The gut microbiome is considered an organ contributing to the regulation of host metabolism. Since the relationship between the gut microbiome and specific diseases was elucidated, numerous studies ...have deciphered molecular mechanisms explaining how gut bacteria interact with host cells and eventually shape metabolism. Both metagenomic and metabolomic analyses have contributed to the discovery of bacterial-derived metabolites acting on host cells. In this review, we examine the molecular mechanisms by which bacterial metabolites act as paracrine or endocrine factors, thereby regulating host metabolism. We highlight the impact of specific short-chain fatty acids on the secretion of gut peptides (i.e., glucagon-like peptide-1, peptide YY) and other metabolites produced from different amino acids and regulating inflammation, glucose metabolism, or energy homeostasis. We also discuss the role of gut microbes on the regulation of bioactive lipids that belong to the endocannabinoid system and specific neurotransmitters (e.g., γ-aminobutyric acid, serotonin, nitric oxide). Finally, we review the role of specific bacterial components (i.e., ClpB, Amuc_1100) also acting as endocrine factors and eventually controlling host metabolism. In conclusion, this review summarizes the recent state of the art, aiming at providing evidence that the gut microbiome influences host endocrine functions via several bacteria-derived metabolites.
The past decade has been characterized by tremendous progress in the field of the gut microbiota and its impact on host metabolism. Although numerous studies show a strong relationship between the ...composition of gut microbiota and specific metabolic disorders associated with obesity, the key mechanisms are still being studied. The present review focuses on specific complex pathways as well as key interactions. For instance, the nervous routes are explored by examining the enteric nervous system, the vagus nerve, and the brain, as well as the endocrine routes (i.e., glucagon‐like peptide‐1, peptide YY, endocannabinoids) by which gut microbes communicate with the host. Moreover, the key metabolites involved in such specific interactions (e.g., short chain fatty acids, bile acids, neurotransmitters) as well as their targets (i.e., receptors, cell types, and organs) are briefly discussed. Finally, the review highlights the role of metabolic endotoxemia in the onset of metabolic disorders and the implications for alterations in gut microbiota‐host interactions and ultimately the onset of diseases.
Abstract Background Changes in gut microbiota composition and activity have been associated with different metabolic disorders, including obesity, diabetes, and cardiometabolic disorders. Recent ...evidence suggests that different organs are directly under the influence of bacterial metabolites that may directly or indirectly regulate physiological and pathological processes. Scope of review We reviewed seminal as well as recent papers showing that gut microbes influence energy, glucose and lipid homeostasis by controlling different metabolic routes such as endocrine, enteric and central nervous system. These dialogues are discussed in the context of obesity and diabetes but also for brain pathologies and neurodegenerative disorders. Major conclusions The recent advances in gut microbiota investigation as well as the discovery of specific metabolites interacting with host cells has led to the identification of novel inter-organ communication during metabolic disturbances. This suggests that gut microbes may be viewed as “novel” future therapeutic partners. This article is part of a special issue on microbiota.
Data from clinical research suggest that certain probiotic bacterial strains have the potential to modulate colonic inflammation. Nonetheless, these data differ between studies due to the probiotic ...bacterial strains used and the poor knowledge of their mechanisms of action.
By mass-spectrometry, we identified and quantified free long chain fatty acids (LCFAs) in probiotics and assessed the effect of one of them in mouse colitis.
Among all the LCFAs quantified by mass spectrometry in
Nissle 1917 (EcN), a probiotic used for the treatment of multiple intestinal disorders, the concentration of 3-hydroxyoctadecaenoic acid (C18-3OH) was increased in EcN compared with other
strains tested. Oral administration of C18-3OH decreased colitis induced by dextran sulfate sodium in mice. To determine whether other bacteria composing the microbiota are able to produce C18-3OH, we targeted the gut microbiota of mice with prebiotic fructooligosaccharides (FOS). The anti-inflammatory properties of FOS were associated with an increase in colonic C18-3OH concentration. Microbiota analyses revealed that the concentration of C18-3OH was correlated with an increase in the abundance in
,
and
. In culture,
produced high concentration of C18-3OH. Finally, using TR-FRET binding assay and gene expression analysis, we demonstrated that the C18-3OH is an agonist of peroxisome proliferator activated receptor gamma.
The production of C18-3OH by bacteria could be one of the mechanisms implicated in the anti-inflammatory properties of probiotics. The production of LCFA-3OH by bacteria could be implicated in the microbiota/host interactions.
Changes in Gut Microbiota Control Metabolic Endotoxemia-Induced Inflammation in High-Fat Diet–Induced Obesity and Diabetes
in Mice
Patrice D. Cani 1 2 ,
Rodrigo Bibiloni 3 ,
Claude Knauf 2 ,
Aurélie ...Waget 2 ,
Audrey M. Neyrinck 1 ,
Nathalie M. Delzenne 1 and
Rémy Burcelin 2
1 Unit of Pharmacokinetics, Metabolism, Nutrition and Toxicology, Université catholique de Louvain, Brussels, Belgium
2 Rangueil Institute of Molecular Medicine, Toulouse, France
3 Nestlé Research Center, Department of Nutrition and Health, Lausanne, Switzerland
Corresponding author: Prof. Rémy Burcelin, Rangueil Institute of Molecular Medicine, I 2 MR, IFR31, Toulouse, France. E-mail: burcelin{at}toulouse.inserm.fr
Abstract
OBJECTIVE— Diabetes and obesity are characterized by a low-grade inflammation whose molecular origin is unknown. We previously determined,
first, that metabolic endotoxemia controls the inflammatory tone, body weight gain, and diabetes, and second, that high-fat
feeding modulates gut microbiota and the plasma concentration of lipopolysaccharide (LPS), i.e., metabolic endotoxemia. Therefore,
it remained to demonstrate whether changes in gut microbiota control the occurrence of metabolic diseases.
RESEARCH DESIGN AND METHODS— We changed gut microbiota by means of antibiotic treatment to demonstrate, first, that changes in gut microbiota could be
responsible for the control of metabolic endotoxemia, the low-grade inflammation, obesity, and type 2 diabetes and, second,
to provide some mechanisms responsible for such effect.
RESULTS— We found that changes of gut microbiota induced by an antibiotic treatment reduced metabolic endotoxemia and the cecal content
of LPS in both high-fat–fed and ob/ob mice. This effect was correlated with reduced glucose intolerance, body weight gain, fat mass development, lower inflammation,
oxidative stress, and macrophage infiltration marker mRNA expression in visceral adipose tissue. Importantly, high-fat feeding
strongly increased intestinal permeability and reduced the expression of genes coding for proteins of the tight junctions.
Furthermore, the absence of CD14 in ob/ob CD14 − / − mutant mice mimicked the metabolic and inflammatory effects of antibiotics.
CONCLUSIONS— This new finding demonstrates that changes in gut microbiota controls metabolic endotoxemia, inflammation, and associated
disorders by a mechanism that could increase intestinal permeability. It would thus be useful to develop strategies for changing
gut microbiota to control, intestinal permeability, metabolic endotoxemia, and associated disorders.
DGGE, denaturing gradient gel electrophoresis
FITC, fluorescein isothiocyanate
IL, interleukin
LPS, lipopolysaccharide
MDA, malondialdehyde
MCP, monocyte chemotactic protein
PAI-1, plasminogen activator inhibitor 1
RPL19, ribosomal protein L19
TBARS, thiobarbituric acid reactive substances
TNF-α, tumor necrosis factor-α
ZO-1, zonula occludens-1
Footnotes
Published ahead of print at http://diabetes.diabetesjournals.org on 27 February 2008. DOI: 10.2337/db07-1403.
Additional information for this article can be found in an online appendix at http://dx.doi.org/10.2337/db07-1403 .
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore
be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Accepted February 25, 2008.
Received October 3, 2007.
DIABETES
Hypothalamus is a key area involved in the control of metabolism and food intake via the integrations of numerous signals (hormones, neurotransmitters, metabolites) from various origins. These ...factors modify hypothalamic neurons activity and generate adequate molecular and behavioral responses to control energy balance. In this complex integrative system, a new concept has been developed in recent years, that includes reactive oxygen species (ROS) as a critical player in energy balance. ROS are known to act in many signaling pathways in different peripheral organs, but also in hypothalamus where they regulate food intake and metabolism by acting on different types of neurons, including proopiomelanocortin (POMC) and agouti-related protein (AgRP)/neuropeptide Y (NPY) neurons. Hypothalamic ROS release is under the influence of different factors such as pancreatic and gut hormones, adipokines (leptin, apelin,…), neurotransmitters and nutrients (glucose, lipids,…). The sources of ROS production are multiple including NADPH oxidase, but also the mitochondria which is considered as the main ROS producer in the brain. ROS are considered as signaling molecules, but conversely impairment of this neuronal signaling ROS pathway contributes to alterations of autonomic nervous system and neuroendocrine function, leading to metabolic diseases such as obesity and type 2 diabetes. In this review we focus our attention on factors that are able to modulate hypothalamic ROS release in order to control food intake and energy metabolism, and whose deregulations could participate to the development of pathological conditions. This novel insight reveals an original mechanism in the hypothalamus that controls energy balance and identify hypothalamic ROS signaling as a potential therapeutic strategy to treat metabolic disorders.
Propranolol is the first-line treatment for infants suffering from infantile hemangioma. Recently, some authors raised the question of potential neurologic side effects of propranolol due to its ...lipophilic nature and thus its ability to passively cross the blood-brain barrier (BBB) and accumulate into the brain. Hydrophilic beta-blockers, such as atenolol and nadolol, where therefore introduced in clinical practice. In addition to their classical mode of action in the brain, circulating factors may modulate the release of reactive oxygen/nitrogen species (ROS/RNS) from endothelial cells that compose the BBB without entering the brain. Due to their high capacity to diffuse across membranes, ROS/RNS can reach neurons and modify their activity. The aim of this study was to investigate other mechanisms of actions in which these molecules may display a central effect without actually crossing the BBB. We first performed an oral treatment in mice to measure the accumulation of propranolol, atenolol and nadolol in different brain regions
. We then evaluated the ability of these molecules to induce the release of nitric oxide (NO) and hydrogen peroxide (H
O
)
in the hypothalamus. As expected, propranolol is able to cross the BBB and is found in brain tissue in higher amounts than atenolol and nadolol. However, all of these beta-blockers are able to induce the secretion of signaling molecules (i.e., NO and/or H
O
) in the hypothalamus, independently of their ability to cross the BBB, deciphering a new potential deleterious impact of hydrophilic beta-blockers in the brain.
Administration of the probiotic Escherichia coli strain Nissle 1917 (EcN) decreases visceral pain associated with irritable bowel syndrome. Mutation of clbA, a gene involved in the biosynthesis of ...secondary metabolites, including colibactin, was previously shown to abrogate EcN probiotic activity. Here, we show that EcN, but not an isogenic clbA mutant, produces an analgesic lipopeptide. We characterize lipoamino acids and lipopeptides produced by EcN but not by the mutant by online liquid chromatography mass spectrometry. One of these lipopeptides, C12AsnGABAOH, is able to cross the epithelial barrier and to inhibit calcium flux induced by nociceptor activation in sensory neurons via the GABA
receptor. C12AsnGABAOH inhibits visceral hypersensitivity induced by nociceptor activation in mice. Thus, EcN produces a visceral analgesic, which could be the basis for the development of new visceral pain therapies.
...it appears important to pursue research efforts to better understand the mechanisms involved in the relationship between cognition and metabolism. ...this dual effect of oxytocin in weight ...management and prosocial behavior could represent a promising research track for both metabolic and cognitive research fields. ...the authors showed that the reward system in BEPs rats overcame the homeostasis and stress response systems.
The gut is one of the most important sources of bioactive peptides in the body. In addition to their direct actions in the brain and/or peripheral tissues, the intestinal peptides can also have an ...impact on enteric nervous neurons. By modifying the endogenousproduction of these peptides, one may expect modify the "local" physiology such as glucose absorption, but also could have a "global" action
the gut-brain axis. Due to the various origins of gut peptides (i.e., nutrients, intestinal wall, gut microbiota) and the heterogeneity of enteric neurons population, the potential physiological parameters control by the interaction between the two partners are multiple. In this review, we will exclusively focus on the role of enteric nervous system as a potential target of gut peptides to control glucose metabolism and food intake. Potential therapeutic strategies based on
administration of gut peptides to treat type 2 diabetes will be described.
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