Losing Weight With Gut Bacteria Transplant? It Works In Mice

To lose weight, you could try eating better, exercising more, liposuction … or maybe just have some bacteria from your skinny friend’s intestines transplanted into your gut. Scientists found that when they transplanted gut microbes from mice that had undergone gastric bypass surgery into other mice, the recipients started shedding pounds.

The results were described in a paper published on Wednesday in the journal Science Translational Medicine.

"Simply by colonizing mice with the altered microbial community, the mice were able to maintain a lower body fat, and lose weight – about 20 percent as much as they would if they underwent surgery," senior author and Harvard University researcher Peter Turnbaugh said in a statement on Tuesday.

Turnbaugh has been investigating the link between obesity and the gut microbiome -- the population of microbes that lives in the digestive tract -- for some time. In 2009, he was first author on a paper published in Nature that revealed distinct differences in the gut microbiomes of obese twins and skinny twins. Obesity’s traces can be read in the population of bugs in your guts, basically.

He also led a team that found a high-fat, high-sugar “Western” diet wrought sweeping changes to the gut microbiomes of mice that were implanted with human microbial communities. Mice on the “western” diet got fatter, and the scientists were actually able to transfer chubbiness by transplanting the gut microbes of the fat mice into other mice.

Now, they’ve done the reverse.

"Our study suggests that the specific effects of gastric bypass on the microbiota contribute to its ability to cause weight loss and that finding ways to manipulate microbial populations to mimic those effects could become a valuable new tool to address obesity," coauthor Lee Kaplan, director of the Obesity, Metabolism and Nutrition Institute at Massachusetts General Hospital, said in a statement.

Don’t get your hopes up yet for a quick gut bacteria transplant this summer – it could be years before researchers try out the method in humans. Plus, the procedure isn’t for everyone.

"It may not be that we will have a magic pill that will work for everyone who's slightly overweight," Turnbaugh said. "But if we can, at a minimum, provide some alternative to gastric bypass surgery that produces similar effects, it would be a major advance."

Turnbaugh and his colleagues speculated in their paper that the newly transplanted microbiome may slim mice down by producing signals that regulate fat metabolism, or by altering a mouse’s ability to harvest energy from its diet. But it’s still unclear just what exactly the microbiome transplantation does to the recipient.

"A major gap in our knowledge is the underlying mechanism linking microbes to weight loss," Turnbaugh said.

One of the more obvious changes was an increase in bacteria belonging to the Escherichia, Alistipes and Akkermansia genuses. Escherichia includes bacteria that are relatively harmless, as well as E. coli, some strains of which can cause food poisoning. Other strains of E. coli can actually work to an organism’s benefit, both by making vitamin K and preventing harmful bugs from getting a foothold in the gut. Alistipes contains five species, several of which are commonly found in human guts; Akkermansia contains just one species, A. muciniphila, discovered in 2004.

"We think those [bacteria] are good targets for beginning to understand what's taking place,” Turnbaugh said.

SOURCE: Liou et al. “Conserved Shifts in the Gut Microbiota Due to Gastric Bypass Reduce Host Weight and Adiposity.” Science Translational Medicine 5: 178ra41, 27 March 2013.