WBR0936
| Author | PageAuthor::William J Gibson |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Biochemistry |
| Sub Category | SubCategory::Endocrine, SubCategory::Musculoskeletal/Rheumatology |
| Prompt | [[Prompt::A scientist is studying the mechanism of exercise-induced insulin sensitivity in diabetic patients. A biopsy of the vastus lateralis muscle is obtained from the left leg at rest. 3-6 weeks later, the subjects performed 45-60 minutes of cycling at 70% VO2 max, and immediately thereafter a biopsy was obtained from the right vastus lateralis muscle. The investigator performs immunohistochemistry of the obtained tissues. Which of the following will demonstrate increased localization to the plasma membrane?]] |
| Answer A | AnswerA::GLUT1 |
| Answer A Explanation | AnswerAExp::Incorrect: GLUT1 is expressed in erythrocytes and the brain. It does not translocate to the cell membrane with exercise. |
| Answer B | AnswerB::GLUT2 |
| Answer B Explanation | AnswerBExp::Incorrect: GLUT2 is a bidirectional glucose transporter that is expressed in pancreatic islet cells, the liver and the kidney. It does not translocate to the cell membrane with exercise. |
| Answer C | AnswerC::GLUT3 |
| Answer C Explanation | AnswerCExp::Incorrect: GLUT3 is primarily expressed in neurons and does not translocate to the cell membrane with exercise. |
| Answer D | AnswerD::GLUT4 |
| Answer D Explanation | AnswerDExp::Correct: GLUT4 is an insulin-responsive glucose transporter found in adipose tissue and muscle that translocates to the cell membrane upon exercise. |
| Answer E | AnswerE::GLUT5 |
| Answer E Explanation | AnswerEExp::Incorrect: GLUT5 is a fructose transporter expressed on the apical border of enterocytes in the small intestine. It does not translocate to the cell membrane with exercise. |
| Right Answer | RightAnswer::D |
| Explanation | [[Explanation::Educational objective: GLUT4 is an insulin-responsive glucose transporter found in adipose tissue and muscle that translocates to the cell membrane upon exercise.
References: First Aid 2013 page 288 First Aid 2012 page 315 Lund S, Holman GD, Schmitz O, Pedersen O. Contraction stimulates translocation of glucose transporter GLUT4 in skeletal muscle through a mechanism distinct from that of insulin. Proc Natl Acad Sci USA. 1995;92(13):5817-21. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Muscle, WBRKeyword::Insulin, WBRKeyword::Glucose, WBRKeyword::Receptor, WBRKeyword::Exercise, WBRKeyword::Transporter |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |