Relationship between insulin and glucose concentration gradient

Glucose transport - Metabolism and hormones - Diapedia, The Living Textbook of Diabetes

relationship between insulin and glucose concentration gradient

Blood sugar regulation is the process by which the levels of blood sugar, primarily glucose, are the cell, it is phosphorylated into GlucosePhosphate in order to preserve the concentration gradient so glucose will continue to enter the cell. . Edit links. This page was last edited on 12 November , at ( UTC). By presenting cutting-edge advances in the study of diabetes, conferences summaries Scientific Sessions of the American Diabetes Association by Samuel W. Cushman, The concentration gradient is the major determinant of glucose flux. Method of glucose uptake differs throughout tissues depending on two factors; the metabolic This article includes a list of references, related reading or external links, but its GLUT4 transporters are insulin sensitive, and are found in muscle and Therefore, the concentration gradient of glucose opposes its reabsorption.

relationship between insulin and glucose concentration gradient

Transferrin-positive GLUT4 vesicles are utilized during muscle contraction while the transferrin-negative vesicles are activated by insulin stimulation as well as by exercise.

At rest, they prefer to utilize fatty acids as their main energy source. As activity increases and it begins to pump faster, the cardiac muscles begin to oxidize glucose at a higher rate. As the body takes in energy in the form of glucose, some is expended, and the rest is stored as glycogen primarily in the liver, muscle cells, or fat. If GLUT4 is over-expressed, it can actually alter nutrient distribution and send excess glucose into adipose tissue, leading to increased adipose tissue mass.

When glucose in the blood binds to glucose receptors on the beta cell membrane, a signal cascade is initiated inside the cell that results in insulin stored in vesicles in these cells being released into the blood stream.

The effect of insulin on the distribution of glucose between the blood plasma and the liver.

GLUT4 is stored in the cell in transport vesiclesand is quickly incorporated into the plasma membrane of the cell when insulin binds to membrane receptors. As the vesicles fuse with the plasma membrane, GLUT4 transporters are inserted and become available for transporting glucose, and glucose absorption increases. GLUT1 sequence and putative topology. Amino acids are shown using the 1 letter code.

Some amino acids are numbered. Some amino acids fall into multiple categories. Mueckler et al [14].

relationship between insulin and glucose concentration gradient

Glucose transporter 1 GLUT1 structure. The side panel A and cytoplasmic panel B views are shown.

relationship between insulin and glucose concentration gradient

The corresponding transmembrane segments in the four 3-helix repeats are coloured the same. The extracellular and intracellular helices are coloured blue and orange, respectively. A slab of cut-open view of the surface electrostatic potential is shown on the right to facilitate visualization of the inward-facing cavity. IC indicates intracellular helix. Deng et al [15]. GLUT2 - Liver plays a huge role in glucose homeostasis.

With these cell types the amount of incoming glucose is proportional to the amount of glucose in the blood. The presence of GLUT2 in the small intestine and the kidney reflects its role in the transport of glucose across the serosal surface of the epithelial cells which line the intestine and the nephron, after glucose absorption across their luminal surface via the sodium-linked glucose transporter SLGT1[5].

Molecular cloning revealed that human GLUT2 is a amino acid protein with However, its mRNA is widely distributed in human tissues[1]. GLUT3 is a high-affinity glucose transporter with a Km for glucose of around 2 mM[1,13], much less than the average blood glucose concentration of mM, enabling most tissues to take up glucose at a constant rate, regardless of the amount present in the blood.

GLUT2 also transports galactose Km 8. The level of this transporter on the surface of these cells is rapidly regulated by insulin. Cycling between the endosome and these two compartments leads to retention of GLUT4 inside the cell under basal conditions. A slow rate of cycling between the GSV compartment and the plasma membrane does occur, although GSVs do not efficiently engage with the plasma membrane in the basal state [17]. In addition, some GLUT4 traffics to the PM in the basal state via a constitutive, transferrin receptor TR -containing, general trafficking pathway between the endosome and the plasma membrane[17].

Insulin signaling stimulates GSV recruitment to and fusion with the plasma membrane. When insulin binds to the insulin receptor it initiates a signaling cascade that leads to the translocation of GLUT4 glucose transporter vesicles to the plasma membrane.

Fusion of GLUT4 storage vesicles with the plasma membrane in response to insulin results in an increase in the amount of GLUT4 on the cell surface, thereby increasing the transport of glucose into the cell. As muscle is a principal storage site for glucose and adipose tissue for triglyceride into which glucose can be converted for storageGLUT4 is important in post-prandial uptake of excess glucose from the bloodstream. Moreover, several recent papers show that GLUT 4 is present in the brain also.

The effect of insulin on the distribution of glucose between the blood plasma and the liver.

The drug metformin phosphorylates GLUT4, thereby increasing its sensitivity to insulin. During fasting, some GLUT4 transporters will be expressed at the surface of the cell. However, most will be found in cytoplasmic vesicles within the cell. After a meal and at the binding of insulin released from the islets of Langerhans to receptors on the cell surface, a signalling cascade begins by activating phosphatidylinositolkinase activity which culminates in the movement of the cytoplasmic vesicles toward the cell surface membrane.

Normal Regulation of Blood Glucose

Upon reaching the plasmalemma, the vesicles fuse with the membrane, increasing the number of GLUT4 transporters expressed at the cell surface, and hence increasing glucose uptake. Secondary active transport[ edit ] Facilitated diffusion can occur between the bloodstream and cells as the concentration gradient between the extracellular and intracellular environments is such that no ATP hydrolysis is required.

relationship between insulin and glucose concentration gradient

However, in the kidney, glucose is reabsorbed from the filtrate in the tubule lumenwhere it is at a relatively low concentration, passes through the simple cuboidal epithelia lining the kidney tubule, and into the bloodstream where glucose is at a comparatively high concentration. Therefore, the concentration gradient of glucose opposes its reabsorption, and energy is required for its transport.