Substitution of high-dose sucrose with fructose in high-fat diets resulted in higher plasma concentrations of aspartic acid, cystine, glutamic acid, ornithine and phenylalanine, and higher urine concentrations of arginine and citrulline.

High fructose intake has been shown to increase circulating alanine transaminase in humans, which could reflect damage to the liver by fructose but could also be linked to higher level of transamination of amino acids in liver. Therefore, we hypothesized that a diet with high content of fructose would affect the amino acid composition in rat plasma and urine differently from a diet with high sucrose content. Because high intake of sucrose and fructose is often accompanied with high intake of saturated fat in the Western-style diet, we wanted to compare the effects of high fructose/sucrose in diets with normal or high content of coconut oil on individual free amino acids plasma and urine. Male Wistar rats were fed diets with normal (10 wt%) or high (40 wt%) content of sucrose or fructose, with normal or high fat content (7 or 22 wt%) and 20 wt% protein (casein). Rats fed high-fructose high-fat diet had higher plasma concentrations of aspartic acid, cystine, glutamic acid, ornithine, and phenylalanine and higher urine concentrations of arginine and citrulline when compared to rats fed high-sucrose high-fat diet. Substituting normal content of sucrose with fructose in the diets had little impact on amino acids in plasma and urine. Serum concentrations of alanine transaminase, aspartate transaminase, and creatinine, and urine cystatin C and T cell immunoglobulin mucin-1 concentrations were comparable between the groups and within normal ranges. To conclude, substituting high-dose sucrose with high-dose fructose in high-fat diets affected amino acid compositions in plasma and urine.

Ruminal microbes of adult sheep do not degrade extracellular l-citrulline.

This study determined whether extracellular citrulline is degraded by ruminal bacteria of sheep. In the first experiment, whole rumen fluid (3 mL) from six adult Suffolk sheep was incubated at 37 °C with 5 mM l-glutamine (Gln), l-glutamate (Glu), l-arginine (Arg), or l-citrulline (Cit) for 0, 0.5, 1, and 2 h or with 0, 0.5, 2, or 5 mM Gln, Glu, Arg, or Cit for 2 h. An aliquot (50 µL) of the incubation solution was collected at the predetermined time points for amino acids (AA) analyses. Results showed extensive hydrolysis of Gln into Glu and ammonia, of Arg into l-ornithine and l-proline, but little or no degradation of extracellular Cit or Glu by ruminal microbes. In the second experiment, six adult Suffolk sheep were individually fed each of three separate supplements (8 g Gln , Cit, or urea) on three separate days along with regular feed (800 g/animal). Blood (2 mL) was sampled from the jugular vein prior to feeding (time 0) and at 0.5, 1, 2, and 4 h after consuming the supplement. Plasma was analyzed for AA, glucose, ammonia, and urea. The concentrations of Cit in the plasma of sheep consuming this AA increased (P < 0.001) by 117% at 4 h and those of Arg increased by 23% at 4 h, compared with the baseline values. Urea or Gln feeding did not affect (P > 0.05) the concentrations of Cit or Arg in plasma. These results indicate that Cit is not metabolized by ruminal microbes of sheep and is, therefore, absorbed as such by the small intestine and used for the synthesis of Arg by extrahepatic tissues.

Modulation of Free Amino Acid Profile in Healthy Humans Administered with Mastiha Terpenes. An Open-Label Trial.

We aimed to explore whether plasma-free amino acids are modified in response to terpenes administration in healthy humans. In this open-label, single-arm acute trial, seventeen healthy male volunteers were administered with a naturally occurring product of known terpenes-namely mastiha-after overnight fasting. Blood samples were collected at different time points before and after ingestion. We aimed at identifying and quantifying 60 free amino acids in plasma applying Gas Chromatography-Mass Spectrometry. A total of 24 free amino acids were quantified. Branched-chain valine significantly decreased 4 h post-ingestion, whereas proline decreased at 6 h and ornithine at 2 h, compared to 0 h. These novel findings demonstrate that free amino acids levels are modulated in response to terpenes intake in healthy subjects.

Reversal of cystoid macular edema in gyrate atrophy patients.

PURPOSE: This study reports the presentation of two families with gyrate atrophy (GA). The aim of this study was to characterize the potential effect of therapeutic regimens on macular edema. METHODS: Two unrelated patients with GA were studied for the potential effect of low protein diet (≤ 0.8 g/kg/d), and oral administration of pyridoxine (500 mg/day), on serum ornithine levels, best corrected visual acuity (BCVA), slit-lamp, OCT, and auto-fluorescence findings. Blood samples for DNA, mRNA, and exons of the OAT gene were screened for mutations and splicing effect when relevant. RESULTS: At presentation, both patients manifested typical ophthalmic features of GA including cystoid macular edema (CME). One patient also exhibited optic nerve head hamartoma. Following treatment ornithine levels have lessened, BCVA improved, and central macular thickness (CMT) markedly decreased in all four studied eyes. The molecular pathologic features included a novel splice site mutation (c.900+1G>A). CONCLUSIONS: We have identified a novel mutation and two formerly described mutations in patients with GA. Of them, one patient comprised an unusual phenotype including bilateral astrocytic hamartomas. We have recognized for the first time improvement in CME following treatment with low protein intake and pyridoxine supplement. This finding may have significance in the understanding of treatment options for macular edema regardless of underlying etiology.

The LargPAD Trial: Phase IIA evaluation of l-arginine infusion in patients with peripheral arterial disease.

OBJECTIVE: Endothelial function is improved by l-arginine (l-arg) supplementation in preclinical and clinical studies of mildly diseased vasculature; however, endothelial function and responsiveness to l-arg in severely diseased arteries is not known. Our objective was to evaluate the acute effects of catheter-directed l-arg delivery in patients with chronic lower extremity ischemia secondary to peripheral arterial disease. METHODS: The study enrolled 22 patients (45% male) with peripheral arterial disease (mean age, 62 years) requiring lower extremity angiography. Endothelium-dependent relaxation of patent but atherosclerotic superficial femoral arteries was measured using a combination of intravascular ultrasound (IVUS) imaging and a Doppler FloWire (Volcano Corporation, Rancho Cordova, Calif) during the infusion of incremental acetylcholine (10-6 to 10-4 molar concentration) doses. Patients received 50 mg (n = 3), 100 mg (n = 10), or 500 mg (n = 9) l-arg intra-arterially, followed by repeat endothelium-dependent relaxation measurement (limb volumetric flow). IVUS-derived virtual histology of the culprit vessel was also obtained. Endothelium-independent relaxation was measured using a nitroglycerin infusion. Levels of nitrogen oxides and arginine metabolites were measured by chemiluminescence and mass spectrometry, respectively. RESULTS: Patients tolerated limb l-arg infusion well. Serum arginine and ornithine levels increased by 43.6% ± 13.0% and 23.2% ± 10.3%, respectively (P < .005), and serum nitrogen oxides increased by 85% (P < .0001) after l-arg infusion. Average vessel area increased by 6.8% ± 1.3% with l-arg infusion (acetylcholine 10-4; P < .0001). Limb volumetric flow increased in all patients and was greater with l-arg supplementation by 130.9 ± 17.6, 136.9 ± 18.6, and 172.1 ± 24.8 mL/min, respectively, for each cohort. Maximal effects were seen with l-arg at 100 mg (32.8%). Arterial smooth muscle responsiveness to nitroglycerin was intact in all vessels (endothelium-independent relaxation, 137% ± 28% volume flow increase). IVUS-derived virtual histology indicated plaque volume was 14 ± 1.3 mm3/cm, and plaque stratification revealed a predominantly fibrous morphology (46.4%; necrotic core, 28.4%; calcium, 17.4%; fibrolipid, 6.6%). Plaque morphology did not correlate with l-arg responsiveness. CONCLUSIONS: Despite extensive atherosclerosis, endothelial function in diseased lower extremity human arteries can be enhanced by l-arg infusion secondary to increased nitric oxide bioactivity. Further studies of l-arg as a therapeutic modality in patients with endothelial dysfunction (ie, acute limb ischemia) are warranted.

Acute Citrulline-Malate Supplementation and High-Intensity Cycling Performance.

Cunniffe, B, Papageorgiou, M, O'Brien, B, Davies, NA, Grimble, GK, and Cardinale, M. Acute citrulline-malate supplementation and high-intensity cycling performance. J Strength Cond Res 30(9): 2638-2647, 2016-Dietary L-citrulline-malate (CM) consumption has been suggested to improve skeletal muscle metabolism and contractile efficiency, which would be expected to predispose exercising individuals to greater fatigue resistance. The purpose of this study was to examine the effects of CM supplementation on acid-base balance and high-intensity exercise performance. In a double-blind, placebo-controlled, crossover study, 10 well-trained males consumed either 12 g of CM (in 400 ml) or lemon sugar-free cordial (placebo [PL]) 60 minutes before completion of 2 exercise trials. Each trial consisted of subjects performing 10 (×15 seconds) maximal cycle sprints (with 30-second rest intervals) followed by 5 minutes recovery before completing a cycle time-to-exhaustion test (TTE) at 100% of individual peak power (PP). Significant increases in plasma concentrations of citrulline (8.8-fold), ornithine (3.9-fold), and glutamine (1.3-fold) were observed 60 minutes after supplementation in the CM trial only (p ≤ 0.05) and none of the subjects experienced gastrointestinal side-effects during testing. Significantly higher exercise heart rates were observed in CM condition (vs. PL) although no between trial differences in performance related variables (TTE: [120 ± 61 seconds CM vs. 113 ± 50 seconds PL]), PP or mean power, ([power fatigue index: 36 ± 16% CM vs. 28 ± 18% PL]), subjective rating of perceived exertion or measures of acid-base balance (pH, lactate, bicarbonate, base-excess) were observed (p > 0.05). This study demonstrated that acute supplementation of 12 g CM does not provide acute ergogenic benefits using the protocol implemented in this study in well-trained males.

Arginine behaviour after arginine or citrulline administration in older subjects.

Arginine (ARG) and its precursor citrulline (CIT) are popular dietary supplements, especially for the elderly. However, age-related reductions in lean body mass and alterations in organ functions could change their bioavailability. Pharmacokinetics and tolerance to amino acid (AA) loads are poorly documented in elderly subjects. The objective here was to characterise the plasma kinetics of CIT and ARG in a single-dosing study design. Eight fasting elderly men underwent two separate isomolar oral loading tests (10 g of CIT or 9·94 g of ARG). Blood was withdrawn over an 8-h period to measure plasma AA concentrations. Only CIT, ornithine and ARG plasma concentrations were changed. Volume of distribution was not dependent on AA administered. Conversely, parameters related to ARG kinetics were strongly dependent on AA administered: after ARG load, elimination was higher (ARG>CIT; P=0·041) and admission period+time at peak concentration was lower (ARG

Citrulline and Nonessential Amino Acids Prevent Fructose-Induced Nonalcoholic Fatty Liver Disease in Rats.

BACKGROUND: Fructose induces nonalcoholic fatty liver disease (NAFLD). Citrulline (Cit) may exert a beneficial effect on steatosis. OBJECTIVE: We compared the effects of Cit and an isonitrogenous mixture of nonessential amino acids (NEAAs) on fructose-induced NAFLD. METHODS: Twenty-two male Sprague Dawley rats were randomly assigned into 4 groups (n = 4-6) to receive for 8 wk a 60% fructose diet, either alone or supplemented with Cit (1 g · kg(-1) · d(-1)), or an isonitrogenous amount of NEAAs, or the same NEAA-supplemented diet with starch and maltodextrin instead of fructose (controls). Nutritional and metabolic status, liver function, and expression of genes of hepatic lipid metabolism were determined. RESULTS: Compared with controls, fructose led to NAFLD with significantly higher visceral fat mass (128%), lower lean body mass (-7%), insulin resistance (135%), increased plasma triglycerides (TGs; 67%), and altered plasma amino acid concentrations with decreased Arg bioavailability (-27%). This was corrected by both NEAA and Cit supplementation. Fructose caused a 2-fold increase in the gene expression of fatty acid synthase (Fas) and 70% and 90% decreases in that of carnitine palmitoyl-transferase 1a and microsomal TG transfer protein via a nearly 10-fold higher gene expression of sterol regulatory element-binding protein-1c (Srebp1c) and carbohydrate-responsive element-binding protein (Chrebp), and a 90% lower gene expression of peroxisome proliferator-activated receptor α (Ppara). NEAA or Cit supplementation led to a Ppara gene expression similar to controls and decreased those of Srebp1c and Chrebp in the liver by 50-60%. Only Cit led to Fas gene expression and Arg bioavailability similar to controls. CONCLUSION: In our rat model, Cit and NEAAs effectively prevented fructose-induced NAFLD. On the basis of literature data and our findings, we propose that NEAAs may exert their effects specifically on the liver, whereas Cit presumably acts at both the hepatic and whole-body level, in part via improved peripheral Arg metabolism.

Strategies to rescue the consequences of inducible arginase-1 deficiency in mice.

Arginase-1 catalyzes the conversion of arginine to ornithine and urea, which is the final step of the urea cycle used to remove excess ammonia from the body. Arginase-1 deficiency leads to hyperargininemia in mice and man with severe lethal consequences in the former and progressive neurological impairment to varying degrees in the latter. In a tamoxifen-induced arginase-1 deficient mouse model, mice succumb to the enzyme deficiency within 2 weeks after inducing the knockout and retain <2 % enzyme in the liver. Standard clinical care regimens for arginase-1 deficiency (low-protein diet, the nitrogen-scavenging drug sodium phenylbutyrate, ornithine supplementation) either failed to extend lifespan (ornithine) or only minimally prolonged lifespan (maximum 8 days with low-protein diet and drug). A conditional, tamoxifen-inducible arginase-1 transgenic mouse strain expressing the enzyme from the Rosa26 locus modestly extended lifespan of neonatal mice, but not that of 4-week old mice, when crossed to the inducible arginase-1 knockout mouse strain. Delivery of an arginase-1/enhanced green fluorescent fusion construct by adeno-associated viral delivery (rh10 serotype with a strong cytomegalovirus-chicken ß-actin hybrid promoter) rescued about 30% of male mice with lifespan prolongation to at least 6 months, extensive hepatic expression and restoration of significant enzyme activity in liver. In contrast, a vector of the AAV8 serotype driven by the thyroxine-binding globulin promoter led to weaker liver expression and did not rescue arginase-1 deficient mice to any great extent. Since the induced arginase-1 deficient mouse model displays a much more severe phenotype when compared to human arginase-1 deficiency, these studies reveal that it may be feasible with gene therapy strategies to correct the various manifestations of the disorder and they provide optimism for future clinical studies.

Effect of long-term treatment of L-ornithine on visual function and retinal histology in the rats.

L-Ornithine is a non-proteinogenic amino acid, abundant in freshwater clams and commercially available as an oral nutritional supplement. L-Ornithine is metabolized by ornithine-δ-aminotransferase. Deficiency of this enzyme causes gyrate atrophy of the choroid and retina, an autosomal recessive hereditary disease characterized by the triad of progressive chorioretinal degeneration, early cataract formation, and type II muscle fiber atrophy, with hyperornithinemia. However, it is unknown whether long-term L-ornithine supplementation affects visual function and retinal histology. The aim of the present study is to determine the effect of long-term supplementation of excess amounts of L-ornithine on visual function and retinal histology in rats. Male Brown Norway rats at six weeks of age were allowed free access to chow containing 4% (w/w) L-ornithine (the high ornithine diet) or that containing 4% (w/w) casein (the control diet) for 49 weeks. The dose of L-ornithine calculated from the food intake was approximately 0.8 g/d/animal, which was 100 times higher than the recommended dose for healthy humans. The amplitude of the a-wave of the scotopic rod-cone electroretinogram and the number of cells in the ganglion cell layer in the L-ornithine-treated group were larger than those in the control group 49 weeks after initiating the test diet. No functional or histological damage to the retina was seen up to 49 weeks after the start of the high-ornithine diet. The present study demonstrated that long-term supplementation of very high doses of L-ornithine for at least 49 weeks did not induce retinal damage.

Safety of long-term dietary supplementation with L-arginine in pigs.

This study was conducted with a swine model to determine the safety of long-term dietary supplementation with L-arginine-HCl or L-arginine free base. Beginning at 30 days of age, pigs were fed a corn- and soybean meal-based diet (31.5 g/kg body weight/day) supplemented with 0, 1.21, 1.81 or 2.42 % L-arginine-HCl (Experiment 1) or with 0, 1, 1.5 or 2 % L-arginine (Experiment 2). The supplemental doses of 0, 1, 1.5, and 2 % L-arginine provided pigs with 0, 315, 473, and 630 mg L-arginine/kg body weight/day, respectively, which were equivalent to 0, 286, 430, and 573 mg L-arginine/kg body weight/day, respectively, in humans. At 121 days of age (91 days after initiation of supplementation), blood samples were obtained from the jugular vein of pigs at 1 and 4 h after feeding for hematological and clinical chemistry tests. Dietary supplementation with L-arginine increased plasma concentrations of arginine, ornithine, proline, albumin and reticulocytes, while reducing plasma concentrations of ammonia, free fatty acids, triglyceride, cholesterol, and neutrophils. L-Arginine supplementation enhanced protein gain and reduced white-fat deposition in the body. Other variables in standard hematology and clinical chemistry tests, serum concentrations of insulin, growth hormone and insulin-like growth factor-I did not differ among all the groups of pigs. These results indicate that dietary supplementation with L-arginine (up to 630 mg/kg body weight/day) is safe in pigs for at least 91 days. Our findings help guide clinical studies to determine the safety of long-term oral administration of L-arginine to humans.

Dietary arginine affects energy metabolism through polyamine turnover in juvenile Atlantic salmon (Salmo salar).

In the present study, quadruplicate groups of juvenile Atlantic salmon (Salmo salar) were fed plant protein-based diets with increasing arginine inclusions (range 28·8-37·4 g/kg DM) to investigate whether arginine supplementation affects growth and lipid accumulation through an elevated polyamine turnover. Dietary lysine was held at a constant concentration, just below the requirement. All other amino acids were balanced and equal in the diets. Arginine supplementation increased protein and fat accretion, without affecting the hepatosomatic or visceralsomatic indices. Dietary arginine correlated with putrescine in the liver (R 0·78, P= 0·01) and with ornithine in the muscle, liver and plasma (P= 0·0002, 0·003 and 0·0002, respectively). The mRNA of ornithine decarboxylase, the enzyme producing putrescine, was up-regulated in the white adipose tissue of fish fed the high-arginine inclusion compared with those fed the low-arginine diet. Concomitantly, spermidine/spermine-(N1)-acetyltransferase, the rate-limiting enzyme for polyamine turnover that consumes acetyl-CoA, showed an increased activity in the liver of fish fed the arginine-supplemented diets. In addition, lower acetyl-CoA concentrations were observed in the liver of fish fed the high-arginine diet, while ATP, which is used in the process of synthesising spermidine and spermine, did not show a similar trend. Gene expression of the rate-limiting enzyme for ß-oxidation of long-chain fatty acids, carnitine palmitoyl transferase-1, was up-regulated in the liver of fish fed the high-arginine diet. Taken together, the data support that increased dietary arginine activates polyamine turnover and ß-oxidation in the liver of juvenile Atlantic salmon and may act to improve the metabolic status of the fish.

Hyperammonemia in a patient with late-onset ornithine carbamoyltransferase deficiency.

Ornithine carbamoyltransferase (OTC) deficiency is a urea cycle disorder that causes the accumulation of ammonia, which can lead to encephalopathy. Adults presenting with hyperammonemia who are subsequently diagnosed with urea cycle disorders are rare. Herein, we report a case of a late-onset OTC deficient patient who was successfully treated with arginine, benzoate and hemodialysis. A 59-yr-old man was admitted to our hospital with progressive lethargy and confusion. Although hyperammonemia was suspected as the cause of the patient's mental changes, there was no evidence of chronic liver disease. A plasma amino acid and urine organic acid analysis revealed OTC deficiency. Despite the administration of a lactulose enema, the patient's serum ammonia level increased and he remained confused, leading us to initiate acute hemodialysis. After treatment with arginine, sodium benzoate and hemodialysis, the patient's serum ammonia level stabilized and his mental status returned to normal.

Hyperammonemia in a Patient with Late-Onset Ornithine Carbamoyltransferase Deficiency

Ornithine carbamoyltransferase (OTC) deficiency is a urea cycle disorder that causes the accumulation of ammonia, which can lead to encephalopathy. Adults presenting with hyperammonemia who are subsequently diagnosed with urea cycle disorders are rare. Herein, we report a case of a late-onset OTC deficient patient who was successfully treated with arginine, benzoate and hemodialysis. A 59-yr-old man was admitted to our hospital with progressive lethargy and confusion. Although hyperammonemia was suspected as the cause of the patient's mental changes, there was no evidence of chronic liver disease. A plasma amino acid and urine organic acid analysis revealed OTC deficiency. Despite the administration of a lactulose enema, the patient's serum ammonia level increased and he remained confused, leading us to initiate acute hemodialysis. After treatment with arginine, sodium benzoate and hemodialysis, the patient's serum ammonia level stabilized and his mental status returned to normal.

Retinal risks of high-dose ornithine supplements: a review.

We reviewed the literature on ornithine supplementation and related topics. Nutritionists and physicians have reported that ornithine supplementation is useful. Paediatricians and biochemists have reported that ornithine is supplemented for NH(3) detoxification in the hyperornithinaemia-hyperammonaemia-homocitrullinuria (HHH) syndrome. In contrast, ophthalmic researchers have reported retinotoxicity associated with high-dose ornithine. In vivo and in vitro experiments have shown that high concentrations of ornithine or its metabolites are toxic to the retinal pigment epithelial (RPE) cells. Long-term (exceeding a few years) and high concentrations (exceeding 600 µmol/l) of ornithine in the blood induce retinal toxicity in gyrate atrophy of the choroid and retina (GA). Intermittent high levels of ornithine do not lead to retinal lesions. Constant blood ornithine levels between 250 and 600 µmol/l do not induce retinal lesions or cause a very slowly progressive retinal degeneration. Blood ornithine levels below 250 µmol/l do not produce retinal alteration. We concluded that short-term, low-dose or transient high-dose ornithine intake is safe for the retina; its nutritional usefulness and effect on NH(3) detoxification are supported by many researchers, but the effect may be limited; and long-term, high-dose ornithine intake may be risky for the retina. Patients with GA should avoid taking ornithine; amino acid supplementation should be administered carefully for patients with the HHH syndrome, relatives of patients with GA (heterozygotes) and subjects with RPE lesions; and blood ornithine levels and retinal conditions should be evaluated in individuals taking long-term, high-dose ornithine.

Enternal [corrected] arginine supplementation stimulates DNA synthesis in skin donor wound.

BACKGROUND & AIMS: Arginine infusion has been demonstrated to increase wound protein deposition; however, the effects of its enteral supplementation on wound cell proliferation have not been studied. METHODS: Skin donor wound was created on the back of rabbits. The rabbits were randomly assigned to receive a control enteral diet, or the control enteral diet with supplemental arginine. On day 5 L-[ring-(13)C(6)]phenylalanine and D-[U-(13)C(6)]glucose were infused to measure the fractional synthetic rates of DNA (reflecting cell proliferation) and protein in the wound. RESULTS: In the arginine group (n = 6) plasma arginine concentration was increased to 2.8 fold that in the control group (n = 8), which was a less increase than that of 6.4 fold for ornithine. Wound DNA fractional synthetic rate was 5.37 ± 0.21%/day in the arginine group, greater (p < 0.05) than that of 4.27 ± 0.35%/day in the control group. Protein fractional synthetic rates in the wound were comparable between the two groups. CONCLUSIONS: Enternal arginine supplementation increased wound DNA synthesis, which is anticipated to promote cell proliferation for wound healing. The failure of enteral arginine to stimulate protein synthesis is explained by limited increase in plasma arginine. Decreased availability of essential amino acids, especially branched chain amino acids, may also contribute to the failure to stimulate protein synthesis.

Gyrate atrophy of the choroid and retina with hyperornithinemia, cystinuria and lysinuria responsive to vitamin B6.

In this report, an 8-year-old girl is presented with the complaint of progressive night blindness. The authors have performed eye funduscopy, which showed chorioretinal atrophy in gyrate shape. A high level of plasma ornithine was determined. Urinary excretion of ornithine as well as lysine and cystine were increased. Patient was treated with high dose pyridoxine supplement (500 mg/dl). The night blindness condition of the patient improved. After 1 month of pyridoxine therapy ornithine level of her plasma was successfully reduced and blindness improved.

Enteral arginase II provides ornithine for citrulline synthesis.

The synthesis of citrulline from arginine in the small intestine depends on the provision of ornithine. To test the hypothesis that arginase II plays a central role in the supply of ornithine for citrulline synthesis, the contribution of dietary arginine, glutamine, and proline was determined by utilizing multitracer stable isotope protocols in arginase II knockout (AII(-/-)) and wild-type (WT) mice. The lack of arginase II resulted in a lower citrulline rate of appearance (121 vs. 137 µmol·kg(-1)·h(-1)) due to a reduced availability of ornithine; ornithine supplementation was able to restore the rate of citrulline production in AII(-/-) to levels comparable with WT mice. There were significant differences in the utilization of dietary citrulline precursors. The contribution of dietary arginine to the synthesis of citrulline was reduced from 45 to 10 µmol·kg(-1)·h(-1) due to the lack of arginase II. No enteral utilization of arginine was observed in AII(-/-) mice (WT = 25 µmol·kg(-1)·h(-1)), and the contribution of dietary arginine through plasma ornithine was reduced in the transgenic mice (20 vs. 13 µmol·kg(-1)·h(-1)). Dietary glutamine and proline utilization were greater in AII(-/-) than in WT mice (20 vs. 13 and 1.4 vs. 3.7 µmol·kg(-1)·h(-1), respectively). Most of the contribution of glutamine and proline was enteral rather than through plasma ornithine. The arginase isoform present in the small intestinal mucosa has the role of providing ornithine for citrulline synthesis. The lack of arginase II results in a greater contribution of plasma ornithine and dietary glutamine and proline to the synthesis of citrulline.

Effect of oral arginine supplementation on exhaled nitric oxide concentration in sickle cell anemia and acute chest syndrome.

INTRODUCTION: Decreased exhaled nitric oxide levels (FE(NO)) have been described in patients with sickle cell disease (SCD) and a history of acute chest syndrome (ACS) when compared with non-ACS controls. Oral arginine supplementation has been shown to increase FE(NO) in healthy participants, but its effect in SCD patients is not known. OBJECTIVE: To determine the effect of oral arginine intake on FENO in sickle cell patients with and without history of ACS, and in healthy controls. HYPOTHESIS: No differences in the FE(NO) increase were seen in SCD patients with a history of ACS (ACS+) compared with healthy controls (HC) and SCD patients without history of ACS (ACS-). MATERIALS AND METHODS: ACS+ (n=6), ACS- (n=9), and HC (n=7) patients were studied. At baseline, and after the administration of escalating doses of oral L-arginine (0.1, 0.2, and 0.4 g/kg), serial measurements were made of the following: FE(NO), plasma concentrations of arginine, ornithine, citrulline, aspartate, glutamate, arginine/ornithine ratio, nitrite, nitrate, heart rate (HR), respiratory rate (RR), blood pressure (BP), oxygen saturation (SpO2), forced expiratory volume in 1 second (FEV1), and forced vital capacity (FVC). MAIN RESULTS: At baseline, FE(NO) did not differ among the groups. ACS- and ACS+ groups were deficient in arginine, and had decreased FEV1, FVC, and SaO2 when compared with HC patients. After arginine supplementation, FE(NO), arginine, ornithine, citrulline, nitrite, and the arginine/ornithine ratio increased similarly in all groups. Changes from baseline for HR, BP, SpO2, RR, FEV1, and FVC were minimal and similar in all groups. CONCLUSIONS: In contrast to our earlier study, ACS+ patients had similar FE(NO) values when compared with ACS- and HC patients. All SCD patients were arginine deficient at baseline and showed impairment in respiratory physiology when compared with HC patients. After arginine supplementation, FE(NO) concentration increased in all groups to a similar degree, and lung function and physiologic parameters were minimally affected. The physiologic significance of alterations in FE(NO) in SCD patients and its relationship to ACS predilection requires further delineation.

The effect of L-ornithine hydrochloride ingestion on performance during incremental exhaustive ergometer bicycle exercise and ammonia metabolism during and after exercise.

OBJECTIVES: L-Ornithine has an important role in ammonia metabolism via the urea cycle. This study aimed to examine the effect of L-ornithine hydrochloride ingestion on performance during incremental exhaustive ergometer bicycle exercise and ammonia metabolism during and after exercise. SUBJECTS/METHODS: In all, 14 healthy young adults (age: 22.2±1.0 years, height: 173.5±4.6 cm, body mass: 72.5±12.5 kg) who trained regularly conducted incremental exhaustive ergometer bicycle exercises after -ornithine hydrochloride supplementation (0.1 g/kg, body mass) and placebo conditions with a cross-over design. The exercise time (sec) of the incremental ergometer exercise, exercise intensity at exhaustion (watt), maximal oxygen uptake (ml per kg per min), maximal heart rate (beats per min) and the following serum parameters were measured before ingestion, 1 h after ingestion, just after exhaustion and 15 min after exhaustion: ornithine, ammonia, urea, lactic acid and glutamate. All indices on maximal aerobic capacity showed insignificant differences between both the conditions. RESULTS: Plasma ammonia concentrations just after exhaustion and at 15 min after exhaustion were significantly more with ornithine ingestion than with placebo. Plasma glutamate concentrations were significantly higher after exhaustion with ornithine ingestion than with placebo. CONCLUSIONS: It was suggested that, although the ingestion of L-ornithine hydrochloride before the exercise cannot be expected to improve performance, it does increase the ability to buffer ammonia, both during and after exercise.