Glucose Transporters GLUT and SGLT: Biochemistry Lesson. The body’s cells use glucose for energy. Glucose is transported through the bloodstream to cells where it is used as a source of energy. Two different proteins, called glucose transporters, move glucose through the cells. Glucose uptake transporter 1 (GLUT1) moves glucose from the bloodstream into cells, and glucose transporter 2 (SGLT1) moves glucose from cells back into the bloodstream.
There are two major types of glucose transporters in the body: GLUT1 and GLUT2. These transporters are responsible for transporting glucose from the blood into different tissues, including the brain. The two transporters work together to shuttle glucose between the bloodstream and different cells in the body. GLUTs function as “pumps” while SGLTs function as “sieves”.
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GLUT is a large family of glucose transporters that are found in all cells. GLUT1 is the best-studied transporter and is responsible for transporting glucose into cells for energy production. SGLT1 is the most important transporter for transporting glucose out of cells and into the blood. These transporters play important roles in maintaining blood sugar levels, and can be affected by diabetes and other diseases.
Glucose Transporters GLUT and SGLT: Biochemistry Lesson
Hey, guys, in this lesson, I’m going to be talking about glucose transporters, what they are the different types of glucose transporters where they are found in the body and their relevance to whole body metabolism. So to begin, why do we need glucose those transporters? Well, the reason is because glucose is hydrophilic. And as you can see in this depiction of glucose here, glucose has many hydroxyl groups, which makes it very hydrophilic. So that means it’s not easily transported across cellular membranes.
So that’s why we need transporters. There are actually two types of transporters. The first type are the glutes or the glucose transporters, and they’re actually 14 different types of gluten. They are all sodium and ATP independent, and they are ubiquitous. So they’re found all throughout the body in all cell types.
The other type of glucose transporter are known as the sodium dependent glucose transporters or the SGLTs. And these are as the name suggests, they’re sodium dependent, and they require ATP because ATP is actually used to form a sodium gradient that is used to transport glucose into the cell.
And they’re located in a few different locations in the body, particularly the intestine, renal tubules, and the blood brain barrier. So to begin with glucose transporters, there are actually five very important glucose transporters in the body, glute one to glute five. The rest of the glucose transporters have not really been well characterized, and they don’t seem to be very significant to whole body metabolism.
Glucose transporters SlideShare
So I’m just going to talk to you guys about gluten to glute five. So for glute one, these ones are found in the blood. So in red blood cells or erythrocytes, they are also found in the blood brain barrier, and they are also found in the heart, but to a lesser extent. So the heart has very minimal amounts of gluten. But the red blood cells actually use glute one heavily to uptake glucose.
And the main important key point for gluten one is that they are insulin independent. So, for instance, red blood cells never need insulin to uptake glucose, so they always use glucose, even without insulin present. So for glute, too, these are found in the liver, pancreas, and in small intestine as well. And these are also insulin independent. And they have a high mechaelism constant or high Km, which means they have a very low affinity for glucose.
So that means that the liver, the pancreas, and small intestine only uptake glucose through glute two when glucose concentrations are very high. So this makes sense. A lot of times, the liver won’t take up any glucose. It’ll let the rest of the body take glucose for other usage, but the liver will uptake glucose through glute two when glucose concentrations are very high. So it’ll update glucose to stored as glycogen.
And the pancreas does this as well. With beta cells, beta cells will uptake glucose when glucose concentrations are relatively high, which means then the beta cells will uptake glucose, and then the beta cells will release insulin to compensate for the high glucose level. The next glucose transporter is Glute three. This is found in the brain, in the neurons, and also in sperm. This one is also insulin independent.
Glucose transporters mnemonic
And the key point with Glute three is that it has a low mechaelosentin constant, which means it has a very high affinity for glucose. So that means that the brain and the neurons in the brain always take up glucose and they do it with a high affinity. So if there’s any glucose present at all, they will make sure that they take up the glucose. So as always, the brain makes sure that it takes up its required energy substrates. It makes sure that it maintains its metabolism at a constant state regardless of what’s going on in the rest of the body.
So just remember, guys, that Glute three has a very high affinity for glucose, which means it’s always typically always saturated with glucose. And as well, it’s also insulin independent for Glute four. These are found in skeletal muscle, adipose tissue, and the heart. So as I mentioned before, the heart has gluten as well, which is insulin independent. And it also has Glute four.
Now Glute four actually outnumbers Glute one in the heart by about a three to one ratio. So Glute four is a little bit more important for heart metabolism than Glute one is. And the main key point for Glute four is that Glute four is actually insulin dependent. So this is why insulin actually allows uptake of glucose is because it actually acts through Glute four. And again, this glute transporter has a moderate Km, which means it has a moderate affinity for glucose.
GLUT2 insulin independent
But the main point for Glute four is that it is insulin dependent. So when insulin is released, that allows the translocation and the incorporation of Glute four into the cell membranes of skeletal muscle adaptation in the heart to allow those organs to uptake glucose. The last glute I want to talk to you guys about is Glute five. And these glucose transporters are found in entrocytes of the intestinal epithelium. So they’re particularly on the lumenal side.
Glucose Transporters GLUT and SGLT: Biochemistry Lesson So they face the Lumen of the small intestines. And again, these are also insulin independent. And these are important for fructose transport. So they actually uptake fructose through Glute five. So that means that fructose is always taken up by Glute five.
And finally, I’m going to talk to you guys about the sodium dependent glucose transporters. So SGLT one is also found in entracytes of the intestinal epithelium. Again, this is also on the lumenal side. So it faces the aluminum of the small intestine. And these two are also insulin independent.
And they are also ATP and sodium dependent, as they are SGLT and they’re important for glucose absorption. So typically, glucose is first up taken into the entracet of the intestinal epithelium through SGLT one. So this is the first transporter that glucose typically comes into contact with and SGLT two is found in the proximal tubule of a nephron so a nephron is the functional unit of the kidney and these are also insulin independent and ATP and sodium dependent and these are very important for glucose retention so these transporters are very important.
so that you do not lose glucose in your urine this comes into play during diabetes when blood levels of glucose are so high that these transporters become saturated and you actually lose some of your glucose in your urine so that’s why you get glycosuria so that’s the main reason but the main function of these transporters SGLT two transporters is glucose retention anyways guys that was a quick lesson on glucose transporters I hope you found it helpful.
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Conclusion
the GLUT family of glucose transporters play an important role in the body’s glucose homeostasis. This lesson has introduced you to the GLUT family of glucose transporters, their roles in the body, and how they transport glucose. In addition, this lesson has provided you with a basic understanding of how these proteins work and how they can be used to treat diseases. Now that you are armed with this information, continue your education by exploring related topics in further biochemistry lessons.
