What’s All the Talk About Insulin? Hyperinsulinemic Associated Laminitis

Thirty years ago, laminitis was usually a career-ending diagnosis, if not a life-ending one.  Aside from mechanical support and pain management, little was known about the contributing factors associated with laminitis and the multitude of clinical factors that affect the severity, outcome, and likelihood of recurrence.  Today, we know a great deal more about metabolic laminitis and specifically the role that insulin plays in mediating this disease process. 

Current data shows that horses with an elevated baseline insulin value are at a higher risk of developing hyperinsulinemic associated laminitis (HAL).  The ability to establish a direct relationship between elevated serum insulin levels and the onset of laminitis has enabled veterinary practitioners to make great strides in combating this disease process. 

Hyperinsulinemic Associated Laminitis Diagnosis and Treatment

When presented with a patient suffering from HAL, the first step is to determine just how high the insulin values are.  Seasoned practitioners can usually estimate the severity of hyperinsulinemia by assessing the extent of regional adiposity (fat deposition in the horse’s body).  The most common site of regional adipose tissue deposition are the crest of the neck, on either side of the withers, along either side of the horse’s topline, and on either side of the tail head.  The greater the accumulation of fat in these areas, the higher the baseline insulin value in that patient.  Bloodwork, in the form of a metabolic panel, is then used to quantify those observations to establish an appropriate therapeutic regimen and track progress throughout the treatment period. 

If the patient is actively suffering from HAL, all therapeutic methods are implemented in an attempt to slow down the damage associated with the laminitic process.  In addition to dietary management and the eradication of starch from the horse’s feed, medical intervention with metformin has proven to be a very successful strategy in our practice. 

Metformin increases tissue sensitivity to insulin in the patient. Insulin is a signaling molecule which instructs cells to recover glucose (starch/sugar) from the GI tract to use to power cellular processes.  In horses with hyperinsulinemia, the tissues of the body aren’t responding to the insulin currently being produced, so, the body produces more insulin, leading to a hyperinsulinemic state. 

The physiologic process by which elevated insulin values lead to laminitis are still unknown.  However, current research shows that insulin is capable of binding to receptors in lamellar epithelial cells which stimulates excessive growth of the horn tubules, leading to the traditional elongated hoof structure of chronically laminitic feet.  Metformin helps to increase tissue sensitivity to insulin which in turn down regulates the body’s natural production of insulin. 

Hyperinsulinemic Associated Laminitis Treatment Outcomes

The success of treatment of horses with insulin dysregulation is highly dependent upon the severity of the HAL, the chronicity of the disease process, and the condition of the hoof capsule.  Optimal outcomes are associated with high compliance on the part of the horse owner when it comes to implementing therapeutic regimens and dietary management, as well as the employment of a farrier who is willing to work with your veterinarian when making strategic decisions around trimming and shoeing your horse. 

These patients require several series of radiographs over the course of their case in order to ensure optimal trimming is being performed in addition to tracking the sole depth of the patient.  Most cases, when identified in their chronic stages, usually require many months to restore physiologic function of the hoof capsule and achieve an acceptable level of comfort on the part of the patient.  Depending upon the integrity of the hoof capsule, metabolic stability, and comfort of the patient, these patients can sometimes return to their previous level of work.  While not all cases have the perfect outcome, with the knowledge and medical advancements the veterinary profession has seen over the past few decades, it is absolutely worth trying to combat hyperinsulinemia associated laminitis. 

Caring for Your Senior Horse

At what age is a horse considered geriatric or senior? Does owning a senior horse mean that he must eat a feed labeled as a “senior” feed? As always, the answer is, it depends. Our horses are living longer lives than ever, thanks to an evolving understanding of the needs of geriatric horses and our ability to provide high quality care. There is no set age cutoff as to when a horse is considered geriatric, but most experts agree this can be around age 20. However, age is just a number, and many horses are still active and competing into their twenties, while others are happily retired. The main issues we see in our older horse population include dental disease, altered dietary needs, metabolic disease/PPID (Cushings), and arthritis.

 

Photo Courtesy PugnoM on Flickr

Dental Changes

The ideal time to begin focusing on your horse’s regular preventative veterinary care is when he is young. Horses receiving regular preventative care, especially veterinary dentistry, preserve their teeth longer and can age more gracefully. Waiting until signs of dental disease or difficulty chewing are observed often indicates advanced disease and more limited treatment options. Most horses benefit from yearly dentistry, which includes a thorough sedated oral exam with a dental speculum, light source, and mirror. A thorough oral exam is vital to accurately assess, document, and treat any issues.

Horses suffering from abnormal dental wear, cracked or missing teeth, or severe periodontal disease may require more frequent care. Even though horse teeth are described as “long rooted,” they do eventually wear out, so proper care ensures the longest possible life of the tooth. Common dental issues in older horses include fracture of cheek teeth, complete expiration or wearing out of cheek teeth, loose/painful teeth, and periodontal disease. The incisors can also be affected by similar conditions.

Staying on top of your senior horse’s dental care helps ensure that he gets what is needed from his diet. Sometimes severe dental disease and impaired chewing ability necessitates eliminating hay from the diet entirely. Complete feeds are formulated specifically for horses that can no longer chew hay effectively. These diets have greatly improved the quality and length of life for senior horses with compromised teeth.

Nutritional Changes

Nutrition recommendations for the geriatric horse are formulated around maintaining an ideal body condition. In the geriatric horse, this can be complicated by difficulty chewing, poor teeth, metabolic disease, and decreased ability to digest fiber and protein. For older horses in good weight and with adequate dentition, little dietary change may be required. For older horses who have difficulty maintaining weight and/or compromised teeth, complete feeds as mentioned above can help. These feeds are high in easily digestible fat, fiber, and protein, and are designed as easy-to-chew. They are formulated to replace hay entirely for those horses that can no longer adequately chew hay.
Adding water to soften the feed can reduce the risk of choke and ensure additional water intake. Feeding recommendations are often listed as pounds of feed per day depending on whether the horse is also eating hay, so it is important to weigh out your horse’s portion so that any necessary adjustments can be made more accurately.

Metabolic Changes

A curly haircoat and muscle loss over the back aren’t just signs of aging- They can indicate a common underlying condition: equine pars pituitary intermedia dysfunction, more commonly known as PPID or Cushings disease. This is a treatable (but not cureable) condition that is very common in geriatric horses, resulting in hormonal imbalances and symptoms such as delayed shedding, curly hair coat, muscle loss over topline, increased drinking and urinating, personality changes, and increased susceptibility to infections and laminitis. Diagnosis is made by a blood test as well as by history and clinical signs. Management involves daily administration of pergolide (Prascend) tablets, which help restore normal hormone levels and alleviate the clinical signs of the disease.

Equine Metabolic Syndrome (EMS) is a separate metabolic condition, but it sometimes occurs in conjunction with PPID. EMS horses typically show signs of being an “easy keeper”- cresty neck, regional fat deposits behind the shoulders and at the tail head. Horses with EMS are more susceptible to laminitis and usually have a higher baseline insulin level than normal. EMS horses are managed with strict attention to diet (minimizing sugar and starch) and exercise to help them maintain a lean body weight.

Joint and Muscle Changes

Just like us, aging horses suffer from daily aches and pains. An examination with your vet can help identify major and minor issues and

Photo Courtesy nikki_tate on Flickr

determine what treatment plan works best for you and your horse. Many options are available to keep our old horses comfortable.
Nutraceuticals (supplements) are very popular, although many of these products lack proof of efficacy and ingredients. More researched options include medications such as adequan (administered intramuscularly) and Legend (administered intravenously). These medications help provide the components necessary to keep joints healthy.

Joint injections target individual joints to reduce pain and inflammation and improve mobility. Non-steroidal anti-inflammatories such as Equioxx are also helpful, along with acupuncture and chiropractic care. Stable management is equally important- maximum turn out time allows horses to move at will, and monitoring herd dynamics ensures that older horses are not prevented from accessing food and water. In addition to these considerations, regular veterinary and farrier care will help your senior horse enjoy his golden years with you.

As always, if you have any questions about caring for your senior horse, please contact your veterinarian who can offer a personalized plan to help keep your geriatric horse happy, healthy, and comfortable well into their senior years.

Equine Metabolic Syndrome and all it Entails

By Dr. Allison Hartman

 

the-hoof-473095_1280Laminitis has been a bane of horseman and farriers since the horse was first domesticated.  As our medical knowledge and diagnostic abilities have evolved, so has our understanding of the contributing factors of this disease process, including Equine Metabolic Syndrome.  Equine Metabolic Syndrome is a term that’s been thrown around the equine community for the past few decades, but what does it mean?

 

What is EMS?

 

Equine metabolic syndrome (EMS) is a condition most commonly characterized by an inability to properly metabolize carbohydrates. The disease has been known by many names, including hypothyroidism, peripheral Cushing disease and pre-laminitic syndrome. Today, we know that Equine Metabolic Syndrome is characterized in horses, ponies and donkeys by obesity, regional deposition of fat, and systemic insulin resistance.Shetland_pony_dalmatian2

 

Insulin is an important hormone that allows the cells to obtain glucose from food.  Without insulin, or a proper response to insulin, cells cannot utilize glucose, regardless of how much food the horse is fed.  This starvation process at the cellular level pushes the horse into a stressed state (characterized by elevated cortisol levels) where the body is encouraged to hold on to as much fat as possible, making weight loss next to impossible in these horses.  In addition, glucose deprivation in the laminae of the horse’s feet can lead to laminitis.
How is it Diagnosed?

 

When we suspect a horse may have EMS, we will recommend bloodwork to confirm our suspicions as well as guide us in the proper treatment of your horse.  Horses with EMS may also have concurrent Cushing disease, which has been shown to be a contributing factor to the initial development of EMS.  It is important for us to understand the underlying metabolic factors that are contributing to your horse’s case in order to provide the most efficacious recommendations both medically and diet.

 

The key values we assess when running blood work for EMS include:

  • ACTH: When elevated, this value can be indicative of Equine Cushing’s Disease.
  • Insulin: Elevated levels of insulin indicate insulin resistance.
  • Leptin: This is a secondary value, used to ascertain the validity of elevated Insulin. When leptin is elevated in addition to elevated insulin, EMS and IR (insulin resistance) are valid diagnoses.
  • Glucose: When both ACTH and insulin are elevated, glucose can help differentiate the primary disease process.

 

What Can You Do About It?

 

Horses that are merely overweight but not actively laminitic should be put on a low starch diet, comprised of hay with less than 12% non-structural carbohydrates fed at 1-1.5% body weight.  (in this example, a 1000lb horse should be fed 10-15lbs of hay per day).  Their forage diet can be adequately balanced using either a ration balancer or a specifically formulated low starch feed.  These horses also benefit from routine exercise as an additional aid for weight loss.

 

In those patients that are actively laminitic, exercise is not recommended but the same dietary recommendations apply.  In addition, if your horse is diagnosed as insulin resistant (IR), metformin is a beneficial medication used to increase tissue sensitivity to insulin.  Horses with IR are comparable to humans with type 2 diabetes, in that they produce adequate amounts of insulin, but their body simply fails to respond appropriately.  Metformin is a medication commonly used in humans with IR and its efficacy in equine IR cases has been confirmed both in laboratory and field studies.

 

pony-2472424_1920Another option to stimulate weight loss in EMS horses is levothyroxine, commonly sold in the equine community as Thyro-L.  Thyro-L functions by increasing the rate of the horse’s metabolism to further stimulate weight loss.  It is important to understand that Thyro-L has no direct impact on the laminae of an actively laminitic horse and instead works indirectly over a longer period of time.

 

EMS is a frustrating disease for practitioners, clients and patients alike.  The more we understand of the disease process the better our chances at restoring metabolic equilibrium and preventing further deterioration of the laminae.  If you suspect your horse may have EMS, talk to your vet about appropriate diagnostic measures.

What is equine founder/ laminitis?

QUESTION:
I have a 6-year-old Quarter mare that foundered a couple of months ago. She has been on a diet and needs to lose quite a few pounds. Is there any possibility that in the future I could let her out in the pasture for a couple of hours or so?

ANSWER:
To answer your question, there is a VERY limited possibility of pasture time, but most likely that will involve wearing a grazing muzzle, and strictly controlling the length of time that the mare is allowed to graze.  This would also presume that before trying this schedule, the mare had already been controlled enough to return to a “normal” weight and was not concurrently experiencing any foot pain associated with founder.
Founder is a disease that most commonly affects the front (toe) region of the foot, but can affect the whole foot.  The cause of founder can be varied, but is usually due to inflammation in a hoof tissue called the lamina.  This inflammation (also called laminitis), can be caused by a primary (like too much grain), or secondary (such as severe colic) reason, both of which can be complicated by metabolic factors and obesity.  Most obese horses are set up to be “at-risk” for founder/laminitis, and only need a small change in feed to cause the inflammation in the lamina.  This change can be as simple as getting into the grain or as innocent as some extra time on rich pasture.
With this in mind, in your mare’s situation it would be VERY important to monitor her pasture time and feed intake.  This would also include monitoring the time of day she is on pasture (nights and mornings are better than the heat of the day) and the season of the pasture (first cutting vs. spring growth vs. late fall) to limit her exposure to simple sugars in the pasture.