A new variant of galactosemia: galactose-1-phosphate uridylytransferase sensitive to product inhibition by glucose 1-phosphate

In the erythrocytes of a patient with the clinical symptoms of galactosemia, a galactose-1-phosphate uridylyltransferase with abnormal kinetics was observed. Under standard assay conditions, the uridylyltransferase activity was almost normal initially and became completely inactivated within 30 min. The abnormal kinetics could be ascribed to a product inhibition by glucose 1-phosphate. The inhibition was produced by a variety of sugar phosphates, the most potent of which proved to be glucose 1-phosphate, mannose 1-phosphate, and fructose 6-phosphate. The variant galactose-1-phosphate uridylyltransferase was further characterized by a lowered affinity towards galactose 1-phosphate, non-Michaelis-Menten kinetics towards UDP-glucose, an increased thermal stability, and complete inactivity upon Cellogel electrophoresis.     

Sequential intrahepatic metabolic effects of enteric galactose alimentation in newborn rats

We determined metabolic responses after enteric galactose alimentation in 5- to 7-day-old newborn rats fasted for 24 h. The glycemic response was attenuated after enteric galactose feeding compared with the response after enteric glucose-fed rat pups. 14C radioactivity in blood from galactose-fed pups was reduced as counts in blood galactose were lower than counts in blood glucose in glucose-fed pups. Nonetheless within 15 min, [14C] from galactose appeared in blood glucose suggesting rapid conversion of galactose to glucose. The plasma insulin response was also attenuated after galactose feeding compared with the insulin response after enteric glucose. Hepatic glycogen content increased rapidly after enteric galactose feeding and was higher than after glucose feeding at 60, 120, and 180 min. Significant glycogen synthesis after oral glucose was delayed and occurred at 240 min. Carbon radioactivity in glycogen was higher in galactose fed pups between 15 and 360 min of the study. Serial determination of hepatic metabolites revealed an increase of galactose-1-phosphate levels after oral galactose at 240 and 300 min and a transient decline of ATP at 15 min. Other hepatic metabolites did not demonstrate significant differences between the two groups. These data suggest that hepatic glycogen synthesis is more rapid and occurs sooner after galactose than after glucose alimentation in previously fasted newborn rats. Galactose may enter a more direct pathway for neonatal hepatic glycogen synthesis. The relatively delayed entry of glucose label into hepatic glycogen and the delay of net glycogen synthesis after oral glucose suggest that glucose entry is not direct and may require further metabolism before incorporation into glycogen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Familial Fanconi syndrome with malabsorption and galactose intolerance, normal kinase and transferase activity. A report on two siblings

Two siblings of Turkish-Assyrian extraction, whose parents were first cousins, had poor appetite, slow weight gain and retarded psychomotor development. When given milk the galactose concentration in blood increased. An oral galactose load showed a markedly reduced capacity to metabolize galactose. Fanconi syndrome was present as in classical galactosemia. A galactose-free diet reduced the aminoaciduria but did not normalize the renal tubular function nor the children's general condition. Galactokinase and galactose-1-phosphate uridyltransferase activities in red blood cells were normal. The physical appearance of the children (sparse subcutaneous fat, thin extremities and distended abdomen) and the results of vitamin A and xylose absorption tests, were in accordance with a malabsorption condition. Glucose, however, seemed to be absorbed normally from the gut. There was no evidence of primary liver disease. Since the condition did not normalize with a galactose-free diet, an enzyme defect of galactose metabolism is unlikely. Instead, a more general transport defect with autosomal recessive inheritance is proposed.     

Generalized epimerase deficiency galactosemia

Galactosemia is caused by inherited deficiencies in one of three enzymes involved in the metabolism of galactose: galactose-1-phosphate uridyltransferase (GALT), galactokinase (GALK), and uridine diphosphate galactose-4-epimerase (GALE). The rarest and most poorly understood form of galactosemia is due to epimerase deficiency. We are reporting such a rarest form of galactosemia presenting with progressively increasing cholestatic jaundice and failure to thrive at one month of age. After confirmation of decreased epimerase level in RBC hemolysate, the patient was put on galactose restricted diet and vitamins supplementation, which reversed the clinical signs as well as altered liver function. Patient is on regular follow-up and now at 15 months of age he has no marked developmental delay.     

Galactosaemia: a new severe variant due to uridine diphosphate galactose-4-epimerase deficiency.

A baby presented on day 5 with symptoms of classical galactosaemia which are believed to be owing to a lack of uridine diphosphate-4-epimerase, rather than to the usual galactose-1-phosphate uridyl transferase defect. Apart from galactosaemia the condition was characterised biochemically by a red cell accumulation of galactose-1-phosphate and uridine diphosphate galactose. Galactose restriction modified the acute clinical and biochemical abnormality, but it appears essential to include some galactose in the diet in this condition to allow synthesis of galactosides, including the brain gangliosides.     

In vivo evidence of brain galactitol accumulation in an infant with galactosemia and encephalopathy

In a newborn infant with galactose-1-phosphate uridyltransferase deficiency and encephalopathy, brain magnetic resonance imaging revealed cytotoxic edema in white matter. Using in vivo proton magnetic resonance spectroscopy, we detected approximately 8 mmol galactitol per kilogram of brain tissue, an amount potentially relevant to the pathogenesis of brain edema.     

Developmental aspects of galactose-1-phosphate uridylytransferase in rat intestine.

Kinetic and developmental characteristics of rat jejunal galactose-1-phosphate uridylyltransferase have been examined. Km values for the substrates galactose-1-phosphate and uridine diphosphate (UDP) glucose were the same for both the newborn and adult rat enzymes, although the Vmax of the enzyme in newborns was about threefold higher than that of the adult rat. Equal enzyme activity was present in the villus, crypt cells and the muscularis of adult jejunum. The specific activity of the enzyme remained relatively uniform (V about 20 nmoles/min/mg protein) until 18 days of age when the velocity of the reaction began to decrease. The adult value at 42 days of age is about one fifth of that in the young. The pattern of change of specific activity was compared with that for galactokinase and UDP-galactose-4-epimerase, and the observations suggest separated regulatory factors for each enzyme. The total activity of the galactose-metabolizing enzymes in jejunum was also calculated. In the young, transferase has the highest activity, but in the adult, epimerase activity is highest. Jejunal galactokinase activity is low throughout the developmental period which suggests that phosphorylation of galactose may be the limiting step in intestinal metabolism of the sugar.     

Risk factors for premature ovarian failure in females with galactosemia

The risk for premature ovarian failure (POF) in females with galactosemia can be predicted by analyzing 3 areas of risk pathology: the patient's molecular genotype for galactose-1-phosphate uridyltransferase (GALT), alternate pathways for galactose metabolism, and the patient's environment at diagnosis and during treatment. STUDY DESIGN: Retrospective cross-sectional information was collected on 53 females with classic galactosemia, and their ovarian function was analyzed by determination of serum follicle-stimulating hormone and luteinizing hormone levels and by clinical observation. The associations were analyzed between POF and the mutations in GALT, the highest erythrocyte galactose-1-phosphate (Gal-1-P) level at diagnosis, the age at which dietary treatment was initiated, mean erythrocyte Gal-1-P level during treatment, and whole-body carbon 13-labeled galactose oxidation to (13)CO(2). RESULTS: The most prevalent mutation, Q188R, had a significant effect of genotype category (Q188R/Q188R, Q188R/Other, Other/Other) on POF (P =.04, Fisher exact test and an odds ratio of 8.3). Mean erythrocyte Gal-1-P level during treatment was a significant risk factor for POF (P =.04). Also, all patients studied with less than 5% total body oxidation of galactose to (13)CO(2) had POF, whereas those with more than 5% did not have POF (P =.008, Fisher exact test). CONCLUSION: The development of POF in females with galactosemia is more likely if the patient's genotype is Q188R/Q188R, if the mean erythrocyte Gal-1-P is >3.5 mg/dL during therapy, and if the recovery of (13)CO(2) from whole-body (13)C-galactose oxidation is reduced below 5% of administered (13)C-galactose.     

Verbal dyspraxia and galactosemia

Classical galactosemia is an autosomal recessive disorder resulting from deficient galactose-1-phosphateuridyl transferase (GALT) activity. Verbal dyspraxia is an unusual outcome in galactosemia. Here we validated a simplified breath test of total body galactose oxidation against genotype and evaluated five potential biochemical risk indicators for verbal dyspraxia in galactosemia: cumulative percentage dose (CUMPCD) of (13)CO(2) in breath, mean erythrocyte galactose-1-phosphate, highest erythrocyte galactose-1-phosphate, mean urinary galactitol, and erythrocyte GALT activity. Thirteen controls and 42 patients with galactosemia took a (13)C-galactose bolus, and the (CUMPCD) of (13)CO(2) in expired air was determined. Patients with <5% CUMPCD had mutant alleles that severely impaired human GALT enzyme catalysis. Patients with > or =5% CUMPCD had milder mutant human GALT alleles. Twenty-four patients consented to formal speech evaluation; 15 (63%) had verbal dyspraxia. Dyspraxic patients had significantly lower CUMPCD values (2.84 +/- 5.76% versus 11.51 +/- 7.67%; p < 0.008) and significantly higher mean erythrocyte galactose-1-phosphate (3.38 +/- 0.922 mg/dL versus 1.92 +/- 1.28 mg/dL; p = 0.019) and mean urinary galactitol concentrations (192.4 +/- 75.8 mmol/mol creatinine versus 122.0 +/- 56.4; p = 0.048) than patients with normal speech. CUMPCD values <5%, mean erythrocyte galactose-1-phosphate levels >2.7 mg/dL, and mean urinary galactitol levels >135 mmol/mol creatinine were associated with dyspraxic outcome with odds ratios of 21, 13, and 5, respectively. We conclude that total body oxidation of galactose to CO(2) in expired air reflects genotype and that this breath test is a sensitive predictor of verbal dyspraxia in patients with galactosemia.     

Transient galactosemia detected by neonatal mass screening

BACKGROUND: The Paigen method has detected not only persistently galactosemic patients, but also many children with transient galactosemia during the neonatal period. The diagnosis and clinical course of 389 patients with transient galactosemia detected by neonatal mass-screening from 1986 to 1996 in the Hiroshima prefecture were evaluated. METHODS: Enzyme assays for galactose metabolism, measurement of blood galactose levels, erythrocyte galactose-1-phosphate levels, serum total bile acid (TBA) levels and liver function tests were performed at the first visit by patients to our hospital. Liver function and the mental and physical development of patients were evaluated during the follow-up period (approximately 1 year). RESULTS: The diagnoses were classified as follows: 253 patients with unknown cause, 128 heterozygotes and two homozygotes for galactose enzyme deficiency (galactose-1-phosphate uridyltransferase, galactokinase, UDP-galactose 4-epimerase) and six heterozygotes for Duarte variant. Twelve patients showed high serum levels of TBA (> 80 mumol/L), which suggests the presence of portal-systemic shunts during the neonatal period causing galactosemia. Most patients showed normal mental and physical development during infancy. However, of 25 patients with mild to moderate abnormal liver function tests of unknown etiology after the neonatal period, five showed poor weight gain coincident with liver dysfunction. In almost all patients, levels of transferase decreased to the normal range by 1 year of age. CONCLUSION: We found that the prognosis of transient galactosemia was almost always favorable. However, patients should be followed for at least 1 year, because late liver dysfunction, which might cause poor weight gain, occurred in 6% of our patients.     

FAMILIAL FANCONI SYNDROME WITH MALABSORPTION AND GALACTOSE INTOLERANCE, NORMAL KINASE AND TRANSFERASE ACTIVITY

ABSTRACT. Aperia, A., Bcrgqvist, G., Linné, T. and Zetterström, R. (Department of Paediatrics, Karolinska Institute, St. Göran's Children's Hospital, Stockholm, Sweden). Familial Fanconi syndrome with malabsorption and galactose intolerance, normal kinase and transferase activity. A report on two siblings. Acta Paediatr Scand, 70:527,.–Two siblings of Turkish-Assyrian extraction, whose parents were first cousins, had poor appetite, slow weight gain and retarded psychomotor development. When given milk the galactose concentration in blood increased. An oral galactose load showed a markedly reduced capacity to metabolize galactose. Fanconi syndrome was present as in classical galactosemia. A galactose-free diet reduced the aminoaciduria but did not normalize the renal tubular function nor the children's general condition. Galactokinase and galactose-1-phosphate uri-dyltransferase activities in red blood cells were normal. The physical appearance of the children (sparse subcutaneous fat, thin extremities and distended abdomen) and the results of vitamin A and xylose absorption tests, were in accordance with a malabsorption condition. Glucose, however, seemed to be absorbed normally from the gut. There was no evidence of significant primary liver disease. Since the condition did not normalize with a galactose-free diet, an enzyme defect of galactose metabolism is unlikely. Instead, a more general transport defect with autosomal recessive inheritance is proposed.     

Galactose metabolism by the mouse with galactose-1-phosphate uridyltransferase deficiency

The ability of mice deficient in galactose-1-phosphate uridyltransferase (GALT) to metabolize galactose was determined in animals weaned to a mouse chow diet for a 4-wk period. When given [14C]galactose intraperitoneally, these animals slowly oxidized the sugar, excreting only 5.5% of the dose as 14CO2 in 4 h, whereas normal animals excreted 39.9%. These results mimic those seen in human galactosemic patients given isotopic galactose. When given 10 micromol of [1-13C]galactose, normal animals excrete small amounts of labeled galactose and galactonate but no galactitol in urine whereas GALT-deficient mice excrete significant amounts of all of these as labeled compounds in urine. When challenged with galactose, only about 20% of the dose is excreted in urine, and even on the chow diet, significant amounts of galactose, galactonate, and galactitol are excreted in urine. These compounds are also found to be present in liver, kidney, and brain, except that galactonate is not found in brain. Galactose-1-phosphate accumulates in red blood cells to levels found in humans exposed to large amounts of galactose, and galactose-1-phosphate is found in increased amounts in liver, kidney, and brain of GALT-deficient animals. There was no difference in the hepatic concentration of uridine diphosphate galactose and uridine diphosphate glucose between normal and GALT-deficient mice. The explanation for the presence of galactose and its conversion products in tissues and urine of affected mice appears to be related to the presence of approximately 1.75% of galactose-containing carbohydrates in the chow, which becomes bioavailable to mice. Despite the presence of galactose and its metabolites in tissues and urine and impaired ability to oxidize the sugar, the GALT-deficient animals are indistinguishable from normal animals and do not exhibit the phenotype of humans with GALT-deficiency galactosemia.     

Galactose breath testing distinguishes variant and severe galactose-1-phosphate uridyltransferase genotypes

A galactose breath test that quantitates [1-(13)C]galactose conversion to 13CO2 provides information on the whole body galactose oxidative capacity. As there is little information on the relationship between whole body oxidation and the genotype in patients with galactosemia, we measured the 13CO2 excretion for 2 h after administration of [1-(13)C]galactose in 37 patients (3-48 y old) with galactose-1-phosphate uridyltransferase (GALT) deficiency and 20 control subjects (3-37 y old). Eleven patients with the common Q188R/Q188R genotype and no detectable erythrocyte GALT activity eliminated <2% of a bolus of [1-(13)C]galactose as 13CO2 compared with 8.47 to 28.23% in controls. This defines a severe metabolic phenotype. Seven patients with one Q188R allele and a second mutant allele such as L195P, E308K, V151A, M142K, or Q344K and one patient with a K285N/unknown genotype also released <2% as 13CO2 in 2 h. The presence of N314D or S135L as the second mutant allele does not impair total body galactose oxidation, as individuals with the GALT genotype of Q188R/N314D, K285N/N314D, and Q188R/S135L had normal 2-h galactose breath tests. Subjects with S135L/S135L, N314D/N314D, S135L/deltaT2359 as well as other rarer genotypes such as R258C/Y209C, E203K/IVSC-N314D, K285N/T138M, Q188R/D113N, S135L/F171S, R148W/N314D, and IVSC-N314D/N314D oxidized galactose comparable to controls. The dissociation of residual erythrocyte GALT activity and whole body galactose oxidative capacity is exemplified by blacks with a S135L/S135L genotype and absent erythrocyte GALT activity. An oral 2-h [1-(13)C]galactose breath test distinguishes severe and variant GALT genotypes and enables delineation of the extent of impaired galactose metabolism in an array of patients who possess diverse GALT mutations. It may prove to be useful in establishing whether a patient is capable of manifesting disease similar to patients with a Q188R/Q188R genotype.     

Galactosemia—A clinical and enzymological study in a family

Summary A case of galactosemia, proved by erythrocyte galactose-1-phosphate uridyl transferase studies, apart from a suggestive family history, typical clinical picture and other supportive investigations, has been reported. Both the parents were first cousins. The parents and one younger sibling of the patient had heterozygous enzyme levels. The patient showed some improvement on a modified Holzel's diet but later deteriorated and died due to hepatic failure resulting from continued but unwitting administration of galactose. Cr⁵¹ studies demonstrated markedly reduced red cell life span. The autosomal recessive nature of the galactosemia trait has been brought out. The diagnostic criteria are reviewed and the importance of enzyme studies as a confirmatory investigation is stressed. From the Department of Pediatrics, K.G. Medical College and Central Drug Research Institute, Lucknow.     

Effects of galactosemia in utero

There is direct evidence that in galactosemia, due to galactose-1-phosphate uridyltransferase deficiency, galactose, galactose-1-phosphate and galactitol accumulate in the fetus by week 20 of gestation. The metabolic abnormality may develop earlier than this, however, since the key enzymes in galactose metabolism have been shown to be present in normal fetal liver from the 10th week of gestation. There has been a single report of increased galactitol in amniotic fluid obtained at 10 weeks gestation, the outcome being a baby affected with galactosemia. Cataract formation in the fetus is rare and the only direct evidence that galactosemia may have harmful effects in utero. However, it has been concluded that the liver pathology seen in some patients who died in the neonatal period originated prenatally, and some studies have found that galactosemia is associated with reduced birth weight. Reports of two patients with histologically normal ovaries very soon after birth have been cited as evidence against gonadal dysfunction arising during fetal life, but it should be noted that this is not a constant feature in female galactosemics. Other observations, particularly those made from animal models, would suggest that ovarian dysfunction is most likely to have been caused in utero.     

A PATIENT WITH HEREDITARY GALACTOSEMIA STUDIED WITH A SCREENING METHOD FOR GALACTOSE IN URINE

A case of hereditary galactosemia in a newborn infant is reported. Dietary treatment was started on the 9th day of life, which caused a dramatical improvement in the patient's condition. Diagnosis was confirmed by assay of galactose in urine and blood, and finally by demonstration of the enzyme deficiency in the red blood cells of the patient. Both parents had low values for galactose-1-phosphate uridyl transferase activity in red blood cells, in agreement with the fact that they are heterozygotes for hereditary galactosemia. A recently described test paper for galactose in urine was used both in the diagnosis of the disease and for the control of the suitability of the patient's diet. In addition to galactose, the urine also contained large anounts of galactitol. On the introduction of galactose-free diet, galactitol dis-appeared from the urine more slowly than did galactose. There was an increased concentration of amino acids in the blood and in the urine, as a result of liver damage and also decreased tubular reabsorption. Also the aminoaciduria and the increased blood amino acid concentration disappeared on galactose-free diet.     

Uridine diphosphate galactose 4'-epimerase deficiency. IV. Report of eight cases in three families.

Eight persons who had no activity of uridine diphosphate galactose 4'-epimerase in their circulating blood cells are known today. They were healthy members of three different families. Propositi were newborns discovered in a mass screening test for blood galactose which registered high levels of erythrocyte galactose-1-phosphate. Epimerase deficiency was restricted to circulating blood cells, but in liver biopsy specimens, in cultured skin fibroblasts and in activated lymphocytes epimerase was found to be normally active. Heterozygotes had intermediate red cell epimerase activity. There were no symptoms of galactose intolerance and no pathology related to the enzyme defect. All 8 epimerase deficient persons had a ccdee Rhesus genotype. Attempts at demonstrating genetic linkage between the epimerase and Rhesus loci were unsuccessful because of the difficulty encountered in ascertaining epimerase heterozygosity. Individuals with hereditary UDP-galactose 4'-epimerase deficiency appear to produce an unstable mutant enzyme requiring higher NAD concentration for maximum activity.     

Cerebral energy metabolism in phenylketonuria: findings by quantitative In vivo 31P MR spectroscopy

Both severe impairments of brain development in untreated infants and acute reversible neurotoxic effects on brain function are clinical features of phenylketonuria (PKU). For determining whether impairments of cerebral energy metabolism play a role in the pathophysiology of PKU, quantitative in vivo 31P magnetic resonance spectroscopy (MRS) was performed in a supratentorial voxel of 11 adult PKU patients and controls. Peak areas of inorganic phosphate; phosphocreatine; alpha-, beta-, and gamma-ATP; NAD; phosphomonoesters; phosphodiesters; and a broad phospholipid signal were converted to millimolar concentrations. Mg2+, pH, ADP, the phosphorylation potential, and the relative velocity of oxidative metabolism V/Vmax were derived. Clinical evaluation included mutation analysis, neurologic investigation, intelligence testing, magnetic resonance imaging, and concurrent plasma and brain phenylalanine (Phe), the last by 1H-MRS. Phe loading was performed in five patients with an oral dose of 100 mg/kg body wt L-Phe monitored by spectral EEG analysis. Under steady-state conditions, 31P-MRS revealed normal values for ATP, phosphocreatine, NAD, phosphomonoesters, phosphodiesters, Mg2+, and pH in PKU. ADP (+11%) and the phosphorylation potential (+22%) were increased. Peak areas of inorganic phosphate (-22%) and phospholipid (-8%) were decreased. ADP correlated with concurrent plasma (r = 0.65) and brain (r = 0.55) Phe. During the Phe load, blood Phe levels increased steeply. EEG revealed slowing of background activity. The phosphorylation potential decreased, whereas ADP and V/Vmax increased. In vivo 31P-MRS demonstrated subtle abnormalities of cerebral energy metabolism in PKU in steady-state conditions that were accentuated by a Phe load, indicating a link between Phe neurotoxicity and imbalances of cerebral energy metabolism.     

Galactosemia with chorea — an unusual presentation

Galactosemia, an inborn neurometabolic disorder, results from an aberrant galactose metabolism due to the deficiency of serum galactose-1-phosphate uridyltransferase activity. It manifests in the central nervous system in the form of hypotonia, seizures, mental retardation, tremor, ataxia, and progressive cerebellar as well as extrapyramidal features. To the best of our knowledge, chorea due to galactosemia has not been reported in infancy.     

Abnormal galactosylation of complex carbohydrates in cultured fibroblasts from patients with galactose-1-phosphate uridyltransferase deficiency.

An abnormality in galactosylation of complex carbohydrates may be important in the pathogenesis of the long-term complications of classic (galactose-1-phosphate uridyltransferase-deficient) galactosemia. The ability of nine galactosemic fibroblast preparations to be galactosylated with a purified galactosyltransferase was measured as an indicator of vacant sites where galactose would normally reside. The amount of galactose transferred to cell protein from galactosemic patients was significantly higher than that transferred to a group of seven controls (p less than 0.005). Galactosyltransferase activity of the galactosemic cell preparation toward N-acetylglucosamine was also significantly higher than normal (p less than 0.01), and there was a linear relationship between these two parameters in galactosemic but not normal cells. These findings suggest that there is defective galactosylation of galactosemic cell complex carbohydrates and that such cells increase their galactosyltransferase levels in an attempt to compensate for the defect. Defective galactosylation may be implicated as an etiologic factor in complications observed in galactosemic patients even when treated with galactose-restricted diets.