Differential Effects of Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) on Platelet, Endothelial and Vascular Function

• Platelet Monocyte Aggregates (PMA) [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  The endothelium plays a vital role in the regulation of blood flow, thrombosis and inflammation. Endothelium-derived anti-adhesive and anti-aggregant substances, including prostacyclin and nitric oxide, are known to inhibit platelet activation. Endothelial dysfunction or vessel wall injury lead to the activation of platelets, of which platelet-monocyte-aggregates (PMA) are a sensitive marker, and were shown to inversely correlate with markers of EF in patients with stable CHD. The measurement of PMA by flow cytometry is a method which reduces ex vivo platelet activation to its minimum and is believed to represent platelet activation in vivo.
  
  
• Endothelial Progenitor Cell (EPC) counts [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  EPCs are a subgroup of circulating progenitor cells that are recruited from the bone marrow to repair the injured vasculature. They have been associated with a reduced CVD risk and may serve as markers of endothelial function because they represent a greater capacity for the endothelium to repair itself. Two populations of EPCs were measured by flow cytometry, described as 'early EPC' (KDR+/CD34+/CD133+) and 'late EPCs' (KDR+/CD34+/CD31+).
  
  

• Capillary density [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  Capillary rarefaction has been associated to CVD risk factors such as hypertension, smoking and obesity. The cutaneous circulation has emerged as an accessible and representative vascular bed to look at microvascular dysfunction. Capillary density was measured by a Capiscope (kk technologies)
  
  
• Arterial stiffness [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  Pulse wave analysis (PWA) was used to measure indices of arterial stiffness, including peripheral and central augmentation index, as well as central systolic and diastolic blood pressure. Digital volume pulse (DVP) was used to measure reflection and stiffness indices.
  
  
• Blood Pressure (BP) and Heart Rate (HR) [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  Resting HR and BP were measured in the seated and supine position after 15 minute rest, on the days of both baseline and endpoint visits. In addition, ambulatory BP and HR (24h, daytime, nighttime) was measured 2-3 days prior to each visit.
  
  
• Plasma isoprostane concentrations [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  8-iso-prostaglandin-F2α (8-IsoP-F2α), a prostaglandin F2-like compound biosynthesized nonenzymatically by a free-radical oxygenation of arachidonic acid, was measured in plasma in order to assess oxidative stress.
  
  
• Plasma Nitrate and Nitrites (NOx) concentrations [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  Plasma NOx was measured as a circulating marker of endothelial function.
  
  
• Serum total cholesterol concentration [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  
• Serum Triacylglycerol concentrations [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  
• Serum high density lipoprotein concentration [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  
• Serum low density lipoprotein concentration [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  
• Serum non esterified fatty acids (NEFA) concentration [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  
• Serum Apolipoprotein B concentration [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  
• Plasma glucose concentration [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  
• Plasma insulin concentration [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  
• Serum adiponectin concentration [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  
• Serum resistin concentration [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  
• Erythrocyte phospholipid fatty acid profiles [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  The EPA and DHA content of erythrocyte lipids were used as a marker of compliance.
  
  
• Fatty acid profile of plasma non esterified fatty acid fraction [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]
  

Relatively few studies have made a head-to-head comparison of DHA (22:6n-3) with EPA (20:5n-3). The understanding of this differential effect may be of great interest in populations with low EPA intake such as vegetarians, who may choose to supplement their dietary intake of long-chain n-3 PUFA in the form of DHA-rich algal oil.

This study aimed to investigate the effect of supplementation with oils rich in either EPA or DHA (3g/day, 6 weeks) in healthy young males on platelet, endothelial and vascular function, as well as other CVD risk factors. The primary outcomes were platelet monocyte aggregates and endothelial progenitor cells - novel markers of platelet and endothelial function, measured by flow cytometry, Secondary outcomes included capillary density, measured by capillaroscopy to assess changes in microvascular function, pulse wave analysis, digital volume pulse and ambulatory blood pressure. Other secondary outcomes included lipid profiles (TAG, cholesterol, NEFA), glycaemic control (HOMA, QUICKI) and oxidative stress (isoprostane). The omega-3 index (erythrocyte EPA+DHA) was used as a marker of compliance.