Altered distribution of adrenergic constrictor responses contributes to skeletal muscle perfusion abnormalities in metabolic syndrome.

Purpose: Although studies suggest elevated adrenergic activity paralleling metabolic syndrome in OZRs, the moderate hypertension and modest impact on organ perfusion question the multi-scale validity of these data.
Methods: To understand how adrenergic function contributes to vascular reactivity in OZR, we utilized a multi-scale approach to investigate pressure responses, skeletal muscle blood flow, and vascular reactivity following adrenergic challenge.
Results: For OZR, adrenergic challenge resulted in increased pressor responses vs LZRs, mediated via α ₁ receptors, with minimal contribution by either ROS or NO bioavailability. In situ gastrocnemius muscle of OZR exhibited blunted functional hyperemia, partially restored with α ₁ inhibition, although improved muscle performance and VO ₂ required combined treatment with TEMPOL. Within OZR in situ cremaster muscle, proximal arterioles exhibited a more heterogeneous constriction to adrenergic challenge, biased toward hyperresponsiveness, vs LZR. This increasingly heterogeneous pattern was mirrored in ex vivo arterioles, mediated via α ₁ receptors, with roles for ROS and NO bioavailability evident in hyperresponsive vessels only.
Conclusions: These results support the central role of the α ₁ adrenoreceptor for augmented pressor responses and elevations in vascular resistance, but identify an increased heterogeneity of constrictor reactivity in OZR that is presently of unclear purpose.
(© 2016 John Wiley & Sons Ltd.)