bacteroides/firmicute

Fish oil may be important to altering the microbiome, reducing anxiety

Last week we published a blog on the gut-brain axis, and the various associations between brain health and the gut microbiome.  One of the ailments we discussed was depression, which is often studied in mice by inducing early life stress on the mice.  One way to do this is by separating mice from their mothers for hours at a time at a young age.  The Maternal Separation model, as it is known, causes stress and anxiety in these mice, but more importantly, research has shown that it creates a dysbiosis of their gut microbiomes as well.  Many scientists believe the dysbiosis may be implicated in causing some of the stress phenotypes, and so reversing this dysbiosis could have therapeutic value.  Researchers from the University College Cork, in Cork Ireland, experimented with N-3 polyunsaturated fatty acids (PUFAs), like those found in fish oil, in these maternally separated mice, and found they may be important to preventing the dysbiosis.  They published their findings in the journal PLoS ONE.

In the study, the researchers separated mice into two groups, one underwent maternal separation, and the other had a normal upbringing.  Within each group the mice were separated into two more groups, one that received fish oil supplements and the other that didn’t.  Over the course of 17 weeks each groups’ feces were sampled for their microbiomes.  The Maternal separation tended to decrease the bacteroidetes to firmicutes ratio of the mice’s microbiome, which has previously been linked to depression in humans.  Interestingly, supplementation with the fish oil increased this ratio in those maternally separated mice.  In addition, the fish oil also increased the concentration of bacteria that were higher in non-separated mice, such as populations of Rikenella.  Finally, the fish oil increased the amount of butyrate producing bacteria, and as we have seen many times before, butyrate and other short chained fatty acids (SCFAs) are often associated with health.

Overall this study showed that fish oil shifted stressed mice’s microbiome to a more natural state, presumably helping them in the process.  While the scientists did not directly measure stress levels in these mice to support the microbiome connection, hopefully that will be part of a follow up study.  The scientists noted that fish oil is clinically shown to reduce inflammation, and made it a point to connect the stress in the mice to systemic inflammation.  Systemic inflammation is also mediated by the microbiome.  Indeed, people that have inflammation from IBD, for example, do tend to have more stress and anxiety.  In the end, fish oil could make for an interesting prebiotic to shift the microbiome, counteract inflammation, and improve mental health. 

Please email blog@MicrobiomeInstitute.org for any comments, news, or ideas for new blog posts.

The views expressed in the blog are solely those of the author of the blog and not necessarily the American Microbiome Institute or any of our scientists, sponsors, donors, or affiliates.

Clinical trial for probiotics in irritable bowel syndrome fails to show efficacy

Irritable bowel syndrome is the most common functional gastrointestinal disorder, affecting about 10-15% of people in the United States alone, according to the International Foundation for Functional Gastrointestinal Disorders website. Fortunately, as described by the IFFGD, IBS is a functional disorder, meaning that while it does affect quality of life, it does not affect life expectancy. Probiotics have been studied as treatment for IBS because, as we’ve seen in many other examples of probiotic use, it is safe and rarely has any negative effects on the consumer. Some trials have shown that probiotics help relieve the symptoms of IBS; however the conclusions are controversial due to study structure and participant numbers. For this reason, scientists in Seoul, South Korea recently published a study in the Journal of Clinical Biochemistry and Nutrition, which studied the effects of a multi-species probiotic mixture on IBS symptoms using a double-blind study with a large number of participants.

Eighty-one patients participated in the 4-week-long double-blind study, with 42 people receiving a multi-species probiotic (containing Lactobacilli, Bifidobacteria, and Streptococci) and 38 people receiving a placebo. Baseline fecal samples were collected before probiotic/placebo consumption, revealing no significant difference between the two groups of participants. After consumption, the probiotic group showed a significant increase in concentrations of the probiotic bacterial strains in fecal samples, but not significant increase of levels of Bacteroidetes and Firmicutes.

In terms of symptom relief, while the probiotic group reported a greater percentage of relief, it was not significantly greater than the placebo group. This could be a classic case of the placebo effect, which is a phenomenon in which a sham treatment can actually improve symptoms because the person receiving the placebo believes it will help them. The results of this study are not concrete because there was no significant difference in symptom improvement; however there were significant increases in probiotic strains in fecal samples of the probiotic group. This study could be a step in the right direction toward relieving IBS symptoms.

Please email blog@MicrobiomeInstitute.org for any comments, news, or ideas for new blog posts.

The views expressed in the blog are solely those of the author of the blog and not necessarily the American Microbiome Institute or any of our scientists, sponsors, donors, or affiliates.

Introducing specific molecules in the gut could help protect beneficial bacteria

(this is a caffeine molecule, not what was used in the study but something we could all use on this Friday morning)

(this is a caffeine molecule, not what was used in the study but something we could all use on this Friday morning)

Antibiotics save countless lives by fighting off pathogens in the body, however they also kill beneficial bacteria in the body that are necessary for keeping us alive and healthy. A team of scientists in Portugal and Spain may have found a molecule that can help restore beneficial bacteria in the gut.

Quorum sensing is how bacteria interact and coordinate with one another. The scientists showed that by increasing levels of a specific quorom-sensing molecule, autoinducer-2 (AI-2), in the gut, mice that had been given antibiotics were repopulated of beneficial bacteria.

The scientists sequenced the bacteria in fecal samples of mice before and after a 28-day regimen of streptomycin treatment. Prior to antibiotic treatment, bacteria of the Bacteroidetes and Firmicutes phyla made up 48 and 43 percent, respectively, of the bacteria in the gut. After 28 days, diversity in the guy decreased significantly and the Bacteroidetes and Firmicutes ratios shifted to 90% of Bacteroidetes species and Firmicutes species made up only 0.7% of all species.

They then repeated this experiment but also generated E. coli that were mutated and not able to absorb AI-2 and introduced these bacteria into the mice that were treated with antibiotics. They used E. coli because streptomycin increases levels of E. coli in the gut when exposed to it. This resulted in AI-2 levels in the gut to be increased as well as increase of bacteria from the Firmicutes phylum, which had been greatly destroyed by the antibiotic in the previous experiment.  

They were able to increase AI-2 levels and therefore beneficial bacteria by introducing bacteria that could not absorb it.  AI-2 could also be directly given to individuals who were given antibiotics and the scientists are now working on developing drugs that would release AI-2 only in the gut. However, antibiotics are not the only cause of dysbiosis.  Diet and other factors can result in changes to gut bacteria and by introducing this molecule and other molecules that bacteria use to communicate with one another, it may be possible to treat gastrointestinal diseases as well as dysbiosis caused by external factors. 

Please email blog@MicrobiomeInstitute.org for any comments, news, or ideas for new blog posts.

The views expressed in the blog are solely those of the author of the blog and not necessarily the American Microbiome Institute or any of our scientists, sponsors, donors, or affiliates.

Does eating fermented foods help you lose weight?

Kimchi is a Korean food that traditionally consists of fermented cabbage and spices.  It is a staple in the South Korean diet, and is one of the most frequently consumed fermented foods.  The presence of bacteria in the kimchi has led many to speculate that it can exert a positive influence on the microbiome, and kimchi is believed to have anti-obesity effects.  In order to test this hypothesis researchers from South Korea conducted a clinical trial in which they put obese women on a kimchi diet.  The women were split into two groups, one of which consumed fermented kimchi, while the other consumed non-fermented kimchi.  A summary of the study was recently published by Molecular Nutrition and Food Research.

Surprisingly, fermentated kimchi did not appear to affect the women’s body measurements or specific health indicators when compared to the non-fermented version.  For example, women on both diets had similar decreases in weight, waist circumference, body fat, blood pressure, and cholesterol. There were some important differences though, fermented kimchi increased fasting insulin levels and fasting blood glucose.

The scientists also measured the two groups’ gut microbiomes and blood gene-expression in the study.  The group that ate fermented kimchi had higher abundances of Bacteroides and Prevotella in their microbiomes, and an increased Bacteroides/Firmicute ratio, which has been linked to weight loss.  Bifidobacterium longum, a major lactic acid bacterium that ferments kimchi, has also been linked to weight loss, and to this end, a significant correlation between an increase of this bacterium in the microbiome and decrease in waist circumference was observed.    In addition, a gene known as Acyl-CoA synthetase long-chain family member 1 was found to be significantly upregulated in subjects consuming fermented kimchi compared to those consuming fresh kimchi. This gene plays an important role in metabolism, and it is important in breaking down fatty acids. A second gene, aminopeptidase N (ANPEP) was also expressed more in subjects consuming fermented kimchi.  ANPEP is important for regulating inflammation, and has been associated with a healthy blood pressure.

Overall, this study showed fermented kimchi possibly has beneficial effects on metabolism and immunity when compared to the non-fermented variety. While this study is limited by its small sample size, among other factors, it still shows that the bacteria involved in the fermentation process could benefit us in more ways than we currently know.  These bacteria not only make kimchi taste good, but they may make us healthy too!

Please email blog@MicrobiomeInstitute.org for any comments, news, or ideas for new blog posts.

The views expressed in the blog are solely those of the author of the blog and not necessarily the American Microbiome Institute or any of our scientists, sponsors, donors, or affiliates.