Won G. Ng

Galactose consumption and metabolism in relation to the risk of ovarian cancer.

In a case-control study, consumption of dairy foods by 235 white women with epithelial ovarian cancer and by 239 control women, and activity of red blood cell galactose-1-phosphate uridyl transferase (transferase) in a subset of 145 cases and 127 controls were determined. Yogurt was consumed at least monthly by 49% of cases and 36% of controls. The mean transferase activity of cases was significantly lower than that of controls. When a ratio of lactose consumption to transferase (L/T) was calculated, cases had a mean L/T of 1.17 compared with 0.98 for controls; there was a highly significant trend for increasing ovarian cancer risk with increasing L/T ratio. Lactose consumption may be a dietary risk factor and transferase a genetic risk factor for ovarian cancer.

Deficit of uridine diphosphate galactose in galactosaemia

SummaryThe levels of uridine diphosphate galactose (UDPGal) and uridine diphosphate glucose (UDPGlc) have been determined in liver autopsy samples, erythrocytes and cultured skin fibroblasts from galactosaemic patients and compared to non-galactosaemic controls. In patients with undetectable erythrocyte galactose-1-phosphate uridyltransferase (transferase) activity, the levels of UDPGal were substantially lower than in controls. In patients with detectable transferase activity, even though in less than 1% of normal values, both UDPGal and UDPGlc levels were in the normal range. Incubation of erythrocytes from both galactosaemic patients and normal individuals with 10 mmol/L uridine increased UDPGal and UDPGlc levels several-fold, both in the presence or absence of galactose in the incubation medium. We hypothesize that a deficit of UDPGal is responsible for the late onset clinical manifestations in galactosaemia which include ovarian failure, speech defect and neurological abnormalities. We suggest that uridine administration may be of therapeutic value in raising the intracellular concentrations of UDPGal. We conclude that the transferase reaction, however small in activity, is essential for optimal UDPGal formation.

A new variant of galactose-1-phosphate uridyltransferase in man: the Los Angeles variant

The first known variant of human erythrocyte galactose1 -phosphate uridyltransferase (E.C. 2 .7 .7 .12 ) , the Duarte variant, was described by Beutler and his associates (Beutler, Baluda, Sturgeon & Day, 1965). The Duarte variant gene is allelic with the gene for galactosaemia and is transmitted as an autosomal recessive trait (Beutler, Baluda, Sturgeon & Day, 1966; Gitzelmann, Poley & Prader, 1967; Mellman, Tedesco & Feigl, 1968). The variant is characterized by reduced activity and by a different electrophoretic mobility (Mathai & Beutler, 1966). Haemolysates from Duarte homozygotes have approximately half normal transferase activity, from Duarte-normal heterozygotes three-quarters and from Duartegalactosaemia heterozygotes one-quarter. Upon starch-gel electrophoresis in phosphate buffer at pH 7.0, the variant enzyme moves as a single band of greater mobility than for the normal enzyme. In a different electrophoretic system, the Duarte variant enzyme appears as three equidistant bands, in contrast to the single band of activity found for normal individuals (Ng, Bergren, Fields & Donnell, 1969). The haemolysates from some individuals exhibiting triple bands were found to have either normal or elevated transferase activity rather than the reduced activity characteristic of the Duarte variant. This unexpected finding suggested a new variant. Family studies showed that normal or elevated transferase activity in association with a three-banded electrophoretic pattern was an inherited characteristic. The new variant provisionally has been named the Los Angeles variant (Ng, 1971). The isozyme pattern in leucocyte extracts from these individuals also differs from that of the normal transferase genotype.

An improved procedure for the assay of hemolysate galactose-1-phosphate uridyl transferase activity by the use of 14C-labeled galactose-1-phosphate.

Abstract 1. 1. An improved procedure is described for assay of hemolysate galactose-1-phosphate uridyl transferase based on the formation of carbon-labeled uridine diphosphate galactose (UDPGal) from [1-14C]galactose-1-phosphate. 2. 2. Separation of labeled UDPGal from radioactive galactose-1-phosphate is carried out by chromatography with lithium chloride on DEAE-cellulose strips. Appropriate sections of the chromatogram are counted directly in a liquid scintillation system. 3. 3. In contrast to the use of charcoal for separation of the labeled nucleotide, as previously employed in this assay, the Chromatographie separation described is simpler and more rapid. Results are reproducible and consistent.

Correlation of cognitive, neurologic, and ovarian outcome with the Q188R mutation of the galactose-1-phosphate uridyltransferase gene

This study was conducted to determine whether there is a genotype/phenotype correlation between aspects of cognitive, neurologic, and ovarian outcome in patients with galactosemia and the Q188R mutation of the galactose-1-phosphate uridyltransferase gene. The results showed that the Q188R mutation was found in 72% of alleles: 38 patients were homozygous and 21 were heterozygous for Q188R; eight patients did not have the mutation. The mean Broad Cognitive score for the group homozygous for Q188R was 75 (SD = 16), which was not statistically different from the outcome for the heterozygous group (mean score, 67; SD = 25) or the negative group (mean score, 88; SD = 21). Tremor, ataxia, and dysmetria were found in 12 subjects, and there was no association with Q188R status. Similarly, there was no association of this mutation with the development of primary amenorrhea (8 subjects) versus secondary amenorrhea (found in 14 women). Our findings suggests that the variability of outcome for patients with classic galactosemia cannot be explained by Q188R status alone, at least with regard to cognitive functioning, presence of neurologic symptoms, and timing of the onset of ovarian failure.

Galactose Metabolism in Human Ovarian Tissue

ABSTRACT: Galactose metabolism was studied in human ovarian tissue obtained from 14 women controls between 21 and 72 y of age, and one 21-y-old galactosemic patient with hypergonadotrophic hypogonadism. Tissue slices were incubated with l-14C-galactose, and labeled intermediates were analyzed by anion-exchange column chromatography. Activities of enzymes related to the galactose pathway: galactokinase, transferase, epimerase, uridine diphosphoglucose (UDPGlc) and uridine diphosphogalactose pyrophosphorylases, and UDPGlc and uridine diphosphogalactose pyrophosphatases were measured in ovarian homogenates using radioisotopic, spectrophotometric, and fluorometric techniques. Incorporation of carbon label from l-14C-galactose into various galactose and glycolytic intermediates, as well as carbon dioxide and TCA-insoluble materials was demonstrated in samples from non-galactosemic controls. In tissue from the galactosemic individual, no labeled carbon dioxide was produced and very little incorporation into TCA-insoluble material was found. Labeled galactose-1-phosphate was elevated. In normal ovarian tissue, specific activities of galactokinase, transferase, epimerase, and UDPGlc pyrophosphorylase are much higher than those found in the red cells and in testes. UDPGlc pyrophosphorylase activity is about 50 times that of transferase, suggesting that uridine nucleotide sugars have an important role in the normal development and function of the ovary. It is hypothesized that premature ovarian failure, often observed in patients with galactosemia, is due to interference with nucleotide sugar metabolism and the synthesis of galactose containing glycoproteins and glycolipids consequent to the enzymatic defect in the major pathway of galactose metabolism.

On the molecular nature of the Duarte variant of galactose-1-phosphate uridyl transferase (GALT)

Galactosemia is an inborn error of galactose metabolism secondary to deficiency of galactose-1-phosphate uridyl transferase (GALT). GALT is a polymorphic enzyme and Duarte (D) is the most common enzyme variant. This variant is characterized by faster electrophoretic mobility and reduced activity. Duarte/galactosemia compound heterozygotes (D/G) are commonly identified in galactosemia newborn screening programs. However, these patients do not generally require treatment. By using a “candidate mutation” approach to define the molecular basis of the Duarte variant of GALT, a close association between the previously reported N314D polymorphism and the Duarte variant of GALT was found. We suggest that N314D encodes the D variant of GALT and that molecular testing for N314D might be useful to confirm a biochemical diagnosis of Duarte variant of GALT.

Galactose-1-phosphate uridyl transferase (GALT) genotype and phenotype, galactose consumption, and the risk of borderline and invasive ovarian cancer (United States)

Objective: Previous studies have suggested that high levels of galactose consumption and/or low levels of galactose-1-phosphate uridyl transferase (GALT) activity may result in an increased risk of epithelial ovarian cancer. Similarly, some have reported that carriers of the N314D (asparagine at codon 314 replaced by aspartate) GALT polymorphism, which can be associated with low GALT activity, may have a higher risk of ovarian cancer. We examined these issues as part of a large case–control study of ovarian cancer conducted in Los Angeles between 1992 and 1998. Methods: A total of 1439 histologically confirmed borderline and invasive ovarian cancer cases among English-speaking non-Asian women were ascertained through the population-based cancer registry for Los Angeles County and completed in-person interviews were obtained from 689 of these (78% of cases approached). Controls consisted of 645 English-speaking non-Asian women with at least one intact ovary matched to cases on race/ethnicity (African-American, Latina, non-Latina White), date of birth (±3 years), and neighborhood of residence. Interviewer-administered questionnaires included information on reproductive factors, exogenous hormone use, medical history, and diet. Dietary information for the year before each cases diagnosis (and the same period for her matched control) was obtained using a self-administered food-frequency questionnaire. Blood samples were obtained from 452 controls, 136 cases with borderline ovarian cancer, and 312 cases with invasive ovarian cancer. The N314D polymorphism was characterized using PCR-RFLP and GALT enzyme activity, and was determined for a sample of the subjects with GALT genotype using an erythrocyte-based radioactive enzyme assay. Results: We found no effect of N314D GALT genotype on the risk of borderline ovarian cancer (odds ratio (OR) = 0.91; 95% confidence interval (CI) = 0.54–1.6) or invasive ovarian cancer (OR = 0.78; 95% CI & equals; 0.53–1.2). Neither did we observe a relationship between GALT activity or lactose/galactose intake and risk of borderline or invasive ovarian cancer. Among N314D carriers, galactose consumption was associated with an increased risk of borderline (OR = 2.7, p = 0.01), but not invasive (OR = 1.2, p = 0.34), ovarian cancer; however, this result was based on only 24 N314D-positive borderline cases. Conclusions: Differences in galactose intake and GALT metabolism do not contribute significantly to the risk of ovarian cancer. There is some evidence that galactose intake may play a role in the development of borderline ovarian cancer among women who carry the uncommon GALT N314D polymorphism. More data are needed if this latter suggestion is to be definitively addressed.

Childbearing by a galactosemic woman.

A Negro woman with galactosemia, maintained on a galactose-restricted diet since infancy, had an uncomplicated pregnancy and delivered an apparently healthy infant who was shown to be heterozygous for galactosemia. The father was normal with respect to galactose-1-phosphate uridyl transferase. Maternal blood, urine, and amniotic fluid were monitored during the pregnancy. Following delivery the mothers milk and the infants urine were studied. The present study shows for the first time that a woman, homozygous for galactosemia, can produce a clinically normal infant.

Urinary galactitol in galactosemic patients

Abstract The possibility was explored of using the measurement of urinary galactitol to monitor the galactose-restricted diet of patients with galactosemia. The response to the addition of graded doses of galactose to the galactose-restricted diet was measured. It was found that urinary galactitol excretion is a relatively insensitive index of galactose intake and that it is of limited value in diet monitoring. Unexpectedly, galactitol was found in the urine of all patients receiving a galactose-restricted diet, and it was postulated that this sugar alcohol has its origin in part from endogenously produced galactose.