63. After overnight fasting level of glucose transporters get reduced in?

SCTIMST Staff Nurse - 2016

Biochemistry & Nutrition

Hard

Appeared in: SCTIMST Staff Nurse - 2016

Explanation

Adipocytes (fat cells) primarily use the GLUT4 transporter for glucose uptake.
GLUT4 is an insulin-dependent transporter, meaning its presence on the cell surface is regulated by insulin levels.
During overnight fasting, insulin levels are low.
Low insulin causes GLUT4 transporters to be internalized from the cell membrane into intracellular vesicles.
This internalization leads to a reduced number of active glucose transporters on the surface of adipocytes, thereby decreasing their glucose uptake.

Option A: Brain cells primarily use GLUT1 and GLUT3 transporters, which are insulin-independent. This ensures the brain receives a constant supply of glucose, its primary fuel, regardless of fasting or feeding states.
Option C: Red blood cells (RBCs) rely exclusively on GLUT1 transporters for glucose uptake. GLUT1 is insulin-independent, providing a continuous glucose supply for glycolysis, as RBCs lack mitochondria.
Option D: Hepatocytes (liver cells) use the GLUT2 transporter. GLUT2 is a high-capacity, low-affinity, and insulin-independent transporter. It facilitates bidirectional glucose movement, allowing the liver to take up glucose after a meal and release it during fasting (gluconeogenesis), but the number of transporters does not decrease.

Clinical Relevance

Nursing practice connection: Safe nursing care depends on performing Regulation of glucose transport in different tissues in the correct sequence, documenting the action clearly, and monitoring for the expected response.
Understanding GLUT4 regulation is fundamental to the pathophysiology of Type 2 Diabetes, where insulin resistance impairs this translocation process, leading to hyperglycemia.
This mechanism explains why fasting is necessary before certain blood tests, as it brings the body to a baseline metabolic state.
What if? - What if the person was exercising? In skeletal muscle (which also uses GLUT4), muscle contraction itself can stimulate GLUT4 translocation to the membrane, independent of insulin. This is why exercise is a key recommendation for managing blood glucose levels.

How to Approach the Question

First, identify the key elements of the question: 'overnight fasting' and 'reduced glucose transporters'.
Recognize that 'overnight fasting' corresponds to a state of low blood insulin.
The question is therefore asking: In which cell type is the number of glucose transporters on the surface regulated by insulin?
Systematically review the options based on your knowledge of glucose transporter types (GLUTs) and their tissue distribution.
Recall that adipocytes and muscle use insulin-dependent GLUT4.
Recall that the brain (GLUT1/3), RBCs (GLUT1), and liver (GLUT2) use insulin-independent transporters.

Concept Tested & Keywords

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