMINITIS EXPLAINEDEquine metabolic syndrome is not aAdiposity isnt the only thing that cre-singular disease but, rather, a compilationates insulin overload; intestinal changes of risk factors contributing to endocrino- contribute, as well. Specialized endo-pathic laminitis. Typically, EMS horsescrine cells present throughout the gas-are obese with excessive fat depositiontrointestinal tract are distributed along and a cresty neck score of at least 3the mucosal surface that lines the gut, out of 5. They are predisposed to thatsays Manfredi. Their interaction with weight gain and refractory to weight lossintestinal microbiota increases secretion programs. As easy keepers, they tend toof incretin (stimulating a decrease in develop generalized or regional adiposityblood glucose levels) hormones such as (fat pads) if fed too many calories.glucagonlike peptides (GLP1 and 2) in Statistics indicate that 51% of matureresponse to high nonstructural carbohy-light-breed horses in the United States aredrate (NSC) meals, like grain. GLPs are obese. But not all easy keepers on high- implicated in inducing more pronounced calorie diets develop EMS or laminitis. Aand undesirable insulin responses. genetic component might contribute toCathy McGowan, BVSc, MACVSc, body condition and alterations in endo-DEIM, Dipl. ECEIM, PhD, FHEA,FRCVS, crine factors.head of the Department of Equine Clini-Additionally, thin horses of high-riskcal Science at the University of Liverpool, breeds can develop endocrinopathicin the U.K., has pioneered enlightening laminitis from other risk factorshorsesresearch into endocrinopathic laminitis. dont have to be obese to be susceptible,She describes insulins effect on the hoof says Jane Manfredi, DVM, MS, PhD, Dipl.and, in particular, the lamellae. ISTOCK.COMACVS-LA, ACVSMR, assistant professorInsulin alters the messages or signal-at Michigan State Universitys College ofing within lamellar epithelial cells of Veterinary Medicine, in East Lansing.Laminitis can be secondary to PPID, a diseasethe hoof, causing them to change their Just losing weight isnt always enough toprimarily of older horses that causes abnormalstructuremorphing from nice firm avoid endocrine issues.hair growth, shedding, and fat distribution. little boxes to unstructured blobs with The nutrition and body condition of astretched lamellae that wont spring pregnant mare could be another contrib- (ACTH), which in turn amplifies cortisolback, she explains. This is due to dis-uting factor to a foals endocrine state(the stress hormone) secretion from theruption of the cells cytoskeleton (struc-later in life. adrenal glands. Horses with PPID growtural shape). Think of a rubber band that Intestinal health might also play a role.shaggy hair and dont shed normally, theirloses its spring when left out in the sun. Less species diversity in the intestinalfat is distributed abnormally, and theyThen imagine, the harder you force that microbiome is reported in EMS horses,experience muscle wastage. They tendrubber band out of shape (i.e., the more similar to that experienced by humansto drink and urinate excessively and areweight put on the hooves), the more it with metabolic syndrome, says Man- prone to sinus infections, hoof abscesses,deforms with the potential to break. fredi. Additionally, human metabolicand poor wound healing. Infertility is syndrome has been linked with a lossanother common complaint. In 32% ofSigns of Endocrinopathic Laminitisof intestinal barrier function leading toPPID-affected horses, excess circulatingEndocrine-associated laminitis starts increased intestinal permeability, referredinsulin (hyperinsulinemia) amplifies thewith a sometimes-lengthy subclinical to as leaky gut syndrome, which adds torisk of developing laminitis.(nonapparent) phase that causes chronic systemic inflammation, which could alsoA consequence of obesity thats presentchanges in the hoof capsule. McGowan be occurring in horses.in many PPID horses is insulin dys- says it can develop without warning. Endocrine-disrupting chemicalsregulation (ID), which can further leadHowever, as soon as a horse starts (EDCs) are also associated with EMS,to laminitis. Normally, dietary glucosedeveloping telltale divergent hoof rings with reports that they alter gene expres- gets absorbed into the bloodstream tothat are wider at the heel, we know it is a sion and affect metabolism. Many EDCsstimulate the pancreas to secrete insulin.prime candidate for full-blown laminitis persist in fat for prolonged periods, saysWith ID, cells fail to respond to insulinsany day, she says. Some horses can have Manfredi.hormonal signals to take up glucose intoover a years worth of bouts of laminitis The other predominant endocrinemuscle, liver, and fat cells for storage orwith rings extending all the way down the condition that can lead to laminitis ismetabolism. The pancreas then secreteshoof wall, yet have never shown lamini-PPID, which is caused by dysfunction ofmore and more insulin in an attempt totis lameness. Others have more obvious the pituitary pars intermedia, usually insignal glucose uptake. signs, including flaring or distortion of aged horses. That portion of the pituitaryNormally, the liver clears nearly three- the dorsal hoof wall, a flat or convex sole, gland overdevelops, leading to excessivequarters of secreted insulin. Obese horsesand widening of the white line region. production of pituitary hormones, par- and/or those with insulin dysregulationThese horses are really trying to tell their ticularly adrenocorticotropin hormonecannot clear it as well. owners something.18March 2020The Horse|TheHorse.comEndocrineLaminitis.indd 18 2/4/20 9:18 AM'