Insulin secretion Flashcards
Hormone involved in lowering blood glucose?
insulin
for post prandial state
Hormone involved in increasing blood glucose?
glucagon
catecholamines (adrenaline/noradrenaline)
somatotrophin
cortisol
What state is life threatening?
hypoglycaemia
What is T1DM?
elevated glucose where insulin required to prevent ketoacidosis
What is T2DM?
more common
disease of all intermediary metabolism not just glucose
related to hypertension and dyslipidaemia
What causes T2DM?
obesity may trigger onset but is not the cause
significant genetic component
What are some complications of diabetes?
diabetic retinopathy
nephropathy
heart attacks
stroke
Importance of glucose?
important energy substrate especially for CNS that mainly respires glucose normally (cannot respire fats) can use ketones in extreme circumstances
below (4-5.5.mM = hypoglycaemia) increasingly impaired brain function
below 2mM could cause unconsciousness, coma and death
What avoids drops in glucose [] in the body?
a counter regulatory system
pancreatic cells make glucagon
hypothalamus and pituitary make ACTH that causes adrenals to make glucocorticoid (cortisol)
Describe the organisation of the pancreas?
98% = exocrine secretions via duct to small intestine 2% = endocrine secretions via islets of Langerhans
Describe the cells of the pancreas?
alpha = glucagon beta = insulin delta = somatostatin
cells have gap junctions to allow hormones to have effect on adjacent cells by passing directly between cells (paracrine effect)
also small collections of fluid between cells formed by tight junctions
What is the function of somatostatin?
decrease production of insulin and glucagon
What is the function of somatostatin?
decrease production of insulin and glucagon
What is the function of insulin?
decreases blood glucose
growth hormone (stimulates growth and development) acting through insulin like growth factor receptors
What is the effect of insulin?
glycogenesis
glycolysis
glucose transport into cells via GLUT4
OVERALL AIM: lower blood glucose
increases AA transport and increases protein synthesis
increases lipogenesis, decrease lipolysis
How is insulin stimulated?
increase blood glucose glucagon certain AAs certain GI hormones (food in gut, gut makes us produce insulin before we eat) PNS activity B receptors (some)
How is insulin inhibited?
sympathetic activity
alpha receptors
somatostatin
What does Glucagon Like Peptide do?
It is a gut hormone that is secreted in response to nutrients in the gut
= transcription product of proglucagon gene (from L cell)
make us produce insulin and suppress glucagon
increase satiety
How are beta cells controlled neurologically?
SNS - switch off insulin to increase blood glucose
PNS - increase insulin secretion
What is the effect of glucagon?
increase hepatic glycogenolysis
increase blood glucose in emergency
increase AA transport to liver –> increase gluconeogenesis
increase lipolysis –> increase gluconeogenesis
How is glucagon production stimulated?
decrease blood glucose certain AAs certain GI hormones SNS activity PNS activity
How is glucagon production inhibited?
somatostatin
insulin
How are T1DM patients protected in case of emergency?
glucagon injection
IV glucose
How is insulin secretion of B cells regulated?
By rate determining step of glucokinase (hexokinase IV)
- glucose enters cells via GLUT2
- GLUT2 not insulin regulated
- glucose converted to G6P by glucokinase (RDS) that allows B cell to sense glucose
- rate of production of G6P regulates rate of insulin release
Energy generated from G6P production (ATP) blocks ATP sensitive K channels, opens voltage dependent Ca channels –> Ca rushes in –> stored insulin secreted and increased insulin production
