The Systemic Redox Status Is Maintained in Non-Smoking Type 2 Diabetic Subjects Without Cardiovascular Disease:Association with Elevated Triglycerides and Large VLDL

Decreased circulating levels of free thiols (R-SH, sulfhydryl groups) reflect enhanced oxidative stress, which plays an important role in the pathogenesis of cardiometabolic diseases. Since hyperglycemia causes oxidative stress, we questioned whether plasma free thiols are altered in patients with type 2 diabetes mellitus (T2DM) without cardiovascular disease or renal function impairment. We also determined their relationship with elevated triglycerides and very low density lipoproteins (VLDL), a central feature of diabetic dyslipidemia. Fasting plasma free thiols (colorimetric method), lipoproteins, VLDL (nuclear magnetic resonance spectrometry), free fatty acids (FFA), phospholipid transfer protein (PLTP) activity and adiponectin were measured in 79 adult non-smoking T2DM subjects (HbA1c 51 ± 8 mmol/mol, no use of insulin or lipid lowering drugs), and in 89 non-smoking subjects without T2DM. Plasma free thiols were univariately correlated with glucose (r = 0.196, p < 0.05), but were not decreased in T2DM subjects versus non-diabetic subjects (p = 0.31). Free thiols were higher in subjects with (663 ± 84 µmol/L) versus subjects without elevated triglycerides (619 ± 91 µmol/L; p = 0.002). Age- and sex-adjusted multivariable linear regression analysis demonstrated that plasma triglycerides were positively and independently associated with free thiols (β = 0.215, p = 0.004), FFA (β = 0.168, p = 0.029) and PLTP activity (β = 0.228, p = 0.002), inversely with adiponectin (β = -0.308, p < 0.001) but not with glucose (β = 0.052, p = 0.51). Notably, the positive association of free thiols with (elevated) triglycerides appeared to be particularly evident in men. Additionally, large VLDL were independently associated with free thiols (β = 0.188, p = 0.029). In conclusion, circulating free thiols are not decreased in this cohort of non-smoking and generally well-controlled T2DM subjects. Paradoxically, higher triglycerides and more large VLDL particles are likely associated with higher plasma levels of thiols, reflecting lower systemic oxidative stress

Local and Systemic Oxidative Stress Biomarkers for Male Infertility: The ORION Study

Infertility problems occur in around 10% of all couples worldwide, with male-factor infertility as the sole contributor in 20–30% of these cases. Oxidative stress (OS) is suggested to be associated with the pathophysiology of male infertility. In spermatozoa, OS can lead to damage to the cell membrane, resulting in disruption of DNA integrity and a decrease in motility. Established biomarkers for OS include free thiols and malondialdehyde (MDA), both representing different components of the reactive species interactome (RSI). This exploratory study aimed to investigate seminal plasma-free thiol and MDA levels in relation to semen parameters as defined by the World Health Organization (WHO) to determine if these markers are adequate to define local OS status. Furthermore, this study investigated if there is a relation between systemic and local OS status by comparing seminal concentrations of free thiol (R-SH, sulfhydryl groups, representing the extracellular redox status) and MDA (lipid peroxidation product) levels to those measured in serum. Free thiol and MDA measurements in both serum and semen plasma were performed in 50 males (18–55 y) of couples seeking fertility treatment. A significant positive correlation was found between seminal plasma-free thiol levels and sperm concentration and progressive motility (r = 0.383, p = 0.008 and r = 0.333, p = 0.022, respectively). In addition, a significant positive correlation was found between MDA levels in seminal plasma and sperm concentration (r = 0.314, p = 0.031). This study supports that seminal plasma-free thiols may be promising as local OS biomarkers. No associations were observed between local and systemic OS biomarker concentrations

The effect of induction therapy with infliximab or vedolizumab on hepcidin and iron status in patients with Inflammatory Bowel Disease

Background Differentiating absolute iron deficiency from functional iron restriction is challenging in active Inflammatory Bowel Disease (IBD). Hepcidin, the systemic iron regulator, could be the key in the diagnosis and management of absolute iron deficiency. In this study, we assessed hepcidin as a diagnostic iron deficiency marker and we explored the relationship between hepcidin, inflammation, hypoxia, and iron deficiency in patients receiving induction therapy with infliximab (IFX) or vedolizumab (VEDO). Methods 130 patients with IBD, who received induction therapy with IFX or VEDO for active disease, were included in this study. Clinical and biochemical data were extracted from medical records. Serum samples at baseline and week 6 of induction therapy were retrieved from the University Medical Center Groningen (UMCG) biobank and analysed for: hepcidin, inflammation (e.g., interleukins [IL] 6, 10, and Tumour Necrosis Factor-α [TNFα]), oxidative stress (free thiols), and hypoxia (e.g., erythropoietin [EPO], Macrophage Inflammatory Protein-3α [MIP3α]). For comparison, serum samples from 50 age- and gender-matched healthy controls were obtained from pre-donation biobank at the UMCG. Response to therapy was defined by either General Physician’s Assessment at week 14 of induction therapy, normalisation or at least a three-point decrease in clinical scores: Harvey-Bradshaw Index (HBI) for Crohn’s Disease, Simple Clinical Colitis Activity Index (SCCAI) for ulcerative colitis. Results Hepcidin correlated with ferritin and sTfR/log ferritin index [ρ = 0.74 and ρ = -0.79, respectively; P<0.001 for both markers], while inflammation- and hypoxia-associated markers showed only marginal correlations. Hepcidin accurately identified absolute iron deficiency: AUC(hepcidin) = 0.89 [95% CI: 0.82–0.95; P<0.001]. Induction with either IFX or VEDO decreased hepcidin [13.5 ng/mL vs. 9.5 ng/mL; P<0.001], ferritin [45.5 ug/L vs. 37.0 ug/L, P<0.05], and inflammatory markers at week 6, while transferrin increased [2.4 g/L vs. 2.5 g/L, P<0.001]. In total, 75.4% of patients responded to the induction therapy. Hepcidin and ferritin decreased, while transferrin increased (P<0.001 for all changes) in patients who responded to the therapy. In addition, hypoxia (EPO and MIP3α) and inflammatory markers such as faecal calprotectin, IL-6, IL-22, and TNFα improved significantly. In contrast, none of these improvements were observed in patients who did not respond to the therapy. Conclusion Hepcidin reflects iron deficiency in active IBD, but inflammation masks the severity of the deficiency. Induction therapy with either IFX or VEDO modulates hepcidin and iron indices, especially in patients who respond to the therapy

Acute Kidney Injury is Associated with Lowered Plasma-Free Thiol Levels

Acute kidney injury (AKI) is associated with the abrupt loss of kidney function. Oxidative stress plays an important role in the pathophysiology of AKI. Free thiols (R-SH) are crucial components of the extracellular antioxidant machinery and reliably reflect systemic oxidative stress. Lower levels of thiols represent higher levels of oxidative stress. In this preliminary study, we hypothesized that plasma-free thiols are associated with AKI upon admission to the intensive care unit (ICU). In this study, 301 critically ill patients were included. Plasma samples were taken upon admission, and albumin-adjusted plasma-free thiols were determined. Albumin-adjusted plasma-free thiols were lower in patients with AKI (n = 43, median (interquartile range) 7.28 mu mol/g (3.52, 8.95)) compared to patients without AKI (8.50 mu mol/g (5.82, 11.28); p < 0.05) upon admission to the ICU. Higher age (B = -0.72), higher levels of neutrophil gelatinase-associated lipocalin (B = -0.002), creatinine (B = -0.01) and lower serum albumin (B = 0.47) were associated with lower free thiol levels. Further, albumin-adjusted free thiol levels were significantly reduced in patients with sepsis (8.30 (5.52-10.64) mu mol/g) compared to patients without sepsis (6.95 (3.72-8.92) mu mol/g; p < 0.05). Together, albumin-adjusted plasma-free thiols were significantly reduced in patients with AKI and patients with sepsis compared with patients without AKI and sepsis

[18F]-sodium fluoride autoradiography imaging of nephrocalcinosis in donor kidneys and explanted kidney allografts

Nephrocalcinosis is present in up to 43% of kidney allograft biopsies at one-year after transplantation and is associated with inferior graft function and poor graft survival. We studied [18F]-sodium fluoride ([18F]-NaF) imaging of microcalcifications in donor kidneys (n = 7) and explanted kidney allografts (n = 13). Three µm paraffin-embedded serial sections were used for histological evaluation of calcification (Alizarin Red; Von Kossa staining) and ex-vivo [18F]-NaF autoradiography. The images were fused to evaluate if microcalcification areas corresponded with [18F]-NaF uptake areas. Based on histological analyses, tubulointerstitial and glomerular microcalcifications were present in 19/20 and 7/20 samples, respectively. Using autoradiography, [18F]-NaF uptake was found in 19/20 samples, with significantly more tracer activity in kidney allograft compared to deceased donor kidney samples (p = 0.019). Alizarin Red staining of active microcalcifications demonstrated good correlation (Spearman's rho of 0.81, p < 0.001) and Von Kossa staining of consolidated calcifications demonstrated significant but weak correlation (0.62, p = 0.003) with [18F]-NaF activity. This correlation between ex-vivo [18F]-NaF uptake and histology-proven microcalcifications, is the first step towards an imaging method to identify microcalcifications in active nephrocalcinosis. This may lead to better understanding of the etiology of microcalcifications and its impact on kidney transplant function

Crohn’s Disease in Clinical Remission Is Marked by Systemic Oxidative Stress

Introduction: Crohn’s disease (CD) is characterized by chronic and relapsing inflammation of the gastro-intestinal tract. It is assumed that oxidative stress contributes to CD pathogenesis, but systemic biomarkers for oxidative stress in CD are not yet identified. A reduction in free thiol groups in plasma proteins (“plasma free thiols”) reflects systemic oxidative stress since they are prime substrates for reactive oxygen species. Here, we determined the concentrations of plasma free thiols in CD patients and healthy controls and studied the putative correlation with disease parameters.Methods: Free thiols were quantified in plasma of patients with CD in clinical remission [according to the Harvey Bradshaw Index (HBI)] and healthy controls and adjusted for plasma albumin. Albumin-adjusted free thiol concentrations were analyzed for associations with clinical and biochemical disease markers.Results: Mean plasma free thiol concentrations were significantly lower in patients with CD (n = 51) compared to healthy controls (n = 27) (14.7 ± 2.4 vs. 17.9 ± 1.8 μmol/g albumin; P &lt; 0.001). Patients with CD with above-average free thiols had significantly lower CRP levels (median 1.4 [interquartile range] [0.4; 2.6] vs. 3.6 [0.6; 7.0] mg/L; P &lt; 0.05) and BMI (23.6 ± 4.8 vs. 27.1 ± 5.2 kg/m2; P &lt; 0.05). Patients with CD having solely colonic disease demonstrated markedly reduced plasma free thiol concentrations compared to patients with ileocolonic involvement (13.2 ± 1.8 vs. 15.2 ± 2.2 μmol/g; P &lt; 0.05). Finally, plasma free thiol concentrations negatively correlated with biomarkers of inflammation, including hsCRP, SAA, IL-17A (all P &lt; 0.05), and VEGF.Conclusion: Plasma free thiols are reduced in patients with CD in clinical remission compared to healthy controls. Thus, subclinical CD disease activity is reflected by systemic oxidative stress and plasma free thiols may be a relevant therapeutic target and biomarker to monitor disease activity in CD

Systemic Oxidative Stress Is Increased in Postmenopausal Women and Independently Associates with Homocysteine Levels

Oxidative stress plays a pivotal role in the pathogenesis of cardiovascular diseases (CVD). Postmenopausal women have an increased risk of developing CVD due to decreased estrogen availability, which is accompanied by increased oxidative stress. Serum free thiols (R-SH) provide a robust and powerful read-out of systemic oxidative stress. In this study, we aimed to establish serum levels of free thiols and explore associations between free thiols and demographic, clinical, and biochemical parameters related to obesity and the risk for developing CVD in both pre-and postmenopausal women. Serum free thiols were measured in a cohort consisting of healthy pre-(n = 223) and postmenopausal (n = 118) Omani women. Postmenopausal women had significantly lower levels of serum free thiols as compared to premenopausal women (762.9 ± 85.3 vs. 780 ± 80.9 µM, age-adjusted p < 0.001). Women′ s age was positively associated with serum free thiol levels in premenopausal women (β = 0.36, p = 0.002), whereas an inverse association was observed in postmenopausal women (β = −0.29, p = 0.002). Homocysteine levels were significantly inversely associated with serum free thiol levels in both pre-(β = −0.19, p = 0.005) and postmenopausal (β = −0.20, p = 0.032) women, independent from known cardiovascular risk factors. In this study, we show that postmenopausal women are affected by increased systemic oxidative stress, which independently associates with homocysteine levels

Serum free sulfhydryl status associates with new-onset chronic kidney disease in the general population

BACKGROUND: Serum sulfhydryl groups (R-SH, free thiols) reliably reflect the systemic redox status in health and disease. As oxidation of R-SH occurs rapidly by reactive oxygen species (ROS), oxidative stress is accompanied by reduced levels of free thiols. Oxidative stress has been implicated in the pathophysiology of chronic kidney disease (CKD), in which redox imbalance may precede the onset of CKD. Therefore, we aimed to investigate associations between serum free thiols and the risk of incident CKD as defined by renal function decline and albuminuria in a population-based cohort study. METHODS: Subjects without CKD (n = 4,745) who participated in the Prevention of REnal and Vascular ENd-stage Disease (PREVEND) study, a prospective, population-based cohort study in the Netherlands, were included. Baseline protein-adjusted serum free thiols were studied for their associations with the development of CKD, defined as a composite outcome of an estimated glomerular filtration rate (eGFR)  30 mg/24-h, or both. RESULTS: Median level of protein-adjusted serum free thiols at baseline was 5.14 μmol/g of protein (interquartile range [IQR]: 4.50–5.75 μmol/g) and median eGFR was 96 mL/min/1.73 m(2) [IQR: 85–106]. Protein-adjusted serum free thiols were significantly associated with incident CKD (hazard ratio [HR] per doubling 0.42 [95% confidence interval [CI]: 0.36–0.52, P 30 mg/24-h after full adjustment for confounding factors (HR per doubling 0.70 [95% CI: 0.51–0.96], P=0.028). CONCLUSION: Higher levels of serum R-SH, reflecting less oxidative stress, are associated with a decreased risk of developing CKD in subjects from the general population. This association is primarily driven by incident CKD as defined by UAE

Serum free thiols predict cardiovascular events and all-cause mortality in the general population:a prospective cohort study

BACKGROUND: Serum free thiols (R-SH, sulfhydryl groups) reliably reflect systemic oxidative stress. Since serum free thiols are rapidly oxidized by reactive species, systemic oxidative stress is generally associated with reduced serum free thiol levels. Free thiols associate with favorable disease outcomes in many patient cohorts, and the current hypothesis is that oxidative stress might also play an important role in cardiovascular disease. In this study, we aimed to establish the role of serum free thiols in the general population by investigating their relationship with the risk of cardiovascular (CV) events and all-cause mortality. METHODS: Participants (n = 5955) of the Prevention of REnal and Vascular ENd-stage Disease (PREVEND) cohort study from the general population were included. At baseline, serum levels of free thiols were quantified and adjusted to total protein levels. Protein-adjusted serum free thiol levels were studied for their associations with clinical and biochemical parameters, as well as with the risk of CV events and all-cause mortality. RESULTS: The mean protein-adjusted serum free thiol level was 5.05 ± 1.02 μmol/g of protein. Protein-adjusted serum free thiols significantly predicted the risk of CV events, even after adjustment for potential confounding factors (hazard ratio [HR] per doubling 0.68 [95% confidence interval [CI] 0.47-1.00], P = 0.048). Similarly, protein-adjusted serum free thiols were significantly predictive of the risk of all-cause mortality (HR per doubling 0.66 [95% CI 0.44-1.00], P = 0.050). Stratified analyses revealed lower HRs for subjects with a lower body mass index (BMI), without hypertension, and without diabetes. Conversely, HRs were lower in subjects with albuminuria. CONCLUSIONS: In this large population-based cohort study, serum free thiols significantly predicted the risk of CV events and all-cause mortality. Our results highlight the potential significance and clinical applicability of serum free thiols since they are amendable to therapeutic intervention