GLUT4
The glucose transporter in muscle and fat that insulin — and exercise — bring to the surface.
GLUT4 is the glucose transporter protein found mainly in skeletal muscle, heart and fat tissue. It sits in storage vesicles inside the cell and moves to the membrane when called, allowing glucose to enter.
It matters because it is the point where two separate signals converge. Insulin recruits GLUT4 through its signalling cascade; muscle contraction recruits it independently, through an AMPK-linked route. Both open the same door.
In practice this is the mechanism behind one of the most useful facts in metabolic health: a walk after a meal lowers the glucose response, and regular training both increases total GLUT4 content in muscle and improves how readily it is recruited. It is why exercise works when insulin sensitivity is already impaired.
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Written and reviewed by Mathew Beale, MSc Biotechnology, University of Reading.
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