Horse-disease study by Oklahoma professor may help people

BY DAVID ZIZZO
Published: December 16, 2008

Many old horses suffer muscle loss and immune deficiencies. Some old people develop tremors, difficulty with movements and other symptoms. Dianne McFarlane hopes her work might someday provide help for both.

McFarlane, assistant professor of physiological sciences at the Center for Veterinary Health Services at Oklahoma State University, has been studying degenerative diseases in old horses for almost a decade. She is investigating the similarities between Cushing’s disease in horses, also known as Pituitary Pars Intermedia Dysfunction, or PPID, and Parkinson’s disease in humans.

"We are interested in understanding the disease for the benefit of horses, but also it may provide some understanding for what goes on in humans that have degenerative diseases,” she said.

McFarlane, who is collaborating with Gary White, an OSU alumnus now with the University of Oklahoma Health Science Center, is looking at degenerative disease in baboons. Many researchers use mice and rats for studies. But to use those rodents to study Parkinson’s would require inducing a degenerative disease since it does not occur naturally, as it does in horses and baboons, McFarlane said. Animals that are higher in the animal kingdom, such as horses and baboons, are better models overall for human physiology, she said.

"The closer evolutionarily you are, the more likely the processes will be handled the same,” she said.

Still, there are many differences between human Parkinson’s disease and PPID in horses. PPID, which occurs in one-quarter of horses more than 20 years old, affects the part of the brain that controls hormone output. The horses can develop sway back, potbelly or general muscle loss. The most obvious symptom is very long hair.

Parkinson’s affects the part of the human brain that controls movement, producing movement disorders, trouble sleeping, tremors and other problems.

"We have completely different clinical signs,” she said.

However, both diseases affect the same kind of dopamine-producing neurons, and both problems appear in old age. "It does appear animals have some of the same basic factors contributing to degeneration,” she said.

McFarlane’s research has produced its "first wave of data,” which was recently published.

The research is expected to continue for at least another four years.