Fermented Beetroot Supplementation Increases Urinary NOx and Reduces Thromboxane B₂ in eNOS-Deficient Mice

Endothelial nitric oxide synthase (eNOS) deficiency reduces nitric oxide (NO) bioavailability and contributes to vascular dysfunction and prothrombotic signaling. Dietary nitrate may support NO-related pathways through NOS-independent mechanisms. We hypothesized that a fermented beetroot preparation (BRL) would increase urinary nitrate/nitrite (NOx) output and reduce urinary thromboxane B2 more effectively than l-arginine (ARG) in an eNOS-deficient mouse model. In this focused pilot study, a BRL generated from beetroot (BR), carrot, and apple was administered to eNOS-knockout mice in drinking water for 10 days following a 5-day baseline period. Mice were housed individually in metabolic cages for 24-h urine collection, and urinary NOx and thromboxane B2 were measured daily and normalized to creatinine. Compared with l-ARG, the BRL increased urinary NOx and reduced urinary thromboxane B2. The baseline sampling design allowed each animal to serve as its own internal control throughout the longitudinal study. These pilot findings support further investigation of fermented BR-derived functional foods and provide a rationale for larger mechanistic studies examining nitrate exposure, additional molecular endpoints, and the contribution of fermentation-derived constituents.