What Is Type 1 Diabetes
Type 1 diabetes, is a disease that typically develops in children or teenagers. This disease is characterized by the body actually stopping production of insulin. Not to be confused with type 2 diabetes where insulin production is typically normal or even elevated and the body just loses sensitivity to it. Diabetes is very prevalent, in the US alone over 9% of the population is known to be diabetic, however they are predominantly type 2 diabetics. Type 1 diabetes accounts for only 5% of total diabetes cases (roughly 1.5 million people in the US). (Source).
The immune system of type 1 diabetics attacks insulin generating cells in the sufferers pancreas ultimately destroying them. These cells are called islets and are responsible for detecting blood glucose levels and producing insulin to keep those levels constant.
Figure 1: Pancreatic Islet Cells
In the above image several fluorescent molecules and stains have been added to a section of mouse pancreatic cells, including a cluster of islet cells so you can see parts of them. The blue color is fluorescence from a DAPI stain, DAPI or (4',6-diamidino-2-phenylindole) is a fluorescent molecule that binds to DNA. So what we see in blue is actually the nuclei of the cells (as that is where the DNA is). In red is a fluorescently tagged antibody which binds specifically to insulin, so you can see that inside of the islet cells is a lot of insulin but other nearby non islet pancreas cells are not red (as they are not producing insulin). The green color is a separate antibody which binds to the extracellular matrix of a mouse cell.
Enter Enterovirus Infection
A question that has plagued the scientific community with regards to type one diabetes is what makes the body recognize its own cells as foreign? What initiates the autoimmune condition? A recent publication in the journal Diabetologia titled "Detection of enteroviruses in stools precedes islet autoimmunity by several months: possible evidence for slowly operating mechanisms in virus-induced autoimmunity" indicates that it may be linked to infection by an enterovirus.
Figure 2: An Enterovirus (Polio)
Enteroviruses are RNA viruses (a bit like the retroviruses we discussed a bit ago) with a single stranded RNA genome. Their name comes from the way they infect, which is through the intestines (entero = intestines). They cause a variety of human diseases with the most notable one being polio, however not all enteroviruses are known to cause a disease in humans (yet at least).
In the Diabetologia publication the authors were screening stool samples where they found that enterovirus infection in children (they report coxsackievirus A4, coxsakievirus A2 and coxsakievirus A16 were the most common) was correlated with later detection of antibodies for islet cells. Suggesting that these enterovirus infections are associated with development of Type 1 diabetes. Perhaps they are the causative agent which begins the immune system attacking the islet cells.
Additional References
- http://link.springer.com/article/10.1007/s00125-016-4177-z
- http://acsh.org/news/2017/01/11/diabetes-and-germs-more-evidence-link-10716
- https://www.diabetesresearch.org/what-is-type-one-diabetes
- https://steemit.com/science/@justtryme90/science-lesson-what-is-an-antibody-and-how-does-the-body-use-them
- http://www.diabetes.org/diabetes-basics/statistics/
- https://en.wikipedia.org/wiki/Enterovirus
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