Posted: February 1st, 2023

How are blood glucose levels maintained?

However, glucose needs distinct transport proteins from the main facilitator superfamily to get in and out the cell membranes and compartments. In the jejunum, glucose is transported to the intestinal epithelium with the support of glucose carriers through a secondary active transport mechanism known as SGLT1 (sodium ion-glucose symport via sodium/glucose cotransporter). Additionally, transportation takes place on the basolateral side of the epithelial cells of the intestine through GLUT2 (glucose transporter) and also transports into the kidney cells, liver cells, islets of Langerhans cells, astrocytes, neurons as well as tanycytes. Into the liver, glucose goes in through the portal vein and is deposited there as cellular glycogen. In some cells, simply by passive transport uptake occurs via one of the 14 GLUT proteins. The glucose is taken up from the bloodstream through GLUT4 in muscles cells and adipose cells, causing a reduction in the blood glucose level. Glucose in the urine is absorbed in the kidney (apical cell membrane) by SGLT1 and 2 and is transported in the basolateral cell membranes through GLUT2.

How does the body absorb glucose?
Glucose is a byproduct of carbohydrate breakdown, and its absorption into the bloodstream occurs in two stages: When carbohydrates are broken down, the concentration of glucose in the small intestine is higher than in the blood, resulting in a concentration gradient. As a result, glucose passes through the epithelial cells of the small intestine and into the blood. Diffusion ceases when the levels of glucose in the small intestine lumen equals that in the circulation. In active transport, the remaining glucose is absorbed by sodium ions.

Step 1: The sodium-potassium pump actively transports sodium ions out of small intestine epithelial cells and into the bloodstream. As a result, sodium ion concentrations in the small intestine lumen are now higher than in epithelial cells, creating a concentration gradient.

Step 2: A sodium-glucose co-transporter protein carries sodium ions along a concentration gradient from the small intestine lumen into the cell while also transporting glucose into the cell. As a result, the glucose concentration in the cell rises.

Step 3: A protein channel allows glucose to permeate out of the cell and into the bloodstream. This is referred to as assisted dissemination.

How are blood glucose levels maintained?
Controlling the blood glucose level in a healthy person is tightly controlled by the following mechanisms: When blood glucose levels rise after a meal and insulin is released, two-thirds of the glucose absorbed from the gut is stored in the liver as glycogen. The liver then releases glucose into the bloodstream over the next few hours to retain blood glucose levels in a tight range. Insulin is secreted when blood glucose concentrations reach too high, lowering the amount. When glucose levels fall too low, glucagon is produced to raise them. When glucose levels decrease over an extended length of time, the adrenal gland secretes epinephrine (adrenaline), growth hormone, and cortisol, which restores the level.