Effect of insulin and exercise Flashcards
- Describe the different types of glucose transporters expressed in cells and discuss their structural and functional properties - Describe the experiments that elucidated how insulin stimulates glucose uptake in muscle - Describe the signalling molecules involved in the activation of glucose transport by insulin - Describe the effects of muscle contraction on glucose uptake - Describe how muscle exercise and drugs such as metformin stimulate glucose uptake
Glucose transport is mediated by
- sodium-coupled glucose transporters (SGLT) expressed in intestines and kidneys
- facilitative glucose transporters
Facilitative glucose transporters (second class of glucose carrier)
- intregal membrane proteins
- present on the surface of all cell membranes
- transport glucose down a concentration gradient by facilitative diffusion
- energy independent process
- can operate bidirectionally and mediate trans-cellular glucose transport, but always in the direction of the chemical gradient
GLUT glucose transporters
- 13 facilitated hexone carriers
- saturable, stereoselective, 12 transmembrane domain-containing protein
Class I glucose transporters
- high affinity binding proteins: GLUT1 GLUT3 GLUT4
- low affinity binding protein: GLUT2
Class II
very low affinity for glucose, transport fructose
GLUT5 GLUT7 GLUT9 GLUT11
myoinositol transporter (HMIT1)
Class III
GLUT6 GLUT8 GLUT10 GLUT12
Where is GLUT1 expressed
red blood cells, blood-brain barrier, foetus
Where is GLUT2 expressed
kidneys, small intestine, liver, pancreas
Where is GLUT3 expressed
placenta, neurons, kidney
Where is GLUT4 expressed
skeletal muscle, adipose tissue
Role of insulin in glucose transport
responsible for mediating insulin-sensitive glucose transport - important for facilitating peripheral glucose disposal after a meal when blood glucose is high
How does insulin stimulate sugar uptake in fat and muscle
