Richard Gitzelmann

Changes of liver metabolite concentrations in adults with disorders of fructose metabolism after intravenous fructose by 31P magnetic resonance spectroscopy.

ABSTRACT: A novel 31P magnetic resonance spectroscopy procedure allows the estimation of absolute concentrations of certain phosphorus-containing compounds in liver. We have validated this approach by measuring ATP, phosphomonesters, and inorganic phosphate (Pi during fasting and after an i.v. fructose bolus in healthy adults and in three adults with disorders of fructose metabolism and by comparing results with known metabolite concentrations measured chemically. During fasting, the ATP concentration averaged 2.7 ± 0.3 (SD, n = 9) mmol/L, which, after due correction for other nucleoside triphosphates, was 2.1 mmol/L and corresponded well with known concentrations. Fructose-1-phosphate (F-1-P) could not be measured during fasting; its concentration after fructose was calculated from the difference of the phosphomonester signals before (2.9 ± 0.2 mmol/L) and after fructose. Pi was 1.4 ± 0.3 mmol/L and represented the one fourth of Pi visible in magnetic resonance spectra. In the three healthy controls after fructose (200 mg/kg, 20% solution, 2.5 min), the fructokinase-mediated increase of F-l-P was rapid, reaching 4.9 mmol/L within 3 min, whereas the uncorrected ATP decreased from 2.7 to 1.8 mmol/L and the Pi from 1.4 to 0.3 mmol/L. The subsequent decrease of F-l-P, mediated by fructaldolase, was accompanied by an overshooting rise of Pi to 2.7 mmol/L. In the patient with essential fructosuria, the concentrations of F-l-P, ATP, and Pi remained unchanged, confirming that fructokinase was indeed inactive. In the patient with hereditary fructose intolerance, initial metabolic changes were the same as in the controls, but baseline concentrations were not yet reestablished after 7 h, indicating weak fructaldolase activity. In the patient with fructose-1,6-diphosphatase deficiency, initial metabolic changes were the same as in the controls, but normalization was slightly delayed.

Formation of Galactose-1-Phosphate from Uridine Diphosphate Galactose in Erythrocytes from Patients with Galactosemia [31]

Extract: Erythrocyte lysates of galactosemic patients were found to form galactose-1-phosphate from uridine diphosphate galactose. The enzymatic reaction most likely responsible for this conversion is uridine diphosphate galactose pyrophosphorylase, an enzyme believed to be absent from human erythrocytes, but other reactions might be involved.Speculation: Galactose-1-phosphate concentration in red cells of galactosemic infants may prove useless as an indicator of galactose uptake from foodstuffs.

The P28T Mutation in the GALK1 Gene Accounts for Galactokinase Deficiency in Roma (Gypsy) Patients across Europe

Galactokinase deficiency is an inborn error of metabolism that, if untreated, results in the development of cataracts in the first weeks of life. The disorder is rare worldwide, but has a high incidence among the Roma (Gypsies). In 1999, we reported the founder Romani mutation, P28T, identified in affected families from Bulgaria. Subsequent studies have detected the same mutation in Romani patients from different European countries. The screening of 803 unrelated control individuals of Romani ethnicity from Bulgaria, Hungary, and Spain has shown an overall carrier rate of 1:47 and an expected incidence of affected births about 1:10,000. Using disease haplotype analysis, the age of the P28T mutation was estimated at 750 y, preceding the splits of the proto-Roma into the numerous populations resident in Europe today. The findings suggest that the mutation has spread with the early diaspora of the Roma throughout Europe. Superimposed on this old distribution pattern is the new migration wave of the last decade, with large numbers of Roma moving to Western Europe as a result of the economic changes in the East and the wars in former Yugoslavia. The changing demographic pattern of Romani minorities can be expected to lead to a homogenization of the incidence of “private” Romani disorders and founder mutations. The P28T mutation is thus likely to account for a high proportion of galactokinase deficiency cases across Europe. Mutation-based pilot newborn screening programs would provide current incidence figures and help to design long-term prevention of infantile cataracts due to galactokinase deficiency.

Short communication. Glycogenosis Ib: neutrophil microbicidal defects due to impaired hexose monophosphate shunt.

Summary: We studied neutrophil microbicidal function and oxidative metabolic activity in a patient with glycogenosis Ib. The intracellular killing defect and the respiratory burst abnormality in gycogenosis Ib neutrophils were confirmed. The impaired oxygen-dependent microbicidal activity was shown to result from impaired hexose monophosphate shunt activity (impaired endogenous NADPH synthesis) and could be corrected by homogenization of the cells, followed by the addition of exogenous NADPH. Our data are thus consistent with a possible role for glucose-6-phosphate transport in neutrophil microbicidal function. We recommend a continuous prophylaxis with co-trimoxazole in patients with glycogen storage disease Ib.

The Renal Handling of Carnitine in Patients with Selective Tubulopathy and with Fanconi Syndrome

ABSTRACT: Fractional tubular reabsorption (FTR) of free and acyl carnitine was measured in 15 patients with various selective tubular transport defects and in 19 patients with more generalized tubular dysfunction (Fanconi syndrome). FTR of free carnitine was normal in all patients with a selective tubulopathy, FTR of acyl carnitine was normal in most, and plasma carnitine levels were normal without exception. In these patients, there was no evidence for the existence of a defective renal transport mechanism shared by carnitine. In the patients with Fanconi syndrome, mean FTR of free and acyl carnitine was low; their plasma carnitine levels were lowered and correlated with the FTR. In individual patients, FTR of free and acyl carnitine also correlated with the severity of the disease. In the group of Fanconi syndrome patients, FTR of free and acyl carnitine correlated linearly with that of valine. We concluded that the lowering of plasma carnitine in the patients with Fanconi syndrome was caused by excessive loss of carnitine in urine. Its pathophysiological significance remained to be established.

A DELETION IN ONE PRO-ALPHA1 (III) COLLAGEN GENE IN EHLERS-DANLOS SYNDROME TYPE IV

We have previously reported a now 23-year-old patient with a long history of bleeding due to dominantly inherited Ehlers-Danlos syndrome type IV (“vascular” type) whose fibroblasts produced a structurally abnormal type III collagen with shortened triple-helical structure (Superti-Furga et al., Pediat Res 20:1043, 1986). Immunoblot analysis of protoalpha1(III) chains in his fibroblasts identified a normal-sized species and an additional species of lower molecular weight. Similarly, Northern blots probed with cDNAs for type III collagen showed equal quantities of a normal and a mutant mRNA for type III collagen, the mutant mRNA being 600 bp shorter than the normal one. Southern blots probed with genomic clones for type III collagen showed an abnormal pattern, best explained by a multi-exon deletion of approx. 3 kb in the middle of the gene, within the triple-helical coding region. This is the first description of a mutation in the human alpha1(III) collagen gene.(Genomic clones courtesy of Dr.F.Ramirez, SUNY Medical School, New York, USA)

140 METABOLIC CHANGES IN LIVER AFTER INTRAVENOUS FRUCTOSE IN ADULTS WITH DISCORDERS OF FRUCTOSE METABOLISM AND IN HEALTHY CONTROLS, FOLLOWED BY PHOSPHORUS MAGNETIC RESONNANCE SPECTROSCOPY

The effect of fructose on liver metabolism was studied by in vivo magnetic resonance spectroscopy in fasting healthy controls and in adults with inherited disorders of fructose metabolism, essential fructosuria (EF), hereditary fructose intolerance (HFI), and fructose-1,6-diphosphatase deficiency (FDD). Novel procedures of spectrometer calibration and spectrum analysis allowed accurate measurements of absolute concentrations of phosphorous compounds in liver. In healthy controls, after fructose infusion (200mg/kg, 20% solution, 2.5min), a fructokinase-mediated, rapid increase of fructose-1-phosphate (F-1-P) from 2.9 to 7.8 mmol per liter of liver was seen, while ATP dropped from 2.7 to 1.8 and inorganic phosphorus (Pi) from 1.4 to 0.3 mmol/l. The subsequent return of F-1-P, mediated by fructaldolase, to its initial concentration was accompagnied by an overshooting rise of Pi up to 2.7 mmol/l. In a patient with EF, concentrations of F-1-P. ATP, and Pi remained unchanged confirming that fructokinase was indeed inactive. In a patient with HFI, initial metabolic changes were as in controls, but baseline concentrations were reestablished only after a tenfold delay indicating weak fructaldolase activity. In a patient with FDD, i.e. the most distal of the three defects, initial metabolic changes occured as in controls at the normal rate and normalization was only slightly delayed.

88 MATERNAL PKU SYNDROME IN COUSINS CAUSED BY MILD, UNRECOGNIZED PHENYLKETONURIA IN THEIR MOTHERS HOMOZYGOUS FOR THE PHENYLALANINE HYDROXYLASE 261 ARG |[ndash]| GLN MUTATION

Microcephaly observed at birth in 2 first cousins lead to the recognition of phenylketonuria in their mothers, 24- and 23-year-old sisters with blood phenylalanine around 1, 2 mmol/l who had never been treated and had no overt mental retardation. PCR amplification and direct sequencing of exon 7 of the phenylalanine hydroxylase gene in one sister revealed a homozygous G → A transition leading to a ARG → GLN substitution at codon 261, a mutation which has recently been associated with mild PKU (Y. Okano et al., Am J Hum Genet 46:18-25, 1990). A positive/negative PCR amplification system employing wild type and 3′end-mutation specific primers was used to confirm homozygosity for this mutation in both sisters with PKU and heterozygosity in their parents and an unaffected sister. We conclude that (1) homozygosity for the 261 ARG → GLN mutation indeed can result in a mild variant of PKU with little or no mental retardation, but that (2) elevation of blood phenylalanine in such individuals suffices to cause the maternal PKU syndrome.