This model compares the processes of glucose regulation by the liver and muscle. Students may examine the two processes separately or in one system. Students may also observe the changes in blood sugar level regulated by glucose transportation, glycogenesis, and glycogenolysis.
People have more muscle than liver.
The glucose transporters 2 (GLUT-2) permanently exist in the cytomembrane of liver cells, but the glucose transporters 4 (GLUT-4) do not permanently exist in the cytomembrane of muscle cells. The GLUT-4s are dependent on insulin.
Glucose passes the cytomembrane through facilitated diffusion.
Insulin stimulates glycolysis and glycogenesis in liver and muscle cells.
Glucagon stimulates glycogenolysis.
Exercise may recruit the glucose transporters in the muscle cells.
A higher Metabolic rate enables the glucose to be broken down faster.
The blood sugar level has been calibrated to simulate the levels in real life. The glycogen level is not calibrated, but the model still represents the overall trends.
1. Click on the "setup/reset" button to initiate or reset the model.
2. Put down the time you want to model to run. For a preliminary investigation, put down a large number (e.g., 1000) to get a sufficient observation time. To set experiments, set time as 1 ~4 hours to get the results close to the real-life.
3. Click on the "Run/pause" button to run or pause the model. Click on the "Run a tick" button to run the model for just one tick.
4. Use switches to explore/test the impacts of insulin production and sensitivity.
5. Use sliders to adjust the initial blood sugar level, cytoplasmic glucose level, and metabolic rate.
6. Use the "snack" button to simulate a small food intake. Use the "eat-every-4-hrs?" switch to add glucose into the bloodstream regularly.
7. Use the "watch a glucose" and "stop watching" buttons to track the behaviors of an individual glucose molecule.
8. Examine results in the simulation window, the numeric monitors, and plots.
**Run the model at a lower speed to get a better visual effect.**
KEEP IN MIND
This model only shows the blood sugar regulation by the liver and skeletal muscles. When you turn on the switch "eat-every-4-hrs?", you should see that blood sugar will build up over time as the liver and muscle cells can only store a certain amount of glucose as glycogen. Other cells, such as adipose cells, also participate in regulating blood sugar.
THINGS TO NOTICE AND TRY
Where do the glucose molecules move? Out of the cell or into the cell? When?
When is insulin produced?
When may glucagon be produced?
How quickly does the blood sugar level change with and without insulin resistance?
How does insulin resistance affect glycogenesis, i.e., glycogen synthesis?
What happens to the blood sugar level and glycogen level when "you" keep eating?
What happens to the blood sugar level when glycogen reaches the max level?
How does exercise affect glucose transportation by muscle cells?
How does the blood sugar level change over time when you separate and connect the liver and muscle systems?
What are the real-life examples of the simulated scenarios above? Can you simulate Type 1 diabetes and Type 2 diabetes in this model?
This model is made by Dr. Lin Xiang at the University of Kentucky .If you mention this model in a publication, we ask that you include the citations below.
Xiang, L. (2021). Blood sugar regulation by the liver and muscle. Department of STEM Education, University of Kentucky, Lexington, KY.
Questions? Comments? Email us.