glucose homeostasis

Question 1

islets of langerhans

Answer 1

• 1 million
• 1-2% of pancreas mass but 20% blood flow
• within exocrine tissue
• neuromuscular bundle enters each islet through beta cell core
• paracrine interaction
  venous effluent to portal vein and liver

Question 2

hormones produced by the islets of langerhans and cell type

Answer 2

insulin = beta cells

somatostatin = Delta cells

glucagon = alpha cells

pancreatic peptide = F cells

Question 3

GLUT2

Answer 3

glucose transporter in the liver and pancreas

Question 4

GLUT4

Answer 4

glucose transporter in fat and muscles

- insulin mediated and present in vesicles
also exercise induced

Question 5

insulin regulation

Answer 5

• basal secretion is pulsatile 9-14 minutes
• major regulator is glucose with acute phase release and then slower 2nd phase
• other regulators are A.A. e.g. glucagon, incretins = all increase
• somatostatin = decrease

Question 6

explain how blood glucose is control from the ingestion of food

Answer 6

food that is ingested, enters the GI tract. Active GLP-1 and GIP release incretin gut hormones. These act on beta and alpha cells in the pancreas. The beta cells increase insulin release which increases peripheral glucose uptake. The alpha cells decrease glucagon , which again increases insulin and causes decrease glucagon reduce hepatic glucose output.

Question 7

insulin signalling

Answer 7

binds to insulin receptors

Question 8

insulins metabolic action of carbs

Answer 8

1. liver - inhibits glyogenolysis and gluconeogenesis (both make glucose)
2. muscle - increase glucose transport and glycolysis
3. adipose tissue - same as muscle

Question 9

insulin actions on fat

Answer 9

increases triglyceride storage and inhibits lipolysis (decreases hormone sensitive lipase) and FFA production

inhibits ketone production

Question 10

insulin actions of protein

Answer 10

anabolic by increasing transport of AA into liver and muscle

Question 11

energy storage

Answer 11

fat = 20-30% of body weight but 70-80% of stored energy

lipolysis - FFA and ketones
-glycerol —–> Krebs

protein 20% energy
-protein hydrolysis releasing A.A

carbs 1-2% but rapidly available

Question 12

ketogenesis

Answer 12

• oxidation of FFA to acute acetate, acetone and beta hydroxybutyrate
• insulin deficiency results in hormone sensitive lipase being unchecked
• uncontrolled glycogenesis and protein hydrolysis
• GLUT4 inactive
• overall nett result = Diabetic Ketoacidosis

Question 13

what stops hyperglycaemia

Answer 13

insulin

Question 14

falling glucose

Answer 14

as glucose falls in fasting state, insulin switched off and counter-regulatory hormones released

Question 15

normal fasting glucose

Answer 15

3.5-5.5mmol/l

Question 16

causes of hypoglycaemia

Answer 16

• insulin in patients with diabetes
• sulphonylurea therapy
• insulinoma (-rare)
• severe hormone deficiency e.g. Addisons disease (-rare)

Question 17

somatostatin action

Answer 17

binds to receptors on beta cells and blocks voltage-gated calcium channels. No influx of calcium and therefore inhibits insulin secretion

= hypoglycaemia