EMBO: An unhealthy diet changes the composition of the gut flora and it is
generally assumed that this maladaptation called “dysbiosis” triggers
disease. A study by Matteo Serino and his colleagues at the Université
Paul Sabatier in Toulouse, France, now challenges this view. Using mice
as a model organism, the researchers show that dysbiosis may have
beneficial effects on liver metabolism and may protect against metabolic
disease. The study is published today in Molecular Systems Biology.
The intestine is covered with a plethora of microorganisms,
collectively termed gut microbiota, that are thought to play an
important role in regulating the metabolism and shaping the immune
system. Many studies have shown that dysbiotic bacteria can cause
disease. However, these studies generally follow a similar protocol that
may impact on the outcome: They transfer dysbiotic bacteria to axenic
mice that do not have any microbiota. For example, axenic mice that
receive microbiota from the gut of obese mice would increase their total
body fat, indicating that microbiota play a causative role in the
development of obesity.
Serino and his colleagues now took a different approach to addressing
the role of microbiota. The researchers reasoned that axenic mice are
ill-equipped to deal with dysbiotic microbiota. Their gut barrier is
impaired, favoring an uncontrolled spread of bacteria throughout the
body. In addition, their immune system is not well developed. Thus,
instead of using axenic mice as recipients of dysbiotic microbiota, the
team used normal, healthy mice, which have not been treated with
antibiotics before. In contrast to previous research, the team found
that a dysbiosis is not necessarily harmful. In fact, it may even lead
to metabolic adaptions that protect the body against disease.
High fat diet increases the production of glucose by the liver and
can eventually lead to metabolic disease. However, when Serino and his
colleagues transplanted dysbiotic microbiota from mice on high-fat diet
to healthy mice, they found that the production of glucose in the liver
was reduced rather than increased. Therefore, dysbiotic microbiota
counter the metabolic effect of high-fat diet and may thus protect the
host from its consequences. Similar effects were also observed when the
researchers used microbiota from genetically obese mice.
In another set of experiments, the researchers transplanted dysbiotic
microbiota from obese mice to healthy mice and then put these mice on a
high-fat diet. Normally, a high-fat diet would lead to weight gain.
However, the body mass of mice that had received dysbiotic microbiota
did not change, and their adipose tissue showed smaller fat cells,
consistent with increased plasma free-fatty acids.
In conclusion, dysbiosis after high-fat diet may not all be
detrimental. As long as the gut barrier is intact and the immune system
is functional, dysbiosis may even protect the body from metabolic
effects of unhealthy diets. “Our observation may encourage a new debate
on the role of gut microbiota dysbiosis in the induction of metabolic
diseases,” said Serino.
Transfer of dysbiotic gut microbiota has beneficial effects on host liver metabolism
Nicolas, V. Blasco-Baque, A. Fournel, J. Gilleron, P. Klopp, A. Waget, F. Ceppo, A. Marlin, R. Padmanabhan, J. S. Iacovoni, F. Tercé, P.D. Cani, J-F. Tanti, R. Burcelin, C. Knauf, M. Cormont & M. Serino.
Read the paper: DOI 10.15252/msb.20167356