Arginases and arginine deficiency syndromes

Citrulline and ADI-PEG20 reduce inflammation in a juvenile porcine model of acute endotoxemia

Background

Arginine is a conditionally essential amino acid that is depleted in critically ill or surgical patients. In pediatric and adult patients, sepsis results in an arginine-deficient state, and the depletion of plasma arginine is associated with greater mortality. However, direct supplementation of arginine can result in the excessive production of nitric oxide (NO), which can contribute to the hypotension and macrovascular hypo-reactivity observed in septic shock. Pegylated arginine deiminase (ADI-PEG20, pegargiminase) reduces plasma arginine and generates citrulline that can be transported intracellularly to generate local arginine and NO, without resulting in hypotension, while maintaining microvascular patency. The objective of this study was to assess the efficacy of ADI-PEG20 with and without supplemental intravenous citrulline in mitigating hypovolemic shock, maintaining tissue levels of arginine, and reducing systemic inflammation in an endotoxemic pediatric pig model.

Methods

Twenty 3-week-old crossbred piglets were implanted with jugular and carotid catheters as well as telemetry devices in the femoral artery to measure blood pressure, body temperature, heart rate, and respiration rate. The piglets were assigned to one of three treatments before undergoing a 5 h lipopolysaccharide (LPS) infusion protocol. Twenty-four hours before LPS infusion, control pigs (LPS; n=6) received saline, ADI-PEG20 pigs (n=7) received an injection of ADI-PEG20, and seven pigs (ADI-PEG20 + CIT pigs [n=7]) received ADI-PEG20 and 250 mg/kg citrulline intravenously. Pigs were monitored throughout LPS infusion and tissue was harvested at the end of the protocol.

Results

Plasma arginine levels decreased and remained low in ADI-PEG20 + CIT and ADI-PEG20 pigs compared with LPS pigs but tissue arginine levels in the liver and kidney were similar across all treatments. Mean arterial pressure in all groups decreased from 90 mmHg to 60 mmHg within 1 h of LPS infusion but there were no significant differences between treatment groups. ADI-PEG20 and ADI-PEG20 + CIT pigs had less CD45+ infiltrate in the liver and lung and lower levels of pro-inflammatory cytokines in the plasma.

Conclusion

ADI-PEG20 and citrulline supplementation failed to ameliorate the hypotension associated with acute endotoxic sepsis in pigs but reduced systemic and local inflammation in the lung and liver.

Co-administration of curcumin and polyamines in high-fat diet induced obese rats: Assessment of changes in serum polyamine levels and some tissue parameters

Obesity is a non-communicable chronic disease that continues to increase around the world. Recently, it has been shown that curcumin positively affects lipid, energy metabolism, and body weight change. Moreover, polyamines are aliphatic polycations, which can be found in all mammalian cells and foods and have been shown to prevent obesity through many different mechanisms. However, whether the co-administration of curcumin and polyamines has synergistic effects has yet to be clarified. Our study aimed to examine the effects of curcumin and polyamines on obesity and to assess the changes in serum polyamine levels and tissue parameters. 28 Sprague-Dawley male rats were fed a high-fat diet for 10 weeks to develop obesity, and then they were randomly divided into 4 groups as the control group (CONT), curcumin group (CUR), polyamine group (POL), curcumin and polyamine group (CUR+POL) and supplements were administered for 6 weeks. As a result, the lowest feed consumption in rats was recorded in the CUR+POL group, and the group with the lowest weight after supplements was the POL group, then the CUR+POL, CONT, and CUR groups, respectively. N-acetyl putrescine and GABA levels increased significantly after obesity development. The total histopathological score in fat, liver, and kidney tissues increased significantly in the CONT group. In the CUR+POL group, damage to the tissues was in the direction of recovery compared to the other groups, and the expression of NF-κB was significantly low. These results suggest that combined curcumin and polyamines may have protective effects.

Role of Arbuscular Mycorrhizal Fungi in Regulating Growth, Enhancing Productivity, and Potentially Influencing Ecosystems under Abiotic and Biotic Stresses

Arbuscular mycorrhizal fungi (AMF) form symbiotic relationships with the roots of nearly all land-dwelling plants, increasing growth and productivity, especially during abiotic stress. AMF improves plant development by improving nutrient acquisition, such as phosphorus, water, and mineral uptake. AMF improves plant tolerance and resilience to abiotic stressors such as drought, salt, and heavy metal toxicity. These benefits come from the arbuscular mycorrhizal interface, which lets fungal and plant partners exchange nutrients, signalling molecules, and protective chemical compounds. Plants' antioxidant defence systems, osmotic adjustment, and hormone regulation are also affected by AMF infestation. These responses promote plant performance, photosynthetic efficiency, and biomass production in abiotic stress conditions. As a result of its positive effects on soil structure, nutrient cycling, and carbon sequestration, AMF contributes to the maintenance of resilient ecosystems. The effects of AMFs on plant growth and ecological stability are species- and environment-specific. AMF's growth-regulating, productivity-enhancing role in abiotic stress alleviation under abiotic stress is reviewed. More research is needed to understand the molecular mechanisms that drive AMF-plant interactions and their responses to abiotic stresses. AMF triggers plants' morphological, physiological, and molecular responses to abiotic stress. Water and nutrient acquisition, plant development, and abiotic stress tolerance are improved by arbuscular mycorrhizal symbiosis. In plants, AMF colonization modulates antioxidant defense mechanisms, osmotic adjustment, and hormonal regulation. These responses promote plant performance, photosynthetic efficiency, and biomass production in abiotic stress circumstances. AMF-mediated effects are also enhanced by essential oils (EOs), superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), hydrogen peroxide (H2O2), malondialdehyde (MDA), and phosphorus (P). Understanding how AMF increases plant adaptation and reduces abiotic stress will help sustain agriculture, ecosystem management, and climate change mitigation. Arbuscular mycorrhizal fungi (AMF) have gained prominence in agriculture due to their multifaceted roles in promoting plant health and productivity. This review delves into how AMF influences plant growth and nutrient absorption, especially under challenging environmental conditions. We further explore the extent to which AMF bolsters plant resilience and growth during stress.

Peripheral nerve repair is associated with augmented cross-tissue inflammation following vascularized composite allotransplantation

Introduction

Vascularized composite allotransplantation (VCA), with nerve repair/coaptation (NR) and tacrolimus (TAC) immunosuppressive therapy, is used to repair devastating traumatic injuries but is often complicated by inflammation spanning multiple tissues. We identified the parallel upregulation of transcriptional pathways involving chemokine signaling, T-cell receptor signaling, Th17, Th1, and Th2 pathways in skin and nerve tissue in complete VCA rejection compared to baseline in 7 human hand transplants and defined increasing complexity of protein-level dynamic networks involving chemokine, Th1, and Th17 pathways as a function of rejection severity in 5 of these patients. We next hypothesized that neural mechanisms may regulate the complex spatiotemporal evolution of rejection-associated inflammation post-VCA.

Methods

For mechanistic and ethical reasons, protein-level inflammatory mediators in tissues from Lewis rats (8 per group) receiving either syngeneic (Lewis) or allogeneic (Brown-Norway) orthotopic hind limb transplants in combination with TAC, with and without sciatic NR, were compared to human hand transplant samples using computational methods.

Results

In cross-correlation analyses of these mediators, VCA tissues from human hand transplants (which included NR) were most similar to those from rats undergoing VCA + NR. Based on dynamic hypergraph analyses, NR following either syngeneic or allogeneic transplantation in rats was associated with greater trans-compartmental localization of early inflammatory mediators vs. no-NR, and impaired downregulation of mediators including IL-17A at later times.

Discussion

Thus, NR, while considered necessary for restoring graft function, may also result in dysregulated and mis-compartmentalized inflammation post-VCA and therefore necessitate mitigation strategies. Our novel computational pipeline may also yield translational, spatiotemporal insights in other contexts.

Nutrition and Flavor Evaluation of Amino Acids in Guangyuan Grey Chicken of Different Ages, Genders and Meat Cuts

The composition and content of amino acids in foodstuffs have a vital impact on the nutritional value and taste. With the aim of understanding the nutrition and flavor of Guangyuan grey chicken, the composition and content of amino acids in the pectoralis and thigh muscle of chickens at the age of 90 d, 120 d and 150 d were determine using liquid chromatography–tandem mass spectrometry (LC-MS/MS) and an amino acid analyzer. A total of 17 amino acids were detected both in pectoralis and thigh muscle via the amino acid analyzer, of which the content of glutamate was the highest. Additionally, 21 deproteinized free amino acids were detected via LC-MS/MS. Among all samples, the content of glutamine in thigh muscle was the highest. The content of histidine in the pectoralis was the highest. In terms of the flavor amino acids (FAAs), the umami-taste and sweet-taste amino acids were higher in the thigh muscle of 120 d male chicken. From the perspective of protein nutrition, the essential amino acid was higher in pectoral muscle, and the composition was better. The results of the amino acid score showed that the content of leucine and valine were inadequate in Guangyuan grey chicken. Collectively, the content of amino acid in Guangyuan grey chicken was affected by age, gender and meat cut. This study confirms that meat of chicken in different ages, genders, and cuts presents different nutritional values and flavors owing to the variation of amino acids content.

Dual role of nitric oxide in Alzheimer's Disease

Nitric oxide (NO), an enzymatic product of nitric oxide synthase (NOS), has been associated with a variety of neurological diseases such as Alzheimer's disease (AD). NO has long been thought to contribute to neurotoxic insults caused by neuroinflammation in AD. This perception shifts as more attention is paid to the early stages before cognitive problems manifest. However, it has revealed a compensatory neuroprotective role for NO that protects synapses by increasing neuronal excitability. NO can positively affect neurons by inducing neuroplasticity, neuroprotection, and myelination, as well as having cytolytic activity to reduce inflammation. NO can also induce long-term potentiation (LTP), a process by which synaptic connections among neurons become more potent. Not to mention that such functions give rise to AD protection. Notably, it is unquestionably necessary to conduct more research to clarify NO pathways in neurodegenerative dementias because doing so could help us better understand their pathophysiology and develop more effective treatment options. All these findings bring us to the prevailing notion that NO can be used either as a therapeutic agent in patients afflicted with AD and other memory impairment disorders or as a contributor to the neurotoxic and aggressive factor in AD. In this review, after presenting a general background on AD and NO, various factors that have a pivotal role in both protecting and exacerbating AD and their correlation with NO will be elucidated. Following this, both the neuroprotective and neurotoxic effects of NO on neurons and glial cells among AD cases will be discussed in detail.

Anti-cancer effect of in vivo inhibition of nitric oxide synthase in a rat model of breast cancer

Increased expression of nitric oxide synthase (NOS) is associated with different cancers such as cervical, breast, lung, brain, and spinal cord. Inhibition of NOS activity has been suggested as potential tool to prevent breast cancer. The anti-tumor therapeutic effect of L-nitro arginine methyl ester (L-NAME), NOS inhibitor, using in vivo models is currently under investigation. We hypothesized that L-NAME will show an anti-tumor effect by delaying a progression of breast cancer via a modulation of cell death and proliferation, and angiogenesis. We used a novel model of anti-cancer treatment by the administration of L-NAME (30 mg/kg in a day, intraperitoneal) injected every third day for five weeks to rat model of 7,12-dimethylbenz[a]anthracene (DMBA)-induced breast tumor. Concentrations of nitrite anions, polyamines, malondialdehyde, NH₄⁺ levels, and arginase activity in the blood were decreased in DMBA + L-NAME-treated rats compared with DMBA rats. The mortality rates, tumor number, weight, and volume, as well as the histopathological grade of breast cancer were also significantly reduced. In addition, L-NAME treatment showed a delay in tumor formation, and in body weight compared with rats administrated only with DMBA. In conclusion, our data show that L-NAME is a promising anti-cancer agent to treat breast cancer, which can lead to development of anti-tumor therapeutic tools in future.

Correlation of Asymmetric Dimethyl Arginine Level to Sickle Retinopathy in Children With Sickle Cell Disease

Asymmetric dimethyl arginine (ADMA) is a competitive inhibitor of nitric oxide synthetase especially in L-arginine deficiency, which is the case in sickle cell disease (SCD). we aimed to assess the level of ADMA in children with sickle retinopathy and to correlate it to the degree of retinopathy. In this cross-sectional study 40 children with SCD were included, 20 of them with sickle cell retinopathy (SCR) (group I), 20 with normal fundus examination (group II), and another 20 healthy children served as controls (group III). We measured ADMA level by ELISA and performed fundus examination. Seventeen of the 20 children included in group I had Grade I retinopathy (85%), 2 children had Grade II retinopathy (10%), and 1 child had Grade III retinopathy (5%). ADMA was significantly higher in SCD than controls ( P -value <0.001), and it was even higher in patients with SCR compared those without retinopathy ( P -value <0.002), and there was positive linear correlation between ADMA and the grade of retinopathy. The type of retinopathy detect in the studied patients was the nonproliferative type. In conclusion, ADMA is elevated in children with SCD, and its level is even higher in those who develop SCR.

Natural history of arginase 1 deficiency and the unmet needs of patients: A systematic review of case reports

Background

Arginase 1 deficiency (ARG1-D) is a rare, progressive and debilitating urea cycle disorder characterized by clinical manifestations including spasticity, seizures, developmental delay, and intellectual disability. The aim of this systematic review was to identify and summarize the natural history of ARG1-D and the unmet needs of patients.

Methods

A comprehensive search of published case reports was undertaken to identify patients with ARG1-D regardless of interventions, comparisons, or outcomes. MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and other evidence-based medicine literature databases were searched on 20 April 2020. Quality was assessed using the Joanna Briggs Institute (JBI) Critical Appraisal Checklist. (PROSPERO registration: CRD42020212142.).

Results

One hundred and fifty seven ARG1-D patients were included from 111 publications (good overall quality based on JBI's Checklist); 84 (53.5%) were males. Motor deficits (including spasticity), intellectual disability, and seizures were reported in >50% of the cases. Mean age (SD) at diagnosis was 6.4 years and the laboratory findings most commonly reported to support diagnosis included elevated plasma arginine (81.5%), mutation in ARG1 gene through genetic testing (60%), and absence/reduction of red blood cell arginase activity (51%). Reported management approaches mainly included dietary protein restriction (68%), nitrogen scavengers (45%), and essential amino acid supplements (21%). Author-reported clinical improvement was documented for 26% of patients, 15% deteriorated, and 19% had limited or no change; notably, no indication of clinical outcome was reported for 40% cases.

Conclusion

This review illustrates a significant burden of disease and highlights a considerable unmet need for clinically effective treatment options for patients with ARG1-D.

Health care resource utilization in the management of patients with Arginase 1 Deficiency in the US: a retrospective, observational, claims database study

BACKGROUND

Arginase 1 Deficiency (ARG1-D) is an inherited metabolic disease that leads to significant morbidity.

AIMS

Despite the recognized burden of disease, information on health care resource utilization (HCRU) among patients with ARG1-D is lacking. We, therefore, sought to evaluate HCRU in ARG1-D relative to non-ARG1-D cohort.

MATERIALS AND METHODS

Patients with ≥2 ICD-10-CM diagnosis codes for ARG1-D were identified (first diagnosis code = index date) using professional fee claims linked with prescription claims. Patients with ARG1-D were matched 1:1 to a comparator cohort of patients with other medical conditions. Matching variables included age, sex, index year, payer type (Medicare, Medicaid, third party) and geographic region.

RESULTS

A total of 77 patients met the inclusion criteria for the ARG1-D cohort, with a median age of 15 years, 52% <18 years, and 52% male. Several concurrent diagnoses were recorded at a higher frequency in the ARG1-D cohort versus the matched comparator (spasticity 7 times higher; developmental delay ∼2 times higher; intellectual disability 5 times higher; and seizures 8 times higher). Emergency room visits occurred twice as often, laboratory tests were performed 1.5 times more often, hospitalization was required 3 times more often, and mean length of stay was longer for patients with ARG1-D than the comparator cohort (2.4 days vs. 0.3 days).

LIMITATIONS

A relatively short study period while the burden of ARG1-D increases over a lifetime due to disease progression.

CONCLUSIONS

Patients with ARG1-D had significantly greater HCRU compared with those without the disease; they presented with a more extensive comorbidity profile, accessed the health care system more frequently, required more intense monitoring and management, and had more frequent and longer hospitalizations relative to the comparator group. These findings demonstrate a high health burden in ARG1-D that is not mitigated by standard-of-care measures and emphasize the need for improved treatment options.

Arginine and Arginases Modulate Metabolism, Tumor Microenvironment and Prostate Cancer Progression

Arginine availability and activation of arginine-related pathways at cancer sites have profound effects on the tumor microenvironment, far beyond their well-known role in the hepatic urea cycle. Arginine metabolism impacts not only malignant cells but also the surrounding immune cells behavior, modulating growth, survival, and immunosurveillance mechanisms, either through an arginase-mediated effect on polyamines and proline synthesis, or by the arginine/nitric oxide pathway in tumor cells, antitumor T-cells, myeloid-derived suppressor cells, and macrophages. This review presents evidence concerning the impact of arginine metabolism and arginase activity in the prostate cancer microenvironment, highlighting the recent advances in immunotherapy, which might be relevant for prostate cancer. Even though further research is required, arginine deprivation may represent a novel antimetabolite strategy for the treatment of arginine-dependent prostate cancer.

Hepatic Ischemia-Reperfusion Impairs Blood-Brain Barrier Partly Due to Release of Arginase From Injured Liver

Aim: Hepatic ischemia-reperfusion (HIR) induces remote organs injury, including the brain. The homeostasis of the brain is maintained by the blood-brain barrier (BBB); thus, we aimed to investigate whether HIR impaired BBB and attempted to elucidate its underlying mechanism.

Methods: Cell viability of human cerebral microvascular endothelial cells (hCMEC/D3) was measured following 24 h incubation with a serum of HIR rat undergoing 1 h ischemia and 4 h reperfusion, liver homogenate, or lysate of primary hepatocytes of the rat. The liver homogenate was precipitated using (NH₄)₂SO₄ followed by separation on three columns and electrophoresis to identify the toxic molecule. Cell activity, apoptosis, proliferation, cell cycle, and expressions of proteins related to cell cycle were measured in hCMEC/D3 cells incubated with identified toxic molecules. HIR rats undergoing 1 h ischemia and 24 h reperfusion were developed to determine the release of an identified toxic molecule. BBB function was indexed as permeability to fluorescein and brain water. Endothelial cell proliferation and expressions of proteins related to the cell cycle in cerebral microvessels were measured by immunofluorescence and western blot.

Results: Toxic molecule to BBB in the liver was identified to be arginase. Arginase inhibitor nor-NOHA efficiently attenuated hCMEC/D3 damage caused by liver homogenate and serum of HIR rats. Both arginase and serum of HIR rats significantly lowered arginine (Arg) in the culture medium. Arg addition efficiently attenuated the impairment of hCMEC/D3 caused by arginase or Arg deficiency, demonstrating that arginase impaired hCMEC/D3 via depriving Arg. Both arginase and Arg deficiency damaged hCMEC/D3 cells by inhibiting cell proliferation, retarding the cell cycle to G1 phase, and downregulating expressions of cyclin A, cyclin D, CDK2, and CDK4. HIR notably increased plasma arginase activity and lowered Arg level, increased the BBB permeability accompanied with enhanced brain water, and decreased the proliferative cells (marked by Ki67) in cerebral microvessels (marked by CD31) and protein expressions of cyclin A, cyclin D, CDK2 and CDK4 in isolated brain microvessels. Oral supplement of Arg remarkably attenuated these HIR-induced alterations.

Conclusion: HIR leads to substantial release of arginase from the injured liver and then deprives systemic Arg. The Arg deficiency further impairs BBB via inhibiting the proliferation of brain microvascular endothelial cells by cell cycle arrest.

Sexual Dimorphism in Alternative Metabolic Pathways of L-Arginine in Circulating Leukocytes in Young People with Type 1 Diabetes Mellitus

Background: Sexual dimorphism in specific biochemical pathways and immune response, underlies the heterogeneity of type 1 diabetes mellitus (T1DM) and affects the outcome of immunotherapy. Arginase and nitric oxide (NO) synthase (NOS) metabolize L-arginine and play opposite roles in the immune response and autoimmune processes.Objective: We hypothesized that the above mentioned enzymes can be involved in sex and age differences in T1DM and its treatment. Based on this, the enzymes have been studied in peripheral blood leukocytes (PBL) and plasma of young people with T1DM.Methods: Patients were recruited from Muratsan University Hospital (Yerevan, Armenia) and were divided into groups: girls and boys by age, from children to adolescents and adolescents/young adults with recent-onset T1DM (RO-T1DM) (0.1-1 years) and long-term T1DM (LT-T1DM) (1.6-9.9 years). Arginase activity was assessed by L-arginine-dependent production of L-ornithine, and the NOS activity was assessed by NO/nitrite production. Glycemic control was assessed using hemoglobin A1c test. Plasma HbA1c concentration below 7.5% (median (range) 6.7 [6.2-7.5]) was taken as good glycemic control (+) and above 7.5% (median (range) 10.5 [7.6-13]) as poor glycemic control (-). Healthy volunteers with corresponding sex and age were used as the control group.Results: All the patients with RO-T1DM, with poor glycemic control, had increased arginase activity in the cytoplasm (cARG) and mitochondria (mARG) in PBL. In girls with RO-T1DM, with good glycemic control, the subcellular arginase activity decreased, and normalized in LT-T1DM, regardless of age. In contrast, boys from both age groups showed high arginase activity, regardless of glycemic control and duration of T1DM along with insulin therapy. At the same time, a significant decrease in the subcellular production of bioavailable NO was observed in children/preadolescents, regardless of glycemic control and duration of diabetes. In adolescents/young adult boys with RO-T1DM, with (-), the subcellular production of NO decreased significantly, and with LT-T1DM, the decrease was attenuated, but even with (+) remained lower than in healthy people. In contrast, in the group of same age girls with RO-T1DM, NO production increased above normal in both cellular compartments, while with LT-T1DM it normalized in the cytoplasm. In adolescents/young adults with LT-T1DM, NO production in PBL mitochondria decreased by almost a half, regardless of glycemic control and gender. Changes in the metabolic pathways of L-arginine in plasma differed and were less substantial than in the PBL cellular compartments in T1DM.Conclusions: Glycemic status and duration of T1DM along with insulin therapy affect the activity of arginase and NOS-dependent production of bioavailable NO in the cytoplasm and mitochondria in PBL of young patients with T1DM, depending on sex and age. Arginase and NOS can directly affect the processes occurring in the pancreas and the outcome of therapy through infiltrated leukocytes. Obtained data can be useful for understanding the heterogeneity of T1DM and using it to develop available criteria for assessing the severity and treatment of autoimmune diabetes.

Citrulline, Biomarker of Enterocyte Functional Mass and Dietary Supplement. Metabolism, Transport, and Current Evidence for Clinical Use

L-Citrulline is a non-essential but still important amino acid that is released from enterocytes. Because plasma levels are reduced in case of impaired intestinal function, it has become a biomarker to monitor intestinal integrity. Moreover, oxidative stress induces protein citrullination, and antibodies against anti-citrullinated proteins are useful to monitor rheumatoid diseases. Citrullinated histones, however, may even predict a worse outcome in cancer patients. Supplementation of citrulline is better tolerated compared to arginine and might be useful to slightly improve muscle strength or protein balance. The following article shall provide an overview of L-citrulline properties and functions, as well as the current evidence for its use as a biomarker or as a therapeutic supplement.

The Mechanisms of L-Arginine Metabolism Disorder in Endothelial Cells

L-arginine is a key metabolite for nitric oxide production by endothelial cells, as well as signaling molecule of the mTOR signaling pathway. mTOR supports endothelial cells homeostasis and regulates activity of L-arginine-metabolizing enzymes, endothelial nitric oxide synthase, and arginase II. Disruption of the L-arginine metabolism in endothelial cells leads to the development of endothelial dysfunction. Conflicting results of the use of L-arginine supplement to improve endothelial function reveals a controversial role of the amino acid in the endothelial cell biology. The review is aimed at analysis of the current data on the role of L-arginine metabolism in the development of endothelial dysfunction.

Impact of arginine therapy on mitochondrial function in children with sickle cell disease during vaso-occlusive pain

Altered mitochondrial function occurs in sickle cell disease (SCD), due in part to low nitric oxide (NO) bioavailability. Arginine, the substrate for NO production, becomes acutely deficient in SCD patients with vaso-occlusive pain episodes (VOE). To determine if arginine improves mitochondrial function, 12 children with SCD-VOE (13.6 ± 3 years; 67% male; 75% hemoglobin-SS) were randomized to 1 of 3 arginine doses: (1) 100 mg/kg IV 3 times/day (TID); (2) loading dose (200 mg/kg) then 100 mg/kg TID; or (3) loading dose (200 mg/kg) followed by continuous infusion (300 mg/kg per day) until discharge. Platelet-rich plasma mitochondrial activity, protein expression, and protein-carbonyls were measured from emergency department (ED) presentation vs discharge. All VOE subjects at ED presentation had significantly decreased complex-V activity compared to a steady-state cohort. Notably, complex-V activity was increased at discharge in subjects from all 3 arginine-dosing schemes; greatest increase occurred with a loading dose (P < .001). Although complex-IV and citrate synthase activities were similar in VOE platelets vs steady state, enzyme activities were significantly increased in VOE subjects after arginine-loading dose treatment. Arginine also decreased protein-carbonyl levels across all treatment doses (P < .01), suggesting a decrease in oxidative stress. Arginine therapy increases mitochondrial activity and reduces oxidative stress in children with SCD/VOE. This trial was registered at www.clinicaltrials.gov as #NCT02536170.

Preoperative Immunonutrition vs. Standard Dietary Advice in Normo-Nourished Patients Undergoing Fast-Track Laparoscopic Colorectal Surgery

Immunonutrition (IN) appears to reduce infective complications and in-hospital length of stay (LOS) after major gastrointestinal surgery, but its use in normo-nourished patients is still controversial. The primary aim of this comparative observational study was to evaluate if pre-operative IN reduces in-hospital stay in patients undergoing laparoscopic colorectal resection for cancer under an enhanced recovery after surgery (ERAS) program. The influence of IN on time to first bowel movements, time to full oral diet tolerance, number and type of complications, reasons of prolonged LOS and readmission rate was evaluated as secondary outcome. Patients undergoing ERAS laparoscopic colorectal resection between December 2016 and December 2019 were reviewed. Patients who have received preoperative IN (group A) were compared to those receiving standard dietary advice (group B). Mean in-hospital LOS was significantly shorter in patients receiving preoperative IN than standard dietary advice (4.85 ± 2.25 days vs. 6.06 ± 3.95 days; p < 0.0492). No differences in secondary outcomes were observed. Preoperative IN associated with ERAS protocol in normo-nourished patients undergoing laparoscopic colorectal cancer resection seems to reduce LOS.

Arginase II Plays a Central Role in the Sexual Dimorphism of Arginine Metabolism in C57BL/6 Mice

BACKGROUND

Sex differences in plasma concentration of arginine and arginase activity of different tissues have been reported in mice. In addition, male but not female C57BL/6 mice have a dietary arginine requirement for growth.

OBJECTIVE

The goal of this research was to test the hypothesis that arginase II is a key factor in the sexual dimorphism of arginine metabolism.

METHODS

Young adult male and female wild type (WT), and heterozygous and arginase II knockout mice on a C57BL/6 background mice were infused with labeled citrulline, arginine, ornithine, phenylalanine, and tyrosine to determine the rates of appearance and interconversion of these amino acids. Tissue arginase activity was measured in the liver, heart, jejunum, kidney, pancreas, and spleen with an arginine radioisotope. The effect of genotype, sex, and their interaction was tested.

RESULTS

Female mice produced ∼36% more citrulline than their male littermates, which translated into a greater arginine endogenous synthesis, flux, and plasma concentration (42, 6, and 27%, respectively; P < 0.001). Female mice also had a greater phenylalanine flux (10%) indicating a greater rate of whole protein breakdown; however, they had a lower protein synthesis rate than males (18%; P < 0.001). The ablation of arginase II reduced the production of citrulline and the de novo synthesis of arginine in females and increased the rate of appearance of arginine and plasma arginine concentration in male mice (16 and 22%, respectively; P < 0.001). No effect of arginase II deletion, however, was observed for whole-body protein kinetics. Arginase II activity was present in the pancreas, kidney, jejunum, and spleen; WT females had a ∼2-fold greater renal arginase activity than their WT counterparts.

CONCLUSIONS

A clear sexual dimorphism exists in the endogenous synthesis of arginine and its disposal. Female mice have a greater arginine availability than their male littermates. The ablation of arginase II increases arginine availability in male mice.

Oxidative Stress and Redox-Modulating Therapeutics in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is associated with the production of reactive species that target cysteine redox switches in proteins, thereby affecting gene regulation, DNA damage, ion transport, intermediary metabolism, and mitochondrial function. Precursors of reactive species are derived from organic and inorganic compounds and their cofactors, including amino acids, vitamins, oxygen, nitrite, and sulfate. Nutrition and the gut microbiome fuel this process to a significant extent. The production of reactive species in IBD is reflected by a reduction in systemic free thiols, the major components of the antioxidant machinery. Systemic free thiols are amenable to nutritional or therapeutic intervention. This opens up future avenues for therapeutic modulation of redox status in IBD.

Guanidinoacetic acid deficiency: a new entity in clinical medicine?

Guanidinoacetic acid (GAA, also known as glycocyamine or betacyamine) is a naturally-occurring derivative of glycine and a direct metabolic precursor of creatine, a key player in high-phosphate cellular bioenergetics. GAA is found in human serum and urine, with circulating GAA likely reflects an equilibrium between its endogenous production and utilization/excretion. GAA deficiency (as indicated by low serum GAA) has been reported in various conditions yet this intriguing clinical entity appears to be poorly characterized as yet, either as a primary deficit or a sequel of secondary disease. This minireview article summarizes the inherited and acquired disorders with apparent GAA deficiency and discusses a possible relevance of GAA shortfall in clinical medicine.

Nutrition: reducing the hypermetabolic response to thermal injury

Nutritional support is seen as a vital component in the battle to attenuate the extreme hypermetabolic response experienced by patients suffering from large thermal injuries. Protein catabolism precipitating protein malnutrition places patients at greater risk of wound infection and sepsis due to delayed wound healing. Underfeeding, aggressive feeding, feeding routes, timing of initiation of feeding and tight insulin control have all been explored extensively in the quest to understand what nutritional treatment will best attenuate the hypermetabolic response. Despite this it is suggested that the majority of patients with large thermal injuries do not receive adequate nutritional support immediately post injury. Nurses have a pivotal role to play in ensuring that thermal injury patients receive appropriate nutritional support based on the best available evidence.

Role of tumor and host autophagy in cancer metabolism

Macroautophagy (referred to here as autophagy) degrades and recycles cytoplasmic constituents to sustain cellular and mammalian metabolism and survival during starvation. Deregulation of autophagy is involved in numerous diseases, such as cancer. Cancers up-regulate autophagy and depend on it for survival, growth, and malignancy in a tumor cell-autonomous fashion. Recently, it has become apparent that autophagy in host tissues as well as the tumor cells themselves contribute to tumor growth. Understanding how autophagy regulates metabolism and tumor growth has revealed new essential tumor nutrients, where they come from, and how they are supplied and used, which can now be targeted for cancer therapy.

Host Control of Tumor Feeding: Autophagy Holds the Key

Cancer cells are dependent on functional autophagy both within their cytoplasm and systemically in the host to maintain growth. How systemic autophagy directly contributes to tumor growth remains unclear. In a study published in Nature, Poillet-Perez et al. (2018) show that host autophagy helps to maintain the levels of circulating arginine that feed tumor growth.

Role of arginine deiminase in thymic atrophy during experimental Streptococcus pyogenes infection

Expression of gene of arginine deiminase (AD) allows adaptation of Streptococcus pyogenes to adverse environmental conditions. AD activity can lead to L-arginine deficiency in the host cells' microenvironment. Bioavailability of L-arginine is an important factor regulating the functions of the immune cells in mammals. By introducing a mutation into S pyogenes M46-16, we obtained a strain with inactivated arcA/sagp gene (M49-16 delArcA), deficient in AD. This allowed elucidating the function of AD in pathogenesis of streptococcal infection. The virulence of the parental and mutant strains was examined in a murine model of subcutaneous streptococcal infection. L-arginine concentration in the plasma of mice infected with S pyogenes M49-16 delArcA remained unchanged in course of the entire experiment. At the same time mice infected with S pyogenes M49-16 demonstrated gradual diminution of L-arginine concentration in the blood plasma, which might be due to the activity of streptococcal AD. Mice infected with S pyogenes M49-16 delArcA demonstrated less intensive bacterial growth in the primary foci and less pronounced bacterial dissemination as compared with animals infected with the parental strain S pyogenes M46-16. Similarly, thymus involution, alterations in apoptosis, thymocyte subsets and Treg cells differentiation were less pronounced in mice infected with S pyogenes M49-16 delArcA than in those infected with the parental strain. The results obtained showed that S pyogenes M49-16 delArcA, unable to produce AD, had reduced virulence in comparison with the parental S pyogenes M49-16 strain. AD is an important factor for the realization of the pathogenic potential of streptococci.

Autophagy maintains tumour growth through circulating arginine

Autophagy captures intracellular components and delivers them to lysosomes, where they are degraded and recycled to sustain metabolism and to enable survival during starvation^1-5. Acute, whole-body deletion of the essential autophagy gene Atg7 in adult mice causes a systemic metabolic defect that manifests as starvation intolerance and gradual loss of white adipose tissue, liver glycogen and muscle mass¹. Cancer cells also benefit from autophagy. Deletion of essential autophagy genes impairs the metabolism, proliferation, survival and malignancy of spontaneous tumours in models of autochthonous cancer^6,7. Acute, systemic deletion of Atg7 or acute, systemic expression of a dominant-negative ATG4b in mice induces greater regression of KRAS-driven cancers than does tumour-specific autophagy deletion, which suggests that host autophagy promotes tumour growth^1,8. Here we show that host-specific deletion of Atg7 impairs the growth of multiple allografted tumours, although not all tumour lines were sensitive to host autophagy status. Loss of autophagy in the host was associated with a reduction in circulating arginine, and the sensitive tumour cell lines were arginine auxotrophs owing to the lack of expression of the enzyme argininosuccinate synthase 1. Serum proteomic analysis identified the arginine-degrading enzyme arginase I (ARG1) in the circulation of Atg7-deficient hosts, and in vivo arginine metabolic tracing demonstrated that serum arginine was degraded to ornithine. ARG1 is predominantly expressed in the liver and can be released from hepatocytes into the circulation. Liver-specific deletion of Atg7 produced circulating ARG1, and reduced both serum arginine and tumour growth. Deletion of Atg5 in the host similarly regulated [corrected] circulating arginine and suppressed tumorigenesis, which demonstrates that this phenotype is specific to autophagy function rather than to deletion of Atg7. Dietary supplementation of Atg7-deficient hosts with arginine partially restored levels of circulating arginine and tumour growth. Thus, defective autophagy in the host leads to the release of ARG1 from the liver and the degradation of circulating arginine, which is essential for tumour growth; this identifies a metabolic vulnerability of cancer.

The Involvement of Arginase and Nitric Oxide Synthase in Breast Cancer Development: Arginase and NO Synthase as Therapeutic Targets in Cancer

It is well established that, during development of malignancies, metabolic changes occur, including alterations of enzyme activities and isoenzyme expression. Arginase and nitric oxide (NO) synthase (NOS) are two of those enzymes considered to be involved in tumorigenesis. The goal of this article was to study the involvement of arginase and NOS in the development of different stages of breast cancer. Our results have shown that human serum arginase activity and NO (resp., and NOS activity) and polyamines quantities increased in parallel with cancer stage progression and decreased after neoadjuvant chemotherapy. For breast cancer, the only isoenzyme of arginase expressed in serum before and after chemotherapy was in a cationic form. The data of Lineweaver-Burk plot with a Km value of 2 mM was calculated, which is characteristic for human liver type isoform of arginase. During electrophoresis at pH 8.9, the enzyme exhibited high electrophoretic mobility and was detected near the anode. The presented results demonstrated that arginase in human serum with breast cancer and after chemotherapy is not polymorphic. We suggest that arginase and NOS inhibition has antitumor effects on cancer development, as it can inhibit polyamines and NO levels, a precursor of cancer cell proliferation, metastasis, and tumor angiogenesis.

An arginase-1 SNP that protects against the development of pulmonary hypertension in bronchopulmonary dysplasia enhances NO-mediated apoptosis in lymphocytes

Arginase and nitric oxide synthase (NOS) share a common substrate, l‐arginine, and have opposing effects on vascular remodeling. Arginase is the first step in polyamine and proline synthesis necessary for cellular proliferation, while NO produced from NOS promotes apoptosis. Previously, we identified a single nucleotide polymorphism (SNP) in the arginase‐1 (ARG1) gene, rs2781666 (T‐allele) that was associated with a decreased risk for developing pulmonary hypertension (PH) in a cohort of infants with bronchopulmonary dysplasia (BPD). In this study, we utilized lymphocytes from neonates (the only readily available cells from these patients expressing the two genotypes of interest) with either the rs2781666 SNP (TT) or wild type (GG) to test the hypothesis that the protection of the ARG1 SNP against the development of PH in BPD would involve augmented NO production leading to more apoptosis. Lymphocytes were stimulated with IL‐4, IL‐13, and phorbol myristate acetate (PMA). We found that TT lymphocytes had similar levels of arginase I and arginase II expression, but there was a tendency for lower urea production (a surrogate marker of arginase activity), than in the GG lymphocytes. The TT lymphocytes also had significantly greater NO production than did GG lymphocytes despite no differences in iNOS expression between genotypes. Furthermore, the TT lymphocytes had lower numbers of viable cells, and higher levels of cleaved caspase‐3 than did GG lymphocytes. Inhibiting NOS activity using N_ω‐Nitro‐l‐arginine methyl ester hydrochloride (l‐NAME) significantly decreased cleaved caspase‐3 levels in the TT lymphocytes. These data demonstrate that the TT genotype results in greater levels of NO production leading to more apoptosis, which is consistent with the concept that BPD patients with the TT genotype are protected against the development of PH by producing greater basal levels of endogenous NO.

Obesity-induced vascular dysfunction and arterial stiffening requires endothelial cell arginase 1

AIMS

Elevation of arginase activity has been linked to vascular dysfunction in diabetes and hypertension by a mechanism involving decreased nitric oxide (NO) bioavailability due to L-arginine depletion. Excessive arginase activity also can drive L-arginine metabolism towards the production of ornithine, polyamines, and proline, promoting proliferation of vascular smooth muscle cells and collagen formation, leading to perivascular fibrosis. We hypothesized that there is a specific involvement of arginase 1 expression within the vascular endothelial cells in this pathology.

METHODS AND RESULTS

To test this proposition, we used models of type 2 diabetes and metabolic syndrome. Studies were performed using wild type (WT), endothelial-specific arginase 1 knockout (EC-A1-/-) and littermate controls(A1con) mice fed high fat-high sucrose (HFHS) or normal diet (ND) for 6 months and isolated vessels exposed to palmitate-high glucose (PA/HG) media. Some WT mice or isolated vessels were treated with an arginase inhibitor, ABH [2-(S)-amino-6-boronohexanoic acid. In WT mice, the HFHS diet promoted increases in body weight, fasting blood glucose, and post-prandial insulin levels along with arterial stiffening and fibrosis, elevated blood pressure, decreased plasma levels of L-arginine, and elevated L-ornithine. The HFHS diet or PA/HG treatment also induced increases in vascular arginase activity along with oxidative stress, reduced vascular NO levels, and impaired endothelial-dependent vasorelaxation. All of these effects except obesity and hypercholesterolemia were prevented or significantly reduced by endothelial-specific deletion of arginase 1 or ABH treatment.

CONCLUSION

Vascular dysfunctions in diet-induced obesity are prevented by deletion of arginase 1 in vascular endothelial cells or arginase inhibition. These findings indicate that upregulation of arginase 1 expression/activity in vascular endothelial cells has an integral role in diet-induced cardiovascular dysfunction and metabolic syndrome.

The Nitric Oxide Pathway in Pulmonary Vascular Disease

Nitric oxide is an endogenous pulmonary vasodilator that is synthesized from L-arginine in pulmonary vascular endothelial cells by nitric oxide synthase and diffuses to adjacent vascular smooth muscle cells where it activates soluble guanylyl cyclase. This enzyme converts GTP to cGMP which activates cGMP dependent protein kinase leading to a series of events that decrease intracellular calcium and reduce vascular muscle tone. Nitric oxide is an important mediator of pulmonary vascular tone and vascular remodeling. A number of studies suggest that the bioavailability of nitric oxide is reduced in patients with pulmonary vascular disease and that augmentation of the nitric oxide/cGMP pathway may be an effective strategy for treatment. Several medications that target nitric oxide/cGMP signaling are now available for the treatment of pulmonary hypertension. This review explores the history of nitiric oxide research, describes the major NO synthetic and signaling pathways and discusses a variety of abnormalities in NO production and metabolism that may contribute to the pathophysiology of pulmonary vascular disease. A summary of the clinical use of presently available medications that target nitric oxide/cGMP signaling in the treatment of pulmonary hypertension is also presented.

The Reactive Species Interactome: Evolutionary Emergence, Biological Significance, and Opportunities for Redox Metabolomics and Personalized Medicine

SIGNIFICANCE

Oxidative stress is thought to account for aberrant redox homeostasis and contribute to aging and disease. However, more often than not, administration of antioxidants is ineffective, suggesting that our current understanding of the underlying regulatory processes is incomplete. Recent Advances: Similar to reactive oxygen species and reactive nitrogen species, reactive sulfur species are now emerging as important signaling molecules, targeting regulatory cysteine redox switches in proteins, affecting gene regulation, ion transport, intermediary metabolism, and mitochondrial function. To rationalize the complexity of chemical interactions of reactive species with themselves and their targets and help define their role in systemic metabolic control, we here introduce a novel integrative concept defined as the reactive species interactome (RSI). The RSI is a primeval multilevel redox regulatory system whose architecture, together with the physicochemical characteristics of its constituents, allows efficient sensing and rapid adaptation to environmental changes and various other stressors to enhance fitness and resilience at the local and whole-organism level.

CRITICAL ISSUES

To better characterize the RSI-related processes that determine fluxes through specific pathways and enable integration, it is necessary to disentangle the chemical biology and activity of reactive species (including precursors and reaction products), their targets, communication systems, and effects on cellular, organ, and whole-organism bioenergetics using system-level/network analyses.

FUTURE DIRECTIONS

Understanding the mechanisms through which the RSI operates will enable a better appreciation of the possibilities to modulate the entire biological system; moreover, unveiling molecular signatures that characterize specific environmental challenges or other forms of stress will provide new prevention/intervention opportunities for personalized medicine. Antioxid. Redox Signal. 00, 000-000.

Pathways to pulmonary hypertension in sickle cell disease: the search for prevention and early intervention

INTRODUCTION

Pulmonary hypertension (PH) develops in a significant number of patients with sickle cell disease (SCD), resulting in increased morbidity and mortality. This review focuses on PH pathophysiology, risk stratification, and new recommendations for screening and treatment for patients with SCD. Areas covered: An extensive PubMed literature search was performed. While the pathophysiology of PH in SCD is yet to be fully deciphered, it is known that the etiology is multifactorial; hemolysis, hypercoagulability, hypoxemia, ischemic-reperfusion injury, oxidative stress, and genetic susceptibility all contribute in varying degrees to endothelial dysfunction. Hemolysis, in particular, seems to play a key role by inciting an imbalance in the regulatory axis of nitric oxide and arginine metabolism. Systematic risk stratification starting in childhood based on clinical features and biomarkers that enable early detection is necessary. Multi-faceted, targeted interventions, before irreversible vasculopathy develops, will allow for improved patient outcomes and life expectancy. Expert commentary: Despite progress in our understanding of PH in SCD, clinically proven therapies remain elusive and additional controlled clinical trials are needed. Prevention of disease starts in childhood, a critical window for intervention. Given the complex and multifactorial nature of SCD, patients will ultimately benefit from combination therapies that simultaneously targets multiple mechanisms.

Adipose tissue and metabolic and inflammatory responses to stroke are altered in obese mice

Obesity is an independent risk factor for stroke, although several clinical studies have reported that obesity improves stroke outcome. Obesity is hypothesised to aid recovery by protecting against post-stroke catabolism. We therefore assessed whether obese mice had an altered metabolic and inflammatory response to stroke. Obese ob/ob mice underwent a 20-min middle cerebral artery occlusion and 24-h reperfusion. Lipid metabolism and expression of inflammatory cytokines were assessed in the plasma, liver and adipose tissue. The obese-specific metabolic response to stroke was assessed in plasma using non-targeted ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) metabolomics coupled with univariate and multivariate analysis. Obesity had no effect on the extent of weight loss 24 h after stroke but affected the metabolic and inflammatory responses to stroke, predominantly affecting lipid metabolism. Specifically, obese mice had increases in plasma free fatty acids and expression of adipose lipolytic enzymes. Metabolomics identified several classes of metabolites affected by stroke in obese mice, including fatty acids and membrane lipids (glycerophospholipids, lysophospholipids and sphingolipids). Obesity also featured increases in inflammatory cytokines in the plasma and adipose tissue. Overall, these results demonstrate that obesity affected the acute metabolic and inflammatory response to stroke and suggest a potential role for adipose tissue in this effect. These findings could have implications for longer-term recovery and also further highlight the importance of considering comorbidities in preclinical stroke research, especially when identifying biomarkers for stroke. However, further work is required to assess whether these changes translate into long-term effects on recovery.

Summary: Obesity, a co-morbidity for stroke, affected the acute metabolic and inflammatory response to stroke, highlighting the importance of considering comorbidities in preclinical stroke research, especially when identifying biomarkers.

Acquired Amino Acid Deficiencies: A Focus on Arginine and Glutamine

Nonessential amino acids are synthesized de novo and therefore not diet dependent. In contrast, essential amino acids must be obtained through nutrition since they cannot be synthesized internally. Several nonessential amino acids may become essential under conditions of stress and catabolic states when the capacity of endogenous amino acid synthesis is exceeded. Arginine and glutamine are 2 such conditionally essential amino acids and are the focus of this review. Low arginine bioavailability plays a pivotal role in the pathogenesis of a growing number of varied diseases, including sickle cell disease, thalassemia, malaria, acute asthma, cystic fibrosis, pulmonary hypertension, cardiovascular disease, certain cancers, and trauma, among others. Catabolism of arginine by arginase enzymes is the most common cause of an acquired arginine deficiency syndrome, frequently contributing to endothelial dysfunction and/or T-cell dysfunction, depending on the clinical scenario and disease state. Glutamine, an arginine precursor, is one of the most abundant amino acids in the body and, like arginine, becomes deficient in several conditions of stress, including critical illness, trauma, infection, cancer, and gastrointestinal disorders. At-risk populations are discussed together with therapeutic options that target these specific acquired amino acid deficiencies.

Effects of a chronic l-arginine supplementation on the arginase pathway in aged rats

While ageing is frequently associated with l-arginine deficiency, clinical and experimental studies provided controversial data on the interest of a chronic l-arginine supplementation with beneficial, no or even deleterious effects. It was hypothesized that these discrepancies might relate to a deviation of l-arginine metabolism towards production of l-ornithine rather than nitric oxide as a result of age-induced increase in arginase activity. This study investigated the effect of ageing on arginase activity/expression in target tissues and determined whether l-arginine supplementation modulated the effect of ageing on arginase activity. Arginase activity and expression were measured in the heart, vessel, brain, lung, kidney and liver in young rats (3-months old) and aged Wistar rats (22-24-months-old) with or without l-arginine supplementation (2.25% in drinking water for 6weeks). Plasma levels of l-arginine and l-ornithine were quantified in order to calculate the plasma l-arginine/l-ornithine ratio, considered as a reflection of arginase activity. Cardiovascular parameters (blood pressure, heart rate) and aortic vascular reactivity were also studied. Ageing dramatically reduced plasma l-arginine and l-arginine/l-ornithine ratio, decreased liver and kidney arginase activities but did not change activities in other tissues. l-Arginine supplementation normalized plasma l-arginine and l-arginine/l-ornithine ratio, improved endothelial function and decreased systolic blood pressure. These effects were associated with decreased arginase activity in aorta along with no change in the other tissues except in the lung in which activity was increased. A strong mismatch was therefore observed between arginase activity and expression in analyzed tissues. The present study reveals that ageing selectively changes arginase activity in clearance tissues, but does not support a role of the arginase pathway in the potential deleterious effect of the l-arginine supplementation in aged patients. Moreover, our data argue against the use of the measurement of plasma l-arginine/l-ornithine ratio to estimate arginase activity in aged patients.

Preoperative Immunonutrition and Elective Colorectal Resection Outcomes

BACKGROUND

Randomized controlled trials demonstrate the efficacy of arginine-enriched nutritional supplements (immunonutrition) in reducing complications after surgery. The effectiveness of preoperative immunonutrition has not been evaluated in a community setting.

OBJECTIVE

This study aims to determine whether immunonutrition before elective colorectal surgery improves outcomes in the community at large.

DESIGN

This is a prospective cohort study with a propensity score-matched comparative effectiveness evaluation.

SETTINGS

This study was conducted in Washington State hospitals in the Surgical Care Outcomes Assessment Program from 2012 to 2015.

PATIENTS

Adults undergoing elective colorectal surgery were selected.

INTERVENTIONS

Surgeons used a preoperative checklist that recommended that patients take oral immunonutrition (237 mL, 3 times daily) for 5 days before elective colorectal resection.

MAIN OUTCOME MEASURES

Serious adverse events (infection, anastomotic leak, reoperation, and death) and prolonged length of stay were the primary outcomes measured.

RESULTS

Three thousand three hundred seventy-five patients (mean age 59.9 ± 15.2 years, 56% female) underwent elective colorectal surgery. Patients receiving immunonutrition more commonly were in a higher ASA class (III-V, 44% vs 38%; p = 0.01) or required an ostomy (18% vs 14%; p = 0.02). The rate of serious adverse events was 6.8% vs 8.3% (p = 0.25) and the rate of prolonged length of stay was 13.8% vs 17.3% (p = 0.04) in those who did and did not receive immunonutrition. After propensity score matching, covariates were similar among 960 patients. Although differences in serious adverse events were nonsignificant (relative risk, 0.76; 95% CI, 0.49-1.16), prolonged length of stay (relative risk, 0.77; 95% CI, 0.58-1.01 p = 0.05) was lower in those receiving immunonutrition.

LIMITATIONS

Patient compliance with the intervention was not measured. Residual confounding, including surgeon-level heterogeneity, may influence estimates of the effect of immunonutrition.

CONCLUSIONS

Reductions in prolonged length of stay, likely related to fewer complications, support the use of immunonutrition in quality improvement initiatives related to elective colorectal surgery. This population-based study supports previous trials of immunonutrition, but shows a lower magnitude of benefit, perhaps related to compliance or a lower rate of adverse events, highlighting the value of community-based assessments of comparative effectiveness.

Genome-wide association reveals that common genetic variation in the kallikrein-kinin system is associated with serum L-arginine levels

L-arginine is the essential precursor of nitric oxide, and is involved in multiple key physiological processes, including vascular and immune function. The genetic regulation of blood L-arginine levels is largely unknown. We performed a genome-wide association study (GWAS) to identify genetic factors determining serum L-arginine levels, amongst 901 Europeans and 1,394 Indian Asians. We show that common genetic variations at the KLKB1 and F12 loci are strongly associated with serum L-arginine levels. The G allele of single nucleotide polymorphism (SNP) rs71640036 (T/G) in KLKB1 is associated with lower serum L-arginine concentrations (10 µmol/l per allele copy, p=1×10-24), while allele T of rs2545801 (T/C) near the F12 gene is associated with lower serum L-arginine levels (7 µmol/l per allele copy, p=7×10-12). Together these two loci explain 7 % of the total variance in serum L-arginine concentrations. The associations at both loci were replicated in independent cohorts with plasma L-arginine measurements (p<0.004). The two sentinel SNPs are in nearly complete LD with the nonsynonymous SNP rs3733402 at KLKB1 and the 5'-UTR SNP rs1801020 at F12, respectively. SNPs at both loci are associated with blood pressure. Our findings provide new insight into the genetic regulation of L-arginine and its potential relationship with cardiovascular risk.

Argininemia and plasma arginine bioavailability - predictive factors of mortality in the severe trauma patients?

BACKGROUND

Arginine is an amino acid determinant in the metabolic, immune and reparative responses to severe trauma. The present study aims to determine argininemia and plasma arginine bioavailability (PAB) in critical trauma patients and to analyze its correlation with prognosis.

METHODS

A prospective study of 23 critical trauma patients was undertaken. Aminoacidemias were determined, by ion exchange chromatography, at admission and in the first and third days and compared with those of 11 healthy individuals. PAB was calculated. Severity indexes and outcome parameters were recorded.

RESULTS

Values of argininemia, citrullinemia and ornithinemia at the admission were significantly lower than those of the controls (arginine: 41.2 ± 20.6 versus 56.1 ± 11.9 μmol/L, P = 0.034). Hipoargininemia (<60 μmol/L) prevalence was 82.6 %. Mean PAB was 62.4 ± 25.6 %. Argininemia < 26 μmol/L constituted a significant predictive factor of in-hospital mortality [n = 4 (17.4 %); 75 versus 15.8 %, P = 0.04; odds ratio = 4.7; accuracy = 87 %] and lower actuarial survival (63.5 ± 43.9 versus 256.1 ± 33.3 days, P = 0.031). PAB <42 % [n = 6 (26.1 %)] was associated with higher lactacidemia levels (P = 0.033), higher in-hospital mortality (66.7 versus 11.8 %, P = 0.021; odds ratio = 5.7, accuracy = 82.6 %) and lower actuarial survival (87.2 ± 37.5 versus 261.4 ± 34.7 days, n.s.). Probability of in-hospital mortality was inversely and significantly related with PAB [61.8 ± 8.8 % (95 % CI 50.8-72.7) when PAB <41 % and 2.8 ± 1.9 % (95 % CI 1.9-8.3) when PAB > 81 %, P = 0.0001]. Charlson's index ≥1, APACHE II ≥19.5, SOFA ≥7.5, and glutaminemia < 320 μmol/L were also predictive factors of actuarial survival.

CONCLUSIONS

Those results confirm the high prevalence of arginine depletion in severe trauma patients and the relevance of argininemia and PAB as predictive factors of mortality in this context.

Monocyte polarization in children with falciparum malaria: relationship to nitric oxide insufficiency and disease severity

We earlier established that nitric oxide (NO) is protective against severe malaria and that arginine and NO levels are reduced in malaria patients. We now show that an M2-like blood monocyte phenotype is significantly associated with hypoargininemia, NO insufficiency, and disease severity in Tanzanian children with falciparum malaria. Compared to control children (n = 106), children with moderately severe (n = 77) and severe falciparum malaria (n = 129) had significantly higher mononuclear cell arginase 1 mRNA, protein, and enzyme activity; lower NOS2 mRNA; lower plasma arginine; and higher plasma IL-10, IL-13, and IL-4. In addition, monocyte CD206 and CD163 and plasma soluble CD163 were elevated. Multivariate logistic regression analysis revealed a significant correlation of risk of severe malaria with both plasma IL-10 and soluble CD163 levels. Monocyte M2 skewing likely contributes to NO bioinsufficiency in falciparum malaria in children. Treatments that reverse the M2 polarization may have potential as adjunctive treatment for malaria.

Alterations in whole-body arginine metabolism in chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a condition characterized by systemic low-grade inflammation that could increase the production of nitric oxide (NO), of which arginine is the sole precursor. Arginine is derived from the breakdown of protein and through the conversion of citrulline to arginine (de novo arginine production).

OBJECTIVE

Our objective was to study whole-body arginine and citrulline and related metabolism in stable COPD patients.

DESIGN

With the use of stable isotope methodology, we studied whole-body arginine and citrulline rates of appearance, de novo arginine (citrulline-to-arginine flux) and NO (arginine-to-citrulline flux) production, protein synthesis and breakdown rates, and plasma amino acid concentrations in a heterogeneous group of patients with moderate-to-severe COPD [n = 23, mean ± SE age: 65 ± 2 y, forced expiratory volume in 1 s (FEV1): 40% ± 2% of predicted], and a group of healthy older adults (n = 19, mean ± SE age: 64 ± 2 y, FEV1: 95% ± 4% of predicted).

RESULTS

Although plasma arginine and citrulline concentrations were comparable between COPD patients and controls, whole-body arginine (P = 0.015) and citrulline (P = 0.026) rates of appearance were higher in COPD patients and related to a 57% greater de novo arginine production (P < 0.0001). Despite a higher whole-body arginine clearance in COPD patients (P < 0.0001), we found no difference in NO production.

CONCLUSION

In stable patients with moderate-to-severe COPD, endogenous arginine production is upregulated to support a higher arginine utilization that is unrelated to whole-body NO production. This trial was registered at clinicaltrials.gov as NCT01173354 and NCT01172314.

Reduced arginine availability and nitric oxide synthesis in cancer is related to impaired endogenous arginine synthesis

Reduced plasma arginine (ARG) concentrations are found in various types of cancer. ARG and its product nitric oxide (NO) are important mediators in the immune function and the defense against tumour cells. It remains unclear whether the diminished systemic ARG availability in cancer is related to insufficient endogenous ARG synthesis, negatively affecting NO synthesis, and whether a dietary amino acid mixture is able to restore this. In 13 patients with advanced non-small cell lung cancer (NSCLC) and 11 healthy controls, whole body ARG and CIT (citrulline) rates of appearance were measured by stable isotope methodology before and after intake of a mixture of amino acids as present in whey protein. The conversions of CIT to ARG (indicator of de novo ARG synthesis) and ARG to CIT (marker of NO synthesis), and ARG clearance (reflecting ARG disposal capacity) were calculated. Plasma isotopic enrichments and amino acid concentrations were measured by LC-MS/MS. Conversions of CIT to ARG and ARG to CIT (P<0.05), and CIT rate of appearance (P=0.07) were lower in NSCLC. ARG rate of appearance and clearance were comparable suggesting no enhanced systemic ARG production and disposal capacity in NSCLC. After intake of the mixture, ARG rate of appearance and concentration increased (P<0.001), and ARG to CIT conversion was restored in NSCLC. In conclusion, an impaired endogenous ARG synthesis plays a role in the reduced systemic ARG availability and NO synthesis in advanced NSCLC. Nutritional approaches may restore systemic ARG availability and NO synthesis in cancer, but the clinical implication remains unclear.

Biochemical and biological activity of arginine deiminase from Streptococcus pyogenes M22

Streptococcus pyogenes (group A Streptococcus; GAS) is an important gram-positive extracellular bacterial pathogen responsible for a number of suppurative infections. This micro-organism has developed complex virulence mechanisms to avoid the host’s defenses. We have previously reported that SDSC from GAS type M22 causes endothelial-cell dysfunction, and inhibits cell adhesion, migration, metabolism, and proliferation in a dose-dependent manner, without affecting cell viability. This work aimed to isolate and characterize a component from GAS type M22 supernatant that suppresses the proliferation of endothelial cells (EA.hy926). In the process of isolating a protein possessing antiproliferative activity we identified arginine deiminase (AD). Further study showed that this enzyme is most active at pH 6.8. Calculating Km and Vmax gave the values of 0.67 mmol·L–1 and 42 s−1, respectively. A distinctive feature of AD purified from GAS type M22 is that its optimum activity and the maximal rate of the catalytic process is close to neutral pH by comparison with enzymes from other micro-organisms. AD from GAS type M22 suppressed the proliferative activity of endothelial cells in a dose-dependent mode. At the same time, in the presence of AD, the proportion of cells in G0/G1 phase increased. When l-Arg was added at increasing concentrations to the culture medium containing AD (3 μg·mL–1), the enzyme’s capacity to inhibit cell proliferation became partially depressed. The proportion of cells in phases S/G2 increased concomitantly, although the cells did not fully recover their proliferation activity. This suggests that AD from GAS type M22 has potential for the suppression of excessive cell proliferation.

The role of the arginine metabolome in pain: implications for sickle cell disease

Sickle cell disease (SCD) is the most common hemoglobinopathy in the US, affecting approximately 100,000 individuals in the US and millions worldwide. Pain is the hallmark of SCD, and a subset of patients experience pain virtually all of the time. Of interest, the arginine metabolome is associated with several pain mechanisms highlighted in this review. Since SCD is an arginine deficiency syndrome, the contribution of the arginine metabolome to acute and chronic pain in SCD is a topic in need of further attention. Normal arginine metabolism is impaired in SCD through various mechanisms that contribute to endothelial dysfunction, vaso-occlusion, pulmonary complications, risk of leg ulcers, and early mortality. Arginine is a semiessential amino acid that serves as a substrate for protein synthesis and is the precursor to nitric oxide (NO), polyamines, proline, glutamate, creatine, and agmatine. Since arginine is involved in multiple metabolic processes, a deficiency of this amino acid has the potential to disrupt many cellular and organ functions. NO is a potent vasodilator that is depleted in SCD and may contribute to vaso-occlusive pain. As the obligate substrate for NO production, arginine also plays a mechanistic role in SCD-related pain, although its contribution to pain pathways likely extends beyond NO. Low global arginine bioavailability is associated with pain severity in both adults and children with SCD as well as other non-SCD pain syndromes. Preliminary clinical studies of arginine therapy in SCD demonstrate efficacy in treating acute vaso-occlusive pain, as well as leg ulcers and pulmonary hypertension. Restoration of arginine bioavailability through exogenous supplementation of arginine is, therefore, a promising therapeutic target. Phase II clinical trials of arginine therapy for sickle-related pain are underway and a Phase III randomized controlled trial is anticipated in the near future.

L-arginine, an active component of salmon milt nucleoprotein, promotes thermotolerance via Sirtuin in Caenorhabditis elegans

We previously showed that salmon milt nucleoprotein (NP) promotes thermotolerance in Caenorhabditis elegans; however, the active component and physiological mechanism of this effect has remained unclear. l-arginine (AR) is a major component of protamine and thus it has been proposed as the possible active component of NP. In this study, the viability of C. elegans treated with AR under heat stress was assessed and AR was shown to extend the survival term of the heat-stressed organisms. Additionally, AR was shown to restore the thrashing movement of the worms that is suppressed by heat stress. Treatment with AR was furthermore shown to promote thermotolerance in a DAF-16- and SIR-2.1-dependent manner, where DAF-16 and SIR-2.1 are homologs of FoxO and SirT1, respectively. Taken together, these data suggest that AR is one of the active components of NP and promotes thermotolerance via the activation of DAF-16 and SIR-2.1.

Autosomal-Recessive Intellectual Disability with Cerebellar Atrophy Syndrome Caused by Mutation of the Manganese and Zinc Transporter Gene SLC39A8

Manganese (Mn) and zinc (Zn) are essential divalent cations used by cells as protein cofactors; various human studies and animal models have demonstrated the importance of Mn and Zn for development. Here we describe an autosomal-recessive disorder in six individuals from the Hutterite community and in an unrelated Egyptian sibpair; the disorder is characterized by intellectual disability, developmental delay, hypotonia, strabismus, cerebellar atrophy, and variable short stature. Exome sequencing in one affected Hutterite individual and the Egyptian family identified the same homozygous variant, c.112G>C (p.Gly38Arg), affecting a conserved residue of SLC39A8. The affected Hutterite and Egyptian individuals did not share an extended common haplotype, suggesting that the mutation arose independently. SLC39A8 is a member of the solute carrier gene family known to import Mn, Zn, and other divalent cations across the plasma membrane. Evaluation of these two metal ions in the affected individuals revealed variably low levels of Mn and Zn in blood and elevated levels in urine, indicating renal wasting. Our findings identify a human Mn and Zn transporter deficiency syndrome linked to SLC39A8, providing insight into the roles of Mn and Zn homeostasis in human health and development.