Plant foods and cardiovascular health: looking for mechanisms of action

Abstract

Given the importance of vegetable foods in the prevention of CVDs and in the maintenance of vascular health, this PhD researcher project was aimed to investigate the role of specific vegetable components, such as betaine, choline and polyphenol metabolites on different mechanisms putatively related to CVD health. Betaine and choline are two methyl donors that convert homocysteine to methionine while polyphenols diminish the oxidative stress. Specifically, the work has been focused on the evaluation of the role of betaine and choline on different inflammatory markers and on the role of phenolic metabolites on the modulation of NADPH oxidase activity, the key enzyme of oxidative stress through its role in reactive oxygen species production. In particular, the research work addressed two questions: 1) whether betaine and choline intake from the diet are related to inflammation, and 2) what is the effect of metabolites derived from berries and coffee polyphenols on the reduction of superoxide anion production in a cell line suitable as an in vitro model for atheroma. The two research lines hereby described resulted into two research papers. Survey on betaine and choline content in food products consumed in Italy, dietary intake and relation with traditional and emerging CVD risk factors. We have determined the content of betaine and free choline in products commonly consumed in Italy in order to estimate the daily intake in the Italian population and to assess the association with markers of inflammation and components of the metabolic syndrome in a cross-sectional study of a healthy population living in Northern Italy. Betaine and free choline content was measured by high-pressure liquid chromatography – tandem mass spectrometry (HPLC MS/MS) in 28 common cereal products mainly consumed in Italy such as pasta, bread and other bakery products and in 23 vegetables such as spinach, beet and others. Under the context of the cross-sectional survey that enrolled 469 healthy subjects living in the Parma area, data on clinical biochemistry and functional anthropometry were gathered and the correlation of betaine and choline with inflammatory marker was studied. Information on diet was collected via 3-day dietary questionnaires. The outcomes of this survey revealed a high content of betaine and free choline in wholemeal foods; betaine was also found at high concentrations in beetroot and spinach. In population of this study, betaine intake showed a positive correlation with component of metabolic syndrome and inflammatory biomarker C-reactive protein, an independent risk factor of cardiovascular event, while dietary choline showed no association. Superoxide anion production in cultured human promonocyte cells THP-1 due to polyphenol metabolites. In the in vitro study we have investigated the effect of different colonic metabolites derived from berries and coffee polyphenols on the modulation of NADPH oxidase-dependent superoxide anion production in monocytes THP-1. The molecules were tested at the low concentrations actually found in the bloodstream after absorption on a cell line implicated in atheroma after PMA stimulation. The bioluminescence technique was employed for the assessment of O2.- production. The results obtained in our in vitro study demonstrated that polyphenol catabolites of colonic origin are not capable to reduce the oxidative stress through modulation of NADPH system.

Taken altogether, these data seem to indicate that the protection exerted by dietary sources of these classes of molecules, such as whole grain cereals, fruits and vegetables, is not directly related to the compounds assessed in this study, or at least, is not specifically related to the mechanisms investigated. Further studies are warranted in order to elucidate the role of betaine and choline, as well as the role of phenolic metabolites, in the beneficial effects of whole grain cereals, fruits and vegetables on risk of cardiovascular disease and atherosclerosis.