Polyphenol-rich Diet Research Articles

Dark chocolate protects against colon carcinogenesis by favorable alteraion of cell kinetics

Colonic tumors arise from perturbations of the homeostasis among cell proliferation and apoptosis. Cocoa and chocolate products have among the highest concentrations of polyphenols and an increasing body of epidemiologic evidence supports that polyphenol‐rich diets promote health and attenuate or delay the onset of various diseases, including colon cancer. We determined whether dark chocolate protects against colon cancer by favorable alteration of cell kinetics (cell proliferation and apoptosis). Forty eight male Spague Dawley rats were assigned to receive diets containing control (no chocolate), regular or bloomed dark chocolate (10% of diet) and injected with saline or azoxymethane (2 times at wk 3 and 4). Cell proliferation and apoptosis were determined using Ki‐67 antibody and TUNEL assay, respectively. Carcinogen treatment increased proliferation index (P=0.003) and expanded proliferation zone (P=0.007). Dark chocolate diets, regardless regular or bloomed, lowered proliferation index (P=0.001) especially in lower 1/3 of colonic crypt (P<0.001) compared to control. Apoptosis was not significantly different among diets. These results suggest that cell proliferation was one of the key responses to carcinogen as a function of diet. Dark chocolate reduces risk of colon cancer by inhibiting cell proliferation rather than alteration of apoptosis. Supported by CHNR08‐810 and SDSU NUTR 302L class.

Chemistry and Biochemistry of Dietary Polyphenols

Polyphenols are the biggest group of phytochemicals, and many of them have been found in plant-based foods. Polyphenol-rich diets have been linked to many health benefits. This paper is intended to review the chemistry and biochemistry of polyphenols as related to classification, extraction, separation and analytical methods, their occurrence and biosynthesis in plants, and the biological activities and implications in human health. The discussions are focused on important and most recent advances in the above aspects, and challenges are identified for future research.

Untargeted metabolite discovery in kinetic data from multi-dose intervention studies

A new strategy for biomarker discovery is presented that is based on multi-dose kinetic metabolomics data. Gas chromatography–mass spectrometry (GC–MS) data sets recorded in the full scan mode are scanned for compounds showing a meaningful trend following the different doses and sampling time points. From a biological point of view, a meaningful trend denotes a compound that responds similarly at all doses and follows a smooth trend along the time points. This type of information can be used to distinguish relevant metabolites from those compounds not following the expected trends. The method is based on analysing the time and dosage trends of each compound via principal component analysis. As only local information is analysed at a time (meaning no correlation with other metabolites is taken into account), the proposed model flags relevant metabolites even if their trend is different from that of any other compound. The new method is therefore an attractive way to reduce the long list of detected compounds in a metabolomics sample set to include only those having the expected smooth time profile that is common for all doses. The new strategy is tested on a sample set obtained from a gut fermentation study of a polyphenol-rich diet. For this study, the initial list of over 25,000 potentially interesting features was reduced to less than 250, thus significantly reducing the expensive and time-consuming manual examination.

Effects of Polyphenol-rich Diet on the Antioxidative and Physical Capacity After Exhaustive Endurance Exercise

Effects of Polyphenol-rich Diet on the Antioxidative and Physical Capacity After Exhaustive Endurance Exercise

Impact of Dietary Polyphenols on Carbohydrate Metabolism

Polyphenols, including flavonoids, phenolic acids, proanthocyanidins and resveratrol, are a large and heterogeneous group of phytochemicals in plant-based foods, such as tea, coffee, wine, cocoa, cereal grains, soy, fruits and berries. Growing evidence indicates that various dietary polyphenols may influence carbohydrate metabolism at many levels. In animal models and a limited number of human studies carried out so far, polyphenols and foods or beverages rich in polyphenols have attenuated postprandial glycemic responses and fasting hyperglycemia, and improved acute insulin secretion and insulin sensitivity. The possible mechanisms include inhibition of carbohydrate digestion and glucose absorption in the intestine, stimulation of insulin secretion from the pancreatic β–cells, modulation of glucose release from the liver, activation of insulin receptors and glucose uptake in the insulin-sensitive tissues, and modulation of intracellular signalling pathways and gene expression. The positive effects of polyphenols on glucose homeostasis observed in a large number of in vitro and animal models are supported by epidemiological evidence on polyphenol-rich diets. To confirm the implications of polyphenol consumption for prevention of insulin resistance, metabolic syndrome and eventually type 2 diabetes, human trials with well-defined diets, controlled study designs and clinically relevant end-points together with holistic approaches e.g., systems biology profiling technologies are needed.

Trend analysis of time-series data: A novel method for untargeted metabolite discovery

A new strategy for biomarker discovery is presented that uses time-series metabolomics data. Data sets from samples analysed at different time points after an intervention are searched for compounds that show a meaningful trend following the intervention. Obviously, this requires new data-analytical tools to distinguish such compounds from those showing only random variation. Two univariate methods, autocorrelation and curve-fitting, are used either as stand-alone methods or in combination to discover unknown metabolites in data sets originating from target-compound analysis. Both techniques reduce the long list of detected compounds in the kinetic sample set to include only those having a pre-defined interesting time profile. Thus, new metabolites may be discovered within data structures that are usually only used for target-compound analysis. The new strategy is tested on a sample set obtained from a gut fermentation study of a polyphenol-rich diet. For this study, the initial list of over 9000 potentially interesting features was reduced to less than 150, thus significantly reducing the expensive and time-consuming manual examination.

Impact of dietary polyphenols on human platelet function – A critical review of controlled dietary intervention studies

Cardiovascular disease is a chronic disease influenced by many factors, with activated blood platelets being one of them. Platelets play a central role in the formation of plaques within blood vessels, contributing to early inflammatory events. Consumption of diets rich in plant-based products protects against the development of cardiovascular disease. Polyphenols, which are secondary plant metabolites found in a wide range of foodstuffs and beverages, may be partially responsible for these effects. Their protective properties include inhibitory effects on platelet function in vitro and in vivo. However, the bioavailability of many polyphenols is poor and it is unclear whether sufficient quantities can be obtained by dietary means to exert protective effects. Consequently, this review summarizes 25 well-controlled human intervention studies examining the effect of polyphenol-rich diets on platelet function. These studies report a huge variety of research methods, study designs, and study subjects, resulting in controversial assertions. One consistent finding is that cocoa-related products, however, have platelet-inhibiting effects when consumed in moderate amounts. To assess whether other classes of dietary polyphenols, or their metabolites, also beneficially affect platelet function requires more well-controlled intervention studies as well as the adoption of more uniform methods to assess platelet aggregation and activation.

GSTT2, a phase II gene induced by apple polyphenols, protects colon epithelial cells against genotoxic damage

The potential protective effect of a polyphenol-rich diet for colon carcinogenesis is of great scientific and medical interest. Apples are a main source of polyphenols, and apple juice has been shown to attenuate chemically induced colon carcinogenesis in animal models. In addition to an antioxidant and antiproliferative activity, apple polyphenols have been shown to elevate expression of the phase II gene glutathione S-transferase T2 (GSTT2) in colon epithelial cells. We hypothesized that apple polyphenols may thereby provide protection against oxidant-induced DNA damage. Using GSTT2 promoter constructs and luciferase reporter assays, we found that polyphenolic apple extracts (AE) can directly enhance GSTT2 promoter activity. Comet assays demonstrated that the genotoxicity of the GSTT2 substrate cumene hydroperoxide (CumOOH) was significantly reduced when HT29 colon epithelial cells were pretreated with AE. Overexpression of GSTT2 in HT29 cells significantly reduced CumOOH induced DNA damage, whereas shRNA mediated knockdown of GSTT2 gene expression resulted in higher damage. Our results causally link GSTT2 levels with protection from genotoxic stress, and provide evidence that the antigenotoxic effects of apple polyphenols in vitro are at least in part due to an induction of GSTT2 expression. Induction of phase II genes may contribute to primary chemoprevention of colon cancer by apple polyphenols.

Apple Polyphenols and Products Formed in the Gut Differently Inhibit Survival of Human Cell Lines Derived from Colon Adenoma (LT97) and Carcinoma (HT29)

Colorectal tumor risks could be reduced by polyphenol-rich diets that inhibit cell growth. Here, apple polyphenols were studied for effects on the survival of colon adenoma (LT97) and carcinoma-derived (HT29) cell lines. Three apple extracts (AEs) from harvest years 2002-2004 were isolated (AE02, AE03, and AE04) and fermented in vitro with human fecal flora. Extracts and fermentation products were analyzed for polyphenols with HPLC. The cells were treated with AEs (0-850 microg/mL) or fermented AEs (F-AEs, 0-9%), and survival was measured by DNA staining. All AEs contained high amounts of polyphenols (311-534 mg/g) and reduced cell survival (in LT97 > HT29). AE03 was most potent, possibly because it contained more quercetin compounds. Fermentation of AEs resulted in an increase of short chain fatty acids, and polyphenols were degraded. The F-AEs were approximately 3-fold less bioactive than the corresponding AEs, pointing to a loss of chemoprotective properties through fermentation.

Xanthohumol inhibits angiogenic vessels but not stable vessels

Angiogenesis has been associated with several pathologies such as cancer and atherosclerosis. Recent studies demonstrate an inverse correlation between these diseases and the consumption of a polyphenol-rich diet. The aim of this study was to investigate the effect of xanthohumol (XN) in the angiogenic process. Treatment with 10 μM XN decreased human umbilical vein endothelial cells (HUVEC) and vascular smooth muscle cells (FLTR) viability (MTT assay) and increased apoptotic rates (TUNEL assay) in both cells. Migration capacity (injury assay and double-chamber assay) diminished with XN in a dose-dependent manner. XN reduced tubule-like structures formation when HUVEC were cultured on Matrigel-coated plates. However, it was not able to prevent the formation of these structures when HUVEC were co-cultured with FLTR. XN might be a useful therapeutic agent against pathological situations where angiogenesis is stimulated, without exerting adverse effects on stable vessels. The inhibition of FLTR migration is also interesting, as this process is fundamental for the establishment of atherosclerosis. (Supported by FCT (POCI/SAU-BMA/55556/2004); iBeSa (P02–05) and University of Porto, “Investigação na Pré-graduação”)

Acute Effect of Tea, Wine, Beer, and Polyphenols on ecto-Alkaline Phosphatase Activity in Human Vascular Smooth Muscle Cells

Alkaline phosphatase (ALP) is an ecto-enzyme widely distributed across species. It modulates a series of transmembranar transport systems, has an important role in bone mineralization, and can also be involved in vascular calcification. Polyphenol-rich diets seem to have protective effects on human health, namely, in the prevention of cardiovascular diseases. We aimed to investigate the effects of polyphenols and polyphenol-rich beverages upon membranar alkaline phosphatase (ecto-ALP) activity in intact human vascular smooth muscle cells (AALTR). The ecto-ALP activity was determined at pH 7.8, with p-nitrophenyl phosphate as the substrate, by absorbance spectrophotometry at 410 nm. Cell viability was assessed by the lactate dehydrogenase (LDH) method, and the polyphenol content of beverages was assessed using the Folin-Ciocalteu reagent. All polyphenols tested inhibited ecto-ALP activity, in a concentration-dependent way. Teas, wines, and beers also inhibited ecto-ALP activity, largely according to their polyphenol content. All tested compounds and beverages improved or did not change AALTR cell viability. Stout beer was an exception to the described behavior. Although more studies must be done, the inhibition of AALTR ecto-ALP activity by polyphenolic compounds and polyphenol-containing beverages may contribute to their cardiovascular protective effects.

Prevention of Bone Loss by Phloridzin, an Apple Polyphenol, in Ovariectomized Rats under Inflammation Conditions

Aging and sex hormones related changes lead to inflammatory and oxidant conditions, which are involved in the pathogenesis of osteoporosis. Recent studies have suggested that polyphenols may exert a protective effect in such conditions. We assessed the effect of phloridzin (Phlo), a flavonoid exclusively found in apple, on bone metabolism in ovariectomized (OVX) or sham-operated (SH) rats with and without inflammation. Six-month-old Wistar rats were allocated to two equal groups that received either a control diet or a diet supplemented with 0.25% Phlo for 80 days. Three weeks before necropsy, inflammation was induced by subcutaneous injection of talc in 10 animals of each group. At necropsy, ovariectomy decreased both total (T-BMD) and metaphyseal (M-BMD) femoral bone mineral density (P < 0.01). Inflammation conditions, checked by an increase in the spleen weight and alpha1-acid glycoprotein concentration in OVX rats, exacerbated the decrease in T-BMD (g/cm2) (as well as M-BMD) observed in castrated animals (P < 0.05). Daily Phlo intake prevented ovariectomy-induced bone loss in conditions of inflammation as shown by T-BMD and M-BMD (P < 0.05). At the diaphyseal site, BMD was improved by Phlo in OVX rats with or without inflammation (P < 0.05). These results could be explained by changes in bone remodeling as the increased urinary deoxypyridinoline excretion in OVX and OVXinf animals was prevented by the polyphenol-rich diet (P < 0.001), while plasma osteocalcin concentration was similar in all experimental groups. In conclusion, Phlo consumption may provide protection against ovariectomy-induced osteopenia under inflammation conditions by improving inflammation markers and bone resorption.

Determination of malondialdehyde (MDA) by high-performance liquid chromatography in serum and liver as a biomarker for oxidative stressApplication to a rat model for hypercholesterolemia and evaluation of the effect of diets rich in phenolic antioxidants from fruits

A high-performance liquid chromatography (HPLC) method to determine malondialdehyde (MDA) as the 2,4-dinitrophenylhydrazine (DNPH) derivative was applied to biological samples (serum and liver homogenates). Since MDA is considered a presumptive biomarker for lipid peroxidation in live organisms, a model for nutritionally induced oxidative stress (hypercholesterolemic rats) was studied in comparison with normocholesterolemic animals. The effect of diet supplementation with fruits rich in antioxidant polyphenols was assessed. The proposed method showed to be precise and reproducible, as well as sensitive enough to reflect differences in the oxidative status in vivo. A significant decrease of serum and liver MDA concentrations in animals fed diets containing 0.3% of polyphenols from strawberry, cocoa or plum was observed in the normocholesterolemic groups. This reduction was especially noteworthy in the hypercholesterolemic animals, with increased MDA levels indicating enhanced lipid peroxidation in the controls, yet with values parallel to the normocholesterolemic groups in animals fed the polyphenol-rich diets. These results point out the beneficial effects of phenolic antioxidants from fruits in preventing oxidative damage in vivo.

Role of Circulating S -Nitrosothiols in Control of Blood Pressure

The biological effects of nitric oxide (NO) are in large part mediated by S -nitrosylation of peptides and proteins to produce bioactive S -nitrosothiols (SNOs).1–3 The observation of abnormal SNO levels in numerous pathophysiological states2 suggests that dysregulation of SNO homeostasis may contribute to disease pathogenesis. For example, the hypotension of human sepsis is accompanied by increases in circulating levels of vasodilatory SNOs.3 Although such altered SNO levels may simply mirror NO production (eg, induction of inducible NO synthase in sepsis), they may also reflect changes specific to SNO biosynthesis and metabolism. Indeed, mice lacking a SNO-metabolizing enzyme are profoundly hypotensive under anesthesia.3 Thus, blood pressure is evidently regulated by both synthesis and turnover of SNOs. In this issue of Hypertension , Gandley et al4 extend this paradigm by proposing that a defect in SNO turnover contributes to the hypertension of preeclampsia. In the blood, S- nitrosoalbumin (SNO-albumin) and S -nitrosohemoglobin (SNO-Hb) constitute the major conduits for circulating NO bioactivity. Although both SNOs may influence blood pressure, they operate within distinct signaling circuits. SNO-Hb can be viewed as a principal regulator of SNO homeostasis, adaptively modulating NO chemistry to control NO bioactivity. SNO-Hb is formed by transfer of NO from heme-iron to Cysβ93 thiol on T to R structural transition (oxygenation) of the hemoglobin tetramer.5 SNO-Hb associates with the red blood cell (RBC) membrane via an interaction with the cytoplasmic domain of anion-exchanger 1 protein (CDAE1, Band 3); on deoxygenation (R→T) transfer of the NO group from SNO-Hb to a cysteine thiol within CDAE1 supports export of RBC vasodilatory activity.6 SNO-Hb thus serves as an O2 sensor and O2-dependent transducer of NO bioactivity. In contrast, it appears that rather than transducing a specific signal, albumin operates as a buffer to …

Effects of Phenol-Depleted and Phenol-Rich Diets on Blood Markers of Oxidative Stress, and Urinary Excretion of Quercetin and Kaempferol in Healthy Volunteers

Objective: Epidemiological studies have suggested beneficial effects of dietary polyphenols in reducing the risk of chronic diseases. This study was performed to investigate the effects of polyphenol-depleted and polyphenol-rich diets on blood oxidative stress markers and urinary excretions of major phenols.Methods: Nineteen healthy female non-smokers 19 to 21 years of age took part in the study, which consisted of two dietary intervention periods separated by three days. Experimental diets were composed of common foods selected to comply with low contents of polyphenols for phenol-depleted intervention and high contents of polyphenols for phenol-rich diets. Blood and urine samples were collected on day 0, 3 and 6 of each intervention. Duplicate portions of foods provided to the subjects were also collected. Blood oxidative stress markers included plasma antioxidant vitamins, erythrocyte superoxide dismutase (SOD) activity and lymphocyte DNA damage. Urinary excretions of major phenols were measured to affirm bioavailability of dietary phenols.Results: Plasma α-tocopherol and β-carotene concentrations were slightly decreased on day 3 and 6 of the phenol-depleted dietary intervention period, although no change was observed with phenol-rich diets. The erythrocyte SOD activity was also slightly decreased during phenol-depleted dietary intervention. However, at day 6 of the phenol-rich intervention, the activity of SOD was significantly increased by 41%. Tail moment and tail length of lymphocyte DNA as markers of DNA damage were higher on day 6 of phenol-depleted intervention, although only tail moment showed a statistical significance. The average intakes of quercetin and kaempferol during the phenol-rich intervention were 21 mg/day and 9 mg/day, respectively. The average urinary excretion rates during phenol-rich intervention were 2.06% for quercetin and 0.46% for kaempferol. There were positive correlations between erythrocyte SOD activity and urinary concentration of quercetin or kaempferol.Conclusions: These results suggest that polyphenol-rich diets may decrease the risk of chronic diseases by reducing oxidative stress.

Novel liquid chromatography–electrospray ionization mass spectrometry method for the quantification in human urine of microbial aromatic acid metabolites derived from dietary polyphenols

An HPLC–ESI-MS–MS method was developed to quantify in human urine fourteen aromatic acids known as metabolites of dietary polyphenols. These metabolites were determined simultaneously in a single 20-min chromatographic analysis with multiple reaction monitoring detection. The inter- and intra-day precisions, calculated from quality control samples were 8.8 and 5.3%, respectively, and the mean accuracy was 2.3%. The method was tested on urine samples collected from one healthy volunteer who consumed a polyphenol-rich diet for 3 days. Increased levels of several aromatic acid metabolites were observed, demonstrating that the method can be used to detect changes in the excretion of microbial metabolites induced by the consumption of polyphenol-containing foods in humans.