Butyrate and the colonocyte. Implications for neoplasia

Harnessing and delivering microbial metabolites as therapeutics via advanced pharmaceutical approaches

Microbial metabolites have emerged as key players in the interplay between diet, the gut microbiome, and host health. Two major classes, short-chain fatty acids (SCFAs) and tryptophan (Trp) metabolites, are recognized to regulate inflammatory, immune, and metabolic responses within the host. Given that many human diseases are associated with dysbiosis of the gut microbiome and consequent reductions in microbial metabolite production, the administration of these metabolites represents a direct, multi-targeted treatment. While a multitude of preclinical studies showcase the therapeutic potential of both SCFAs and Trp metabolites, they often rely on high doses and frequent dosing regimens to achieve systemic effects, thereby constraining their clinical applicability. To address these limitations, a variety of pharmaceutical formulations approaches that enable targeted, delayed, and/or sustained microbial metabolite delivery have been developed. These approaches, including enteric encapsulations, esterification to dietary fiber, prodrugs, and nanoformulations, pave the way for the next generation of microbial metabolite-based therapeutics. In this review, we first provide an overview of the roles of microbial metabolites in maintaining host homeostasis and outline how compromised metabolite production contributes to the pathogenesis of inflammatory, metabolic, autoimmune, allergic, infectious, and cancerous diseases. Additionally, we explore the therapeutic potential of metabolites in these disease contexts. Then, we provide a comprehensive and up-to-date review of the pharmaceutical strategies that have been employed to enhance the therapeutic efficacy of microbial metabolites, with a focus on SCFAs and Trp metabolites.

Extirpating the cancer stem cell hydra: Differentiation therapy and Hyperthermia therapy for targeting the cancer stem cell hierarchy

Ever since the discovery of cancer stem cells (CSCs), they have progressively attracted more attention as a therapeutic target. Like the mythical hydra, this subpopulation of cells seems to contribute to cancer immortality, spawning more cells each time that some components of the cancer cell hierarchy are destroyed. Traditional modalities focusing on cancer treatment have emphasized apoptosis as a route to eliminate the tumor burden. A major problem is that cancer cells are often in varying degrees of dedifferentiation contributing to what is known as the CSCs hierarchy and cells which are known to be resistant to conventional therapy. Differentiation therapy is an experimental therapeutic modality aimed at the conversion of malignant phenotype to a more benign one. Hyperthermia therapy (HT) is a modality exploiting the changes induced in cells by the application of heat produced to aid in cancer therapy. While differentiation therapy has been successfully employed in the treatment of acute myeloid leukemia, it has not been hugely successful for other cancer types. Mounting evidence suggests that hyperthermia therapy may greatly augment the effects of differentiation therapy while simultaneously overcoming many of the hard-to-treat facets of recurrent tumors. This review summarizes the progress made so far in integrating hyperthermia therapy with existing modules of differentiation therapy. The focus is on studies related to the successful application of both hyperthermia and differentiation therapy when used alone or in conjunction for hard-to-treat cancer cell niche with emphasis on combined approaches to target the CSCs hierarchy.

Hypoglycemic effects of different molecular weight konjac glucomannans via intestinal microbiota and SCFAs mediated mechanism

The hypoglycemic effects of konjac glucomannans (KGMs) are well recognized, and our previous study showed KGMs with different molecular weight have different hypoglycemic effects on diabetes rats, but the detailed mechanisms still remain unclear. In this study, KGMs with medium molecular weight (KGM-M, 757.1 kDa) and low molecular weight (KGM-L, 87.3 kDa) were utilized to investigate the possible mechanism on hypoglycemic effects of type 2 diabetic (T2DM) rats. The results revealed that KGM-M had better effects than KGM-L on decreasing fasting blood glucose, mitigating insulin resistance and improving inflammation. Further mechanism analysis showed that KGM-M better enriched gut flora diversity and the abundance of Ruminococcus and Lachnoclostridium, which was accompanied by increased short chain fatty acids (SCFAs) production and expression of G protein-coupled receptors (GPCRs), and improved regulation on bile acid synthesis. Antibiotics treatment eliminated the beneficial effects of KGMs on gut flora, SCFAs, GPCRs and bile acid synthesis. By contrast, fecal microbiota transplantation (FMT) treatment restored the structure of intestinal microbiota. And after FMT treatment, KGM-M displayed higher hypoglycemic activity than KGM-L, probably due to the better effects on intestinal microbiota, SCFAs production, GPCRs expression and bile acid synthesis inhibition.

Comparative effects of different enzymatic hydrolysates of konjac glucomannan on gut flora and constipation rats

This study aimed to compare the effects of different hydrolysates (named GKOS and MKOS) on constipated rats, which were degraded to obtain from konjac glucomannan by β-glucanase and β-mannanase, respectively....

Impact of Plant-Based Meat Alternatives on the Gut Microbiota of Consumers: A Real-World Study

Eating less meat is increasingly seen as a healthier, more ethical option. This is leading to growing numbers of flexitarian consumers looking for plant-based meat alternatives (PBMAs) to replace at least some of the animal meat they consume. Popular PBMA products amongst flexitarians, including plant-based mince, burgers, sausages and meatballs, are often perceived as low-quality, ultra-processed foods. However, we argue that the mere industrial processing of ingredients of plant origin does not make a PBMA product ultra-processed by default. To test our hypothesis, we conducted a randomised controlled trial to assess the changes to the gut microbiota of a group of 20 participants who replaced several meat-containing meals per week with meals cooked with PBMA products and compared these changes to those experienced by a size-matched control. Stool samples were subjected to 16S rRNA sequencing. The resulting raw data was analysed in a compositionality-aware manner, using a range of innovative bioinformatic methods. Noteworthy changes included an increase in butyrate metabolising potential-chiefly in the 4-aminobutyrate/succinate and glutarate pathways-and in the joint abundance of butyrate-producing taxa in the intervention group compared to control. We also observed a decrease in the Tenericutes phylum in the intervention group and an increase in the control group. Based on our findings, we concluded that the occasional replacement of animal meat with PBMA products seen in flexitarian dietary patterns can promote positive changes in the gut microbiome of consumers.

Dietary Factors Modulating Colorectal Carcinogenesis

The development of colorectal cancer, responsible for 9% of cancer-related deaths, is favored by a combination of genetic and environmental factors. The modification of diet and lifestyle may modify the risk of colorectal cancer (CRC) and prevent neoplasia in up to 50% of cases. The Western diet, characterized by a high intake of fat, red meat and processed meat has emerged as an important contributor. Conversely, a high intake of dietary fiber partially counteracts the unfavorable effects of meat through multiple mechanisms, including reduced intestinal transit time and dilution of carcinogenic compounds. Providing antioxidants (e.g., vitamins C and E) and leading to increased intraluminal production of protective fermentation products, like butyrate, represent other beneficial and useful effects of a fiber-rich diet. Protective effects on the risk of developing colorectal cancer have been also advocated for some specific micronutrients like vitamin D, selenium, and calcium. Diet-induced modifications of the gut microbiota modulate colonic epithelial cell homeostasis and carcinogenesis. This can have, under different conditions, opposite effects on the risk of CRC, through the production of mutagenic and carcinogenic agents or, conversely, of protective compounds. The aim of this review is to summarize the most recent evidence on the role of diet as a potential risk factor for the development of colorectal malignancies, as well as providing possible prevention dietary strategies.

Black tea benefits short-chain fatty acid producers but inhibits genus Lactobacillus in the gut of healthy Sprague-Dawley rats

BACKGROUND

The gut microbiota plays important roles in physiological and pathological processes of the host. The effect of black tea on the gut microbiota of healthy individuals remains unclear.

RESULTS

Healthy Sprague-Dawley (SD) rats were given black tea for 4 weeks, and cecum content, serum, intestinal, and hepatic samples were collected. The results showed that black tea increased α-diversity and modulated β-diversity of the gut microbiota. Additionally, black tea enriched several short-chain fatty acid (SCFA) producers but suppressed genus Lactobacillus. Further tests revealed that the enrichment of SCFA producers was associated with a decrease in the oxidative stress of cecum content caused by black tea, and related to increased luminal butyric acid levels and enhanced intestinal barrier function. The suppression of genus Lactobacillus was related to the increase in luminal total bile acids caused by black tea. In vitro tests showed that bile acids rather than black tea directly inhibited Lactobacillus strains. The reduction in genus Lactobacillus did not affect the effects of black tea on intestinal barrier function and lipid levels.

CONCLUSION

Our results imply that the effects of black tea on gut microbiota in healthy individuals are complex and provide a new perspective on the associations among black tea, gut microbiota, and health. © 2020 Society of Chemical Industry.

Microbiota reprogramming for treatment of alcohol-related liver disease

In the past decade knowledge has expanded regarding the importance of the gut microbiota in maintaining intestinal homeostasis and overall health. During this same time, we have also gained appreciation for the role of the gut-liver axis in the development of liver diseases. Alcohol overconsumption is one of the leading causes of liver failure globally. However, not all people with alcohol use disorder progress to advanced stages of liver disease. With advances in technology to investigate the gut microbiome and metabolome, we are now beginning to delineate alcohol's effects on the gut microbiome in relation to liver disease. This review presents our current understanding on the role of the gut microbiota during alcohol exposure, and various therapeutic attempts that have been made to reprogram the gut microbiota with the goal of alleviating alcoholic-related liver disease.

Faecalibacterium prausnitzii and a Prebiotic Protect Intestinal Health in a Mouse Model of Antibiotic and Clostridium difficile Exposure

BACKGROUND

Clostridium difficile (CD) infection (CDI) increases patient morbidity, mortality and healthcare costs. Antibiotic treatment induces gut dysbiosis and is both a major risk factor for CD colonization and treatment of CDI. Probiotics have been trialed to support commensal gut microbiota and reduce CDI. This study investigated commensal microbe Faecalibacterium prausnitzii (FP) and a prebiotic, both known to yield butyrate and be anti-inflammatory and immunomodulatory, on CD colonization and gut integrity in mice.

METHODS

Mice were randomly grouped and supplemented daily with FP, prebiotic, FP + prebiotic, FP/prebiotic supernatant, or saline throughout the entire study. Following treatment with clindamycin for 3 days, mice were exposed to CD. Feces were collected at baseline, the day after antibiotic, and 1, 3, and 5 days after CD exposure and cultured for bacterial overgrowth and CD colonization. On days 1 and 5 after CD exposure, mice were randomly euthanized, and proximal colon was dissected for histological analysis and preparation of RNA for analysis of proinflammatory and anti-inflammatory cytokines.

RESULTS

Although all mice exhibited bacterial overgrowth and CD colonization, bacterial burden resolved quicker in the FP + prebiotic group. This was associated with induction and resolution of innate immune responses, anion exchanger, and tight junction protein preservation in proximal colon. CD toxin virulence potential was questionable as expression of CD toxin B receptor was depleted in the FP + prebiotic group.

CONCLUSION

Supplementation with anti-inflammatory butyrate-supporting commensal bacteria and prebiotic may support innate immune responses and minimize bacterial burden and negative effects during antibiotic and CD exposure.

Prophylactic tributyrin treatment mitigates chronic-binge ethanol-induced intestinal barrier and liver injury

BACKGROUND AND AIM

Impaired gut-liver axis is a potential factor contributing to alcoholic liver disease. Ethanol depletes intestinal integrity and causes gut dysbiosis. Butyrate, a fermentation byproduct of gut microbiota, is altered negatively following chronic ethanol exposure. This study aimed to determine whether prophylactic tributyrin could protect the intestinal barrier and liver in mice during combined chronic-binge ethanol exposure.

METHODS

C57BL/6J mice exposed to 5% v/v ethanol-containing diet for 10 days received a single ethanol gavage (5 g/kg) 9 h before euthanasia. Control mice were isocalorically pair-fed maltose dextrin for ethanol. Diets were supplemented (5 mM) with tributyrin or glycerol. Intestine and liver disease activity was assessed histologically. Protein and mRNA expression of tight junction (TJ) proteins, toll-like receptors, and tumor necrosis factor-alpha were assessed. Caco-2 monolayers with or without ethanol exposure and/or sodium butyrate were used to test butyrate's direct effects on intestinal integrity.

RESULTS

Chronic-binge ethanol feeding impaired intestinal TJ protein co-localization staining; however, tributyrin co-treatment mitigated these effects. Ethanol depleted TJ and transepithelial electrical resistance in Caco-2 monolayers, but butyrate co-treatment reduced these effects. Hepatic toll-like receptor mRNA expression and tumor necrosis factor-alpha protein expression was induced by ethanol; however, the response was significantly dampened in mice co-treated with tributyrin. Tributyrin altered localization of both neutrophils and single hepatocyte death: Leukocytes and apoptotic hepatocytes localized predominantly around the portal tract in ethanol-only treated mice, whereas localization predominated around the central vein in ethanol-tributyrin mice.

CONCLUSIONS

Prophylactic tributyrin supplementation mitigated effects of combined chronic-binge ethanol exposure on disruption of intestinal TJ localization and intestinal permeability and liver injury.

In vitro analysis of partially hydrolyzed guar gum fermentation differences between six individuals

Partially hydrolyzed guar gum (PHGG) is a fermentable, soluble, non-gelling fiber consumed as both a supplement and ingredient. PHGG supports bifidogenic and lactogenic growth, and increases the concentration of short chain fatty acids (SCFAs) in the distal intestine due to its fermentability. Changes in SCFA development due to the fermentation of dietary fibers in the colon have been widely studied, but there are limited studies analyzing the differences in SCFA development across multiple individuals (ages 23-68) exposed to the same dietary fiber (PHGG). With the six donors analyzed in this study, gas production varied from 59-80 mL/0.5 g fiber at 12 h and 85-93 mL/0.5 g fiber at 24 h between the six donors. At 12 h butyrate concentrations varied from 6.99 μmol mL(-1) to 23.84 μmol mL(-1) and from 8.78 μmol mL(-1) to 22.84 μmol mL(-1) at 24 h. Total SCFA concentration at 24 h ranged from 42.85 μmol mL(-1) to 91.17 μmol mL(-1). The overall average SCFA ratio for the six fecal donors was 30 : 45 : 25 (acetate : propionate : butyrate), which is similar to other fermentable fibers analyzed using in vitro systems. SCFA development in the distal intestine increases the amount of metabolizable energy from the diet, but varies greatly among people based primarily on the composition and changes of their gut microflora. With over a 2-fold difference in SCFA production, significant differences were found among healthy individuals fecal microflora when exposed to PHGG. Donor 6 SCFA concentrations decreased at 24 h, indicating a quicker fermentation process than the other five donors. All SCFAs measured fluctuated greatly among the six individuals within 24 h of analysis. Results of in vitro fermentation analyses are limited by the wide variation found with fecal donor.

Experimental support for the effects of a probiotic/digestive enzyme supplement on serum cholesterol concentrations and the intestinal microbiome

Background

Elevated levels of blood cholesterol are associated with cardiovascular disease, a leading cause of morbidity and mortality worldwide. Current therapies for addressing elevated blood cholesterol can be inadequate, ineffective or associated with side effects; therefore, the search for additional therapies is ongoing. This study evaluated Daily Body Restore (DBR), a proprietary blend of 9 probiotic organisms of the genera Lactobacillus and Bifidobacterium, and 10 digestive enzymes, for its effects on cholesterol metabolism using an in vitro system and a mouse model.

Methods

We used a murine model of hypercholesterolemia induced by a high fat diet to evaluate the effects of DBR on blood cholesterol concentrations. Hypercholesterolemic mice were supplemented with DBR in their drinking water for 8 weeks and compared to control mice given low fat diets or unsupplemented high fat diets. To evaluate the effects of DBR on the activity of gut microbiota in vitro, the Shime^® system consisting of sequential colon reactors was supplemented with DBR for analysis of short chain fatty acid production.

Results

Analysis of hypercholesterolemic mice after 4 and 8 weeks of DBR supplementation revealed significant decreases in blood concentrations of low-density lipoprotein (LDL) and increases in high-density lipoprotein (HDL) while triglyceride concentrations were unaltered. Specifically, after 4 weeks of DBR supplementation, there was a 47 % decrease in LDL and a 32 % increase in HDL in peripheral blood compared to unsupplemented, high fat diet-fed mice. After 8 weeks of DBR treatment, LDL concentrations were dramatically reduced by 78 % and HDL was increased by 52 % relative to control mice. Addition of DBR to the Shime^® system led to significantly increased production of propionate in colon reactors, indicative of microbial production of short chain fatty acids known to inhibit cholesterol synthesis.

Conclusions

DBR, a probiotic and digestive enzyme supplement, lowered harmful LDL and increased HDL levels in a mouse model and also exerted in vitro effects consistent with cholesterol-lowering activity. Given the magnitude of the effects of DBR, these findings are promising for clinical implementation of DBR for treating hypercholesterolemia.

Effects of Walnut Consumption on Colon Carcinogenesis and Microbial Community Structure

Walnuts are composed of a complex array of biologically active constituents with individual cancer-protective properties. Here, we assessed the potential benefit of whole walnut consumption in a mouse tumor bioassay using azoxymethane. In study 1, a modest reduction (1.3-fold) in tumor numbers was observed in mice fed a standard diet (AIN-76A) containing 9.4% walnuts (15% of total fat). In study 2, the effects of walnut supplementation was tested in the Total Western Diet (TWD). There was a significant reduction (2.3-fold; P < 0.02) in tumor numbers in male mice fed TWD containing 7% walnuts (10.5% of total fat). Higher concentrations of walnuts lacked inhibitory effects, particularly in female mice, indicating there may be optimal levels of dietary walnut intake for cancer prevention. Since components of the Mediterranean diet have been shown to affect the gut microbiome, the effects of walnuts were therefore tested in fecal samples using 16S rRNA gene sequencing. Carcinogen treatment reduced the diversity and richness of the gut microbiome, especially in male mice, which exhibited lower variability and greater sensitivity to environmental changes. Analysis of individual operational taxonomic units (OTU) identified specific groups of bacteria associated with carcinogen exposure, walnut consumption, and/or both variables. Correlation analysis also identified specific OTU clades that were strongly associated with the presence and number of tumors. Taken together, our results indicate that walnuts afford partial protection to the colon against a potent carcinogenic insult, and this may be due, in part, to walnut-induced changes to the gut microbiome. Cancer Prev Res; 9(8); 692-703. ©2016 AACR.

Prebiotic Effects and Fermentation Kinetics of Wheat Dextrin and Partially Hydrolyzed Guar Gum in an In Vitro Batch Fermentation System

Scientific research demonstrates that two indigenous gut bacteria, Lactobacillus and Bifidobacterium can contribute to human health. Although these bacteria can be consumed as probiotics, they can also be produced in the gut by bacteria, and are then called prebiotics. The primary objective of this in vitro study was to quantitatively analyze at the genus level how two dietary fibers, wheat dextrin (WD) and partially hydrolyzed guar gum (PHGG) changed the levels of these two gut bacteria at 12 and 24 h, via real time qualitative polymerase chain reaction (qPCR). Secondary objectives were changes in fecal pH, short chain fatty acids (SCFAs) and total gas volume produced. At 12 h WD was more bifidogenic (9.50 CFU log₁₀/mL) than PHGG (9.30 CFU log₁₀/mL) (p = 0.052), and also at 24 h WD (9.41 CFU log₁₀/mL) compared with PHGG (9.27 CFU log₁₀/mL) (p = 0.043). WD produced less total SCFAs at both 12 and 24 h than PHGG, and produced significantly lower amounts of gas at 12 and 24 h (p < 0.001). Both PHGG and WD also promoted growth of Lactobacilli when measured at 12 and 24 h compared with the 0 h analysis, indicating that both fibers are lactogenic. These results demonstrate the prebiotic effect of WD and PHGG. Based on fermentation kinetics, PHGG is more rapidly fermented than WD, and both fibers show prebiotic effects as early as 12 h.

Cross-feeding by Bifidobacterium breve UCC2003 during co-cultivation with Bifidobacterium bifidum PRL2010 in a mucin-based medium

BACKGROUND

Bifidobacteria constitute a specific group of commensal bacteria that commonly inhabit the mammalian gastrointestinal tract. Bifidobacterium breve UCC2003 was previously shown to utilize a variety of plant/diet/host-derived carbohydrates, including cellodextrin, starch and galactan, as well as the mucin and HMO-derived monosaccharide, sialic acid. In the current study, we investigated the ability of this strain to utilize parts of a host-derived source of carbohydrate, namely the mucin glycoprotein, when grown in co-culture with the mucin-degrading Bifidobacterium bifidum PRL2010.

RESULTS

B. breve UCC2003 was shown to exhibit growth properties in a mucin-based medium, but only when grown in the presence of B. bifidum PRL2010, which is known to metabolize mucin. A combination of HPAEC-PAD and transcriptome analyses identified some of the possible monosaccharides and oligosaccharides which support this enhanced co-cultivation growth/viability phenotype.

CONCLUSION

This study describes the potential existence of a gut commensal relationship between two bifidobacterial species. We demonstrate the in vitro ability of B. breve UCC2003 to cross-feed on sugars released by the mucin-degrading activity of B. bifidum PRL2010, thus advancing our knowledge on the metabolic adaptability which allows the former strain to colonize the (infant) gut by its extensive metabolic abilities to (co-)utilize available carbohydrate sources.

Metabolomics in cell culture--a strategy to study crucial metabolic pathways in cancer development and the response to treatment

Metabolomics is a comprehensive tool for monitoring processes within biological systems. Thus, metabolomics may be widely applied to the determination of diagnostic biomarkers for certain diseases or treatment outcomes. There is significant potential for metabolomics to be implemented in cancer research because cancer may modify metabolic pathways in the whole organism. However, not all biological questions can be answered solely by the examination of small molecule composition in biofluids; in particular, the study of cellular processes or preclinical drug testing requires ex vivo models. The major objective of this review was to summarise the current achievement in the field of metabolomics in cancer cell culture-focusing on the metabolic pathways regulated in different cancer cell lines-and progress that has been made in the area of drug screening and development by the implementation of metabolomics in cell lines.

Tributyrin supplementation protects mice from acute ethanol-induced gut injury

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Tributyrin supplementation protects mice from acute ethanol-induced gut injury

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Calcium butyrate: Anti-inflammatory effect on experimental colitis in rats and antitumor properties

Butyric acid is a physiological component of the colonic environment that possesses anti-inflammatory and antitumor properties, among others. However, little is known regarding its effects following direct application on the colonic surface. This study was conducted to investigate the topical anti-inflammatory effect of calcium butyrate in chemically-induced colitis in rats and to evaluate its antitumor properties in vivo and in vitro. The anti-inflammatory activity of calcium butyrate was evaluated in dinitrobenzene sulfonic acid-induced colitis in rats, following intracolonic instillation for 6 consecutive days and its in vivo antitumor activity was evaluated in F344 rats with the azoxymethane (AOM)-induced aberrant crypt foci (AFC) test, following intracolonic instillation for 4 weeks. The in vitro antiproliferative activity was assessed by incubation for 48 h with the HT29, SW620 and HCT116 intestinal tumour cell lines to evaluate the rate of ³H-thymidine uptake. In dinitrobenzene-induced colitis, the intracolonic instillation of calcium butyrate completely prevented body weight reduction in the animals and counteracted the local noxious effects of the irritant by reducing colon edema (-22.7%, P=0.048) and the area of mucosal damage (-48%, P=0.045). In the AOM-induced AFC test, the intracolonic instillation of calcium butyrate significantly reduced the number of AFC in the entire colon (-22.7%, P<0.05). Calcium butyrate, following incubation with the HT29, SW620 and HCT116 tumour cell lines, induced a significant antiproliferative, dose-dependent effect (P=0.046 to P=0.002) in all three strains, as measured by the reduction in ³H-thymidine uptake. Calcium butyrate directly applied to the mucosa of the rat colon was able to ameliorate colonic inflammation, suggesting a possible beneficial role in the treatment of inflammatory colon diseases. Moreover, calcium butyrate exhibited notable antitumor effects in vivo and in vitro; however, their clinical relevance requires confirmation by additional clinical investigations.

Non-extractable polyphenols, a major dietary antioxidant: occurrence, metabolic fate and health effects

Current research on dietary antioxidants misses the so-called non-extractable polyphenols (NEPP), which are not significantly released from the food matrix either by mastication, acid pH in the stomach or action of digestive enzymes, reaching the colon nearly intact. NEPP, not detected by the usual analytical procedures, are made up of macromolecules and single phenolic compounds associated with macromolecules. Therefore, NEPP are not included in food and dietary intake data nor in bioavailability, intervention or observational studies. The present paper aims to provide an overview of dietary NEPP - nature, occurrence in diet, metabolic fate and possible health effects. NEPP are a relevant fraction of dietary polyphenols exerting their main biological action in the colon, where they are extensively fermented by the action of microbiota, giving place to absorbable metabolites. NEPP exhibit different potential health-related properties, in particular in relation to gastrointestinal health, such as increases in antioxidant and antiproliferative capacities, reduction of intestinal tumorigenesis and modification of gene expression, as observed in different animal models. Further research into NEPP may provide a better understanding of the health effects of dietary antioxidants.

Lactobacillus acidophilus CRL 1014 improved "gut health" in the SHIME reactor

BACKGROUND

How to maintain "gut health" is a goal for scientists throughout the world. Therefore, microbiota management models for testing probiotics, prebiotics, and synbiotics have been developed.

METHODS

The SHIME model was used to study the effect of Lactobacillus acidophilus 1014 on the fermentation pattern of the colon microbiota. Initially, an inoculum prepared from human feces was introduced into the reactor vessels and stabilized over 2-wk using a culture medium. This stabilization period was followed by a 2-wk control period during which the microbiota was monitored. The microbiota was then subjected to a 4-wk treatment period by adding 5 mL of sterile peptone water with L. acidophilus CRL1014 at the concentration of 10⁸ CFU/mL to vessel one (the stomach compartment). Plate counts, Denaturing Gradient Gel Electrophoresis (DGGE), short-chain fatty acid (SCFA) and ammonium analyses were carried out for monitoring of the microbial community from the colon compartments.

RESULTS

A significant increase (p < 0.01) in the Lactobacillus spp. and Bifidobacterium spp. populations was observed during the treatment period. The DGGE obtained showed changes in the lactobacilli community from the colon compartments of the SHIME reactor. The (SCFA) concentration increased (p < 0.01) during the treatment period, due mainly to significant increased levels of acetic, butyric, and propionic acids. However, ammonium concentrations decreased during the same period (p < 0.01).

CONCLUSIONS

This study showed the beneficial influence of L. acidophilus CRL 1014 on microbial metabolism and lactobacilli community composition for improving human health.

Lactobacillus GG and tributyrin supplementation reduce antibiotic-induced intestinal injury

BACKGROUND

Antibiotic therapy negatively alters the gut microbiota. Lactobacillus GG (LGG) decreases antibiotic-associated diarrhea (AAD) symptoms, but the mechanisms are unknown. Butyrate has beneficial effects on gut health. Altered intestinal gene expression occurs in the absence of gut microbiota. We hypothesized that antibiotic-induced changes in gut microbiota reduce butyrate production, varying genes involved with gut barrier integrity and water and electrolyte absorption, lending to AAD, and that simultaneous supplementation with LGG and/or tributyrin would prevent these changes.

METHODS

C57BL/6 mice aged 6-8 weeks received a chow diet while divided into 8 treatment groups (± saline, ± LGG, ± tributyrin, or both). Mice received treatments orally for 7 days with ± broad-spectrum antibiotics. Water intake was recorded daily and body weight was measured. Intestine tissue samples were obtained and analyzed for expression of genes and proteins involved with water and electrolyte absorption, butyrate transport, and gut integrity via polymerase chain reaction and immunohistochemistry.

RESULTS

Antibiotics decreased messenger RNA (mRNA) expression (butyrate transporter and receptor, Na(+)/H(+) exchanger, Cl(-)/HCO3 (-), and a water channel) and protein expression (butyrate transporter, Na(+)/H(+) exchanger, and tight junction proteins) in the intestinal tract. LGG and/or tributyrin supplementation maintained intestinal mRNA expression to that of the control animals, and tributyrin maintained intestinal protein intensity expression to that of control animals.

CONCLUSION

Broad-spectrum antibiotics decrease expression of anion exchangers, butyrate transporter and receptor, and tight junction proteins in mouse intestine. Simultaneous oral supplementation with LGG and/or tributyrin minimizes these losses. Optimizing intestinal health with LGG and/or tributyrin may offer a preventative therapy for AAD.

Short-chain fatty acid level and field cancerization show opposing associations with enteroendocrine cell number and neuropilin expression in patients with colorectal adenoma

BACKGROUND

Previous reports have suggested that the VEGF receptor neuropilin-1 (NRP-1) is expressed in a singly dispersed subpopulation of cells in the normal colonic epithelium, but that expression becomes dysregulated during colorectal carcinogenesis, with higher levels in tumour suggestive of a poor prognosis. We noted that the spatial distribution and morphology if NRP-1 expressing cells resembles that of enteroendocrine cells (EEC) which are altered in response to disease state including cancer and irritable bowel syndrome (IBS). We have shown that NRP-1 is down-regulated by butyrate in colon cancer cell lines in vitro and we hypothesized that butyrate produced in the lumen would have an analogous effect on the colon mucosa in vivo. Therefore we sought to investigate whether NRP-1 is expressed in EEC and how NRP-1 and EEC respond to butyrate and other short-chain fatty acids (SCFA - principally acetate and propionate). Additionally we sought to assess whether there is a field effect around adenomas.

METHODOLOGY

Biopsies were collected at the mid-sigmoid, at the adenoma and at the contralateral wall (field) of 28 subjects during endoscopy. Samples were fixed for IHC and stained for either NRP-1 or for chromogranin A (CgA), a marker of EEC. Stool sampling was undertaken to assess individuals' butyrate, acetate and propionate levels.

RESULT

NRP-1 expression was inversely related to SCFA concentration at the colon landmark (mid-sigmoid), but expression was lower and not related to SCFA concentration at the field. Likewise CgA+ cell number was also inversely related to SCFA at the landmark, but was lower and unresponsive at the field. Crypt cellularity was unaltered by field effect. A colocalisation analysis showed only a small subset of NRP-1 localised with CgA. Adenomas showed extensive, weaker staining for NRP-1 which contrastingly correlated positively with butyrate level. Field effects cause this relationship to be lost. Adenoma tissue shows dissociation of the co-regulation of NRP-1 and EEC.

CONCLUSION

NRP-1 is inversely associated with levels of butyrate and other SCFA in vivo and is expressed in a subset of CgA expressing cells. EEC number is related to butyrate level in the same way.

Butyrate induces cell apoptosis through activation of JNK MAP kinase pathway in human colon cancer RKO cells

Butyrate has been shown to display anti-cancer activity through the induction of apoptosis in various cancer cells. However, the underlying mechanism involved in butyrate-induced apoptosis is still not fully understood. Here, we investigated the cytotoxicity mechanism of butyrate in human colon cancer RKO cells. The results showed that butyrate induced a strong growth inhibitory effect against RKO cells. Butyrate also effectively induced apoptosis in RKO cells, which was characterized by DNA fragmentation, nuclear staining of DAPI, and the activation of caspase-9 and caspase-3. The expression of anti-apoptotic protein Bcl-2 decreased, whereas the apoptotic protein Bax increased in a dose-dependent manner during butyrate-induced apoptosis. Moreover, treatment of RKO cells with butyrate induced a sustained activation of the phosphorylation of c-jun N-terminal kinase (JNK) in a dose- and time-dependent manner, and the pharmacological inhibition of JNK MAPK by SP600125 significantly abolished the butyrate-induced apoptosis in RKO cells. These results suggest that butyrate acts on RKO cells via the JNK but not the p38 pathway. Butyrate triggered the caspase apoptotic pathway, indicated by an enhanced Bax-to-Bcl-2 expression ratio and caspase cascade reaction, which was blocked by SP600125. Taken together, our data indicate that butyrate induces apoptosis through JNK MAPK activation in colon cancer RKO cells.

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.

Comparative effect of orally administered sodium butyrate before or after weaning on growth and several indices of gastrointestinal biology of piglets

Sodium butyrate (SB) provided orally favours body growth and maturation of the gastrointestinal tract (GIT) in milk-fed pigs. In weaned pigs, conflicting results have been obtained. Therefore, we hypothesised that the effects of SB (3 g/kg DM intake) depend on the period (before v. after weaning) of its oral administration. From the age of 5 d, thirty-two pigs, blocked in quadruplicates within litters, were assigned to one of four treatments: no SB (control), SB before (for 24 d), or after (for 11–12 d) weaning and SB before and after weaning (for 35–36 d). Growth performance, feed intake and various end-point indices of GIT anatomy and physiology were investigated at slaughter. The pigs supplemented with SB before weaning grew faster after weaning than the controls (P < 0·05). The feed intake was higher in pigs supplemented with SB before or after weaning (P < 0·05). SB provided before weaning improved post-weaning faecal digestibility (P < 0·05) while SB after weaning decreased ileal and faecal digestibilities (P < 0·05). Gastric digesta retention was higher when SB was provided before weaning (P < 0·05). Post-weaning administration of SB decreased the activity of three pancreatic enzymes and five intestinal enzymes (P < 0·05). IL-18 gene expression tended to be lower in the mid-jejunum in SB-supplemented pigs. The small-intestinal mucosa was thinner and jejunal villous height lower in all SB groups (P < 0·05). In conclusion, the pre-weaning SB supplementation was the most efficient to stimulate body growth and feed intake after weaning, by reducing gastric emptying and intestinal mucosa weight and by increasing feed digestibility.

Probiotic bacteria influence the composition and function of the intestinal microbiota

Probiotics have a range of proposed health benefits for the consumer, which may include modulating the levels of beneficial elements in the microbiota. Recent investigations using molecular approaches have revealed a human intestinal microbiota comprising over 1000 phylotypes. Mechanisms whereby probiotics impact on the intestinal microbiota include competition for substrates, direct antagonism by inhibitory substances, competitive exclusion, and potentially host-mediated effects such as improved barrier function and altered immune response. We now have the microbial inventories and genetic blueprints to begin tackling intestinal microbial ecology at an unprecedented level of detail, aided by the understanding that dietary components may be utilized differentially by individual phylotypes. Controlled intervention studies in humans, utilizing latest molecular technologies, are required to consolidate evidence for bacterial species that impact on the microbiota. Mechanistic insights should be provided by metabolomics and other analytical techniques for small molecules. Rigorous characterization of interactions between the diet, microbiota, and probiotic bacteria will provide new opportunities for modulating the microbiota towards improving human health.

Feeding potato flakes affects cecal short-chain fatty acids, microflora and fecal bile acids in rats

BACKGROUND/AIMS

Feeding rats potato resistant starch improves large bowel health; however, there is little information on the physiological effects of preprocessed starch like potato flakes in animal experiments. The present study was designed to investigate the effects of the consumption of various colored potato (white, red and purple) flakes on cecal fermentation and fecal bile acid excretions in rats.

METHODS

The control group was fed a basal diet (BD) containing alpha-cornstarch for 4 weeks. The potato flake-treated groups were fed one of the following diets containing a mixture of 299.5 g/kg alpha-cornstarch plus 250 g/kg Hokkai kogane flakes (HK, white), Hokkai No. 91 flakes (H91, red) or Hokkai No. 92 flakes (H92, purple).

RESULTS

There were no significant differences in the body weight, food intake and cecum weight among the groups. Cecal pH values in the HK, H91 and H92 groups were significantly lower than that in the BD group, and matter excretion in the H91 group was significantly higher than in the BD and HK groups. Cecal short-chain fatty acid (SCFA) concentrations in the HK, H91 and H92 groups were significantly higher than in the BD group, and the molar ratio of butyrate to total SCFA in the HK, H91 and H92 groups was greatly increased compared with the BD group. Rats fed the HK, H91 and H92 potato flake diets presented significantly higher counts of total anaerobes in the cecum than rats fed the BD. The cecal Lactobacillus count in the H91 group was significantly increased compared to the BD group and the Bifidobacterium count was similar for all groups. Fecal total bile acid excretion in the H92 flake group and secondary bile acid excretions in the H91 and H92 groups were significantly greater than those in the other groups and in the BD and HK groups, respectively.

CONCLUSION

The results indicate that potato flakes act like resistant starch and raise bowel SCFA, probably through anaerobic bacterial activities and fermentation of residual starch. These actions are helpful for the improvement of the colonic environment.

Health potential of polyols as sugar replacers, with emphasis on low glycaemic properties

Abstract Polyols are hydrogenated carbohydrates used as sugar replacers. Interest now arises because of their multiple potential health benefits. They are non-cariogenic (sugar-free tooth-friendly), low-glycaemic (potentially helpful in diabetes and cardiovascular disease), low-energy and low-insulinaemic (potentially helpful in obesity), low-digestible (potentially helpful in the colon), osmotic (colon-hydrating, laxative and purifying) carbohydrates. Such potential health benefits are reviewed. A major focus here is the glycaemic index (GI) of polyols as regards the health implications of low-GI foods. The literature on glycaemia and insulinaemia after polyol ingestion was analysed and expressed in the GI and insulinaemic index (II) modes, which yielded the values: erythritol 0, 2; xylitol 13, 11; sorbitol 9, 11; mannitol 0, 0; maltitol 35, 27; isomalt 9, 6; lactitol 6, 4; polyglycitol 39, 23. These values are all much lower than sucrose 65, 43 or glucose 100, 100. GI values on replacing sucrose were independent of both intake (up to 50 g) and the state of carbohydrate metabolism (normal, type 1 with artificial pancreas and type 2 diabetes mellitus). The assignment of foods and polyols to GI bands is considered, these being: high (> 70), intermediate (> 55–70), low (> 40–55), and very low (< 40) including non-glycaemic; the last aims to target particularly low-GI-carbohydrate-based foods. Polyols ranged from low to very low GI. An examination was made of the dietary factors affecting the GI of polyols and foods. Polyol and other food GI values could be used to estimate the GI of food mixtures containing polyols without underestimation. Among foods and polyols a departure of II from GI was observed due to fat elevating II and reducing GI. Fat exerted an additional negative influence on GI, presumed due to reduced rates of gastric emptying. Among the foods examined, the interaction was prominent with snack foods; this potentially damaging insulinaemia could be reduced using polyols. Improved glycated haemoglobin as a marker of glycaemic control was found in a 12-week study of type 2 diabetes mellitus patients consuming polyol, adding to other studies showing improved glucose control on ingestion of low-GI carbohydrate. In general some improvement in long-term glycaemic control was discernible on reducing the glycaemic load via GI by as little as 15–20 g daily. Similar amounts of polyols are normally acceptable. Although polyols are not essential nutrients, they contribute to clinically recognised maintenance of a healthy colonic environment and function. A role for polyols and polyol foods to hydrate the colonic contents and aid laxation is now recognised by physicians. Polyols favour saccharolytic anaerobes and aciduric organisms in the colon, purifying the colon of endotoxic, putrefying and pathological organisms, which has clinical relevance. Polyols also contribute towards short-chain organic acid formation for a healthy colonic epithelium. Polyol tooth-friendliness and reduced energy values are affirmed and add to the potential benefits. In regard to gastrointestinal tolerance, food scientists and nutritionists, physicians, and dentists have in their independent professional capacities each now described sensible approaches to the use and consumption of polyols.

In vitro fermentability of differently digested resistant starch preparations

The in vitro fermentability of two resistant starch preparations type 2 (RS2) and type 3 (RS3) was investigated using human colonic microbiota. Prior to the fermentation experiments, samples were digested using two in vitro models, a batch (ba) and a dynamic (dy), as well as an in vivo method (il) for RS3. Digestion residues were fermented in vitro using a simple batch model lasting 24 h and a more sophisticated dynamic model enduring 72 h. During batch fermentation, metabolite productions and starch degradation rates were similar for RS2 and RS3 but higher for dy- compared to ba-digested samples. RS3il led to the lowest fermentability. Furthermore, increased butyrate ratios were observed for all preparations. The varying RS preparations behaved similarly in the dynamic fermentation but showed high SDs. Moreover, the fermentability was slow during the first 24 h, indicating that the microbiota needed an adaptation period to ferment RS. Propionate ratios increased at the expense of butyrate with exception for RS2dy showing an increase in acetate only. Differences in fermentability observed between the dynamic model, allowing a closer simulation of the in vivo behavior, and the batch model, recommended for screening purposes, could be due to the varying microbiota used.

A novel high-amylose barley cultivar (Hordeum vulgare var. Himalaya 292) lowers plasma cholesterol and alters indices of large-bowel fermentation in pigs

Hordeum vulgare var. Himalaya 292 is a new barley cultivar with altered starch synthesis and less total starch but more amylose, resistant starch (RS) and total and soluble NSP including β-glucan. To determine its nutritional potential, young pigs were fed diets containing stabilised wholegrain flours from either Himalaya 292, Namoi (a commercial barley), wheat bran or oat bran at equivalent dietary NSP concentrations for 21 d. Serum total cholesterol was significantly lowered by the Himalaya 292 diet relative to wheat bran, indicating that Himalaya 292 retained its hypocholesterolaemic potential. In all groups SCFA concentrations were highest in the proximal colon and decreased towards the rectum. Digesta pH was lowest in the proximal colon and highest in the distal colon. Large-bowel and faecal pH were significantly lower in the pigs fed the barley and oat diets, indicating greater bacterial fermentation. Caecal and proximal colonic pH was lowest and SCFA pools highest in the pigs fed Himalaya 292. Total and individual SCFA were lowest in the mid- and distal colon of the pigs fed Himalaya 292 or oat bran. These data suggest the presence of more RS in Himalaya 292 and suggest that its fermentation was rapid relative to transit. Differences in faecal and large-bowel anaerobic, aerobic, coliform and lactic acid bacteria were relatively small, indicating a lack of a specific prebiotic action. These data support the potential of this novel barley cultivar to improve health through plasma cholesterol reduction and increased large-bowel SCFA production.

Physiological and metabolic properties of a digestion-resistant maltodextrin, classified as type 3 retrograded resistant starch

There is a growing interest in highly fermentable dietary fibers having the potential to reduce risks of disease through the production of short-chain fatty acids (SCFA). Recently a digestion-resistant retrograded maltodextrin (RRM), classified as type 3 resistant starch was developed. Systematic work to determine its molecular and physiological properties was carried out to determine (1) the fraction resistant to digestion in vitro and in vivo, (2) its postconsumption effect on blood glucose in healthy volunteers, and (3) its in vitro fermentation pattern, at different ages, by use of pooled fresh human fecal inoculum.

RESULTS

The digestion resistant fraction obtained in vivo from ileostomy patients (59.4%) is similar to that obtained by the AOAC method for measuring retrograded resistant starch (59.7%). The relative glycemic response after consumption of 50 g of RRM was 58.5% compared to glucose set as 100%. When exposed to colonic microbiota, in vitro obtained indigestible fractions behave similarly to those obtained in vivo in ileostomy patients. Fermentation of RRM and production of butyric acid is negligible during the first months of life but develops subsequently during weaning. In adults, RRM fermentation results in a high yield of SCFA, with butyrate representing 21-31 mol % of total SCFA. The high yield of SCFA during colonic fermentation, observed from weaning age on, as well as the potential to help reduce glycemic load may be of benefit to a number of health-related functions in the host. Further study on clear clinical end points is warranted.

Butyrate induces necrotic cell death in murine colonic epithelial cell MCE301

Recent findings have suggested that organic acids produced by anaerobic intestinal bacteria might contribute to the pathogenesis of colonic ulcers. In this study, it was shown that butyrate caused potent cytotoxicity in the murine normal colonic epithelial cells MCE301 at physiological concentrations. Several markers of apoptosis, such as phosphatidyl serine externalization, cytochrome c release, DNA fragmentation, and chromatin condensation were negative after butyrate exposure. Inhibitor of caspases failed to protect against butyrate cytotoxicity. By transmission electron microscopy, marked swollen mitochondria and vacuolization within the cytoplasm was observed by treatment of butyrate. Collective, these data indicated that butyrate-induced cell death caused through a necrosis-like process. Butyrate induced cell death was reduced partially by treatment with prednisolone or 5-aminosalicylates in a concentration dependent manner. These results suggest that (1) butyrate induces necrotic cell death but not apoptotic cell death, and (2) the necrotic cell death induced by butyrate may be useful as a novel in vitro model of ulcerative colitis to screen useful drugs for the treatment of the disease.

Hydrothermal treatment of Novelose 330 results in high yield of resistant starch type 3 with beneficial prebiotic properties and decreased secondary bile acid formation in rats

Annealing and heat-moisture treatment (HMT) are shown to be suitable methods to increase the yield of resistant starch type 3 (RS3) from Novelose 330 by up to 75%. Peak temperatures of approximately 121 degrees C were used to produce to a sufficiently high thermal stability of the hydrothermal modified RS3 products for a wide range of applications. HMT significantly increased the crystallinity up to 40%. An in vivo feeding experiment with Wistar rats showed that fermentation of Novelose 330 dominated in the proximal colon, but degradation of HMT-Novelose was more dominant in the distal colon, leading to higher butyrate concentrations in this segment of the large bowel. Large-bowel surface and crypt length increased in the proximal colon in rats fed the Novelose 330-containing diet. In contrast, after the intake of HMT-Novelose, maximal values were found in the distal segment. The lower pH and higher butyrate concentration of the caecal and colonic contents significantly suppressed the formation of secondary bile acids in RS3-fed rats. The formation of secondary bile acids was inhibited more strongly by HMT-Novelose than by Novelose 330. The Ki-67-immunopositive epithelial cells in the colon of RS3-fed rats indicated the establishment of an optimal balance in the dynamic process of mucosal regeneration. HMT provides a method for the economical production of a high-quality RS3 with dominating prebiotic properties in the distal colon for health-promoting applications.

Effects of inositol hexaphosphate on proliferation of HT-29 human colon carcinoma cell line

AIM: To investigate the effects of inositol hexaphosphate (IP₆) on proliferation of HT-29 human colon carcinoma cell line.

METHODS: Cells were exposed to various concen-trations (0, 1.8, 3.3, 5.0, 8.0, 13.0 mmol/L) of IP₆ for a certain period of time. Its effect on growth of HT-29 cells was measured by MTT assay. The expressions of cell cycle regulators treated with IP₆ for 2 d were detected by immunocytochemistry.

RESULTS: IP₆ inhibited the HT-29 cell growth in a dose- and time-dependent manner. Analysis of cell cycle regulator expression revealed that IP₆ reduced the abnormal expression of P53 and PCNA and induced the expression of P21.

CONCLUSION: IP₆ has potent inhibitory effect on proliferation of HT-29 cells by modulating the expression of special cell cycle regulators.

Effect of polyunsaturated fatty acid-enriched phosphatidylcholine and phosphatidylserine on butyrate-induced growth inhibition, differentiation and apoptosis in Caco-2 cells

Phospholipids are fascinating in terms of important bio-functional compounds. The present work investigated the effect of polyunsaturated phosphatidylcholine (PC) and phosphatidylserine (PS) on butyrate-induced growth inhibition, differentiation and apoptosis using Caco-2 cells. Growth inhibition of Caco-2 cells became apparent 24 h after addition of PC while it took 48 h with PS. Alkaline phosphatase activity of Caco-2 cells increased with combined PC or PS and sodium butyrate (NaBT) at 72 h, indicating that PC and PS enhanced cell differentiation in the presence of NaBT. An increased enrichment factor was also found when cells were treated with combinations of PC or PS and NaBT. These results suggest that marine PC and PS can be considered to be potentially useful colon cancer chemotherapy agents with high bio-availability.

Effect of isomalt consumption on faecal microflora and colonic metabolism in healthy volunteers

Due to its low digestibility in the small intestine, a major fraction of the polyol isomalt reaches the colon. However, little is known about effects on the intestinal microflora. During two 4-week periods in a double-blind, placebo-controlled, cross-over design, nineteen healthy volunteers consumed a controlled basal diet enriched with either 30 g isomalt or 30 g sucrose daily. Stools were collected at the end of each test phase and various microbiological and luminal markers were analysed. Fermentation characteristics of isomalt were also investigated in vitro. Microbiological analyses of faecal samples indicated a shift of the gut flora towards an increase of bifidobacteria following consumption of the isomalt diet compared with the sucrose diet (P<0.05). During the isomalt phase, the activity of bacterial beta-glucosidase decreased (P<0.05) whereas beta-glucuronidase, sulfatase, nitroreductase and urease remained unchanged. Faecal polyamines were not different between test periods with the exception of cadaverine, which showed a trend towards a lower concentration following isomalt (P=0.055). Faecal SCFA, lactate, bile acids, neutral sterols, N, NH3, phenol and p-cresol were not affected by isomalt consumption. In vitro, isomalt was metabolized in several bifidobacteria strains and yielded high butyrate concentrations. Isomalt, which is used widely as a low-glycaemic and low-energy sweetener, has to be considered a prebiotic carbohydrate that might contribute to a healthy luminal environment of the colonic mucosa.

Sodium butyrate induces apoptosis and cell cycle arrest in primary effusion lymphoma cells independently of oxidative stress and p21(CIP1/WAF1) induction

Primary effusion lymphoma, a peculiar type of B cell non-Hodgkin lymphoma, preferentially develops in immunodeficient individuals and its pathogenesis is closely linked with human herpesvirus 8 (HHV-8). HHV-8 is present primarily persistence in primary effusion lymphoma cells, and the lytic cycle of HHV-8 can be induced by sodium butyrate (NaB) treatment. HHV-8 gene expression is affected by NaB in BCBL-1 cells, but the cellular response of BCBL-1 cells upon NaB treatment has not been investigated to date. Using BCBL-1 cells, a HHV-8 harboring cell line, we demonstrated that sodium butyrate could induce the reactive oxygen species generation, apoptosis and cell cycle arrest in BCBL-1 cells. The sodium butyrate-induce cell cycle arrest was associated with the decrease of Cdc2, Cdk4 and cyclin A in BCBL-1 cells without altering the protein levels of p21(CIP1/WAF1). The apoptosis induced by sodium butyrate in BCBL-1 cells was independent of oxidative stress.

DNA mismatch repair status may influence anti-neoplastic effects of butyrate

HNPCC (hereditary non-polyposis colon cancer) is an autosomal-dominant disorder characterized by early-onset CRC (colorectal cancer). HNPCC is most often associated with mutations in the MMR (mismatch repair) genes hMLH1, hMSH2, hMSH6 or hPMS2. The mutator phenotype of a defective MMR system is MSI (microsatellite instability), which also occurs in approx. 15-25% of sporadic CRC cases, where it is associated with the hypermethylation of the promoter region of hMLH1. Dietary factors, including excessive alcohol consumption, ingestion of red meat and low folate intake, may increase the risk of MSI high tumour development. In contrast, aspirin may suppress MSI in MMR-deficient CRC cell lines. Butyrate, a short-chain-fatty-acid end product of carbohydrate fermentation in the colon, shares a number of anti-neoplastic properties with aspirin, including inhibiting proliferation and inducing apoptosis of CRC cells. Recent in vitro studies suggest that physiological concentrations of butyrate (0.5-2 mM) may have more potent anti-neoplastic effects in CRC cell lines deficient in MMR, but mechanisms for such a differential response remain to be established.