The effects of bowel cleansing for colonoscopies on our microbiome

Colonoscopies and colonic surgeries are known to require bowel cleansing prior to the procedure.  To accomplish this, what are thought to be generally safe and effective products are used in order to cleanse the bowel. One commonly used cleanser is polyethylene glycol (PEG) supplemented with electrolytes. While the efficiency of this product has been tested, limited data has been collected on its effects on the microbiome of the colon.

A new study published on January 6th in the journal Gut tested the effects of bowel cleansing on the bacteria that colonize an individual’s gastrointestinal tract. 23 human subjects were put into two study groups, one group consuming the PEG electrolyte solution in a single dose of 2 L and the other group consuming the solution in two doses of 1 L.

They found that bowel cleansing had little long-term effect on an individual’s colonic microbiota though a substantial change was initially seen after consumption. In subjects who consumed the PEG electrolyte solution in two 1 L doses, the microbiota recovered to original composition after two weeks. In subjects who consumed the solution in a single 2 L dose, however, it took up to one month after treatment for the colonic microbiome composition to recover.

Due to these findings, the authors suggest that separating the dosage into two 1 L doses may benefit the microbiome of the patient and may be preferred in clinical practice. There are several new microbiome studies such as this one that could impact medical practice and it will be exciting to see how (and if) the outcomes outlined in these papers are adopted by clinicians into practice.  

Microbiome based therapy prevents weight gain in obese individuals

New microbiome based drug may cause people to eat less!

Many people have heard that eating fiber is good for your health and helps to prevent weight gain.  One of the reasons for this, as we have blogged about before, is thought to be related to the short chained fatty acids (SCFAs) that are produced by the microbiome from fiber.  In mouse models, mice that receive a fecal transplant containing a microbiome with a high capacity for generating SCFAs show reduced weight gain.  The SCFAs appear to induce the production of certain hormones associated with appetite control.  The problem with human interventions of fiber-based diets is that an unpalatable amount of fiber is normally required, and very little of it is eventually converted into SCFAs.  Scientists from England recently tried to tackle this problem by introducing one type of SCFA, propionate, into the colons of obese humans to investigate its effects on weight gain.  The results of their study were published in the journal Gut.

The researchers chemically modified propionate so that after it was eaten it would only be released in the colon.  They then performed a double blind trial with 60 obese participants that took either the propionate or a placebo every day for 24 weeks.  The scientists discovered that, as hypothesized, ingesting the propionate increased the production of the appetite control hormones in the colon.  In addition, people who took the propionate tended to have a suppressed appetite and ate less overall food than their placebo counterparts.  Overall, the propionate prevented weight gain in the individuals who ingested it compared to the placebo group.

Recent advances in microbiome research have shown hormones produced by the gut are critical to managing hunger and food intake, and that research has allowed these scientists to create a new drug that stimulates the microbiome into producing those hormones.  In addition, the scientists show a new method of drug delivery to the colon which may have applications for other therapies.  At the AMI, we hope that their research continues to be as fruitful as it is promising.

A new drug from the microbiome may someday treat acne

Optical microscope image of Propionibacterium acnes, the bacteria that causes acne.

One of the most prevalent diseases caused by our microbiome is acne.  As many people know, those little red pimples are caused by an immune response to the otherwise normal skin bacterium, Propionibacterium acnes.  Many treatments for acne use broad spectrum oral antibiotics to eliminate the bacteria, which we at the AMI discourage for reasons we have blogged about before.  New research suggests that another common microbiome bacterium, Helicobacter pylori, may have utility in fighting P. acnes and preventing acne.

Research recently published by the British Journal of Dermatology investigated the effects of using a peptide made from the microbiome bacterium Helicobacter pylori to reduce levels of P. acnes and to decrease the immune response to these bacteria.  The researchers discovered that the peptide, known as HPA3NT3, was quite effective in destroying various strains of P. acnes.  Moreover, the treatment decreased the production of interleukin-8, which is responsible for inflammation.  Finally, the researchers showed the peptide did not destroy the skin of mice nor elicit an immune response on its own.

While the study did not use humans, which would have been ideal, it showed a potential new treatment for acne.  In addition, it is another example of using natural products from the microbiome to develop new drugs, and in this case treat a common microbiome disease.  Acne is among the top 10 most common diseases in the world, and while not usually medically dangerous it does have negative consequences, so we are glad that this microbiome disease is getting some attention.

Saliva regulates our oral microbiome

We know that saliva is important during eating and digestion, but researchers from Harvard and MIT investigated how saliva may be influencing the microbiome.  In an article recently published in Applied and Environmental Microbiology the scientists describe results that show saliva also includes molecules that influence oral bacteria so as to prevent cavities.

Cavities are formed when bacterial biofilms form on teeth and produce acids that go on to dissolve tooth enamel.  Saliva, which flows through the mouth, works to wash away these bacteria and helps remineralize teeth.  Beyond this, it contains molecules called mucins, which are a component of body mucous that are known to influence the microbiome and which have been associated with many autoimmune disaeases.    Before now, it was unknown how salivary mucins impacted the oral microbiome.

Researchers combined the bacteria Streptococcus mutans, which is known to be one of the many bacterial culprits behind cavities, with salivary mucins in the presence of artificial teeth.  They discovered that while the mucins did not prevent the bacteria from growing and proliferating, they did in fact prevent the S. mutans from attaching to the artificial teeth.  In fact over 95% of biofilm formation (which can cause cavities) was decreased between control samples and samples with the mucins.  The scientists noted that in the samples with mucins the cells simply never formed biofilms, and stayed in the planktonic (i.e. free floating) form.  They speculate that the mucins either physically prevent binding or are somehow changing the genetics of S. mutans so as to prevent production of binding proteins.

Follow-up studies in human subjects that compare the presence of mucins with cavity abundance would be interesting to see.  We all know people who, despite brushing and flossing multiple times a day, still seem to get cavities (myself included!), and others who, despite not going to a dentist in years and never brushing, don’t get any cavities at all.  Perhaps the concentration of mucins is responsible, and perhaps we could add mucins to toothpaste and forget about cavities all together.  

Diet plays a more important role than genetics in shaping the microbiome in mice

Today is December 31st which means it’s time to make our New Years Resolutions! Luckily for all of us, a new paper by Peter Turnbaugh’s laboratory gives us good reason to make improving our diet an important goal for the New Year. Dr. Turnbaugh and colleagues at Harvard University and University of California, San Francisco have shown that diet plays the dominant role over genetics in shaping the gut microbiome in mammals. 

Published in Cell Host and Microbe, the team of scientists used several strains of mice to investigate whether diet or the genetics of the mice played a more important role in what bacteria colonized the gut.  They exposed the mice to a low-fat, plant-based (LFPP) diet and a high-fat, high-sugar (HFHS) diet. When mice were given the HFHS, an increase in Firmicutes bacteria and a decrease in Bacteroidetes bacteria was seen, regardless as to what their genetic background was.  When the LFPP diet was given, the shift went in the other direction.  Further investigation needs to be done to better understand whether diet plays a direct role in shaping the bacterial communities in the gut or if it is due to an indirect role that the food has on the entire body of the host.

Another important takeaway from the study was that most changes to the microbiome are reversible. This means that once you shift to a new diet, the microbiome changes with the new diet and the new microbial communities are established within 3 days of exposure to the new diet.  However, the microbiome does remember past dietary patterns.  They leave an imprint on the microbial communities in the gut and some bacterial species are dependent on prior consumption.  

Dr. Turnbaugh suggests that in the future it may be possible to design diets that shape the microbiome in ways that are therapeutically beneficial.  He also states that due to this finding that diet plays a more important role than genetics on establishing gut bacteria, diets won’t need to be tailored to every individual person and specific diets may be useful for most people. 

So while you make your New Years Resolution to eat better and have a healthier diet, know that you are not only impacting your nutritional intake but you are also shaping your microbiome.

We wish all of our readers a happy and healthy New Year. This has been a particularly exciting first year for us and we look forward to another great year ahead.  

The continent you were born on may increase your risk for diabetes

Researchers are finding that imbalances in the gut microbiome can be linked to many diseases, especially autoimmune diseases like type I diabetes. A study called The Environmental Determinants of Diabetes in the Young (TEDDY) was formed to test what environmental factors can trigger type I diabetes in young children that are genetically at-risk for the disease.

In a study published by Diabetes Care, researchers working on the TEDDY study collected fecal samples from infants,at centers located in Finland, Sweden, Germany, Colorado, Washington state, and Georgia/Florida. The samples were collected monthly, and were tested on factors including age, sex, delivery method, early feeding, and later diet.

 The results of the study showed that young type I diabetes at-risk children have specific patterns of microbiome colonization per study site. In other words, there was a significant geographical association with diversity of gut bacteria. Finland, which has the highest incidence of type I diabetes, had  relatively low microbiome diversity and significantly higher abundances of Bacteroides and Veillonella and a lower abundance of traditional infant microbiome bacteria like  Bifidobacterium.  Interestingly, while there were intracontinental similarities between microbiomes, geography did not appear to be a dominant factor.  For example, Swedish microbiomes were more similar to those from Washington state than from Finaland..

 These results are among the first published from the TEDDY study, from which there should be significant discoveries.  For now, it appears the microbiome may play a role in the incidence of diabetes, but as is always the case, until an actual mechanism is proven it is too early to draw further conclusions.