Animal models have demonstrated an association between microbiota composition and obesity.  Now, a study shows that the transfer of intestinal microbiota from lean human donors to individuals with metabolic syndrome can improve insulin sensitivity (Gastroenterology 2012; 143: 913-16).

It is known that the small intestine has sensing mechanisms to improve insulin sensitivity via neuronal circuits and changes in microbe composition may be one of the stimuli for this mechanism.  Given the association of altered microbiota with obesity, the investigators divided 18 patients with metabolic syndrome to receive either an allogenic infusion (n=9) of gut microbiota or an autologus infusion (n=9) of gut microbiota.

All subjects underwent small bowel biopsies and then subsequently had lavage through a duodenal tube.  In the allogenic group, the infusate was derived from lean male donors (BMI <23 kg/m-squared).  Insulin sensitivity was measured before and 6 weeks after infusions.

Results:

• Fecal microbiota of obese subjects was characterized by lower microbial diversity and higher amounts of certain microbes (eg. Bacteroidetes).
• Peripheral insulin sensitivity improved after allogenic infusion with a median of 26.2 μmol/kg/min prior to 45.3 μmol/kg/min at the six-week measurement.  It was unchanged in those with the autologous infusion as noted in Figure 1.
• Gut microbial diversity increased significantly after allogenic infusion 178 ± 62 –>234 ± 40 species.  It was essentially unchanged in the autologous group (from 184 ± 71 to 211 ± 50).  Heat maps (Figure 2) help illustrate the microbial changes in the subjects.
• The authors conclude that butyrate derived from many of the increased bacterial group probably has a regulatory role in improving insulin sensitivity.  Butyrate can prevent translocation of endotoxic compounds derived from gut microbiota which can promote insulin resistance.

Perhaps in a few years, besides limiting the consumption of sugary beverages in places like NYC, beverages with “lean” microbes and or “lean” probiotics may become important.