Red wine and coffee modulate the microbiome

Prebiotics are foods that alter the microbiome.  They are important to many potential microbiome therapeutics because they could be used to shift the microbiome from a dysbiotic, or unhealthy state, to a normal healthy state.  Most scientists that study prebiotics investigate indigestible fiber, because these are known to survive digestion are broken down by specific microbes, thus predictably selecting for specific organisms’ growth.  Recently though, other prebiotics are being studied.  A major class of these are polyphenolic compounds, which provide the antioxidant characteristics of plant material.  Last week researchers from Spain studied the shift in the microbiome that may be induced by red wine and coffee in particular.  They published their results in the journal Food & Function.

The researchers studied 23 patients that had allergic rhinosinusitis or asthma as well as 22 age-matched controls.  They chose individuals with autoimmune diseases because of the promise of prebiotics affecting their diseases.  They asked all of the individuals to fill out a food survey of what they had eaten in the past year, and how often they ate it.  After, the scientists took samples of their feces and measured the bacteria within it.  The scientists found that the abundance of Clostridium, Lactococcus and Lactobacillus was directly associated with polyphenol intake from coffee, and that Bacteroides was positively associated with red wine consumption.  Unfortunately, they noted that these did not differ between allergic people and healthy ones.

This study was certainly lacking in its scope and rigor.  It did not attempt any interventional studies to controllably reproduce these effects, and it did not identifiy specific polyphenols that are responsible.  Nonetheless, it does begin to define how alternative prebiotics may affect our microbiome.  Polyphenols in particular are linked to all sorts of health benefits, normally attributed to their anti-oxidation, however perhaps they positively impact the microbiome as well. 

Yogurt may help combat colitis

Editor's note:  The following work comes out of Wendy Garrett's lab at Harvard.  Wendy will be an upcoming guest on the podcast.  If you have questions for her, feel free to email or call, and we will ask her on the show. 

A key signature of colitis is the build-up of reactive oxygen species (ROS) in the colon due to chronic inflammation.  One of major functions of ROS is actually to act as an antibiotic, and destroy any foreign bacteria that may exist at the site of inflammation.  However, ROS are known to be toxic to the host as well, and their high concentrations in colitis are likely a major contributor to the disease.  With this in mind, researchers at Harvard studied how probiotics from yogurt could ameliorate the disease by disposing the excess ROS.  They published their results last month in the Proceedings of the National Academy of Sciences.

The researchers had previously determined that a common yogurt that contained 5 strains of bacteria was helpful in decreasing symptoms in multiple mouse models of colitis.  In this study though, they identified Lactococcus lactis as being the most important of these strains in treating colitis symptoms.  They then compared the genome of L. lactis with the other strains in the yogurt and determined that a specific gene that codes for the enzyme, superoxide dismutase (SOD), which is capable of breaking down superoxide, an ROS, may be imparting L. lactis’ beneficial effects.  In order to support this hypothesis, the scientists showed that when this gene was removed from L. lactis the bacteria no longer reduced colitis.  They took this notion a step further and showed that superoxide levels were in fact decreased in vitro when combined with lysed L. lactis.  Finally, the scientists showed that the L. lactis must actually be lysed in the colons in order to release its SOD, destroy superoxide, and reduce colitis: when the scientists attempted to deliver SOD on its own to mice with colitis it was not as effective, and caused diarrhea.

This study is really interesting for two reasons.  The first is that it shows yogurt, like Activia, may be very helpful in dealing with colitis.  The second reason though, is that it shows a new system for deliverying SOD to a site of inflammation: via bacteria.  As they showed in the paper, simply using SOD was not effective, but using the bacteria as a vehicle for SOD, and then lysing it at the site was an effective means of drug delivery.  This has many important implications because ROS are important contributors to a variety of diseases.  

Obesity and the daily cycle of the microbiome

We recently wrote a blog about an article discussing how sleeping patterns affected the microbiome and may contribute to obesity, but what about eating patterns?  A paper published last week in Cell Metabolism aimed to answer this question. 

Three groups of mice were used in the experiment.  The first group of mice was given unlimited access to a high fat diet.  These mice ate their food all day and night.  The second group of mice mice was given a high fat diet but restricted to eat for only 8 hours per day.  The final group of mice was given unlimited access to normal food.  These mice tended to eat for only 8 hours per day, so they were actually no different than a group of mice restricted to eating normal food for 8 hours per day.  The researchers measured all of the mice’s microbiomes, weights, cholesterol, and other metabolites at various time points throughout the day.

Most shockingly, they found that by restricting the mice to a high fat diet for only 8 hours per day decreased their obesity and cholesterol and these mice were indiscriminant from mice eating normally.  The mice that ate the high fat diet at all hours were obese, and had high cholesterol.  When investigating the mice’s stool, the scientists discovered that the stool of mice with restricted eating times was of higher caloric density than mice eating a high fat diet at all times.  This means that mice that eat the high fat diet at any time extract more calories from their food than those mice that restrict their eating.  They also discovered that while all mice that ate a high fat diet had similar microbiomes, the mice that only ate for 8 hours had many cyclic bacteria that would flourish and dissipate depending on the feeding schedule, whereas there were less cyclic bacteria in the mice that ate at all times.  Furthermore, there seemed to be a decrease in one bacteria associated with obesity, Lactococcus, in the mice with restricted eating times, even with the high fat diet, whereas these bacteria flourished in mice that ate the high fat diet at all times. 

From a microbiome science standpoint, this study demonstrates the need to consider diurnal cycles when making microbiome measurements.  From a nutrition standpoint it makes one reconsider the benefits of eating many small meals a day versus fasting.   If nothing else, the study demonstrates how complex the microbiome, diet, and obesity puzzle really is, and how much we have yet to understand.