In the last two newsletters, we discussed seasonal rhythms (Available here) and elevated ACTH (Available here).
This newsletter focuses on elevated insulin levels, sometimes referred to as insulin resistance.
◆︎ Why study elevated insulin?
Elevated insulin has been shown to be one of the causative factors in laminitis. Despite our advances in understanding laminitis, it is still a major reason why we euthanize our horses.
◆︎ Background on the role of insulin:
In order for glucose to enter a cell, a transporter is necessary to take it across the cell membrane. When the transporter does not function appropriately, the horse may create more insulin to try to drive more glucose into the cell. This may result in elevated insulin levels. Elevated insulin has been shown to affect the smooth muscle cells within the blood vessels. This is thought to be the basis of the mechanism of action of insulin related laminitis.
Be aware that elevated insulin levels tend to be more common in horses that are thrifty keepers, such as ponies, Arabian horses, and morgan horses.
◆︎ Situations that can elevate insulin levels:
➡ Lack of exercise. One of the most potent regulators of insulin is exercise. In one study, insulin levels dropped 35% after intense exercise. It took several hours to return to normal. The problem with relying on exercise is that if your horse is foot-sore or laminitic, intense exercise is not an option.
➡ High carbohydrate diet. High carbohydrate diets can come from spring grasses or from the additional grain that we feed our horse. Another common source for high carbohydrates is from the treats that we give. We know that grains, such as oats, wheat, and barley are high in carbohydrates. Sometimes marketing is deceptive, claiming “No added sugar”, “No molasses”, or “All natural”, but having main feed ingredients of oats or wheat. It’s important to really look at what you’re feeding a horse with high insulin levels.
➡ Seasonal changes:
» Autumn ACTH rise. As discussed in the last newsletter, the seasonal rise in ACTH may have an effect on the insulin levels.
» Spring grasses. Early growth in the spring frequently has a higher sugar content than mature grasses. This can raise insulin levels – not because of the time of year, but because of the elevated sugar levels in the forage.
» Cold weather. Although it’s not well understood, insulin levels can fluctuate in cold temperatures. It is thought that insulin affects heat production at the level of genes.
➡ Hormonal changes in mares. Some mares have issues with their reproductive cycle, which results in elevated insulin levels. This is still poorly understood and needs more research.
➡ Iron overload. Horses do not have a convenient mechanism to excrete iron. Because of this, iron accumulates over time. The source of this iron is in the water they drink, the food they eat, dirt that may be consumed with their feed, and supplements or treats that we give them. The exact relationship between iron overload and elevated insulin levels still needs to be researched.
➡ Corticosteroids. Joint injections using corticosteroids have been associated with elevated insulin levels. Care should be taken when treating horses that have elevated insulin. The additional rise in insulin levels may be sufficient to tip the horse into active laminitis. If your horse needs intra-articular joint support, work with your vet to come up with a game plan for a safe treatment protocol, such as intra-articular injections of hyaluronic acid; or orthobiologics, such as platelet rich plasma, or irap.
➡ Sedatives. Certain sedatives, such as xylazine, have been shown to increase insulin levels. However, detomidine appears to be safer for horses with elevated insulin because it does not cause an additional rise.
◆︎ How can you know if your horse has elevated insulin levels?
A non-fasting blood test is the most reliable way to know. This is a single blood draw about 4 hours after a meal, and sent to the lab.
Presence of a cresty neck. Although some horses will have a cresty neck with elevated insulin levels, some breeds of horses will have thick necks without elevated insulin. This is not a reliable method to determine elevated insulin levels.
◆︎ Potential treatments:
➡ Exercise: If the horse is not laminitic, exercise is the best way to help regulate insulin levels. Movement of all types is good, but not on compromised hooves.
➡ Low sugar/starch diet: Diet is a key to lowering insulin levels. A low sugar/starch diet is best achieved through testing hay, and removing treats and grain from the diet. It is also advised to limit or eliminate grazing, as the sugars in the grass can vary widely with temperature and stress.
➡ Medication:
» Metformin can frequently lower insulin levels at the dose of 30 mg/kg of body weight. However, after about 30 days, the insulin levels usually creep back up to the original levels.
» Sodium glucose cotransporter 2 inhibitors (SGLT2 inhibitors) can rapidly bring down blood sugar levels in some horses. New research indicates that elevated triglycerides is a potential side effect.
➡ Supplements: Supplements may be helpful for some horses. However, there currently is no consensus as to which supplements are most helpful and more research is needed. Anecdotal reports indicate that the following may be helpful:
» Spirulina. Reports of anywhere from 40 grams per day to 100 grams per day may be helpful. Some horses object to the smell. In those cases, it’s advisable to start with a small amount in their bucket, gradually increasing the amount until you get to the full serving size.
» Acetyl L-carnitine. Some horses benefit from 10 grams per day.
➡ Avoid triggers such as corticosteroids or certain sedatives.
◆︎ Treatments that may not work.
Some strategies that help human diabetics may not work in horses. Unlike humans, horses usually do not have high glucose levels. Any medication or supplement that lowers glucose levels may not be effective because the glucose levels are not usually high to begin with.
It’s important to work with your veterinarian to develop the best course of action.
We do the best we can for our horses. Being aware of the potential of elevated insulin is part of that.
Disclaimer: Statements regarding dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease or health condition.
©Joan Kulifay 2024