Search

Background: Cystic fibrosis (CF) is a rare genetic multisystemic disorder with progressive abdominal and pulmonary involvement. Pain is still an underestimated symptom in CF patients., Methods: A comprehensive review of guidelines and scientific literature on the topic was performed and combined with findings from pain management in a young CF patient with progressive thoracic pain., Results: German CF guidelines do not cover diagnosis and management of pain in these patients. Studies from Europe and the United States report interactions between intensity of pain and mortality in CF, but do not include data on the efficacy of pain management. These data and clinical observations of a CF patient with episodes of intense thoracic pain are used to illustrate the specific challenges in pain relief., Conclusion: Pain management in CF requires meticulous monitoring as well as an interdisciplinary approach and should be implemented in the German CF guidelines. The authors also want to suggest recommendations for the treatment of thoracic pain in CF. The range and severity of organ involvement complicates the use both of opioids and non-opioids. Especially opioid treatment carries the risk of hypoxia and opioid-induced constipation (OIC) and needs close medical supervision., (© 2021. The Author(s).)

Background: Optic neuritis (ON) is the most prevalent manifestation of pediatric multiple sclerosis (MS ped ) and myelin-oligodendrocyte glycoprotein antibody-associated disease (MOGAD ped ) in children > 6 years. In this study, we investigated retinal atrophy patterns and diagnostic accuracy of optical coherence tomography (OCT) in differentiating between both diseases after the first ON episode., Methods: Patients were retrospectively identified in eight tertial referral centers. OCT, VEP and high/low-contrast visual acuity (HCVA/LCVA) have been investigated > 6 months after the first ON. Prevalence of pathological OCT findings was identified based on data of 144 age-matched healthy controls., Results: Thirteen MOGAD ped (10.7 ± 4.2 years, F:M 8:5, 21 ON eyes) and 21 MS ped (14.3 ± 2.4 years, F:M 19:2, 24 ON eyes) patients were recruited. We observed a significantly more profound atrophy of both peripapillary and macular retinal nerve fiber layer in MOGAD ped compared to MS ped (pRNFL global: 68.2 ± 16.9 vs. 89.4 ± 12.3 µm, p < 0.001; mRNFL: 0.12 ± 0.01 vs. 0.14 ± 0.01 mm 3 , p < 0.001). Neither other macular layers nor P100 latency differed. MOGAD ped developed global atrophy affecting all peripapillary segments, while MS ped displayed predominantly temporal thinning. Nasal pRNFL allowed differentiation between both diseases with the highest diagnostic accuracy (AUC = 0.902, cutoff < 62.5 µm, 90.5% sensitivity and 70.8% specificity for MOGAD ped ). OCT was also substantially more sensitive compared to VEP in identification of ON eyes in MOGAD (pathological findings in 90% vs. 14%, p = 0.016)., Conclusion: First MOGAD-ON results in a more severe global peripapillary atrophy compared to predominantly temporal thinning in MS-ON. Nasal pRNFL allows differentiation between both diseases with the highest accuracy, supporting the additional diagnostic value of OCT in children with ON., (© 2022. The Author(s).)

We recently found that renal carbonic anhydrase (CA) is involved in the reabsorption of inorganic nitrite (NO 2 - ), an abundant reservoir of nitric oxide (NO) in tissues and cells. Impaired NO synthesis in the endothelium and decreased NO bioavailability in the circulation are considered major contributors to the development and progression of renal and cardiovascular diseases in different conditions including diabetes. Isolated human and bovine erythrocytic CAII and CAIV can convert nitrite to nitrous acid (HONO) and its anhydride N 2 O 3 which, in the presence of thiols (RSH), are further converted to S-nitrosothiols (RSNO) and NO. Thus, CA may be responsible both for the homeostasis of nitrite and for its bioactivation to RSNO/NO. We hypothesized that enhanced excretion of nitrite in the urine may contribute to NO-related dysfunctions in the renal and cardiovascular systems, and proposed the urinary nitrate-to-nitrite molar ratio, i.e., U NOx R, as a measure of renal CA-dependent excretion of nitrite. Based on results from clinical and experimental animal studies, here, we report on a first evaluation of U NOx R. We determined U NOx R values in preterm neonates, healthy children, and adults, in children suffering from type 1 diabetes mellitus (T1DM) or Duchenne muscular dystrophy (DMD), in elderly subjects suffering from chronic rheumatic diseases, type 2 diabetes mellitus (T2DM), coronary artery disease (CAD), or peripheral arterial occlusive disease (PAOD). We also determined U NOx R values in healthy young men who ingested isosorbide dinitrate (ISDN), pentaerythrityl tetranitrate (PETN), or inorganic nitrate. In addition, we tested the utility of U NOx R in two animal models, i.e., the LEW.1AR1-iddm rat, an animal model of human T1DM, and the APOE*3-Leiden.CETP mice, a model of human dyslipidemia. Mean U NOx R values were lower in adult patients with rheumatic diseases (187) and in T2DM patients of the DALI study (74) as compared to healthy elderly adults (660) and healthy young men (1500). The intra- and inter-variabilities of U NOx R were of the order of 50% in young and elderly healthy subjects. U NOx R values were lower in black compared to white boys (314 vs. 483, P = 0.007), which is in line with reported lower NO bioavailability in black ethnicity. Mean U NOx R values were lower in DMD (424) compared to healthy (730) children, but they were higher in T1DM children (1192). ISDN (3 × 30 mg) decreased stronger U NOx R compared to PETN (3 × 80 mg) after 1 day (P = 0.046) and after 5 days (P = 0.0016) of oral administration of therapeutically equivalent doses. In healthy young men who ingested NaNO 3 (0.1 mmol/kg/d), U NOx R was higher than in those who ingested the same dose of NaCl (1709 vs. 369). In LEW.1AR1-iddm rats, mean U NOx R values were lower than in healthy rats (198 vs. 308) and comparable to those in APOE*3-Leiden.CETP mice (151).

L-Arginine (Arg) and L-homoarginine (hArg) are precursors of nitric oxide (NO), a signalling molecule with multiple important roles in human organism. In the circulation of adults, high concentrations of asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) and low concentrations of hArg emerged as cardiovascular risk factors. Yet, the importance of the Arg/hArg/NO pathway, especially of hArg and ADMA, in preterm neonates is little understood. We comprehensively investigated the Arg/hArg/NO pathway in 106 healthy preterm infants (51 boys, 55 girls) aged between 23 + 6 and 36 + 1 gestational weeks. Babies were divided into two groups: group I consisted of 31 babies with a gestational age of 23 + 6 - 29 + 6 weeks; group II comprised 75 children with a gestational age of 30 + 0 - 36 + 1 weeks. Plasma and urine concentrations of ADMA, SDMA, hArg, Arg, dimethylamine (DMA) which is the major urinary ADMA metabolite, as well as of nitrite and nitrate, the major NO metabolites, were determined by GC-MS and GC-MS/MS methods. ADMA and hArg plasma levels, but not the hArg/ADMA molar ratio, were significantly higher in group II than in group I: 895 ± 166 nM vs. 774 ± 164 nM (P = 0.001) for ADMA and 0.56 ± 0.04 µM vs. 0.48 ± 0.08 µM (P = 0.010) for hArg. There was no statistical difference between the groups with regard to urinary ADMA (12.2 ± 4.6 vs 12.8 ± 3.6 µmol/mmol creatinine; P = 0.61) and urinary SDMA. Urinary hArg, ADMA, SDMA correlated tightly with each other. Urinary excretion of DMA was slightly higher in group I compared to group II: 282 ± 44 vs. 247 ± 35 µmol/mmol creatinine (P = 0.004). The DMA/ADMA molar ratio in urine was tendentiously higher in neonates of group I compared to group II: 27 ± 13 vs. 20 ± 5 (P = 0.065). There were no differences between the groups with respect to Arg in plasma and to nitrite and nitrate in plasma and urine. In preterm neonates, ADMA and hArg biosynthesis increases with gestational age without remarkable changes in the hArg/ADMA ratio or NO biosynthesis. Our study suggests that ADMA and hArg are involved in foetal growth.

High circulating levels of asymmetric dimethylarginine (ADMA) and low circulating levels of homoarginine (hArg) are known cardiovascular risk factors in adults. While in adults with type 1 diabetes mellitus (T1DM) circulating ADMA is significantly elevated, in children and adolescents the reported ADMA data are contradictory. In 102 children with T1DM and 95 healthy controls (HC) serving as controls, we investigated the L-arginine (Arg)/nitric oxide (NO) pathway. Children with T1DM were divided into two groups, i.e., in children with newly diagnosed diabetes mellitus [T1DM-ND; n = 10; age, 8.8 (4.4-11.2) years; HbA1c, 13 (8.9-13.9) %] and in those with long-term treatment [T1DM-T; n = 92; age, 12.5 (10.5-15.4) years; HbA1c, 8.0 (7.2-8.6) %]. The age of the HC was 11.3 (8-13.3) years. Amino acids and NO metabolites of the Arg/NO pathway, creatinine and the oxidative stress biomarker malondialdehyde (MDA) were measured by GC-MS or GC-MS/MS. Plasma hArg, ADMA and the hArg/ADMA molar ratio did not differ between the T1DM and HC groups. There was a significant difference between T1DM-T and HC with regard to plasma nitrite [0.53 (0.48-0.61) vs 2.05 (0.86-2.36) µM, P < 0.0001] as well as to urinary nitrite [0.09 (0.06-0.17) vs 0.22 (0.13-0.37) μmol/mmol creatinine, P < 0.0001]. Plasma, but not urinary nitrite, differed between T1DM-ND and HC [0.55 (0.50-0.66) vs 2.05 (0.86-2.36) µM, P < 0.0001]. Plasma MDA did not differ between the groups. The urinary nitrate-to-nitrite molar ratio (UNOXR), a measure of nitrite-dependent renal carbonic anhydrase (CA) activity, was higher in T1DM-T [1173 (738-1481), P < 0.0001] and T1DM-ND [1341 (1117-1615), P = 0.0007] compared to HC [540 (324-962)], but did not differ between T1DM-T and T1DM-ND (P = 0.272). The lower nitrite excretion in the children with T1DM may indicate enhanced renal CA-dependent nitrite reabsorption compared with healthy children. Yet, lower plasma nitrite concentration in the T1DM patients may have also contributed to the higher UNOXR. Patients' age correlated positively with plasma hArg and hArg/ADMA and urinary DMA/ADMA. Plasma ADMA and urinary ADMA, DMA, nitrite and nitrate correlated negatively with age of the T1DM-T children. Significant correlations were found between plasma hArg and plasma Arg (r = 0.468, P < 0.0001), and urinary DMA (r = -0.426, P = 0.0001), ADMA (r = -0.266, P = 0.021) and nitrate (r = -0.234, P = 0.043). Plasma hArg correlated positively with age at diagnosis (r = +0.337, P = 0.002). ADMA, but not hArg, correlated with HbA1c in T1DM-T (r = -0.418, P < 0.0001) and T1DM-ND (r = +0.879, P = 0.0016). The greatest differences between T1DM-T and T1DM-ND were observed for urinary ADMA, DMA/ADMA ratio, nitrite and nitrate. The Arg/NO pathway is altered in T1DM in childhood and adolescence, yet the role and the importance of hArg and ADMA in T1DM remain to be elucidated. In young T1DM patients, oxidative stress (lipid peroxidation) is not elevated.

The L-arginine/nitric oxide (L-Arg/NO) pathway regulates endothelial function and may play an important role in the pathogenesis of Duchenne muscular dystrophy (DMD). Yet, this pathway is poorly investigated in children suffering from DMD. Endothelial dysfunction can affect the perfusion of contracting muscles, thus leading to ischemia and hypoxia. In the present study, we tested the hypothesis that reduced NO production due to elevated synthesis of N (G),N (G)-dimethyl-L-arginine (asymmetric dimethylarginine, ADMA), an endogenous inhibitor of NO synthesis, is a possible pathophysiological mechanism for progressive intramuscular muscle ischemia and disturbed endothelial function in children with DMD. Given the possible antagonistic action of homoarginine (hArg) on ADMA, we also analyzed this amino acid. We investigated 55 male patients with DMD and 54 healthy male controls (HC; aged 11.9 ± 4.8 vs. 11.1 ± 4.9 years, mean ± SD). Urinary creatinine and metabolites of the L-Arg/NO pathway were measured in plasma and urine by GC-MS or GC-MS/MS. Urine levels of ADMA and its major urinary metabolite dimethylamine (DMA), nitrite and nitrate (P < 0.001 for all) and hArg (P = 0.002) were significantly higher in DMD patients compared to HC, while the urinary DMA/ADMA molar ratio was lower (P = 0.002). In plasma, nitrate (P < 0.001), hArg (P = 0.002) and the hArg/ADMA ratio (P < 0.001) were lower in DMD than in HC. In plasma, ADMA (631 ± 119 vs. 595 ± 129 nM, P = 0.149), arginine and nitrite did not differ between DMD and HC. In DMD, positive correlations between ADMA, DMA or nitrate excretion and the stage of disease (according to Vignos and Thompson) were found. In DMD patients on steroid medication, lower concentrations of ADMA in plasma, and of DMA, ADMA, nitrate and hArg in urine were observed compared to non-treated patients. The L-Arg/NO pathway is impaired in DMD patients, with the disease progression being clinically negatively correlated with the extent of impairment. One of the underlying mechanisms in DMD may involve insufficient antagonism of ADMA by hArg. Steroids, but not creatine supplementation, seems to improve the L-Arg/NO pathway in DMD.

Adult subjects with growth hormone (GH) deficiency (GHD) are known to have reduced life expectancy due to increased cardiovascular and cerebrovascular events. In adults, these events are associated with elevated circulating concentrations of asymmetric dimethylarginine (ADMA) which is an endogenous inhibitor of L-arginine (Arg)-derived nitric oxide (NO). Low circulating concentrations of homoarginine (hArg) emerged as a cardiovascular risk factor. In adults, hArg seems to antagonize ADMA. In the present work, we tested the hypothesis that children with short stature without or with GHD have altered Arg/NO pathway as compared to children with normal growth. We studied 66 short stature children (38 boys, 28 girls) aged 3.5-17.3 years, who underwent the routine L-Arginine Test to diagnose presence of GHD. GHD was confirmed in 47 children (GHD group; 30 boys, 17 girls) and was absent in the remaining 19 children (non-GHD group; 8 boys, 11 girls). In addition, we investigated 24 healthy age- and gender-matched children (10 boys, 14 girls) with normal growth. In EDTA plasma samples of all children, we determined by mass spectrometry-based methods the concentrations of Arg, hArg and ADMA, and calculated the Arg/ADMA and hArg/ADMA molar ratios. With respect to these biochemical parameters, we did not find statistically significant differences between the GHD and non-GHD groups. Comparing short with normal stature children, we found small differences regarding plasma hArg concentrations [mean ± SD; median (25th-75th percentile)]: 2.06 ± 0.52 µM; 2.12 (1.74-2.36) µM vs. 1.7 ± 0.5 µM; 1.6 (1.4-1.8) µM, P < 0.001. Compared to normal stature children, short stature children had considerably higher plasma concentrations of ADMA [0.77 ± 0.15 µM; 0.77 (0.66-0.85) µM vs. 0.57 ± 0.09 µM; 0.58 (0.50-0.63) µM, P < 0.001], but not of Arg [83.3 ± 19.2 µM; 82.2 (71.9-90.3) µM vs. 86.5 ± 17.8 µM; 84.8 (77.2-94.8) µM, P = 0.336], or the hArg/ADMA ratio [2.74 ± 0.76; 2.7 (2.2-3.1) vs. 3.1 ± 1.2; 2.85 (2.42-3.66), P = 0.161. hArg in the GHD group (r = 0.41, P = 0.004) and the hArg/ADMA ratio in both groups (r = 0.44, P = 0.002 in GHD; r = 0.55, P = 0.01 in non-GHD)], but not ADMA were positively correlated with insulin-like growth factor-1 (IGF-1). hArg and hArg/ADMA differed between girls and boys in the GHD and non-GHD groups but in the normal growth group. The hArg/ADMA ratio increased with age in all groups. Our study suggests that hArg and ADMA are involved in growth in the childhood, presumably in an antagonistic manner, with ADMA slowing and hArg accelerating growth.

Despite saturation of nitric oxide (NO) synthase (NOS) by its substrate L-arginine (Arg), oral and intravenous supplementation of Arg may enhance NO synthesis, a phenomenon known as "The L-arginine paradox". Yet, Arg is not only a source of NO, but is also a source for guanidine-methylated (N (G)) arginine derivatives which are all inhibitors of NOS activity. Therefore, Arg supplementation may not always result in enhanced NO synthesis. Concomitant synthesis of N (G)-monomethyl arginine (MMA), N (G),N (G)-dimethylarginine (asymmetric dimethylarginine, ADMA) and N (G),N (G´)-dimethylarginine (symmetric dimethylarginine, SDMA) from supplemented Arg may outweigh and even outbalance the positive effects of Arg on NO. Another possible, yet little investigated effect of Arg supplementation may be alteration of renal function, notably the influence on the excretion of nitrite in the urine. Nitrite is the autoxidation product of NO and the major reservoir of NO in the circulation. Nitrite and Arg are reabsorbed in the proximal tubule of the nephron and this reabsorption is coupled, at least in part, to the renal carbonic anhydrase (CA) activity. In the present placebo-controlled studies, we investigated the effect of chronic oral Arg supplementation of 10 g/day for 3 or 6 months in patients suffering from peripheral arterial occlusive disease (PAOD) or coronary artery disease (CAD) on the urinary excretion of nitrite relative to nitrate. We determined the urinary nitrate-to-nitrite molar ratio (UNOxR), which is a measure of nitrite-dependent renal CA activity before and after oral intake of Arg or placebo by the patients. The UNOxR was also determined in 6 children who underwent the Arg test, i.e., intravenous infusion of Arg (0.5 g Arg/kg bodyweight) for 30 min. Arg was well tolerated by the patients of the three studies. Oral Arg supplementation increased Arg (plasma and urine) and ADMA (urine) concentrations. No appreciable changes were seen in NO (in PAOD and CAD) and prostacyclin and thromboxane synthesis (in PAOD). In the PAOD study, UNOxR did not change in the Arginine group (480 ± 51 vs 486 ± 50), but fell in the Placebo group (422 ± 67 vs 332 ± 42, P = 0.025). In the CAD study, UNOxR did not change significantly in the Arginine group (518 ± 77 at start vs 422 ± 40 after 3 months vs 399 ± 66 after 6 months), but fell in the Placebo group (524 ± 69 vs 302 ± 36 vs 285 ± 31; P = 0.025 for 0 vs 3 months). Infusion of Arg tended to decrease the UNOxR in the children (317 ± 41 vs 208 ± 16, P = 0.06). We propose that oral long-term Arg supplementation prevents loss of NO bioactivity by saving nitrite. The optimum Arg dose needs to be elaborated and is likely to be less than 10 g per day in adults. Orally and intravenously administered arginine was well tolerated by the elderly patients and young children, respectively.

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide (NO) synthesis, whereas L-arginine (Arg) and L-homoarginine (hArg) serve as substrates for NO synthesis. ADMA and other methylated arginines are generally believed to exclusively derive from guanidine (N (G))-methylated arginine residues in proteins by protein arginine methyltransferases (PRMTs) that use S-adenosylmethionine (SAM) as the methyl donor. L-Lysine is known for decades as a precursor for hArg, but only recent studies indicate that arginine:glycine amidinotransferase (AGAT) is responsible for the synthesis of hArg. AGAT catalyzes the formation of guanidinoacetate (GAA) that is methylated to creatine by guanidinoacetate methyltransferase (GAMT) which also uses SAM. The aim of the present study was to learn more about the mechanisms of ADMA and hArg formation in humans. Especially, we hypothesized that ADMA is produced by N (G)-methylation of free Arg in addition to the known PRMTs-involving mechanism. In knockout mouse models of AGAT- and GAMT-deficiency, we investigated the contribution of these enzymes to hArg synthesis. Arg infusion (0.5 g/kg, 30 min) in children (n = 11) and ingestion of high-fat protein meals by overweight men (n = 10) were used to study acute effects on ADMA and hArg synthesis. Daily Arg ingestion (10 g) or placebo for 3 or 6 months by patients suffering from peripheral arterial occlusive disease (PAOD, n = 20) or coronary artery disease (CAD, n = 30) was used to study chronic effects of Arg on ADMA synthesis. Mass spectrometric methods were used to measure all biochemical parameters in plasma and urine samples. In mice, AGAT but not GAMT was found to contribute to plasma hArg, while ADMA synthesis was independent of AGAT and GAMT. Arg infusion acutely increased plasma Arg, hArg and ADMA concentrations, but decreased the plasma hArg/ADMA ratio. High-fat protein meals acutely increased plasma Arg, hArg, ADMA concentrations, as well as the plasma hArg/ADMA ratio. In the PAOD and CAD studies, plasma Arg concentration increased in the verum compared to the placebo groups. Plasma ADMA concentration increased only in the PAOD patients who received Arg. Our study suggests that in humans a minor fraction of free Arg is rapidly metabolized to ADMA and hArg. In mice, GAMT and N (G)-methyltransferases contribute to ADMA and hArg synthesis from Arg, whereas AGAT is involved in the synthesis of hArg but not of ADMA. The underlying biochemical mechanisms remain still elusive.

In Huntington's disease (HD), a neurodegenerative-inherited disease, chorea as the typical kind of movement disorder is described. Beside chorea, however, all other kinds of movement disturbances, such as bradykinesia, dystonia, tremor or myoclonus can occur. Aim of the current study was to investigate alterations in the echogenicity of basal ganglia structures in different Huntington's disease phenotypes. 47 patients with manifest and genetically confirmed HD were recruited. All participants underwent a thorough neurological examination. According to a previously described method, classification into predominantly choreatic, mixed or bradykinetic-rigid motor phenotypes was performed depending on subscores of the Unified Huntington's Disease Rating Scale. In addition, findings in juvenile HD were compared to adult HD. Transcranial sonography was performed by investigators blinded to clinical classification. There were no significant differences in basal ganglia echogenicities between the three phenotypes. Size of echogenic area of substantia nigra (SN) correlated positively with CAG repeat and bradykinesia subscore, and negatively with age of onset and chorea subscore. Comparing juvenile and adult HD subtypes, SN hyperechogenicity was significantly more often detectable in the juvenile form (100 vs. 29.3 %, p = 0.002). Regarding echogenicity of caudate or lentiform nuclei, no significant differences were detected. HD patients with the juvenile variant exhibit marked hyperechogenicity of substantia nigra. No significant differences in basal ganglia echogenicities between predominantly choreatic, mixed or bradykinetic-rigid motor phenotypes were detected.

Asymmetric dimethylarginine (ADMA) systemic concentrations are elevated in hypercholesterolemic adults and contribute to nitric oxide (NO) dependent endothelial dysfunction. Decreased activity of the key ADMA-hydrolyzing enzyme dimethylarginine dimethylaminohydrolase (DDAH) may be involved. Yet, the ADMA/DDAH/NO pathway has not been investigated in childhood hypercholesterolemia. We studied 64 children with hypercholesterolemia type II (HCh-II) and 54 normocholesterolemic (NCh) children (mean ± SD; age, years: 11.1 ± 3.5 vs. 11.9 ± 4.6). Plasma and urine ADMA was measured by GC-MS/MS. Dimethylamine (DMA), the ADMA metabolite, creatinine, nitrite and nitrate in urine were measured by GC-MS. The DMA/ADMA molar ratio in urine was calculated to estimate whole body DDAH activity. ADMA plasma concentration (mean ± SD; nM: 571 ± 85 vs. 542 ± 110, P = 0.17) and ADMA urinary excretion rate (mean ± SD: 7.1 ± 2 versus 7.2 ± 3 μmol/mmol creatinine, P = 0.6) were similar in HCh-II and NCh children. Both DMA excretion rate [median (25th-75th percentile): 56.3 (46.4-109.1) vs. 45.2 (22.2-65.5) μmol/mmol creatinine, P = 0.0004] and DMA/ADMA molar ratio [median (25th-75th percentile): 9.2 (6.0-16.3) vs. 5.4 (3.8-9.4), P = 0.0004] were slightly but statistically significantly increased in HCh-II children compared to NCh children. Plasma and urinary nitrite and nitrate were similar in both groups. In HCh-II whole body DDAH activity is elevated as compared to NCh. HCh-II children treated with drugs for hypercholesterolemia had lower plasma ADMA levels than untreated HCh-II or NCh children, presumably via increased DDAH activity. Differences between treated and untreated HCh-II children were not due to differences in age. In conclusion, HCh-II children do not have elevated ADMA plasma levels, largely due to an apparent increase in DDAH activity. While this would tend to limit development of endothelial dysfunction, it is not clear whether this might be medication-induced or represent a primary change in HCh-II children.

Plasma concentration of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthesis from L-arginine and a cardiovascular risk factor, was found to be elevated in plasma of homocysteinemic adults. Enhanced cardiovascular risk due to homocystinuria and impaired renal function has been found in patients with phenylketonuria (PKU) on protein-restricted diet. However, it is still unknown whether ADMA synthesis is also elevated in children with homocystinuria due to cystathionine beta-synthase deficiency (classical homocystinuria), and whether ADMA may play a role in phenylketonuria in childhood. In the present study, we investigated the status of the L-arginine/NO pathway in six young patients with homocystinuria, in 52 young phenylketonuria patients on natural protein-restricted diet, and in age- and gender-matched healthy children serving as controls. ADMA in plasma and urine was determined by GC-MS/MS. The NO metabolites nitrate and nitrite in plasma and urine, and urinary dimethylamine (DMA), the dimethylarginine dimethylaminohydrolase (DDAH) metabolite of ADMA, were measured by GC-MS. Unlike urine ADMA excretion, plasma ADMA concentration in patients with homocystinuria was significantly higher than in controls (660±158 vs. 475±77 nM, P=0.035). DMA excretion rate was considerably higher in children with homocystinuria as compared to controls (62.2±24.5 vs. 6.5±2.9 μmol/mmol creatinine, P=0.068), indicating enhanced DDAH activity in this disease. In contrast and unexpectedly, phenylketonuria patients had significantly lower ADMA plasma concentrations compared to controls (512±136 vs. 585±125 nM, P=0.009). Phenylketonuria patients and controls had similar L-arginine/ADMA molar ratios in plasma. Urinary nitrite excretion was significantly higher in phenylketonuria as compared to healthy controls (1.7±1.7 vs. 0.7±1.2 μmol/mmol creatinine, P=0.003). Our study shows that the L-arginine/NO pathway is differently altered in children with phenylketonuria and homocystinuria. Analogous to hyperhomocysteinemic adults, elevated ADMA plasma concentrations could be a cardiovascular risk factor in children with homocystinuria. In phenylketonuria, the L-arginine/NO pathway seems not be altered. Delineation of the role of ADMA in childhood phenylketonuria and homocystinuria demands further investigation.

Plasma and urine amino acids were determined by ion-exchange chromatography in 80 healthy preterm infants divided into three groups: (1) 23 0/7-28 0/7, (2) 28 1/7-32 0/7 and (3) 32 1/7-35 0/7 weeks of gestation. Samples were collected from days 5 to 57 of life, when infants were exclusively orally fed. Infants with evidence of underlying diseases were excluded. Concentrations of most plasma amino acids increased with gestational and maturational age; urinary excretion followed an opposite course. Few amino acids depended on postnatal age. Plasma amino acids did not correlate inversely to their counterparts in urine indicating that plasma amino acids do not simply reflect kidney function. Some amino acids in blood and urine were linked to nutrient intake and body weight. Our data clearly indicate the heterogeneity of the preterm cohort; therefore, gestational age-matched reference values have to be used for diagnostic purposes in preterm infants.

This study was performed to study an association between nutritional status on one hand and BCAA- and Phe-concentrations on the other hand in PKU patients free of infection. AA profiles from 70 PKU patients were measured. 9 patients (subgroup I) with elevated Phe- and BCAA-concentrations as well as 23 patients (subgroup II) with only elevated Phe-levels were included. Dietary records were obtained from both groups; low caloric intake in subgroup I was increased with Duocal or p-am ANAMIX without modifying total protein- and Phe-intake. AA profiles were controlled after 2 weeks. Additionally, we investigated AA profiles from 26 liver transplanted patients with increased carbohydrate and caloric intake as an example for anabolism. In subgroup I Phe- and Isoleu-concentrations decreased sign. After dietary intervention. Leu, Val and Tyr levels decreased not sign. Initial Phe-levels correlated negatively with protein and caloric intake. BCAA concentrations of liver transplanted patients receiving high amounts of carbohydrates were in the lower range of normal. Increased caloric intake lowered most of the elevated Phe- and BCAA- concentrations.