Down-regulation of the monocarboxylate transporter 1 is involved in butyrate deficiency during intestinal inflammation

Effects of a proinflammatory response on metabolic function of cultured, primary ruminal epithelial cells

Inflammation of ruminal epithelium may occur during ruminal acidosis as a result of translocation and interaction of ruminal epithelial cells (REC) with molecules such as lipopolysaccharide (LPS). Such inflammation has been reported to alter cellular processes such as nutrient absorption, metabolic regulation, and energy substrate utilization in other cell types but has not been investigated for REC. The objectives of this study were to investigate the effects of LPS on metabolism of short-chain fatty acids by primary REC, as well as investigating the effects of media containing short-chain fatty acids on the proinflammatory response. Ruminal papillae from 9 yearling Speckle Park beef heifers were used to isolate and culture primary REC. Cells were grown in minimum essential medium (MEM) for 12 d before use and then reseeded in 24-well culture plates. The study was conducted as a 2 × 2 factorial, where cells were grown in unaltered MEM (REG) or medium containing 2 mM butyrate and 5 mM propionate (SCFA) with (50,000 EU/mL; +LPS) or without LPS (-LPS) for 24 h. Supernatant samples were collected for analysis of glucose and SCFA consumption. Cells were collected to determine the expression of mRNA for genes associated with inflammation (TNF, IL1B, CXCL2, CXCL8, PTGS2, and TLR4), purinergic signaling (P2RX7, ADORAB2, and CD73), nutrient transport [SLC16A1 (MCT1), SLC16A3 (MCT4), SLC5A8, and MCU], and cell metabolism [ACAT1, SLC2A1 (GLUT1), IGFBP3, and IGFBP5]. Protein expression of TLR4 and ketogenic enzymes (BDH1 and HMGCS1) were also analyzed using flow cytometry. Statistical analysis was conducted with the MIXED model of SAS version 9.4 (SAS Institute Inc., Cary, NC) with medium, LPS exposure, and medium × LPS interaction as fixed effects and animal within plate as a random effect. Cells tended to consume more glucose when exposed to LPS as opposed to no LPS exposure (31.8 vs. 28.7 ± 2.7), but consumption of propionate and butyrate was not influenced by LPS. Expression of TNF and IL1B was upregulated when exposed to LPS, and expression of CXCL2 and CXCL8 increased following LPS exposure with SCFA (medium × LPS). For cells exposed to LPS, we found a downregulation of ACAT1 and IGFBP5 and an upregulation of SLC2A1, SLC16A3, MCU, and IGFBP3. Medium with SCFA led to greater expression of MCU. SLC16A1 was upregulated in cells incubated with SCFA and without LPS compared with the other groups. Protein expression of ketogenic enzymes was not affected; however, BDH1 mean fluorescence intensity (MFI) expression tended to be less in cells exposed to LPS. These data are interpreted to indicate that when REC are exposed to LPS, they may increase glucose metabolism. Moreover, transport of solutes was affected by SCFA in the medium and by exposure to LPS. Overall, the results suggest that metabolic function of REC in vitro is altered by a proinflammatory response, which may lead to a greater glucose requirement.

Cyclosporine protects from intestinal epithelial injury by modulating butyrate uptake via upregulation of membrane monocarboxylate transporter 1 levels

Background and aims

A relationship between treatment outcomes and intestinal microbiota in patients with inflammatory bowel diseases has been demonstrated. Cyclosporine treatment leads to rapid improvement in severe ulcerative colitis. We hypothesized that the potent effects of cyclosporine would be exerted through relationships between intestinal epithelial cells (IECs) and the host microbiota. The present study was designed to elucidate the effects of cyclosporine on monocarboxylate transporter 1 (MCT1) regulation and butyrate uptake by IECs.

Methods

Colitis was induced in C57BL6 mice via the administration of 4% dextran sulfate sodium in drinking water, following which body weights, colon lengths, and histological scores were evaluated. To examine the role of butyrate in the protective effects of cyclosporine, MCT1 inhibitor and an antibiotic cocktail was administered and tributyrin (TB; a prodrug of butyrate) was supplemented; MCT1 protein expression and acetylated histone 3 (AcH3) signals in IECs, as well as the MCT1-membrane fraction of Caco-2 cells, were evaluated. To explore butyrate uptake, as s butyrate derivatives, 3-bromopyruvic acid (3-BrPA) and 1-pyrenebutyric acid were used.

Results

Treatment with cyclosporine inhibited body weight loss and colon length shortening. However, treatment with MCT1 inhibitor and the antibiotic cocktail negated the efficacy of cyclosporine, whereas TB supplementation restored its protective effect. Furthermore, cyclosporine upregulated MCT1 expression in the membrane and the AcH3 signal in IECs, while also inducing higher anti-inflammatory cytokine production compared to that in the vehicle-treated mice. The transcription level of MCT1 mRNA in IECs and Caco-2 cells did not increase with cyclosporine treatment; however, cyclosporine treatment increased membrane MCT1 expression in these cells and uptake of butyrate derivative.

Conclusion

Cyclosporine treatment modulates butyrate uptake via the post-transcriptional upregulation of membrane MCT1 levels in IECs.

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The protective effect of cyclosporine needs microbiota-derived butyrate.

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Cyclosporine increased the fraction of MCT1 at the cell membrane.

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Cyclosporine enhanced butyrate uptake and regulatory cytokine expression.

Links Between Inflammatory Bowel Disease and Chronic Obstructive Pulmonary Disease

Inflammatory bowel disease (IBD) and chronic obstructive pulmonary disease (COPD) are chronic inflammatory diseases of the gastrointestinal and respiratory tracts, respectively. These mucosal tissues bear commonalities in embryology, structure and physiology. Inherent similarities in immune responses at the two sites, as well as overlapping environmental risk factors, help to explain the increase in prevalence of IBD amongst COPD patients. Over the past decade, a tremendous amount of research has been conducted to define the microbiological makeup of the intestine, known as the intestinal microbiota, and determine its contribution to health and disease. Intestinal microbial dysbiosis is now known to be associated with IBD where it impacts upon intestinal epithelial barrier integrity and leads to augmented immune responses and the perpetuation of chronic inflammation. While much less is known about the lung microbiota, like the intestine, it has its own distinct, diverse microflora, with dysbiosis being reported in respiratory disease settings such as COPD. Recent research has begun to delineate the interaction or crosstalk between the lung and the intestine and how this may influence, or be influenced by, the microbiota. It is now known that microbial products and metabolites can be transferred from the intestine to the lung via the bloodstream, providing a mechanism for communication. While recent studies indicate that intestinal microbiota can influence respiratory health, intestinal dysbiosis in COPD has not yet been described although it is anticipated since factors that lead to dysbiosis are similarly associated with COPD. This review will focus on the gut-lung axis in the context of IBD and COPD, highlighting the role of environmental and genetic factors and the impact of microbial dysbiosis on chronic inflammation in the intestinal tract and lung.

The SLC transporter in nutrient and metabolic sensing, regulation, and drug development

The prevalence of metabolic diseases is growing worldwide. Accumulating evidence suggests that solute carrier (SLC) transporters contribute to the etiology of various metabolic diseases. Consistent with metabolic characteristics, the top five organs in which SLC transporters are highly expressed are the kidney, brain, liver, gut, and heart. We aim to understand the molecular mechanisms of important SLC transporter-mediated physiological processes and their potentials as drug targets. SLC transporters serve as ‘metabolic gate’ of cells and mediate the transport of a wide range of essential nutrients and metabolites such as glucose, amino acids, vitamins, neurotransmitters, and inorganic/metal ions. Gene-modified animal models have demonstrated that SLC transporters participate in many important physiological functions including nutrient supply, metabolic transformation, energy homeostasis, tissue development, oxidative stress, host defense, and neurological regulation. Furthermore, the human genomic studies have identified that SLC transporters are susceptible or causative genes in various diseases like cancer, metabolic disease, cardiovascular disease, immunological disorders, and neurological dysfunction. Importantly, a number of SLC transporters have been successfully targeted for drug developments. This review will focus on the current understanding of SLCs in regulating physiology, nutrient sensing and uptake, and risk of diseases.

Ion Transport Basis of Diarrhea in a Mouse Model of Adoptive T Cell Transfer Colitis

BACKGROUND

Diarrhea, a major pathological hallmark of inflammatory bowel disease, is characterized by a significant reduction in the expression and function of key intestinal ion transporters. The adoptive naïve CD4⁺ T cell transfer colitis is an immune-based, chronic colitis mouse model which resembles human Crohn's disease. Although mice with T cell transfer colitis demonstrate diarrhea, the ion transporter basis of this phenotype has not been explored.

AIMS/METHODS

In the current studies, we aimed to determine the mRNA and protein levels of the key NaCl transporters DRA and NHE3 along with the mRNA expression of other transporters in the inflamed intestine.

RESULTS

Naïve CD4⁺ T cells, transferred to Rag2 knockout mice, induced severe colonic inflammation characterized by histological damage and increased mRNA levels of cytokines in the colon with no effect in the ileum. Diarrheal phenotype was a key feature of the excised colons of mice where loose stools were evident. Our results demonstrated that the key chloride transporter DRA, mRNA, and protein levels were significantly reduced in the inflamed colon. However, expression of the key sodium hydrogen exchanger NHE3 was unaffected. The mRNA expression of other important transporters was also determined; in this regard, the sodium channel ENACα and the monocarboxylate transporters MCT1 and SMCT1 mRNA levels were also significantly lower compared to control mice. However, CFTR mRNA was not altered in the colon or ileum.

CONCLUSIONS

The studies conducted herein for the first time demonstrate the downregulation of important intestinal ion transporters in proximal and distal colon in T cell transfer colitis mouse model, providing valuable evidence for the ion transporter basis of diarrhea in this chronic model of inflammation.

Disease progression-associated alterations in fecal metabolites in SAMP1/YitFc mice, a Crohn's disease model

Crohn's disease (CD) is a chronic, relapsing inflammatory bowel disease affecting the gastrointestinal tract. Although its precise etiology has not been fully elucidated, an imbalance of the intestinal microbiota has been known to play a role in CD. Fecal metabolites derived from microbiota may be related to the onset and progression of CD OBJECTIVES: This study aimed to clarify the transition of gut microbiota and fecal metabolites associated with disease progression using SAMP1/YitFc mice, a model of spontaneous CD METHODS: The ileum tissues isolated from SAMP1/YitFc mice at different ages were stained with hematoxylin-eosin for histologic characterization with CD progression. Feces from control, Institute of Cancer Research (ICR; n = 6), and SAMP1/YitFc (n = 8) mice at different ages were subjected to microbial analysis and ¹H nuclear magnetic resonance (NMR) analysis to investigate fluctuations in gut microbiota and fecal metabolites with CD progression RESULTS: Relative abundance of the Lachnospiraceae, Ruminococcaceae, Bacteroidaceae, and Bacteroidales S24-7 at family-level gut microbiota and fecal metabolites, such as short-chain fatty acids, lactate, glucose, xylose, and choline, dramatically fluctuated with histologic progression of intestinal inflammation in SAMP1/YitFc mice. Unlike the other metabolites, fecal taurine concentration in SAMP1/YitFc mice was higher than ICR mice regardless of age CONCLUSION: The fecal metabolites showing characteristic fluctuations may help to understand the inflammatory mechanism associated with CD, and might be utilized as potential biomarkers in predicting CD pathology.

Timing of complementary feeding is associated with gut microbiota diversity and composition and short chain fatty acid concentrations over the first year of life

BACKGROUND

Early introduction of complementary foods has been associated with various immune disorders, oxidative stress, and obesity in childhood. The gut microbiota and the short chain fatty acids (SCFAs) they produce are postulated to be on the causal pathway. The objective of this study was to determine if early complementary feeding (i.e. consumption of solids or non-water/formula liquids at or before 3 months) is prospectively associated with infant gut microbiota composition, diversity and SCFAs at 3 and 12 months of age in the Nurture birth cohort.

RESULTS

Mother-infant dyads in the early complementary feeding group (n = 18) had similar baseline characteristics to those in the later feeding group (n = 49). We assessed differential abundance of microbial taxa (measured by 16S rRNA gene sequencing of the V4 region) by timing of complementary feeding using beta-binomial regression models (considering a two-sided FDR corrected p-value of < 0.05 as significant), and we fittted linear regression models to assess the association between early complementary feeding and SCFA concentrations (quantified using gas chromatography). After multivariable adjustment for breastfeeding, delivery method, birth weight, and gestational age, there were 13 differentially abundant microbial amplicon sequence variants (ASVs) by timing of introduction to complementary foods at 3 months and 20 ASVs at 12 months. Infants introduced to complementary foods early (vs. later) had higher concentrations of the SCFA butyric acid (mean difference = 0.65, 95% CI: 0.27, 1.04, p < 0.01) and total SCFAs (mean difference = 38.8, 95% CI: 7.83, 69.7) at 12 months. Bilophila wadsworthia and Lachnospiraceae Roseburia were associated with early (vs. later) complementary feeding and with higher butyric acid concentrations at 3 and 12 months, respectively.

CONCLUSIONS

Our findings are consistent with the hypothesis that early (vs. later) introduction to complementary foods is associated with altered gut microbiota composition and butyric acid concentrations measured in stool until at least 1 year of age. Further research is needed to determine if these changes mediate future development of metabolic and immune conditions.

Intestinal OCTN2- and MCT1-targeted drug delivery to improve oral bioavailability

Various drug transporters are widely expressed throughout the intestine and play important roles in absorbing nutrients and drugs, thus providing high quality targets for the design of prodrugs or nanoparticles to facilitate oral drug delivery. In particular, intestinal carnitine/organic cation transporter 2 (OCTN2) and mono-carboxylate transporter protein 1 (MCT1) possess high transport capacities and complementary distributions. Therefore, we outline recent developments in transporter-targeted oral drug delivery with regard to the OCTN2 and MCT1 proteins in this review. First, basic information of the two transporters is reviewed, including their topological structures, characteristics and functions, expression and key features of their substrates. Furthermore, progress in transporter-targeting prodrugs and nanoparticles to increase oral drug delivery is discussed, including improvements in the oral absorption of anti-inflammatory drugs, antiepileptic drugs and anticancer drugs. Finally, the potential of a dual transporter-targeting strategy is discussed.

Intestinal Inflammation Modulates the Epithelial Response to Butyrate in Patients With Inflammatory Bowel Disease

BACKGROUND

Butyrate-producing gut bacteria are reduced in patients with active inflammatory bowel disease (IBD), supporting the hypothesis that butyrate supplementation may be beneficial in this setting. Nonetheless, earlier studies suggest that the oxidation of butyrate in IBD patients is altered. We propose that inflammation may decrease epithelial butyrate consumption.

METHODS

Non-IBD controls and IBD patients were recruited for the study. Stool samples were used for short-chain fatty acid and bacterial butyryl CoA:acetate CoA-transferase quantification. Colonic biopsies and ex vivo differentiated epithelial organoids (d-EpOCs) treated with butyrate and/or tumor necrosis factor alpha (TNFα) were used for analyzing the expression of transporters MCT1 and ABCG2, metabolic enzyme ACADS, and butyrate receptor GPR43, and for butyrate metabolism and consumption assays.

RESULTS

We observed that lower stool content of butyrate-producing bacteria in active IBD patients did not correlate with decreased butyrate concentrations. Indeed, the intestinal epithelial expression of MCT1, ABCG2, ACADS, and GPR43 was altered in active IBD patients. Nonetheless, d-EpOCs derived from IBD patients showed SLC16A1 (gene encoding for MCT1 protein), ABCG2, ACADS, and GPR43 expression levels comparable to controls. Moreover, IBD- and non-IBD-derived d-EpOCs responded similarly to butyrate, as assessed by transcriptional regulation. TNFα significantly altered SLC16A1, ABCG2, and GPR43 transcription in d-EpOCs, mimicking the expression profile observed in biopsies from active IBD patients and resulting in reduced butyrate consumption.

CONCLUSIONS

We provide evidence that the response to butyrate is not intrinsically altered in IBD patients. However, TNFα renders the epithelium less responsive to this metabolite, defeating the purpose of butyrate supplementation during active inflammation.

Evaluation and comparison of short chain fatty acids composition in gut diseases

BACKGROUND

An altered (dysbiosis) and unhealthy status of the gut microbiota is usually responsible for a reduction of short chain fatty acids (SCFAs) concentration. SCFAs obtained from the carbohydrate fermentation processes are crucial in maintaining gut homeostasis and their determination in stool samples could provide a faster, reliable and cheaper method to highlight the presence of an intestinal dysbiosis and a biomarker for various gut diseases. We hypothesize that different intestinal diseases, such as celiac disease (CD), adenomatous polyposis (AP) and colorectal cancer (CRC) could display a particular fecal SCFAs' signature.

AIM

To compare the fecal SCFAs' profiles of CD, AP, CRC patients and healthy controls, using the same analytical method.

METHODS

In this cross-sectional study, we defined and compared the SCFAs' concentration in fecal samples of 9 AP, 16 CD, 19 CRC patients and 16 healthy controls (HC). The SCFAs' analysis were performed using a gas-chromatography coupled with mass spectrometry method. Data analysis was carried out using Wilcoxon rank-sum test to assess pairwise differences of SCFAs' profiles, partial least squares-discriminate analysis (PLS-DA) to determine the status membership based on distinct SCFAs' profiles, and Dirichlet regression to determine factors influencing concentration levels of SCFAs.

RESULTS

We have not observed any difference in the SCFAs' amount and composition between CD and healthy control. On the contrary, the total amount of SCFAs was significantly lower in CRC patients compared to HC (P = 0.044) and CD (P = 0.005). Moreover, the SCFAs' percentage composition was different in CRC and AP compared to HC. In detail, HC displayed higher percentage of acetic acid (P value = 1.3 × 10-6) and a lower amount of butyric (P value = 0.02192), isobutyric (P value = 7.4 × 10-5), isovaleric (P value = 0.00012) and valeric (P value = 0.00014) acids compared to CRC patients. AP showed a lower abundance of acetic acid (P value = 0.00062) and higher percentages of propionic (P value = 0.00433) and isovaleric (P value = 0.00433) acids compared to HC. Moreover, AP showed higher levels of propionic acid (P value = 0.03251) and a lower level of isobutyric acid (P value = 0.00427) in comparison to CRC. The PLS-DA model demonstrated a significant separation of CRC and AP groups from HC, although some degree of overlap was observed between CRC and AP.

CONCLUSION

Analysis of fecal SCFAs shows the potential to provide a non-invasive means of diagnosis to detect patients with CRC and AP, while CD patients cannot be discriminated from healthy subjects.

Butyrate regulates inflammatory cytokine expression without affecting oxidative respiration in primary astrocytes from spontaneously hypertensive rats

Neurons and glia exhibit metabolic imbalances in hypertensive animal models, and loss of metabolic homeostasis can lead to neuroinflammation and oxidative stress. The objective of this study was to determine the effects of the microbial metabolite butyrate on mitochondrial bioenergetics and inflammatory markers in mixed brainstem and hypothalamic primary cultures of astrocytes between normotensive (Sprague-Dawley, S-D) and spontaneously hypertensive (SHR) rats. Bioenergetics of mitochondria in astrocytes from normotensive S-D rats were modified with butyrate, but this was not the case in astrocytes derived from SHR, suggesting aberrant mitochondrial function. Transcripts related to oxidative stress, butyrate transporters, butyrate metabolism, and neuroinflammation were quantified in astrocyte cultures treated with butyrate at 0, 200, 600, and 1000 μmol/L. Butyrate decreased catalase and monocarboxylate transporter 1 mRNA in astrocytes of S-D rats but not in the SHR. Moreover, while butyrate did not directly regulate the expression of 3-hydroxybutyrate dehydrogenase 1 and 2 in astrocytes of either strain, the expression levels for these transcripts in untreated cultures were lower in the SHR compared to S-D. We observed higher levels of specific inflammatory cytokines in astrocytes of SHR, and treatment with butyrate decreased expression of Ccl2 and Tlr4 in SHR astrocytes only. Conversely, butyrate treatment increased expression of tumor necrosis factor in astrocytes from SHR but not from the S-D rats. This study improves our understanding of the role of microbial metabolites in regulating astrocyte function, and provides support that butyrate differentially regulates both the bioenergetics and transcripts related to neuroinflammation in astrocytes from SHR versus S-D rats.

MCT4 has a potential to be used as a prognostic biomarker - a systematic review and meta-analysis

The role of several metabolic changes, such as hypoxia and acidosis, in the tumour environment has caught the attention of researchers in cancer progression and invasion. Lactate transport is one of the acidosis-enhancing processes that are mediated via monocarboxylate transporters (MCTs). We conducted a systematic review and meta-analysis to investigate the expression of two cancer-relevant MCTs (MCT1 and MCT4) and their potential prognostic significance in patients with metastasis of different types of cancer. Studies were included if they reported the number of metastatic tissue samples expressing either low or high levels of MCT1 and/or MCT4 or those revealing the hazard ratios (HRs) of the overall survival (OS) or disease-free survival (DFS) as prognostic indicators. During the period between 2010 and 2018, a total of 20 articles including 3831 patients (56.3% males) were identified. There was a significant association between MCT4 expression (high versus low) and lymph node metastasis [odds ratio (OR)=1.87, 95% confidence interval (CI)=1.10-3.17, P=0.02] and distant metastasis (OR=2.18, 95%CI=1.65-2.86, P<0.001) and the correlation remained significant for colorectal and hepatic cancer in subgroup analysis. For survival analysis, patients with shorter OS periods exhibited a higher MCT4 expression [hazard ratio (HR)=1.78, 95%CI=1.49-2.13, P<0.001], while DFS was shorter in patients with high MCT1 (HR=1.48, 95%CI=1.04-2.10, P=0.03) and MCT4 expression (HR=1.70, 95%CI=1.19-2.42, P=0.003) when compared to their counterparts with low expression levels. Future research studies should consider the pharmacologic inhibition of MCT4 to effectively inhibit cancer progression to metastasis.

Physiology of Electrolyte Transport in the Gut: Implications for Disease

We now have an increased understanding of the genetics, cell biology, and physiology of electrolyte transport processes in the mammalian intestine, due to the availability of sophisticated methodologies ranging from genome wide association studies to CRISPR-CAS technology, stem cell-derived organoids, 3D microscopy, electron cryomicroscopy, single cell RNA sequencing, transgenic methodologies, and tools to manipulate cellular processes at a molecular level. This knowledge has simultaneously underscored the complexity of biological systems and the interdependence of multiple regulatory systems. In addition to the plethora of mammalian neurohumoral factors and their cross talk, advances in pyrosequencing and metagenomic analyses have highlighted the relevance of the microbiome to intestinal regulation. This article provides an overview of our current understanding of electrolyte transport processes in the small and large intestine, their regulation in health and how dysregulation at multiple levels can result in disease. Intestinal electrolyte transport is a balance of ion secretory and ion absorptive processes, all exquisitely dependent on the basolateral Na⁺ /K⁺ ATPase; when this balance goes awry, it can result in diarrhea or in constipation. The key transporters involved in secretion are the apical membrane Cl^- channels and the basolateral Na⁺ -K⁺ -2Cl^- cotransporter, NKCC1 and K⁺ channels. Absorption chiefly involves apical membrane Na⁺ /H⁺ exchangers and Cl^- /HCO₃ ^- exchangers in the small intestine and proximal colon and Na⁺ channels in the distal colon. Key examples of our current understanding of infectious, inflammatory, and genetic diarrheal diseases and of constipation are provided. © 2019 American Physiological Society. Compr Physiol 9:947-1023, 2019.

Metabolite-Sensing G Protein-Coupled Receptors Connect the Diet-Microbiota-Metabolites Axis to Inflammatory Bowel Disease

Increasing evidence has indicated that diet and metabolites, including bacteria- and host-derived metabolites, orchestrate host pathophysiology by regulating metabolism, immune system and inflammation. Indeed, autoimmune diseases such as inflammatory bowel disease (IBD) are associated with the modulation of host response to diets. One crucial mechanism by which the microbiota affects the host is signaling through G protein-coupled receptors (GPCRs) termed metabolite-sensing GPCRs. In the gut, both immune and nonimmune cells express GPCRs and their activation generally provide anti-inflammatory signals through regulation of both the immune system functions and the epithelial integrity. Members of GPCR family serve as a link between microbiota, immune system and intestinal epithelium by which all these components crucially participate to maintain the gut homeostasis. Conversely, impaired GPCR signaling is associated with IBD and other diseases, including hepatic steatosis, diabetes, cardiovascular disease, and asthma. In this review, we first outline the signaling, function, expression and the physiological role of several groups of metabolite-sensing GPCRs. We then discuss recent findings on their role in the regulation of the inflammation, their existing endogenous and synthetic ligands and innovative approaches to therapeutically target inflammatory bowel disease.

N-(1-carbamoyl-2-phenylethyl) butyramide reduces antibiotic-induced intestinal injury, innate immune activation and modulates microbiota composition

The use/misuse of antibiotics leads to pathological features referring to antibiotic-induced intestinal injury (AIJ), a clinical issue that plays a prominent role in the development of severe digestive disturbances. AIJ is characterized by loss of intestinal architecture and function, dysbiosis and bacterial translocation into the liver, triggering hepatic inflammation. This study aimed at determining the beneficial effect of N-(1-carbamoyl-2-phenylethyl) butyramide (FBA), a butyrate releasing compound, in ceftriaxone-induced intestinal injury. To this purpose, mice receiving ceftriaxone (8 g∙kg⁻¹/die, per os) for five days, were treated with FBA (212,5 mg∙kg⁻¹/die, per os) for five or fifteen days. FBA modulated key players of innate immunity in antibiotic-injured gut tissues, reducing inflammatory process and improving the anti-inflammatory and resolving pattern. FBA also improved colonic architecture and intestinal integrity. Interestingly, we also observed a remodeling of gut microbiota composition related to an increase of metabolic pathways related to lactate and butyrate production. At mechanistic level, FBA induced histone acetylation and increased the expression of GPR43 and monocarboxylate transporter 1 in colon. Our data clearly demonstrated that FBA has multiple converging mechanisms in limiting intestinal and hepatic alterations to counteract AIJ.

Short Chain Fatty Acids (SCFAs)-Mediated Gut Epithelial and Immune Regulation and Its Relevance for Inflammatory Bowel Diseases

Ulcerative colitis (UC) and Crohn's disease (CD), collectively known as Inflammatory Bowel Diseases (IBD), are caused by a complex interplay between genetic, immunologic, microbial and environmental factors. Dysbiosis of the gut microbiome is increasingly considered to be causatively related to IBD and is strongly affected by components of a Western life style. Bacteria that ferment fibers and produce short chain fatty acids (SCFAs) are typically reduced in mucosa and feces of patients with IBD, as compared to healthy individuals. SCFAs, such as acetate, propionate and butyrate, are important metabolites in maintaining intestinal homeostasis. Several studies have indeed shown that fecal SCFAs levels are reduced in active IBD. SCFAs are an important fuel for intestinal epithelial cells and are known to strengthen the gut barrier function. Recent findings, however, show that SCFAs, and in particular butyrate, also have important immunomodulatory functions. Absorption of SCFAs is facilitated by substrate transporters like MCT1 and SMCT1 to promote cellular metabolism. Moreover, SCFAs may signal through cell surface G-protein coupled receptors (GPCRs), like GPR41, GPR43, and GPR109A, to activate signaling cascades that control immune functions. Transgenic mouse models support the key role of these GPCRs in controlling intestinal inflammation. Here, we present an overview of microbial SCFAs production and their effects on the intestinal mucosa with specific emphasis on their relevance for IBD. Moreover, we discuss the therapeutic potential of SCFAs for IBD, either applied directly or by stimulating SCFAs-producing bacteria through pre- or probiotic approaches.

Oral neonatal antibiotic treatment perturbs gut microbiota and aggravates central nervous system autoimmunity in Dark Agouti rats

Gut microbiota dysbiosis has been considered the essential element in the pathogenesis of multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE). Antibiotics were administered orally to Dark Agouti (DA) rats early in their life with the aim of perturbing gut microbiota and investigating the effects of such intervention on the course of EAE. As a result, the diversity of the gut microbiota was reduced under the influence of antibiotics. Mainly, Firmicutes and Actinobacteria were replaced by Proteobacteria and Bacteroidetes, while decreased proportions of Clostridia and Bacilli classes were accompanied by an increase in Gamma-Proteobacteria in antibiotic-treated animals. Interestingly, a notable decrease in the Helicobacteraceae, Spirochaetaceae and Turicibacteriaceae was scored in antibiotic-treated groups. Also, levels of short chain fatty acids were reduced in the faeces of antibiotic-treated rats. Consequently, aggravation of EAE, paralleled with stronger immune response in lymph nodes draining the site of immunization, and increased inflammation within the CNS, were observed in antibiotic-treated DA rats. Thus, the alteration of gut microbiota leads to an escalation of CNS-directed autoimmunity in DA rats. The results of this study indicate that antibiotic use in early life may have subsequent unfavourable effects on the regulation of the immune system.

The Role of Dietary Nutrients in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic and relapsing inflammatory disease of the gastrointestinal tract. Although the precise etiology of IBD remains incompletely understood, accumulating evidence suggests that various environmental factors, including dietary nutrients, contribute to its pathogenesis. Dietary nutrients are known to have an impact on host physiology and diseases. The interactions between dietary nutrients and intestinal immunity are complex. Dietary nutrients directly regulate the immuno-modulatory function of gut-resident immune cells. Likewise, dietary nutrients shape the composition of the gut microbiota. Therefore, a well-balanced diet is crucial for good health. In contrast, the relationships among dietary nutrients, host immunity and/or the gut microbiota may be perturbed in the context of IBD. Genetic predispositions and gut dysbiosis may affect the utilization of dietary nutrients. Moreover, the metabolism of nutrients in host cells and the gut microbiota may be altered by intestinal inflammation, thereby increasing or decreasing the demand for certain nutrients necessary for the maintenance of immune and microbial homeostasis. Herein, we review the current knowledge of the role dietary nutrients play in the development and the treatment of IBD, focusing on the interplay among dietary nutrients, the gut microbiota and host immune cells. We also discuss alterations in the nutritional metabolism of the gut microbiota and host cells in IBD that can influence the outcome of nutritional intervention. A better understanding of the diet-host-microbiota interactions may lead to new therapeutic approaches for the treatment of IBD.

Qualitative modelling of the interplay of inflammatory status and butyrate in the human gut: a hypotheses about robust bi-stability

Background

Gut microbiota interacts with the human gut in multiple ways. Microbiota composition is altered in inflamed gut conditions. Likewise, certain microbial fermentation products as well as the lipopolysaccharides of the outer membrane are examples of microbial products with opposing influences on gut epithelium inflammation status. This system of intricate interactions is known to play a core role in human gut inflammatory diseases. Here, we present and analyse a simplified model of bidirectional interaction between the microbiota and the host: in focus is butyrate as an example for a bacterial fermentation product with anti-inflammatory properties.

Results

We build a dynamical model based on an existing model of inflammatory regulation in gut epithelial cells. Our model introduces both butyrate as a bacterial product which counteracts inflammation, as well as bacterial LPS as a pro-inflammatory bacterial product. Moreover, we propose an extension of this model that also includes a feedback interaction towards bacterial composition. The analysis of these dynamical models shows robust bi-stability driven by butyrate concentrations in the gut. The extended model hints towards a further possible enforcement of the observed bi-stability via alteration of gut bacterial composition. A theoretical perspective on the stability of the described switch-like character is discussed.

Conclusions

Interpreting the results of this qualitative model allows formulating hypotheses about the switch-like character of inflammatory regulation in the gut epithelium, involving bacterial products as constitutive parts of the system. We also speculate about possible explanations for observed bimodal distributions in bacterial compositions in the human gut. The switch-like behaviour of the system proved to be mostly independent of parameter choices. Further implications of the qualitative character of our modeling approach for the robustness of the proposed hypotheses are discussed, as well as the pronounced role of butyrate compared to other inflammatory regulators, especially LPS, NF- κB and cytokines.

Electronic supplementary material

The online version of this article (10.1186/s12918-018-0667-6) contains supplementary material, which is available to authorized users.

Inulin-type fructans improve active ulcerative colitis associated with microbiota changes and increased short-chain fatty acids levels

The intestinal microbiota is involved in ulcerative colitis (UC) pathogenesis. Prebiotics are hypothesized to improve health through alterations to gut microbiota composition and/or activity. Our aim was therefore to determine if inulin-type fructans induce clinical benefits in UC, and identify if benefits are linked to compositional and/or functional shifts of the luminal (fecal) and mucosal (biopsy) bacterial communities. Patients (n = 25) with mild/moderately active UC received 7.5 g (n = 12) or 15 g (n = 13) daily oral oligofructose-enriched inulin (Orafti®Synergy1) for 9 weeks. Total Mayo score, endoscopic activity and fecal calprotectin were assessed. Fecal and mucosal bacterial communities were characterized by 16S rRNA tag sequencing, and short chain fatty acids (SCFA) production were measured in fecal samples. Fructans significantly reduced colitis in the high-dose group, with 77% of patients showing a clinical response versus 33% in the low-dose group (P = 0.04). Fructans increased colonic butyrate production in the 15 g/d dose, and fecal butyrate levels were negatively correlated with Mayo score (r = -0.50; P = 0.036). The high fructan dose led to an increased Bifidobacteriaceae and Lachnospiraceae abundance but these shifts were not correlated with improved disease scores. In summary, this pilot study revealed that 15 g/d dose inulin type fructans in UC produced functional but not compositional shifts of the gut microbiota, suggesting that prebiotic-induced alterations of gut microbiota metabolism are more important than compositional changes for the benefits in UC. The findings warrant future well-powered controlled studies for the use of β-fructans as adjunct therapy in patients with active UC.

Altered Expression of Small Intestinal Drug Transporters and Hepatic Metabolic Enzymes in a Mouse Model of Familial Alzheimer's Disease

Drug transporter expression and function at the blood-brain barrier is altered in Alzheimer's disease (AD). However, the impact of AD on the expression of transporters and metabolizing enzymes in peripheral tissues has received little attention. The current study evaluated the expression of drug transporters and metabolizing enzymes in the small intestine and liver from 8- to 9-month-old female wild-type (WT) and APPswe/PSEN 1dE9 (APP/PS1) transgenic mice, a widely used AD model, using a quantitative targeted absolute proteomics (QTAP) approach. Furthermore, the general morphological appearance of the liver was assessed by immunohistochemistry, and lipid content was visualized using Oil Red O staining. The small intestines of APP/PS1 mice exhibited a significant 2.3-fold increase in multidrug resistance-associated protein 2 (Mrp2), a 1.9-fold decrease in monocarboxylate transporter 1 (Mct1), and a 3.6-fold increase in UDP-glucuronosyltransferase (Ugt) 2b5 relative to those from WT mice based on QTAP analysis. While the liver from APP/PS1 mice exhibited no changes in drug transporter expression, there was a 1.3-fold elevation in cytochrome P450 (Cyp) 51a1 and a 1.2-fold reduction in Cyp2c29 protein expression, and this was associated with morphological alterations including accumulation of hepatocyte lipids. These studies are the first to demonstrate that the protein expression of transporters and metabolizing enzymes important in oral drug absorption are modified in a mouse model of familial AD, which may lead to altered disposition of some orally administered drugs in AD.

Mitochondrial function - gatekeeper of intestinal epithelial cell homeostasis

The intestinal epithelium is a multicellular interface in close proximity to a dense microbial milieu that is completely renewed every 3-5 days. Pluripotent stem cells reside at the crypt, giving rise to transient amplifying cells that go through continuous steps of proliferation, differentiation and finally anoikis (a form of programmed cell death) while migrating upwards to the villus tip. During these cellular transitions, intestinal epithelial cells (IECs) possess distinct metabolic identities reflected by changes in mitochondrial activity. Mitochondrial function emerges as a key player in cell fate decisions and in coordinating cellular metabolism, immunity, stress responses and apoptosis. Mediators of mitochondrial signalling include molecules such as ATP and reactive oxygen species and interrelate with pathways such as the mitochondrial unfolded protein response (MT-UPR) and AMP kinase signalling, in turn affecting cell cycle progression and stemness. Alterations in mitochondrial function and MT-UPR activation are integral aspects of pathologies, including IBD and cancer. Mitochondrial signalling and concomitant changes in metabolism contribute to intestinal homeostasis and regulate IEC dedifferentiation-differentiation programmes in the context of diseases, suggesting that mitochondrial function as a cellular checkpoint critically contributes to disease outcome. This Review highlights mitochondrial function and MT-UPR signalling in epithelial cell stemness, differentiation and lineage commitment and illustrates mitochondrial function in intestinal diseases.

Implications of butyrate and its derivatives for gut health and animal production

Butyrate is produced by microbial fermentation in the large intestine of humans and animals. It serves as not only a primary nutrient that provides energy to colonocytes, but also a cellular mediator regulating multiple functions of gut cells and beyond, including gene expression, cell differentiation, gut tissue development, immune modulation, oxidative stress reduction, and diarrhea control. Although there are a large number of studies in human medicine using butyrate to treat intestinal disease, the importance of butyrate in maintaining gut health has also attracted significant research attention to its application for animal production, particularly as an alternative to in-feed antibiotics. Due to the difficulties of using butyrate in practice (i.e., offensive odor and absorption in the upper gut), different forms of butyrate, such as sodium butyrate and butyrate glycerides, have been developed and examined for their effects on gut health and growth performance across different species. Butyrate and its derivatives generally demonstrate positive effects on animal production, including enhancement of gut development, control of enteric pathogens, reduction of inflammation, improvement of growth performance (including carcass composition), and modulation of gut microbiota. These benefits are more evident in young animals, and variations in the results have been reported. The present article has critically reviewed recent findings in animal research on butyrate and its derivatives in regard to their effects and mechanisms behind and discussed the implications of these findings for improving animal gut health and production. In addition, significant findings of medical research in humans that are relevant to animal production have been cited.

Evaluation of Monocarboxylate Transporter 4 in Inflammatory Bowel Disease and Its Potential Use as a Diagnostic Marker

Background

Monocarboxylate transporter 4 (MCT4), encoded by SLC16A3 gene, is responsible for exporting lactic acid into the extracellular microenvironment, and an acidic microenvironment promotes cytokine production and remodels chronic inflammation, providing a link from glycolysis to inflammatory bowel disease (IBD).

Objective

The aim of this study is to explore the value of MCT4 as a potential biomarker in IBD.

Methods

The study group consisted of 39 cases with UC and 15 cases with CD. The centration of lactate level in serum was assessed by blood gas analysis, and MCT4 expression was analyzed by IHC.

Results

Lactate level was increased in the forty-three of 54 patients (79.6%) with IBD by blood gas analysis compared with normal level (P < 0.001), in line with the result that showed increased MCT4 expression in inflamed colonic mucosa analyzed by immunohistochemistry. Most importantly, abundance of MCT4 expression was significantly associated with mucosal inflammation, which could be a clinical prognosis marker.

Conclusion

The data suggested that increased lactate level in blood was possibly due to highly expressed MCT4 expression caused by inflammation in intestinal mucosal epithelial tissue, which could be a prognosis indicator of IBD in children.

Emerging Functions of Regulatory T Cells in Tissue Homeostasis

CD4⁺Foxp3⁺ regulatory T-cells (Tregs) are a unique subset of helper T-cells, which regulate immune response and establish peripheral tolerance. Tregs not only maintain the tone and tenor of an immune response by dominant tolerance but, in recent years, have also been identified as key players in resolving tissue inflammation and as mediators of tissue healing. Apart from being diverse in their origin (thymic and peripheral) and location (lymphoid and tissue resident), Tregs are also phenotypically heterogeneous as per the orientation of ongoing immune response. In this review, we discuss the recent advances in the field of Treg biology in general, and non-lymphoid and tissue-resident Tregs in particular. We elaborate upon well-known visceral adipose tissue, colon, skin, and tumor-infiltrating Tregs and newly identified tissue Treg populations as in lungs, skeletal muscle, placenta, and other tissues. Our attempt is to differentiate Tregs based on distinctive properties of their location, origin, ligand specificity, chemotaxis, and specific suppressive mechanisms. Despite ever expanding roles in maintaining systemic homeostasis, Tregs are employed by large varieties of tumors to dampen antitumor immunity. Thus, a comprehensive understanding of Treg biology in the context of inflammation can be instrumental in effectively managing tissue transplantation, autoimmunity, and antitumor immune responses.

Clinical and Functional Relevance of the Monocarboxylate Transporter Family in Disease Pathophysiology and Drug Therapy

The solute carrier (SLC) SLC16 gene family comprises 14 members and encodes for monocarboxylate transporters (MCTs), which mediate the absorption and distribution of monocarboxylic compounds across plasma membranes. As the knowledge about their physiological function, activity, and regulation increases, their involvement and contribution to cancer and other diseases become increasingly evident. Moreover, promising opportunities for therapeutic interventions by directly targeting their endogenous functions or by exploiting their ability to deliver drugs to specific organ sites emerge.

A Cross-Talk Between Microbiota-Derived Short-Chain Fatty Acids and the Host Mucosal Immune System Regulates Intestinal Homeostasis and Inflammatory Bowel Disease

Gut microbiota has a fundamental role in the energy homeostasis of the host and is essential for proper "education" of the immune system. Intestinal microbial communities are able to ferment dietary fiber releasing short-chain fatty acids (SCFAs). The SCFAs, particularly butyrate (BT), regulate innate and adaptive immune cell generation, trafficing, and function. For example, BT has an anti-inflammatory effect by inhibiting the recruitment and proinflammatory activity of neutrophils, macrophages, dendritic cells, and effector T cells and by increasing the number and activity of regulatory T cells. Gut microbial dysbiosis, ie, a microbial community imbalance, has been suggested to play a role in the development of inflammatory bowel disease (IBD). The relationship between dysbiosis and IBD has been difficult to prove, especially in humans, and is probably complex and dynamic, rather than one of a simple cause and effect relationship. However, IBD patients have dysbiosis with reduced numbers of SCFAs-producing bacteria and reduced BT concentration that is linked to a marked increase in the number of proinflammatory immune cells in the gut mucosa of these patients. Thus, microbial dysbiosis and reduced BT concentration may be a factor in the emergence and severity of IBD. Understanding the relationship between microbial dysbiosis and reduced BT concentration to IBD may lead to novel therapeutic interventions.

Short-Chain Fatty Acid Transporters: Role in Colonic Homeostasis

Short-chain fatty acids (SCFA; acetate, propionate, and butyrate) are generated in colon by bacterial fermentation of dietary fiber. Though diffusion in protonated form is a significant route, carrier-mediated mechanisms constitute the major route for the entry of SCFA in their anionic form into colonic epithelium. Several transport systems operate in cellular uptake of SCFA. MCT1 (SLC16A1) and MCT4 (SLC16A3) are H+-coupled and mediate electroneutral transport of SCFA (H+: SCFA stoichiometry; 1:1). MCT1 is expressed both in the apical membrane and basolateral membrane of colonic epithelium whereas MCT4 specifically in the basolateral membrane. SMCT1 (SLC5A8) and SMCT2 (SLC5A12) are Na+-coupled; SMCT1-mediated transport is electrogenic (Na+: SCFA stoichiometry; 2:1) whereas SMCT2-mediated transport is electroneutral (Na+: SCFA stoichiometry; 1:1). SMCT1 and SMCT2 are expressed exclusively in the apical membrane. An anion-exchange mechanism also operates in the apical membrane in which SCFA entry in anionic form is coupled to bicarbonate efflux; the molecular identity of this exchanger however remains unknown. All these transporters are subject to regulation, notably by their substrates themselves; this process involves cell-surface receptors with SCFA as signaling molecules. There are significant alterations in the expression of these transporters in ulcerative colitis and colon cancer. The tumor-associated changes occur via transcriptional regulation by p53 and HIF1α and by promoter methylation. As SCFA are obligatory for optimal colonic health, the transporters responsible for the entry and transcellular transfer of these bacterial products in colonic epithelium are critical determinants of colonic function under physiological conditions and in disease states. © 2018 American Physiological Society. Compr Physiol 8:299-314, 2018.

An orally administered butyrate-releasing derivative reduces neutrophil recruitment and inflammation in dextran sulphate sodium-induced murine colitis

BACKGROUND AND PURPOSE

Butyrate has shown benefits in inflammatory bowel diseases. However, it is not often administered orally because of its rancid smell and unpleasant taste. The efficacy of a more palatable butyrate-releasing derivative, N-(1-carbamoyl-2-phenylethyl) butyramide (FBA), was evaluated in a mouse model of colitis induced by dextran sodium sulphate (DSS).

EXPERIMENTAL APPROACH

Male 10 week-old BALB/c mice received DSS (2.5%) in drinking water (for 5 days) followed by DSS-free water for 7 days (DSS group). Oral FBA administration (42.5 mg·kg-1 ) was started 7 days before DSS as preventive (P-FBA), or 2 days after DSS as therapeutic (T-FBA); both treatments lasted 19 days. One DSS-untreated group received only tap water (CON).

KEY RESULTS

FBA treatments reduced colitis symptoms and colon damage. P-FBA and T-FBA significantly decreased polymorphonuclear cell infiltration score compared with the DSS group. FBA reversed the imbalance between pro- and anti-inflammatory cytokines (reducing inducible NOS protein expression, CCL2 and IL-6 transcripts in colon and increasing TGFβ and IL-10). Morever, P-FBA and T-FBA limited neutrophil recruitment (by expression and localization of the neutrophil granule protease Ly-6G), restored deficiency of the butyrate transporter and improved intestinal epithelial integrity, preventing tight-junction impairment (zonulin-1 and occludin). FBA, similar to its parental compound sodium butyrate, inhibited histone deacetylase-9 and restored H3 histone acetylation, exerting an anti-inflammatory effect through NF-κB inhibition and the up-regulation of PPARγ.

CONCLUSIONS AND IMPLICATIONS

FBA reduces inflammatory intestinal damage in mice indicating its potential as a postbiotic derivative without the problems associated with the oral administration of sodium butyrate.

LINKED ARTICLES

This article is part of a themed section on Principles of Pharmacological Research of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.11/issuetoc.

The Effect of Inflammatory Status on Butyrate and Folate Uptake by Tumoral (Caco-2) and Non-Tumoral (IEC-6) Intestinal Epithelial Cells

OBJECTIVE

Colorectal cancer (CRC) is the second leading cause of cancer death in occidental countries. Chronic inflammatory bowel disease (crohn's disease and ulcerative colitis) is associated with an increased risk for CRC development. The aim of this work was to investigate the relationship between inflammatory status and absorption of nutrients with a role in CRC pathogenesis.

MATERIALS AND METHODS

In this experimental study, we evaluated the in vitro effect of tumour necrosis factor-alpha (TNF-α), interferon-γ (IF-γ), and acetylsalicylic acid on 14C-butyrate (14C- BT), 3H-folic acid (3H-FA) uptake, and on proliferation, viability and differentiation of Caco-2 and IEC-6 cells in culture.

RESULTS

The proinflammatory cytokines TNF-α and INF-γ were found to decrease uptake of a low concentration of 14C-BT (10 µM) by Caco-2 (tumoral) and IEC-6 (normal) intestinal epithelial cell lines. However, the effect of TNF-α and INF-γ in IEC-6 cells is most probably related to a cytotoxic and antiproliferative impact. In contrast, INF-γ increases uptake of a high concentration (10 mM) of 14C-BT in Caco-2 cells. The anticarcinogenic effect of BT (10 mM) in these cells is not affected by the presence of this cytokine. On the other hand, acetylsalicylic acid stimulates 14C-BT uptake by Caco-2 cells and potentiates its antiproliferative effect. Finally, both TNF-α and INF-γ cause a significant decrease in 3H-FA uptake by Caco-2 cells.

CONCLUSION

The inflammatory status has an impact upon cellular uptake of BT and FA, two nutrients with a role in CRC pathogenesis. Moreover, the anti-inflammatory acetylsalicylic acid potentiates the anticarcinogenic effect of BT in Caco-2 cells by increasing its cellular uptake.

Impact of Novel Sorghum Bran Diets on DSS-Induced Colitis

We have demonstrated that polyphenol-rich sorghum bran diets alter fecal microbiota; however, little is known regarding their effect on colon inflammation. Our aim was to characterize the effect of sorghum bran diets on intestinal homeostasis during dextran sodium sulfate (DSS)-induced colitis. Male Sprague-Dawley rats (N = 20/diet) were provided diets containing 6% fiber from cellulose, or Black (3-deoxyanthocyanins), Sumac (condensed tannins) or Hi Tannin Black (both) sorghum bran. Colitis was induced (N = 10/diet) with three separate 48-h exposures to 3% DSS, and feces were collected. On Day 82, animals were euthanized and the colon resected. Only discrete mucosal lesions, with no diarrhea or bloody stools, were observed in DSS rats. Only bran diets upregulated proliferation and Tff3, Tgfβ and short chain fatty acids (SCFA) transporter expression after a DSS challenge. DSS did not significantly affect fecal SCFA concentrations. Bran diets alone upregulated repair mechanisms and SCFA transporter expression, which suggests these polyphenol-rich sorghum brans may suppress some consequences of colitis.

Characterization of the Pro-Inflammatory Cytokine IL-1β on Butyrate Oxidation in Colorectal Cancer Cells

Cancer, in part, is driven, by alterations in cellular metabolism that promote cell survival and cell proliferation. Identifying factors that influence this shift in cellular metabolism in cancer cells is important. Interleukin-1β (IL-1β) is a pro-inflammatory cytokine that has been reported to be elevated in colorectal cancer patients. While much is known toward the effect of dietary nutrients on regulating inflammation and the inflammatory response, which includes cytokines such as IL-1β, far less is understood how cytokines impact nutrient fate to alter cancer cell metabolism. Butyrate, a nutrient derived from the fermentation of dietary fiber in the colon, is the preferential exogenous energetic substrate used by non-cancerous colonocytes, but is used less efficiently by colorectal cancer cells. To test whether IL-1β alters colonocyte energy metabolism, we measured butyrate oxidation in HCT116 colorectal cancer cells with and without IL-1β. We hypothesize that IL-1β will push cancerous colonocytes away from the utilization and oxidation of butyrate. In this study, we demonstrate that pretreatment of colorectal cancer cells with IL-1β diminished butyrate oxidation and NADH levels. This effect was blocked with the interleukin receptor antagonist A (IL-1RA). Moreover, IL-1β suppressed basal mitochondrial respiration and lowered the mitochondrial spare capacity. By using inhibitors to block downstream targets of the interleukin-1 receptor pathway, we show that p38 is required for the IL-1β-mediated decrease in butyrate oxidation. These data provide insight into the metabolic effects induced by IL-1β in colorectal cancer, and identify relevant targets that may be exploited to block the effects of this cytokine. J. Cell. Biochem. 118: 1614-1621, 2017. © 2016 Wiley Periodicals, Inc.

Precision medicine in alcoholic and nonalcoholic fatty liver disease via modulating the gut microbiota

Alcoholic liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD) represent a major health burden in industrialized countries. Although alcohol abuse and nutrition play a central role in disease pathogenesis, preclinical models support a contribution of the gut microbiota to ALD and NAFLD. This review describes changes in the intestinal microbiota compositions related to ALD and NAFLD. Findings from in vitro, animal, and human studies are used to explain how intestinal pathology contributes to disease progression. This review summarizes the effects of untargeted microbiome modifications using antibiotics and probiotics on liver disease in animals and humans. While both affect humoral inflammation, regression of advanced liver disease or mortality has not been demonstrated. This review further describes products secreted by Lactobacillus- and microbiota-derived metabolites, such as fatty acids and antioxidants, that could be used for precision medicine in the treatment of liver disease. A better understanding of host-microbial interactions is allowing discovery of novel therapeutic targets in the gut microbiota, enabling new treatment options that restore the intestinal ecosystem precisely and influence liver disease. The modulation options of the gut microbiota and precision medicine employing the gut microbiota presented in this review have excellent prospects to improve treatment of liver disease.

Altered Transport and Metabolism of Phenolic Compounds in Obesity and Diabetes: Implications for Functional Food Development and Assessment

Interest in the application of phenolic compounds from the diet or supplements for the prevention of chronic diseases has grown substantially, but the efficacy of such approaches in humans is largely dependent on the bioavailability and metabolism of these compounds. Although food and dietary factors have been the focus of intense investigation, the impact of disease states such as obesity or diabetes on their absorption, metabolism, and eventual efficacy is important to consider. These factors must be understood in order to develop effective strategies that leverage bioactive phenolic compounds for the prevention of chronic disease. The goal of this review is to discuss the inducible metabolic systems that may be influenced by disease states and how these effects impact the bioavailability and metabolism of dietary phenolic compounds. Because current studies generally report that obesity and/or diabetes alter the absorption and excretion of these compounds, this review includes a description of the absorption, conjugation, and excretion pathways for phenolic compounds and how they are potentially altered in disease states. A possible mechanism that will be discussed related to the modulation of phenolic bioavailability and metabolism may be linked to increased inflammatory status from increased amounts of adipose tissue or elevated plasma glucose concentrations. Although more studies are needed, the translation of benefits derived from dietary phenolic compounds to individuals with obesity or diabetes may require the consideration of dosing strategies or be accompanied by adjunct therapies to improve the bioavailability of these compounds.

Differential protein abundance of a basolateral MCT1 transporter in the human gastrointestinal tract

Bacterially derived short chain fatty acids (SCFAs), such as butyrate, are vital in maintaining the symbiotic relationship that exists between humans and their gastrointestinal microbial populations. A key step in this process is the transport of SCFAs across colonic epithelial cells via MCT1 transporters. This study investigated MCT1 protein abundance in various human intestinal tissues. Initial RT-PCR analysis confirmed the expected MCT1 RNA expression pattern of colon > small intestine > stomach. Using surgical resection samples, immunoblot analysis detected higher abundance of a 45 kDa MCT1 protein in colonic tissue compared to ileum tissue (P < 0.001, N = 4, unpaired t-test). Importantly, MCT1 abundance was found to be significantly lower in sigmoid colon compared to ascending colon (P < 0.01, N = 8-11, ANOVA). Finally, immunolocalization studies confirmed MCT1 to be abundant in the basolateral membranes of surface epithelial cells of the ascending, transverse, and descending colon, but significantly less prevalent in the sigmoid colon (P < 0.05, N = 5-21, ANOVA). In conclusion, these data confirm that basolateral MCT1 protein abundance is correlated to levels of bacterially derived SCFAs along the human gastrointestinal tract. These findings highlight the importance of precise tissue location in studies comparing colonic MCT1 abundance between normal and diseased states.

Regulation of colonic epithelial butyrate transport: Focus on colorectal cancer

Highlights

Fermentation of the dietary fiber by intestinal microflora results in production of butyrate.Butyrate possesses anticarcinogenic effect at the colonic level.Three transporters (MCT1, SMCT1 and BCRP) regulate the intracellular concentration of BT in colonic epithelial cells.Changes in the expression of these transporters occur in colorectal cancer.

Abstract

Colorectal cancer (CRC) is one of the most common solid tumors worldwide. Consumption of dietary fiber is associated with a low risk of developing CRC. The fermentation of the dietary fiber by intestinal microflora results in production of butyrate (BT). This short-chain fatty acid is an important metabolic substrate in normal colonic epithelial cells and has important homeostatic functions at the colonic level. Because the cellular effects of BT (e.g. inhibition of histone deacetylases) are dependent on its intracellular concentration, knowledge on the mechanisms involved in BT membrane transport and its regulation seems particularly relevant. In this review, we will present the carrier-mediated mechanisms involved in BT membrane transport at the colonic epithelial level and their regulation, with an emphasis on CRC. Several xenobiotics known to modulate the risk for developing CRC are able to interfere with BT transport at the intestinal level. Thus, interference with BT transport certainly contributes to the anticarcinogenic or procarcinogenic effect of these compounds and these compounds may interfere with the anticarcinogenic effect of BT. Finally, we suggest that differences in BT transport between normal colonocytes and tumoral cells contribute to the "BT paradox" (the apparent opposing effect of BT in CRC cells and normal colonocytes).

The diet-microbiota-metabolite axis regulates the host physiology

The intestinal microbiota has been implicated in a wide range of diseases, including inflammatory bowel disease, obesity and cancer. Food ingredients are considered a major determinant of gut microbial composition, as exemplified by high-fat diet-induced dysbiosis that can affect host physiology. Accumulating studies show that microbial metabolites are key regulators of the intestinal epithelial barrier and gut immunity. In particular, short-chain fatty acids produced by bacterial fermentation of indigestible polysaccharides have profound impacts on host physiology beyond the gut. In this review, we describe the influences of the diet-microbiota-metabolite axis on host physiology, and especially on the immune and metabolic systems.

Prebiotics: Definition and protective mechanisms

The increase in chronic metabolic and immunologic disorders in the modern society is linked to major changes in the dietary patterns. These chronic conditions are associated with intestinal microbiota dysbiosis where important groups of carbohydrate fermenting, short-chain fatty acids-producing bacteria are reduced. Dietary prebiotics are defined as a selectively fermented ingredients that result in specific changes in the composition and/or activity of the gastrointestinal microbiota, thus conferring benefit(s) upon host health. Application of prebiotics may then restore the gut microbiota diversity and activity. Unlike the previously accepted prebiotics definition, where a limited number of bacterial species are involved in the prebiotic activity, new data from community-wide microbiome analysis demonstrated a broader affect of the prebiotics on the intestinal microbiota. These new findings require a revision of the current definition. In addition, prebiotics may exert immunomodulatory effects through microbiota-independent mechanisms that will require future investigations involving germ-free animal disease models.

Intraperitoneal administration of butyrate prevents the severity of acetic acid colitis in rats

Intrarectal infusion of butyrate improves colorectal disorders including ulcerative colitis (UC). However, it is not established whether systemically administered butyrate benefits such patients. The current study aimed at exploring and comparing the potential of intraperitoneally, intrarectally, and orally administered butyrate against acetic acid (AA)-induced UC in rats. Intrarectal administration of 2 ml of 50% AA was done after or without prior treatment of rats for 7 consecutive days with 100 mg/kg sodium butyrate (SB) intraperitoneally, intrarectally, or orally. Rats were sacrificed after 48 h of AA-treatment. Subsequently, colon sections were processed routinely for histopathological examination. We clinically observed diarrhea, loose stools, and hemoccult-positive stools, and histologically, epithelial loss and ulceration, crypt damage, goblet cell depletion, hemorrhage, and mucosal infiltration of inflammatory cells. The changes were significantly reduced by intraperitoneal, intrarectal, or oral butyrate, with intraperitoneal butyrate exhibiting the highest potency. It is concluded that intraperitoneal administration of butyrate abrogates the lesions of AA-induced UC and its potency surpasses that of intrarectal or oral butyrate.

Inflammation-Induced Downregulation of Butyrate Uptake and Oxidation Is Not Caused by a Reduced Gene Expression

In ulcerative colitis (UC) the butyrate metabolism is impaired, leading to energy-deficiency in the colonic cells. The effect of inflammation on the butyrate metabolism was investigated. HT-29 cells were incubated with pro-inflammatory cytokines (TNF-α and/or IFN-γ) for 1 and 24 h. Cells were additionally stimulated with butyrate to investigate its anti-inflammatory potential. Butyrate uptake and oxidation were measured using (14)C-labeled butyrate. Gene expression of the butyrate metabolism enzymes, interleukin 8 (IL-8; inflammatory marker) and villin-1 (VIL-1; epithelial cell damage marker) was measured via quantitative RT-PCR. Significantly increased IL-8 expression and decreased VIL-1 expression after 24 h incubation with TNF-α and/or IFN-γ confirmed the presence of inflammation. These conditions induced a decrease of both butyrate uptake and oxidation, whereas the gene expression was not reduced. Simultaneous incubation with butyrate counteracted the reduced butyrate oxidation. In contrast, 1 h incubation with TNF-α induced a significant increased IL-8 expression and decreased butyrate uptake. Incubation with TNF-α and/or IFN-γ for 1 h did not induce cell damage nor influence butyrate oxidation. The inflammation-induced downregulation of the butyrate metabolism was not caused by a reduced gene expression, but appeared consequential to a decreased butyrate uptake. Increasing the luminal butyrate levels might have therapeutic potential in UC.

Lactobacillus acidophilus counteracts enteropathogenic E. coli-induced inhibition of butyrate uptake in intestinal epithelial cells

Butyrate, a key short-chain fatty acid metabolite of colonic luminal bacterial action on dietary fiber, serves as a primary fuel for the colonocytes, ameliorates mucosal inflammation, and stimulates NaCl absorption. Absorption of butyrate into the colonocytes is essential for these intracellular effects. Monocarboxylate transporter 1 (MCT1) plays a major role in colonic luminal butyrate absorption. Previous studies (Tan J, McKenzie C, Potamitis M, Thorburn AN, Mackay CR, Macia L. Adv Immunol 121: 91-119, 2014.) showed decreased MCT1 expression and function in intestinal inflammation. We have previously shown (Borthakur A, Gill RK, Hodges K, Ramaswamy K, Hecht G, Dudeja PK. Am J Physiol Gastrointest Liver Physiol 290: G30-G35, 2006.) impaired butyrate absorption in human intestinal epithelial Caco-2 cells due to decreased MCT1 level at the apical cell surface following enteropathogenic E. coli (EPEC) infection. Current studies, therefore, examined the potential role of probiotic Lactobacilli in stimulating MCT1-mediated butyrate uptake and counteracting EPEC inhibition of MCT1 function. Of the five species of Lactobacilli, short-term (3 h) treatment with L. acidophilus (LA) significantly increased MCT1-mediated butyrate uptake in Caco-2 cells. Heat-killed LA was ineffective, whereas the conditioned culture supernatant of LA (LA-CS) was equally effective in stimulating MCT1 function, indicating that the effects are mediated by LA-secreted soluble factor(s). Furthermore, LA-CS increased apical membrane levels of MCT1 protein via decreasing its basal endocytosis, suggesting that LA-CS stimulation of butyrate uptake could be secondary to increased levels of MCT1 on the apical cell surface. LA-CS also attenuated EPEC inhibition of butyrate uptake and EPEC-mediated endocytosis of MCT1. Our studies highlight distinct role of specific LA-secreted molecules in modulating colonic butyrate absorption.

Polyphenol-rich sorghum brans alter colon microbiota and impact species diversity and species richness after multiple bouts of dextran sodium sulfate-induced colitis

The microbiota affects host health, and dysbiosis is involved in colitis. Sorghum bran influences butyrate concentrations during dextran sodium sulfate (DSS) colitis, suggesting microbiota changes. We aimed to characterize the microbiota during colitis, and ascertain if polyphenol-rich sorghum bran diets mitigate these effects. Rats (n = 80) were fed diets containing 6% fiber from cellulose, or Black (3-deoxyanthocyanins), Sumac (condensed tannins), or Hi Tannin black (both) sorghum bran. Inflammation was induced three times using 3% DSS for 48 h (40 rats, 2 week separation), and the microbiota characterized by pyrosequencing. The Firmicutes/Bacteroidetes ratio was higher in Cellulose DSS rats. Colonic injury negatively correlated with Firmicutes, Actinobacteria, Lactobacillales and Lactobacillus, and positively correlated with Unknown/Unclassified. Post DSS#2, richness was significantly lower in Sumac and Hi Tannin black. Post DSS#3 Bacteroidales, Bacteroides, Clostridiales, Lactobacillales and Lactobacillus were reduced, with no Clostridium identified. Diet significantly affected Bacteroidales, Bacteroides, Clostridiales and Lactobacillus post DSS#2 and #3. Post DSS#3 diet significantly affected all genus, including Bacteroides and Lactobacillus, and diversity and richness increased. Sumac and Hi Tannin black DSS had significantly higher richness compared to controls. Thus, these sorghum brans may protect against alterations observed during colitis including reduced microbial diversity and richness, and dysbiosis of Firmicutes/Bacteroidetes.

Down-regulation of monocarboxylate transporter 1 (MCT1) gene expression in the colon of piglets is linked to bacterial protein fermentation and pro-inflammatory cytokine-mediated signalling

The present study investigated the influence of bacterial metabolites on monocarboxylate transporter 1 (MCT1) expression in pigs using in vivo, ex vivo and in vitro approaches. Piglets (n 24) were fed high-protein (26 %) or low-protein (18 %) diets with or without fermentable carbohydrates. Colonic digesta samples were analysed for a broad range of bacterial metabolites. The expression of MCT1, TNF-α, interferon γ (IFN-γ) and IL-8 was determined in colonic tissue. The expression of MCT1 was lower and of TNF-α and IL-8 was higher with high-protein diets (P< 0·05). MCT1 expression was positively correlated with l-lactate, whereas negatively correlated with NH₃ and putrescine (P< 0·05). The expression of IL-8 and TNF-α was negatively correlated with l-lactate and positively correlated with NH₃ and putrescine, whereas the expression of IFN-γ was positively correlated with histamine and 4-ethylphenol (P< 0·05). Subsequently, porcine colonic tissue and Caco-2 cells were incubated with Na-butyrate, NH₄Cl or TNF-α as selected bacterial metabolites or mediators of inflammation. Colonic MCT1 expression was higher after incubation with Na-butyrate (P< 0·05) and lower after incubation with NH₄Cl or TNF-α (P< 0·05). Incubation of Caco-2 cells with increasing concentrations of these metabolites confirmed the up-regulation of MCT1 expression by Na-butyrate (linear, P< 0·05) and down-regulation by TNF-α and NH₄Cl (linear, P< 0·05). The high-protein diet decreased the expression of MCT1 in the colon of pigs, which appears to be linked to NH₃- and TNF-α-mediated signalling.

Characterization of butyrate transport across the luminal membranes of equine large intestine

The diet of the horse, pasture forage (grass), is fermented by the equine colonic microbiota to short-chain fatty acids, notably acetate, propionate and butyrate. Short-chain fatty acids provide a major source of energy for the horse and contribute to many vital physiological processes. We aimed to determine both the mechanism of butyrate uptake across the luminal membrane of equine colon and the nature of the protein involved. To this end, we isolated equine colonic luminal membrane vesicles. The abundance and activity of cysteine-sensitive alkaline phosphatase and villin, intestinal luminal membrane markers, were significantly enriched in membrane vesicles compared with the original homogenates. In contrast, the abundance of GLUT2 protein and the activity of Na(+)-K(+)-ATPase, known markers of the intestinal basolateral membrane, were hardly detectable. We demonstrated, by immunohistochemistry, that monocarboxylate transporter 1 (MCT1) protein is expressed on the luminal membrane of equine colonocytes. We showed that butyrate transport into luminal membrane vesicles is energized by a pH gradient (out < in) and is not Na(+) dependent. Moreover, butyrate uptake is time and concentration dependent, with a Michaelis-Menten constant of 5.6 ± 0.45 mm and maximal velocity of 614 ± 55 pmol s(-1) (mg protein)(-1). Butyrate transport is significantly inhibited by p-chloromercuribenzoate, phloretin and α-cyano-4-hydroxycinnamic acid, all potent inhibitors of MCT1. Moreover, acetate and propionate, as well as the monocarboxylates pyruvate and lactate, also inhibit butyrate uptake. Data presented here support the conclusion that transport of butyrate across the equine colonic luminal membrane is predominantly accomplished by MCT1.

Tributyrin supplementation protects mice from acute ethanol-induced gut injury

BACKGROUND

Excessive alcohol consumption leads to liver disease. Interorgan crosstalk contributes to ethanol (EtOH)-induced liver injury. EtOH exposure causes gut dysbiosis resulting in negative alterations in intestinal fermentation byproducts, particularly decreased luminal butyrate concentrations. Therefore, in the present work, we investigated the effect of butyrate supplementation, in the form of trybutyrin, as a prophylactic treatment against EtOH-induced gut injury.

METHODS

C57BL/6J mice were treated with 3 different EtOH feeding protocols: chronic feeding (25 days, 32% of kcal), short-term (2 days, 32%), or acute single gavage (5 g/kg). Tributyrin (0.83 to 10 mM) was supplemented either into the liquid diet or by oral gavage. Intestinal expression of tight junction (TJ) proteins and a butyrate receptor and transporter were evaluated, as well as liver enzymes and inflammatory markers.

RESULTS

All 3 EtOH exposure protocols reduced the expression and co-localization of TJ proteins (ZO-1, occludin) and the expression of a butyrate receptor (GPR109A) and transporter (SLC5A8) in the ileum and proximal colon. Importantly, tributyrin supplementation protected against these effects. Protection of the intestine with tributyrin supplementation was accompanied by mitigation of EtOH-induced increases in aspartate aminotransferase and inflammatory measures in the short-term and acute EtOH exposure protocols, but not after chronic EtOH feeding.

CONCLUSIONS

These findings suggest that tributyrin supplementation could serve as a prophylactic treatment against gut injury caused by short-term EtOH exposure.