Impact of Acute and Chronic Red Beetroot Juice Consumption on Postprandial Endothelial Function and Levels of Nitrate/Nitrite in Plasma and Saliva (P06-113-19)

High-fat meal (HFM) consumption has been shown to impair postprandial endothelial function. Red beetroot juice (RBJ) contains polyphenols, betalains, carotenoids, ascorbic acid, and inorganic nitrate, and has been shown to improve endothelial function. This study investigated the acute and chronic effects of RBJ and its bioactive components on postprandial endothelial function. We hypothesized that a HFM would impair postprandial endothelial function, and that RBJ would attenuate this, in part, through increased circulating nitrate/nitrite (NOx) levels.A 4-period randomized, double-blind, placebo-controlled crossover clinical trial was conducted. Fifteen overweight and obese middle-aged/older men and postmenopausal women underwent baseline (T0) assessment of endothelial function (via reactive hyperemia index, RHI) and collection of blood and saliva. Participants consumed one of the following 70 mL treatments (acute exposure): 1) RBJ, 2) nitrate-free RBJ (NF-RBJ), 3) placebo + nitrate (PBO + NIT), and 4) placebo (PBO), followed by a HFM. RHI was measured at 4 hours (T4) post-HFM, and blood and saliva were collected at 1 hour (T1), 2 hours (T2), and T4. Participants then consumed treatments daily for 4 weeks (chronic exposure), and all assessments were repeated before/after the HFM but without consuming treatments.No significant time or treatment effects were observed for RHI. Following acute and chronic exposure to RBJ and PBO + NIT, plasma NOx levels were higher at T0 (chronic only), T1, T2, and T4 compared to PBO and NF-RBJ (P < 0.001). After chronic exposure to RBJ, saliva NOx levels were higher at T0, T1, T2, and T4 compared to PBO and NF-RBJ (P < 0.001). Saliva NOx levels for PBO + NIT were higher than both PBO and NF-RBJ at T0 (P < 0.001), but only higher than NF-RBJ at T1 (P = 0.02), and higher than PBO at T4 (P = 0.02). Additionally, there was a time*treatment interaction for plasma and saliva NOx levels following 4 weeks of daily exposure to RBJ and PBO + NIT (P < 0.001).The preliminary results of this study suggest that HFM consumption does not significantly impair postprandial endothelial function in this population. In addition, acute and chronic RBJ exposure does not significantly improve endothelial function despite increases in plasma and saliva NOx.Colorado Agricultural Experiment Station, NIFA, USDA.

高脂肪膳食（HFM）的摄入已被证明会损害餐后内皮功能。红甜菜根汁（RBJ）含有多酚、甜菜红素、类胡萝卜素、抗坏血酸和无机硝酸盐，且已被证明可改善内皮功能。本研究探讨了RBJ及其生物活性成分对餐后内皮功能的急性和慢性影响。我们假设高脂肪膳食会损害餐后内皮功能，而RBJ会部分通过提高循环硝酸盐/亚硝酸盐（NOx）水平来减轻这种损害。 进行了一项4周期随机、双盲、安慰剂对照交叉临床试验。15名超重和肥胖的中老年男性以及绝经后女性接受了内皮功能（通过反应性充血指数，RHI）的基线（T0）评估，并采集了血液和唾液。参与者摄入以下70毫升的一种处理物（急性暴露）：1）RBJ，2）无硝酸盐RBJ（NF - RBJ），3）安慰剂 + 硝酸盐（PBO + NIT），以及4）安慰剂（PBO），然后摄入高脂肪膳食。在高脂肪膳食后4小时（T4）测量RHI，并在1小时（T1）、2小时（T2）和T4采集血液和唾液。参与者随后每日摄入处理物持续4周（慢性暴露），并在高脂肪膳食前后重复所有评估，但不摄入处理物。 未观察到RHI有显著的时间或处理效应。在急性和慢性暴露于RBJ以及PBO + NIT后，与PBO和NF - RBJ相比，血浆NOx水平在T0（仅慢性暴露时）、T1、T2和T4更高（P < 0.001）。慢性暴露于RBJ后，与PBO和NF - RBJ相比，唾液NOx水平在T0、T1、T2和T4更高（P < 0.001）。PBO + NIT的唾液NOx水平在T0时高于PBO和NF - RBJ（P < 0.001），但在T1时仅高于NF - RBJ（P = 0.02），在T4时高于PBO（P = 0.02）。此外，每日暴露于RBJ和PBO + NIT 4周后，血浆和唾液NOx水平存在时间×处理交互作用（P < 0.001）。 本研究的初步结果表明，在该人群中高脂肪膳食的摄入并未显著损害餐后内皮功能。此外，尽管血浆和唾液NOx水平升高，但急性和慢性RBJ暴露并未显著改善内皮功能。 美国科罗拉多农业试验站，美国农业部国家食品与农业研究所