Dataset Information

Role of Tryptophan in Microbiota-Induced Depressive-Like Behavior: Evidence From Tryptophan Depletion Study.

ABSTRACT: During the past decade, there has been a substantial rise in the knowledge about the effects of gut microbiota on host physiology and behavior, including depressive behavior. Initial studies determined that gut microbiota can regulate host tryptophan levels, which is a main serotonin precursor. A dysfunctional serotonergic system is considered to be one of the main factors contributing to the development of depression. Therefore, we hypothesized that regulation of brain tryptophan and serotonin can explain, at least partly, the effects of microbiota on depressive behavior. To test this hypothesis, we examined depressive-like behavior and brain levels of serotonin and tryptophan, of germ free (GF) and specific-pathogen free (SPF) mice under basal conditions, or after acute tryptophan depletion (ATD) procedure, which is a method to decrease tryptophan and serotonin levels in the brain. In basal conditions, GF mice exhibited less depressive-like behavior in sucrose preference, tail-suspension and forced swim tests, compared to SPF mice. In addition, in mice that were not subjected to ATD, GF mice displayed higher levels of tryptophan, serotonin and 5-hydroxyindoleacetic acid (the main degradation product of serotonin) in medial prefrontal cortex (mPFC) and hippocampus (HIPPO), compared to SPF mice. Interestingly, ATD increased depressive-like behavior of GF, but not of SPF mice. These behavioral changes were accompanied by a stronger reduction of tryptophan, serotonin and 5-hydroxyindoleacetic acid in mPFC and HIPPO in GF mice after ATD, when compared to SPF mice. Therefore, the serotonergic system of GF mice is more vulnerable to the acute challenge of tryptophan reduction, and GF mice after tryptophan reduction behave more similarly to SPF mice. These data provide functional evidence that microbiota affects depression-like behavior through influencing brain tryptophan accessibility and the serotonergic system.

SUBMITTER: Lukic I

PROVIDER: S-EPMC6558209 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Role of Tryptophan in Microbiota-Induced Depressive-Like Behavior: Evidence From Tryptophan Depletion Study.

Lukić Iva I Getselter Dmitriy D Koren Omry O Elliott Evan E

Frontiers in behavioral neuroscience 20190604

During the past decade, there has been a substantial rise in the knowledge about the effects of gut microbiota on host physiology and behavior, including depressive behavior. Initial studies determined that gut microbiota can regulate host tryptophan levels, which is a main serotonin precursor. A dysfunctional serotonergic system is considered to be one of the main factors contributing to the development of depression. Therefore, we hypothesized that regulation of brain tryptophan and serotonin ...[more]

PMID: 31231198

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Project description:BackgroundSelective serotonin reuptake inhibitors (SSRIs) are amongst the most prescribed antidepressants for adolescents with depressive symptoms and major depressive disorder. However, SSRIs have significant shortcomings as a first-line treatment considering that not all patients respond to these antidepressants. Amongst paediatric populations, meta-analyses indicate that up to approximately 40% of patients do not respond, and for those who do show benefit, there is substantial heterogeneity in response onset. The neurotransmitter serotonin (5-HT) plays a role in the clinical effectiveness and mechanisms of action of SSRIs. However, the exact and complete mechanism of action and reasons for the low response rate to SSRIs in some adolescent populations remains unknown.MethodsTo examine SSRI response and the role of 5-HT, this study will employ a randomised double-blind within subject, repeated measures design, recruiting adolescent patients with major depressive disorder. Participants will be subjected to acute tryptophan depletion (ATD) and the balanced control condition on two separate study days within a first study phase (Phase A), and the order in which these conditions (ATD/balanced control condition) occur will be random. This phase will be followed by Phase B, where participants will receive open label pharmacological treatment as usual with the SSRI fluoxetine and followed-up over a 12-week period.DiscussionATD is a neurodietary method typically used to investigate the impact of lowered brain 5-HT synthesis on mood and behaviour. The major hypothesis of this study is that ATD will be negatively associated with mood and cognitive functioning, therefore reflecting individual serotonergic sensitivity and related depressive symptoms. Additionally, we expect the aforementioned effects of ATD administration on mood to predict clinical improvement with regard to overall depressive symptomatology 12 weeks into SSRI treatment.Trial registrationAustralian and New Zealand Clinical Trials Registry (ANZCTR) ACTRN12616001561471 . Registered on 11 November 2016.

Project description:Despite depression being one of the most prevalent and debilitating disorders worldwide, it has been difficult to understand its pathophysiology and to develop more effective treatments. Maladaptive transcriptional regulation within limbic neural circuits, including reward processing regions such as the nucleus accumbens (NAc), in response to chronic stress is thought to be a major contributor to the development of the syndrome. Epigenetic events?in particular, histone writers and erasers?that alter chromatin structure to regulate programs of gene expression have increasingly been associated with depression-related behavioral abnormalities in animal models and in depressed humans examined postmortem. However, very little is known about the ATP-dependent chromatin remodelers that control nucleosome positioning and the packing state of chromatin. Here we show that the ACF complex, part of the ISWI family of chromatin remodelers, is persistently and selectively upregulated in the NAc of mice that are susceptible to chronic social stress, as well as in the NAc of depressed human. We further establish that ACF induction is both necessary and sufficient for susceptibility to stress-induced depressive-like behaviors. Using ChIP-seq, we demonstrate that altered ACF binding after chronic stress is strongly correlated with altered nucleosome positioning, in particular, around the transcriptional start sites of affected genes. These alterations in ACF binding and nucleosome repositioning are associated with repressed expression of a subset of genes in animals that are susceptible to chronic stress. Together, these findings establish that active ATP-dependent chromatin remodeling by the ACF complex is a key regulator in the repression of genes that mediate susceptibility to social stress, and provide novel candidate targets for improved therapeutics of depression and other stress-related disorders. c57bl/6 mice underwent chronic social defeat stress (CSDS), and social interaction test was used to separate animals into control, susceptible and resilient groups. Nucleus accumbens (NAc) tissue was collected 48 hours after the last defeat session, and then Acf1, SNF2H ChIP-seq or H3 MNase-seq were performed based on the control, susceptible, and resilient groups. Three sequencing replicates were performed on each group.

Dataset Information

Role of Tryptophan in Microbiota-Induced Depressive-Like Behavior: Evidence From Tryptophan Depletion Study.

Publications

Role of Tryptophan in Microbiota-Induced Depressive-Like Behavior: Evidence From Tryptophan Depletion Study.

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