Insulin Dysregulation in Horses: What It Is & Its Link to Laminitis

Insulin Dysregulation – The main driver of laminitis in horses

Insulin dysregulation is a type of metabolic dysfunction within the modern horse. Depending on your horse breed and type, it is estimated that up to 60% of domesticated horses are insulin dysregulated, but what is insulin dysregulation?

What is insulin dysregulation (ID)?

To describe insulin dysregulation in the least technical way is to say that the system within the body that controls how much insulin is released from the pancreas becomes unchecked and out of control. The result is a continual release of insulin into the bloodstream in an attempt to lower the amount of glucose detected in the blood, even when there is more than enough insulin already present. The result is an increased accumulation of the hormone leading to a condition called hyperinsulinemia, and this is where things become bad for your horse.

How does a horse become insulin dysregulated?

There are different reasons why a horse becomes insulin dysregulated, but the main reason appears to be due to the cells within the muscles becoming resistant and non-responsive to the insulin in the blood. Normally, when a horse eats a food or treat, the sugars and non-resistant starches are digested then absorbed as glucose into the body. The body, through special receptors, detects the increased amount of glucose and sends a signal to the pancreas to release insulin.

The newly released insulin travels throughout the body where it binds (attaches) to the surface cells of muscles to start a specific chemical reaction. This reaction brings special transporters, like GLUT4, to the surface of the cells so they can effectively “open a door” to let glucose pass from the blood into the cells.

When too much glucose enters the body continuously over a long period of time (it becomes a chronic condition) the cells stop responding to the insulin signal. They become insulin resistant and don’t “open the door” as often. The horse is now insulin dysregulated. This leads to a buildup of glucose in the blood which triggers the pancreas to produce more insulin, even though there is more than enough already in the blood. The result is a condition called hyperinsulinemia which means continually having higher than normal levels of insulin in the blood.

In summary:

• Glucose enters the body after eating
• Insulin is released from the pancreas and travels to the muscles
• Insulin attaches to the muscle cells and “opens a door” to allow glucose to enter
• When too much glucose enters the body continuously over a long time
  • More insulin is released by the pancreas
  • The muscle cells start to ignore the insulin (become resistant)
  • Less glucose enters the muscles
  • More glucose stays in the blood
  • More insulin released
  • Horse becomes insulin dysregulated

Some of this extra glucose can be stored as fat in the body, a common situation found in Equine Metabolic Syndrome (EMS) horses. To learn more about this, read our article on Equine Metabolic Syndrome and what horse owners need to know.

How does insulin dysregulation increase the risk of laminitis in horses?

Laminitis is a major debilitating disease in horses and is a rather common condition found in those who are overweight and obese, like those diagnosed as EMS and PPID. To read more about the causes, signs of, and how to manage a laminitis-prone horse or pony, check out our article on laminitis and metabolic dysfunction.

In brief, laminitis is when the laminae tissue; which is found on the front, inside of the hoof capsule; starts to weaken, resulting in the descent of the coffin (also known as pedal) bone down towards the sole of the hoof. The result is a very painful and potentially life-threatening condition which eventually requires specialised farrier and veterinary treatment. How exactly hyperinsulinemia from insulin dysregulation causes laminitis is not fully understood yet but below is what we do know:

• Laminitis is a result of the dysregulation of specific hormones found in the body
  • This is the main cause of laminitis in horses and is referred to as Endocrinopathic Laminitis
• Insulin can act like (mimic) another key hormone called Insulin-Like Growth Factor 1 (IGF-1)
• One theory as to how hyperinsulinemia causes laminitis is “IGF-1 receptor overactivation”
  • IGF-1 receptors (sites where the IGF-1 hormone can attach to the cell) are bountiful (found in very large numbers) on the hoof laminae
  • With hyperinsulinemia, it is thought that the excessive insulin binds to the IGF-1 receptor in very large numbers, over activating the release of other hormones like growth hormones
  • This results in excessive cell growth and stretching, causing the laminae cells to change shape
  • The laminae cells become weaker and detach from the hoof membrane leading to laminitis
    • This theory has been questioned in recent times though as it is now known that even though insulin may be able to act like the IGF-1 hormone, it doesn’t bind to their receptors very well, even when there is a lot of insulin due to dysregulation
• Another theory is that the high circulating insulin restricts and blocks (impairs) the normal blood flow to the tissues in the hoof. It is thought that the reduced blood flow starves the laminae of vital nutrients and energy, including oxygen, causing the cells in the laminae to weaken, stretch, and eventually break, leading to laminitis.
• One thing that is certain is that the high levels of insulin in the blood, due to insulin dysregulation, causes the release of pro-inflammatory chemicals which are capable of damaging the laminae tissue while also causing discomfort for the horse.
  • Insulin dysregulation results in too much glucose in the blood
  • Some of this excessive glucose is stored in the body as fat deposits like cresty necks and fat pads commonly found in Equine Metabolic Syndrome horses.
  • This fatty tissue produces its own pro-inflammatory chemicals (cytokines) like TNF-α and IL-6
  • The constant release of these pro-inflammatory cytokines from the fatty deposits results in constant (chronic) low-grade inflammation of many different tissues throughout the body, including the laminae in hooves leading to tissue damage and breakdown

Targeted nutritional supplements can help lessen the impact of insulin dysregulation in vulnerable horses, particularly those overweight or prone to episodes of laminitis. A product like PROTEKMD^TM has been formulated to support healthy metabolic function by addressing the biggest drivers of metabolic health.  PROTEKMD^TM is designed to be a part of your horse’s management plan. Find out how  PROTEKMD^TM is a great fit for your insulin dysregulated horse.

In summary

Insulin dysregulation is a form of metabolic dysfunction in horses and is currently thought to be due to long term, consistent (chronic) oversupply of sugars in the diet resulting in a constant overproduction of the hormone, insulin, leading to insulin dysregulation. Researchers and veterinarians are of the opinion that insulin dysregulation is the main underlying cause of laminitis in horses but the actual way in which this happens is still to be fully understood.

While we may not fully understand yet how insulin dysregulation and hyperinsulinemia cause laminitis, minimising the impact and effects of insulin dysregulation are currently the best prevention measures available today. Including a targeted supplement like  PROTEKMD^TM may also assist in supporting horses with insulin dysregulation.

Remember,  not all insulin dysregulated horses will become laminitic, but all laminitic horses are insulin dysregulated.