Exogenous Melatonin Regulates Puberty and the Hypothalamic GnRH-GnIH System in Female Mice

Association of screen exposure/sedentary behavior and precocious puberty/early puberty

Background

In recent years, with the development of society, children's daily exposure to screen time has gradually increased. Screen exposure and sedentary behavior have brought a host of harms to children's lives. The aim of this study was to explore the effects of screen exposure and sedentary behavior on precocious puberty and early development.

Methods

This is a cross-sectional study in the school-based population. A total of 3,560 children were recruited from Qufu City, Shandong province using multistage stratified cluster random sampling. All study subjects had a physical examination by professional pediatricians in October 2019, and were investigated with health questionnaires. Precocious puberty is defined as development of secondary sexual signs in boys before 9 years or in girls before 8 years. Screen time was calculated as the average of screen time on weekdays and weekend days, and sedentary time was calculated as the average of sedentary time on weekdays and weekend days. After adjusting for potential confounders, logistic regression was used to examine the association between screen exposure and sedentary behavior and early puberty and precocious puberty.

Results

Sedentary time was a risk factor for precocious puberty and early development (OR = 1.428, 95% CI = 1.087-1.876) in girls without adjustment. No significant association was found between screen exposure and early puberty and early development both in girls and boys.

Conclusions

Excessive sedentary behavior was associated with an increased risk of early puberty, especially in girls, while there was no significant association between screen exposure and early puberty and early development. In addition, further longitudinal investigations are needed to determine the causal relationship between screen exposure, sedentary behavior and precocious puberty.

Overlapping action of melatonin and female reproductive hormones-Understand the impact in pregnancy and menopause

Melatonin is an indolamine secreted to circulation by the pineal gland according to a circadian rhythm. Melatonin levels are higher during nighttime, and the principal function of this hormone is to organize the temporal night and day distribution of physiological adaptive processes. Besides hormonal pineal production, melatonin is synthesized in various organs and tissues like the ovaries or the placenta for local utilization. In addition to its function as a circadian messenger, melatonin is also associated with many physiological functions. For example, melatonin has antioxidant properties and is involved in the regulation of energy and bone metabolism, and reproduction. Melatonin impacts several stages of reproduction and the action across the hypothalamus-pituitary-gonadal axis is well described. However, it is not well understood how those actions impact the female reproductive hormones secretion nor the consequent physiological outcomes. Thus, the first part of this chapter describes the regulation of female reproductive hormone synthesis by melatonin. Moreover, melatonin and female reproductive hormones have coincident physiological functions. Life stages like pregnancy or menopause are characterized by alterations in the reproductive hormones secretion that may be associated with certain physiological stages. Therefore, the second part discusses whether melatonin fluctuations could have an overlapping role with reproductive hormones in contributing to clinical outcomes associated with pregnancy and menopause.

Therapeutic effects of melatonin in female mice with central precocious puberty by regulating the hypothalamic Kiss-1/Kiss1R system

In recent years, central precocious puberty (CPP) in children is becoming more common, which seriously affects their physical and psychological health and requires finding a safe and effective treatment method. The aim of this study was to investigate the therapeutic effect of melatonin on CPP. A CPP model was established by subcutaneous injection of 300 micrograms of danazol into 5-day-old female mice, followed by treatment with melatonin and leuprolide. The vaginal opening was checked daily. Mice were weighed, gonads were weighed, gonadal index was calculated, and gonadal development was observed by hematoxylin and eosin (HE) staining. Serum follicle stimulating hormone (FSH), luteinizing hormone (LH) and estradiol (E2) levels were measured by ELISA. By using RT-PCR and Western blotting, the mRNA and protein expression of the hypothalamus Kiss-1, Kiss-1 receptor (Kiss1R), gonadotropin-releasing hormone (GnRH), and pituitary GnRH receptor (GnRHR) were identified. The results showed that melatonin delayed vaginal opening time and reduced body weight, gonadal weight and indices in female CPP mice. Melatonin treatment prevents uterine wall thickening and ovarian luteinization in female CPP mice. Melatonin treatment reduces serum concentrations of FSH, LH, and E2 in female CPP mice. Melatonin suppressed the expressions of Kiss-1, Kiss1R and GnRH in the hypothalamus, and the expression of GnRHR in the pituitary of the female CPP mice. Our results suggest that melatonin can inhibit the hypothalamic-pituitary-gonadal (HPG) axis by down-regulating the Kiss-1/Kiss1R system, thereby treating CPP in female mice.

Pineal cysts may promote pubertal development in girls with central precocious puberty: a single-center study from China

Introduction

Pineal cysts have long been considered a benign intracranial variation. However, in our clinical practice, it has been observed that some children with central precocious puberty (CPP) who have pineal cysts experience rapid progression in adolescent development. In recent years, there has been a significant increase in the prevalence of CPP in girls, leading to more diagnoses of CPP among children with pineal cysts. Despite this, there is no consensus regarding whether pineal cysts contribute to CPP as one of its organic factors. This study aimed to analyze the clinical characteristics of pineal cysts in children with CPP and explore the potential effects of pineal cysts on puberty development.

Methods

This single-center study retrospectively analyzed clinical data from girls aged 3 to 10 years who underwent head/pituitary magnetic resonance imaging at the Children's Hospital Affiliated to Zhengzhou University between 2019 and 2022. The study categorized the detection rates of pineal cysts based on systematic disease classification and compared the rates of cyst detection between girls diagnosed with CPP and those without CPP. Subsequently, CPP-diagnosed girls with pineal cysts were examined. Among CPP-diagnosed girls meeting the study's criteria, those with pineal cysts formed the 'cyst group,' while those without cysts were matched in a 1:1 ratio based on age and body mass index to form the 'non-cyst group.' Comparative analyses were conducted to assess the clinical characteristics between these two groups. CPP-diagnosed girls with cysts were further subdivided into three groups according to cyst size (≤5 mm, 5.1-9.9 mm, and ≥10 mm) to investigate potential differences in clinical characteristics among these subgroups. The study involved an analysis of clinical data from girls diagnosed with CPP and included imaging follow-ups to explore the progression of pineal cysts over time.

Results

Among the 23,245 girls who underwent head/pituitary magnetic resonance imaging scans, the detection rate of pineal cysts was 3.6% (837/23,245), with most cases being associated with endocrine diseases. The detection rate of pineal cysts in CPP patients was 6.4% (262/4099), which was significantly higher than the 3.0% (575/19,146) in patients without CPP. In comparison to the non-cyst group, the cyst group exhibited statistically significant increases in estradiol levels, peak luteinizing hormone (LH) levels, peak LH/follicle-stimulating hormone (FSH) ratios, uterine body length, and cervix length (P < 0.001). As cyst size increased, there were significant rises in LH peak, peak LH/FSH ratio, uterine body length, and cervical length (P < 0.01). Estradiol levels and left ovarian volume also showed an increasing trend (P < 0.05). Among girls who underwent follow-up imaging, 26.3% (5/19) exhibited an increase in cyst size.

Conclusion

Pineal cysts are relatively common in children with CPP. They may affect the pubertal development process, with larger cysts correlating to faster pubertal development. Therefore, the authors hypothesize that pineal cysts may trigger CPP in some cases, especially when the cysts are larger than 5 mm in size, as indicated by our data.

Analysis of the Imprinting Status and Expression of the MAGEL2 Gene During Initiation at Puberty in the Dolang Sheep

Genomic imprinting refers to the expression of parent-specific genes in diploid mammalian cells. MAGEL2 gene is a maternally imprinted gene that has been identified in mice and humans and is associated with the onset of puberty. The purpose of this study was to investigate its imprinting status and its relationship with the onset of puberty in Dolang sheep. The sequence of 3734 bp cDNA of MAGEL2 in Dolang sheep was obtained by cloning and sequencing, encoding 1173 amino acids. The results of the nucleotide and amino acid similarity analysis showed that it was highly conserved among different mammalian species. The MAGEL2 gene was expressed monoallelically in the tissues of adult and neonatal umbilical cords, and the expressed allele was paternally inherited. Real Time quantitative PCR (RT-qPCR) results showed that the MAGEL2 gene was highly expressed in the hypothalamus and pituitary gland, increased significantly from prepuberty to puberty, and decreased significantly after puberty. This study suggests that MAGEL2 is a paternally expressed and maternally imprinted gene in Dolang sheep, which may be involved in the initiation of puberty in Dolang sheep. This study provides a theoretical basis for further research on the mechanism of the imprinted gene MAGEL2 regulating the onset of puberty in sheep, and provides a new idea for the future research on the mechanism of onset of puberty in sheep.