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Aims\ud To test if 6 months' intervention with dietary nitrate and spironolactone could affect carotid subclinical atherosclerosis and stiffness, respectively, vs. placebo/doxazosin, to control for blood pressure (BP).\ud \ud Methods\ud A subgroup of participants in our double-blind, randomized-controlled, factorial VaSera trial had carotid imaging. Patients with hypertension and with/at risk of type 2 diabetes were randomized to active nitrate-containing beetroot juice or placebo nitrate-depleted juice, and spironolactone or doxazosin. Vascular ultrasound for carotid diameter (CD, mm) and intima–media thickness (CIMT, mm) was performed at baseline, 3- and 6-months. Carotid local stiffness (CS, m/s) was estimated from aortic pulse pressure (Arteriograph) and carotid lumen area. Data were analysed by modified intention to treat and using mixed-model effect, adjusted for confounders.\ud \ud Results\ud In total, 93 subjects had a baseline evaluation and 86% had follow-up data. No statistical interactions occurred between the juice and drug arms and BP was similar between the juices and between the drugs. Nitrate-containing vs. placebo juice significantly lowered CIMT (−0.06 [95% confidence interval −0.12, −0.01], P = .034), an overall difference of ~8% relative to baseline; but had no effect on CD or CS. Doxazosin appeared to reduce CS from baseline (−0.34 [−0.62, −0.06]) however, no difference was detected vs. spironolactone (−0.15 [−0.46, 0.16]). No differences were detected between spironolactone or doxazosin on CIMT and CD.\ud \ud Conclusions\ud Our results show that 6 months' intervention with dietary nitrate influences vascular remodelling, but not carotid stiffness or diameter. Neither spironolactone nor doxazosin had a BP-independent effect on carotid structure and function.

Although the antimicrobial potential of nitric oxide (NO) is widely published, it is little used clinically. NO is a key signalling molecule modulating vascular, neuronal, inflammatory and immune responses. Endogenous antimicrobial activity is largely mediated by high local NO concentrations produced by cellular inducible nitric oxide synthase, and by derivative reactive nitrogen oxide species including peroxynitrite and S-nitrosothiols. NO may be taken as dietary substrate (inorganic nitrate, L-arginine), and therapeutically as gaseous NO, and transdermal, sublingual, oral, intranasal and intravenous nitrite or nitrate. Numerous preclinical studies have demonstrated that NO has generic static and cidal activities against viruses (including ?-coronaviruses such as SARS-CoV-2), bacteria, protozoa and fungi/yeasts in vitro. Therapeutic effects have been seen in animal models in vivo, and phase II trials have demonstrated that NO donors can reduce microbial infection. Nevertheless, excess NO, as occurs in septic shock, is associated with increased morbidity and mortality. In view of the dose-dependent positive and negative effects of NO, safety and efficacy trials of NO and its donors are needed for assessing their role in the prevention and treatment of infections. Trials should test dietary inorganic nitrate for pre- or post-exposure prophylaxis and gaseous NO or oral, topical or intravenous nitrite and nitrate for treatment of mild-to-severe infections, including due to SARS-CoV-2 (COVID-19). This review summarises the evidence base from in vitro, in vivo and early phase clinical studies of NO activity in viral, bacterial, protozoal and fungal infections.

Aims:\ud Dietary nitrate from sources such as beetroot juice lowers blood pressure (BP) via the nitrate-nitrite-nitric oxide (NO) pathway. However, NO and nitrite are inactivated via re- oxidation to nitrate, potentially limiting their activity. Cytochrome P450-3A4 inhibition with troleandomycin prevents nitrite re-oxidation to nitrate in rodent liver. Grapefruit juice contains the CYP3A4 inhibitor furanocoumarin. We therefore hypothesized that grapefruit juice would enhance BP-lowering with beetroot juice by maintaining circulating [nitrite].\ud Methods:\ud We performed a randomized, placebo-controlled, 7-hour crossover study in 11 healthy volunteers, attending on 3 occasions, receiving: a 70ml-shot of active beetroot juice (Beet- It®) and either (i) 250 ml grapefruit juice (“Active Beet+GFJ”), or (ii) 250 ml water (Buxton®, “Active Beet+H2O”); or (iii) Placebo Beet+GFJ.\ud Results:\ud The addition of grapefruit juice to active beetroot juice lowered systolic BP (SBP): Active Beet+GFJ versus Active Beet+H2O (P=0.02), and pulse pressure, PP (P=0.0003). Peak mean differences in SBP and PP were seen at T=5 hours: -3.3mmHg (95% CI -6.43 to -0.15) and at T=2.5 hours: -4.2 mmHg (95% CI -0.3 to -8.2), respectively. Contrary to the hypothesis, plasma [nitrite] was lower with Active Beet+GFJ versus Active Beet+H2O (P=0.006), as was salivary nitrite production (P=0.002) and saliva volume (-0.34 ml/min (95% CI -0.05 to - 0.68)). The taste score of Beet+GFJ was 1.4/10 points higher than Beet+H2O (P=0.03).\ud This article is protected by copyright. All rights reserved.\ud Conclusions:\ud Grapefruit juice enhanced beetroot juice’s effect on lowering SBP and PP despite decreasing plasma [nitrite]. Besides suggesting more complex mechanisms, there is potential for maximising the clinical benefit of dietary nitrate and targeting isolated systolic hypertension.