Equine Metabolic Syndrome Flashcards
The key central and consistent feature of EMS is insulin dysregulation. What does this mean?
ID is used to indicate disturbances of the balanced interrelationship among plasma concentrations of insulin, glucose and lipids.
Other than obesity, what are other inconsistent features of equine metabolic syndrome?
Cardiovascular changes (increased blood pressure, heart rate, cardiac dimensions), adipose dysregulation, obesity
What is the primary clinical consequence of equine metabolic syndrome?
Laminitis
What signalment is equine metabolic syndrome most common in?
Sex does not appear to influence most markers of insulin dysregulation.
EMS is more common in physically inactive animals. Shetland ponies, donkeys and mini horses are those which are least likely to be exercised.
Which stimulates a greater insulin secretion: oral administration or IV admin. of glucose?
Oral administration of glucose stimulates a greater insulin secretion. This indicates that the GI releases factors that augment glucose-induced pancreatic insulin secretion. Incretins like gastric inhibitory polypeptide (GIP) and glucagon-like peptides 1 and 2. Active GLP 1 stimulates insulin secretion in the horse.
What are the lesions found in endocrinopathic laminitis?
Initially found in the secondary epidermal lamellae, including lengthening and narrowing, developing tapered tips and with SELs angled more acutely to the primary epidermal lamellar axis. Stretching of the lamellar epithelial cells is the earliest histological change observed after 6 hours of hyperinsulinemia and subsequent cellular changes include an accelerated cell death and proliferation cycle.
What are some theories for how hyperinsulinemia causes laminitis?
Changes in intracellular insulin signaling resulting in endothelial dysfunction and mechanisms involving insulin-like growth factor 1.
Obesity can cause dysregulation of what adipokines, that can contribute to equine metabolic syndrome?
Leptin - relays signals to the brain indicating fat status and maintains body condition by appetite suppression and increased energy expenditure during energy excess; increased leptin [ ] correlate with hyperinsulinemia.
Adiponectin - secreted exclusively from adipose tissue, which improves insulin sensitivity and reduces inflammation; [ ] is inversely related to fat mass and insulin resistance.
Are there any genetic roles to the expression of equine metabolic syndrome?
Genes contributing to being a “easy keeper” are likely to be advantageous for survival in the wild during periods of famine by enhancing feed efficiency.
What are the options for testing insulin dysregulation? Are there any pretest considerations?
Acute stress can affect insulin and glucose concentrations via activation of the adrenocortical axis and by catecholamine release.
Postprandial glucose or insulin responses will be affected by gastric emptying, which in turn will be influenced by the presence of absence of ingesta in the stomach and SI.
Basal testing - Insulin, glucose, triglycerides, adipokines, C-peptide, incretins (most of these prove to be unhelpful)
Dynamic testing - oral glucose test, oral sugar test, IV challenge tests, insulin response test, combined glucose insulin test
Testing for PPID should also occur.
What is C-peptide and how might it be useful in diagnosing equine metabolic syndrome?
C-peptide is a co-secreted and released equimolar to insulin. Unlike insulin, it is unaffected by the hepatic first pass effect and provides a more accurate assessment of pancreatic secretion of insulin.
Why are dynamic tests better than basal tests when evaluating the relationship between insulin and glucose? How do tests measuring responses to PO administration vs IV administration?
Dynamic tests are generally more sensitive than basal tests.
Responses to PO administration of nonstructural carbohydrates closely mimic the more complete sequence of glucose and insulin dynamics.
Tests using IV admin. of insulin, glucose or both, focus on tissue insulin sensitivity and beta cell responsiveness.
In the oral glucose test, how long after administration of glucose does peak plasma glucose occur?
60-120 minutes after consuming meal
Test results can be affected by ingestion time, gastric emptying, and intestinal absorption.
What does the glucose curve in healthy horses look like after an injection of glucose, followed by insulin?
Healthy horses show a biphasic blood glucose curve, starting with hyperglycemia, followed by a negative phase in which glucose drops below the initial baseline value. Glucose then increases back to baseline concentrations within 45 minutes.
Horses with equine metabolic syndrome may show hyperinsulinemia and a delayed return to baseline glucose.
Why might metformin be of value in treating horses with severe equine metabolic syndrome?
Metformin has a direct effect on the enterocytes and decreases enteric glucose absorption and consequently the insulin response to an OGT in horses.
