Glucose Homeostasis Flashcards
What are the normal blood glucose levels?
4-5 mmol/L
Below this is hypoglycaemia in which cerebral function is impaired
Below 2 mmol/L you may be unconscious or go into a coma
Which hormones are involved in glucose regulation?
Increasing: glucagon, cortisol, GH, catecholamines
Decreasing: insulin
What happens if you are consistently hyperglycaemic?
You may get type 2 diabetes mellitus
This is the most common type of diabetes
What is the main gland i Volvos in glucose regulation?
The pancreas
A retroperitinael structure
What is the pancreas made up of?
Acinar cells - exocrine secretions via duct to small intestine. Such as enzymes (98%) of pancreas
Islets of Langergans - involved in glucose control
What are some properties of the islets of langerhans?
Made up of Theres types of islet cells:
Alpha - glucagon
Beta - insulin
Delta - somatostatin
They have gap junctions - allow small molecules to pass directly between cells (paracrine)
Tight junctions - create small intercellular spaces
What is the simple action of pancreatic hormones?
Insulin- stimulates growth and development. Reduces blood glucose
Glucagon - increases blood glucose
(Both of these are inhibited by somatostatin)
What is the reaction of the pancreas to increased blood glucose?
Activates beta cells
Secrete insulin
This is also triggered by amino acids, GI hormones, and PNS activity (inhibited by SNS)
Also triggered by glucagon
What are the effects of insulin?
In the liver
Increases amino acid transport, protein synthesis, lipogenesis (decreases lipolysis), glycogenesis, glycolysis, glucose transport into cells via GLUT4
Decreases blood glucose
(Increase build up of glycogen stores, breakdown of glucose, increased uptake of glucose)
What is the reaction of the pancreas to reduced blood glucose?
Activates alpha cells
Secreted glucagon
Also activated by some amino acid and GI hormones, SNS and PNS activity
Inhibited by insulin and somatostatin
What are the effects of glucagon?
In liver
Increases amino acid transport to liver, lipolysis, gluconeogenesis, hepatic glycogenolysis
This increases blood glucose
How does insulin release happen?
Glucose travels through GLUT 2 transporters
Glucokinase (a hexokinase enzyme) converts it to glucose-6-phosphate (rate limiting step)
This makes ATP
ATP binds to potassium ion transporters and blocks them (so the K+ remains inside the beta cells)
K+ activates Ca+ transporters, so there is an influx of calcium into the cells
This triggers the release of insulin from vesicles and into the blood
How is insulin made from pro insulin?
Pro insulin undergoes proteolytic cleavage
This forms c peptide and insulin (which is made of an A and B chain with some sisphide bridges)
C peptide is a more reliable way to measure insulin levels in the body
What is the incretin effect?
Incretins are a group of metabolic hormones that stimulate a decrease in blood glucose levels. Incretins are released after eating and augment the secretion of insulin released from pancreatic beta cells of the islets of Langerhans by a blood glucose-dependent mechanism.
A healthy individual will have a large peak in plasma insulin with oral glucose but not iv glucose
Type II diabetics have a reduced incretin effect
What is glucagon like peptide 1?
GLP-1
A gut hormone that is secreted in response to nutrients in the gut
A transcription product of pro glucagon gene mostly from L-cell
It stimulates insulin and suppresses glucagon
Involved in satiety (feeling full)
Has a short Haag life due to degradation by Dipeptidyl peptidase-4
Used In treatment of diabetes and type 2 diabetics have less of this
