The Impact of Fish-oil Fatty Acids on Postprandial Vascular Reactivity

The primary aim of this study is to determine the impact of individual fish oil fatty acids on vascular reactivity and to identify underlying physiological and molecular mechanism of any observed effects. In addition response to intervention according to genotype will be determined retrospectively.

A loss of vascular reactivity and increased vascular tone is being increasingly recognised as a significant cardiovascular disease (CVD) risk factor and highly predictive of future CVD events. A previous study by our group has shown the inclusion of a fish oil mixture administered alongside a high fat meal preserves postprandial vascular function in healthy men \[1\]. In this three arm, placebo controlled cross over study, the impact of individual fatty acids contained within fish-oil on postprandial vascular reactivity (measured at 4 hour post test meal) will be assessed for the first time. Clinical measurements of vascular function which correlate with CVD risk factors and are predictive of future CVD events will be undertaken in order to assess any potentially beneficial effects. In addition plasma samples will be taken at 0 and 4 hours to determine the change in concentration of modulators of vascular tone. Accordingly, our nutrients of interest which will be administered in the intervention arms of the study, will be present in this lipoprotein rich fraction. By exposing cells in culture to these EPA- and DHA-enriched lipoproteins, mechanisms underlying the vascular response in our human volunteers will be investigated. Finally we will measure the plasma fatty acid profile to confirm that circulating concentrations of EPA and DHA are increasing postprandially according to intake.

As it is now recognised that genetic variation, in addition to being an important determinant of the risk of all known chronic diseases, plays a large part in determining an individual's response to dietary change, DNA will be extracted from whole blood taken at the clinical screening and stored for subsequent genotyping for variants likely to be important in the regulation of EPA and DHA metabolism and vascular tone. Although the current study will not be fully powered to generate definite conclusion regarding genotype\*diet interactions, it will serve to generate pilot data for future studies.

Eligibility Criteria:
Inclusion Criteria:

In order to recruit a population at a relative risk of developing CVD of \>1.5 males aged 35-55 years, who possess one of the following risk factors for CVD will be recruited through local advertisement:

* Total cholesterol \> 6mmol/L
* High density lipoprotein cholesterol (HDLC) \< 1.0mmol/L
* Systolic blood pressure \> 140 mmHg
* Diastolic blood pressure \> 90 mmHg
* Waist circumference \> 102cm

Exclusion Criteria:

Current smokers, or ex-smokers ceasing \< 3 months ago

Subjects with existing or significant past medical history of vascular disease or any medical condition likely to affect the study measures e.g. vascular disease, circulatory (i.e. Reynaud's), diabetes, systemic lupus erythematosus, hepatic, renal, digestive, haematological, neurological, cancer or thyroidal disease.

Those with known allergies to the intervention foods / commercially available supplements.

Those unprepared to adhere to dietary restrictions during the trial i.e. for 3 days preceding each assessment visit (and for a 3 day run-in period) or unwilling to comply with the assessments per protocol.

Parallel participation in another research project which involves concurrent dietary intervention and/or sampling of biological fluids/material.

Having vaccinations (excluding the flu vaccination) or antibiotics within 3 months of start of trial, and those with vaccinations scheduled for during the trial.

Taking EPA or DHA containing food / dietary supplements likely to affect the study results e.g. supplements derived from marine organisms which equate to a greater than 1 gram of EPA and DHA per daily serving. Prospective participants who are willing to cease supplementation 2 month preceding, and during, the trial will be considered on a case by case basis.

Habitual consumption of more than one portion of oily fish per week (as defined as 140g of any oil fish, including salmon, trout, mackerel, sardines, pilchards, herring, kipper, eel, whitebait, etc).

Prescribed lipid lowering, medicine affecting lipoprotein metabolism or blood blotting, hypertension, vasodilators (e.g. Viagra) or antibiotic medication.

Assessed from the clinical screening.

Unsatisfactory biochemical or haematological assessment assessed by the studies clinical advisor