Metabolites Short-chain Fatty Acids Research Articles

Sodium butyrate causes α-synuclein degradation by an Atg5-dependent and PI3K/Akt/mTOR-related autophagy pathway

Aggregation of α-Synuclein is central to the pathogenesis of Parkinson's disease (PD). However, these α-Synuclein inclusions are not only present in brain, but also in gut. Enteroendocrine cells (EECs), which are directly exposed to the gut lumen, can express α-Synuclein and directly connect to α-Synuclein-containing nerves. Dysbiosis of gut microbiota and microbial metabolite short-chain fatty acids (SCFAs) has been implicated as a driver for PD. Butyrate is an SCFA produced by the gut microbiota. Our aim was to demonstrate how α-Synuclein expression in EECs responds to butyrate stimulation. Interestingly, we found that sodium butyrate (NaB) increases α-Synuclein mRNA expression, enhances Atg5-mediated autophagy (increased LC3B-II and decreased SQSTM1 (also known as p62) expression) in murine neuroendocrine STC-1 cells. Further, α-Synuclein mRNA was decreased by the inhibition of autophagy by using inhibitor bafilomycin A1 or by silencing Atg5 with siRNA. Moreover, the PI3K/Akt/mTOR pathway was significantly inhibited and cell apoptosis was activated by NaB. Conditioned media from NaB-stimulated STC-1 cells induced inflammation in SH-SY5Y cells. Collectively, NaB causes α-Synuclein degradation by an Atg5-dependent and PI3K/Akt/mTOR-related autophagy pathway.

Hypertension Programmed by Perinatal High-Fat Diet: Effect of Maternal Gut Microbiota-Targeted Therapy.

Hypertension can originate in early life caused by perinatal high-fat (HF) consumption. Gut microbiota and their metabolites short chain fatty acids (SCFAs), trimethylamine (TMA), and trimethylamine N-oxide (TMAO) are involved in the development of hypertension. Despite the beneficial effects of prebiotic/probiotic on human health, little is known whether maternal use of prebiotics/probiotics could protect offspring against the development of hypertension in adulthood. We investigated whether perinatal HF diet-induced programmed hypertension in adult offspring can be prevented by therapeutic uses of prebiotic inulin or probiotic Lactobacillus casei during gestation and lactation. Pregnant Sprague–Dawley rats received regular chow or HF diet (D12331, Research Diets), with 5% w/w long chain inulin (PRE), or 2 × 108 CFU/day Lactobacillus casei via oral gavage (PRO) during pregnancy and lactation. Male offspring (n = 8/group) were assigned to four groups: control, HF, PRE, and PRO. Rats were sacrificed at 16 weeks of age. Maternal prebiotic or probiotic therapy prevents elevated blood pressure (BP) programmed by perinatal HF consumption. Both prebiotic and probiotic therapies decreased the Firmicutes to Bacteroidetes ratio and renal mRNA expression of Ace, but increased abundance of genus Lactobacillus and Akkermansia. Additionally, prebiotic treatment prevents HF-induced elevation of BP is associated with reduced fecal propionate and acetate levels, while probiotic therapy restored several Lactobacillus species. Maternal probiotic or prebiotic therapy caused a reduction in plasma TMAO level and TMAO-to-TMA ratio. The beneficial effects of prebiotic or probiotic therapy on elevated BP programmed by perinatal HF diet are relevant to alterations of microbial populations, modulation of microbial-derived metabolites, and mediation of the renin-angiotensin system. Our results cast a new light on the use of maternal prebiotic/probiotic therapy to prevent hypertension programmed by perinatal HF consumption. The possibility of applying gut microbiota-targeted therapies as a reprogramming strategy for hypertension warrants further clinical translation.

Effects of acute heat stress on intestinal microbiota in grow-finishing pigs, and associations with feed intake and serum profile.

This study was conducted to assess the effects of acute heat stress (HS) on intestinal microbiota, and the associations with the changes in feed intake (FI) and serum profile. Twenty four individually housed pigs (Duroc×Large White×Landrace, 30±1kg body weight) were randomly assigned to receive one of three treatments (8 pigs/treatment): (i) thermal neutral (TN) conditions (25±1°C), (ii) HS conditions (35±1°C), (iii) pair-feeding (PF) with HS under TN conditions. After 24-h treatment, pigs were monitored to assess FI, and samples of serum and faeces were collected to investigate serum profile, microbial composition and short chain fatty acids (SCFAs). The results showed that HS decreased (P<0·05) FI compared with the TN group. Compared with TN group, HS changed the serum profile by affecting biochemical parameters and hormones related with energy metabolism and stress response; immune indicators were also altered in HS group. Most of changes in serum profile were independent of FI reduction. Additionally, HS shifted the diversity and composition of faecal microbial community by increasing (P<0·05) Proteobacteria and decreasing (P<0·05) Bacteroidetes. Moreover, HS decreased (P<0·05) the concentrations of propionate, butyrate, valerate, iso-valerate and total SCFAs in faeces in an FI-independent manner. Furthermore, the Spearman correlation analysis implied that changes of serum profile have potential correlation with alterations of faecal microbiota and their SCFAs metabolites in acute HS-treated grow-finishing pigs. Metabolism disorders caused by 24-h acute HS associated with changes of faecal microbiota and their SCFAs metabolites in an FI-independent manner in grow-finishing pigs. These results give us a new insight of the intestinal damage caused by acute HS and the underlying mechanisms.

Protective effect of Ganoderma atrum polysaccharides in acute lung injury rats and its metabolomics

The present study aimed to evaluate effect of Ganoderma atrum polysaccharide (PSG) on acute lung injury (ALI) rats and its mechanisms. Results showed that PSG exhibited protective effects against ALI by maintaining pulmonary histology, reducing levels of pro-inflammatory cytokines and NO both in serum and lung tissue. Moreover, this study further evaluated the metabolic effects of PSG based on UPLC-Triple-TOF/MS metabolomics analysis in rats. Compared with control group, LysoPC (18:2), LPA (18:1), taurocholic acid, L-histidine, and L-tryptophan were identified as metabolic biomarkers in serum of ALI group. Furthermore, biological pathways analysis demonstrated that histidine metabolism, nitrogen metabolism, tryptophan and part glycerophospholipids metabolism were notably modified by PSG treatment in ALI rats. Additionally, improved gut microbial metabolite short-chain fatty acids were found after intake of PSG in ALI rat. Altogether, PSG could control ALI-induced aberrant inflammation and its mechanisms were linked to inhibit release of pro-inflammatory mediators and reverse metabolic pathway disturbances.

The Short-Chain Fatty Acid Acetate in Body Weight Control and Insulin Sensitivity.

The interplay of gut microbiota, host metabolism, and metabolic health has gained increased attention. Gut microbiota may play a regulatory role in gastrointestinal health, substrate metabolism, and peripheral tissues including adipose tissue, skeletal muscle, liver, and pancreas via its metabolites short-chain fatty acids (SCFA). Animal and human data demonstrated that, in particular, acetate beneficially affects host energy and substrate metabolism via secretion of the gut hormones like glucagon-like peptide-1 and peptide YY, which, thereby, affects appetite, via a reduction in whole-body lipolysis, systemic pro-inflammatory cytokine levels, and via an increase in energy expenditure and fat oxidation. Thus, potential therapies to increase gut microbial fermentation and acetate production have been under vigorous scientific scrutiny. In this review, the relevance of the colonically and systemically most abundant SCFA acetate and its effects on the previously mentioned tissues will be discussed in relation to body weight control and glucose homeostasis. We discuss in detail the differential effects of oral acetate administration (vinegar intake), colonic acetate infusions, acetogenic fiber, and acetogenic probiotic administrations as approaches to combat obesity and comorbidities. Notably, human data are scarce, which highlights the necessity for further human research to investigate acetate’s role in host physiology, metabolic, and cardiovascular health.

Fecal microbiota transplantation alleviated Alzheimer\u2019s disease-like pathogenesis in APP/PS1 transgenic mice

Alzheimer’s disease (AD) is the most common dementia in the elderly. Treatment for AD is still a difficult task in clinic. AD is associated with abnormal gut microbiota. However, little is known about the role of fecal microbiota transplantation (FMT) in AD. Here, we evaluated the efficacy of FMT for the treatment of AD. We used an APPswe/PS1dE9 transgenic (Tg) mouse model. Cognitive deficits, brain deposits of amyloid-β (Aβ) and phosphorylation of tau, synaptic plasticity as well as neuroinflammation were assessed. Gut microbiota and its metabolites short-chain fatty acids (SCFAs) were analyzed by 16S rRNA sequencing and 1H nuclear magnetic resonance (NMR). Our results showed that FMT treatment could improve cognitive deficits and reduce the brain deposition of amyloid-β (Aβ) in APPswe/PS1dE9 transgenic (Tg) mice. These improvements were accompanied by decreased phosphorylation of tau protein and the levels of Aβ40 and Aβ42. We observed an increases in synaptic plasticity in the Tg mice, showing that postsynaptic density protein 95 (PSD-95) and synapsin I expression were increased after FMT. We also observed the decrease of COX-2 and CD11b levels in Tg mice after FMT. We also found that FMT treatment reversed the changes of gut microbiota and SCFAs. Thus, FMT may be a potential therapeutic strategy for AD.

Blood Pressure Abnormalities Associated with Gut Microbiota-Derived Short Chain Fatty Acids in Children with Congenital Anomalies of the Kidney and Urinary Tract.

Both kidney disease and hypertension can originate from early life. Congenital anomalies of the kidney and urinary tract (CAKUT) are the leading cause of chronic kidney disease (CKD) in children. Since gut microbiota and their metabolite short chain fatty acids (SCFAs) have been linked to CKD and hypertension, we examined whether gut microbial composition and SCFAs are correlated with blood pressure (BP) load and renal outcome in CKD children with CAKUT. We enrolled 78 children with CKD stage G1–G4. Up to 65% of children with CAKUT had BP abnormalities on 24 h ambulatory blood pressure monitoring (ABPM). CKD children with CAKUT had lower risk of developing BP abnormalities and CKD progression than those with non-CAKUT. Reduced plasma level of propionate was found in children with CAKUT, which was related to increased abundance of phylum Verrucomicrobia, genus Akkermansia, and species Bifidobacterium bifidum. CKD children with abnormal ABPM profile had higher plasma levels of propionate and butyrate. Our findings highlight that gut microbiota-derived SCFAs like propionate and butyrate are related to BP abnormalities in children with an early stage of CKD. Early assessments of these microbial markers may aid in developing potential targets for early life intervention for lifelong hypertension prevention in childhood CKD.

Low-dose tetracycline exposure alters gut bacterial metabolism and host-immune response: “Personalized” effect?

The human gut microbiome (GM) in healthy people is chronically exposed to tetracycline (TET) via environmental exposure and dietary uptake. However, limited information is available on its effect on the GM metabolome and effect on the host, especially at the dietary exposure level. Here, we investigated how TET at both sub-pharmaceutical and dietary exposure levels affects the metabolome and the secretome-induced host immune response by studying several representative gut bacteria. Interestingly, the metabolome showed a highly species-specific pattern with a distinct dose-response relationship. B. fragilis was highly sensitive to TET and vitamin, nucleotide, and amino acid metabolism pathways were the most vulnerable metabolic pathways at dietary exposure level. For key metabolite short chain fatty acids, TET significantly induced the synthesis of butyrate in B. fragilis, rather than C. sporogenes and E. coli. Furthermore, TET induced the release of lipopolysaccharides (LPS) in E. coli and enhanced the immune response; however, there was no obvious effect on B. fragilis. Interestingly, the overall immune response modulation with TET exposure relied on the ratio between E. coli and B. fragilis, possibly due to the neutralization of active LPS from E. coli by the LPS from B. fragilis. Overall, our results showed that the effect of TET from environmental exposure on the host health would be highly dependent on the GM composition, especially for the gut bacterial metabolome and secretome induced immune response.

Decreased maternal serum acetate and impaired fetal thymic and regulatory T cell development in preeclampsia

Maternal immune dysregulation seems to affect fetal or postnatal immune development. Preeclampsia is a pregnancy-associated disorder with an immune basis and is linked to atopic disorders in offspring. Here we show reduction of fetal thymic size, altered thymic architecture and reduced fetal thymic regulatory T (Treg) cell output in preeclamptic pregnancies, which persists up to 4 years of age in human offspring. In germ-free mice, fetal thymic CD4+ T cell and Treg cell development are compromised, but rescued by maternal supplementation with the intestinal bacterial metabolite short chain fatty acid (SCFA) acetate, which induces upregulation of the autoimmune regulator (AIRE), known to contribute to Treg cell generation. In our human cohorts, low maternal serum acetate is associated with subsequent preeclampsia, and correlates with serum acetate in the fetus. These findings suggest a potential role of acetate in the pathogenesis of preeclampsia and immune development in offspring.

Microbiota Metabolite Short-Chain Fatty Acids Facilitate Mucosal Adjuvant Activity of Cholera Toxin through GPR43.

The gut microbiota has been shown critical for mucosal adjuvant activity of cholera toxin (CT), a potent mucosal adjuvant. However, the mechanisms involved remain largely unknown. In this study, we report that depletion of gut bacteria significantly decreased mucosal and systemic Ab responses in mice orally immunized with OVA and CT. Feeding mice short-chain fatty acids (SCFAs) promoted Ab responses elicited by CT, and, more importantly, rescued Ab responses in antibiotic-treated mice. In addition, mice deficient in GPR43, a receptor for SCFAs, showed impaired adjuvant activity of CT. Administering CT did not promote SCFA production in the intestines; thus, SCFAs facilitated but did not directly mediate the adjuvant activity of CT. SCFAs promoted B cell Ab production by promoting dendritic cell production of BAFF and ALDH1a2, which induced B cell expression of IFN regulatory factor 4, Blimp1, and XBP1, the plasma B cell differentiation-related genes. Furthermore, when infected with Citrobacter rodentium, GPR43-/- mice exhibited decreased Ab responses and were more susceptible to infection, whereas the administration of SCFAs promoted intestinal Ab responses in wild-type mice. Our study thereby demonstrated a critical role of gut microbiota and their metabolite SCFAs in promoting mucosal adjuvant activity of CT through GPR43.

The ApoE-dependent Neuroprotective Effects of Sesamol on Diet-induced Obese Mice: The Role of Gut Microbiota and SCFAs (P06-049-19)

ObjectivesSesamol, an antioxidant lignan from sesame oil, possesses lipid lowering and neuroprotective bioactivities. Considering the distribution of sesamol in gut is much higher than brain after administration, the present work was aimed to elucidate the systemic protective effects of sesamol on dietary-induced cognitive deficits, and to determine the possible link between gut and brain. MethodsBoth wildtype and ApoE-/- mice were fed with high-fat diet (HFD) and treated with sesamol (0.05%, w/v) in drinking water for 10 weeks. The cognitive and anxiety behavioral assessment were evaluated by Morris-water maze, Y-maze, and elevated plus maze tests. The synapse ultrastructure was also detected by transmission electron microscope. Moreover, the alteration of gut microbiome and microbial metabolites short chain fatty acids (SCFAs) were also determined by 16S rDNA sequencing and GC, respectively. ResultsSesamol prevented HFD-induced bodyweight gain, insulin resistance, and hyperlipidemia. However, the behavioral tests including Morris-water maze, Y-maze, and elevated plus maze tests indicated that sesamol could only improve cognitive deficits and anxiety behaviors in wildtype but not ApoE deficient mice. Consistently, sesamol improved synapse ultrastructure and inhibited brain Aβ accumulation in brain in an ApoE-dependent manner. Moreover, sesamol prevented HFD-induced gut barrier damages and systemic inflammation. Sesamol also re-shaped gut microbiome and consequently improved the generation of microbial metabolites short chain fatty acids including acetate, propionate, and butyrate. ConclusionsTo summarized, this study revealed that the possible mechanism of neuroprotective effects of sesamol might be ApoE-dependent, and the beneficial effects of sesamol on gut microbiota/metabolites could be translated into metabolic and neurodegenerative diseases treatment. Funding SourcesThis work was financially supported by the National Key Research and Development Program of China, National Natural Science Foundation of China. Supporting Tables, Images and/or Graphs▪

ApoE-Dependent Protective Effects of Sesamol on High-Fat Diet-Induced Behavioral Disorders: Regulation of the Microbiome-Gut-Brain Axis.

Sesamol, an antioxidant lignan from sesame oil, possesses neuroprotective bioactivities. The present work was aimed to elucidate the systemic protective effects of sesamol on cognitive deficits and to determine the possible link between gut and brain. Wildtype and ApoE-/- mice were treated with a high-fat diet and sesamol (0.05%, w/v, in drinking water) for 10 weeks. Behavioral tests including Morris-water maze, Y-maze, and elevated plus maze tests indicated that sesamol could only improve cognitive deficits and anxiety behaviors in wildtype. Consistently, sesamol improved synapse ultrastructure and inhibited Aβ accumulation in an ApoE-dependent manner. Moreover, sesamol prevented dietary-induced gut barrier damages and systemic inflammation. Sesamol also reshaped gut microbiome and improved the generation of microbial metabolites short-chain fatty acids. To summarize, this study revealed that the possible mechanism of neuroprotective effects of sesamol might be ApoE-dependent, and its beneficial effects on gut microbiota/metabolites could be translated into neurodegenerative diseases treatment.

Microbiota Metabolite Butyrate Differentially Regulates Th1 and Th17 Cells' Differentiation and Function in Induction of Colitis.

How the gut microbiota regulates intestinal homeostasis is not completely clear. Gut microbiota metabolite short-chain fatty acids (SCFAs) have been reported to regulate T-cell differentiation. However, the mechanisms underlying SCFA regulation of T-cell differentiation and function remain to be investigated. CBir1, an immunodominant microbiota antigen, transgenic T cells were treated with butyrate under various T-cell polarization conditions to investigate butyrate regulation of T-cell differentiation and the mechanism involved. Transfer of butyrate-treated CBir T cells into Rag1-/- mice was performed to study the in vivo role of such T cells in inducing colitis. Although butyrate promoted Th1 cell development by promoting IFN-γ and T-bet expression, it inhibited Th17 cell development by suppressing IL-17, Rorα, and Rorγt expression. Interestingly, butyrate upregulated IL-10 production in T cells both under Th1 and Th17 cell conditions. Furthermore, butyrate induced T-cell B-lymphocyte-induced maturation protein 1 (Blimp1) expression, and deficiency of Blimp1 in T cells impaired the butyrate upregulation of IL-10 production, indicating that butyrate promotes T-cell IL-10 production at least partially through Blimp1. Rag1-/- mice transferred with butyrate-treated T cells demonstrated less severe colitis, compared with transfer of untreated T cells, and administration of anti-IL-10R antibody exacerbated colitis development in Rag-/- mice that had received butyrate-treated T cells. Mechanistically, the effects of butyrate on the development of Th1 cells was through inhibition of histone deacetylase but was independent of GPR43. These data indicate that butyrate controls the capacity of T cells in the induction of colitis by differentially regulating Th1 and Th17 cell differentiation and promoting IL-10 production, providing insights into butyrate as a potential therapeutic for the treatment of inflammatory bowel disease.

Importance of the intestinal microbiota in ocular inflammatory diseases: A review.

The purpose of this article is to review the literature on relationships between the intestinal microbiota and ocular inflammatory disease, specifically non-infectious uveitis and age-related macular degeneration. The importance of the intestinal microbiota in uveitis pathogenesis has been shown by multiple groups demonstrating that alterations in the microbiota induced by certain oral antibiotics results in reduced uveitis severity, and another group demonstrating that a commensal intestinal bacterial antigen activates retina-specific autoreactive T cells, potentially indicating a commensal trigger for uveitis. Additionally, commensal intestinal bacterial metabolite short chain fatty acids can be utilized to suppress autoimmune uveitis. Age-related macular degeneration is associated with intestinal dysbiosis, which is partially influenced by genetic risk alleles and AREDS supplementation. Strategies for therapeutically targeting the intestinal microbiota might involve several approaches, including the use of antibiotics, dietary changes, drugs that supplement beneficial bacterial metabolites or target causative bacterial strains, dietary strategies or faecal microbial transplantation. In summary, the intestinal microbiota are at the cross-roads of genetic and environmental factors that can promote ocular conditions such as non-infectious uveitis and age-related macular degeneration, partially via its dynamic influence on mucosal and systemic immunity. The intestinal microbiome thus represents a salient potential target for therapeutic modulation to treat these potentially blinding conditions.

The Effect of Inulin on Lifespan, Related Gene Expression and Gut Microbiota in InRp5545/TM3 Mutant Drosophila melanogaster: A Preliminary Study.

Inulin is considered an efficient prebiotic and is beneficial for metabolic diseases via promoting intestinal probiotic enrichment and the metabolites of short-chain fatty acids (SCFAs). However, the effect of inulin on patients with InR deficiencies has seldom been reported. In this study, the lifespan, related gene expression, and gut microbiota of InRp5545/TM3 (insulin receptor mutant) Drosophila melanogaster under inulin treatment were investigated. The results showed that the lifespan was extended in only males and not in females. Furthermore, distinctly different patterns of gene expression were found between males and females, especially in the insulin/insulin-like growth factor (IGF)-like signalling (IIS) and target of rapamycin (TOR) pathways. Additionally, as a link between inulin and lifespan responses, the gut microbiota was distinctly separated by gender in both the standard diet group and the inulin treatment group, and the relationship between lifespan and the gut microbiota community was stronger in male flies than in females. This study provides preliminary evidence for the gender-dependent lifespan responses to inulin in insulin signalling-deficient Drosophila. However, controls such as wild-type and TM3 flies, and more InR mutant strains with different genetic backgrounds need to be further investigated to elucidate the mechanisms underlying the phenomenon.

A sensitive GC/MS detection method for analyzing microbial metabolites short chain fatty acids in fecal and serum samples

Gut microbiota and their major metabolites, short-chain fatty acids (SCFAs), are recognized as important players in gut homeostasis and metabolic disease occurance. A convenient and sensitive detection method is needed to profile SCFAs in limited and complex biological samples. The gas chromatography/mass spectrometry (GC/MS) is the most common method for SCFAs profiling in biological samples. Trimethylsilyl (TMS) derivatization reagents such as N, O-bis(trimethyl-silyl)-trifluoroacetamide (BSTFA) are commonly used in GC/MS analysis to improve sensitivity and accuracy, but they were barely used in SCFA analysis due to their sensitivity to moisture and the volatility of SCFAs. Here, we developed a rapid, convenient and reliable method for SCFAs profiling in small amounts of fecal and serum samples by GC/MS using BSTFA in combination with sodium sulfate dehydration pretreatment. SCFAs were extracted with anhydrous ether from acidified fecal water extract or serum samples, followed by dehydration with sodium sulfate and BSTFA derivatization at a reduced temperature. Select ion monitoring mode was used for highly sensitive quantification of SCFAs by GC/MS. The derivation with BSTFA at 37 °C or 22 °C showed an excellent linearity (R2 > 0.999), good recoveries (81.27–128.42%), high repeatability (RSD < 2%) and low limit of detections (LODs) of different SCFAs ranging from 0.064 to 0.067 µM. All major SCFAs including acetic acid, propionic acid, isobutyric acid, butyric acid, isovaleric acid and valeric acid were identified and quantified accurately in fecal and serum samples. In conclusions, a reliable, convenient and sensitive method wasdeveloped for the measurement of SCFA and other volatile compounds in small biological samples using sodium sulfate dehydration pretreatment and BSTFA derivatization-based GC/MS analyses.

Progress and perspectives of short‐chain fatty acids in aquaculture

AbstractGut microbiota is important and plays a crucial role in the host health and nutritional metabolism through multiple mechanisms. Short‐chain fatty acids (SCFAs), which are carboxylic acids with aliphatic tails &lt; 6 carbons, are mainly produced by anaerobic microbiota through fermentation of carbohydrates in the intestine. Acetate, propionate and butyrate are the most abundant SCFAs metabolites, important in energy homoeostasis, metabolism and the maintenance of gut health. In this review, we describe and document what is known about the production, absorption, transport and receptors as well as the factors that affect SCFA production in aquatic animals. Some evidence on the roles that SCFAs as feed additives play in improving growth performance, digestibility, survival rate, immune responses, disease resistance and structure and function of the intestinal tract and abundance of commensal microbiota in aquatic animals is summarized. In addition, the immune regulatory mechanism of SCFAs is highlighted. Although the effects of SCFAs in aquatic animals have been explored, further research is needed to profoundly investigate the mechanisms that by which SCFAs induce their effects on host metabolism.

Short-chain fatty acids: microbial metabolites that alleviate stress-induced brain-gut axis alterations.

Chronic (psychosocial) stress changes gut microbiota composition, as well as inducing behavioural and physiological deficits. The microbial metabolites short-chain fatty acids (SCFAs) have been implicated in gastrointestinal functional, (neuro)immune regulation and host metabolism, but their role in stress-induced behavioural and physiological alterations is poorly understood. Administration of SCFAs to mice undergoing psychosocial stress alleviates enduring alterations in anhedonia and heightened stress-responsiveness, as well as stress-induced increases in intestinal permeability. In contrast, chronic stress-induced alterations in body weight gain, faecal SCFAs and the gene expression of the SCFA receptors FFAR2 and FFAR3 remained unaffected by SCFA supplementation. These results present novel insights into mechanisms underpinning the influence of the gut microbiota on brain homeostasis, behaviour and host metabolism, informing the development of microbiota-targeted therapies for stress-related disorders. There is a growing recognition of the involvement of the gastrointestinal microbiota in the regulation of physiology and behaviour. Microbiota-derived metabolites play a central role in the communication between microbes and their host, with short-chain fatty acids (SCFAs) being perhaps the most studied. SCFAs are primarily derived from fermentation of dietary fibres and play a pivotal role in host gut, metabolic and immune function. All these factors have previously been demonstrated to be adversely affected by stress. Therefore, we sought to assess whether SCFA supplementation could counteract the enduring effects of chronic psychosocial stress. C57BL/6J male mice received oral supplementation of a mixture of the three principle SCFAs (acetate, propionate and butyrate). One week later, mice underwent 3weeks of repeated psychosocial stress, followed by a comprehensive behavioural analysis. Finally, plasma corticosterone, faecal SCFAs and caecal microbiota composition were assessed. SCFA treatment alleviated psychosocial stress-induced alterations in reward-seeking behaviour, and increased responsiveness to an acute stressor and in vivo intestinal permeability. In addition, SCFAs exhibited behavioural test-specific antidepressant and anxiolytic effects, which were not present when mice had also undergone psychosocial stress. Stress-induced increases in body weight gain, faecal SCFAs and the colonic gene expression of the SCFA receptors free fatty acid receptors 2 and 3 remained unaffected by SCFA supplementation. Moreover, there were no collateral effects on caecal microbiota composition. Taken together, these data show that SCFA supplementation alleviates selective and enduring alterations induced by repeated psychosocial stress and these data may inform future research into microbiota-targeted therapies for stress-related disorders.

Short-Chain Fatty Acids Prevent Diabetic Nephropathy In Vivo and In Vitro

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease (ESRD). Over the past decade, the gut microbiota metabolites—short-chain fatty acids (SCFAs), have emerged as new therapeutic targets of systemic inflammatory diseases and kidney injury such as acute kidney injury (AKI) via GPRs-β-arrestins signaling pathway and histone deacetylase-inhibiting (HDACi) properties. However, it is unclear whether SCFAs might prevent DN. Therefore, we evaluated the role and mechanism of the three main SCFAs (acetate, propionate, and butyrate) in streptozotocin (STZ) and high-fat diet (HFD)-induced type 2 diabetes (T2D) and DN mouse model in vivo and in high glucose-induced mouse glomerular mesangial cells (GMCs) and human proximal renal tubular epithelia cells in vitro. Our results found that exogenous SCFAs administration, especially butyrate, protected from experimental T2D, preventing the renal dysfunction and inhibiting oxidative stress and NF-κB inflammatory signaling in vivo. The GPR43 expression decreased, however, β-arrestin-2 expression increased in both high glucose-stimulated renal intrinsic cells and in DN kidney tissue. We hypothesized that SCFAs-mediated GPR43-β-arrestin-2 signaling might modulate kidney injury. GPR43 was over-expressed or suppressed by transfection with a GPR43 expressing vector or siRNA-GPR43 respectively. Exogenous SCFAs-mediated the anti-oxidative stress and anti-inflammatory effects were significantly facilitated or imitated by over-expression GPR43 or GPR43 agonist, but which were inhibited by siRNA-GPR43. Specifically, co-IP revealed that butyrate regulated the interaction between I-κBα and β-arrestin-2 via GPR43. Overall, this is the first observation of the potential therapeutic role of SCFAs in DN, we demonstrated that SCFAs improved STZ and HFD-induced renal dysfunction and inhibited NF-κB activation through GPR43-β-arrestin-2 signaling, suggesting a likely mechanism for SCFAs-mediated therapeutic effect in DN. Disclosure W. Huang: None. Y. Xu: None. Y. Xu: None. L. Zhou: None. C. Gao: None.

Cholera toxin requires microbiota metabolites short-chain fatty acids for its mucosal adjuvant activity

Abstract Cholera toxin (CT) is a potent mucosal adjuvant, however, the mechanisms by which CT induces both mucosal and systemic immune responses are still not completely understood. It has been shown recently that gut microbiota is critical in inducing immune response by CT, however, the mechanisms involved remain largely unknown. We demonstrated in this study that gut microbiota metabolites short-chain fatty acids (SCFA), which are solely metabolic products of gut microbiota from dietary fiber, are required for CT in inducing antigen-specific IgG and IgA responses after oral immunization. Depleting of gut bacteria by antibiotics significantly decreased mucosal and systemic IgG and IgA responses in mice orally immunized with ovalbumin (OVA) and CT. Feeding SCFA acetate and butyrate rescued antibody responses in antibiotics-treated WT mice. Furthermore, deficiency of GPR43, a SCFA binding receptor, impaired CT’s adjuvant activity. Acetate and butyrate did not directly act on B cells to promote IgG production, but promoted B cell IgG production and plasma B cell differentiation related genes in the presence of WT but not GPR43−/− DC. Furthermore, SCFA increased IgG production by both WT and GPR43−/− B cells when cultured with WT DC, indicating a crucial role for DC expression of GPR43 in SCFA induction of B cell IgG production. Mechanistically, SCFA promoted DC expressions of BAFF, a B cell activating factor, and Aldh1a2, an enzyme promoting production of retinoic acid (RA) from Vitamin A. Blockade either RA or BAFF signaling significantly inhibited SCFA induced B-cell IgG production. Therefore, our study indicated a critical role of gut microbiota and their metabolites SCFA in promoting the mucosal adjuvant activity of CT through partially GPR43.