What is it?
Type 1 diabetes is a metabolic disease caused by the autoimmune destruction of insulin-producing cells in the pancreas. This means that the body’s own immune system has gone wrong and attacked the body. Insulin is essential to the movement of glucose from the blood into the cells: hence the disease leads to heightened glucose levels in blood and urine. Typical symptoms include increased thirst, hunger, and need of urination, as well as weight loss. T1D affects about 0.5-1.0% of the population, the rates varying by country.
What causes it?
The exact cause of T1D is unknown but several different theories have been proposed, and the truth probably involves many interacting factors.
More than 50 different genes have been found to be associated with T1D. Some risk genes are dominant, which means that a child only needs to get one copy from one parent to develop the disease. Some are recessive, which means that a child needs a copy from both parents. Some are somewhere in between. In general, a child with a father or a sibling with T1D has a likelihood of 10% of developing it, while a child with a mother with T1D is many times less likely to develop it.
When a virus or bacteria invades the body, the immune system is built not only to recognize and destroy it, but also to remember it. If the same pathogen tries to infect the body again, the immune system knows what it’s dealing with and can quickly and effectively prevent illness. T1D is associated with viral infection, and it has been proposed that certain surface proteins of the viruses are very much like the surface proteins of the insulin-producing beta cells in the pancreas. When the immune system comes into contact with this kind of virus, it classifies that protein as “something to destroy”. The proteins on beta cells then activate an immune reaction and are killed by the same mechanisms that, when functioning ideally, keep the body safe.
What happens during it?
There are specific glucose transporters in cells whose job it is to create pathways through which glucose can move into cells. Normally these transporters are inside the cell. What insulin does is that it binds to the cell membrane and starts a complex series of reactions, which leads to the glucose transporters moving to the membrane, allowing the movement of glucose. Without insulin these transporters stay inactive inside the cell, and the glucose remains “trapped” in the bloodstream.
The job of the kidneys is to control the concentrations of different substances in the blood. If the concentration of a substance is too low, the kidneys make sure that it all passes back to the bloodstream: if the concentration of a substance is too high, the kidneys direct it to the urine. This doesn’t really apply to glucose, though. The function of glucose is to provide energy to the cells and the body doesn’t want to loose any. While glucose does in the kidneys pass to the tubules that lead to the bladder, it is actively taken back to the blood. In diabetes, the glucose concentration of blood is very high. There aren’t enough “portals” for glucose to be taken back to the blood, and some gets passed to the urine.
If two solutions with different concentrations are combined, the concentrations equal out. This is called diffusion (or osmosis if talking about a solvent moving across a semipermeable membrane, like we are). In the scenario described, the concentration of the liquid that is to become urine is higher than normal due to the excessive glucose. This makes more water than usual to also move to the urine and out of the body. That is why diabetes is often accompanied by increased urination and thirst.
How can it be treated?
The aim of T1D treatment is to lower the glucose concentration of the blood. Regular injections of insulin are necessary. Sometimes the balance can shift too far to the other side and lead to very low levels of blood glucose, which in mild cases is treated by ingesting something sugary. Monitoring glucose levels and eating few carbohydrates is also useful.
Although risky with regards to complications, pancreas transplantations are able to help some sufferers. Sometimes only some insulin-producing cells are transplanted but, so far, this operation hasn’t had very high success rates.
Sources: https://en.wikipedia.org/wiki/Diabetes_mellitus_type_1, https://timesulin.com/why-does-diabetes-cause-excessive-thirst/, https://en.wikipedia.org/wiki/Insulin, https://en.wikipedia.org/wiki/GLUT4#Insulin, https://www.niddk.nih.gov/health-information/health-topics/Diabetes/causes-diabetes/Pages/index.aspx#causes