Menu

Close

Chemogenetic analysis of how receptors for short chain fatty acids regulate the gut-brain axis

Natasja Barki, Daniele Bolognini, Ulf Börjesson, Laura Jenkins, John Riddell, David I. Hughes, Trond Ulven, Brian D. Hudson, Elisabeth Rexen Ulven, Niek Dekker, Andrew B. Tobin, Graeme Milligan

Preprint posted on January 13, 2020 https://www.biorxiv.org/content/10.1101/2020.01.11.902726v1

Following your gut – using chemogenetics to understand how short chain fatty acids regulate the gut-brain axis

Selected by Phyllis Phuah

Categories: biochemistry, cell biology

Background

The gut-brain axis allows for bidirectional communication between the gastrointestinal tract and the brain to maintain homeostasis. The involvement of gut microbiota in such interactions has become increasingly evident – the microbiota generates a wide array of metabolites that can act as signalling molecules (1), while gut microbial imbalances have been implicated in disease development (2). Short chain fatty acids (SCFAs), which are generated in large amounts after dietary fibre fermentation, are important regulators at the gut-brain axis interface (3). However, it has been challenging to characterise the exact mechanistic pathways that SCFAs act on, because they co-activate a pair of closely related G protein-coupled receptors, FFA2 and FFA3, and the respective downstream targets of each receptor are  presently poorly characterised (4).

Experimental model

The authors applied an integrated chemogenetic approach using Designer Receptor Exclusively Activated by Designer Drugs (DREADDs) to characterise the specific roles of FFA2 and FFA3.

They generated a transgenic mouse model, where a DREADD derived from human FFA2 is expressed in place of endogenous mouse FFA2. The authors identified 4-methoxy-3-methyl-benzoic acid (MOMBA), as a highly selective activator of hFFA2-DREADD, implying that any responses to MOMBA in these transgenic hFFA2-DREADD mice reflect an FFA2-mediated effect. In contrast, since FFA3 showed intact expression in these transgenic mice, any observed responses to endogenous SCFAs like propionate are potentially mediated by FFA3, as the hFFA2-DREADD variant does not respond to propionate.

Key findings

  1. Specific FFA2 activation promotes colonic release of GLP-1 and PYY

FFA2 and FFA3, which are expressed by various enteroendocrine cells throughout the gut, are thought to be involved in the release of glucagon-like peptide 1 (GLP-1) and peptide YY (PYY). GLP-1 and PYY are important hormones secreted after nutrient intake which stimulate insulin release to lower blood glucose levels.  Using colonic crypt cultures derived from hFFA2-DREADD mice, the authors show that MOMBA promotes the release of GLP-1 and PYY, and these effects can be antagonised by a FFA2-selective antagonist. In contrast, propionate was unable to produce an effect. This reflects the specific involvement of FFA2 in regulating hormone secretion in response to SCFAs.

  1. FFA2 and FFA3 mediate Ca2+ elevation in cells of dorsal root ganglia via different G proteins

The dorsal root ganglion (DRG) contains a cluster of sensory neurons that bring information from peripheral organs like the gut to the spinal cord. A substantial elevation of intracellular Ca2+ was observed in isolated DRG-derived cells in response to MOMBA, which was again antagonised by a FFA2-selective antagonist. Likewise, the separate addition of both propionate and a novel FFA3 agonist also produced a broad and rapid Ca2+ elevation in DRG cultures. Taken together, these results confirm the functionality of FFA2 and FFA3 in DRGs, and their involvement in mediating communication between the gut and the spinal cord.

  1. FFA3 promotes activation of neurons in the dorsal horn of spinal cord in vivo

Finally, to investigate if SCFAs in the gut stimulate the central nervous system, the authors perfused propionate intra-rectally to stimulate colonic receptors of wild type mice. They noted a substantial increase in the number of activated neurons in the dorsal horn of the spinal cord. They then repeated these experiments using both propionate and MOMBA in hFFA2-DREADD expressing mice, and showed that only propionate but not MOMBA promoted neuronal activation. This implies that only FFA3 activation at the level of the gut initiates spinal cord stimulation.

 

Why this is interesting

In this preprint, the authors have employed a sophisticated chemogenetic approach where combinations of receptor-agonists are tested in their hFFA2-DREADD mouse model. This allows for the unambiguous dissection of the specific functions of FFA2 and FFA3 at different levels within the gut-brain axis. While DREADDs are widely utilised in neurobiology to characterise brain circuits, this preprint has uniquely shown that DREADDs are a useful tool in GPCR biology to delineate the functions of closely related GPCRs. Very interestingly, the authors have also shown that the activation of SCFA receptors in the colon produces neuronal activation not just in the enteric nervous system but in the spinal cord as well. This provides further insight into the involvement of SCFAs in the gut-brain axis of communication, which can potentially be exploited therapeutically. In doing so, the authors also established the potential of utilising this chemogenetic approach to investigate GPCR biology and to validate drug targets.

Questions for authors

There appears to be a large number of DRG cells that show Ca2+ elevation following application of propionate/ MOMBA. However, there seem to be a smaller number of c-Fos expressing neurons in the dorsal horn. Any idea why there could be a discrepancy between calcium mobilisation and eventual neuronal activation?

 

  1. Bonaz B, Bazin T, Pellissier S. The Vagus Nerve at the Interface of the Microbiota-Gut-Brain Axis. Front Neurosci 2018;12, 49. doi: 10.3389/fnins.2018.00049
  2. Lynch, S. V., and Pedersen, O. The human intestinal microbiome in health and disease. N. Engl. J. Med. 2016;375, 2369–2379. doi: 10.1056/NEJMra1600266
  3. Dalile B, Van Oudenhove L, Vervliet B, Verbeke K. The role of short-chain fatty acids in microbiota–gut–brain communication. Nature Reviews Gastroenterology and Hepatology. 2019;16, 461–78. doi: 10.1038/s41575-019-0157-3
  4. Brown AJ, Goldsworthy SM, Barnes AA, Eilert MM, Tcheang L, Daniels D, et al. The orphan G protein-coupled receptors GPR41 and GPR43 are activated by propionate and other short chain carboxylic acids. J Biol Chem. 2003;278(13):11312–9.

 

Posted on: 25th February 2020

doi: https://doi.org/10.1242/prelights.17116

Read preprint (No Ratings Yet)




  • Have your say

    Your email address will not be published. Required fields are marked *

    This site uses Akismet to reduce spam. Learn how your comment data is processed.

    Sign up to customise the site to your preferences and to receive alerts

    Register here

    Also in the cell biology category:

    FENS 2020

    A collection of preprints presented during the virtual meeting of the Federation of European Neuroscience Societies (FENS) in 2020

     



    List by Ana Dorrego-Rivas

    Planar Cell Polarity – PCP

    This preList contains preprints about the latest findings on Planar Cell Polarity (PCP) in various model organisms at the molecular, cellular and tissue levels.

     



    List by Ana Dorrego-Rivas

    BioMalPar XVI: Biology and Pathology of the Malaria Parasite

    [under construction] Preprints presented at the (fully virtual) EMBL BioMalPar XVI, 17-18 May 2020 #emblmalaria

     



    List by Gautam Dey, Samantha Seah

    1

    Cell Polarity

    Recent research from the field of cell polarity is summarized in this list of preprints. It comprises of studies focusing on various forms of cell polarity ranging from epithelial polarity, planar cell polarity to front-to-rear polarity.

     



    List by Yamini Ravichandran

    TAGC 2020

    Preprints recently presented at the virtual Allied Genetics Conference, April 22-26, 2020. #TAGC20

     



    List by Maiko Kitaoka, Madhuja Samaddar, Miguel V. Almeida, Sejal Davla, Jennifer Ann Black, Gautam Dey

    3D Gastruloids

    A curated list of preprints related to Gastruloids (in vitro models of early development obtained by 3D aggregation of embryonic cells)

     



    List by Paul Gerald L. Sanchez and Stefano Vianello

    ECFG15 – Fungal biology

    Preprints presented at 15th European Conference on Fungal Genetics 17-20 February 2020 Rome

     



    List by Hiral Shah

    ASCB EMBO Annual Meeting 2019

    A collection of preprints presented at the 2019 ASCB EMBO Meeting in Washington, DC (December 7-11)

     



    List by Madhuja Samaddar, Ramona Jühlen, Amanda Haage, Laura McCormick, Maiko Kitaoka

    EMBL Seeing is Believing – Imaging the Molecular Processes of Life

    Preprints discussed at the 2019 edition of Seeing is Believing, at EMBL Heidelberg from the 9th-12th October 2019

     



    List by Gautam Dey

    Autophagy

    Preprints on autophagy and lysosomal degradation and its role in neurodegeneration and disease. Includes molecular mechanisms, upstream signalling and regulation as well as studies on pharmaceutical interventions to upregulate the process.

     



    List by Sandra Malmgren Hill

    Lung Disease and Regeneration

    This preprint list compiles highlights from the field of lung biology.

     



    List by Rob Hynds

    Cellular metabolism

    A curated list of preprints related to cellular metabolism at Biorxiv by Pablo Ranea Robles from the Prelights community. Special interest on lipid metabolism, peroxisomes and mitochondria.

     



    List by Pablo Ranea Robles

    BSCB/BSDB Annual Meeting 2019

    Preprints presented at the BSCB/BSDB Annual Meeting 2019

     



    List by Gautam Dey

    Biophysical Society Annual Meeting 2019

    Few of the preprints that were discussed in the recent BPS annual meeting at Baltimore, USA

     



    List by Joseph Jose Thottacherry

    ASCB/EMBO Annual Meeting 2018

    This list relates to preprints that were discussed at the recent ASCB conference.

     



    List by Gautam Dey, Amanda Haage
    Close