Colonic metabolites from flavanols stimulate nitric oxide production in human endothelial cells and protect against oxidative stress-induced toxicity and endothelial dysfunction

Abstract

Oxidative stress is involved in endothelial dysfunction, the key player in the development of vascular events. Flavanols, the major antioxidants in cocoa have been related to vascular protection and lower cardiovascular risk. However, the bioavailability of cocoa flavanols is very low and their bioactivity in vivo seems to be greatly mediated by the derived phenolic metabolites formed by intestinal microbiota. Hence, we investigated whether microbial-derived flavanol metabolites 3,4-dihydroxyphenylacetic acid (DHPAA), 2,3-dihydroxybenzoic acid (DHBA), 3-hydroxyphenylpropionic acid (HPPA) and a mix of them could influence endothelial function and prevent oxidative stress in human endothelial cells (Ea.hy926). Our results revealed that a mixture of flavanol colonic metabolites significantly increased phosphorylation of endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) production. By using specific inhibitors, we also established the participation of the adenosine monophosphate-activated protein kinase (AMPK) and protein kinase B (AKT) in eNOS activation. Likewise, flavanol metabolite mix protected against oxidative stress-induced endothelial dysfunction and cell death by preventing increased ROS generation and activation of signaling pathways related to oxidative stress. We concluded that flavanol colonic metabolites could exert beneficial effects in endothelial cells and prevent oxidative stress-induced vascular dysfunction.

(−)-Epicatechin and the colonic metabolite 2,3-dihydroxybenzoic acid protect against high glucose and lipopolysaccharide-induced inflammation in renal proximal tubular cells through NOX-4/p38 signalling

“…The rationale for selecting these concentrations of phenolic compounds is that these doses are considered to be within the range recommended for in vitro studies, and they can be found in biological fluids; 11 in addition, beneficial effects have been reported with similar concentrations of phenolic compounds in previous studies with cellular models resembling diabetes, including renal cells. 6,7,16,17,24 As shown in Table 2, none of the tested concentrations of EC or phenolic metabolites increased the levels of TNF-α or IL-6 in the culture medium, indicating no induced cellular inflammation. In agreement with these results, we have already reported that in NRK-52E a 24 h-treatment with the same concentrations of EC and phenolic metabolites used in the present work did not evoke damaging changes or enhanced ROS generation.…”

“…11,12 Indeed, similarly to the monomer EC, colonic phenolic acids seem to exert antidiabetic effects by multiple mechanisms. 7 EC and some colonic polyphenolic metabolites are able to prevent key features of diabetic complications related to insulin sensitivity and oxidative stress, 12,[16][17][18] and avert inflammation in insulinsensitive tissues. 6,9,12,19 Nevertheless, the role of the inflammatory cytokines in injury during DKD is largely unknown, and in line with this, it also remains unclear whether EC and the colonic phenolic metabolites derived from the intake of flava-nols exert a protective effect on renal tubular cells against inflammation during diabetes.…”

Polyphenols in human nutrition: from thein vitroantioxidant capacity to the beneficial effects on cardiometabolic health and related inter-individual variability – an overview and perspective

“…The results of in silico docking were confirmed with Western blot analysis, demonstrating a decreased phosphorylation of mitogenactivated protein kinase and p65 unit of NF-κB, pertinent to the modulation of upstream kinases, and the degreased leucocyte transendothelial migration and inflammation (84) . In addition, it has been demonstrated that flavanol colonic metabolites activate endothelial nitric oxide synthase in human endothelial cells via AKT and AMP-activated protein kinase signalling and increase intracellular nitric oxide, which plays a pivotal role in regulation of endothelial function (85) . An integrated systems' biology approach has been taken recently to elucidate the multi-target and multi-layer cellular effects of circulating epicatechin metabolites on endothelial cells, demonstrating modulation in gene and microRNA expressions and DNA methylation.…”

Cocoa intake attenuates renal injury in Zucker Diabetic fatty rats by improving glucose homeostasis

“…The role of the insulin signalling pathway in the kidney is thought to contribute to the maintenance of the renal glucose homeostasis (Alvarez-Cilleros, D. et al, 2018, Artunc, F. et al, 2016, Mitrakou, A., 2011, Rahmoune, H. et al, 2005.…”