Symmetric dimethylarginine, high-density lipoproteins and cardiovascular disease

Meta-analysis of the correlation between pulmonary hypertension and echocardiographic parameters in patients with chronic kidney disease

Objective

To investigate the correlation between pulmonary hypertension (PH) and echocardiographic parameters in patients with chronic kidney disease (CKD).

Methods

PubMed, Embase, Web of Science, Cochrane, VIP, CNKI, and Wanfang databases were systematically searched for articles published from inception to 19 May 2023. Study quality was estimated using the Quality Assessment of Case-Control Studies tool. Forest plots were drawn using R language software. The "metacor" function in the "meta" package was utilized for meta-analysis of the r-values and their standard errors. Heterogeneity and sensitivity analyses were carried out, with the main outcomes as r-value, p-value, and I2 value.

Results

Eleven studies were included, with 1,809 CKD patients. The correlations between 12 echocardiographic parameters and PH were analyzed. Except for FS and LVEF which were negatively correlated with CKD-PH, the other 10 parameters were positively correlated with CKD-PH. Among them, LA was highly correlated with CKD-PH (0.70 < r < 0.89); LVDD, RA, RV, LVMI, and LVDS were moderately correlated with CKD-PH (0.40 < r < 0.69); while PA, IVS, LVPW, SV, FS, and LVEF were lowly correlated with CKD-PH (0.20 < r < 0.39). The synthesized estimates were stable against heterogeneity.

Conclusion

CKD-PH patients may have large cardiac chambers, thickened septal tissue on both sides of the chambers, reduced pulmonary artery flow rates, and decreased left ventricular function.

Phosphate and Coronary Artery Disease in Patients with Chronic Kidney Disease

Cardiovascular disease (CVD) is the leading cause of death in patients with chronic kidney disease (CKD). Both traditional and CKD-related factors are associated with CVD in CKD patients. Traditional factors that play an important role in the atherosclerotic process directly contribute to a higher risk of coronary artery disease in patients with early-stage CKD. Among CKD-related factors, CKD-mineral and bone disorder plays a critical role in the pathomechanism of nonatherosclerotic diseases, which increases the risk of cardiovascular morbidity and mortality in patients with advanced CKD. Higher serum phosphate levels were significantly associated with cardiovascular events and all-cause mortality in patients with or without CKD. An increased phosphate load, directly and indirectly, promotes arterial medial calcification and left ventricular hypertrophy, both of which predispose patients to coronary artery disease. Calciprotein particles that form in a hyperphosphatemic state promote the transformation of vascular smooth muscle cells (VSMCs) into osteoblastic cells, thereby providing a scaffold for medial calcification in the artery. Increases in fibroblast growth factor-23 and disturbed vitamin D metabolism induced by an excessive phosphate load play a significant role in the development of cardiomyocyte hypertrophy and cardiac fibrosis. Recently, hyperphosphatemia was reported to promote de novo cholesterol synthesis in VSMCs and macrophages, which is likely to contribute to statin resistance in patients with end-stage kidney disease. This review outlines the association between increased phosphate load and coronary artery disease in patients with CKD.

Plasma arginine metabolites in health and chronic kidney disease

BACKGROUND

Elevated plasma asymmetric and symmetric dimethylarginine (ADMA and SDMA) are risk factors for chronic kidney disease (CKD) and cardiovascular disease. Using plasma cystatin C (pCYSC)-based estimated glomerular filtration rate (eGFR) trajectories, we identified a cohort at high risk of poor kidney-related health outcomes amongst members of the Dunedin Multidisciplinary Health and Development Study (DMHDS). We therefore examined associations between methylarginine metabolites and kidney function in this cohort.

METHODS

ADMA, SDMA, L-arginine and L-citrulline were measured in plasma samples from 45-year-olds in the DMHDS cohort by liquid chromatography-tandem mass spectrometry.

RESULTS

In a healthy DMHDS subset (n = 376), mean concentrations were: ADMA (0.40 ± 0.06 µmol/L), SDMA (0.42 ± 0.06 µmol/L), L-arginine (93.5 ± 23.1 µmol/L) and L-citrulline (24.0 ± 5.4 µmol/L). In the total cohort (n = 857), SDMA correlated positively with serum creatinine (Pearson's r = 0.55) and pCYSC (r = 0.55), and negatively with eGFR (r = 0.52). A separate cohort of 38 patients with stage 3-4 CKD (eGFR 15-60 mL/min/1.73 m2) confirmed significantly higher mean ADMA (0.61 ± 0.11 µmol/L), SDMA (0.65 ± 0.25 µmol/L) and L-citrulline (42.7 ± 11.8 µmol/L) concentrations. DMHDS members classified as high-risk of poor kidney health outcomes had significantly higher mean concentrations of all four metabolites compared with individuals not at risk. ADMA and SDMA individually predicted high-risk of poor kidney health outcomes with areas under the ROC curves (AUCs) of 0.83 and 0.84, and together with an AUC of 0.90.

CONCLUSIONS

Plasma methylarginine concentrations facilitate stratification for risk of CKD progression.

High-density lipoprotein protects vascular endothelial cells from indoxyl sulfate insults through its antioxidant ability

Chronic kidney disease (CKD) patients have a high risk of cardiovascular disease. Indoxyl sulfate (IS) is a uremic toxin that has been shown to inhibit nitric oxide production and cause cell senescence by inducing oxidative stress. High-density lipoprotein (HDL) has a protective effect on the cardiovascular system; however, its impacts on IS-damaged endothelial cells are still unknown. This study aimed to explore the effects of exogenous supplement of HDL on vascular endothelial cells in a uremia-mimic environment. Tube formation, migration, adhesion, and senescence assays were used to evaluate the cell function of human aortic endothelial cells (HAECs). Reactive oxygen species generation was measured by using Amplex red assay. L-NAME and MCI186 were used as a nitric oxide synthase inhibitor and a free radical scavenger, respectively. HDL exerted anti-inflammatory and antioxidant effects via HIF-1α/HO-1 activation and IL-1β/TNF-α/IL-6 inhibition in IS-stimulated HAECs. HDL improved angiogenesis ability through upregulating Akt/eNOS/VEGF/SDF-1 in IS-stimulated HAECs. HDL decreased endothelial adhesiveness via downregulating VCAM-1 and ICAM-1 in IS-stimulated HAECs. Furthermore, HDL reduced cellular senescence via upregulating SIRT1 and downregulating p53 in IS-stimulated HAECs. Importantly, the above beneficial effects of HDL were mainly due to its antioxidant ability. In conclusion, HDL exerted a comprehensive protective effect on vascular endothelial cells against damage from IS through its antioxidant ability. The results of this study might provide a theoretical basis for potential HDL supplementation in CKD patients with endothelial damage.

[Laboratory diagnostics of lipid metabolism disorders]

Clinically, disorders of lipid metabolism often remain without symptoms. Typical skin lesions, however, can be indicative. Secondary hyperlipoproteinemias (HLP) are more common than primary hyperlipoproteinemias; they can (partially) be improved by treating the underlying disease. Basic diagnostics consist of the determination of cholesterol, triglycerides, LDL cholesterol and HDL cholesterol. To exclude secondary HLP, glucose, HbA1C, TSH, transaminases, creatinine, urea, protein and protein in the urine are useful. Since virtually all routine methods for LDL-C are biased by high triglycerides, lipoprotein electrophoresis is indicated for triglycerides above 400 mg/dl (4.7 mmol/l). Primary HLPs have known or yet unknown genetic causes. Primary hyperlipidemias should be taken into consideration especially in young patients with an LDL cholesterol concentration are above 190 mg/dl (4.9 mmol/l) and/or triglycerides above 400 mg/dl (10 mmol/l) and secondary HLP (obesity, alcohol, diabetes mellitus, kidney disease) is excluded. The basic diagnostics is meaningfully extended by the measurement of lipoprotein (a) (Lp(a)). It is indicated in moderate and high risk of vascular disease, progression of atherosclerosis in "well-controlled" LDL cholesterol, familial clustering of atherosclerosis or high Lp(a), evidence for elevated Lp(a) coming from lipoprotein electrophoresis, aortic stenosis and in patients in whom statins have a poor effect. Genetic diagnostics needs to be considered if primary HLP is suspected. It is most frequently conducted for suspected familial hypercholesterolemia and has already been recommended in guidelines.

Leukocyte-endothelial interaction in CKD

Chronic kidney disease (CKD) represents an independent risk factor for cardiovascular diseases (CVD). Accordingly, CKD patients show a substantial increased risk of cardiovascular mortality. Inflammation represents an important link between CKD and CVD. The interaction between endothelial cells and effector cells of the innate immune system plays a central role in the development and progression of inflammation. Vascular injury causes endothelial dysfunction, leading to augmented oxidative stress, increased expression of leukocyte adhesion molecules and chronic inflammation. CKD induces numerous metabolic changes, creating a uremic milieu resulting in the accumulation of various uremic toxins. These toxins lead to vascular injury, endothelial dysfunction and activation of the innate immune system. Recent studies describe CKD-dependent changes in monocytes that promote endothelial dysfunction and thus CKD progression and CKD-associated CVD. The NLR family pyrin domain containing 3-interleukin-1β-interleukin-6 (NLRP3-IL-1β-IL-6) signaling pathway plays a pivotal role in the development and progression of CVD and CKD alike. Several clinical trials are investigating targeted inhibition of this pathway indicating that anti-inflammatory therapeutic strategies may emerge as novel approaches in patients at high cardiovascular risk and nonresolving inflammation. CKD patients in particular would benefit from targeted anti-inflammatory therapy, since conventional therapeutic regimens have limited efficacy in this population.

Significance of Kidney Disease in Cardiovascular Disease Patients

Cardiorenal syndrome is a condition where is a bidirectional and mutually detrimental relationship between the heart and kidneys. The mechanisms underlying cardiorenal syndrome are multifactorial and complex. Patients with kidney disease exhibit increased cardiovascular risk, presenting as coronary and peripheral artery disease, structural heart disease, arrhythmias, heart failure, and sudden cardiac death, largely occurring because of a systemic proinflammatory state, causing myocardial and vascular remodeling, manifesting as atherosclerotic lesions, vascular and valvular calcification, and myocardial fibrosis, particularly among those with advanced disease. This review summarizes the current understanding and clinical implications of kidney disease in patients with cardiovascular disease.

Differences in HDL-related mortality risk between individuals with and without hypertension: a prospective cohort study in UK Biobank

BACKGROUND AND AIMS

Very high levels of high-density lipoprotein cholesterol (HDL-C) have been paradoxically linked to increased mortality risk. The present study aimed to examine associations of HDL-C and varied sizes of the HDL particle (HDL-P) with mortality risk stratified by hypertension.

METHODS AND RESULTS

This prospective cohort study included 429 792 participants (244 866 with hypertension and 184 926 without hypertension) from the UK Biobank. During a median follow-up of 12.7 years, 23 993 (9.8%) and 8142 (4.4%) deaths occurred among individuals with and without hypertension, respectively. A U-shaped association of HDL-C with all-cause mortality was observed in individuals with hypertension after multivariable adjustment, whereas an L-shape was observed in individuals without hypertension. Compared with individuals with normal HDL-C of 50-70 mg/dL, those with very high HDL-C levels (>90 mg/dL) had a significantly higher risk of all-cause mortality among individuals with hypertension (hazard ratio, 1.47; 95% confidence interval, 1.35-1.61), but not among those without hypertension (1.05, 0.91-1.22). As for HDL-P, among individuals with hypertension, a larger size of HDL-P was positively whereas smaller HDL-P was negatively associated with all-cause mortality. After additional adjustment for larger HDL-P in the model, the U-shaped association between HDL-C and mortality risk was altered to an L-shape among individuals with hypertension.

CONCLUSIONS

The increased risk of mortality associated with very high HDL-C existed only in individuals with hypertension, but not in those without hypertension. Moreover, the increased risk at high HDL-C levels in hypertension was likely driven by larger HDL-P.

Effects of Finerenone on Cardiovascular and Chronic Kidney Diseases: A New Weapon against Cardiorenal Morbidity and Mortality-A Comprehensive Review

Patients with cardiovascular disease (CVD) and chronic kidney disease (CKD) show high rates of cardiorenal outcomes. In addition, the progression towards renal failure and cardiovascular events rises as CKD worsens. Several studies suggest that the activation of the mineralocorticoid receptor (MR) induces cardiac and renal injury, including inflammation and fibrosis. Finerenone is a novel, nonsteroidal, selective MR antagonist (MRA) which has demonstrated anti-inflammatory and anti-fibrotic effects in pre-clinical studies. Moreover, two large trials (FIDELIO-DKD and FIGARO-DKD) investigated the renal and cardiovascular outcomes in patients with mild to severe CKD in type 2 diabetes which received finerenone. On these bases, this comprehensive review aims to summarize the current knowledge regarding finerenone and its effects on CKD and the cardiovascular system, emphasizing its role in modifying cardiorenal outcomes.

[HDL - Quo vadis]

Many epidemiological studies found low plasma levels of high-density lipoprotein (HDL) cholesterol (HDL-C) associated with an increased risk of atherosclerotic cardiovascular disease (ASCVD). In cell culture and animal models, HDL particles show many anti-atherogenic actions. However, until now, clinical trials did not find any prevention of ASCVD events by drugs elevating HDL-C levels, at least not beyond statins. Also, genetic studies show no associations of HDL-C levels altering variants with cardiovascular risk. Therefore, the causal role and clinical benefit of HDL-C elevation in ASCVD are questioned. However, the interpretation of previous data has important limitations: First, the inverse relationship of HDL-C with the risk of ASCVD is limited to concentrations < 60 mg/dl (< 1.5 mmol/l). Higher concentrations do not reduce the risk of ASCVD events and are even associated with increased mortality. Therefore, neither the higher-the-better strategies of earlier drug developments nor the assumption of linear cause-and-effect relationships in Mendelian randomization trials are justified. Second, most of the drugs tested so far do not act specifically on HDL metabolism. Therefore, the futile endpoint studies question the clinical benefit of the investigated drugs, but not the importance of HDL in ASCVD. Third, the vascular functions of HDL are not exerted by its cholesterol content (i.e. HDL-C), but by a variety of other molecules. Comprehensive knowledge of the structure-function-disease relationships of HDL particles and their molecules is a prerequisite for testing their physiological and pathogenic relevance and possibly for optimizing the diagnosis and treatment of persons with HDL-associated risk of ASCVD, but also for other diseases, such as diabetes, chronic kidney disease, infections, autoimmune and neurodegenerative diseases.

Innate Immunity System in Patients With Cardiovascular and Kidney Disease

With a global burden of 844 million, chronic kidney disease (CKD) is now considered a public health priority. Cardiovascular risk is pervasive in this population, and low-grade systemic inflammation is an established driver of adverse cardiovascular outcomes in these patients. Accelerated cellular senescence, gut microbiota-dependent immune activation, posttranslational lipoprotein modifications, neuroimmune interactions, osmotic and nonosmotic sodium accumulation, acute kidney injury, and precipitation of crystals in the kidney and the vascular system all concur in determining the unique severity of inflammation in CKD. Cohort studies documented a strong link between various biomarkers of inflammation and the risk of progression to kidney failure and cardiovascular events in patients with CKD. Interventions targeting diverse steps of the innate immune response may reduce the risk of cardiovascular and kidney disease. Among these, inhibition of IL-1β (interleukin-1 beta) signaling by canakinumab reduced the risk for cardiovascular events in patients with coronary heart disease, and this protection was equally strong in patients with and without CKD. Several old (colchicine) and new drugs targeting the innate immune system, like the IL-6 (interleukin 6) antagonist ziltivekimab, are being tested in large randomized clinical trials to thoroughly test the hypothesis that mitigating inflammation may translate into better cardiovascular and kidney outcomes in patients with CKD.

Antidyslipidemia Pharmacotherapy in Chronic Kidney Disease: A Systematic Review and Bayesian Network Meta-Analysis

BACKGROUND AND AIMS

The benefits and safety of antidyslipidemia pharmacotherapy in patients with chronic kidney disease were not well defined so the latest evidence was summarized by this work.

METHODS

This systematic review and Bayesian network meta-analysis (NMA) included searches of PubMed, Embase, and Cochrane Library from inception to 28 February 2022, for randomized controlled trials of any antilipidaemic medications administered to adults with chronic kidney disease [CKD: defined as estimated glomerular filtration rate (eGFR) ≤ 60 mL/min/1.73 m² not undergoing transplantation], using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) tool to assess the certainty of the evidence.

RESULTS

55 trials and 30 works of them were included in our systematic review and NMA, respectively. In comparisons with no antidyslipidemia therapy or placebo, proprotein convertase subtilisin/Kexin type 9 inhibitors plus statin (PS) was the most effective drug regimen for reducing all-cause mortality (OR 0.62, 95% CI [0.40, 0.93]; GRADE: moderate), followed by moderate-high intensity statin (HS, OR 0.76, 95% CI [0.60, 0.93]; I² = 66.9%; GRADE: moderate). PS, HS, low-moderate statin (LS), ezetimibe plus statin (ES), and fibrates (F) significantly decreased the composite cardiovascular events. The subgroup analysis revealed the null effect of statins on death (OR 0.92, 95% CI [0.81, 1.04]) and composite cardiovascular events (OR 0.94, 95% CI [0.82, 1.07]) in dialysis patients.

CONCLUSION

In nondialysis CKD patients, statin-based therapies could significantly and safely reduce all-cause death and major composite cardiovascular events despite the presence of arteriosclerotic cardiovascular disease and LDL-c levels. Aggressive medication regimens, PS and HS, appeared to be more effective, especially in patients with established CAD.

Targeting innate immunity-driven inflammation in CKD and cardiovascular disease

Mortality among patients with chronic kidney disease (CKD) is largely a consequence of cardiovascular disease (CVD) and is a particular concern given the increasing prevalence of CKD. Sterile inflammation triggered by activation of the innate immune system is an important driver of both CKD and associated CVD. Several endogenous mediators, including lipoproteins, crystals such as silica, urate and cholesterol crystals, or compounds released from dying cells interact with pattern recognition receptors expressed on a variety of different cell types, leading to the release of pro-inflammatory cytokines. Disturbed regulation of the haematopoietic system by damage-associated molecular patterns, or as a consequence of clonal haematopoiesis or trained innate immunity, also contributes to the development of inflammation. In observational and genetic association studies, inflammation is linked to the progression of CKD and cardiovascular events. In 2017, the CANTOS trial of canakinumab provided evidence that inhibiting inflammation driven by NLRP3-IL-1-IL-6-mediated signalling significantly reduced cardiovascular event rates in individuals with and without CKD. Other approaches to target innate immune pathways are now under investigation for their ability to reduce cardiovascular events and slow disease progression among patients with atherosclerosis and stage 3 and 4 CKD. This Review summarizes current understanding of the role of inflammation in the pathogenesis of CKD and its associated CVD, and how this knowledge may translate into novel therapeutics.

Pathomechanism of oxidative stress in cardiovascularrenal remodeling and therapeutic strategies

The high prevalence of cardiovascular disease in patients with chronic kidney disease indicates significant interactions between pathogenic pathways operating in the kidney and heart. These interactions involve all cell types (endothelial cells, smooth muscle cells, macrophages, and others), components of the vasculature, glomeruli, and heart that are susceptible to oxidative damage and structural alterations. A vicious cycle occurs whereby harmful factors such as reactive oxygen species and inflammation damage of vascular structures that themselves become sources of additional dangerous/toxic components released into the local environment. The evidence of this vicious cycle in chronic kidney disease should therefore lead to add other factors to both traditional and nontraditional risk factors. This review will examine the processes occurring during progressive kidney dysfunction with regard to vascular injury, renal remodeling, cardiac hypertrophy, and the transversal role of oxidative stress in the development of these complications.

Mechanisms of Post-critical Illness Cardiovascular Disease

Prolonged critical care stays commonly follow trauma, severe burn injury, sepsis, ARDS, and complications of major surgery. Although patients leave critical care following homeostatic recovery, significant additional diseases affect these patients during and beyond the convalescent phase. New cardiovascular and renal disease is commonly seen and roughly one third of all deaths in the year following discharge from critical care may come from this cluster of diseases. During prolonged critical care stays, the immunometabolic, inflammatory and neurohumoral response to severe illness in conjunction with resuscitative treatments primes the immune system and parenchymal tissues to develop a long-lived pro-inflammatory and immunosenescent state. This state is perpetuated by persistent Toll-like receptor signaling, free radical mediated isolevuglandin protein adduct formation and presentation by antigen presenting cells, abnormal circulating HDL and LDL isoforms, redox and metabolite mediated epigenetic reprogramming of the innate immune arm (trained immunity), and the development of immunosenescence through T-cell exhaustion/anergy through epigenetic modification of the T-cell genome. Under this state, tissue remodeling in the vascular, cardiac, and renal parenchymal beds occurs through the activation of pro-fibrotic cellular signaling pathways, causing vascular dysfunction and atherosclerosis, adverse cardiac remodeling and dysfunction, and proteinuria and accelerated chronic kidney disease.

Precise Metabolomics Reveals a Diversity of Aging-Associated Metabolic Features

Mass spectrometry-based metabolomics has emerged as a powerful technique for biomedical research, although technical issues with its analytical precision and structural characterization remain. Herein, a robust non-targeted strategy for accurate quantitation and precise profiling of metabolomes is developed and applied to investigate plasma metabolic features associated with human aging. A comprehensive set of isotope-labeled standards (ISs) covering major metabolic pathways is incorporated to quantify polar metabolites. Matching rules to select ISs for calibration follow a primary criterion of minimal coefficients of variations (COVs). If minimal COVs between specific ISs for a particular metabolite fall within 5% window, a further selection of ISs is conducted based on structural similarities and proximity in retention time. The introduction and refined selection of appropriate ISs for quantitation reduces the COVs of 480 identified metabolites in quality control samples from 14.3% to 9.8% and facilitates identification of additional metabolite. Finally, the precise metabolomics approach reveals perturbations in a diverse array of metabolic pathways across aging that principally implicate steroid metabolism, amino acid metabolism, lipid metabolism, and purine metabolism, which allows the authors to draw correlates to the pathology of various age-related diseases. These findings provide clues for the prevention and treatment of these age-related diseases.

Lipid Profile Is Negatively Associated with Uremic Toxins in Patients with Kidney Failure-A Tri-National Cohort

Patients with kidney failure (KF) have a high incidence of cardiovascular (CV) disease, partly driven by insufficient clearance of uremic toxins. Recent investigations have questioned the accepted effects of adverse lipid profile and CV risk in uremic patients. Therefore, we related a panel of uremic toxins previously associated with CV morbidity/mortality to a full lipid profile in a large, tri-national, cross-sectional cohort. Total, high-density lipoprotein (HDL), non-HDL, low-density lipoprotein (LDL), and remnant cholesterol, as well as triglyceride, levels were associated with five uremic toxins in a cohort of 611 adult KF patients with adjustment for clinically relevant covariates and other patient-level variables. Univariate analyses revealed negative correlations of total, non-HDL, and LDL cholesterol with all investigated uremic toxins. Multivariate linear regression analyses confirmed independent, negative associations of phenylacetylglutamine with total, non-HDL, and LDL cholesterol, while indole-3 acetic acid associated with non-HDL and LDL cholesterol. Furthermore, trimethylamine-N-Oxide was independently and negatively associated with non-HDL cholesterol. Sensitivity analyses largely confirmed findings in the entire cohort. In conclusion, significant inverse associations between lipid profile and distinct uremic toxins in KF highlight the complexity of the uremic milieu, suggesting that not all uremic toxin interactions with conventional CV risk markers may be pathogenic.

Signaling pathways of chronic kidney diseases, implications for therapeutics

Chronic kidney disease (CKD) is a chronic renal dysfunction syndrome that is characterized by nephron loss, inflammation, myofibroblasts activation, and extracellular matrix (ECM) deposition. Lipotoxicity and oxidative stress are the driving force for the loss of nephron including tubules, glomerulus, and endothelium. NLRP3 inflammasome signaling, MAPK signaling, PI3K/Akt signaling, and RAAS signaling involves in lipotoxicity. The upregulated Nox expression and the decreased Nrf2 expression result in oxidative stress directly. The injured renal resident cells release proinflammatory cytokines and chemokines to recruit immune cells such as macrophages from bone marrow. NF-κB signaling, NLRP3 inflammasome signaling, JAK-STAT signaling, Toll-like receptor signaling, and cGAS-STING signaling are major signaling pathways that mediate inflammation in inflammatory cells including immune cells and injured renal resident cells. The inflammatory cells produce and secret a great number of profibrotic cytokines such as TGF-β1, Wnt ligands, and angiotensin II. TGF-β signaling, Wnt signaling, RAAS signaling, and Notch signaling evoke the activation of myofibroblasts and promote the generation of ECM. The potential therapies targeted to these signaling pathways are also introduced here. In this review, we update the key signaling pathways of lipotoxicity, oxidative stress, inflammation, and myofibroblasts activation in kidneys with chronic injury, and the targeted drugs based on the latest studies. Unifying these pathways and the targeted therapies will be instrumental to advance further basic and clinical investigation in CKD.

Hypertriglyceridemia and Other Risk Factors of Chronic Kidney Disease in Type 2 Diabetes: A Hospital-Based Clinic Population in Greece

Aims/Introduction: Several reports indicate an increasing prevalence of chronic kidney disease (CKD) in type 2 diabetes mellitus (T2DM). Hyperglycemia and hypertension are the main risk factors for CKD development and progression. However, despite the achievement of recommended targets for blood glucose and blood pressure (BP), the residual risk of diabetic chronic kidney disease (DCKD) remains relatively high. The aim of this study is to examine dyslipidemia and other major risk factors to provide support for the prevention and treatment of DCKD. Materials and Methods: Participants are from the Redit-2-Diag study that examines 1759 subjects within a period of 6 months. DCKD severity is staged according to KDIGO criteria. Results: An increase in hemoglobin A_1c (1 unit) and systolic blood pressure (1 mm Hg) increases the probability of being classified into a higher CKD stage by 14% and 26%, respectively. Moreover, an increase of triglycerides by 88.5 mg/dL increases the risk of classification to a worse CKD stage by 24%. Conclusions: Elevated triglycerides, systolic blood pressure, and poor glycemic control increase the risk of CKD in T2DM and should be addressed in the treatment strategies.

Guanidinylated Apolipoprotein C3 (ApoC3) Associates with Kidney and Vascular Injury

BACKGROUND

Coexistent CKD and cardiovascular diseases are highly prevalent in Western populations and account for substantial mortality. We recently found that apolipoprotein C-3 (ApoC3), a major constituent of triglyceride-rich lipoproteins, induces sterile systemic inflammation by activating the NOD-like receptor protein-3 (NLRP3) inflammasome in human monocytes via an alternative pathway.

METHODS

To identify posttranslational modifications of ApoC3 in patients with CKD, we used mass spectrometry to analyze ApoC3 from such patients and from healthy individuals. We determined the effects of posttranslationally modified ApoC3 on monocyte inflammatory response in vitro, as well as in humanized mice subjected to unilateral ureter ligation (a kidney fibrosis model) and in a humanized mouse model for vascular injury and regeneration. Finally, we conducted a prospective observational trial of 543 patients with CKD to explore the association of posttranslationally modified ApoC3 with renal and cardiovascular events in such patients.

RESULTS

We identified significant posttranslational guanidinylation of ApoC3 (gApoC3) in patients with CKD. We also found that mechanistically, guanidine and urea induce guanidinylation of ApoC3. A 2D-proteomic analysis revealed that gApoC3 accumulated in kidneys and plasma in a CKD mouse model (mice fed an adenine-rich diet). In addition, gApoC3 augmented the proinflammatory effects of ApoC3 in monocytes in vitro . In humanized mice, gApoC3 promoted kidney tissue fibrosis and impeded vascular regeneration. In CKD patients, higher gApoC3 plasma levels (as determined by mass spectrometry) were associated with increased mortality as well as with renal and cardiovascular events.

CONCLUSIONS

Guanidinylation of ApoC3 represents a novel pathogenic mechanism in CKD and CKD-associated vascular injury, pointing to gApoC3 as a potential therapeutic target.

Altered vitamin K biodistribution and metabolism in experimental and human chronic kidney disease

Chronic kidney disease (CKD) is accompanied with extensive cardiovascular calcification, in part correlating with functional vitamin K deficiency. Here, we sought to determine causes for vitamin K deficiency beyond reduced dietary intake. Initially, vitamin K uptake and distribution into circulating lipoproteins after a single administration of vitamin K1 plus K2 (menaquinone 4 and menaquinone 7, respectively) was determined in patients on dialysis therapy and healthy individuals. The patients incorporated very little menaquinone 7 but more menaquinone 4 into high density lipoprotein (HDL) and low-density lipoprotein particles than did healthy individuals. In contrast to healthy persons, HDL particles from the patients could not be spiked with menaquinone 7 in vitro and HDL uptake was diminished in osteoblasts. A reduced carboxylation activity (low vitamin K activity) of uremic HDL particles spiked with menaquinone 7 vs. that of controls was confirmed in a bioassay using human primary vascular smooth muscle cells. Kidney menaquinone 4 tissue levels were reduced in 5/6-nephrectomized versus sham-operated C57BL/6 mice after four weeks of a vitamin K rich diet. From the analyzed enzymes involved in vitamin K metabolism, kidney HMG-CoA reductase protein was reduced in both rats and patients with CKD. In a trial on the efficacy and safety of atorvastatin in 1051 patients with type 2 diabetes receiving dialysis therapy, no pronounced vitamin K deficiency was noted. However, the highest levels of PIVKA-II (biomarker of subclinical vitamin K deficiency) were noted when a statin was combined with a proton pump inhibitor. Thus, profound disturbances in lipoprotein mediated vitamin K transport and metabolism in uremia suggest that menaquinone 7 supplementation to patients on dialysis therapy has reduced efficacy.

Carbamylated sortilin associates with cardiovascular calcification in patients with chronic kidney disease

Sortilin, an intracellular sorting receptor, has been identified as a cardiovascular risk factor in the general population. Patients with chronic kidney disease (CKD) are highly susceptible to develop cardiovascular complications such as calcification. However, specific CKD-induced posttranslational protein modifications of sortilin and their link to cardiovascular calcification remain unknown. To investigate this, we examined two independent CKD cohorts for carbamylation of circulating sortilin and detected increased carbamylated sortilin lysine residues in the extracellular domain of sortilin with kidney function decline using targeted mass spectrometry. Structure analysis predicted altered ligand binding by carbamylated sortilin, which was verified by binding studies using surface plasmon resonance measurement, showing an increased affinity of interleukin 6 to in vitro carbamylated sortilin. Further, carbamylated sortilin increased vascular calcification in vitro and ex vivo that was accelerated by interleukin 6. Imaging by mass spectrometry of human calcified arteries revealed in situ carbamylated sortilin. In patients with CKD, sortilin carbamylation was associated with coronary artery calcification, independent of age and kidney function. Moreover, patients with carbamylated sortilin displayed significantly faster progression of coronary artery calcification than patients without sortilin carbamylation. Thus, carbamylated sortilin may be a risk factor for cardiovascular calcification and may contribute to elevated cardiovascular complications in patients with CKD.

Reproducible Determination of High-Density Lipoprotein Proteotypes

High-density lipoprotein (HDL) is a heterogeneous mixture of blood-circulating multimolecular particles containing many different proteins, lipids, and RNAs. Recent advancements in mass spectrometry-based proteotype analysis show promise for the analysis of proteoforms across large patient cohorts. In order to create the required spectral libraries enabling these data-independent acquisition (DIA) strategies, HDL was isolated from the plasma of more than 300 patients with a multiplicity of physiological HDL states. HDL proteome spectral libraries consisting of 296 protein groups and more than 786 peptidoforms were established, and the performance of the DIA strategy was benchmarked for the detection of HDL proteotype differences between healthy individuals and a cohort of patients suffering from diabetes mellitus type 2 and/or coronary heart disease. Bioinformatic interrogation of the data using the generated spectral libraries showed that the DIA approach enabled robust HDL proteotype determination. HDL peptidoform analysis enabled by using spectral libraries allowed for the identification of post-translational modifications, such as in APOA1, which could affect HDL functionality. From a technical point of view, data analysis further shows that protein and peptide quantities are currently more discriminative between different HDL proteotypes than peptidoforms without further enrichment. Together, DIA-based HDL proteotyping enables the robust digitization of HDL proteotypes as a basis for the analysis of larger clinical cohorts.

Associations of circulating dimethylarginines with the metabolic syndrome in the Framingham Offspring study

Background

Circulating levels of the endogenous inhibitor of nitric oxide synthase, asymmetric dimethylarginine (ADMA), are positively associated with the prevalence of metabolic syndrome (MetS) in cross-sectional investigations. It is unclear if circulating ADMA and other methylarginines are associated with incident MetS prospectively.

Methods

We related circulating ADMA, symmetric dimethylarginine (SDMA), L-arginine (ARG) concentrations (measured with a validated tandem mass spectrometry assay) and the ARG/ADMA ratio to MetS and its components in 2914 (cross-sectional analysis, logistic regression; mean age 58 years, 55% women) and 1656 (prospective analysis, Cox regression; mean age 56 years, 59% women) individuals from the Framingham Offspring Study who attended a routine examination.

Results

Adjusting for age, sex, smoking, and eGFR, we observed significant associations of ADMA (direct) and ARG/ADMA (inverse) with odds of MetS (N = 1461 prevalent cases; Odds Ratio [OR] per SD increment 1.13, 95%CI 1.04–1.22; and 0.89, 95%CI 0.82–0.97 for ADMA and ARG/ADMA, respectively). Upon further adjustment for waist circumference, systolic and diastolic blood pressure, glucose, high-density lipoprotein cholesterol, and triglycerides, we observed a positive relation between SDMA and MetS (OR per SD increment 1.15, 95% CI 1.01–1.30) but the other associations were rendered statistically non-significant. We did not observe statistically significant associations between any of the methylarginines and the risk of new-onset MetS (752 incident events) over a median follow-up of 11 years.

Conclusion

It is unclear whether dimethylarginines play an important role in the incidence of cardiometabolic risk in the community, notwithstanding cross-sectional associations. Further studies of larger samples are needed to replicate our findings.

The Association Between Uric Acid and Symmetric Dimethylarginine Levels in the Patients Undergoing Twice-weekly Hemodialysis

Background: Uric acid (UA) levels are associated with increased risk of cardiovascular events and mortality in hemodialysis patients. However, there are still conflicting data on the mechanism of increased risks related to uric acid levels. Objectives: This study assessed the association between uric acid levels and symmetric dimethylarginine (SDMA), as a marker of cardiovascular disease, in the subjects undergoing hemodialysis twice weekly. Methods: This was a cross-sectional study conducted in a tertiary hospital in Jakarta, Indonesia. We included all the adults who underwent hemodialysis twice weekly for at least three months in our hospital. Subjects already on uric acid lowering therapy, pregnant or lactating women and those with a history of malignancy were excluded. Uric acid and SDMA levels were measured at the same time in pre-dialysis venous blood samples. Bivariate analysis was performed using the Mann-Whitney U test or one-way ANOVA. Results: A total of 126 subjects were included. The median level of UA was 8.4 mg/dL (IQR: 2.6, min: 4.1, max: 13.6), and 72 subjects (57.14%) had UA levels of 8 mg/dL or higher. The median SDMA level was 535.5 (312.7) mmol/dL (min: 119.7, max: 1895.5). Subjects with UA levels > 8 mg/dL had significantly higher SDMA levels compared to subjects with UA levels < 8 mg/dL (550.1 (IQR: 357.25) vs 491.35 (IQR: 181.1), P: 0.0475). Conclusions: In twice-weekly hemodialysis patients, UA levels above 8 mg/dL were associated with increased SDMA levels.

Lipoproteins and fatty acids in chronic kidney disease: molecular and metabolic alterations

Chronic kidney disease (CKD) induces modifications in lipid and lipoprotein metabolism and homeostasis. These modifications can promote, modulate and/or accelerate CKD and secondary cardiovascular disease (CVD). Lipid and lipoprotein abnormalities - involving triglyceride-rich lipoproteins, LDL and/or HDL - not only involve changes in concentration but also changes in molecular structure, including protein composition, incorporation of small molecules and post-translational modifications. These alterations modify the function of lipoproteins and can trigger pro-inflammatory and pro-atherogenic processes, as well as oxidative stress. Serum fatty acid levels are also often altered in patients with CKD and lead to changes in fatty acid metabolism - a key process in intracellular energy production - that induce mitochondrial dysfunction and cellular damage. These fatty acid changes might not only have a negative impact on the heart, but also contribute to the progression of kidney damage. The presence of these lipoprotein alterations within a biological environment characterized by increased inflammation and oxidative stress, as well as the competing risk of non-atherosclerotic cardiovascular death as kidney function declines, has important therapeutic implications. Additional research is needed to clarify the pathophysiological link between lipid and lipoprotein modifications, and kidney dysfunction, as well as the genesis and/or progression of CVD in patients with kidney disease.

Unraveling the Complexity of HDL Remodeling: On the Hunt to Restore HDL Quality

Increasing evidence has cast doubt over the HDL-cholesterol hypothesis. The complexity of the HDL particle and its proven susceptibility to remodel has paved the way for intense molecular investigation. This state-of-the-art review discusses the molecular changes in HDL particles that help to explain the failure of large clinical trials intending to interfere with HDL metabolism, and details the chemical modifications and compositional changes in HDL-forming components, as well as miRNA cargo, that render HDL particles ineffective. Finally, the paper discusses the challenges that need to be overcome to shed a light of hope on HDL-targeted approaches.

Lipoproteins in chronic kidney disease: from bench to bedside

Chronic kidney disease (CKD) is associated with high cardiovascular risk. CKD patients exhibit a specific lipoprotein pattern termed 'uraemic dyslipidaemia', which is characterized by rather normal low-density lipoprotein cholesterol, low high-density lipoprotein cholesterol, and high triglyceride plasma levels. All three lipoprotein classes are involved in the pathogenesis of CKD-associated cardiovascular diseases (CVDs). Uraemia leads to several modifications of the structure of lipoproteins such as changes of the proteome and the lipidome, post-translational protein modifications (e.g. carbamylation) and accumulation of small-molecular substances within the lipoprotein moieties, which affect their functionality. Lipoproteins from CKD patients interfere with lipid transport and promote inflammation, oxidative stress, endothelial dysfunction as well as other features of atherogenesis, thus contributing to the development of CKD-associated CVD. While, lipid-modifying therapies play an important role in the management of CKD patients, their efficacy is modulated by kidney function. Novel therapeutic agents to prevent the adverse remodelling of lipoproteins in CKD and to improve their functional properties are highly desirable and partially under development.

Combined application of rapamycin and atorvastatin improves lipid metabolism in apolipoprotein E-deficient mice with chronic kidney disease

Atherosclerosis arising from the pro-inflammatory conditions associated with chronic kidney disease (CKD) increases major cardiovascular morbidity and mortality. Rapamycin (RAPA) is known to inhibit atherosclerosis under CKD and non-CKD conditions, but it can cause dyslipidemia; thus, the co-application of lipid-lowering agents is recommended. Atorvastatin (ATV) has been widely used to reduce serum lipids levels, but its synergistic effect with RAPA in CKD remains unclear. Here, we analyzed the effect of their combined treatment on atherosclerosis stimulated by CKD in apolipoprotein E-deficient (ApoE^−/−) mice. Oil Red O staining revealed that treatment with RAPA and RAPA＋ ATV, but not ATV alone, significantly decreased the atherosclerotic lesions in the aorta and aortic sinus, compared to those seen in the control (CKD) group. The co-administration of RAPA and ATV improved the serum lipid profile and raised the expression levels of proteins involved in reverse cholesterol transport (LXRα, CYP7A1, ABCG1, PPARγ, ApoA1) in the liver. The CKD group showed increased levels of various genes encoding atherosclerosis-promoting cytokines in the spleen (Tnf-α, Il-6 and Il-1β) and aorta (Tnf-α and Il-4), and these increases were attenuated by RAPA treatment. ATV and RAPA＋ATV decreased the levels of Tnf-α and Il-1β in the spleen, but not in the aorta. Together, these results indicate that, in CKD-induced ApoE^−/− mice, RAPA significantly reduces the development of atherosclerosis by regulating the expression of inflammatory cytokines and the co-application of ATV improves lipid metabolism.

Cardiovascular Disease in Chronic Kidney Disease: Pathophysiological Insights and Therapeutic Options

Patients with chronic kidney disease (CKD) exhibit an elevated cardiovascular risk manifesting as coronary artery disease, heart failure, arrhythmias, and sudden cardiac death. Although the incidence and prevalence of cardiovascular events is already significantly higher in patients with early CKD stages (CKD stages 1-3) compared with the general population, patients with advanced CKD stages (CKD stages 4-5) exhibit a markedly elevated risk. Cardiovascular rather than end-stage kidney disease (CKD stage 5) is the leading cause of death in this high-risk population. CKD causes a systemic, chronic proinflammatory state contributing to vascular and myocardial remodeling processes resulting in atherosclerotic lesions, vascular calcification, and vascular senescence as well as myocardial fibrosis and calcification of cardiac valves. In this respect, CKD mimics an accelerated aging of the cardiovascular system. This overview article summarizes the current understanding and clinical consequences of cardiovascular disease in CKD.

Effect of High-Density Lipoprotein from Healthy Subjects and Chronic Kidney Disease Patients on the CD14 Expression on Polymorphonuclear Leukocytes

In uremic patients, high-density lipoprotein (HDL) loses its anti-inflammatory features and can even become pro-inflammatory due to an altered protein composition. In chronic kidney disease (CKD), impaired functions of polymorphonuclear leukocytes (PMNLs) contribute to inflammation and an increased risk of cardiovascular disease. This study investigated the effect of HDL from CKD and hemodialysis (HD) patients on the CD14 expression on PMNLs. HDL was isolated using a one-step density gradient centrifugation. Isolation of PMNLs was carried out by discontinuous Ficoll-Hypaque density gradient centrifugation. CD14 surface expression was quantified by flow cytometry. The activity of the small GTPase Rac1 was determined by means of an activation pull-down assay. HDL increased the CD14 surface expression on PMNLs. This effect was more pronounced for HDL isolated from uremic patients. The acute phase protein serum amyloid A (SAA) caused higher CD14 expression, while SAA as part of an HDL particle did not. Lipid raft disruption with methyl-β-cyclodextrin led to a reduced CD14 expression in the absence and presence of HDL. HDL from healthy subjects but not from HD patients decreased the activity of Rac1. Considering the known anti-inflammatory effects of HDL, the finding that even HDL from healthy subjects increased the CD14 expression was unexpected. The pathophysiological relevance of this result needs further investigation.

Whole-body arginine dimethylation is associated with all-cause mortality in adult renal transplant recipients

Arginine residues in proteins can be singly or doubly methylated post-translationally. Proteolysis of arginine-methylated proteins provides monomethyl arginine, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA). ADMA and SDMA are considered cardiovascular risk factors, with the underlying mechanisms being not yet fully understood. SDMA lacks appreciable metabolism and is almost completely eliminated by the kidney, whereas ADMA is extensively metabolized to dimethylamine (DMA), with a minor ADMA fraction of about 10% being excreted unchanged in the urine. Urinary DMA and ADMA are useful measures of whole-body asymmetric arginine-dimethylation, while urinary SDMA serves as a whole-body measure of symmetric arginine-dimethylation. In renal transplant recipients (RTR), we previously found that higher plasma ADMA concentrations and lower urinary ADMA and SDMA concentrations were associated with a higher risk of all-cause mortality. Yet, in this RTR collective, no data were available for urinary DMA. For the present study, we additionally measured the excretion rate of DMA in 24-h collected urine samples of the RTR and of healthy kidney donors in the cohort, with the aim to quantitate whole-body asymmetric (ADMA, DMA) and symmetric (SDMA) arginine-dimethylation. We found that lower DMA excretion rates were associated with higher all-cause mortality, yet not with cardiovascular mortality. In the healthy donors, kidney donation was associated with considerable decreases in ADMA (by - 39%, P < 0.0001) and SDMA (by - 21%, P < 0.0001) excretion rates, yet there was no significant change in DMA (by - 9%, P = 0.226) excretion rate. Our results suggest that protein-arginine dimethylation is altered in RTR compared to healthy kidney donors and that it is pronouncedly shifted from symmetric to asymmetric arginine-dimethylation, with whole-body protein-arginine dimethylation being almost unaffected.

High-density lipoprotein remodelled in hypercholesterolaemic blood induce epigenetically driven down-regulation of endothelial HIF-1α expression in a preclinical animal model

AIMS

High-density lipoproteins (HDLs) are circulating micelles that transport proteins, lipids, and miRNAs. HDL-transported miRNAs (HDL-miRNAs) have lately received attention but their effects on vascular cells are not fully understood. Additionally, whether cardiovascular risk factors affect HDL-miRNAs levels and miRNA transfer to recipient cells remains equally poorly known. Here, we have investigated the changes induced by hypercholesterolaemia on HDL-miRNA levels and its effect on recipient endothelial cells (ECs).

METHODS AND RESULTS

Pigs were kept on a high-fat diet (HC; n = 10) or a normocholesterolaemic chow (NC; n = 10) for 10 days reaching cholesterol levels of 321.0 (229.7-378.5) mg/dL and 74.0 (62.5-80.2) mg/dL, respectively. HDL particles were isolated, purified, and quantified. HDL-miRNA profiling (n = 149 miRNAs) of HC- and NC-HDLs was performed by multipanel qPCR. Cell cultures of porcine aortic ECs were used to determine whether HDL-miRNAs were delivered to ECs. Potential target genes modulated by miRNAs were identified by bioinformatics and candidate miRNAs were validated by molecular analysis. In vivo effects in the coronary arteries of normocholesterolaemic swine administered HC- or NC-HDLs were analysed. Among the HDL-miRNAs, four were found in different amounts in HC- and NC-HDL (P < 0.05). miR-126-5p and -3p and miR-30b-5p (2.7×, 1.7×, and 1.3×, respectively) were found in higher levels and miR-103a-3p and miR-let-7g-5p (-1.6×, -1.4×, respectively) in lower levels in HC-HDL. miR-126-5p and -3p were transferred from HC-HDL to EC (2.5×; P < 0.05), but not from NC-HDL, by a SRB1-mediated mechanism. Bioinformatics revealed that HIF1α was the miR-126 target gene with the highest predictive value, which was accordingly found to be markedly reduced in HC-HDL-treated ECs and in miR126 mimic transfected ECs. In vivo validation confirmed that HIF1α was diminished in the coronary endothelial layer of NC pigs administered HC-HDL vs. those administered NC-HDL (P < 0.05).

CONCLUSION

Hypercholesterolaemia induces changes in the miRNA content of HDL enhancing miR126 and its delivery to ECs with the consequent down-regulation of its target gene HIF1α.

HDL cholesterol efflux capacity is inversely associated with subclinical cardiovascular risk markers in young adults: The cardiovascular risk in Young Finns study

The atherogenic process begins already in childhood and progresses to symptomatic condition with age. We investigated the association of cholesterol efflux capacity (CEC) and vascular markers of subclinical atherosclerosis in healthy, young adults. CEC was determined in 2282 participants of the Young Finns study using cAMP treated ³H-cholesterol-labeled J774 cells. The CEC was correlated to baseline and 6-year follow-up data of cardiovascular risk factors and ultrasound measurements of arterial structure and function. CEC was higher in women, correlated with total cholesterol, HDL-C, and apolipoprotein A-I, but not with LDL-C or apolipoprotein B. Compared to the lowest CEC quartile, the highest CEC quartile was significantly associated with high CRP levels and inversely associated with adiponectin. At baseline, high CEC was associated with decreased flow-mediated dilation (FMD) and carotid artery distensibility, as well as an increased Young's modulus of elasticity, indicating adverse changes in arterial structure, and function. The association reversed with follow-up FMD data, indicating the interaction of preclinical parameters over time. A higher CEC was directly associated with a lower risk of subclinical atherosclerosis at follow-up. In young and healthy subjects, CEC was associated with important lipid risk parameters at baseline, as in older patients and CAD patients, but inversely with early risk markers for subclinical atherosclerosis.

Elevated high-density lipoprotein in adolescents with Type 1 diabetes is associated with endothelial dysfunction in the presence of systemic inflammation

AIMS

High-density lipoprotein (HDL) function may be altered in patients with chronic disease, transforming the particle from a beneficial vasoprotective molecule to a noxious pro-inflammatory equivalent. Adolescents with Type 1 diabetes often have elevated HDL, but its vasoprotective properties and relationship to endothelial function have not been assessed.

METHODS AND RESULTS

Seventy adolescents with Type 1 diabetes (age 10-17 years) and 30 age-matched healthy controls supplied urine samples for the measurement of early renal dysfunction (albumin:creatinine ratio; ACR), blood samples for the assessment of cardiovascular risk factors (lipid profiles, HDL functionality, glycaemic control, and inflammatory risk score), and had their conduit artery endothelial function tested using flow-mediated dilation (FMD). HDL-c levels (1.69 ± 0.41 vs. 1.44 ± 0.29mmol/L; P < 0.001), and glycated haemoglobin (HbA1c) (8.4 ± 1.2 vs. 5.4 ± 0.2%; P < 0.001) were increased in all patients compared with controls. However, increased inflammation and HDL dysfunction were evident only in patients who also had evidence of early renal dysfunction (mean ± standard deviation for high-ACR vs. low-ACR and healthy controls: inflammatory risk score 11.3 ± 2.5 vs. 9.5 ± 2.4 and 9.2 ± 2.4, P < 0.01; HDL-mediated nitric-oxide bioavailability 38.0 ± 8.9 vs. 33.3 ± 7.3 and 25.0 ± 7.7%, P < 0.001; HDL-mediated superoxide production 3.71 ± 3.57 vs. 2.11 ± 3.49 and 1.91 ± 2.47nmol O2 per 250 000 cells, P < 0.05). Endothelial function (FMD) was impaired only in those who had both a high inflammatory risk score and high levels of HDL-c (P < 0.05).

CONCLUSION

Increased levels of HDL-c commonly observed in individuals with Type 1 diabetes may be detrimental to endothelial function when accompanied by renal dysfunction and chronic inflammation.

Immune Dysfunction in Uremia 2020

Cardiovascular disease and infections are major causes for the high incidence of morbidity and mortality of patients with chronic kidney disease. Both complications are directly or indirectly associated with disturbed functions or altered apoptotic rates of polymorphonuclear leukocytes, monocytes, lymphocytes, and dendritic cells. Normal responses of immune cells can be reduced, leading to infectious diseases or pre-activated/primed, giving rise to inflammation and subsequently to cardiovascular disease. This review summarizes the impact of kidney dysfunction on the immune system. Renal failure results in disturbed renal metabolic activities with reduced renin, erythropoietin, and vitamin D production, which adversely affects the immune system. Decreased kidney function also leads to reduced glomerular filtration and the retention of uremic toxins. A large number of uremic toxins with detrimental effects on immune cells have been identified. Besides small water-soluble and protein-bound compounds originating from the intestinal microbiome, several molecules in the middle molecular range, e.g., immunoglobulin light chains, retinol-binding protein, the neuropeptides Met-enkephalin and neuropeptide Y, endothelin-1, and the adipokines leptin and resistin, adversely affect immune cells. Posttranslational modifications such as carbamoylation, advanced glycation products, and oxidative modifications contribute to uremic toxicity. Furthermore, high-density lipoprotein from uremic patients has an altered protein profile and thereby loses its anti-inflammatory properties.

Concepts and Controversies: Lipid Management in Patients with Chronic Kidney Disease

Atherosclerotic cardiovascular disease (ASCVD) remains an important contributor of morbidity and mortality in patients with chronic kidney disease (CKD). CKD is recognized as an important risk enhancer that identifies patients as candidates for more intensive low-density lipoprotein (LDL) cholesterol lowering. However, there is controversy regarding the efficacy of lipid-lowering therapy, especially in patients on dialysis. Among patients with CKD, not yet on dialysis, there is clinical trial evidence for the use of statins with or without ezetimibe to reduce ASCVD events. Newer cholesterol lowering agents have been introduced for the management of hyperlipidemia to reduce ASCVD, but these therapies have not been tested in the CKD population except in secondary analyses of patients with primarily CKD stage 3. This review summarizes the role of hyperlipidemia in ASCVD and treatment strategies for hyperlipidemia in the CKD population.

Arginine derivatives in atrial fibrillation progression phenotypes

Arginine, homoarginine (hArg), asymmetric dimethylarginine (ADMA), and symmetric dimethylarginine (SDMA) affect nitric oxide metabolism and altered concentrations are associated with cardiovascular morbidity and mortality. We analyzed these metabolites using liquid chromatography-tandem mass spectrometry in patients with atrial fibrillation (AF) (n = 241) with a focus on heart rhythm at blood withdrawal, AF progression phenotypes, and successful sinus rhythm (SR) restoration (n = 22). AF progression phenotypes were defined as paroxysmal AF with/without low voltage areas (LVA) and persistent AF with/without LVA. While arginine, ADMA, and hArg were within reference limits for healthy controls, SDMA was higher in the AF cohort (0.57 ± 0.12 vs. 0.53 μmol/L (97.5th percentile in reference cohort)). SR restoration in AF patients resulted in normalization of SDMA concentrations (0.465 ± 0.082 vs. 0.570 ± 0.134 μmol/L at baseline, p < 0.001). Patients with AF at the time of blood sampling had significantly lower hArg (1.65 ± 0.51 vs. 1.85 ± 0.60 μmol/L, p = 0.006) and higher ADMA concentrations (0.526 ± 0.08 vs. 0.477 ± 0.08 μmol/L, p < 0.001) compared with AF patients in SR. hArg concentrations were lower in patients with advanced AF progression phenotypes (persistent AF with LVA (p = 0.046)) independent of heart rhythm at blood sampling. Summarizing, arginine metabolism imbalance is associated with AF in general and AF progression and may contribute to associated risk. KEY MESSAGES: • Heart rhythm at blood withdrawal affects ADMA and hArg level in AF patients. • SDMA is higher in AF patients. • SDMA levels normalize after sinus rhythm restoration. • hArg levels decrease in advanced AF progression phenotypes.

High Density Lipoproteins: Metabolism, Function, and Therapeutic Potential

High Density Lipoproteins (HDLs) have long been considered as “good cholesterol,” beneficial to the whole body and, in particular, to cardio-vascular health. However, HDLs are complex particles that undergoes dynamic remodeling through interactions with various enzymes and tissues throughout their life cycle, making the complete understanding of its functions and roles more complicated than initially expected. In this review, we explore the novel understanding of HDLs' behavior in health and disease as a multifaceted class of lipoprotein, with different size subclasses, molecular composition, receptor interactions, and functionality. Further, we report on emergent HDL-based therapeutics tested in small and larger scale clinical trials and their mixed successes.

Arginine Derivatives in Cerebrovascular Diseases: Mechanisms and Clinical Implications

The amino acid L-arginine serves as substrate for the nitric oxide synthase which is crucial in vascular function and disease. Derivatives of arginine, such as asymmetric (ADMA) and symmetric dimethylarginine (SDMA), are regarded as markers of endothelial dysfunction and have been implicated in vascular disorders. While there is a variety of studies consolidating ADMA as biomarker of cerebrovascular risk, morbidity and mortality, SDMA is currently emerging as an interesting metabolite with distinct characteristics in ischemic stroke. In contrast to dimethylarginines, homoarginine is inversely associated with adverse events and mortality in cerebrovascular diseases and might constitute a modifiable protective risk factor. This review aims to provide an overview of the current evidence for the pathophysiological role of arginine derivatives in cerebrovascular ischemic diseases. We discuss the complex mechanisms of arginine metabolism in health and disease and its potential clinical implications in diverse aspects of ischemic stroke.

GC-MS and LC-MS/MS pilot studies on the guanidine (NG)-dimethylation in native, asymmetrically and symmetrically NG-dimethylated arginine-vasopressin peptides and proteins in human red blood cells

Protein-arginine methyltransferases catalyze the methylation of the guanidine (N^G) group of proteinic L-arginine (Arg) to produce monomethyl and dimethylarginine proteins. Their proteolysis releases the free amino acids monomethylarginine (MMA), symmetric dimethylarginine (SDMA) and asymmetric dimethylarginine (ADMA), respectively. MMA, SDMA and ADMA are inhibitors of the nitric oxide synthase (NOS) activity. High circulating and low urinary concentrations of ADMA and SDMA are considered risk factors in the cardiovascular and renal systems, mainly due to their inhibitory action on NOS activity. Identity, biological activity and concentration of N^G-methylated proteins are largely unknown. The present study addressed these issues by using GC-MS and LC-MS/MS approaches. GC-MS was used to quantify free ADMA released by classical HCl-catalyzed hydrolysis of three synthetic Arg-vasopressin (V) peptides and of unknown endogenous N^G-dimethylated proteins. The cyclic (c) disulfide forms of Arg-vasopressin analogs, i.e., Arg-vasopressin (cV-Arg-Gly-NH₂), asymmetrically N^G-dimethylated vasopressin (cV-ADMA-Gly-NH₂) and symmetrically N^G-dimethylated vasopressin (cV-SDMA-Gly-NH₂) were used as model peptides in quantitative GC-MS analyses of ADMA, SDMA and other expected amino acids from the hydrolyzed Arg-vasopressin analogs. cV-ADMA-Gly-NH₂ and cV-SDMA-Gly-NH₂ were discriminated from cV-Arg-Gly-NH₂ by LC-MS and LC-MS/MS, yet they were indistinguishable from each other. The same applies to the respective open (o) reduced and di-S-acetamide forms of oV-ADMA-Gly-NH₂, oV-SDMA-Gly-NH₂ and oV-Arg-Gly-NH₂. Our LC-MS and LC-MS/MS studies suggest that the Arg-vasopressin analogs form [(M-H)]⁺ and [(M-H)+H]⁺ in the positive ESI mode and undergo in part conversion of their terminal Gly-NH₂ (NH₂, 16 Da) group to Gly-OH (OH, 17 Da). The product ion mass spectra of the di-S-acetamide forms are complex and contain several intense mass fragments differing by 1 Da. cV-ADMA-Gly-NH₂ and cV-SDMA-Gly-NH₂ induced platelet aggregation in platelet-rich human plasma with moderately different initial velocity and maximal aggregation rates compared to cV-Arg-Gly-NH₂. Previous studies showed that human red blood cells are rich in large (>50 kDa) ADMA-containing proteins of unknown identity. Our LC-MS/MS proteomic study identified several membrane and cytosolic erythrocytic N^G-dimethylated proteins, including spectrin-α (280 kDa), spectrin-β (247 kDa) and protein 4.1 (80 kDa). Being responsible for the stability of the erythrocyte membrane, the newly identified main targets for N^G-dimethylation in human erythrocytes should be given a closer look in erythrocytic diseases like hereditary spherocytosis.

Advances in HDL: Much More than Lipid Transporters

High Density Lipoprotein (HDL) particles, beyond serving as lipid transporters and playing a key role in reverse cholesterol transport, carry a highly variable number of proteins, micro-RNAs, vitamins, and hormones, which endow them with the ability to mediate a plethora of cellular and molecular mechanisms that promote cardiovascular health. It is becoming increasingly evident, however, that the presence of cardiovascular risk factors and co-morbidities alters HDLs cargo and protective functions. This concept has led to the notion that metrics other than HDL-cholesterol levels, such as HDL functionality and composition, may better capture HDL cardiovascular protection. On the other hand, the potential of HDL as natural delivery carriers has also fostered the design of engineered HDL-mimetics aiming to improve HDL efficacy or as drug-delivery agents with therapeutic potential. In this paper, we first provide an overview of the molecules known to be transported by HDL particles and mainly discuss their functions in the cardiovascular system. Second, we describe the impact of cardiovascular risk factors and co-morbidities on HDL remodeling. Finally, we review the currently developed HDL-based approaches.

Symmetric dimethylarginine in dysfunctional high-density lipoprotein mediates endothelial glycocalyx breakdown in chronic kidney disease

Dysfunctional high-density lipoprotein (d-HDL) in chronic kidney disease is known to have a change in composition towards an endothelial-damaging phenotype, amongst others, via the accumulation of symmetric dimethylarginine. The endothelial glycocalyx, a carbohydrate-rich layer lining the endothelial luminal surface, is a first line defense against vascular diseases including atherosclerosis. Here we conducted a translational, cross-sectional study to determine the role of symmetric dimethylarginine in d-HDL as a mediator of glycocalyx damage. Using confocal and atomic force microscopy, intact HDL from healthy donors was found to maintain the glycocalyx while isolated HDL from hemodialysis patients and exogenous symmetric dimethylarginine caused significant damage to the glycocalyx in endothelial cells in vitro in a dose-dependent manner. Symmetric dimethylarginine triggered glycocalyx deterioration via molecular pathways mediated by toll-like-receptor 2 and matrix metalloprotease-9. Corresponding intravital microscopy revealed that exogenous symmetric dimethylarginine and d-HDL from hemodialysis patients caused glycocalyx breakdown, which subsequently contributed to alterations in leukocyte rolling. Biologically effective HDL, which estimates the functionality of HDL, was calculated from circulating HDL-cholesterol and symmetric dimethylarginine, as described in the literature. Biologically effective HDL was the only parameter that could independently predict glycocalyx damage in vivo. Thus, our data suggest that symmetric dimethylarginine in d-HDL mediates glycocalyx breakdown in chronic kidney disease.

Metabolites of the Nitric Oxide (NO) Pathway Are Altered and Indicative of Reduced NO and Arginine Bioavailability in Patients with Cardiometabolic Diseases Complicated with Chronic Wounds of Lower Extremities: Targeted Metabolomics Approach (LC-MS/MS)

OBJECTIVE

The status of metabolites of the nitric oxide (NO) pathway in patients with chronic wounds in the course of cardiometabolic diseases is largely unknown. Yet arginine supplementation and citrulline supplementation as novel therapeutic modalities aimed at increasing NO are tested.

MATERIAL AND METHODS

Targeted metabolomics approach (LC-MS/MS) was applied to determine the concentrations of L-arginine, L-citrulline, asymmetric and symmetric dimethylarginines (ADMA and SDMA), and arginine/ADMA and arginine/SDMA ratios as surrogate markers of NO and arginine availability in ulnar and femoral veins, representing systemic and local levels of metabolites, in patients with chronic wounds in the course of cardiometabolic diseases (n = 59) as compared to patients without chronic wounds but with similar cardiometabolic burden (n = 55) and healthy individuals (n = 88).

RESULTS

Patients with chronic wounds had significantly lower systemic L-citrulline and higher ADMA and SDMA concentrations and lower L-arginine/ADMA and L-arginine/SDMA as compared to healthy controls. The presence of chronic wounds in patients with cardiometabolic diseases was associated with decreased L-arginine but with increased L-citrulline, ADMA, and SDMA concentrations and decreased L-arginine/ADMA and L-arginine/SDMA. Serum obtained from the ulnar and femoral veins of patients with chronic wounds differed by L-arginine concentrations and L-arginine/SDMA ratio, both lower in the femoral vein. Wound etiology affected L-citrulline and SDMA concentrations, lower and higher, respectively, in patients with venous stasis, and the L-arginine/SDMA ratio-lower in venous stasis. The wound type affected L-arginine/ADMA and citrulline-lower in patients with ulcerations or gangrene. IL-6 was an independent predictor of L-arginine/ADMA, VEGF-A of ADMA, G-CSF of L-arginine/SDMA, and GM-CSF of L-citrulline and SDMA.

CONCLUSION

Chronic wounds in the course of cardiometabolic diseases are associated with reduced NO and arginine availability due to ADMA and SDMA accumulation rather than arginine deficiency, not supporting its supplementation. Wound character seems to affect NO bioavailability and wound etiology-arginine bioavailability. Arginine concentration and its availability are more markedly reduced at the local level than the systemic level.