Measurement of nitric oxide bioavailability during dynamic handgrip exercise in women with Metabolic Syndrome.

Abstract

BackgroundThe bioavailability of nitric oxide (NO) has been shown to contribute to vascular function during peak exercise. Young women with Metabolic Syndrome (MetSyn) have presented with a deficit in vascular conductance during exercise hyperemia. Since NO has been shown to play a key role in vasodilation during exercise, it is crucial to identify if there is a deficit in the NO synthesis and how it affects vasculature of these young women. The aim of this study is to measure changes in bioavailable blood NO levels at rest and during peak handgrip exercise and determine its correlation to vascular conductance in women with MetSyn compared to healthy controls.MethodsIn this study, 15 participants (6 MetSyn and 9 Controls) performed the procedure of graded handgrip exercise on a dynamic handgrip device while beat‐to‐beat blood pressure (CNAP finger plethysmography), brachial artery diameter and blood flow with Doppler ultrasound and B‐mode imaging were measured continuously. During this exercise, participants used a handgrip dynamometer at a cadence of 30 contractions/minute. Exercise workload was increased in a ramp fashion (0.5 kg·min−1) until task failure. At rest and immediately upon task failure, a venipuncture was performed to take rest and peak NO levels to be later measured by a EPR Spectroscopy and Colorimetric Nitrate/Nitrite commercial ELISA kit. Whole blood was drawn into a prepared vacutainer in a 1:1 venous blood to the metal chelator, deferoxamine (DF), in diethyldithiocarbamate (DETC) Krebs buffer. Plasma was preserved with EDTA and all samples were immediately flash frozen in liquid nitrogen and stored at −80 degrees Celsius.ResultsThere was a significant difference in resting NO values (p=0.034) as well as end NO concentration values (p=0.053) between MetSyn and control groups. However, the MetSyn showed higher resting and peak NO values than control group as measured by ELISA. The change in plasma NO did not show any significant changes from rest to peak exercise in both groups (MetSyn p=0.757, control p=0.562). However, using the EPR spectroscopy method there is a significant difference identified between rest and peak exercise (p<0.05). There was no significant change in NO between the groups (p=0.633). The MetSyn group has a significantly diminished arterial conductance in the brachial artery during handgrip as well as a attenuated response in the femoral artery during dynamic leg kick. The change in brachial conductance did not show significant correlation to the change in NO levels in either of the groups (MetSyn p=0.792, r=−0.321, control p=0.549, r=−0.310) with the ELISA method.ConclusionsThe colorimetric nitrate/nitrite ELISA assay is not a reliable technique to measure the degree of change of NO concentrations at peak exercise. The whole blood EPR technique previously used in our laboratory work showed more significant results associated with the declining exercise hyperemia of the MetSyn group. Future studies will focus on clarifying methodologies for quantifying blood NO bioavailability at 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.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.