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Early life manganese exposure upregulates tumor-associated genes in the hypothalamus of female rats: relationship to manganese-induced precocious puberty.

ABSTRACT: Prepubertal exposure to low, but elevated levels of manganese (Mn) can induce increased secretions of puberty-related hormones resulting in precocious pubertal development in female rats. These events are due to an action of the element within the hypothalamus to induce the secretion of gonadotropin-releasing hormone (GnRH). Because of these prepubertal effects of Mn and because precocious puberty is a serious neuroendocrine disorder, we have assessed whether early life exposure to this environmental element is capable of precociously upregulating the expression of a select group of genes previously associated with tumor growth or suppression, and that have more recently been shown to increase at the normal time of puberty. Female rat pups received a daily dose of either 10mg/kg manganese(II) chloride or an equal volume of saline by gastric gavage from postnatal day 12 through day 22 or 29. At this time, blood was collected for estradiol analysis and hypothalamic brain tissue frozen on dry ice until assessed for gene expressions. Rats exposed to the elevated levels of Mn showed a precocious increase in GnRH gene expression in the preoptic area and rostral hypothalamus on day 29, an action associated with precociously increased expressions of specific tumor-associated, puberty-related genes. These results demonstrate for the first time that prepubertal Mn exposure is capable of activating specific upstream genes regulating hypothalamic GnRH and suggest that these actions are involved in the mechanism by which this element can induce precocious puberty.

SUBMITTER: Srivastava VK

PROVIDER: S-EPMC3858189 | biostudies-literature | 2013 Dec

REPOSITORIES: biostudies-literature

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Early life manganese exposure upregulates tumor-associated genes in the hypothalamus of female rats: relationship to manganese-induced precocious puberty.

Srivastava Vinod K VK Hiney Jill K JK Dees William L WL

Toxicological sciences : an official journal of the Society of Toxicology 20130831 2

Prepubertal exposure to low, but elevated levels of manganese (Mn) can induce increased secretions of puberty-related hormones resulting in precocious pubertal development in female rats. These events are due to an action of the element within the hypothalamus to induce the secretion of gonadotropin-releasing hormone (GnRH). Because of these prepubertal effects of Mn and because precocious puberty is a serious neuroendocrine disorder, we have assessed whether early life exposure to this environm ...[more]

PMID: 23997110

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Project description:IntroductionEstrogenic endocrine disrupting chemicals (EDCs) such as diethylstilbestrol (DES) are known to alter the timing of puberty onset and reproductive function in females. Accumulating evidence suggests that steroid synthesis inhibitors such as ketoconazole (KTZ) or phthalates may also affect female reproductive health, however their mode of action is poorly understood. Because hypothalamic activity is very sensitive to sex steroids, we aimed at determining whether and how EDCs with different mode of action can alter the hypothalamic transcriptome and GnRH release in female rats.DesignFemale rats were exposed to KTZ or DES during perinatal (DES 3-6-12μg/kg.d; KTZ 3-6-12mg/kg.d), pubertal or adult periods (DES 3-12-48μg/kg.d; KTZ 3-12-48mg/kg.d).ResultsEx vivo study of GnRH pulsatility revealed that perinatal exposure to the highest doses of KTZ and DES delayed maturation of GnRH secretion before puberty, whereas pubertal or adult exposure had no effect on GnRH pulsatility. Hypothalamic transcriptome, studied by RNAsequencing in the preoptic area and in the mediobasal hypothalamus, was found to be very sensitive to perinatal exposure to all doses of KTZ before puberty with effects persisting until adulthood. Bioinformatic analysis with Ingenuity Pathway Analysis predicted "Creb signaling in Neurons" and "IGF-1 signaling" among the most downregulated pathways by all doses of KTZ and DES before puberty, and "PPARg" as a common upstream regulator driving gene expression changes. Deeper screening ofRNAseq datasets indicated that a high number of genes regulating the activity of the extrinsic GnRH pulse generator were consistently affected by all the doses of DES and KTZ before puberty. Several, including MKRN3, DNMT3 or Cbx7, showed similar alterations in expression at adulthood.ConclusionnRH secretion and the hypothalamic transcriptome are highly sensitive to perinatal exposure to both DES and KTZ. The identified pathways should be exploredfurther to identify biomarkers for future testing strategies for EDC identification and when enhancing the current standard information requirements in regulation.

Project description:Study questionIs in utero exposure to mercury associated with the risk of precocious puberty?Summary answerPrenatal exposure to high levels of mercury was associated with increased risk of precocious puberty, which was strengthened by concomitant maternal cardiometabolic conditions and adverse birth outcomes.What is known alreadyThe developing fetus is sensitive to mercury, a well-known endocrine disruptor which impacts the endocrine and reproductive system.Study design, size, durationThis study included 1512 mother-child pairs from the Boston Birth Cohort, a longitudinal cohort which recruited at birth and followed prospectively up to 21 years of age.Participants/materials, setting, methodsMother-child pairs, from a predominantly urban minority population, were enrolled from 2002 to 2013. Prenatal exposure was assessed by maternal mercury concentration in red blood cells (RBCs) collected at 1-3 days after delivery. Precocious puberty was defined based on International Classification of Disease codes. Cox proportional hazards models were applied to the association between maternal mercury concentrations and the risk of precocious puberty.Main results and the role of chanceThe median (interquartile range) of maternal mercury concentrations among children with and without precocious puberty were 3.4 (1.9-4.6) µg/l and 2.0 (1.0-3.7) µg/l, respectively. Compared to those in the lowest tertile for mercury, the highest tertile was associated with increased risk of precocious puberty, with an adjusted hazard ratio (HR) of 2.41, 95% CI: 1.16-5.03. In addition, concomitant maternal cardiometabolic conditions and adverse birth outcomes strengthened the effects of mercury on the risk of precocious puberty. The highest risk of precocious puberty was observed among children who had adverse birth outcomes and whose mothers had high RBC-mercury concentrations along with cardiometabolic conditions, with an HR of 4.76 (95% CI: 1.66-13.60) compared to children with favorable profiles of all three risk factors.Limitations, reasons for cautionPrecocious puberty was defined based on medical records, not on a direct assessment, which may have led to underdiagnosis and the inability to make a subclassification. The study included a predominately urban, low-income, minority population and as such our findings may not be widely generalizable.Wider implications of the findingsPrenatal Hg exposure was associated with an increased risk of precocious puberty. This risk was strengthened by concomitant maternal cardiometabolic conditions during pregnancy and adverse birth outcomes.Study funding/competing interest(s)This study was funded by the NIH/National Institute of Environmental Health Sciences, NIH/Eunice Kennedy Shriver National Institute of Child Health and Human Development and the Health Resources and Services Administration of the U.S. Department of Health and Human Services. The authors declare no conflicts of interest.Trial registration numberN/A.

Project description:ObjectivesObesity is reported to be closely relevant to early sexual development but the relationship between sexual precocity and obesity or central obesity is still inconsistent, especially in boys. We aimed to investigate the relationship between precocious puberty and obesity as well as central obesity.DesignA large population-based cross-sectional study using multistage, stratified cluster random sampling.SettingData from the Shanghai Children's Health, Education and Lifestyle Evaluation (SCHEDULE) study in June 2014.Participants17?620 Chinese children aged 6-12 years.Primary and secondary outcome measuresObesity was defined by WHO Child Growth Standards. Central obesity was defined by sex-specific waist-to-height ratio (WHtR) cut-offs (WHtR ?0.48 for boys, WHtR ?0.46 for girls). Precocious puberty was identified by Tanner stage of breast, pubic hair and testicle development. A ?2 test was performed to compare rates. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to assess the association between precocious puberty and general obesity and central obesity. Probit analysis was used for estimating the median age at entry into Tanner stage 2 or greater for breast, pubic hair and testicle development. Linear regression was utilised to compare the effects of WHtR and body mass index (BMI) on sex development indicators.Results25.98% and 38.58%?of boys with precocious puberty were respectively accompanied by obesity (OR=2.15, 95%?CI=1.31 to 3.50) or central obesity (OR=2.10, 95%?CI=1.46 to 3.03); meanwhile, 13.86% and 29.42%?of girls with precocious puberty were respectively accompanied by obesity (OR=9.00, 95%?CI=5.60 to 14.46) or central obesity (OR=5.40, 95%?CI=4.10 to 7.12). The median ages of breast, pubic hair and testicle development decreased with BMI increase and median ages of thelarche and testicular development rather than pubarche were earlier in children with central obesity.ConclusionsEarlier pubertal development was positively associated with obesity and central obesity in Chinese children.

Project description:BackgroundIn 90% cases of girls and 25-60% cases of boys the cause of gonadotropin-dependent precocious puberty (PP) is unclear. Up to 25-27.5% of gonadotropin-dependent PP cases are monogenic and suggest autosomal-dominant inheritance with incomplete sex-dependent penetrance. To date, mutations in genes KISS1, KISS1R, MKRN3, DLK1 have been described as causal variants leading to precocious hypothalamic-pituitary axis activation in childhood. Genetic testing in patients with hereditary forms of PP can expand our knowledge of underlying molecular mechanisms of the disease and it is also necessary for genetic counselling.AimTo study clinical features and genetic characteristics of patients with idiopathic gonadotropin-dependent precocious puberty.Materials and methodsA group of patients with idiopathic gonadotropin-dependent precocious puberty and positive family history (early or precocious puberty) was examined. Laboratory and instrumental diagnostic tests, full-exome sequencing (NGS, next-generation sequencing) were provided for all patients.ResultsThe study included 30 patients (29 girls, 1 boy) with idiopathic gonadotropin-dependent precocious puberty. The median of patients age at the time of the examination was 7,2 years [6,5; 7,7]. Positive family history presented in all cases: in 40% of patients on father's side, in 37% - on mother's side, in 23% of patients PP was diagnosed in siblings. The fullexome sequencing was conducted to 21 patients: in 61,9% of cases (95% CI [40;79]) nucleotide variants were identified in genes, associated with gonadotropin-dependent precocious puberty. MKRN3 gene defect was detected in most cases (77% cases (95% CI [49; 92]), which consistent with international data on its highest prevalence in the monogenic forms of PP. In 23% of cases (95% CI [7; 50]) nucleotide variants were identified in other candidate genes associated with neuroontogenesis and neuroendocrine regulation mechanisms of hypothalamic-pituitary axis.ConclusionOur study confirms that detailed family history data in children with PP provides a rational approach to molecular-genetic testing. Data of inheritance pattern and clinical manifestations will simplify the diagnosis of hereditary forms of disease and enhance genetic counselling of families, followed by timely examination and administration of pathogenetic therapy.

Project description:BackgroundThe gonadotropin-releasing hormone (GnRH) stimulation test is the benchmark for diagnosing precocious puberty (PP). However, it is invasive, time-consuming, costly, and may create an unpleasant experience for participants. Moreover, some overlaps may occur between PP and premature thelarche (PT) in the early stage of PP. Female pelvic ultrasonography may provide additional information to help differentiate PP from PT and subsequently initiate early treatment. In this study, we aimed to first directly compare pelvic ultrasonography parameters between PP and PT groups and secondly, investigate their diagnostic accuracy compared with the GnRH stimulation test.MethodsA systematic search of the PubMed/MEDLINE, EMBASE, Scopus, and Cochrane Library databases was performed up to March 31, 2021. All types of studies, except for case reports and review articles, were included. The GnRH stimulation test was used to confirm PP diagnosis. Those whose organic conditions might cause PP were excluded. The mean, standard deviation, sensitivity, and specificity of each parameter were documented. Forest plots were constructed to display the estimated standardized mean differences (SMDs) from each included study and the overall calculations. A bivariate model was used to calculate the pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR).ResultsA total of 13 studies were included for analysis. The SMDs (95% confidence interval - CI) in ovarian volume, fundal-cervical ratio, uterine length, uterine cross-sectional area, and uterine volume between PP and PT groups were 1.12 (0.78-1.45; p < 0.01), 0.90 (0.07-1.73; p = 0.03), 1.38 (0.99-1.78; p < 0.01), 1.06 (0.61-1.50; p < 0.01), and 1.21 (0.84-1.58; p <0.01), respectively. A uterine length of 3.20 cm yielded a pooled sensitivity of 81.8% (95% CI 78.3%-84.9%), specificity of 82.0% (95% CI 61.0%-93.0%), PLR of 4.56 (95% CI 2.15-9.69), NLR of 0.26 (95% CI 0.17-0.39), and DOR of 19.62 (95% CI 6.45-59.68). The area under the summary receiver operating characteristics curve was 0.82.ConclusionFemale pelvic ultrasonography may serve as a complementary tool to the GnRH stimulation test in differentiating PP from PT.Systematic review registrationhttps://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021232427, ID: CRD42021232427.

Dataset Information

Early life manganese exposure upregulates tumor-associated genes in the hypothalamus of female rats: relationship to manganese-induced precocious puberty.

Publications

Early life manganese exposure upregulates tumor-associated genes in the hypothalamus of female rats: relationship to manganese-induced precocious puberty.

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