Measurement of Nitric Oxide with EPR in Whole Blood during Peak Hand Grip Exercise in Women with Metabolic Syndrome

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The contribution of bioavailable Nitric Oxide to the change in vascular function during exercise hyperemia is primarily concluded through the lack of functional changes in the presence of eNOS inhibitors. The aim of this study is to utilize EPR techniques to measure the changes in NO production during peak hand grip exercise to identify mechanistic differences of vascular function in women with Metabolic Syndrome compared to healthy controls.MethodsIn this study, 13 participants (5 MetSyn and 8 Controls) performed the procedure of graded handgrip exercise on a dynamic handgrip device while brachial blood flow was continuously measured with Doppler ultrasound and B‐mode (GE Vivid E with 6MHz linear probe). Following a brief rest, individuals were asked to perform handgrip exercise whereby the workload progressively increased in a ramp fashion (0.5 kg·min−1) until the required contraction rate (30 cpm) could no longer be maintained. At rest and immediately after halting exercise at task failure for individual peak resistance, whole blood was drawn into a prepared vaccutainer in a 1:1 venous blood to the metal chelator, defferoxamine (DF), in diethyldithiocarbamate (DETC) Krebs buffer. The samples were immediately flash frozen in liquid nitrogen and stored at −80 degrees Celsius. All pre and peak NO samples were measured and compared with known NO samples using an X‐band electron paramagnetic resonance spectrometer (Bruker Biospin, Karlsruhe, Germany). Whole blood with known concentrations of NO2 (1–10mM) and Na2S2O4 (20 mM) served as a reference.ResultsWhole blood NO increased significantly from rest to peak exercise in both groups (p=0.047) in addition to brachial conductance (p=0.0001). There was no significant difference in the rise in NO during peak exercise between the MetSyn and Control groups (p=0.67) however there is a significant difference in brachial conductance starting, peak and delta between the groups (p=0.021, 0.028, and 0.019).ConclusionThe whole blood Iron Chelated EPR technique is capable of detecting the degree of change in NO potentially contributing exercise hyperemia in different groups and potentially at variable grades of exercise. Although there is a significant difference in the vascular conductance between the groups, with the number of participants included in this study, there was no difference indicated between the groups for NO at rest and peak exercise.Support or Funding InformationResearch reported in this publication was supported by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number P20GM103451.