Lecture 8 Flashcards
Is SGLT1 high or low affinity?
High affinity, low capacity. This means it becomes saturated quickly. We must have other mechanisms to absorb all the monosaccharides.
What is mannitol?
A sugar with the same MW as glucose but is not transported by SGLT1. It was used to keep osmolarity constant.
What is phoretin?
An inhibitor of GLUT2.
What is the effect of phloretin at differing luminal glucose concentrations?
The phloretin-inhibitable component is greater the higher the concentration of glucose
GLUT2 is used for glucose absorption…
at high glucose concentrations.
Does SGLT1 differ in fasted and fed states?
No
Does GLUT2 differ in fasted and fed states?
Yes, it is not present in fasted states.
How does SGLT1 affect GLUT2?
Transport via SGLT1 aids the exocytosis of pre-formed pools of GLUT2 into the BBM to provide a high capacity route for glucose and galactose transport.
At lower glucose concentrations, what occurs?
Ca1.3 calcium channel opens which primes GLUT2 for insertion via cytoskeletal rearrangement.
At high glucose concentrations, what occurs?
The glucose activates taste receptors TIR2/TIR3 which causes GLUT2 to move to the membrane.
What also activates the TIR2/TIR3 receptors?
Fructose and artificial sweeteners.
What does GLUT2 colocalise with?
Sucroisomaltase
What does insulin do to GLUT2
Causes its retrieval from the BBM.
What does a high fructose diet do in terms of insulin?
Reduces the effect of insulin for retrieving GLUT2 from the membrane. Insulin resistance.
In a fasted state, obese individuals will have a high glucose levels in the gut because…
GLUT2 is still in the BBM so glucose moves from the blood out the cell into the gut which disturbs the gut microbiome.
