Dietary Supplementation with Homoarginine Preserves Cardiac Function in a Murine Model of Post-Myocardial Infarction Heart Failure

Low plasma homoarginine (HA) is an emerging biomarker for cardiovascular disease and an independent predictor of mortality in patients with heart failure. Plasma levels appear to reflect cardiac dysfunction, positively correlating with ejection fraction and inversely with circulating brain natriuretic peptide. However, whether this outcome is a bystander or cause-and-effect has yet to be established. Within the context of stroke, a direct causal relationship has been inferred because normal mice pretreated with 14 mg/L HA had a smaller stroke size. In the present study, we show for the first time that dietary supplementation with HA improves cardiac function in the setting of chronic heart failure, suggesting a novel preventive strategy and inferring that low HA levels may be inherently detrimental because of a loss of this effect

Impaired cardiac contractile function in arginine:glycine amidinotransferase knockout mice devoid of creatine is rescued by homoarginine but not creatine

Aims: Creatine buffers cellular adenosine triphosphate (ATP) via the creatine kinase reaction. Creatine levels are reduced in heart failure, but their contribution to pathophysiology is unclear. Arginine:glycine amidinotransferase (AGAT) in the kidney catalyses both the first step in creatine biosynthesis as well as homoarginine (HA) synthesis. AGAT-/- mice fed a creatine-free diet have a whole body creatine-deficiency. We hypothesized that AGAT-/- mice would develop cardiac dysfunction and rescue by dietary creatine would imply causality. Methods and results: Withdrawal of dietary creatine in AGAT-/- mice provided an estimate of myocardial creatine efflux of ∼2.7%/day; however, in vivo cardiac function was maintained despite low levels of myocardial creatine. Using AGAT-/- mice naïve to dietary creatine we confirmed absence of phosphocreatine in the heart, but crucially, ATP levels were unchanged. Potential compensatory adaptations were absent, AMPK was not activated and respiration in isolated mitochondria was normal. AGAT-/- mice had rescuable changes in body water and organ weights suggesting a role for creatine as a compatible osmolyte. Creatine-naïve AGAT-/- mice had haemodynamic impairment with low LV systolic pressure and reduced inotropy, lusitropy, and contractile reserve. Creatine supplementation only corrected systolic pressure despite normalization of myocardial creatine. AGAT-/- mice had low plasma HA and supplementation completely rescued all other haemodynamic parameters. Contractile dysfunction in AGAT-/- was confirmed in Langendorff perfused hearts and in creatine-replete isolated cardiomyocytes, indicating that HA is necessary for normal cardiac function. Conclusions: Our findings argue against low myocardial creatine per se as a major contributor to cardiac dysfunction. Conversely, we show that HA deficiency can impair cardiac function, which may explain why low HA is an independent risk factor for multiple cardiovascular diseases

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

Racial Differences in Cardiovascular Biomarkers in the General Population

Background-The incidence and clinical manifestations of cardiovascular disease (CVD) differ between blacks and whites. Biomarkers that reflect important pathophysiological pathways may provide a window to allow deeper understanding of racial differences in CVD. Methods and Results-The study included 2635 white and black participants from the Dallas Heart Study who were free from existing CVD. Cross-sectional associations between race and 32 biomarkers were evaluated using multivariable linear regression adjusting for age, traditional CVD risk factors, imaging measures of body composition, renal function, insulin resistance, left ventricular mass, and socioeconomic factors. In fully adjusted models, black women had higher lipoprotein(a), leptin, D-dimer, osteoprotegerin, antinuclear antibody, homoarginine, suppression of tumorigenicity-2, and urinary microalbumin, and lower adiponectin, soluble receptor for advanced glycation end products and N-terminal pro-B-type natriuretic peptide versus white women. Black men had higher lipoprotein(a), leptin, D-dimer, high-sensitivity C-reactive protein, antinuclear antibody, symmetrical dimethylarginine, homoarginine, high-sensitivity cardiac troponin T, suppression of tumorigenicity-2, and lower adiponectin, soluble receptor for advanced glycation end products, and N-terminal pro-B-type natriuretic peptide versus white men. Adjustment for biomarkers that were associated with higher CVD risk, and that differed between blacks and whites, attenuated the risk for CVD events in black women (unadjusted hazard ratio 2.05, 95% CI 1.32, 3.17 and adjusted hazard ratio 1.15, 95% CI 0.69, 1.92) and black men (unadjusted hazard ratio 2.39, 95% CI 1.64, 3.46, and adjusted hazard ratio 1.21, 95% CI 0.76, 1.95). Conclusions-Significant racial differences were seen in biomarkers reflecting lipids, adipokines, and biomarkers of endothelial function, inflammation, myocyte injury, and neurohormonal stress, which may contribute to racial differences in the development and complications of CVD

Low-Circulating Homoarginine is Associated with Dilatation and Decreased Function of the Left Ventricle in the General Population

Low homoarginine is an independent marker of mortality in heart failure patients and incident cardiovascular events. Whether homoarginine is related with healthier cardiac structure and function is currently unclear. We used data of the population-based Study of Health in Pomerania (SHIP-Trend) to assess this relation. Homoarginine was measured in serum using liquid chromatography-tandem mass spectrometry. Linear regression models assessed the relation between homoarginine and several structural as well as functional parameters and N-terminal pro B-type natriuretic peptide (NTproBNP). All models were adjusted for age, sex, body mass index, and renal function. A total of 3113 subjects (median age 48 (25th percentile 37 to 75th percentile 60) years, 46% male) were included. A standard deviation decrease in homoarginine was associated with a larger left ventricular diastolic diameter (0.3;95%-confidence interval (CI): 0.2 to 0.5 mm;p < 0.001), left ventricular systolic diameter (0.38;95%-CI: -0.22 to 0.54 mm;p < 0.001) as well as a less relative wall thickness (-0.003 95%-CI: -0.006 to -0.0008;p = 0.01), left ventricular ejection fraction (-0.47;95%-CI: -0.79 to -0.15%;p < 0.01) and fractional shortening (-0.35;95%-CI: -0.62 to 0.07%;p = 0.01). Low homoarginine was also related to higher NTproBNP (-0.02 95%-CI: -0.034 to -0.009 log pg/mL;p < 0.01). Lower serum homoarginine is associated with dilatation of the heart and decreased function. Prospective clinical studies should assess if homoarginine supplementation improves cardiac health in subjects with low serum concentrations

Dimethylarginine Dimethylaminohydrolase-1 Transgenic Mice Are Not Protected from Ischemic Stroke

Methylated arginines are endogenous analogues of L-arginine, the substrate for nitric oxide (NO) synthase. Asymmetric dimethylarginine (ADMA) interferes with NO formation, causing endothelial dysfunction. ADMA is a predictor of cardiovascular events and mortality in humans. It is eliminated primarily by enzymatic activity of dimethylarginine dimethylaminohydrolase (DDAH).We investigated whether human DDAH-1 (hDDAH-1) transgenicity protects from ischemic tissue damage in temporary middle cerebral artery occlusion (tMCAO) in mice. Infarct sizes did not significantly differ between hDDAH-1 transgenic (TG) mice and wild-type littermates (WT). As expected, ADMA plasma concentrations were significantly decreased, cerebral hDDAH expression and protein significantly increased in transgenic animals. Interestingly, neither brain tissue DDAH activity nor ADMA concentrations were different between TG and WT mice. In contrast, muscular DDAH activity was generally lower than in brain but significantly increased in TG mice.Our study demonstrates that hDDAH-1 transgenic mice are not protected from ischemic cerebral tissue damage in tMCAO. This lack of protection is due to high basal cerebral DDAH activity, which is not further increasable by transgenic overexpression of DDAH

Cross-Sectional Associations between Homoarginine, Intermediate Phenotypes, and Atrial Fibrillation in the CommunityThe Gutenberg Health Study

Homoarginine has come into the focus of interest as a biomarker for cardiovascular disease. Atrial fibrillation (AF) causes a substantial increase in morbidity and mortality. Whether circulating homoarginine is associated with occurrence or persistence of AF and may serve as a new predictive biomarker remains unknown. We measured plasma levels of homoarginine in the population-based Gutenberg health study (3761 patients included, of them 51.7% males), mean age 55.6 +/- 10.9 years-old. Associations between homoarginine and intermediate electrocardiographic and echocardiographic phenotypes and manifest AF were examined. Patients with AF (124 patients, of them 73.4% males) had a mean age 64.8 +/- 8.6 years-old compared to a mean age of 55.3 +/- 10.9 in the population without AF (p-value < 0.001) and showed a less beneficial risk factor profile. The median homoarginine levels in individuals with and without AF were 1.9 mol/L (interquartile range (IQR) 1.5-2.5) and 2.0 mol/L (IQR 1.5-2.5), respectively, p = 0.56. In multivariable-adjusted regression analyses homoarginine was not statistically significantly related to electrocardiographic variables. Among echocardiographic variables beta per standard deviation increase was -0.12 (95% confidence interval (CI) -0.23-(-0.02);p = 0.024) for left atrial area and -0.01 (95% CI -0.02-(-0.003);p = 0.013) for E/A ratio. The odds ratio between homoarginine and AF was 0.91 (95% CI 0.70-1.16;p = 0.45). In our large, population-based cross-sectional study, we did not find statistically significant correlations between lower homoarginine levels and occurrence or persistence of AF or most standard electrocardiographic phenotypes, but some moderate inverse associations with echocardiographic left atrial size and E/A. Homoarginine may not represent a strong biomarker to identify individuals at increased risk for AF. Further investigations will be needed to elucidate the role of homoarginine and cardiac function

Identification of a non-canonical chemokine-receptor pathway suppressing regulatory T cells to drive atherosclerosis

CCL17 is produced by conventional dendritic cells, signals through CCR4 on regulatory T (Treg) cells and drives atherosclerosis by suppressing Treg functions through yet undefined mechanisms. Here we show that conventional dendritic cells from CCL17-deficient mice display a pro-tolerogenic phenotype and transcriptome that is not phenocopied in mice lacking its cognate receptor CCR4. In the plasma of CCL17-deficient mice, CCL3 was the only decreased cytokine/chemokine. We found that CCL17 signaled through CCR8 as an alternate high-affinity receptor, which induced CCL3 expression and suppressed Treg functions in the absence of CCR4. Genetic ablation of CCL3 and CCR8 in CD4+ T cells reduced CCL3 secretion, boosted FoxP3+ Treg numbers and limited atherosclerosis. Conversely, CCL3 administration exacerbated atherosclerosis and restrained Treg differentiation. In symptomatic versus asymptomatic human carotid atheroma, CCL3 expression was increased, whereas FoxP3 expression was reduced. Together, we identified a non-canonical chemokine pathway whereby CCL17 interacts with CCR8 to yield a CCL3-dependent suppression of atheroprotective Treg cells. Doring, van der Vorst, Yan, Neideck et al. present a non-canonical chemokine pathway involving CCL17 signaling through CCR8, which induces CCL3 expression independent of CCR4 and suppresses the functions of atheroprotective Treg cells

Hyperlipidaemia elicits an atypical, T helper 1-like CD4 + T-cell response: a key role for very low-density lipoprotein.

AIMS: Hyperlipidemia and T cell driven inflammation are important drivers of atherosclerosis, the main underlying cause of cardiovascular disease. Here, we detailed the effects of hyperlipidemia on T cells. METHODS AND RESULTS: In vitro, exposure of human and murine CD4+ T cells to very low-density lipoprotein (VLDL), but not to low-density lipoprotein (LDL) resulted in upregulation of Th1 associated pathways. VLDL was taken up via a CD36-dependent pathway and resulted in membrane stiffening and a reduction in lipid rafts. To further detail this response in vivo, T cells of mice lacking the LDL receptor (LDLr), which develop a strong increase in VLDL cholesterol and triglyceride levels upon high cholesterol feeding were investigated. CD4+ T cells of hyperlipidemic Ldlr-/- mice exhibited an increased expression of the C-X-C-chemokine receptor 3 (CXCR3) and produced more interferon-γ (IFN-γ). Gene set enrichment analysis identified IFN-γ-mediated signaling as the most upregulated pathway in hyperlipidemic T cells. However, the classical Th1 associated transcription factor profile with strong upregulation of Tbet and Il12rb2 was not observed. Hyperlipidemia did not affect levels of the CD4+ T cell's metabolites involved in glycolysis or other canonical metabolic pathways but enhanced amino acids levels. However, CD4+ T cells of hyperlipidemic mice showed increased cholesterol accumulation and an increased arachidonic acid (AA) to docosahexaenoic acid (DHA) ratio, which was associated with inflammatory T cell activation. CONCLUSIONS: Hyperlipidemia, and especially its VLDL component induces an atypical Th1 response in CD4+ T cells. Underlying mechanisms include CD36 mediated uptake of VLDL, and an altered AA/DHA ratio