Study tracks human milk nutrients in infant microbiome

Date:
September 1, 2020
Source:
Cornell University
Summary:
A new study in mice helps explain why gut microbiomes of breastfed
infants can differ greatly from those of formula-fed infants.



FULL STORY ==========================================================================
A new study in mice helps explain why gut microbiomes of breastfed
infants can differ greatly from those of formula-fed infants.


==========================================================================
The study, "Dietary Sphinganine Is Selectively Assimilated by Members
of the Mammalian Gut Microbiome," was published in July in the Journal
of Lipid Research.

Sphinganine from milk Johnson Lab/Provided A new technique allows
researchers to track specific nutrients as they are taken up by gut
microbes in a mouse's digestive tract. The image shows certain microbes
(red) taking in a nutrient common in human milk called sphinganine;
blue microbes have not taken it in.

The paper describes an innovative technique developed at Cornell to
track the fate of metabolites -- nutrients formed in or necessary for metabolism - - through a mouse's digestive tract and identify how they
interact with specific gut microbes.

"We think the methods are expandable to many different microbiome
systems," said senior author Elizabeth Johnson, assistant professor of nutritional sciences in the College of Agriculture and Life Sciences. She
noted that researchers investigating effects of a high-fat vs. low-fat
diet, or a keto diet, might use the technique to track metabolites.

The methodology could reveal how specific metabolites promote specific bacteria. This could allow nutritionists to prescribe that patients
eat foods containing specific metabolites to intentionally change the composition of their microbiomes, Johnson said.



========================================================================== Human milk and many other foods contain a class of lipid metabolites
called sphingolipids. Previous research suggested that these metabolites
help shape an infant's microbiome, but it was not known if they actually interact with the microbiome.

The study identified two types of gut microbes, Bacteroides and Bifidobacterium, that use sphingolipids for their own metabolism.

While very little is known about the specific roles of gut microbes in
human health, Bacteroides have been implicated in both beneficial and
not-so- beneficial effects, depending on context. They are generally
associated with microbiomes of healthy breastfed infants. Bifidobacterium, shown for the first time in this study to process dietary sphingolipids,
are considered the quintessential beneficial bacteria, comprising up to
95% of breastfed infants microbiome.

They're also a highly popular over-the-counter probiotic.

"Our lab is very interested in how the diet interacts with the microbiome
in order to really understand how you can best modulate it to have
positive effects on health," Johnson said. "In this study, we were able
to see that yes, these dietary lipids that are a big part of [breastfed] infants diets, are interacting quite robustly with the gut microbiome." Sphingolipids originate from three main sources: diet; bacteria that
can produce them; and most host tissues.



========================================================================== Johnson, along with first author Min-Ting Lee, a doctoral student, and
Henry Le, a postdoctoral researcher, both in Johnson's lab, created a
technique to specifically track dietary sphingolipids as they passed
through the mouse gut.

"We custom synthesized the sphingolipid we added to the diet," Johnson
said.

"It is almost identical to ones derived from breast milk but with a
small chemical tag so we could trace the location of the sphingolipid
once it was ingested by the mice." Lee then used a fluorescent label
that attached to cells or microbes that absorbed the tagged lipid, such
that any bacteria that had taken up sphingolipids lit up red. Microbes
from the mice's microbiomes were then isolated and analyzed. Populations
with red microbes were separated from the others, and these were then genetically sequenced to identify the species of bacteria.

With further investigation, Le was able to identify the metabolites
that Bacteroides and Bifidobacterium produce when exposed to dietary sphingolipids.

Further investigations are underway to determine whether these
microbially- produced metabolites are beneficial for infant health.

Johnson recently received a five-year, $1.9 million Maximizing
Investigators' Research Award from the National Institutes of Health
(NIH) to expand on this work, to better understand how lipid-dependent host-microbe interactions affect human health..

The study was supported by seed funds from the Genomics Facility of the Biotechnology Resource Center at Cornell's Institute of Biotechnology.


========================================================================== Story Source: Materials provided by Cornell_University. Original written
by Krishna Ramanujan. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Min-Ting Lee, Henry H Le, Elizabeth L Johnson. Dietary sphinganine
is
selectively assimilated by members of the mammalian gut microbiome.

Journal of Lipid Research, 2020; jlr.RA120000950 DOI: 10.1194/
jlr.RA120000950 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200901142725.htm

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