EMS Flashcards
Define Equine Metabolic Syndrome?
Collection of risk factors associated with an increased risk of laminitis
Name EMS risk factors associated with an increased risk of laminitis?
- Obesity (any obese horse has greatly increased risk of laminitis. Similar pathology to cardiac disease in obese humans but the effects on the vascular system in the horse are seen in the hoof)
- Insulin resistance (IR) (obesity leading to IR)
- Predisposition toward laminitis:
- Additional components
- Dyslipidaemia (hypertriglyceridaemia)
- Hypertension
- Hyperleptinemia
- Altered reproductive cycling
- Increased systemic markers of inflammation
Which ages is EMS prevelent in?
5-15 years
Which breeds are predisposed to EMS?
- Any breed affected but some predisposed
- Ponies, minis but also Arabians, Warmbloods, native breeds (good doers genetically predisposed as they are genetically predisposed to store/build up fat)
What happens to the grass in spring-summer?
During periods of high sunshine, when sugars are produced in excess of the energy requirement of the pasture for growth and development, they are converted into storage, or reserve, carbohydrates, such as fructans and starches. Means very high in calories and more likely to become obese. A lot of sugars can mean horse remains hyperglycemia for a long time which can lead onto laminitis.
Where is fat seen in obesity?
Neck: cresty and large
Fat pads infront and behind shoulders
Cant see ribs
Supraorbital fossa full of fat
Large fat belly
How is obesity defined in the horse?
- BCS: ≥3/5 (or >7/9)
“crest enlarged and thickened, so fat is deposited heavily in middle of neck rather than toward poll and withers… mounded appearance..crest fills cupped hand.. loses side-to side flexibility”
- Crest has the most correlation with EMS
- Accurate BCS may be hard in some cases with regional adiposity
Neck
Tail head
Shoulder
How can a neck crest be assessed?
Neck assessment
- Subjective assessment
- Mid-neck measurement - ponies
- Circumference : heightwithers >0.71 predicts laminitis
- Neck-to-height ratio
- Cresty neck scoring system
When can EMS occur in lean horses?
Occasionally lean horses have EMS
Caused by an enzyme:
- 11β-hydroxysteroid dehydrogenase-1 (11β-HSD1)
- Enzyme that increases local production of cortisol in adipose tissue
- High cortisol concentration promotes insulin resistance
Alternatively pancreatic disease can result in reduced insulin production and T2DM (type 2 Diabetes mellitus)
Describe the pathophysiology of EMS?
What are the functions of adipose tissue?
- Main function of fat tissue is Energy storage
- But also has an endocrine function: Hormone production
- Adipokines (leptin, resistin, adiponectin and apelin) Main ones we can measure clinically in bold.
- Adipocytokines (TNF, IL-1, IL-6)
- Increased adipose tissue= Chronic low grade inflammation
It is generally assumed that obesity predisposes the animal to insulin resistance. What are the 3 theories to explain this association?
- Lipotoxicity theory
- Proinflammatory theory
- Adipokine theory
What is the lipotoxicity theory of obesity and insulin resistance?
There is a limit to how much fat can be stored in the subcutaneous area. When this is too full, fat then goes to be stored in the visceral fat
- One the viscera has reached its limit, the fat then ends up in the portal system where it goes to the liver to be laid down
- Causes some degree of liver dysfunction
- Ends up in any other tissue (e.g. skeletal muscle) and causes dysfunction and disrupted signal transduction of insulin
- Leads to lipotoxicity and IR
What is the proinflammatory theory of obesity and insulin resistance?
- Adipose tissues reach their capacity for fat storage, which stresses them
- Stressed adipocytes release inflammatory cytokines called adipokines
- These alter intracellular signal transduction pathways leading to insulin resistance
- IR
What is the adipokine theory of obesity and insulin resistance?
- Adipocytes produce cytokines that can be classified as hormones called adipokines
- Obesity alters the balance of adipokines produced by the adipocytes
- Adiponectin enhances the action of insulin
- Lower adiponectin levels contribute to IR