Dark Chocolate and Platelet Function in Humans
Condition: Cardiovascular Disease
MeSH terms: Cardiovascular Diseases
Study type: Interventional

Summary: 
      Cardiovascular disease is a major cause of mortality worldwide and responsible for one out of
      three global deaths. A main characteristic of cardiovascular disease is impaired blood flow
      and formation of blood clots. Platelets are clot-forming cells responsible for the prevention
      of bleeding. However, in disease conditions they may be overly activated, promoting blood
      clots and blockage of blood vessels.

      Consumption of diets rich in fruits and vegetables decreases mortality from cardiovascular
      disease through a number of mechanisms, including the prevention of platelet clotting and
      aggregation. There is some evidence suggesting that platelet aggregation may be modulated
      through a group of compounds known as flavan-3-ols, which are found in various foods, and
      especially in cocoa. However, the mechanisms by which those compounds affect platelet
      function are not yet fully understood. We designed a human study assessing the mechanisms by
      which flavan-3-ols from cocoa beneficially affect platelet function and the platelet
      proteome.
    

Detailed description: 
      Cardiovascular disease (CVD) is a primary cause of premature deaths worldwide, with incidence
      rates in the United Kingdom, particularly in Scotland, being amongst the highest worldwide.
      Thus identification of dietary components that most effectively prevent CVD is potentially of
      wide public health benefit.

      Consumption of diets rich in plant-based products protects against the development of CVD.
      Such effects have been ascribed in part to polyphenols, which are non-nutritive but,
      potentially bioactive secondary metabolites ubiquitous found in fruits, vegetables, herbs,
      spices, teas and wines. The beneficial effects of polyphenols on CVD is believed to be
      mediated, at least in part, though improving platelet function. At least 10 human
      intervention studies found a consistent and robust beneficial effect of cocoa products on
      platelet function, but unfortunately all of these studies used only one or two methods to
      assess platelet function, therefore only getting limited insights into the complex
      physiological behavior of platelets. In addition, none of these studies assessed potential
      mechanisms by which flavan-3-ols may inhibit platelet function. Schramm et al. have shown
      that consumption of chocolate rich in flavan-3-ols and their oligomers (procyanidins) lead to
      increased production of prostacyclin, a strong platelet inhibitor. This finding has also been
      observed when aortic endothelial cells are treated with procyanidins in vitro. Thus the
      stimulation of prostacyclin production in endothelial cells may reflect one pathway by which
      flavan-3-ols indirectly inhibit platelet activation. Many other potential mechanisms are
      discussed in the literature but so far the evidence for such mechanisms is limited or
      non-existing.

      In this study we assess effects of consumption of chocolate enriched in flavan-3-ols on
      platelet function by measuring not only platelet aggregation, but also in vitro coagulation
      and platelet activation in healthy humans. In addition, we examine the effects of consumption
      of flavan-3-ols on the regulation of the platelet proteome to elucidate pathways by which
      these bioactive cocoa compounds affect platelet function.

      HYPOTHESIS

      Acute consumption of a moderate amount of dark chocolate enriched in flavan-3-ols results in
      decreased platelet activation and aggregation by decreasing the levels of thromboxane A2
      produced by endothelial cells.

      OBJECTIVES

      The main objective of the proposed study is to determine whether consumption of 60 g dark
      chocolate enriched in flavan-3-ols results in decreased platelet activation and aggregation
      by decreasing levels of thromboxane A2, as well as assessing what other mechanisms could be
      involved.

      The specific objectives of the proposed study are to determine:

        1. whether acute intake of 60 g dark chocolate enriched in flavan-3-ols, as compared with
           standard dark chocolate low in flavan-3-ols and white chocolate containing no
           flavan-3-ols, affects platelet aggregation, thromboxane A2 formation upon aggregation,
           in vitro bleeding time, P-selectin expression, and activation of the fibrinogen
           receptor;

        2. whether and how acute intake of 60 g dark chocolate enriched in flavan-3-ols, as
           compared with standard dark chocolate and white chocolate, affects the platelet
           proteome, and thereby potential new biomarkers of platelet function, as well as protein
           levels of anti-oxidant enzymes;

        3. identities and concentrations of flavan-3-ols and their metabolites in plasma and/ or
           urine 2 and 6 h after acute intake of 60 g dark chocolate enriched in flavan-3-ols, as
           compared with standard dark chocolate and white chocolate.
    

Intervention name(s): Dark chocolate enriched in flavan-3-ols and procyanidins; Standard dark chocolate; White chocolate
Intervention type(s): Dietary Supplement; Dietary Supplement; Dietary Supplement
Intervention description(s): Acute consumption (within 15 minutes) of 60 g of chocolate containing ~900 mg of total flavan-3-ols and procyanidins.; Acute consumption (within 15 minutes) of 60 g of chocolate containing ~400 mg total flavan-3-ols and procyanidins.; Acute consumption (within 15 minutes) of 60 g of white chocolate containing no flavan-3-ols and procyanidins.
Other intervention name(s): CocoanOX12%-containing chocolate
Intervention MeSH terms: Proanthocyanidin; Procyanidin
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Single (Investigator)
Primary purpose: Prevention
Keywords: Platelets; Platelet aggregation; Platelet activation; Platelet function; Light transmission aggregometry; Platelet Function Analyzer-100 (PFA-100); P-selectin; Fibrinogen receptor; Glycoprotein IIb-IIIa; Chocolate; Cocoa; Flavan-3-ols; Procyanidins