CORRESPONDENCE: LETTER TO THE EDITOR
Olive Oil and Ischemic Reactive Hyperemia in Hypercholesterolemic Patients
Tommaso Gori, MD, PhD*
* University of Siena, Internal Cardiovascular and Geriatric Medicine, Viale Sclavo, Siena, Tuscany 53100, Italy (Email: tomgori{at}hotmail.com).
I read with interest the study by Ruano et al. (1) reporting on the protective effect of olive oil on cardiovascular markers. In their study, the investigators demonstrate that olive oil reduces plasma evidence of oxidative stress, increases nitric oxide (NO) production, and limits the blunting in cutaneous reactive hyperemia observed in hypercholesterolemic subjects. The researchers conclude that "olive oil [...] improves endothelium-dependent microvascular vasodilatation." Whereas the evidence of the beneficial effect of olive oil on plasma markers is convincing, the interpretation of laser Doppler data appears somewhat simplistic and worthy of further discussion.
First, the evidence that ischemic reactive hyperemia can be used as an index of endothelial function is very inconclusive. Recently, Binggeli et al. (2) showed that cutaneous reactive hyperemia is absolutely NO-independent and only marginally (approximately 30%) influenced by release of cyclooxygenase products. Of importance, Rossi et al. (3) convincingly showed that the influence of the endothelium accounts only for approximately one-quarter of the forces regulating resting vasomotion, and that this percentage does not increase after ischemia. Moreover, hundreds of studies employing the brachial artery flow-mediated dilation method have shown that reactive hyperemia is preserved in a number of conditions associated with impaired endothelial function.
With this evidence, one should be very careful in attributing a blunted reactive hyperemia to dysfunction of any of the factors determining vascular tone (e.g., metabolic vasodilation, myogenic tone, endothelial function, and others). The investigators quote the study by Vuilleumier et al. (4) However, that study shows an association between cutaneous reactive hyperemia and cardiovascular risk factors, and it provides no mechanistic information regarding a causal relationship between laser Doppler parameters and release of vasoactive endothelium-derived autacoids. There is no discussion that microvascular vasomotion (including its endothelial component) is of critical importance to vascular homeostasis and that laser Doppler indexes can be reliably used as surrogate markers of cardiovascular health. However, there is a worrying trend toward identification of "endothelial" and "microvascular" vasomotor control. It should be emphasized that these terms are not synonyms, and that they should not be used interchangeably.
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1. Ruano J, Lopez-Miranda J, Fuentes F, et al. Phenolic content of virgin olive oil improves ischemic reactive hyperemia in hypercholesterolemic patients J Am Coll Cardiol 2005;46:1864-1868.[Abstract/Free Full Text]2. Binggeli C, Spieker LE, Corti R, et al. Statins enhance postischemic hyperemia in the skin circulation of hypercholesterolemic patients. A monitoring test of endothelial dysfunction for clinical practice? J Am Coll Cardiol 2003;42:71-77.[Abstract/Free Full Text] 3. Rossi M, Ricco R, Carpi A. Spectral analysis of skin laser Doppler blood perfusion signal during cutaneous hyperemia in response to acetylcholine iontophoresis and ischemia in normal subjects Clin Hemorheol Microcirc 2004;31:303-310.[Medline] 4. Vuilleumier P, Decosterd D, Maillard M, Burnier M, Hayoz D. Postischemic forearm skin reactive hyperemia is related to cardiovascular risk factors in a healthy female population J Hypertens 2002;20:1753-1757.[CrossRef][Web of Science][Medline]
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