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Published January 22, 2019 | Submitted + Published + Supplemental Material
Journal Article Open

High-molecular-weight polymers from dietary fiber drive aggregation of particulates in the murine small intestine


The lumen of the small intestine (SI) is filled with particulates: microbes, therapeutic particles, and food granules. The structure of this particulate suspension could impact uptake of drugs and nutrients and the function of microorganisms; however, little is understood about how this suspension is re-structured as it transits the gut. Here, we demonstrate that particles spontaneously aggregate in SI luminal fluid ex vivo. We find that mucins and immunoglobulins are not required for aggregation. Instead, aggregation can be controlled using polymers from dietary fiber in a manner that is qualitatively consistent with polymer-induced depletion interactions, which do not require specific chemical interactions. Furthermore, we find that aggregation is tunable; by feeding mice dietary fibers of different molecular weights, we can control aggregation in SI luminal fluid. This work suggests that the molecular weight and concentration of dietary polymers play an underappreciated role in shaping the physicochemical environment of the gut.

Additional Information

© 2019 Preska Steinberg et al. This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited. Received: 24 July 2018; Accepted: 28 December 2018; Published: 22 January 2019. This work was supported in part by DARPA Biological Robustness in Complex Settings (BRICS) contract HR0011-15-C-0093, Army Research Office (ARO) Multidisciplinary University Research Initiative (MURI) contract #W911NF-17-1-0402, the Jacobs Institute for Molecular Engineering for Medicine, and an NSF Graduate Research Fellowship DGE-144469 (to APS). We acknowledge Michael Porter, Joong Hwan Bahng, Jacob Barlow, Zhen-Gang Wang, Julia Kornfield, David Tirrell, Justin Bois, and Greg Donaldson for useful discussions; the Beckman Institute Biological Imaging Facility, the Broad Animal Facility, and the Church Animal Facility for experimental resources; Jennifer Costanza, Taren Thron, the Caltech Office of Laboratory Animal Resources, and the veterinary technicians at the California Institute of Technology for technical support; Joanne Lau for assistance with Western blot measurements; Emily Wyatt for assistance with zeta potential measurements; the Mazmanian laboratory for providing Rag1KO mice; the Eugene Chang Lab (University of Chicago) for providing the initial breeding pairs for the MUC2KO colony and Leonard H Augenlicht at the Department of Oncology of Albert Einstein Cancer Center for providing the original MUC2KO line to them; and Natasha Shelby for contributions to writing and editing this manuscript. The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication. Competing interests: Rustem F Ismagilov: The technology described in this publication is the subject of provisional patent application 62/696,743, filed by Caltech on 7/11/18. The other authors declare that no competing interests exist. Author contributions: Asher Preska Steinberg, Conceptualization, Resources, Data curation, Software, Formal analysis, Funding acquisition, Validation, Investigation, Visualization, Methodology, Writing—original draft, Writing—review and editing, Co-designed all experiments and co-analyzed all experimental results; developed theoretical tools and performed all calculations; co-developed imaging analysis pipeline in ImageJ; developed computational tools for bootstrapping procedure; co-developed microscopy assay (Fig 1C-D;Co-performed, designed, and analyzed data from gavage experiments in Fig 1;per- formed, designed, and analyzed data from all ex vivo SI aggregation experiments in Figs 2, 3, 5-7; performed, designed, and analyzed data from all GPC measurements in Figs 3, 5-7, and Tables 1-7; performed, designed, and analyzed data from all in vitro PEG aggregation experiments in Fig 4D, Fig 4 - supplements2-3, and with dietary fiber in Fig 7A; developed a computational approach forth-eoretical calculations in 4H and 4I and performed all calculations; performed, designed, and analyzed data from Western blots in Figs 5E, 6E, Fig 6- supplements 1-2; helped supervise animal husbandry of MUC2KO colony; performed animal husbandry for WT mice on autoclaved diets in Fig 6; performed animal husbandry for mice on pectin and Fibersol-2 diets in Fig 7; performed, designed, and analyzed all zeta potential measurements in Table 8; performed pH measurements on luminal fluid in Fig 4 - supplement 1; co-interpreted results.; Sujit S Datta, Conceptualization, Investigation, Methodology, Writing—review and editing, Conceived and co-planned the project; initially observed the aggregation phenomenon; co-designed and co-analyzed preliminary experiments; performed preliminary ex vivo and in vitro aggregation experiments; co-developed microscopy assay used in Fig 1C and 1D; developed exvivo/in vitro aggregation assay used in Figs 2-7; co-developed approach to extract liquid fraction of murine intestinal contents; co-developed NMR protocol; organized transfer and initial set up of MUC2KO colony; co-interpreted results.; Thomas Naragon, Data curation, Software, Formal analysis, Methodology, Writing—original draft, Co-developed imaging analysis pipeline in ImageJ; co-analyzed ex vivo aggregation data in Fig 2; co-designed and co-analyzed preliminary ex vivo aggregation experiments with MUC2KO mice; provided useful advice on boot-strapping procedure; co-interpreted results.; Justin C Rolando, Data curation, Formal analysis, Investigation, Methodology, Writing—original draft, Developed protocol for NMR measurements on PEG-coated particles, Performed synthesis of particles, Performed NMR measurements in Table 8; Said R Bogatyrev, Investigation, Methodology, Writing—review and editing, Co-performed preliminary experiments; developed fluorescent laser scanning approach appearing in Fig 1A and 1B; Administered particles to mice in Fig 1; co-developed approach to extract liquid fraction of murine intestinal contents; co-organized transfer and initial set up of MUC2KO colony; setup genotyping of MUC2KO mice; helped supervise animal husbandry of MUC2KO colony; helped with interpretation of results.; Rustem F Ismagilov, Resources, Formal analysis, Supervision, Funding acquisition, Investigation, Methodology, Writing—original draft, Project administration, Writing—review and editing. Ethics: Animal experimentation: All animal experiments were approved by the California Institute of Technology (Caltech) Institutional Animal Care and Use Committee (IACUC) under IACUC protocol #1691, and the U.S. Army's Animal Care and Use Review Office (ACURO) under ACURO protocols #DARPA-533.02 and #70905-LS-MUR.03. Mice were euthanized via CO2 inhalation as approved by the Caltech IACUC in accordance with the American Veterinary Medical Association Guidelines on Euthanasia.

Attached Files

Published - elife-40387-v1.pdf

Submitted - 490920.full.pdf

Supplemental Material - elife-40387-transrepform-v1.pdf


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