Nitric Oxide at Altitude
Nitric oxide (NO) is a signaling molecule that controls vital bodily functions including the regulation of blood flow and blood pressure. For many years it was believed to be produced only by conversion of the amino acid L-arginine, but recent research has uncovered yet another way of producing NO that makes use of the simple anions, nitrite and nitrate. Nitrite and nitrate are found in all cells and body fluids and in our food. Interestingly, high altitude residents including Tibetan highlanders were shown to have high concentrations of these anions in their blood, suggesting that this may provide some benefit. Recent research suggests that virtually every cell and tissue has the capacity to produce NO not only from L-arginine but also via reduction of nitrite and nitrate, especially when oxygen concentrations are low. This opens up the interesting possibility that our bodily NO system might be modulated by simple changes in dietary intake of nitrite/nitrate. If true, this may be of particular significance to performance at altitude where supply with oxygen is limited.
We are testing a dietary intervention using a natural source of nitrate (produced by our partner, aurapa) to see whether blood pressure, exercise performance and lung function can be improved by supplying an extra portion of NO via this newly discovered pathway. A battery of functional tests are being performed to see whether blood flow changes in specific vascular beds using techniques such as forearm venous occlusion plethysmography and sublingual intravital microscopy, and results from these measurements will be compared to tissue oxygenation, cardiopulmonary exercise performance and other functional tests. We are also measuring NO in exhaled breath to see how concentrations change over time and collect blood and other body fluids for later biochemical measurements to complement our functional studies and provide mechanistic insight.
We are already seeing some interesting changes from the measurements we performed at sea level in London a couple of weeks ago. Let?s hope that the weather conditions will allow us to descend from the Margherita Hut in time to meet Team B at the Gnifetti Hut as they make their way up here to continue this exciting body of research.
Written by Martin Feelisch
Story by Ali Cobb