Elevated Skeletal Muscle Blood Flow in Noncomplicated Type 1 Diabetes Mellitus

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Abstract
Abstract —Capillary hyperperfusion precedes and contributes to the occurrence of diabetic microangiopathy. Vascular tone is regulated by the balance of vasodilating and vasoconstricting factors, of which nitric oxide (NO; an endothelium dependent vasodilator) and norepinephrine (NE; a potent vasoconstrictor), respectively, are of primary importance. To investigate the role of these factors in hyperperfusion, we measured forearm blood flow (FBF) in 50 patients with noncomplicated type 1 diabetes (DP) and 50 healthy control subjects (CS) under baseline conditions and during intrabrachial infusion of N G -monomethyl- l -arginine (L-NMMA), an endothelium-dependent vasoconstrictor, and acetylcholine (ACh), an endothelium-dependent vasodilator. Furthermore, we determined arterial plasma NE concentration at baseline and then determined α-adrenergic receptor sensitivity by measuring FBF response to intra-arterially infused NE. We found that basal FBF was increased in DP (2.9±0.1 versus 2.0±0.1 mL · min −1 · dL −1 in CS; P P =NS). Maximum blood flow during infusion of ACh was not different (23.3±1.9 mL · min −1 · dL −1 in DP versus 20.1±1.6 in CS). Arterial plasma NE concentrations were significantly decreased in DP (0.57±0.03 versus 0.81±0.05 nmol/L in CS; P P <0.01). We conclude that basal FBF is increased in noncomplicated type 1 diabetes. We found no evidence of a disturbance of basal or stimulated NO production. Arterial plasma NE concentrations are decreased in noncomplicated type 1 diabetes. This may explain the vasodilatation at baseline and the increased vascular response to intra-arterially NE.

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