Banse's research—cell metabolism
In people, mechanisms associated with insulin resistance and metabolic syndrome include mitochondrial dysfunction, oxidative
stress, increased intracellular lipid accumulation and inflammation. The goal of Banse's research is to determine the mechanism
of insulin resistance associated with EMS.
Banse's research to date has focused on metabolic gene expression in horses and markers of mitochondrial dysfunction. Thus
far, there has not been evidence that expression of genes involved in glucose and lipid metabolism are impaired with obesity
and insulin resistance in horses. Furthermore, indirect evaluation of mitochondria within skeletal muscle has not demonstrated
a role of impaired mitochondrial function in insulin resistance in the horse.
A lot of research in EMS that has been done has involved horses that are obese but not necessarily those that fulfill the
definition of EMS, with a history of laminitis.
"Much of what we know about EMS is derived from insulin-resistance horses," says Banse. "What has been established is that
horses with insulin resistance have a dysregulation of the insulin pathway. Research out of Ohio State University has demonstrated
that the number of glucose transporter vesicles within the cell is unchanged, but there are not as many on the cell surface
in horses with insulin resistance compared with those that are not insulin resistant."
Further work is needed to clarify the mechanism responsible for the failure of the glucose transporter to reach the cell surface.
In addition, it is important to determine whether horses with clinical EMS are similar to those with obesity and insulin resistance
Another issue that people have been looking at is the presence of inflammation in horses with insulin resistance and EMS.
In people, there is evidence that inflammation promotes insulin resistance. However, thus far, "there hasn't been a lot of
data to indicate that inflammation is associated with EMS in the horse," says Banse. Furthermore, studies examining the role
of inflammation in insulin resistance and obesity have yielded mixed results. The role of inflammation with both insulin resistance
and EMS will continue to be investigated.
"Since there are breeds that are predisposed to EMS, it does indicate that there may be some genetic basis for the syndrome,"
Banse says. The University of Minnesota has an ongoing large-scale study designed to determine the genetic basis for EMS.
The results of this study may provide future directions for research into the pathophysiology of EMS in horses of all breeds.
"We're doing our studies in a step-wise fashion," says Banse, "looking first broadly at the role of metabolic pathways, insulin
signaling, inflammation and mitochondrial function in the skeletal muscle in horses with obesity, insulin resistance and EMS.
We will let the results of our ongoing experiments lead us toward the area that looks most promising. At this point, it is
not clear which of the pathologic mechanisms we will be pursuing as our work progresses."
Ed Kane, PhD, is a researcher and consultant in animal nutrition. He is an author and editor on nutrition, physiology and veterinary medicine
with a background in horses, pets and livestock. Kane is based in Seattle.
1. Frank N. Equine metabolic syndrome. Vet Clin North Am Equine Pract 2011;27(1):73-92.