[show abstract][hide abstract] ABSTRACT: The pathophysiology of orthostatic hypotension in Parkinson's disease (PD) is incompletely understood. The primary focus has thus far been on failure of the baroreflex, a central mediated vasoconstrictor mechanism. Here, we test the role of two other possible factors: 1) a reduced peripheral vasoconstriction (which may contribute because PD includes a generalized sympathetic denervation); and 2) an inadequate plasma volume (which may explain why plasma volume expansion can manage orthostatic hypotension in PD). We included 11 PD patients with orthostatic hypotension (PD + OH), 14 PD patients without orthostatic hypotension (PD - OH), and 15 age-matched healthy controls. Leg blood flow was examined using duplex ultrasound during 60° head-up tilt. Leg vascular resistance was calculated as the arterial-venous pressure gradient divided by blood flow. In a subset of 9 PD + OH, 9 PD - OH, and 8 controls, plasma volume was determined by indicator dilution method with radiolabeled albumin ((125)I-HSA). The basal leg vascular resistance was significantly lower in PD + OH (0.7 ± 0.3 mmHg·ml(-1)·min) compared with PD - OH (1.3 ± 0.6 mmHg·ml(-1)·min, P < 0.01) and controls (1.3 ± 0.5 mmHg·ml(-1)·min, P < 0.01). Leg vascular resistance increased significantly during 60° head-up tilt with no significant difference between the groups. Plasma volume was significantly larger in PD + OH (3,869 ± 265 ml) compared with PD - OH (3,123 ± 377 ml, P < 0.01) and controls (3,204 ± 537 ml, P < 0.01). These results indicate that PD + OH have a lower basal leg vascular resistance in combination with a larger plasma volume compared with PD - OH and controls. Despite the increase in leg vascular resistance during 60° head-up tilt, PD + OH are unable to maintain their blood pressure.
Journal of Applied Physiology 06/2011; 111(2):443-8. · 3.48 Impact Factor
[show abstract][hide abstract] ABSTRACT: Children with type 1 diabetes mellitus (DM1) show endothelial dysfunction and mild artery wall thickening compared to their age-matched healthy peers. In this study, we examined the effect of 18-week exercise training on physical fitness and vascular function and structure in children with DM1. We examined physical fitness, brachial artery endothelial function [flow-mediated dilation (FMD)], common carotid artery diameter, wall thickness and wall-to-lumen ratio before and after 18-week exercise training in children with DM1 (n = 7). Physical fitness, measured as maximal oxygen consumption, improved after training (p = 0.039). Brachial artery FMD improved from 7.5 ± 4.2 to 12.4 ± 5.2 (p = 0.038). Carotid artery diameter, wall thickness and wall-to-lumen ratio did not change significantly (p = 0.26, 0.53 and 0.27, respectively). We showed that exercise training in children with DM1 effectively reverses endothelial dysfunction and improves physical fitness. These data emphasize the important role for physical activity in the management of DM1.
Diabetes Obesity and Metabolism 04/2011; 13(4):382-4. · 5.18 Impact Factor