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Insulin resistance in horses

In horses with insulin resistance, the blood glucose level initially rises the same as it would in a healthy horse, after consuming some feed. The difference is that in the presence of insulin resistance, the insulin produced by the pancreas is not able to lower the blood glucose level by channelling the glucose into muscle or liver cells and other corresponding stores.

Consequences of insulin resistance

This results in increased blood sugar (hyperglycaemia) and insulin levels (hyperinsulinaemia). As a high blood sugar level is potentially life-threatening, the body reacts by increasing the production of insulin by the pancreas. This removes the excess glucose from the blood. This is known as insulin resistance or insulin dysregulation. In the long term, the pancreas becomes exhausted in terms of insulin production. In these cases, high glucose levels are found together with low insulin levels. In humans, this condition is known as type 2 diabetes.

Diagnosis of insulin dysregulation

Whether the horse is insulin dysregulated can be determined by an oral sugar test or by a simple blood glucose and insulin determination in the blood after 12 hours of exclusive hay feeding.

Risk of laminitis

Horses with high blood sugar and insulin levels are always at risk of laminitis. Research is therefore endeavouring to find treatment options to help affected horses.

Medication against insulin resistance: SGLT2 inhibitors

In new studies, around 60 horses were used to investigate whether the blood sugar-lowering active substances from the group of sodium-glucose cotransporter 2 inhibitors (SGLT2i), which are used in humans with insulin resistance / type 2 diabetes, also have the corresponding effect in horses.

These two drugs canagliflozin and ertugliflozin were tested in horses. Although both drugs showed a significant improvement in the measured blood glucose and insulin concentrations, these drugs are not free of side effects.

Side effects and risks of the medication

The most common side effects are high triglyceride concentrations, which can lead to a loss of appetite and fatty deposition of the organs – so you are trading one health problem for another. In humans, side effects include toe and metatarsal amputations, dizziness, low blood pressure and headaches. The side effects that can occur in horses under long-term administration have not yet been researched.

These drugs are therefore by no means suitable for treating a “normal” insulin dysregulated horse in the long term, not to mention the purchase price involved.

Reduce weight; riding out with Haflinger
Sufficient exercise – even at a brisker pace – is an important component in restoring insulin sensitivity.
© Adobe Stock/citikka

Management and prevention

Therapy and management of horses with insulin resistance should first and foremost focus on improving exercise, feeding and turn-out regime.

One of the most common causes, of high sugar and insulin levels in the blood or the development of insulin resistance, is increased sugar levels in hay or grass caused by high-sugar grasses such as perennial ryegrass. In combination with a lack of exercise. If the horse is unsettled with the current yard management, the development of insulin resistance is accelerated.

Measure to restore / maintain insulin sensitivity

The correct starting point to restore insulin sensitivity in affected horses would: Reduce sugar, increase energy consumption, reduce stress.

The challenge for the livery yard owner is to offer low-sugar hay and improving the fields by sowing lean grasses. Owners need to make time to exercise their horses regularly, including brisk canters (once reached appropriate health levels) and watch the sugar intake. It’s the only way to get the horse healthy again, and then keep up the management long term accordingly.

Elke Malenke