A corollary truth to the conclusion of my last post, “Mother Nature knows best,” is that tinkering with her finely tuned system can cause massive changes downstream. There’s definitely a biological butterfly effect to consider. (For those not familiar, the Butterfly Effect is defined as “The scientific theory that a single occurrence, no matter how small, can change the course of the universe forever.”[i]) The Butterfly Effect does not necessarily imply that those changes are bad. But, they could be.
A new paper[ii] out of Harvard University looked at the downstream effects, on metabolism and weight gain, of changing a single gene in one particular strain of gut bacteria. We already know that the microbiome is directly responsible, in part, for obesity and metabolic disorders – but the exact HOW is not yet known.
These researchers decided to use bile acids – the substances that break down fat for digestion – as a starting point, as imbalances in bile are thought to be in the questionable category, potentially responsible for diet-induced obesity. The scientists focused on a kind of bacterial enzyme called bile salt hydrolases, which help regulate metabolism. They isolated the gut bacteria, Bacteroides thetaiotaomicron, and removed 1 gene from some, leading those bacteria to be hydrolase-deficient. (A hydrolase is an enzyme that breaks something down…in this case, bile salts.) Mice in this experimental group, colonized with these altered bacteria, had much higher amounts of un-metabolized bile salts in their intestines than did the controls, which were given the normal bacteria.
The downstream effect of the missing bacteria gene: the mice in the experimental group, who had higher levels of bile salts and therefore were more efficient at using fat for energy (as opposed to carbohydrates), gained less weight than the controls. More than that, they had lower levels of fats and cholesterol in their blood and liver. The changes did not stop there. These mice also were found to have changes in genes regulating their circadian rhythms and immune response.[iii]
I find it astounding that changing 1 gene in 1 type of bacteria in an ecosystem that has trillions, could cause such profound effect. Then again, maybe not.
We know that genetically modified probiotics, pharmaceutically-enhanced to treat disease, are on the near-horizon. I am, of course, really looking forward to these scientific advances. These could be the greatest scientific discoveries since penicillin, revolutionizing human health! But a part of me worries. Considering that our biomes are a part of what makes us human, as Dr. Lorimer said in his latest article (see my last post), is this the best way to handle our growing epidemic of biome-related diseases? Shouldn’t we perhaps recognize that today’s epidemic of inflammatory disease came from messing with Mother Nature’s biome in the first place?
I’d love to hear your thoughts.
[ii] ina Yao, Sarah Craven Seaton, Sula Ndousse-Fetter, Arijit A Adhikari, Nicholas DiBenedetto, Amir I Mina, Alexander S Banks, Lynn Bry, A Sloan Devlin. A selective gut bacterial bile salt hydrolase alters host metabolism. eLife, 2018; 7 DOI: 10.7554/eLife.37182