New data, published in eLife, suggests large dietary fibre polymers can physically influence the environment in the small intestine by causing other solid particles to group together (aggregate).
It is the first time that it has been shown that dietary polymers can have such an effect.
The study, performed in mice, provides new insight on how various types of solid particles found within the small intestine - including microbes, cell debris, particles for drug delivery, and food granules - move together through the gut.
This is important because the size and composition of such aggregates could potentially affect the gut environment, including how nutrients and drug particles are absorbed during digestion, say the researchers behind the new data.
"When particles in the gut form aggregates it can impact the uptake of drugs and nutrients, as well as the function of microorganisms in the gut. But little is understood about how these aggregates form," commented first author Asher Preska Steinberg, from the California Institute of Technology in the USA.
While the idea of polymer aggregation is now new, this is the first time it has been shown that dietary fibres can have such effects, said the team who noted that a diversity of polymers exists naturally in the gut.
It is well known that host-secreted polymers can cause the aggregation of microbes through chemical binding, they added.
However, the new work shows that polymers from dietary fibre can also cause aggregation through physical interactions that are dependent on the physical properties of the polymers, such as their molecular weight and concentration, instead of chemical interactions.
"We often think about dietary fibres in the context of nutrition and feeding our gut microbes, but like all polymers, they are also governed by the laws of polymer physics,” added Preska. “We wanted to investigate whether physical forces induced by these polymers play a role in structuring particles in the small intestine.”
The team initially studied interactions between polystyrene particles that were densely coated with polyethylene glycol (PEG), and the contents of the mouse small intestine. This sort of PEG-coating has previously been used to minimize chemical interactions between particles and biopolymers, allowing the team to focus on the role of physical interactions.
Such PEG-coated particles are often used in drug delivery.
According to the findings, these PEG-coated particles group together as aggregates within the small-intestine fluid – with analysis showing that polymers contribute to the aggregation.
“Our results suggested that aggregation can be controlled using polymers from fibres the mice were eating," said senior author Rustem Ismagilov, at the California Institute of Technology.
"What's more, this aggregation is tunable. By feeding the mice dietary fibers of different molecular weights, we found that we were able to control aggregation in their intestinal fluid,” he said.
The team added that further studies will be required to understand the effects of industrial food processing on the molecular weight of dietary polymers in foods, and which processing methods preserve or produce the high-molecular weight polymers that impact mucus compression and particle aggregation in the gut.
"This previously underappreciated role of dietary fibre polymers may also occur in the aggregation of other particles in the intestine, and it will be important for us to explore this further,” added Ismagilov.
Published online, Open Access, doi: 10.7554/eLife.40387
“High-molecular-weight polymers from dietary fiber drive aggregation of particulates in the murine small intestine”
Authors: Asher Preska Steinberg, et al