Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating disease characterized by severe and persistent fatigue. Along with clinical studies showing endothelial dysfunction (ED) in a subset of ME/CFS patients, we have recently reported altered ED-related microRNAs in plasma from affected individuals. Inadequate nitric oxide (NO), mainly produced by the endothelial isoform of nitric oxide synthase (eNOS) in endothelial cells (ECs), is a major cause of ED. In this study, we hypothesized that plasma from that cohort of ME/CFS patients induces eNOS-related ED in vitro. To test this, we cultured human umbilical vein endothelial cells (HUVECs) in the presence of plasma from either ME/CFS patients (ME/CFS-plasma, n = 11) or healthy controls (HC-plasma, n = 12). Then, we measured the NO production in the absence and presence of tyrosine kinase and G protein-coupled receptors agonists (TKRs and GPCRs, respectively), well-known to activate eNOS in ECs. Our data showed that HUVECs incubated with ME/CFS-plasma produced less NO either in the absence or presence of eNOS activators compared to ones in presence of HC-plasma. Also, the NO production elicited by bradykinin, histamine, and acetylcholine (GPCRs agonists) was more affected than the one triggered by insulin (TKR agonist). Finally, inhibitory eNOS phosphorylation at Thr⁴⁹⁵ was higher in HUVECs treated with ME/CFS-plasma compared to the same treatment with HC-plasma. In conclusion, this study in vitro shows a decreased NO production in HUVECs exposed to plasma from ME/CFS patients, suggesting an unreported role of eNOS in the pathophysiology of this disease.

The association between advanced oxidation protein products (AOPPs) and lipoprotein subclasses remains unexplored. Therefore, we performed comprehensive lipoprotein profiling of serum using NMR spectroscopy and examined the associations of lipoprotein subclasses with the serum levels of AOPPs in healthy volunteers (HVs) and patients with metabolic syndrome (MS). The serum levels of AOPPs were significantly positively correlated with the serum levels of very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and low-density lipoprotein (LDL); however, they were significantly negatively correlated with high-density lipoprotein (HDL). These lipoproteins (and their subclasses) differed markedly regarding the direction of correlations between their lipid contents and AOPPs. The strength of the correlations and the relative contributions of the subclasses to the correlations were different in the HVs and patients with MS. As revealed by orthogonal partial least squares discriminant analyses, the serum levels of IDL were strong determinants of AOPPs in the HVs, whereas the serum levels of VLDL and the lipid content of LDL were strong determinants in both groups. We conclude that IDL, VLDL, and LDL facilitate, whereas HDL diminishes the bioavailability of serum AOPPs. The presence of MS and the lipid contents of the subclasses affect the relationship between lipoproteins and AOPPs.

Acute heart failure (AHF) is associated with high short- and long-term mortality, and early identification of patients at highest risk remains challenging despite the use of established biomarkers and clinical risk scores. Oxidative stress plays a central role in the pathophysiology of AHF but has been insufficiently investigated as a prognostic target. This study aimed to evaluate the prognostic value of serum oxidative stress biomarkers for predicting short- and long-term mortality in AHF patients and to determine whether they improve risk stratification beyond established tools. Admission serum levels of malondialdehyde (MDA), advanced oxidation protein products (AOPPs), catalase, and superoxide dismutase (SOD) were measured in a cohort of 315 hospitalized AHF patients. Univariable and multivariable logistic regression analyses were performed to assess associations with in-hospital, 6-month, and 12-month mortality. Prognostic performance was compared with N-terminal pro-brain natriuretic peptide (NT-proBNP) and established risk scores (ADHERE, GWTG-HF, OPTIMIZE-HF) using receiver operating characteristics curves, the continuous net reclassification index (cNRI) and decision curve analysis. Serum MDA, catalase, and SOD were significantly elevated in non-survivors at all time points. In the adjusted analyses, MDA was the only oxidative stress marker independently associated with mortality. MDA showed robust prognostic performance, with improvements in AUC and cNRI as well as increased net benefit, when added to NT-proBNP or clinical scores. Survival analysis confirmed lower survival in patients with MDA ≥1.45 nmol/L (the median in our cohort). Other biomarkers (AOPPs, catalase, SOD) showed limited prognostic utility. Serum MDA is a robust, independent predictor of mortality in AHF. Incorporating MDA into routine assessment may enhance early identification of high-risk patients and support personalized management strategies in AHF.