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

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

A comparative study of gluten-free sprouts in the gluten-free bread-making process

The addition of sprouted grains and seeds to cereal products has been identified as one of the upcoming trends in recent market reports. In this study, seven types of sprouts (amaranth, brown millet, corn, lentil, lupin, pea, quinoa) were milled and characterised with respect to their compositional (starch, protein, fat, ash, fibre, moisture) and functional properties (water hydration properties). These sprouted flours were included in a gluten-free bread formulation at a level of 5% and the impact on dough (temperature-dependent rising behaviour, pasting and rheological properties) and bread quality parameters (volume, crumb structure and texture) was evaluated. Factors such as the method of germination and the botanical origin influenced the chemical composition of the applied raw material. The functional properties of the different malts and sprouts are affected by the chemical composition of the individual grains. The differences in functional properties were, in turn, found to affect the dough properties and the quality parameters of the baked gluten-free breads. However, statistical analysis showed no correlation between the various factors. Based on this, effects on dough and bread properties were hypothesised to be caused by a combination of multiple factors. All bread formulations containing sprouted flour had significantly improved bread quality parameters in comparison to the control (without sprouted flour). The addition of amaranth sprouted flour, however, resulted in the highest loaf volume and the softest breadcrumb, suggesting its potential for further investigations in further studies

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

Sex differences in the associations between L-arginine pathway metabolites, skeletal muscle mass and function, and their responses to resistance exercise, in old age

This work was supported by the Biotechnology and Biological Sciences Research Council (BB/J015911/1) and was registered at clinicaltrials.gov (ClinicalTrials. gov Identifier: NCT02843009). Supplementary email included with articlePeer reviewedPostprin

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

Deficiency of the T cell regulator Casitas B-cell lymphoma-B aggravates atherosclerosis by inducing CD8+ T cell-mediated macrophage death

The E3-ligase CBL-B (Casitas B-cell lymphoma-B) is an important negative regulator of T cell activation that is also expressed in macrophages. T cells and macrophages mediate atherosclerosis, but their regulation in this disease remains largely unknown; thus, we studied the function of CBL-B in atherogenesis.The expression of CBL-B in human atherosclerotic plaques was lower in advanced lesions compared with initial lesions and correlated inversely with necrotic core area. Twenty weeks old Cblb−/−Apoe−/− mice showed a significant increase in plaque area in the aortic arch, where initial plaques were present. In the aortic root, a site containing advanced plaques, lesion area rose by 40%, accompanied by a dramatic change in plaque phenotype. Plaques contained fewer macrophages due to increased apoptosis, larger necrotic cores, and more CD8+ T cells. Cblb−/−Apoe−/− macrophages exhibited enhanced migration and increased cytokine production and lipid uptake. Casitas B-cell lymphoma-B deficiency increased CD8+ T cell numbers, which were protected against apoptosis and regulatory T cell-mediated suppression. IFNγ and granzyme B production was enhanced in Cblb−/−Apoe−/− CD8+ T cells, which provoked macrophage killing. Depletion of CD8+ T cells in Cblb−/−Apoe−/− bone marrow chimeras rescued the phenotype, indicating that CBL-B controls atherosclerosis mainly through its function in CD8+ T cells. Casitas B-cell lymphoma-B expression in human plaques decreases during the progression of atherosclerosis. As an important regulator of immune responses in experimental atherosclerosis, CBL-B hampers macrophage recruitment and activation during initial atherosclerosis and limits CD8+ T cell activation and CD8+ T cell-mediated macrophage death in advanced atherosclerosis, thereby preventing the progression towards high-risk plaques.Biopharmaceutic

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

Admission levels of asymmetric and symmetric dimethylarginine predict long-term outcome in patients with community-acquired pneumonia

During infection, there is an activation of the L-arginine-nitric-oxide pathway, with a shift from nitric oxide synthesis to a degradation of L-arginine to its metabolites, asymmetric and symmetric dimethylarginine (ADMA and SDMA). However, the prognostic implications for short-term or long-term survival remains unclear. We investigated the association of L-arginine, ADMA, and SDMA with adverse clinical outcomes in a well-defined cohort of patients with community-acquired pneumonia (CAP).; We measured L-arginine, ADMA, and SDMA in 268 CAP patients from a Swiss multicenter trial by mass spectrometry and used Cox regression models to investigate associations between blood marker levels and disease severity as well as mortality over a period of 6 years.; Six-year mortality was 44.8%. Admission levels of ADMA and SDMA (μmol/L) were correlated with CAP severity as assessed by the pneumonia severity index (r = 0.32, p &lt; 0.001 and r = 0.56, p &lt; 0.001 for ADMA and SDMA, respectively) and higher in 6-year non-survivors versus survivors (median 0.62 vs. 0.48; p &lt; 0.001 and 1.01 vs. 0.85; p &lt; 0.001 for ADMA and SDMA, respectively). Both ADMA and SDMA were significantly associated with long-term mortality (hazard ratios [HR] 4.44 [95% confidence intervals (CI) 1.84 to 10.74] and 2.81 [95% CI 1.45 to 5.48], respectively). The effects were no longer significant after multivariate adjustment for age and comorbidities. No association of L-arginine with severity and outcome was found.; Both ADMA and SDMA show a severity-dependent increase in patients with CAP and are strongly associated with mortality. This association is mainly explained by age and comorbidities.; ISRCTN95122877 . Registered 31 July 2006