Albumin and whole-body protein synthesis respond differently to intraperitoneal and oral amino acids.

Patients with peritoneal dialysis are at risk for malnutrition and hypoalbuminemia, which are indicators of poor outcome. Recently, it was shown that dialysis solutions containing amino acids (AAs) and glucose improve protein anabolism in peritoneal dialysis patients. We determined if the same solutions could increase the fractional synthesis rate of albumin along with whole-body protein synthesis. Changes in the fractional albumin synthetic rate reflect acute change in hepatic albumin synthesis. A random-order cross-over study compared the effects of Nutrineal (AA source) plus Physioneal (glucose) dialysate with Physioneal alone dialysate. Eight patients in the overnight fasting state were compared to 12 patients in the daytime-fed state. Fractional albumin synthetic rate and whole-body protein synthesis were determined simultaneously using a primed-continuous infusion of L-[1-(13)C]-leucine. Fractional albumin synthesis on AAs plus glucose dialysis did not differ significantly from that on glucose alone in the fasting or the fed state. Protein intake by itself (fed versus fasting) failed to induce a significant increase in the fractional synthetic rate of albumin. Conversely, the oral protein brought about a significant stimulation of whole-body protein synthesis. Our findings show that the supply of AAs has different effects on whole-body protein synthesis and the fractional synthetic rate of albumin.

[Lactic acidosis and accumulation of glutamate in the blood of neonates following treatment with calcium levulinate for hypocalcaemia]. / Lactaatacidose en glutamaatophoping in het bloed van neonaten na behandeling met calciumlevulaat wegens hypocalciëmie.

The data from 5 clinics concerning 8 infants, who had developed severe lactic acidosis and hyperglutamic acidaemia were reviewed. Blood-lactate levels were up to 15 mmol/l (reference level: < 2) and plasma-glutamate levels up to 1632 pmol/l (reference level: 14-78), and there was no concomitant hyperglutaminaemia (levels up to 1032 micromol/l (reference level: 333-809)). A positive correlation between the amount of calcium levulinate administered and the degree of hyperglutamic acidaemia was found. Replacement of the calcium levulinate by another calcium salt caused a reversal of the biochemical abnormalities of the patients. Two of the infants had a 22q11 microdeletion. This development of severe acidosis in infants who had been given a calcium supplement in the form of calcium levulinate may be related to genetic predisposition. The paradoxal hyperketonaemia and generalized aminoaciduria in 4 other patients suggested disturbed function ofthe mitochondrial respiratory chain. The hypothesis of the occurrence of an underlying defect of the mitochondrial respiratory chain was tested in the muscle tissue of one 22q11 patient, but this showed no abnormalities. Excessive accumulation of glutamate because of dysfunction ofglutamine synthetase, which forms glutamate from glutamine seems unlikely because of the relatively low values of plasma glutamate compared to the glutamine plasma levels. Calcium levulinate should no longer be used in neonates as it may lead to lactic acidosis.

Peritoneal protein losses and cytokine generation in automated peritoneal dialysis with combined amino acids and glucose solutions.

OBJECTIVES: Protein-energy malnutrition as a consequence of deficient protein intake frequently occurs in peritoneal dialysis (PD) patients. Previously, we showed that peritoneal dialysate containing a mixture of amino acids (AA) and glucose has anabolic effects. However AA-dialysate has been reported to increase intraperitoneal protein and AA losses and the release of proinflammatory cytokines (interleukine-6 (IL-6) and tumor necrosis factor alpha (TNFalpha)). We investigated the effect of AA plus glucose (AAG) solutions on peritoneal protein losses and cytokine generation. METHODS: In 6 patients on standard automated peritoneal dialysis (APD) 12 APD sessions of 6 cycles each were performed during the night using dialysate containing 1.1% AA plus glucose or glucose alone as control. Protein losses and TNFalpha and IL-6 concentrations were measured in dialysates separately collected from nightly cycling and daytime dwell. RESULTS: The 24 hour-protein losses with AAG (median 6.7 g, range 4.7-9.4 g) were similar to control dialysate (median 6.0 g, range 4.2-9.2 g). Daytime dialysate IL-6 levels were higher after nightly AAG dialysis than after control dialysis (142 pg/ml and 82 pg/ml, respectively, P<.05). TNFalpha concentrations were very low. CONCLUSION: Nightly APD with amino acids containing dialysate was associated with an increase in peritoneal IL-6 generation during the day. The addition of AA to standard glucose dialysis solutions did not induce a significant increase of peritoneal protein losses.

Brain abnormalities in a case of malonyl-CoA decarboxylase deficiency.

Malonyl-CoA decarboxylase (MCD) deficiency is an extremely rare inborn error of metabolism that presents with metabolic acidosis, hypoglycemia, and/or cardiomyopathy. Patients also show neurological signs and symptoms that have been infrequently reported. We describe a girl with MCD deficiency, whose brain MRI shows white matter abnormalities and additionally diffuse pachygyria and periventricular heterotopia, consistent with a malformation of cortical development. MLYCD-gene sequence analysis shows normal genomic sequence but no messenger product, suggesting an abnormality of transcription regulation. Our patient has strikingly low appetite, which is interesting in the light of the proposed role of malonyl-CoA in the regulation of feeding control, but this remains to be confirmed in other patients. Considering the incomplete understanding of the role of metabolic pathways in brain development, patients with MCD deficiency should be evaluated with brain MRI and unexplained malformations of cortical development should be reason for metabolic screening.

[Diagnosis of vitamin B12 deficiency revised]. / De diagnostiek van vitamine-B12-deficiëntie herzien.

Vitamin B12 (cobalamin) deficiency is a common disorder with potential irreversible haematological and neurological consequences. Currently used diagnostic tests such as the evaluation of serum vitamin B12 and the Schilling test are insufficient, e.g. the positive predictive value of a low serum vitamin B12 level for actual vitamin B12 deficiency (i.e. tissue deficiency) is low. Insufficient availability of vitamin B12 will lead to the accumulation of methylmalonic acid and homocysteine in the body. Nearly all patients with vitamin B12 deficiency also have substantially increased levels of methylmalonic acid and homocysteine. New tests of serum methylmalonic acid and homocysteine are highly sensitive for vitamin B12 deficiency and may obviate the need for the somewhat cumbersome Schilling test.

Clinical, enzymatic, and molecular genetic characterization of a biochemical variant type of argininosuccinic aciduria: prenatal and postnatal diagnosis in five unrelated families.

A biochemical variant of argininosuccinate lyase deficiency, found in five individuals, is introduced. In comparison to classical patients, the variant cases of argininosuccinate lyase deficiency were characterized by residual enzyme activity as measured by the incorporation of [14C]citrulline into proteins. The five patients of different ethnic backgrounds presented with relatively mild clinical symptoms, variable age of onset, marked argininosuccinic aciduria and severe, but not complete, deficiency of argininosuccinate lyase. [14C]Citrulline incorporation into proteins, which is completely blocked in classical argininosuccinic aciduria, was only partially reduced in fibroblasts of these patients. Further investigation showed that previous standard conditions of the assay were not optimal. Higher concentrations of citrulline in the incubation medium strongly stimulated 14C incorporation in normal cells, but not in the patients; as a result, the relative incorporation level in the patients dropped to 6-28% compared to 18-75% of normal in the original procedure. Prenatal diagnosis was successfully performed in three of the families. Affected pregnancies were indicated by (partial) deficiency of [14C]citrulline incorporation in chorionic villi and/or increased levels of argininosuccinate in amniotic fluid. Analysis of the ASL gene in the five patients revealed a considerable allelic heterogeneity. Three novel mutations--R385C (2 patients), V178M and R379C--were detected in homozygous states, whereas one patient was compound heterozygous for the known mutations R193Q and Q286R. In conclusion, there are patients of different ethnic backgrounds who are characterized by residual activity of argininosuccinate lyase and who present with less severe clinical courses. In addition, we present an improved biochemical assay for accurate prenatal and postnatal diagnosis.

Prenatal diagnosis of the Hunter syndrome and the introduction of a new fluorimetric enzyme assay.

Prenatal diagnosis of the Hunter syndrome (mucopolysaccharidosis type II; MPS II) is preferably achieved by the assay of iduronate-2-sulphate sulphatase (IDS) in uncultured chorionic villi (CV) as this allows early (12th week), rapid (2-3 days) and reliable results. We summarize the results of 174 prenatal analyses in the past 30 years, using various methods such as radiolabelled sulphate incorporation in amniotic fluid (AF) cells, glycosaminoglycan (GAG)-electrophoresis in AF and IDS assay in CV, CV-cells, AF and AF-cells. Twenty-seven fetuses with MPS II were diagnosed after finding clearly abnormal results in pregnancies with a male fetus; very low IDS activity has also been measured in some pregnancies with a (heterozygous) female fetus, emphasizing the need to combine enzyme assay with fetal sex determination. IDS activity has until recently been assessed by a cumbersome radioactive enzyme assay. Here we describe the use of a novel fluorigenic 4-methylumbelliferyl substrate, which allows a sensitive, rapid and convenient assay of IDS activity and reliable early prenatal diagnosis. This novel IDS assay was validated in retrospective analyses of 14 CV, CV-cell, AF and AF-cell samples from affected pregnancies in addition to prospective prenatal diagnosis in eight pregnancies at risk with one MPS II-affected fetus.