Critique 002: Red wine, endothelial function

International Scientific Forum on Alcohol Research

 Critique 002:  26 April 2010

Subject:  Red wine, endothelial function

Red wine, but not other types of alcohol, improve endothelial function in a randomized trial

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Article:  Huang PH, Chen YH, Tsai HY, Chen JS, Wu TC, Lin FY, Sata M, Chen JW, Lin SJ.

Intake of red wine increases the number and functional capacity of circulating  endothelial progenitor cells by enhancing nitric oxide bioavailability.  Arteriosclerosis Thrombosis and Vascular Biology 2010;30:869-877.

 Authors’ Abstract

 Objective: Red wine (RW) consumption has been associated with a reduction of cardiovascular events, but limited data are available on potential mediating mechanisms. This study tested the hypothesis that intake of RW may promote the circulating endothelial progenitor cell (EPC) level and function through enhancement of nitric oxide bioavailability.  Methods and Results: Eighty healthy, young subjects were randomized and assigned to consume water (100 mL), RW (100 mL), beer (250 mL), or vodka (30 mL) daily for 3 weeks. Flow cytometry was used to quantify circulating EPC numbers, and in vitro assays were used to evaluate EPC functions. After RW ingestion, endothelial function determined by flow-mediated vasodilation was significantly enhanced; however, it remained unchanged after water, beer, or vodka intake. There were significantly increased numbers of circulating EPC (defined as KDR(+)CD133(+), CD34(+)CD133(+), CD34(+)KDR(+)) and EPC colony-forming units only in the RW group (all P<0.05). Only RW ingestion significantly enhanced plasma levels of nitric oxide and decreased asymmetrical dimethylarginine (both P<0.01). Incubation of EPC with RW (but not beer or ethanol) and resveratrol in vitro attenuated tumor necrosis factor-alpha-induced EPC senescence and improved tumor necrosis factor-alpha-suppressed EPC functions and tube formation. Incubation with nitric oxide donor sodium nitroprusside significantly ameliorated the inhibition of tumor necrosis factor-alpha on EPC proliferation, but incubation with endothelial nitric oxide synthase inhibitor L-NAME and PI3K inhibitor markedly attenuated the effect of RW on EPC proliferation.       

Authors’ Conclusion: The intake of RW significantly enhanced circulating EPC levels and improved EPC functions by modifying nitric oxide bioavailability. These findings may help explain the beneficial effects of RW on the cardiovascular system. This study demonstrated that a moderate intake of RW can enhance circulating levels of EPC in healthy subjects by increasing nitric oxide availability. Direct incubation of EPC with RW and resveratrol can modify the functions of EPC, including attenuation of senescence and promotion of EPC adhesion, migration, and tube formation. These data suggest that RW ingestion may alter the biology of EPC, and these alterations may contribute to its unique cardiovascular-protective effect.

Forum Comments:  This well-done randomized trial in healthy adults demonstrated that a small amount of red wine (100 ml) consumed daily over three weeks resulted in an increase in circulating endothelial progenitor cells (EPC) and enhanced endothelial function.  A significant effect did not occur after the similar consumption of water, 250 ml of beer, or 30 ml of vodka, suggesting that non-alcoholic constituents of red wine led to the effects seen.  The authors also carried out a number of in-vitro experiments that supported the effects from the clinical trial.  Previous research has clearly shown that endothelial function is related strongly to the development and progression of atherosclerosis and coronary artery disease.

            The resveratrol concentration used for the incubation studies was high 50 µM (about 11.4 mg/L), while red wine typically has levels of <1 mg/L (although occasional wines are higher).  Thus, a 1% wine solution is more likely to have a resveratrol concentration of about 0.01 mg/L (about 1000 times lower than those used in the resveratrol incubations in this study). This suggests that the study cannot really show the effects on endothelial function of levels of resveratrol that are present in red wine.  Some data on the polyphenol analysis of the wine would have been helpful.  Further, it would have been interesting if the known stereo isomer of catechin, that dilates blood vessel walls, was also used for the in vitro work.

           An extra study group in the clinical trial that consumed a red wine extract or grape seed extract could have confirmed whether a similar effect was observed to RW without any alcohol consumption.  Further, it would have been useful to have a wash-out period at the end of the trial to determine if the changes returned to their baseline values.  It is interesting that the authors state that levels of HDL-cholesterol were not increased by the interventions containing alcohol.  No specific details are given in the paper, and Apo E4 levels of the subjects (which could blunt the HDL response to alcohol) are not reported.    

           It has been shown that phenolic compounds (mainly procyanidins) activate NO release.  The recent paper by Caton et al (Caton PW, Pothecary MR, Lees DM, Khan NQ, Wood EG, Shoji T, Kanda T, Rull G, Corder R.  Regulation of vascular endothelial function by procyanidin-rich foods and beverages,  J Agric Food Chem 2010;58:4008-4013), on the regulation of vascular endothelial function by procyanidin-rich food and vegetables, reviews such data and proposes a rather convincing mechanistic model.  Thus, it comes as no surprise that the present paper found that red wine improves endothelial function in terms of flow-mediated vasodilation.

          The reported effect or red wine on EPC is also clear cut.  Granted that the observed effects in vitro are correct, the link to the macroscopic evidence on humans is not straightforward.  If we consider that Viagra produces a quite similar effect on EPC as red wine (Dussault S. et al. Sildenafil increases endothelial progenitor cell function and improves ischemia-induced neovascularization in hypercholesterolemic apolipoprotein E-deficient mice. Hypertension 2009;54:1043-1049) a different mechanism, based on cGMP signaling and vasodilation could be involved, although different studies seem to converge on Akt signaling as the final outcome. On a more speculative ground this study corroborates the concept that the protective effect of wine descends from an hormetic effect of ethanol, with xeno-hormetic effects of some natural compounds.

          Overall, many observational epidemiologic studies, especially in Europe, suggest that the consumption of wine may have additional beneficial effects over those of alcohol itself in terms of lower cardiovascular risk.  However, there has always been a question of potential confounding by other lifestyle factors associated with wine consumption (in that wine drinkers in many studies tend to drink more moderately, smoke less, eat a healthier diet, etc.).  Thus, the importance of this study is that among young healthy subjects with similar characteristics at baseline, those randomly assigned to consume a small amount of red wine (abut 3 ounces) showed significant beneficial effects on endothelial function, an effect not seen with other beverages (beer, vodka) containing similar amounts of alcohol.  The results of this trial are consistent with a very large number of in-vitro studies and animal experiments showing beneficial effects of red wine, red wine extract, or certain polyphenols or other constituents of wine.

Lay Summary:  In a randomized trial among healthy young adults, the daily consumption of about 3 ounces of red wine for three weeks led to significant improvement in endothelial function, a key factor associated with the development and progression of atherosclerosis and coronary heart disease.  Such improvements were not seen with the consumption of water or of beer or vodka containing similar amounts of alcohol.  Further, in a series of in-vitro studies, the authors showed very similar effects from red wine and from a high concentration of resveratrol (but not from beer or ethanol) on factors associated with improved endothelial function.  The study supports many epidemiologic and animal experiments suggesting that certain non-alcoholic constituents of red wine have additional beneficial effects on cardiovascular risk over those of just the alcohol itself.

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 Contributions to this critique by the International Scientific Forum on Alcohol Research were made by  

Dee Blackhurst, PhD, Lipid Laboratory, University of Cape Town Health Sciences Faculty, Cape Town, South Africa

Roger Corder, PhD, MRPharmS, William Harvey Research Institute, Queen Mary University of London, UK

Luc Djoussé, MD, DSc, Dept. of Medicine, Division of Aging, Brigham & Women’s Hospital and Harvard Medical School, Boston, MA, USA

Gordon Troup, MSc, DSc, School of Physics, Monash University, Victoria, Australia

Fulvio Ursini, MD, Dept. of Biological Chemistry, University of Padova, Padova, Italy

R. Curtis Ellison, MD, Section of Preventive Medicine & Epidemiology, Boston University School of Medicine, Boston, MA, USA