ENDOTHELIAL DYSFUNCTION AND THE EXPRESSION OF ENDOTHELIAL NITRIC-OXIDE SYNTHETASE IN DIABETIC NEUROPATHY, VASCULAR-DISEASE, AND FOOT ULCERATION

We studied endothelial-mediated microvascular blood flow in neuropathi c diabetic patients to determine the association between endothelial r egulation of the microcirculation and the expression of endothelial co nstitutive nitric oxide synthetase (ecNOS) in the skin. Vasodilation o n the dorsal foot in response to heating and iontophoresis of acetylch oline (endothelium-dependent) and sodium nitroprusside ( endothelium-i ndependent) were measured using single-point laser Doppler and laser D oppler imaging in diabetic patients with neuropathy (DN), with neuropa thy and vascular disease (DI), with Charcot arthropathy (DA), and with out complications (D), and in healthy control subjects (C). The respon se to heat was reduced in the DN (321 [21-629] percentage of increase over the baseline, median [interquartile range]) and DI(225 [122-470]) groups but was preserved in the DA (895 [359-1,229]), D(699 [466-1,02 9]), and C (810 [440-1,064], P < 0.0001) groups. The endothelial-media ted response to acetylcholine was reduced in the DN (17 [11-25]), DA ( 22 [2-34]), and DI (13 [2-30]) groups compared with the D (47 [24-58]) and C (44 [31-70], P < 0.001) groups. The non-endothelial-mediated re sponse to sodium nitroprusside was also reduced in the DI (4 [0-18]), DN (17 [9-26]), and DA (21 [11-31]) groups compared with the D (37 [19 -41]) and C (44 [26-67], P < 0.0001) groups. There was a significant r eduction in vasodilation in the DI group compared with all other group s (P < 0.0001). Full thickness skin biopsies from the dorsum of the fo ot of 15 DN, 10 DI, and 11 C study subjects were immunostained with an tiserum to human ecNOS, the functional endothelial marker GLUT1, and t he anatomical endothelial marker von Willebrand factor. The staining i ntensity of ecNOS was reduced in both diabetic groups. No differences were found among the three groups in the staining intensity of von Wil lebrand factor and GLUT1. We conclude that the endothelium-dependent a nd endothelium-independent vasodilations are impaired in diabetic pati ents predisposed to foot ulceration and that neuropathy is the main fa ctor associated with this abnormality. Reduced expression of ecNOS may be a major contributing factor for endothelial dysfunction. These dat a provide support for a close association of neuropathy and microcircu lation in the pathogenesis of foot ulceration.