The Warburg effect dictates the mechanism of butyrate-mediated histone acetylation and cell proliferation

Association of dietary fibre intake and gut microbiota in adults

Increasing evidence indicates that gut microbiota may influence colorectal cancer risk. Diet, particularly fibre intake, may modify gut microbiota composition, which may affect cancer risk. We investigated the relationship between dietary fibre intake and gut microbiota in adults. Using 16S rRNA gene sequencing, we assessed gut microbiota in faecal samples from 151 adults in two independent study populations: National Cancer Institute (NCI), n 75, and New York University (NYU), n 76. We calculated energy-adjusted fibre intake based on FFQ. For each study population with adjustment for age, sex, race, BMI and smoking, we evaluated the relationship between fibre intake and gut microbiota community composition and taxon abundance. Total fibre intake was significantly associated with overall microbial community composition in NYU (P=0·008) but not in NCI (P=0·81). In a meta-analysis of both study populations, higher fibre intake tended to be associated with genera of class Clostridia, including higher abundance of SMB53 (fold change (FC)=1·04, P=0·04), Lachnospira (FC=1·03, P=0·05) and Faecalibacterium (FC=1·03, P=0·06), and lower abundance of Actinomyces (FC=0·95, P=0·002), Odoribacter (FC=0·95, P=0·03) and Oscillospira (FC=0·96, P=0·06). A species-level meta-analysis showed that higher fibre intake was marginally associated with greater abundance of Faecalibacterium prausnitzii (FC=1·03, P=0·07) and lower abundance of Eubacterium dolichum (FC=0·96, P=0·04) and Bacteroides uniformis (FC=0·97, P=0·05). Thus, dietary fibre intake may impact gut microbiota composition, particularly class Clostridia, and may favour putatively beneficial bacteria such as F. prausnitzii. These findings warrant further understanding of diet-microbiota relationships for future development of colorectal cancer prevention strategies.

The gut microbiota and the brain-gut-kidney axis in hypertension and chronic kidney disease

Crosstalk between the gut microbiota and the host has attracted considerable attention owing to its involvement in diverse diseases. Chronic kidney disease (CKD) is commonly associated with hypertension and is characterized by immune dysregulation, metabolic disorder and sympathetic activation, which are all linked to gut dysbiosis and altered host-microbiota crosstalk. In this Review, we discuss the complex interplay between the brain, the gut, the microbiota and the kidney in CKD and hypertension and explain our brain-gut-kidney axis hypothesis for the pathogenesis of these diseases. Consideration of the role of the brain-gut-kidney axis in the maintenance of normal homeostasis and of dysregulation of this axis in CKD and hypertension could lead to the identification of novel therapeutic targets. In addition, the discovery of unique microbial communities and their associated metabolites and the elucidation of brain-gut-kidney signalling are likely to fill fundamental knowledge gaps leading to innovative research, clinical trials and treatments for CKD and hypertension.

Metabolites as regulators of insulin sensitivity and metabolism

The cause of insulin resistance in obesity and type 2 diabetes mellitus (T2DM) is not limited to impaired insulin signalling but also involves the complex interplay of multiple metabolic pathways. The analysis of large data sets generated by metabolomics and lipidomics has shed new light on the roles of metabolites such as lipids, amino acids and bile acids in modulating insulin sensitivity. Metabolites can regulate insulin sensitivity directly by modulating components of the insulin signalling pathway, such as insulin receptor substrates (IRSs) and AKT, and indirectly by altering the flux of substrates through multiple metabolic pathways, including lipogenesis, lipid oxidation, protein synthesis and degradation and hepatic gluconeogenesis. Moreover, the post-translational modification of proteins by metabolites and lipids, including acetylation and palmitoylation, can alter protein function. Furthermore, the role of the microbiota in regulating substrate metabolism and insulin sensitivity is unfolding. In this Review, we discuss the emerging roles of metabolites in the pathogenesis of insulin resistance and T2DM. A comprehensive understanding of the metabolic adaptations involved in insulin resistance may enable the identification of novel targets for improving insulin sensitivity and preventing, and treating, T2DM.

Precise Prediction of Calpain Cleavage Sites and Their Aberrance Caused by Mutations in Cancer

As a widespread post-translational modification of proteins, calpain-mediated cleavage regulates a broad range of cellular processes, including proliferation, differentiation, cytoskeletal reorganization, and apoptosis. The identification of proteins that undergo calpain cleavage in a site-specific manner is the necessary foundation for understanding the exact molecular mechanisms and regulatory roles of calpain-mediated cleavage. In contrast with time-consuming and labor-intensive experimental methods, computational approaches for detecting calpain cleavage sites have attracted wide attention due to their efficiency and convenience. In this study, we established a novel computational tool named DeepCalpain (http://deepcalpain.cancerbio.info/) for predicting the potential calpain cleavage sites by adopting deep neural network and the particle swarm optimization algorithm. Through critical evaluation and comparison, DeepCalpain exhibited superior performance against other existing tools. Meanwhile, we found that protein interactions could enrich the calpain-substrate regulatory relationship. Since calpain-mediated cleavage was critical for cancer development and progression, we comprehensively analyzed the calpain cleavage associated mutations across 11 cancers with the help of DeepCalpain, which demonstrated that the calpain-mediated cleavage events were affected by mutations and heavily implicated in the regulation of cancer cells. These prediction and analysis results might provide helpful information to reveal the regulatory mechanism of calpain cleavage in biological pathways and different cancer types, which might open new avenues for the diagnosis and treatment of cancers.

Metabolic Dysregulations and Epigenetics: A Bidirectional Interplay that Drives Tumor Progression

Cancer has been considered, for a long time, a genetic disease where mutations in keyregulatory genes drive tumor initiation, growth, metastasis, and drug resistance. Instead, theadvent of high-throughput technologies has revolutionized cancer research, allowing to investigatemolecular alterations at multiple levels, including genome, epigenome, transcriptome, proteome,and metabolome and showing the multifaceted aspects of this disease. The multi-omics approachesrevealed an intricate molecular landscape where different cellular functions are interconnected andcooperatively contribute to shaping the malignant phenotype. Recent evidence has brought to lighthow metabolism and epigenetics are highly intertwined, and their aberrant crosstalk can contributeto tumorigenesis. The oncogene-driven metabolic plasticity of tumor cells supports the energeticand anabolic demands of proliferative tumor programs and secondary can alter the epigeneticlandscape via modulating the production and/or the activity of epigenetic metabolites. Conversely,epigenetic mechanisms can regulate the expression of metabolic genes, thereby altering themetabolome, eliciting adaptive responses to rapidly changing environmental conditions, andsustaining malignant cell survival and progression in hostile niches. Thus, cancer cells takeadvantage of the epigenetics-metabolism crosstalk to acquire aggressive traits, promote cellproliferation, metastasis, and pluripotency, and shape tumor microenvironment. Understandingthis bidirectional relationship is crucial to identify potential novel molecular targets for theimplementation of robust anti-cancer therapeutic strategies.

Glycan utilisation system in Bacteroides and Bifidobacteria and their roles in gut stability and health

Gut residential hundred trillion microbial cells are indispensable for maintaining gut homeostasis and impact on host physiology, development and immune systems. Many of them have displayed excellence in utilising dietary- and host-derived complex glycans and are producing useful postbiotics including short-chain fatty acids to primarily fuel different organs of the host. Therefore, employing individual microbiota is nowadays becoming a propitious target in biomedical for improving gut dysbiosis conditions of the host. Among other gut microbial communities, Bacteroides and Bifidobacteria are coevolved to utilise diverse ranges of diet- and host-derived glycans through harmonising distinct glycan utilisation systems. These gut symbionts frequently share digested oligosaccharides, carbohydrate-active enzymes and fermentable intermediate molecules for sustaining gut microbial symbiosis and improving fitness of own or other communities. Genomics approaches have provided unprecedented insights into these functions, but their precise mechanisms of action have poorly known. Sympathetic glycan-utilising strategy of each gut commensal will provide overview of mechanistic dynamic nature of the gut environment and will then assist in applying aptly personalised nutritional therapy. Thus, the review critically summarises cutting edge understanding of major plant- and host-derived glycan-utilising systems of Bacteroides and Bifidobacteria. Their evolutionary adaptation to gut environment and roles of postbiotics in human health are also highlighted.

Unraveling the effects of the gut microbiota composition and function on horse endurance physiology

An integrated analysis of gut microbiota, blood biochemical and metabolome in 52 endurance horses was performed. Clustering by gut microbiota revealed the existence of two communities mainly driven by diet as host properties showed little effect. Community 1 presented lower richness and diversity, but higher dominance and rarity of species, including some pathobionts. Moreover, its microbiota composition was tightly linked to host blood metabolites related to lipid metabolism and glycolysis at basal time. Despite the lower fiber intake, community type 1 appeared more specialized to produce acetate as a mean of maintaining the energy supply as glucose concentrations fell during the race. On the other hand, community type 2 showed an enrichment of fibrolytic and cellulolytic bacteria as well as anaerobic fungi, coupled to a higher production of propionate and butyrate. The higher butyrate proportion in community 2 was not associated with protective effects on telomere lengths but could have ameliorated mucosal inflammation and oxidative status. The gut microbiota was neither associated with the blood biochemical markers nor metabolome during the endurance race, and did not provide a biomarker for race ranking or risk of failure to finish the race.

Microbes, metabolites, and the gut-lung axis

The microbiota plays an essential role in the education, development, and function of the immune system, both locally and systemically. Emerging experimental and epidemiological evidence highlights a crucial cross-talk between the intestinal microbiota and the lungs, termed the 'gut-lung axis'. Changes in the constituents of the gut microbiome, through either diet, disease or medical interventions (such as antibiotics) is linked with altered immune responses and homeostasis in the airways. The importance of the gut-lung axis has become more evident following the identification of several gut microbe-derived components and metabolites, such as short-chain fatty acids (SCFAs), as key mediators for setting the tone of the immune system. Recent studies have supported a role for SCFAs in influencing hematopoietic precursors in the bone marrow-a major site of innate and adaptive immune cell development. Here, we review the current understanding of host-microbe cross-talk along the gut-lung axis. We highlight the importance of SCFAs in shaping and promoting bone marrow hematopoiesis to resolve airway inflammation and to support a healthy homeostasis.

Gut microbiota metabolite regulation of host defenses at mucosal surfaces: implication in precision medicine

The gut microbiota has a well-established role in the regulation of host homeostasis. Multiple factors control the composition and function of the microbiota. The westernization of diet, a shift away from nutrient-dense foods toward diets high in saturated fats, has been implicated in the rise of chronic inflammatory diseases such as inflammatory bowel disease (IBD). Diet is critical in the development and maintenance of a healthy microbiome, where dietary fiber (found in the highest amounts in fruits, vegetables, and legumes) is metabolized by the microbiome. In turn, the bacterial metabolites of dietary fiber, short chain fatty acids (SCFAs), regulate gut homeostasis. SCFAs engage G-protein coupled receptors (GPRs) and act as histone deacetylase inhibitors (HDACi) to module epithelial and immune cell functions in the intestines, where they generally promote an anti-inflammatory state. This review highlights the functions of SCFAs and their roles in the pathogenesis of IBD to provide insights into their potential therapeutic application for the treatment of IBD for the purposes of precision medicine.

Workshop Report: Modulation of Antitumor Immune Responses by Dietary and Microbial Metabolites

The human microbiota maintains an enormous and diverse capacity to produce a diet-dependent metabolome that impacts both host tissue and microbial community homeostasis. Recent discoveries support a growing appreciation that microbial metabolites derived from bioactive foods are also important regulators of host immune and metabolic functions. To gain a better understanding of the current evidence for the roles of dietary and microbial metabolites in tumor immunity, the Division of Cancer Biology and the Division of Cancer Prevention, National Cancer Institute, cosponsored a workshop on August 31 and September 1, 2016, in Bethesda, Maryland. Workshop participants examined several lines of converging science that link nutrition, microbiology, and tumor immunology and identified key concepts and research opportunities that will accelerate our understanding of these interactions. In addition, the participants identified some of the critical gaps and research challenges that could be addressed through interdisciplinary collaborations, including future opportunities for translating new information into novel cancer prevention and treatment strategies based on targeting host immune functions that are altered by metabolite sensing pathways.

The microbiota and microbiome in pancreatic cancer: more influential than expected

Microbiota is just beginning to be recognized as an important player in carcinogenesis and the interplay among microbes is greater than expected. Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease for which mortality closely parallels incidence. Early detection would provide the best opportunity to increase survival rates. Specific well-studied oral, gastrointestinal, and intrapancreatic microbes and some kinds of hepatotropic viruses and bactibilia may have potential etiological roles in pancreatic carcinogenesis, or modulating individual responses to oncotherapy. Concrete mechanisms mainly involve perpetuating inflammation, regulating the immune system-microbe-tumor axis, affecting metabolism, and altering the tumor microenvironment. The revolutionary technology of omics has generated insight into cancer microbiomes. A better understanding of the microbiota in PDAC might lead to the establishment of screening or early-stage diagnosis methods, implementation of cancer bacteriotherapy, adjustment of therapeutic efficacy even alleviating the adverse effects, creating new opportunities and fostering hope for desperate PDAC patients.

Ingestion of Non-digestible Carbohydrates From Plant-Source Foods and Decreased Risk of Colorectal Cancer: A Review on the Biological Effects and the Mechanisms of Action

The hypothesis that links the increase in the intake of plant-source foods to a decrease in colorectal cancer (CRC) risk has almost 50 years. Nowadays, systematic reviews and meta-analysis of case-control and cohort studies confirmed the association between dietary patterns and CRC risk, in which the non-digestible carbohydrates (NDC) from plant-source foods are known to play beneficial effects. However, the mechanisms behind the physicochemical properties and biological effects induced by NDC on the decrease of CRC development and progression remain not fully understood. NDC from plant-source foods consist mainly of complex carbohydrates from plant cell wall including pectin and hemicellulose, which vary among foods in structure and in composition, therefore in both physicochemical properties and biological effects. In the present review, we highlighted the mechanisms and described the recent findings showing how these complex NDC from plant-source foods are related to a decrease in CRC risk through induction of both physicochemical effects in the gastrointestinal tract, fermentation-related effects, and direct effects resulting from the interaction between NDC and cellular components including toll-like receptors and galectin-3. Studies support that the definition of the structure-function relationship-especially regarding the fermentation-related effects of NDC, as well as the direct effects of these complex carbohydrates in cells-is crucial for understanding the possible NDC anticancer effects. The dietary recommendations for the intake of NDC are usually quantitative, describing a defined amount of intake per day. However, as NDC from plant-source foods can exert effects that vary widely according to the NDC structure, the dietary recommendations for the intake of NDC plant-source foods are expected to change from a quantitative to a qualitative perspective in the next few years, as occurred for lipid recommendations. Thus, further studies are necessary to define whether specific and well-characterized NDC from plant-source foods induce beneficial effects related to a decrease in CRC risk, thereby improving nutritional recommendations of healthy individuals and CRC patients.

Diagnostic and therapeutic potential of the gut microbiota in patients with early hepatocellular carcinoma

The gut microbiota is involved in the maintenance of the homeostasis of the human body and its alterations are associated with the development of different pathological conditions. The liver is the organ most exposed to the influence of the gut microbiota, and recently important connections between the intestinal flora and hepatocellular carcinoma (HCC) have been described. In fact, HCC is commonly associated with liver cirrhosis and develops in a microenvironment where inflammation, immunological alterations, and cellular aberrations are dramatically evident. Prevention and diagnosis in the earliest stages are still the most effective weapons in fighting this tumor. Animal models show that the gut microbiota can be involved in the promotion and progression of HCC directly or through different pathogenic mechanisms. Recent data in humans have confirmed these preclinical findings, shedding new light on HCC pathogenesis. Limitations due to the different experimental design, the ethnic and hepatological setting make it difficult to compare the results and draw definitive conclusions, but these studies lay the foundations for a pathogenetic redefinition of HCC. Therefore, it is evident that the characterization of the gut microbiota and its modulation can have an enormous diagnostic, preventive, and therapeutic potential, especially in patients with early stage HCC.

Metabolic Intermediates in Tumorigenesis and Progression

Traditional antitumor drugs inhibit the proliferation and metastasis of tumour cells by restraining the replication and expression of DNA. These drugs are usually highly cytotoxic. They kill tumour cells while also cause damage to normal cells at the same time, especially the hematopoietic cells that divide vigorously. Patients are exposed to other serious situations such as a severe infection caused by a decrease in the number of white blood cells. Energy metabolism is an essential process for the survival of all cells, but differs greatly between normal cells and tumour cells in metabolic pathways and metabolic intermediates. Whether this difference could be used as new therapeutic target while reducing damage to normal tissues is the topic of this paper. In this paper, we introduce five major metabolic intermediates in detail, including acetyl-CoA, SAM, FAD, NAD⁺ and THF. Their contents and functions in tumour cells and normal cells are significantly different. And the possible regulatory mechanisms that lead to these differences are proposed carefully. It is hoped that the key enzymes in these regulatory pathways could be used as new targets for tumour therapy.

Peroxisomal β-oxidation regulates histone acetylation and DNA methylation in Arabidopsis

Epigenetic markers, such as histone acetylation and DNA methylation, determine chromatin organization. In eukaryotic cells, metabolites from organelles or the cytosol affect epigenetic modifications. However, the relationships between metabolites and epigenetic modifications are not well understood in plants. We found that peroxisomal acyl-CoA oxidase 4 (ACX4), an enzyme in the fatty acid β-oxidation pathway, is required for suppressing the silencing of some endogenous loci, as well as Pro35S:NPTII in the ProRD29A:LUC/C24 transgenic line. The acx4 mutation reduces nuclear histone acetylation and increases DNA methylation at the NOS terminator of Pro35S:NPTII and at some endogenous genomic loci, which are also targeted by the demethylation enzyme REPRESSOR OF SILENCING 1 (ROS1). Furthermore, mutations in multifunctional protein 2 (MFP2) and 3-ketoacyl-CoA thiolase-2 (KAT2/PED1/PKT3), two enzymes in the last two steps of the β-oxidation pathway, lead to similar patterns of DNA hypermethylation as in acx4 Thus, metabolites from fatty acid β-oxidation in peroxisomes are closely linked to nuclear epigenetic modifications, which may affect diverse cellular processes in plants.

Effects of Intestinal Microbial⁻Elaborated Butyrate on Oncogenic Signaling Pathways

The intestinal microbiota is well known to have multiple benefits on human health, including cancer prevention and treatment. The effects are partially mediated by microbiota-produced short chain fatty acids (SCFAs) such as butyrate, propionate and acetate. The anti-cancer effect of butyrate has been demonstrated in cancer cell cultures and animal models of cancer. Butyrate, as a signaling molecule, has effects on multiple signaling pathways. The most studied effect is its inhibition on histone deacetylase (HDAC), which leads to alterations of several important oncogenic signaling pathways such as JAK2/STAT3, VEGF. Butyrate can interfere with both mitochondrial apoptotic and extrinsic apoptotic pathways. In addition, butyrate also reduces gut inflammation by promoting T-regulatory cell differentiation with decreased activities of the NF-κB and STAT3 pathways. Through PKC and Wnt pathways, butyrate increases cancer cell differentiation. Furthermore, butyrate regulates oncogenic signaling molecules through microRNAs and methylation. Therefore, butyrate has the potential to be incorporated into cancer prevention and treatment regimens. In this review we summarize recent progress in butyrate research and discuss the future development of butyrate as an anti-cancer agent with emphasis on its effects on oncogenic signaling pathways. The low bioavailability of butyrate is a problem, which precludes clinical application. The disadvantage of butyrate for medicinal applications may be overcome by several approaches including nano-delivery, analogue development and combination use with other anti-cancer agents or phytochemicals.

The Role of the Microbiome in Immunologic Development and its Implication For Pancreatic Cancer Immunotherapy

Our understanding of the microbiome and its role in immunity, cancer initiation, and cancer progression has evolved significantly over the past century. The "germ theory of cancer" was first proposed in the early 20^th century, and shortly thereafter the bacterium Helicobacter pylori, and later Fusobacterium nucleatum, were implicated in the development of gastric and colorectal cancers, respectively. However, with the development of reliable mouse models and affordable sequencing technologies, the most fascinating aspect of the microbiome-cancer relationship, where microbes undermine cancer immune surveillance and indirectly promote oncogenesis, has only recently been described. In this review, we highlight the essential role of the microbiome in immune system development and maturation. We review how microbe-induced immune activation promotes oncogenesis, focusing particularly on pancreatic carcinogenesis, and show that modulation of the microbiome augments the anti-cancer immune response and enables successful immunotherapy against pancreatic cancer.

Short chain fatty acid butyrate uptake reduces expressions of prostanoid EP4 receptors and their mediation of cyclooxygenase-2 induction in HCA-7 human colon cancer cells

Microbiota produce short chain fatty acids (SCFAs), which are known to maintain gut homeostasis, by the fermentation of dietary fiber in the human colon. Among SCFAs, butyrate has been considered as the most physiologically effective SCFA in colorectal epithelial cells for growth and differentiation. Here we show that the E-type prostanoid 4 (EP₄) receptor expression level is regulated by different concentrations of butyrate, but not by other SCFAs, in human colon cancer HCA-7 cells, through sodium-coupled monocarboxylate transporter-1 (SMCT-1)-mediated uptake followed by the activation of histone acetyltransferase: cAMP response element binding protein-binding protein/p300. Of particular interest, the prostanoid EP₄ receptors are known to be expressed in normal colorectal crypt epithelial cells and maintain intestinal homeostasis by preserving mucosal integrity, while they are also known to be involved in the early stage of carcinogenesis. Thus, the links between butyrate and the expression of prostanoid EP₄ receptors are both important factors for maintaining homeostasis. Based on in silico analysis, almost half of colorectal cancer tissues have lost the expression of SMCT-1 mRNA when compared with healthy corresponding tissues. Therefore, with the collapse of homeostasis systems such as a decrease in the concentration of butyrate in colorectal tissues, or reduced butyrate uptake, there is a possibility of early stage colorectal cancer development; the transformation of normal cells to the cancerous phenotype may be due to the overexpression of prostanoid EP₄ receptors followed by excessive cyclooxygenase-2 induction, which are caused by a reduced amount of butyrate and/or its uptake, in/around colorectal epithelial cells.

The Complex Interplay between Metabolic Reprogramming and Epigenetic Alterations in Renal Cell Carcinoma

Renal cell carcinoma (RCC) is the most common malignancy affecting the kidney. Current therapies are mostly curative for localized disease, but do not completely preclude recurrence and metastization. Thus, it is imperative to develop new therapeutic strategies based on RCC biological properties. Presently, metabolic reprograming and epigenetic alterations are recognized cancer hallmarks and their interactions are still in its infancy concerning RCC. In this review, we explore RCC biology, highlighting genetic and epigenetic alterations that contribute to metabolic deregulation of tumor cells, including high glycolytic phenotype (Warburg effect). Moreover, we critically discuss available data concerning epigenetic enzymes' regulation by aberrant metabolite accumulation and their consequences in RCC emergence and progression. Finally, we emphasize the clinical relevance of uncovering novel therapeutic targets based on epigenetic reprograming by metabolic features to improve treatment and survival of RCC patients.

1H, 13C and 15N backbone and side-chain assignment of a carbohydrate binding module from a xylanase from Roseburia intestinalis

The N-terminal domain (residues 28-165) from the glycoside hydrolase family 10 from Roseburia intestinalis (RiCBMx), has been isotopically labeled and recombinantly expressed in Escherichia coli. Here we report ¹H, ¹³C and ¹⁵N NMR chemical shift assignments for this carbohydrate binding module (CBM).

Rat Intestinal Acetic Acid and Butyric acid and Effects of Age, Sex, and High-fat Diet on the Intestinal Levels in Rats

Background

High-fat diet is known to be implicated in the pathogenesis of various metabolic disorders related to an inflammatory response. The aim of this study was to investigate the influence of high-fat diet for intestinal acetic acid and butyric acid concentrations which are related to inflammation-associated colon cancer risk.

Methods

Both male and female rats of 6, 31, 74 and 104-week of age were fed chow diet or high-fat diet for 8 weeks. Body weight and food intake were measured weekly during the feeding period. Intestinal acetic acid and butyric acid levels were measured by high-performance liquid chromatography from luminal contents of ileum and cecum.

Results

Male rats showed greater weight change than female rats in every age. Calorie-adjusted food intake was also higher in male rats compared to female rats. Male rats showed similar intake of food in every age while 31-week old female rats showed increased intake, which was decreased at 74-week and 104-week of age. The ileal acetic acid concentration was increased in male rats fed high-fat diet, while female rats fed high-fat diet showed no significant change in the ileal acetic acid level. On the other hand, butyric acid almost disappeared in high-fat diet fed rats regardless of sex.

Conclusions

High-fat diet increases the intestinal acetic acid concentration while reducing the butyric acid concentration which may account for increased risk of inflammation-associated colon cancer.

Impact of Different Types of Diet on Gut Microbiota Profiles and Cancer Prevention and Treatment

: Diet is frequently considered as a food regimen focused on weight loss, while it is actually the sum of food consumed by the organism. Western diets, modern lifestyle, sedentary behaviors, smoking habits, and drug consumption have led to a significant reduction of gut microbial diversity, which is linked to many non-communicable diseases (NCDs). The latter kill 40 million people each year, equivalent to more than 70% of all deaths globally. Among NCDs, tumors play a major role, being responsible for 29% of deaths from NCDs. A link between diet, microbiota, and cancer prevention and treatment has recently been unveiled, underlining the importance of a new food culture based on limiting dietary surplus and on preferring healthier foods. Here, we review the effects of some of the most popular "cancer-specific" diets on microbiota composition and their potential impact on cancer prevention and treatment.

Role of SCFAs in gut microbiome and glycolysis for colorectal cancer therapy

Increased risk of colorectal cancer (CRC) is associated with altered intestinal microbiota as well as short-chain fatty acids (SCFAs) reduction of output The energy source of colon cells relies mainly on three SCFAs, namely butyrate (BT), propionate, and acetate, while CRC transformed cells rely mainly on aerobic glycolysis to provide energy. This review summarizes recent research results for dysregulated glucose metabolism of SCFAs, which could be initiated by gut microbiome of CRC. Moreover, the relationship between SCFA transporters and glycolysis, which may correlate with the initiation and progression of CRC, are also discussed. Additionally, this review explores the linkage of BT to transport of SCFAs expressions between normal and cancerous colonocyte cell growth for tumorigenesis inhibition in CRC. Furthermore, the link between gut microbiota and SCFAs in the metabolism of CRC, in addition, the proteins and genes related to SCFAs-mediated signaling pathways, coupled with their correlation with the initiation and progression of CRC are also discussed. Therefore, targeting the SCFA transporters to regulate lactate generation and export of BT, as well as applying SCFAs or gut microbiota and natural compounds for chemoprevention may be clinically useful for CRCs treatment. Future research should focus on the combination these therapeutic agents with metabolic inhibitors to effectively target the tumor SCFAs and regulate the bacterial ecology for activation of potent anticancer effect, which may provide more effective application prospect for CRC therapy.

Secondary Bile Acids and Short Chain Fatty Acids in the Colon: A Focus on Colonic Microbiome, Cell Proliferation, Inflammation, and Cancer

Secondary bile acids (BAs) and short chain fatty acids (SCFAs), two major types of bacterial metabolites in the colon, cause opposing effects on colonic inflammation at chronically high physiological levels. Primary BAs play critical roles in cholesterol metabolism, lipid digestion, and host–microbe interaction. Although BAs are reabsorbed via enterohepatic circulation, primary BAs serve as substrates for bacterial biotransformation to secondary BAs in the colon. High-fat diets increase secondary BAs, such as deoxycholic acid (DCA) and lithocholic acid (LCA), which are risk factors for colonic inflammation and cancer. In contrast, increased dietary fiber intake is associated with anti-inflammatory and anticancer effects. These effects may be due to the increased production of the SCFAs acetate, propionate, and butyrate during dietary fiber fermentation in the colon. Elucidation of the molecular events by which secondary BAs and SCFAs regulate colonic cell proliferation and inflammation will lead to a better understanding of the anticancer potential of dietary fiber in the context of high-fat diet-related colon cancer. This article reviews the current knowledge concerning the effects of secondary BAs and SCFAs on the proliferation of colon epithelial cells, inflammation, cancer, and the associated microbiome.

RNA Sequencing Analysis of Molecular Basis of Sodium Butyrate-Induced Growth Inhibition on Colorectal Cancer Cell Lines

Butyrate is a short-chain fatty acid decomposed from dietary fiber and has been shown to have effects on inhibition of proliferation but induction of apoptosis in colorectal cancer cells. However, clinical trials have yielded ambiguous outcomes with regard to its antitumor activities. In this study, we aimed to explore the molecular mechanisms underlying the sensitivity of colorectal cancer cells to sodium butyrate (NaB). RNA sequencing was used to establish the whole-transcriptome profile in NaB-treated versus untreated colorectal cancer cells. Differentially expressed genes were bioinformatically analyzed to predict their possible involvement in NaB-triggered cell death, and the expression of eight dysregulated genes was validated by quantitative real-time PCR. We found that there were a total of 7192 genes (5720 upregulated and 1472 downregulated, fold-change ≥ 2 or ≤ 0.5 for upregulation or downregulation, q-value < 0.05) differentially expressed in NaB-treated cells as compared with the untreated controls. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis demonstrated that the differentially expressed genes were enriched in DNA replication, cell cycle, homologous recombination, pyrimidine metabolism, mismatch repair, and other signaling pathways and may take part in NaB-induced cell death. Among the identified factors, the MCM2-7 complex might be a target of NaB. Our findings provide an important basis for further studies of the complicate network that might regulate sensitivity of colorectal cancer cells to NaB.

The human gut Firmicute Roseburia intestinalis is a primary degrader of dietary β-mannans

β-Mannans are plant cell wall polysaccharides that are commonly found in human diets. However, a mechanistic understanding into the key populations that degrade this glycan is absent, especially for the dominant Firmicutes phylum. Here, we show that the prominent butyrate-producing Firmicute Roseburia intestinalis expresses two loci conferring metabolism of β-mannans. We combine multi-“omic” analyses and detailed biochemical studies to comprehensively characterize loci-encoded proteins that are involved in β-mannan capturing, importation, de-branching and degradation into monosaccharides. In mixed cultures, R. intestinalis shares the available β-mannan with Bacteroides ovatus, demonstrating that the apparatus allows coexistence in a competitive environment. In murine experiments, β-mannan selectively promotes beneficial gut bacteria, exemplified by increased R. intestinalis, and reduction of mucus-degraders. Our findings highlight that R. intestinalis is a primary degrader of this dietary fiber and that this metabolic capacity could be exploited to selectively promote key members of the healthy microbiota using β-mannan-based therapeutic interventions.

How dietary β-mannans are utilized by gut Gram-positive bacteria is unclear. Here, the authors uncover the enzymatic pathway for β-mannan metabolism in Roseburia intestinalis and show that these polysaccharides promote beneficial gut bacteria, highlighting a potential for β-mannan-based therapeutic interventions.

Elevated Gut Microbiome-Derived Propionate Levels Are Associated With Reduced Sterile Lung Inflammation and Bacterial Immunity in Mice

Short-chain fatty acids (SCFA) are important dietary and microbiome metabolites that can have roles in gut immunity as well as further afield. We previously observed that gut microbiome alteration via antibiotics led to attenuated lung inflammatory responses. The rationale for this study was to identify gut microbiome factors that regulate lung immune homeostasis. We first investigated key factors within mouse colonic lumen filtrates (CLF) which could elicit direct inflammatory effects in vitro. We identified lipopolysaccharide (LPS) and SCFAs as key CLF ingredients whose levels and inflammatory capacity changed after antibiotic exposure in mice. Specifically, the SCFA propionate appeared to be a key regulator of LPS responses in vitro. Elevated propionate: acetate ratios, as seen in CLF after antibiotic exposure, strongly blunted inflammatory responses in vitro. In vivo, exposure of lungs to high dose propionate, to mimic how prior antibiotic exposure changed SCFA levels, resulted in diminished immune containment of Staphylococcus aureus pneumonia. Finally, we discovered an enrichment of propionate-producing gut bacteria in mice with reduced lung inflammation following lung ischemia reperfusion injury in vivo. Overall, our data show that propionate levels can distinctly modulate lung immune responses in vitro and in vivo and that gut microbiome increased production of propionate is associated with reduced lung inflammation.

Gastric infusion of short-chain fatty acids can improve intestinal barrier function in weaned piglets

Background

The present study was conducted to investigate the effects of gastric infusion of short-chain fatty acids (SCFA) on gut barrier function in a pig model. In this study, 21 DLY barrows with an average initial body weight of (8.31 ± 0.72) kg were randomly allotted into three treatments: (1) control, (2) infusing low SCFA, S1, (3) infusing high SCFA, S2. The experimental period lasted for 7 days.

Results

Gastric infusion of SCFA increased the concentrations of SCFA in serum and digesta, and enhanced the mRNA and protein abundances of SCFA receptors in pig intestine (P < 0.05). Moreover, gastric infusion of SCFA led to alteration of intestinal morphology, elevation of intestinal development-related gene abundances, and decrease of apoptotic cell percentage, as well as reduction of pro-apoptosis gene and protein abundances (P < 0.05). Besides, the jejunal SLC₇A₁ and ileal DMT1 mRNA abundances in the SCFA infusion groups were higher than those in the control group (P < 0.05). Additionally, gastric infusion of SCFA increased the mRNA abundances of Occludin and Claudin-1 in the duodenum and ileum, enhanced Lactobacillus spp counts in the ileal digesta, decreased the mRNA and protein abundances of IL-1β in the colon, and reduced Escherichia coli count in the ileal digesta (P < 0.05).

Conclusions

These data indicated that gastric infusion of SCFA, especially high SCFA concentration, may be beneficial to gut development of piglets via improving gut morphology, decreasing apoptotic cell percentage, and maintaining intestinal barrier function.

Electronic supplementary material

The online version of this article (10.1186/s12263-019-0626-x) contains supplementary material, which is available to authorized users.

Microbiota-accessible pectic poly- and oligosaccharides in gut health

Diverse human intestinal microbiota are regarded as a prerequisite for a healthy intestine. Commercial prebiotic products have a limited ability to provide microbial diversity in the human gut, because they mostly comprise oligomers of the same monosaccharide residues and a small fraction of them can reach the distal colon. Therefore, the demand for diverse prebiotic ingredients and dietary fibers with improved functional properties is increasing tremendously. The main sources of carbohydrates in our diet are plant-derived polysaccharides, which are consumed by the bacteria present in the intestine. Among these, pectin-derived poly- and oligosaccharides serve as the best alternative, as they are resistant to human gastric juice and are fermented slowly in the large intestine to impart a prebiotic effect. The main components of pectin are polygalacturonic acids in association with neutral polysaccharides such as arabinan, arabinogalactan, and galactan. The present review deals with the health-related functional properties of pectic poly- and oligosaccharides and their applications in the food industry. Different mechanisms involved in the hydrolysis of these carbohydrates by the intestinal bacteria and in maintaining the microbial diversity of the intestine are also discussed. It also emphasizes the current methods for the production and purification of different pectins and their oligosaccharides.

A requirement for septins and the autophagy receptor p62 in the proliferation of intracellular Shigella

Shigella flexneri, a Gram-negative enteroinvasive pathogen, causes inflammatory destruction of the human intestinal epithelium. During infection of epithelial cells, Shigella escape from the phagosome to the cytosol, where they reroute host cell glycolysis to obtain nutrients for proliferation. Septins, a poorly understood component of the cytoskeleton, can entrap cytosolic Shigella targeted to autophagy in cage-like structures to restrict bacterial proliferation. Although bacterial entrapment by septin caging has been the subject of intense investigation, the role of septins and the autophagy machinery in the proliferation of noncaged Shigella is mostly unknown. Here, we found that intracellular Shigella fail to efficiently proliferate in SEPT2-, SEPT7-, or p62/SQSTM1-depleted cells. Consistent with a failure to proliferate, single cell analysis of bacteria not entrapped in septin cages showed that the number of metabolically active Shigella in septin- or p62-depleted cells is reduced. Targeted metabolomic analysis revealed that host cell glycolysis is dysregulated in septin-depleted cells, suggesting a key role for septins in modulation of glycolysis. Together, these results suggest that septins and the autophagy machinery may regulate metabolic pathways that promote the proliferation of intracellular Shigella not entrapped in septin cages.

Isotopic Labeling and Quantitative Proteomics of Acetylation on Histones and Beyond

Lysine acetylation is an important posttranslational modification (PTM) that regulates the function of proteins by affecting their localization, stability, binding, and enzymatic activity. Aberrant acetylation patterns have been observed in numerous diseases, most notably cancer, which has spurred the development of potential therapeutics that target acetylation pathways. Mass spectrometry (MS) has become the most adopted tool not only for the qualitative identification of acetylation sites but also for their large-scale quantification. By using heavy isotope labeling in cell culture combined with MS, it is now possible to accurately quantify newly synthesized acetyl groups and other PTMs, allowing differentiation between dynamically regulated and steady-state modifications. Here, we describe MS-based protocols to identify acetylation sites and quantify acetylation rates on both proteins in general and in the special case of histones. In the experimental approach for the former, ¹³C-glucose and D₃-acetate are used to metabolically label protein acetylation in cells with stable isotopes, thus allowing isotope incorporation to be tracked over time. After protein extraction and digestion, acetylated peptides are enriched via immunoprecipitation and then analyzed by MS. For histones, a similar metabolic labeling approach is performed, followed by acid extraction, derivatization with propionic anhydride, and trypsin digestion prior to MS analysis. The procedures presented may be adapted to investigate acetylation dynamics in a broad range of experimental contexts, including different cell types and stimulation conditions.

Butyrate stimulates hepatic gluconeogenesis in mouse primary hepatocytes

Butyrate is a major short-chain fatty acid (SCFA) produced by microbial fermentation of dietary fiber in the gastrointestinal tract. Butyrate is also a well-known broad-spectrum histone deacetylase (HDAC) inhibitor. Butyrate has been reported to improve energy metabolism in rodents, which is associated with its beneficial effects on skeletal muscle, brown fat tissue and pancreatic β-cells. The present study investigated the direct effect of butyrate on hepatic gluconeogenesis in mouse primary hepatocytes and the underlying mechanism. Isolated mouse primary hepatocytes were incubated with sodium butyrate, other HDAC inhibitors and other SCFAs. Hepatic glucose production was measured and gluconeogenic gene expression was detected by polymerase chain reaction analysis. The phosphorylation of cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) was assessed by western blot analysis. The results revealed that sodium butyrate dose-dependently increased hepatic glucose production and gluconeogenic gene expression in isolated mouse primary hepatocytes. Trichostatin A, a potent broad-spectrum HDAC inhibitor, had the opposite effect. Similar to sodium butyrate, propionate, which is another SCFA, promoted hepatic glucose production and gluconeogenic gene expression in the presence or absence of gluconeogenic substrates, which were further enhanced by cAMP. Furthermore, sodium butyrate also increased the accumulation of intracellular ATP and induced the phosphorylation of CREB in mouse hepatocytes. In conclusion, the present study suggested that butyrate stimulates hepatic gluconeogenesis and induces gluconeogenic gene expression as a substrate and cAMP/CREB signaling activator.

Butyrate inhibits HBV replication and HBV-induced hepatoma cell proliferation via modulating SIRT-1/Ac-p53 regulatory axis

Butyrate, a histone deacetylase inhibitor, has several therapeutic applications, including cancer. However, the effect of butyrate in HBV replication is not known so far. It was hypothesized that butyrate might inhibit HBV replication and host cell proliferation via SIRT-1. It was found that the increased expression of SIRT-1 in Hep G2.2.15 cells (HBV expressing cells) than Hep G2 cells. Next the expression of SIRT-1 and Acetylated p53 (Ac-p53) were measured in the liver biopsy samples of chronic hepatitis B (CHB) patients with high viral load and compared to CHB patients with low viral load and found that there was a high SIRT-1 expression and a low Ac-p53 levels in CHB patients with high viral load compared to CHB patients with low viral load. Incubation of butyrate inhibited SIRT-1 expression and cell proliferation. Inhibition of SIRT-1 by butyrate or SIRT-1 siRNA increased the levels of Ac-p53. The elevated Ac-p53 decreased p-akt, cyclin D1, and thereby inhibited cell proliferation. Incubation of butyrate with Hep G2.2.15 cells also inhibited HBx protein expression, HBV-DNA and hepatitis B surface antigen (HBsAg). Taken together, the data showed that butyrate inhibited HBV replication and cell proliferation by inhibiting SIRT-1 expression in hepatoma cells.

Role of gut microbiota in chronic low-grade inflammation as potential driver for atherosclerotic cardiovascular disease: a systematic review of human studies

A hallmark of obesity is chronic low-grade inflammation, which plays a major role in the process of atherosclerotic cardiovascular disease (ACVD). Gut microbiota is one of the factors influencing systemic immune responses, and profound changes have been found in its composition and metabolic function in individuals with obesity. This systematic review assesses the association between the gut microbiota and markers of low-grade inflammation in humans. We identified 14 studies which were mostly observational and relatively small (n = 10 to 471). The way in which the microbiome is analysed differed extensively between these studies. Lower gut microbial diversity was associated with higher white blood cell counts and high sensitivity C-reactive protein (hsCRP) levels. The abundance of Bifidobacterium, Faecalibacterium, Ruminococcus and Prevotella were inversely related to different markers of low-grade inflammation such as hsCRP and interleukin (IL)-6. In addition, this review speculates on possible mechanisms through which the gut microbiota can affect low-grade inflammation and thereby ACVD. We discuss the associations between the microbiome and the inflammasome, the innate immune system, bile acids, gut permeability, the endocannabinoid system and TMAO. These data reinforce the importance of human research into the gut microbiota as potential diagnostic and therapeutic strategy to prevent ACVD.

Sodium Phenylbutyrate Ameliorates Inflammatory Response Induced by Staphylococcus aureus Lipoteichoic Acid via Suppressing TLR2/NF-κB/NLRP3 Pathways in MAC-T Cells

This study aimed to investigate the anti-inflammatory properties of sodium phenylbutyrate (SPB) against Staphylococcus aureus (S. aureus) lipoteichoic acid (LTA)-stimulated bovine mammary alveolar (MAC-T) cells. Quantitative PCR was performed to examine the effect of SPB on inflammatory cytokines and host defense peptide (HDP) gene expression. Western blot wanalysis was used to detect the effect of SPB on the TLR2/NF-κB/NLRP3 signaling pathway. The results showed that SPB significantly suppressed the expression of TNF-α, IL-1β, IL-6; meanwhile, the markedly decreased expression of LTA-stimulated TLR2, NLRP3, ASC, caspase-1, and IL-1β, and the inhibited IkBα and p65 phosphorylation were also observed. However, increased TAP and Bac5 expression in LTA-stimulated MAC-T cells was further detected. In summary, these results suggest that SPB ameliorates the inflammatory response induced by S. aureus LTA via suppressing the TLR2/NF-κB/NLRP3 signaling pathway, which indicates that SPB may be a potential agent for the treatment of bovine mastitis.

Colorectal Cancer and Metabolism

Purpose of Review

Metabolic reprogramming is essential for the rapid proliferation of cancer cells and is thus recognized as a hallmark of cancer. In this review, we will discuss the etiologies and effects of metabolic reprogramming in colorectal cancer.

Recent Findings

Changes in cellular metabolism may precede the acquisition of driver mutations ultimately leading to colonocyte transformation. Oncogenic mutations and loss of tumor suppressor genes further reprogram CRC cells to upregulate glycolysis, glutaminolysis, one-carbon metabolism, and fatty acid synthesis. These metabolic changes are not uniform throughout tumors, as subpopulations of tumor cells may rely on different pathways to adapt to nutrient availability in the local tumor microenvironment. Finally, metabolic cross-communication between stromal cells, immune cells, and the gut microbiota enable CRC growth, invasion, and metastasis.

Summary

Altered cellular metabolism occurs in CRC at multiple levels, including in the cells that make up the bulk of CRC tumors, cancer stem cells, the tumor microenvironment, and host-microbiome interactions. This knowledge may inform the development of improved screening and therapeutics for CRC.

Butyrate interacts with benzo[a]pyrene to alter expression and activities of xenobiotic metabolizing enzymes involved in metabolism of carcinogens within colon epithelial cell models

Butyrate helps to maintain colon homeostasis and exhibits chemopreventive effects in colon epithelium. We examined the interactive effects of butyrate and benzo[a]pyrene (BaP), dietary carcinogen, in regulation of expression of a panel of phase I and II xenobiotic metabolizing enzymes (XMEs) in human colon cells. In human colon carcinoma HCT-116 and HT-29 cell lines, butyrate alone increased mRNA levels of some enzymes, such as N-acetyltransferases (in particular NAT2). In combination with BaP, butyrate potentiated induction of cytochrome P450 family 1 enzymes (CYP1A1), aldo-keto reductases (AKR1C1) or UDP-glucuronosyltransferases (UGT1A1). There were some notable differences between cell lines, as butyrate potentiated induction of NAD(P)H:quinone oxidoreductase 1 (NQO1) and UGT1A4 only in HCT-116 cells, and it even repressed AKR1C3 induction in HT-29 cells. Butyrate also promoted induction of CYP1, NQO1, NAT2, UGT1A1 or UGT1A4 in human colon Caco-2 cells, in a differentiation-dependent manner. Differentiated Caco-2 cells exhibited a higher inducibility of selected XME genes than undifferentiated cells. Butyrate increased induction of enzymatic activities of NATs, NQO1 and UGTs by BaP in HCT-116 and HT29 cells, whereas in differentiated Caco-2 cells it helped to increase only enzymatic activity of NQO1 and UGTs. Together, the present data suggest that butyrate may modulate expression/activities of several enzymes involved in metabolism of carcinogens in colon. In some cases (NAT2, UGT1 A1), this was linked to inhibition of histone deacetylases (HDAC), as confirmed by using HDAC inhibitor trichostatin A. These results may have implications for our understanding of the role of butyrate in regulation of XMEs and carcinogen metabolism in colon.

Gut microbiota-mediated inflammation in obesity: a link with gastrointestinal cancer

Overweight and obesity are associated with increased risk of developing metabolic disorders such as diabetes and cardiovascular diseases. However, besides these metabolic diseases, excess body weight is also associated with different cancers, including gastrointestinal cancers, such as liver, pancreatic and colon cancers. Inflammation is a common feature of both obesity and cancer; however, the origin of this inflammation has been largely debated. Over the past decade, growing evidence has shown that the composition of the gut microbiota and its activity might be associated not only with the onset of inflammation but also with metabolic disorders and cancer. Here, we review the links between the gut microbiota, gut barrier function and the onset of low-grade inflammation in the development of gastrointestinal cancer. We also describe the mechanisms by which specific microorganism-associated molecular patterns crosstalk with the immune system and how the metabolic activity of bacteria induces specific signalling pathways beyond the gut that eventually trigger carcinogenesis.

Pancreatic Cancer and Obesity: Molecular Mechanisms of Cell Transformation and Chemoresistance

Cancer and obesity are the two major epidemics of the 21st century. Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of death, with a five-year overall survival rate of only 8%. Its incidence and mortality have increased in recent years, and this cancer type is expected to be among the top five leading causes of cancer-related death by 2030 in the United States (US). In the last three decades, the prevalence of overweight people has boosted with a consequent increase in obesity-related diseases. Considerable epidemiologic evidence correlates overweight and obese conditions to an increased risk of several types of cancer, including PDAC. Besides being a risk factor for multiple metabolic disorders, the tumor-promoting effects of obesity occur at the local level via inflammatory mediators that are associated with adipose inflammation and metabolic or hormones mediators and microbiota dysbiosis. Although an excess of body mass index (BMI) represents the second most modifiable risk factor for PDAC with an increased cancer related-death of more than 20–40%, still little is known about the molecular mechanisms that underlie this strong association. In this review, we focused on the role of obesity as a preventable risk factor of PDAC, discussing the molecular mechanisms linking obesity to cancer initiation and progression. Moreover, we highlighted the role of obesity in defining chemoresistance, showing how a high BMI can actually reduce response to chemotherapy.

Sodium butyrate induces autophagy in colorectal cancer cells through LKB1/AMPK signaling

Butyrate is produced by the fermentation of undigested dietary fibers and acts as the promising candidate for cancer treatment. However, the mechanism underlying sodium butyrate (NaB)-induced autophagy in colorectal cancer is not yet completely understood. The expressions of LC3-II protein and mRNA were detected by western blot and quantitative RT-PCR in colorectal cancer (CRC) cell lines HCT-116 and HT-29, respectively. Autolysosome formation was observed by transmission electron microscope. AMPK and LKB1 were inhibited by chemical inhibitor or siRNAs and confirmed by western blot. NaB elevated the protein and mRNA expressions of LC3 in a dose-dependent manner. NaB treatment increased the formation of autolysosome and expression of phosphorylated liver kinase B1 (LKB1), AMP-activated protein kinase (AMPK), and acetyl-CoA carboxylase (ACC). Treatment with compound C (an inhibitor of AMPK) and siRNA-mediated knockdown of AMPK and LKB1 significantly attenuated NaB-induced autophagy in CRC cells. Collectively, these findings indicated that LKB1 and AMPK are critical for NaB-mediated autophagy and may act as the novel targets for colorectal cancer therapy in the future.

Dysregulated Microbial Fermentation of Soluble Fiber Induces Cholestatic Liver Cancer

Dietary soluble fibers are fermented by gut bacteria into short-chain fatty acids (SCFA), which are considered broadly health-promoting. Accordingly, consumption of such fibers ameliorates metabolic syndrome. However, incorporating soluble fiber inulin, but not insoluble fiber, into a compositionally defined diet, induced icteric hepatocellular carcinoma (HCC). Such HCC was microbiota-dependent and observed in multiple strains of dysbiotic mice but not in germ-free nor antibiotics-treated mice. Furthermore, consumption of an inulin-enriched high-fat diet induced both dysbiosis and HCC in wild-type (WT) mice. Inulin-induced HCC progressed via early onset of cholestasis, hepatocyte death, followed by neutrophilic inflammation in liver. Pharmacologic inhibition of fermentation or depletion of fermenting bacteria markedly reduced intestinal SCFA and prevented HCC. Intervening with cholestyramine to prevent reabsorption of bile acids also conferred protection against such HCC. Thus, its benefits notwithstanding, enrichment of foods with fermentable fiber should be approached with great caution as it may increase risk of HCC.

Metabolism and Epigenetic Interplay in Cancer: Regulation and Putative Therapeutic Targets

Alterations in the epigenome and metabolism affect molecular rewiring of cancer cells facilitating cancer development and progression. Modulation of histone and DNA modification enzymes occurs owing to metabolic reprogramming driven by oncogenes and expression of metabolism-associated genes is, in turn, epigenetically regulated, promoting the well-known metabolic reprogramming of cancer cells and, consequently, altering the metabolome. Thus, several malignant traits are supported by the interplay between metabolomics and epigenetics, promoting neoplastic transformation. In this review we emphasize the importance of tumour metabolites in the activity of most chromatin-modifying enzymes and implication in neoplastic transformation. Furthermore, candidate targets deriving from metabolism of cancer cells and altered epigenetic factors is emphasized, focusing on compounds that counteract the epigenomic-metabolic interplay in cancer.