Resistant starches and health

It was initially hypothesized that resistant starches, i.e., starch that enters the colon, would have protective effects on chronic colonic diseases, including reduction of colon cancer risk and in the treatment of ulcerative colitis. Recent studies have confirmed the ability of resistant starch to increase fecal bulk, increase the molar ratio of butyrate in relation to other short-chain fatty acids, and dilute fecal bile acids. However the ability of resistant starch to reduce luminal concentrations of compounds that are damaging to the colonic mucosa, including fecal ammonia, phenols, and N-nitroso compounds, still requires clear demonstration. As such, the effectiveness of resistant starch in preventing or treating colonic diseases remains to be assessed. Nevertheless, there is a fraction of what has been termed resistant (RS1) starch, which enters the colon and acts as slowly digested or lente carbohydrate in the small intestine. Foods in this class are low glycemic index and have been shown to reduce the risk of chronic disease. They have been associated with systemic physiological effects such as reduced postprandial insulin levels and higher HDL cholesterol levels. Consumption of low glycemic index foods has been shown to be related to reductions in risk of coronary heart disease and Type 2 diabetes. Type 2 diabetes has in turn been related to a higher risk of colon cancer. If carbohydrates have a protective role in colon cancer prevention this may lie partly in the systemic effects of low glycemic index foods. The colonic advantages of different carbohydrates, varying in their glycemic index and resistant starch content, therefore, remain to be determined. However, as recent positive research findings continue to mount, there is reason for optimism over the possible health advantages of those resistant starches, which are slowly digested in the small intestine.     

Physiological aspects of resistant starch and in vivo measurements

Resistant starch (RS) is the sum of starch and products of starch degradation not absorbed in the small intestine of healthy individuals. There are a number of RS with different characteristics which may have a different fate in the colon. As a consequence, all RS should not be considered equivalent as far as physiological properties are concerned; indeed, they may have a different impact on colonic health. This statement may explain part of the apparent contradictions in the literature on RS and cancer or inflammatory disease prevention. RS is fermented in the large intestine into short-chain fatty acids and, among those, butyrate, which is recognized as the main nutrient of the colonocyte. This fermentation pattern seems to be responsible for most of the effects of RS on colonic health. Another important property is linked to its ability to lower colonic pH, which is usually considered as beneficial for mineral biovailability in the colon or cancer prevention. Due to their fate in the digestive tract, RS materials do not seem to have any significant impact on glucose absorption or metabolism. On the contrary, they may have a hypocholesterolemic effect, but available information is contradictory.     

Murine fecal proteomics: A model system for the detection of potential biomarkers for colorectal cancer

Tumor related products shed into the feces offer a potential source of biomarkers for the detection of colorectal cancer (CRC). Using SDS-PAGE followed by nanoflow reversed-phased LC–MS/MS to analyse fecal samples from Apc^Min/+ mice (that develop spontaneous multiple intestinal neoplasia with age) we have identified 336 proteins (115 proteins of murine origin, 201 from fecal bacteria, 18 associated with food intake and 2 of apparent parasitic origin). 75% of the murine proteins identified in this study are predicted to be extracellular or associated with the cell plasma membrane. Of these proteins, a number of the murine homologues of colorectal cancer associated proteins (CCAP) such as hemoglobin, haptoglobin, hemopexin, alpha-2-macroglobulin and cadherin-17 have been identified, demonstrating the potential of fecal proteomics for detecting potential biomarkers and paving the way for subsequent MS/MS based biomarker studies on similar human samples.     

Use of multiple reaction monitoring for multiplex analysis of colorectal cancer-associated proteins in human feces

Colorectal cancer (CRC) is the second most common cause of cancer-related deaths worldwide with an annual incidence of almost a million cases and an annual mortality around 500,000. The fecal occult blood test is currently the first line method for CRC screening, but has unacceptably low sensitivity and specificity. Improved screening tests are therefore urgently required for early-stage CRC screening when therapy is most likely to be effective. We describe a discovery-based proteomics hypothesis using orthogonal multi-dimensional fractionation (1-D SDS-PAGE, RP-HPLC, size exclusion chromatography) to mine deep into the fecal proteome for the initial discovery process, which generated a library containing 108 human fecal proteins with the associated peptide and MS/MS data. These data were then used to develop and optimize a multiplex multiple reaction monitoring assay for 40 non-redundant human proteins present in the feces. To show proof of principal for clinical analysis, multiplex screening of these 40 proteins was carried out on fecal samples from eight CRC patient and seven normal volunteers. We identified 24 proteins consistently found in all samples and nine proteins found only in the CRC patients, showing the potential of this approach for the analysis of potential CRC biomarkers. Absolute quantitation using C-terminal isotopically labeled synthetic peptides corresponding to hemoglobin and carcinoembryonic antigen 5 was also performed.     

Resistant starch as related to companion animal nutrition

Companion animal diets may contain up to 50% starch, derived from cereal grains. The amount of resistant starch (RS) in an ingredient depends on the origin and form of the ingredient and on the processing conditions to which the ingredient has been exposed. Extrusion has proven to be a means of optimizing utilization of starch by companion animals. Although the RS fraction of starch typically decreases by extrusion, retrogradation can result in increased concentrations of this fraction. Limited research exists regarding the effects of RS in companion animal nutrition and gastrointestinal health. Existing in vitro and in vivo research indicates that certain RS sources are readily fermented in the large bowel, producing short-chain fatty acids, whereas others are less fermentable, resulting in excellent laxation properties. Feeding dogs a diet high in RS may result in an increase in fecal bulk due to an increased excretion of microbial matter in those cases where RS is highly fermentable, or to indigestibility of the RS source in other cases. RS has a role to play as a potential proxy for dietary fiber, especially for those companion animals fed diets high in protein and fat and devoid of traditional dietary fiber.     

Physiological functions of resistant proteins: proteins and peptides regulating large bowel fermentation of indigestible polysaccharide

Animal studies have shown conclusively that feeding of resistant starch (RS) increases production of large bowel total short-chain fatty acids (SCFAs). However, fermentation products of RS may be affected considerably by other dietary ingredients. In rats fed a 20% high-amylose cornstarch (HAS) with casein as the sole protein source, greater cecal SCFAs production was observed compared with that in rats fed a regular cornstarch diet. However, with this diet, the cecal succinate production was also very high. In contrast, when rice or potato protein with lower digestibility was used in place of casein, cecal succinate production decreased with a concomitant increase in butyrate. These observations suggest that nondigested protein, namely resistant protein, might play a role in correcting an imbalance in the ratio of carbohydrate and nitrogen as fermentative substrates for cecal bacteria and in promoting butyrate production. Epidemiological and biochemical data indicate a possible linkage between the fermentation products of starch (butyrate in particular) and the prevention of colorectal cancer as well as ulcerative colits. Accordingly, a fermentation strategy of RS favoring SCFA production should be established to elucidate the potentially beneficial effects of SCFAs on large bowel physiology.     

In vitro and in vivo digestibility of native maize starch granules varying in amylose contents

Digestibility of maize starch granules with different amylose content (AL-0, 22, 54, 68, 80, or 90%) was investigated. Measurement of the in vivo resistant starch (RS) content of the starches was performed using surgically prepared ileorectostomized rats. The rats were fed a purified diet containing one of the starches at 652.5 g/kg diet. The in vivo RS content was determined based on the fecal starch excretion. The dietary fiber (DF) value increased as a function of the amylose content in the starch and showed a positive linear correlation with the gelatinization temperature of the granules. In contrast, the in vitro RS content was likely to depend on both the surface area and amylose contents of the starch granules. The maximum in vitro RS content was obtained with AL-68 (54.4%). In vivo RS content showed a significant correlation with the amount of in vitro RS but not in respect to the DF detected. The in vivo RS content of AL-68 (43.4%) was higher than that found in AL-90 (37.8%). A profound gap was observed for AL-54 between the amount of DF (6.4%) and RS (in vitro = 46.6% and in vivo = 40.9%) present. The results suggest that both in vitro and in vivo digestibility of maize starch is affected by the amylose content and surface area of the granules. The current evaluation suggests that the physiological occurrence of RS from maize starch might be predictable by reference to the in vitro RS value.     

Metabolic Profiling of Human Colorectal Cancer Using High Resolution 1H Nuclear Magnetic Resonance Spectroscopy

Colorectal cancer (CRC) is the third commonest malignancy cancer worldwide. Clear understandings of global metabolic profiling of the normal mucosa and cancer tissues are vitally important to aid optimizing the clinical management strategy and understanding CRC biology. We studied metabolic characteristics of 20 CRC and 20 distant normal mucosa tissues extracts from 20 patients using high resolution ¹H NMR spectroscopy in conjunction with multivariate analyses, such as principal component analysis (PCA). Compared with distant normal mucosa tissues, lactate, taurine, ornithine and polyamine were present at significantly higher levels in CRC tissue extracts whereas myo‐inositol was present at significantly lower level. Two metabolites ratios such as myo‐inositol/taurine and myo‐inositol/(ornithine+polyamine) appear to be the most valuable biomarkers for the differentiation CRC from normal mucosa tissues. Our data suggested that HR ¹H NMR spectroscopy combined with multivariate analyses is a potentially useful technology for detecting malignant changes in the normal mucosa tissues, the technique may be further exploited for future CRC biomarker research or identification of targets for therapeutic manipulations.     

Resistant starch: safe intakes and legal status

Resistant starch (RS) can provide added values such as health benefits and fiber content to many processed foods without compromising taste and product quality. RS is defined as the total amount of starch and the products of starch degradation that resists digestion in the small intestine of healthy people, and the class is comprised of many chemically and physically distinct entities. Some forms of RS are present naturally in many foods, and average global consumption is estimated at 3-10 g/day. Among the best-characterized forms of RS are those derived from high-amylose maize (HAM). Animal and human studies confirm the health benefits and safety of HAM-derived RS as a food ingredient. Legally, RS can be sold in most countries if it falls under current food classifications. However, approved fiber measurements vary throughout the world, and different methods are required to measure RS derived from specific sources. A particular RS can only be claimed as fiber on the nutrition label (and as a source for a high-fiber claim) if the method appropriate to that product is approved in the country of interest. Similarly, each individual country's regulations must be consulted prior to developing health or other nutrition label claims, such as calorie content for RS-containing products, as these regulations vary widely around the world.     

Resistant starch: metabolic effects and potential health benefits

Although there is strong evidence that the amount and type of fat in the diet can have dramatic effects on metabolism, the case for carbohydrate subtypes influencing metabolic parameters is emerging. By definition, resistant starch (RS) is any starch that is not digested in the small intestine but passes to the large bowel. Here, RS is a good substrate for fermentation which gives rise to an increase in short-chain fatty acid production. The differing rates of absorption between RS and digestible starch are thought to denote their differential metabolic responses. RS intake is associated with several changes in metabolism which may confer some health benefits. RS intake seems to decrease postprandial glycemic and insulinemic responses, lower plasma cholesterol and triglyceride concentrations, improve whole body insulin sensitivity, increase satiety, and reduce fat storage. These properties make RS an attractive dietary target for the prevention of diseases associated with dyslipidemia and insulin resistance as well as the development of weight loss diets and dietary therapies for the treatment of Type 2 diabetes and coronary heart disease. This review analyzes the body of literature examining the metabolic effects of RS consumption and discusses possible mechanisms whereby increased short-chain fatty acid production in the bowel could account for some of these effects. The effects of RS in the large bowel per se are the topic of other reviews and are not addressed in this paper.     

Antiproliferative Effect of Colonic Fermented Phenolic Compounds from Jaboticaba (Myrciaria trunciflora) Fruit Peel in a 3D Cell Model of Colorectal Cancer

Jaboticaba is a Brazilian native berry described as a rich source of phenolic compounds (PC) with health promoting effects. PC from jaboticaba peel powder (JPP) have low intestinal bio-accessibility and are catabolized by gut microbiota. However, the biological implication of PC-derived metabolites produced during JPP digestion remains unclear. This study aimed to evaluate the antiproliferative effects of colonic fermented JPP (FJPP) in a 3D model of colorectal cancer (CRC) composed by HT29 spheroids. JPP samples fermented with human feces during 0, 2, 8, 24 or 48 h were incubated (10,000 µg mL⁻¹) with spheroids, and cell viability was assessed after 72 h. Chemometric analyses (cluster and principal component analyses) were used to identify the main compounds responsible for the bioactive effect. The antiproliferative effect of FJPP in the CRC 3D model was increased between 8 h and 24 h of incubation, and this effect was associated with HHDP-digalloylglucose isomer and dihydroxyphenyl-γ-valerolactone. At 48 h of fermentation, the antiproliferative effect of FJPP was negligible, indicating that the presence of urolithins did not improve the bioactivity of JPP. These findings provide relevant knowledge on the role of colonic microbiota fermentation to generate active phenolic metabolites from JPP with positive impact on CRC.     

Identification of differential metabolic characteristics between tumor and normal tissue from colorectal cancer patients by gas chromatography–mass spectrometry

Colorectal cancer (CRC) is one of the most common human malignancies and encompasses cancers of the colon and rectum. Although the gold‐standard colonoscopy screening method is effective in detecting CRC, this method is invasive and can result in severe complications for patients. The purpose of this study was to determine differences in metabolites between CRC and matched adjacent nontumor tissues from CRC patients, to identify potential biomarkers that may be informative and developed screening methods. Metabolomic analysis was performed on clinically localized CRC tissue and matched adjacent nontumor tissue from 20 CRC patients. Unsupervised analysis, supervised analysis, univariate analysis and pathway analysis were used to identify potential metabolic biomarkers of CRC. The levels of 25 metabolites in CRC tissues were significantly altered compared with the matched adjacent nontumor tissues. Four metabolites (lactic acid, alanine, phosphate and aspartic acid) demonstrated good area under the curve of receiver‐operator characteristic with acceptable sensitivities and specificities, indicating their potential as important biomarkers for CRC. Alterations of amino acid metabolism and enhanced glycolysis may be major factors in the development and progression of CRC. Lactic acid, alanine, phosphate, and aspartic acid could be effective diagnostic indicators for CRC.     

Molecules Present in Plant Essential Oils for Prevention and Treatment of Colorectal Cancer (CRC)

Essential oils (EOs) are a complex mixture of hydrophobic and volatile compounds synthesized from aromatic plants, commonly present in the human diet. In recent years, many in vitro studies have suggested possible anticancer properties of single EO compounds, on colorectal cancer (CRC) cells. However, the majority of these studies did not compare the effects of these compounds on normal and cancer colon cells. By using NCM-460, a normal human mucosal epithelial cell line, Caco-2, a human colon epithelial adenocarcinoma cell line, and SW-620, colon cancer cells derived from lymph node metastatic site, we identified cinnamaldehyde, derived from cinnamon EO and eugenol, derived from bud clove EO, as compounds with a specific anticancer action selectively targeting the transformed colonic cells. Both cinnamaldehyde (75 µM) and eugenol (800 µM), after 72 h of treatment, were capable to induce apoptosis, necrosis and a cell cycle slowdown in Caco-2 and in SW-620, but not in NCM-460 cells. If associated with a targeted delivery to the colon, these two compounds could prove effective in the prevention or treatment of CRC.     

Zinc oxide nanoparticle attenuates chemotherapy resistance by inducing cell stemness progression of colorectal cancer via miR-1321/HIF-2α axis

BackgroundColorectal cancer (CRC) is the most malignant cancer type with high morbidity and mortality worldwide. Developed drug resistance severely affected the prognosis of CRC patients. This work aimed to explore the effects of zinc oxide nanoparticles (ZONs) in chemo-resistant CRC.MethodsWe established Oxaliplatin (Oxa)-resistant CRC cells, and in vitro and in vivo model to evaluate the function effect of ZONs. Cell counting kit-8 (CCK-8), colony formation, and 5-ethynyl-2′-deoxyuridine (EDU) assay were performed to detect CRC cell viability and proliferation. CRC cell apoptosis was checked by flow cytometry. Tumor cell proliferation was checked by immunohistochemistry (IHC). Cell stemness was determined by sphere formation assay. Luciferase reporter gene assay was conducted to assess the binding of miR-1321 and HIF-2α 3′UTR region.ResultsZONs suppressed the viability and proliferation of Oxa-resistant CRC cells both in vitro and in vivo. ZONs suppressed CRC cell stemness and enhanced the sensitivity of CRC cells to chemo-therapy, along with decreased expression of stem cell biomarkers. ZONs elevated level of miR-1321 and reduced level of HIF-2α in CRC cells. MiR-1321 targeted the 3′UTR region of HIF-2α to suppress its expression. ZONs repressed HIF-2α expression by inducing miR-1321 in CRC cells.ConclusionZONs treatment remarkably converted the drug resistance and stemness of CRC cells, via upregulating miR-1321 to repress the expression of HIF-2α. Our findings suggested that ZONs are potential and effective agent for chemo-resistant CRC patients.     

Measurement of resistant starch by enzymatic digestion in starch and selected plant materials: collaborative study

Interlaboratory performance statistics was determined for a method developed to measure the resistant starch (RS) content of selected plant food products and a range of commercial starch samples. Food materials examined contained RS (cooked kidney beans, green banana, and corn flakes) and commercial starches, most of which naturally contain, or were processed to yield, elevated RS levels. The method evaluated was optimized to yield RS values in agreement with those reported for in vivo studies. Thirty-seven laboratories tested 8 pairs of blind duplicate starch or plant material samples with RS values between 0.6 (regular maize starch) and 64% (fresh weight basis). For matrixes excluding regular maize starch, repeatability relative standard deviation (RSDr) values ranged from 1.97 to 4.2%, and reproducibility relative standard deviation (RSDR) values ranged from 4.58 to 10.9%. The range of applicability of the test is 2-64% RS. The method is not suitable for products with <1% RS (e.g., regular maize starch; 0.6% RS). For such products, RSDr and RSDR values are unacceptably high.     

Synthesis of resistant starches in plants

The increased incidence in many countries in lifestyle diseases such as colorectal cancer, cardiovascular disease, and diabetes has led to an enhanced interest in disease-prevention measures that can be delivered to target populations through diet. Resistant starch (RS) is emerging as an important dietary component that has the potential to reduce the incidence of bowel health disorders. However, the range of crop species that can serve as effective sources of RS is limited. In this paper the state of knowledge of the starch biosynthesis pathway is reviewed and opportunities to manipulate crop genetics in order to generate additional sources of RS are discussed. The need for a "whole of chain" approach to delivery of RS to the consumer is highlighted because of the impact that different food-processing technologies can have in maintaining, enhancing, or destroying the RS potential of a raw material or food.     

Health Effects of Soy Isoflavones and Green Tea Catechins on Cancer and Cardiovascular Diseases Based on Urinary Biomarker Levels

Plant polyphenols have various health effects. Genistein, which is abundant in soybeans, and epigallocatechin-3-gallate, which is abundant in green tea, are major flavonoids, a subclass group of polyphenols. Several epidemiological studies have shown that these flavonoids have beneficial effects against cancer and cardiovascular diseases. However, other studies did not show such effects. Several confounding factors, including recall bias, are related to these inconsistent findings, and the determination of metabolites in the urine may be useful in reducing the number of confounding factors. Equipment, which can be used by research participants to collect samples from a portion of voided urine within 24 h without the help of medical workers, has been developed for epidemiological investigations. Previous studies, in which flavonoid metabolites in these urine samples were measured, revealed that soy intake was correlated with a reduced risk of certain types of cancer and cardiovascular diseases worldwide. Although soybeans and green tea consumption may have protective effects against cancer and cardiovascular diseases, further clinical studies that consider different confounding factors are required to provide evidence for the actual impact of dietary flavonoids on human diseases, including cancer and cardiovascular diseases. One possible mechanism involved is discussed in relation to the downregulation of reactive oxygen species and the upregulation of 5′-adenosine monophosphate-activated protein kinase elicited by these flavonoids.     

Natural Compounds in Cancer Prevention: Effects of Coffee Extracts and Their Main Polyphenolic Component, 5‐O‐Caffeoylquinic Acid,on Oncogenic Ras Proteins

Recent epidemiological studies have demonstrated that the consumption of healthy foods that are particularly rich in polyphenols might reduce the incidence of cancer and neurodegenerative diseases. In particular, chlorogenic acids (CGAs) occur ubiquitously in food and represent the most abundant polyphenols in the human diet. A number of beneficial biological effects of CGAs, such as anti‐inflammatory activity, anti‐carcinogenic activity, and protection against neurodegenerative diseases, have been reported. However, the molecular mechanisms at the base of these biological activities have not yet been investigated in depth. By combining NMR spectroscopy, molecular docking, surface plasmon resonance and ex vivo assays of the Ras‐dependent breast cancer cell line MDA‐MB‐231, we contribute to the elucidation of the molecular basis of the activity of CGAs and natural extracts from green and roasted coffee beans as chemoprotective dietary supplements.     

Screening of exon methylation biomarkers for colorectal cancer via LC‐MS/MS strategy

The identification of biomarkers would be of benefit for the diagnosis and treatment of colorectal cancer. DNA methylation in specific genomic regions, which had shown strongly association with disease genotypes, was an effective indicator to reveal the occurrence and development of cancers. To screen out methylation biomarkers for colorectal cancer (CRC), genomic DNA was isolated from colorectal cancerous and corresponding cancer‐adjacent tissues collected from 30 CRC patients and then bisulfite‐converted. The exon regions of 5 targeted genes (CNRIP1 , HIC1 , RUNX3 , p15 , and SFRP2 ) were amplified by using nested polymerase chain reaction with specific primers, and the amplicon was purified and hydrolyzed. The methylation levels of these specific regions were detected by liquid chromatography tandem mass spectrometry (LC‐MS/MS). The results showed that 5 targeted exon regions were successfully amplified and confirmed by sequencing. The methodological validations indicated that LC‐MS/MS was highly sensitive and accurate. The methylation levels of CNRIP1 and RUNX3 were remarkably high in CRC tissues with statistical difference when compared with corresponding cancer‐adjacent individuals, while that of HIC1 , p15 , and SFRP2 had no difference between 2 subjects. These findings supported CNRIP1 and RUNX3 as potential DNA methylation biomarkers for CRC diagnosis and treatment, and our LC‐MS/MS approach exhibited great advantages in the identification of regional DNA methylation biomarkers.     

Research Progress on Hypoglycemic Mechanisms of Resistant Starch: A Review

In recent years, the prevalence of diabetes is on the rise, globally. Resistant starch (RS) has been known as a kind of promising dietary fiber for the prevention or treatment of diabetes. Therefore, it has become a hot topic to explore the hypoglycemic mechanisms of RS. In this review, the mechanisms have been summarized, according to the relevant studies in the recent 15 years. In general, the blood glucose could be regulated by RS by regulating the intestinal microbiota disorder, resisting digestion, reducing inflammation, regulating the hypoglycemic related enzymes and some other mechanisms. Although the exact mechanisms of the beneficial effects of RS have not been fully verified, it is indicated that RS can be used as a daily dietary intervention to reduce the risk of diabetes in different ways. In addition, further research on hypoglycemic mechanisms of RS impacted by the RS categories, the different experimental animals and various dietary habits of human subjects, have also been discussed in this review.