Effect of nitrate supplementation on hepatic blood flow and glucose homeostasis: a double-blind, placebo controlled, randomised control trial.

Nitric oxide alters gastric blood flow, improves vascular function and mediates glucose uptake within the intestines and skeletal muscle. Dietary nitrate, acting as a source of nitric oxide, appears to be a potential low cost therapy that may help maintain glucose homeostasis. In a randomised, double-blind, placebo-controlled crossover study, 31 young and older adult participants had a standardised breakfast, supplemented with either nitrate rich beetroot juice (11.91 mmol nitrate) or nitrate depleted beetroot juice as placebo (0.01 mmol nitrate). MRI was used to assess apparent diffusion coefficient (ADC), portal vein flux and velocity. Plasma glucose, incretin and C-peptide concentrations and BP were assessed. Outcome variables were measured at baseline and hourly for 3 hours. Compared with a placebo, beetroot juice resulted in a significant elevation in plasma nitrate and plasma nitrite concentration. No differences were seen for the young or older adult cohorts between placebo and beetroot juice for ADC, or portal vein flux. There was an interaction effect in the young adults, which was absent in the older adults between visits for portal vein velocity. Nitrate supplementation did not reduce plasma glucose active GLP-1, total GLP-1 or plasma C-peptide concentrations for the young or older adult cohorts. Despite a significant elevation in plasma nitrite concentration following an acute dose of 11.91 mmol of nitrate, there was no effect on hepatic blood flow, plasma glucose, C-peptide, or incretin concentration in healthy adults.