How Trillions of Bacteria in Your Body Can Change Your Genes

The body’s microbiome and its impact on health

New research is spurring exciting developments in the microbiome, the trillions of bacteria that make up communities living in our bodies.

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Scientists are exploring how being aware of imbalances in these bacteria could lead to new diagnoses and treatments. All this could have a positive impact on people’s health.

The Federal government recently announced a multimillion dollar initiative that “aims to advance microbiome science in ways that will benefit individuals, communities and the planet.”

In a comment about the National Microbiome Initiative, the White House said:  “If there’s one thing we know for sure, it’s that while microbes may be small, their impacts are mighty!”

I agree.

What is the microbiome?

The bacteria that make up bacterial communities (microbiota) in our bodies exist on our skin, and in our gut, urine, nose, and even breast tissue.

They can be helpful, even essential, to our lives and are very active in our bodies. They emit chemicals that can affect how we digest food, how we react to medicines and how diseases tend to progress or not.

So how is the microbiome related to genetics?

The short answer is that the bacteria can affect how our genes express themselves. They do not cause changes in actual genetic materials (the DNA or RNA). Rather they may cause a gene to switch on or off, to activate or not.

For instance, different microbial communities can trigger inflammation (the body’s response to injury), and that inflammation can lead to changes in gene expression.

So bacteria cause inflammation, which leads to changes in the expression of the genes. We call this epigenetics, or how factors switch genes on and off and how our body’s cells react to this activation.

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Research suggests that microbes in our gut or elsewhere in the body may play a role in the development of a wide range of diseases, including Type 2 diabetes, obesity, cardiovascular disease, cancer, asthma, multiple sclerosis and chronic pelvic pain.

Harnessing the power of the microbiome

Biotech companies and researchers are actively working on harnessing the microbiome’s potential in medicine. We are looking at ways to diagnose disease by detecting microbial imbalances, and to treat disease by correcting such imbalances.

The following offer a snapshot of the ways the microbiome is involved with five conditions:

1.Inflammatory bowel disease

One interesting avenue is fecal transplantation, a promising treatment for people with digestive problems, such as irritable bowel syndrome, Crohn’s disease, and ulcerative colitis

Healthy people tend to be grossed out by the idea, but if you are really sick and grasping at straws, you are likely to welcome this remedy, which involves transplanting fecal matter from one person into another.

Many patients with inflammatory bowel disese (IBD) or the difficult gut infection C. difficile have been effectively treated with fecal transplants, which can help make stubborn, unhealthy gut flora healthy again.

But this treatment doesn’t work for everyone. Why it cures some patients but makes others worse is something we are investigating. The answer may lie in a person’s genetic makeup.

2. Cancer

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Investigation continues into the relationship between cancer and the human microbiome. One line of research focuses on helping bacteria compete with cancer cells for nutrients, thereby starving tumors. We are also figuring out ways to help bacteria activate the immune system to attack tumor cells.

At Cleveland Clinic, we have pioneered microbiome research in cancer. We have investigated the relationship between squamous cell cancer of the head and neck and its correlation with dental hygiene, implying a role for bacteria-induced inflammation. We are looking into the breast microbiome and its relationship to the development of breast cancer.

3. Chronic pelvic pain

One of our newest investigations involves the link between chronic pelvic pain syndrome (as a result of chronic prostatitis in men) and the microbiome. We have detected differences in microbiome profiles in the urine and gut of men who suffer from this disease compared to those without. My colleagues are planning clinical trials to investigate the effectiveness of certain medications on these dysfunctional microbiota.

4. Heart disease

A whole line of investigation at Cleveland Clinic focuses on the link between intestinal bacteria and heart disease. Certain intestinal bacteria feed on nutrients in red meat, egg yolks and high-fat dairy products. As they feed, they give off a chemical called TMA (trimethylamine). Your liver turns TMA into TMAO (trimethylamine-N-oxide) and releases it into the bloodstream. There, TMAO promotes vascular inflammation and formation of unstable plaques in arterial walls – heart disease. So one question is whether diet can impact TMAO. We think it can.

5. Obesity

A recent study of twins by researchers elsewhere found that those with a certain bacteria in their gut tended to have low BMI (body mass index), adding to the thinking that bacteria may play a role in obesity and metabolic disease. These researchers also proposed that a person’s genetics influence the composition of the gut microbiome. So again, fecal transplantation – from a skinny person to one who is obese – may prove helpful in those whose obesity cannot be controlled by usual measures.

What’s next?

Researchers throughout the nation and around the world are devoting themselves to understanding the human microbiome and how bacteria affect our genes and disease. I look forward to reporting back to you as their research uncovers paths to health.

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Charis Eng, MD, PhD

Charis Eng, MD, PhD is founding chairwoman of the Genomic Medicine Institute and founding director of its Center for Personalized Genetic Healthcare. Dr. Eng is a global leader in cancer genetics and cancer genomic medicine.
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