Jan

26

You Are What You Eat: The Biology And Possibilities Of The Human Gut

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no, it’s not a mondrian painting. this is a microbiome bacterial heat map, one of the techniques used to determine the most significant types of bacteria

Bwog Science Editor, Alex Tang, attended the Bio Department’s Horwitz Prize Lecture, and introduces us to the role of the gut bacteria in childhood nutrition. Among his gathered insights: glycobiologists are a valuable, endangered species, and poop can tell us a lot about ourselves. More seriously, a viable solution to childhood undernutrition could be simpler than we think.

There’s a fascinating city within each of us, located specifically within our stomach, and inhabited by a population of bacteria many orders of magnitude greater than New York’s. These bacteria aren’t made by us – they’re foreign guests of our gut, who engage in a symbiotic relationship with us. We give them the safe home and resources they need to survive, and they produce invaluable nutrients that we wouldn’t be able to produce on our own. We call this city the gut microbiota.

Yesterday, Columbia’s Department of Biological Sciences invited Dr. Jeffrey Gordon, professor at the Washington University School of Medicine in Missouri, to give the Horwitz Prize Lecture, an honor bestowed on researchers who’ve done amazing work in the life sciences. Gordon’s talk, entitled “The Gut Microbiota and Childhood Undernutrition: Looking at Human Developmental Biology from a Microbial Perspective,” provided a fascinating glimpse into the complex ecosystem that our guts contain, and suggested a tantalizingly efficient solution to undernutrition, a condition that’s plagued humanity its entire history.

Gordon began his lecture with a deceptively simple hypothesis: impaired development of the microbiota is related to childhood undernutrition. Sponsored by the Bill and Melinda Gates Foundation, Gordon’s team identified specific types of bacteria that seemed to be instrumental in the development of a healthy child’s gut, and produced therapeutic foods that, when fed to young children, aided in healthy development and reduced long-term risks of malnutrition.

It’s been known that the cells in your gut and the bacteria that inhabit the microbiome need each other to survive. Specifically, bacteria can produce proteins, lipids, and carbohydrates that aid in nutrient absorption, mucosal barrier fortification (the strengthening of the gut lining), and other factors related to the digestion of food. Gordon was interested in finding out which types of bacteria were most instrumental in the early development of the healthy gut.

Gordon’s dedicated team traveled to Bangladesh, where over the course of years, they collected fecal samples from cohorts of undernourished and healthy children. They analyzed each sample, and were able to determine the types of bacteria that had a greater presence in healthier children than in undernourished children. The lab then compared results with similar studies in South Africa, India, Peru, and Brazil. The data was consistent – the bacterial composition of healthy gut microbiotas was generally universal.

The next logical step was to introduce the necessary bacteria, via therapeutic foods, to undernourished children, and to see if their guts would then develop normally, thereby reducing the long-term risks of undernutrition. After sustaining on this therapeutic diet, children with severe acute malnutrition (SAM) immediately progressed into the moderate acute malnutrition (MAM) category. Through molecular analysis, Gordon’s team identified the key metabolic shifts that allowed for this progress. Gordon’s team noticed that the levels of plasma amino acids and C3 carnitine increased. Effectively, the child’s gut switched from fatty acid to amino acid oxidation. This freed up the fatty acids, which allowed for fat deposition and weight gain. Furthermore, ponderal growth, or weight gain, during recovery from SAM was associated with increased activity of growth hormone signalling, and a reduction in systemic inflammation, associated with malnutrition.

How do we know that the unhealthy gut microbiome is responsible for undernutrition, and not the other way around? To see whether the gut microbiome’s development was engaged in causation or correlation with undernutrition, the researchers designed a transplant experiment test in mice. The scientists colonized germ-free mice with fecal microbiota from human donors. The mice who received material from an immature (undeveloped) microbiota began to express characteristics associated with childhood undernutrition, including impaired growth and alterations in bone growth. This critical sequence, of immature microbiome transplant followed by undernutrition, underscored the idea that the gut microbiome is largely responsible for nutritional status.

In the future, Gordon’s team plans to produce culturally relevant foods, which contain beneficial bacteria that aid in the development of the gut microbiome. The hope is that newly-borns, upon sustaining on this diet, will grow a healthy gut microbiome that will work as a long-lasting bulwark against undernutrition.

At this point, you could feel the excitement of the audience for the potential of this research. Gordon reiterated his respect for the members of his lab, citing an African proverb that he encountered: “If you want to go fast, go alone. If you want to go far, go together.” This research was made possible by Gordon’s lab, the other labs that helped gather relevant data, and the countless families that participated in the research; indeed, they’ve gone far.

images via delish.com and researchgate.net

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5 Comments

  1. Aha!

    So that explains why I've turned into an asshole.

  2. Anonymous

    Thee are great articles.

  3. This is incredibly offensive

    Please remove this -- the human gut isn't something that should be turned into a punchline.

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