Effects of resistant starch on colonic preneoplastic aberrant crypt foci in rats

Resistant Starch-Encapsulated Probiotics Attenuate Colorectal Cancer Cachexia and 5-Fluorouracil-Induced Microbial Dysbiosis

5-Fluorouracil (5-FU) is commonly used as the primary chemotherapy for colorectal cancer (CRC). However, it can lead to unwanted chemoresistance. Resistant starch (RS), which functions similarly to fermentable dietary fiber, has the potential to reduce the risk of CRC. The effects of RS on improving CRC-associated cachectic symptoms and 5-FU chemotherapy-induced microbial dysbiosis remain unknown. Female BALB/cByJNarl mice were randomly divided into four groups: one tumor group (with CT26 colonic carcinoma but no treatment) and three CT26 colonic carcinoma-bearing groups that were administered 20 mg/kg 5-FU (T+5-FU group), a probiotic cocktail (4 × 108 CFUs) plus chemotherapy (T+5-FU+Pro), or resistant-starch-encapsulated probiotics plus chemotherapy (T+5-FU+RS-Pro). T+5-FU and T+5-FU+RS-Pro administration significantly suppressed tumor growth and activated apoptotic cell death in CT26-bearing mice. 5-FU-induced increases in inflammatory cytokines and NF-κB signaling were mitigated by the Pro or RS-Pro supplementation. A gut microbial composition comparison indicated that the abundance of intestinal bacteria in the T and T+5-FU groups decreased significantly, while the groups receiving Pro or RS-Pro maintained a greater abundance and healthy gut microbiota composition, suggesting that RS can reduce the microbial dysbiosis that occurs during 5-FU chemotherapy. The use of RS-Pro before chemotherapy should be considered for the regulation of chemotherapy-associated cachectic symptoms, inflammation, and chemotherapy-induced microbial dysbiosis.

Resistant starch levels and in vitro starch digestibility of selected cooked Philippine brown and milled rices varying in apparent amylose content and glycemic index

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Resistant starch content of rice correlates well with apparent amylose content.

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Cooked brown rices generally have more resistant starch than cooked milled rices.

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Resistant starch, hydrolysis index, and glycemic index of rice are all correlated.

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In vitro starch digestibility of cooked milled rice is greater than brown rice.

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Starch digestibility properties of cooked rice are vital in human nutrition and health.

Resistant starch (RS) content, starch digestibility, and hydrolysis index (HI) were analyzed in vitro for four selected Philippine rice varieties varying in apparent amylose content (AC) and glycemic index (GI), in cooked brown and milled rice forms. Starch digestibility curves were studied in relation to AC and reported GI values. Brown and milled rices of Improved Malagkit Sungsong 2 (IMS2), NSIC Rc160, IR64, and PSB Rc10 were cooked on separate beakers placed in automatic electric rice cookers and based on pre-determined water:rice ratios. RS levels of cooked milled rices ranged from 0.15 to 0.99% (mean = 0.45%). Their corresponding cooked brown rices had RS contents ranging from 0.24 to 1.61% (mean = 1.05%), with PSB Rc10 having the highest levels in both forms. HI ranged from 59.3 to 102.2%, with the highest noted for the waxy rice, IMS2, while corresponding brown rices had significantly lower HI spanning 49.2–66.9%. Previously reported GI values of these varieties were positively correlated with HI and estimated GI in this study. RS and non-resistant starch levels, and HI were highly correlated with AC. In vitro starch digestibility studies, as related to AC and GI, may be useful in screening for rice grain and nutritional properties aimed at developing new varieties with desirable quality and enhanced nutritional and functional properties.

Polysaccharides: bowel health and gut microbiota

Polysaccharides that contain many sugar monomers include starch and non-starch polysaccharides (NSPs) together with resistant starch (RS). Dietary polysaccharides are well known to have a wide range of biological benefits for bowel health. Gut microbiota and their fermentative products, short chain fatty acids (SCFA), which have recently been highlighted as metabolic regulators, are thought to mediate the function of dietary complex carbohydrates and bowel health. We discuss the influence of various polysaccharides on human bowel health and the mechanisms underlying these effects. We also describe their biological effects on intestinal health and the mechanisms underlying their activity; the polysaccharides were divided into three categories: dietary, microbial, and host-derived polysaccharides. Physiological impacts of non-starch polysaccharides (NSPs) and resistant starch (RS), both of which pass through the small intestine nearly intact and can be fermented by gut microbiota in the large intestine, are similar to each other. They exert a wide range of beneficial effects including anti-inflammation, gut epithelial barrier protection, and immune modulation through both microbiota-dependent and -independent mechanisms. Bacterial polysaccharides usually found in the cell wall generally act as immune modulators, and host-derived polysaccharides not only protect host cells from pathogenic microbial neighbors but also affect overall intestinal health via interactions with gut microbes. Considering these observations, further studies on polysaccharides will be important for bowel health.

Effects of Dietary Resistant Starch on the Wnt Signaling Pathway and Preneoplastic Cells in the Colons of Azoxymethane-Treated Rats

Dietary resistant starch (RS) has been suggested to reduce colonic neoplasia. To determine the effects of digestion-resistant cornstarch on colonic carcinogenesis and Wnt signaling in azoxymethane (AOM)-treated F344 rats, diets containing naturally occurring RS from corn lines derived partially from Guat209 (GUAT), AR16035 (AR), or a hybrid (ARxGUAT), containing 34.5 ± 2.0, 0.2 ± 0.1, and 1.9 ± 0.1% RS, respectively, were fed at 55% of the diet. GUAT-fed rats had increased cecal content and tissue weight and decreased cecal pH compared with AR- or ARxGUAT-fed rats. Numbers of aberrant crypt foci (ACF) were not different among diet groups. Increased numbers of crypts/focus were observed in AOM-injected rats fed GUAT compared with rats fed other diets. β-catenin mRNA expression of the crypts was significantly increased in GUAT-fed rats injected with AOM relative to those injected with saline. These findings suggest that selected dietary RSs may at some level further enhance colonocyte proliferation and differentiation in an AOM-treated colon.

Effects of dual modified resistant indica rice starch on azoxymethane-induced incipient colon cancer in mice

In this study, the effects of different doses of dual modification-treated (DMT) indica rice resistant starch (IR-RS) on azoxymethane (AOM)-induced early colon cancer in mice were investigated. The investigated factors included body weight, gastrointestinal emptying rate, the number and morphology of aberrant crypt foci (ACFs) and the specific expressions of adenomatous polyposis coli (APC), B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax) and cytochrome c genes. The results demonstrated that DMT IR-RS controlled the increase in the body weights of the mice, increased the gastrointestinal emptying rates and reduced the numbers of ACFs and aberrant crypts. Reverse transcription-polymerase chain reaction revealed that DMT IR-RS promoted the expression of APC, Bax and cytochrome c and inhibited the expression of Bcl-2. These results demonstrate that a DMT IR-RS diet may induce apoptosis and has beneficial health effects in AOM-induced early colon cancer in mice.

Resistant starch in food: a review

The nutritional property of starch is related to its rate and extent of digestion and absorption in the small intestine. For nutritional purposes, starch is classified as rapidly available, slowly available and resistant starch (RS). The exact underlying mechanism of relative resistance of starch granules is complicated because those factors are often interconnected. The content of RS in food is highly influenced by food preparation manner and processing techniques. Physical or chemical treatments also alter the level of RS in a food. Commercial preparations of RS are now available and can be added to foods as an ingredient for lowering the calorific value and improving textural and organoleptic characteristics along with increasing the amount of dietary fiber. RS has assumed great importance owing to its unique functional properties and health benefits. The beneficial effects of RS include glycemic control and control of fasting plasma triglyceride and cholesterol levels and absorption of minerals. This review attempts to analyze the information published, especially in the recent past, on classification, structure, properties, applications and health benefits of RS.

Is resistant starch protective against colorectal cancer via modulation of the WNT signalling pathway?

Epidemiological and experimental evidence suggests that non-digestible carbohydrates (NDC) including resistant starch are protective against colorectal cancer. These anti-neoplastic effects are presumed to result from the production of the SCFA, butyrate, by colonic fermentation, which binds to the G-protein-coupled receptor GPR43 to regulate inflammation and other cancer-related processes. The WNT pathway is central to the maintenance of homeostasis within the large bowel through regulation of processes such as cell proliferation and migration and is frequently aberrantly hyperactivated in colorectal cancers. Abnormal WNT signalling can lead to irregular crypt cell proliferation that favours a hyperproliferative state. Butyrate has been shown to modulate the WNT pathway positively, affecting functional outcomes such as apoptosis and proliferation. Butyrate's ability to regulate gene expression results from epigenetic mechanisms, including its role as a histone deacetylase inhibitor and through modulating DNA methylation and the expression of microRNA. We conclude that genetic and epigenetic modulation of the WNT signalling pathway may be an important mechanism through which butyrate from fermentation of resistant starch and other NDC exert their chemoprotective effects.

Influences of exogenous probiotics and tea polyphenols on the production of three acids during the simulated colonic fermentation of maize resistant starch

In the present study, influences of nine probiotics and tea polyphenols on the production of acetic, butyric, and lactic acid from simulated colonic fermentation of maize resistant starch (RS) were investigated. RS was fermented by fecal extracts of healthy adults at 12 g L(-1) and 37 °C for 18-48 h in the presence and absence of exogenous probiotics and tea polyphenols. The added probiotics increased acetic and butyric acid production by 25-216 %. Eubacterium faecalis, Lactobacillus acidophilus, L. casei, and L. helveticus increased lactic acid production by 7-58 %; however, other probiotics decreased lactic acid production. Tea polyphenols facilitated lactic acid production but inhibited acetic and butyric acid production clearly. More importantly, the added probiotics weakened the inhibitory effects of tea polyphenols on the two acids, enhancing acetic and butyric acid production by 152-641 and 825-1,777 %, respectively. It is concluded that both probiotics and tea polyphenols have different impacts on the production of acetic, butyric and lactic acid during the colonic fermentation of RS. The impacts of other probiotics and food components on the colonic fermentation of RS and other dietary fibers should be investigated in future study to clarify their possible interactions.

Optimization of in vitro inhibition of HT-29 colon cancer cell cultures by Solanum tuberosum L. extracts

Secondary metabolites in potato have been reported to possess bioactive properties, including growth inhibition of cancer cells. Because potatoes are widely consumed globally, potential health benefits may have broad application. Thus we investigated growth inhibition of HT-29 colon cancer cell cultures by extracts from 13 diverse genetic breeding clones. Extracts from three pigmented selections (CO97226-2R/R, CO97216-1P/P, CO04058-3RW/RW) inhibited growth of in vitro HT-29 cell cultures more effectively than other clones tested. While inhibition was highest from pigmented selections and pigmented tuber tissue sectors, not all pigmented breeding lines tested had appreciable inhibitory properties. Thus, inhibition was not uniquely linked to pigmentation. Immature tubers had the highest inhibitory properties, and in most cases mature tubers retained very low inhibition properties. Flowers and skins inhibited strongly at lower extract concentrations. An extract consisting of 7.2 mg mL⁻¹ cell culture medium was the lowest effective concentration. While raw tuber extracts inhibited most effectively, a few clones at higher concentrations retained inhibition after cooking. Heated whole tubers retained higher inhibition than heated aqueous extracts. While all aqueous extracts from the two tuber selections (CO97216-1P/P and CO97226-2R/R) inhibited HT-29 cell cultures, inhibition was significantly enhanced in purple pigmented tubers of CO97216-1P/P prepared cryogenically as liquid nitrogen powders compared to extracts from freeze dried samples. Upregulation of caspase-3 protease activity, indicative of apoptosis, was highest among the most inhibitory clone samples. The unique sectorial red pigment expressing selection (CO04058-3RW/RW) provided a model system that isolated expression in pigmented sectors, and thus eliminated developmental, environmental and genetic confounding.

Resistant starch induces catabolic but suppresses immune and cell division pathways and changes the microbiome in the proximal colon of male pigs

Consumption of resistant starch (RS) has been associated with various intestinal health benefits, but knowledge of its effects on global gene expression in the colon is limited. The main objective of the current study was to identify genes affected by RS in the proximal colon to infer which biologic pathways were modulated. Ten 17-wk-old male pigs, fitted with a cannula in the proximal colon for repeated collection of tissue biopsy samples and luminal content, were fed a digestible starch (DS) diet or a diet high in RS (34%) for 2 consecutive periods of 14 d in a crossover design. Analysis of the colonic transcriptome profiles revealed that, upon RS feeding, oxidative metabolic pathways, such as the tricarboxylic acid cycle and β-oxidation, were induced, whereas many immune response pathways, including adaptive and innate immune system, as well as cell division were suppressed. The nuclear receptor peroxisome proliferator-activated receptor γ was identified as a potential key upstream regulator. RS significantly (P < 0.05) increased the relative abundance of several butyrate-producing microbial groups, including the butyrate producers Faecalibacterium prausnitzii and Megasphaera elsdenii, and reduced the abundance of potentially pathogenic members of the genus Leptospira and the phylum Proteobacteria. Concentrations in carotid plasma of the 3 main short-chain fatty acids acetate, propionate, and butyrate were significantly higher with RS consumption compared with DS consumption. Overall, this study provides novel insights on effects of RS in proximal colon and contributes to our understanding of a healthy diet.

Effects of genetically modified T2A-1 rice on the GI health of rats after 90-day supplement

Bacillus thuringiensis insecticidal toxin (Bt) rice will be commercialized as a main food source. Traditional safety assessments on genetically modified products pay little attention on gastrointestinal (GI) health. More data about GI health of Bt rice must be provided to dispel public' doubts about the potential effects on human health. We constructed an improved safety assessment animal model using a basic subchronic toxicity experiment, measuring a range of parameters including microflora composition, intestinal permeability, epithelial structure, fecal enzymes, bacterial activity, and intestinal immunity. Significant differences were found between rice-fed groups and AIN93G-fed control groups in several parameters, whereas no differences were observed between genetically modified and non-genetically modified groups. No adverse effects were found on GI health resulting from genetically modified T2A-1 rice. In conclusion, this study may offer a systematic safety assessment model for GM material with respect to the effects on GI health.

Accumulation of promutagenic DNA adducts in the mouse distal colon after consumption of heme does not induce colonic neoplasms in the western diet model of spontaneous colorectal cancer

SCOPE

Red meat is considered a risk factor for colorectal cancer (CRC). Heme is considered to promote colonic hyperproliferation and cell damage. Resistant starch (RS) is a food that ferments in the colon with studies demonstrating protective effects against CRC. By utilizing the western diet model of spontaneous CRC, we determined if feeding heme (as hemin chloride) equivalent to a high red meat diet would increase colonic DNA adducts and CRC and whether RS could abrogate such effects.

METHODS AND RESULTS

Four groups of mice: control, heme, RS and heme + RS were fed diets for 1 or 18 months. Colons were analyzed for apoptosis, proliferation, DNA adducts "8-hydroxy-2-deoxyguanosine" and "O(6) -methyl-2-deoxyguanosine" (O(6) MeG), and neoplasms. In the short term, heme increased cell proliferation (p < 0.05). Changes from 1 to 18 months showed increased cell proliferation (p < 0.01) and 8-hydroxy-2-deoxyguanosine adducts (p < 0.05) in all groups, but only heme-fed mice showed reduced apoptosis (p < 0.01) and increased O(6) MeG adducts (p < 0.01). The incidence of colon neoplasms was not different between any interventions.

CONCLUSION

We identified heme to increase proliferation in the short term, inhibit apoptosis over the long term, and increase O(6) MeG adducts in the colon over time although these changes did not affect colonic neoplasms within this mouse model.

High-amylose rice improves indices of animal health in normal and diabetic rats

A high-amylose rice with 64.8% amylose content (AC) was developed by transgenic inhibition of two isoforms of starch branching enzyme (SBE), SBEI and SBEIIb, in an indica rice cultivar. The expression of SBEI and SBEIIb was completely inhibited in the transgenic line, whereas the expression of granule-bound starch synthase was normal. Compared with wild-type rice, drastic reductions in both SBEs in the transgenic rice increased apparent AC in flour from 27.2% to 64.8%, resistant starch (RS) content from 0% to 14.6% and total dietary fibre (TDF) from 6.8% to 15.2%. Elevated AC increased the proportion of long unit chains in amylopectin and increased onset gelatinization temperature and resistance to alkaline digestion; however, kernel weight was decreased. A rat feeding trial indicated that consumption of high-amylose rice decreased body weight gain significantly (P < 0.01); increased faecal mass, faecal moisture and short-chain fatty acids; and lowered the faecal pH. An acute oral rice tolerance test revealed that the high-amylose rice had a positive effect on lowering the blood glucose response in diabetic Zucker fatty rats. This novel rice with its high AC, RS and TDF offers potential benefits for its use in foods and in industrial applications.

Sodium butyrate does not decrease the evolution of precancerous lesions in rats

PURPOSE

To evaluate the preventive effect of sodium butyrate in the appearance of aberrant crypt foci (ACF) in rats after induction with the carcinogen 1,2-dimethylhydrazine (DMH).

METHODS

Forty Wistar rats were separated into four groups (n=10) distributed as follows: control 1, control 2, butyrate 1 and butyrate 2. The groups control 1 and butyrate 1 remained under experimentation for 4 weeks, while the groups control 2 and butyrate 2 remained for 8 weeks. In the first four weeks, the animals of the control groups received water ad libitum and the animals of the butyrate groups received a sodium butyrate solution (3.4%) ad libitum. Injections of the drug 1,2-dimethylhydrazine were applied during the two first weeks of the experiment in all the animals, concurrently with the application of sodium butyrate. The large intestine of the animals was removed, for the analysis of the ACF and of the content of polyamines. The animal feces were collected for the analysis of the SCFA profile.

RESULTS

The spermidine presented a higher concentration in the group butyrate 2 in comparison to the group control 2. There was a significant difference in the concentration value (µmol/mL) of acetate in comparison to the groups control 2 and butyrate 2.

CONCLUSION

The use of sodium butyrate together with the induction of colorectal cancer was not effective in the prevention of the disease progression.

Chemopreventive effect of raw and cooked lentils (Lens culinaris L) and soybeans (Glycine max) against azoxymethane-induced aberrant crypt foci

Although lentils (Lens culinaris L) contain several bioactive compounds that have been linked to the prevention of cancer, the in vivo chemopreventive ability of lentils against chemically induced colorectal cancer has not been examined. Our present study examined the hypothesis that lentils could suppress the early carcinogenesis in vivo by virtue of their bioactive micro- and macroconstituents and that culinary thermal treatment could affect their chemopreventive potential. To accomplish this goal, we used raw whole lentils (RWL), raw split lentils (RSL), cooked whole lentils (CWL), and cooked split lentils (CSL). Raw soybeans (RSB; Glycine max) were used for the purpose of comparison with a well-studied chemopreventive agent. Sixty weanling Fischer 344 male rats, 4 to 5 weeks of age, were randomly assigned to 6 groups (10 rats/group): the control group (C) received AIN-93G diet, and treatment leguminous groups of RWL, CWL, RSL, CSL, and RSB received the treatment diets containing AIN-93G+5% of the above-mentioned legumes. After acclimatization for 1 week (at 5th to 6th week of age), all animals were put on the control and treatment diets separately for 5 weeks (from 6th to 11th week of age). At the end of the 5th week of feeding (end of 11th week of age), all rats received 2 subcutaneous injections of azoxymethane carcinogen at 15 mg/kg rat body weight per dose once a week for 2 consecutive weeks. After 17 weeks of the last azoxymethane injection (from 12th to 29th week of age), all rats were euthanized. Chemopreventive ability was assessed using colonic aberrant crypt foci and activity of hepatic glutathione-S-transferases. Significant reductions (P < .05) were found in total aberrant crypt foci number (mean +/- SEM) for RSB (27.33 +/- 4.32), CWL (33.44 +/- 4.56), and RSL (37.00 +/- 6.02) in comparison with the C group (58.33 +/- 8.46). Hepatic glutathione-S-transferases activities increased significantly (P < .05) in rats fed all treatment diets (from 51.38 +/- 3.66 to 67.94 +/- 2.01 micromol mg(-1) min(-1)) when compared with control (C) diet (26.13 +/- 1.01 micromol mg(-1) min(-1)). Our findings indicate that consumption of lentils might be protective against colon carcinogenesis and that hydrothermal treatment resulted in an improvement in the chemopreventive potential for the whole lentils.