Alba Billie K, Stanhewicz Anna E, Kenney W Larry, Alexander Lacy M
1Department of Kinesiology,The Pennsylvania State University,University Park,PA 16802,USA.
2Center for Healthy Aging,The Pennsylvania State University,University Park,PA 16802,USA.
Br J Nutr. 2016 Jul;116(2):204-10. doi: 10.1017/S0007114516001835. Epub 2016 May 16.
In epidemiological studies, chronic dairy milk consumption is associated with improved vascular health and reduced age-related increases in blood pressure. Although milk protein supplementation augments conduit artery flow-mediated dilation, whether or not acute dairy milk intake may improve microvascular function remains unclear. We hypothesised that dairy milk would increase direct measurement of endothelial nitric oxide (NO)-dependent cutaneous vasodilation in response to local skin heating. Eleven men and women (61 (sem 2) years) ingested two or four servings (473 and 946 ml) of 1 % dairy milk or a rice beverage on each of 4 separate study days. In a subset of five subjects, an additional protocol was completed after 473 ml of water ingestion. Once a stable blood flow occurred, 15 mm-N G -nitro-l-arginine methyl ester was perfused (intradermal microdialysis) to quantify NO-dependent vasodilation. Red-blood-cell flux (RBF) was measured by laser-Doppler flowmetry, and cutaneous vascular conductance (CVC=RBF/mean arterial pressure) was calculated and normalised to maximum (%CVCmax; 28 mm-sodium nitroprusside). Full expression of cutaneous vasodilation was not different among dairy milk, rice beverage and water, and there was no effect of serving size on the total vasodilatory response. Contrary to our hypothesis, NO-dependent vasodilation was lower for dairy milk than rice beverage (D: 49 (sem 5), R: 55 (sem 5) %CVCmax; P<0·01). Acute dairy milk ingestion does not augment NO-dependent vasodilation in the cutaneous microcirculation compared with a rice beverage control.
在流行病学研究中，长期饮用牛奶与改善血管健康以及降低与年龄相关的血压升高有关。尽管补充乳蛋白可增强导管动脉血流介导的血管舒张，但急性摄入牛奶是否能改善微血管功能仍不清楚。我们假设，牛奶会增加对局部皮肤加热作出反应的内皮一氧化氮（NO）依赖性皮肤血管舒张的直接测量值。11名男性和女性（61（标准误2）岁）在4个不同的研究日中，每天分别摄入两份或四份（473毫升和946毫升）1%的牛奶或一份米饮料。在五名受试者的子集中，摄入473毫升水后完成了另一项方案。一旦出现稳定的血流，灌注15毫米-N G-硝基-L-精氨酸甲酯（皮内微透析）以量化NO依赖性血管舒张。通过激光多普勒血流仪测量红细胞通量（RBF），并计算皮肤血管传导率（CVC = RBF/平均动脉压），并将其归一化为最大值（%CVCmax；28毫米硝普钠）。牛奶、米饮料和水之间皮肤血管舒张的充分表达没有差异，且份量大小对总血管舒张反应没有影响。与我们的假设相反，牛奶的NO依赖性血管舒张低于米饮料（牛奶：49（标准误5），米饮料：55（标准误5）%CVCmax；P<0·01）。与米饮料对照相比，急性摄入牛奶不会增强皮肤微循环中NO依赖性血管舒张。
