bile acids

Emulsifiers in food cause many adverse health effects in mice

Emulsifiers are often used in ice cream to keep it stable and to give it it's texture.

Emulsifiers are often used in ice cream to keep it stable and to give it it's texture.

People often have spirited and impassioned views on the safety and consequences of adding ‘unnatural’ molecules to food.  An important aspect of this debate that everyone must keep in mind is the impossibility of testing every component of every molecule for its safety and long term impacts.  That being said, it should come as no surprise that new research can often teach us about the unexpected and overlooked safety issues regarding many food additives.  The newest class of compounds to come under scrutiny is emulsifiers, and a new paper published in Nature last week shows that these compounds may negatively impact the body through modulation of the intestinal lining and the microbiome. 

Emulsifiers are compounds that increase the stability of an emulsion.  They are often molecules like surfactants that have two parts, hydrophobic carbon chains and hydrophilic polar head groups.  Soap and egg yolks are common examples of emulsifiers.  There  are, of course, chemically produced emulsifiers as well that are often used in food.  Two examples of these, which were the emulsifying compounds used in the study, are polysorbate-80 (P80) and carboxymethylcellulose (CMC), and they are added to all sorts of foods like ice cream and pudding.  Evidence from this paper suggests though, that at least in mice these emulsifiers are wreaking havoc on the gut and microbiome.

A team of researchers from Israel, Cornell, and Emory did a variety of experiments on mice that were fed either of these emulsifiers in their water (at a concentration of 1%, similar to the levels added to human food.)  They first noticed that these mice had greatly compromised mucous layers on their gut, which allowed for bacteria to actually reach and be in contact with their epithelial gut cells.  In these mice gut permeability (leaky gut), inflammation, and incidences of colitis were all increased.  In addition, the inflammatory response and gut permeability were directly related to the average distance of bacteria to the actual epithelial layer; the closer the bacteria the more inflammation and permeability.

The researchers also measured the microbial populations of the feces in these mice and those that were eating emulsifiers had much less diverse microbiomes, which were enriched in Proteobacter, which are known to be associated with inflamed guts, and reduced in Bacteroidales, which are associated with healthy guts.  Also those eating emulsifiers had in increase in Ruminococcus gnavus which is associated with type 1 diabetes, as we have written about in the past. Interestingly, those mice that were given the emulsifiers tended to eat a lot more food than there control counterparts, and this led to weight gain and obesity amongst the mice drinking emulsifiers.  Moreover, these same mice had higher fasting glucose levels, indicative of impaired glycemic control and metabolic syndrome.  The scientists tested if these effects were seen in mice that were fed the emulsifiers in their food, rather than in their water, and the same outcomes were observed.  In addition, the scientists observed shifts in the production of certain short chained fatty acids and bile acids produced by the microbiome in mice fed emulsifiers (click on the tags below to read about the wide range of health effects that both these compounds have been implicated with).

The researchers then did a series of experiments that showed that it was the actual shifts in the microbiome populations and not just the change in mucous that was primarily responsible for the adverse health effects in the mice given emulsifiers.  For example, germ free mice that were given  emulsifiers did not have compromised mucous, and many of the negative health effects like inflammation were not observed.  On the other hand, performing a microbiome transplant from a mouse given the emulsifiers to a mouse that was not given the emulsifiers did result in these negative health effects, including the bacterial penetration of mucous to the epithelial lining.

This was a fantastic article that may, in time, prove to be immensely important.  Of course all the usual caveats apply, such as studies in mice are not indicative of human responses, and more studies must be performed in order to confirm these findings.  Still though, the introduction of emulsifiers into the mice’s diets resulted in many of the negative health impacts that are associated with the microbiome, something that we really haven’t seen in the literature before now.

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.

New research on the timeline and mechanisms of C. diff infections

Protein structure of  C. diff  toxin B

Protein structure of C. diff toxin B

Clostridia difficile infections are often the subject of this blog, but we rarely ever discuss how the infection actually occurs.  Scientists know that C. diff spores, which are not very uncommon in nature, can enter the gut from a variety of sources.  Once the spores reach the gut they normally just pass through unnoticed.  However, given the right conditions, these spores can take hold, germinate, and grow.  At some point during infection, the C. diff produces toxins which can compromise gut permeability (i.e. cause ‘leaky gut’) which leads to inflammation and all the nasty effects associated with the disease.  The exact gut conditions that trigger C. diff spore germination are not known, but scientists are convinced that the microbiome is involved because taking antibiotics, which wipe out the normal gut flora, make people susceptible to C. diff infection.  Some research has suggested that certain bugs in the microbiome outcompete C. diff for resources.  Other research shows that secondary bile acids, which are produced when the microbiome breaks down bile acids, inhibit C. diff germination.  Scientists are still working hard to understand the mechanisms of this infection, and just this week research out of the University of Michigan, published in Infection and Immunity, has shed new light on the process. 

The scientists first gave a group of mice antibiotics to make them susceptible to infection, and then fed the mice C. diff spores.  After, they euthanized mice every 6 hours to measure the progression of C. diff infection.  They learned that within 6 hours the spores had already germinated and entered the vegetative state in the feces and large intestine of the mice.  Over time, the C. diff progressed their way up the distal end of the large intestine all the way to the stomach, until the entire gastrointestinal (GI) tract was infected.  After 30 hours, sporulation of C. diff occurred, and interestingly this coincided with the production of C. diff toxins.  These toxins were found throughout the GI tract, however, inflammation only occurred in the large intestine, and not in the small intestine.  After 36 hours the infection had become severe enough that all animals were euthanized.

The scientists also measured the bacterial population and bile acid content of the gut during the infection.  After antibiotic treatment the microbiome was drastically altered and Lactobacillaceae flourished.  Once infection took hold the Lactobacillaceae were supplanted by C. diff in the large intestine, although the Lactobacillaceae still dominated the small intestine population, which, notably, did not become inflamed.  Secondary bile acids, which are produced by the microbiome and linked to C. diff germination, were abundant prior to antibiotics.  After antibiotic treatment, the large intestine had fewer secondary bile acids, and in the most infected regions had no detectable secondary bile acids.

This research is the first to develop a timeline for C. diff infection in mice, and strikingly it occurs very rapidly, with symptoms showing within 2 days.  This study also supports the notion that an altered microbiome is critical to C. diff infection, and that secondary bile acids may in fact play a crucial role in keeping C. diff from vegetating.  Interestingly, this study fits in well with a previous study we wrote about that showed the benefits of secondary bile acids in preventing C. diff infection.

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.

A new probiotic candidate to treat C. diff

Molecular structure of the antibiotic enroflaxcin.

Molecular structure of the antibiotic enroflaxcin.

A brief letter was recently published in Nature that identifies a bacteria that may confer resistance to C. difficile.  In addition, they discovered how three commonly prescribed antibiotics alter a patient's risk for C. diff.  

The researchers treated mice with 3 different antibiotics, enrofloxacin, ampicillin, and clindamycin. While the overall microbiome bacterial density was unchanged for each antibiotic, each one altered C. diff susceptibility differently: enrofloxacin did not increase likelihood of getting infected, ampicillin induced transient susceptibility, and clindamycin greatly increased long-term chances of getting infected.

The researchers then identified 11 bacteria that were associated with C. diff resistance.  They  tested one of these bacteria, Clostridium scindens, on humans taking antibiotics that either already had C. diff infections or were susceptible for infection.  They discovered that the probiotic conferred substantial resistance to infection.  Interestingly, this probiotic also led to weight loss.

The researchers then studied how this bacteria could be preventing C. diff infection.  They discovered that this particular bacteria had a rare ability to break down bile into secondary structures, called secondary bile acids.  They tested these secondary bile acids against C. diff and they inhibited C. diff growth.

These results, taken collectively, may be immensely important in treating d. Diff.  Specific types of antibiotics that are known to not increase infection risk, along with probiotics like C. scindens could be combined into new therapies.  This could be important in treating this disease without more rudimentary approaches like fecal microbiota transfers (FMTs).

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.