Physiology of Diabetes Mellitus

Question 1

• What are the two main types of diabetes mellitus?

Answer 1

Insulin dependent diabetes mellitus (type 1)

Non-insulin dependent diabetes mellitus (type 2)

Question 2

• What are the potential causes of diabetes mellitus?

Answer 2

Immune-mediated (T cell) destruction of β cells, pancreatitis with β cell destruction, specific hormones antagonise insulin action, obesity-induced insulin resistance, insulin-antagonistic drugs, insulin-antagonistic disease & genetics

Question 3

• What are the counter regulatory hormones that can be evoked in hypoglycaemia?

Answer 3

Cortisol, growth hormone, catecholamines, glucagon, progesterone

Question 4

• What are the sits of dysfunction relating to obesity-induced insulin resistance?

Answer 4

A Inadequate number of insulin receptors, defective insulin receptor structure, cell signalling pathway, defective GLUT4 transport proteins, problems with translocation of GLUT4 to the membrane, interference with the function of GLUT4

Question 5

• What is islet amyloid polypeptide (amylin)?

Answer 5

Co-secreted with insulin by feline β cells, chronic increased secretion occurs with obesity, amylin deposited in the islets as amyloid, amyloid fibrils are cytotoxic, apoptosis of islet cells, defective insulin secretion. Therefore insulin resistance in cats results in islet destruction

Question 6

• What are the two methods of treatment?

Answer 6

Administering insulin or not administering insulin

Question 7

• Why does diabetes mellitus cause PU/PD?

Answer 7

Glucose acts as an osmotic particle, high concentrations of glucose in the tubule prevent water being reabsorbed

Question 8

• Why does polyphagia and weight loss occur?

Answer 8

Glucose cannot enter satiety centre, cells perceive starvation state, gluconeogenesis results, causing increased muscle wastage

Question 9

• Why might cataracts occur?

Answer 9

Excess glucose in lens cannot be converted to lactate, converted into fructose and sorbitol instead that cannot diffuse out, trapped fructose and sorbitol draw water into the lens

Question 10

• Why is fructosamine measured instead of glucose in cats?

Answer 10

Avoids stress induced cortisol and catecholamines causing hyperglycaemia, fructosamine will reflect previous 2-3 weeks of blood glucose

Question 11

• What are the major differences between diabetes mellitus and stress induced hyperglycaemia?

Answer 11

Glucosuria present in diabetes mellitus, fructosamine levels normal in stress cases

Question 12

• What other laboratory abnormalities will be seen?

Answer 12

Hypercholesterolemia, hypertriglyceridemia, increased liver enzymes

Question 13

• What will urinalysis show?

Answer 13

USG >1.025 g/mL, glucose, ± ketones, urinary tract infection (WBCs, RBCs, bacteria & protein)