Modulation of endothelial and smooth muscle function by bed rest and hypoenergetic, low-fat nutrition

Christiane Hesse, Heike Siedler, Steffen P. Luntz, Bianca M. Arendt, Roland Goerlich, Ruth Fricker, Martina Heer, Walter E. Haefeli
2005 Journal of applied physiology  
Modulation of endothelial and smooth muscle function by bed rest and hypoenergetic, low-fat nutrition. Prolonged microgravity alters the regulation of the peripheral vasculature. The influence of reduced food intake, as often observed in astronauts, on vascular function is unclear. In a randomized, four-phase, crossover study, the effect of simulated microgravity (13 days of bed rest), energetic restriction (Ϫ25%, fat reduced), and their combination on endothelium-dependent and -independent
more » ... dilation was compared with ambulatory control conditions. Using venous occlusion plethysmography, cumulative intra-arterial dose-response curves to endotheliumdependent (acetylcholine) and -independent (sodium nitroprusside) vasodilators were constructed in 10 healthy male volunteers before and on day 13 of each of the four intervention periods. Bed rest combined with normoenergetic nutrition impaired the dose-response to acetylcholine (ANOVA, P ϭ 0.004) but not to sodium nitroprusside, whereas hypoenergetic diet under ambulatory conditions improved responses to acetylcholine (P ϭ 0.044) and sodium nitroprusside (P Ͻ 0.001). When bed rest was combined with hypoenergetic diet, acetylcholine responses did not change. Similarly, under control conditions, no change was observed. Individual changes in the total cholesterol-to-HDL ratio were correlated with changes in endothelial and vascular smooth muscle relaxation. In conclusion, short-term bed rest impairs endothelium-dependent arterial relaxation in humans. A hypoenergetic, low-fat diet modulates serum lipids, improves endothelium-dependent and -independent relaxation, and may antagonize the unfavorable effects of simulated microgravity on endothelial function. human endothelium; nitric oxide; vasodilation; simulated microgravity ENDOTHELIAL DYSFUNCTION IS an early essential step in the development of atherosclerosis and vascular diseases in humans (12). Regular physical activity improves endotheliumdependent vasodilation in the forearm (17) and coronary circulation (14) and prevents cardiovascular mortality and morbidity (29, 35), whereas physical inactivity (sedentary state) is a risk factor for cardiovascular disease (5). The positive effect of exercise on endothelial function may be explained by the increase in vascular shear stress, which enhances the expression of the vascular endothelial nitric oxide
doi:10.1152/japplphysiol.00888.2005 pmid:16099888 fatcat:wi6sf5rhnzgohg2ttztnhlugtq