A new
multi-university study reports that differences in bacterial colonization of
the infant gut in formula-fed and breast-fed babies lead to changes in the
expression of genes involved in the infant's immune system.
The study, published in the April 30 issue of
BioMed Central's open access journal Genome Biology, is
an Editor's Pick. The research was a joint effort of University of Illinois,
Texas A&M University, Miami University, and University of Arkansas
scientists.
"This study provides a first insight into the
interactions between microbes and the developing infant and how these
interactions are affected by diet. It also demonstrates the power of new
experimental and analytical approaches that enable the simultaneous analysis of
the microbiome and the host response," said Mihai Pop of the University of
Maryland in a review of the study for the publishing journal.
There is strong evidence that the colonization of
the body by microbes has an important influence on the development of infants'
immune systems, he added.
In the study, the researchers compared the genes expressed in cells
from the intestines of three-month-old exclusively breast-fed or formula-fed
infants and related this to their gut microbes. The human intestine is lined by
epithelial cells that process nutrients and provide the first line of defense
against food antigens and pathogens.
Approximately one-sixth of the intestinal
epithelial cells are shed every day into feces, providing a non-invasive
picture of what is going on inside the gut.
The baby's gene expression profile was compared to
the genes contained in the microbes in its gut, or the bacterial metagenome.
This analysis provides a picture of who the bacteria are and what they are
doing.
The study showed that babies that had been fed only
breast milk had a more diverse bacterial
colonization than formula-fed babies. The scientists also found a link
between the expression of genes in the bacteria and genes of theimmune system in
the baby.
"While we found that the microbiome of
breast-fed infants is significantly enriched in genes associated with
'virulence,' including resistance to antibiotics and toxic compounds, we also
found a correlation between bacterial pathogenicity and the expression of host
genes associated with immune and defense mechanisms," said Robert Chapkin
of Texas A&M University.
Iddo Friedberg of Miami University in Ohio said
that the differences in virulence genes probably do not reflect an infection.
"The breast-fed babies had a larger complement of gram-negative bacteria
than the formula-fed babies.
Gram-negative bacteria have genes that, although classified as 'virulent,' can
activate the immune system but not cause an infection in the process. We are
now studying this finding in greater depth," he said.
"The findings show that human milk feeding
promotes the beneficial microbe population in the gut and crosstalk between
these bacteria and the immune system of the infant and are helping us to define
exactly why breast is best," said U of I scientist Sharon Donovan.
Provided by University
of Illinois at Urbana-Champaign
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