(-)-Epicatechin metabolites promote vascular health through epigenetic reprogramming of endothelial-immune cell signaling and reversing systemic low-grade inflammation.

Ingestion of (-)-epicatechin flavanols reverses endothelial dysfunction by increasing flow mediated dilation and by reducing vascular inflammation and oxidative stress, monocyte-endothelial cell adhesion and transendothelial monocyte migration in vitro and in vivo. This involves multiple changes in gene expression and epigenetic DNA methylation by poorly understood mechanisms. By in silico docking and molecular modeling we demonstrate favorable binding of different glucuronidated, sulfated or methylated (-)-epicatechin metabolites to different DNA methyltransferases (DNMT1/DNMT3A). In favor of this model, genome-wide DNA methylation profiling of endothelial cells treated with TNF and different (-)-epicatechin metabolites revealed specific DNA methylation changes in gene networks controlling cell adhesion-extravasation endothelial hyperpermeability as well as gamma-aminobutyric acid, renin-angiotensin and nitric oxide hypertension pathways. Remarkably, blood epigenetic profiles of an 8 weeks intervention with monomeric and oligomeric flavanols (MOF) including (-)-epicatechin in male smokers revealed individual epigenetic gene changes targeting similar pathways as the in vitro exposure experiments in endothelial cells. Furthermore, epigenetic changes following MOF diet intervention oppose atherosclerosis associated epigenetic changes. In line with biological data, the individual epigenetic response to a MOF diet is associated with different vascular health parameters (glutathione peroxidase 1 and endothelin-1 expression, acetylcholine-mediated microvascular response), in part involving systemic shifts in blood immune cell types which reduce the neutrophil-lymphocyte ratio (NLR). Altogether, our study suggests that different (-)-epicatechin metabolites promote vascular health in part via epigenetic reprogramming of endothelial-immune cell signaling and reversing systemic low-grade inflammation.

A systems biology network analysis of nutri(epi)genomic changes in endothelial cells exposed to epicatechin metabolites.

Although vasculo-protective effects of flavan-3-ols are widely accepted today, their impact on endothelial cell functions and molecular mechanisms of action involved is not completely understood. The aim of this study was to characterize the potential endothelium-protective effects of circulating epicatechin metabolites and to define underlying mechanisms of action by an integrated systems biology approach. Reduced leukocyte rolling over vascular endothelium was observed following epicatechin supplementation in a mouse model of inflammation. Integrative pathway analysis of transcriptome, miRNome and epigenome profiles of endothelial cells exposed to epicatechin metabolites revealed that by acting at these different levels of regulation, metabolites affect cellular pathways involved in endothelial permeability and interaction with immune cells. In-vitro experiments on endothelial cells confirmed that epicatechin metabolites reduce monocyte adhesion and their transendothelial migration. Altogether, our in-vivo and in-vitro results support the outcome of a systems biology based network analysis which suggests that epicatechin metabolites mediate their vasculoprotective effects through dynamic regulation of endothelial cell monocyte adhesion and permeability. This study illustrates complex and multimodal mechanisms of action by which epicatechin modulate endothelial cell integrity.

Flavanol metabolites reduce monocyte adhesion to endothelial cells through modulation of expression of genes via p38-MAPK and p65-Nf-kB pathways.

SCOPE: Consumption of flavanol-rich foods is associated with an improvement in endothelial function. However, the specific biologically active flavanol metabolites involved in this benefit, as well as their molecular mechanisms of action have not been identified. The aim of this work was to examine the effect of plasma flavanol metabolites on adhesion of monocytes to TNF-α-activated endothelial cells and identify potential underlying mechanisms. METHODS AND RESULTS: 4'-O-methyl(-)-epicatechin, 4'-O-methyl(-)-epicatechin-7-ß-d-glucuronide, and (-)-epicatechin-4'-sulfate decreased the adhesion of monocytes to endothelial cells at physiologically relevant concentrations, from 0.2 to 1 µM. Transcriptomic studies showed that each of the flavanol metabolites affected the expression of different genes in endothelial cells. However, these genes are involved in the cellular processes that control adhesion and migration of monocytes to vascular endothelium, most notably those regulating cell adhesion, cell-cell junctions, focal adhesion, and cytoskeleton remodeling. Gene expression profiles obtained suggest lower monocyte recruitment, in agreement with results from cell adhesion assays. The nutrigenomic effect of metabolites seems to be mediated through their capacity to modulate phosphorylation of p65 and p38 cell-signaling proteins. CONCLUSION: Our study provides findings into the molecular mechanisms by which plasma flavanol metabolites could be efficient to preserve vascular endothelium integrity in nutritionally relevant conditions.

Mass spectrometry-based metabolomics for the discovery of biomarkers of fruit and vegetable intake: citrus fruit as a case study.

Elucidation of the relationships between genotype, diet, and health requires accurate dietary assessment. In intervention and epidemiological studies, dietary assessment usually relies on questionnaires, which are susceptible to recall bias. An alternative approach is to quantify biomarkers of intake in biofluids, but few such markers have been validated so far. Here we describe the use of metabolomics for the discovery of nutritional biomarkers, using citrus fruits as a case study. Three study designs were compared. Urinary metabolomes were profiled for volunteers that had (a) consumed an acute dose of orange or grapefruit juice, (b) consumed orange juice regularly for one month, and (c) reported high or low consumption of citrus products for a large cohort study. Some signals were found to reflect citrus consumption in all three studies. Proline betaine and flavanone glucuronides were identified as known biomarkers, but various other biomarkers were revealed. Further, many signals that increased after citrus intake in the acute study were not sensitive enough to discriminate high and low citrus consumers in the cohort study. We propose that urine profiling of cohort subjects stratified by consumption is an effective strategy for discovery of sensitive biomarkers of consumption for a wide range of foods.

Flavanone metabolites decrease monocyte adhesion to TNF-α-activated endothelial cells by modulating expression of atherosclerosis-related genes.

Flavanones are found specifically and abundantly in citrus fruits. Their beneficial effect on vascular function is well documented. However, little is known about their cellular and molecular mechanisms of action in vascular cells. The goal of the present study was to identify the impact of flavanone metabolites on endothelial cells and decipher the underlying molecular mechanisms of action. We investigated the impact of naringenin and hesperetin metabolites at 0·5, 2 and 10 µM on monocyte adhesion to TNF-α-activated human umbilical vein endothelial cells (HUVEC) and on gene expression. Except hesperetin-7-glucuronide and naringenin-7-glucuronide (N7G), when present at 2 µM, flavanone metabolites (hesperetin-3'-sulphate, hesperetin-3'-glucuronide and naringenin-4'-glucuronide (N4'G)) significantly attenuated monocyte adhesion to TNF-α-activated HUVEC. Exposure of both monocytes and HUVEC to N4'G and N7G at 2 µM resulted in a higher inhibitory effect on monocyte adhesion. Gene expression analysis, using TaqMan Low-Density Array, revealed that flavanone metabolites modulated the expression of genes involved in atherogenesis, such as those involved in inflammation, cell adhesion and cytoskeletal organisation. In conclusion, physiologically relevant concentrations of flavanone metabolites reduce monocyte adhesion to TNF-α-stimulated endothelial cells by affecting the expression of related genes. This provides a potential explanation for the vasculoprotective effects of flavanones.