Last November during the Frank J. Milne State-of-the-Art Lecture at the 57th Annual American Association of Equine Practitioners
(AAEP) Convention, Oklahoma State University PhD student Heidi Banse, DVM, Dipl. ACVIM, was one of two inaugural recipients
of a $5,000 fellowship to support her endeavors in equine research. The AAEP Foundation and The EQUUS Foundation have partnered
to support this fellowship, which seeks to assist equine researchers in exploring horse healthcare topics.
According to the AAEP, Banse's doctoral research, performed under the direction of Dianne McFarlane, DVM, PhD, Dipl. ACVIM,
focuses on the molecular events underlying equine metabolic syndrome (EMS). Middle-aged horses are most commonly affected
by this endocrine disorder, which results in obesity, regional adiposity, insulin resistance and a predisposition to laminitis.
If we can identify the metabolic events that lead to EMS, we may be able to diagnose and treat it earlier, resulting in a
better outcome. Banse's long-term goal is to identify an intervention for horses with EMS that is based on better knowledge
of endocrine disorder's pathophysiology.
Equine metabolic syndrome: An overview
Obesity (body condition score of 8 or 9) (Photo 1), regional adiposity (on the neck crest, tail head, prepuce, mammary gland
region) (Photo 2) and insulin resistance are all associated with EMS, a condition associated with a predisposition to laminitis
(Photo 3). However, the molecular events underlying how laminitis develops in these horses is still not fully understood.
EMS most commonly occurs in Morgan horses, Paso Finos, Arabians, Saddlebreds, Quarter horses, Tennessee Walkers and ponies.
Most horses with EMS within these breeds are "easy-keepers"—likely to easily put on excessive body weight despite feed restriction.
Photo 1: An obese horse with EMS. (Photos courtesy of Dr. Banse)
Pasture-associated laminitis is common, as access to new rapidly growing spring pasture with a high water-soluble carbohydrate
content can allow for high-energy intake and the development of obesity. When horses graze such pasture, increased resting
plasma insulin often results.
Photo 2: Regional adipose tissue on a pony’s neck.
In a recent report, Nicholas Frank, DVM, PhD, Department of Large Animal Clinical Sciences, University of Tennessee's College
of Veterinary Medicine suggested that for these animals, "hyperinsulinemia is the trigger for disease."1 He also noted, "Pasture grazing also raises the risk of intestinal carbohydrate overload, particularly when animals are
moved onto new pastures without gradual transition."
Photo 3: Laminitis in the same pony as in Photo 2.
This allows for increased high-energy substrate for the lower gut fermentation, which increases lactic acid concentrations,
decreases pH and raises mucosal permeability. This may lead to an increase of various toxins and pro-inflammatory cytokines
(tumor necrosis factor alpha, interleukin-1-beta) in the circulation and a potential inflammatory response—in other words,