Measurements of Calf Muscle Oxygenation during Standing and Exercise in Patients with Chronic Venous Insufficiency

Background: Varicose vein tissues have been shown to have differential metabolic profiles as compared with non-varicose veins, suggesting a metabolic component of the disease. Vein wall stretch has been suggested as a potential etiological factor in the development of varicose veins. However, the relation between vein wall stretch and the metabolic profile of the vein wall is unclear. The aim of the study was to determine whether vein wall stretch alters the metabolic profile of the vein wall. Methods: Segments of male rat inferior vena cava (IVC) were suspended in tissue bath under 0.5 g basal tension for 1 hour, and a control contraction to phenylephrine (PHE, 10 5 M) and KCl (96 mM) was elicited. The veins were then exposed to normal 0.5 g or high 2 g tension for short 4 or prolonged 18 hours (five vein segments in each group). The veins were frozen, then hydrophilic and organic metabolites were extracted using a bilayer extraction method. Aqueous and organic extracts obtained from stretched (2 g tension) and non-stretched (0.5 g basal tension) IVC segments were run on 1-dimensional H Nuclear Magnetic Resonance (NMR) spectroscopy (800 MHz) and liquid-chromatography coupled to Mass Spectrometry (LC-MS) LCT QTOF premier (Waters Corporation, Milford, MA), respectively. Spectra acquired from NMR and chromatograms from LC-MS were mathematically modelled and statistically analysed using multivariate statistical models including MATLAB (Mathworks ) and SIMPCA-P + 12.0 (UMETRICS Sweden). 2-Dimensional NMR and tandem MS experiments were performed on selected samples for structural elucidation of molecules. Results: H NMR spectra of aqueous extracts of stretched and nonstretched veins for 4 hrs revealed the presence of several metabolites including leucine, isoleucine, valine, creatine, myo-inositol, choline, glucose, and aspartate. There was no significant difference in aqueous or lipid metabolic profiles of non-stretched and stretched IVC segments for 4 hours. Univariate analysis revealed increased concentrations of leucine, isoleucine, and valine metabolites in IVC segments stretched as compared with nonstretched for 18 hours (P value range, 0.01-0.004). Orthogonal partial least square-discriminatory (OPLS-DA) identified triglycerides moieties as a differentiating markers and were present in higher concentrations in stretched segments as compared with non-stretched vein segments for 18 hours (P value range, 0.01-0.003). Conclusions: We have shown, for the first time, a complete metabolic profile of aqueous and organic extracts from rat veins subjected to normal (0.5 g) and high (2 g) mechanical stretch. Elucidation of cellular pathways linked to these differential metabolites may disclose cellular mechanisms affected by stretch and may improve our understanding about varicose vein disease.