Developmental sex differences in the peri-pubertal pattern of hypothalamic reproductive gene expression, including Kiss1 and Tac2, may contribute to sex differences in puberty onset

Early-Life Risks of Central Precocious Puberty

OBJECTIVES

To investigate the factors in early life that may contribute to central precocious puberty (CPP).

METHODS

The study utilized data from the Taiwan Puberty Longitudinal Study, including 2241 children under pubertal assessment and a questionnaire of risk factors. We analyzed associations using the Fitting Generalized Linear Models in R (R Core Team, 2023), with R studio (Posit, 2023) version 4.3.1.

RESULTS

Among the 2241 children examined, 745 had CPP. Overall, higher gestational weight gain (GWG) increased the risk of CPP (odds ratio [OR]: 1.03, 95% CI: 1.01-1.05); while higher GWG served as a protective factor in females (OR: 0.97, 95% CI: 0.95-0.99). Maternal gestational diabetes mellitus (GDM) also increased the CPP risk, particularly in males (OR: 2.66, 95% CI: 1.00-7.25). Longer exclusive breastfeeding was linked to lower CPP risk overall (OR: 0.96, 95% CI: 0.93-1.00) but was not significant when analyzed by gender.

CONCLUSIONS

Higher maternal GWG was associated with an increased risk of CPP overall, while GWG became negatively associated with CPP, only in females. Maternal GDM was linked to a higher risk of CPP, particularly in males. The duration of exclusive breastfeeding was inversely correlated with CPP risk, but this effect was not significant when analyzed by gender.

Neuroendocrine and Developmental Impacts of Early Life Exposure to EDCs

Polychlorinated biphenyls (PCBs) pose a global challenge to environmental and human health. Although toxic and carcinogenic at higher exposure levels, at lower concentrations they can act as endocrine-disrupting chemicals. Individuals are more vulnerable to endocrine-disrupting effects of PCB exposures during the perinatal period, when the neuroendocrine system is developing, although assessing the full impact of PCB exposure is difficult because of the often-latent onset of adverse effects. The goal of this study was to determine developmental effects of an estrogenic PCB mixture, Aroclor 1221 (A1221), on KNDy and kisspeptin neuron numbers in the hypothalamic arcuate nucleus and anteroventral periventricular nucleus (AVPV), together with measures of hypothalamic-pituitary-gonadal hormones and postnatal development. We conducted RNAscope of kisspeptin, prodynorphin, neurokinin B, and estrogen receptor alpha genes in the P30 hypothalamus. Early-life PCBs caused small but significant changes in development (body weight and anogenital index) but had no effect on puberty. We found sex-specific effects of treatment on serum LH, FSH, and estradiol in a sex- and developmental age-dependent manner. RNAscope results revealed increased prodynorphin in the AVPV of male rats, but no effects on kisspeptin or neurokinin B in AVPV or arcuate nucleus. An unexpected species difference was found: we were unable to detect prodynorphin coexpression with kisspeptin within KNDy neurons in rats, unlike mice, sheep, and primates. These data show that early-life PCBs can induce developmental and hormonal changes that together with other reports showing latent effects on behavior and the hypothalamic-pituitary-gonadal axis, indicate adverse endocrine and neurobehavioral outcomes.

Selective depletion of kisspeptin neurons in the hypothalamic arcuate nucleus in early juvenile life reduces pubertal LH secretion and delays puberty onset in mice

Puberty is the critical developmental transition to reproductive capability driven by the activation of gonadotropin-releasing hormone (GnRH) neurons. The complex neural mechanisms underlying pubertal activation of GnRH secretion still remain unknown, yet likely include kisspeptin neurons. However, kisspeptin neurons reside in several hypothalamic areas and the specific kisspeptin population timing pubertal onset remains undetermined. To investigate this, we strategically capitalized on the differential ontological expression of the Kiss1 gene in different hypothalamic nuclei to selectively ablate just arcuate kisspeptin neurons (aka KNDy neurons) during the early juvenile period, well before puberty, while sparing RP3V kisspeptin neurons. Both male and female transgenic mice with a majority of their KNDy neurons ablated (KNDyABL) by diphtheria toxin treatment in juvenile life demonstrated significantly delayed puberty onset and lower peripubertal LH secretion than controls. In adulthood, KNDyABL mice demonstrated normal in vivo LH pulse frequency with lower basal and peak LH levels, suggesting that only a small subset of KNDy neurons is sufficient for normal GnRH pulse timing but more KNDy cells are needed to secrete normal LH concentrations. Unlike prior KNDy ablation studies in rats, there was no alteration in the occurrence or magnitude of estradiol-induced LH surges in KNDyABL female mice, indicating that a complete KNDy neuronal population is not essential for normal LH surge generation. This study teases apart the contributions of different kisspeptin neural populations to the control of puberty onset, demonstrating that a majority of KNDy neurons in the arcuate nucleus are necessary for the proper timing of puberty in both sexes.

Mechanism of Arcuate Kisspeptin Neuron Synchronization in Acute Brain Slices From Female Mice

The mechanism by which arcuate kisspeptin (ARNKISS) neurons co-expressing glutamate, neurokinin B, and dynorphin intermittently synchronize their activity to drive pulsatile hormone secretion remains unclear in females. In order to study spontaneous synchronization within the ARNKISS neuron network, acute brain slices were prepared from adult female Kiss1-GCaMP6 mice. Analysis of both spontaneous synchronizations and those driven by high frequency stimulation of individual ARNKISS neurons revealed that the network exhibits semi-random emergent excitation dependent upon glutamate signaling through AMPA receptors. No role for NMDA receptors was identified. In contrast to male mice, ongoing tachykinin receptor tone within the slice operated to promote spontaneous synchronizations in females. As previously observed in males, we found that ongoing dynorphin transmission in the slice did not contribute to synchronization events. These observations indicate that a very similar AMPA receptor-dependent mechanism underlies ARNKISS neuron synchronizations in the female mouse supporting the "glutamate two-transition" model for kisspeptin neuron synchronization. However, a potentially important sex difference appears to exist with a more prominent facilitatory role for tachykinin transmission in the female.

Sleep duration, sleep quality, and weapon carrying in a sample of adolescents from Texas

Objectives

Studies are beginning to document an association between sleep duration and a range of adolescent delinquent behaviors, including weapon carrying. However, little is known about whether and to what extent sleep quality - another dimension of sleep for healthy adolescent functioning - is associated with weapon carrying. We address this gap in knowledge by evaluating the role of restless sleep and sleep duration in adolescent weapon carrying.

Methods

We analyze data from a diverse sample of 994 adolescents from Texas, USA collected in 2010. Multivariate logistic regression models estimate the association of sleep duration and restless sleep on weapon carrying after controlling for theoretical covariates and demographic characteristics.

Results

Adolescents sleeping 4 h or less on school nights were more than twice as likely to report carrying a weapon (OR = 2.38, 95% CI = 1.16-4.89, p =.018). Sleeping 5-6 h was associated with higher odds of carrying a weapon, while 6-7 h and 8 or more hours were associated with lower odds; however, all associations were non-significant. Restless sleep was associated with weapon carrying at the bivariate level (Pearson χ2 (3) = 10.56, p =.014), but not at the multivariate (OR = 1.10, 95% CI = 0.91-1.32, p =.299).

Conclusions

Our findings align with previous research demonstrating that sleeping 4 or less hours increases the likelihood of adolescent weapon carrying. Restless sleep appears to play less of a role. Future research should elucidate the longitudinal pathways between sleep duration, sleep quality, and forms of adolescent weapon carrying.

Associations of Obesity With Growth and Puberty in Children: A Cross-Sectional Study in Fuzhou, China

Objectives: To investigate the associations of obesity with growth and puberty in children. Methods: From November 2017 to December 2019, height, weight, and Tanner stages of 26,879 children aged 3-18 years in Fuzhou, China were assessed. Results: The obese group was significantly taller than the non-obese group after age 4 years for both genders, yet there was no significant difference in height between obese and non-obese group after 15.5 years old for boys and 12.5 years old for girls. The inflection points of significant growth deceleration in obese and non-obese groups were 14.4 and 14.6 years old for boys, and 11.8 and 12.8 years old for girls, respectively. The proportions of testicular development in boys with obesity and non-obesity were 7.96% and 5.08% at 8.5-8.9 years old, respectively, while the proportions of breast development in girls were 17.19% and 3.22% at age 7.5-7.9 years old, respectively. Conclusion: Children with obesity were taller in early childhood, earlier onset of puberty and earlier cessation of growth than children with non-obesity of the same age. However, there was sex dimorphism on the effect of obesity on the incidence of precocious puberty.

Conditional Deletion of KOR (Oprk1) in Kisspeptin Cells Does Not Alter LH Pulses, Puberty, or Fertility in Mice

Classic pharmacological studies suggested that endogenous dynorphin-KOR signaling is important for reproductive neuroendocrine regulation. With the seminal discovery of an interconnected network of hypothalamic arcuate neurons co-expressing kisspeptin, neurokinin B, and dynorphin (KNDy neurons), the KNDy hypothesis was developed to explain how gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) pulses are generated. Key to this hypothesis is dynorphin released from KNDy neurons acting in a paracrine manner on other KNDy neurons via kappa opioid receptor (KOR) signaling to terminate neural "pulse" events. While in vitro evidence supports this aspect of the KNDy hypothesis, a direct in vivo test of the necessity of KOR signaling in kisspeptin neurons for proper LH secretion has been lacking. We therefore conditionally knocked out KOR selectively from kisspeptin neurons of male and female mice and tested numerous reproductive measures, including in vivo LH pulse secretion. Surprisingly, despite validating successful knockout of KOR in kisspeptin neurons, we found no significant effect of kisspeptin cell-specific deletion of KOR on any measure of puberty, LH pulse parameters, LH surges, follicle-stimulating hormone (FSH) levels, estrous cycles, or fertility. These outcomes suggest that the KNDy hypothesis, while sufficient normally, may not be the only neural mechanism for sculpting GnRH and LH pulses, supported by recent findings in humans and mice. Thus, besides normally acting via KOR in KNDy neurons, endogenous dynorphin and other opioids may, under some conditions, regulate LH and FSH secretion via KOR in non-kisspeptin cells or perhaps via non-KOR pathways. The current models for GnRH and LH pulse generation should be expanded to consider such alternate mechanisms.