Nanomolar Caffeic Acid Decreases Glucose Uptake and the Effects of High Glucose in Endothelial Cells
November
Nanomolar Caffeic Acid Decreases Glucose Uptake and the Effects of High Glucose in Endothelial Cells
Lucia Natarelli 0 1 2
Giulia Ranaldi 0 1 2
Guido Leoni 0 1 2
Marianna Roselli 0 1 2
Barbara Guantario 0 1 2
Raffaella Comitato 0 1 2
Roberto Ambra 0 1 2
Francesco Cimino 0 1 2
Antonio Speciale 0 1 2
Fabio Virgili 0 1 2
Raffaella Canali 0 1 2
0 Current address: Institute for Cardiovascular Prevention, Ludwig-Maximilians-University , Munich , Germany
1 1 Council for Agricultural Research and Economics, Food and Nutrition Research Centre , Rome , Italy , 2 Department of Physics, Sapienza University of Rome , Rome , Italy , 3 Department of Drug Sciences and Health Products, University of Messina , Messina , Italy
2 Editor: Shilpa J Buch, University of Nebraska Medical Center , UNITED STATES
Epidemiological studies suggest that moderate and prolonged consumption of coffee is associated with a reduced risk of developing type 2 diabetes but the molecular mechanisms underlying this effect are not known. In this study, we report the effects of physiological concentrations of caffeic acid, easily achievable by normal dietary habits, in endothelial cells cultured in 25 mM of glucose (high glucose, HG). In HG, the presence of 10 nM caffeic acid was associated with a decrease of glucose uptake but not to changes of GLUT-1 membrane localization or mRNA levels. Moreover, caffeic acid countered HG-induced loss of barrier integrity, reducing actin rearrangement and FITC-dextran passage. The decreased flux of glucose associated to caffeic acid affected HG induced apoptosis by down-regulating the expression of initiator (caspase 8 and 9) and effector caspases (caspase 7 and 3) and by increasing the levels of phosphorylated Bcl-2. We also observed that caffeic acid in HG condition was associated to a reduction of p65 subunit nuclear levels with respect to HG alone. NF-κB activation has been shown to lead to apoptosis in HG treated cells and the analysis of the expression of a panel of about 90 genes related to NF-κB signaling pathway revealed that caffeic acid significantly influenced gene expression changes induced by HG. In conclusion, our results suggest that caffeic acid, decreasing the metabolic stress induced by HG, allows the activation of survival mechanisms mediated by a different modulation of NFκB-related signaling pathways and to the activation of anti-apoptotic proteins.
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Funding: This work was supported by the Italian
Ministry of Agricultural and Nutritional Policies and
Forestry (Special Research Projects MiPAAF
NUME and MiPAAF - MEDITO). The authors are
grateful to the Epigenomics Flagship Project—
EPIGEN. The funders had no role in study design,
data collection and analysis, decision to publish, or
preparation of the manuscript.
Persistent hyperglycemia, a chronic increase of blood glucose levels, is one of the most evident
features of type 2 diabetes (T2D). At cellular level, high glucose (HG) significantly affects the
Competing Interests: The authors have declared
that no competing interests exist.
metabolic homeostasis and is associated to a progressive failure of several tissues and of the
system response, including immune response and vascular function [1]. Endothelium is
profoundly affected by HG as it is the first tissue exposed to changes of glucose levels. A chronic
and prolonged exposure to elevated glucose levels has been recognized to cause endothelium
dysfunction and correlated diseases, from blindness to atherosclerosis [2]. At molecular level,
HG has been reported to impair cellular responses associated to increased permeability [3, 4]
and to a generalized condition of vascular inflammation, eventually leading to cell death [5, 6].
The activations of protein kinase C (PKC), hexosamine flux [7] and NF-κB activation [8] have
been reported as mainly effectors of HG in endothelial cells.
Together with wine and tea, coffee is one of the most widely consumed polyphenol and
phenolic acid rich beverages in the world. Hydroxycinnamic acids are the major class of phenolic
acids in coffee. Among them, chlorogenic acid that is eventually metabolized to caffeic acid
(CA), p-coumaric acid and ferulic acids are the most represented ones. Health benefits of
polyphenols have been widely claimed on the basis of the evident inverse relationship linking the
consumption of polyphenols-rich food items with a wide spectrum of degenerative diseases,
including cardio-vascular disease and cancer, and chronic inflammation [9, 10]. More
specifically, several epidemiological studies reported that moderate and prolonged consumption of
coffee is associated with a reduced risk T2D [11, 12]. However, in spite of the general
agreement about the potential beneficial effects of coffee polyphenol consumption, only few in vitro
studies considered their real bioavailability in humans and therefore no information are
available about the effects of physiological concentrations of CA. This aspect is obviously
fundamental f (...truncated)