Insulin Secretion and Intermediary Metabolism Flashcards
State four hormones that increase blood glucose concentration.
Glucagon Cortisol Catecholamines Somatotrophin
State some complications of diabetes.
Diabetic retinopathy Diabetic ketoacidosis Peripheral neuropathy Coma Heart Attacks Stroke
What is the normal blood glucose range?
4.0-5.5 Mm
What percentage of pancreatic cells are islets of Langerhans?
2%
What do the delta cells in the islets of Langerhans produce?
Somatostatin
Why do cells in the islets of Langerhans have gap junctions?
Allow hormones to have a paracrine effect
What effect does somatostatin have on glucagon and insulin secretion?
Decreases both insulin and glucagon secretion (it is sometimes called ‘endocrine cyanide’)
What are the main effects of insulin?
Increase glycogenesis Increase glycolysis Increase glucose transport via GLUT-4 Decrease lipolysis Increased protein synthesis ( and AA transport) Overall decrease blood glucose
State some factors that increase and decrease insulin secretion.
Increase: Certain amino acids Gastrointestinal hormones Parasympathetic activity Decrease: Sympathetic activity Somatostatin
What is the effect of GLP-1?
Amplifies our insulin response - it makes us produce more insulin
What are the main effects of glucagon?
Increased lipolysis Increased AA transport x Increased hepatic gluconeogenesis Increase blood glucose INSULIN inhibits glucagon release (via paracrine)
What is the role of glucokinase?
It is the rate limiting step that regulates insulin secretion It converts glucose to G6P Glucose moves into the beta cell via Glut-2 (which is NOT insulin regulated) It is then converted to G6P by glucokinase (hexokinase IV), which then determines insulin secretion
Describe the structure of insulin and what can be measured to indirectly give an indication of blood insulin concentration?
Insulin is synthesised as a prohormone with an A, B and C chains The C chain is removed in the conversion of proinsulin to insulin so the ratio of insulin: C peptide is 1:1 This means that C peptide can be measured to give an indication of insulin output
Describe how glucose uptake causes release of insulin from the beta cell.
Glucose enters through Glut-2 and is metabolised to produce ATP There is an increase in intracellular ATP concentration This BLOCKS ATP sensitive potassium channels —> changes membrane potential Leads to opening of voltage dependent Ca2+ channels Ca2+ influx causes insulin exocytosis
What is the incretin effect?
Oral glucose load stimulates more insulin release than IV glucose load This is to do with intestinal hormones