The ability of an LC-MS/MS-based erythrocyte GALT enzyme assay to predict the phenotype in subjects with GALT deficiency

BACKGROUND

GALT deficiency is a rare genetic disorder of carbohydrate metabolism. Due to the decreased activity or absence of the enzyme galactose-1-phosphate uridylyltransferase (GALT), cells from affected individuals are unable to metabolize galactose normally. Lactose consumption in the newborn period could potentially lead to a lethal disease process with multi-organ involvement. In contrast to the newborn-stage disease, however, a galactose-restricted diet does not prevent long-term complications such as central nervous system (CNS) dysfunction with speech defects, learning disability and neurological disease in addition to hypergonadotropic hypogonadism or primary ovarian insufficiency (POI) in females. As the literature suggests an association between GALT enzyme activity and the long-term complications, it is of importance to have a highly sensitive assay to quantify the GALT enzyme activity. To that end, we had developed a sensitive and accurate LC-MS/MS method to measure GALT enzyme activity. Its ability to predict outcome is the subject of this report.

MATERIALS AND METHODS

The GALT enzyme activity in erythrocytes from 160 individuals, in which 135 with classic, clinical variant or biochemical variant galactosemia, was quantified by LC-MS/MS. Individuals with GALT deficiency were evaluated for the long-term complications of speech defects, dysarthria, ataxia, dystonia, tremor, POI, as well as intellectual functioning (full scale IQ). The LC-MS/MS results were compared to a variety of assays: radioactive, [¹⁴C]-galactose-1-phosphate, paper chromatography with scintillation counting, enzyme-coupled assays with spectrophotometric or fluorometric readout or high-pressure liquid chromatography with UV detection of UDP-galactose.

RESULTS

The LC-MS/MS method measured GALT activity as low as 0.2%, whereas other methods showed no detectable activity. Largely due to GALT activities that were over 1%, the LC-MS/MS measurements were not significantly different than values obtained in other laboratories using other methodologies. Severe long-term complications were less frequently noted in subjects with >1% activity. Patients with a p.Q188R/p.Q188R genotype have no residual enzyme activity in erythrocytes.

CONCLUSION

Our LC-MS/MS assay may be necessary to accurately quantify residual GALT activities below 5%. The data suggest that patients with >1% residual activity are less likely to develop diet-independent long-term complications. However, much larger sample sizes are needed to properly assess the clinical phenotype in patients with residual enzyme activities between 0.1 and 5%.

Multiplex tandem mass spectrometry assay for newborn screening of X-linked adrenoleukodystrophy, biotinidase deficiency, and galactosemia with flexibility to assay other enzyme assays and biomarkers

All States screen for biotinidase deficiency and galactosemia, and X-linked adrenoleukodystrophy (X-ALD) has recently been added to the Recommended Uniform Screening Panel (RUSP).We sought to consolidate these tests by combining them into a single multiplex tandem mass spectrometry assay as well as to improve the current protocol for newborn screening of galactosemia.A 3 mm punch of a dried blood spot (DBS) was extracted with organic solvent for analysis of the C26:0-lysophosphatidylcholine biomarker for X-ALD.An additional punch was used to assay galactose-1-phosphate uridyltransferase (GALT) and biotinidase.All assays were combined for a single injection for analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS) (2.3 min per sample).The GALT LC-MS/MS assay does not give a false positive for galactosemia if glucose-6-phosphate dehydrogenase is deficient.The multiplex assay shows acceptable reproducibility and provides for rapid analysis of X-ALD, biotinidase deficiency, and galactosemia.The throughput and ease of sample preparation are acceptable for newborn screening laboratories.We also show that the LC-MS/MS assay is expandable to include several other diseases including Pompe and Hurler diseases (enzymatic activities and biomarkers).Because of consolidation of assays, less manpower is needed compared to running individual assays on separate platforms.The flexibility of the LC-MS/MS platform allows each newborn screening laboratory to analyze the set of diseases offered in their panel.

Accurate prediction of gestational age using newborn screening analyte data

BACKGROUND

Identification of preterm births and accurate estimates of gestational age for newborn infants is vital to guide care. Unfortunately, in developing countries, it can be challenging to obtain estimates of gestational age. Routinely collected newborn infant screening metabolic analytes vary by gestational age and may be useful to estimate gestational age.

OBJECTIVE

We sought to develop an algorithm that could estimate gestational age at birth that is based on the analytes that are obtained from newborn infant screening.

STUDY DESIGN

We conducted a population-based cross-sectional study of all live births in the province of Ontario that included 249,700 infants who were born between April 2007 and March 2009 and who underwent newborn infant screening. We used multivariable linear and logistic regression analyses to build a model to predict gestational age using newborn infant screening metabolite measurements and readily available physical characteristics data (birthweight and sex).

RESULTS

The final model of our metabolic gestational dating algorithm had an average deviation between observed and expected gestational age of approximately 1 week, which suggests excellent predictive ability (adjusted R-square of 0.65; root mean square error, 1.06 weeks). Two-thirds of the gestational ages that were predicted by our model were accurate within ±1 week of the actual gestational age. Our logistic regression model was able to discriminate extremely well between term and increasingly premature categories of infants (c-statistic, >0.99).

CONCLUSION

Metabolic gestational dating is accurate for the prediction of gestational age and could have value in low resource settings.

Galactose-1-phosphate uridyltransferase dried blood spot quality control materials for newborn screening tests

OBJECTIVES

We aimed to prepare dried-blood-spot (DBS) quality control (QC) materials for galactose-1-phosphate uridyltransferase (GALT), to evaluate their stability during storage and use, and to evaluate their performance in five DBS GALT test methods.

DESIGN AND METHODS

We prepared and characterized GALT-normal and GALT-deficient DBS materials and compared GALT activities in DBSs after predetermined storage intervals at controlled temperatures and humidities. External evaluators documented the suitability of the DBS QC materials for use in five GALT test methods.

RESULTS

GALT activity losses from DBSs stored in low (<30%) humidity for 14 days at 45°C, 35 days at 37°C, 91 days at room temperature, 182 days at 4°C, and 367 days at -20°C were 54%, 53%, 52% 23%, and 7% respectively. In paired DBSs stored in high humidity (>50%) for identical intervals, losses were: 45°C-68%; 37°C-79%; room temperature-72%, and 4°C-63%. GALT activities in DBSs stored at 4°C were stable throughout 19 excursions to room temperature. Twenty-five of 26 external evaluators, using five different GALT test methods, classified the GALT-deficient DBSs as "outside normal limits". All evaluators classified the GALT-normal DBSs as "within normal limits".

CONCLUSIONS

Most of the GALT activity loss from DBSs stored at elevated or room temperature was attributable to the effects of storage temperature. Most of the loss from DBSs stored at 4°C was attributable to the effects of elevated humidity. Loss from DBSs stored at -20°C was insignificant. The DBS materials were suitable for monitoring performance of all five GALT test methods.

Galactosemia: when is it a newborn screening emergency?

Classic galactosemia is an autosomal recessive disorder of carbohydrate metabolism, due to a severe deficiency of the enzyme, galactose-1-phosphate uridyltransferase (GALT), that catalyzes the conversion of galactose-1-phosphate and uridine diphosphate glucose (UDPglucose) to uridine diphosphate galactose (UDPgalactose) and glucose-1-phosphate. Upon consumption of lactose in the neonatal period, the affected infants develop a potentially lethal disease process with multiorgan involvement. Since the advent of newborn screening (NBS) for galactosemia, we rarely encounter such overwhelmingly ill newborns. After ascertainment that the positive NBS indicates the possibility of galactosemia due to GALT deficiency, the critical question for the physician is whether the infant has the classic or a variant form of GALT deficiency, as classic galactosemia is a medical emergency. However, there are over 230 GALT gene mutations that have been detected around the world. Yet, most positive NBS tests are due to the Duarte biochemical variant condition or a simple false positive. In order to make the correct decision as well as provide informative counseling to parents of infants with a positive NBS, I utilize a relatively simple classification scheme for GALT deficiency. There are three basic forms of GALT deficiency: 1) classic galactosemia; 2) clinical variant galactosemia; and 3) biochemical variant galactosemia. The classic genotype is typified by Q188R/Q188R, the clinical variant by S135L/S135L and the biochemical variant by N314D/Q188R. In classic galactosemia, the erythrocyte GALT enzyme activity is absent or markedly reduced, the blood galactose and erythrocyte galactose-1-phosphate levels are markedly elevated, and the patient is at risk to develop potentially lethal E. coli sepsis, as well as the long-term diet-independent complications of galactosemia. Patients with the clinical variant form require treatment but do not die from E. coli sepsis in the neonatal period. If the clinician suspects galactosemia, even if based on clinical findings alone, then the infant should be immediately placed on a lactose-restricted diet. The purpose of this review is to help the clinician make the correct therapeutic decision after an NBS test has returned positive for galactosemia.

The stability of markers in dried-blood spots for recommended newborn screening disorders in the United States

OBJECTIVE

We aimed to measure separately the contributions of heat and humidity to changes in levels of 34 markers of inborn disorders in dried-blood-spot (DBS) samples.

DESIGN AND METHODS

We stored paired sets of DBSs at 37°C for predetermined intervals in low-humidity and high-humidity environments. Marker levels of all samples in each complete sample set were measured in a single analytic run.

RESULTS

During the 30 ± 5 day studies, galactose-1-phosphate uridyltransferase and biotinidase lost almost 65% of initial activities in low-humidity storage; most of the degradation in 27 other markers was attributable to adverse effects of high-humidity storage; seven markers in DBSs stored at high humidity lost more than 90% of initial levels by the end of the study and 4 of the 7 lost more than 50% of initial levels within the first week of storage.

CONCLUSIONS

Minimizing both humidity and temperature in DBS transportation and storage environments is essential to maintaining sample integrity.

Ultra fast and sensitive liquid chromatography tandem mass spectrometry based assay for galactose-1-phosphate uridylyltransferase and galactokinase deficiencies

The diagnosis of transferase and galactokinase deficiency galactosemia usually involves the measurement of erythrocyte galactose-1-phosphate uridylyltransferase (GALT) and galactokinase (GALK) enzyme activity, respectively. The current gold standard assays for these enzymes are radioactive assays, which are laborious and/or incapable of measuring low enzyme activities. To further our knowledge of genotype-phenotype relationships, we had developed an assay for GALT activity alone using LC-MS/MS. In this study we generated a robust and sensitive LC-MS/MS based GALT and GALK assay using a novel normal phase chromatographic condition. We improved upon our earlier assay by drastically reducing the instrument run time and eliminating the use of an ion pairing reagent. Stable isotope labeled substrates were utilized in the GALT and GALK assays. The enzymatic products ([(13)C(6)]-uridine diphosphate galactose in GALT assay and [(13)C(6)]-galactose-1-phosphate in GALK assay) were quantified in a 3 min LC-MS/MS run. The assays were sensitive enough to allow for the quantification of enzyme activities as low as 0.2% and 0.3% of normal control values in the GALT and GALK assays, respectively. Thirty-three samples from non-galactosemic patients were assayed to have erythrocyte GALT activity of 23.4±4.2 and GALK activity of 1.8±0.47 (mean±SD) μmol⋅(g Hgb)(-1) h(-1). Erythrocyte GALT activities in a cohort of 16 patients with classic or severe galactosemia were measured: 4 patients had GALT activity less than 1% of normal control values and the remaining 12 had no detectable GALT activity. No GALK activity was detected in a GALK deficient sample we analyzed. Lastly, we tested the feasibility of adapting this LC-MS/MS based GALT/GALK assay as a newborn screening (NBS) test.

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.

Functional analysis of the human galactose-1-phosphate uridyltransferase promoter in Duarte and LA variant galactosemia

Human galactose-1-phosphate uridyltransferase (hGALT) is an evolutionarily conserved enzyme central to D-galactose metabolism. The impairment of hGALT causes galactosemia. One missense mutation, an aspartate to asparagine substitution at amino acid 314 (N314D), impairs 50% activity in the homozygous state in some patients but gives near normal activity in others. The former condition is called Duarte (D) and the latter, Los Angeles (LA). The D allele is linked to hGALT polymorphisms including a deletion 5'to the translation start site (-119 to -116delGTCA), g1391G --> A and g1105G --> C. The LA allele is linked to a g1721C --> T transition. To investigate possible mechanisms for differences in hGALT activity between the D and LA alleles, we sequenced 3951 nucleotides of genomic DNA 5' to the hGALT translation start site. Using a dual-luciferase reporter system to express deletion constructs of the hGALT promoter, we noted both positive and negative regulatory regions. Two putative positive regulatory domains overlap with the naturally occurring -119 to -116delGTCA linked to Duarte. One is an E-box motif (CACGTG) at -117 to -112 bp. The second is an AP-1 motif (TCAGTCAG) at -124 to -119 bp. The delGTCA mutation confers reduced luciferase activity to transfected cell lines derived from human ovarian and liver neoplasms. Additionally, human lymphoblasts derived from patients with the Duarte allele have reduced GALT mRNA. We conclude that the human GALT gene is regulated in the first -165 bp of its promoter region by positive regulators of GALT gene expression. The -119 to -116delGTCA reduces hGALT transcription resulting in reduced GALT activity in the Duarte allele.

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.

Plasma galactose and galactitol concentration in patients with galactose-1-phosphate uridyltransferase deficiency galactosemia: determination by gas chromatography/mass spectrometry

The plasma concentration of galactose and galactitol was measured in 27 patients with galactose-1-phosphate uridyltransferase (GALT) deficiency galactosemia on a lactose-restricted diet, 17 infants on lactose-free formula, and 21 infants and children on a normal diet, by a newly devised isotope dilution gas chromatograph/mass spectrometry (GC/MS) method. The method was linear in the range of 0.1 to 10 micromol/L for galactose and 1 to 20 micromol/L for galactitol with good reproducibility and a coefficient of variation less than 3%. The mean plasma galactose in 15 patients who were homozygous for the most common Q188R mutation of the GALT gene was 2.72 +/- 0.70 micromol/L (mean +/- SE) with a range of 0.58 to 3.98 in specimens obtained at regular clinic visits. In 12 patients with other GALT mutations, it was 2.45 +/- 0.75 micromol/L. The mean value in nongalactosemic subjects on lactose-free formula was 0.52 +/- 0.08 micromol/L, with a range of 0.12 to 1.25. The range in 21 normal subjects without diet restriction was 0.11 to 6.33 micromol/L, with a mean of 1.48 +/- 0.32. The plasma galactitol level was 11.63 +/- 0.46 and 10.85 +/- 1.38 micromol/L in the 2 galactosemic groups. There was no relationship between plasma galactose and galactitol levels, with variable ratios of the two substances in the galactosemic patients. Galactitol was not detectable in the plasma of normal subjects. The red blood cell galactose-1-phosphate level was also measured in the galactosemic patients, and no relationship between plasma galactose and red blood cell galactose-1-phosphate was found. The galactose-1-phosphate concentration was 28 to 54 times higher than the ambient galactose. The low galactose concentration in the plasma of galactosemics on galactose-restricted diets in relation to the higher plasma galactitol and red blood cell galactose-1-phosphate is a metabolic enigma. The ability to measure plasma galactose accurately presents a new way of characterizing the galactosemic patient and the levels monitored over time may provide insight into the development of long-term complications associated with the disorder.

Duarte allele impairs biostability of galactose-1-phosphate uridyltransferase in human lymphoblasts

The Duarte allele (D) is a missense mutation (N314D) that produces a characteristic isoform and partial impairment of galactose-1-phosphate uridyltransferase (GALT) in human erythrocytes, fibroblasts, and transformed lymphoblasts. The position of this amino acid is distant, however, from presumptive catalytic site(s) as deduced from a three-dimensional model of crystallized Escherichia coli galT protein. To evaluate the mechanism(s) involved in the partial impairment of enzymatic activity, we compared the activity, abundance, biological stability, and mRNA of GALT in human lymphoblastoid cell lines cultured from individuals homozygous for wild-type (WT/WT) and Duarte alleles (N314D/N314D). No other nucleotide differences were present in their GALT genes. The apparent Vmax was reduced in N314D/N314D cells to 31 +/- 3.6 compared to WT/WT of 54 +/- 6.5 nmole UDP-galactose formed/g cell protein/hour. Both genotypes had similar apparent KMs for UDP-glucose of 0.142 +/- 0.057 mM and 0.133 +/- 0.056 mM. This reduced Vmax was associated with a reduced abundance of the 86kD GALT dimer as determined by Western blots and densitometry. Using RNase protection assays, this reduced GALT protein in the N314D/N314D cell lines was not associated with reduced abundance of GALT mRNA. Using cycloheximide (3-[2-(3,5-Dimethyl-2-oxocyclohexyl)-2-hydroxyethyl]glutarimide) inhibition of de novo protein synthesis, GALT enzyme activity, and its dimeric protein had a biological T1/2 of approximately 24 hours in N314D/N314D cell lines as compared to 50 hours for WT/WT lymphoblasts. Upon exposure to 50 degrees C for 15 minutes, N314D/ N314D lymphoblasts retained 45% of GALT activity, whereas controls retained 77% activity. Reduced activity and thermal sensitivity caused by the N314D mutation reverted to control values when a lysine was substituted for a glutamic acid at amino acid 203 in cis (E203K). In summary, N314D/N314D lymphoblasts have reduced GALT enzyme capacity, dimeric protein abundance, biological, and thermal stability. We conclude that the substitution of aspartate for asparagine at amino acid 314 in the human GALT protein reduces the biostability of the active enzyme in human lymphoblasts.

Quantitative Beutler test for newborn mass screening of galactosemia using a fluorometric microplate reader

BACKGROUND

The Beutler enzyme spot test is an effective assay for newborn mass screening of galactosemia, but it is qualitative and relies on visual interpretation. We describe a quantitative, instrumental modification of the assay.

METHODS

We modified the macroscopic visual Beutler enzyme spot test by adding extraction of blood components from filter paper, deproteinization with acetone-methanol, and quantification and recording by a fluorescent microplate reader and personal computer. All handling was performed in microplates. The measurement time was 90 min.

RESULTS

Fluorescence intensity (FI) of healthy controls correlated with hematocrit and galactose-1-phosphate uridyltransferase (GALT) activity. Patients with GALT deficiency were distinguished clearly from healthy subjects and heterozygous carriers by FI. FI decreased to 75% of the initial activity after storage at 25 degrees C for 3 days and to 40% after storage at 37 degrees C for 7 days. Screening of 46 742 newborns yielded 1 false-positive result (in a heterozygous carrier), 1 patient with glucose-6-phosphate dehydrogenase deficiency, and no apparent false negatives as judged by concurrent measurements of galactose and galactose-1-phosphate.

CONCLUSIONS

The quantitative Beutler test can provide precise GALT activity in newborn mass screening, and can take into consideration the influence of high temperature and humidity, duration between sampling and testing, and anemia. This method is clinically useful, simple, automated, and highly reliable for newborn mass screening of galactosemia.

Milk consumption, galactose metabolism and ovarian cancer (Australia)

OBJECTIVES

It has been suggested that increased exposure to galactose, due to high consumption of dairy foods or reduced galactose metabolism, is associated with the development of ovarian cancer. We have investigated this in a large case-control study conducted in three Australian states between 1990 and 1993.

METHODS

Approximately 800 histologically-confirmed cases, 800 community controls and 300 controls recruited through breast-screening clinics completed dietary questionnaires. Approximately 100 cases and all breast-screening controls also provided a blood sample for analysis of galactose-1-phosphate-uridyltransferase (GALT).

RESULTS

Ovarian cancer risk was positively associated with increasing consumption of whole milk and other full-fat dairy foods, but was not associated with consumption of low-fat dairy foods and was inversely related to consumption of skimmed milk. There was no association between ovarian cancer and GALT except among women with abnormally low GALT who had a non-significant 2.5-fold increased risk of ovarian cancer.

CONCLUSIONS

These data do not support the hypothesis that galactose plays a major role in the development of ovarian cancer and suggest that reported associations between milk consumption and ovarian cancer are due to the fat content of milk and not to lactose or galactose. An increased risk of ovarian cancer in women with abnormally low levels of GALT cannot, however, be ruled out.

Newborn screening for galactosemia: ultramicro assay for galactose-1-phosphate-uridyltransferase activity

An enzymatically optimized, miniaturized (20 microl) fluorimetric assay of galactose-1-phosphate-uridyltransferase using dried blood spots for newborn screening is presented. The Beutler reaction principle has been adapted to the microtiter plate technology and acetone/methanol was used for complete deproteinization. A special ultramicro multiwell screening plate resistant to organic solvents has been developed and employed. The assay is simple, sensitive and inexpensive, due to small reagent volumes and the low prices of ultramicro screening plates. The reaction is linear with galactose-1-phosphate-uridyltransferase activity up to 120 min of incubation time. It shows low imprecision and good correlation to a quantitative validation test. For standardization the use of plate means or medians of activity or fluorescence values is proposed. Individual blank measurement prevents false negative assessments.

Radiochemical assay of minute quantities of galactose-1-phosphate uridyltransferase activity in erythrocytes and leukocytes of galactosemia patients

A sensitive radioisotopic method has been developed which can detect galactose-1-phosphate uridyltransferase (GALT) activity as low as 0.1% of normal control values in both erythrocytes and leukocytes. This assay utilizes carbon-14 labeled galactose-1-phosphate with high specific activity and requires removal of endogenous galactose-1-phosphate (Gal-1-P) and uridine diphosphate glucose (UDPGlc) through dialysis. Optimal exogenous UDPGlc concentration has been determined with a fixed concentration of Gal-1-P in the incubation. The rate of product, uridine diphosphate galactose (UDPGal), formation is monitored at three different times. Among 423 patients with galactosemia studied by this method, 363 patients exhibited no detectable GALT activity in their erythrocytes and 60 patients were found to have detectable erythrocyte GALT activity ranging from 0.02 to 5.0 units normal values: > 20 units). The former group of patients was designated as classic galactosemia (GG) and the latter group as galactosemia variant (GV). Leucocytes from ten patients belonging to the GG group also showed complete absence of GALT activity while leukocytes from two patients belonging to the GV group showed GALT activity at levels comparable with those found in their erythrocytes. Because there is extensive biochemical heterogeneity among galactosemia patients, we recommend that an assay with increase sensitivity be carried out on blood samples from galactosemia patients so that clinical, biochemical and molecular correlations made by different groups of investigators can be compared.

Biochemical and molecular studies of 132 patients with galactosemia

We evaluated 132 galactosemia patients for the Q188R (glutamine-188 to arginine) mutation in the human galactose-1-phosphate uridyltransferase (GALT) gene and for GALT activity in their hemolysates by a sensitive radioisotopic method. In those without any detectable GALT activity (GG), the Q188R mutation constituted 67% of the alleles. In patients with detectable GALT activity (GV), only 16% of the alleles were accounted for by Q188R. In all patients who were homozygous for the Q188R mutation, no erythrocyte GALT activity could be demonstrated. There was an extensive variation in the amount of detectable GALT activity ranging from 0.1% to 5% of the normal values among the GV patients. There was a difference in the frequency of Q188R mutation in the GALT alleles among patients belonging to different racial and ethnic groups. In Caucasian and Hispanic patients, the frequency was not far different (64% and 58%, respectively). On the other hand, only 12% of the GALT alleles with Q188R were found in African-American patients.

Determinants of basal follicle-stimulating hormone levels in premenopausal women

The (basal) level of FSH measured during early menses is emerging as a predictor of ovarian competence. In this study, correlates of basal FSH were examined in 222 premenopausal women who were not using oral contraceptives and selected from either the general population or a clinic for women with family histories of ovarian cancer. Using analysis of variance, the effect on FSH by age, smoking history, and reproductive variables was examined. Dietary galactose (as a potential oocyte toxin) was estimated, and red cell activity of galactose-1-phosphate uridyl transferase (GALT) was measured. Qualitative features of GALT were described by its electrophoretic or molecular genetic patterns. Possession of GALT polymorphisms previously linked with low GALT activity, including the Q188R mutation of classic galactosemia or N314D mutation of the Duarte galactosemia variant, was associated with significantly higher FSH, even in the heterozygous state. Other factors significantly influencing FSH included age, smoking history, cycle length, and cycle regularity. No effect of current galactose consumption was found, and GALT activity was only weakly correlated (inversely) with FSH. Applying multiple linear regression, variables independently predictive of high FSH were age of 40 yr or more, current smoking, and possession of a GALT polymorphism.

Characteristics of women with a family history of ovarian cancer. II. Follicular phase hormone levels

BACKGROUND

Although there is a basis for linking pituitary or ovarian hormones with experimentally induced ovarian cancer, establishing their role in women is complicated because the usual case-control methods cannot be applied. In this study, hormonal levels in women with a family history of ovarian cancer (FOC) and who are at higher risk for the disease are compared with women without such a history.

METHODS

The authors studied 106 unrelated women (FOC patients) with at least one primary or two second-degree relatives with ovarian cancer compared with 116 age- and residence-matched controls without a family history of ovarian cancer (FOC control subjects). All women were premenopausal, between the ages of 25 and 49 years, not currently using oral contraceptives, and had blood drawn during the early follicular phase for gonadotropins, estradiol (E2), and CA-125.

RESULTS

Women with a family history of ovarian cancer and control subjects did not differ significantly in follicle stimulating hormone (FSH) levels, E2, or CA-125. Patients with a family history of ovarian cancer had significantly lower luteinizing hormone (LH) levels compared with control subjects and produced more E2 and FSH relative to their level of LH. The ratios of LH to E2 and LH to FSH were correlated with the enzymatic activity of galactose-1-phosphate uridyl transferase, which was shown previously to differ between FOC patients and control subjects.

CONCLUSION

Lower LH and higher E2 are reported in women with breast, endometrial, and ovarian cancer (before surgery). The authors speculate that these observations reflect greater LH binding and estradiol production in ovaries at risk for these cancers--the ovarian cortical hyperplasia postulated in older gynecologic literature as the precursor to estrogen dependent neoplasia.

Characteristics of women with a family history of ovarian cancer. I. Galactose consumption and metabolism

BACKGROUND

Galactose metabolism may be a risk factor for ovarian cancer based upon evidence that galactose causes ovarian failure and that ovarian cancer arises from premature ovarian failure. This study examines galactose-1-phosphate uridyl transferase (GALT) activity in women with a family history of ovarian cancer (FOC) to determine if low GALT activity occurs in women who are at risk for but in whom ovarian cancer has not yet developed.

METHODS

The authors studied 106 premenopausal women (FOC patients) with one primary or two second-degree relatives with ovarian cancer compared with 116 age matched control subjects without a family history of ovarian cancer (FOC controls). All women completed questionnaires and had blood drawn to measure GALT activity and genotype.

RESULTS

Mean erythrocyte GALT activity, in micromoles of hexose conversion per hour per gram of hemoglobin was 21.5 in FOC patients, significantly lower than the mean of 23.1 observed in FOC control subjects, (P = 0.001). FOC patients more frequently displayed the Duarte variant of galactosemia as detected by electrophoresis. In a subset of 87 patients and 113 control subjects for whom DNA was available, the allelelic frequency of the Duarte variant based upon molecular genetic detection of the N314D mutation that is associated with the Duarte variant was 15.5% among FOC cases compared with 7.5% among control subjects (P < 0.02). Galactose consumption did not differ between FOC patients and control subjects.

CONCLUSION

Galactose metabolism differs between women with and without a family history of ovarian cancer, suggesting that it may be a genetic risk factor for ovarian cancer, possibly mediated through oocyte toxicity from galactose.

[Late diagnosis of classical galactosemia. An adult with special biochemistry]

The atypical case history of a galactosemic patient who was not recognized as such until his 22nd year is described. As in classical galactosemia there was not found any galactose-1-phosphate uridyl transferase activity in the erythrocytes. However, after the patient was on a galactose-free diet, there was no demonstrable elevation of galactose-1-phosphate in the erythrocytes. We would advocate a limited screening on galactosemia.

Disturbed galactose metabolism in elderly and diabetic humans is associated with cataract formation

Lactose consumption has been associated with a high incidence of cataract in northern Indian and southern Italian populations. Galactose absorbed after hydrolysis of lactose from milk in individuals with normal lactase activity is considered responsible. However, lactase-deficient subjects who often avoid drinking milk are able to digest lactose and absorb free galactose in fermented milk and yogurt. This study was conducted to evaluate the relationships between milk and yogurt consumption, galactose metabolism and cataract risk. Milk ingestion was dose-related with cataract risk in lactose digesters (particularly in diabetics) but not in lactose maldigesters. Conversely, yogurt intake had a protective dose-effect on cataract formation for the whole population. Maximal galactose concentrations after an oral galactose test increased exponentially with age. Red blood cell galactokinase activity was significantly lower in elderly subjects (> 60 y) than in young individuals (P < 0.05), and galactose-1-phosphate uridyl-transferase activity was significantly lower in institutionalized subjects and in home-living elderly with cataract than in healthy elderly subjects (P < 0.05). We conclude that the cataractogenic action of milk lactose is dependent on the disturbance of galactose metabolism in elderly subjects and that yogurt is not cataractogenic, although the mechanism of the protective effect of yogurt remains unknown.

The effect of dietary fruits and vegetables on urinary galactitol excretion in galactose-1-phosphate uridyltransferase deficiency

Even on a lactose-restricted diet, urinary galactitol excretion and erythrocyte galactose-1-phosphate levels are persistently elevated in patients with galactose-1-phosphate uridyltransferase deficiency. In order to determine the contribution of galactose in dietary fruits and vegetables to this phenomenon, (1) the content of galactose in a lactose-free diet was directly measured when a galactosaemic patient's diet was specifically enriched in those fruits and vegetables which contain relatively large amounts of free galactose and (2) galactitol excretion was determined during ingestion of this diet for 3 weeks and while on a synthetic diet for 1 week that provided < 8 mg galactose/day. For comparison the effect of a 3-week supplementation of 200 mg galactose/day was determined. The measured intake in total foodstuffs matched the theoretical content of galactose in the patient's diet based on amounts in fruits and vegetables alone, thus supporting the concept that fruits and vegetables are primarily responsible for galactose intake in a lactose-free diet. All of the dietary manipulations, however, had relatively little effect on metabolite levels, suggesting that endogenous galactose production is primarily responsible for the elevated levels of galactose metabolites routinely detected in patients on lactose-restricted diets.

Minimizing false positive diagnoses in newborn screening for galactosemia

Heat and humidity, rather than summertime heat alone, cause extensive loss of galactose-1-phosphate uridyltransferase activity in mailed blood spots and seem to account for false positive diagnoses of galactosemia. The spots are partially protected from the effects of atmospheric humidity if they are allowed to dry and then are sealed in a plastic freezer bag before being exposed to higher humidity. Conversely, extensive loss of transferase activity occurs if the samples are sealed in the bags before the spots are dry. The fluorescence from transferase activity can be monitored with greater sensitivity fluorometrically than visually. A simultaneous fluorometric determination of phosphoglucomutase activity reveals whether decreased transferase activity represents sample deterioration or galactosemia. Mg2+ and a sulfhydryl agent, such as dithiothreitol, are needed for activity of phosphoglucomutase, an enzyme in the sequence leading to the fluorescent substance (NADPH). They must be added in certain modifications of the assay.

[Study of galactose-1-phosphate uridyltransferase activity in erythrocytes of patients with presenile cataract]

In connection with the increased incidence of cataract in middle-aged patients investigations were carried out in order to clear up one of the possible causes of this condition. The detection of a substantial decrease of galactose-1-phosphate uridyl transferase activity in patients with presenile cataract evidences the disturbance of galactose metabolism these patients and allows to accept this genetic defect as the causes of opacification of the lens. Attention was called to the eventual importance of these investigations because of the adoption of a diet without galactose in person threatened+ by cataract could prevent or check this disease.

[Galactose-1-phosphate uridyl transferase and congenital cataract]

The activity of red blood cells galactose-1-p-uridyl transferase (GPUT) was determined by the spectrophotofluorometric method. The average GPUT activity in 102 control subjects was 13. 34 +/- 2. 03u. There were no differences in the sexes and ages. The average GPUT activity in 108 patients with congenital cataract was 11.58 +/- 4. 03u and was lower than that of the controls (P < 0.01). The GPUT activity in 14 of the 108(12.96%)patients was all-3SD below the mean value of the controls (< 7.24u) and the range was from 4.02u to 7.13u with the mean value of 5. 93u being about 44.45% of the normal. The difference between the two groups was statistically significant (P < 0.001). The results indicated that some of the patients with congenital cataract were due to decrease in the GPUT activity. The patients with decrease GPUT activity were mainly suffering from cataracts and their systemic disease were mild.

Florida newborn screening for galactosemia

Galactosemia, an inborn error of metabolism characterized by the inability to transform galactose-1-phosphate into glucose-1-phosphate, occurs in 1:50,000 live births. If not diagnosed and treated within the newborn period, it can lead to severe morbidity and mortality within a few weeks of life. All children in Florida are screened for this disorder by a fluorescence assay system to measure galactose-1-phosphate uridyltransferase (GALT) activity in a dried blood spot. Genetic factors and external forces can affect the activity of the GALT enzyme and lead to confusing results. Parents of infants heterozygous for galactosemia should be offered the opportunity for carrier detection. If both are carriers, genetic counseling should be provided.

Polymorphisms of the enzyme systems galactose-1-phosphate uridyltransferase (GALT) and esterase D (EsD) in the province of Cádiz, southern Spain

Galactose-phosphate uridyltransferase (GALT) and esterase D (EsD) phenotypes were determined by isoelectric focusing in ultrathin-layer polyacrylamide gel (PAGIF) for 406 healthy subjects randomly chosen and residing in the province of Cádiz, in Southern Spain. The following gene frequencies were observed: for GALT, GALT1 = 0.952 970 3 and GALT2 = 0.047 029 71; for EsD, EsD1 = 0.895 320 2, EsD2 = 0.094 827 59, and EsD5 = 0.009 852 21.

[Identification of inborn errors of galactose metabolism in patients with cataracts]

133 patients with congenital or idiopathic cataracts were studied (94 patients had ages between 1 month and 14 years; 10 patients had ages between 16 and 50 years and 29 patients did not have an age registry) along with 18 patients with a clinical diagnosis of classic galactosemia. The activity of galactokinase (GALAK) and that of erythrocyte galactose-1-phosphate uridyl transferase (GALT) was measured. There were no individuals with a total deficiency of GALK or GALT. The cataract patients of ages between 1 monthly and 14 years, 3 (3.19%) and 4 (4.25%) showed GALK and GALT levels in the range corresponding to the respective heterozygotes. As compared with the expected incidence of heterozygotes in the general population (0.2% for GALK and 0.8% for GALT) we found a significant rise of individuals with low levels of enzymes for the metabolism of galactose. The possibility that heterozygote galactosemic states contribute a risk factor in the development of cataracts and its therapeutic implications are discussed.

Evaluation of reduced activity galactose-1-phosphate uridyl transferase by combined radioisotopic assay and high-resolution isoelectric focusing

Fifty-nine patients referred for testing of galactose-1-phosphate uridyl transferase (GALT) activity were evaluated by a combination of radioisotopic assay and an improved high-resolution isoelectric focusing (IEF) method for determination of individual genotypes. The majority of evaluations (43 of 59) were undertaken because of an abnormal fluorometric GALT screening assay conducted as part of a state newborn galactosemia screening program or as a diagnostic test for an infant with one or more clinical signs of galactosemia. Only 12 of the 43 patients with an abnormal fluorometric screening test were found to have less than 3% GALT activity by quantitative assay, no GALT-staining by IEF, and a clinical history consistent with classical galactosemia. The majority of the remainder (24 of 43) were found to be heterozygotes for galactosemia, the Duarte variant, or both. IEF was found to be a fast and accurate technique for assignment of GALT genotypes in conjunction with quantitative enzymatic assay.

Galactose-1-phosphate uridyl transferase in density-fractionated erythrocytes. Studies of normal and mutant enzymes

Galactose-1-phosphate uridyl transferase (GALT), the deficient enzyme in classical galactosemia, was studied by Percoll-gradient age-fractionation of erythrocytes. For normal GALT, a rapid and substantial decrease in GALT activity and loss of most of two isozymes was found to occur in the reticulocyte fractions. The loss of activity was then followed by relative stabilization of both GALT-specific activity and microheterogeneity in mature and aging erythrocytes. When applied to the study of mutant GALT from galactosemic patients, the Percoll-gradient fractionation method permitted detection in the reticulocyte-enriched fractions of up to 5% of normal GALT-specific activity and an isoelectric focusing pattern essentially the same as that of normal GALT. Percoll-gradient fractionation of erythrocytes offers a simple and direct method to study characteristics of GALT activity and microheterogeneity in normal and galactosemic human erythrocytes.

Gonadal failure in young women and galactose-1-phosphate uridyl transferase activity

The present study allows the conclusion that low Gal-1-P transferase activity resulting from GtD/gt heterozygosity is not an major cause of early ovarian failure. However, larger groups of patients need to be examined to fully exclude an association between these rare conditions.

Idiopathic presenile cataract formation and galactosaemia

Five hundred patients undergoing cataract surgery were prospectively examined, and 46 Caucasian patients were found to have strictly idiopathic cataracts severe enough to warrant surgery on or before age 55. In a masked fashion we determined the activity of galactokinase (GK) and galactose-1-phosphate uridyl transferase (GPUT) in these patients as well as on 53 age matched controls. With respect to GK no cataract patient had an enzyme level of less than 2 standard deviations below the control mean. However, 3 of 45 (6.7%) patients in the cataract group had a GPUT level less than 2 standard deviations below the mean for controls, and were presumably heterozygotes for this enzyme. In comparison with the expected population rate of 0.8% this is highly significant (p = 0.006). Abnormalities in galactose pathway enzymes may therefore predispose to development of presenile cataracts. In affected people there is a possibility of treating these patients clinically by dietary restriction of dairy products or by using aldose reductase inhibitors to prevent or reverse cataract formation.

Galactose metabolism in transferase-deficient galactosaemic and normal long-term lymphoid cell lines

The activity (mean +/- SD) of galactose-1-phosphate uridyl transferase in two long-term lymphoid cell lines from Caucasian patients with transferase deficiency galactosaemia, a heterozygote, and eight normal subjects was 0, 78 and 168 +/- 55 nmol UDPG consumed (mg protein)-1h-1, respectively. Also, no activity was found in erythrocytes and cultured fibroblasts from the patients. A small number of cells of the galactosaemic lines cultured in medium, in which galactose was substituted for glucose, survived for 37 days. Normal and galactosaemic lines incubated with D-galactose-[1-14C] liberated 218.2 +/- 65.6 and 18.1 pmol 14CO2 (mg cellular protein)-1 (6h)-1, respectively. The evolution of 14CO2 from D-glucose-[1-14C] was similar in normal and galactosaemic lines. In the presence of [3H]galactose the radioactivity incorporated into TCA-precipitated material of the galactosaemic lines was 6.8% of the normal lines. Approximately 26% and 1.3% of the total radioactivity was incorporated into molecular species with a molecular weight greater than 400,000 daltons in normal and galactosaemic cells, respectively. Similar molecules were identified in the cell-free medium of both normal and deficient cells except for an 18,000 daltons molecule identified only in the medium of the normal cells. These findings indicate that a small amount of galactose is metabolized in galactosaemic lines with no transferase activity.

Polymorphism of human red cell galactose-1-phosphate uridyl transferase in Serbia, Yugoslavia

Phenotypes of human red cell galactose-1-phosphate uridyl transferase (GALT) were determined in 283 unrelated adults from Serbia (Yugoslavia). The gene frequencies were 0.959 for GALT N, 0.018 for GALT D and 0.023 for GALT N.

Application of digital image analysis in cataract retroillumination photography

The Stuttgart digital image analysis system for Scheimpflug photography can be applied without additional extension for pattern recording and densitometric measurements in retroillumination photographic techniques. A preliminary investigation with serial photographs in human cataract showed a large variation in the measured results. Standardisation of photographs taken by the retroillumination technique is not yet possible. For this reason, application of the retroillumination technique is not suitable at this time for clinical longitudinal studies.

Development of a protocol for newborn screening for disorders of the galactose metabolic pathway

The protocol evaluated in this paper employs an enzymatic assay of galactose metabolites, thin layer chromatography, and an assay of galactose-1-phosphate uridyl transferase on a single sample of blood collected routinely for newborn screening. Its effectiveness was tested by a retrospective study of known galactosemic blood samples, and also by a prospective study of 207,000 newborn samples from which 6 infants with severe transferase deficient galactosaemia and 2 infants with red cell epimerase deficiency were identified. The detection rate for severe transferase deficiency in the newborn population was 1:35,000. Advantages include low false positive rate, definitive diagnosis within 6 hours of sample receipt, and the use of technically simple and robust procedures. This protocol overcomes the difficulties encountered with previously described procedures.

Possible role of galactose-1-P-uridyl transferase activity deficiency in red blood cells in the development of the presenile and senile cataract

The activity of red blood cells galactose-1-P-uridyl transferase in 64 patients with presenile and senile cataracts (nondiabetics) and in 41 age-matched controls was investigated. All control subjects examined have shown normal enzymatic levels, while 21.9% of patients with presenile cataracts and 21.7% of patients with senile cataracts presented a statistically significant reduced enzymatic activity (mean +/- 2 SD in controls).

De novo tandem duplication 9p (p12----p24) with normal GALT activity in red cells

A 3 month old boy with a tandem duplication 9p (p12----p24) is reported. Both clinical and dermatoglyphic features were consistent with those of the trisomy 9p syndrome. However, the red cell galactose-1-P uridyl transferase (GALT) activity was normal despite the presence of the duplicated segment 9p13.

Curious neurologic sequelae in galactosemia

Two siblings with classic transferase deficiency galactosemia that was detected at birth have been treated with lactose restriction since the neonatal period. Both patients developed a unique and progressive neurologic syndrome of mental retardation, tremor, and ataxia. Careful review of the family history and medical records, the absence of metabolic disturbances other than those related to galactosemia, and the aggregate physical findings and neurodiagnostic studies ruled out other neurologic disorders in these siblings. It is therefore proposed that these patients represent a subgroup of transferase-deficient galactosemic patients, who develop characteristic neurologic sequelae with conventional dietary management. The existence of this subgroup should be considered in evaluations of therapeutic responses in cohorts of patients with galactosemia. Further, galactosemia should be included in the differential diagnosis of tremor and ataxia in the setting of mental retardation.

Molecular studies on galactose 1 phosphate uridylyl transferase from normal and mutant subjects. An immunological approach

The mutant forms of uridylyl transferase of eight galactosemic patients and two 'Rennes' variants were characterized with regard to the presence and level of immunoreactive protein, the apparent subunit molecular weight and the isoelectric point. Semi-purified haemolysates were studied by various electrophoretic techniques, then proteins were electrophoretically transferred on to nitrocellulose filters. They were treated with specific anti-transferase antibodies, and then with radioiodinated protein A, followed by autoradiography. We have found that: in all cases, a cross-reacting material was detectable, with a molecular subunit size of 46 000, indistinguishable from that of controls. a biochemical heterogeneity of the mutant enzyme was found: the amount of apparent immunologically reactive protein varied from 20 to 100% of that of controls; electrophoretic experiments performed on two 'Rennes' variants showed an increased negative charge.

Galactosemic enzyme levels in presenile cataracts

Galactose-1-phosphate uridyl transferase and galactokinase activities have been measured in the red blood cells of a group of patients with "idiopathic" presenile cataract and of a group of nondiabetic patients with senile cataract. The activity of both galactosemic enzymes was found to be within the normal range in all the patients with presenile cataract. In the group of patients with senile cataract, galactokinase activity was normal in all 24 subjects examined, and galactose-1-phosphate uridyl transferase activity was moderately reduced in 3 of 14.