Are Obesity, Type 2 Diabetes, and Heart Disease Communicable?

small intestine

Our intestine contains a large population of microorganisms. (Illustration by Bruce Blaus, CC BY 3.0 license)

A fascinating idea has been proposed by researchers at the University of British Columbia. The suggestion isn’t a proven fact and is still at the hypothesis stage. It could be very significant if it’s shown to be true, however. The scientists involved in the research suspect that obesity, type 2 diabetes, and heart disease may be in at least some cases communicable or contagious disorders. The researchers suggest that they might by transmitted from one person to another via our intestinal microbiome, or the community of microorganisms that live in the intestine.

Noncommunicable and Communicable Diseases

Noncommunicable diseases (NCDs) can’t be passed from one person to another. They are caused by some combination of genetics, exposure to a specific environmental factor or factors, and lifestyle choices. Communicable diseases are caused by an infectious agent that passes from one person to another. The agent is often a virus, a bacterium, or a fungus. These infectious organisms are considered to be dangerous and generally don’t live in our body under normal conditions. There are some organisms that alternate periods of activity and latency in our body and make us sick when they are active, however.

The process in which an infectious organism passes from a sick person to a healthy one and then causes the healthy person to develop a communicable disease is comparatively well known. As in almost every area of biology, there are still points that aren’t completely understood about the process.

Obesity, type 2 diabetes, and heart disease have been placed in the noncommunicable or noncontagious category. As far as I know, people haven’t challenged this idea before. Though the idea of the disorders spreading from one person to another may sound very strange, understanding the human microbiome and its significance makes the situation more plausible. It should be noted that the hypothesis is related to type 2 diabetes and not to other types of the disease.

E_coli_at_10000x

Some strains of Escherichia coli live in our intestine. (Photo from the USDA, public domain license)

The Human Microbiome

Many microorganisms live in and on the human body. Most of them are harmless or even beneficial. The greatest population of the organisms lives in our intestine. The community is often referred to as the intestinal microbiome or the human microbiota. In a healthy person, potentially harmful microbes in the microbiome seem to be kept under control.

Escherichia coli, or E. coli, which is shown above, is very often part of our intestinal community. Multiple strains of this bacterium exist. Some strains are harmful for us, but others are a useful part of the gut microbiome.

Researchers have discovered that the microbe community in the intestine appears to  be beneficial for most of us. It stimulates our immune system, causing it to work better. It also produces nutrients, some of which we absorb. One of these nutrients in vitamin K. Some of the microbes also produce short chain fatty acids, or SCFAs, as they ferment plant fibres that we’ve ingested. Researchers suspect that these acids might help to prevent certain health problems in the intestine, including cancer.

Altering the Microbiome

In the case of one disease, altering the intestinal microbiome to treat a noncommunicable disease is already an accepted part of medical practice (at least in my part of the world) . A fecal transplant or fecal microbiota transplant (FMT) can have a dramatic benefit for people with a persistent Clostridium difficile (C. diff) infection. Some people with Crohn’s disease have also been helped by the procedure, though not as many people have benefited from the treatment as in the case of a C. diff infection.

A fecal transplant must be performed by a doctor. A sample of feces may contain harmful or even dangerous microbes that may hurt the recipient. It must be checked carefully by experts before it’s placed in someone else’s body.

Disease and Discoveries

The research related to microbe transmission in noncommunicable diseases was led by a professor of microbiology at the University of British Columbia. He’s also a CIFAR fellow (Canadian Institute for Advanced Research). The discoveries made by the scientists (and other research teams) and some possible conclusions are described below.

  • People with obesity, type 2 diabetes, and heart disease have altered microbiomes. This could be because the disorders produce conditions that alter the intestinal microbe community and not because the microbe community causes the disorders, however.
  • Samples of the altered microbiome have been taken from patients and placed in healthy lab animals, where they have caused problems such as obesity, cardiovascular disease, and type 2 diabetes. This could be a significant observation, though results in animals are not always the same as the results in humans.
  • “Cohabitants and spouses” who share a home have more similar microbiomes than twins who live separately. This might suggest that microorganisms are being transmitted from one cohabitant to another. As the researchers admit, however, a possible reason for the observation is that cohabitants are likely to follow a similar diet, are exposed to the same non-living aspects of the environment in their home, and probably experience some of the same infections. This may well affect their intestinal microbiome.

It is difficult to uncouple environment (diet, social habits) from microbiota composition, because they are intimately connected. Currently, microbial transmission of NCDs has only been demonstrated in controlled FMT experiments in genetically similar animal models with the same diets and environments. (Quotation from B. B. Finlay et al in the Science journal)

Despite some doubts surrounding the observations, it could be very worth while to explore the situation in more detail. I find the second observation in the list above especially interesting. The disorders that are being investigated are serious and their incidence is increasing. If researchers discover a major factor that is causing or contributing to them, it may be possible to offer new and improved treatments.

Maintaining a healthy lifestyle is important for many reasons, including resistance to and recovery from disease. People with the noncommunicable disorders mentioned in the title of this article should certainly try to safely improve their lifestyle if this is necessary and should follow their doctor’s instructions carefully. Altering the intestinal microbiome might one day be another helpful treatment for some people with the disorders, however. We know that microorganisms outside our body can affect us. Discovering more about how the ones that live inside us affect our lives seems like an idea that is worth exploring.

References

  • Information about the human microbiome from the Harvard School of Public Health
  • “The Intestinal Microbiome and Health” from Current Opinion in Infectious Diseases
  • Three diseases that may be communicable from the Medical Xpress news service
  • “Are noncommunicable diseases communicable?” from the Science journal

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