Question

Which receptor (transporter) helps in improvement of insulin resistance in DM2 (type 2 diabetes mellitus) with regular exercise and physical activity?

• A. GLUT1
• B. GLUT4
• C. GLUT2
• D. GLUT3

Hint:

Which GLUT is insulin-responsive in skeletal muscle and also recruited to the membrane by muscle contraction (via AMPK/Ca²⁺)?

Answer 1

The Correct Option is B

Step 1: Recall the GLUT family distribution.
GLUT1 - ubiquitous, basal glucose uptake (RBCs, brain, blood-brain barrier). GLUT2 - liver, pancreatic \(\beta\)-cells, intestine, kidney (high-Km glucose sensor). GLUT3 - neurons (high affinity). GLUT4 - the insulin-responsive transporter in skeletal muscle and adipose tissue.

Step 2: Link exercise to the right transporter.
In skeletal muscle, GLUT4 normally translocates to the cell membrane in response to insulin. Muscle contraction during exercise also recruits GLUT4 to the membrane by an insulin-INDEPENDENT pathway (mediated by AMPK and raised intracellular calcium). Regular physical activity increases muscle GLUT4 expression and membrane translocation, so muscle takes up glucose even when insulin signalling is impaired - this is exactly how exercise improves insulin resistance in type 2 diabetes.

Step 3: Eliminate the distractors.
(A) GLUT1 gives constant basal uptake and is not insulin/exercise regulated. (C) GLUT2 is a low-affinity sensor in liver and \(\beta\)-cells, not the muscle exercise transporter. (D) GLUT3 serves neurons. None of these are recruited by exercising muscle.

Final answer: B - GLUT4.