Acute Effects of the Consumption of Dark Chocolate Enriched in Flavan-3-ols on Platelet Function and the Platelet Proteome
Trial Snapshot
- Phase
- Not Applicable
- Status
- Completed
- Sponsor
- University of Aberdeen
- Enrollment
- 42
- Locations
- 2
- Primary Endpoint
- Change in light transmission aggregometry of platelet-rich plasma
Study Overview
Brief 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.
Study Design
- Study Type
- Interventional
- Allocation
- Randomized
- Intervention Model
- Crossover
- Primary Purpose
- Prevention
- Masking
- Single (Investigator)
Eligibility Criteria
- Ages
- 18 Years to 70 Years (Adult, Older Adult)
- Sex
- All
- Accepts Healthy Volunteers
- Yes
Inclusion Criteria
- •Healthy male and/or female volunteers, aged between 18 and 70 years
Exclusion Criteria
- •Subjects are excluded if:
- •they are taking aspirin or aspirin-containing drugs, other anti-inflammatory drugs, or any drugs or herbal medicines known to alter platelet function or the haemostatic system in general (without a minimum washout period of one month)
- •they are taking fish oils or evening primrose oil, or fat soluble vitamin supplements within the last 4 weeks
- •they are taking any medicine known to affect lipid and/or glucose metabolism
- •they are taking hormone replacement therapy
- •they have any known clinical signs of diabetes, hypertension, renal, hepatic, hematological disease, gastrointestinal disorders, endocrine disorders, coronary heart disease, infection or cancer
- •they are suffering from alcohol or any other substance abuse or are having eating disorders
- •they are usually consuming a vegetarian diet
- •they have a BMI below 18 or above 35 kg/ sqm
- •they are undertaking more than 6 hours of vigorous exercise per week
- •they are having an abnormal menstrual cycle
- •they are pregnant
- •they suffer from an allergy to cocoa or any of the ingredients contained within either of the chocolate bars
- •they have been giving a pint of blood for transfusion purposes within the last month
- •they have a low platelet count (< 170 x 10E09/ L)
- •they have unsuitable veins for blood sampling and/ or cannulation
- •their hematocrit is below 40 % for males and 35 % for females
- •their haemoglobin is below 130 g/ L for males and 115 g/ L for females
- •they are not able to travel on their own to the Rowett Institute of Nutrition and Health, Aberdeen for each of the interventions
Outcomes
Primary Outcomes
Change in light transmission aggregometry of platelet-rich plasma
Time Frame: Post-prandial, up to 6 hours after chocolate consumption
* Using a Helena Platelet Aggregation Chromogenic Kinetics System-4 (PACKS-4) light transmission aggregometer * Induced by adenosine diphosphate (ADP) and thrombin receptor-activating peptide (TRAP)
Secondary Outcomes
- Levels of prostacyclin and/ or leukotrienes in plasma(Post-prandial, up to 6 hours after chocolate consumption)
- Total phenolics in urine(Post-prandial, up to 6 hours after chocolate consumption)
- Change in ex vivo bleeding time using the Platelet Function Analyzer-100 (PFA-100)(Post-prandial, up to 6 hours after chocolate consumption)
- Change in P-selectin expression and activation of the fibrinogen receptor by flow cytometry(Post-prandial, up to 6 hours after chocolate consumption)
- Levels of flavan-3-ols and their metabolites in plasma and urine(Post-prandial, up to 6 hours after chocolate consumption)
- Changes in the platelet proteome(Post-prandial, 2 hours after chocolate ingestion)
- Changes in thromboxane A2 production induced by ADP and TRAP(Post-prandial, up to 6 hours after chocolate consumption)
- Total catechins in urine(Post-prandial, up to 6 hours after chocolate consumption)
- Urinary creatinine(Post-prandial, up to 6 hours after chocolate consumption)
- Analysis of flavan-3-ol and procyanidin contents in study chocolates(At the beginning (April 2009) and end (October 2009) of the intervention period)
- Non-targeted 1H-NMR of plasma and urine samples(Post-prandial, up to 6 hours after chocolate consumption)
- Non-targeted LC-MS of urine samples(Post-prandial, just before and 6 hours after chocolate consumption)
- Markers of oxidative stress in plasma(Post-prandial, up to 6 hours after chocolate consumption)
- Fatty acid analysis of study chocolates(Shortly after the intervention period was finished (February 2009))