Global Arginine Bioavailability Ratio Research Articles

Prognostic implications of the arginine metabolism in patients at nutritional risk: A secondary analysis of the randomized EFFORT trial

BackgroundArginine, a conditionally essential amino acid, is key component in metabolic pathways including immune regulation and protein synthesis. Depletion of arginine contributes to worse outcomes in severely ill and surgical patient populations. We assessed prognostic implications of arginine levels and its metabolites and ratios in polymorbid medical inpatients at nutritional risk regarding clinical outcomes and treatment response. MethodsWithin this secondary analysis of the randomized controlled Effect of early nutritionalsupporton Frailty, Functional Outcomes, and Recovery of malnourished medical inpatients Trial (EFFORT), we investigated the association of arginine, its metabolites and ratios (i.e., ADMA and SDMA, ratios of arginine/ADMA, arginine/ornithine, and global arginine bioavailability ratio) measured on hospital admission with short-term and long-term mortality by means of regression analysis. ResultsAmong the 231 patients with available measurements, low arginine levels ≤90.05 μmol/l (n=86; 37%) were associated with higher all-cause mortality at 30 days (primary endpoint, adjusted HR 3.27, 95% CI 1.86 to 5.75, p<0.001) and at 5 years (adjusted HR 1.50, 95% CI 1.07 to 2.12, p=0.020). Arginine metabolites and ratios were also associated with adverse outcome, but had lower prognostic value. There was, however, no evidence that treatment response was influenced by admission arginine levels. ConclusionThis secondary analysis focusing on medical inpatients at nutritional risk confirms a strong association of low plasma arginine levels and worse clinical courses. The potential effects of arginine-enriched nutritional supplements should be investigated in this population of patients. Clinical Trial Registrationclinicaltrials.gov as NCT02517476 (registered 7 August 2015)

Low Arginine Bioavailability and Clinical Outcomes in Children with Sickle Cell Disease Hospitalized with Vaso-Occlusive Pain Episode

Introduction: Global arginine bioavailability ratio (GABR) (Arginine/[Citrulline+Ornithine]) is associated with clinical outcomes including pain, pulmonary hypertension, and mortality in patients with sickle cell disease (SCD). Arginine replacement therapy has demonstrated opioid-sparing effects, improved blood pressure and cardiovascular function, and shorten length of hospital stay. Arginine is a conditionally essential amino acid synthesized from citrulline in the kidneys. During a vaso-occlusive pain episode (VOE), hemolysis leads to the release of erythrocyte-arginase (arginine-metabolizing enzyme) that metabolizes arginine into ornithine. Arginine-to-ornithine ratio (arg/orn) is a biomarker of arginase activity and GABR incorporates the impact of kidney function on global arginine bioavailability. The association between arginine bioavailability and clinical outcomes has not been sufficiently explored in children with SCD-VOE. Objective: To evaluate associations between arginine bioavailability and clinical outcomes in children with SCD-VOE who received intravenous (IV) arginine replacement therapy. Methods: We conducted a secondary analysis of a prospective, single-center, double-blinded randomized controlled trial of IV arginine therapy (TID, up to 7 days) in children with SCD age 3-21 years hospitalized for VOE requiring IV opioids. Patients with significant liver/renal dysfunction or those previously enrolled were excluded. Subjects were randomized into 1 of 3 arms: 1) 100 mg/kg/dose arginine (standard dose), 2) loading dose: 200 mg/kg followed by standard dose or 3) placebo. Demographics, total parenteral opioid (TPO) use (morphine equivalents, mg/kg) time to crisis resolution (time of study drug delivery to last IV opioid in hours), pain scores, and targeted amino acids were obtained before treatment and at discharge. Mean±SD, paired t-tests, and Pearson correlation analyses between groups were performed. This trial was registered at www.clinicaltrials.goc as #NCT02536170 Results: 1,548 patients were screened, 266 were eligible, 114 consented, and 108 were randomized (54.4% were female, mean age 12.44 ± 3.90). All participants identified as African American and 75% had genotype Hb-SS. 69.1% were on hydroxyurea. Safety results of this RCT have been previously reported ( Reyes et al, Am J Hematol 2022). Plasma arginine levels were low at VOE presentation (mean 50±28 μM), with low arginine levels (&amp;lt;60 μM) found in 74% of patients. Arginine replacement therapy increased arginine concentration by 182% (p&amp;lt;0.0001) compared to 26% (p=0.24) in placebo. Arg/orn correlated to arginase concentration ( r= - 0.38, p&amp;lt;0.0001). Time-to-crisis-resolution strongly correlated with TPO ( r=0.72, p&amp;lt;0.0001). Arginine bioavailability at presentation was inversely correlated to time-to-crisis-resolution for both arg/orn and GABR ( r= -0.37 p=0.02) in the placebo arm only but not in those participants who received arginine therapy (GABR: r= - 0.05, p=0.6; arg/orn: r= - 0.07, p=0.55) (Fig1A,1B). Similar trends were observed for TPO. Pain scores at presentation positively correlated with TPO ( r= 0.33, p=0.04) in the placebo arm only, but not in the arm that received arginine therapy ( r= 0.03, p=0.76). Time-to-crisis-resolution positively correlated with age ( r= 0.2, p=0.03). Conclusion: In the absence of arginine replacement therapy, low arginine bioavailability predicted longer time-to-crisis resolution and a higher use of IV opioids in patients with SCD-VOE. Arginine bioavailability may represent a novel biomarker of SCD-pain severity. This data further confirms arg/orn as a surrogate for arginase activity reflective of hemolytic rate as previously described. Arginine replacement therapy ameliorates the influence of arginine deficiency on clinical outcomes related to pain in SCD. An NHLBI/ Pediatric Emergency Care Applied Research Network (PECARN) supported Phase-3 multi-center trial of arginine replacement therapy enrolling 360 children with SCD (SCD Treatment with Arginine Therapy - STArT) is ongoing.

Mechanism(s)-of-Action for Arginine Therapy in Children with Sickle Cell Disease and Vaso-Occlusive Pain: Results of a Pharmacokinetics/Pharmacodynamics Study

Introduction: Low L-Arginine (Arg) bioavailability is associated with sickle cell disease (SCD) mortality and morbidity, including acute pain severity. Multiple phase 2 trials support the safety and efficacy of Arg therapy in children with SCD experiencing vaso-occlusive pain. Nitric oxide (NO) is a potent vasodilator depleted in SCD due to hemolysis. As the obligate substrate for NO production, Arg's mechanism-of-action is unknown but thought to be related in part to NO production. Kyotorphin (KTP) is an endogenous opioid analgesic composed of the amino acids tyrosine and Arg. Its nociceptive effects are through induction of Met-enkephalins release in the brain. Oral administration of Arg in wild-type mice increases the levels of KTP centrally. We have previously shown that Arg supplementation increases NO metabolites (NOx), improves mitochondrial function, decreases oxidative stress, and has opioid sparing effects in children with SCD. The association between IV Arg supplementation as a precursor to KTP in SCD is unknown and may represent a novel mechanism by which Arg decreases pain in patients with SCD. Objective: To analyze the results of a pharmacokinetics/pharmacodynamics study, evaluating the association between Arg supplementation and plasma levels of KTP and other potential mechanisms-of-action related to Arg in children with SCD and vaso-occlusive pain episodes (VOE). Methods: We conducted a pharmacokinetics/pharmacodynamics study of children aged 7-21 years with SCD hospitalized for VOE and randomized to treatment utilizing one of 3 dosing arms of Arg: 1) 100mg/kg IV three times/day, standard dose (n=4); 2) loading dose (200mg/kg) followed by standard dose (n=5); or 3) loading dose (200mg/kg) followed by continuous infusion (300mg/kg/day) until discharge (n=4). Plasma amino acids (arginine, ornithine, citrulline), global arginine bioavailability ratio (GABR; Arginine/[Citrulline+Ornithine]), KTP, NOx, exhaled NO, plasma arginase activity, and arginase-1 and -2 were measured. Mean±SD, paired t-tests, and Pearson correlation analyses between groups were performed where appropriate. Results: A total of 13 patients (age 13±3 years, 56% male, 88% Hb-SS, 85% on hydroxyurea) were enrolled. Statistically significant increases in plasma arginine levels (Fig1A), plasma KTP levels (Fig1B), and GABR from pre-dose (0 hour) to 1, 1.5, and 2 hours after arginine infusion were observed, with a return to baseline 8 hours after Arg administration. Arg and KTP levels peaked between 60-90 minutes after arginine infusion in all study arms (p&amp;lt;0.001, p=0.004 respectively). There were no significant differences in peak concentration across all study arm doses. Rise in KTP levels strongly correlated with changes in plasma Arg concentration ( r=0.72, p&amp;lt;0.0001). Plasma NOx levels significantly increased from pre-dose to Tmax (Tmax= 1-2 hours; mean percent change 156±313%, p=0.02), as did exhaled NO (mean percent change 31±27%, p=0.02). Arginase activity also increased significantly after IV Arg infusion peaking at approximately 90 minutes (mean percent change 137±183%, p= 0.03) with return to baseline at 8 hours, while there was no significant change in arginase-1 or -2 concentrations over time. Conclusion: IV Arg therapy increased plasma arginine concentration 2-5 times above baseline at presentation for VOE, and GABR also increased as expected in this pharmacokinetics study with both reaching a maximum concentration within 1 hour of infusion initiation in all dosing schemes. IV Arg supplementation increases plasma NOx levels suggesting a role for vasodilation as a potential mechanism-of-action during SCD-VOE. Exhaled NO also increased significantly, consistent with previous reports. Interestingly, IV Arg supplementation acutely increased arginase activity without a significant change in arginase concentration. Most notably, we report for the first time the impact of IV Arg therapy on plasma levels of KTP in SCD. As KTP is an endogenous opioid analgesic, this may represent a novel mechanism-of-action of Arg therapy that warrants further investigation. This observation may also have implications for the potential use of arginine supplementation in pain syndromes beyond sickle cell disease.

Predictive Ability of Serum Amino Acid Levels to Differentiate Fibromyalgia Patients from Healthy Subjects.

Fibromyalgia is a complex illness to diagnose and treat. To evaluate a broad range of circulating free amino acid (AA) levels in fibromyalgia patients as well as the ability of the AAs to differentiate fibromyalgia patients from healthy subjects. We carried out a case-control study to evaluate AA levels in 62 patients with fibromyalgia and 78 healthy subjects. This study adheres to the STROBE guidelines. AAs content was assayed by HPLC in serum samples. The predictive value of AA levels in fibromyalgia was determined by receiver operating characteristic (ROC) curve and forward binary logistic regression analyses. Fibromyalgia patients showed higher serum levels of aspartic acid, glutamic acid, aminoadipic acid, asparagine, histidine, 3-methyl-histidine, 5-methyl-histidine, glycine, threonine, taurine, tyrosine, valine, methionine, isoleucine, phenylalanine, leucine, ornithine, lysine, branched chain AAs (BCAAs), large neutral AAs, essential AAs (EAAs), non-essential AAs (NEAAs), basic AAs, EAAs/NEAAs ratio, phenylalanine/tyrosine ratio, and global arginine bioavailability ratio than the controls. Serum alanine levels were lower in patients than in controls. According to ROC analysis, most of these AAs may be good markers for differentiating individuals with fibromyalgia from healthy subjects. Results of logistic regression showed that the combination of glutamic acid, histidine, and alanine had the greatest predictive ability to diagnose fibromyalgia. Our results show an imbalance in serum levels of most AAs in patients with fibromyalgia, which suggest a metabolic disturbance. The determination of serum levels of these AAs may aid in the diagnosis of fibromyalgia, in combination with clinical data of the patient.

Plasma urea cycle metabolite levels and the risk of moyamoya disease.

Urea cycle metabolites are expected to be the biomarkers for cerebrovascular diseases. However, the effects of circulating urea cycle metabolites on the risk of MMD and its subcategories remain unclear. The aim of this study was to prospectively investigate the association between plasma urea cycle metabolites and the risk of MMD and its subcategories. We measured plasma urea cycle metabolite levels for 360 adult MMD patients and 89 matched healthy controls. Clinical and laboratory characteristics were obtained from the medical record. The study was conducted from July 2020 to December 2021. After multivariate adjustment, the risk of MMD increased with each increment in ornithine level (per natural log [ornithine] increment: OR, 3.893; 95% CI, 1.366-11.090). The risk of MMD decreased with each increment in arginine level (per natural log [arginine] increment: OR, 0.109; 95% CI, 0.028-0.427), urea level (per natural log [urea] increment: OR, 0.261; 95% CI, 0.072-0.940), and global arginine bioavailability ratio (GABR) level (per natural log [GABR] increment: OR, 0.189; 95% CI, 0.074-0.484). The addition of plasma arginine (integrated discrimination improvement: 1.76%, p = 0.021) or GABR (integrated discrimination improvement: 1.76%, p = 0.004) to conventional risk factors significantly improved the risk reclassification for MMD. Plasma ornithine levels are positively associated with the risk of MMD. By contrast, the levels of arginine, urea, and GABR are inversely related to the risk of MMD. Plasma urea cycle metabolites might be potential biomarkers for the risk of MMD.

Arginine concentration in arterial vs venous blood in a bleomycin-induced lung inflammation model in mice.

Pneumonia, always a major malady, became the main public health and economic disaster of historical proportions with the COVID-19 pandemic. This study was based on a premise that pathology of lung metabolism in inflammation may have features invariant to the nature of the underlying cause. Amino acid uptake by the lungs was measured from plasma samples collected pre-terminally from a carotid artery and vena cava in mice with bleomycin-induced lung inflammation (N = 10) and compared to controls treated with saline instillation (N = 6). In the control group, the difference in concentrations between the arterial and venous blood of the 19 amino acids measured reached the level of statistical significance only for arginine (-10.7%, p = 0.0372) and phenylalanine (+5.5%, p = 0.0266). In the bleomycin group, 11 amino acids had significantly lower concentrations in the arterial blood. Arginine concentration was decreased by 21.1% (p<0.0001) and only that of citrulline was significantly increased (by 20.1%, p = 0.0002). Global Arginine Bioavailability Ratio was decreased in arterial blood by 19.5% (p = 0.0305) in the saline group and by 30.4% (p<0.0001) in the bleomycin group. Production of nitric oxide (NO) and citrulline from arginine by the inducible nitric oxide synthase (iNOS) is greatly increased in the immune system's response to lung injury. Deprived of arginine, the endothelial cells downstream may fail to provide enough NO to prevent the activation of thrombocytes. Thrombotic-related vascular dysfunction is a defining characteristic of pneumonia, including COVID-19. This experiment lends further support to arginine replacement as adjuvant therapy in pneumonia.

Raised total methylated arginine load in patients with gout.

Aim: The aim of this study was to measure serum levels of methylarginine derivatives and related metabolites in patients with gout. Materials & methods: This study enrolled 100 patients with gout and 80 patients in the control group. Serum asymmetric dimethylarginine, symmetric dimethylarginine, L-N-monomethylarginine, arginine, homoarginine, citrulline and ornithine levels were measured with tandem mass spectrometry. Results: Serum ornithine, citrulline and total methylated arginine load levels were statistically significantly higher in patients with gout compared with the control group, while serum arginine and homoarginine levels and global arginine bioavailability ratio were statistically significantly lower. Conclusion: There may be an association between gout, methylarginine levels and hyperuricemia and increased risk of cardiovascular disease.

Determination of serum methylarginine levels by tandem mass spectrometric method in patients with ankylosing spondylitis

Our aim in this study was to measure serum levels of methylarginines and related metabolites in patients with ankylosing spondylitis (AS), moreover, to investigate the relationship between these parameters and various clinical and laboratory parameters of patients with AS. The study included 60 patients with AS and 60 healthy volunteers. Serum asymmetric dimethylarginine (ADMA), L-N monomethylarginine (L-NMMA), symmetric dimethylarginine (SDMA), arginine (Arg), homoarginine (hArg), ornithine, and citrulline concentrations were measured with tandem mass spectrometry. In addition, participants were divided into three groups according to the treatment regimen: TNF-α inhibitor group (n = 25), conventional therapy group (n = 35), and control group (n = 60). These groups were compared in terms of serum levels of methylarginine pathway metabolites and various biochemical parameters. It was found that total methylated arginine load significantly increased in patients with AS (p < 0.001), and the Arg/ADMA ratio was positively correlated with HDL levels and negatively correlated with glucose, ESR, total cholesterol, triglyceride, and LDL levels. In addition, serum ADMA, SDMA, total methylated arginine load, and CRP levels were lower (p < 0.05) in the TNF-α group compared to the conventional treatment group. To thebestof ourknowledge, this is the first study to comprehensively investigate serum methylarginine levels in patients with AS. Elevated total methylated arginine load and decreased global arginine bioavailability ratio (GABR) indicate that NO metabolism is impaired in patients with AS. Therefore, the increased cardiovascular risk in patients with AS may be related to the decreased NO production or bioavailability due to the elevated total methylarginine load.

Impact of Oral Arginine Therapy on Global Arginine Bioavailability in Nigerian Children with Sickle Cell Anemia and Vaso-Occlusive Pain

Introduction: Severe vaso-occlusive pain episodes (VOE) are a major cause of morbidityand mortality in sickle cell anemia (SCA). Low arginine bioavailability is associated with pain severity and predicts need for pediatric hospitalization (Morris et. al, 2000). Arginine supplementation has opioid-sparing effects and was found to significantly decrease pain scores in children hospitalized with SCA-VOE compared to placebo in phase-2 randomized placebo-controlled trials (RCT) performed in the United States (US, Morris et. al, 2013) and Nigeria (Onalo et al, ASH 2019), while also significantly decreased time-to-crisis-resolution and length of hospital stay (LOS) in Nigerian children (Onalo et al, ASH 2019). Its mechanism-of-action and impact on arginine bioavailability is unclear. Objectives: To determine the impact of oral arginine supplementation on arginine bioavailability and total opioid use in children with SCA-VOE. Methods: A double-blind RCT of oral L-arginine (100 mg/kg/dose every 8 hours until discharge; up to 15 doses maximum) was performed in children with SCA hospitalized with severe VOE defined as a Numerical Pain Scale Score (PS) of at least 7 on a scale of 0-10, at one of two hospitals in Abuja, Nigeria (clinical outcomes previously reported, Onalo et al ASH 2019). Plasma arginine concentration and the global arginine bioavailability ratio (GABR, defined as arginine/[ornithine+citrulline]) was measured with high performance liquid chromatography tandem mass spectrometry before supplementation and at day 5 or discharge, whichever came first. Indices of arginine bioavailability were calculated and compared between the study groups. Demographics, clinical characteristics and total opioid use (mg/kg of morphine equivalents) were obtained. The impact of oral arginine supplementation on arginine bioavailability, and correlation of changes in arginine bioavailability with total opioid use was assessed. Results: Sixty-eight children with SCA were recruited, aged 5-17years (mean: 10.6±0.4 years), and 85% were male; 35 children were randomized into the arginine arm and 33 into the placebo arm. Baseline characteristics were similar between arms. Clinical outcomes of significantly lower total analgesic use, lower pain scores, decreased time-to-crisis resolution and shorter LOS in the arginine group vs. placebo were previously reported (Onalo et al, ASH 2019). Oral arginine supplementation increases plasma arginine levels by 125% [95% CI, 61-187%] in the arginine as against 29% [1-58%] in the placebo group (Table 1), p=0.007. GABR was higher after supplementation in patients treated with arginine: 59% [20-98%] vs. -2% [-27-22%] in the placebo group (p=0.009). Patients with the lowest arginine level at presentation experienced the greatest increase in plasma arginine concentration, particularly patients with acute chest syndrome (ACS). Percent increase in GABR inversely correlated with total opioid used (mg/kg; r=-0.35;p=0.02, figure 1). Conclusion: Arginine deficiency plays a role in acute pain requiring hospitalization in Nigerian children with SCA, similar to what has been reported in the US. Plasma arginine levels significantly increased with arginine supplementation, and improved global arginine bioavailability was inversely associated with total opioids used in VOE management. Lowest arginine levels were found in children with ACS, as previously reported in the US (Morris et al, 2000), a phenomenon that warrants further investigation. Low arginine bioavailability in children with SCA-VOE is improved by oral arginine supplementation. Funded by Tertiary Education Trust Fund (to RO) and in part by NIH/NCCIH K24AT009893 (to CRM); Pan African Clinical Trial Registry number PACTR 201611001864290). Disclosures No relevant conflicts of interest to declare. OffLabel Disclosure: Oral L-arginine for treatment of sickle cell anemia; it is a nutritional supplement

Novel Markers of the Metabolic Impact of Exogenous Retinoic Acid with A Focus on Acylcarnitines and Amino Acids.

Treatment with all-trans retinoic acid (ATRA), the carboxylic form of vitamin A, lowers body weight in rodents by promoting oxidative metabolism in multiple tissues including white and brown adipose tissues. We aimed to identify novel markers of the metabolic impact of ATRA through targeted blood metabolomics analyses, with a focus on acylcarnitines and amino acids. Blood was obtained from mice treated with a high ATRA dose (50 mg/kg body weight/day, subcutaneous injection) or placebo (controls) during the 4 days preceding collection. LC-MS/MS analyses with a focus on acylcarnitines and amino acids were conducted on plasma and PBMC. Main results showed that, relative to controls, ATRA-treated mice had in plasma: increased levels of carnitine, acetylcarnitine, and longer acylcarnitine species; decreased levels of citrulline, and increased global arginine bioavailability ratio for nitric oxide synthesis; increased levels of creatine, taurine and docosahexaenoic acid; and a decreased n-6/n-3 polyunsaturated fatty acids ratio. While some of these features likely reflect the stimulation of lipid mobilization and oxidation promoted by ATRA treatment systemically, other may also play a causal role underlying ATRA actions. The results connect ATRA to specific nutrition-modulated biochemical pathways, and suggest novel mechanisms of action of vitamin A-derived retinoic acid on metabolic health.

Dysregulated Urinary Arginine Metabolism in Older Adults With Amnestic Mild Cognitive Impairment.

Background: Urine samples, which capture an individual’s metabolic profile, are ideal for the exploration of non-invasive biomarkers to confirm the amnestic mild cognitive impairment (aMCI) status of patients vs. unimpaired ones.Objective: We aimed to detect differentially metabolized amino acids, which are important objectives in metabolomics, garnering particular attention in biomedical pathogenesis from the urine of aMCI patients, which may give clinicians the possibility to intervene with early treatments that curb Alzheimer’s disease (AD).Methods: The study included 208 subjects, 98 of whom were aMCI patients, and 110 who were control subjects without dementia. Urine samples were taken from each participant and supernatant was obtained for analysis. The concentrations of amino acids were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS).Results: Urinary arginine levels in aMCI patients are obviously lower than in normal controls (q < 0.2 and p < 0.05). Meanwhile, aMCI patients had significant reduced urinary global arginine bioavailability ratio (GABR), and GABR in urine displayed a positive correlation with the score of CMMSE.Conclusion: Urinary dysregulated arginine metabolism that may serve as a helpful clinical diagnostic biomarker for aMCI in older adults.

Development and validation of GC-MS methods for the comprehensive analysis of amino acids in plasma and urine and applications to the HELLP syndrome and pediatric kidney transplantation: evidence of altered methylation, transamidination, and arginase activity.

We developed and validated gas chromatography-mass spectrometry (GC-MS) methods for the simultaneous measurement of amino acids and their metabolites in 10-µL aliquots of human plasma and urine. De novo synthesized trideutero-methyl esters were used as internal standards. Plasma proteins were precipitated by acidified methanol and removed by centrifugation. Supernatants and native urine were evaporated to dryness. Amino acids were first esterified using 2M HCl in methanol and then amidated using pentafluoropropionic anhydride for electron-capture negative-ion chemical ionization. Time programmes were used for the gas chromatograph oven and the selected-ion monitoring of specific anions. The GC-MS methods were applied in clinical studies on the HELLP syndrome and pediatric kidney transplantation (KTx) focusing on L-arginine-related pathways. We found lower sarcosine (N-methylglycine) and higher asymmetric dimethylarginine (ADMA) plasma concentrations in HELLP syndrome women (n = 7) compared to healthy pregnant women (n = 5) indicating altered methylation. In plasma of pediatric KTx patients, lower guanidinoacetate and homoarginine concentrations were found in plasma but not in urine samples of patients treated with standard mycophenolate mofetil-based immunosuppression (MMF; n = 22) in comparison to matched patients treated with MMF-free immunosuppression (n = 22). On average, the global arginine bioavailability ratio was by about 40% lower in the MMF group compared to the EVR group (P = 0.004). Mycophenolate, the major pharmacologically active metabolite of MMF, is likely to inhibit the arginine:glycine amidinotransferase (AGAT), and to enhance arginase activity in leukocytes and other types of cell of MMF-treated children.

Effects of Linagliptin on Endothelial Function and Global Arginine Bioavailability Ratio in Coronary Artery Disease Patients with Early Diabetes

Aims: To investigate the effects of the DPP-4 inhibitor Linagliptin in subjects with coronary artery disease (CAD) and early type 2 diabetes mellitus (T2DM) on a set of cardiovascular surrogate measurements. Materials and Methods: In this randomized, placebo-controlled, double-blind, single-center study, we included subjects with early diabetes (postchallenge diabetes (2h glucose &amp;gt;200mg/dl) or T2DM treated with diet only or on a stable dose of metformin monotherapy, HbA1c&amp;lt;75mmol/mol) and established CAD. Participants were randomized to receive either Linagliptin (5mg) once daily orally or placebo for 12 weeks. The primary outcome was the change in flow mediated dilatation (FMD). Results: We investigated 43 patients with a mean age of 6±8 years. FMD at baseline was 3.5±3.1% in the Linagliptin group vs. 4.0±2.9% in the placebo group. The change in mean FMD in the Linagliptin group (0.4±4.8%) was not significantly different compared to the change in the placebo group (-0.45±3.01%; p=0.486). No significant improvements were seen in the arginine bioavailability ratios (GABR); p=0.6and AOR; p=0.549), body weight, blood pressure and lipid parameters. Of note, HbA1c was significantly reduced in the linagliptin group (-1.5 vs. -0.4; p=0.026). Conclusion: Linagliptin treatment in subjects with CAD and early T2DM did not improve endothelial function or GABR. Disclosure F. Aberer: None. N.J. Tripolt: None. J. Url: None. R. Hödl: None. G. Dimsity: None. F. Aziz: None. R. Riedl: None. F. Hafner: None. D. Strunk: None. T. Stojakovic: None. M. Brodmann: None. H. Sourij: Speaker's Bureau; Self; Boehringer Ingelheim GmbH, Novo Nordisk A/S, Amgen Inc., Sanofi, MSD K.K.. Research Support; Self; AstraZeneca, Boehringer Ingelheim GmbH, MSD K.K., GI Dynamics Inc..

Elevated levels of plasma symmetric dimethylarginine and increased arginase activity as potential indicators of cardiovascular comorbidity in rheumatoid arthritis

BackgroundRheumatoid arthritis (RA) patients are at high risk of developing cardiovascular disease (CVD). In RA, chronic inflammation may lead to endothelial dysfunction, an early indicator of CVD, owing to diminished nitric oxide (NO) production. Because l-arginine is the sole precursor of NO, we hypothesized that levels of l-arginine metabolic products reflecting NO metabolism are altered in patients with RA.MethodsPlasma samples from patients with RA (n = 119) and age- and sex-matched control subjects (n = 238) were used for this study. Using LC-MS/MS, we measured plasma levels of free l-arginine, l-ornithine, l-citrulline, l-NG-monomethyl arginine (MMA), asymmetric dimethylarginine (ADMA), and symmetric dimethylarginine (SDMA). We compared global arginine bioavailability ratio (GABR) (i.e., ratio of l-arginine to l-ornithine + l-citrulline) and arginine methylation index (ArgMI) (i.e., ADMA + SDMA/MMA) in patients with RA vs. control subjects. Plasma arginase activity was measured using a sensitive arginase assay kit. The relationship of l-arginine metabolites and arginase activity to CVD risk factors was evaluated using Pearson’s chi-square test.ResultsCompared with healthy control subjects, the RA cohort showed significantly lower levels of plasma l-arginine (46.11 ± 17.29 vs. 74.2 ± 22.53 μmol/L, p < 0.001) and GABR (0.36 ± 0.16 vs. 0.73 ± 0.24, p < 0.001), elevated levels of ADMA (0.76 ± 0.12 vs. 0.62 ± 0.12 μmol/L, p < 0.001), SDMA (0.54 ± 0.14 vs. 0.47 ± 0.13 μmol/L, p < 0.001), and ArgMI (6.51 ± 1.86 vs. 5.54 ± 1.51, p < 0.001). We found an approximately fourfold increase in arginase activity (33.8 ± 1.1 vs. 8.4 ± 0.8 U/L, p < 0.001), as well as elevated levels of arginase-mediated l-arginine catalytic product l-ornithine (108.64 ± 30.26 vs. 69.3 ± 20.71 μmol/L, p < 0.001), whereas a nitric oxide synthase (NOS) catalytic product, the l-citrulline level, was diminished in RA (30.32 ± 9.93 vs. 36.17 ± 11.64 μmol/L, p < 0.001). Patients with RA with existing CVD had higher arginase activity than patients with RA without CVD (p = 0.048).ConclusionsGlobal l-arginine bioavailability was diminished, whereas plasma arginase activity, ADMA, and SDMA levels were elevated, in patients with RA compared with healthy control subjects. Plasma SDMA was associated with hypertension and hyperlipidemia in patients with RA. This dysregulated l-arginine metabolism may function as a potential indicator of CVD risk in patients with RA.

Effects of linagliptin on endothelial function and postprandial lipids in coronary artery disease patients with early diabetes: a randomized, placebo-controlled, double-blind trial

BackgroundEarly glucose lowering intervention in subjects with type 2 diabetes mellitus was demonstrated to be beneficial in terms of micro- and macrovascular risk reduction. However, most of currently ongoing cardiovascular outcome trials are performed in subjects with manifest atherosclerosis and long-standing diabetes. Therefore, the aim of this study is to investigate the effects of the dipeptidylpeptidase-4 inhibitor linagliptin in subjects with coronary artery disease (CAD) but early type 2 diabetes mellitus (T2DM) on a set of cardiovascular surrogate measurements.MethodsIn this randomized, placebo-controlled, double-blind, single-center study, we included subjects with early diabetes (postchallenge diabetes (2 h glucose > 200 mg/dl) or T2DM treated with diet only or on a stable dose of metformin monotherapy and an HbA1c < 75 mmol/mol) and established CAD. Participants were randomized to receive either linagliptin (5 mg) once daily orally or placebo for 12 weeks. The primary outcome was the change in flow mediated dilatation (FMD). The secondary objective was to investigate the effect of linagliptin treatment on arginine bioavailability ratios [Global arginine bioavailability ratio (GABR) and arginine to ornithine ratio (AOR)]. Arginine, ornithine and citrulline were measured in serum samples with a conventional usual amino acid analysis technique, involving separation of amino acids by ion exchange chromatography followed by postcolumn continuous reaction with ninhydrin. GABR was calculated by l-arginine divided by the sum of (l-ornithine plus l-citrulline). The AOR was calculated by dividing l-arginine by l-ornithine levels. Group comparisons were calculated by using a two-sample t-test with Satterthwaite adjustment for unequal variances.ResultsWe investigated 43 patients (21% female) with a mean age of 63.3 ± 8.2 years. FMD at baseline was 3.5 ± 3.1% in the linagliptin group vs. 4.0 ± 2.9% in the placebo group. The change in mean FMD in the linagliptin group was not significantly different compared to the change in the placebo group (0.43 ± 4.84% vs. − 0.45 ± 3.01%; p = 0.486). No significant improvements were seen in the arginine bioavailability ratios (GABR; p = 0.608 and AOR; p = 0.549).ConclusionLinagliptin treatment in subjects with CAD and early T2DM did not improve endothelial function or the arginine bioavailability ratios.Trial registration ClinicalTrials.gov, NCT02350478 (https://clinicaltrials.gov/ct2/show/NCT02350478)

Arginine deficiency measured by global arginine bioavailability ratio in patients with acute coronary syndrome

Arginine deficiency measured by global arginine bioavailability ratio in patients with acute coronary syndrome

Global arginine bioavailability ratio is decreased in patients with major depressive disorder

BackgroundMajor depressive disorder (MDD) is characterized by increased oxidative and nitrosative stress. We compared nitric oxide metabolism, i.e., the global arginine bioavailability ratio (GABR) and related serum amino acids, between MDD patients and non-depressed controls, and between remitted and non-remitted MDD patients. MethodsNinety-nine MDD patients and 253 non-depressed controls, aged 20–71 years, provided background data via questionnaires. Fasting serum samples were analyzed using ultra-performance liquid chromatography coupled to mass spectrometry to determine the serum levels of ornithine, arginine, citrulline, and symmetric and asymmetric dimethylarginine. GABR was calculated as arginine divided by the sum of ornithine plus citrulline. We compared the above measures between: 1) MDD patients and controls, 2) remitted (n=33) and non-remitted (n = 45) MDD patients, and 3) baseline and follow-up within the remitted and non-remitted groups. ResultsLower arginine levels (OR 0.98, 95% CI 0.97–0.99) and lower GABR (OR 0.13, 95% CI 0.03–0.50) were associated with the MDD vs. the non-depressed group after adjustments for potential confounders. The remitted group showed a decrease in GABR, arginine, and symmetric dimethylarginine, and an increase in ornithine after the follow-up compared with within-group baseline values. The non-remitted group displayed an increase in arginine and ornithine levels and a decrease in GABR. No significant differences were recorded between the remitted and non-remitted groups. LimitationsThe MDD group was not medication-free. ConclusionsArginine bioavailability may be decreased in MDD. This could impair the production of nitric oxide, and thus add to oxidative stress in the central nervous system.

Global arginine bioavailability ratio is decreased in patients with major depressive disorder

IntroductionThe global arginine bioavailability ratio (GABR) is used to estimate arginine supply. Arginine is precursor to nitric oxide (NO) that has been suggested to play a role in major depressive disorder (MDD). NO also participates in neuronal, inflammatory and cardioprotective functions.ObjectivesTo compare GABR between:– D patients and non-depressed controls;– remitted and non-remitted MDD patients;– baseline and follow-up within remitted and non-remitted MDD groups.AimsTo investigate the role of NO production in MDD.MethodsThe sample comprised 99 MDD patients and 253 non-depressed controls (Beck Depression Inventory scores &lt; 10) aged 20–71 years. Altogether, 78 patients returned for the follow-up; 33 were remitted and 45 non-remitted. GABR was calculated from serum levels of arginine, citrulline and ornithine, which were analysed using ultra-performance liquid chromatography. Differences between the study groups were examined using logistic regression adjusted for age, gender, smoking, alcohol use, physical exercise and glycated haemoglobin. The follow-up regression analyses were adjusted for age, gender and physical exercise.ResultsLowered GABR was associated with belonging to the MDD group (OR 0.13, 95% CI 0.03–0.50). Exclusion of participants using anti-depressants that were associated with measured metabolites did not change the results. Over the follow-up period, the remitted and non-remitted groups both showed an increase in GABR (Z = –.53, P &lt; 0.001 and Z = –3.00, P = 0.003, respectively).ConclusionsDecreased GABR may characterise MDD. This could affect neuronal, immunological and cardioprotective functions of NO.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Comprehensive assessment of the arginine pathway and its relationship to inflammation in HIV.

Nitric oxide helps maintain vascular function and is generated through the oxidation of arginine. Whether altered arginine metabolism may lead to elevated levels of inflammation in HIV is unclear. We performed a cross-sectional analysis of HIV-infected adults on stable antiretroviral therapy with HIV-1 RNA less than 50 copies/ml and HIV-uninfected controls. We measured biomarkers in the arginine pathway, markers of systemic inflammation, and monocyte activation. T-tests, χ tests, and propensity score matching analyses were used to compare markers by HIV status, and multiple linear regressions were used to assess associations of arginine metabolites with markers of inflammation. Overall, 131 participants were enrolled (93 HIV-infected and 38 HIV-uninfected controls); 70% were men; 58% African-Americans; median age was 51 years, median absolute CD4 was 735 cell/mm. Lysine, arginine, citrulline, global arginine bioavailability ratio, and symmetrical dimethylarginine were different between HIV-infected and HIV-uninfected adults (P = ≤0.02), but asymmetric dimethylarginine was not (P ≥ 0.13). Arginine biomarkers in HIV-infected, but not in HIV-uninfected controls, were associated with all measured markers of inflammation, endothelial activation, and coagulation (P ≤ 0.05). HIV-infected participants on antiretroviral therapy with virologic suppression have altered plasma levels of biomarkers in the arginine pathway compared with controls. These biomarkers are independently associated with markers of inflammation and monocyte activation in HIV.

PS 14-56 EFFECT OF WATERMELON JUICE CONSUMPTION ON BRACHIAL BLOOD PRESSURE AND GLOBAL ARGININE BIOAVAILABILITY RATIO AMONG SUDANESE HYPERTENSIVE PATIENTS

Objective: The purpose of this study is: First, to test the hypothesis that watermelon juice supplementation as a rich source of L-arginine and L-citrulline reduces systolic and diastolic blood pressure among Sudanese hypertensive patients even at low concentrations ((L-citrulline/L-arginine: 1 g/0.5 g per day). Second: to assess the credibility of GABR as a biomarker for the progression of hypertension. Design and Method: among 31 stage 1 hypertensive Sudanese patients. Exclusion criteria included pregnancy, metabolic diseases, diabetes, liver, kidney and cardiovascular diseases. Participants received one liter of freshly prepared watermelon juice daily for three weeks (L-citrulline/L-arginine:1 g/0.5 g per day). Results: Results showed that watermelon juice supplement significantly increased plasma L-arginine, L-citrulline and L-ornithine levels and reduced brachial blood pressure and global arginine bioavailability ratio. Conclusions: On conclusion, we suggest that watermelon juice could be used as a potential natural hypotensive agent even at low doses. Although watermelon juice increases plasma arginine level, GABR may not be a useful biomarker to assess the progression of hypertension.