Fiber-derived butyrate and the prevention of colon cancer

Characterization of butyrate-metabolism in colorectal cancer to guide clinical treatment

Colorectal cancer (CRC) is the third most prevalent one in the world among the most common malignant tumors. Numerous studies have shown that butyrate has demonstrated promise as an antitumor agent in a variety of human cancer types. However, butyrate remains understudied in CRC tumorigenesis and progression. In this study, we explored therapeutic strategies to treat CRC by examining the role of butyrate metabolism. First, from the Molecular Signature Database (MSigDB), we identified 348 butyrate metabolism-related genes (BMRGs). Next, we downloaded 473 CRC and 41 standard colorectal tissue samples from The Cancer Genome Atlas (TCGA) database and the transcriptome data of GSE39582 dataset from Gene Expression Omnibus (GEO) database. Then we evaluated the expression patterns of butyrate metabolism-related genes with difference analysis in CRC. Through univariate Cox regression and least absolute shrinkage and selection operator (LASSO) analysis, a prognostic model was constructed based on differentially expressed BMRGs. In addition, we discovered an independent prognostic marker for CRC patients. According to the expression levels and coefficients of identified BMRGs, the risk scores of all CRC samples were calculated. Utilizing differentially expressed genes in the high- and low-risk groups, we also constructed a Protein-Protein Interaction (PPI) network to visualize the interactions between proteins. Through the results of PPI network, we screened out differentially expressed target butyrate metabolism-related genes from ten hub genes. Finally, we performed clinical correlation analysis, immune cell infiltration analysis, and mutation analysis for these target genes. One hundred and seventy three differentially expressed butyrate metabolism-related genes were screened out in all the CRC samples. The prognostic model was established with univariate Cox regression and LASSO regression analysis. CRC patients' overall survival was significantly lower in the high-risk group than in the low-risk group for both training and validation set. Among the ten hub genes identified from the PPI network, four target butyrate metabolism-related genes were identified containing FN1, SERPINE1, THBS2, and COMP, which might provide novel markers or targets for treating CRC patients. Eighteen butyrate metabolism-related genes were used to develop a risk prognostic model that could be helpful for doctors to predict CRC patients' survival rate. Using this model, it is beneficial to forecast the response of CRC patients to immunotherapy and chemotherapy, thus making it easier to custom tailor cancer chemotherapy and immunotherapy to the individual patient.

Dietary fiber in the prevention of obesity and obesity-related chronic diseases: From epidemiological evidence to potential molecular mechanisms

Obesity is a mostly preventable diet-related disease and currently a major challenge for human populations worldwide. Obesity is a major risk factor for diseases such as type 2 diabetes mellitus (T2DM), cardiovascular disease (CVD) and certain cancers. Dietary fiber is a complex mixture of non-digestible molecules, mostly polysaccharides. Multiple epidemiological studies have demonstrated statistically significant reductions in risks of obesity, T2DM, CVD, colorectal cancer, and pre-menopausal breast cancer with higher dietary fiber intakes. Various direct and indirect mechanisms have been proposed including altered digestion and absorption, stimulation of gut hormones including glucagon-like-peptide-1 (GLP-1) and peptide YY (PYY), reduced appetite, and altered metabolism of bile and cholesterol. These may act via pathways involving G-protein-coupled receptors (GPRs), histone deacetylase (HDAC), and aromatase enzymes. Ultimately, fiber intake contributes to improving glucose levels and insulin sensitivity, lowering risk of T2DM, CVD and certain cancers. Therefore, diets rich in dietary fiber should be encouraged to prevent obesity and associated chronic disease.

Targeting Histone Deacetylases: Opportunities for Cancer Treatment and Chemoprevention

The dysregulation of gene expression is a critical event involved in all steps of tumorigenesis. Aberrant histone and non-histone acetylation modifications of gene expression due to the abnormal activation of histone deacetylases (HDAC) have been reported in hematologic and solid types of cancer. In this sense, the cancer-associated epigenetic alterations are promising targets for anticancer therapy and chemoprevention. HDAC inhibitors (HDACi) induce histone hyperacetylation within target proteins, altering cell cycle and proliferation, cell differentiation, and the regulation of cell death programs. Over the last three decades, an increasing number of synthetic and naturally derived compounds, such as dietary-derived products, have been demonstrated to act as HDACi and have provided biological and molecular insights with regard to the role of HDAC in cancer. The first part of this review is focused on the biological roles of the Zinc-dependent HDAC family in malignant diseases. Accordingly, the small-molecules and natural products such as HDACi are described in terms of cancer therapy and chemoprevention. Furthermore, structural considerations are included to improve the HDACi selectivity and combinatory potential with other specific targeting agents in bifunctional inhibitors and proteolysis targeting chimeras. Additionally, clinical trials that combine HDACi with current therapies are discussed, which may open new avenues in terms of the feasibility of HDACi’s future clinical applications in precision cancer therapies.

Metabolomics profile in gastrointestinal cancers: Update and future perspectives

Despite recent progress in diagnosis and therapy, gastrointestinal (GI) cancers remain one of the most important causes of death with a poor prognosis due to late diagnosis. Serum tumor markers and detection of occult blood in the stool are the current tests used in the clinic of GI cancers; however, these tests are not useful as diagnostic screening since they have low specificity and low sensitivity. Considering that one of the hallmarks of cancer is dysregulated metabolism and metabolomics is an optimal approach to illustrate the metabolic mechanisms that belong to living systems, is now clear that this -omics could open a new way to study cancer. In the last years, nuclear magnetic resonance (NMR) metabolomics has demonstrated to be an optimal approach for diseases' diagnosis nevertheless a few studies focus on the NMR capability to find new biomarkers for early diagnosis of GI cancers. For these reasons in this review, we will give an update on the status of NMR metabolomic studies for the diagnosis and development of GI cancers using biological fluids.

Epigenetic Regulation at the Interplay Between Gut Microbiota and Host Metabolism

Gut microbiota communities have coevolved for millions of years in a symbiotic relationship with their mammalian hosts. Elucidating and understanding the molecular mechanisms by which microbiota interacts with its host and how this contributes to the homeostasis of the host is crucial. One of these molecular relationships is the so-called chemical crosstalk between microbiota and host metabolisms, including the poorly explored epigenetic regulation of host tissues by the metabolic activity of gut microbiota in response to changes in diet. DNA methylation and histone modifications are epigenetic marks partly regulated by enzymes such as methylases and acetylases, whose activity depend on host and microbiota metabolites that act as substrates and cofactors for these reactions. However, providing a complete mechanistic description of the regulatory interactions between both metabolisms and the impact on the expression of host genes through an epigenetic modulation, remains elusive. This article presents our perspective on how metabolomic, metagenomic, transcriptomic, and epigenomic data can be used to investigate the “microbiota–nutrient metabolism–epigenetics axis.” We also discuss the implications and opportunities this knowledge may have for basic and applied science, such as the impact on the way we structure future research, understand, and prevent diseases like type 2 diabetes or obesity.

Trichostatin a inhibits phenotypic transition and induces apoptosis of the TAF-treated normal colonic epithelial cells through regulation of TGF-β pathway

Tumor-associated fibroblasts (TAFs) contribute to transdifferentiation of stromal cells in tumor microenvironment. Epithelial-mesenchymal transition (EMT) is a procedure of phenotypic remodeling of epithelial cells and extensively exists in local tumoral stroma. Histone deacetylase (HDAC) inhibitor Tricostatin A (TSA) and sodium butyrate (SB) are reported to play important roles in the regulation of biological behaviour of cancer cells. However, whether TSA or SB is involved in control of EMT in colon epithelial cells induced by TAFs remains unidentified. In present study, we used conditioned medium (CM) form TAF-like CCD-18Co cells to stimulate 2D- and 3D-cultured colon epithelial HCoEpiC cells for 24 h and 4 d. We found that the CCD-18Co CM triggered multiple morphological changes in HCoEpiCs including prolonged cell diameters, down-regulation of E-cadherin and up-regulation of vimentin and α-SMA. Besides, ZEB1 and Snail expression and migration were also promoted by the CM. These phenomena were abolised by 5 μg/ml LY364947, a TGF-β receptor inhibitor. CCD-18Co induced up-regulation of HDAC1 and HDAC2 in the 2D and 3D models, while no change of HDAC4 exprerssion was found. Treatment of 2 μg/ml TSA reversed the CCD-18Co-induced morphological changes and migration of the HCoEpiCs, and suppressed the downregulation of E-cadherin and upregulation of vimentin, α-SMA, ZEB1 and Snail. However, the suppressive effect of 4 mg/ml SB on the EMT was not observed. TSA down-regulated the expressions of Smad2/3, p-Smad2/3 amd HDAC4. Besides, TSA promoted the apoptosis rate (36.84 ± 6.52%) comparing with the CCD-18Co-treated HCoEpiCs (3.52 ± 0.85%, P < 0.05), with promotion of Bax (0.5893±0.0498 in 2D and 0.8867±0.0916 in 3D) and reduction of Bcl-2 (0.0476±0.0053 in 2D and 0.0294±0.0075 in 3D). TSA stimulated expression of phosphorylated-p38 MAPK in 2D (0.3472±0.0249) and 3D (0.3188±0.0248). After pre-treatment with p38 MAPK inhibitor VX-702 (0.5 mg/ml), the apoptosis rate of TSA was decreased in 2D (10.32%) and 3D (5.26%). Our observations demonstrate that epigenetic treatment with HDAC inhibitor TSA may be a useful therapeutic tool for the reversion of TAF-induced EMT in colon epithelium through mediating canonical Smads pathway and non-canonical p38 MAPK signalling.

Effect of edible oil on health: Relationship with intestinal microflora

Oil is an important nutrient in the human diet, and it is closely related to human life. For a long time, people's understanding of oil has been insufficient, resulting in some blind spots for oil intake. Excessive oil intake will increase blood triglyceride (TG), cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) concentrations, and the risk of chronic diseases such as cardiovascular and cerebrovascular diseases, obesity, fatty liver, and gastrointestinal tract diseases will be increased. Moreover, high-fat diets can also disrupt intestinal microbes and cause intestinal cancer. On the other hand, if oil intake is too low, the intake of essential fatty acids will be insufficient, and the absorption and utilization of fat-soluble vitamins will be reduced. The energy substances required for probiotics in the intestine will be reduced, and eventually the imbalance of human flora will lead to a variety of metabolic diseases. This article makes some simple discussions from the perspective of improper intake of edible oils, which will lead to dysbacteriosis and cause various diseases, with an aim to guide people to correctly choose dietary oils to improve the balance of intestinal flora.

The Human Gut Microbiome - A Potential Controller of Wellness and Disease

Interest toward the human microbiome, particularly gut microbiome has flourished in recent decades owing to the rapidly advancing sequence-based screening and humanized gnotobiotic model in interrogating the dynamic operations of commensal microbiota. Although this field is still at a very preliminary stage, whereby the functional properties of the complex gut microbiome remain less understood, several promising findings have been documented and exhibit great potential toward revolutionizing disease etiology and medical treatments. In this review, the interactions between gut microbiota and the host have been focused on, to provide an overview of the role of gut microbiota and their unique metabolites in conferring host protection against invading pathogen, regulation of diverse host physiological functions including metabolism, development and homeostasis of immunity and the nervous system. We elaborate on how gut microbial imbalance (dysbiosis) may lead to dysfunction of host machineries, thereby contributing to pathogenesis and/or progression toward a broad spectrum of diseases. Some of the most notable diseases namely Clostridium difficile infection (infectious disease), inflammatory bowel disease (intestinal immune-mediated disease), celiac disease (multisystemic autoimmune disorder), obesity (metabolic disease), colorectal cancer, and autism spectrum disorder (neuropsychiatric disorder) have been discussed and delineated along with recent findings. Novel therapies derived from microbiome studies such as fecal microbiota transplantation, probiotic and prebiotics to target associated diseases have been reviewed to introduce the idea of how certain disease symptoms can be ameliorated through dysbiosis correction, thus revealing a new scientific approach toward disease treatment. Toward the end of this review, several research gaps and limitations have been described along with suggested future studies to overcome the current research lacunae. Despite the ongoing debate on whether gut microbiome plays a role in the above-mentioned diseases, we have in this review, gathered evidence showing a potentially far more complex link beyond the unidirectional cause-and-effect relationship between them.

Impact of Phytochemicals and Dietary Patterns on Epigenome and Cancer

Cancer remains one of the leading causes of death around the world. Initially it is recognized as a genetic disease, but now it is known to involve epigenetic abnormalities along with genetic alterations. Epigenetics refers to heritable changes that are not encoded in the DNA sequence itself, but play an important role in the control of gene expression. It includes changes in DNA methylation, histone modifications, and RNA interference. Although it is heritable, environmental factors such as diet could directly influence epigenetic mechanisms in humans. This article will focus on the role of dietary patterns and phytochemicals that have been demonstrated to influence the epigenome and more precisely histone and non-histone proteins modulation by acetylation that helps to induce apoptosis and phosphorylation inhibition, which counteracts with cells proliferation. Recent developments discussed here enhance our understanding of how dietary intervention could be beneficial in preventing or treating cancer and improving health outcomes.

Natural Compound Histone Deacetylase Inhibitors (HDACi): Synergy with Inflammatory Signaling Pathway Modulators and Clinical Applications in Cancer

The remarkable complexity of cancer involving multiple mechanisms of action and specific organs led researchers Hanahan and Weinberg to distinguish biological capabilities acquired by cancer cells during the multistep development of human tumors to simplify its understanding. These characteristic hallmarks include the abilities to sustain proliferative signaling, evade growth suppressors, resist cell death, enable replicative immortality, induce angiogenesis, activate invasion and metastasis, avoid immune destruction, and deregulate cellular energetics. Furthermore, two important characteristics of tumor cells that facilitate the acquisition of emerging hallmarks are tumor-promoting inflammation and genome instability. To treat a multifactorial disease such as cancer, a combination treatment strategy seems to be the best approach. Here we focus on natural histone deacetylase inhibitors (HDACi), their clinical uses as well as synergies with modulators of the pro-inflammatory transcription factor signaling pathways.

New Insights into the Connection Between Histone Deacetylases, Cell Metabolism, and Cancer

SIGNIFICANCE

Histone deacetylases (HDACs) activity and cell metabolism are considered important targets for cancer therapy, as both are deregulated and associated with the onset and maintenance of tumors.

RECENT ADVANCES

Besides the classical function of HDACs as HDAC enzymes controlling the transcription, it is becoming increasingly evident that these proteins are involved in the regulation of several other cellular processes by their ability to deacetylate hundreds of proteins with different functions in both the cytoplasm and the nucleus. Importantly, recent high-throughput studies have identified as important target proteins several enzymes involved in different metabolic pathways. Conversely, it has been also shown that metabolic intermediates may control HDACs activity. Consequently, the acetylation/deacetylation of metabolic enzymes and the ability of metabolic intermediates to modulate HDACs may represent a cross-talk connecting cell metabolism, transcription, and other HDACs-controlled processes in physiological and pathological conditions.

CRITICAL ISSUES

Since metabolic alterations and HDACs deregulation are important cancer hallmarks, disclosing connections among them may improve our understanding on cancer mechanisms and reveal novel therapeutic protocols against this disease.

FUTURE DIRECTIONS

High-throughput metabolic studies performed by using more sophisticated technologies applied to the available models of conditional deletion of HDACs in cell lines or in mice will fill the gap in the current understanding and open directions for future research.

Inhibitory Activity of Linoleic Acid Isolated from Proso and Japanese Millet toward Histone Deacetylase

Linoleic acid was isolated from both the methanol extracts of proso and Japanese millet as a histone deacetylase inhibitor. It showed uncompetitive inhibitory activity toward histone deacetylase (IC(50)=0.51 mM) and potent cytotoxicity toward human leukemia K562 (IC(50)=68 microM) and prostate cancer LNCaP cells (IC(50)=193 microM). Millet containing linoleic acid might have anti-tumor activity.

Metabolomic profiling in colorectal cancer: opportunities for personalized medicine

Colorectal cancer (CRC) is one of the most common types of cancer in the world, with high prevalence and mortality. Understanding the alterations of cancer metabolism and identifying reliable biomarkers would facilitate the development of novel technologies of CRC screening and early diagnosis, as well as new approaches to providing personalized medicine. Metabolomics, as an emerging molecular phenotyping approach, provides a clinical platform technology with an unprecedented amount of metabolic readout information, which is ideal for theranostic biomarker discovery. Metabolic signatures can link the unique pathophysiological states of patients to personalized health monitoring and intervention strategies. This article presents an overview of the metabolomic studies of CRC with a focus on recent advances in the biomarker discovery in serum, urine, fecal water and tissue samples for cancer diagnosis. The development and application of metabolomics towards personalized medicine, including early diagnosis, cancer staging, treatment and drug discovery are also discussed.

Recent advances in metabolomics in oncology

The burden of cancer is growing worldwide and with it a more desperate need for better tools to detect, diagnose and monitor the disease is required. It is well recognized that cancer cells are characterized by distinct metabolic perturbations. The metabolomics approach involves the comprehensive profiling of the full complement of low MW compounds in a biological system. By applying advanced analytical and statistical tools, the 'metabolome' is mined for biomarkers that are associated with the state of cancer. This review presents an introduction to the main analytical platforms used in metabolomics analyses, such as NMR spectroscopy and MS, as well as the statistical tools used to mine these datasets. The discussion focuses on 'state-of-the-art' investigations on the four cancer types that have received the most study by metabolomics, namely breast, prostate, colorectal and liver cancer.

In vitro studies on the inhibition of colon cancer by butyrate and carnitine

OBJECTIVE

Epidemiologic studies support an association between diet and the incidence of colorectal cancer. Butyrate, a short-chain fatty acid present in dietary fiber and dairy products, is a potential anticarcinogenic compound. We previously showed that carnitine can enhance the bioavailability of butyrate in vivo. In the present study, we evaluated the effects of butyrate alone and in combination with carnitine on colon cancer cells in vitro, examining proliferation and apoptosis and the molecular mechanisms by which these nutrients may inhibit colon cancer.

METHODS

Caco-2 cells, a well-established cell model, were incubated with butyrate (2.5-20mM) with or without carnitine (10mM) for various incubation periods. Proliferation was measured by incorporation of (3)H-thymidine, and apoptosis was detected using flow cytometry, and then confirmed by analyzing the presence of single-strand DNA breaks typical of apoptotic cells. Prostaglandin E(2) production was assayed and Bcl-2 and cyclo-oxygenase-2 expressions were examined by western blotting.

RESULTS

Butyrate and carnitine inhibited Caco-2 cell proliferation (P<0.05) and induced apoptosis (P<0.05). Prostaglandin E(2) production was decreased in treated Caco-2 cells. At the molecular level, the expression of proapoptotic Bax and Bak proteins were increased in cells incubated with butyrate and carnitine, whereas expression of antiapoptotic Bcl-x(L) was decreased. Cyclo-oxygenase-2 expression was decreased in cells incubated with butyrate and carnitine.

CONCLUSIONS

Butyrate and carnitine inhibit human colon carcinoma cell proliferation and induce apoptosis in human colon carcinoma cells. This is accompanied by an appreciable alteration of the Bax-to-Bcl-x(L) and Bak-to-Bcl-x(L) ratios in favor of apoptosis. This study provides a scientific rationale to study the effects of carnitine and butyrate in colon cancer in vivo.

3,3'-diindolylmethane enhances the efficacy of butyrate in colon cancer prevention through down-regulation of survivin

Butyrate is an inhibitor of histone deacetylase (HDAC) and has been extensively evaluated as a chemoprevention agent for colon cancer. We recently showed that mutations in the adenomatous polyposis coli (APC) gene confer resistance to HDAC inhibitor-induced apoptosis in colon cancers. Here, we show that APC mutation rendered colon cancer cells resistant to butyrate-induced apoptosis due to the failure of butyrate to down-regulate survivin in these cells. Another cancer-preventive agent, 3,3'-diindolylmethane (DIM), was identified to be able to down-regulate survivin in colon cancers expressing mutant APC. DIM inhibited survivin mRNA expression and promoted survivin protein degradation through inhibition of p34(cdc2)-cyclin B1-mediated survivin Thr(34) phosphorylation. Pretreatment with DIM enhanced butyrate-induced apoptosis in colon cancer cells expressing mutant APC. DIM/butyrate combination treatment induced the expression of proapoptotic Bax and Bak proteins, triggered Bax dimerization/activation, and caused release of cytochrome c and Smac proteins from mitochondria. Whereas overexpression of survivin blocked DIM/butyrate-induced apoptosis, knocking down of survivin by small interfering RNA increased butyrate-induced apoptosis in colon cancer cells. We further showed that DIM was able to down-regulate survivin and enhance the effects of butyrate in apoptosis induction and prevention of familial adenomatous polyposis in APC(min/+) mice. Thus, the combination of DIM and butyrate is potentially an effective strategy for the prevention of colon cancer.

Metabolite profiling of fecal water extracts from human colorectal cancer

Colorectal cancer is the second leading cause of cancer death in developed countries. There is a need for better preventive strategies to improve the outcome of this disease. The increasing availability of high-throughput methodologies opens up new possibilities for screening new markers. The application of NMR metabolic profiling to fecal water extracts has interesting potential as a diagnostic tool for detecting colorectal cancer. We obtained NMR metabolic profiles of fecal water extracts from patients with colorectal cancer and healthy individuals, to characterize possible differences between them and to identify potential diagnostic markers. Our results show that metabolic profiling of fecal water extracts is a cheap, reproducible and effective method for detecting colorectal cancer markers and therefore complements other stool-screening methods. A low concentration of short-chain fatty acids, such as acetate and butyrate, previously associated with the development of colorectal cancer, appears to be the most effective marker. Concentrations of proline and cysteine, which are major components of most colonic epithelium mucus glycoproteins, also display significant changes in samples from colorectal cancer. Differentiation between fecal water extracts from controls and patients with colorectal cancer by NMR spectroscopy combined with chemometric techniques opens up new possibilities for developing new, efficient, high-throughput screening protocols.

ATM phosphorylates ZBP-89 at Ser202 to potentiate p21waf1 induction by butyrate

Histone deacetylase inhibitors (HDACi) induce growth arrest and differentiation, particularly in the colon where they are potential chemotherapeutic agents. A key mediator of HDACi action is the cyclin dependent kinase (CDK) inhibitor p21(waf1). HDACi treatment of colonic cells promotes the formation of an ATM/ZBP-89/p300 complex on p21(waf1) proximal promoter, and this multi-molecular complex plays an important role in HDACi induction of p21(waf1) expression in vitro and mucosal protection in vivo. Here we found that ZBP-89 is phosphorylated by ATM kinase in vitro and in vivo. Disruption of the ATM phosphorylation motif (202)SQ within the zinc finger domain of ZBP-89 attenuated its ability to enhance p21(waf1) activation by butyrate. Moreover, disruption of the ATM phosphorylation site abrogated the ability of ZBP-89 to potentiate butyrate induction of endogenous p21(waf1) expression. These results demonstrate that ATM phosphorylation of ZBP-89 contributes to HDACi induction of p21(waf1) gene expression.

Why do African Americans get more colon cancer than Native Africans?

The incidence of colorectal cancer (CRC) is dramatically higher in African Americans (AAs) than in Native Africans (NAs) (60:100,000 vs. <1:100,000) and slightly higher than in Caucasian Americans (CAs). To explore whether the difference could be explained by interactions between diet and colonic bacterial flora, we compared randomly selected samples of healthy 50- to 65-y-old AAs (n = 17) with NAs (n = 18) and CAs (n = 17). Diet was measured by 3-d recall, and colonic metabolism by breath hydrogen and methane responses to oral lactulose. Fecal samples were cultured for 7-alpha dehydroxylating bacteria and Lactobacillus plantarum. Colonoscopic mucosal biopsies were taken to measure proliferation rates. In comparison with NAs, AAs consumed more (P < 0.01) protein (94 +/- 9.3 vs. 58 +/- 4.1 g/d) and fat (114 +/- 11.2 vs. 38 +/- 3.0 g/d), meat, saturated fat, and cholesterol. However, they also consumed more (P < 0.05) calcium, vitamin A, and vitamin C, and fiber intake was the same. Breath hydrogen was higher (P < 0.0001) and methane lower in AAs, and fecal colony counts of 7-alpha dehydroxylating bacteria were higher and of Lactobacilli were lower. Colonic crypt cell proliferation rates were dramatically higher in AAs (21.8 +/- 1.1% vs. 3.2 +/- 0.8% labeling, P < 0.0001). In conclusion, the higher CRC risk and mucosal proliferation rates in AAs than in NAs were associated with higher dietary intakes of animal products and higher colonic populations of potentially toxic hydrogen and secondary bile-salt-producing bacteria. This supports our hypothesis that CRC risk is determined by interactions between the external (dietary) and internal (bacterial) environments.

Recruitment of ataxia-telangiectasia mutated to the p21(waf1) promoter by ZBP-89 plays a role in mucosal protection

BACKGROUND & AIMS

Histone deacetylase inhibitors (HDACi) induce growth arrest, apoptosis, and differentiation, particularly in colon cancer cells where they are potential chemopreventive agents. HDACi induction of the cyclin-dependent kinase inhibitor p21(waf1) has been shown to require ataxia-telangiectasia mutated (ATM). Nevertheless, how ATM participates in p21(waf1) gene expression has not been defined.

METHODS

In vivo protein complexes forming in response to butyrate were studied using co-immunoprecipitation and mass spectroscopy. DNA elements in the p21(waf1) promoter were analyzed in vivo by chromatin immunoprecipitation and in vitro DNA affinity precipitation assays. The expression of p21(waf1) was analyzed by immunoblots and reporter assays.

RESULTS

Reduction of ZBP-89 or ATM with small interfering RNAs blocked HDACi-induced p21(waf1) expression. Chromatin immunoprecipitation and DNA affinity precipitation assays showed that both ZBP-89 and ATM are recruited to the GC-rich DNA elements of the p21(waf1) promoter with HDACi treatment. Co-immunoprecipitation revealed that ATM associates with ZBP-89 in an HDACi-dependent manner. Serial deletions revealed that ATM interacts with both the N-terminal and DNA binding domains of ZBP-89. Moreover, we found that immunodepletion of ZBP-89 prevented recruitment of ATM to the p21(waf1) promoter in vitro. Silencing of ZBP-89 expression blocked HDACi-induced phosphorylation of ATM(Ser1981) and p53(Ser15). ATM(Ser1981) phosphorylation in the colons of mutant mice expressing an N-terminally truncated form of ZBP-89 was not observed after ingestion of dextran sodium sulfate and correlated with exacerbation of the mucosal injury.

CONCLUSIONS

ZBP-89 interacts with ATM in a butyrate-dependent manner and is essential for colonic homeostasis in the setting of acute mucosal injury.

Composition, structure and absorption of milk lipids: a source of energy, fat-soluble nutrients and bioactive molecules

Milkfat is a remarkable source of energy, fat-soluble nutrients and bioactive lipids for mammals. The composition and content of lipids in milkfat vary widely among mammalian species. Milkfat is not only a source of bioactive lipid components, it also serves as an important delivery medium for nutrients, including the fat-soluble vitamins. Bioactive lipids in milk include triacylglycerides, diacylglycerides, saturated and polyunsaturated fatty acids, and phospholipids. Beneficial activities of milk lipids include anticancer, antimicrobial, anti-inflammatory, and immunosuppression properties. The major mammalian milk that is consumed by humans as a food commodity is that from bovine whose milkfat composition is distinct due to their diet and the presence of a rumen. As a result of these factors bovine milkfat is lower in polyunsaturated fatty acids and higher in saturated fatty acids than human milk, and the consequences of these differences are still being researched. The physical properties of bovine milkfat that result from its composition including its plasticity, make it a highly desirable commodity (butter) and food ingredient. Among the 12 major milk fatty acids, only three (lauric, myristic, and palmitic) have been associated with raising total cholesterol levels in plasma, but their individual effects are variable-both towards raising low-density lipoproteins and raising the level of beneficial high-density lipoproteins. The cholesterol-modifying response of individuals to consuming saturated fats is also variable, and therefore the composition, functions and biological properties of milkfat will need to be re-evaluated as the food marketplace moves increasingly towards more personalized diets.

Increased colonic luminal synthesis of butyric acid is associated with lowered colonic cell proliferation in piglets

Butyrate inhibits colonic cell proliferation in vitro but reportedly has an opposite effect in vivo. Because lactulose feeding decreases cecal cell proliferation, an effect attenuated by prefeeding inulin, we hypothesized that lactulose feeding would decrease colonic luminal synthesis of butyrate, and that prefeeding and cofeeding inulin would prevent this effect. Piglets (n = 31) were catheterized and randomly assigned to 1 of 4 groups: Control formula (C); control formula + lactulose (L); control formula + lactulose + inulin (L + I); and control formula + inulin (I). At 6 and 7 d postsurgery, the rate of cecal synthesis of butyrate, cecal cell proliferation and apoptosis, and cecal and distal colon butyrate concentration were measured. In groups C, L, L + I, and I, the rates of synthesis of butyrate (mean +/- SEM) were 10.6 +/- 3.2, 23.3 +/- 4.5, 12.4 +/- 3.6, and 14.6 +/- 4.0 micromol/min, respectively (Group Effect, P = 0.1; C vs. L, P = 0.03; L vs. L + I, P = 0.06). The cecal butyrate concentrations did not differ among the 4 groups and were 8.7 +/- 3.2, 2.4 +/- 0.8, 3.4 +/- 1.9, and 2.0 +/- 0.7 micromol/g dry wt, respectively. The total cecal cell proliferation index was higher in C than in L (P = 0.008) or I (P = 0.026) and was higher in L + I than in L (P = 0.013) or I (P = 0.046). The increased supply of butyrate to the cecum was associated with decreased cell proliferation, but cecal butyrate concentration did not reflect synthesis.

Activation of PPARγ is not involved in butyrate-induced epithelial cell differentiation

Histone deacetylase-inhibitors affect growth and differentiation of intestinal epithelial cells by inducing expression of several transcription factors, e.g. Peroxisome proliferator-activated receptor gamma (PPARgamma) or vitamin D receptor (VDR). While activation of VDR by butyrate mainly seems to be responsible for cellular differentiation, the activation of PPARgamma in intestinal cells remains to be elucidated. The aim of this study was to determine the role of PPARgamma in butyrate-induced cell growth inhibition and differentiation induction in Caco-2 cells. Treatment with PPARgamma ligands ciglitazone and BADGE (bisphenol A diglycidyl) enhanced butyrate-induced cell growth inhibition in a dose- and time-dependent manner, whereas cell differentiation was unaffected after treatment with PPARgamma ligands rosiglitazone and MCC-555. Experiments were further performed in dominant-negative PPARgamma mutant cells leading to an increase in cell growth whereas butyrate-induced cell differentiation was again unaffected. The present study clearly demonstrated that PPARgamma is involved in butyrate-induced inhibition of cell growth, but seems not to play an essential role in butyrate-induced cell differentiation.

HDAC inhibition prevents NF-kappa B activation by suppressing proteasome activity: down-regulation of proteasome subunit expression stabilizes I kappa B alpha

The short chain fatty acid (SCFA) butyrate (BA) and other histone deacetylase (HDAC) inhibitors can rapidly induce cell cycle arrest and differentation of colon cancer cell lines. We found that butyrate and the specific HDAC inhibitor trichostatin A (TSA) can reprogram the NF-(kappa)B response in colon cancer cells. Specifically, TNF-alpha activation is suppressed in butyrate-differentiated cells, whereas IL-1beta activation is largely unaffected. To gain insight into the relationship between butyrate-induced differentiation and NF-(kappa)B regulation, we determined the impact of butyrate on proteasome activity and subunit expression. Interestingly, butyrate and TSA reduced the cellular proteasome activity in colon cancer cell lines. The drop in proteasome activity results from the reduced expression of the catalytic beta-type subunits of the proteasome at both the protein and mRNA level. The selective impact of HDAC inhibitors on TNF-alpha-induced NF-(kappa)B activation appears to relate to the fact that the TNF-alpha-induced activation of NF-(kappa)B is mediated by the proteasome, whereas NF-kappaB activation by IL-1beta is largely proteasome-independent. These findings indicate that cellular differentation status and/or proliferative capacity can significantly impact proteasome activity and selectively alter NF-(kappa)B responses in colon cancer cells. This information may be useful for the further development and targeting of HDAC inhibitors as anti-neoplastic and anti-inflammatory agents.

Biological functions of SLC5A8, a candidate tumour suppressor

SLC5A8 is a candidate tumour suppressor gene that is silenced in colon cancer, gastric cancer and possibly other cancers in humans. This gene codes for a transporter belonging to the Na+/glucose co-transporter gene family (SLC5). The cancer-associated silencing of the gene involves hypermethylation of CpG islands present in exon 1 of the gene. SLC5A8 is expressed in colon, ileum, kidney and thyroid gland. The protein coded by the gene mediates the Na+-coupled and electrogenic transport of a variety of monocarboxylates, including short-chain fatty acids, lactate and nicotinate. It may also transport iodide. The normal physiological function of this transporter in the intestinal tract and kidney is likely to facilitate the active absorption of short-chain fatty acids, lactate and nicotinate. One of the short-chain fatty acids that serves as a substrate for SLC5A8 is butyrate. This fatty acid is an inhibitor of histone deacetylases and is known to induce apoptosis in a variety of tumours including colonic tumour. Since butyrate is produced in the colonic lumen at high concentrations by bacterial fermentation of dietary fibre, we speculate that the ability of SLC5A8 to mediate the entry of this short-chain fatty acid into colonic epithelial cells underlies the potential tumour suppressor function of this transporter.

Saturated fats: what dietary intake?

Public health recommendations for the US population in 1977 were to reduce fat intake to as low as 30% of calories to lower the incidence of coronary artery disease. These recommendations resulted in a compositional shift in food materials throughout the agricultural industry, and the fractional content of fats was replaced principally with carbohydrates. Subsequently, high-carbohydrate diets were recognized as contributing to the lipoprotein pattern that characterizes atherogenic dyslipidemia and hypertriacylglycerolemia. The rising incidences of metabolic syndrome and obesity are becoming common themes in the literature. Current recommendations are to keep saturated fatty acid, trans fatty acid, and cholesterol intakes as low as possible while consuming a nutritionally adequate diet. In the face of such recommendations, the agricultural industry is shifting food composition toward lower proportions of all saturated fatty acids. To date, no lower safe limit of specific saturated fatty acid intakes has been identified. This review summarizes research findings and observations on the disparate functions of saturated fatty acids and seeks to bring a more quantitative balance to the debate on dietary saturated fat. Whether a finite quantity of specific dietary saturated fatty acids actually benefits health is not yet known. Because agricultural practices to reduce saturated fat will require a prolonged and concerted effort, and because the world is moving toward more individualized dietary recommendations, should the steps to decrease saturated fatty acids to as low as agriculturally possible not wait until evidence clearly indicates which amounts and types of saturated fatty acids are optimal?

Gene expression profile of butyrate-inhibited vascular smooth muscle cell proliferation

Excessive proliferation of vascular smooth muscle cells (VSMCs) is a critical element in the development of several vascular pathologies, particularly in atherosclerosis and in restenosis due to angioplasty. We have shown that butyrate, a powerful antiproliferative agent, a strong promoter of cell differentiation and an inducer of apoptosis inhibits VSMC proliferation at physiological concentrations with no cytotoxicity. In the present study, we have used cDNA array technology to unravel the molecular basis of the antiproliferative effect of butyrate on VSMCs. To assess the involvement of gene expression in butyrate-inhibited VSMC proliferation, proliferating VSMCs were exposed to 5 mmol/l butyrate 1 through 5 days after plating. Expression profiles of 1.176 genes representing different functional classes in untreated control and butyrate treated VSMCs were compared. A total of 111 genes exhibiting moderate (2.0-5.0 fold) to strong (> 5.0 fold) differential expression were identified. Analysis of these genes indicates that butyrate treatment mainly alters the expression of four different functional classes of genes, which include: 43 genes implicated in cell growth and differentiation, 13 genes related to stress response, 11 genes associated with vascular function and 8 genes normally present in neuronal cells. Examination of differentially expressed cell growth and differentiation related genes indicate that butyrate-inhibited VSMC proliferation appears to involve down-regulation of genes that encode several positive regulators of cell growth and up-regulation of some negative regulators of growth or differentiation inducers. Some of the down-regulated genes include proliferating cell nuclear antigen (PCNA), retinoblastoma susceptibility related protein p130 (pRb), cell division control protein 2 homolog (cdc2), cyclin B1, cell division control protein 20 homolog (p55cdc), high mobility group (HMG) 1 and 2 and several others. Whereas the up-regulated genes include cyclin D1, p21WAF1, p141NK4B/p15INK5B, Clusterin, inhibitor of DNA binding 1 (ID1) and others. On the other hand, butyrate-responsive stress-related genes include some of the members of heat shock protein (HSP), glutathione-s-transferase (GST), glutathione peroxidase (GSH-PXs) and cytochrome P450 (CYP) families. Additionally, several genes related to vascular and neuronal function are also responsive to butyrate treatment. Although involvement of genes that encode stress response, vascular and neuronal functional proteins in cell proliferation is not clear, cDNA expression array data appear to suggest that they may play a role in the regulation of cell proliferation. However, cDNA expression profiles indicate that butyrate-inhibited VSMC proliferation involves combined action of a proportionally large number of both positive and negative regulators of growth, which ultimately causes growth arrest of VSMCs. Furthermore, these butyrate-induced differential gene expression changes are not only consistent with the antiproliferative effect of butyrate but are also in agreement with the roles that these gene products play in cell proliferation.

Butyrate inhibits cytokine-induced VCAM-1 and ICAM-1 expression in cultured endothelial cells: the role of NF-κB and PPARα

Adhesion and migration of leukocytes into the surrounding tissues is a crucial step in inflammation, immunity, and atherogenesis. Expression of cell adhesion molecules by endothelial cells plays a leading role in this process. Butyrate, a natural short-chain fatty acid produced by bacterial fermentation of dietary fiber, has been attributed with anti-inflammatory activity in inflammatory bowel disease. Butyrate in vitro is active in colonocytes and several other cell types. We have studied the effect of butyrate on expression of endothelial leukocyte adhesion molecules by cytokine-stimulated human umbilical vein endothelial cells (HUVEC). Pretreatment of HUVEC with butyrate-inhibited tumor necrosis factor-alpha (TNFalpha)-induced expression of vascular cell adhesion molecule-1 (VCAM-1) and intracellular cell adhesion molecule-1 (ICAM-1) in a time and concentration-dependent manner. Butyrate at 10 mM/L inhibited interleukin-1 (IL-1)-stimulated VCAM-1 and ICAM-1 expression. The effect of butyrate on cytokine-stimulated VCAM-1 expression was more pronounced than in the case of ICAM-1. Butyrate decreased TNFalpha-induced expression of mRNA for VCAM-1 and ICAM-1. Suppressed expression of VCAM-1 and ICAM-1 was associated with reduced adherence of monocytes and lymphocytes to cytokine-stimulated HUVEC. Butyrate inhibited TNFalpha-induced activation of nuclear factor-kappaB (NF-kappaB) in HUVEC. Finally, butyrate enhanced peroxisome proliferator-activated receptor-alpha (PPARalpha) expression in HUVEC. These results demonstrate that butyrate may have anti-inflammatory properties not only in colonocytes but also in endothelial cells. The anti-inflammatory and (perhaps) antiatherogenic properties of butyrate may partly be attributed to an effect on activation of NF-kappaB and PPARalpha and to the associated expression of VCAM-1 and ICAM-1. The present findings support further investigations on the therapeutic benefits of butyrate in several pathological events involving leukocyte recruitment.

Dose-dependent blockade to cardiomyocyte hypertrophy by histone deacetylase inhibitors

Postnatal cardiac myocytes respond to stress signals by hypertrophic growth and activation of a fetal gene program. Recently, we showed that class II histone deacetylases (HDACs) suppress cardiac hypertrophy, and mice lacking the class II HDAC, HDAC9, are sensitized to hypertrophic signals. To further define the roles of HDACs in cardiac hypertrophy, we analyzed the effects of HDAC inhibitors on the responsiveness of primary cardiomyocytes to hypertrophic agonists. Paradoxically, HDAC inhibitors imposed a dose-dependent blockade to hypertrophy and fetal gene activation. We conclude that distinct HDACs play positive or negative roles in the control of cardiomyocyte hypertrophy. HDAC inhibitors are currently being tested in clinical trials as anti-cancer agents. Our results suggest that these inhibitors may also hold promising clinical value as therapeutics for cardiac hypertrophy and heart failure.

Butyrate down-regulates CD44 transcription and liver colonisation in a highly metastatic human colon carcinoma cell line

Over-expression of the adhesion molecule CD44 and its splice variants, especially CD44v6, is associated with poor prognosis and metastasis. We aimed at regulating the expression of CD44 in the highly metastatic human colon cancer cell line HM7 and thereby affecting its metastatic ability. HM7 cells show constitutive expression of CD44 standard and variants isoforms, which were significantly down-regulated by treatment with butyrate. Butyrate significantly inhibited transcription of the CD44 gene and abolished epidermal growth factor-mediated up-regulation of the reporter gene luciferase subcloned upstream to the CD44 promoter (-1.1 kb) and transfected to HM7 cells. Nuclear proteins from butyrate-treated cells bound to an epidermal growth factor receptor element motif present in the CD44 promoter. Epidermal growth factor receptor element-site directed mutations eliminated the inducibility of the luciferase reporter gene and did not allowed binding of nuclear proteins harvested from butyrate-treated cells. Butyrate induced CD44 gene repression by specifically interacting with an epidermal growth factor receptor element nuclear transcriptional factor. This interaction affects CD44 transcriptional activity vis-à-vis in vivo metastatic ability of HM7 cells. These results provide additional insight into the anticarcinogenic properties of butyrate.

In vitro and in vivo treatment of colon cancer by VIP antagonists

Vasoactive intestinal peptide (VIP) is secreted from many cancer lines and VIP binding was observed in many tumors. We have shown before that VIP antagonists are potent inhibitors of neoplastic growth of neuroblastoma, lung and breast cancer cells in vitro. Here, the cultured colon cancer cell line HCT-15 that exhibited VIP receptor expression was treated with the VIP hybrid antagonist neurotensin(6-11)VIP(7-28). The antineoplastic activity was assessed by thymidine incorporation. Neurotensin(6-11)VIP(7-28) efficiently inhibited cancer growth with a maximal effect at nanomolar concentrations. Once the inhibitory properties of the VIP antagonist on colon cancer cells were established, the in vivo curative effects were analyzed. Sprague-Dawley rats were injected with azoxymethane (AOM) (15 mg/kg/week) for 2 weeks, providing artificial induction of colon tumors. The rats were then allocated into four experimental groups: (1) receiving no treatment; (2) receiving treatment with saline; (3, 4) receiving treatment with 10 or 20 microg of neurotensin(6-11)VIP(7-28), respectively. After 10 weeks of daily injections, rats were sacrificed and tumors assessed for stage, volume, location, differentiation and lymphocytic infiltrate. Embedded mucosa was assessed for dysplastic crypts. Results showed that the antagonist treatment reduced the tumor volume, staging, lymphocyte infiltrate and the number of dysplastic crypts. Thus, neurotensin(6-11)VIP(7-28) could serve as an effective cancer treatment and a preventing agent.

COI1 links jasmonate signalling and fertility to the SCF ubiquitin-ligase complex in Arabidopsis

Jasmonates (JAs) regulate Arabidopsis thaliana wound and defence responses, pollen development, and stress-related growth inhibition. Significantly, each of these responses requires COI1, an F-box protein. Other F-box proteins interact with SKP1 and cullin proteins to form SCF complexes that selectively recruit regulatory proteins targeted for ubiquitination. To determine whether COI1 also functions in an SCF complex, we have characterized Arabidopsis proteins that bind to COI1. An Arabidopsis cDNA expression library was screened in yeast for clones that produce proteins which can bind to COI1. We recovered two SKP1 homologues and a histone deacetylase. The Arabidopsis F-box protein TIR1 interacted with SKP1 proteins, but not with the histone deacetylase. Mutant COI1 proteins revealed that the F-box is required for interaction with SKP1s, but that sequences in leucine-rich repeat domains are required for interaction with the histone deacetylase. Epitope-tagged COI1 was introduced into Arabidopsis plants and cell cultures. Co-immunoprecipitation experiments confirmed the interaction in planta of COI1 with SKP1-like proteins and histone deacetylase, and also indicated that COI1 interacted with cullin. These results suggest that COI1 forms an SCFCOI1 complex in vivo. COI1 is therefore expected to form a functional E3-type ubiquitin ligase in plants and to regulate expression of jasmonate responsive genes, possibly by targeted ubiquitination of a histone deacetylase.

External control of Her2 expression and cancer cell growth by targeting a Ras-linked coactivator

Overproduction of the Her2 oncoprotein has been found in approximately 30% of breast tumors, and patients who have Her2 excesses typically have more aggressive disease. Here we show that the expression of the Her2 gene can be decreased by inhibiting the interaction of the two cancer-linked proteins, DRIP130/CRSP130/Sur-2 (a Ras-linked subunit of human mediator complexes) and ESX (an epithelial-restricted transcription factor). Disruption of the interaction by a short cell-permeable peptide reduced the expression of the Her2 gene and specifically impaired the growth and viability of Her2-overexpressing breast cancer cells. The association of ESX with DRIP130 is mediated by a small hydrophobic face of an 8-aa helix in ESX, suggesting a therapeutic approach to incapacitating the Her2 gene by small organic molecules.

Quantitation of colonic luminal synthesis of butyric acid in piglets

OBJECTIVES

Butyric acid, synthesized via bacterial fermentation in colonic lumen, may play an important role in the nutrition of the colonic mucosa. Since disaccharides, especially lactose, are the principal dietary carbohydrates during infancy, it is important to determine if their fermentation is associated with butyric acid synthesis. The objective of this paper is to describe a newly developed stable isotope method for quantifying butyric acid synthesis in the colonic lumen and to demonstrate its application during cecal infusions of lactose and lactulose in piglets.

METHODS

Nine piglets aged 21 to 30 days were studied during acute anesthesia. The C enrichment of butyric acid was monitored in the portal vein before and during a 120 minutes cecal infusion of [1- C]-butyric acid and either unlabeled lactose (N = 4) or lactulose (N = 5).

RESULTS

The luminal synthesis of BA (micromol x kg x min ) (Mean +/- S.D.) was respectively 1.5 +/- 0.9 and 1.2 +/- 0.6 during lactulose and lactose infusion.

CONCLUSIONS

This study provides new quantitative data on in vivo butyric acid production in the mammalian colon.

Different molecular events account for butyrate-induced apoptosis in two human colon cancer cell lines

We studied the molecular events underlying butyrate-induced apoptosis in two different colon cancer cell lines: Caco-2, a well defined cancer cell and RSB, a cell line obtained from a colonic tumor of an ulcerative colitis patient. Caco-2 and RSB cells were exposed to 2, 5 and 10 mmol/L butyrate for 48 h. Caspase-1 was cleaved in Caco-2-cells at all butyrate concentrations, whereas in RSB-cells caspase-1 expression was undetectable. In RSB cells, butyrate dose-dependently induced caspase-3 cleavage, whereas in Caco-2-cells, butyrate up-regulated expression of the caspase-3 active subunit. Caspase-3-specific activity, cytoplasmic nucleosome concentration and growth were directly correlated with butyrate doses in both cell lines; however, the response was more pronounced in Caco-2 than in RSB cells. Expression of the cleaved poly(ADP-ribose) polymerase (PARP) product was elevated in both cell lines at the highest butyrate concentration. Bak expression gradually increased as a function of butyrate concentrations in both cell lines. At 10 mmol/L butyrate, expression increased by fivefold and sevenfold in Caco-2 and RSB cells, respectively. The highest expression of Bcl-2 was observed in control Caco-2 cells, and expression decreased with increasing butyrate concentration. This effect was not observed in RSB cells. Inactivation of caspase-1 with Z-YVAD-FMK abrogated butyrate-induced apoptosis in Caco-2 but not in RSB cells. Inactivation of caspase-3 with Z-DVED-FMK completely inhibited butyrate-induced apoptosis in RSB cells whereas this effect was less pronounced in Caco-2 cells. Our data demonstrate that butyrate-induced apoptosis is activated via different apoptotic pathways in diversely stratified colon cancers.

Differentiation of PC12 cells induced by N8-acetylspermidine and by N8-acetylspermidine deacetylase inhibition

Spermidine is one of the simple polyamines found in cells of virtually all living organisms. It undergoes a metabolic conversion to N8-acetylspermidine catalyzed by an enzyme in cell nuclei and is converted back to spermidine by a deacetylase in the cytoplasm. In this study, two different mechanisms were used to produce an elevation in the level of N8-acetylspermidine in PC12 cells: inhibition of N8-acetylspermidine deacetylase and direct addition of N8-acetylspermidine to the cell culture. The increasing intracellular concentration of N8-acetylspermidine was accompanied by signs of PC12 cell differentiation including increased content of dopamine and morphological changes (neurite outgrowths), suggesting a strong and perhaps causal relationship among these effects. This effect on differentiation appears to be specific for N8-acetylspermidine as the addition of other polyamines including spermidine and N1-acetylspermidine did not elicit these changes. Nerve growth factor (NGF) and dexamethasone, commonly used inducers of differentiation in PC12 cells, produced differentiation without measurable changes in N8-acetylspermidine levels, suggesting that different (or multiple) mechanisms may be involved in these differentiation processes.

Substrate-induced regulation of the human colonic monocarboxylate transporter, MCT1

Butyrate is the principal source of energy for colonic epithelial cells, and has profound effects on their proliferation, differentiation and apoptosis. Transport of butyrate across the colonocyte luminal membrane is mediated by the monocarboxylate transporter 1 (MCT1). We have examined the regulation of expression of human colonic MCT1 by butyrate, in cultured colonic epithelial cells (AA/C1). Treatment with sodium butyrate (NaBut) resulted in a concentration- and time-dependent upregulation of both MCT1 mRNA and protein. At 2 mM butyrate, the magnitude of induction of mRNA (5.7-fold) entirely accounted for the 5.2-fold increase in protein abundance, and was mediated by both activation of transcription and enhanced mRNA stability. The other monocarboxylates found naturally in the colon, acetate and propionate, had no effect. The properties of butyrate uptake by AA/C1 cells were characteristic of MCT1. Induction of the MCT1 protein resulted in a corresponding increase in the maximal rate of butyrate transport. The V(max) for uptake of [U-(14)C]butyrate was increased 5-fold following pre-incubation with 2 mM NaBut, with no significant change in the apparent K(m). In conclusion, this study is the first to show substrate-induced regulation of human colonic MCT1. The basis of this regulation is a butyrate-induced increase in MCT1 mRNA abundance, resulting from the dual control of MCT1 gene transcription and stability of the MCT1 transcript. We suggest that butyrate-induced increases in the expression and resulting activity of MCT1 serve as a mechanism to maximise intracellular availability of butyrate, to act both as a source of energy and to influence processes maintaining cellular homeostasis in the colonic epithelium.

Butyrate suppression of colonocyte NF-kappa B activation and cellular proteasome activity

Butyrate is derived from the microbial metabolism of dietary fiber in the colon where it plays an important role in linking colonocyte turnover and differentiation to luminal content. In addition, butyrate appears to have both anti-inflammatory and cancer chemopreventive activities. Using confocal microscopy and cell fractionation studies, butyrate pretreatment of a human colon cell line (HT-29 cells) inhibited the tumor necrosis factor-alpha (TNF-alpha)-induced nuclear translocation of the proinflammatory transcription factor NF-kappaB. Butyrate inhibited NF-kappaB DNA binding within 30 min of TNF-alpha stimulation, consistent with an inhibition of nuclear translocation. IkappaB.NF-kappaB complexes extracted from butyrate-treated cells were relatively resistant to in vitro dissociation by deoxycholate, suggesting a change in cellular IkappaB composition. Butyrate treatment increased p100 expression, an IkappaB that was not degraded upon TNF-alpha treatment. Butyrate also reduced the extent of TNF-alpha-induced IkappaB-alpha degradation and enhanced the presence of ubiquitin-conjugated IkappaB-alpha. The suppression of IkappaB-alpha degradation corresponded with a reduction in cellular proteasome activity as determined by in vitro proteasome assays and the increased presence of ubiquitin-conjugated proteins. The butyrate suppression of IkappaB-alpha degradation and proteasome activity may derive from its ability to inhibit histone deacetylases since the specific deacetylase inhibitor trichostatin A had similar effects. These results suggest a potential mechanism for the anti-inflammatory activity of butyrate and demonstrate the interplay between short chain fatty acids and cellular proteasome activity.

Expression of p21Waf1/Cip1 and cyclin D1 is increased in butyrate-resistant HeLa cells

Sodium butyrate induced cell cycle arrest in mammalian cells through an increase in p21Waf1/Cip1, although another study showed that this arrest is related to pRB signaling. We isolated variants of HeLa cells adapted to growth in 5 mm butyrate. One of these variants, clone 5.1, constitutively expressed elevated levels of p21Waf1/Cip1 when incubated in regular growth medium and in the presence of butyrate. Despite this elevated level of p21Waf1/Cip1, the cells continue to proliferate, albeit at a slower rate than parental HeLa cells. Western blot analyses showed that other cell cycle regulatory proteins were not up-regulated to compensate for the elevated expression of p21Waf1/Cip1. However, cyclin D1 was down-regulated by butyrate in HeLa cells but not in clone 5.1. We conclude that continued expression of cyclin D1 allowed clone 5.1 to grow in the presence of butyrate and elevated levels of p21Waf1/Cip1.

Biomarkers of human colonic cell growth are influenced differently by a history of colonic neoplasia and the consumption of acarbose

The nutritional effects of butyrate on the colonic mucosa and studies of transformed cells suggest that butyrate has anti-colon cancer effects. If butyrate has antineoplastic effects, mucosal growth contrasts between normal subjects and those with a history of colonic neoplasia would parallel changes in growth characteristics caused by butyrate in a colon neoplasia population. To test this hypothesis, rectal biopsies from a survey of colonoscopy patients (n = 50) with and without a history of colonic neoplasia (controls) were compared. Similarly, rectal biopsies were compared from subjects (n = 44) with a colon neoplasia history in an acarbose-placebo crossover trial. Control subjects in the colonoscopy survey had higher bromodeoxyuridine (BrdU) uptake than subjects with a history of neoplasia (P = 0.05). The control subjects also had a higher correlation of BrdU and Ki-67 labeling (P = 0.003). Both findings were paralleled by acarbose use. Acarbose augmented BrdU uptake (P = 0.0001) and improved the correlation of BrdU and Ki-67 labeling (P = 0.013). Acarbose also augmented fecal butyrate (P = 0.0001), which was positively correlated with Ki-67 labeling (P = 0.003). p52 antigen had an earlier pattern of crypt distribution in subjects with a history of colon neoplasia but was not affected by acarbose use. Lewis-Y antigen was expressed earlier in the crypt with acarbose but had similar expression in the colonoscopy survey groups. The use of acarbose to enhance fecal butyrate concentration produced mucosal changes paralleling the findings in control subjects as opposed to those with neoplasia, supporting the concept of an antineoplastic role for butyrate.

Butyric acid is synthesized by piglets

We hypothesized that there is no synthesis of butyric acid within organs or tissues not drained by the portal vein (PV). Two experiments were performed. In six piglets, the colonic vasculature was clamped (n = 4) or the entire colon resected while [1-13C]-butyric acid (99% enriched) was infused into a jejunal vein for 120 min; 13C enrichment of butyric acid was measured in the PV and carotid artery (ART) during the last 30 min of the infusion. In a second experiment, butyric acid tracer and unlabeled disaccharide were infused into the cecum for 120 min, and blood again was sampled from the PV and ART. For the four piglets studied during ligation of the colonic vasculature, the mean (+/- SD) ratio of the butyric acid enrichment in the ART to that in the PV (ART/PV) was 0.80+/-0.05 (ART vs. PV, P = 0.002) and for all six piglets in expt. 1, the ART/PV ratio was 0.74+/-0.1 (ART vs. PV, P = 0.001). The enrichment of butyric acid in the PV averaged 96.0% for the six studies, implying that splanchnic tissues other than the colon did not produce a substantial amount of butyric acid. For the second experiment, the ART/PV ratio was 0.80+/-0.15 (ART vs. PV, P = 0.03). These studies provide the first evidence for endogenous synthesis of butyric acid by piglets.

Butyrate regulates E-cadherin transcription, isoform expression and intracellular position in colon cancer cells

Cell-to-cell adhesion, an important event in differentiation, is impaired during advanced stages of tumorigenesis. In this study, we examined the possible regulation of cell-adhesion proteins by the differentiation agent butyrate in LS174T and HM7 cells, two types of human colon cancer cells that differ in their ability to produce mucin and colonize the liver of experimental animals. The more aggressive, high-mucin-producing cell line (HM7), a clone selected from LS174T cells, showed a scattered and undifferentiated ultramorphological appearance and low basal alkaline phosphatase activity; the proteins beta-catenin and E-cadherin, as detected by immunostaining, were expressed in the cells' nuclei. All of these properties were significantly less pronounced in the less aggressive, low-mucin-producing LS174T cells. In both cell lines, butyrate treatment enhanced cell-to-cell interaction, alkaline phosphate activity, translocation of beta-catenin and E-cadherin from the nuclei to the membrane junctions, and transcription and translation of the 120-kDa E-cadherin isoform, but not of its 100-kDa isoform. Analysis of possible mechanisms of E-cadherin up-regulation revealed that butyrate induces the release of nuclear proteins from the E-cadherin promoter sequence, reducing transcription repression. We suggest that butyrate activates E-cadherin transcription through translocation of nuclear transcription factors bearing specific repressor activity. We surmise that abrogation of nuclear 100-kDa E-cadherin and beta-catenin expression following butyrate treatment is related to the control of E-cadherin gene transcription.

IGF-II enhances trichostatin A-induced TGFbeta1 and p21(Waf1,Cip1, sdi1) expression in Hep3B cells

Cell growth and division are controlled through the actions of cyclin-dependent kinases (CDKs) and cyclin dependent kinase inhibitors (CKIs). Treatment of cell lines with Trichostatin A leads to induction of one of these CKIs, p21, and growth arrest. Induction of p21 can also occur through the actions of TGFbeta1. Latent TGFbeta1 can be activated by the M6P/IGF2R. In the present study we have examined the effect of TSA on members of the IGF axis, the CKIs p21 and p27, and also TGFbeta1 in Hep3B cells. The only member of the IGF axis to be affected by treatments was IGF2. Expression of another gene from the same chromosomal location, H19, was also affected. TGFbeta1 expression was greatly enhanced by TSA. In addition, both CKIs, p21 and p27, were upregulated by TSA. Effects of adding IGF-II or TGFbeta1 to TSA-treated cells on p21 induction were examined. The results show that the induction of p21 by TSA can be modulated by additions of IGF-II whereas addition of TGFbeta1 affects its own expression but not p21. In conclusion, the results indicate that the induction of p21 and cell growth arrest caused by Trichostatin A may involve multiple signaling pathways.

Histone deacetylase inhibition selectively alters the activity and expression of cell cycle proteins leading to specific chromatin acetylation and antiproliferative effects

Histone acetylation is emerging as a major regulatory mechanism thought to modulate gene expression by altering the accessibility of transcription factors to DNA. In this study, treatment of human tumor cells with the histone deacetylase inhibitor, trapoxin (TPX), resulted in selective changes in genes that control the cell cycle. TPX activated p21(waf1) transcription that led to elevated p21(waf1) protein levels in three human tumor cell lines without altering the protein levels of cdk2, cdk4, or cyclin B. In addition, TPX increased cyclin E transcription without increasing the levels of Rb, E2F, dihydrofolate reductase, or glyceraldehyde-3-phosphate dehydrogenase. The elevated levels of p21(waf1) protein led to decreased Rb phosphorylation and cdk2 activity. These effects resulted in G(1) and G(2) cell cycle arrest in H1299 human lung and MDA-MB-435 breast carcinoma cells and apoptosis in A549 lung carcinoma cells. Chromatin immunoprecipitation assays revealed that TPX increased the level of chromatin acetylation associated with histone H3 in the trapoxin-responsive region of the p21(waf1) promoter. This study demonstrates that inhibition of HDAC by TPX increases acetylation of H3-associated chromatin and alters gene expression with marked selectivity.