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Type 1 Diabetes and the Possible Role of Viruses

Updated on August 1, 2017
AliciaC profile image

Linda Crampton is a teacher with a first class honors degree in biology. She writes about human biology and the scientific basis of disease.

The pancreas is located next to the first part of the small intestine or small bowel. The pancreatic duct joins the hepatic duct from the liver before entering the small intestine.
The pancreas is located next to the first part of the small intestine or small bowel. The pancreatic duct joins the hepatic duct from the liver before entering the small intestine. | Source

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 pancreas is a long and narrow organ.
The pancreas is a long and narrow organ. | Source

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.

Insulin Resistance

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.

Coxsackievirus virions (individual virus particles)
Coxsackievirus virions (individual virus particles) | Source

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.

One type of influenza (flu) virus
One type of influenza (flu) virus | Source

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.

References

© 2012 Linda Crampton

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    • AliciaC profile image
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      Linda Crampton 6 months ago from British Columbia, Canada

      Congratulations on the improvement in your health, saidulakon!

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      Thank you very much, teaches. I appreciate your comment and the vote!

    • teaches12345 profile image

      Dianna Mendez 4 years ago

      Hi Alicia, great information and so educational. Voted up!

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      Thank you for the comment, Nell. I appreciate the vote and the tweet, too! It is very interesting to learn about the suspected role of viruses in triggering some cases of type 1 diabetes. I hope researchers discover more about this situation soon.

    • Nell Rose profile image

      Nell Rose 4 years ago from England

      Hi Alicia, this doesn't surprise me, to be honest I can quite believe that certain virus's start of a whole load of diseases, fascinating look at how it may work, and all the info on diabetes, voted up and tweeted, nell

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      Thank you very much for the visit and the comment, stephhicks68. It's so interesting to hear about the personal experiences of people with type 1 diabetes and to hear about the history of the disease in their particular case or family.

    • stephhicks68 profile image

      Stephanie Hicks 4 years ago from Bend, Oregon

      In my case, I developed Type 1 diabetes at the age of 34 when I was pregnant with twins. My endocrinologist told me that, while technically, the autoimmune reaction was set off by the pregnancy, I was just lucky that I had made it 34 years before developing the disease. A virus or bacterial infection could have set it off.

      Another cousin of mine contracted Lyme Disease when he was 9 years old, which triggered the autoimmune reaction, resulting in Type 1 diabetes.

      Good work on this hub!

    • AliciaC profile image
      Author

      Linda Crampton 4 years ago from British Columbia, Canada

      Hi, nicediabetes. Yes, as I say in my article researchers think that people need to have a genetic susceptibility for developing type 1 diabetes and in addition be exposed to an environmental trigger before diabetes will develop. It's very interesting to hear that you had a bad case of flu before your diagnosis. I hope that scientists find out more about type 1 diabetes very soon and find a way to help people with the disease and also prevent it from occurring.

    • nicediabetes profile image

      nicediabetes 4 years ago from Australia

      My understanding is the latest research may trigger not cause diabetes in people who possess the diabetes genetic make-up.

      I had a bad case of flu in the lead up to my diagnosis so I can believe it

      Will be interesting to see if this is confirmed whether scientists can then work out how to stop the trigger progress

    • AliciaC profile image
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      Linda Crampton 4 years ago from British Columbia, Canada

      Thank you, drbj! I appreciate all your visits and comments very much. Thank you for the vote, too!

    • drbj profile image

      drbj and sherry 4 years ago from south Florida

      This is fascinating research, Alicia, and I commend you for making this information so easy-to-understand for the general public. Your graphics and videos are a perfect complement. Voted up, of course!