Type 1 Diabetes and the Possible Role of Viruses
A Problem With the Pancreas and Perhaps With a Virus
Type 1 diabetes is a condition in which the pancreas no longer makes insulin, a hormone that enables glucose molecules to leave the blood and enter the body's cells. As a result, glucose collects in the blood and may reach a dangerous level. Glucose is also known as blood sugar. It's obtained from food and used by cells as an energy source. High blood sugar can damage blood vessels and cause organ and nerve damage. One of the factors that may cause at least some cases of type 1 diabetes is an infection by certain viruses.
People with type 1 diabetes can manage their condition with the aid of insulin injections or an insulin pump, although they always have to be careful with their diet, exercise, and the amount of insulin that they receive. High blood sugar is dangerous, but so is low blood sugar. Patients have to measure their blood sugar level and make adjustments to their insulin dose multiple times during the day.
Type 1 diabetes may eventually cause eye, kidney, or nerve problems, even when it's treated. It would be wonderful to prevent or cure the disease. In order to do this, researchers have to know its cause (or causes).
The amount of insulin released by a healthy pancreas varies through the day. It depends on the blood sugar level, which in turn depends on factors such as food intake and exercise.
An Autoimmune Disease
Type 1 diabetes is generally considered to be an autoimmune disease. Our immune systems protect us from disease by attacking—or attempting to attack—invaders such as viruses and bacteria. In people with an autoimmune condition, the immune system mistakenly attacks the person's own cells. It's thought that people with type 1 diabetes have a genetic predisposition to develop the disease. However, even with this predisposition, diabetes won't develop unless an environmental trigger stimulates the immune system to destroy the beta cells in the pancreas. These cells make the insulin.
There is a growing body of evidence suggesting that one of the environmental triggers for type 1 diabetes could be an infection by a virus. Several types of virus have been implicated in the disease process. Although viruses aren't thought to cause all cases of the disease, they may well be responsible for some of them.
What Is Type 1 Diabetes?
What Is the Difference Between Type 1 and Type 2 Diabetes?
In people with type 1 diabetes, also known as type 1 diabetes mellitus, the pancreas produces no or very little insulin. Glucose is unable to enter cells and collects in the blood. Most people with type 1 diabetes are diagnosed as children or as teenagers. In fact, the disorder used to be called juvenile diabetes. Adults may also develop the disease, however.
In people with type 2 diabetes, the pancreas is still producing insulin. However, the body's cells aren't responding to this insulin, a condition known as insulin resistance. Once again, glucose collects in the blood. Most people with type 2 diabetes are diagnosed as adults. However, as the number of obese children increases, more cases of type 2 diabetes in children are being reported. Obesity is a risk factor for the disorder.
Possible Symptoms of Diabetes
The increase in blood sugar level causes excessive thirst and urination in untreated diabetics. Other symptoms may include extreme tiredness, extreme hunger, and unexplained weight loss. These symptoms may be present in both forms of the disease. There may be additional symptoms in type 2 diabetes, such as slow healing of wounds, tingling or numbness in the hands or feet, blurred vision, and frequent infections.
Anyone with symptoms that might suggest the presence of diabetes should visit a doctor.
Be Aware of Symptoms
What Are Enteroviruses?
A virus consists of a coat of protein surrounding genetic material. This material is usually DNA (the same chemical which contains our genetic code) but is sometimes a related chemical known as RNA. The enteroviruses are small RNA viruses that multiply in the gut.
Enteroviruses are primarily transmitted from person to person by the transfer of respiratory secretions or by the contamination of objects by feces. If a contaminated hand or other item contacts the mouth or nose, a person may become infected by the virus. This is one reason why washroom hygiene is very important when using a restroom. Even a tiny sample of feces can contain many bacteria and viruses.
There are many types of enteroviruses and they can cause many diseases. One type that has been linked to type 1 diabetes is the group known as coxsackieviruses.
DNA stands for deoxyribonucleic acid. It's an amazing substance that controls many of the characteristics of living things and viruses. In humans, RNA, or ribonucleic acid, helps DNA to do its job. In enteroviruses, RNA replaces DNA.
Enteroviruses and Type 1 Diabetes
Medical researchers at the Academy of Finland (Suomen Akatemia) have found that people with type 1 diabetes are far more likely to have a persistent enterovirus infection in their intestinal mucosa than people without diabetes. The mucosa is the lining of the intestine. The researchers have also found that the infection is associated with mucosal inflammation.
A survey by Australian researchers found that children with type 1 diabetes were nearly ten times as likely as other children to have an enterovirus infection. 4,448 children were involved in the study—some with type 1 diabetes and some who were healthy.
Some experiments have found that people with type 1 diabetes have antibodies against enteroviruses in their bloodstream or bits of protein or RNA from the viruses in their blood.
The pancreas continues cells of different types. It produces digestive enzymes as well as the hormones insulin (made by beta cells) and glucagon (made by alpha cells). Glucagon has the opposite effect to insulin. It raises blood sugar level instead of lowering it. Researchers have found enteroviruses inside the pancreas in people with diabetes. The viruses are found in the Islets of Langerhans, the tissue that contains the beta cells, and only occasionally in other tissues in the pancreas.
Coxsackieviruses and Disease
Do Enteroviruses Cause Diabetes?
The above observations suggest that enteroviruses are linked to type 1 diabetes. However, they don't prove that the viruses actually cause the disease. The evidence could indicate that when a person becomes sick with diabetes they become more susceptible to an enterovirus infection. It could also indicate that the genetic susceptibility to type 1 diabetes is accompanied by a genetic susceptibility to an enterovirus infection.
In lab mice, a direct connection between enteroviruses and the development of diabetes has been demonstrated. Enteroviruses have been administered to healthy animals and have caused prolonged infections of the pancreas and intestine. Specific enteroviruses have caused beta cell damage in the pancreas and the development of type 1 diabetes. This type of direct evidence isn't available for humans.
A Flu Virus Infecting the Body
Flu Viruses and Type 1 Diabetes
In another experiment, Italian researchers added two types of flu viruses to human pancreatic tissue. They found that the viruses multiplied very well inside the pancreatic cells, including the beta cells that make insulin. In addition, once inside the pancreatic tissue the viruses triggered the production of inflammatory chemicals that are present in the autoimmune reaction. They also triggered the beta cell destruction that leads to type 1 diabetes.
This research doesn't prove that the flu virus causes diabetes, but it does suggest that there may be a link. It should be noted that the research involved isolated pancreatic tissue instead of tissue inside the human body. The researchers did find that the flu virus triggered pancreatic damage and diabetes in many of the turkeys that were tested, however.
Scientists think that cells in the immune system present bits of infected pancreatic tissue to a type of white blood cell known as a helper T-cell. Presentation is a normal activity in the immune system. It "teaches" the T-cells to recognize that a virus or another organism is an enemy. However, researchers theorize that the T-cells are also learning to recognize the beta cells in the infected tissue and are treating these cells as enemies, too.
The process described above could only happen if the flu virus can enter the pancreas inside our bodies. Scientists say that this is possible. The virus normally stays in the respiratory system and the digestive tract, but it could travel up the duct that connects the pancreas to the duodenum (the first part of the small intestine). In addition, the virus sometimes enters the blood, which could then carry it to the pancreas.
Doctors in some countries have noticed an increase in type 1 diabetes diagnosis after flu epidemics. The flu vaccine may therefore protect some people from this form of diabetes.
Viruses That Protect and Ones That Harm
In 2017, researchers at the Washington University in St. Louis produced an interesting report. The scientists have found more evidence supporting the idea that viruses play a role in type 1 diabetes. Interestingly, the results of their study suggest that viruses may be protective as well as harmful with respect to the disease.
All of the children in the study were genetically predisposed to developing diabetes, but not all of them developed the disease. The discoveries included the following:
- Children with a more diverse collection of viruses in their intestine were less likely to generate antibodies that attack the pancreas (auto-antibodies). The researchers note that the existence of the antibodies can lead to diabetes, but it doesn't always do so.
- Children who had a specific circovirus in their intestine didn't produce the auto-antibodies.
- Bacteriophages, or phages, are viruses that attack bacteria. The study showed that children who had phages that attacked bacteria known as Bacteroides in their intestine "were more likely to start down the path toward diabetes".
The study needs to be repeated with a larger number of children. Still, the results are interesting and could be very significant.
Dealing with the Disease
Why Is the Incidence of Type 1 Diabetes Increasing?
The incidence of type 2 diabetes is increasing, but this is not unexpected. Obesity is a known risk factor for type 2 diabetes. Obesity is becoming more prevalent in many countries. However, the incidence of type 1 diabetes is also increasing in many parts of the world. The increase has been too recent to be due to genetic changes in humans. (A genetic change across a whole species takes a long period of time.) Researchers think that there must be environmental factors that are causing the increased number of type 1 diabetes cases.
There have been several suggested causes for the increase in type 1 diabetes. The "hygiene hypothesis" is one proposal. This hypothesis says that in many countries young children are being protected from microbes to such a large extent that their immune systems aren't developing properly.
People with type 1 diabetes seem to be more likely to develop celiac disease. In this condition, the ingestion of the gluten that is present in certain grains leads to the destruction of the villi on the lining of the small intestine. The villi are tiny folds that greatly increase the intestine's ability to absorb food. Most people today ingest far more gluten than people in the past. Some people have proposed that gluten is an environmental trigger for diabetes. An intolerance to cow's milk has also been proposed as a trigger. Inadequate vitamin D levels in the body and exposure to toxins in pollutants have also been suggested as environmental triggers for type 1 diabetes.
Obesity is a known risk factor for type 2 diabetes. It's been suggested that it may sometimes be involved in the type 1 version of the disease. Obesity in children may accelerate an autoimmune process that has already started and increase the damage to the beta cells in the pancreas.
The Future for Diabetics
It's important that researchers discover the specific causes of type 1 diabetes, whatever they are. This discovery should help them find a cure for diabetes or help them find better treatments for the disease. Curing and treating any type of diabetes is important. It's especially important in type 1 diabetes, however, since this disease has the potential to affect people for a large proportion of their lives and may eventually produce additional problems. If viruses are proven to be a cause, it may be possible to develop effective vaccines to prevent some cases of the disease.
- Suomen Akatemia (Academy of Finland). (2013, October 22). New evidence for role of specific virus causing type 1 diabetes. ScienceDaily. Retrieved August 1, 2017 from www.sciencedaily.com/releases/2013/10/131022091721.htm
- Diabetes linked to flu from New Scientist
- Enteroviruses linked to type 1 diabetes from the NHS (National Health Service)
- Type 1 diabetes risk linked to intestinal viruses from the Washington University School of Medicine in St. Louis
© 2012 Linda Crampton