Obesity and Insulin Resistance

Question 1

• What is insulin resistance?

Answer 1

The diminished ability of cells to respond to the action of insulin in transporting glucose from the blood into tissues

Question 2

• What is the difference between type 1 and type 2 diabetes mellitus?

Answer 2

Type 1 – inadequate insulin secretion, type 2 – insulin resistance

Question 3

• What are the sites of dysfunction relating to insulin resistance?

Answer 3

Inadequate number of insulin receptors, defective insulin receptor structure, cell signalling pathway, defective GLUT4 transport proteins

Question 4

• What location of fat accumulation has the greatest effect on insulin insensitivity?

Answer 4

Neck (horse)

Question 5

• What is de novo lipogenesis?

Answer 5

Synthesis of fat from carbohydrates

Question 6

• What are the three theories which explain the link between obesity and insulin resistance?

Answer 6

Lipotoxicity theory – lipid accumulation within myocytes disrupts normal cell functions
Proinflammatory theory – stressed adipocytes release inflammatory cytokines which create a proinflammatory state
Adipokine theory – adipocytes produce cytokines such as adiponectin (enhances the action of insulin), adiponectin production decreases as obesity develops contributing to IR

Question 7

• What are the consequences of insulin resistance?

Answer 7

Impaired glucose uptake into tissues, increased glucose synthesis by the liver via gluconeogenesis, increased lipolysis, higher blood free fatty acid levels, amino acids used for gluconeogenesis

Question 8

• What is glucosuria?

Answer 8

Glucose appears in the urine – severe clinical finding

Question 9

• What are the two possible outcomes of the body being unable to respond adequately to insulin?

Answer 9

Hyperinsulinaemia or hyperglycaemia

Question 10

• What is the glucose tolerance test?

Answer 10

Injection of dextrose – assesses ability to bring glucose levels back to baseline and determines how much insulin must be secreted to accomplish this

Question 11

• When is GTT not required?

Answer 11

When glucosuria is detected

Question 12

• What is the difference between diabetes insipidus and diabetes mellitus?

Answer 12

Diabetes insipidus – inability to concentrate urine, diabetes mellitus – dilute urine because glucose is being excreted

Question 13

• Why can ketoacidosis occur as a result of diabetes mellitus?

Answer 13

Shift to fat metabolism for energy, more fatty acids converted into ketones

Question 14

• What is glucotoxicity?

Answer 14

Hyperglycaemia alters the amino acid lysine, formation of fructosamine, alters other amino acids, creates advanced glycosylation end-products (AGEs)

Question 15

• What effects on tissues can an accumulation of AGEs cause?

Answer 15

Kidney (diabetic nephropathy), eye (diabetic retinopathy), neurons (diabetic neuropathy) & skin damage