A way to get six pack abs
BIO230 correspondent Heather G sent me this link from the International Journal of Clinical Medicine, which details a fascinating case study of Gut Fermentation Syndrome. A 61 year old male presented with a long history of intoxication, however there were numerous times when it was clear that he had not been drinking. His blood alcohol levels were frequently noted to be 5 times over the legal limit. The episodes appeared to begin following treatment with antibiotics following surgery, and were more frequent after missing a meal or having a drink the night before. Exam by emergency room physicians in 2009 didn’t know of any way to become drunk without ingesting alcohol, and therefore assumed that he was a “closet” drinker. After referral to a gastroenterology practice in 2010, cultures of H. pylori were isolated from his stomach, and cultures of Saccharomyces cerevisiae and other yeasts were isolated from stool cultures. Following a controlled hospital stay where his blood alcohol levels were carefully monitored over the course of 24 hours following glucose challenge, it was concluded that the alcohol was being produced by his gut microorganisms.
Since this is a topic I could easily be passionate about, I decided to try and learn more. The article linked above had a brief review of the literature, and listed a few primary literature articles describing the phenomenon. My go-to citation finder at the National Library of Medicine was a bust, and turned up little of interest. A search of Google Scholar was perhaps a little bit more encouraging with the number of hits, however again most of the relevant items were not novel. Interestingly, most of the articles that I found dealing with alcohol and fermentation in the intestines dealt with the production of acetaldehyde from ethanol, which is in turn a potent carcinogen. In articles such as this one, the presence of alcohol in the upper digestive tract (presumably from long term alcohol consumption) acts as a substrate that can be further fermented by a variety of microorganisms into the terminal fermentation product acetaldehyde. This compound is strongly correlated with the development of tumors of the small intestine. The production of ethanol as a terminal fermentation product in the mammalian gastrointestinal system appears to be extremely uncommon.
All of the cases in the literature about the topic seem to have several things in common, and patients who develop the condition are typically on a unique diet which contains fermentable sugars, have a diminished bacterial gut flora due to antibiotic use, and have a unique mixture of yeasts which have in turn colonized their system. Fungi do make up an important part of the human gut flora, mainly Candida species, however I can find little evidence that Candida is able to produce ethanol as a terminal fermentation product. Most individuals who exhibit Gut Fermentation Syndrome appear to be colonized with a mixture of yeasts, including Saccharomyces cerevisiae. This is interesting in itself, as S. cerevisiae is a poor colonizer of the human body due to our body temperature, and few articles can be found describing this organism in a disease setting.
And so: an experiment for Science! We will need to start with the yeast. As I prefer a nice IPA, my searching indicates that something like yeast strain 1272 might be a good starter culture. We will need to get the organism adapted for growth in the human body, so we will have to do an enrichment culture at 37 degC, followed by assessment of alcohol production in vitro in the YCP Biology labs. Fortunately, we have in our possession a Vernier alcohol concentration probe, so this is trivial to accomplish. At this point, we will have two options in which to proceed. First, we could jump straight to human trials, however since most BIO230 students are under the age of 21, I think we will go with option two which is to conduct animal studies. We will use outbred CD-1 mice, and administer a broad spectrum oral antibiotic to reduce their normal gut flora, and repopulate with our new IPA yeast via the diet. Control animals will receive heat killed yeast in their diet. We also will administer one of two diets: either a normal rodent chow diet, or a diet which we have supplemented with fermentable sugars–this carbohydrate rich diet looks to be just what we would need. Mice which have been recolonized with our IPA yeast and fed the carb rich diet ought to exhibit behavioral traits that can be measured.
BONUS: For Bonus to be added to your course grade, suggest a method for assessing whether this works in vivo. Do not suggest having the mice recite the alphabet backwards, because unless you are these guys, it isn’t going to work.