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Polyphenol-rich diets improve glucose metabolism in people at high cardiometabolic risk: a controlled randomised intervention trial.
Bozzetto, L, Annuzzi, G, Pacini, G, Costabile, G, Vetrani, C, Vitale, M, Griffo, E, Giacco, A, De Natale, C, Cocozza, S, et al
Diabetologia. 2015;(7):1551-60
Abstract
AIM/HYPOTHESIS Dietary polyphenols and long chain n-3 polyunsaturated fatty acids (LCn3) are associated with lower cardiovascular risk. This may relate to their influence on glucose metabolism and diabetes risk. We evaluated the effects of diets naturally rich in polyphenols and/or LCn3 of marine origin on glucose metabolism in people at high cardiometabolic risk. METHODS According to a 2 × 2 factorial design, individuals with high waist circumference and at least one more component of the metabolic syndrome were recruited at the obesity outpatient clinic. Eighty-six participants were randomly assigned by MINIM software to an isoenergetic diet: (1) control, low in LCn3 and polyphenol (analysed n = 20); (2) rich in LCn3 (n = 19); (3) rich in polyphenols (n = 19); or (4) rich in LCn3 and polyphenols (n = 19). The assigned diets were known for the participants and blinded for people doing measurements. Before and after the 8 week intervention, participants underwent a 3 h OGTT and a test meal with a similar composition as the assigned diet for the evaluation of plasma glucose, insulin and glucagon-like peptide 1 (GLP-1) concentrations, and indices of insulin sensitivity and beta cell function. RESULTS During OGTT, polyphenols significantly reduced plasma glucose total AUC (p = 0.038) and increased early insulin secretion (p = 0.048), while LCn3 significantly reduced beta cell function (p = 0.031) (two-factor ANOVA). Moreover, polyphenols improved post-challenge oral glucose insulin sensitivity (OGIS; p = 0.05 vs control diet by post hoc ANOVA). At test meal, LCn3 significantly reduced GLP-1 total postprandial AUC (p < 0.001; two-factor ANOVA). CONCLUSION/INTERPRETATION Diets naturally rich in polyphenols reduce blood glucose response, likely by increasing early insulin secretion and insulin sensitivity. These effects may favourably influence diabetes and cardiovascular risk. The implications of the decrease in insulin secretion and postprandial GLP-1 observed with diets rich in marine LCn3 need further clarification. TRIAL REGISTRATION ClinicalTrials.gov NCT01154478. FUNDING The trial was funded by European Community's Seventh Framework Programme FP7/2009-2012 under grant agreement FP7-KBBE-222639, Etherpaths Project and 'Ministero Istruzione Università e Ricerca' PRIN 2010-2011 - 2010JCWWKM.
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Diets naturally rich in polyphenols improve fasting and postprandial dyslipidemia and reduce oxidative stress: a randomized controlled trial.
Annuzzi, G, Bozzetto, L, Costabile, G, Giacco, R, Mangione, A, Anniballi, G, Vitale, M, Vetrani, C, Cipriano, P, Della Corte, G, et al
The American journal of clinical nutrition. 2014;(3):463-71
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Abstract
BACKGROUND The postprandial triglyceride-rich lipoprotein (TRL) concentration is a recognized independent cardiovascular disease risk factor. Diet is the natural approach for these postprandial alterations. Dietary polyphenols and long chain n-3 polyunsaturated fatty acids (LCn3s) are associated with a lower cardiovascular disease risk. OBJECTIVE This randomized controlled study evaluated, in persons with a high risk of cardiovascular disease, the effects of diets naturally rich in polyphenols and/or marine LCn3s on plasma TRLs and urinary 8-isoprostane concentrations, a biomarker of oxidative stress. DESIGN According to a 2 × 2 factorial design, 86 overweight/obese individuals with a large waist circumference and any other component of the metabolic syndrome were randomly assigned to an isoenergetic diet 1) poor in LCn3s and polyphenols, 2) rich in LCn3s, 3) rich in polyphenols, or 4) rich in LCn3s and polyphenols. The diets were similar in all other components. Before and after the 8-wk intervention, fasting and postmeal TRLs and 8-isoprostane concentrations in 24-h urine samples were measured. RESULTS Dietary adherence was good in all participants. Polyphenols significantly reduced fasting triglyceride concentrations (2-factor ANOVA) in plasma (P = 0.023) and large very-low-density lipoproteins (VLDLs) (P = 0.016) and postprandial triglyceride total area under the curve in plasma (P = 0.041) and large VLDLs (P = 0.004). LCn3s reduced postprandial chylomicron cholesterol and VLDL apolipoprotein B-48. The concentrations of urinary 8-isoprostane decreased significantly with the polyphenol-rich diets. Lipoprotein changes induced by the intervention significantly correlated with changes in 8-isoprostane. CONCLUSIONS Diets naturally rich in polyphenols positively influence fasting and postprandial TRLs and reduce oxidative stress. Marine LCn3s reduce TRLs of exogenous origin. Through their effects on postprandial lipemia and oxidative stress, polyphenols may favorably affect cardiovascular disease risk.