Summary:
The evolution of dietary and
hygienic habits in Western countries is associated with a decrease in the
bacteria that help in digestion. These very bacteria were also found in the
Iceman, who lived 5300 years ago, and are still present in non-Westernized
populations in various parts of the world. The depletion of the microbiome may
be associated with the increased prevalence, in Western countries, of complex
conditions like allergies, autoimmune and gastrointestinal diseases, obesity.
The
intestinal microbiome is a delicate ecosystem made up of billions and billions
of microorganisms, bacteria in particular, that support our immune system,
protect us from viruses and pathogens, and help us absorb nutrients and produce
energy.
The
industrialization process in Western countries had a huge impact on its content.
This was confirmed by a study on the bacteria found in the intestine of Ötzi,
the Iceman who, in 1991, emerged from the ice of the Ötztal Alps, where Italy
borders with Austria. Scientists of Eurac Research examined samples of the
mummy's bacteria, confirming the findings of the researchers of the University
of Trento who had analyzed the genome of intestinal microorganisms of over 6500
individuals from all continents.
Previous
studies by the University of Trento had demonstrated that there is a connection
between the microbiome's bacterial content and the increase, in Western
countries, of obesity, autoimmune and gastrointestinal diseases, allergies and
other complex conditions. In the study that appeared today in Cell Host &
Microbe, researchers from Cibio of the University of Trento and Eurac in
Bolzano/Bozen demonstrated that the differences between Western and non-Western
or prehistoric microbiome lie in the decrease of some types of bacteria that
process complex and vegetal fibers in the intestine.
That may
have been caused by the Westernization process. Changes in diet, which is now
higher in fat and low in fibers, a sedentary lifestyle in an urban setting, the
development of new hygiene habits and the widespread use of antibiotics and
other medical products have, with no doubt, made our life safer, but impacted
the delicate balance of our microbiome.
About the study
The
scientists of Eurac Research in Bolzano/Bozen sequenced the Iceman's DNA and
were able to identify his set of bacteria, while the researchers of the
University of Trento compared it with the microbiome of contemporary
non-Westernized populations (from Tanzania and Ghana in particular), which are
not used to processed food and have non-Westernized hygiene practices and
lifestyle. Their findings were surprising.
The study
focused, in particular, on Prevotella copri, a microbe that, when is found in
our intestine, is usually the most represented. P. copri is present in 30% of
Western individuals.
"First
of all, we found out that P. copri it is not a monotypic species but is
composed of four distinct but similar clades," explained Nicola Segata,
coordinator of the study with Adrian Tett of Cibio of the University of Trento.
"We then noticed that at least three of these four clades are almost
always present in non-Westernized populations, but are much less prevalent in
Westernized individuals. And when it is so, there usually is only one of the
four clades. We postulated that the complex process of Westernization had a
considerable impact on the gradual disappearance of this bacterium. Our
hypothesis was confirmed by the analysis of ancient samples of DNA that were
made available by Frank Maixner of the Institute for Mummy Studies at Eurac
Research. The Iceman's guts contained three of the four clades of P. copri. And
the four clades were also co-present in fossilized stool samples from Mexico
that are more than one thousand years old. We still do not know what are the
biomedical consequences of these changes of the microbiome which has evolved
considerably in recent decades while the human body it colonizes has remained
genetically practically unchanged for centuries,"
"Through
these 'ancient' samples," continued Tett, "we were able to study the
evolution of these clades and now we know that they genetically delineated with
the human species and before the initial human migrations out of the African
continent."
The study is
the result of close collaboration with the research group of Albert Zink and
Frank Maixner at Eurac Research in Bolzano/Bozen. Their team was responsible
for the collection and pre-analysis of the Iceman's DNA samples. "The
relation between the evolution of the human species and the diversity of
intestinal microorganisms, as a field of research, is still rather unexplored,
but can yield important results in the future through the analysis of ancient
DNA. For this reason, finding more advanced and less invasive techniques to
obtain and analyze DNA from human remains is one of the major areas of research
at Eurac" concluded the microbiologist of Eurac Research Frank Maixner.
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