19.4.2: Equine metabolic syndrome Flashcards
What clinical signs of Equine Metabolic Syndrome are shown here?
- Increased adiposity in specific locations (regional adiposity) or generally (obesity)
- Insulin resistance characterised by hyperinuslinaemia or abnormal glycaemia and insulinaemic response to oral/IV glucose ± insulin challenges
- Clinical or subclinical laminitis that develops in the absence of recognised causes e.g. grain overload, colic, colitis, retained placenta
What are the 3 components to Equine Metabolic Syndrome?
- Obesity
- Incretins
- Genetics
How do incretins play a role in Equine Metabolic Syndrome?
- The GIT releases incretins that increase glucose-induced pancreatic secretion of glucagon-like peptides and glucose-dependent insulinotropic peptide
- Oral administration of glucose stimulates greater insulin release than IV
- Long-term feeding of high non-structural carbohydrate (NSC) diets decreases insulin sensitivity and adiponectin compared to forage or fat-rich diets
Which breeds are more prone to EMS and why is this the case?
- Some breeds are genetically predisposed to insulin dysfunction -> they are better adapted to harsh environmental conditions and maximise energy storage
- These breeds may develop insulin resistance despite not being obese, especially if maintained on high starch
- Breeds: Spanish horse derived breeds e.g. Andalusians, Mustangs, Paso fino, Arabs, Caspian-derived breeds, UK native pony breeds
Describe insulin dysregulation (ID) in EMS
Describe the link between EMS and laminitis
EMS = obese + incretins + genetics
* Obesity leads to insulin resistance
* Insulin resistance leads to laminitis
* Exact mechanism unclear by hyperglycaemia and hyperinsulinaemia cause lamellae lesions
What other health impacts does obesity or EMS have on horses?
- Poorer prognosis for full recovery from laminitis if horse has EMS
- Can get strangulating small intestinal lesions from pedunculated mesenteric lipomas
- At increased risk of hyperlipaemia
- Impairment of normal thermoregulation
- Altered oestrus cycles and decreased fertility
- Greater risk of OCD in foals born to obese mares
True/false: lean horses cannot have insulin dysregulation - this is only seen in obese horses.
False
Lean horses (especially thrifty breeds on high starch diets) can still have insulin dysregulation
True/false: insulin resistance leads to laminitis.
True
What are the 3 stages of insulin resistance?
- Compensated insulin resistance: normal glucose concentrations maintained by increased insulin output (hyperinsulinaemia)
- Uncompensated insulin resistance: glucose concentrations increasing and increased insulin concentration.
- Type 2 diabetes mellitus: end stage - persistent hyperglycaemia because of inadequate insulin output (pancreatic beta-cell exhaustion).
Testing for EMS
- Insulin test - need to collect several samples over a few hrs - referral hospital
- **Oral glucose test (OGT) **- owner gives sugar syrup and then get samples a couple of hours later
- Basal glucose and insulin - not very helpful due to fluctuation throughout the day; false -ves possible
All these tests aim to demonstrate insulin resistance.
Some vets and happy to proceed to treatment based on clinical signs/ presentation of the horse.
Treatment of EMS
Need to lose weight and manage laminitis.
* Good farrier
* Soft bedding
* Pain relief in bad episodes
* Adjust diet - do not feed too much grain; feed mostly poor quality forage low in sugar e.g. (soaked) hay is good
* Exercise once laminitis completely under control
* Drugs: metformin, levothyroxine, ertuglifozin
How might metformin help in the treatment of EMS?
It might reduce the insulinaemic response to ingested carbohydrate
How might levothyroxine help in the treatment of EMS?
- It increases the metabolic rate
- It has been shown to induce weight loss
- Its use is not widespread
Clinical signs of EMS
- Generalised obesity
- Regional adiposity e.g. enlarged crest, bulging supraorbital fat, rump, tail head
- Recurrent laminitis
- Infertility in mares
