Effects of purple cabbage anthocyanin extract on the gluten characteristics and the gluten network evolution of high-gluten dough.

BACKGROUND: Anthocyanins are polyphenolic pigments that have hypoglycemic, antioxidation, anti-aging, and other effects. Research has shown that polyphenols can optimize the processing of dough and improve the texture and nutritional characteristics of dough products. The formation of gluten networks is decisive for the quality of flour products. The effects of purple cabbage anthocyanin (PCA) extract on the structure, microscopic morphology, and network formation of gluten protein were studied, and the types of cross-linking between PCA and gluten protein are discussed. RESULTS: The results show that PCA extract increased the free sulfhydryl (SH) group content and the free amino group of gluten proteins, stimulated an increase in the ß-sheet ratio and the decrease of α-helix ratio, and increased the gluten index significantly (P < 0.05). The PCA extract also induced gluten protein aggregation, increased the height of protein molecular chains, and stimulated the formation of gluten networks. When PCA extract concentrations were 4 g kg-1 and 8 g kg-1, the gluten network was more homogeneous, continuous, and dense. CONCLUSION: Appropriate anthocyanins have a positive effect on the properties of gluten and promote the formation of gluten networks. Excessive anthocyanins destroy gluten protein interaction and harm gluten cross-linking. This study may provide a useful source of data for the production of functional flour products rich in anthocyanins. © 2024 Society of Chemical Industry.

Efficacy of Butyrate to Inhibit Colonic Cancer Cell Growth Is Cell Type-Specific and Apoptosis-Dependent.

Increasing dietary fiber consumption is linked to lower colon cancer incidence, and this anticancer effect is tied to elevated levels of short-chain fatty acids (e.g., butyrate) because of the fermentation of fiber by colonic bacteria. While butyrate inhibits cancer cell proliferation, the impact on cancer cell type remains largely unknown. To test the hypothesis that butyrate displays different inhibitory potentials due to cancer cell type, we determined half-maximal inhibitory concentrations (IC50) of butyrate in HCT116, HT-29, and Caco-2 human colon cancer cell proliferation at 24, 48, and 72 h. The IC50 (mM) butyrate concentrations of HCT116, HT-29, and Caco-2 cells were [24 h, 1.14; 48 h, 0.83; 72 h, 0.86], [24 h, N/D; 48 h, 2.42; 72 h, 2.15], and [24 h, N/D; 48 h, N/D; 72 h, 2.15], respectively. At the molecular level, phosphorylated ERK1/2 and c-Myc survival signals were decreased by (>30%) in HCT116, HT-29, and Caco-2 cells treated with 4 mM butyrate. Conversely, butyrate displayed a stronger potential (>1-fold) for inducing apoptosis and nuclear p21 tumor suppressor in HCT116 cells compared to HT-29 and Caco-2 cells. Moreover, survival analysis demonstrated that a cohort with high p21 gene expression in their colon tissue significantly increased survival time compared to a low-p21-expression cohort of colon cancer patients. Collectively, the inhibitory efficacy of butyrate is cell type-specific and apoptosis-dependent.

Tumor necrosis factor-α knockout mitigates intestinal inflammation and tumorigenesis in obese Apc1638N mice.

Strong evidence from observational studies shows that having body fatness is associated with an individual's risk of developing colorectal cancer (CRC), but the causality between obesity and CRC remains inadequately elucidated. Our previous studies have shown diet-induced obesity is associated with elevated TNF-α and enhanced activation of Wnt-signaling, yet the causal role of TNF-α on intestinal tumorigenesis has not been precisely studied. The present study aims to examine the functionality of TNF-α in the development of CRC associated with obesity. We first examined the extent to which diet-induced obesity elevates intestinal tumorigenesis by comparing Apc1638N mice fed a low fat diet (LFD, 10 kcal% fat) with those fed a high fat diet (HFD, 60 kcal% fat), and then investigated the degree that the genetic ablation of TNF-α attenuates the effect by crossing the TNF-α-/- mice with Apc1638N mice and feeding them with the same HFD (TNF-α KO HFD). After 16-weeks of feeding, the HFD significantly increased intestinal tumorigenesis, whereas the deletion of TNF-α attenuated the effect (P < .05). Accompanying the changes in macroscopic tumorigenesis, HFD significantly elevated intestinal inflammation and procarcinogenic Wnt-signaling, whereas abolishment of TNF-α mitigated the magnitude of these elevations (P < .05). In summary, our findings demonstrate that the knockout of TNF-α attenuates obesity-associated intestinal tumorigenesis by decreasing intestinal inflammation and thereby the Wnt-signaling, indicating that TNF-α signaling is a potential target that can be utilized to reduce the risk of CRC associated with obesity.

Optimization of glutathione production in Saccharomyces cerevisiae HBSD-W08 using Plackett-Burman and central composite rotatable designs.

BACKGROUND: Glutathione is an important bioactive tripeptide and is widely used in the food, medicine, and cosmetics industries. The aim of this study was to provide an efficient method for producing GSH and to explore its synthesis mechanism. Saccharomyces cerevisiae strain HBSD-W08 was screened for GSH production, and its fermentation medium was optimized using single-factor experiments of the Plackett-Burman and central composite rotatable designs. This method was used to analyze the effects of the presence and concentration of various carbon sources, organic and inorganic nitrogen sources, metal ions, and precursor amino acids on GSH production and catalase, superoxide dismutase, and γ-glutamylcysteine synthetase activity. RESULTS: The three most significant factors affecting GSH production were peptone (optimal concentration [OC]: 2.50 g L- 1), KH2PO4 (OC: 0.13 g L- 1), and glutamic acid (OC: 0.10 g L- 1). GSH productivity of HBSD-W08 was obtained at 3.70 g L- 1 in the optimized medium. The activity of γ-GCS, which is a marker for oxidative stress, was found to be highly positively correlated with GSH production. CONCLUSIONS: This finding revealed an underlying relationship between GSH synthesis and oxidative stress, providing useful information for developing effective GSH fermentation control strategies.

Identification of oncogenic signatures in the inflammatory colon of C57BL/6 mice fed a high-fat diet.

Adoption of an obesogenic diet such as a high-fat diet (HFD) results in obesity, bacterial dysbiosis, chronic inflammation, and cancer. Gut bacteria and their metabolites are recognized by interleukin-1 (IL-1R)/toll-like receptors (TLRs) which are essential to maintain intestinal homeostasis. Moreover, host extracellular microRNAs (miRNAs) can alter bacterial growth in the colon. Characterization of the underlying mechanisms may lead to identifying fecal oncogenic signatures reflecting colonic health. We hypothesize that an HFD accelerates the inflammatory process and modulates IL-1R/TLR pathways, gut microbiome, and disease-related miRNA in the colon. In this study, 4-week-old C57BL/6 mice were fed a modified AIN93G diet (AIN, 16% energy fat) or an HFD (45% energy fat) for 15 weeks. In addition to increased body weight and body fat composition, the concentrations of plasma interleukin 6 (IL-6), inflammatory cell infiltration, ß-catenin, and cell proliferation marker (Ki67) in the colon were elevated > 68% in the HFD group compared to the AIN group. Using a PCR array analysis, we identified 14 out of 84 genes with a ≥ 24% decrease in mRNA content related to IL-1R and TLR pathways in colonic epithelial cells in mice fed an HFD compared to the AIN. Furthermore, the content of Alistipes bacteria, the Firmicutes/Bacteroidetes ratio, microRNA-29a, and deoxycholic and lithocholic acids (secondary bile acids with oncogenic potential) were 55% greater in the feces of the HFD group compared to the AIN group. Collectively, this composite, a multimodal profile may represent a unique HFD-induced fecal signature for colonic inflammation and cancer in C57BL/6 mice.

Optimisation of the production of a selenium-enriched polysaccharide from Cordyceps cicadae S1 and its structure and antioxidant activity.

The fermentation medium of a newly identified Cordyceps cicadae S1 was optimized by response surface methodology, with the optimal medium containing sucrose (80 g/L), yeast powder (60 g/L), KH2PO4 (5 g/L), MgSO4·7H2O (1 g/L) and Na2SeO3 (0. 1 g/L). Under these conditions, the extracellular polysaccharide yield was 8.09 g/L. A novel selenium-enriched polysaccharide (PACI-1) was isolated from Cordyceps cicadae, purified and identified as a homofructose polysaccharide with a low average molecular weight of 9.95 × 103 Da. The fine structure of PACI-1 was analyzed using NMR, CD, and AFM. Additionally, the in vitro antioxidant results showed that the PACI-1 had stronger antioxidant capacity than natural polysaccharides. These results provided a candidate strain for producing selenium polysaccharide and a new polysaccharide from C. cicadae, which showed good antioxidant activity.

Changes in the Fecal Metabolome Accompany an Increase in Aberrant Crypt Foci in the Colon of C57BL/6 Mice Fed with a High-Fat Diet.

High-fat diet (HFD)-induced obesity is a risk factor for colon cancer. Our previous data show that compared to an AIN-93 diet (AIN), a HFD promotes azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) formation and microbial dysbiosis in C57BL/6 mice. To explore the underlying metabolic basis, we hypothesize that AOM treatment triggers a different fecal metabolomic profile in C57BL/6 mice fed the HFD or the AIN. We found that 65 of 196 identified metabolites were significantly different among the four groups of mice (AIN, AIN + AOM, HFD, and HFD + AOM). A sparse partial least squares discriminant analysis (sPLSDA) showed that concentrations of nine fecal lipid metabolites were increased in the HFD + AOM compared to the HFD, which played a key role in overall metabolome group separation. These nine fecal lipid metabolite concentrations were positively associated with the number of colonic ACF, the cell proliferation of Ki67 proteins, and the abundance of dysbiotic bacteria. These data suggest that the process of AOM-induced ACF formation may increase selective fecal lipid concentrations in mice fed with a HFD but not an AIN. Collectively, the accumulation of these critical fecal lipid species may alter the overall metabolome during tumorigenesis in the colon.

Transcriptome and Metabolome Analysis Revealing the Improved ε-Poly-l-Lysine Production Induced by a Microbial Call from Botrytis cinerea.

ε-Poly-l-lysine (ε-PL) is a wide-spectrum antimicrobial agent, while its biosynthesis-inducing signals are rarely reported. This study found that Botrytis cinerea extracts could act as a microbial call to induce a physiological modification of Streptomyces albulus for ε-PL efficient biosynthesis and thereby resulted in ε-PL production (34.2 g/liter) 1.34-fold higher than control. The elicitors could be primary isolated by ethanol and butanol extraction, which resulted in more vibrant, aggregate and stronger mycelia. The elicitor-derived physiological changes focused on three aspects: ε-PL synthase, energy metabolism, and lysine biosynthesis. After elicitor addition, upregulated sigma factor hrdD and improved transcription and expression of pls directly contributed to the high ε-PL productivity; upregulated genes in tricarboxylic acid (TCA) cycle and energy metabolism promoted activities of citrate synthase and the electron transport system; in addition, pool enlargements of ATP, ADP, and NADH guaranteed the ATP provision for ε-PL assembly. Lysine biosynthesis was also increased based on enhancements of gene transcription, key enzyme activities, and intracellular metabolite pools related to carbon source utilization, the Embden-Meyerhof pathway (EMP), the diaminopimelic acid pathway (DAP), and the replenishment pathway. Interestingly, the elicitors stimulated the gene transcription for the quorum-sensing system and resulted in upregulation of genes for other antibiotic production. These results indicated that the Botrytis cinerea could produce inducing signals to change the Streptomyces mycelial physiology and accelerate the ε-PL biosynthesis. IMPORTANCE This work identified the role of microbial elicitors on ε-PL production and disclosed the underlying mechanism through analysis of gene transcription, key enzyme activities, and intracellular metabolite pools, including transcriptome and metabolome analysis. It was the first report for the inducing effects of the "microbial call" to Streptomyces albulus and ε-PL biosynthesis, and these elicitors could be potentially obtained from decayed fruits infected by Botrytis cinerea; hence, this may be a way of turning a biohazard into bioproduct wealth. This study provided a reference for application of microbial signals in secondary metabolite production, which is of theoretical and practical significance in industrial antibiotic production.

Azoxymethane Alters the Plasma Metabolome to a Greater Extent in Mice Fed a High-Fat Diet Compared to an AIN-93 Diet.

Consumption of a high-fat diet (HFD) links obesity to colon cancer in humans. Our data show that a HFD (45% energy fat versus 16% energy fat in an AIN-93 diet (AIN)) promotes azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) formation in a mouse cancer model. However, the underlying metabolic basis remains to be determined. In the present study, we hypothesize that AOM treatment results in different plasma metabolomic responses in diet-induced obese mice. An untargeted metabolomic analysis was performed on the plasma samples by gas chromatography time-of-flight mass spectrometry (GC-TOF-MS). We found that 53 of 144 identified metabolites were different between the 4 groups of mice (AIN, AIN + AOM, HFD, HFD + AOM), and sparse partial least-squares discriminant analysis showed a separation between the HFD and HFD + AOM groups but not the AIN and AIN + AOM groups. Moreover, the concentrations of dihydrocholesterol and cholesterol were inversely associated with AOM-induced colonic ACF formation. Functional pathway analyses indicated that diets and AOM-induced colonic ACF modulated five metabolic pathways. Collectively, in addition to differential plasma metabolomic responses, AOM treatment decreases dihydrocholesterol and cholesterol levels and alters the composition of plasma metabolome to a greater extent in mice fed a HFD compared to the AIN.

Dietary Selenium Requirement for the Prevention of Glucose Intolerance and Insulin Resistance in Middle-Aged Mice.

BACKGROUND: Although dietary selenium (Se) deficiency or excess induces type 2 diabetes-like symptoms in mice, suboptimal body Se status usually causes no symptoms but may promote age-related decline in overall health. OBJECTIVES: We sought to determine the dietary Se requirement for protection against type 2 diabetes-like symptoms in mice. METHODS: Thirty mature (aged 4 mo) male C57BL/6J mice were fed a Se-deficient torula yeast AIN-93M diet supplemented with Na2SeO4 in graded concentrations totaling 0.01 (basal), 0.04, 0.07, 0.10, and 0.13 (control) mg Se/kg for 4 mo (n = 6) until they were middle-aged (8 mo). Droplets of whole blood were used to determine glucose tolerance and insulin sensitivity in the mice from ages 5 to 8 mo. Postmortem serum, liver, and skeletal muscle were collected to assay for selenoprotein expression and markers of glucose metabolism. Data were analyzed by 1-way ANCOVA with or without random effects for time-repeated measurements using live mice or postmortem samples, respectively. RESULTS: Compared with control, the consumption of basal diet increased (P < 0.05) fasting serum insulin (95% CI: 52%, 182%) and leptin (95% CI: 103%, 118%) concentrations in middle-aged mice. Dietary Se insufficiency decreased (P < 0.05) 1) glucose tolerance (13-79%) and insulin sensitivity (15-65%) at ≤0.10 mg Se/kg; 2) baseline thymoma viral proto-oncogene phosphorylation on S473 (27-54%) and T308 (22-46%) at ≤0.10 and ≤0.07 mg Se/kg, respectively, in the muscle but not the liver; and 3) serum glutathione peroxidase 3 (51-83%), liver and muscle glutathione peroxidase 1 (32-84%), serum and liver selenoprotein P (28-42%), and liver and muscle selenoprotein H (39-48%) and selenoprotein W (16-73%) protein concentrations at ≤0.04, ≤0.10, ≤0.07, and ≤0.10 mg Se/kg, respectively. CONCLUSIONS: Mice fed diets containing ≤0.10 mg Se/kg display impaired glucose tolerance and insulin sensitivity, suggesting increased susceptibility to type 2 diabetes by suboptimal Se status at levels ≤23% of nutritional needs.

Adequacy of calcium and vitamin D reduces inflammation, ß-catenin signaling, and dysbiotic Parasutterela bacteria in the colon of C57BL/6 mice fed a western-style diet.

Adoption of an obesogenic diet low in calcium and vitamin D (CaD) leads to increased obesity, colonic inflammation, and cancer. However, the underlying mechanisms remain to be elucidated. We tested the hypothesis that CaD supplementation (from inadequacy to adequacy) may reduce colonic inflammation, oncogenic signaling, and dysbiosis in the colon of C57BL/6 mice fed a Western diet. Male C57/BL6 mice (4-weeks old) were assigned to 3 dietary groups for 36 weeks: (1) AIN76A as a control diet (AIN); (2) a defined rodent "new Western diet" (NWD); or (3) NWD with CaD supplementation (NWD/CaD). Compared to the AIN, mice receiving the NWD or NWD/CaD exhibited more than 0.2-fold increase in the levels of plasma leptin, tumor necrosis factor α (TNF-α) and body weight. The levels of plasma interleukin 6 (IL-6), inflammatory cell infiltration, and ß-catenin/Ki67 protein (oncogenic signaling) were increased more than 0.8-fold in the NWD (but not NWD/CaD) group compared to the AIN group. Consistent with the inflammatory phenotype, colonic secondary bile acid (inflammatory bacterial metabolite) levels increased more than 0.4-fold in the NWD group compared to the NWD/CaD and AIN groups. Furthermore, the abundance of colonic Proteobacteria (e.g., Parasutterela), considered signatures of dysbiosis, was increased more than four-fold; and the α diversity of colonic bacterial species, indicative of health, was decreased by 30% in the NWD group compared to the AIN and NWD/CaD groups. Collectively, CaD adequacy reduces colonic inflammation, ß-catenin oncogenic signaling, secondary bile acids, and bacterial dysbiosis in mice fed with a Western diet.

Superior inhibitory efficacy of butyrate over propionate and acetate against human colon cancer cell proliferation via cell cycle arrest and apoptosis: linking dietary fiber to cancer prevention.

Intake of dietary fiber may protect against colon cancer. The anticancer property is associated with an increased production of short chain fatty acids (SCFAs), including acetate, propionate and butyrate, during dietary fiber fermentation in the colon. However, the mechanisms remain to be determined. We hypothesized that butyrate exhibits a stronger inhibitory potential against colon cancer cell proliferation compared with acetate and propionate. We determined the half maximal inhibitory concentrations (IC50) of SCFAs in HCT116 human colon cancer cell proliferation by examining cell growth curves. At 24- and 48-hour time points, IC50 (mmol/L) concentrations of acetate, propionate, and butyrate were [66.0 and 29.0], [9.2 and 3.6], and [2.5 and 1.3], respectively. Consistent with the greater anti-proliferative effect, butyrate exhibits >3-fold stronger potential for inducing cell cycle arrest at the G2 phase with a drop in S-phase fraction (including c-Myc/p21 signaling) and apoptosis when compared with acetate and propionate. Subsequently, we focused on the effect of butyrate on apoptotic gene expression. Using a PCR array analysis, we identified 17 pro-apoptotic genes, 6 anti-apoptotic genes, and 4 cellular mediator genes with >1-fold increase or decrease in mRNA levels out of 93 apoptosis related genes in butyrate-treated HCT116 cells when compared with untreated HCT116 cells. These genes were mainly involved in the TNF, NFκB, CARD, and BCL-2 regulated pathways. Taken together, our data indicate a greater inhibitory efficacy of butyrate over propionate and acetate against human colon cancer cell proliferation via cell cycle arrest and apoptosis.

Butyrate Inhibits Deoxycholic-Acid-Resistant Colonic Cell Proliferation via Cell Cycle Arrest and Apoptosis: A Potential Pathway Linking Dietary Fiber to Cancer Prevention.

SCOPE: Butyrate, an intestinal microbiota metabolite of dietary fiber, exhibits colon cancer preventive effects. In contrast, a high fat intake increases fecal secondary bile acids, such as deoxycholic acid (DCA, a potential cancer promoter), which selectively enrich mutant epithelial cells with an abnormally high resistance to DCA-induced apoptosis in the colon. This study is conducted to test the hypothesis that physiological concentrations of butyrate inhibit DCA-resistant colonic cell proliferation. METHODS AND RESULTS: With human HCT-116 cells as parental colonic cells, a human DCA-resistant colonic cell line (DCA-RCL) is developed. DCA treatment increases apoptosis and intracellular reactive oxygen species (an apoptotic trigger) at a rate threefold greater in HCT-116 cells than in DCA-RCL cells. Subsequently, 41 apoptosis related genes (including signaling pathways) with greater than onefold (mRNA) change in DCA-RCL cells are identified compared with HCT-116 cells. Moreover, butyrate treatment inhibits DCA-RCL cell proliferation with similar efficacy when compared with HCT116 cells via cellular myelocytomatosis oncogene (c-Myc)/p38 mitogen-activated protein kinase pathway. CONCLUSION: It is demonstrated that butyrate inhibits DCA-RCL cell proliferation at the cellular and molecular level. These data provide a proof of concept that butyrate can protect against colon carcinogenesis through a specific targeting of DCA-resistant colonic cells.

Genetic ablation of tumor necrosis factor-alpha attenuates the promoted colonic Wnt signaling in high fat diet-induced obese mice.

Obesity is an established risk factor for colorectal cancer, but the mechanisms responsible for this relationship are not adequately delineated. Using a TNF-α-/- mouse model, the present study aimed to test the causal role of TNF-α in mediating the promotion of tumorigenic Wnt signaling by high-fat diet-induced obesity. A 2×2 factorial study was performed with wild-type and TNF-α-/- mice on a 60 kcal% high-fat diet or a 10 kcal% low-fat diet. The inflammatory cytokine profile and genes within the Wnt signaling pathway were measured by electrochemiluminescence assay, real-time PCR, Western blotting or immunohistochemistry. The high-fat diet increased body weights in both wild-type and TNF-α-/- animals (P<.05), but males were more sensitive to high-fat diet-induced weight gain and increases of colonic TNF-α than females (P<.05). Genetic ablation of TNF-α suppressed the obesity-promoted elevation of Wnt signaling, as indicated by decreased levels of phospho-GSK3ß and active ß-catenin, two key components within the Wnt pathway (P<.05). The transcriptional expression of several Wnt signaling targets (C-myc, Cyclin D1 and Axin 2) and cell proliferation, as indicated by Ki-67 staining, were attenuated by the deletion of TNF-α in the high-fat-fed TNF-α-/- animals comparing with the wild-type animals (P<.05). Our data collectively showed that the genetic deletion of TNF-α attenuated the tumorigenic Wnt signaling, which was otherwise elevated by high-fat diet-induced obesity, and demonstrated a causal role of TNF-α in mediating obesity-associated Wnt signaling, which indicates a potential mechanism of inflammation-driven Wnt signaling for obesity-associated colorectal carcinogenesis.

Comparison of Chemical Compositions, Bioactive Ingredients, and In Vitro Antitumor Activity of Four Products of Cordyceps (Ascomycetes) Strains from China.

The chemical compositions, bioactive ingredients, and in vitro antitumor activity were analyzed using water extracts from the dried fermented mycelia of Cephalosporium sinensis (C1), Paecilomyces hepiali (C2), Cordyceps cicadae (C3), as well as the dried fruiting bodies of C. militaris (C4). Total amino acid content was highest in C3, compared with C1, C2, C4, and natural C. militaris (S1). The contents of Fe, Zn, Mn, and Ca as well as the Zn/Cu ratio in C1-C3 were obviously different than those of C4 and S1, whereas Na contents and K/Na ratios in C3, C4, and S1 were obviously different from those in C1 and C2. Except for C4, cordycepin was not detected in C1-C3 or S1. The crude polysaccharide contents in C4 and total triterpenoid content in C4 were relatively lower than that in C1-C3. Detailed analysis of the crude polysaccharide from C4 did not detect fucose, but it contained the highest amount of glucose, compared with C1-C3. Additionally, the antitumor activities of the respective water extracts were ranked in the order of C3 > C4 > C1 > C2. These results can help us better understand products of Cordyceps strains.

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

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

Colonic aberrant crypt formation accompanies an increase of opportunistic pathogenic bacteria in C57BL/6 mice fed a high-fat diet.

The increasing worldwide incidence of colon cancer has been linked to obesity and consumption of a high-fat Western diet. To test the hypothesis that a high-fat diet (HFD) promotes colonic aberrant crypt (AC) formation in a manner associated with gut bacterial dysbiosis, we examined the susceptibility to azoxymethane (AOM)-induced colonic AC and microbiome composition in C57/BL6 mice fed a modified AIN93G diet (AIN, 16% fat, energy) or an HFD (45% fat, energy) for 14 weeks. Mice receiving the HFD exhibited increased plasma leptin, body weight, body fat composition and inflammatory cell infiltration in the ileum compared with those in the AIN group. Consistent with the gut inflammatory phenotype, we observed an increase in colonic AC, plasma interleukin-6, tumor necrosis factor-α, monocyte chemoattractant protein-1 and inducible nitric oxide synthase in the ileum of the HFD-AOM group compared with the AIN-AOM group. Although the HFD and AIN groups did not differ in bacterial species number, the HFD and AIN diets resulted in different bacterial community structures in the colon. The abundance of certain short-chain fatty acid (SCFA) producing bacteria (e.g., Barnesiella) and fecal SCFA (e.g., acetic acid) content were lower in the HFD-AOM group compared with the AIN and AIN-AOM groups. Furthermore, we identified a high abundance of Anaeroplasma bacteria, an opportunistic pathogen in the HFD-AOM group. Collectively, we demonstrate that an HFD promotes AC formation concurrent with an increase of opportunistic pathogenic bacteria in the colon of C57BL/6 mice.

High Fat Diet Alters Gut Microbiota and the Expression of Paneth Cell-Antimicrobial Peptides Preceding Changes of Circulating Inflammatory Cytokines.

Obesity is an established risk factor for many diseases including intestinal cancer. One of the responsible mechanisms is the chronic inflammation driven by obesity. However, it remains to be defined whether diet-induced obesity exacerbates the intestinal inflammatory status by cytokines produced in adipose tissue or the high fat diet first alters the gut microbiota and then drives intestinal inflammation. To address this question, we fed C57BL/6 mice with a high fat diet (HF, 60%) and sacrificed them sequentially after 8, 12, and 16 weeks, and then compositions of gut microbiota and expressions of antimicrobial peptides were determined. The compositions of gut microbiota were altered at 8 wk HF feeding, followed with reduced Paneth antimicrobial peptides lysozyme and Reg IIIγ after 12 and 16 wk HF feeding (p < 0.05), whereas elevations of circulating inflammatory cytokines IFNγ and TNF-α were observed until feeding a HF diet for 16 weeks (p < 0.05). These results indicated that high fat diet may stimulate intestinal inflammation via altering gut microbiota, and it occurs prior to the potential influence by circulating inflammatory cytokines. These findings emphasized the importance of microbiota, in addition to adipose tissue per se, in driving intestinal inflammation, which may thereafter promote intestinal tumorigenesis.

Butyrate Inhibits Cancerous HCT116 Colon Cell Proliferation but to a Lesser Extent in Noncancerous NCM460 Colon Cells.

Butyrate, an intestinal microbiota metabolite of dietary fiber, exhibits chemoprevention effects on colon cancer development. However, the mechanistic action of butyrate remains to be determined. We hypothesize that butyrate inhibits cancerous cell proliferation but to a lesser extent in noncancerous cells through regulating apoptosis and cellular-signaling pathways. We tested this hypothesis by exposing cancerous HCT116 or non-cancerous NCM460 colon cells to physiologically relevant doses of butyrate. Cellular responses to butyrate were characterized by Western analysis, fluorescent microscopy, acetylation, and DNA fragmentation analyses. Butyrate inhibited cell proliferation, and led to an induction of apoptosis, genomic DNA fragmentation in HCT116 cells, but to a lesser extent in NCM460 cells. Although butyrate increased H3 histone deacetylation and p21 tumor suppressor expression in both cell types, p21 protein level was greater with intense expression around the nuclei in HCT116 cells when compared with that in NCM460 cells. Furthermore, butyrate treatment increased the phosphorylation of extracellular-regulated kinase 1/2 (p-ERK1/2), a survival signal, in NCM460 cells while it decreased p-ERK1/2 in HCT116 cells. Taken together, the activation of survival signaling in NCM460 cells and apoptotic potential in HCT116 cells may confer the increased sensitivity of cancerous colon cells to butyrate in comparison with noncancerous colon cells.

Colonic inflammation accompanies an increase of ß-catenin signaling and Lachnospiraceae/Streptococcaceae bacteria in the hind gut of high-fat diet-fed mice.

Consumption of an obesigenic/high-fat diet (HFD) is associated with a high colon cancer risk and may alter the gut microbiota. To test the hypothesis that long-term high-fat (HF) feeding accelerates inflammatory process and changes gut microbiome composition, C57BL/6 mice were fed HFD (45% energy) or a low-fat (LF) diet (10% energy) for 36 weeks. At the end of the study, body weights in the HF group were 35% greater than those in the LF group. These changes were associated with dramatic increases in body fat composition, inflammatory cell infiltration, inducible nitric oxide synthase protein concentration and cell proliferation marker (Ki67) in ileum and colon. Similarly, ß-catenin expression was increased in colon (but not ileum). Consistent with gut inflammation phenotype, we also found that plasma leptin, interleukin 6 and tumor necrosis factor α concentrations were also elevated in mice fed the HFD, indicative of chronic inflammation. Fecal DNA was extracted and the V1-V3 hypervariable region of the microbial 16S rRNA gene was amplified using primers suitable for 454 pyrosequencing. Compared to the LF group, the HF group had high proportions of bacteria from the family Lachnospiraceae/Streptococcaceae, which is known to be involved in the development of metabolic disorders, diabetes and colon cancer. Taken together, our data demonstrate, for the first time, that long-term HF consumption not only increases inflammatory status but also accompanies an increase of colonic ß-catenin signaling and Lachnospiraceae/Streptococcaceae bacteria in the hind gut of C57BL/6 mice.