Wall-to-lumen ratio of retinal arterioles is related with urinary albumin excretion and altered vascular reactivity to infusion of the nitric oxide synthase inhibitor N-monomethyl-L-arginine

<p>Objective: We hypothesized that wall-to-lumen ratio (WLR) of retinal arterioles might serve as an in-vivo parameter of vascular damage. To test this hypothesis we examined whether WLR of retinal arterioles is related with increased urinary albumin excretion and altered vascular reactivity to infusion of the nitric oxide synthase inhibitor N-monomethyl-L-arginine (L-NMMA).</p> <p>Methods: Thirty-nine never-treated male patients aged 18-65 years with a body mass index at least 25 kg/m<sup>2</sup> and without diabetes mellitus or secondary or stage 3 arterial hypertension were examined. WLR of retinal arterioles was assessed using scanning laser Doppler flowmetry. Urinary albumin-to-creatinine ratio (UACR) was measured from first morning spot urine. Vascular reactivity was measured by the change of aortic augmentation index (aAIx) to infusion of L-NMMA.</p> <p>Results: UACR was related with WLR of retinal arterioles (r = 0.352, P = 0.032). In response to L-NMMA infusion aAIx increased (from 10.7 ± 11 to 19.7 ± 11%, P < 0.001). The change of aAIx to L-NMMA infusion was inversely related with WLR of retinal arterioles (r = -0.462, P = 0.003) even after adjustment for changes of hemodynamic parameters to L-NMMA infusion (partial r = -0.475, P = 0.005). The relationships of UACR and the change of aAIx to L-NMMA infusion with WLR of retinal arterioles were found to be independently of other cardiovascular risk factors (ß = 0.386, P = 0.006; β = -0.369, P = 0.004, respectively) in multiple regression analyses with separate models for both parameters.</p> <p>Conclusion: Increased WLR of retinal arterioles may thus serve as an in-vivo marker of vascular damage.</p&gt

Analysis of retinal arteriolar structure in never-treated patients with essential hypertension

The changes in arteriolar structure of retinal vessels in our study cohort revealed a similar pattern to that observed previously by other investigators in subcutaneous small arteries in essential hypertension. Blood pressure emerged as an important and independent determinant of wall-to-lumen ratio of retinal arterioles

Basal nitric oxide activity is an independent determinant of arteriolar structure in the human retinal circulation.

<p>Objective: Experimental data indicate that nitric oxide might play a role in structure and remodeling of peripheral small arteries and arterioles. We hypothesized that retinal arteriolar structure is modulated by basal nitric oxide activity.</p> <p>Methods: The study cohort comprised 97 male untreated patients with normal and elevated blood pressure but without clinical evidence for cardiovascular disease. The changes of retinal capillary blood flow (RCF) to nitric oxide synthase inhibitor N-monomethyl-L-arginine (L-NMMA), that reflects basal nitric oxide activity of retinal vasculature, and to flicker light, that in part nitric oxide dependently provokes retinal vasodilatation, and parameters of retinal arteriolar structure, for example wall-to-lumen ratio (WLR), were assessed noninvasively and in vivo by scanning laser Doppler flowmetry.</p> <p>Results: Participants were stratified according to the median WLR of retinal arterioles into two groups. In the group with WLR above the median RCF in response to infusion of L-NMMA decreased to a smaller extent (−3.82 ± 26 vs. −26.0 ± 45 arbitrary units and −0.83 ± 8.4 vs. −5.88 ± 11%, P = 0.004 and P = 0.015; respectively), whereas RCF in response to flicker light did not differ significantly compared to the counter group (22.2 ± 56 vs. 39.8 ± 51 arbitrary units and 7.42 ± 15 vs. 11.9 ± 14%, P = 0.112 and P = 0.149). In the whole study cohort WLR of retinal arterioles was related with the decrease of RCF to L-NMMA infusion [when expressed in absolute terms (r = 0.252, P = 0.013) and in percentage change (r = 0.213, P = 0.036)] and inversely related with the change of RCF to flicker light [when expressed in absolute terms (r = −0.203, P = 0.048) but not clearly when expressed in percentage change (r = −0.161, P = 0.120)]. Adjustment for major cardiovascular risk factors and changes of systemic hemodynamics in response to L-NMMA infusion revealed an independent relationship between WLR of retinal arterioles and percentage change of RCF to L-NMMA infusion (β = 0.300, P = 0.007).</p> <p>Conclusion: Basal nitric oxide activity emerged as an independent determinant of arteriolar remodeling in the human retinal circulation in vivo.</p&gt