Glucose Uptake and Exercise (LOIL 2) Flashcards
what family do the ‘Facilitative Glucose Transporters (GLUTs)’ belong to ?
Solute Carrier Gene Family (SLC2a)
state 4 facts about the GLUT family
- different substrate specificity and affinity for glucose and other sugars
- different functions and tissue distribution
- transport glucose don the concentration gradient (facilitative diffusion)
- bidirectional transport
GLUT2 - a glucose sensing glucose transporter - is found in what 4 locations ?
- pancreatic beta cells
- hepatocytes
- basolateral membrane of the intestine
- kidney proximal tubule
state 3 facts about GLUT2
- a high capacity glucose transporter
- has a low affinity for glucose (Km of approx. 11 mM)
- doesn’t saturate easily, so when there is an abundance of glucose in the blood, it will transport as much glucose as it can inside the cell
state 4 facts about GLUT3
- found predominantly in the neurones / brain
- has a very high affinity for glucose
- brain requires a lot of glucose to survive
- ensures that the brain receives glucose constantly so that it can function properly
what is GLUT4 ?
GLUT4 is a highly specialised glucose transporter regulated by insulin and contraction and is in all insulin sensitive tissue
what its GLUT4’s original name ?
Insulin-Responsive Glucose Transporter (IRGT)
how does GLUT4 work ?
GLUT4 translocates/traffics to the plasma membrane in response to insulin stimulation or muscular contraction
what does GLUT4 have, and what is the effect of this ?
has a specialised intracellular storage component called ‘GLUT4 Storage Component (GSC)’ - from there it is recruited to the plasma membrane
what is the effect of GLUT4 also being stimulated by muscle contraction ?
muscular contraction can also stimulate the translocation / trafficking of GLUT4 to increase glucose uptake during exercise
what is the effect of a defect in GLUT4 trafficking ?
defects in GLUT4 trafficking is an early manifestation of insulin resistance and the pre-diabetic phase of T2D
state an additional fact about GLUT5
GLUT5 is an exclusive transporter present in the gut enterocytes
state 5 expansionary facts to the following heading:
‘regulation of glucose metabolism during exercise’
- glucagon secretion inc^ to promote glycogenolysis
- (nor)epinephrine release further inc^ glycogenolysis
- cortisol inc^ to promote protein catabolism for later gluconeogenesis
- GH inc^ to inc^ FFA oxidation, lipolysis and gluconeogenesis
- insulin secretion dec^ to dec^ glucose storage
state what it is meant by the key term - ‘Glucose-Fatty Acid Cycle’
a homeostatic mechanism to control circulating concentrations of glucose and fatty acids
state what the following mean:
1) LCFA
2) TAG
3) Pyr
1) LGFA = long chain fatty acid
2) TAG = triaglycerol
3) Pyr = pyruvate