The role of plasma aminothiols in the prediction of coronary microvascular dysfunction and plaque vulnerability

Circulating Biomarkers in Coronary Microvascular Dysfunction

Coronary microvascular dysfunction is an underdiagnosed pathologic process that is associated with adverse clinical outcomes. Biomarkers, molecules measurable in the blood, could inform the clinician by aiding in the diagnosis and management of coronary microvascular dysfunction. We present an updated review of circulating biomarkers in coronary microvascular dysfunction representing key pathologic processes, including inflammation, endothelial dysfunction, oxidative stress, coagulation, and other mechanisms.

The Impact of Genetic Polymorphisms in Glutamate-Cysteine Ligase, a Key Enzyme of Glutathione Biosynthesis, on Ischemic Stroke Risk and Brain Infarct Size

The purpose of this pilot study was to explore whether polymorphisms in genes encoding the catalytic (GCLC) and modifier (GCLM) subunits of glutamate-cysteine ligase, a rate-limiting enzyme in glutathione synthesis, play a role in the development of ischemic stroke (IS) and the extent of brain damage. A total of 1288 unrelated Russians, including 600 IS patients and 688 age- and sex-matched healthy subjects, were enrolled for the study. Nine common single nucleotide polymorphisms (SNPs) of the GCLC and GCLM genes were genotyped using the MassArray-4 system. SNP rs2301022 of GCLM was strongly associated with a decreased risk of ischemic stroke regardless of sex and age (OR = 0.39, 95%CI 0.24−0.62, p < 0.0001). Two common haplotypes of GCLM possessed protective effects against ischemic stroke risk (p < 0.01), but exclusively in nonsmoker patients. Infarct size was increased by polymorphisms rs636933 and rs761142 of GCLC. The mbmdr method enabled identifying epistatic interactions of GCLC and GCLM gene polymorphisms with known IS susceptibility genes that, along with environmental risk factors, jointly contribute to the disease risk and brain infarct size. Understanding the impact of genes and environmental factors on glutathione metabolism will allow the development of effective strategies for the treatment of ischemic stroke and disease prevention.

Glycogen storage disease type I patients with hyperlipidemia have no signs of early vascular dysfunction and premature atherosclerosis

BACKGROUND AND AIMS

Glycogen storage disease type I (GSD I) is associated with hyperlipidemia, a known risk factor for premature atherosclerosis. Few studies have addressed endothelial dysfunction in patients with GSD I, and these studies yielded controversial results.

METHODS AND RESULTS

We investigated vascular dysfunction in a cohort of 32 patients with GSD I (26 GSD Ia, 6 GSD Ib, mean age 20.7 (4.8-47.5) years) compared to 32 age-, gender-, and BMI-matched healthy controls using non-invasive techniques such as quantification of carotid intima media thickness, retinal vessel analysis and 24 h-blood pressure measurements. In addition, early biomarkers of inflammatory and oxidative endothelial stress were assessed in blood. Although GSD I patients had a clearly proatherogenic lipid profile, increased oxidative stress, higher levels of high sensitivity C-reactive protein and increased lipoprotein associated phospholipase A2 activity, functional and structural parameters including carotid intima media thickness and retinal vessel diameters did not indicate premature atherosclerosis in this patient cohort. Blood pressure values and pulse wave velocity were comparable in patients and healthy controls, while central blood pressure and augmentation index were higher in GSD patients.

CONCLUSION

Our data suggest that GSD I is not associated with early vascular dysfunction up to the age of at least 20 years. Further studies are needed to elucidate the possibly protective mechanisms that prevent early atherosclerosis is GSD I. Longer follow-up studies are required to assess the long-term risk of vascular disease with increased oxidative stress being present in GSD I patients.

Targeting Enrichment and Correlation Studies of Glutathione and Homocysteine in IgAVN Patient Urine Based on a Core-Shell Zr-Based Metal-Organic Framework

Aminothiols are closely related to chronic kidney disease, but little is known regarding levels of related aminothiols in the urine of immunoglobulin A vasculitis with nephritis (IgAVN) patients. Herein, a well-defined core-shell Zr-based metal-organic framework (Zr-MOF) composite SiO₂@50Benz-Cys was constructed as a mercury ion affinity material via a solvent-assisted ligand exchange strategy for the selective extraction and enrichment of low-concentration aminothiols in IgAVN patient urine. SiO₂@50Benz-Cys was competent to enrich the total glutathione (GSH) and total homocysteine (Hcy) in virtue of the excellent affinity after chelation with mercury ions. The extraction efficiencies were closely related to the pH, dithiothreitol amount, and the dose of functional Zr-MOF. Coupled with HPLC-MS/MS in optimized conditions, GSH and Hcy were determined with low detection limits of 0.5 and 1 nmol L^-1, respectively. The recoveries of GSH and Hcy for the urine sample at three spiked levels were in the range of 85.3-105% and 79.5-103%, which showed good precision and accuracy. Benefiting from the matrix interference elimination in the process of extraction, the simultaneous detection of aminothiols in the urine of the healthy group and immunoglobulin A vasculitis (IgAV) and IgAVN patients was successfully carried out, suggesting that the Zr-MOF and the robust method together provided a potential application in the analysis of urinary biomolecules. The analysis of variance (ANOVA) showed that the levels of GSH and Hcy had significant differences between the patients and the control. This work is very valuable as it provides a better understanding of concentration alterations of GSH and Hcy in urine involved with IgAVN for clinical research.

Biomarkers of Coronary Microvascular Dysfunction in Patients With Microvascular Angina: A Narrative Review

The current gold standard for diagnosis of coronary microvascular dysfunction (CMD) in the absence of myocardial diseases, whose clinical manifestation is microvascular angina (MVA), is reactivity testing using adenosine or acetylcholine during coronary angiography. This invasive test can be difficult to perform, expensive, and harmful. The identification of easily obtainable blood biomarkers which reflect the pathophysiology of CMD, characterized by high reliability, precision, accuracy, and accessibility may reduce risks and costs related to invasive procedures and even facilitate the screening and diagnosis of CMD. In this review, we summarized the results of several studies that have investigated the possible relationships between blood biomarkers involved with CMD and MVA. More specifically, we have divided the analyzed biomarkers into 3 different groups, according to the main mechanisms underlying CMD: biomarkers of "endothelial dysfunction," "vascular inflammation," and "oxidative stress." Finally, in the last section of the review, we consider mixed mechanisms and biomarkers which are not included in the 3 major categories mentioned above, but could be involved in the pathogenesis of CMD.

Coronary microvascular adaptations distal to epicardial artery stenosis

Until recently, epicardial coronary stenosis has been considered the primary outcome of coronary heart disease, and clinical interventions have been dedicated primarily to the identification and removal of flow-limiting stenoses. However, a growing body of literature indicates that both epicardial stenosis and microvascular dysfunction contribute to damaging myocardial ischemia. In this review, we discuss the coexistence of macro- and microvascular disease, and how the structure and function of the distal microcirculation is impacted by the hemodynamic consequences of an epicardial, flow-limiting stenosis. Mechanisms of endothelial dysfunction as well as alterations of smooth muscle function in the coronary microcirculation distal to stenosis are discussed. Risk factors including diabetes, metabolic syndrome, and aging exacerbate microvascular dysfunction in the myocardium distal to a stenosis, and our current understanding of the role of these factors in limiting collateralization and angiogenesis of the ischemic myocardium is presented. Importantly, exercise training has been shown to promote collateral growth and improve microvascular function distal to stenosis; thus, the current literature reporting the mechanisms that underlie the beneficial effects of exercise training in the microcirculation distal to epicardial stenosis is reviewed. We also discuss recent studies of therapeutic interventions designed to improve microvascular function and stimulate angiogenesis in clinically relevant animal models of epicardial stenosis and microvascular disease. Finally, microvascular adaptation to removal of epicardial stenosis is considered.

Oxidative Stress Is Associated With Diastolic Dysfunction in Women With Ischemia With No Obstructive Coronary Artery Disease

Background Women with signs and symptoms of ischemia and no obstructive coronary artery disease often have evidence of diastolic dysfunction. Oxidative stress (OS) is associated with cardiovascular risk factors and adverse outcomes. The relationship between systemic OS and diastolic dysfunction is unknown. Methods and Results A subgroup of women (n=75) with suspected ischemia and no obstructive coronary artery disease who had both cardiac magnetic resonance imaging and OS measurements were enrolled in the WISE-CVD (Women Ischemia Syndrome Evaluation-Coronary Vascular Dysfunction) study. Left ventricular end-diastolic pressure was measured invasively. Left ventricular end-diastolic volume and peak filling rate were assessed using cardiac magnetic resonance imaging. Aminothiol levels of plasma cystine and glutathione were measured as markers of OS. Spearman correlation and linear regression analyses were conducted. The group mean age was 54±11 years, and 61% had a resting left ventricular end-diastolic pressure >12 mm Hg. Cystine levels correlated negatively with the peak filling rate (r=-0.31, P=0.007) and positively with left ventricular end-diastolic pressure (r=0.25; P=0.038), indicating that increased OS was associated with diastolic dysfunction. After multivariate adjustment including multiple known risk factors for diastolic dysfunction and cardiovascular medications, cystine levels continued to be associated with peak filling rate (β=-0.27, P=0.049) and left ventricular end-diastolic pressure (β=0.25; P=0.035). Glutathione levels were not associated with indices of diastolic function. Conclusions OS, measured by elevated levels of cystine, is associated with diastolic dysfunction in women with evidence of ischemia and no obstructive coronary artery disease, indicating the role of OS in patients with ischemia and no obstructive coronary artery disease. Its role in the progression of heart failure with preserved ejection fraction should be explored further.

Systemic transsulfuration pathway thiol concentrations in chronic obstructive pulmonary disease patients

BACKGROUND

It is amply reported that patients with chronic obstructive pulmonary disease (COPD) have increased risk of cardiovascular disease (CVD). Recent evidence suggests that COPD patients have elevated concentrations of plasma homocysteine (Hcy), a transsulfuration pathway analyte that is commonly regarded as a CVD risk factor.

DESIGN

We comprehensively investigated the plasma concentrations of transsulfuration pathway analytes, and their relationship with markers of oxidative stress and inflammation, to identify which low molecular thiols might play a pathophysiological role both in CVD and in COPD. Hcy, cysteine (Cys), glutathione (GSH), cysteinylglycine (CysGly), glutamylcysteine (GluCys), taurine (Tau), oxidative stress markers (TBARS and protein-SH, PSH) and the inflammation marker kynurenine/tryptophan (Kyn/Trp) ratio were measured in 54 COPD patients and 54 control subjects.

RESULTS

We found increased concentrations of total Hcy (P < .01) and total CysGly (P < .05) in COPD patients when compared to controls. Total Hcy and CysGly were also significantly associated with abnormal lung function parameters and COPD severity. In COPD patients, total Hcy was significantly associated with the Kyn/Trp ratio (P = .0017) whereas total CysGly was significantly associated with both PSH (P = .0298) and the Kyn/Trp ratio (P = <.0001).

CONCLUSION

Both total Hcy and CysGly concentrations were significantly associated with the presence and severity of COPD and with markers of oxidative stress (total CysGly) and inflammation (total Hcy and CysGly). This suggests that specific low molecular mass thiols might play a role in the inflammatory and oxidative stress pathways involved in both CVD and COPD.

Hypercysteinemia, A Potential Risk Factor for Central Obesity and Related Disorders in Azores, Portugal

In Azores, the standardized mortality rate for coronary artery disease (CAD) is nearly the double when compared to mainland Portugal. The aim of this study was to compare the prevalence of conventional CAD risk factors, as well as the plasma aminothiol profile (and its major determinants), between two groups of healthy subjects from Ponta Delgada (in Azores) and Lisbon (in mainland) cities, searching for precocious biomarker(s) of the disease. The study groups consisted of 101 healthy volunteers from Ponta Delgada (PDL) and 121 from Lisbon, aged 20–69 years. No differences in the prevalence of classical CAD risk factors were found between the study groups, except in physical inactivity and related central obesity, which were both higher in PDL men than in those from Lisbon. Hypercysteinemia, which seems to result from sulfur-rich amino acid diets and/or vitamin B₁₂ malabsorption, revealed to be significantly more prevalent in PDL vs. Lisbon subjects (18% vs. 4%, P=0.001), namely, in male gender. Moreover, plasma Cys levels predicted waist circumference (β coefficient = 0.102, P=0.032) and concomitant central obesity and were also associated with insulin resistance. Nevertheless, hyperhomocysteinemia prevalence was similar in both groups, despite the fact that PDL subjects exhibited a higher rate of vitamin B₁₂ deficiency compared to those from Lisbon (19% vs. 6%, P=0.003). Owing to the nature of this study design, a cause-effect relationship between high plasma Cys levels and central obesity or CAD risk could not be derived, but results strongly suggest that hypercysteinemia is a potential risk factor for metabolic disorders, i.e., obesity and insulin resistance, and CAD in Azores, a hypothesis that asks for confirmation through further large prospective studies.

The mercapturomic profile of health and non-communicable diseases

The mercapturate pathway is a unique metabolic circuitry that detoxifies electrophiles upon adducts formation with glutathione. Since its discovery over a century ago, most of the knowledge on the mercapturate pathway has been provided from biomonitoring studies on environmental exposure to toxicants. However, the mercapturate pathway-related metabolites that is formed in humans—the mercapturomic profile—in health and disease is yet to be established. In this paper, we put forward the hypothesis that these metabolites are key pathophysiologic factors behind the onset and development of non-communicable chronic inflammatory diseases. This review goes from the evidence in the formation of endogenous metabolites undergoing the mercapturate pathway to the methodologies for their assessment and their association with cancer and respiratory, neurologic and cardiometabolic diseases.

Implications of plasma thiol redox in disease

Thiol groups are crucially involved in signaling/homeostasis through oxidation, reduction, and disulphide exchange. The overall thiol pool is the resultant of several individual pools of small compounds (e.g. cysteine), peptides (e.g. glutathione), and thiol proteins (e.g. thioredoxin (Trx)), which are not in equilibrium and present specific oxidized/reduced ratios. This review addresses mechanisms and implications of circulating plasma thiol/disulphide redox pools, which are involved in several physiologic processes and explored as disease biomarkers. Thiol pools are regulated by mechanisms linked to their intrinsic reactivity against oxidants, concentration of antioxidants, thiol-disulphide exchange rates, and their dynamic release/removal from plasma. Major thiol couples determining plasma redox potential (Eh) are reduced cysteine (CyS)/cystine (the disulphide form of cysteine) (CySS), followed by GSH/disulphide-oxidized glutathione (GSSG). Hydrogen peroxide and hypohalous acids are the main plasma oxidants, while water-soluble and lipid-soluble small molecules are the main antioxidants. The thiol proteome and thiol-oxidoreductases are emerging investigative areas given their specific disease-related responses (e.g. protein disulphide isomerases (PDIs) in thrombosis). Plasma cysteine and glutathione redox couples exhibit pro-oxidant changes directly correlated with ageing/age-related diseases. We further discuss changes in thiol-disulphide redox state in specific groups of diseases: cardiovascular, cancer, and neurodegenerative. These results indicate association with the disease states, although not yet clear-cut to yield specific biomarkers. We also highlight mechanisms whereby thiol pools affect atherosclerosis pathophysiology. Overall, it is unlikely that a single measurement provides global assessment of plasma oxidative stress. Rather, assessment of individual thiol pools and thiol-proteins specific to any given condition has more solid and logical perspective to yield novel relevant information on disease risk and prognosis.

Novel biomarkers of coronary microvascular disease

Coronary microvascular disease in the absence of myocardial diseases has traditionally been diagnosed through coronary reactivity testing in the cardiac catheterization laboratory. Compared with invasive procedures, blood-based biomarkers may have reduced cost, less risk of physical harm and greater accessibility, making them ideal for an outpatient management strategy. There are a variety of biomarkers available with potential utility in the management of microvascular disease; however, none have yet been extensively validated or established in this clinical patient population.

Elevated Levels of Serum Fibrin and Fibrinogen Degradation Products Are Independent Predictors of Larger Coronary Plaques and Greater Plaque Necrotic Core

BACKGROUND

Co-existence of vulnerable plaque and pro-thrombotic state may provoke acute coronary events. It was hypothesized that elevated serum levels of fibrin and fibrinogen degradation products (FDP) are associated with larger total plaque and necrotic core (NC) areas.

METHODS AND RESULTS

Seventy-five patients presenting with stable anginal symptoms (69%) or stabilized acute coronary syndrome (ACS; 31%), and found to have non-obstructive coronary artery disease (CAD) with a fractional flow reserve >0.8, were studied. Invasive virtual histology intravascular ultrasound (VH-IVUS) was performed in 68 LAD arteries, 6 circumflex arteries, and 1 right coronary artery. Serum FDP levels were measured using ELISA technique. Plaque volumetrics and composition were assessed in each VH-IVUS frame and averaged. The median age of patients was 56 (47-63) years; 52% were men and 23% had diabetes. The average length of coronary artery studied was 62 mm. After adjustment for systemic risk factors, medications, CRP levels and ACS, male gender (P<0.001) and serum FDP levels (P=0.02) were independent predictors of a larger NC area. Older age (P<0.001), male gender (P<0.0001) and increased serum FDP level (P=0.03) were associated with a larger plaque area.

CONCLUSIONS

In patients with CAD, a higher serum level of FDP is independently associated with larger plaques and greater plaque NC.

Comprehensive Assessment of Coronary Plaque Progression With Advanced Intravascular Imaging, Physiological Measures, and Wall Shear Stress: A Pilot Double-Blinded Randomized Controlled Clinical Trial of Nebivolol Versus Atenolol in Nonobstructive Coronary Artery Disease

Background

We hypothesized that nebivolol, a β‐blocker with nitric oxide–mediated activity, compared with atenolol, a β‐blocker without such activity, would decrease oxidative stress and improve the effects of endothelial dysfunction and wall shear stress (WSS), thereby reducing atherosclerosis progression and vulnerability in patients with nonobstructive coronary artery disease.

Methods and Results

In this pilot double‐blinded randomized controlled trial, 24 patients treated for 1 year with nebivolol 10 mg versus atenolol 100 mg plus standard medical therapy underwent baseline and follow‐up coronary angiography with assessments of inflammatory and oxidative stress biomarkers, microvascular function, endothelial function, and virtual histology intravascular ultrasound. WSS was calculated from computational fluid dynamics. Virtual histology intravascular ultrasound segments were assessed for vessel volumetrics and remodeling. There was a trend toward more low‐WSS segments in the nebivolol cohort (P=0.06). Low‐WSS regions were associated with greater plaque progression (P<0.0001) and constrictive remodeling (P=0.04); conversely, high‐WSS segments demonstrated plaque regression and excessive expansive remodeling. Nebivolol patients had decreased lumen and vessel areas along with increased plaque area, resulting in more constrictive remodeling (P=0.002). There were no significant differences in biomarker levels, microvascular function, endothelial function, or number of thin‐capped fibroatheromas per vessel. Importantly, after adjusting for β‐blocker, low‐WSS segments remained significantly associated with lumen loss and plaque progression.

Conclusion

Nebivolol, compared with atenolol, was associated with greater plaque progression and constrictive remodeling, likely driven by more low‐WSS segments in the nebivolol arm. Both β‐blockers had similar effects on oxidative stress, microvascular function, and endothelial function.

Clinical Trial Registration

URL: https://clinicaltrials.gov/. Unique identifier: NCT01230892.

Preparation of a conjugation-ready thiol responsive molecular switch

In this work we synthesize molecular switches that are responsive to cysteine, homocysteine, and glutathione; three redox systems that make up the majority of the body's antioxidant defenses. Synthesized spiropyran isomers with conjugation-ready linkages showed good selectivity of response to these major antioxidant thiols over nucleophilic amino acids; however the position of the linking group can affect selectivity and reversibility of the switching response. An isomer with selectivity for cysteine against GSH and Hcy was identified.

Plasma soluble urokinase-type plasminogen activator receptor level is independently associated with coronary microvascular function in patients with non-obstructive coronary artery disease

BACKGROUND

Soluble urokinase-type plasminogen activator receptor (suPAR) is a novel biomarker released from leukocytes and endothelial cells that has been associated with atherosclerotic cardiovascular disease. We hypothesized that plasma suPAR level is an independent predictor of coronary microvascular function.

METHODS

Coronary blood flow velocity and plasma suPAR levels were evaluated in patients with non-obstructive coronary artery disease. Coronary flow reserve (CFR) was calculated as the ratio of hyperemic to basal average peak blood flow velocity and coronary microvascular dysfunction was defined as CFR ≤ 2.0 in the setting of a fractional flow reserve value of ≥0.75. Plasma suPAR levels were measured using ELISA technique. The association between suPAR and CFR was investigated using univariate and multivariate regression analyses.

RESULTS

In 66 patients, 47% were men, 26% had diabetes, 68% had hypertension and 76% had dyslipidemia. Mean age was 55 ± 12 years and median suPAR level 2.82 (2.08-3.40) ng/mL. Plasma suPAR levels correlated with age (r = 0.31, p = 0.01), body mass index (r = 0.25, p = 0.04) and high-sensitivity C-reactive protein (hs-CRP) (r = 0.33, p = 0.009). While median suPAR level was not significantly different in patients with different cardiovascular risk factors, patients on statin therapy had significantly higher suPAR level (p = 0.03). SuPAR correlated negatively with CFR and, after multivariate adjustment for established cardiovascular risk factors, medications profiles and hs-CRP, suPAR remained an independent predictor of CFR (B = -0.30, p = 0.04), indicating an independent association between suPAR level and coronary microvascular function.

CONCLUSIONS

In this cross-sectional study, plasma suPAR level was an independent predictor of coronary microvascular function. Larger prospective clinical trials are warranted to investigate the prognostic value of this novel biomarker and the role of immune dysregulation in coronary microvascular disease.

Disturbed flow enhances inflammatory signaling and atherogenesis by increasing thioredoxin-1 level in endothelial cell nuclei

BACKGROUND

Oxidative stress occurs with disturbed blood flow, inflammation and cardiovascular disease (CVD), yet free-radical scavenging antioxidants have shown limited benefit in human CVD. Thioredoxin-1 (Trx1) is a thiol antioxidant protecting against non-radical oxidants by controlling protein thiol/disulfide status; Trx1 translocates from cytoplasm to cell nuclei due to stress signaling, facilitates DNA binding of transcription factors, e.g., NF-κB, and potentiates inflammatory signaling. Whether increased nuclear Trx1 contributes to proatherogenic signaling is unknown.

METHODOLOGY/PRINCIPAL FINDINGS

In vitro and in vivo atherogenic models were used to test for nuclear translocation of Trx1 and associated proinflammatory signaling. Disturbed flow by oscillatory shear stress stimulated Trx1 nuclear translocation in endothelial cells. Elevation of nuclear Trx1 in endothelial cells and transgenic (Tg) mice potentiated disturbed flow-stimulated proinflammatory signaling including NF-κB activation and increased expression of cell adhesion molecules and cytokines. Tg mice with increased nuclear Trx1 had increased carotid wall thickening due to disturbed flow but no significant differences in serum lipids or weight gain compared to wild type mice. Redox proteomics data of carotid arteries showed that disturbed flow stimulated protein thiol oxidation, and oxidation was higher in Tg mice than wild type mice.

CONCLUSIONS/SIGNIFICANCE

Translocation of Trx1 from cytoplasm to cell nuclei plays an important role in disturbed flow-stimulated proatherogenesis with greater cytoplasmic protein oxidation and an enhanced nuclear transcription factor activity. The results suggest that pharmacologic interventions to inhibit nuclear translocation of Trx1 may provide a new approach to prevent inflammatory diseases or progression.

Nitric oxide synthetic pathway in patients with microvascular angina and its relations with oxidative stress

A decreased nitric oxide (NO) bioavailability and an increased oxidative stress play a pivotal role in different cardiovascular pathologies. As red blood cells (RBCs) participate in NO formation in the bloodstream, the aim of this study was to outline the metabolic profile of L-arginine (Arg)/NO pathway and of oxidative stress status in RBCs and in plasma of patients with microvascular angina (MVA), investigating similarities and differences with respect to coronary artery disease (CAD) patients or healthy controls (Ctrl). Analytes involved in Arg/NO pathway and the ratio of oxidized and reduced forms of glutathione were measured by LC-MS/MS. The arginase and the NO synthase (NOS) expression were evaluated by immunofluorescence staining. RBCs from MVA patients show increased levels of NO synthesis inhibitors, parallel to that found in plasma, and a reduction of NO synthase expression. When summary scores were computed, both patient groups were associated with a positive oxidative score and a negative NO score, with the CAD group located in a more extreme position with respect to Ctrl. This finding points out to an impairment of the capacity of RBCs to produce NO in a pathological condition characterized mostly by alterations at the microvascular bed with no significant coronary stenosis.

Increase or decrease hydrogen sulfide exert opposite lipolysis, but reduce global insulin resistance in high fatty diet induced obese mice

Objective

Adipose tissue expressed endogenous cystathionine gamma lyase (CSE)/hydrogen sulfide (H₂S) system. H₂S precursor inhibited catecholamine stimulated lipolysis. Thus, we hypothesized that CSE/H₂S system regulates lipolysis which contributed to the pathogenesis of insulin resistance.

Methods

We treated rat adipocyte with DL-propargylglycine (PAG, a CSE inhibitor), L-cysteine (an H₂S precursor) plus pyridoxial phosphate (co-enzyme) or the H₂S chronic release donor GYY4137, then the glycerol level was assayed for assessing the lipolysis. Then, the effects of PAG and GYY4137 on insulin resistance in high fatty diet (HFD) induced obese mice were investigated.

Results

Here, we found that PAG time-dependently increased basal or isoproterenol stimulated lipolysis. However, L-cysteine plus pyridoxial phosphate or GYY4137 significantly reduced it. PAG increased phosphorylated protein kinase A substrate, perilipin 1 and hormone sensitive lipase, but L-cysteine and GYY4137 decreased the parameters. In HFD induced obese mice, PAG increased adipose basal lipolysis, thus blunted fat mass increase, resulting in lowering insulin resistance evidenced by reduction of fasting glucose, insulin level, HOMA index, oral glucose tolerance test (OGTT) curve area and elevating the insulin tolerance test (ITT) response. GYY4137 inhibited lipolysis in vivo without increasing fat mass, but also ameliorated the insulin resistance in HFD mice.

Conclusion

These results implicated that inhibition endogenous CSE/H₂S system in adipocytes increased lipolysis by a protein kinase A-perilipin/hormone-sensitive lipase pathway, thus blunted fat mass increase and reduced insulin resistance in obese mice; giving H₂S donor decreased lipolysis, also reduced insulin resistance induced by HFD. Our data showed that increase or decrease H₂S induced opposite lipolysis, but had the same effect on insulin resistance. The paradoxical regulation may be resulted from different action of H₂S on metabolic and endocrine function in adipocyte.

Nitric oxide synthetic pathway in red blood cells is impaired in coronary artery disease

Background

All the enzymatic factors/cofactors involved in nitric oxide (NO) metabolism have been recently found in red blood cells. Increased oxidative stress impairs NO bioavailability and has been described in plasma of coronary artery disease (CAD) patients. The aim of the study was to highlight a potential dysfunction of the metabolic profile of NO in red blood cells and in plasma from CAD patients compared with healthy controls.

Methods

We determined L-arginine/NO pathway by liquid-chromatography tandem mass spectrometry and high performance liquid chromatography methods. The ratio of oxidized and reduced forms of glutathione, as index of oxidative stress, was measured by liquid-chromatography tandem mass spectrometry method. NO synthase expression and activity were evaluated by immunofluorescence staining and ex-vivo experiments of L-[¹⁵N₂]arginine conversion to L-[¹⁵N]citrulline respectively.

Results

Increased amounts of asymmetric and symmetric dimethylarginines were found both in red blood cells and in plasma of CAD patients in respect to controls. Interestingly NO synthase expression and activity were reduced in CAD red blood cells. In contrast, oxidized/reduced glutathione ratio was increased in CAD and was associated to arginase activity.

Conclusion

Our study analyzed for the first time the whole metabolic pathway of L-arginine/NO, both in red blood cells and in plasma, highlighting an impairment of NO pathway in erythrocytes from CAD patients, associated with decreased NO synthase expression/activity and increased oxidative stress.

Serum thiols and cardiovascular risk scores: a combined assessment of transsulfuration pathway components and substrate/product ratios

Background

Serum thiols have shown associations with surrogate markers of cardiovascular disease. However, little information is available on their combined association with validated cardiovascular risk scores for primary prevention at population level. We sought to determine whether individual serum thiol concentrations and substrate/product ratios within the transsulfuration pathway are independently associated with such scores.

Methods

Data on clinical and demographic characteristics, serum thiols (homocysteine, cysteine, taurine, glutamylcysteine, total glutathione and cysteinylglycine) and high-sensitivity C-reactive protein (CRP) were collected from a sample of the Hunter Community Study without previous cardiovascular events [n=350, median age (IQR) = 62 (59–66) years]. Five-year absolute cardiovascular risk score for each subject was calculated using the Framingham Risk Equation.

Results

Median risk score was 7% (IQR 4–10). After adjusting for body mass index, estimated glomerular filtration rate and physical activity regression analysis showed independent associations between cardiovascular risk scores and a) higher serum homocysteine (B 0.066, 95% CI 0.040 to 0.091, P<0.001) and lower cysteine (B −0.003, 95% CI −0.005 to −0.001, P=0.003) and glutathione (B −0.029, 95% CI −0.056 to −0.003, P=0.03) concentrations; and b) higher homocysteine/cysteine (B 0.114, 95% CI 0.066 to 0.161, P<0.001) and lower glutathione/cysteinylglycine (B −1.145, 95% CI −2.030 to −0.260, P=0.011) ratios. No significant associations were observed between cardiovascular risk scores, taurine and CRP.

Conclusions

Serum homocysteine, cysteine and glutathione are independently associated with cardiovascular risk scores at population level. Enzymatic pathways involved in reduced bioconversion of homocysteine into cysteine and increased glutathione degradation might play an important role in such associations.

Methodology for a rapid and simultaneous determination of total cysteine, homocysteine, cysteinylglycine and glutathione in plasma by isocratic RP-HPLC

Alterations in the plasma aminothiols levels can be considered as important biomarkers for the diagnosis and screening of several human disorders, namely cardiovascular diseases. We aimed to optimize a rapid, sensitive and accurate RP-HPLC methodology with fluorescence detection, for the simultaneous determination of the total concentrations of cysteine, homocysteine, cysteinylglycine and glutathione in blood plasma, as well as its application to the evaluation of those thiols levels in plasma of a group of Azorean subjects. Aminothiols were reduced with tri-n-butylphosphine and derivatized with a thiol-specific fluorogenic reagent ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulphonate. The thiols adducts were separated by an isocratic elution on a Platinum EPS C18 analytical column (53mm×7mm I.D., 3μm) using a phosphate buffer containing 4% of acetonitrile as a mobile phase. Results indicated an excellent linearity for all the analytes over their respective concentration ranges with correlation coefficients (r(2)) ≥0.99. The LOD for the four plasma thiols was lower than 0.10μmol/L, while LOQ varied from 0.5 to 15μmol/L. For both intra- and inter-day precision, the RSD (%) values were lower than 1.9%, and the CV (%) values were found under 0.5%. The recovery ranged from 92% to 100% indicating a high degree of the method's accuracy. This method allows a simultaneous, complete analysis of the four plasma aminothiols and the internal standard in 6min. By reducing the total run time, a larger number of analysis can be performed daily.

A new metabolomic assay to examine inflammation and redox pathways following LPS challenge

BACKGROUND

Shifts in intracellular arginine (Arg) and sulfur amino acid (SAA) redox metabolism modulate macrophage activation, polarization and phenotype. Despite their importance in inflammation and redox regulatory pathways, comprehensive analysis of these metabolic networks was not previously possible with existing analytical methods.

METHODS

The Arg/thiol redox LC-MS/MS metabolomics assay permits simultaneous assessment of amino acids and derivative products generated from Arg and SAA metabolism. Using this assay, LPS-induced changes in macrophage amino acid metabolism were monitored to identify pathway shifts during activation and their linkage to cellular redox regulation.

RESULTS

Metabolite concentrations most significantly changed after treatment of a macrophage-like cell line (RAW) with LPS for 24 hrs were citrulline (Cit) (48-fold increase), ornithine (Orn) (8.5-fold increase), arginine (Arg) (66% decrease), and aspartic acid (Asp) (73% decrease). The ratio Cit + Orn/Arg + Asp (CO/AA) was more sensitive to LPS stimulation than other amino acid ratios commonly used to measure LPS-dependent inflammation (e.g., SAM/SAH, GSH/GSSG) and total media NOx. The CO/AA ratio was also the first ratio to change significantly after LPS treatment (4 hrs). Changes in the overall metabolomic profile over time indicated that metabolic pathways shifted from Arg catabolism to thiol oxidation.

CONCLUSIONS

Simultaneous quantification of Arg and SAA metabolic pathway shifts following LPS challenge of macrophage indicate that, in this system, the Arg-Citrulline/NO cycle and arginase pathways are the amino acid metabolic pathways most sensitive to LPS-challenge. The cellular (Cit + Orn)/(Arg + Asp) ratio, which summarizes this pathway, was more responsive to lower concentrations of LPS and responded earlier than other metabolic biomarkers of macrophage activation including GSH redox. It is suggested that the CO/AA ratio is a redox- independent early biomarker of macrophage activation. The ability to measure both the CO/AA and GSH-redox ratios simultaneously permits quantification of the relative effects of LPS challenge on macrophage inflammation and oxidative stress pathways. The use of this assay in humans is discussed, as are clinical implications.

Coronary angiographic scoring systems: an evaluation of their equivalence and validity

BACKGROUND

Multiple scoring systems have been devised to quantify angiographic coronary artery disease (CAD) burden, but it is unclear how these scores relate to each other and which scores are most accurate. The aim of this study was to compare coronary angiographic scoring systems (1) with each other and (2) with intravascular ultrasound (IVUS)-derived plaque burden in a population undergoing angiographic evaluation for CAD.

METHODS

Coronary angiographic data from 3600 patients were scored using 10 commonly used angiographic scoring systems and interscore correlations were calculated. In a subset of 50 patients, plaque burden and plaque area in the left anterior descending coronary artery were quantified using IVUS and correlated with angiographic scores.

RESULTS

All angiographic scores correlated with each other (range for Spearman coefficient [ρ] 0.79-0.98, P < .0001); the 2 most widely used scores, Gensini and CASS-70, had a ρ = 0.90 (P < .0001). All scores correlated significantly with average plaque burden and plaque area by IVUS (range ρ 0.56-0.78, P < .0001 and 0.43-0.62, P < .01, respectively). The CASS-50 score had the strongest correlation (ρ 0.78 and 0.62, P < .0001) and the Duke Jeopardy score the weakest correlation (ρ 0.56 and 0.43, P < .01) with plaque burden and area, respectively.

CONCLUSIONS

Angiographic scoring systems are strongly correlated with each other and with atherosclerotic plaque burden. Scoring systems therefore appear to be a valid estimate of CAD plaque burden.