Butyrate attenuates the stemness of lung cancer cells through lysosome Fe2+- and SLC7A11-mediated ferroptosis.

Cancer stem cells (CSCs) are considered key contributors to tumor progression, and ferroptosis has been identified as a potential target for CSCs. We have previously shown that butyrate enhances the ferroptosis induced by erastin in lung cancer cell, this study aimed to investigate the impact of butyrate on the progression of lung CSCs. To investigate these effects, we constructed a series of in vitro experiments, including 3D non-adherent sphere-formation, cytometry analysis, assessment of CSC marker expression, cell migration assay, and in vivo tumorigenesis analyses. Additionally, the influence of butyrate on chemotherapeutic sensitivity were determined through both in vitro and in vivo experiments. Mechanistically, immunofluorescence analysis was employed to examine the localization of biotin-conjugated butyrate. We identified that butyrate predominantly localized in the lysosome and concurrently recruited Fe2+ in lysosome. Moreover, butyrate reduced the stability of SLC7A11 protein stability in lung cancer cells through ubiquitination and proteasome degradation. Importantly, the effects of butyrate on lung CSCs were found to be dependent on lysosome Fe2+- and SLC7A11-mediated ferroptosis. In summary, our results demonstrate that butyrate could induce the ferroptosis in lung CSCs by recruiting Fe2+ in lysosome and promoting the ubiquitination-lysosome degradation of SLC7A11 protein.

Chronotropic and vasoactive properties of the gut bacterial short chain fatty acids in larval zebrafish.

Short-chain fatty acids (SCFAs) by the gut bacteria have been associated with cardiovascular dysfunction in humans and rodents. However, studies exploring effects of SCFAs on cardiovascular parameters in the zebrafish, an increasingly popular model in cardiovascular research, remain limited. Here, we performed fecal bacterial 16S sequencing and gas chromatography/mass spectrometry (GC-MS) to determine the composition and abundances of gut microbiota and SCFAs in adult zebrafish. Following this, the acute effects of major SCFAs on heart rate and vascular tone were measured in anaesthetized zebrafish larvae using fecal concentrations of butyrate, acetate, and propionate. Lastly, we investigated if co-incubation with butyrate may lessen the effects of angiotensin II (Ang II) and phenylephrine (PE) on vascular tone in anaesthetized zebrafish larvae. We found that the abundance in Proteobacteria, Firmicutes, and Fusobacteria phyla in the adult zebrafish resembled those reported in rodents and humans. SCFA levels with highest concentration of acetate (27.43µM), followed by butyrate (2.19µM) and propionate (1.65µM) were observed in the fecal samples of adult zebrafish. Immersion in butyrate and acetate produced a ~20% decrease in heart rate (HR), respectively, with no observed effects of propionate. Butyrate alone also produced a ~25% decrease in the cross-sectional width of the dorsal aorta (DA) at 60 min (*P<0.05), suggesting compensatory vasoconstriction, with no effects of either acetate or propionate. In addition, butyrate significantly alleviated the decrease in DA cross-sectional width produced by both Ang II and PE. We demonstrate the potential for zebrafish in investigation of host-microbiota interactions in cardiovascular health.

Dietary sodium acetate and sodium butyrate improve high-carbohydrate diet utilization by regulating gut microbiota, liver lipid metabolism, oxidative stress, and inflammation in largemouth bass (Micropterus salmoides).

BACKGROUND: Adequate level of carbohydrates in aquafeeds help to conserve protein and reduce cost. However, studies have indicated that high-carbohydrate (HC) diet disrupt the homeostasis of the gut-liver axis in largemouth bass, resulting in decreased intestinal acetate and butyrate level. METHOD: Herein, we had concepted a set of feeding experiment to assess the effects of dietary sodium acetate (SA) and sodium butyrate (SB) on liver health and the intestinal microbiota in largemouth bass fed an HC diet. The experimental design comprised 5 isonitrogenous and isolipidic diets, including LC (9% starch), HC (18% starch), HCSA (18% starch; 2 g/kg SA), HCSB (18% starch; 2 g/kg SB), and HCSASB (18% starch; 1 g/kg SA + 1 g/kg SB). Juvenile largemouth bass with an initial body weight of 7.00 ± 0.20 g were fed on these diets for 56 d. RESULTS: We found that dietary SA and SB reduced hepatic triglyceride accumulation by activating autophagy (ATG101, LC3B and TFEB), promoting lipolysis (CPT1α, HSL and AMPKα), and inhibiting adipogenesis (FAS, ACCA, SCD1 and PPARγ). In addition, SA and SB decreased oxidative stress in the liver (CAT, GPX1α and SOD1) by activating the Keap1-Nrf2 pathway. Meanwhile, SA and SB alleviated HC-induced inflammation by downregulating the expression of pro-inflammatory factors (IL-1ß, COX2 and Hepcidin1) through the NF-κB pathway. Importantly, SA and SB increased the abundance of bacteria that produced acetic acid and butyrate (Clostridium_sensu_stricto_1). Combined with the KEGG analysis, the results showed that SA and SB enriched carbohydrate metabolism and amino acid metabolism pathways, thereby improving the utilization of carbohydrates. Pearson correlation analysis indicated that growth performance was closely related to hepatic lipid deposition, autophagy, antioxidant capacity, inflammation, and intestinal microbial composition. CONCLUSIONS: In conclusion, dietary SA and SB can reduce hepatic lipid deposition; and alleviate oxidative stress and inflammation in largemouth bass fed on HC diet. These beneficial effects may be due to the altered composition of the gut microbiota caused by SA and SB. The improvement effects of SB were stronger than those associated with SA.

The effect of oral butyrate on colonic short-chain fatty acid transporters and receptors depends on microbial status.

Butyrate, a metabolite produced by gut bacteria, has demonstrated beneficial effects in the colon and has been used to treat inflammatory bowel diseases. However, the mechanism by which butyrate operates remains incompletely understood. Given that oral butyrate can exert either a direct impact on the gut mucosa or an indirect influence through its interaction with the gut microbiome, this study aimed to investigate three key aspects: (1) whether oral intake of butyrate modulates the expression of genes encoding short-chain fatty acid (SCFA) transporters (Slc16a1, Slc16a3, Slc16a4, Slc5a8, Abcg2) and receptors (Hcar2, Ffar2, Ffar3, Olfr78, Olfr558) in the colon, (2) the potential involvement of gut microbiota in this modulation, and (3) the impact of oral butyrate on the expression of colonic SCFA transporters and receptors during colonic inflammation. Specific pathogen-free (SPF) and germ-free (GF) mice with or without DSS-induced inflammation were provided with either water or a 0.5% sodium butyrate solution. The findings revealed that butyrate decreased the expression of Slc16a1, Slc5a8, and Hcar2 in SPF but not in GF mice, while it increased the expression of Slc16a3 in GF and the efflux pump Abcg2 in both GF and SPF animals. Moreover, the presence of microbiota was associated with the upregulation of Hcar2, Ffar2, and Ffar3 expression and the downregulation of Slc16a3. Interestingly, the challenge with DSS did not alter the expression of SCFA transporters, regardless of the presence or absence of microbiota, and the effect of butyrate on the transporter expression in SPF mice remained unaffected by DSS. The expression of SCFA receptors was only partially affected by DSS. Our results indicate that (1) consuming a relatively low concentration of butyrate can influence the expression of colonic SCFA transporters and receptors, with their expression being modulated by the gut microbiota, (2) the effect of butyrate does not appear to result from direct substrate-induced regulation but rather reflects an indirect effect associated with the gut microbiome, and (3) acute colon inflammation does not lead to significant changes in the transcriptional regulation of most SCFA transporters and receptors, with the effect of butyrate in the inflamed colon remaining intact.

Relationship of endogenous plasma concentrations of ß-hydroxy ß-methyl butyrate (HMB) with frailty in community dwelling older adults with type-2 diabetes mellitus.

BACKGROUND: Supplementation with ß-hydroxy ß-methyl butyrate (HMB) appears to be effective in preserving muscle in older adults. However, the association between endogenously produced HMB with frailty has not been studied in people with chronic disease. OBJECTIVES: The purpose of this study is to explore whether an association exists between endogenous HMB levels and frailty status in older adults with type-2 diabetes mellitus (T2DM). METHODS: Data were taken from the Toledo Study of Healthy Ageing, a community-dwelling aged (65 years+) cohort. Frailty was assessed at baseline and at 2.99 median years according to the Frailty Phenotype (FP) standardized to our population and the Frailty Trait Scale 12 (FTS12). The associations between HMB levels and frailty were assessed using three nested multivariate logistic regressions and segmented by sex. Glucose, HMB and glucose interaction, age and body composition were used as covariables. RESULTS: 255 participants (mean age 75.3 years, 52.94% men) were included. HMB levels showed an inverse cross-sectional association with frailty, which was modified when the interaction term HMB*glucose was included, remaining significant only for FTS12 [OR (95% CI): 0.436 (0.253, 0.751), p-value 0.003]. The association between HMB endogenous levels and FTS12 appears to be independent of sex, in which the association was maintained after adjusting for the covariates. However, there appears to be threshold points for glucose levels, above which the protective effect of HMB is lost: 145.4 mg/dl adjusted by gender for the whole sample and 149.6 mg/dl and 138.9 mg/dl for men and women, respectively. Endogenous HMB levels were not found to be associated with incident frailty. CONCLUSIONS: Cross-sectional analysis revealed that endogenous HMB levels were inversely associated with frailty as assessed by the FTS12 in older people with T2DM. This association was found to be dependent on circulating fasted glucose levels.

Comparative transcriptome and metabolite profiling reveal diverse pattern of CYP-TS gene expression during corosolic acid biosynthesis in Lagerstroemia speciosa (L.) Pers.

KEY MESSAGE: Extensive leaf transcriptome profiling and differential gene expression analysis of field grown and elicited shoot cultures of L. speciosa suggest that differential synthesis of CRA is mediated primarily by CYP and TS genes, showing functional diversity. Lagerstroemia speciosa L. is a tree species with medicinal and horticultural attributes. The pentacyclic triterpene, Corosolic acid (CRA) obtained from this species is widely used for the management of diabetes mellitus in traditional medicine. The high mercantile value of the compound and limited availability of innate resources entail exploration of alternative sources for CRA production. Metabolic pathway engineering for enhanced bioproduction of plant secondary metabolites is an attractive proposition for which, candidate genes in the pathway need to be identified and characterized. Therefore, in the present investigation, we focused on the identification of cytochrome P450 (CYP450) and oxidosqualene cyclases (OSC) genes and their differential expression during biosynthesis of CRA. The pattern of differential expression of these genes in the shoot cultures of L. speciosa, elicited with different epigenetic modifiers (azacytidine (AzaC), sodium butyrate (NaBu) and anacardic acid (AA)), was studied in comparison with field grown plant. Further, in vitro cultures with varying (low to high) concentrations of CRA were systematically assessed for the expression of CYP-TS and associated genes involved in CRA biosynthesis by transcriptome sequencing. The sequenced samples were de novo assembled into 180,290 transcripts of which, 92,983 transcripts were further annotated by UniProt. The results are collectively given in co-occurrence heat maps to identify the differentially expressed genes. The combined transcript and metabolite profiles along with RT-qPCR analysis resulted in the identification of CYP-TS genes with high sequence variation. Further, instances of concordant/discordant relation between CRA biosynthesis and CYP-TS gene expression were observed, indicating functional diversity in genes.

Tranilast alleviates visceral hypersensitivity and colonic hyperpermeability by suppressing NLRP3 inflammasome activation in irritable bowel syndrome rat models.

Visceral hypersensitivity resulting from compromised gut barrier with activated immune system is a key feature of irritable bowel syndrome (IBS). Corticotropin-releasing factor (CRF) and Toll-like receptor 4 (TLR4) activate proinflammatory cytokine signaling to induce these changes, which is one of the mechanisms of IBS. As activation of the NLRP3 inflammasome by lipopolysaccharide (LPS) or TLR4 leads to release interleukin (IL)-1ß, the NLRP3 inflammasome may be involved in the pathophysiology of IBS. Tranilast, an anti-allergic drug has been demonstrated to inhibit the NLRP3 inflammasome, and we evaluated the impact of tranilast on visceral hypersensitivity and colonic hyperpermeability induced by LPS or CRF (IBS rat model). Visceral pain threshold caused by colonic balloon distention was measured by monitoring abdominal muscle contractions electrophysiologically. Colonic permeability was determined by quantifying the absorbed Evans blue within the colonic tissue. Colonic protein levels of NLRP3 and IL-1ß were assessed by immunoblot or ELISA. Intragastric administration of tranilast (20-200 mg/kg) for 3 days inhibited LPS (1 mg/kg)-induced visceral hypersensitivity and colonic hyperpermeability in a dose-dependent manner. Simultaneously, tranilast also abolished these alterations induced by CRF (50 µg/kg). LPS increased colonic protein levels of NLRP3 and IL-1ß, and tranilast inhibited these changes. ß-hydroxy butyrate, an NLRP3 inhibitor, also abolished visceral hypersensitivity and colonic hyperpermeability caused by LPS. In contrast, IL-1ß induced similar GI alterations to LPS, which were not modified by tranilast. In conclusion, tranilast improved visceral pain and colonic barrier by suppression of the NLRP3 inflammasome in IBS rat models. Tranilast may be useful for IBS treating.

Intratumor microbiome-derived butyrate promotes lung cancer metastasis.

Most recurrences of lung cancer (LC) occur within 3 years after surgery, but the underlying mechanism remains unclear. Here, we collect LC tissues with shorter (<3 years, recurrence group) and longer (>3 years, non-recurrence group) recurrence-free survival. By using 16S sequencing, we find that intratumor microbiome diversity is lower in the recurrence group and butyrate-producing bacteria are enriched in the recurrence group. The intratumor microbiome signature and circulating microbiome DNA can accurately predict LC recurrence. We prove that intratumor injection of butyrate-producing bacteria Roseburia can promote subcutaneous tumor growth. Mechanistically, bacteria-derived butyrate promotes LC metastasis by increasing expression of H19 in tumor cells through inhibiting HDAC2 and increasing H3K27 acetylation at the H19 promoter and inducing M2 macrophage polarization. Depletion of macrophages partially abolishes the metastasis-promoting effect of butyrate. Our results provide evidence for the cross-talk between the intratumor microbiome and LC metastasis and suggest the potential prognostic and therapeutic value of the intratumor microbiome.

Butyric acid and prospects for creation of new medicines based on its derivatives: a literature review.

The widespread use of antimicrobials causes antibiotic resistance in bacteria. The use of butyric acid and its derivatives is an alternative tactic. This review summarizes the literature on the role of butyric acid in the body and provides further prospects for the clinical use of its derivatives and delivery methods to the animal body. Thus far, there is evidence confirming the vital role of butyric acid in the body and the effectiveness of its derivatives when used as animal medicines and growth stimulants. Butyric acid salts stimulate immunomodulatory activity by reducing microbial colonization of the intestine and suppressing inflammation. Extraintestinal effects occur against the background of hemoglobinopathy, hypercholesterolemia, insulin resistance, and cerebral ischemia. Butyric acid derivatives inhibit histone deacetylase. Aberrant histone deacetylase activity is associated with the development of certain types of cancer in humans. Feed additives containing butyric acid salts or tributyrin are used widely in animal husbandry. They improve the functional status of the intestine and accelerate animal growth and development. On the other hand, high concentrations of butyric acid stimulate the apoptosis of epithelial cells and disrupt the intestinal barrier function. This review highlights the biological activity and the mechanism of action of butyric acid, its salts, and esters, revealing their role in the treatment of various animal and human diseases. This paper also discussed the possibility of using butyric acid and its derivatives as surface modifiers of enterosorbents to obtain new drugs with bifunctional action.

Gut microbiota-derived butyrate restores impaired regulatory T cells in patients with AChR myasthenia gravis via mTOR-mediated autophagy.

More than 80% of patients with myasthenia gravis (MG) are positive for anti-acetylcholine receptor (AChR) antibodies. Regulatory T cells (Tregs) suppress overproduction of these antibodies, and patients with AChR antibody-positive MG (AChR MG) exhibit impaired Treg function and reduced Treg numbers. The gut microbiota and their metabolites play a crucial role in maintaining Treg differentiation and function. However, whether impaired Tregs correlate with gut microbiota activity in patients with AChR MG remains unknown. Here, we demonstrate that butyric acid-producing gut bacteria and serum butyric acid level are reduced in patients with AChR MG. Butyrate supplementation effectively enhanced Treg differentiation and their suppressive function of AChR MG. Mechanistically, butyrate activates autophagy of Treg cells by inhibiting the mammalian target of rapamycin. Activation of autophagy increased oxidative phosphorylation and surface expression of cytotoxic T-lymphocyte-associated protein 4 on Treg cells, thereby promoting Treg differentiation and their suppressive function in AChR MG. This observed effect of butyrate was blocked using chloroquine, an autophagy inhibitor, suggesting the vital role of butyrate-activated autophagy in Tregs of patients with AChR MG. We propose that gut bacteria derived butyrate has potential therapeutic efficacy against AChR MG by restoring impaired Tregs.

Protective effects of sodium butyrate on fluorosis in rats by regulating bone homeostasis and serum metabolism.

Fluorosis due to high fluoride levels in drinking water profoundly affects the development of human skeletal and dental structures. Sodium butyrate (NaB) has been found to regulate overall bone mass and prevent pathological bone loss. However, the mechanism of NaB action on fluorosis remains unclear. In this study, a rat model of fluorosis induced by 100 mg/L sodium fluoride was used to investigate the impact of NaB on bone homeostasis and serum metabolomics. It was found that NaB significantly reduced the levels of bone resorption markers CTX-Ⅰ and TRACP-5B in fluorosis rats. Moreover, NaB increased calcium and magnesium levels in bone, while decreasing phosphorus levels. In addition, NaB improved various bone microstructure parameters, including bone mineral density (BMD), trabecular thickness (Tb. Th), trabecular bone separation (Tb. SP), and structural model index (SMI) in the femur. Notably, NaB intervention also enhanced the antioxidant capacity of plasma in fluorosis rats. Furthermore, a comprehensive analysis of serum metabolomics by LC-MS revealed a significant reversal trend of seven biomarkers after the intervention of NaB. Finally, pathway enrichment analysis based on differential metabolites indicated that NaB exerted protective effects on fluorosis by modulating arginine and proline metabolic pathways. These findings suggest that NaB has a beneficial effect on fluorosis and can regulate bone homeostasis by ameliorating metabolic disorders.

Swapping White for High-Fibre Bread Increases Faecal Abundance of Short-Chain Fatty Acid-Producing Bacteria and Microbiome Diversity: A Randomized, Controlled, Decentralized Trial.

A low-fibre diet leads to gut microbiota imbalance, characterized by low diversity and reduced ability to produce beneficial metabolites, such as short-chain fatty acids (SCFAs). This imbalance is associated with poor gastrointestinal and metabolic health. We aimed to determine whether one dietary change, substitution of white bread with high-fibre bread, improves gut microbiota diversity and SCFA-producing capability. Twenty-two healthy adults completed a two-phase randomized, cross-over trial. The participants consumed three slices of a high-fibre bread (Prebiotic Cape Seed Loaf with BARLEYmax®) or control white bread as part of their usual diet for 2 weeks, with the treatment periods separated by a 4-week washout. High-fibre bread consumption increased total dietary fibre intake to 40 g/d, which was double the amount of fibre consumed at baseline or during the white bread intervention. Compared to white bread, the high-fibre bread intervention resulted in higher faecal alpha diversity (Shannon, p = 0.014) and relative abundance of the Lachnospiracae ND3007 group (p < 0.001, FDR = 0.019) and tended to increase the butyrate-producing capability (p = 0.062). In conclusion, substituting white bread with a high-fibre bread improved the diversity of gut microbiota and specific microbes involved in SCFA production and may enhance the butyrate-producing capability of gut microbiota in healthy adults. These findings suggest that a single dietary change involving high-fibre bread provides a practical way for adults to exceed recommended dietary fibre intake levels that improve gut microbiota composition and support gastrointestinal and metabolic health.

Mechanism of sodium butyrate, a metabolite of gut microbiota, regulating cardiac fibroblast transdifferentiation via the NLRP3/Caspase-1 pyroptosis pathway.

BACKGROUND: Cardiac fibroblasts (CFs) are activated after initial injury, and then differentiate into myofibroblasts (MFs), which play a pivotal role as the primary mediator cells in pathological remodeling. Sodium butyrate (NaB), being a metabolite of gut microbiota, exhibits anti-inflammatory property in local therapies on sites other than the intestine. Thus, this study aimed to probe the mechanism by which NaB regulates CFs transdifferentiation through the NLRP3/Caspase-1 pyroptosis pathway. METHODS: CFs were cultured in vitro and induced into MFs by TGFß1. CFs were identified by immunofluorescence labelling technique of vimentin and α-SMA, followed by treatment with NaB or NLRP3 inflammasome inhibitor (CY-09) and its activator [nigericin sodium salt (NSS)]. The expression levels of α-SMA, GSDMD-N/NLRP3/cleaved Caspase-1 proteins, and inflammatory factors IL-1ß/IL-18/IL-6/IL-10 were determined using immunofluorescence, Western blot and ELISA. Cell proliferation and migration were evaluated using the CCK-8 assay and the cell scratch test, respectively. RESULTS: Following the induction of TGFß1, CFs exhibited increased expression levels of α-SMA proteins and IL-6/IL-10, as well as cell proliferative and migratory abilities. TGFß1 induced CFs to differentiate into MFs, while NaB inhibited this differentiation. NaB inactivated the NLRP3/Caspase-1 pyroptosis pathway. CY-09 demonstrated inhibitory effects on the NLRP3/Caspase-1 pyroptosis pathway, leading to a reduction in TGFß1-induced CFs transdifferentiation. NSS activated the NLRP3/Caspase-1 pyroptosis pathway, and thus partially counteracting the inhibitory effect of intestinal microbiota metabolite NaB on CFs transdifferentiation. CONCLUSION: NaB, a metabolite of the gut microbiota, inhibited the activation of the NLRP3/Caspase-1 pyroptosis pathway in TGFß1-induced CFs, repressed the transdifferentiation of CFs into MFs.

A high fiber diet or supplementation with Lactococcus lactis subspecies cremoris to pregnant mice confers protection against intestinal injury in adult offspring.

The diet during pregnancy, or antenatal diet, influences the offspring's intestinal health. We previously showed that antenatal butyrate supplementation reduces injury in adult murine offspring with dextran sulfate sodium (DSS)-induced colitis. Potential modulators of butyrate levels in the intestine include a high fiber diet or dietary supplementation with probiotics. To test this, we supplemented the diet of pregnant mice with high fiber, or with the probiotic bacteria Lactococcus lactis subspecies cremoris or Lactobacillus rhamnosus GG. We then induced chronic colitis with DSS in their adult offspring. We demonstrate that a high fiber antenatal diet, or supplementation with Lactococcus lactis subspecies cremoris during pregnancy diminished the injury from DSS-induced colitis in offspring. These data are evidence that antenatal dietary interventions impact offspring gut health and define the antenatal diet as a therapeutic modality to enhance offspring intestinal health.

ß-hydroxybutyrate exposure restores mitochondrial function in skeletal muscle satellite cells of critically ill patients.

BACKGROUND & AIM: Dysfunction of skeletal muscle satellite cells might impair muscle regeneration and prolong ICU-acquired weakness, a condition associated with disability and delayed death. This study aimed to elucidate the distinct metabolic effects of critical illness and ß-OH-butyrate on satellite cells isolated from these patients. METHODS: Satellite cells were extracted from vastus lateralis muscle biopsies of patients with ICU-acquired weakness (n = 10) and control group of healthy volunteers or patients undergoing elective hip replacement surgery (n = 10). The cells were exposed to standard culture media supplemented with ß-OH-butyrate to assess its influence on cell proliferation by ELISA, mitochondrial functions by extracellular flux analysis, electron transport chain complexes by high resolution respirometry, and ROS production by confocal microscopy. RESULTS: Critical illness led to a decline in maximal respiratory capacity, ATP production and glycolytic capacity and increased ROS production in ICU patients' cells. Notably, the function of complex II was impaired due to critical illness but restored to normal levels upon exposure to ß-OH-butyrate. While ß-OH-butyrate significantly reduced ROS production in both control and ICU groups, it had no significant impact on global mitochondrial functions. CONCLUSION: Critical illness induces measurable bioenergetic dysfunction of skeletal muscle satellite cells. ß-OH-butyrate displayed a potential in rectifying complex II dysfunction caused by critical illness and this warrants further exploration.

Brain histamine improves colonic hyperpermeability through the basal forebrain cholinergic neurons, adenosine A2B receptors and vagus nerve in rats.

Intestinal barrier dysfunction, leaky gut, is implicated in various diseases, including irritable bowel syndrome (IBS) and neurodegenerative conditions like Alzheimer's disease. Our recent investigation revealed that basal forebrain cholinergic neurons (BFCNs), critical for cognitive function, receive signals from butyrate and orexin, playing a role in regulating intestinal barrier function through adenosine A2B signaling and the vagus. This study explores the involvement and function of brain histamine, linked to BFCNs, in the regulation of intestinal barrier function. Colonic permeability, assessed by quantifying absorbed Evans blue in rat colonic tissue, showed that histamine did not affect increased colonic permeability induced by LPS when administered subcutaneously. However, intracisternal histamine administration improved colonic hyperpermeability. Elevating endogenous histamine levels in the brain with SKF91488, a histamine N-methyltransferase inhibitor, also improved colonic hyperpermeability. This effect was abolished by intracisternal chlorpheniramine, an histamine H1 receptor antagonist, not ranitidine, an H2 receptor antagonist. The SKF91488-induced improvement in colonic hyperpermeability was blocked by vagotomy, intracisternal pirenzepine (suppressing BFCNs activity), or alloxazine (an adenosine A2B receptor antagonist). Additionally, intracisternal chlorpheniramine injection eliminated butyrate-induced improvement in colonic hyperpermeability. These findings suggest that brain histamine, acting via the histamine H1 receptor, regulates intestinal barrier function involving BFCNs, adenosine A2B signaling, and the vagus. Brain histamine appears to centrally regulate intestinal barrier function influenced by butyrate, differentiating its actions from peripheral histamine in conditions like IBS, where mast cell-derived histamine induces leaky gut. Brain histamine emerges as a potential pharmacological target for diseases associated with leaky gut, such as dementia and IBS.

Butyrate promotes kidney resilience through a coordinated kidney protective response in tubular cells.

Acute kidney injury (AKI) is common in hospitalized patients and increases short-term and long-term mortality. Treatment options for AKI are limited. Gut microbiota products such as the short-chain fatty acid butyrate have anti-inflammatory actions that may protect tissues, including the kidney, from injury. However, the molecular mechanisms of tissue protection by butyrate are poorly understood. Treatment with oral butyrate for two weeks prior to folic acid-induced AKI and during AKI improved kidney function and decreased tubular injury and kidney inflammation while stopping butyrate before AKI was not protective. Continuous butyrate preserved the expression of kidney protective factors such as Klotho, PGC-1α and Nlrp6 which were otherwise downregulated. In cultured tubular cells, butyrate blunted the maladaptive tubular cell response to a proinflammatory milieu, preserving the expression of kidney protective factors. Kidney protection afforded by this continuous butyrate schedule was confirmed in a second model of nephrotoxic AKI, cisplatin nephrotoxicity, where the expression of kidney protective factors was also preserved. To assess the contribution of preservation of kidney protective factors to kidney resilience, recombinant Klotho was administered to mice with cisplatin-AKI and shown to preserve the expression of PGC-1α and Nlrp6, decrease kidney inflammation and protect from AKI. In conclusion, butyrate promotes kidney resilience to AKI and decreases inflammation by preventing the downregulation of kidney protective genes such as Klotho. This information may be relevant to optimize antibiotic management during hospitalization.

Alterations in gut microbiota contribute to cognitive deficits induced by chronic infection of Toxoplasma gondii.

Chronic infection with Toxoplasma gondii (T. gondii) emerges as a risk factor for neurodegenerative diseases in animals and humans. However, the underlying mechanisms are largely unknown. We aimed to investigate whether gut microbiota and its metabolites play a role in T. gondii-induced cognitive deficits. We found that T. gondii infection induced cognitive deficits in mice, which was characterized by synaptic ultrastructure impairment and neuroinflammation in the hippocampus. Moreover, the infection led to gut microbiota dysbiosis, barrier integrity impairment, and inflammation in the colon. Interestingly, broad-spectrum antibiotic ablation of gut microbiota attenuated the adverse effects of the parasitic infection on the cognitive function in mice; cognitive deficits and hippocampal pathological changes were transferred from the infected mice to control mice by fecal microbiota transplantation. In addition, the abundance of butyrate-producing bacteria and the production of serum butyrate were decreased in infected mice. Interestingly, dietary supplementation of butyrate ameliorated T. gondii-induced cognitive impairment in mice. Notably, compared to the healthy controls, decreased butyrate production was observed in the serum of human subjects with high levels of anti-T. gondii IgG. Overall, this study demonstrates that gut microbiota is a key regulator of T. gondii-induced cognitive impairment.

Butyrate as a potential therapeutic agent for neurodegenerative disorders.

Maintaining an optimum microbial community within the gastrointestinal tract is intricately linked to human metabolic, immune and brain health. Disturbance to these microbial populations perturbs the production of vital bioactive compounds synthesised by the gut microbiome, such as short-chain fatty acids (SCFAs). Of the SCFAs, butyrate is known to be a major source of energy for colonocytes and has valuable effects on the maintenance of intestinal epithelium and blood brain barrier integrity, gut motility and transit, anti-inflammatory effects, and autophagy induction. Inducing endogenous butyrate production is likely to be beneficial for gut-brain homeostasis and for optimal neuronal function. For these reasons, butyrate has gained interest as a potential therapy for not only metabolic and immunological disorders, but also conditions related to the brain, including neurodegenerative diseases. While direct and indirect sources of butyrate, including prebiotics, probiotics, butyrate pro-drugs and glucosidase inhibitors, offer a promising therapeutic avenue, their efficacy and dosage in neurodegenerative conditions remain largely unknown. Here, we review current literature on effects of butyrate relevant to neuronal function, the impact of butyrate in a range of neurodegenerative diseases and related treatments that may have potential for the treatment of neurodegenerative diseases.

Butyrate increases methylglyoxal production through regulation of the JAK2/Stat3/Nrf2/Glo1 pathway in castration­resistant prostate cancer cells.

Cancer cells are characterized by increased glycolysis, known as the Warburg effect, which leads to increased production of cytotoxic methylglyoxal (MGO) and apoptotic cell death. Cancer cells often activate the protective nuclear factor erythroid 2­related factor2 (Nrf2)/glyoxalase1 (Glo1) system to detoxify MGO. The effects of sodium butyrate (NaB), a product of gut microbiota, on Nrf2/Glos/MGO pathway and the underlying mechanisms in prostate cancer (PCa) cells were investigated in the present study. Treatment with NaB induced the cell death and reduced the proliferation of PCa cells (DU145 and LNCap). Moreover, the protein kinase RNA-like endoplasmic reticulum kinase/Nrf2/Glo1 pathway was greatly inhibited by NaB, thereby accumulating MGO-derived adduct hydroimidazolone (MG-H1). In response to a high amount of MGO, the expression of Nrf2 and Glo1 was attenuated, coinciding with an increased cellular death. NaB also markedly inhibited the Janus kinase 2 (JAK2)/Signal transducer and activator of transcription 3 (Stat3) pathway. Conversely, co­treatment with Colivelin, a Stat3 activator, significantly reversed the effects of NaB on Glo1 expression, MG-H1 production, and the cell migration and viability. As expected, overexpression of Stat3 or Glo1 reduced NaB­induced cell death. The activation of calcium/calmodulin dependent protein kinase II gamma and reactive oxygen species production also contributed to the anticancer effect of NaB. The present study, for the first time, demonstrated that NaB greatly increases MGO production through suppression of the JAK2/Stat3/Nrf2/Glo1 pathway in DU145 cells, a cell line mimicking castration­resistant PCa (CRPC), suggesting that NaB may be a potential agent for PCa therapy.