Updated date:

Type 1 Diabetes and the Possible Role of Viruses in the Disease

Linda Crampton is a writer and teacher with a first-class honors degree in biology. She often writes about 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.

Type 1 Diabetes and a Link to Viruses

Type 1 diabetes is a condition in which the pancreas no longer makes insulin or makes an insignificant amount. Insulin is a hormone that enables glucose molecules to leave the blood and enter the body's cells. When the hormone is absent, 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.

Type 1 diabetes is usually classified as an autoimmune condition (one in which the body attacks itself), but its cause might involve additional factors. One of the factors that may contribute to at least some cases of the disease is an infection by certain viruses, including enteroviruses and flu ones.

Type 1 and Type 2 Diabetes

A doctor's diagnosis is essential if someone suspects that they have diabetes, not only to confirm that they have the disease but also to identify the type and to get suitable treatment. Adults and children can develop the type 1 version of the illness and the type 2 version.

The Type 1 Disorder

In people with type 1 diabetes, the pancreas produces no or very little insulin. Glucose is unable to enter cells and collects in the blood. Most people with the disorder are diagnosed as children or as teenagers. In fact, the condition used to be called juvenile diabetes. Today researchers known that adults can also develop the disease.

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. Unfortunately, some diabetes patients eventually develop additional problems. Understanding the nature of the disease in more detail is important.

The Type 2 Disorder

In people with type 2 diabetes, the pancreas is still producing insulin. Either the body's cells aren't responding to this insulin (a condition known as insulin resistance), or the body is not creating enough insulin for the person’s needs. 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 Type 1 Diabetes

The increase in blood sugar level can cause excessive thirst and urination in untreated type 1 diabetics. Other symptoms may include extreme tiredness, extreme hunger, and unexplained weight loss. Some patients may experience additional symptoms, such as slow healing of wounds, tingling or numbness in the hands or feet, blurred vision, and frequent infections.

The symptoms mentioned above may also appear in someone with type 2 diabetes, so a doctor's diagnosis is essential. A doctor should be consulted if any of the symptoms mentioned above appear, especially if they are severe, long term, or recurrent. Medically prescribed treatment is very important.

Years of research have shown that type 1 diabetes is complex and heterogeneous, meaning that more than one pathway...can lead to its onset.

— Dr. Kendra Vehik, University of South Florida

An Autoimmune Disease

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) in detail.

The disorder 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 may not 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 the entities aren't thought to cause all cases of the disease, they may well be responsible for some of them.

What Are Enteroviruses?

A virus consists of a coat of protein surrounding genetic material. This material is usually DNA (the same chemical that contains our genetic code) but is sometimes a related chemical known as RNA. 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 hygiene is very important when using a restroom. Even a tiny sample of feces can contain many bacteria and viruses.

Many types of enteroviruses exist, 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 contains 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, which is the tissue that contains the beta cells, and only occasionally in other tissues in the pancreas.

Do Enteroviruses Cause Diabetes?

The above observations suggest that enteroviruses are linked to type 1 diabetes. However, they don't prove that the viruses 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. Studies in mice often apply to humans, but this is not always the case.

Discoveries in the TEDDY Study in Children

Researchers at the University of South Florida, the Baylor College of Medicine, and other institutions are exploring the effects of environmental factors on children with a genetic tendency to develop type 1 diabetes. The study is know as TEDDY (The Environmental Determinants of Diabetes in the Young). Youngsters in both the United States and Europe are involved in the study and enter it soon after birth.

Enterovirus infections are common in children, but only some of the infected children develop diabetes. The researchers have found that children suffering from an infection for longer than a month have a higher risk of developing the disorder.

The scientists exploring the results obtained in the study have made another interesting discovery. Like other cells, beta cells in the pancreas have protein receptors on their surface. These bind to particular substances, which causes a specific response in the cell. The researchers have found that in children with a particular genetic variant, the Coxsackievirus B virus binds to some of the receptors and produces a higher risk of beta cell autoimmunity.

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 they were inside the pancreatic tissue they triggered the production of inflammatory chemicals that are present in an 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.

Potentially Protective and Harmful Viruses

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.

The TEDDY study mentioned above has also found that a virus can be protective if exposure happens early in life. The virus that they explored was adenovirus C. It produces a respiratory infection, but it also appears to reduce the incidence of type 1 diabetes. It binds to the same beta cell receptor as the Coxsackievirus B. Viruses are still puzzling entities. Studying them is important for multiple reasons.

A phage is a virus that attacks bacteria, not human cells, but one type might play an indirect role in type 1 diabetes.

A phage is a virus that attacks bacteria, not human cells, but one type might play an indirect role in type 1 diabetes.

Why Is Diabetes Becoming More Common?

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. Some of them are listed below. They are interesting ideas, but they are only possibilities and not certainties.

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 may 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 the type 1 version, however, since this disease has the potential to affect people for a large proportion of their lives and may eventually produce additional problems.

Human biology and the world of nature are complex. Understanding the processes that occur in body can be difficult, but it’s an important endeavor. If viruses are proven to be a cause of type 1 diabetes, it may be possible to develop effective vaccines to prevent some cases of the disease. The ability to prevent the disease would be a wonderful development.

References

  • Type 1 diabetes information and possible causes from the CDC (Centers for Disease Control and Prevention
  • Information about Type 2 diabetes from the Mayo Clinic
  • Type 1 diabetes risk linked to intestinal viruses from the Washington University School of Medicine in St. Louis
  • "New evidence for role of specific virus causing type 1 diabetes" from the ScienceDaily news service
  • Diabetes linked to flu from New Scientist
  • Enteroviruses linked to type 1 diabetes from the American Diabetes Association
  • ”Unexpected viral behavior linked to type 1 diabetes in high-risk children” from the Baylor College of Medicine

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2012 Linda Crampton

Comments

Linda Crampton (author) from British Columbia, Canada on March 24, 2017:

Congratulations on the improvement in your health, saidulakon!

Linda Crampton (author) from British Columbia, Canada on November 05, 2012:

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

Dianna Mendez on November 05, 2012:

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

Linda Crampton (author) from British Columbia, Canada on November 05, 2012:

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 from England on November 05, 2012:

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

Linda Crampton (author) from British Columbia, Canada on November 04, 2012:

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.

Stephanie Marshall from Bend, Oregon on November 04, 2012:

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!

Linda Crampton (author) from British Columbia, Canada on November 04, 2012:

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 from Australia on November 04, 2012:

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

Linda Crampton (author) from British Columbia, Canada on November 04, 2012:

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

drbj and sherry from south Florida on November 04, 2012:

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!

Related Articles