Insulin Secretion and Intermediary Metabolism Flashcards
What is the hormone that lowers blood glucose?
Insulin
What are the hormones responsible for increasing blood glucose?
Glucagon
Catecholamines
Somatotophin
Cortisol
What is T1D?
Elevated glucose where insulin is required to prevent ketoacidosis.
Insulin dependent Diabetes
What is T2D?
Insulin resistant diabetes
Name 4 complications of diabetes:
Diabetic retinopathy
Nephropathy
Heart attacks
Stroke
What is the range of glucose concentration for hypoglycemia?
4-5.5mM
What could happen if blood glucose falls below 2mM?
Not enough glucose for respiration in the brain; leads to unconsciousness, coma and death
What percentage of the pancreas are the islets of langerhans?
2%
What are the three main cell types in islets of langerhans?
Alpha - Glucagon
Beta - Insulin
Delta - Somatostatin
What is the function of Gap junctions between islet cells?
Allow hormones to have an effect on adjacent cells - paracrine effect
What is the function of Tight junctions in islet cells?
Allow formation of small collections of fluid between cells
What factors increase insulin secretion? (5)
Increased blood glucose Certain gastrointestinal hormones Glucagon Parasympathetic activity certain amino acids
What are the effects of insulin? (7)
Increaed glycogenesis Increased glycolysis Increased glucose transport into cells via GLUT4 Decreased lipolysis Increased Lipogenesis Increased protein synthesis Decreased protein break down
What is the effect of somatostatin on insulin/glucagon?
Decreased production
What factors affect Glucagon secretion?
Increase secretion: Decreased blood glucose Sympathetic activity Parasympathetic activity Certain gastrointestinal hormones Certain amino acids
Decrease secretion:
Insulin
Somatostain
What are the main effects of Glucagon?
Increased blood glucose
Main effects are on liver; increase hepatic glycogenolysis
Increased lipolysis/amino acid transport into liver resulting in increased gluconeogenesis
How does the glucokinase ‘Glucose sensor’ work?
Glucose enters ß-cells via Glut 2 insulin independent transporter
Glucokinase in ß-cells converts Glucose into G6P; rate limiting step.
This produces ATP which binds to ATP sensitive K+ channel, blocking it, causing depolarisation.
This causes Ca2+ to rush into cell causing Insulin vesicles to exocytose
What is used to measure endogenous insulin production levels?
C peptide levels, as produced on 1:1 ratio as cleaved from prohormone
What is the incretin effect?
Food stimulates insulin production much more than an IV injection of glucose
What is GLP-1? What does it do?
Glucagon like peptide-1
Gut hormone secreted in response to gut nutrients, that increases satiety, stimulating insulin, suppressing glucagon; has a short half life due to the enzyme dipeptidyl peptidase-4
Describe the Insulin receptor:
Extracellular alpha subunits bind to the insulin, causing transmembrane beta subunits to allow phosphorylation of cell protein substrates using tyrosine kinase domains
How does insulin resistance arise?
Post-receptor cytoplasmic elements of receptor do not work properly
