Abstract
Cerebral blood vessels are lined with endothelial cells and form the blood-brain barrier. Their dysfunction constitutes a crucial event in the physiopathology of neurodegenerative disorders and cognitive impairment. Epicatechin can improve cognitive functions and lower the risk for Alzheimer’s disease or stroke. However, molecular mechanisms of epicatechin on brain vascular endothelium are still unexplored. The objective of this study was to investigate the biological effects of gut microbiome-derived metabolites of epicatechin, 5-(4′-Hydroxyphenyl)-γ-valerolactone-3′-sulfate and 5-(4′-Hydroxyphenyl)-γ-valerolactone-3′-O-glucuronide, in TNF-α-stimulated human brain microvascular endothelial cells at low (nM) concentrations by evaluating their multi-omic modification (expression of mRNA, microRNA, long non-coding RNAs, and proteins). We observed that metabolites are biologically active and can simultaneously modulate the expression of protein-coding and non-coding genes as well as proteins. Integrative bioinformatics analysis of obtained data revealed complex networks of genomics modifications by acting at different levels of regulation. Metabolites modulate cellular pathways including cell adhesion, cytoskeleton organization, focal adhesion, signaling pathways, pathways regulating endothelial permeability, and interaction with immune cells. This study demonstrates multimodal mechanisms of action by which epicatechin metabolites could preserve brain vascular endothelial cell integrity, presenting mechanisms of action underlying epicatechin neuroprotective properties.
Highlights
Polyphenols are among the most abundant phytochemicals found in plant foods
The objective of this study was to investigate the biological effects of major gut microbiome-derived metabolites of epicatechin, 5-(4 -Hydroxyphenyl)-γ-valerolactone-3 -sulfate and 5-(4 -Hydroxyphenyl)-γ-valerolactone-3 -O-glucuronide, in TNF-α-stimulated human brain microvascular endothelial cells at low concentrations and times of exposure by evaluating their multi-omic modification, including changes in the expression of protein-coding genes, non-coding microRNA and long non-coding RNA genes together with proteomics modifications
We found that of the total differentially expressed transcripts, 85.5% correspond to proteincoding genes (642 mRNAs), 3.1% to miRNAs (23 miRNAs), and 11.4% to long non-coding RNA (lncRNA) (86 lncRNAs) (Figure 1B)
Summary
Polyphenols are among the most abundant phytochemicals found in plant foods. They comprehend several families of compounds, with the most represented in the human diet being phenolic acids and flavonoids (Vogiatzoglou et al, 2015). Flavanols are a class of flavonoids found in fruits and they exist in monomeric (cathechins and epicatechins), and polymeric (proanthocyanidines) forms They are commonly found in cocoa, tea, and various fruits, such as apple or grape. Epicatechin can be absorbed in the small intestine, rapidly conjugated by phase I and phase II detoxification enzymes, and appears in the circulation between 1–4 h after ingestion with major metabolites such as E3 G, E3 S, 3 ME5S, and 3 ME7S (Ottaviani et al, 2016). These metabolites are absent from plasma after 8 h, at the point when the ingested epicatechin reaches the intestine and the colon. Very few studies suggested that these γ-valerolactones are bioactive by exerting anti-inflammatory properties or decreasing blood pressure (Mena et al, 2019), such studies remain very scarce
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