Effects of antibiotics on gut microbiome and glucose metabolism

The gut bacteria in the human gut plays an important role in glucose (sugar) metabolism. Alterations to the gut microbiome have been linked to obesity and Type-2 diabetes, as a result of inability to breakdown sugar. Scientists wanted to see the effect of removing as much bacteria as possible using antibiotics and what the effect was on human health after eating meals and published their results in PLOS ONE.

The study design included twelve healthy male volunteers, with a mean age of 23.4 years and no glucose intolerances. The participants were tested 5 separate days (day 0, 4,8, 42, and 180) during the study. Between days 0 and 4, the participants consumed a 4-day 30 drug antibiotic mix, made of meropenem, vancomycin, and gentamicin. On days 0, 4, and 42 the males participated in a liquid meal test, in which blood samples were taken 30, 15, and 0 minutes before and 15, 30, 45, 60, 75, 90,120, 150, 180, 210, and 240 minutes after ingestion of a specially concocted liquid meal. At 270 minutes, the participants were given a solid food meal. On days 8 and 180, blood pressure and sample was taken. The day before each of the 5 visits, the participants collected a fecal sample.

Antibiotic treatment did not seem to cause any serious or unexpected adverse effects. Between day 0 and day 180, an increase of mean body weight was found at only 1.3 kg and the corresponding change in BMI was 0.3. No changes in average blood pressure was observed, nor were any health complaints or symptoms.

As for the gut microbiome, after the 4 days of antibiotics, total anaerobic bacterial count decreased from 8.5 log10CFU/g to 6.2 log10 CFU/g. Enertococci, coliforms and bifidobacteria decreased significantly as well. On day 8 of the study, the abundance of aerobic bacteria had actually significantly increased passed the concentration number before antibiotics were consumed. By day 180 of the study, however, bacterial counts returned to the same baseline level from before antibiotic consumption. Overall, no significant effect on glucose consumption or metabolism was observed in this study as a result of changed gut bacteria composition. 

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