The new findings, published in Nature, find a link between the ‘richness’ of bacterial species in our gut and susceptibility to metabolic complications related to obesity.
Led by Professor Jeroen Raes from VIB, the Netherlands, the MetaHIT team have demonstrated that people with fewer bacterial species in their intestines are more likely to develop complications, including cardiovascular diseases and diabetes.
Such flora, with decreased bacterial richness, appear to function entirely differently to the healthy varieties that have greater diversity, said the team.
"We were able to distinguish between two groups based on their intestinal flora: people with a large richness of bacterial species in their intestines and people with a few less bacterial species,” explained Raes.
“A species-rich bacterial flora appeared to function differently compared to the poorer variety. It was surprising to see that obese and non-obese people were found in both groups."
The team found that the group with lower species richness in the intestinal flora was more susceptible to developing obesity-related conditions and chronic inflammation – with the obese people in this group are more at risk of cardiovascular conditions than the obese people in the group with a higher diversity of gut bacteria.
"This is an amazing result with possibly enormous implications for the treatment and even prevention of the greatest public health issue of our time."
“But we are not there yet, now we need studies in which we can monitor people for a longer period,” Raes said, adding that the consortium now want to perform this sort of long-term study together with the Flemish Gut Flora Project (Vlaams Darmflora Project).
Over the past five years the EU-funded MetaHIT project has advanced DNA analysis and bioinformatics methods to map the human intestinal bacteria. The team have previously shown that our gut flora come in three distinct types known as enterotypes, and that these enterotypes are linked to diet.
Now, a genetic analysis of intestinal bacteria from 292 Danish people has shown that around a quarter of those tested had a lower ‘richness’ of gut bacteria – with around 40% less gut bacteria genes and correspondingly fewer bacteria than average.
The team said that this lack of bacteria also seems to lead to a preponderance of bacteria which have potential to cause mild inflammation in the digestive tract and in the entire body, and that this is reflected in blood samples that reveal a state of chronic inflammation.
This low level chronic inflammation is known to affect metabolism and increase the risk of type 2 diabetes and cardiovascular diseases, said the team.
“Individuals with a low bacterial richness (23% of the population) are characterised by more marked overall adiposity, insulin resistance and dyslipidaemia and a more pronounced inflammatory phenotype when compared with high bacterial richness individuals,” wrote the researchers.
Professor Oluf Pedersen from the University of Copenhagen, co-author of the study, noted that the team also found that people who belong to the group with less intestinal bacteria, and have already developed obesity, will also gain more weight over a number of years.
“We don't know what came first, the chicken or the egg, but one thing is certain: it is a vicious circle that poses a health threat,” he said.
“The obese individuals among the lower bacterial richness group also gain more weight over time,” said the authors.
“Our classifications based on variation in the gut microbiome identify subsets of individuals in the general white adult population who may be at increased risk of progressing to adiposity-associated co-morbidities.”
Published online ahead of print, doi: 10.1038/nature12506
“Richness of human gut microbiome correlates with metabolic markers”
Authors: Emmanuelle Le Chatelier, Trine Nielsen, Junjie Qin, et al