Glucose transpoer in myocyte stimulated by insulin is
**Core Concept**
Glucose transporter 4 (GLUT4) is a type of facilitative glucose transporter found primarily in adipose tissue and striated muscle (skeletal and cardiac muscle), including myocytes. It plays a crucial role in insulin-regulated glucose uptake in these tissues.
**Why the Correct Answer is Right**
In the presence of insulin, GLUT4 translocates to the plasma membrane of myocytes, increasing glucose uptake. This process involves the activation of protein kinase B (Akt) and phosphatidylinositol 3-kinase (PI3K), which phosphorylate and activate the insulin receptor substrate 1 (IRS-1). IRS-1 then recruits and activates the phosphatidylinositol 3-kinase (PI3K) regulatory subunit p85, leading to the activation of Akt. Akt phosphorylates and inhibits the activity of AS160 (Akt substrate of 160 kDa), a GTPase-activating protein for Rab GTPases that regulate GLUT4 vesicle fusion with the plasma membrane.
**Why Each Wrong Option is Incorrect**
* **Option A:** Insulin stimulates glucose uptake in myocytes primarily through the translocation of GLUT1, which is a constitutively expressed glucose transporter. While GLUT1 does contribute to basal glucose uptake, it is not the primary glucose transporter responsible for insulin-stimulated glucose uptake.
* **Option B:** Glucose uptake in myocytes stimulated by insulin is not primarily mediated by the sodium-glucose cotransporter 1 (SGLT1). SGLT1 is a high-affinity, low-capacity glucose transporter that is primarily expressed in the small intestine and renal proximal tubules.
* **Option C:** The glucose transporter 2 (GLUT2) is primarily expressed in the liver, pancreas, and kidneys, and is involved in the regulation of glucose and glucagon levels. It is not the primary glucose transporter responsible for insulin-stimulated glucose uptake in myocytes.
**Clinical Pearl / High-Yield Fact**
Insulin resistance, a hallmark of type 2 diabetes, is characterized by impaired glucose uptake in myocytes due to reduced GLUT4 translocation and activation of the insulin signaling pathway.
**Correct Answer:** C.