Effects of increased nitrate intake from beetroot juice on blood markers of oxidative stress and inflammation in older adults with hypertension

• Published in: Free radical biology & medicine 2024-09, Vol.222, p.519-530
• Main Authors: Fejes, Rebeka, Pilat, Nina, Lutnik, Martin, Weisshaar, Stefan, Weijler, Anna M., Krüger, Karsten, Draxler, Agnes, Bragagna, Laura, Peake, Jonathan M., Woodman, Richard J., Croft, Kevin D., Bondonno, Catherine P., Hodgson, Jonathan M., Wagner, Karl-Heinz, Wolzt, Michael, Neubauer, Oliver
• Format: Article
• Language: English
• Subjects: Aged; Beta vulgaris - chemistry; Biomarkers - blood; C-Reactive Protein - metabolism; Cardiovascular health; Cross-Over Studies; Female; Fruit and Vegetable Juices; Humans; Hypertension - blood; Hypertension - diet therapy; Hypertension - drug therapy; Inflammation - blood; Inflammation - diet therapy; Inflammation - drug therapy; Inorganic nitrate-nitrite-nitric oxide (NO)-Pathway; Lipoproteins, LDL - blood; Low-grade inflammation; Male; Middle Aged; Nitrates - blood; Nitrites - blood; Oxidative Stress - drug effects; Plant foods; Vascular aging; Vascular oxidative stress
• ISSN: 0891-5849; 1873-4596; 1873-4596
• DOI: 10.1016/j.freeradbiomed.2024.07.004

Vascular oxidative stress and low-grade inflammation are important in the pathology of cardiovascular disorders, including hypertension. Cell culture and animal studies suggest that inorganic dietary nitrate may attenuate oxidative stress and inflammation through nitric oxide (NO), and there is a need to investigate whether this translates to humans. In this randomised, placebo-controlled crossover study, by measuring a combination of multiple blood biomarkers, we evaluated whether previously reported benefits of dietary nitrate translate to a reduced oxidative stress and an improved inflammation status in 15 men and women (age range: 56–71 years) with treated hypertension. We investigated the effects of a single ∼400 mg-dose of nitrate at 3 h post-ingestion (3H POST) and the daily consumption of 2 × ∼400 mg of nitrate over 4 weeks (4WK POST), through nitrate-rich versus nitrate-depleted (placebo) beetroot juice. Measurements included plasma nitrate and nitrite (NOx), oxidised low-density lipoprotein (oxLDL), F2-isoprostanes, protein carbonyls, oxidised (GSSG) and reduced glutathione (GSH); and serum high-sensitive C-reactive protein (hsCRP), chemokines, cytokines, and adhesion molecules. Flow cytometry was used to assess the relative proportion of blood monocyte subsets. At 4WK POST nitrate intervention, the oxLDL/NOx ratio decreased (mainly due to increases in plasma nitrate and nitrite) and the GSH/GSSG ratio (a sensitive biomarker for alterations in the redox status) increased, compared with placebo (for both ratios P