Glucose Transporters..

1. Introduction
Glucose
Glucose is the most common
carbohydrate .Glucose is called
blood sugar as it circulates in the
blood at a concentration of 65-110
mg/100 ml of blood. Glucose is an
important fuel for contracting
muscle, and normal glucose
metabolism is vital for health.
Glucose enters the muscle cell via
facilitated diffusion through the
GLUT4 glucose.

2. Glucose Transporters

3. Glucose Transporters
GLUT 1 Most cells High capacity,
relatively low
Km
GLUT2 Liver, beta cells,
hypothalamus
High capacity
but low affinity
(high Km
GLUT3 Neurons,
placenta, testes
Low Km (1mM)
and high
capacity
GLUT4 Skeletal and
cardiac muscle,
fat
Activated by
insulin. Km 5mM
GLUT5 Mucosal surface
in small intestine,
sperm
Primarily
fructose carrier
in intestine

4. GLUT 1
Glut1 catalyzes the rate-limiting
step in supplying cells of the
central nervous system with
glucose, an essential fuel for these
cells. The ability to acutely
regulate Glut1 activity might be a
very useful strategy to counter the
effect of strokes due to arterial
blockage as well as the damage
that occurs to cardiomyocytes
during cardiac infarction.

5. GLUT 2
Glut2 is required for the function of
glucose sensors present in the
hepatoportal vein area and in the
central nervous system. These sensors
appear to control glucagon
secretion, feeding behavior, insulin
secretion, and peripheral tissue
glucose uptake.

6. GLUT 3
They don’t need insulin to transport
glucose
Always present in the plasma membrane
at their sites of action for facilitated
diffusion.
In the liver ,insulin facilitate transport of
glucose in a different way through
increase conversion of glucose to
glucose 6- phosphate.

7. GLUT 4
Insulin dependent cells
Found in resting muscles and
adipose tissue.
Insulin promotes glucose uptake
by transporter recruitment.
Exposure to increased amount of
insulin decreases insulin receptors,
while Exposure to decreased
amount of insulin increases insulin
receptors

8. References
1.↵Abbott MJ, Bogachus LD, Turcotte LP.
AMPKα2 deficiency uncovers time-
dependency in the regulation of
contraction-induced palmitate and glucose
uptake in mouse muscle.
2.↵Abbott MJ, Edelman AM, Turcotte LP.
CaMKK is an upstream signal of AMP-
activated protein kinase in regulation of
substrate metabolism in contracting skeletal
muscle.
3.↵Ahlborg G, Björkman O. Carbohydrate
utilization by exercising muscle following pre-
exercise glucose ingestion.