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Low Nitric Oxide in winter may increase cardiovascular risk - Oct 2022
Reduced nitric oxide synthesis in winter: A potential contributing factor to increased cardiovascular risk
Nitric Oxide Volume 127, 1 October 2022, Pages 1-9 https://doi.org/10.1016/j.niox.2022.06.007
Luke Liddle ab Christopher Monaghan a Mia C.Burleigh a Katarzyn a A.Baczynsk ac David J.Muggeridge d ChrisEaston a
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Highlights
- Ultraviolet radiation (UVR) mobilise skin stores of nitric oxide metabolites.
- In this cohort of U.K. adults, UVR exposure was greater in summer than in winter.
- Plasma nitrite concentration was higher and blood pressure lower in the summer.
- A lower availability of nitric oxide may increase cardiovascular risk in winter months.
Background
Nitric oxide is a key signalling molecule that elicits a range of biological functions to maintain vascular homeostasis. A reduced availability of nitric oxide is implicated in the progression of cardiovascular diseases and increases the risk of pathogenic events.
Aims
To compare the concentration of nitric oxide metabolites in healthy adults between winter and summer months.
Design
An observational study of healthy adults (age 32 ± 9 years) living in central Scotland.
Methods
Thirty-four healthy adults (13 females) were monitored for 7 days in summer and winter to record sunlight exposure (ultraviolet-A (UV-A) radiation), diet, and physical activity. At the end of each phase, blood pressure was measured, and samples of blood and saliva collected. The samples were analysed to determine the concentrations of plasma and salivary nitrate and nitrite and serum 25-hydroxyvitamin D (25(OH)D).
Results
The participants maintained similar diets in each measurement phase but were exposed to more UV-A radiation (550%) and undertook more moderate-vigorous physical activity (23%) in the summer than in winter. Plasma nitrite (46%) and serum 25(OH)D (59%) were higher and blood pressure was lower in the summer compared to winter months. Plasma nitrite concentration was negatively associated with systolic, diastolic, and mean arterial blood pressure.
Conclusions
Plasma nitrite, an established marker of nitric oxide synthesis, is higher in healthy adults during the summer than in winter. This may be mediated by a greater exposure to UV-A which stimulates the release of nitric oxide metabolites from skin stores. While it is possible that seasonal variation in nitric oxide availability may contribute to an increased blood pressure in the winter months, the overall impact on cardiovascular health remains to be determined.