Comparison of flow-mediated dilatation with local thermal hyperaemia as a measure of endothelial function.

Measurement of flow-mediated dilatation of the brachial artery in response to
forearm occlusion for 5 min (FMD) using ultrasonography is a well-accepted, but
investigator-demanding method, to determine endothelial function. Local thermal
hyperaemia of the skin measured with a laser Doppler flow imaginer (LTH) is
less demanding and may be a suitable alternative to determine endothelial
function at frequent intervals. We want to investigate whether LTH correlates
with FMD response in a group of healthy non-smoking and smoking men and to what
extent LTH can be inhibited by the nitric-oxide synthase (NOS) inhibitor L-NMMA
applied locally on the skin. In addition we want to replicate the reported
improved FMD response to nitrate-rich beetroot juice and correlate this to the
LTH response. Post occlusive reactive hyperaemia (PORH) of the skin is
considered to be a measure of microvascular function and is also thought to be
correlated to the FMD response. We will also determine the PORH response during
this study.

The main objective of our study is to explore whether LTH and FMD are
correlated. Main secondary objectives are to investigate whether the LTH
response is largely NO-mediated and whether drinking beetroot juice acutely
improves both FMD and LTH.

Randomised, double-blind, placebo-controlled cross-over study

Beetroot juice and placebo.

All the techniques applied are non-invasive and without risk and only provide
minimal discomfort related to the 5 minute lasting arterial occlusion of the
forearm by a blood pressure cuff and the dietary ristrictions. Participants
have to visit our research department twice for FMD and LTH measurements. For
their time investment they will be reimbursed. The intervention with
commercially available beetroot juice (Beet-it) or placebo is not associated
with any risk.