What exactly does stored fat do to a horse’s body? It wreaks serious havoc on at least 11 vital body functions. Nat Messer, DVM, Dipl. ABVP, an associate professor of equine medicine and surgery at the University of Missouri (UM), presented a compelling discussion at the 2006 AAEP Convention of the relatively new field of adipobiology–the study of fat and its causes and effects. He discussed a paper submitted by Philip Johnson, BVSc(Hons), MS, Dipl. ACVIM, Dipl. ECEIM, MRCVS, professor of veterinary medicine and surgery at UM.

Excess body fat (both subcutaneous fat, such as the squishy stuff around a horse’s tailhead, and visceral fat that accumulates near various internal organs) isn’t just an unsightly way to store extra calories. Researchers are learning that fat–or adipose tissue as it’s scientifically called–is much more active biochemically in many species than was previously thought (particularly visceral fat), noted Johnson in his paper. Fat produces more than 100 substances (collectively called adipokines or adipocytokines) that can affect:

• Lipid and glucose homeostasis (normal fat and glucose balance in the body);
  
• Inflammation;
  
• Hemostasis (control of bleeding);
  
• Osteogenesis (bone production);
  
• Hematopoiesis (formation and development of blood cells);
  
• Complement activities (complement is a sequence of proteins in the blood that work to help the animal respond to inflammatory and infectious challenges);
  
• Reproduction;
  
• Angiogenesis (development of blood vessels in tissue);
  
• Blood pressure; and
  
• Feeding behavior.

In horses, adipokine-mediated alteration of these body functions can cause or contribute to chronic inflammation, metabolic problems such as insulin resistance and possibly pituitary pars intermedia dysfunction (Cushing’s disease), circulatory (blood vessel) compromise, and increased risk of laminitis. Also, hyperglycemia (high blood sugar, which is common in horses with severe metabolic syndrome) has been shown to generate oxidative stress–the production of oxygen free radicals that can damage many kinds of tissues. “In fact, adipokines have recently been claimed to represent the ‘missing link’ between IR (insulin resistance) and cardiovascular disease in humans,” said Johnson.

For example, he noted that the branch of the coronary artery passing through an area of fat storage is the one most likely to develop arthrosclerosis (progressive narrowing and hardening of the artery, which can lead to a heart attack or stroke). Local effects of hormones produced by that fat deposit have been implicated as the cause.

Get research and health news from the American Association of Equine Practitioners 2006 Convention in The Horse’s AAEP 2006 Wrap-Up sponsored by OCD Equine. Files are available as free PDF downloads