Free fatty acids are essential nutritional components and recent studies identified them as signaling molecules in various physiological processes. It has now been shown that high levels of free fatty acids, particularly saturated fatty acids, may be associated with insulin resistance in obese patients with type 2 diabetes mellitus. Insulin resistance is important in clinical since it is related to various diseases including type 2 diabetes mellitus, dyslipidemia, and abnormalities at cardiovascular level. Recent studies have proposed different molecular mechanisms by which these lipids may alter the signaling pathway of insulin. The purpose of this review is to highlight recent advances in the study of the effect of free fatty acids as modulators of insulin response.

Background and purpose: It has been suggested that during a migraine attack capsaicin-sensitive trigeminal sensory nerves release calcitonin gene-related peptide (CGRP), resulting in cranial vasodilatation and central nociception; hence, trigeminal inhibition may prevent this vasodilatation and abort migraine headache. This study investigated the effects of the agonists sumatriptan (5-HT 1B/1D water-soluble), donitriptan (5-HT 1B/1D lipid-soluble), PNU-142633 (5-HT 1D water-soluble) and PNU-109291 (5-HT 1D lipid-soluble) on vasodilator responses to capsaicin, a-CGRP and acetylcholine in dog external carotid artery. Experimental approach: 59 vagosympathectomized dogs were anaesthetized with sodium pentobarbitone. Blood pressure and heart rate were recorded with a pressure transducer, connected to a cannula inserted into a femoral artery. A precalibrated flow probe was placed around the common carotid artery, with ligation of the internal carotid and occipital branches, and connected to an ultrasonic flowmeter. The thyroid artery was cannulated for infusion of agonists. Key results: Intracarotid infusions of capsaicin, a-CGRP and acetylcholine dose-dependently increased blood flow through the carotid artery. These responses remained unaffected after intravenous (i.v.) infusions of sumatriptan, PNU-142633, PNU-109291 or physiological saline; in contrast, donitriptan significantly attenuated the vasodilator responses to capsaicin, but not those to a-CGRP or acetylcholine. Only sumatriptan and donitriptan dose-dependently decreased the carotid blood flow. Interestingly, i.v. administration of the antagonist, SB224289 (5-HT 1B ), but not of BRL15572 (5-HT 1D ), abolished the inhibition by donitriptan. Conclusions and implications: Our results suggest that the inhibition produced by donitriptan of capsaicin-induced external carotid vasodilatation is mainly mediated by 5-HT 1B , rather than 5-HT 1D , receptors, probably by a central mechanism.

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