Risk factors for premature ovarian failure in females with galactosemia

ARHI: A new target of galactose toxicity in Classic Galactosemia

In humans, deficiency of galactose-1-phosphate uridyltransferase (GALT) activity can lead to a potentially lethal disease called Classic Galactosemia. Although a galactose-restricted diet can prevent the acute lethality associated with the disorder, chronic complications persist in many well-treated patients. Approximately 85% of young women with Classic Galactosemia experience hypergonadotropic hypogonadism and premature ovarian failure (POF). Others suffer from mental retardation, growth restriction, speech dyspraxia, and ataxia. Despite decades of intense biochemical characterization, little is known about the molecular etiology, as well as the chronology of the pathological events leading to the poor outcomes. Several hypotheses have been proposed, most of which involved the accumulation of the intermediates and/or the deficit of the products, of the blocked GALT pathway. However, none of these hypotheses satisfactorily explained the absence of patient phenotypes in the GALT-knockout mice. Here we proposed that the gene encoded the human tumor suppressor gene aplysia rashomolog I (ARHI) is a target of toxicity in Classic Galactosemia, and because ARHI gene is lost in rodents in through evolution, it thus accounts for the lack of clinical phenotypes in the GALT-knockout mice.

Screening newborns for galactosemia using total body galactose oxidation to CO2 in expired air

Classic galactosemia is caused by impaired galactose-1-phosphate uridyltransferase (GALT EC 2.7.712). If discovered and treated within the first days of life, the acute problems of hepatocellular damage, sepsis, and death are prevented. However, chronic problems such as ataxia, tremor, dyspraxic speech, and ovarian failure may occur. To determine whether screening newborns before discharge from the nursery for GALT deficiency is feasible and whether acute and chronic signs could be prevented by earlier intervention, we developed a simplified "breath test." We quantitated total body oxidation of C-D-galactose to CO2 in expired air by normal newborns between 2 h and 2 mo of age and compared their results to older children with GALT deficiency. We found no differences in total body galactose oxidation (TBGO) among normal newborns up to 48 h of age, but a 2-fold rise in TBGO developed during their first 2 wk of life. Older children with galactosemia had significantly less oxidative capacity than normal newborns. We conclude that newborn breath testing for total body galactose oxidation is feasible before discharge from nursery. It has potential utility for both preventing acute neonatal toxicity and determining the mechanisms producing long-term complications such as ovarian failure, dyspraxia, ataxia, and tremors.

Premenopausal factors influencing premature ovarian failure and early menopause

OBJECTIVES

We conducted this study to examine premenopausal risk factors associated with premature ovarian failure (POF) and early menopause (EM) among Korean women.

METHODS

A 73% of total women aged 30-69 at four districts in the KMCC (Korean Multi-center Cancer Cohort) was participated in this study during 2002-2003. We selected 137 POF and 281 EM cases who had menopause before age 40 and at age 40-44, respectively, and 1318 normal menopause (NM) controls that experienced menopause at age 45-60, and among them, selected idiopathic POF (n=84) and EM (n=261) after excluding surgical/medical menopause. We collected the information of premenopausal lifestyle and reproductive risk factors. Multivariate and polytomous logistic regression were used to estimate POF and EM risk and to differentiate POF and EM risk using ordinal and nominal scale.

RESULTS

Cigarette smoking was associated with an increased risk of idiopathic POF (OR=1.82 [1.03-3.23]), whereas oral contraceptive use was associated with a reduced risk of natural EM (OR=0.62 [0.43-0.90]). Idiopathic POF risk by both factors differed from idiopathic EM risk (p-nominal<0.05). Factors related to ovulation, such as later menarche, irregular menstruation and longer breast feeding cumulatively reduced the risk of natural EM and POF (p-ordinal<0.05). In analysis including medical and surgical menopause, lung tuberculosis, hysterectomy, past cancers, and lower number of deliveries before menopause were associated with POF.

CONCLUSIONS

Our findings indicate that etiology in POF development may partly differ from that in EM.

A prospective study of dairy foods intake and anovulatory infertility

BACKGROUND

Dairy foods and lactose may impair fertility by affecting ovulatory function. Yet, few studies have been conducted in humans and their results are inconsistent. We evaluated whether intake of dairy foods was associated with anovulatory infertility and whether this association differed according to fat content.

METHODS

We prospectively followed 18,555 married, premenopausal women without a history of infertility who attempted a pregnancy or became pregnant during an 8-year period. Diet was assessed twice during the study using food-frequency questionnaires.

RESULTS

During follow-up, 438 women reported infertility due to an ovulatory disorder. The multivariate-adjusted relative risks (RR) [95% confidence interval (CI); P, trend] of anovulatory infertility comparing women consuming > or = 2 servings per day to women consuming < or = 1 serving per week was 1.85 (1.24-2.77; 0.002) for low-fat dairy foods. The RR (95% CI; P, trend) comparing women consuming > or = 1 serving per day of high-fat dairy foods to those consuming < or = 1 serving per week was 0.73 (0.52-1.01; 0.01). There was an inverse association between dairy fat intake and anovulatory infertility (P, trend = 0.05). Intakes of lactose, calcium, phosphorus and vitamin D were unrelated to anovulatory infertility.

CONCLUSIONS

High intake of low-fat dairy foods may increase the risk of anovulatory infertility whereas intake of high-fat dairy foods may decrease this risk. Further, lactose (the main carbohydrate in milk and dairy products) may not affect fertility within the usual range of intake levels in humans.

Classical galactosaemia revisited

Classical galactosaemia (McKusick 230400) is an: autosomal recessive disorder of galactose metabolism, caused by a deficiency of the enzyme galactose-1-phosphate uridyltransferase (GALT; EC 2.7.712). Most patients present in the neonatal period, after ingestion of galactose, with jaundice, hepatosplenomegaly, hepatocellular insufficiency, food intolerance, hypoglycaemia, renal tubular dysfunction, muscle hypotonia, sepsis and cataract. The gold standard for diagnosis of classical galactosaemia is measurement of GALT activity in erythrocytes. Gas-chromatographic determination of urinary sugars and sugar alcohols demonstrates elevated concentrations of galactose and galactitol. The only therapy for patients with classical galactosaemia is a galactose-restricted diet, and initially all galactose must be removed from the diet as soon as the diagnosis is suspected. After the neonatal period, a lactose-free diet is advised in most countries, without restriction of galactose-containing fruit and vegetables. In spite of the strict diet, long-term complications such as retarded mental development, verbal dyspraxia, motor abnormalities and hypergonadotrophic hypogonadism are frequently seen in patients with classical galactosaemia. It has been suggested that these complications may result from endogenous galactose synthesis or from abnormal galactosylation. Novel therapeutic strategies, aiming at the prevention of galactose 1-phosphate production, should be developed. In the meantime, the follow-up protocol for patients with GALT deficiency should focus on early detection, evaluation and, if possible, early intervention in problems of motor, speech and cognitive development.

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.

The Duarte (N314D) variant in the GALT gene has no effect on in vitro fertilization outcome

We assessed the effect of the Duarte (N314D) variant in the GALT gene on in vitro fertilization outcome measures. Our data do not definitely exclude variants in the GALT gene as factors influencing outcome, but the lack of suggestive evidence makes it difficult to justify a larger, more definitive study.

Prevention of a molecular misdiagnosis in galactosemia

PURPOSE

The polymerase chain reaction is generally used for mutational analysis of the galactose-1-phosphate uridyl transferase (GALT) gene in the diagnosis of galactosemia. This method is problematic when used in families of Ashkenazi Jewish descent.

METHODS

We amplified the GALT gene from leukocyte DNA followed by allele specific oligonucleotide hybridization, DNA sequencing and Southern Blot analysis to determine the mutant alleles causing galactosemia in a representative Jewish family.

RESULTS

The proband's diagnosis of galactosemia was confirmed by high levels of erythrocyte galactose-1-phosphate, absence of erythrocyte GALT activity and impaired total body oxidation of galactose to expired CO2. Initial molecular analysis of GALT alleles in the family showed homozygosity for a K285N missense mutation in the proband, homozygosity for N314D in the mother and heterozygosity for N314D and K285N in the father. These results contradicted Mendelian logic. Southern blot hybridization with GALT cDNA proved the presence of a complex 5 kb GALT deletion in the proband and her mother's DNA enabling a corrected genotype.

CONCLUSIONS

Since a deletion of the GALT gene is a common mutation causing galactosemia among Ashkenazim Jewish families, this deletion should be suspected and tested for by genomic hybridization or by using primers specific for the 5 kb deletion.

Screening of the galactose-1-phosphate uridyltransferase gene in Indian women with ovarian failure

The present study was aimed at mutational screening of the gene coding for galactose-1-phosphate uridyltransferase in females with premature ovarian failure within an Indian population. A case-control-based study approach was used. It included females with premature ovarian failure (n = 108), primary amenorrhoea (n = 37) and secondary amenorrhoea (n = 9), and a control group of 136 women with a normal ovarian pattern. Gene sequencing analysis for the presence of mutations in the promoter and the coding regions of GALT has shown the absence of any mutation. A hexanucleotide deletion was found in the third intronic region of GALT in both cases and controls. These data support the hypothesis that there is no significant association between GALT mutations and ovarian failure, and hence the present authors conclude that there is no relationship between ovarian failure and GALT polymorphisms in Indian women.

Hypoglycosylation with increased fucosylation and branching of serum transferrin N-glycans in untreated galactosemia

Untreated classic galactosemia (galactose-1-phosphate uridyltransferase [GALT] deficiency) is known as a secondary congenital disorders of glycosylation (CDG) characterized by galactose deficiency of glycoproteins and glycolipids (processing defect or CDG-II). The mechanism of this undergalactosylation has not been established. Here we show that in untreated galactosemia, there is also a partial deficiency of whole glycans of serum transferrin associated with increased fucosylation and branching as seen in genetic glycosylation assembly defects (CDG-I). Thus galactosemia seems to be a secondary "dual" CDG causing a processing as well as an assembly N-glycosylation defect. We also demonstrated that in galactosemia patients, transferrin N-glycan biosynthesis is restored upon dietary treatment.

Q188R, K285N, and N314D mutation-associated alleles in the galactose-1-phosphate uridyltransferase gene and female infertility

In a retrospective case-control study, the frequencies of Q188R, K285N, N314D, and IVS5-24G>A mutations were determined with the use of polymerase chain reaction and restriction fragment length polymorphism in the group of infertile women and the controls. No statistically significant differences were observed in the allele frequencies between the infertile women and control groups.

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.

Galactosemia

Despite the dramatic response of sick neonates with galactosemia to the withdrawal of galactose from the diet, over the long-term, complications, including learning disorders, verbal apraxia, and ataxia, often develop. It is clear that, although lifelong galactose restriction remains the basis of treatment for this disease, additional treatment methods are needed. The neurologist familiar with galactosemia can assist in diagnosis of neonates presenting with central nervous system symptoms. Familiarity with the long-term neurologic consequences of galactosemia can help the neurologist assist the family with prognostic information and to avoid unnecessary tests when complications occur.

Verbal dyspraxia and galactosemia

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

[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.

Frequencies of Q188R and N314D mutations and IVS5-24g>A intron variation in the galactose-1-phosphate uridyl transferase (GALT) gene in the Slovenian population

Numerous mutations in the galactose-1-phosphate uridyl transferase (GALT) gene have been found to impair GALT activity to different extent, causing galactosemia. This disorder exhibits considerable allelic heterogeneity in different populations and ethnic groups. The Q188R mutation accounts for 60-70% of classical galactosemia alleles in the Caucasian population. Individuals homoallelic for Q188R have a severe phenotype with complete loss of enzyme activity. Another form of GALT deficiency is Duarte galactosemia with N314D mutation associated alleles (Duarte-2). Although heterozygotes for classical galactosemia are asymptomatic at birth and Duarte galactosemia appears to be quite benign, there are some indications that these disorders can increase the risk of developing certain diseases later in life. The aim of our study was to analyze a healthy Slovenian population for the frequencies of Q188R and N314D mutations, and for the Duarte-2 indicative intronic variation IVS5-24G>A. DNA samples from 174 healthy subjects were analyzed for all three mutations by polymerase chain reaction and digestion with restriction enzymes. Allele frequencies for Q188R and N314D mutations and IVS5-24G>A intron variation were found to be 0.29%, 8.0% and 5.7%, respectively. These results correlate well with those reported for most other healthy Caucasian populations.

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.

Structure-function analyses of a common mutation in blacks with transferase-deficiency galactosemia

We previously identified a missense mutation at amino acid 135 of human galactose 1-phosphate uridyltransferase (hGALT) in which a leucine (TTG) was substituted for a serine (TCG), S135L. This mutation was common in black patients with galactosemia and homozygotes (S135L/S135L) had no GALT activity or protein in their erythrocytes or lymphoblasts. However, there was residual GALT activity and protein in their leukocytes, and they had near normal total body [13C]galactose oxidation to 13CO2 in breath. To evaluate the biochemical mechanism(s) producing these effects, we overexpressed hGALT proteins with site-directed mutations in this nonconserved amino acid in a GALT-minus Escherichia coli. Enzyme activities detected in bacterial lysates overexpressing either S135 (wild type), A135, C135, H135, L135, S132-H135, T135, or Y135 were 100, 4.7, 3.0, 4.0, 2.7, 0.7, 35.4, and 1.4%, respectively. Only the threonine substitution (S135T) had significant enzyme activity in these lysates. There was also decreased abundance of all mutant proteins in the lysates exposed to bacterial proteolysis during preparation and analysis. This added the variable of bio-instability to analysis of enzyme activities in lysates. To further characterize the catalytic role of serine at amino acid 135 and to differentiate bio-instability from impaired catalysis by the leucine substitution, we purified wild-type and L135-hGALT proteins to homogeneity and analyzed identical amounts of enzyme protein. We found that the apparent Vmax of the purified L135-hGALT protein was significantly reduced from 80 +/- 5.9 to 5.8 +/- 1.8 micromol glucose 1-phosphate released/min/mg hGALT protein with no increase in KM for galactose 1-phosphate for the second displacement. The first displacement reaction, although three orders of magnitude slower, was similar between the wild type and L135-hGALT. We conclude that a hydroxyl group on amino acid 135 is required for the catalysis of uridyl transfer from UDP-glucose to UDP-galactose in the presence of galactose 1-phosphate, and plays a role in the bio-stability of hGALT.

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.