Institute of Food Research Health benefits of dietary polyphenols current evidence for plausible mechanisms Paul Kroon Polyphenols & Health Group Plant Natural Products & Health Programme paul.kroon@ifr.ac.uk 3 rd Serbian Conference on Dietary Supplements, 25-27 November 2011, Belgrade
Norwich Research Park Institute of Food Research N&NUH UEA Institute of Food Research John Innes Centre Genome Analysis s Centre BUPA PBL
Presentation overview Flavonoids in plants, foods & diets Health benefits of flavonoid consumption: - Evidence from epidemiological & intervention studies Flavonoid absorption and metabolism Pharmacokinetics Phase-2 metabolism How should we establish evidence for the mechanisms underlying health benefit? Mechanisms an example using transcriptomics Conclusions, future priorities
PART 1 Flavonoids in plants, foods and diets
Classification of flavonoids HO OH OH B O HO O HO O A C OH OH O OH O OH O Flavones Flavonols Flavanones OH OH OH HO O HO O HO O OH OH OH OH O OH Catechins Anthocyanidins Isoflavones (flavan-3-ols) (anthocyanins) OH
FLAVONOLS (Quercetin, kaempferol) FLAVONES (Apigenin, luteolin, tangeretin) FLAVANONES (Naringenin, hesperetin) ANTHOCYANINS - Cyanidin (pelargonidin, delphinidin) FLAVAN-3-OLS (CATECHINS) (-)-Epicatechin, (+)-catechin, Gallocatechins, galloyl-catechins pro(antho)cyanidins ISOFLAVONES Daidzein, i genistein, i glycitein i
SIMPLE PHENOLICS HYDROXYCINNAMATES e.g. Ferulic, p-coumaric, sinapic acids HYDROXYBENZOIC ACIDS e.g. Gallic acid Esterified soluble forms e.g. Caffeic acid-quinic acid esters Esterified insoluble forms (bound) e.g. Ferulic acid esterified to cereal fiber OTHERS e.g. Hydroxytyrosol
Supplements
Flavonoid contents / concentrations in foods 2-3 mg per cup QUERCETIN 2.5-20 mg per 100g FW (dessert low, cider high) 30-50 mg per 100 g FW (yellow and red) ~90 g / kg in cocoa beans ~ 5 g / kg in dark chocolate 57 mg per 100 g in fresh fruit Hollands et al. (2008) MNFR 52, 1050-1057. ANTHOCYANINS ~900 mg per 100 g in fresh fruits <32 mg per 100 ml in juices Hollands et al., (2008) Food Chem 108, 869-878 >500 mg / kg FW of cider apples <100 mg / kg desert apples FLAVANOLS Up to 2 g / L in tannic red wine
Estimating flavonoid intakes The future. online databases PhenolExplorer Developed in Augustin Scalbert s group (INRA, Clermont-Ferand, France) Comprehensive composition data for polyphenols in foods Data from peer-reviewed publications Fully searchable on-line database (www.phenol-explorer.eu) l EuroFIR BASIS Developed within the EuroFIR NoE (http://www.eurofir.net/index/) Composition and biological activity data for plants / plant foods Critically evaluated published data Conforms with EuroFIR quality standards d (+ LanguaL, L plant list) Fully searchable on-line database (http://www.polytec.dk/ebasis/)
PART 2 Health benefits of flavonoid consumption
Evidence from: Epidemiological studies Intervention studies OH HO O OH O OH Flavonoids and other phenols Flavonoid / phenolic- rich foods, beverages
Evidence of health benefit Epidemiology Dietary FLAVONOLS and cardiovascular disease: Meta-analysis:-analysis: Huxley & Neil (2003) Eur J Clin Nutr 57, 904-8 7 prospective cohort studies included (1993-2001; 107,000 subjects) 2087 fatal CHD events Most flavonols from tea, onions and apples Adjusted d Risk Ratios 0.47-0.89 089(6) and d16(1) 1.6 Combined RR for highest tertile vs lowest = 0.80 (95% CI = 0.69-0.93) Conclusion: High flavonol intakes may be associated with risk from CHD mortality
Epidemiology - flavanol intake and CVD Prospective studies on CATECHIN intake and risk of CVDs: ------------------------------------------------------------------------------------------------------------------------------- High vs Outcome # cases Adjusted RR P for Country low intake (high vs low) trend ------------------------------------------------------------------------------------------------------------------------------- US 1 74.8 vs 3.6 CAD 767 0.85 (0.67, 1.07) - Netherlands 2 124.0 vs 25.3 CAD 90 0.49 (0.27, 0.88) 0.02 Netherlands 124.0 vs 25.3 Incident stroke 88 0.92 (0.51, 1.68) 0.75 ------------------------------------------------------------------------------------------------------------------------------- 1 Arts et al. (2001) Epidemiology 12, 668-675. 2 Arts et al. (2001) Am J Clin Nutr 24, 227-232. Limited it data available The Zutphen Elderly Study showed an inverse relationship between catechin intake and CAD but not stroke A75mg 7.5mg intake of catechins not from tea associated with 20% reduction in CAD mortality (p = 0.114)
Epidemiologic studies Flavonoid intake and CVD mortality: a prospective study in post-menopausal women Mink, Scrafford et al. (2007) Am J Clin Nutr 85, 895-909. 34,489 women from Iowa Women s Health Study Used USDA databases All flavonoid classes included Quintiles of flavonoid intake versus CVD, CHD, stroke, total mortality Food sources grouped into frequency categories Anthocyanins Rel. Risk (95% CI) ------------------------------------------ CHD: 088(0780 0.88 (0.78-0.99) Flavanones CVD: 0.91 (0.83-0.99) All mortality: 0.90 (0.86-0.95) Rel. Risk (95% CI) Apples/pears CHD, -------------------------------------- Red wine CVD CHD: 0.78 (0.65-0.94) Flavones Rel. Risk (95% CI) -------------------------------------- CHD: 0.78 (0.65-0.94) Grapefruit CHD Strawberries CHD Chocolate CHD
Epidemiology FLAVONOID SUBCLASSES and incident hypertension Habitual intake of flavonoid sub-classes and incident hypertension in adults Cassidy, O Reilly, Rimm et al. (2011) Am J Clin Nutr 93, 338-347. 87,242 women from Nurses Health Study II, 46,672 women from the Nurses Health Study I, and 23,043 men from the Health Professionals Follow-Up Study Updated USDA databases All flavonoid classes included Quintiles of flavonoid intake versus CVD, CHD, stroke, total mortality 29,018 and 5629 cases of hypertension in women and men, respectively (14 y) 8% Apigenin Catechin [0.92 (0.86-0.98)] Pooled analyses individual compounds -12% in 60y -5% -6% -4% in 60 y
Epidemiology Summary Data from numerous epidemiological studies support the notion that increased consumption of dietary polyphenols protects against various chronic diseases...but these studies cannot prove cause and effect...
The EFSA health claim evaluation process
Flavonoid intervention studies Flavonoids, flavonoid-rich i foods and cardiovascular risk: a meta-analysis of randomized controlled trials. Lee Hooper, Paul Kroon, Eric Rimm, Jeffrey Cohn, Ian Harvey, Kathryn Le Cornu, Jonathan Ryder, Wendy Hall, Aedín Cassidy. Am J Clin Nutr 88, 38-50. Structured search strategy (MEDLINE, EMBASE and Cochrane databases) formal inclusion/exclusion, data extraction, validity assessment; and meta-analysis 133 trials included (RCTs) CocoanOX TM FMD after acute intake (+3.99%, 95% CI 2.86 to 5.12, 6 studies) chronic intake (+1.45%, 0.62 to 2.28, 2 studies) Systolic bp (-5.88mmHg, -9.55 to -2.21, 4 studies) Diastolic bp (-3.30mmHg, -5.77 to -0.83, 4 studies) ISP Diastolic bp (-1.99mmHg, -2.86 to -1.12, 9 studies) LDL cholesterol (-0.19mmol/L, -0.24 to -0.14, 39 studies) Systolic bp (+5.69mmHg; 4 studies) Diastolic bp (+2.56mmHg; 4 studies) LDL (-0.23mmol/L, -0.34 to -0.12, 4 studies)
Intervention studies Green & black tea, FMD and blood pressure Dose Acute FMD ----------------------------------------------- 0 mg 7.8% 100 mg 9.0% (p=0.0113) 200 mg 9.1% 400 mg 9.6% 800 mg 10.3% Overall p <0.0001 ----------------------------------------------- Black tea also improved sbp (p<0.01), dbp (p<0.01), 01) and stiffness index (p<0.05) 05) Grassi D et al. (2009) J Hypertens. 27, 774-781.
Orange flavanones and cardiovascular health Intervention studies Design: Randomised, double-blind placebo-controlled crossover trial 24 healthy, overweight men (age 50-65 y) Four weeks of daily intervention with: - 500 ml orange juice (OJ) - 500 ml control drink plus hesperidin (CDH) - 500 ml control drink plus placebo (CDP). Outcomes: Fasted: OJ and CDH reduced dbp compared to CDP (p<0.02) Microvascular endothelial activity not affected Post-prandial: OJ and CDH improved microvascular endothelial activity at plasma hesperetin C max (p<0.05) Morand C, Dubray C, Milenkovic D et al. (2011). Hesperidin contributes to the vascular protective effects of orange juice: a randomized crossover study in healthy volunteers. Am J Clin Nutr. 93, 73-80.
Overall, the evidence from clinical trials is strongest for flavanols (cocoa, tea) and isoflavones i.e. for foods / compounds that have been most studied!
PART 3 Flavonoid absorption and metabolism
Blood supply Small intestine epithelial cells Small intestine lumen PP-sugar PP-sugar CBG Active transport SGLT-1 Sugar + PP LPH PP-metabolites (glucuronides, sulphates) Metabolising enzymes PP Passive diffusion PP + sugar PP-sugar To colon and microbial hydrolysis/metabolism
Flavonol glycosides are not present in plasma after oral dosing Relativ ve absorb bance at 370 nm Q3Glc Q4 Glc Q IS Retention time (min) 10 12 14 16 18 20 22 Day et al. Free Rad Res 35 (2001) 941-952 Volunteers consumed 200 g onions, blood collected after 1.5 h
Dietary quercetin is present in human plasma as sulfate and glucuronide conjugates of quercetin and methylquercetinc Efficient extraction methods HPLC with diode array and LC-MS/MS Authentic standards (synthesised in IFR) Sensitivity to enzyme hydrolysis Q3 SO 4 - IS UV absorbanc ce No free quercetin or glucosides QdiGlcA QGlcASO 4 - Q3GlcA 3 MeQ3GlcA Q4 GlcA Q3 GlcA 3 MeQ 4 GlcA Time
Bioavailability - Polyphenol structure is vital Manach et al. (2005) Am J Clin Nutr 81, 230-242. ( µmo ol / L ) 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 Gallic acid Cmax: 4.5µM 45 Tmax: 90 min. Single dose of 50 mg aglycone equivalent Genistein (9) Daidzein (9) Querc Gluc. (7) Rutin (6) Naringin (6) Hesperidin (5) Catechins (12) EGCg (11) Anthocyanins (6) 0.00 0 2 4 6 8 10 12 14 16 18 Time (h) Literature survey, (x) =Number of studies
PART 4 How should we establish evidence for the mechanisms underlying health benefit?
The classic response to epidemiological findings So dietary quercetin protects against CVD How does it do that?
Paul A Kroon et al. (2004) How should we assess the effects of exposure to dietary polyphenols in vitro? Am J Clin Nutr 80, 15-21.
To investigate the possible effects of diet-derived flavonoids on the vascular system we need to know... The nature of the flavonoids or Their metabolites tes in blood concentrations, over time Th i bilit t Their ability to influence cell function
Impact on cell function - mechanisms Human Umbilical Vein Endothelial Cells Endothelium: Lines inner side of blood vessels Large secretory tissue (720g in human) Produces various mediators (NO, ET-1, prostacyclin, prostaglandin) that are important for haemostasis & fibrinolysis, and regulation of vascular tone. Expresses adhesion molecules involved in recruitment and binding of monocytes Endothelial dysfunction reflects an imbalance in the production of mediators We have investigated: Adhesion molecules (ICAM-1, VCAM-1, E-selectin) Inflammatory cytokines (IL6, MCP1) inflammatory status Vasomodulators (ET-1, cgmp, inos, enos) vasomodulator balance
The three major metabolites inhibited VCAM surface expression in HUVECs at physiological concentrations 150 VC CAM-1 (%M MFI) 100 50 0 * * * * ** ** C I Q Q3'S Q3GlcA IR3GlcA Qmet 2 µmol/l 10 µmol/l Tribolo et al. (2008), Atherosclerosis 197, 50-56.
None of the physiological metabolites of quercetin retained the ability to inhibit prostaglandin E2 production (stimulated peripheral monocytes) Loki et al. (2008), J Agric Food Chem 56, 3609-3615 Loki et al. (2008), Biochem Pharmacol 75, 1045-1053.
Quercetin-3 -sulfate, but not other quercetin metabolites, retained the ability to inhibit leukotriene B 4 synthesis Effect of Quercetin and its Metabolites on LTB 4 production in peripheral neutrophils % Inh hibition 110 100 Q 90 Q3'Me 80 70 Q3'S 60 Q3Glu 50 Q3'Me3Glu 40 30 20 10 0-10 0 1 2 3 4 5 6 7 8 9 10 [Polyphenols] ( M) Loki et al. (2008), J Agric Food Chem 56, 3609-3615 Loki et al. (2008), Biochem Pharmacol 75, 1045-1053.
All of the metabolites efficiently inhibited F2-isoprostane production by PMS-activated neutrophils MeQ Q MeQ Q-3 -S 3 MeQ 3-GlcA Q-3-GlcA Loki et al. (2008), J Agric Food Chem 56, 3609-3615 Loki et al. (2008), Biochem Pharmacol 75, 1045-1053.
Mechanisms can be demonstrated in vivo
Cocoa flavan-3-ols and cardiovascular health Effects of cocoa beverage on FMD (A), nitric oxide (B), and plasma flavanols (C) Schroeter et al. (2006) PNAS 103, 1024-9. FMD and NO effects appeared to be transient And were correlated with plasma peak [total epicatechin] and especially [epicatechin and its glucuronide] Pure epicatechin elicited similar responses (n=3) Vasodilation effects of metabolites confirmed with rabbit aortic rings Role of NO confirmed using i.v. infusion of L-NMMA (NOS inhibitor)
Using transcriptomics to identify mechanisms
Effects of dp3.9 on HUVECs gene expression profiles dp3.9 vs DMSO dp3.9 (45 ) + TNFα (6h) TNFα vs DMSO vs control ---------------------------------------------------------------------------------------------------------- Selected probes 1318 (2.4%) 1036 (1.9%) 2220 (4.0%) Downregulated 628 572 509 (0.09-0.7, 0.7, 356) (0.1-0.7, 0.7, 352) (0.09-0.7, 0.7, 393) Upregulated 690 464 1711 (1.5-13.0, 258) (1.5-11.2, 221) (1.5-95, 1167) ---------------------------------------------------------------------------------------------------------- No substantial and significant effects of (-)-epicatechin or procyanidin B2 Many dp3.9-induced d d changes occurred + / - TNFα 8/8 gene changes confirmed by qrt-pcr Significant changes in genes and pathways concerned with angiogenesis, cell proliferation, apoptosis, cell growth, and maintenance of vascular tone Garcia-Conesa et al. (2009), Mol Nutr Food Res 53
Effects of apple procyanidins on migration activity Vehicle control Procyanidin (dp 3.9) 4 h 24 h 48 h
Vascular Endothelial Growth Factor Is the most potent regulator of angiogenesis i Is a protein that stimulates vascular endothelial cell growth, survival and proliferation It binds to specific VEGF receptors on the endothelial cell surface.
Conclusions Flavonoids and other polyphenols have good potential to be effective functional food ingredients and nutraceuticals - multiple activities - huge range of structures and sources There are also problems / challenges - poor bioavailability, efficient metabolism -organoleptic propertiesp Current evidence of health benefit is encouraging - >200 well-designed RCTs In vitro mechanistic research - must consider metabolism - amenable to post-genomic technologies (transcriptomics, proteomics, metabolomics, etc )
Future priorities Focus on establishing cause and effect Randomised double-blind placebo-controlled trials - Very well characterised foods - Work with food technologists to develop placebos for foods - Pure compounds versus foods - Sufficiently long studies - Longitudinal measurements for more power and information - Established risk factors and markers - Bioavailability - Mechanism in vivo (if possible) - [Eventually, hard end-point studies] Complementary in vitro mechanistic studies Use of omics for new biomarkers, new mechanisms
Acknowledgements IFR: David Hughes Sandra Tribolo Federica Lodi Shikha Saha Wendy Hollands Gary Brett Paul Needs Christina Moyle University of W Australia (Perth) Kevin Croft Jonathan Hodgson Wai Mun Loki University of East Anglia: Aedin Cassidy Lee Hooper University of Nottingham Vince Wilson Sunita Suri Moira Taylor CSIC, Murcia, Spain Maria Teresa Garcia Conesa Paco Tomas Barberan
Thank you for your attention ti