Ovarian function in Duarte galactosemia

Selected Genetic Factors Associated with Primary Ovarian Insufficiency

Primary ovarian insufficiency (POI) is a heterogeneous disease resulting from non-functional ovaries in women before the age of 40. It is characterized by primary amenorrhea or secondary amenorrhea. As regards its etiology, although many POI cases are idiopathic, menopausal age is a heritable trait and genetic factors play an important role in all POI cases with known causes, accounting for approximately 20% to 25% of cases. This paper reviews the selected genetic causes implicated in POI and examines their pathogenic mechanisms to show the crucial role of genetic effects on POI. The genetic factors that can be found in POI cases include chromosomal abnormalities (e.g., X chromosomal aneuploidies, structural X chromosomal abnormalities, X-autosome translocations, and autosomal variations), single gene mutations (e.g., newborn ovary homeobox gene (NOBOX), folliculogenesis specific bHLH transcription factor (FIGLA), follicle-stimulating hormone receptor (FSHR), forkhead box L2 (FOXL2), bone morphogenetic protein 15 (BMP15), etc., as well as defects in mitochondrial functions and non-coding RNAs (small ncRNAs and long ncRNAs). These findings are beneficial for doctors to diagnose idiopathic POI cases and predict the risk of POI in women.

A multinational study of acute and long-term outcomes of Type 1 galactosemia patients who carry the S135L (c.404C > T) variant of GALT

Patients with galactosemia who carry the S135L (c.404C > T) variant of galactose-1-P uridylyltransferase (GALT), documented to encode low-level residual GALT activity, have been under-represented in most prior studies of outcomes in Type 1 galactosemia. What is known about the acute and long-term outcomes of these patients, therefore, is based on very limited data. Here, we present a study comparing acute and long-term outcomes of 12 patients homozygous for S135L, 25 patients compound heterozygous for S135L, and 105 patients homozygous for two GALT-null (G) alleles. This is the largest cohort of S135L patients characterized to date. Acute disease following milk exposure in the newborn period was common among patients in all 3 comparison groups in our study, as were long-term complications in the domains of speech, cognition, and motor outcomes. In contrast, while at least 80% of both GALT-null and S135L compound heterozygous girls and women showed evidence of an adverse ovarian outcome, prevalence was only 25% among S135L homozygotes. Further, all young women in this study with even one copy of S135L achieved spontaneous menarche; this is true for only about 33% of women with classic galactosemia. Overall, we observed that while most long-term outcomes trended milder among groups of patients with even one copy of S135L, many individual patients, either homozygous or compound heterozygous for S135L, nonetheless experienced long-term outcomes that were not mild. This was true despite detection by newborn screening and both early and life-long dietary restriction of galactose. This information should empower more evidence-based counseling for galactosemia patients with S135L.

Transient developmental delays in infants with Duarte-2 variant galactosemia

Duarte galactosemia is not classic galactosemia, but rather an example of biochemical variant galactosemia that results in approximately 25% residual activity of galactose-1-phosphate uridylyltransferase (GALT) enzyme. In contrast, classic galactosemia is associated with complete or near complete absence of GALT activity. While infants with classic galactosemia are placed on galactose-restricted diets to prevent the acute and long-term manifestations of their metabolic disorder, while individuals with Duarte variant galactosemia (Duarte-2 galactosemia) do not require diet therapy. The long-term complications that are seen in classic galactosemia such as cerebellar ataxia, and hypergonadotropic hypogonadism do not occur in Duarte-2 galactosemia. While Duarte galactosemia does not appear to be a metabolic disease, it may have an impact on early neurodevelopmental outcomes. This study examined developmental outcomes and the need for special services in individuals with Duarte-2 galactosemia in comparison to individuals with classic galactosemia. We performed a medical record review of individuals with GALT deficiency who were evaluated at Boston Children's Hospital and enrolled in our study of outcomes in galactosemia. This included 95 participants, 21 with Duarte-2 galactosemia and 73 with classic galactosemia. Duarte-2 participants had developmental test scores within the average range. However, 42% of subjects with Duarte-2 galactosemia had participated in early intervention and/or special education and 32% received speech therapy. Their pattern of strengths and weaknesses in cognitive/language/motor domains was similar to that noted in participants with classic galactosemia, albeit to a milder degree. The data indicate that in children with Duarte-2 variant galactosemia, the cognitive/language and motor skills were within normal limits with their cognitive/language skills developing earlier than their motor skills during their first year of life. A history of diet treatment was not related to the use of special services. These results suggest that Duarte-2 galactosemia increases the risk for early mild developmental delays irrespective of treatment history, which resolves over time, and highlights the need to further assess neurodevelopment in early infancy, in Duarte-2 galactosemia. As Duarte-2 galactosemia is not a bona fide biochemical genetic disease, we hypothesize that elements in the genomic space that include the GALT gene are responsible for a transient delay in language-related motor skills during early infancy.

Pathophysiology and management of classic galactosemic primary ovarian insufficiency

Classic galactosemia is an inborn error of carbohydrate metabolism associated with early-onset primary ovarian insufficiency (POI) in young women. Our understanding of the consequences of galactosemia upon fertility and fecundity of affected women is expanding, but there are important remaining gaps in our knowledge and tools for its management, and a need for continued dialog so that the special features of the condition can be better managed. Here, we review galactosemic POI and its reproductive endocrinological clinical sequelae and summarize current best clinical practices for its management. Special consideration is given to the very early-onset nature of the condition in the pediatric/adolescent patient. Afterward, we summarize our current understanding of the reproductive pathophysiology of galactosemia, including the potential action of toxic galactose metabolites upon the ovary. Our work establishing that ovarian cellular stress reminiscent of endoplasmic reticulum (ER) stress is present in a mouse model of galactosemia, as well as work by other groups, are summarized.

LAY SUMMARY

Patients with the condition of classic galactosemia need to maintain a strict lifelong diet that excludes the sugar galactose. This is due to having mutations in enzymes that process galactose, resulting in the buildup of toxic metabolic by-products of the sugar. Young women with classic galactosemia often lose the function of their ovaries very early in life (termed 'primary ovarian insufficiency'), despite adherence to a galactose-restricted diet. This means that in addition to the consequences of the disease, these women also face infertility and the potential need for hormone replacement therapy. This article summarizes current strategies for managing the care of galactosemic girls and women and also what is known of how the condition leads to early primary ovarian insufficiency.

Developmental Outcomes in Duarte Galactosemia

: media-1vid110.1542/5849572227001PEDS-VA_2018-2516Video Abstract OBJECTIVES: For decades, infants with Duarte galactosemia (DG) have been identified by newborn screening (NBS), but whether they should be treated with dietary restrictions of galactose has remained unknown. To clarify, we conducted a study of dietary and developmental outcomes in 206 children with DG (case patients) and 144 controls, all of whom were 6 to 12 years old.

METHODS

We recruited case patients from states where they were identified by NBS; unaffected siblings served as controls. Diet in infancy was ascertained by retrospective parent surveys; developmental outcomes were assessed in 5 domains, yielding 73 outcome measures for each child. We divided subjects randomly into independent discovery (n = 87) and validation (n = 263) sets. We tested the discovery set to order the 73 outcome measures by ascending P values and tested the 10 outcomes with the lowest P values for possible association with DG in the validation set. We also tested these same 10 outcomes for possible association with milk exposure in infancy among case patients in the validation set.

RESULTS

None of the 73 outcomes tested in the discovery set revealed significant association with DG, and none of the 10 outcomes tested in the validation set revealed either significant association with DG or significant association with milk exposure among children with DG.

CONCLUSIONS

Through our results, we demonstrated that there were no significant differences in outcomes tested between case patients and controls or among case patients as a function of milk exposure in infancy. In this study, we provide a long-needed foundation of knowledge for health care providers, families, and NBS professionals seeking to make evidence-based decisions about DG.

Basic pituitary-ovarian hormones and ultrasound parameters of uterine appendages in full-term and preterm neonate girls

Objective To determine the basic pituitary-ovarian hormones and ultrasound parameters of uterine appendages in full-term and preterm newborn girls. Materials and methods One hundred full-term and premature newborn girls (58 and 42, respectively) were studied with clinical, instrumental, laboratory (enzyme immunoassay) and statistical methods. Results Statistically significant differences in the pituitary-ovarian hormones and ultrasound parameters of uterine appendages in preterm neonate girls compared to full-term girls were defined. The pituitary hormone levels (follicle-stimulating and luteinizing hormone levels) were higher in preterm newborn girls [0.15 (0.06-0.53) and 0.06 (0.05-0.08) (p = 0.0001); 0.03 (0.00-0.23) and 0.00 (0.00-0.03), (p = 0.003)]; the ovarian hormone levels (estradiol, anti-Müllerian hormone and inhibin В levels) were lower [0.44 (0.25-0.85) and 1.55 (1.06-1.84) (p = 0.0001); 2.73 (2.12-3.65) and 3.66 (2.59-5.0), (p = 0.026), 60.81 (37.19-128.80) and 104.75 (54.35-159.18), (p = 0.019), respectively]. Ultrasound investigation showed that the ovarian reserve in preterm neonates was smaller compared to the full-term neonates [38.48 (22.01-56.49) and 102.47 (85.36-111.37), (p = 0.0001); 36.95 (25.21-70.59) and 108.05 (91.74-116.44), (p = 0.0001), respectively (p = 0.0001)]. The number of antral follicles in the slice was also statistically significantly smaller [2 - in the right ovary, 1 - in the left ovary, vs. 4 and 4, respectively (p = 0.0001)]. Conclusion Premature neonates have different pituitary-ovarian hormones and ovarian size compared to full-term babies.

Primary ovarian insufficiency in classic galactosemia: current understanding and future research opportunities

Classic galactosemia is an inborn error of the metabolism with devastating consequences. Newborn screening has been successful in markedly reducing the acute neonatal symptoms from this disorder. The dramatic response to dietary treatment is one of the major success stories of newborn screening. However, as children with galactosemia achieve adulthood, they face long-term complications. A majority of women with classic galactosemia develop primary ovarian insufficiency and resulting morbidity. The underlying pathophysiology of this complication is not clear. This review focuses on the reproductive issues seen in girls and women with classic galactosemia. Literature on the effects of classic galactosemia on the female reproductive system was reviewed by an extensive Pubmed search (publications from January 1975 to January 2017) using the keywords: galactosemia, ovarian function/dysfunction, primary ovarian insufficiency/failure, FSH, oxidative stress, fertility preservation. In addition, articles cited in the search articles and literature known to the authors was also included in the review. Our understanding of the role of galactose metabolism in the ovary is limited and the pathogenic mechanisms involved in causing primary ovarian insufficiency are unclear. The relative rarity of galactosemia makes it difficult to accumulate data to determine factors defining timing of ovarian dysfunction or treatment/fertility preservation options for this group of women. In this review, we present reproductive challenges faced by women with classic galactosemia, highlight the gaps in our understanding of mechanisms leading to primary ovarian insufficiency in this population, discuss new advances in fertility preservation options, and recommend collaboration between reproductive medicine and metabolic specialists to improve fertility in these women.

Genetics of primary ovarian insufficiency: new developments and opportunities

BACKGROUND

Primary ovarian insufficiency (POI) is characterized by marked heterogeneity, but with a significant genetic contribution. Identifying exact causative genes has been challenging, with many discoveries not replicated. It is timely to take stock of the field, outlining the progress made, framing the controversies and anticipating future directions in elucidating the genetics of POI.

METHODS

A search for original articles published up to May 2015 was performed using PubMed and Google Scholar, identifying studies on the genetic etiology of POI. Studies were included if chromosomal analysis, candidate gene screening and a genome-wide study were conducted. Articles identified were restricted to English language full-text papers.

RESULTS

Chromosomal abnormalities have long been recognized as a frequent cause of POI, with a currently estimated prevalence of 10-13%. Using the traditional karyotype methodology, monosomy X, mosaicism, X chromosome deletions and rearrangements, X-autosome translocations, and isochromosomes have been detected. Based on candidate gene studies, single gene perturbations unequivocally having a deleterious effect in at least one population include Bone morphogenetic protein 15 (BMP15), Progesterone receptor membrane component 1 (PGRMC1), and Fragile X mental retardation 1 (FMR1) premutation on the X chromosome; Growth differentiation factor 9 (GDF9), Folliculogenesis specific bHLH transcription factor (FIGLA), Newborn ovary homeobox gene (NOBOX), Nuclear receptor subfamily 5, group A, member 1 (NR5A1) and Nanos homolog 3 (NANOS3) seem likely as well, but mostly being found in no more than 1-2% of a single population studied. Whole genome approaches have utilized genome-wide association studies (GWAS) to reveal loci not predicted on the basis of a candidate gene, but it remains difficult to locate causative genes and susceptible loci were not always replicated. Cytogenomic methods (array CGH) have identified other regions of interest but studies have not shown consistent results, the resolution of arrays has varied and replication is uncommon. Whole-exome sequencing in non-syndromic POI kindreds has only recently begun, revealing mutations in the Stromal antigen 3 (STAG3), Synaptonemal complex central element 1 (SYCE1), minichromosome maintenance complex component 8 and 9 (MCM8, MCM9) and ATP-dependent DNA helicase homolog (HFM1) genes. Given the slow progress in candidate-gene analysis and relatively small sample sizes available for GWAS, family-based whole exome and whole genome sequencing appear to be the most promising approaches for detecting potential genes responsible for POI.

CONCLUSION

Taken together, the cytogenetic, cytogenomic (array CGH) and exome sequencing approaches have revealed a genetic causation in ∼20-25% of POI cases. Uncovering the remainder of the causative genes will be facilitated not only by whole genome approaches involving larger cohorts in multiple populations but also incorporating environmental exposures and exploring signaling pathways in intragenic and intergenic regions that point to perturbations in regulatory genes and networks.

Circulating AMH reflects ovarian morphology by magnetic resonance imaging and 3D ultrasound in 121 healthy girls

CONTEXT

In adult women, Anti-Müllerian hormone (AMH) is produced by small growing follicles, and circulating levels of AMH reflect the number of antral follicles as well as primordial follicles. Whether AMH reflects follicle numbers in healthy girls remains to be elucidated.

OBJECTIVE

This study aimed to evaluate whether serum levels of AMH reflects ovarian morphology in healthy girls.

DESIGN AND SETTING

This was a population-based cohort study involving the general community.

PARTICIPANTS

Included in the study were 121 healthy girls 9.8-14.7 years of age.

MAIN OUTCOME MEASURES

Clinical examination, including pubertal breast stage (Tanner's classification B1-5), ovarian volume, as well as the number and size of antral follicles were assessed by two independent modalities: magnetic resonance imaging (MRI), Ellipsoid volume, follicles ≥2 mm; and Transabdominal ultrasound, Ellipsoid and 3D volume, follicles ≥1 mm. Circulating levels of AMH, inhibin B, estradiol, FSH, and LH were assessed by immunoassays; T and androstenedione were assessed by liquid chromatography-tandem mass spectrometry.

RESULTS

AMH reflected the number of small (MRI 2-3 mm) and medium (4-6 mm) follicles (Pearson's Rho [r] = 0.531 and r = 0.512, P < .001) but not large follicles (≥7 mm) (r = 0.109, P = .323). In multiple regression analysis, small and medium follicles (MRI ≤ 6 mm) remained the main contributors to circulating AMH (β, 0.501; P < .001) whereas the correlation between AMH and estradiol was negative (β, -0.318; P = .005). In early puberty (B1-B3), the number of AMH-producing follicles (2-6 mm) correlated positively with pubertal stages (r = 0.453, P = .001), whereas AMH levels were unaffected (-0.183, P = .118).

CONCLUSIONS

Similarly to adult women, small and medium antral follicles (≤6 mm) were the main contributors to circulating levels of AMH in girls.

Anti-Mullerian hormone levels in American girls by age and race/ethnicity

BACKGROUND

Anti-Mullerian Hormone (AMH), a proposed indicator of ovarian follicle reserve in adults, has not been characterized in pediatric and adolescent females by race and/or ethnicity.

OBJECTIVES

To describe AMH levels in healthy American girls and determine the influence of age and race/ethnicity on AMH.

SUBJECTS

SUBJECTS aged 10-21 years were recruited from primary care settings and emergency departments. Race/ethnicity was characterized as White, Black or Hispanic.

METHODS

Serum for AMH levels (ng/mL) was measured using an enzyme-linked immunosorbent assay.

RESULTS

Thirty-one White, 60 Black and 24 Hispanic subjects were recruited. Mean AMH levels were 3.19 ng/mL (22.8 pmol/L) (SD 2.12) for Whites, 3.25 ng/mL (23.2 pmol/L) (SD 2.23) for Blacks and 2.97 ng/mL (21.2 pmol/L) (SD 1.75) for Hispanics. ANCOVA showed no difference in AMH levels among race/ethnicities, controlling for age (p=0.91). Age was significantly associated with AMH (p<0.001, R²=0.12).

CONCLUSION

AMH levels do not vary by race/ethnicity, and AMH levels increase with age.

Modifiers of ovarian function in girls and women with classic galactosemia

CONTEXT

Classic galactosemia is a potentially lethal genetic disorder resulting from profound impairment of galactose-1P uridylyltransferase (GALT). More than 80% of girls and women with classic galactosemia experience primary or premature ovarian insufficiency despite neonatal diagnosis and rigorous lifelong dietary galactose restriction.

OBJECTIVE

The goal of this study was to test the relationship between markers of ovarian reserve, cryptic residual GALT activity, and spontaneous pubertal development in girls with classic galactosemia.

DESIGN AND SETTING

This was a cross-sectional study with some longitudinal follow-up in a university research environment.

PATIENTS

Patients included girls and women with classic galactosemia and unaffected controls, <1 month to 30 years old.

MAIN OUTCOME MEASURES

We evaluated plasma anti-Müllerian hormone (AMH) and FSH levels, antral follicle counts ascertained by ultrasound, and ovarian function as indicated by spontaneous vs assisted menarche.

RESULTS

More than 73% of the pre- and postpubertal girls and women with classic galactosemia in this study, ages >3 months to 30 years, demonstrated AMH levels below the 95% confidence interval for AMH among controls of the same age, and both pre- and postpubertal girls and women with classic galactosemia also demonstrated abnormally low antral follicle counts relative to age-matched controls. Predicted residual GALT activity ≥ 0.4% significantly increased the likelihood that a girl with classic galactosemia would demonstrate an AMH level ≥ 0.1 ng/mL.

CONCLUSIONS

A majority of girls with classic galactosemia demonstrate evidence of diminished ovarian reserve by 3 months of age, and predicted cryptic residual GALT activity is a modifier of ovarian function in galactosemic girls and women.