Diabetes: pancreas physiology and disease Flashcards
is insulin an anabolic or catabolic hormone?
anabolic
what does an anabolic hormone do?
it promotes the storage and synthesis of products
how does insulin increase glucose absorption?
- it binds to receptors which trigger GLUT4 receptors to move from cytoplasm to cell membrane, allowing more glucose in the cell
where is insulin produced, and by which cells?
beta cells in Islets of Langerhans, in the pancreas
what class of hormone is insulin?
peptide hormone
what are the properties of peptide hormones?
- can be stored in vesicles
- bind to membrane receptors
- water soluble
- short half-life
which cellular steps occur for the release of insulin into the circulation?
- glucose binds to GLUT receptors on Beta cells
- metabolism increased, more ATP/K+ activity
- intracellular K+ rises and cell depolarises
- Ca2+ channels open and it flows into the cell
- vesicles merge with cell membrane and insulin flows out
which hormones act as counter-regulatory mechanisms to insulin?
- glucagon
- adrenaline
- cortisol
- growth hormone
list some of the actions of insulin
- increased glucose uptake through GLUT4 receptors
- increased glycogenesis/reduced glycogenolysis
- increased lipogenesis/reduced lypolysis
- increased protein synthesis/reduced gluconeogenesis
- increased K+ uptake into cells
what stimuli trigger insulin release?
- high blood glucose
- amino acids in blood
- glucagon in blood
- vagus nerve stimulation
- incretin hormones acting on GI secretion/motility
where is excess glucose stored in the body, and in what form?
- stored in muscle and liver as glycogen
- stored in liver and adipose tissue as TAG
what is the term for the time period after meals during which insulin is most active?
Absorptive state
which two tissues in the body are insulin-dependent?
muscle and adipose tissue
what are the normal glucose levels in the blood?
around 5.5mM
which specific glucose transporters are found in which body tissues?
GLUT 1 and 3 - kidneys, brain, RBC
GLUT 2 - liver, beta cells in pancreas
GLUT 4 - muscle and adipose tissue
how does insulin act on liver cells?
- insulin binding to liver cell activates hexokinase, which causes glucose in the cell to be phosphorylated to G6P, trapping it in the liver cell and causing more glucose to flow in down concentration gradient
why are insulin levels associated with hypo or hyperkalaemia?
- because insulin stimulates Na/K+ase pump, drawing more K+ into cells
what kind of receptors does insulin bind to on the cell membrane?
tyrosine kinase receptors
what reduces the secretion of insulin?
- low blood glucose
- somatostatin
- stress (eg hypoxia)
- sympathetic stimulation
what class of hormone is glucagon?
a peptide hormone
where is glucagon produced?
in alpha cells in pancreatic Islet of Langerhans cells
what is the main purpose of glucagon?
to mobilise glucose into the circulation
what are the actions of glucagon?
- increase gluconeogenesis
- increase lypolysis
- increase glycogenolysis
- increase ketogenesis
on what kinds of receptors does glucagon act?
G-protein coupled receptors
on which cells do most of the actions of glucagon have effect?
liver cells
what effect do amino acids in the blood have on insulin and glucagon?
raise levels of insulin AND glucagon
what effect do high blood glucose levels have on insulin and glucagon?
high blood glucose - increase insulin and reduce glucagon
what effect do low blood glucose levels have on insulin and glucagon?
low blood glucose - reduce insulin and increase glucagon
what is thought to be the aetiology of diabetes type 1?
genetic predisposition
environmental triggers
autoimmunity
what is the pathology behind diabetes type 1?
lack of insulin secretion due to autoimmune destruction of islets of langerhans
which family member of a type 1 diabetic patient is most likely to also develop the disease?
an identical twin
which type of diabetes is most common worldwide?
type 2 diabetes
how do obesity and genetics possibly lead to DM2?
- obesity causes strain on adipocytes, which therefore release FFA. increase in FFA = reduced insulin sensitivity
- if genes aren’t present that allow higher insulin amounts to be secreted to compensate, this leads to hyperglycaemia and DM2