Type 2 diabetes drug, metformin, impacts gut bacteria

Patients with type 2 diabetes have what is called insulin resistance, an inability to properly use insulin. The pancreas will make more insulin to keep blood glucose levels normal however, eventually, the pancreas can’t keep up and drugs may need to be taken. The most common drug to treat type 2 diabetes is metformin. A large team of scientists throughout Europe and China published a study in Nature showing that metformin affected gut bacteria in type 2 diabetics.

The researchers analyzed stool samples from 784 individuals with and without type 2 diabetes and looked at the effects that metformin had on gut bacteria. Metformin is usually prescribed in high doses and because it is a chronic disease, patients end up taking the drug often for many years. Based just on stool samples, they were not able to identify which sample was from a diabetic patient or control unless they took metformin. Type 2 diabetics who were on metformin had higher levels of E. coli and lower levels of I. bartletti than the controls or type 2 diabetics not taking metformin.

Studying the bacteria that changed in abundance in the gut suggested to the scientists that butyrate and propionate had elevated production. These two short chain fatty acids are associated with lowering blood glucose levels.

Importantly, this study helps explain some existing studies with conflicting results comparing gut bacteria of people with and without type 2 diabetes. This was most likely due to the fact that there were more individuals taking metformin in one study than another and this was not controlled for.

This study not only informs us on what is happening with gut microbes after taking metformin but also shines a light onto the importance of controlling for all external factors in microbiome studies, including treatments that could have confounding effects.  

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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.

Ingesting blueberries and oats may modulate the microbiome and help diabetics

Prebiotics are foods that are consumed in order to modulate the microbiome.  They are normally composed of molecules that are not broken down by our body itself, but rather that remain intact until making it to the large intestine where bacteria can break them down.  Common prebiotics come from plant materials, like long chained complex carbohydrates, as well as polyphenols, like blueberry extract.  In a recent study, scientists from Louisiana State University performed randomized dietary intervention on obese subjects and gave them a mixture of these molecules.  They then monitored the changes in the microbiome that occurred, along with changes in health indicators.  Their results were published in The Journal of Diabetes and its Complications.

The researchers included 30 adults in the study, and split them into two groups: one to receive the microbiome modulating dietary supplement, and the other to receive a placebo.  The dietary supplement included blueberry extract, oat bran cellulose, and inulin (a common oligosaccharide of fructose).  The subjects ingested the supplement daily for four weeks, with samples being collected once before and once at the end of the sudy.

Many positive health consequences were associated with eating the prebiotics.  Those patients had improved glucose tolerance, as well as increases in satiety.  The satiety may have been caused by an increase in fasting PYY concentration, a peptide known to cause hunger suppression, which was higher in those people taking the prebiotic.  In addition, there was an increase in self-reported flatulence from taking the prebiotic, but otherwise no adverse events were recorded.  Interestingly, there were no statistically significant changes in the microbiome that resulted from eating the supplement, however higher levels of short chained fatty acids (SCFAs) were observed in the stools of those patients.  Even though no statistically significant change was measured, it is quite possible that the level of sequencing depth and analysis was robust enough to truly observe changes that may have occurred.

This study is another that shows the benefits of eating prebiotics.  Interestingly, the prebiotic used for this study is the same one used by Microbiome Therapeutics in their metformin formulation.  This prebiotic, when combined with metformin, increases its efficacy for diabetics.  This study shows that possibly the prebiotic alone is responsible for this improvement, although it gets us no closer to explaining how this occurs.  Any of our readers that are taking metformin may want to read the wealth of literature around what Microbiome Therapeutics has done, because just the simple addition of foods to the drug seems to improve the results of taking it.

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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.