L-homoarginine is associated with decreased cardiovascular- and all-cause mortality

A multi-metabolite signature robustly predicts long-term mortality in the PREDIMED trial and several US cohorts

Metabolome-based biomarkers contribute to identify mechanisms of disease and to a better understanding of overall mortality. In a long-term follow-up subsample (n = 1878) of the PREDIMED trial, among 337 candidate baseline plasma metabolites repeatedly assessed at baseline and after 1 year, 38 plasma metabolites were identified as predictors of all-cause mortality. Gamma-amino-butyric acid (GABA), homoarginine, serine, creatine, 1-methylnicotinamide and a set of sphingomyelins, plasmalogens, phosphatidylethanolamines and cholesterol esters were inversely associated with all-cause mortality, whereas plasma dimethylguanidino valeric acid (DMGV), choline, short and long-chain acylcarnitines, 4-acetamidobutanoate, pseudouridine, 7-methylguanine, N6-acetyllysine, phenylacetylglutamine and creatinine were associated with higher mortality. The multi-metabolite signature created as a linear combination of these selected metabolites showed a strong association with all-cause mortality using plasma samples collected in PREDIMED also at 1-year follow-up. This association was subsequently confirmed in 4 independent American cohorts, validating the signature as a consistent predictor of all-cause mortality across diverse populations.

Associations of plasma arginine, homoarginine, and ADMA/SDMA levels with risk of ischemic stroke: A nested case-control study

BACKGROUND AND AIMS

Previous studies have linked aberrant nitric oxide (NO) metabolism with vascular diseases. Although arginine, homoarginine, asymmetric dimethylarginine (ADMA), and symmetric dimethylarginine (SDMA) are involved in NO metabolic pathways, their associations with ischemic stroke (IS) remain unclear.

METHODS AND RESULTS

We conducted a case-control study nested within the Prospective Follow-up Study on Cardiovascular Morbidity and Mortality in China (PFS-CMMC) (2013-2018, n = 16,457; median follow-up time: 5.3 y), which included 321 incident cases of IS and 321 controls matched by age and sex. Plasma arginine, homoarginine, ADMA/SDMA were measured by ultrahigh performance liquid chromatography-tandem mass spectrometry. Conditional logistic regression analyses were used to calculate odds ratios (ORs) and their 95% confidence intervals (CIs) for the association between the plasma metabolites and IS risk. After adjustment for body mass index, educational attainment, smoking, hypertension, hyperlipidemia, diabetes, and family history of stroke, the OR of IS risk for the highest versus the lowest quartile was 2.46 (95% CI: 1.39-4.35, P trend = 0.004) for homoarginine and 2.22 (95% CI: 1.24-3.97, P trend = 0.003) for ADMA/SDMA. Spline regression analyses indicated positive dose-response relationships of homoarginine and ADMA/SDMA with the IS risk (both P for linearity <0.05). No significant association was observed between plasma arginine and IS risk.

CONCLUSIONS

Elevated plasma levels of homoarginine and ADMA/SDMA were associated with a higher risk of IS. Our novel findings suggest a role of NO metabolism in the pathogenesis of IS.

Mechanisms of Homoarginine: Looking Beyond Clinical Outcomes

PURPOSE

Homoarginine (hArg) is an arginine metabolite that has been known for years, but its physiological role in the body remains poorly understood. For instance, it is well known that high hArg concentrations in the blood are protective against several disease states, yet the mechanisms behind these health benefits are unclear. This review compiles what is known about hArg, namely its synthetic pathways, its role in different diseases and conditions, and its proposed mechanisms of action in humans and experimental animals.

FINDINGS

Previous work has identified multiple pathways that control hArg synthesis and degradation in the body. Furthermore, endogenous hArg can modulate the cardiovascular system, with decreased hArg being associated with cardiovascular complications and increased mortality. Studies also suggest that hArg could serve as a diagnostic biomarker for a variety of immune, pancreatic, renal, and hepatic dysfunctions. Finally, in women, hArg concentrations rapidly increase throughout pregnancy and there are suggestions that alterations in hArg could indicate pregnancy complications like pre-eclampsia.

SUMMARY

Homoarginine is an under-appreciated amino acid with potential wide-ranging roles in systemic health, pregnancy, and pathophysiology. Although recent research has focused on its health or disease associations, there is a need for more investigations into understanding the mechanistic pathways by which hArg may operate. This could be aided using metabolomics, which provides a comprehensive approach to correlating multiple metabolites and metabolic pathways with physiological effects. Increasing our knowledge of hArg's roles in the body could pave the way for its routine use as both a diagnostic and therapeutic molecule.

Yu-Xue-Bi capsule ameliorates aggressive synovitis and joint damage in rheumatoid arthritis via modulating the SUCNR1/HIF-1α/TRPV1 axis

BACKGROUND

Specific treatment for rheumatoid arthritis (RA) is still an unmet need. Yu-Xue-Bi (YXB) capsule effectively treats RA with blood stasis syndrome (BS). However, its mechanism remains unclear.

PURPOSE

Exploring and elucidating the therapeutic effect and pharmacological mechanism of YXB capsule in treating RA.

METHODS

This study identified differentially expressed genes (DEGs) in patients with RA and BS compared to healthy controls using clinical transcriptomics data. Clinical symptoms of RA and BS, and the related genes were collected from the SoFDA and HPO databases. Candidate bioactive constituents in YXB were identified via UPLC-QTOF/MS and evaluated using ADMET rules. Putative targets were predicted, and a network linking disease-related DEGs and drug targets was constructed. Key targets were screened utilizing random walk-with-restart (RWR) algorithms and verified through experiments using rat models of collagen-induced arthritis with BS (CIA-BS model) in vivo.

RESULTS

We found 1220 DEGs along with 976 clinical symptom-related genes, as RA with BS-related genes. Chemical profiling identified 193 YXB constituents, with 98 meeting optimal ADMET criteria. We predicted 459 putative targets for these constituents. Network calculations screened 209 key targets, 129 RA with BS-related genes and 92 YXB targets involved in immune inflammation, blood stagnation, and hyperalgesia imbalance. Notably, the SUCNR1/HIF-1α/TRPV1 axis was enriched by YXB targets against RA with BS. Experimentally, YXB inhibited inflamed joint deterioration, including synovial inflammation, cartilage damage and bone erosion, relieving mechanical and cold allodynia hyperglasia. It reversed hemorrheology and vascular function in CIA-BS rats, restoring SDHB and eNOS expression, preventing SDHA, SUCNR1 and HIF-1α activation, reducing SUCN, TNF-α and IL-1β production, and TRPV1 and TRPA1 expression.

CONCLUSION

Our data support YXB's therapeutic effects on aggressive RA-BS by modulating the SUCNR1/HIF-1α/TRPV1 axis.

Homoarginine Associates with Carotid Intima-Media Thickness and Atrial Fibrillation and Predicts Adverse Events after Stroke

Homoarginine is associated with cardio- and cerebrovascular morbidity and mortality. However, the underlying pathomechanisms remain elusive. Here, we evaluated the association of homoarginine with adverse events (i.e., death, stroke, and myocardial infarction) and carotid intima-media thickness (cIMT) in stroke patients. In the prospective bioMARKers in STROKE (MARK-STROKE) cohort, patients with acute ischemic stroke or transient ischemic attack (TIA) were enrolled. Plasma homoarginine concentrations were analyzed and associated with clinical phenotypes in cross-sectional (374 patients) and prospective (273 patients) analyses. Adjustments for possible confounders were evaluated. A two-fold increase in homoarginine was inversely associated with the National Institutes of Health Stroke Scale (NIHSS) score at admission, cIMT, and prevalent atrial fibrillation (mean factor -0.68 [95% confidence interval (CI): -1.30, -0.07], -0.14 [95% CI: -0.22, -0.05]; and odds ratio 0.57 [95% CI: 0.33, 0.96], respectively). During the follow-up (median 284 [25th, 75th percentile: 198, 431] days), individuals with homoarginine levels in the highest tertile had fewer incident events compared with patients in the lowest homoarginine tertile independent of traditional risk factors (hazard ratio 0.22 [95% CI: 0.08, 0.63]). A lower prevalence of atrial fibrillation and a reduced cIMT pinpointed potential underlying pathomechanisms.

Homoarginine in health and disease

PURPOSE OF REVIEW

Homoarginine (hArg) is an endogenous, nonproteinogenic amino acid. It is enzymatically synthesized from L-arginine and L-lysine. Low hArg concentrations appear to be a risk factor in the renal and cardiovascular systems. This review discusses advances in-vitro and in-vivo experimental and clinical research on hArg in health and disease.

RECENT FINDINGS

Recent studies indicate that low circulating and low urinary concentrations of hArg are associated with morbidity and worse outcome. Although the biological activities of hArg remain still unexplored, hArg supplementation is intensely investigated as a strategy to increase hArg concentration to reach normal levels in cases of low hArg concentrations. The greatest changes in circulating hArg concentrations are observed during pregnancy and after delivery. In healthy adults, a daily dose of 125 mg hArg seems to be optimum to normalize circulating levels. Short-term supplementation of inorganic nitrate enhances hArg biosynthesis in healthy young men. Apart from hArg supplementation, dietary L-arginine and L-citrulline appear to be a promising alternative.

SUMMARY

Considerable progress has been made in recent years, but hArg remains still enigmatic. Further research is required to explore the biological activities of hArg. Supplementation of hArg or its precursors L-citrulline/L-arginine seem to be promising strategies to prevent and overcome altered hArg synthesis.

Do Antiepileptic Drugs Change the Levels of Arginine Derivatives in Epileptic Children Treated with Polytherapy? The Results of a Case–Control Study

Previously, a relation between therapy with antiepileptic drugs (AEDs) and the levels of biochemical parameters was observed in adult patients suffering from epilepsy. Among these biochemical factors, arginine derivatives are often analyzed, i.e., asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), and homoarginine (hArg) as they may be linked with increased risk for cardiovascular disease (CVD). Since the levels of arginine derivatives may increase during therapy, and the treatment of epilepsy often lasts many years, patients may experience CVD faster. The aim of the present study was to analyze the levels of arginine derivatives in children with epilepsy who were treated with multiple AEDs to answer the question whether pediatric patients may be at increased risk of CVD in the future. We prospectively analyzed 21 children suffering from epilepsy who took ≥2 AEDs for at least 6 months and 22 children without epilepsy (reference group). The levels of the arginine derivatives, e.g., ADMA, SDMA, and hArg, were determined in the blood serum using the HPLC method. No differences in both the mean levels of ADMA and SDMA, as well as in the mean values of the arginine derivative ratios, were observed between the groups. The tendency toward a lower level of hArg was found in epileptic patients more than in the reference group (p = 0.091). Epileptic children receiving three or more AEDs had significantly lower concentrations of hArg and values of the hArg/ADMA ratio than the reference group (p = 0.023 and p = 0.006, respectively). In turn, the mean hArg/ADMA ratio was lower in children receiving three or more AEDs compared to children receiving two AEDs (p = 0.002). There was also a positive correlation between the hArg and ADMA concentrations in children with epilepsy taking two AEDs; the higher the level of hArg, the greater the level of ADMA on average (r = 0.650, p = 0.022). Taking three or more AEDs by epileptic children resulted in lower levels of both hArg and the value of the hArg/ADMA ratio.

Influence of biological sex and exercise on murine cardiac metabolism

Although the structural and functional effects of exercise on the heart are well established, the metabolic changes that occur in the heart during and after exercise remain unclear. In this study, we used metabolomics to assess time-dependent changes in the murine cardiac metabolome following 1 session of treadmill exercise. After the exercise bout, we also recorded blood lactate, glucose, and ketone body levels and measured cardiac mitochondrial respiration. In both male and female mice, moderate- and high-intensity exercise acutely increased blood lactate levels. In both sexes, low- and moderate-intensity exercise augmented circulating 3-hydroxybutryrate levels immediately after the exercise bout; however, only in female mice did high-intensity exercise increase 3-hydroxybutyrate levels, with significant increases occurring 1 h after the exercise session. Untargeted metabolomics analyses of sedentary female and male hearts suggest considerable sex-dependent differences in basal cardiac metabolite levels, with female hearts characterized by higher levels of pantothenate, pyridoxamine, homoarginine, tryptophan, and several glycerophospholipid and sphingomyelin species and lower levels of numerous metabolites, including acetyl coenzyme A, glucuronate, gulonate, hydroxyproline, prolyl-hydroxyproline, carnosine, anserine, and carnitinylated and glycinated species, as compared with male hearts. Immediately after a bout of treadmill exercise, both male and female hearts had higher levels of corticosterone; however, female mice showed more extensive exercise-induced changes in the cardiac metabolome, characterized by significant, time-dependent changes in amino acids (e.g., serine, alanine, tyrosine, tryptophan, branched-chain amino acids) and the ketone body 3-hydroxybutyrate. Results from experiments using isolated cardiac mitochondria suggest that high-intensity treadmill exercise does not acutely affect respiration or mitochondrial coupling; however, female cardiac mitochondria demonstrate generally higher adenosine diphosphate sensitivity compared with male cardiac mitochondria. Collectively, these findings in mice reveal key sex-dependent differences in cardiac metabolism and suggest that the metabolic network in the female heart is more responsive to physiological stress caused by exercise.

Effects of treatment with SGLT-2 inhibitors on arginine-related cardiovascular and renal biomarkers

BACKGROUND

In patients with type 2 diabetes (T2D) sodium-glucose cotransporter 2 (SGLT-2) inhibitors improve glycaemic control as well as cardiovascular and renal outcomes. Their effects on L-arginine (Arg) related risk markers asymmetric and symmetric dimethylarginine (ADMA and SDMA) and the protective biomarker L-homoarginine (hArg) linking T2D to cardiovascular and renal disease have not yet been reported.

METHODS

Plasma and 24-h urine samples taken before and after 6 weeks of treatment were available from two prospective, randomized, double-blind, placebo-controlled, cross-over trials with empagliflozin (71 patients analyzed, NCT02471963) and dapagliflozin (59 patients analyzed, NCT02383238). In these samples, concentrations of hArg, Arg, ADMA, SDMA, and creatinine were determined by liquid-chromatography coupled to tandem mass-spectrometry. Additionally, intraindividual changes of the biomarkers in plasma were correlated with intraindividual changes of clinical parameters.

RESULTS

Treatment with empagliflozin and dapagliflozin was associated with a reduction of plasma hArg by 17.5% and 13.7% (both p < 0.001), respectively, and increase in plasma SDMA concentration of 6.7% and 3.6%, respectively (p < 0.001 and p < 0.05), while plasma Arg and ADMA concentrations were not significantly altered. 24-h urinary excretion of ADMA was reduced by 15.2% after treatment with empagliflozin (p < 0.001) but not after dapagliflozin treatment, while excretion of the other markers was not significantly altered. Renal clearance of SDMA was reduced by 9.1% and 3.9% for both drugs (both p < 0.05). A reduction in ADMA clearance was observable after empagliflozin treatment only (- 15.5%, p < 0.001), but not after dapagliflozin. Renal clearance of hArg and Arg was not significantly altered. Treatment effects on L-arginine related biomarkers were not constantly correlated with effects on glycated hemoglobin, fasting plasma glucose, body mass index, and systolic blood pressure.

CONCLUSIONS

Treatment with SGLT-2 inhibitors has divergent effects on Arg-related biomarkers and could affect risk estimates associated with these markers. The observed effects are unlikely to explain the known cardiovascular and renal benefits of treatment with empagliflozin or dapagliflozin but still may indicate new therapeutic approaches in patients treated with SGLT-2 inhibitors. Trial registration http://www.clinicaltrials.gov : NCT02471963 (registered 15th June 2015, retrospectively registered) and NCT02383238.

Stereochemical Assignment and Absolute Abundance of Nonproteinogenic Amino Acid Homoarginine in Marine Sponges

Together with arginine, the nonproteinogenic amino acid homoarginine is a substrate for the production of vasodilator nitric oxide in the human body. In marine sponges, homoarginine has been postulated to serve as a precursor for the biosynthesis of pyrrole-imidazole alkaloid and bromotyrosine alkaloid classes of natural products. The absolute abundance of homoarginine, its abundance relative to arginine, and its stereochemical assignment in marine sponges are not known. Here, using stable isotope dilution mass spectrometry, we quantify the absolute abundances of homoarginine and arginine in marine sponges. We find that the abundance of homoarginine is highly variable and can far exceed the concentration of arginine, even in sponges where incorporation of homoarginine in natural products cannot be rationalized. The [homoarginine]/[arginine] ratio in marine sponges is greater than that in human analytes. By derivatization of sponge extracts with Marfey's reagent and comparison with authentic standards, we determine the l-isomer of homoarginine to be exclusively present in sponges. Our results shed light on the presence of the high abundance of homoarginine in marine sponge metabolomes and provide the foundation to investigate the biosynthetic routes and physiological roles of this nonproteinogenic amino acid in sponge physiology.

Exploration study on serum metabolic profiles of Chinese male patients with artificial stone silicosis, silicosis, and coal worker's pneumoconiosis

Long-term exposure to inhaled silica dust induces pneumoconiosis, which remains a heavy burden in developing countries. Modern industry provides new resources of occupational SiO₂ leading to artificial stone silicosis especially in developed countries. This study aimed to characterize the serum metabolic profile of pneumoconiosis and artificial stone silicosis patients. Our case-control study recruited 46 pairs of pneumoconiosis patients and dust-exposed workers. Nontargeted metabolomics and lipidomics by ultra-high-performance liquid chromatography-tandem mass spectrometry platform were conducted to characterize serum metabolic profile in propensity score-matched (PSM) pilot study. 54 differential metabolites were screened, 24 of which showed good screening efficiency through receiver operating characteristics (ROC) in pilot study and validation study (both AUC > 0.75). 4 of the 24 metabolites can predict pneumoconiosis stages, which are 1,2-dioctanoylthiophosphatidylcholine, phosphatidylcholine(O-18:1/20:1), indole-3-acetamide and l-homoarginine. Kynurenine, N-tetradecanoylsphingosine 1-phosphate, 5-methoxytryptophol and phosphatidylethanolamine(22:6/18:1) displayed the potential as specific biomarkers for artificial stone silicosis. Taken together, our results confirmed that tryptophan metabolism is closely related to pneumoconiosis and may be related to disease progression. Hopefully, our results could supplement the biomarkers of pneumoconiosis and provide evidence for the discovery of artificial stone silicosis-specific biomarkers.