Insulin and diabetes mellitus: classification, pathogenesis and diagnosis Flashcards
Where is insulin secreted
Beta cells in the pancreatic islets of Langerhans
Where is insulin secreted
Beta cells in the pancreatic islets of Langerhans
What is the pro hormone precursor to insulin
Proinsulin
What do the pancreatic islets also contain
alpha cells and delta cells
What do alpha cells do and what do delta cells do
alpha cells secrete glucagon and delta ells secrete somatostatin
What is the key regulator of insulin release
glucose
What other factors influence insulin secretion
amino acids
GI peptides neurotransmitters
How is glucose transported into pancreatic beta cells
GLUT2 transporter
What is the function of glucokinase
it phosphorylates glucose to glucose-6-phosphate
What does the metabolism of glucose=6 phosphate generate
ATP which inhibits the activity of an ATP-sensitive potassium channel
What does the inhibition of an ATP-sensitive potassium channel result in
depolarisation of the beta cell membrane, opening of voltage gated calcium channels and insulin release
What does the binding of insulin to its receptor on the cell membrane of the target cells result in
autophosphorylation of the receptor via the receptor’s intrinsic tyrosine kinase activity
How does insulin lower blood glucose levels
Inhibition of gluconeogenesis in the liver and kidney
Inhibition of glycogenolysis
Increased glucose uptake
Increased glycolysis
What else can insulin affect other than metabolic effects
steroidogenesis vascular function fibrinolysis growth regulation cancer
What might insulin resistance and hyperinsulinaemia result in
stimulation of ovarian androgen secretion by stimulating LH release or increasing ovarian LH receptors
this occurs in PCOS
What is diabetes mellitus
a group of common metabolic disorders that share the phenotype of hyperglycaemia
How might patients with diabetes present
fatigue polyuria polydipsia nocturia recent weight loss (Type 1) DKA microvascular complciations macrovascular complications recurrent infections
What is type 1 diabetes caused by
destruction of the pancreatic insulin-producing beta cells, resulting in absolute insulin deficiency
What causes the beta cell destruction in T1DM
Autoimmune process
What is type 2 diabetes characterised by
increased peripheral resistance to insulin action
impaired insulin secretion
increased hepatic glucose output
Describe the level of plasma free fatty acid concentrations in obese patients
high
What is MODY
maturity onset diabetes of the young is a rare cause of type 2 diabetes resulting from mutations transmitted in an autosomal dominant manner
how is a patient diagnosed with DM
if they have 1 or more of the following:
symptoms of diabetes and random plasma glucose 11.1+ mmol/L
Fasting plasma glucose 7.0mmol/L +
2 hour plasma glucose levels 11.1mmol/L + after a 75mg oral glucose tolerance test
