Bock Joshua M, Ueda Kenichi, Feider Andrew J, Hanada Satoshi, Casey Darren P
Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa, Iowa City, IA, USA.
Department of Anesthesia, Carver College of Medicine, University of Iowa, 200 Hawkins Dr, Iowa City, IA, USA.
Nitric Oxide. 2022 Jan 1;118:17-25. doi: 10.1016/j.niox.2021.10.006. Epub 2021 Oct 27.
Patients with type 2 diabetes mellitus (T2DM) have reduced vasodilatory responses during exercise partially attributable to low nitric oxide (NO) levels. Low NO contributes to greater α-adrenergic mediated vasoconstriction in contracting skeletal muscle. We hypothesized boosting NO bioavailability via 8wks of active beetroot juice (BR, 4.03 mmol nitrate, 0.29 mmol nitrite, n = 19) improves hyperemia, via reduced α-mediated vasoconstriction, during handgrip exercise relative to nitrate/nitrite-depleted beetroot juice (BR, n = 18) in patients with T2DM.
Forearm blood flow (FBF) and vascular conductance (FVC) were calculated at rest and during handgrip exercise (20%max, 20contractions·min). Phenylephrine (α-agonist) and dexmedetomidine (α-agonist) were infused intra-arterially during independent trials to determine the influence of α-mediated vasoconstriction on exercise hyperemia. Vasoconstriction was quantified as the percent-reduction in FVC during α-agonist infusion, relative to pre-infusion, as well as the absolute change in %FVC during exercise relative to the respective rest trial (magnitude of sympatholysis).
ΔFBF (156 ± 69 to 175 ± 73 ml min) and ΔFVC (130 ± 54 to 156 ± 63 ml min·100 mmHg, both P < 0.05) during exercise were augmented following BR, but not BR (P = 0.96 and 0.51). Phenylephrine-induced vasoconstriction during exercise was blunted following BR (-17.1 ± 5.9 to -12.6 ± 3.1%, P < 0.01), but not BR (P = 0.58) supplementation; the magnitude of sympatholysis was unchanged by either (beverage-by-time P = 0.15). BR supplementation reduced dexmedetomidine-induced vasoconstriction during exercise (-23.3 ± 6.7 to -19.7 ± 5.2%) and improved the corresponding magnitude of sympatholysis (25.3 ± 11.4 to 34.4 ± 15.5%, both P < 0.05).
BR supplementation improves the hyperemic and vasodilatory responses to exercise in patients with T2DM which appears to be attributable to reduced α-adrenergic mediated vasoconstriction in contracting skeletal muscle.
2型糖尿病（T2DM）患者在运动期间血管舒张反应降低，部分原因是一氧化氮（NO）水平较低。低NO会导致收缩骨骼肌中α-肾上腺素能介导的血管收缩增强。我们假设，与饮用硝酸盐/亚硝酸盐耗尽的甜菜根汁（BR，n = 18）的T2DM患者相比，饮用8周活性甜菜根汁（BR，4.03 mmol硝酸盐，0.29 mmol亚硝酸盐，n = 19）可通过降低α介导的血管收缩来提高充血量，从而改善握力运动期间的充血情况。
在静息状态和握力运动（20%最大力量，20次收缩·分钟）期间计算前臂血流量（FBF）和血管传导率（FVC）。在独立试验期间动脉内注射去氧肾上腺素（α-激动剂）和右美托咪定（α-激动剂），以确定α介导的血管收缩对运动充血的影响。血管收缩程度通过α-激动剂注射期间FVC相对于注射前的降低百分比以及运动期间相对于各自静息试验的FVC%绝对变化（交感神经解制幅度）来量化。
饮用BR后运动期间的ΔFBF（156±69至175±73 ml·分钟）和ΔFVC（130±54至156±63 ml·分钟·100 mmHg，两者P<0.05）增加，但饮用BR后未增加（P = 0.96和0.51）。饮用BR后运动期间去氧肾上腺素诱导的血管收缩减弱（-17.1±5.9至-12.6±3.1%，P<0.01），但饮用BR后未减弱（P = 0.58）；两种饮料对交感神经解制幅度均无影响（饮料×时间P = 0.15）。饮用BR可降低运动期间右美托咪定诱导的血管收缩（-23.3±6.7至-19.7±5.2%）并改善相应的交感神经解制幅度（25.3±11.4至34.4±15.5%，两者P<0.05）。
饮用BR可改善T2DM患者运动时的充血和血管舒张反应，这似乎归因于收缩骨骼肌中α-肾上腺素能介导的血管收缩减弱。
