Fibra fermentável e saúde intestinal

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The virtues of fibre as part of a healthy 
diet are commended. Now, in two new 
studies, researchers have determined 
how a fermentable fibre (inulin) 
contributes to gut health and barrier 
function, protecting against diet-
induced obesity and colonic mucus 
degradation in mouse models.
In the first study, Andrew Gewirtz 
and colleagues examined the role of 
dietary fibre as a possible means 
of promoting healthy host–microbe 
interactions to prevent metabolic 
syndrome. “A peaceful relationship 
between the gut microbiota and 
the intestine promotes metabolic 
health,” explains Gewirtz, noting that 
disturbances in this relationship can 
promote low-grade inflammation that 
can impair metabolic signalling and 
promote metabolic syndrome. 
Mice were fed either standard 
chow or a high-fat diet (HFD, which 
induces obesity and features of 
metabolic syndrome) supplemented 
with either fermentable (inulin) 
or insoluble (cellulose) fibre. 
Compared with standard chow, 
supplementation with inulin protected 
the mice against diet-induced 
obesity and also reduced levels 
of hepatosteatosis.
Looking into the underlying 
processes, a HFD enriched with 
inulin, but not that enriched 
with cellulose, had beneficial effects 
on the intestinal barrier, increasing 
gut epithelial cell proliferation and 
preventing atrophy of the colon 
and the intestinal crypts. Moreover, 
supplementation with inulin (a well-
known prebiotic) restored the gut 
microbiota levels and bacterial growth 
that had become depleted with a 
HFD (HFD resulted in ~10-fold 
reduction in total faecal bacterial 
loads). Interesingly, inulin also 
corrected some of the changes to the 
composition of the gut microbiota 
as a result of a HFD and restored 
microbiota–mucosa separation. 
The beneficial effects of inulin 
for colonic and metabolic health 
were dependent on the microbiota 
and IL-22, but not short-chain fatty 
acids. “Enriching the diet with inulin 
but not cellulose largely restores 
many of the beneficial bacteria and 
re-energizes host defences, thus 
preventing microbiota encroachment 
and protecting against HFD-induced 
metabolic syndrome,” says Gewirtz.
In the second study, Gunnar C. 
Hansson and colleagues focused on 
the effects of diet on the protective 
mucus layer in the mouse intestine 
and the crucial separation of bacteria 
from the intestinal epithelium. 
“Mucus penetrability is dynamic and 
varies with bacterial composition,” 
explains Hansson. Given evidence 
that susceptibility to diabetes increases 
with a low-fibre diet, Hansson asks: 
“Could the link be that a low-fibre 
diet renders the 
inner mucus layer 
more penetrable, 
allowing bacteria 
to come closer to 
the epithelium, 
and by this trigger 
low-grade 
inflammation?”
Mice were fed 
either standard 
chow or a Western style diet (WSD, 
rich in saturated fats and simple 
sugars, but low in dietary fibre), as 
well as drinking water supplemented 
with either inulin, the probiotic 
Bifidobacterium longum NCC2705, 
or a combination of the two before 
analysis of colonic mucus properties.
A WSD profoundly affected 
the inner colonic mucus layer in 
mice, influencing key functions 
(growth rate was impaired with 
increased penetrability). Moreover, 
the composition of both luminal 
microbiota and mucosal microbiota 
in the distal colon were altered by 
a WSD, and distinct shifts in the 
microbiota composition paralleled 
changes in mucus penetrability 
and growth. 
Faecal microbiota transplantation 
from chow-fed mice prevented the 
deterioration of the colonic mucus 
on a WSD. Crucially, treatment 
with B. longum NCC2705 or inulin 
prevented the development of mucus 
defects in mice fed a WSD. 
“Only 3 days of Western diet, 
low in fibre, make the inner mucus 
more penetrable to bacteria,” notes 
Hansson. “The molecular mechanism 
behind the effect of diet on the 
formation of bacterial metabolites and 
the way they signal to the host and 
control mucus properties is poorly 
understood … something that will 
require major efforts to understand 
better,” he adds.
Katrina Ray
 G U T M I C R O B I OTA
Filling up on fibre for a healthy gut
a fermentable 
fibre (inulin) 
contributes 
to gut health 
and barrier 
function
Laura Marshall/Macmillan Publishers Limited
ORIGINAL ARTICLES Zou, J. et al. Fiber-mediated 
nourishment of gut microbiota protects against 
diet-induced obesity by restoring IL-22-mediated 
colonic health. Cell Host Microbe https://doi.org/ 
10.1016/j.chom.2017.11.003 (2017) | 
Schroeder, B. O. et al. Bifidobacteria or fiber 
protects against diet-induced microbiota-
mediated colonic mucus deterioration. 
Cell Host Microbe https://doi.org/10.1016/ 
j.chom.2017.11.004 (2018) 
R E S E A R C H H I G H L I G H T S
NATURE REVIEWS | GASTROENTEROLOGY & HEPATOLOGY www.nature.com/nrgastro
Nature Reviews Gastroenterology & Hepatology | Published online 17 Jan 2018; doi:10.1038/nrgastro.2018.2
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https://doi.org/10.1016/j.chom.2017.11.003
https://doi.org/10.1016/j.chom.2017.11.003
https://doi.org/10.1016/j.chom.2017.11.004
https://doi.org/10.1016/j.chom.2017.11.004
http://dx.doi.org/10.1038/nrgastro.2018.2