Glucose homeostasis and the pancreas Flashcards
Insulin decreases plasma
glucose
AAs
FFAs (free fatty acids)
“anabolic:
Glucagon increases plasma
glucose
ketones
“catabolic” ie breaking down
B cells produce … which…
insulin
stimulates glucose utilisation and uptake
Alpha cells produce.. which..
glucagon
Increases breakdown of glycogen and glucose release
delta-cells produce.. which…
Somatostatin
Supresses GI motility and release of insulin and glucagon
Structure of insulin
A chain 30 aa
B chain 21 aa
C peptide - inactive
Insulin degraded by
insulinase in liver and kidneys
Insulin is secreted in response to
changes in glucose/ATP
Insulin secretion occurs via
calcium dependent exocytosis
Insulin binding to the insulin receptor
dimerization
“ receptor tyrosine kinase”autophosphorylation
Effects on intracellular kinases/phosphatases
effects on key enzymes
2 actions of insulin
Carbohydrate metabolism and lipid metabolism
carbohydrate metabolism
facilitates glucose entry into muscle, adipose (GLUT)
Stimulates liver to store glucose as glycogen
Decreases conc of glucose in the blood
Lipid metabolism
Insulin triggers uptake of glucose into liver
Promotes synthesis of fatty acids in the liver (when glycogen is saturated) leading to increase in lipoproteins in circulation to release FAs (triglyceride synthesis in adipocytes)
Inhibits breakdown of fat in adipose tissue
Promotes glycerol synthesis from glucose and incr triglceride synthesis
Insulin stimulates
muscle glucose uptake
rise in blood glucose triggers
B cells release insulin
B cells release insulin triggers
incr rate of glucose uptake
Incr glucose utilization and ATP generation
Incr glycogenesis- formation of glycogen from sugar (liver, muscle)
Incr protein synthesis
Incr fat synthesis
All this causes blood glucose to decline
How is glucose synthesised
Alpha cells of islets (a portion of tissue structurally distinct from surrounding tissues) synthesise and release glucagon:
Glucagon
peptide hormone
released when blood glucose falls
Counter regulatory hormone to insulin
Stimulates glycogenolysis (break down glycogen)
Promotes gluconeogenesis (glucose from other sources)
Increases breakdown of fats (alternative energy source)
what type of cell releases glucagon
Alpha cells
Release of glucagon triggers
Incr glycogenolysis liver, skeletal muscle
Increased fats to fatty acids
Increased protein breakdown
Increased Gluconeogenesis (liver)
When is glucagon released
Falling blood glucose
Hypoglycaemia
Low blood glucose
Uptake of glucose by glucose dependent tissue not adequate to maintain tissue function
Effects of hypoglycaemia
CNS sensitive: poor vision, slurred speech. confusion, coma death
Overactivity of ANS: palpitations, sweats, shakiness and hunger
Diabetes is characterised by
hyperglycaemia
Gestational diabetes
associated with pregnancy
Serious risks to mother and child
Incr risk of developing type 2
Insulin effect on muscle
glucose and AAs uptake
Glucose converted to glycogen and amino acids to structural proteins
which hormone increases uptake of glucose and where
insulin and muscle and Adipose
Which hormone triggers lipogenesis and where
insulin and in the liver and adipose
Lipolysis where and what hormone
Adipose and glucagon
Amino acid uptake where and what hormone
muscle and insulin
