This is the first study which non-invasively evaluated the NADH skin content in human superficial skin cells in highly trained athletes. Until now methods used to evaluate NADH level, and therefore mitochondrial function, were not easily accessible. Metabolic changes, elicited by exercise to exhaustion, modify the skin NADH metabolism at rest, during ischemia and reperfusion in the most superficial living skin cells. Immediately after exercise, there is a shift of the baseline fluorescence of NADH in the skin cells toward higher values. The absolute NADH amount increases during post-exercise ischemia and reperfusion, compared to resting condition. However, compared to resting conditions, the relative rise in the NADH is significantly lower during ischemia, whereas the relative reduction in the NADH during reperfusion increases. These changes in the NADH metabolism during ischemia and reperfusion before and after exercise to exhaustion appear to be similar in male and female athletes.

There is some balance between the reduced (NADH) and oxidized (NAD+) forms of NAD. Although the 460 nm skin fluorescence measures only NADH, its values also reflect indirectly NAD+ as the total amount of NAD (i.e., combined amount of NADH and NAD+) seems to be rather stable at a relatively short period (a few minutes) necessary to perform the CPET. In other words, the NADH amount changes at the cost of the NAD+ content, and vice versa.

Olga Bugaj et al Front. Physiol., 15 May 2019 | https://doi.org/10.3389/fphys.2019.00600