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PubMed1998

Abnormalities of retinal metabolism in diabetes or experimental galactosemia: V. Relationship between protein kinase C and ATPases.

In the retinas of diabetic animals, protein kinase C (PKC) activity is elevated, and Na+-K+-ATPase and calcium ATPase activities are subnormal. These abnormalities are also present in another model of diabetic retinopathy, experimental galactosemia. We have investigated the relationship between hyperglycemia-induced abnormalities of PKC and ATPases using a selective inhibitor of beta isoform of PKC (LY333531). Diabetes or experimental galactosemia of 2 months' duration resulted in > 50% elevation of PKC activity in the retina, and administration of LY333531 prevented the elevation. In retinas of the same rats, the LY333531 prevented hyperglycemia-induced decreases of both Na+-K+-ATPase and calcium ATPase activities. Retinal microvessels, the main site of lesions in diabetic retinopathy, likewise showed elevated activity of PKC and inhibition of ATPases in diabetes and in experimental galactosemia, and administration of LY333531 to diabetic animals prevented these abnormalities. PKC activity in sciatic nerves, in contrast, became subnormal in diabetes and experimental galactosemia, and LY333531 had no effect on PKC activity in the sciatic nerve. PKC activity in the cerebral cortex was not affected by diabetes or experimental galactosemia. The results suggest that diabetes-induced reductions in Na+-K+-ATPase and calcium ATPase in the retina are mediated in large part by PKC-beta. The availability of an agent that can normalize the hyperglycemia-induced increase in PKC activity in the retina should facilitate investigation of the role of PKC in the development of diabetic retinopathy.

Animals↗
PubMed1979

[Clinical and biochemical diagnosis of galactosemia among our cases].

Clinical and biochemical diagnostic studies concerned 17 cases of galactosemia coming from 15 not consauguineous families. Galactosemia was diagnosed between 1-st day and 11-th month of life. Tentative diagnosis based on clinical picture was made in 12 infants, others were detected through family history of galactosemia and/or biochemical newborn screening carried out at the National Research Institute of Mother and Child since 1969. Clinical symptoms of galactosemia occurred in most patients in the first week of life. They were the following (tab. II): hepatomegaly (in 94%), jaundice (81%), splenomegaly (79%), vomitus (62%) and diarrhoea in 56% of patients. Cataract was found in 6 infants (38%). Biochemical diagnosis was based on the results of enzymatic estimation of galactose-1-phosphate uridyl transferase activity in blood, galactose-1-phosphate in red blood cells and galactose in blood and urine. No activity of galactose-1-phosphate uridyl transferase was found in all patients, and the concentration of galactose-1-phosphate was higher than 25 mg/100 ml of red blood cells. High galactose level was observed in blood and urine in all patients with typical clinical course of galactosemia. In 2 patients however without clinical symptoms of the disease only trace amounts of galactose was detected in blood and urine. All these patients were treated with galactose free diet.

Adult↗
PubMedDate not supplied

Problems in the diagnosis of transferase and galactokinase deficient galactosemia.

Galactose in serum and galactose-1-phosphate in erythrocytes were measured in six transferase deficient children to determine if these metabolites could be used in detecting transferase deficient galactosemia. In all six children the galactose levels were normal and the galactose-1-phosphate elevated. The galactose level depends on diet and the rate of metabolism to galactose-1-phosphate and, therefore, should not be used to predict transferase deficient galactosemia. The galactose-1-phosphate level was elevated in all the transferase deficient children because once formed it cannot be metabolized. Measurement of galactose-1-phosphate is difficult and is usually requested to determine whether or not the child is following the galactose restricted diet. In transferase deficient galactosemia, the enzyme hexose-1-phosphate uridylyltransferase is absent. The diagnosis should be determined by measurement of the activity of the enzyme hexose-1-phosphate uridylyltransferase in erythrocytes. In galactokinase deficient galactosemia, the enzyme galactokinase is absent. Galactose levels are elevated but the amount present depends on diet and how soon the blood was collected after the ingestion of galactose containing foods. The diagnosis of galactokinase deficient galactosemia is based on the measurement of the enzyme galactokinase in erythrocytes.

Adolescent↗
PubMed1999

Identification of mutations in the galactose-1-phosphate uridyltransferase (GALT) gene in 16 Turkish patients with galactosemia, including a novel mutation of F294Y. Mutation in brief no. 235. Online.

Classical galactosemia caused by deficiency of galactose-1-phosphate uridyltransferase (GALT) is a severe autosomal recessive disorder. We report here molecular analysis of 16 unrelated Turkish galactosemia index cases without GALT activity. Almost 84% of all mutant alleles were identified in this study. The most common molecular defect observed in the Turkish population was Q188R (replacement of glutamine-188 by arginine) (57%). In order to facilitate the determination of unknown mutations in the entire coding region of GALT, we established an approach based on GALT cDNA synthesis and direct sequencing. We have identified one novel candidate galactosemia mutation, a T-to-A transversion at the codon 294 (F294Y) in exon 9 in addition to previously reported three missense (M142K K285N, A320T), one stop codon (E340X), and one silent (L218L) mutations in galactosemia patients which reflect considerable genetic heterogeneity in the Turkish population.

Alleles↗
PubMed1995

A molecular approach to galactosemia.

Classical galactosemia (G/G) is caused by the lack of galactose-1-phosphate uridyltransferase (GALT) activity. A more common clinical variant, Duarte/Classical (D/G) produces partial enzymatic impairment. Although neonatal death due to G/G galactosemia has been largely eliminated by population-based screening and intervention, long-term outcome in some is associated with impaired growth, ovarian failure, dyspraxic speech and neurologic deficits. At least 32 variants in the nucleotide sequence of the GALT gene have been identified and 9 have transferred impaired GALT activity to transformed cells in transfection experiments. We here define the prevalence and biochemical phenotype of two mutations. An A to G transition in exon 6 of the GALT gene converts a predicted glutamine at codon 188 to an arginine (Q188R), and introduces a new HpaII cut site into the gene which enables population screening by polymerase chain reaction. An A to G transition in exon 10 in the GALT gene produces a codon change converting an asparagine to aspartic acid at codon 314 (N314D) and adds an AVA II cut site. We screened a large population for the Q188R and N314D sequence changes to investigate the prevalence of Q188R in G/G galactosemia, the effect of homozygosity for Q188R on outcome, and the prevalence and biochemical phenotype of the N314D sequence change. We found that the Q188R mutation has a prevalence of 62% in a predominately Caucasian population of 107 patients with G/G galactosemia. Homozygosity for Q188R was associated with a poor clinical outcome in a subgroup of these patients. The N314D mutation is associated with the Duarte biochemical phenotype with extraordinary concordance.

Base Sequence↗
PubMed1995

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.

Female↗
PubMed1994

Galactosemia produces ARI-preventable nodal changes similar to those of diabetic neuropathy.

The present study was designed to examine the development of structural changes, characteristic of diabetic neuropathy, in chronic galactosemia and their responsiveness to inhibition of the polyol-pathway. Sprague-Dawley rats weighing 70-90 g were given a 50% galactose diet continued for 4 or 8 months. Half of these animals were simultaneously given the aldose reductase inhibitor (ARI) WAY 121-509. ARI-treatment normalized galactitol and myoinositol levels in the sciatic nerve. At 4 months, sciatic nerve conduction velocity (NCV) in galactosemic rats was reduced by 30% which was prevented in ARI-treated rats. At 8 months galactosemia reduced NCV to 58% of control values, while ARI-treatment for 8 months improved NCV to 71% of control values. ARI-treatment prevented in galactosemic rats nodal structural changes characteristic of diabetic neuropathy, whereas axonal atrophy was not affected by ARI-treatment, which may in part account for the only partial prevention of the NCV slowing at 8 months. Nerve fiber regeneration was increased 4-fold in ARI-treated rats compared with untreated galactosemic rats. These data suggest that chronic galactosemia produces a neuropathy structurally similar to diabetic neuropathy. The lack of an ARI-treatment effect on axonal atrophy suggests that this defect is not polyol related in galactosemia.

Aldehyde Reductase↗
PubMed1992

Characterization of two missense mutations in human galactose-1-phosphate uridyltransferase: different molecular mechanisms for galactosemia.

We report the molecular characterization of two novel galactosemia mutations that exhibit different molecular phenotypes. Both are of the missense type with low or no residual enzyme activity. The R148W mutation results in an unstable protein, although messenger RNA is still produced. In contrast, the L195P mutation produces stable but inactive immunoreactive protein. The R148W mutation alters an amino acid that is not evolutionarily conserved, while the L195P mutation affects a well-conserved residue nine amino acids down-stream from the putative active site nucleophile. These mutations provide evidence that different mechanisms can result in galactosemia: destabilizing mutations in any given area of the protein and missense mutations in conserved domains of the enzyme resulting in low or no activity. These two mutant alleles represent the fifth and sixth galactosemia mutations and confirm the hypothesis that galactosemia results from a multiplicity of mutations at the molecular level.

Amino Acid Sequence↗
PubMed1993

Effect of hypogonadism and deficient calcium intake on bone density in patients with galactosemia.

Forty children and adults with classic galactosemia had vertebral bone density determined by standard quantitative computed tomography at 3.4 to 44.2 years of age. Compared with age- and sex-matched control subjects, patients with galactosemia had diminished bone density (p = < 0.001). Prepubertal patients of both sexes had bone density determinations below those of the control group (p = 0.008); similar findings were seen in postpubertal patients as well (women, p = 0.001; men, p = 0.008). Women receiving replacement estrogen-progestin therapy for premature ovarian failure had abnormal bone density (136.3 +/- 17.3 mg/cm3 vs 166.0 +/- 17.5 mg/cm3 for control subjects; p = 0.002); patients with evidence of ovarian insufficiency not receiving replacement sex steroids had even lower bone density (92.4 +/- 14.3 mg/cm3 vs 160.2 +/- 20.2 mg/cm3 for control subjects; p < 0.001). Calcium intake for the entire galactosemia group was 540 +/- 344 mg/day. Calcium intake correlated positively with bone density in women given exogenous estrogen (r = 0.87; p = 0.002) and in men (r = 0.74; p = 0.009). Thus the diminished mineralization of bones appears to be another abnormality associated with galactosemia. The results of our study suggest that this is likely secondary to abnormal levels of sex steroids in female patients, low calcium intake, and perhaps an intrinsic defect in the normal galactosylation of the collagen matrix of bone caused by the enzyme defect. Strategies to improve bone formation should be considered to diminish morbidity in patients with this inborn error of metabolism.

Adolescent↗
PubMed1999

Urine and plasma galactitol in patients with galactose-1-phosphate uridyltransferase deficiency galactosemia.

Urinary excretion of galactitol was determined in 95 normals (N/N), 67 galactosemic (G/G), and 39 compound heterozygotes for the Duarte and galactosemia genotype (D/G). Galactitol excretion is age-dependent in both normal individuals and patients with classic galactosemia on lactose-restricted diets. In galactosemic patients who are homozygous for the Q188R mutation, urinary galactitol levels were fivefold to 10-fold higher than those of normal subjects of comparable age. All but a few patients with classic galactosemia with the Q188R mutation and another mutant G allele had urinary excretion comparable to the Q188R homozygous patients. African-American galactosemic patients with the S135L mutation of the galactose-1-phosphate uridyltransferase (GALT) gene also excreted abnormal quantities of galactitol. Most subjects with a Duarte allele and a G allele excrete normal amounts of the sugar alcohol. There is a correlation between galactitol excretion and red blood cell (RBC) galactose-1-phosphate (gal-1-P). Plasma galactitol was also elevated in galactosemic patients (3.4 to 23.2 micromol/L; undetectable in normal individuals). In contrast to the decrease in urinary galactitol with age, plasma levels remain in a narrow concentration range with no significant difference with age. Urine and plasma galactitol distinguish galactosemic patients from normals. In addition, urinary galactitol excretion may be an important parameter for the assessment of steady-state galactose metabolism in galactosemia.

Adolescent↗
PubMed1992

Molecular characterization of two galactosemia mutations and one polymorphism: implications for structure-function analysis of human galactose-1-phosphate uridyltransferase.

We report here the molecular characterization of two galactosemia mutations, L74P and F171S, and one polymorphism, S135L, in human galactose-1-phosphate uridyltransferase (GALT). Both galactosemia mutations result in reduced enzymatic activity when reconstructed in the cDNA and overexpressed. The polymorphism, in contrast, has near normal activity. Both mutations affect evolutionarily conserved residues, suggesting that they are functionally important, while the polymorphism occurs in a nonconserved domain which is presumably not critical for enzymatic function. The F171S mutation is close to the putative active-site nucleophile. Our data further support the notion of molecular heterogeneity of galactosemia and suggest that galactosemia mutations and GALT polymorphisms may be useful tools in highlighting different functional domains in human GALT.

Base Sequence↗
PubMed1999

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.

Bile Acids and Salts↗
PubMed1991

Molecular analysis of 11 galactosemia patients.

Galactosemia is a human inborn error of galactose metabolism due to deficiency of galactose-1-phosphate uridyl transferase. In this paper, I describe the molecular analysis of genomic DNA, mRNA and protein from 11 different galactosemic patients by Southern, Northern and Western blotting. The results of these experiments lead me to conclude that galactosemia is caused mostly by missense mutations. The unusual preponderance of missense mutations in galactosemia led me to investigate its cause. I demonstrate that all 9 patients I investigated have detectable residual enzyme activity (ranging from 0.7-6.9% of normal). This finding is of potential importance in addressing the long-term complications of galactosemia.

Blotting, Northern↗
PubMed1984

Blood-brain transfer of galactose in experimental galactosemia, with special reference to the competitive interaction between galactose and glucose.

The interaction between glucose and galactose during transport across the cerebral capillary endothelium was studied in anesthetized rats. Although galactose is present in the diet of suckling mammals and is a potential substrate for brain metabolism in adult mammals, its effect on glucose transport in adult rats is unknown. A kinetic model was formulated to analyze the effect of chronically elevated galactose levels on glucose transport in adult rats. The analysis indicated that galactose and glucose compete for the same transport mechanism in the cerebral capillary endothelium. The Tmax of glucose and galactose were both about 380 mumol 100 g-1 min-1 and the Kt of galactose (30 mM) was about three times that of glucose (10 mM). During prolonged galactosemia in adult rats, neither the Tmax, nor the Kt of either competitor changed substantially when compared with rats subjected to acute galactosemia. At 10 mM galactose in plasma in rats with acute galactosemia, the inhibition of glucose transport, simulated a 25% reduction of plasma glucose, and in rats with chronic galactosemia a 20% reduction. This moderate effect is in contrast to the effect of galactose in suckling rats in which 10 mM galactose in plasma reduced the glucose transport to a level corresponding to a 50% reduction of the plasma glucose concentration.

Animals↗
PubMed1980

Borderline galactosemia.

A family with combined heterozygosity for "classical" galactosemia (deficiency of uridyl-transferase) and for galactokinase deficiency is reported. The proband, who had this genetic combination was detected as newborn in the ordinary screening for galactosemia. A lactose tolerance test at the age of three months proved normal and he has no symptoms or signs on ordinary diet. The mother of the proband was not only heterozygote for "classical" galactosemia and galactokinase deficiency but also for the Durarte variant. She had a substantial urine excretion of galactose and high serum galactose after an oral lactose load. She had no clinical symptoms or signs. Patients with combined heterozygosity for galactosemia may develop cataracts and should be followed by clinical examinations.

Adult↗
PubMed2002

The clinical and molecular spectrum of galactosemia in patients from the Cape Town region of South Africa.

BACKGROUND: The objective of this study was to document the clinical, laboratory and genetic features of galactosemia in patients from the Cape Town metropolitan region. METHODS: Diagnoses were based on thin layer chromatography for galactosuria/galactosemia and assays of erythrocyte galactose-1-phosphate uridyltransferase (GALT) and galactokinase activities. Patients were screened for the common S135L and Q188R transferase gene mutations, using PCR-based assays. Screening for the S135L mutation in black newborns was used to estimate the carrier rate for galactosemia in black South Africans. RESULTS: A positive diagnosis of galactosemia was made in 17 patients between the years 1980 to 2001. All had very low or absent galactose-1-phosphate uridyltransferase (GALT) activity, and normal galactokinase levels. The mean age at diagnosis was 5.1 months (range 4 days to 6.5 months). A review of 9 patients showed that hepatomegaly (9/9), and splenomegaly, failure to thrive, developmental delay, bilateral cataracts (6/9) were the most frequent features at diagnosis. Six had conjugated hyperbilirubinemia. Four experienced invasive E. coli infection before diagnosis. Ten patients were submitted to DNA analysis. All 4 black patients and 2 of mixed extraction were homozygous for the S135L allele, while all 3 white patients were homozygous for the Q188R allele. The remaining patient of mixed extraction was heterozygous for the Q188R allele. The estimated carrier frequency of the S135L mutation in 725 healthy black newborns was 1/60. CONCLUSIONS: In the absence of newborn screening the delay in diagnosis is most often unacceptably long. Also, carrier frequency data predict a galactosemia incidence of approximately 1/14 400 for black newborns in the Cape Metropole, which is much higher than the current detection rate. It is thus likely that many patients go undetected.

Carrier State↗
PubMedDate not supplied

[Effectiveness of the screening programme for galactosemia. New strategy in Poland].

Galactosemia is an autosomal recessive disease related to deficiency of one of three different enzymes involved in the metabolism of galactose: galactokinase (GALK), galactoso-J-phosphate uridyltransferase (GALT) or UDP-galactose-4-epimerase (GALE). Classic galactosemia is due to GALT deficiency and is the most common. Longitudinal studies have shown that in spite of early diagnosis and early treatment of children with galactosemia detected in the mass screening programme, the results are poor and mental retardation as well as other complications are of similar severity as in children diagnosed clinically without screening. In many investigations it was also proved that some impairments developed already in the prenatal period. Therefore, many countries among them also Poland, stopped mass screening for galactosemia. At present, in Poland the procedure strategy in galactosemic children and their families include: diagnosis of new cases on the basis of clinical symptoms, selective screening in high-risk families, prophylactic lactose-free diet for mothers during pregnancy. Such management can help to prevent clinical manifestations in newborns and prevent death in the early period of life.

Female↗
PubMed1991

Molecular characterization of two galactosemia mutations: correlation of mutations with highly conserved domains in galactose-1-phosphate uridyl transferase.

Galactosemia is an autosomal recessive disorder of human galactose metabolism caused by deficiency of the enzyme galactose-1-phosphate uridyl transferase (GALT). The molecular basis of this disorder is at present not well understood. We report here two missense mutations which result in low or undetectable enzymatic activity. First, we identified at nucleotide 591 a transition which substitutes glutamine 188 by arginine. The mutated glutamine is not only highly conserved in evolution (conserved also in Escherichia coli and Saccharomyces cerevisiae), but is also two amino acid residues downstream from the active site histidine-proline-histidine triad and results in about 10% of normal enzymatic activity. The arginine 188 mutation is the most common galactosemia mutation characterized to date. It accounts for one-fourth of the galactosemia alleles studied. Second, we report the substitution of arginine 333 by tryptophan, caused by a transition at nucleotide 1025. The area surrounding this missense mutation is the most highly conserved domain in the homologous enzymes from E. coli, yeast, and humans, and this mutation results in undetectable enzymatic activity, suggesting that this is a severe mutation. This second mutation appears to be rare, since it was found only in the patient we sequenced. Our data provide further evidence for the heterogeneity of galactosemia at the molecular level, heterogeneity which might be related to the variable clinical outcome observed in this disorder.

Amino Acid Sequence↗