Commensal microbe-derived propionic acid mediates juvenile social isolation-induced social deficits and anxiety-like behaviors

Prenatal Gut Microbiota Predicts Temperament in Offspring at 1-2 Years

The purpose of this study was to explore whether prenatal gut microbiota (GM) and its functions predict the development of offspring temperament. A total of 53 mothers with a 1-year-old child and 41 mothers with a 2-year-old child were included in this study using a mother-infant cohort from central China. Maternal fecal samples collected during the third trimester were analyzed using 16S rRNA V3-V4 gene sequences. Temperament of the child was measured by self-reported data according to the primary caregiver. The effects of GM in mothers on offspring's temperament were evaluated using multiple linear regression models. The results demonstrated that the alpha diversity index Simpson of prenatal GM was positively associated with the activity level of offspring at 1 year (adj. P = .036). Bifidobacterium was positively associated with high-intensity pleasure characteristics of offspring at 1 year (adj. P = .031). Comparatively, the presence of Bifidobacterium found in the prenatal microbiome was associated with low-intensity pleasure characteristics in offspring at 2 years (adj. P = .031). There were many significant associations noted among the functional pathways of prenatal GM and temperament of offspring at 2 years. Our findings support the maternal-fetal GM axis in the setting of fetal-placental development with subsequent postnatal neurocognitive developmental outcomes, and suggest that early childhood temperament is in part associated with specific GM in the prenatal setting.

CDP-choline modulates cholinergic signaling and gut microbiota to alleviate DSS-induced inflammatory bowel disease

Inflammatory bowel diseases (IBD) represent chronic gastrointestinal inflammatory disorders characterized by a complex and underexplored pathogenic mechanism. Previous research has revealed that IBD patients often have a deficiency of choline and its metabolites, including acetylcholine (ACh) and phosphatidylcholine (PC), within the colon. However, a comprehensive study linking these three substances and their mechanistic implications in IBD remains lacking. This study aimed to investigate the efficacy and underlying mechanism of cytidine diphosphate (CDP)-choline (citicoline), an intermediate product of choline metabolism, in a mouse model of IBD induced by dextran sulfate sodium salt (DSS). The results demonstrated that CDP-choline effectively alleviated colonic inflammation and deficiencies in choline, ACh, and PC by increasing the raw material. Further detection showed that CDP-choline also increased the ACh content by altering the expression of high-affinity choline transporter (ChT1) and acetylcholinesterase (AChE) in DSS-induced mice colon. Moreover, CDP-choline increased the expression of alpha7 nicotinic acetylcholine receptor (α7 nAChR) and activated the cholinergic anti-inflammatory pathway (CAP), leading to reduced colon macrophage activation and proinflammatory M1 polarization in IBD mice, thus reducing the levels of TNF-α and IL-6. In addition, CDP-choline reduced intestinal ecological imbalance and increased the content of hexanoic acid in short-chain fatty acids (SCFAs) in mice. In conclusion, this study elucidates the ability of CDP-choline to mitigate DSS-induced colon inflammation by addressing choline and its metabolites deficiencies, activating the CAP, and regulating the composition of the intestinal microbiome and SCFAs content, providing a potential prophylactic and therapeutic approach for IBD.

Microbial metabolites regulate social novelty via CaMKII neurons in the BNST

Social novelty is a cognitive process that is essential for animals to interact strategically with conspecifics based on their prior experiences. The commensal microbiome in the gut modulates social behavior through various routes, including microbe-derived metabolite signaling. Short-chain fatty acids (SCFAs), metabolites derived from bacterial fermentation in the gastrointestinal tract, have been previously shown to impact host behavior. Herein, we demonstrate that the delivery of SCFAs directly into the brain disrupts social novelty through distinct neuronal populations. We are the first to observe that infusion of SCFAs into the lateral ventricle disrupted social novelty in microbiome-depleted mice without affecting brain inflammatory responses. The deficit in social novelty can be recapitulated by activating calcium/calmodulin-dependent protein kinase II (CaMKII)-labeled neurons in the bed nucleus of the stria terminalis (BNST). Conversely, chemogenetic silencing of the CaMKII-labeled neurons and pharmacological inhibition of fatty acid oxidation in the BNST reversed the SCFAs-induced deficit in social novelty. Our findings suggest that microbial metabolites impact social novelty through a distinct neuron population in the BNST.

Mitigating the impact of adolescence isolation on the development of social anxiety: A potential role for oxytocin

Exposure to isolation can lead to the development of social anxiety disorder (SAD), which affects 13% of Americans. There are sex differences in the prevalence of anxiety disorders, as women experience higher rates of SAD relative to men. Importantly, isolation experienced during adolescence increases the likelihood of developing SAD in adulthood. Unfortunately, the current treatments for SAD are only effective in 50–65% of patients. As such, it is critical to identify therapeutic targets for the treatment and prevention of SAD, particularly in women. Here, we discuss the links between childhood isolation and adulthood SAD. Next, we examine the preclinical models used to study the impact of isolation on social anxiety-like behaviors in rodents. Increasing evidence from both clinical and pre-clinical studies suggests oxytocin signaling is a potential target to modify social anxiety-like behaviors. We present the evidence that sex hormones influence the oxytocin system. Finally, we highlight future directions for both clinical and pre-clinical studies to further evaluate the efficacy of oxytocin as a treatment for isolation-induced SAD.

miR-124 regulates early isolation-induced social abnormalities via inhibiting myelinogenesis in the medial prefrontal cortex

Patients with autism spectrum disorder (ASD) typically experience substantial social isolation, which may cause secondary adverse effects on their brain development. miR-124 is the most abundant miRNA in the human brain, acting as a pivotal molecule regulating neuronal fate determination. Alterations of miR-124 maturation or expression are observed in various neurodevelopmental, neuropsychiatric, and neurodegenerative disorders. In the present study, we analyzed a panel of brain-enriched microRNAs in serums from 2 to 6 year old boys diagnosed with ASD. The hsa-miR-124 level was found significantly elevated in ASD boys than in age and sex-matched healthy controls. In an isolation-reared weanling mouse model, we evidenced elevated mmu-miR-124 level in the serum and the medial prefrontal cortex (mPFC). These mice displayed significant sociability deficits, as well as myelin abnormality in the mPFC, which was partially rescued by expressing the miR-124 sponge in the bilateral mPFC, ubiquitously or specifically in oligodendroglia. In cultured mouse oligodendrocyte precursor cells, introducing a synthetic mmu-miR-124 inhibited the differentiation process through suppressing expression of nuclear receptor subfamily 4 group A member 1 (Nr4a1). Overexpressing Nr4a1 in the bilateral mPFC also corrected the social behavioral deficits and myelin impairments in the isolation-reared mice. This study revealed an unanticipated role of the miR-124/Nr4a1 signaling in regulating early social experience-dependent mPFC myelination, which may serve as a potential therapy target for social neglect or social isolation-related neuropsychiatric disorders.

Pediatric neuropsychiatric syndromes associated with infection and microbiome alterations: clinical findings, possible role of the mucosal epithelium, and strategies for the development of new animal models

INTRODUCTION

: Subsets of pediatric obsessive-compulsive disorder (OCD) and autism spectrum disorder (ASD) respectively have been associated with respiratory tract infections and alterations in the intestinal microbiome. Pediatric Acute-onset Neuropsychiatric Syndromes (PANS) refers to the sudden onset of neuropsychiatric symptoms that are triggered by several different infectious and non-infectious factors. Clinical studies and animal modeling are consistent with the proposal that inflammation plays an important etiological role in PANS, as well as in ASD associated with gut dysbiosis.

AREAS COVERED

The authors provide an overview of clinical studies of PANS and ASD associated with gastrointestinal symptoms, as well as the current strategies for studying these syndromes in rodent models. Finally, the authors highlight similarities between these syndromes that may provide clues to common etiological mechanisms.

EXPERT OPINION

Although data from existing animal models are consistent with an important role for anti-neuronal antibodies in PANS triggered by GAS infection, we lack models for identifying pathophysiological mechanisms of PANS associated with other infectious and non-infectious triggers. The authors propose a strategy for developing such models that incorporates known vulnerability and triggering factors for PANS into the modeling process. This novel strategy should expand our understanding of the pathophysiology of PANS, as well as facilitate the development of new pharmacological treatments for PANS and related syndromes.

Hyperoxia Combined With B-cell Antagonist Rituximab led to Intestinal Dysbiosis in Neonatal Mice

The adverse factors impacting the intestinal microbiota of newborns remain to be elucidated. We put forward a hypothesis that hyperoxia in combination with rituximab exhibits a synergistic effect that interferes with neonatal intestinal microbiota. Six C57BL/6J mice, aged 12 weeks and pregnant 18 days, were purchased. Their pups were breastfed and raised under a 75% oxygen or conventional environment. Low‐ (20 mg/kg) and high‐dose (40 mg/kg) rituximab were intraperitoneally administered. Fecal genomic DNA was extracted and sequenced by a 16S rRNA platform. Severe intestinal dysbiosis in newborns were observed, whereas mild dysbiosis was caused by inducing hyperoxia alone, confirming the synergistic interference of the combination of hyperoxia and B‐cell antagonist (rituximab) in neonatal intestinal microbiota disruption. Slight dysbiosis was observed in the intestinal microbiota of dams, indicating their much robust ability to confront hyperoxic conditions. The abundance of Akkermansia muciniphila was significantly and extensively altered in both pups and dams after being subjecting them to hyperoxic conditions with or without rituximab administration. In conclusion, this work demonstrated that the synergistic effect of hyperoxia and rituximab led to severe intestinal dysbiosis in newborns. More studies are recommended to explore the precise regulatory mode between hyperoxia and rituximab in intestinal microbiota.

Gut Microbiome and Metabolome Changes in Mice With Acute Vestibular Deficit

Vestibular deficit is a very common disorder in clinical practice and is characterized by vertigo, spontaneous nystagmus, and autonomic nervous symptoms, including nausea, vomiting, and sweating. In addition, the comorbidity of vestibular deficit and anxiety has long been an integral component of the medical literature. Previous studies have suggested that the mechanisms underlying this comorbidity involved overlap of vestibular and cerebellar networks. Emerging evidence has shown that the microbiota–gut–brain axis plays a key role in the regulation of affective disorders. Thus, we hypothesized that the gut microbiota may be involved in the comorbidity of vestibular deficit and anxiety. To verify this, we constructed a unilateral labyrinthectomy mouse model to simulate vestibular deficit. Then, 16S rRNA gene sequencing and liquid chromatography–mass spectrometry (LC-MS) were used to analyze the microbiome and metabolome of the cecal samples collected from mice in the unilateral labyrinthectomy, sham surgery, and control groups. Notably, unilateral labyrinthectomy shaped the composition of the mouse gut microbiome, resulting in increased abundance of Lachnospiraceae NK4A136 group, Odoribacter and Roseburia and decreased abundance of Prevotella and Parasutterella at the genus level. Tax4Fun functional prediction indicated a decrease in tryptophan metabolism in mice in the unilateral labyrinthectomy group. Moreover, functional correlation of changes in gut microbes and metabolites between different groups showed that the oleamide level was negatively correlated with Odoribacter abundance (r = -0.89, p = 0.0002). The butyric acid level was positively correlated with Parasutterella abundance (r = 0.85, p = 0.0010). The propanoate level was negatively correlated with Prevotella abundance (r = -0.81, p = 0.0020). The 20-HETE level was positively correlated with Parasutterella abundance (r = 0.84, p = 0.0013). The altered microbes and metabolites were closely related to the pathogenesis of affective disorders. Our results not only offer novel insights into the vestibular deficit comorbid with anxiety but also build an important basis for future research on this etiology.

Ganoderic acids-rich ethanol extract from Ganoderma lucidum protects against alcoholic liver injury and modulates intestinal microbiota in mice with excessive alcohol intake

Alcoholic liver injury is mainly caused by excessive alcohol consumption and has become a global public health problem threatening human health. It is well known that Ganoderma lucidum possesses various excellent beneficial effects on liver function and lipid metabolism. The purpose of this study was to evaluate the underlying protective effect and action mechanism of ganoderic acids-rich G. lucidum ethanol extract (GLE) on alcohol-induced liver injury in mice with excessive alcohol intake. Results showed that oral administration of GLE could obviously inhibit the abnormal increases of serum triglyceride (TG), total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), aspartate aminotransferase (AST) and alanine aminotransferase (ALT), and also significantly protect the liver against alcohol-induced excessive hepatic lipid accumulation and pathological changes. In addition, alcohol-induced oxidative stress in liver was significantly ameliorated by the dietary intervention of GLE through reducing the hepatic levels of maleic dialdehyde (MDA) and lactate dehydrogenase (LDH), and increasing the hepatic levels of glutathione (GSH), catalase (CAT), superoxide dismutase (SOD) and alcohol dehydrogenase (ADH). Compared with the model group, GLE intervention significantly ameliorated the intestinal microbial disorder by elevating the relative abundance of Ruminiclostridium_9, Prevotellaceae_UCG-001, Oscillibacter, [Eubacterium]_xylanophilum_group, norank_f_Clostridiates_vadinBB60_group, GCA-900066225, Bilophila, Ruminococcaceae_UCG-009, norank_f_Desulfovibrionaceae and Hydrogenoanaerobacterium, but decreasing the proportion of Clostridium_sensu_stricto_1. Furthermore, liver metabolomic profiling suggested that GLE intervention had a significant regulatory effect on the composition of liver metabolites in mice with excessive alcohol intake, especially the levels of some biomarkers involved in primary bile acid biosynthesis, riboflavin metabolism, tryptophan metabolism, biosynthesis of unsaturated fatty acids, fructose and mannose metabolism, glycolysis/gluconeogenesis. Additionally, dietary supplementation with GLE significantly regulated the mRNA levels of key genes related to fatty acids metabolism, ethanol catabolism and inflammatory response in liver. Conclusively, these findings indicate that GLE has a potentially beneficial effect on alleviating alcohol-induced liver injury and may be developed as a promising functional food ingredient.

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Phytochemical analysis revealed that ethanol extract of Gaoderma lucidum (GLE) is rich in ganoderic acids.

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GLE ameliorated lipid metabolism, antioxidant function and inflammatory response in mice with excessive alcohol intake.

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Liver metabolomics based on UPLC-QTOF/MS was performed to reveal the underlying hepatoprotective effect of GLE.

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GLE intervention alleviated alcoholic liver injury partly through regulating the “gut-liver-metabolite”axis.

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Hepatic gene transcriptions related to lipid metabolism and inflammation were remarkablyinfluenced by GLE intervention.

Impact of social isolation on the oxytocinergic system: A systematic review and meta-analysis of rodent data

Social isolation (SI) stress results from a combination of intrinsic and environmental factors and is associated with a variety of negative developmental outcomes. Oxytocin (OXT) might play a role in the consequences of SI in the brain and periphery. We conducted a systematic review and meta-analysis to compile data about the effects of SI in the oxytocinergic system of rats and mice, and its relation to behavioral alterations. Five databases (EMBASE, PsychNet, PubMed, Scopus, and Web of Science) in March 2021, using ("Social Isolation" AND (mouse OR rat) AND (oxytocin OR oxytocin receptor)). This review followed the PRISMA guidelines, including registration in PROSPERO, and risk of bias assessment. The twelve articles included in this review indicated that SI was associated with decreased OXTR levels, resulting in behavioral alterations like increased aggression and anxiety-like behavior, hyperactivity, and diminished social behaviors and memory. No significant effects on OXT levels were observed. Administration of synthetic OXT or its agonists partially decreases those unwanted behaviors to similar levels of control animals.

Lingguizhugan Decoction Targets Intestinal Microbiota and Metabolites to Reduce Insulin Resistance in High-Fat Diet Rats

BACKGROUND

The increasing incidence of obesity and its complications has become a global public health problem. Lingguizhugan decoction (LGZGD) is a representative compound of traditional Chinese medicine (TCM) for metabolic diseases, such as nonalcoholic fatty liver disease, but its role in insulin resistance (IR) treatment is still less known. This study aims to evaluate the therapeutic properties of LGZGD on obesity-induced IR and explore the potential mechanism of LGZGD on gut microbiota and its metabolites in the treatment of IR.

METHODS

In this study, we induced an IR model in the form of high-fat diet (HFD) rats gavaged with LGZGD (1.64 g/kg BW) for three weeks. The IR status was measured by biochemical assays and oral glucose tolerance tests. The degrees of damage to liver function and the intestinal barrier were observed by hematoxylin and eosin (H&E) staining and immunohistochemistry. Alterations in intestinal microbiota and metabolites were assessed by 16S rRNA and an untargeted metabolomics platform.

RESULTS

Our results showed that after LGZGD treatment, the body weight, plasma insulin concentration and blood lipids were significantly decreased, and glucose tolerance and hepatic steatosis were ameliorated. In addition, small intestinal villi were restored, and the expression of Occludin was upregulated. The relative abundance of Akkermansia, Faecalibacterium and Phascolarctobacterium in the HFD-LGZG group was upregulated. Obesity-related metabolic pathways, such as bile secretion, biosynthesis of amino acids, phenylalanine metabolism, serotonergic synapse, protein digestion and absorption, taurine and hypotaurine metabolism, and primary bile acid biosynthesis, were changed. After LGZGD intervention, metabolites developed toward the healthy control group. In addition, the expression of bile acid metabolism related genes was also regulated in IR rats.

CONCLUSION

We showed that LGZGD relieved IR, possibly by regulating the composition of the fecal microbiota and its metabolites. The above studies provide a basis for further study of LGZGD in the treatment of IR and its clinical application.

Social isolation in adolescence and long-term changes in the gut microbiota composition and in the hippocampal inflammation: Implications for psychiatric disorders - Dirk Hellhammer Award Paper 2021

Exposure to early adverse experiences induces persistent changes in physiological, emotional and behavioural functions predisposing the individual to an enhanced vulnerability to develop different disorders during lifespan. The adverse outcomes depend upon the timing of the stressful experiences, and in this contest, adolescence represents a key sensitive period for brain development. Among the biological systems involved, gut microbiota has recently been proposed to act on the interplay between the stress response, brain functions and immune system, through the gut-brain axis communication. In the current study we aimed to evaluate, in a preclinical model, changes over time in the microbiota community structure in physiological condition and in response to stress during adolescence. We also aimed to correlate the microbiota composition to the inflammatory status in brain. We used the preclinical model of social deprivation in rats during adolescence, based on the lack of all social contacts, for four weeks after weaning, followed by re-socialization until adulthood. We collected fecal samples at different post-natal days to investigate the short- and long-lasting effects of social isolation on gut microbiota composition and we collected brain areas (dorsal and ventral hippocampus) samples at killing to measure a panel of inflammatory and microglia activation markers. 16 S metataxonomic sequencing analysis revealed that microbial changes were influenced by age in both isolated and controls rats, regardless of sex, whereas social isolation impacted the microbial composition in a sex-dependent manner. A multivariate analysis showed that social isolation induced short-term gut microbiota alterations in females but not in males. We also identified several stress-related genera associated with social isolation condition. In brain areas we found a specific inflammatory pattern, in dorsal and ventral hippocampus, that significantly correlated with gut microbiota composition. Overall, in this study we reported a novel sex-specific association between gut microbiota composition and inflammatory response related to social isolation paradigm during adolescence, suggesting that stressful experiences during this sensitive period could have a long-lasting impact on the development of different biological systems that could in turn influence the vulnerability to develop mental disorders later in life.