AGA technical review: impact of dietary fiber on colon cancer occurrence

The Immunomodulatory Functions of Butyrate

The gastrointestinal (GI) system contains many different types of immune cells, making it a key immune organ system in the human body. In the last decade, our knowledge has substantially expanded regarding our understanding of the gut microbiome and its complex interaction with the gut immune system. Short chain fatty acids (SCFA), and specifically butyrate, play an important role in mediating the effects of the gut microbiome on local and systemic immunity. Gut microbial alterations and depletion of luminal butyrate have been well documented in the literature for a number of systemic and GI inflammatory disorders. Although a substantial knowledge gap exists requiring the need for further investigations to determine cause and effect, there is heightened interest in developing immunomodulatory therapies by means of reprogramming of gut microbiome or by supplementing its beneficial metabolites, such as butyrate. In the current review, we discuss the role of endogenous butyrate in the inflammatory response and maintaining immune homeostasis within the intestine. We also present the experimental models and human studies which explore therapeutic potential of butyrate supplementation in inflammatory conditions associated with butyrate depletion.

Dietary Potassium Intake and Mortality in a Prospective Hemodialysis Cohort

OBJECTIVES

Among hemodialysis patients, clinical practice guidelines recommend dietary potassium restriction given concerns about potential hyperkalemia leading to malignant arrhythmias and mortality. However, there are sparse data informing recommendations for dietary potassium intake in this population. We thus sought to examine the relationship between dietary potassium intake and death risk in a prospective cohort of hemodialysis patients.

DESIGN AND METHODS

Among 415 hemodialysis patients from the prospective "Malnutrition, Diet, and Racial Disparities in Chronic Kidney Disease" cohort recruited across 16 outpatient dialysis clinics, information regarding dietary potassium intake was obtained using Food Frequency Questionnaires administered over October 2011 to March 2015. We first examined associations of baseline dietary potassium intake categorized as tertiles with mortality risk using Cox regression. We then examined clinical characteristics associated with low dietary potassium intake (defined as the lowest tertile) using logistic regression.

RESULTS

In expanded case-mix Cox analyses, patients whose dietary potassium intake was in the lowest tertile had higher mortality (ref: highest tertile) (adjusted hazard ratio 1.74, 95% confidence interval 1.14-2.66). These associations had even greater magnitude of risk following adjustment for laboratory and nutritional covariates (adjusted hazard ratio 2.65, 95% confidence interval 1.40-5.04). In expanded case-mix restricted cubic spline analyses, there was a monotonic increase in mortality risk with incrementally lower dietary potassium intake. In expanded case-mix logistic regression models, female sex; higher serum bicarbonate; and lower dietary energy, protein, and fiber intake were associated with low dietary potassium intake.

CONCLUSIONS

In a prospective cohort of hemodialysis patients, lower dietary potassium intake was associated with higher mortality risk. These findings suggest that excessive dietary potassium restriction may be deleterious in hemodialysis patients, and further studies are needed to determine the optimal dietary potassium intake in this population.

Dietary inflammatory index and risk of colorectal adenoma: effect measure modification by race, nonsteroidal anti-inflammatory drugs, cigarette smoking and body mass index?

PURPOSE

To investigate if the association between dietary inflammatory potential and colorectal adenoma (CRA) is modified by race and factors known to modulate inflammation.

METHODS

We examined effect measure modification of race, nonsteroidal anti-inflammatory drugs (NSAIDs), cigarette smoking and body mass index (BMI) on the diet-CRA association by employing energy-adjusted dietary inflammatory index (E-DII™) to characterize dietary inflammatory potential among 587 cases and 1,313 controls participating in a colonoscopy screening-based cross-sectional study of CRA. Participants completed a food frequency questionnaire from which E-DII score was derived. E-DII score was calculated from 34 food parameters (constituents), utilizing an energy-adjusted global comparative database to compute z scores from which centered proportions were summed to create the score. CRA cases were defined as individuals whose colonoscopy detected at least one pathologically confirmed adenomatous polyp. Unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

A pro-inflammatory diet was not statistically significantly associated with elevated CRA risk (OR 1.07; 95% CI 0.97-1.19; p value = 0.18) in the multivariate regression model. NSAIDs use (OR_never-users 1.19; 95% CI 1.03-1.38; OR_ever-users 0.96; 95% CI 0.83-1.12; P_interaction = 0.04) and race (OR_{African Americans} 1.22; 95% CI 1.03-1.44; OR_{European Americans} 0.99; 95% CI 0.86-1.14; P_interaction = 0.14) appeared to modify the association, whereas cigarette smoking and BMI did not (P_interaction = 0.40 and 0.78, respectively).

CONCLUSION

NSAIDs use and race may modify the diet-CRA association. Further investigation in prospective cohort studies is warranted to confirm these findings.

Role of Diet in Colorectal Cancer Incidence: Umbrella Review of Meta-analyses of Prospective Observational Studies

IMPORTANCE

Several meta-analyses have summarized evidence for the association between dietary factors and the incidence of colorectal cancer (CRC). However, to date, there has been little synthesis of the strength, precision, and quality of this evidence in aggregate.

OBJECTIVE

To grade the evidence from published meta-analyses of prospective observational studies that assessed the association of dietary patterns, specific foods, food groups, beverages (including alcohol), macronutrients, and micronutrients with the incidence of CRC.

DATA SOURCES

MEDLINE, Embase, and the Cochrane Library were searched from database inception to September 2019.

EVIDENCE REVIEW

Only meta-analyses of prospective observational studies with a cohort study design were eligible. Evidence of association was graded according to established criteria as follows: convincing, highly suggestive, suggestive, weak, or not significant.

RESULTS

From 9954 publications, 222 full-text articles (2.2%) were evaluated for eligibility, and 45 meta-analyses (20.3%) that described 109 associations between dietary factors and CRC incidence were selected. Overall, 35 of the 109 associations (32.1%) were nominally statistically significant using random-effects meta-analysis models; 17 associations (15.6%) demonstrated large heterogeneity between studies (I2 > 50%), whereas small-study effects were found for 11 associations (10.1%). Excess significance bias was not detected for any association between diet and CRC. The primary analysis identified 5 (4.6%) convincing, 2 (1.8%) highly suggestive, 10 (9.2%) suggestive, and 18 (16.5%) weak associations between diet and CRC, while there was no evidence for 74 (67.9%) associations. There was convincing evidence of an association of intake of red meat (high vs low) and alcohol (≥4 drinks/d vs 0 or occasional drinks) with the incidence of CRC and an inverse association of higher vs lower intakes of dietary fiber, calcium, and yogurt with CRC risk. The evidence for convincing associations remained robust following sensitivity analyses.

CONCLUSIONS AND RELEVANCE

This umbrella review found convincing evidence of an association between lower CRC risk and higher intakes of dietary fiber, dietary calcium, and yogurt and lower intakes of alcohol and red meat. More research is needed on specific foods for which evidence remains suggestive, including other dairy products, whole grains, processed meat, and specific dietary patterns.

Fibre Intake Is Associated with Cardiovascular Health in European Children

BACKGROUND

We aimed at analysing the association between dietary fibre intake during childhood and cardiovascular health markers.

METHODS

We used observational longitudinal analysis and recorded diet using 3-day diaries at the ages of 3, 4, 5, 6, and 8 years in children from the EU Childhood Obesity Project Trial. At the age of 8, waist circumference, systolic and diastolic blood pressure (SBP and DBP) and biochemical analyses (lipoproteins, triglycerides and homeostasis model for insulin resistance (HOMA-IR)) were evaluated. Those parameters were combined into a cardiometabolic risk score through the sum of their internal z-scores.

RESULTS

Four-hundred children (51.8% girls) attended to the 8-year visit with a 3-day diary. Adjusted linear regression models showed that children who repeatedly stayed in the lowest tertile of fibre intake during childhood had higher HOMA-IR (p = 0.004), higher cardiometabolic risk score (p = 0.02) and a nonsignificant trend toward a higher SBP at 8 years. The higher the dietary intake of soluble fibre (from fruits and vegetables) at 8 years, the lower the HOMA-IR and the cardiometabolic risk score (p = 0.002; p = 0.004). SBP was directly associated with fibre from potatoes and inversely with fibre from nuts and pulses.

CONCLUSION

A diet rich in dietary fibre from fruits, vegetables, pulses and nuts from early childhood was associated to a healthier cardiovascular profile, regardless of children's weight.

Associations between nutritional factors and KRAS mutations in colorectal cancer: a systematic review

BACKGROUND

Between 30 and 50% of colon tumors have mutations in the Kirsten-ras (KRAS) gene, which have a large nutritional attributable risk. Despite its high frequency in colorectal cancer (CRC), data to support specific associations between KRAS mutations in CRC and diet are sparse. Here, we conducted a systematic review to summarize the current epidemiological evidence on the association between various dietary factors and KRAS mutations.

METHODS

PubMed, Science Direct, and Cochrane databases were searched for relevant studies published until December 31, 2019, using inclusion and exclusion criteria in accordance with PRISMA guidelines. We analyzed the studies to find associations between nutritional factors and CRC tumors with KRAS mutations in humans.

RESULTS

We identified 28 relevant studies to include in this systematic review. In-depth analyses showed unclear associations between nutritional factors and KRAS mutations in CRC. Most epidemiological studies in the same nutrient or food often reported conflicting and/or inconclusive findings, whereas for some dietary factors, the results were homogeneous.

CONCLUSIONS

Further research using a more robust prospective cohort study is needed to lend more credence to the epidemiological associations found between KRAS mutations and dietary factors.

Evaluation of bioactivity of butternut squash (Cucurbita moschata D.) seeds and skin

Butternut squash is greatly consumed in United Kingdom and as by-products of its processing are produced large amounts of skin and seeds. However, little research has been reported on the antioxidant properties and bioactive peptides from butternut squash seeds and skin. This study focused on assessing the potential of these wastes as sources of beneficial and bioactive compounds. The results indicated that the squash skin phenolic extract showed higher values of antioxidant activity and phenolic content compared with the values of phenolic for the seed material (3.20 mg GAE/g, 1.82 mg GAE/g, respectively). Furthermore, both squash seed protein hydrolysate and skin phenolic extract inhibited α-amylase activity in a dose-dependent manner (5-20 mg/ml). Hydrolyzed peptides from squash seeds possess antihypertensive ability (which was significantly different from the control group p < .05). Therefore, it can be demonstrated that these squash residues are potentially good sources of bioactive compounds with health benefits.

Associations of gut microbiota, dietary intake, and serum short-chain fatty acids with fecal short-chain fatty acids

In recent years, short-chain fatty acids (SCFAs) have been reported to play an important role in maintaining human health. Fecal SCFA concentrations correlate well with colonic SCFA status and gut microbiota composition. However, the associations with the gut microbiota functional pathway, dietary intake, blood SCFAs, and fecal SCFAs remain uncertain. To clarify these relationships, we collected fecal samples, blood samples, and dietary habit data from 12 healthy adults aged 22–51 years. The relative abundance of several SCFA-producing bacteria, gut microbiota diversity, and functional pathways related to SCFA biosynthesis were positively associated with fecal SCFAs even after adjusting for age and sex. Furthermore, fecal acetate was likely to be positively associated with serum acetate. By contrast, dietary intake was not associated with fecal SCFAs. Overall, the present study highlights the potential usefulness of fecal SCFAs as an indicator of the gut microbiota ecosystem and dynamics of SCFAs in the human body.

R. R, Thomas S, Nisha P. Short chain fatty acids enriched fermentation metabolites of soluble dietary fibre from Musa paradisiaca drives HT29 colon cancer cells to apoptosis

In this study, the prebiotic potential of soluble dietary fibre extracted from plantain inflorescence (PIF) was investigated. PIF demonstrated prebiotic potential by enhancing the growth of the probiotics under study and thereby hindered colon cancer development. The soluble dietary fibre from Musa paradisiaca inflorescence (PIF) was fermented using Lactobacillus casei and Bifidobacterium bifidum. The fermentation supernatants (LS and BS) were enriched with short chain fatty acids (SCFA) and were able to initiate apoptotic signalling in HT29 colon cancer cells leading to cell death. Both BS and LS exhibited cytotoxic effect; induced DNA damage and enhanced generation of reactive oxygen species in HT29 cells leading to apoptosis. The induction of apoptosis was facilitated by the reduction of membrane potential of mitochondria and ATP synthesis; enhanced delivery of cytochrome c and interference with the expression of pro/antiapoptotic proteins. BS, which exhibited better activity, was further analysed for the identification of differentially regulated proteins by performing two dimensional electrophoresis and MALDI-TOF mass spectrometry. Results emphasized on the fact that, the exposure to BSalteredthe HT29 proteins expression, particularly the upregulation of apoptosis- inducing factor-AIFM1 leading to apoptosis of HT29 cells.

Modulation of plasma and urine metabolome in colorectal cancer survivors consuming rice bran

Rice bran has bioactive phytochemicals with cancer protective actions that involve metabolism by the host and the gut microbiome. Globally, colorectal cancer (CRC) is the third leading cause of cancer-related death and the increased incidence is largely attributed to poor dietary patterns, including low daily fiber intake. A dietary intervention trial was performed to investigate the impact of rice bran consumption on the plasma and urine metabolome of CRC survivors. Nineteen CRC survivors participated in a randomized-controlled trial that included consumption of heat-stabilized rice bran (30 g/day) or a control diet without rice bran for 4 weeks. A fasting plasma and first void of the morning urine sample were analyzed by non-targeted metabolomics using ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). After 4 weeks of either rice bran or control diets, 12 plasma and 16 urine metabolites were significantly different between the groups (p≤0.05). Rice bran intake increased relative abundance of plasma mannose (1.373-fold) and beta-citrylglutamate (BCG) (1.593-fold), as well as increased urine N-formylphenylalanine (2.191-fold) and dehydroisoandrosterone sulfate (DHEA-S) (4.488-fold). Diet affected metabolites, such as benzoate, mannose, eicosapentaenoate (20:5n3) (EPA), and N-formylphenylalanine have been previously reported for cancer protection and were identified from the rice bran food metabolome. Nutritional metabolome changes following increased consumption of whole grains such as rice bran warrants continued investigation for colon cancer control and prevention attributes as dietary biomarkers for positive effects are needed to reduce high risk for colorectal cancer recurrence.

Tumor suppression by resistant maltodextrin, Fibersol-2

Resistant maltodextrin Fibersol-2 is a soluble and fermentable dietary fiber that is Generally Recognized As Safe (GRAS) in the United States. We tested whether Fibersol-2 contains anti-tumor activity. Human colorectal cancer cell line, HCT116, and its isogenic cells were treated with FIbersol-2. Tumor growth and tumorigenesis were studied in vitro and in vivo. Apoptotic pathway and generation of reactive oxygen species (ROS) were investigated. We discovered that Fibersol-2 significantly inhibits tumor growth of HCT116 cells by inducing apoptosis. Fibersol-2 strongly induces mitochondrial ROS and Bax-dependent cleavage of caspase 3 and 9, which is shown by isogenic HCT116 variants. Fibersol-2 induces phosphorylation of Akt, mTOR in parental HCT116 cells, but not in HCT116 deficient for Bax or p53. It prevents growth of tumor xenograft without any apparent signs of toxicity in vivo. These results identify Fibersol-2 as a mechanism-based dietary supplement agent that could prevent colorectal cancer development.

Probiotic metabolites as epigenetic targets in the prevention of colon cancer

Dietary interventions for preventing colon cancer have recently attracted increased attention from researchers and clinicians. The probiotics have emerged as potential therapeutic agents but are also regarded as healthy dietary supplements for nutrition and health applications. The probiotic metabolome may interfere with various cellular and molecular processes, including the onset and progression of colon cancer. Probiotic metabolites may lead to the modulation of diverse cellular signal transduction and metabolic pathways. The gut microbial metabolites (organic acids, bacteriocins, peptides, etc.) have been noted to interact with multiple key targets in various metabolic pathways that regulate cellular proliferation, differentiation, apoptosis, inflammation, angiogenesis, and metastasis. Progress in this field suggests that epigenetic alterations will be widely used in the near future to manage colon cancer. The present review provides insights into the molecular basis of the therapeutic applications and the chemopreventive activities of certain probiotic metabolites, with emphasis on the interaction between these metabolites and the molecular signaling cascades that are considered to be epigenetic targets in preventing colon cancer.

Potato fiber protects the small intestinal wall against the toxic influence of acrylamide

OBJECTIVE

Acrylamide is a neurotoxic, genotoxic substance present in many commonly consumed food products and has been shown to have carcinogenic effects in rodents. The protective effects (if any) of potato fiber preparations, composed of cell wall material from potatoes, against the toxic influence of dietary acrylamide on the small intestinal wall were investigated.

METHODS

Male mice of the BALB/c strain were used in the study. Acrylamide was administered to the mice in their drinking water (0.5 mg/kg of body weight per day) and one of two types of potato fiber preparations (heated or raw potato fiber preparation) was added to their feed (2% addition to their feed). Histomorphometry of the small intestinal wall, hemoglobin adducts of acrylamide, animal weight, and feed and water consumption analyses were performed.

RESULTS

Acrylamide altered the morphology and histology of the small intestinal wall, decreasing proliferation, myenteron and submucosal thicknesses, villus length, fractal dimension, crypt depth, crypt number, and the small intestinal absorptive surface. Conversely, apoptosis, hemoglobin adduct levels, intensity of epithelium staining, enterocyte number, villus epithelial thickness, and crypt width and parameters associated with nerve ganglia were increased. The two potato fiber preparations that were used abolished the negative influences of acrylamide on the small intestinal wall and had no influence on the hemoglobin adduct levels of acrylamide.

CONCLUSION

The negative impact of acrylamide on the histologic structure, regeneration, and innervation of the small intestinal wall and the absorptive function of the small intestinal mucosa can be abolished by dietary potato fiber preparations.

Potential beneficial effects of butyrate in intestinal and extraintestinal diseases

The multiple beneficial effects on human health of the short-chain fatty acid butyrate, synthesized from non-absorbed carbohydrate by colonic microbiota, are well documented. At the intestinal level, butyrate plays a regulatory role on the transepithelial fluid transport, ameliorates mucosal inflammation and oxidative status, reinforces the epithelial defense barrier, and modulates visceral sensitivity and intestinal motility. In addition, a growing number of studies have stressed the role of butyrate in the prevention and inhibition of colorectal cancer. At the extraintestinal level, butyrate exerts potentially useful effects on many conditions, including hemoglobinopathies, genetic metabolic diseases, hypercholesterolemia, insulin resistance, and ischemic stroke. The mechanisms of action of butyrate are different; many of these are related to its potent regulatory effects on gene expression. These data suggest a wide spectrum of positive effects exerted by butyrate, with a high potential for a therapeutic use in human medicine.

Butyrate, an HDAC inhibitor, stimulates interplay between different posttranslational modifications of histone H3 and differently alters G1-specific cell cycle proteins in vascular smooth muscle cells

HDACs and HATs regulate histone acetylation, an epigenetic modification that controls chromatin structure and through it, gene expression. Butyrate, a dietary HDAC inhibitor, inhibits VSMC proliferation, a crucial factor in atherogenesis, and the principle mechanism in arterial and in-stent restenosis. Here, the link between antiproliferation action of butyrate and the portraits of global covalent modifications of histone H3 that it induces are characterized to understand the mechanics of butyrate-arrested VSMC proliferation. Analysis of histone H3 modifications specific to butyrate arrested VSMC proliferation display induction of histone H3-Lysine9 acetylation, inhibition of histone H3-Serine10 phosphorylation, reduction of histone H3-Lysine9 dimethylation and stimulation of histone H3-Lysine4 di-methylation, which is linked to transcriptional activation, cell cycle/mitosis, transcriptional suppression and activation, respectively. Conversely, untreated VSMCs exhibit inhibition of H3-Lysine9 acetylation, induction of H3-Serine10 phosphorylation, stimulation of H3-Lysine9 di-methylation and reduction in H3-Lysine4 di-methylation. Butyrate's cooperative effects on H3-Lysine9 acetylation and H3-Serine10 phosphorylation, and contrasting effects on di-methylation of H3-Lysine9 and H3-Lysine4 suggests that the interplay between these site-specific modifications cause distinct chromatin alterations that allow cyclin D1 and D3 induction, G1-specific cdk4, cdk6 and cdk2 downregulation, and upregulation of cdk inhibitors, p15INK4b and p21Cip1. Regardless of butyrate's effect on D-type cyclins, downregulation of G1-specific cdks and upregulation of cdk inhibitors by butyrate prevents cell cycle progression by failing to inactivate Rb. Overall, through chromatin remodeling, butyrate appears to differentially alter G1-specific cell cycle proteins to ensure proliferation arrest of VSMCs, a crucial cellular component of blood vessel wall.

Advances in understanding the relationship between dietary factors and risk of colorectal cancer

The purpose of this paper is to summarize the relationship between dietary factors and risk of colorectal cancer. There is evidence that meat, high-fat diet and drinking increase the chance of developing colorectal cancer, while whole grains, dietary fiber, folacin, selenium, zinc and calcium reduce the risk of colorectal cancer. Therefore, an inadequate diet may contribute to the development of colorectal cancer. These viewpoints provide a basis for prevention of colorectal cancer in terms of diet control.

Role of colonic short-chain fatty acid transport in diarrhea

Short-chain fatty acids (SCFA) are the major anion in stool and are synthesized from nonabsorbed carbohydrate by the colonic microbiota. Nonabsorbed carbohydrate are not absorbed in the colon and induce an osmotically mediated diarrhea; in contrast, SCFA are absorbed by colonic epithelial cells and stimulate Na-dependent fluid absorption via a cyclic AMP-independent process involving apical membrane Na-H, SCFA-HCO(3), and Cl-SCFA exchanges. SCFA production represents an adaptive process to conserve calories, fluid, and electrolytes. Inhibition of SCFA synthesis by antibiotics and administration of PEG, a substance that is not metabolized by colonic microbiota, both result in diarrhea. In contrast, increased production of SCFA as a result of providing starch that is relatively resistant to amylase digestion [so-called resistant starch (RS)] to oral rehydration solution (RS-ORS) improves the efficacy of ORS and represents an important approach to improve the effectiveness of ORS in the treatment of acute diarrhea in children under five years of age.

Colonic cancer in adolescents. A report of three cases

Colorectal cancer is a common malignant neoplasm in adults, with a peak incidence of 60-79 years. About 1 million cases of the disease and half a million deaths associated with it are reported world-wide each year. Colorectal cancer, however, is very uncommon in children and adolescents. This is a presentation of 3 cases of colon cancer in Nigerians aged 17 and 19 years. Two of them were adenocarcinoma and the other leiomyosarcoma. The pathogenesis and aspects of management are discussed.

A human, double-blind, placebo-controlled, crossover trial of prebiotic, probiotic, and synbiotic supplementation: effects on luminal, inflammatory, epigenetic, and epithelial biomarkers of colorectal cancer

BACKGROUND

Diet is an important factor in colorectal carcinogenesis; thus, dietary supplements may have a role in colorectal cancer prevention.

OBJECTIVE

The objective was to establish the relative luminal, epithelial, and epigenetic consequences of prebiotic, probiotic, and synbiotic dietary supplementation in humans.

DESIGN

This was a randomized, double-blind, placebo-controlled, 4-wk crossover trial of resistant starch and Bifidobacterium lactis, either alone or as a combined synbiotic preparation, in 20 human volunteers. Rectal biopsy, feces, and serum samples were collected. The rectal mucosal endpoints were DNA methylation at 16 CpG island loci and LINE-1, epithelial proliferation (Ki67 immunohistochemistry), and crypt cellularity. The fecal endpoints were short-chain fatty acid concentrations, pH, ammonia, and microbiological profiles (by denaturing gradient gel electrophoresis and sequencing). Serum endpoints were a panel of cytokines and high-sensitivity C-reactive protein.

RESULTS

Seventeen subjects completed the entire study. The synbiotic intervention fostered a significantly different fecal stream bacterial community than did either the prebiotic (P = 0.032) or the probiotic (P = 0.001) intervention alone, in part because of a greater proportion of patients harboring fecal Lachnospiraceae spp. These changes developed in the absence of any significant differences in fecal chemistry. There were no differences in epithelial kinetics.

CONCLUSIONS

This synbiotic supplementation with B. lactis and resistant starch, in the doses used, induced unique changes in fecal microflora but did not significantly alter any other fecal, serum, or epithelial variables. This trial was registered in the Australian New Zealand Clinical Trials Registry at www.anzctr.org.au as ACTRN012606000115538.

Modulation of butyrate transport in Caco-2 cells

The aim of this study was to investigate the putative influence of some pharmacological agents and drugs of abuse upon the apical uptake of butyrate (BT) into Caco-2 cells. The apical uptake of (14)C-BT by Caco-2 cells was (1) time and concentration dependent, (2) pH dependent, (3) Na(+) independent and Cl(-) dependent, (4) energy dependent, (5) inhibited by several BT structural analogues (acetate, propionate, alpha-ketobutyrate, pyruvate, lactate), (6) insensitive to the anion exchange inhibitors DIDS and SITS and (7) inhibited by the monocarboxylate transport (MCT) inhibitors NPPB and pCMB. These characteristics are compatible with an involvement of MCT1-mediated transport. Acutely, uptake of a low concentration of (14)C-BT (10 microM) was reduced by acetaldehyde, acetylsalicylic acid, indomethacin, caffeine and theophylline and increased by MDMA. Chronically, uptake was increased by caffeine and decreased by tetrahydrocannabinol and MDMA; reverse transcription quantitative real-time PCR analysis showed that these three compounds decreased the mRNA levels of MCT1. Acutely, acetaldehyde, indomethacin and MDMA reduced the uptake of a high concentration of (14)C-BT (20 mM), and acetylsalicylic acid increased it. Chronically, none of the compounds affected uptake. Acetaldehyde, indomethacin and propionate seem to be competitive inhibitors of (14)C-BT uptake. Acetylsalicylic acid simultaneously increased the K (m) and the V (max) of (14)C-BT uptake. In conclusion, MCT1-mediated transport of (14)C-BT in Caco-2 cells is modulated by either acute or chronic exposure to some pharmacological agents and drugs of abuse (acetaldehyde, acetylsalicylic acid, indomethacin, caffeine, theophylline and the drugs of abuse tetrahydrocannabinol and MDMA).

Awareness of risk factors amongst first degree relative patients with colorectal cancer

BACKGROUND

The association between family history of colorectal cancer (CRC) in first degree relatives (FDRs) and the risk of developing the disease has been well established. However, little is known about the degree of awareness of CRC risk factors amongst FDRs. This study examined awareness of familial, dietary and lifestyle risk amongst FDRs.

METHOD

Consent to approach relatives was obtained from CRC patients who attended outpatients following surgery for CRC. A study specific questionnaire was sent by post to their FDRs. The dietary and lifestyle risk factors tested in the questionnaire were those promoted in CRC educational material.

RESULTS

One hundred and four questionnaires were returned out of 137 sent (76%). Fifty-nine per cent (n = 61) of FDRs were aware of their increased risk. Fifty-five per cent (n = 57) were aware of the link between CRC and smoking; however, knowledge of association of CRC with excessive alcohol consumption (32%) and lack of exercise (40%) was less well appreciated. Higher awareness scores were obtained by those with a university education (P < 0.001). Ninety four per cent believed that relatives of CRC patients were not provided with enough information as to their being at risk and risk factors.

CONCLUSIONS

This study provides an initial assessment of the awareness of CRC risk factors in a population at increased risk. It demonstrates a poor level of knowledge. Improved education strategies allowing FDRs to make dietary and lifestyle modifications that could reduce their lifetime risk of developing CRC are necessary.

Sodium-coupled monocarboxylate transporters in normal tissues and in cancer

SLC5A8 and SLC5A12 are sodium-coupled monocarboxylate transporters (SMCTs), the former being a high-affinity type and the latter a low-affinity type. Both transport a variety of monocarboxylates in a Na(+)-coupled manner. They are expressed in the gastrointestinal tract, kidney, thyroid, brain, and retina. SLC5A8 is localized to the apical membrane of epithelial cells lining the intestinal tract and proximal tubule. In the brain and retina, its expression is restricted to neurons and the retinal pigment epithelium. The physiologic functions of SLC5A8 include absorption of short-chain fatty acids in the colon and small intestine, reabsorption of lactate and pyruvate in the kidney, and cellular uptake of lactate and ketone bodies in neurons. It also transports the B-complex vitamin nicotinate. SLC5A12 is also localized to the apical membrane of epithelial cells lining the intestinal tract and proximal tubule. In the brain and retina, its expression is restricted to astrocytes and Müller cells. SLC5A8 also functions as a tumor suppressor; its expression is silenced in tumors of colon, thyroid, stomach, kidney, and brain. The tumor-suppressive function is related to its ability to mediate concentrative uptake of butyrate, propionate, and pyruvate, all of which are inhibitors of histone deacetylases. SLC5A8 can also transport a variety of pharmacologically relevant monocarboxylates, including salicylates, benzoate, and gamma-hydroxybutyrate. Non-steroidal anti-inflammatory drugs such as ibuprofen, ketoprofen, and fenoprofen, also interact with SLC5A8. These drugs are not transportable substrates for SLC5A8, but instead function as blockers of the transporter. Relatively less is known on the role of SLC5A12 in drug transport.

Review article: the role of butyrate on colonic function

BACKGROUND

Butyrate, a short-chain fatty acid, is a main end-product of intestinal microbial fermentation of mainly dietary fibre. Butyrate is an important energy source for intestinal epithelial cells and plays a role in the maintenance of colonic homeostasis.

AIM

To provide an overview on the present knowledge of the bioactivity of butyrate, emphasizing effects and possible mechanisms of action in relation to human colonic function.

METHODS

A PubMed search was performed to select relevant publications using the search terms: 'butyrate, short-chain fatty acid, fibre, colon, inflammation, carcinogenesis, barrier, oxidative stress, permeability and satiety'.

RESULTS

Butyrate exerts potent effects on a variety of colonic mucosal functions such as inhibition of inflammation and carcinogenesis, reinforcing various components of the colonic defence barrier and decreasing oxidative stress. In addition, butyrate may promote satiety. Two important mechanisms include the inhibition of nuclear factor kappa B activation and histone deacetylation. However, the observed effects of butyrate largely depend on concentrations and models used and human data are still limited.

CONCLUSION

Although most studies point towards beneficial effects of butyrate, more human in vivo studies are needed to contribute to our current understanding of butyrate-mediated effects on colonic function in health and disease.

Dietary fiber intake in two European diets with high (copenhagen, Denmark) and low (Murcia, Spain) colorectal cancer incidence

Contradictory results have been reported in studies associating dietary fiber (DF) intake and the incidence of colorectal cancer. Most studies focused mainly on the amount of total DF, but DF is a heterogeneous complex and its components are generally ignored. The aim of this work was to compare the amount and composition of DF intake in Murcia (Spain) and Copenhagen (Denmark). Total dietary fiber intake was a 31% higher in Murcia than in Copenhagen, the ratio of insoluble DF/soluble DF being similar in the two diets. DF in Murcia contains major amounts of nonstarch polysaccharides and polyphenolic compounds, mainly derived from the high consumption of fruits and vegetables (6.7 servings). Resistant starch intake was of the same order in the two regions while resistant protein intake was higher in Murcia. The quantitative and qualitative differences in DF intake may contribute to understand the differences in colorectal cancer incidence in Mediterranean and Scandinavian areas.

Influence of dietary fiber on inflammatory bowel disease and colon cancer: importance of fermentation pattern

The benefits of dietary fiber on inflammatory bowel disease may be related to the fermentative production of butyrate in the colon, which appears to decrease the inflammatory response. The benefits of dietary fiber against colon cancer may be related to both fermentative and non-fermentative processes, although poorly fermentable fibers appear more influential. Dietary fiber fermentation profiles are important in determining optimal fibers for colonic health, and may be a function of structure, processing conditions, and other food components. A greater understanding of the relationships between fermentation rate and dietary fiber structure would allow for development of dietary fibers for optimum colonic health.

Fibre and colorectal cancer: a controversial question

Since the 1970s it has been postulated that dietary fibre is a protective factor against colorectal cancer. Several epidemiological studies have been performed following different designs (correlation studies, case–control, cohort) and overall they have supported the hypothesis of a benefit of dietary fibre. However, a few intervention trials have not demonstrated the preventive role of dietary fibre on the occurrence of adenomatous colorectal polyps. Nevertheless, there are multiple animal experimental studies that support the role of fibre in the prevention of colorectal cancer. In the present review, the most important contributions to this controversial question are revised. Finally, it is recommended to continue encouraging an increase in the daily consumption of fibre, since it probably plays an important role in the prevention of colorectal cancer, together with other beneficial effects.

Chitosan prevents the development of AOM-induced aberrant crypt foci in mice and suppressed the proliferation of AGS cells by inhibiting DNA synthesis

We study the effect of fungal-derived chitosan on the development of chemical-induced colonic precancerous lesions in ICR mice and delineate its possible molecular mechanisms. In the 2 weeks preventive experiments, mice fed with a diet containing high molecular weight chitosan (HMWC) had significant fewer aberrant crypt foci formation than those fed with control diet. As the treatment extended to 6 weeks, both low molecular weight chitosan (LMWC)- and HMWC-fed mice contained less aberrant crypt foci when compared to control. However, such effect was not observed in mice in the 6 weeks therapeutic experiments. The anti-tumorigenesis effect of water-soluble chitosan oligomer (WSCO) was tested on four cancer cell lines. WSCO significantly suppressed AGS and to a less extent, COLO 205 cells proliferation. Flow cytometry analysis of cell cycle distribution indicated that the percentage of S phase reduced significantly in AGS cells treated with WSCO together with a decrease in DNA synthesis rate in BrdU incorporation assay. WSCO treatment also upregulated cell cycle-related genes p21/Cip and p27/Kip, whereas downregulated that of PCNA.

Dietary intake of calcium, fiber and other micronutrients in relation to colorectal cancer risk: Results from the Shanghai Women's Health Study

We evaluated the associations of dietary intake of calcium, fiber and vitamins with colorectal cancer risk in a population-based prospective cohort study conducted among Chinese women in Shanghai. Subjects were recruited in urban Shanghai from March 1997 to May 2000. All subjects were interviewed in-person to obtain information on demographic and lifestyle factors and anthropometric measurement was conducted. Usual dietary intake, using a validated food frequency questionnaire was assessed at the baseline survey. After following a total of 73,314 women for a median of 5.74 years, 283 incident colorectal cancer cases were recorded. Excluding the first 2 years of follow-up, a high intake of calcium was associated with a decreased risk of colorectal cancer. Comparing the highest quintile of nutrients intake to the lowest, the adjusted relative risk for colorectal cancer was 0.6 (p value for trend = 0.023) for calcium. No apparent associations were found for fiber, total vitamin A, carotene, vitamins B1, B2, B3, C and E with colorectal cancer risk. Our results suggest that calcium may be protective against colorectal cancer development even at a lower consumption level compared to Western populations.

Effects of amino acid-derived luminal metabolites on the colonic epithelium and physiopathological consequences

Depending on the amount of alimentary proteins, between 6 and 18 g nitrogenous material per day enter the large intestine lumen through the ileocaecal junction. This material is used as substrates by the flora resulting eventually in the presence of a complex mixture of metabolites including ammonia, hydrogen sulfide, short and branched-chain fatty acids, amines; phenolic, indolic and N-nitroso compounds. The beneficial versus deleterious effects of these compounds on the colonic epithelium depend on parameters such as their luminal concentrations, the duration of the colonic stasis, the detoxication capacity of epithelial cells in response to increase of metabolite concentrations, the cellular metabolic utilization of these metabolites as well as their effects on colonocyte intermediary and oxidative metabolism. Furthermore, the effects of metabolites on electrolyte movements through the colonic epithelium must as well be taken into consideration for such an evaluation. The situation is further complicated by the fact that other non-nitrogenous compounds are believed to interfere with these various phenomenons. Finally, the pathological consequences of the presence of excessive concentrations of these compounds are related to the short- and, most important, long-term effects of these compounds on the rapid colonic epithelium renewing and homeostasis.

Modern challenges in colorectal cancer

Colorectal cancer is a major problem worldwide and in the United Kingdom it is responsible for some 20,000 deaths per annum. Mortality from the disease is gradually decreasing in developed countries but, in the United Kingdom at least, its incidence is on the increase. In this article the major current challenges in colorectal cancer will be dealt with under the following headings: aetiology and prevention, early detection, diagnosis, surgery, adjuvant therapy and management of advanced disease.

Anal involvement in pemphigus vulgaris

INTRODUCTION

Anal involvement in patients with pemphigus vulgaris has rarely been reported. We report 16 pemphigus vulgaris patients with anal involvement.

METHODS

We retrospectively reviewed the clinical data on 16 patients treated at a tertiary dermatology referral center.

RESULTS

Of 16 patients with anal involvement of pemphigus vulgaris, ten were female and six were male. The mean age of onset was 56 (range, 37-82) years. All patients had involvement of pemphigus vulgaris at multiple sites, including oral involvement. Recurrent episodes of anal pemphigus vulgaris were noted in nine (56 percent) patients, with a mean of 2.4 recurrences (range, 1-11). In all patients, pemphigus vulgaris was controlled with systemic and local therapy. Long-term follow-up for a mean of 53 (range, 4-188) months indicated that no long-term sequela occurred because of anal involvement.

CONCLUSIONS

Anal involvement in pemphigus vulgaris is not very common and generally occurs in patients with severe disease. With appropriate topical and systemic therapy, patients have full recovery with no sequelae.

Quality of systematic reviews used in guidelines for oncology practice

BACKGROUND

Systematic reviews are an important tool for developing clinical recommendations. Those of high quality assure a good level of confidence on the strength of the recommendations.

METHODS

A QUOROM-based checklist was applied to the reviews cited in a sample of guidelines on breast and colon cancer prevention and therapy. The checklist provided a weight for each criterion and a total quality score. Each review was independently evaluated by two reviewers; disagreements were solved by consensus.

RESULTS

Eighty reviews (96%) were retrieved and evaluated; 36 focused on breast, and 44 on colorectal cancer. Twenty-three reviews (29%) did not match the definition of systematic review. In 17 (21%) the searching methods were unclear or described elsewhere. Forty (50%) were systematic. Not systematic, low and very low quality reviews accounted for 70% of the total. No review obtained the A+ class score; only 5 (6%) the A- and 7 (9%) the B+.

CONCLUSIONS

The results of this assessment provide a sober picture of the quality of the sources used to build guidelines. Oncologists should be aware that they could be relying on poor underlying documents. Writing groups should be aware of methodological problems, and should consult the existing manuals for the preparation of guidelines.

The role of fiber in the treatment of irritable bowel syndrome: therapeutic recommendations

Irritable bowel syndrome is a common clinical condition that often presents a therapeutic challenge. There is no standard therapy and a multilevel approach is recommended. A high-fiber diet is often one of these components. Many investigators have studied the effectiveness of either fiber supplementation or bulking agents in patients with irritable bowel syndrome. The purpose of this review is to summarize the current literature on the use of fiber in irritable bowel syndrome and to provide some specific recommendations. Systematic reviews of these trials have generally not found fiber to be significantly more effective than placebo at relieving global irritable bowel syndrome symptoms. There may be differences between results obtained with soluble and insoluble fiber. Adverse effects of fiber use may include abdominal discomfort and bloating. Although dietary fiber or bulking agents do not appear to be useful as sole treatment of irritable bowel syndrome, they may have a limited role in empiric therapy depending upon the patient's symptom complex, especially if constipation is the most significant symptom. The basic principles for using fiber therapy are to start with a low dose and increase slowly, to give an adequate trial and to evaluate the results early and periodically.

The anti-cancer effects of poi (Colocasia esculenta) on colonic adenocarcinoma cells In vitro

Hawaiians tend to have lower incidence rates of colorectal cancer and it was hypothesized that this may be due to ethnic differences in diet, specifically, their consumption of poi, a starchy paste made from the taro (Colocasia esulenta L.) plant corm. Soluble extracts of poi were incubated at 100 mg/mL in vitro for antiproliferative activity against the rat YYT colon cancer cell line. (3)H-thymidine incorporation studies were conducted to demonstrate that the poi inhibited the proliferation of these cancer cells in a dose-dependent manner. The greatest suppression of YYT colon cancer growth occurred when 25% concentration was used. When poi was incubated with the YYT cells after 2 days, the YYT cells underwent apoptotic changes as evidenced by a positive terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) stain. Poi enhanced the proliferation of normal mouse splenocyte control cells, suggesting that poi is not simply toxic to all cells but even has a positive immunostimulatory role. By flow cytometry, T cells (CD4+ and CD8+) were predominantly activated by the poi. Although numerous factors can contribute to the risk of colon cancer, perhaps poi consumption may contribute to the lower colon cancer rates among Hawaiians by two distinct mechanisms. First, by inducing apoptosis within colon cancer cells; second, by non-specifically activating lymphocytes, which in turn can lyse cancerous cells. Our results suggest for the first time that poi may have novel tumor specific anti-cancer activities and future research is suggested with animal studies and human clinical trials.

Fat, fiber, meat and the risk of colorectal adenomas

OBJECTIVE

The aim of this study was to determine the relationship between fat, fiber, and meat intake, and risk of colorectal adenoma recurrence.

METHODS

We determined adenoma recurrence and dietary intake for 1,520 participants in two randomized trials: The Antioxidant Polyp Prevention Study and Calcium Polyp Prevention Study. Subjects underwent baseline colonoscopy with removal of all adenomas, and dietary intake was estimated with a validated semiquantitative food frequency questionnaire. Follow-up colonoscopy was performed 1 and 4 yr later. Pooled risk ratios for adenoma recurrence were obtained by generalized linear regression, with adjustment for age, sex, clinical center, treatment category, study, and duration of observation.

RESULTS

In the total colorectum, fiber intake was weakly and nonsignificantly associated with a risk for all adenomas (RR quartile 4 vs quartile 1=0.85, 95% CI 0.69-1.05) and advanced adenomas (RR=0.88, 95% CI 0.54-1.44). Associations were stronger for adenomas in the proximal colon (RR=0.73, 95% CI 0.56-0.97) and some fiber subtypes (fruit and vegetable, grain). There was no association between fat or total red meat intake and risk of adenoma or advanced adenoma recurrence. However, when considering other meats, risk (quartile 4 vs quartile 1) for advanced adenoma was increased for processed meat (RR=1.75, 95% CI 1.02-2.99) and decreased for chicken (RR=0.61, 95% CI 0.38-0.98).

CONCLUSION

The inverse associations between fiber intake and risk of adenoma recurrence we observed are weak, and not statistically significant. Our data indicate that intake of specific meats may have different effects on risk.

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.

Dietary fibre and colorectal cancer: A model for environment - gene interactions

As environmental factors are clearly associated with risk for colorectal cancer, we set out to model how dietary fibre, or the effects of its ingestion, might impact upon the complex events that characterise colorectal oncogenesis. The diverse nature of dietary fibre and its resultant fate in the gut is outlined. The evidence indicates that different types of fibre create different conditions in different regions of the gut. This is reflected in different effects on oncogenesis especially in animal models. Data from animal models show that insoluble fibre is protective. Evidence from human studies are not consistent, especially considering the interventional studies. However, all such studies have been dependent on biomarkers short of cancer formation, for measurement of an effect. The biological and molecular events characteristic of colorectal oncogenesis are reviewed in an effort to identify how fibre ingestion might regulate oncogenesis. While several mechanisms might account for protection, the results of fermentation and especially butyrate production provide examples of how genomic instability might be controlled. Activation of apoptosis and cell cycle arrest seem likely to be mechanisms that would enable correction of genomic events that drive oncogenesis. Butyrate itself can regulate gene expression by both epigenetic and direct effects.