Correlation of ovarian function with galactose-1-phosphate uridyl transferase levels in galactosemia

Diet and ovarian cancer risk: An umbrella review of systematic reviews and meta-analyses of cohort studies

BACKGROUND & AIMS

Diet may play an important role in the etiology of ovarian cancer (OC). We aimed to evaluate the strength and credibility of evidence pertaining to dietary risk factors for OC.

METHODS

We comprehensively searched PubMed, Web of Science, Cochrane, CINAHL, JBI Database of Systematic Reviews and Implementation Reports, PROSPERO and EMBASE databases to identify related systematic reviews and meta-analyses of prospective cohort studies. This study had been registered at PROSPERO. The registration number is CRD42020187651. For each association, we estimated the summary effect size using fixed and random effects models, the 95% confidence interval and the 95% prediction interval. We assessed heterogeneity, evidence of small-study effects, and excess significance bias.

RESULTS

A total of 22 systematic reviews and meta-analyses were included in the present study. These previous reports evaluated 184 individual studies, which proposed a total of 36 associations between dietary factors and OC risk. Out of the 36 associations, there were no strong, highly suggestive and suggestive evidence, only four (black tea, skim/low-fat milk, lactose, and calcium) were determined to be supported by weak evidence. OC risk was inversely associated with intake of black tea or calcium, and positively associated with intake of skim/low-fat milk or lactose.

CONCLUSIONS

Our studies revealed that four associations between OC risk and dietary factors (black tea, skim/low-fat milk, lactose, and calcium) were supported by weak evidence. The remaining 32 associations were not confirmed. Additional studies are needed to carefully evaluate the relationship between dietary factors and OC risk.

Oral oyster polypeptides protect ovary against d-galactose-induced premature ovarian failure in C57BL/6 mice

BACKGROUND

Oyster polypeptides have various biofunctions, such as anti-cancer and anti-oxidative stress, but whether it has the protective effects to primary ovarian failure (POF) remains poorly understand. To address this issue, daily gavage of oyster polypeptides was performed to investigate their protective effect, basing on d-galactose-induced POF model in C57BL/6 female mice.

RESULTS

Oyster polypeptides restored the irregular estrous cycles and the abnormal serum follicle stimulating hormone (FSH), luteinizing hormone (LH) and progesterone (P) levels as well as the decreased mRNA expression level of Amh that were induced by d-galactose. The follicle development of POF mice was improved by increasing the primordial follicle ratio and decreasing the atretic follicle number after oral administration of oyster polypeptides. Moreover, in the oyster polypeptides treated mice, the total superoxide dismutase (T-SOD) activity was significantly increased, while the malondialdehyde levels were significantly decreased. The mRNA expression levels of stress-related genes (SOD2, SIRT1 and FOXO3a) were remarkably up-regulated after d-galactose induction, but the up-regulation was weakened or disappeared by the gavage of oyster polypeptides. In addition, oyster polypeptides treatment also reduced the apoptosis of the ovarian granulosa cells and down-regulated the mRNA expression levels of apoptosis-related genes (p53 and Bad but not Bcl-2).

CONCLUSION

This study reveals that oyster polypeptides may protect ovary against d-galactose-induced POF by their anti-oxidative stress activity to rescue d-galactose-induced ovarian oxidative damage and therefore to prevent ovarian cells apoptosis, thereby tipping the abnormality trigged by POF to get close to the normal levels. © 2019 Society of Chemical Industry.

Curcumin exerts a protective effect against premature ovarian failure in mice

This study was designed to investigate the protective effect of curcumin against d-galactose (d-gal)-induced premature ovarian failure (POF) in mice. A mouse POF model was induced by subcutaneous injection of d-gal (200 mg/kg/day) daily for 42 days. Mice in the curcumin group received both d-gal treatment and intraperitoneal injection of curcumin (100 mg/kg/day) for 42 days. Ovarian function, oxidative stress and apoptosis were evaluated. The P, E2 and SOD levels were higher, and the FSH, LH and MDA levels were significantly lower in the curcumin group than those in the d-gal group. The proportion of primordial follicles was also significantly higher in the curcumin group than that in the d-gal group. In addition, curcumin treatment after d-gal administration resulted in significantly lower Sod2, Cat, 8-OhdG, 4-HNE, NTY and senescence-associated protein P16 expression levels, higher Amh expression levels and less apoptosis in granulosa cells than was observed in the d-gal group. Moreover, the p-Akt, Nrf2 and HO-1 protein expression levels were significantly higher and the apoptosis-related cleaved caspase-3 and -9 protein expression levels were markedly lower in the curcumin group than in the d-gal group. In conclusion, curcumin effectively inhibited d-gal-induced oxidative stress, apoptosis and ovarian injury via a mechanism involving the Nrf2/HO-1 and PI3K/Akt signaling pathways, suggesting that curcumin is a potential protective agent against POF.

Ginsenoside Rg1 improves fertility and reduces ovarian pathological damages in premature ovarian failure model of mice

This study aims to investigate the effect as well as mechanism of ginsenoside Rg1 (Rg1) on premature ovarian failure (POF) induced by d-galactose (d-gal) in mice. C57BL/6 female mice were divided into four groups randomly, which were the saline group, the d-gal group, the d-gal + Rg1 group, and the Rg1 group. Body weight was recorded. Overall ovarian function including estrous cycles, sex hormone secretion, ovarian follicle development, and ovarian morphology was analyzed by H&E staining and ELISA. Effect of Rg1 on aging was determined by analyzing the activities of oxidation-associated biomarkers, pro-inflammatory cytokine secretion, expression of senescence-associated proteins, and fertility. Compared with the d-gal group, in Rg1 + d-gal group, body weight was increased significantly, estrous cycle block was released, and fertility and the morphology of ovaries were restored. And, Rg1 treatment after d-gal administration significantly reduced senescence-associated protein expression, increased the activity of total superoxide dismutase and glutathione peroxidase from bovine erythrocyte, and induced higher follicle stimulating hormone receptor protein expression. Additionally, the expression levels of malondialdehyde, interleukin-1β, tumor necrosis factor-α, and interleukin-6 were significantly decreased. Together, Rg1 improves mouse fertility and reduces ovarian pathological damage in d-gal-induced POF model possibly through enhancing anti-inflammatory and antioxidant capacities and reducing expression of senescence signal pathway proteins. Impact statement Ginsenoside Rg1 (Rg1) is a kind of natural estrogen and it has antioxidation and antiaging effects. However, whether Rg1 has effects on premature ovarian failure (POF) is still not clear. In this study, aging model induced by d-galactose was used to mimic POF. The effect and possible mechanism of Rg1 on ovary aging was investigated. We found that Rg1 treatment up-regulated the expression of follicle stimulating hormone receptor and down-regulated senescence-associated protein expression in granule cells of POF mice. Particularly, Rg1 improved fertility ability and reduced ovarian pathological damages by its antioxidative and anti-inflammation capacity. Thus, Rg1 enhances the antiaging ability of ovary and fertility ability of POF mice through enhancing the anti-inflammatory and antioxidant capacities of ovary.

Mediators of a long-term movement abnormality in a Drosophila melanogaster model of classic galactosemia

Despite neonatal diagnosis and life-long dietary restriction of galactose, many patients with classic galactosemia grow to experience significant long-term complications. Among the more common are speech, cognitive, behavioral, ovarian and neurological/movement difficulties. Despite decades of research, the pathophysiology of these long-term complications remains obscure, hindering prognosis and attempts at improved intervention. As a first step to overcome this roadblock we have begun to explore long-term outcomes in our previously reported GALT-null Drosophila melanogaster model of classic galactosemia. Here we describe the first of these studies. Using a countercurrent device, a simple climbing assay, and a startle response test to characterize and quantify an apparent movement abnormality, we explored the impact of cryptic GALT expression on phenotype, tested the role of sublethal galactose exposure and galactose-1-phosphate (gal-1P) accumulation, tested the impact of age, and searched for potential anatomical defects in brain and muscle. We found that about 2.5% residual GALT activity was sufficient to reduce outcome severity. Surprisingly, sublethal galactose exposure and gal-1P accumulation during development showed no effect on the adult phenotype. Finally, despite the apparent neurological or neuromuscular nature of the complication we found no clear morphological differences between mutants and controls in brain or muscle, suggesting that the defect is subtle and/or is physiologic rather than structural. Combined, our results confirm that, like human patients, GALT-null Drosophila experience significant long-term complications that occur independently of galactose exposure, and serve as a proof of principle demonstrating utility of the GALT-null Drosophila model as a tool for exploring genetic and environmental modifiers of long-term outcome in GALT deficiency.

Ovotoxic effects of galactose involve attenuation of follicle-stimulating hormone bioactivity and up-regulation of granulosa cell p53 expression

Clinical evidence suggests an association between galactosaemia and premature ovarian insufficiency (POI); however, the mechanism still remains unresolved. Experimental galactose toxicity in rats produces an array of ovarian dysfunction including ovarian development with deficient follicular reserve and follicular resistance to gonadotrophins that characterize the basic tenets of human POI. The present investigation explores if galactose toxicity in rats attenuates the bioactivity of gonadotrophins or interferes with their receptor competency, and accelerates the rate of follicular atresia. Pregnant rats were fed isocaloric food-pellets supplemented with or without 35% D-galactose from day-3 of gestation and continuing through weaning of the litters. The 35-day old female litters were autopsied. Serum galactose-binding capacity, galactosyltransferase (GalTase) activity, and bioactivity of FSH and LH together with their receptor competency were assessed. Ovarian follicular atresia was evaluated in situ by TUNEL. The in vitro effects of galactose were studied in isolated whole follicles in respect of generation of reactive oxygen species (ROS) and expression of caspase 3, and in isolated granulosa cells in respect of mitochondrial membrane potential, expression of p53, and apoptosis. The rats prenatally exposed to galactose exhibited significantly decreased serum GalTase activity and greater degree of galactose-incorporation capacity of sera proteins. LH biopotency and LH-FSH receptor competency were comparable between the control and study population, but the latter group showed significantly attenuated FSH bioactivity and increased rate of follicular atresia. In culture, galactose increased follicular generation of ROS and expression of caspase 3. In isolated granulosa cells, galactose disrupted mitochondrial membrane potential, stimulated p53 expression, and induced apoptosis in vitro; however co-treatment with either FSH or estradiol significantly prevented galactose-induced granulosa cell p53 expression. We conclude that the ovotoxic effects of galactose involves attenuation of FSH bioactivity that renders the ovary resistant to gonadotrophins leading to increased granulosa cell expression of p53 and follicular atresia.

Ovarian function in girls and women with GALT-deficiency galactosemia

Primary or premature ovarian insufficiency (POI) is the most common long-term complication experienced by girls and women with classic galactosemia; more than 80% and perhaps more than 90% are affected despite neonatal diagnosis and careful lifelong dietary restriction of galactose. In this review we explore the complexities of timing and detection of galactosemia-associated POI and discuss potential underlying mechanisms. Finally, we offer recommendations for follow-up care with current options for intervention.

Galactose toxicity in animals

In most organisms, productive utilization of galactose requires the highly conserved Leloir pathway of galactose metabolism. Yet, if this metabolic pathway is perturbed due to congenital deficiencies of the three associated enzymes, or an overwhelming presence of galactose, this monosaccharide which is abundantly present in milk and many non-dairy foodstuffs, will become highly toxic to humans and animals. Despite more than four decades of intense research, little is known about the molecular mechanisms of galactose toxicity in human patients and animal models. In this contemporary review, we take a unique approach to present an overview of galactose toxicity resulting from the three known congenital disorders of galactose metabolism and from experimental hypergalactosemia. Additionally, we update the reader about research progress on animal models, as well as advances in clinical management and therapies of these disorders.

Galactosemia and amenorrhea in the adolescent

Hereditary galactosemia is a biochemical genetic disease due to a deficiency of galactose-1-phosphate uridyltransferase (GALT) enzyme activity (OMIM 606999). Acute manifestations occur in the neonatal period and are, with rare exceptions, related to lactose ingestion. They include poor feeding and growth, emesis, jaundice, liver disease, bleeding diathesis, anemia, renal tubulopathy, cataracts, encephalopathy and death from E. coli sepsis. Chronic manifestations, which also develop in prospectively treated patients, involve (a) the brain, resulting in delayed language acquisition, speech defects, and learning problems, and (b) the ovary, in the majority of females, producing hypergonadotropic hypogonadism. The serum FSH level is elevated in infancy/early childhood in many, but not all patients with a severe phenotype. There are few reports of patients with classic galactosemia having undergone pregnancy, labor, and delivery. The pathologic findings in the ovary, including a persistence of primordial follicles and streak gonads, have been variable. The etiology of primary ovarian insufficiency (POI) in galactosemia is unknown. Clinical surveillance includes screening for abnormalities in ovarian function at an early age. Treatment consists of estrogen/progesterone supplementation at the appropriate age. Reduced BMD has been reported. Future research is needed (1) to delineate the mechanisms behind reduced ovarian function in these young women; (2) to determine the timing of the lesion: prenatal, postnatal, and both pre- and postnatal; (3) to determine whether elevated galactose-1-phosphate is both necessary and sufficient to induce primary ovarian insufficiency; and (4) to understand the mechanism(s) behind the reduced BMD seen in children and adolescents with galactosemia.

Fertility and impact of pregnancies on the mother and child in classic galactosemia

Despite the high prevalence of premature ovarian failure (POF) and subsequent infertility in galactosemic women, spontaneous pregnancies occur and may not be as rare as is generally assumed. This is important for counseling these women on fertility. The purpose of this review is to assess the occurrence and predicting factors of pregnancy, and to evaluate the impact of pregnancy on the mother's and child's health. The female Dutch galactosemia population (age > 18 years) was studied, and a literature search on articles reporting pregnancy in galactosemic women, published between January 1971 and December 2007, was performed. Twenty-two galactosemic women were studied. Nine women have tried to conceive, of which 4 were successful. Three mothers were diagnosed with POF before the first pregnancy and/or in between pregnancies. In literature, 50 pregnancy reports were found. In 10 pregnancy reports from the literature, the mother's genotype is known. Four women were homozygous for the Q188R mutation, which equals the incidence of 40-45% of classic galactosemia caused by this mutation. This study challenges the current opinion that the chance of becoming pregnant is small in classic galactosemia. Despite POF in most galactosemic women, pregnancies do occur. The genotype and GALT-activity do not seem to predict the chance of becoming pregnant, whereas the occurrence of spontaneous menarche might. No evidence for the need of additional check-ups during the pregnancy and puerperium was found. Elevations in galactose-metabolites do occur, but without evidence of clinical impact for the mother or the child, although possible long-term effects have not been thoroughly investigated.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader should be able to summarize the purported causes and sequelae of galactosemia, explain the possible sequelae of galactosemia, distinguish alterations of the ovary and the hypothalamic-pituitary axis, identify the frequency of pregnancy and the possible outcome of the offspring, and outline dietary management of patients with galactosemia.

Pathophysiology of impaired ovarian function in galactosaemia

Classical galactosaemia is an inherited inborn error of the major galactose assimilation pathway, caused by galactose-1-phosphate uridyltransferase (GALT) deficiency. Many GALT mutations have been described, with different clinical consequences. In severe forms, newborns present with a life-threatening, acute toxic syndrome that rapidly regresses under a galactose-restricted diet. However, long-term complications, particularly cognitive and motor abnormalities, as well as hypergonadotrophic hypogonadism in female patients are still unavoidable. The pathogenesis of galactose-induced ovarian toxicity remains unclear but probably involves galactose itself and its metabolites such as galactitol and UDP-galactose. Possible mechanisms of ovarian damage include direct toxicity of galactose and metabolites, deficient galactosylation of glycoproteins and glycolipids, oxidative stress and activation of apoptosis. As there is no aetiological treatment, clinical management of ovarian failure in galactosaemic patients principally relies on hormonal replacement therapy to induce pubertal development and to prevent bone loss and other consequences of estrogen deprivation. Further investigations will be necessary to better understand the metabolic flux of galactose through its biochemical pathways and the mechanisms of these secondary complications. The aim of this article is to present an extensive review on the pathogenesis and clinical management of galactose-induced premature ovarian failure.

Milk, milk products and lactose intake and ovarian cancer risk: a meta-analysis of epidemiological studies

It has been proposed, on the basis of animal models and ecological studies, that consumption or metabolism of dairy sugar may increase the risk of ovarian cancer. Case-control and cohort studies of the association between lactose and dairy food consumption and ovarian cancer risk, however, have yielded varied findings. We summarized the available literature on this topic using a meta-analytic approach. Random-effects models were used to estimate the summary relative risks (RR(summary)). A linear regression analysis of the natural logarithm of the RR was carried out to assess a possible dose-response relationship between lactose intake and ovarian cancer risk. Eighteen case-control and 3 prospective cohort studies were eligible for inclusion in the meta-analysis. The findings of case-control studies were heterogeneous, and, except for whole milk (RR(summary) for highest vs. lowest category = 1.27, 95% confidence interval [CI] = 0.97-1.68), do not provide evidence of positive associations between dairy food and lactose intakes with risk of ovarian cancer. In contrast, the 3 cohort studies are consistent and show significant positive associations between intakes of total dairy foods, low-fat milk, and lactose and risk of ovarian cancer. The RR(summary) for a daily increase of 10 g in lactose intake (the approximate amount in 1 glass of milk) was 1.13 (95% CI = 1.05-1.22) for cohort studies. In conclusion, prospective cohort studies, but not case-control studies, support the hypothesis that high intakes of dairy foods and lactose may increase the risk of ovarian cancer.

Galactosemia: The good, the bad, and the unknown

Alpha-D-galactose is metabolized in species ranging from E. coli to mammals predominantly via a series of sequential reactions collectively known as the Leloir pathway. Deficiency of any one of these enzymes in humans results in a form of the inherited metabolic disorder, galactosemia, although the symptoms and severity depend upon the enzyme impaired, and the degree of functional deficiency (Tyfield and Walter, 2002, The Metabolic and Molecular Bases of Inherited Disease. New York: McGraw Hill.). Studies of these enzymes, and the disorders associated with their loss, have led to a much deeper appreciation of the intricate and interwoven levels of regulation that govern their normal function. These insights have further identified likely mediators of outcome severity in patients, and have enabled a rational approach to the development of novel strategies of intervention.

Galactose-1-phosphate uridyl transferase gene mutations in women with premature ovarian failure

We determined the frequency of galactose-1-phosphate uridyl transferase gene mutations: Q188R, K285N, and the Duarte allelle in 86 patients with idiopathic premature ovarian failure (POF) and 95 controls. No association of the mutations with POF was found.

Primordial germ cell migration in the rat: preliminary evidence for a role of galactosyltransferase

The precise cellular mechanism of primordial germ cell (PGC) migration remains unknown. Cell surface galactosyltransferase (GalTase) is known to play unique roles in the process of locomotion of many migratory cells. With an objective to seek evidence for possible involvement of GalTase in the migratory process of PGC, we evaluated germ cell migration in the rat following experimental modulation of embryonic GalTase activity. Pregnant rats were laparotomized under anesthesia on Day 10 of pregnancy. While embryos of one uterine horn received lysozyme (100 microg/fetus), those of the other received alpha-lactalbumin (LA; 100 microg/fetus), N-acetylglucosamine (GlcNAc; 250 nmole/fetus), uridine 5'-monophosphate (UMP; 2.5 micromole/fetus), uridine diphosphate-galactose (UDP-gal; 250 nmole/fetus), or a combination of 250 nmole of UDP-gal and 2.5 micromole of UMP/fetus. Between gestation Days 12 and 14, embryos were dissected out and processed for histochemical localization of PGC on the basis of binding of Dolichos biflorus agglutinin on the surface glycoconjugate of the germ cells. The number of PGC in each embryo was counted. There was a daywise increase in the number of PGC in all groups. As compared with lysozyme-exposed controls, the numbers of PGCs at the day-specific sites on all days of examination were significantly lower in the LA- as well as GlcNAc-exposed groups. UMP or UDP-gal individually exerted little or no influence, while the total PGC count rose significantly over the respective control values under simultaneous exposure to UMP and UDP-gal. The present findings suggest a likely catalytic role of GalTase in the process of germ cell migration.

A prospective study of dietary lactose and ovarian cancer

The milk sugar lactose is an hypothesized risk factor for epithelial ovarian cancer because of possible direct toxic effects of its metabolites on oocytes or by compensatory gonadotropin stimulation. Women are presently encouraged to consume dairy products as a source of calcium to prevent osteoporosis. The objective of our study was to prospectively assess lactose, milk and milk product consumption in relation to ovarian cancer risk among 80326 participants in the Nurses' Health Study who had no history of cancer other than nonmelanoma skin cancer. Participants in the Nurses' Health Study reported on known and suspected ovarian cancer risk factors in questionnaires mailed biennially from 1976 to 1996. Food frequency questionnaires were included in the years 1980, 1984, 1986 and 1990. Newly reported ovarian cancer was documented by review of medical records. During 16 years of follow-up (1980-1996), 301 cases of invasive epithelial ovarian cancer were confirmed. Pooled logistic regression was used to control for age, body mass index (kg/m(2)), caffeine intake, oral contraceptive use, smoking history, parity and tubal ligation. For all subtypes of invasive ovarian cancer combined, we observed a nonsignificant 40% greater risk for women in the highest category of lactose consumption compared to the lowest (multivariate relative risk (RR) 1.40, 95% confidence interval (CI), 0.98-2.01). We observed a 2-fold higher risk of the serous ovarian cancer subtype among those in the highest category of lactose consumption compared to the lowest (RR 2.07, 95% CI, 1.27-3.40). For each 11-gram increase in lactose consumption (the approximate amount in one glass of milk), we observed a 20% increase in risk of serous cancers (RR 1.20, 95% CI, 1.04-1.39). Skim and low-fat milk were the largest contributors to dietary lactose. Women who consumed one or more servings of skim or low-fat milk daily had a 32% higher risk of any ovarian cancer (RR 1.32, 95% CI, 0.97-1.82) and a 69% higher risk of serous ovarian cancer (RR 1.69, 95% CI, 1.12-2.56) compared to women consuming 3 or less servings monthly. Controlling for fat intake did not change our findings. Our findings provide some support for the hypothesis that lactose intake increases risk of epithelial ovarian cancer. However, the observed excess risk appeared limited to the serous subtype of ovarian cancer in our study.

Inhibitor of apoptosis proteins and ovarian dysfunction in galactosemic rats

Galactosemia is a genetic disease with deficiency of galactose-1-uridyltransferase, resulting in the accumulation of galactose or galactose-1-phosphate in the blood and tissues. Rats were fed with normal rat chow and with a high-galactose diet for 4 weeks to give control and galactosemic groups, and their ovarian function was studied. The two groups of rats were injected with pregnant mare's serum gonadotrophin (PMSG) and were killed at different time points after human chorionic gonadotrophin (hCG) injection. The number of oocytes ovulated in the controls was significantly higher than in the galactosemic group. Morphometric studies of the ovaries also showed a higher number of corpora lutea in the controls. Western blot analysis of granulosa cells showed that the overall expressions of Fas and FasL were lower in the control group and their expressions of inhibitor of apoptosis proteins (IAPs) were higher than in the galactosemic group, especially at 8 h post hCG injection. TDT-mediated dUTP-biotin nick end-labeling (TUNEL) and immunohistochemical staining of ovarian sections with Ki-67 and IAPs showed more apoptotic granulosa cells in the galactosemic group and the expressions of IAPs in granulosa cells also confirmed the result of the Western blot. These findings support our hypothesis that ovarian dysfunction in galactosemic rats is due to increased apoptosis in granulosa cells of maturing follicles.

[Premature ovarian failure in galactosaemia: pathophysiology and clinical management]

Classic galactosaemia is a rare aetiology of premature ovarian failure. It is caused by galactose-1-phosphate uridyltransferase deficiency and leads to a severe disease in the newborn. This acute toxic syndrome will completely regress under a galactose-free diet, but some long-term complications, particularly hypergonadotropic hypogonadism in female patients, are frequently observed. Ovarian toxicity could be due to intracellular accumulation of galactose metabolites or to deficient glycosylation reactions. Moreover, the tremendous follicular decrease in the galactosaemic ovary could also involve programmed cell death (apoptosis). As the exact mechanisms of this ovarian injury are still unknown, there is no prevention of follicular loss, thus clinical management especially includes hormonal replacement therapy in order to prevent bone loss and cardiovascular risks and sometimes to allow patients to become pregnant.

Increased fertility in a woman with classic galactosaemia

A 27-year-old caucasian female with classical galactosaemia due to Q188R homozygous mutation is reported. At 18 years she had triplets and at 23 years a further pregnancy. All infants are well.

The molecular biology of galactosemia

Classic galactosemia is an autosomal recessive disorder caused by the deficiency of galactose 1-phosphate uridyltransferase (GALT). Although the potentially lethal, neonatal hepatotoxic syndrome is prevented by newborn screening and galactose restriction, long-term outcome for older patients with galactosemia remains problematic. After the cloning and sequencing of the GALT gene, more than 130 mutations in the GALT gene have been associated with GALT deficiency; this review relates them to function and clinical outcome. Two common mutations, Q188R and K285N, account for more than 70% of G alleles in the white population and are associated with classic galactosemia and impaired GALT function. In the black population, S135L accounts for 62% of the alleles causing galactosemia and is associated with good outcomes. A large 5 kb deletion in the GALT gene is found in Ashkenazim Jews. The Duarte galactosemia variant is caused by N314D. Homozygosity for N314D reduces GALT activity to 50%. When either E203K or a 1721C-->T transition (Los Angeles variant) are present in cis with N314D, GALT activity reverts to normal. In this review, we discuss the structural biology of these mutations as they affect both the GALT enzyme and patient outcome.

Defective galactosylation in galactosemia: is low cell UDPgalactose an explanation?

There is circumstantial evidence that defective galactosylation of complex glycoconjugates exists in tissues from galactosemic patients. Whether this is an etiologic factor in the long-term complications of the disorder is not known. Also not evident is the basis for the impaired galactosylation. The hypothesis that abnormally low cellular uridine diphosphate galactose (UDPgal) content is responsible has not been established. There is a tendency for galactosemic red cell UDPgal to be in the low normal range with a high uridine diphosphate glucose to UDP-gal ratio. This may reflect an inability of red cell UDPgal-4'-epimerase to maintain a normal ratio and consequently higher levels of UDPgal. In the more complex white blood cells and cultured fibroblasts, the UDPgal content and the uridine diphosphate glucose to UDPgal ratio of galactosemics are normal. Therefore, defective galactosylation observed in galactosemic fibroblasts must result from a defect in the transfer of galactose from UDPgal to these moieties.

Gonadal function in galactosemics and in galactose-intoxicated animals

Gonadal dysfunction, specifically hypergonadotropic hypogonadism, in female galactosemics is an almost universal finding. Minimal transferase activity may modulate ovarian function and the time of menopause. In contrast, male galactosemics have a relatively low risk of gonadal dysfunction. Animal models have variously suggested prenatal and postnatal insults which may play a role in the gonadal pathology. Several candidate toxic states may be involved. Current dietary restrictions are inadequate to prevent ovarian failure. Until such time as the pathophysiology is better understood, therapy will remain palliative and supportive. Exogenous estrogen and progesterone have roles in assisting pubertal changes and in prevention of the sequelae of a post-menopausal state.

Measurements of uridine diphosphate glucose and uridine diphosphate galactose--an appraisal

The recent disproof of a major deficiency of uridine diphosphate galactose in galactosemia should not lead investigators to assume either that enzymatic methods are unreliable for uridine sugar assays or that a defect in galactosylation in galactosemia has been excluded.

Dietary lactose intake, lactose intolerance, and the risk of epithelial ovarian cancer in southern Ontario (Canada)

A case-control study of dietary factors and cancer of the ovary was conducted during 1989-92 in metropolitan Toronto and surrounding areas of southern Ontario, Canada. Four hundred and fifty women aged 35-79 years, with newly diagnosed, histologically verified, primary epithelial ovarian-cancer were interviewed concerning reproduction and diet. Over the same period, 564 randomly-selected population controls, frequency-matched to the cases within three 15-year age groups, also were interviewed. From information obtained by quantitative diet history, average daily macro- and micronutrient intake values were calculated through use of the United States Department of Agriculture Food Composition Databank, which was extended and modified for Canadian items and recipes. Analysis was performed with continuous, unconditional logistic-regression methods, adjusting for age at interview, number of full-term pregnancies, total duration of oral contraceptive use, and total daily caloric intake. Neither reported history of lactose intolerance, nor average daily consumption of lactose or free galactose, were found to be associated with risk of ovarian cancer. Lactose intake or intolerance did not appear to modify the protective effects of parity and oral contraceptive use. Nevertheless, other studies suggest that ovarian galactose metabolism still may have a relationship with risk of ovarian cancer, though more evidence is needed.

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.

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.

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.

Estimates of uridine diphosphate hexoses in erythrocytes: implications for galactosemia

Impurities in a reagent dehydrogenase caused overestimates of erythrocytic uridine diphosphate glucose and accounted for clinically important differences in results between those of one group of investigators using enzymatic methods and those of two other groups using enzymatic methods, high-performance liquid chromatography, and nuclear magnetic resonance. These data have relevance for the current debate regarding the pathophysiologic changes in galactosemia.

Long-term outcome in 134 patients with galactosaemia

In a retrospective study 134 galactosaemic patients, born between 1955 and 1989 in the Federal Republic of Germany were traced and their long-term outcome evaluated. We investigated 83 galactosaemic patients (78 homozygotes, 5 compound heterozygotes) by clinical, psychometric and laboratory testing; 31 patients were evaluated by medical history, the remaining 20 patients had died due to sequelae of the underlying disease. In 48 out of 78 classical galactosaemia patients galactose-free therapy had been started before the 15th day, in 19 between days 15 and 56 and in 11 patients after the 56th day. Physical findings revealed that puberty was delayed in 1 out of 18 males and 6 out of 11 females. Neurological abnormalities included ataxia (n = 6), intention tremor (n = 11) and microcephaly (n = 10). Speech abnormalities were found in 43 out of 66 patients over 3 years of age and disturbance of visual perception and/or arithmetic deficits in 29. Intelligence declined with age, i.e., a DQ or IQ less than 85 was found in 4 out of 34 patients less than 6 years of age (12%), in 10 out of 18 between 7 and 12 years (56%) and in 20 out of 24 older than 12 years (83%). Metabolite patterns (RBC galactose-1-phosphate and UDP-galactose, plasma and urinary galactitol) did not correlate with DQ or IQ. Dietary compliance was good in almost all patients. Compound heterozygotes (n = 5) had normal mental and growth development and all laboratory parameters were in the normal range.(ABSTRACT TRUNCATED AT 250 WORDS)

Rat galactose-1-phosphate uridyltransferase coding sequence, transcription start site and genomic organization

Galactosemia is an inborn error of metabolism in humans due to deficient activity of the enzyme galactose-1-phosphate uridyl-transferase (GALT). Using a 1.3 kb Bam HI restriction fragment of the human GALT cDNA as a probe, three cDNAs, 786 bp, 265 bp and 1.4 kb were isolated from a rat liver cDNA library. The total rat GALT coding sequence obtained from these three clones was 1051 nt. Repeat cDNA library screening failed to isolate cDNA clones with additional 5'-coding sequence. Using the 786 bp cDNA as a probe, three genomic clones, RGG1, RGG2, and RGG3 were isolated from a rat genomic library. RGG2 and RGG3 contained additional 5'-coding sequence, missing from the cDNA clones, which was identified by comparison with the human cDNA sequence. The rat GALT sequence, from transcription start site to the polyadenylation tail, is 1254 nt and is divided into 11 exons which span over 3.5 kb of genomic sequence. Primer extension identified the transcription start site as 17 nt 5' to the translation start site. Rat GALT is 379 amino acids long, identical to human GALT, with a derived molecular weight of 43,312 Da similar to the 43,360 Da weight for human GALT. The derived rat amino acid sequence is 90% identical to the human sequence. The isolation of rat GALT genomic sequence will facilitate future investigations of the regulation of expression of the rat GALT gene.

Red blood cell uridine sugar nucleotide levels in patients with classic galactosemia and other metabolic disorders

While dietary galactose restriction eliminates the life-threatening complications of classic galactosemia, central nervous system and ovarian disease are still evident in these patients, despite milk restriction. Because of the possibility that reduced tissue levels of uridine diphosphate galactose (UDPgalactose), the product of the deficient enzyme, galactose-1-phosphate uridyltransferase, are the cause of these unexplained complications, we have measured the concentration of red blood cell (RBC) uridine sugar nucleotides in these patients, comparing their values not only with those of normal subjects, but also with those of children who have other metabolic disorders. RBC UDPgalactose and uridine diphosphate glucose (UDPglucose) levels were measured by high-performance liquid chromatography (HPLC) in 35 control subjects, 24 galactosemic patients, and 19 patients with inborn errors of amino acid, organic acid, or ammonia metabolism. The last group of patients served as dietary controls, as they were all on special low-protein diets that restricted milk intake. The mean levels of UDPgalactose in galactosemic children and adults were 38% and 54% lower, respectively, than the levels in normal children and adults. While only six of 19 galactosemic children had levels below the 95% confidence limit for normals, four of five galactosemic adults had levels of UDPgalactose in the low range. The mean UDPgalactose level in children with other metabolic diseases who were on a low-milk diet was also reduced by 38%, with a mean not significantly different from galactosemics. Compared with normal adults, the level of UDPglucose in galactosemic adults was also reduced by 29%, with three of five affected adults having UDPglucose values below the 95% confidence limit.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Neurologic complications in galactosemia

Two siblings, a 27-year-old man and his 24-year-old sister were diagnosed with classic transferase deficiency galactosemia at birth and were treated with strict lactose restriction. Despite well-documented dietary management, both siblings are mentally retarded and manifest a progressive neurologic condition characterized by hypotonia, hyperreflexia, dysarthria, ataxia, and a postural and kinetic tremor. Magnetic resonance imaging revealed moderate cortical atrophy, a complete lack of normal myelination, and multifocal areas of increased signal in the periventricular white matter on T2-weighting. These patients suggest that even with early diagnosis and treatment, individuals with galactosemia may have significant neurologic morbidity with abnormalities of white matter development. This finding raises the possibility of biochemical heterogeneity within the classic transferase deficiency group, as well as the possibility of a lack of available galactose metabolites necessary for glycolipid synthesis causing a disruption of normal myelin development.

Management and counseling of children with inherited metabolic disorders

Although rare individually, as a group inborn errors of metabolism are relatively common in the pediatric population. Families need assistance with evaluation and referral, accurate counseling, and management issues. An overview of inherited metabolic disorders is presented, followed by discussion and examples of selected categories of disease.

Genetic basis of galactosemia

Classic galactosemia is an inborn error of galactose metabolism and results from deficiency of the ubiquitously expressed enzyme galactose-1-phosphate uridyltransferase (GALT). Nine missense mutations, three splicing mutations, three GALT protein polymorphisms, and one silent nucleotide substitution have been identified to date. Most of the disease-causing mutations are rare among patients. The most common mutation, Q188R, has a frequency of only one-fourth in the patient population examined. Three classes of disease-causing mutations have been reported: CRM+ missense mutations (the most common class), CRM- missense mutations, and splicing mutations. Thus, galactosemia is heterogeneous at the molecular level, which is noteworthy in light of the well-documented clinical variability observed in this disorder. It has also been shown that eight of nine galactosemia missense mutations occur in evolutionarily well-conserved domains, suggesting that they affect functionally and/or structurally important residues. In contrast, all protein polymorphisms alter variable amino acids which presumably are not important for the enzyme's function.

Erythrocytic uridine diphosphate galactose in galactosaemia

An earlier claim of a deficiency of uridine diphosphate galactose in erythrocytes of galactosaemia patients was not confirmed. Enzymic techniques similar to those of the earlier investigators were used to determine not only the concentration of uridine diphosphate galactose but also the ratio of this concentration to the sum of the uridine sugar diphosphates (uridine diphosphate galactose and uridine diphosphate glucose). The values in erythrocytes of galactosaemic subjects were similar to those of non-galactosaemic children on a galactose-restricted diet and to those of normal adults. These results cast doubt on the claim of a major deficiency of uridine diphosphate galactose in galactosaemia and on the need for treating galactosaemic children with uridine.

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.

Galactose disorders: an overview

There are three separate disorders of galactose metabolism of clinical importance. Galactokinase deficiency mainly causes cataracts which regress without complications providing a galactose-free diet is started early enough. UDPgalactose-4-epimerase deficiency seems extremely rare. A common feature of the two reported cases is nerve deafness. Galactose-1-phosphate uridyl transferase deficiency poses the greatest problems because of the poor long-term outcome in spite of a galactose-restricted diet, and with no clear indications of how and when the underlying damage occurs. Recent evidence of low erythrocyte and tissue UDPgal levels, associated with ovarian dysfunction, may indicate impaired galactoside synthesis. Administration of uridine corrects the UDPgal depletion and trials in which it is added to the galactose-restricted diet have begun.

Long-term prognosis in galactosaemia: results of a survey of 350 cases

An international survey of the long term results of treating galactosaemia has shown poor results. These do not seem to be related to any of the relevant variables studied, for example delayed diagnosis or poor dietary compliance.

Regulation of galactose metabolism: implications for therapy

In view of evidence that dietary therapy of galactose-1-phosphate uridyltransferase deficiency has failed to prevent complications of the disorder, there is a need for new strategies in treatment. The enhancement of residual enzyme activity in tissues of galactosaemic patients should provide such an approach. This possibility is derived from knowledge of the regulation of transferase activity in normal animal tissues. The pertinent observations summarized herein are: (1) that hepatic transferase activity is modulated by various cellular metabolites, uridine nucleotides being of particular significance; (2) that transferase activity in the young rat liver is subject to developmental programming with a several-fold increase after birth; (3) that transferase activity in pregnant rat liver is significantly increased which may be related to hormonal effects of progesterone; and (4) that pharmacological doses of folic acid may increase transferase activity. The basis of such regulation can give insight into sufficient augmentation of the residual activity to increase galactose utilization and thereby better the long-term outcome.

Deficit of uridine diphosphate galactose in galactosaemia

The 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.

Uridine nucleotide sugars in erythrocytes of patients with galactokinase deficiency

The levels of UDPglucose and UDPgalactose (UDPGal) have been measured in erythrocytes of seven patients with galactokinase deficiency. Normal levels of UDPGal were found in all patients with galactokinase deficiency (McKusick 23020). This is in contrast with reduced values of UDPGal found in patients with classical galactosaemia who have complete absence of galactose-1-phosphate uridyl transferase activity. It was demonstrated that patients with galactokinase deficiency had an incomplete enzyme block in erythrocytes by direct enzyme assay, by 14CO2 production from [1-14C]galactose, and by the appearance of labelled intermediates, notably galactose-1-phosphate and UDPhexose.