1.
Inter-Individual Variability in Insulin Response after Grape Pomace Supplementation in Subjects at High Cardiometabolic Risk: Role of Microbiota and miRNA.
Ramos-Romero, S, Léniz, A, Martínez-Maqueda, D, Amézqueta, S, Fernández-Quintela, A, Hereu, M, Torres, JL, Portillo, MP, Pérez-Jiménez, J
Molecular nutrition & food research. 2021;(2):e2000113
Abstract
SCOPE Dietary polyphenols have shown promising effects in mechanistic and preclinical studies on the regulation of cardiometabolic alterations. Nevertheless, clinical trials have provided contradictory results, with high inter-individual variability. This study explores the role of gut microbiota and microRNAs (miRNAs) as factors contributing to the inter-individual variability in polyphenol response. METHODS AND RESULTS 49 subjects with at least two factors of metabolic syndrome are divided between responders (n = 23) or non-responders (n = 26), depending on the variation rate in fasting insulin after grape pomace supplementation (6 weeks). The populations of selected fecal bacteria are estimated from fecal deoxyribonucleic acid (DNA) by quantitative real-time polymerase chain reaction (qPCR), while the microbial-derived short-chain fatty acids (SCFAs) are measured in fecal samples by gas chromatography. MicroRNAs are analyzed on a representative sample, followed by targeted miRNA analysis. Responder subjects show significantly lower (p < 0.05) Prevotella and Firmicutes levels, and increased (p < 0.05) miR-222 levels. CONCLUSION After evaluating the selected substrates for Prevotella and target genes of miR-222, these variations suggest that responders are those subjects exhibiting impaired glycaemic control. This study shows that fecal microbiota and miRNA expression may be related to inter-individual variability in clinical trials with polyphenols.
2.
Grape pomace polyphenols improve insulin response to a standard meal in healthy individuals: A pilot study.
Costabile, G, Vitale, M, Luongo, D, Naviglio, D, Vetrani, C, Ciciola, P, Tura, A, Castello, F, Mena, P, Del Rio, D, et al
Clinical nutrition (Edinburgh, Scotland). 2019;(6):2727-2734
Abstract
BACKGROUND & AIMS Dietary polyphenols have beneficial effects on glucose/lipid metabolism in subjects at high risk to develop type 2 diabetes; however, the underlying mechanisms are not clear. We aimed to evaluate: 1) the acute effects of the consumption of a drink rich in polyphenols from red grape pomace (RGPD) on glucose/insulin and triglyceride responses to a standard meal in healthy individuals, and, 2) the relationship between plasma levels of phenolic metabolites and metabolic parameters. METHODS Twelve healthy men, aged 20-40 years participated in a randomized, controlled study according to a cross-over design. After a 3-day low-polyphenol diet, all participants consumed, on two different days and separated by a one week interval, after an overnight fast, a drink rich in polyphenols (1.562 g gallic acid equivalents (GAE)) or a control drink (CD, no polyphenols), followed after 3 h by a standard meal (960 kcal, 18% protein, 30% fat, 52% CHO). Blood samples were taken at fasting, 3 h after the drink, over 5 h after the standard meal and at fasting on the next day to measure plasma concentrations of glucose, insulin, triglyceride and phenolic metabolites. RESULTS Glycemic and triglyceride post-meal responses were similar after both the RGPD and the control drink. In contrast, postprandial insulin incremental area (iAUC0-5h) was 31% lower (p < 0.05), insulin secretion index was 18% lower (p < 0.016) and insulin sensitivity (SI) index was 36% higher (p = 0.037) after the RGPD compared to CD. Among phenolic metabolites, gallic acid correlated inversely with the insulin response (r = -0.604; p = 0.032) and positively with the SI index (r = 0.588, p = 0.037). CONCLUSIONS RGPD consumption acutely reduced postprandial insulin levels and improved insulin sensitivity. This effect could be likely related to the increase in gallic acid levels. This drink, added to usual diet, could contribute to increase the daily intake of polyphenols, with potential health benefits. CLINICALTRIALS. GOV IDENTIFIER NCT02865278.
3.
Polyphenols From Grape and Blueberry Improve Episodic Memory in Healthy Elderly with Lower Level of Memory Performance: A Bicentric Double-Blind, Randomized, Placebo-Controlled Clinical Study.
Bensalem, J, Dudonné, S, Etchamendy, N, Pellay, H, Amadieu, C, Gaudout, D, Dubreuil, S, Paradis, ME, Pomerleau, S, Capuron, L, et al
The journals of gerontology. Series A, Biological sciences and medical sciences. 2019;(7):996-1007
Abstract
Polyphenols are promising nutritional bioactives exhibiting beneficial effect on age-related cognitive decline. This study evaluated the effect of a polyphenol-rich extract from grape and blueberry (PEGB) on memory of healthy elderly subjects (60-70 years-old). A bicentric, randomized, double-blind, placebo-controlled trial was conducted with 215 volunteers receiving 600 mg/day of PEGB (containing 258 mg flavonoids) or a placebo for 6 months. The primary outcome was the CANTAB Paired Associate Learning (PAL), a visuospatial learning and episodic memory test. Secondary outcomes included verbal episodic and recognition memory (VRM) and working memory (SSP). There was no significant effect of PEGB on the PAL on the whole cohort. Yet, PEGB supplementation improved VRM-free recall. Stratifying the cohort in quartiles based on PAL at baseline revealed a subgroup with advanced cognitive decline (decliners) who responded positively to the PEGB. In this group, PEGB consumption was also associated with a better VRM-delayed recognition. In addition to a lower polyphenol consumption, the urine metabolomic profile of decliners revealed that they excreted more metabolites. Urinary concentrations of specific flavan-3-ols metabolites were associated, at the end of the intervention, with the memory improvements. Our study demonstrates that PEGB improves age-related episodic memory decline in individuals with the highest cognitive impairments.