Pancreas Flashcards
Define glycolysis
Breakdown of glucose into smaller compounds which generates energy
Define glycogenesis
The formation of glycogen from glucose
Define glycogen
Glucose polymer
Define glycogenolysis
Glycogen breakdown to glucose
At what concentration is hyperglycaemia defined?
Above 30 mM
Explain osmotic diuresis
Occurs with high blood glucose. Lots of pee as the body tries to excrete glucose. Can also lead to excessive thirst
Define gluconeogenesis
The formation of glucose from non-carbohydrates substrates like lactate and amino acids
Explain 2 mechanisms of hepatic glucose production
Glycogenolysis
Gluconeogenesis
What concentration of blood glucose defines hypoglycaemia
2-3 mM
Name 3 factors that lower blood glucose levels
Transport of glucose into cells for energy production
Transport of glucose into cells for storage as glycogen
Urinary excretion of glucose
Define an islet of langerhan
The secretory cells of the pancreas
Name the 2 hormones that are secreted by the islets of langerhans and the related cells
Alpha cells - glucagon
Beta cells - insulin
Which hormone secreted by the pancreas is catabolic?
Glucagon
Glucose is hydrophilic. How does it enter the cell?
Through a transport protein
What is a GLUT
Glucose transporter
Location of GLUT 1?
Blood brain barrier
Which glucose transporter starts to work at higher concentrations of glucose? 15-20 mM
GLUT 2
Activation of GLUT 2 (found on the liver and pancreas) initiates what events?
Pancreas - insulin secretion
Liver - removal of glucose from the blood
Which GLUT is found in all tissues?
GLUT 3
Which GLUT, found on muscle and fat cells, can be increased in expression with resistance training?
GLUT 4
Which 2 glucose transports are the most sensitive to glucose?
1 and 3
What effect does insulin have on GLUT4
Stimulates glucose uptake by GLUT4 by promoting exocytosis, causing the vesicles to deposit the transporter into the cell membrane of myocytes and adipocytes
Does insulin promote the synthesis or breakdown of proteins and fats?
Synthesis
What acts on the pancreas to get it to start secreting insulin?
GLP (a gastrointestinal hormone).
GLP is released on food intake
Other than high blood glucose and food intake, what 2 other factors can stimulate insulin secretion?
High blood amino acid concentration
Parasympathetic stimulation
Name the 2 main sites of action of glucagon?
Liver and adipose tissue
Is glucagon catabolic or anabolic?
Catabolic
Low blood glucose levels stimulate the pancreatic alpha cells to secrete what?
Glucagon
Which hormone stimulates gluconeogenesis?
Glucagon
To mobilise glucose from its storage form, glucagon promotes which process?
Glycogenolysis
Other than glucagon and adrenaline, which other 2 molecules increase blood glucose levels?
Glucocorticoids
Growth hormone
Explain type 1 diabetes
It is an autoimmune condition that causes the destruction of the beta cells of the pancreas, inhibiting insulin secretion
What treatment option is used for gestational diabetes?
Recombinant human insulin injections. (Same as for type 1)
Explain 2 non-pharmacological treatment option for diabetes?
- exercise (increases GLUT4 expression)
- diet (limiting sugary foods, non processed, vegetables, lean meat)
- weight loss
Explain the use of a biguanide
It is an oral hypoglycaemic
Inhibits glucose output from the liver and increases glucose uptake by the muscles
Name a biguanide
Metformin
What is an advantage of using a biguanide? Give 1 drug example.
Does not cause hypoglycaemia
Example= metformin
Which oral hypoglycaemic drug class requires functioning beta cells?
Sulfonylureas
Explain the MOA of sulfonylureas
Stimulates insulin secretion
Gliclazide and tolbutamide are examples of which drug class?
Sulfonylureas
Potential problem with sulfonylureas?
Can cause hypoglycaemia. Can also stimulate appetite and weight gain
Explain how thiazolidinediones reduce insulin resistance
It is an agonist for a nuclear insulin receptor. It enhances the uptake of fatty acids which lowers blood glucose
- since free fatty acids increase gluconeogenesis
Give an example of a thiazolidinedione
Rosiglitazone
Give the MOA of Byetta
It is a venom derived peptide that is a GLP agonist. Used in T2DM
Name 2 mechanisms that the body can use to decrease blood glucose levels
- transport of glucose from the blood into cells
- urinary excretion
How does insulin affect GLUT 4 expression
In the presence of insulin, vesicles containing GLUT 4 move to the cell membrane and deposit / undergo exocytosis and the transporter is inserted into the membrane of adipose and muscle cells
Name the two actions of GLUT 4 (one on fat and one on muscles)
Muscles - glut 4 activation increases glycogen synthesis and also increase glucose use in the muscles
Fat - promotes lipogenesis (building of new fat)
What 3 actions does insulin stimulate in the liver
- glycogen synthesis
- inhibits gluconeogenesis and glycogenolysis
Is insulin secreted in the fed or fasted state
Fed
Explain the action of GLP
GLP is a hormone secreted by the hormone in response to food intake. It acts on the pancreas to stimulate the beginning of insulin secretion
Does the parasympathetic system increase or decrease insulin secretion?
Increase
When is glucagon secreted
In fasting state
Which hormone, glucagon or insulin, increases glycogenolysis ang gluconeogenesis?
Glucagon
Which drug class requires functioning beta cells?
Sulfonylureas (e.g. gliclazide)
What affect does insulin have on fatty acids and amino acids?
Promotes their cellular uptake and conversion into storage forms (triglycerides and protein)
Define gluconeogenesis
Conversion of amino acids into glucose in the liver
True or false. Insulin promotes protein synthesis
True
Explain how glucose and amino acids act on the pancreatic beta cell to stimulate insulin secretion.
Glucose and amino acids enter the cell via GLUT 2. They are converted to ATP
ATP closes K channel which depolarises the cell.
Depolarisation opens Calcium channel. Calcium facilitates the exocytosis of insulin vesicles.
What happens after a high protein meal?
Amino acids act on beta cells to stimulate insulin secretion. Insulin then lowers blood amino acid levels by promoting protein synthesis
Does the brain need insulin to access glucose?
No
How can hyperglycaemia be aggravated by protein degradation in diabetic patients?
Due to reduced insulin, protein metabolism becomes catabolic. This increases blood amino acid concentration. These amino acids can then be used by the liver for gluconeogenesis, producing even more glucose and raising BG levels