Scientists have identified the gut microbial pattern that corresponds with excess body weight, and deepen our understanding of how the gut microflora interacts with host metabolism.
A combination of systems biology and in-silico (computer) modeling, researchers have provided a “novel framework to study the human microbiome”, and help us understand human physiology and disease states.
The human microbiome refers to the microbes and their genetic material within each and every one of us. Bacterial cells outnumber human cells by about 10 to 1, and the microbiome is known to be essential for human development, immunity and nutrition.
Previous work has shown that microbial populations of obese and lean people are different.
“We […] demonstrate that obese microbiomes are less modular, a hallmark of adaptation to low-diversity environments,” report Sharon Greenblum and Elhanan Borenstein from the University of Washington in Seattle, and Peter Turnbaugh from Harvard University.
“We additionally link these topological variations to community species composition. The system-level approach presented here lays the foundation for a unique framework for studying the human microbiome, its organization, and its impact on human health,” they wrote in the Proceedings of the National Academy of Sciences.
The potential of probiotics and prebiotics?
While the new study only reports the microflora profile of obese people and not how manipulation of this microflora may influence body fat, there is valuable evidence in the literature that probiotics and prebiotics may play a role in weight management.
In 2006, Jeffrey Gordon and his group at the University of Washington in St Louis reported in Nature (Vol. 444, pp. 1022-1023, 1027-1031) 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.
Dr Gordon and his group recently pushed back the scientific boundaries even further in this area. In an ‘elegant’ study, the St Louis-based scientists reported that probiotics in a yogurt did not colonize the gut microflora when studied in identical twins, but additional study in mice revealed that ingestion of the probiotic bacteria produced a change in many metabolic pathways, particularly those related to carbohydrate metabolism (Science Translational Medicine, Vol. 3, 106ra106).
According to the FAO/WHO, probiotics are defined as "live microorganisms which when administered in adequate amounts confer a health benefit on the host".
New insights and a framework?
For their new study, Greenblum, Borenstein and Turnbaugh sought to fill a knowledge gap in this area and provide a comprehensive, system-level understanding of how variations in the genetic makeup of the microbiome affect its human host and metabolism.
By examining genes in the gut microbiomes of lean and obese individuals and patients with inflammatory bowel disease, and applying advanced computational techniques the team constructed models of these microbial communities and how the interaction between the various genes.
"Our results suggest that the enzyme-level variation associated with obesity and inflammatory bowel disease relates to changes in how the microbiome interacts with the human gut environment, rather than a variation in the microbiome's core metabolic processes," said Borenstein.
The results indicated that obese microbiomes appear to be able to use diverse energy sources, which may account for their increased capacity to extract energy from the diet.
The team’s approach may also provide possible biomarkers for obesity and inflammatory bowel disease.
January 10, 2012 vol. 109 no. 2 594-599, doi: 10.1073/pnas.1116053109
“Metagenomic systems biology of the human gut microbiome reveals topological shifts associated with obesity and inflammatory bowel disease”
Authors: S. Greenblum, P.J. Turnbaugh, E. Borenstein