Glucose Homeostasis Flashcards
(27 cards)
Why is glucose so important?
important energy substrate
If the blood glucose concentration falls much below normal levels of 4-5 mmol/L (hypoglycaemia), then cerebral function is increasingly impaired.
If blood glucose concentration <2 mmol/L, unconsciousness, coma and ultimately death can result.
How is glucose regulated?
Feedback system
What are the 4 hormones involved in regulation?
Glucagon
Cortisol
GH
Catecholamines
What does persistent hyperglycaemia result in?
Diabetes Mellitus
What % of people are affected with diabetes mellitus in the UK?
7%
What is the % risk increase risk of a person with diabetes mellitus dying relative to an age-matched control without diabetes mellitus?
34%
How much of the NHS budget is spent on diabetes mellitus?
10%
What are the different diabetes mellitus phenotypes?
Type 1
Maturity onset diabetes of the young (MODY)
Type 2
What is the structure of the pancreas gland?
Retroperitoneal
What is the majority of the pancreas comprised of?
Most of pancreas (98%) generates exocrine secretions via duct to small intestine
What is the remaining 2%?
Small clumps of cells within pancreatic tissue (remaining 2%) are called islets of Langerhans
What are the three cells of the islets of langerhans?
Alpha- Glucagon
Beta- Insulin
Delta- Somatostatin
What are the cell junctions found in the islets of langerhans?
Gap junctions:
Allow small molecules to pass directly between cells
Tight junctions:
Create small intercellular spaces
What are the actions of pancreatic hormones?
Insulin stimulates growth and development and reduces blood glucose
Glucagon increases blood glucose
What physiological changes occur in response to an increase in plasma concentration?
Beta cells secrete insulin
What does insulin cause?
Build up of glycogen stores Breakdown of glucose Uptake of glucose Increase of protein synthesis Breakdown of fat??
What physiological changes occur in response to an decrease in plasma concentration?
Alpha cells secrete glucagon
What does glucagon cause?
Increased Lipolysis Gluconeogenesis Hepatic glycongenolysis Amino acid transport into liver Glucagon increases blood plasma glucose
What is glucokinase?
Main glucose sensor
Converts glucose to glucose-6-P in a RDS
How is insulin released?
ATP produced from glucose-6-P
Causes release of K+
Causes Ca2+ channels to open
Stimulates release of insulin
What is C-peptide?
Used in Insulin assays, as insulin is difficult to measure
Product of cleavage of Proinsulin to form insulin
More stable
Longer half life than insulin
More accurate representation
Not affected by exogenous insulin
After a heavy meal what would expect the levels of. C-peptide to be?
High in normal
Low in Type 1 diabetic
What is the incretin effect?
The concept that oral glucose administration promotes a much greater degree of insulin secretion compared to a parenteral isoglycemic glucose infusion underlies the incretin effect
Namely the existence of gut-derived factors that enhance glucose-stimulated insulin secretion from the islet β-cell
What are the main features of GLP-1?
Gut hormone
Secreted in response to nutrients in gut
Transcription product of pro-glucagon gene, mostly from L-cell
