US researchers have successfully transferred gut bacteria from obese humans to germ-free mice, a breakthrough that will allow a more detailed study of the link between gut microflora and obesity.
A breakthrough paper published in Nature in December 2006 reported that microbial populations in the gut are different between obese and lean people, and that when the obese people lost weight their microflora reverted back to that observed in a lean person, suggesting that obesity may have a microbial component.
The new study, published in Science Translational Medicine, takes us forward in this exciting area. The study succeeded in showing that the human gut microbiota can successfully be transferred to germ-free mice, and that this can then be passed on from mother to offspring.
The study also shows that “the configuration of the microbiota, its microbiome, and meta transcriptome changes in a rapid, dramatic, and reproducible fashion after switching from a plant polysaccharide-rich, low-fat diet to a high-fat, high-sugar Western diet”, report the researchers led by Peter Turnbaugh from Washington University School of Medicine.
From lean to obese
When Turnbaugh and his co-workers colleagues transplanted microbes from human faeces into mice bred without any microorganisms in their guts (germ-free mice), and fed them a high-fat, high-sugar, Western-style diet, they recorded a rapid change in the population of gut bacteria present, compared to mice fed a low-fat diet.
Furthermore, the mice also showed an increase in body fat.
As further evidence of the important role that the gut microbes play, the researchers also found that simply transplanting the microbiota from the high-fat fed mice into a set of germ-free mice caused the new mice to accumulate more body fat, even though they were fed a low-fat diet.
Implications for prebiotics and probiotics
In an accompanying perspective Jeffrey Flier and John Mekalanos from Harvard Medical School note the implications for food and nutrition.
“As mechanisms for the interrelationship between the microbiota and host metabolism are defined, one can imagine several levels of interventions that might be explored in this model,” they wrote.
“One approach could involve searching for nutritional interventions to modify specific gut microbial species. Dietary components (prebiotics) might be found that alter growth of specific microbial species capable of affecting host physiology, and the Turnbaugh model can be used to pinpoint these elements and decipher the mechanisms of the host-microbe collaboration.
“Dietary ingestion of live microorganisms (probiotics) has been used to alter microbial gut flora with the intention of conferring favorable effects on the host. The germ-free mouse system could be used to explore the actions and efficacy of novel probiotics,” they added.
At a scientific symposium organised by the Beneo Group in April 2008, Dr. Kieran Touhy from the University of Reading noted that obese animals have significantly lower bifidobacteria levels than their lean counterparts, which suggests potential for prebiotic fibres since the growth of these bacteria is selectively promoted by inulin and fructooligosaccharides.
Dr. Nathalie Delzenne from the Catholic University of Louvain in Belgium and Dr. Robert Welch from the University of Ulster presented results from animal and human studies, respectively, which indicated the potential of prebiotic supplementation to regulated food intake.
Source: Science Translational Medicine
Vol 1 Issue 6 6ra14: www.sciencemag.org
"The Effect of Diet on the Human Gut Microbiome: A Metagenomic Analysis in Humanized Gnotobiotic Mice"
Authors: P.J. Turnbaugh; V.K. Ridaura; J.J. Faith; F.E. Rey; J.I. Gordon, R. Knight
Perspective: Science Translational Medicine
11 November 2009
“Gut Check: Testing a Role for the Intestinal Microbiome in Human Obesity”
Authors: J.S. Flier, J.J. Mekalanos