Prevotella in the gut appears to improve glucose tolerance

Last week we wrote about a study that showed that the glycemic response from foods was a function of the microbiome, and alluded to the fact that the microbiome likely affects many aspects of metabolism.  Another paper was published this week, in the journal Cell Metabolism, that describes which bacteria are responsible for some of these effects.  The authors describe how Prevotella improve glucose metabolism in healthy human subjects.

The scientists gave 39 subjects white bread and barley bread for three consecutive days and measured their glucose and insulin responses to the diets.  For the most part, the barley bread was associated with an improved response over white bread, but some of the individuals’ responded with a much more stark improvement than others.  The scientists then measured the gut microbiomes of each individual and noted that the microbiome changed in the most responsive individuals, and this change was characterized by an increase in Prevotella (specifically Prevotella copri) and methanogenic archaea.  The opposite effect was seen in the individuals that responded least to the barley bread intervention.  The scientists then confirmed these results in mice.  Mice that were given fecal microbiota transplants from human responders, or P. copri probiotics had improved glycemic responses to high fiber diets than control mice.

Prevotella comes up in a lot of microbiome literature as a bug seen in ‘traditional’ societies that eat a lot of fiber.  This paper demonstrates that many of the genes from Prevotella are crucial to digest the complex fibers and that this may stimulate an improved glycemic response.  Collectively, many papers now support the idea that Prevotella is a critical bacterium to a ‘healthy’ microbiome.

Microbiome affects blood glucose levels after eating, can help predict glycemic response to foods

Postprandial (post-meal) glycemic response (PPGR) is the effect that food has on blood glucose levels.   Eating a sugary candy, for example, will raise blood glucose levels, whereas drinking water will not.  PPGR remains an important predictor for metabolic syndrome and type II diabetes, so it has an important role the obesity epidemic.  Unfortunately, PPGR is difficult to predict, and efforts that are based on individual foods themselves have failed.  New research shows that there are many factors, including the microbiome, that are important to predicting blood glucose after a meal.  The research out of Israel and published in the journal Cell presents a new model that can more accurately predict PPGR that is based on personalized factors.

The researchers catalogued 800 peoples’ meals over 7 days while continuously measuring their blood glucose levels.  In addition they monitored their gut microbiota, weight, sleep, and various other lifestyle factors.  After evaluating the data, the scientists realized that identical foods had vastly different PPGRs.  For example, bread could have a 8 fold variation in glycemic response depending on the individual.  In order to explain these differences, the scientists identified several significant associations between the microbiome and the PPGR from specific foods.  For example, on the phyla level high abundances of Proteobacteria and Enterobacteriaceae were associated with poor glycemic controls.  On the species level Eubacterium rectale, which is known to ferment fiber, was correlated with low glycemic response, and Parabacteroides distasonis, which had previously been associated with obesity, was correlated with hight glycemic response.  The scientists then aggregated all of their data, including microbiome data, and created a predictive algorithm for the PPGR from foods for individuals.  This algorithm accurately predicted the glycemic response from foods on a personalized level, and was more informative than general food based predictions.

This study speaks to the power of personalized medicine that is based on the microbiome.  Knowledge of our own microbiome could be used to advise our dietary choices in order to choose foods that will lead to low PPGR, and decrease our risk for metabolic syndrome.  Overall, the scientists determined that of all foods, eating fiber was most beneficial because it lowers glycemic response over the long term.