Integrative proteomic and transcriptomic analysis in the female goat ovary to explore the onset of puberty

Puberty is considered a prerequisite for affecting reproductive performance and productivity. Little was known about molecular changes in pubertal goat ovaries. Therefore, we measured and performed a correlation analysis of the mRNA and proteins changes in the pre-pubertal and pubertal goat ovaries. The results showed that only six differentially expressed genes and differentially abundant proteins out of 18,139 genes and 7550 proteins quantified had significant correlations. CNTN2 and THBS1, discovered in the mRNA-mRNA interaction network, probably participated in pubertal and reproductive regulation by influencing GnRH receptor signals, follicular development, and ovulation. The predicted core transcription factors may either promote or inhibit the expression of reproductive genes and act synergistically to maintain normal reproductive function in animals. The interaction between PKM and TIMP3 with other proteins may impact animal puberty through energy metabolism and ovarian hormone secretion. Pathway enrichment analyses revealed that the co-associated key pathways between ovarian genes and proteins at puberty included calcium signalling pathway and olfactory transduction. These pathways were associated with gonadotropin-releasing hormone synthesis and secretion, signal transmission, and cell proliferation. In summary, these results enriched the potential molecules and signalling pathways that affect puberty and provided new insights for regulating and promoting the onset of puberty. SIGNIFICANCE: This study conducted the first transcriptomic and proteomic correlation analysis of pre-pubertal and pubertal goat ovaries and identified six significantly correlated molecules at both the gene and protein levels. Meanwhile, we were drawn to several molecules and signalling pathways that may play a regulatory role in the onset of puberty and reproduction by influencing reproductive-related gene expression, GnRH receptor signals, energy metabolism, ovarian hormone secretion, follicular development, and ovulation. This information contributed to identify potential biomarkers in pubertal goat ovaries, which was vital for predicting the onset of puberty and improving livestock performance.

On Ageing and Maturing

Räsänen draws a distinction between chronological age and biological age and argues that biological ageing is (sometimes) desirable. To demonstrate this, he asks us to consider the case of April, who like Karel Čapek's Elina Makropulos, has stopped biologically ageing. Unlike Makropulos, though, April's biological ageing was halted before puberty, so she will never mature into adulthood. Räsänen contends this case shows ageing can be desirable, but this equivocates between maturing and ageing. Here I argue biological ageing, or the wear and tear normally associated with chronological ageing, is prima facie undesirable, but that maturing can be prima facie desirable.

Grid1 regulates the onset of puberty in female rats

The study aimed to investigate the effect of Grid1, encoding the glutamate ionotropic receptor delta type subunit 1 (GluD1), on puberty onset in female rats. Grid1 mRNA and protein expression was detected in the hypothalamus of female rats at prepuberty and puberty. The levels of Grid1 mRNA in the hypothalamus, the fluorescence intensity in the arcuate nucleus and paraventricular nucleus of the prepubertal rats was significantly lower than pubertal. Additionally, the expression of Grid1 was suppressed in primary hypothalamus cells and prepubertal rat. Finally, investigated the effect of Grid1 knockdown on puberty onset and reproductive performance. Treatment of hypothalamic neurons with LV-Grid1 decreased the level of Grid1 and Rfrp-3 (encoding RFamide-related peptide 3) mRNA expression, but increased the Gnrh (encoding gonadotropin-releasing hormone) mRNA levels. After an ICV injection, the time for the rat vaginal opening occurred earlier. Moreover, Gnrh mRNA expression was increased, whereas Rfrp-3 mRNA expression was decreased in the hypothalamus. The concentration of progesterone (P4) in the serum was significantly decreased compare with control group. Ovary hematoxylin-eosin staining revealed that the LV-Grid1 group mainly contained primary and secondary follicles. The reproductive performance of the rats was not affected by the Grid1 knockdown. Therefore, Grid1 may affect the onset of puberty in female rats by regulating the levels of Gnrh, and Rfrp-3 in the hypothalamus, as well as the concentrations of P4, but not reproduction performance.

New liquid chromatography tandem mass spectrometry reference data for estradiol show mini-puberty in both sexes and typical pre-pubertal and pubertal patterns

CONTEXT

Reliable estradiol (E2) reference intervals (RIs) are crucial in pediatric endocrinology.

OBJECTIVES

This study aims to develop a sensitive ultra-performance liquid chromatographic tandem mass spectrometry (UPLC-MS/MS) method for E2 in serum, to establish graphically represented RI percentiles and annual RIs for both sexes, and to perform a systematic literature comparison.

METHODS

First, a UPLC-MS/MS method for E2 was developed. Second, graphically represented RI percentiles and annual RIs covering 0-18 years were computed (cohort of healthy children [1181 girls and 543 boys]). Subsequently, RIs were compared with published data by systematic searches.

RESULTS

Lower limit of quantification was 11 pmol/L, indicating high sensitivity. Estradiol first peaked during mini-puberty in both sexes (girls up to 192 pmol/L; boys up to 225 pmol/L). As could be expected, girls showed higher pubertal E2 (up to 638 pmol/L). However, boys' RIs (up to 259 pmol/L) overlapped considerably. We found 4 studies in the literature that also used LC-MS/MS to determine E2 and published RIs for the complete pediatric age range. Reference intervals varied considerably. Pre-pubertal and pubertal phases were present in all studies. Higher E2 during the time of mini-puberty in both sexes was documented in 3 studies including ours.

CONCLUSIONS

Variability of RIs for E2 between studies illustrates the importance of laboratory-specific RIs despite using a LC-MS/MS reference method. In boys, the striking E2 peak during mini-puberty as well as high pubertal E2 without phenotypic estrogenization in regular male puberty indicates that the role of E2 in children and, especially in boys, requires better functional understanding.

Pubertal Timing Across Asian American, Native Hawaiian, and Pacific Islander Subgroups

Importance

Earlier puberty is associated with adverse health outcomes, such as mental health issues in adolescence and cardiometabolic diseases in adulthood. Despite rapid growth of the Asian American, Native Hawaiian, and Pacific Islander populations in the US, limited research exists on their pubertal timing, potentially masking health disparities.

Objective

To examine pubertal timing among Asian American, Native Hawaiian, and Pacific Islander children and adolescents by disaggregating ethnic subgroups.

Design, Setting, and Participants

This retrospective cohort study included Asian American, Native Hawaiian, and Pacific Islander youths aged 5 to 18 years assessed for pubertal development at Kaiser Permanente Northern California, a large, integrated health care delivery system. Follow-up occurred from March 2005, through December 31, 2019. Data were analyzed in October 2023.

Exposure

Race and ethnicity, categorized into 11 ethnic subgroups: Asian Indian, Chinese, Filipino, Japanese, Korean, Native Hawaiian and Pacific Islander, Other South Asian, Other Southeast Asian, Vietnamese, multiethnic, and multiracial.

Main Outcomes and Measures

Pubertal timing was determined using physician-assessed sexual maturity ratings (SMRs). Outcomes included the median age at transition from SMR 1 (prepubertal) to SMR 2 or higher (pubertal) for onset of genital development (gonadarche) in boys, breast development (thelarche) in girls, and pubic hair development (pubarche) in both boys and girls.

Results

In this cohort of 107 325 Asian American, Native Hawaiian, and Pacific Islander children and adolescents (54.61% boys; 12.96% Asian Indian, 22.24% Chinese, 26.46% Filipino, 1.80% Japanese, 1.66% Korean, 1.96% Native Hawaiian and Pacific Islander, 0.86% Other South Asian, 3.26% Other Southeast Asian, 5.99% Vietnamese, 0.74% multiethnic, and 22.05% multiracial), the overall median ages for girls' pubarche and thelarche were 10.98 years (95% CI, 10.96-11.01 years) and 10.13 years (95% CI, 10.11-10.15 years), respectively. For boys' pubarche and gonadarche, median ages were 12.08 years (95% CI, 12.06-12.10 years) and 11.54 years (95% CI, 11.52-11.56 years), respectively. Differences between subgroups with earliest and latest median age at onset were 14 months for girls' pubarche, 8 months for thelarche, 8 months for boys' pubarche, and 4 months for gonadarche. In general, Asian Indian, Native Hawaiian and Pacific Islander, and Other South Asian subgroups had the earliest ages at onset across pubertal markers, while East Asian youths exhibited the latest onset. Restricting to those with healthy body mass index did not substantially change the findings.

Conclusions and Relevance

In this cohort study of Asian American, Native Hawaiian, and Pacific Islander children and adolescents, pubertal timing varied considerably across ethnic subgroups. Further investigation is warranted to assess whether these differences contribute to observed health disparities in adulthood, such as type 2 diabetes and cardiovascular diseases.

Influence of sex and sedentary conditions on sympathetic burst characteristics in prepubertal, postpubertal, and young adult rats

Recent evidence indicates that sex-based differences in cardiovascular disease (CVD) begin early in life, particularly when associated with risk factors such as a sedentary lifestyle. CVD is associated with elevated sympathetic nerve activity (SNA), quantified as increased SNA burst activity in humans. Whether burst characteristics are influenced by sex or sedentary conditions at younger ages is unknown. The purpose of our study is to compare SNA bursts in active and sedentary female and male rats at ages including prepuberty and young adulthood. We hypothesized that burst characteristics and blood pressure are higher under sedentary conditions and lower in female rats compared with males. We analyzed splanchnic SNA (SpSNA) recordings from Inactin-anesthetized male and female rats at 4-, 8-, and 16-wk of age. Physically active and sedentary rats were each housed in separate, environmentally controlled chambers where physically active rats had free access to an in-cage running wheel. Sympathetic bursts were obtained by rectifying and integrating the raw SpSNA signal. Burst frequency, burst height, and burst width were calculated using the Peak Parameters extension in LabChart. Our results showed that sedentary conditions produced a greater burst width in 8- and 16-wk-old rats compared with 4-wk-old rats in both males and females (P < 0.001 for both). Burst frequency and incidence were both higher in 16-wk-old males compared with 16-wk-old females (P < 0.001 for both). Our results suggest that there are sedentary lifestyle- and sex-related mechanisms that impact sympathetic regulation of blood pressure at ages that range from prepuberty into young adulthood.NEW & NOTEWORTHY The mechanisms of decreased incidence of cardiovascular disease (CVD) in reproductive-age women compared with age-matched men are unknown. The strong association between elevated sympathetic activity and CVD led us to characterize splanchnic sympathetic bursts in female and male rats. Prepubescent males and females exhibited narrower sympathetic bursts, whereas young adult males had higher resting burst frequency compared with age-matched females. Sex-based regulation of sympathetic activity suggests a need for sex-dependent therapeutic strategies to combat CVD.

Decoding the effect of photoperiodic cues in transducing kisspeptin-melatonin circuit during the pubertal onset in common carp

This study unravels the intricate interplay between photoperiod, melatonin, and kisspeptin to orchestrate the pubertal onset of Common carp. Female fingerlings exposed to long days (LD) exhibited a hormonal crescendo, with upregulated hypothalamic-pituitary-ovarian (HPO) axis genes (kiss1, kiss1r, kiss2, gnrh2, gnrh3) and their downstream targets (lhr, fshr, ar1, esr1). However, the expression of the melatonin receptor (mtnr1a) diminished in LD, suggesting a potential inhibitory role. This hormonal symphony was further amplified by increased activity of key transcriptional regulators (gata1, gata2, cdx1, sp1, n-myc, hoxc8, plc, tac3, tacr3) and decreased expression of delayed puberty genes (mkrn1, dlk1). In contrast, short days (SD) muted this hormonal chorus, with decreased gnrh gene and regulator expression, elevated mtnr1a, and suppressed gonadal development. In in-vitro, estradiol mimicked the LD effect, boosting gnrh and regulator genes while dampening mtnr1a and melatonin-responsive genes. Conversely, melatonin acted as a conductor, downregulating gnrh and regulator genes and amplifying mtnr1a. Our findings illuminate the crucial roles of melatonin and kisspeptin as opposing forces in regulating pubertal timing. LD-induced melatonin suppression allows the kisspeptin symphony to flourish, triggering GnRH release and, ultimately, gonadal maturation. This delicate dance between photoperiod, melatonin, and kisspeptin orchestrates common carp's transition from juvenile to reproductive life.

Reduction in size-at-maturity in unprecedentedly strong cohorts of redfish (Sebastes mentella and S. fasciatus) in the Gulf of St. Lawrence and Laurentian Channel

Life-history traits, such as size-at-maturity, are key parameters to model population dynamics used to inform fisheries management. Fishery-induced evolution, density-dependent effects, and global warming have been shown to affect size- and age-at-maturity, and resulting spawning stock biomass (SSB) in a wide range of commercial fish stocks. Marked changes in redfish biomass and environmental conditions in the Gulf of St. Lawrence and Laurentian Channel over the past decade called for a review and update of size-at-maturity for commercially important deepwater redfish Sebastes mentella and Acadian redfish Sebastes fasciatus stocks. Following a 25-year moratorium, local redfish biomass has recently reached unprecedented levels, co-occurring with an overall warming of bottom water temperatures. Our objectives were (1) to perform a histological assessment of redfish reproduction stages, including the validation and fine-tuning of a robust visual chart to facilitate monitoring of size-at-maturity and SSB in a transforming environment, and (2) to evaluate changes in size-at-maturity in unprecedentedly strong cohorts of redfish, and consequences for stock status assessment and fisheries management. Each specimen was genetically identified to species, and gonad reproduction stages were determined by histology and macroscopic appearances. The present study enabled a robust visual chart for continued and cost-effective monitoring of redfish reproduction stages to be refined and validated, and has shown a large decrease in redfish length when 50% of the individuals are considered mature that led to an increase in estimates of SSB during the 2011-2021 period for S. mentella and S. fasciatus. These changes modified the perception of stock status, thus having significant implications for fisheries management. Given that fishery-induced evolution and community structure changes along with global warming are affecting numerous stocks worldwide, the present study outlines a major and global challenge for scientists and resources managers. As shown by our results, the monitoring and frequent updates of life-history traits in transforming environments are needed to provide reliable science advice for sustainable fisheries.

Early life adversity accelerates hypothalamic drive of pubertal timing in female rats with associated enhanced acoustic startle

Early life adversity in the form of childhood maltreatment in humans or as modeled by maternal separation (MS) in rodents is often associated with an earlier emergence of puberty in females. Earlier pubertal initiation is an example of accelerated biological aging and predicts later risk for anxiety in women, especially in populations exposed to early life trauma. Here we investigated external pubertal markers as well as hypothalamic gene expression of pubertal regulators kisspeptin and gonadotropin-releasing hormone, to determine a biological substrate for MS-induced accelerated puberty. We further investigated a mechanism by which developmental stress might regulate pubertal timing. As kisspeptin and gonadotropin-releasing hormone secretion are typically inhibited by corticotropin releasing hormone at its receptor CRH-R1, we hypothesized that MS induces a downregulation of Crhr1 gene transcription in a cell-specific manner. Finally, we explored the association between pubertal timing and anxiety-like behavior in an acoustic startle paradigm, to drive future preclinical research linking accelerated puberty and anxiety. We replicated previous findings that MS leads to earlier puberty in females but not males, and found expression of kisspeptin and gonadotropin-releasing hormone mRNA to be prematurely increased in MS females. RNAscope confirmed increased expression of these genes, and further revealed that kisspeptin-expressing neurons in females were less likely to express Crhr1 after MS. Early puberty was associated with higher acoustic startle magnitude in females. Taken together, these findings indicate precocial maturation of central pubertal timing mechanisms after MS, as well as a potential role of CRH-R1 in these effects and an association with a translational measure of anxiety.

Aspartame Intake Delayed Puberty Onset in Female Offspring Rats and Girls

SCOPE

The disturbance of the hypothalamic-pituitary-gonadal (HPG) axis, gut microbiota (GM) community, and short-chain fatty acids (SCFAs) is a triggering factor for pubertal onset. The study investigates the effects of the long-term intake of aspartame on puberty and GM in animals and humans.

METHODS AND RESULTS

Aspartame-fed female offspring rats result in vaginal opening time prolongation, serum estrogen reduction, and serum luteinizing hormone elevation. , 60 mg kg-1 aspartame treatment decreases the mRNA levels of gonadotropin-releasing hormone (GnRH), Kiss1, and G protein-coupled receptor 54 (GPR54), increases the mRNA level of RFamide-related peptide-3 (RFRP-3), and decreases the expression of GnRH neurons in the hypothalamus. Significant differences in relative bacterial abundance at the genus levels and decreased fecal SCFA levels are noted by 60 mg kg-1 aspartame treatment. Among which, Escherichia-Shigella is negatively correlated with several SCFAs. In girls, high-dose aspartame consumption decreases the risk of precocious puberty.

CONCLUSIONS

Aspartame reduces the chance of puberty occurring earlier than usual in female offspring and girls. Particularly, 60 mg kg-1 aspartame-fed female offspring delays pubertal onset through the dysregulation of HPG axis and GM composition by inhibiting the Kiss1/GPR54 system and inducing the RFRP-3. An acceptable dose of aspartame should be recommended during childhood.

Metabolic control of puberty: 60 years in the footsteps of Kennedy and Mitra's seminal work

An individual's nutritional status has a powerful effect on sexual maturation. Puberty onset is delayed in response to chronic energy insufficiency and is advanced under energy abundance. The consequences of altered pubertal timing for human health are profound. Late puberty increases the chances of cardiometabolic, musculoskeletal and neurocognitive disorders, whereas early puberty is associated with increased risks of adult obesity, type 2 diabetes mellitus, cardiovascular diseases and various cancers, such as breast, endometrial and prostate cancer. Kennedy and Mitra's trailblazing studies, published in 1963 and using experimental models, were the first to demonstrate that nutrition is a key factor in puberty onset. Building on this work, the field has advanced substantially in the past decade, which is largely due to the impressive development of molecular tools for experimentation and population genetics. In this Review, we discuss the latest advances in basic and translational sciences underlying the nutritional and metabolic control of pubertal development, with a focus on perspectives and future directions.

"Puberty age gap": new method of assessing pubertal timing and its association with mental health problems

Puberty is linked to mental health problems during adolescence, and in particular, the timing of puberty is thought to be an important risk factor. This study developed a new measure of pubertal timing that was built upon multiple pubertal features and their nonlinear changes over time (i.e., with age), and investigated its association with mental health problems. Using the Adolescent Brain Cognitive Development (ABCD) cohort (N ~ 9900, aged 9-13 years), we employed three different models to assess pubertal timing. These models aimed to predict chronological age based on: (i) observed physical development, (ii) hormone levels (testosterone and dehydroepiandrosterone [DHEA]), and (iii) a combination of both physical development and hormones. To achieve this, we utilized a supervised machine learning approach, which allowed us to train the models using the available data and make age predictions based on the input pubertal features. The accuracy of these three models was evaluated, and their associations with mental health problems were examined. The new pubertal timing model performed better at capturing age variance compared to the more commonly used linear regression method. Further, the model based on physical features accounted for the most variance in mental health, such that earlier pubertal timing was associated with higher symptoms. This study demonstrates the utility of our new model of pubertal timing and suggests that, relative to hormonal measures, physical measures of pubertal maturation have a stronger association with mental health problems in early adolescence.

Postweaning Social Isolation Alters Puberty Onset by Suppressing Electrical Activity of Arcuate Kisspeptin Neurons

INTRODUCTION

Postweaning social isolation (PWSI) in rodents is an advanced psychosocial stress model in early life. Some psychosocial stress, such as restrain and isolation, disrupts reproductive physiology in young and adult periods. Mechanisms of early-life stress effects on central regulation of reproduction need to be elucidated. We have investigated the effects of PWSI on function of arcuate kisspeptin (ARCKISS1) neurons by using electrophysiological techniques combining with monitoring of puberty onset and estrous cycle in male and female Kiss1-Cre mice.

METHODS

Female mice were monitored for puberty onset with vaginal opening examination during social isolation. After isolation, the estrous cycle of female mice was monitored with vaginal cytology. Anxiety-like behavior of mice was determined by an elevated plus maze test. Effects of PWSI on electrophysiology of ARCKISS1 neurons were investigated by the patch clamp method after intracranial injection of AAV-GFP virus into arcuate nucleus of Kiss1-Cre mice after the isolation period.

RESULTS

We found that both male and female isolated mice showed anxiety-like behavior. PWSI caused delay in vaginal opening and extension in estrous cycle length. Spontaneous-firing rates of ARCKISS1 neurons were significantly lower in the isolated male and female mice. The peak amplitude of inhibitory postsynaptic currents to ARCKISS1 neurons was higher in the isolated mice, while frequency of excitatory postsynaptic currents was higher in group-housed mice.

CONCLUSION

These findings demonstrate that PWSI alters pre- and postpubertal reproductive physiology through metabolic and electrophysiological pathways.

Maternal cafeteria diet influences kisspeptin (Kiss1), kisspeptin receptor(Gpr54), and sirtuin (Sirt1) genes, hormonal and metabolic profiles, and reproductive functions in rat offspring in a sex-specific manner†

Kisspeptin (KP, encoded by Kiss1, binding to the Gpr54 receptor) is a neuropeptide conveying information on the metabolic status to the hypothalamic-pituitary-gonadal axis. KP acts together with dynorphin A (encoded by Pdyn) and neurokinin B (encoded by Tac2) to regulate reproduction. KP is crucial for the onset of puberty and is under the control of sirtuin (encoded by Sirt1). We hypothesize that the maternal cafeteria (CAF) diet has adverse effects on the offspring's hormonal, metabolic, and reproductive functions due to sex-specific alterations in the expression of Kiss1, Gpr54, Pdyn, Tac2, and Sirt1 in the hypothalamus, and Kiss1, Gpr54, and Sirt1 in the liver. Rats were fed a CAF diet before pregnancy, during pregnancy, and during lactation. The vaginal opening was monitored. Offspring were sacrificed in three age points: PND 30, PND 35, and PND 60 (females) and PND 40, PND 45, and PND 60 (males). Their metabolic and hormonal status was assessed. mRNA for Kiss1, Gpr54, Pdyn, Tac2, and Sirt1 were measured by real-time PCR in the hypothalamus and/or livers. We found that CAF offspring had lower weight and altered body composition; increased cholesterol and triglyceride levels, sex-specific changes in glucose and insulin levels; sex-dependent changes in Sirt1/Kiss1 mRNA ratio in the hypothalamus; sex-specific alterations in Kiss1 and Sirt1 mRNA in the liver with more diversity in males; and a delayed puberty onset in females. We concluded that the mother's CAF diet leads to sex-specific alterations in metabolic and reproductive outcomes via Kiss1/Gpr54 and Sirt1 systems in offspring.

Integrative proteomic and phosphoproteomic analysis in the female goat hypothalamus to study the onset of puberty

BACKGROUND

Puberty marks the end of childhood and achieve sexual maturation and fertility. The role of hypothalamic proteins in regulating puberty onset is unclear. We performed a comprehensive differential proteomics and phosphoproteomics analysis in prepubertal and pubertal goats to determine the roles of hypothalamic proteins and phosphoproteins during the onset of puberty.

RESULTS

We used peptide and posttranslational modifications peptide quantification and statistical analyses, and identified 69 differentially expressed proteins from 5,057 proteins and 576 differentially expressed phosphopeptides from 1574 phosphorylated proteins. Combined proteomic and phosphoproteomics, 759 correlated proteins were identified, of which 5 were differentially expressed only at the protein level, and 201 were only differentially expressed at the phosphoprotein level. Pathway enrichment analyses revealed that the majority of correlated proteins were associated with glycolysis/gluconeogenesis, Fc gamma R-mediated phagocytosis, focal adhesion, GABAergic synapse, and Rap1 signaling pathway. These pathways are related to cell proliferation, neurocyte migration, and promoting the release of gonadotropin-releasing hormone in the hypothalamus. CTNNB1 occupied important locations in the protein-protein interaction network and is involved in focal adhesion.

CONCLUSION

The results demonstrate that the proteins differentially expression only at the protein level or only differentially expressed at the phosphoprotein level and their related signalling pathways are crucial in regulating puberty in goats. These differentially expressed proteins and phosphorylated proteins may constitute the proteomic backgrounds between the two different stages.

Pubertal exposure to dietary advanced glycation end products disrupts ductal morphogenesis and induces atypical hyperplasia in the mammary gland

BACKGROUND

Advanced glycation end products (AGEs) are reactive metabolites intrinsically linked with modern dietary patterns. Processed foods, and those high in sugar, protein and fat, often contain high levels of AGEs. Increased AGE levels are associated with increased breast cancer risk, however their significance has been largely overlooked due to a lack of direct cause-and-effect relationship.

METHODS

To address this knowledge gap, FVB/n mice were fed regular, low AGE, and high AGE diets from 3 weeks of age and mammary glands harvested during puberty (7 weeks) or adulthood (12 weeks and 7 months) to determine the effects upon mammary gland development. At endpoint mammary glands were harvested and assessed histologically (n ≥ 4). Immunohistochemistry and immunofluorescence were used to assess cellular proliferation and stromal fibroblast and macrophage recruitment. The Kruskal-Wallis test were used to compare continuous outcomes among groups. Mammary epithelial cell migration and invasion in response to AGE-mediated fibroblast activation was determined in two-compartment co-culture models. In vitro experiments were performed in triplicate. The nonparametric Wilcoxon rank sum test was used to compare differences between groups.

RESULTS

Histological analysis revealed the high AGE diet delayed ductal elongation, increased primary branching, as well as increased terminal end bud number and size. The high AGE diet also led to increased recruitment and proliferation of stromal cells to abnormal structures that persisted into adulthood. Atypical hyperplasia was observed in the high AGE fed mice. Ex vivo fibroblasts from mice fed dietary-AGEs retain an activated phenotype and promoted epithelial migration and invasion of non-transformed immortalized and tumor-derived mammary epithelial cells. Mechanistically, we found that the receptor for AGE (RAGE) is required for AGE-mediated increases in epithelial cell migration and invasion.

CONCLUSIONS

We observed a disruption in mammary gland development when mice were fed a diet high in AGEs. Further, both epithelial and stromal cell populations were impacted by the high AGE diet in the mammary gland. Educational, interventional, and pharmacological strategies to reduce AGEs associated with diet may be viewed as novel disease preventive and/or therapeutic initiatives during puberty.

Animal- and herd-level factors associated with onset of puberty in grazing dairy heifers

AIMS

To explore animal- and herd-level risk factors influencing age at puberty in predominantly Holstein-Friesian dairy heifers managed in seasonal, pasture-based systems.

METHODS

Heifers born in spring 2018 (n = 5,010) from 54 commercial dairy herds in New Zealand were visited on three occasions when the mean heifer age, within herd, was 10 (visit 1; V1), 11 (V2) and 12 (V3) months old. Blood samples were collected on each visit and liveweight, stature and anogenital distance (AGD) were measured at V2. Heifers were defined as having reached puberty at the first visit where blood progesterone was elevated (≥ 1 ng/mL). Animal-level response variables included pubertal status by V1, V2 and V3, and age at puberty (or age at V3 plus 31 days for those that had not attained puberty by V3). To explore herd-level management factors, farmers answered a questionnaire relating to animal location, land type, health, feeding, and management between weaning and mating. A partial least squares regression was undertaken to identify herd-level factors associated with the greatest influence on puberty rate within herd.

RESULTS

The mean age at puberty was 352 (SD 34.9) days. Heavier animals at a greater proportion of expected mature liveweight based on their breeding value for liveweight, or animals with a higher breed proportion of Jersey and lower breed proportion of Holstein, were associated with earlier puberty. Herd puberty rates varied widely among enrolled herds, and averaged 20%, 39% and 56% by V1, V2 and V3, respectively. Liveweight, followed by breed and land type, had the greatest influence on the herd puberty rate. Heifer herds with a greater mean liveweight (absolute and proportion of expected mature weight) or greater Jersey proportion had more animals that reached puberty at any visit, whereas herds located on steep land or with greater Holstein breed proportions had lower puberty rates. Management-related factors such as vaccinations, provision of feed supplements, and weighing frequency were also herd-level risk factors of puberty but had less influence.

CONCLUSIONS AND CLINICAL RELEVANCE

This study highlights the importance of having well-grown heifers for increasing the chances of earlier puberty onset and the effect of breed and youngstock management to achieve growth targets. These outcomes have important implications for the optimal management of heifers to achieve puberty before their maiden breeding and for the timing of measurements to potentially incorporate a puberty trait in genetic evaluations.

Review: Early and late determinants of puberty in ruminants and the role of nutrition

This article reviews the scientific literature on puberty with a focus on ruminants and draws inference, where appropriate, from recent findings in transgenic mouse models and human pathology. Early genetic determinants of puberty have been discovered in humans suffering from hypogonadotropic hypogonadism or central precocious puberty. Transgenic mouse models selected on the basis of the causative defective genes helped in discovering the cellular and molecular mechanisms involved. Most of the genes found are involved in the development of neuroendocrine networks during embryo development and early postnatal life. Notwithstanding that the development of neuroendocrine networks takes place early in puberty, a delay or acceleration in the development of Gonadotropin Releasing Hormone (GnRH) neurons has an impact on puberty onset inducing a delay or an advance, respectively. Among the genes discovered in humans and laboratory models, only a few of them displayed polymorphisms associated with advanced sexual maturity, but also marbling, growth traits and callipygian conformation. This could be related to the fact that rather than puberty onset, most research monitored sexual maturity. Sexual maturity occurs after puberty onset and involves factors regulating the maturation of gonads and in the expression of sexual behaviour. The association with growth and metabolic traits is not surprising since nutrition is the major environmental factor that will act on late genetic determinants of puberty onset. However, a recent hypothesis emerged suggesting that it is the postnatal activation of the GnRH neuronal network that induces the acceleration of growth and weight gain. Hence, nutritional factors need the activation of GnRH neurons first before acting on late genetic determinants. Moreover, nutritional factors can also affect the epigenetic landscape of parental gamete's genome with the consequence of specific methylation of genes involved in GnRH neuron development in the embryo. Season is another important regulator of puberty onset in seasonal small ruminants and appears to involve the same mechanisms that are involved in seasonal transition in adults. The social environment is also an underestimated factor affecting puberty onset in domestic ruminants, most research studies focused on olfactory cues, but the genetic basis has not heretofore been adequately tackled by the scientific community. Additionally, there is some evidence to suggest transgenerational effects exist, in that nutritional and social cues to which parents were exposed, could affect the epigenetic landscape of parental gametes resulting in the epigenetic regulation of early genetic determinants of puberty onset in their offspring.

The role of puberty on physical and brain development: A longitudinal study in male Rhesus Macaques

This study examined the role of male pubertal maturation on physical growth and development of neurocircuits that regulate stress, emotional and cognitive control using a translational nonhuman primate model. We collected longitudinal data from male macaques between pre- and peri-puberty, including measures of physical growth, pubertal maturation (testicular volume, blood testosterone -T- concentrations) and brain structural and resting-state functional MRI scans to examine developmental changes in amygdala (AMY), hippocampus (HIPPO), prefrontal cortex (PFC), as well as functional connectivity (FC) between those regions. Physical growth and pubertal measures increased from pre- to peri-puberty. The indexes of pubertal maturation -testicular size and T- were correlated at peri-puberty, but not at pre-puberty (23 months). Our findings also showed ICV, AMY, HIPPO and total PFC volumetric growth, but with region-specific changes in PFC. Surprisingly, FC in these neural circuits only showed developmental changes from pre- to peri-puberty for HIPPO-orbitofrontal FC. Finally, testicular size was a better predictor of brain structural maturation than T levels -suggesting gonadal hormones-independent mechanisms-, whereas T was a strong predictor of functional connectivity development. We expect that these neural circuits will show more drastic pubertal-dependent maturation, including stronger associations with pubertal measures later, during and after male puberty.

Comparing the ontogeny, neurobiology, and function of social play in hamsters and rats

Syrian hamsters show complex social play behavior and provide a valuable animal model for delineating the neurobiological mechanisms and functions of social play. In this review, we compare social play behavior of hamsters and rats and underlying neurobiological mechanisms. Juvenile rats play by competing for opportunities to pin one another and attack their partner's neck. A broad set of cortical, limbic, and striatal regions regulate the display of social play in rats. In hamsters, social play is characterized by attacks to the head in early puberty, which gradually transitions to the flanks in late puberty. The transition from juvenile social play to adult hamster aggression corresponds with engagement of neural ensembles controlling aggression. Play deprivation in rats and hamsters alters dendritic morphology in mPFC neurons and impairs flexible, context-dependent behavior in adulthood, which suggests these animals may have converged on a similar function for social play. Overall, dissecting the neurobiology of social play in hamsters and rats can provide a valuable comparative approach for evaluating the function of social play.

Central Irisin Signaling Is Required for Normal Timing of Puberty in Female Mice

Timing of puberty requires exquisite coordination of genes, hormones, and brain circuitry. An increasing level of body adiposity, signaled to the brain via the fat-derived hormone leptin, is recognized as a major factor controlling puberty onset. However, it is clear that leptin is not the only metabolic cue regulating puberty, and that developmental regulation of this process also involves tissues other than adipose, with muscle development potentially playing a role in the timing of puberty. The proteolytic processing of fibronectin type 3 domain-containing protein 5 (FNDC5) releases a hormone, irisin. Irisin is primarily produced by muscle and is released into circulation, where levels increase dramatically as puberty approaches. We investigated the effects of a global deletion of the Fndc5 gene on pubertal timing. The absence of irisin induced a delay in puberty onset in female knockout mice compared with controls, without affecting body weight or gonadotropin-releasing hormone (GnRH) neuronal density. We next treated pre-pubertal wild-type male and female mice with an irisin receptor antagonist, cilengitide, for 7 days and observed a delay in first estrus occurrence compared to vehicle-treated control mice. Male puberty timing was unaffected. Next, we deleted the irisin receptor (integrin subunit alpha V) in all forebrain neurons and found a delay in the occurrence of first estrus in knockout females compared to controls. Taken together, these data suggest irisin plays a role in the timing of puberty onset in female mice via a centrally mediated mechanism.

The pheromone affects reproductive physiology and behavior by regulating hormone in juvenile mice

Pheromones could promote hormone secretions and regulate sexual behavior. It was unclear whether multiparous pheromone could induce variations in puberty. The aim was to ascertain whether pheromone in urine of multiparous females induced central precocious puberty (CPP) in juvenile C57BL/6J females. The precocious puberty was examined by vaginal smear, lordosis reaction, HE stain, and ELISA analysis. Results suggested that the first vaginal opening and the first estrus were significantly earlier. The time interval of the first vaginal opening and estrus was significantly shortened. It was interesting that the first estrus was significantly correlated with the first vaginal opening and the time interval of the first estrus. In the first estrus, female lordosis reaction, the number of mature follicles, and the weight of the ovary and uterus significantly increased. The level of luteinizing hormones also significantly increased. Thus, multiparous pheromone can regulate sex hormone to induce CPP in juvenile C57BL/6J females.

The mechanism underlying the pubertal increase in pulsatile GnRH release in primates

In primates, the gonatotropin-releasing hormone (GnRH) neurosecretory system, consisting of GnRH, kisspeptin, and neurokinin B neurons, is active during the neonatal/early infantile period. During the late infantile period, however, activity of the GnRH neurosecretory system becomes minimal as a result of gonadal steroid independent central inhibition, and this suppressed GnRH neurosecretory state continues throughout the prepubertal period. At the initiation of puberty, the GnRH neurosecretory system becomes active again because of the decrease in central inhibition. During the progress of puberty, kisspeptin and neurokinin B signaling to GnRH neurons further increases, resulting in the release of gonadotropins and subsequent gonadal maturation, and hence puberty. This review further discusses potential substrates of central inhibition and subsequent pubertal modification of the GnRH neurosecretory system by the pubertal increase in steroid hormones, which ensures the regulation of adult reproductive function.

The polygamous GnRH neuron: Astrocytic and tanycytic communication with a neuroendocrine neuronal population

To ensure the survival of the species, hypothalamic neuroendocrine circuits controlling fertility, which converge onto neurons producing gonadotropin-releasing hormone (GnRH), must respond to fluctuating physiological conditions by undergoing rapid and reversible structural and functional changes. However, GnRH neurons do not act alone, but through reciprocal interactions with multiple hypothalamic cell populations, including several glial and endothelial cell types. For instance, it has long been known that in the hypothalamic median eminence, where GnRH axons terminate and release their neurohormone into the pituitary portal blood circulation, morphological plasticity displayed by distal processes of tanycytes modifies their relationship with adjacent neurons as well as the spatial properties of the neurohemal junction. These alterations not only regulate the capacity of GnRH neurons to release their neurohormone, but also the activation of discrete non-neuronal pathways that mediate feedback by peripheral hormones onto the hypothalamus. Additionally, a recent breakthrough has demonstrated that GnRH neurons themselves orchestrate the establishment of their neuroendocrine circuitry during postnatal development by recruiting an entourage of newborn astrocytes that escort them into adulthood and, via signalling through gliotransmitters such as prostaglandin E2, modulate their activity and GnRH release. Intriguingly, several environmental and behavioural toxins perturb these neuron-glia interactions and consequently, reproductive maturation and fertility. Deciphering the communication between GnRH neurons and other neural cell types constituting hypothalamic neuroendocrine circuits is thus critical both to understanding physiological processes such as puberty, oestrous cyclicity and aging, and to developing novel therapeutic strategies for dysfunctions of these processes, including the effects of endocrine disruptors.

Connecting nutritional deprivation and pubertal inhibition via GRK2-mediated repression of kisspeptin actions in GnRH neurons

BACKGROUND

Perturbations in the timing of puberty, with potential adverse consequences in later health, are increasingly common. The underlying neurohormonal mechanisms are unfolded, but nutritional alterations are key contributors. Efforts to unveil the basis of normal puberty and its metabolic control have focused on mechanisms controlling expression of Kiss1, the gene encoding the puberty-activating neuropeptide, kisspeptin. However, other regulatory phenomena remain ill-defined. Here, we address the putative role of the G protein-coupled-receptor kinase-2, GRK2, in GnRH neurons, as modulator of pubertal timing via repression of the actions of kisspeptin, in normal maturation and conditions of nutritional deficiency.

METHODS

Hypothalamic RNA and protein expression analyses were conducted in maturing female rats. Pharmacological studies involved central administration of GRK2 inhibitor, βARK1-I, and assessment of gonadotropin responses to kisspeptin or phenotypic and hormonal markers of puberty, under normal nutrition or early subnutrition in female rats. In addition, a mouse line with selective ablation of GRK2 in GnRH neurons, aka G-GRKO, was generated, in which hormonal responses to kisspeptin and puberty onset were monitored, in normal conditions and after nutritional deprivation.

RESULTS

Hypothalamic GRK2 expression increased along postnatal maturation in female rats, especially in the preoptic area, where most GnRH neurons reside, but decreased during the juvenile-to-pubertal transition. Blockade of GRK2 activity enhanced Ca+2 responses to kisspeptin in vitro, while central inhibition of GRK2 in vivo augmented gonadotropin responses to kisspeptin and advanced puberty onset. Postnatal undernutrition increased hypothalamic GRK2 expression and delayed puberty onset, the latter being partially reversed by central GRK2 inhibition. Conditional ablation of GRK2 in GnRH neurons enhanced gonadotropin responses to kisspeptin, accelerated puberty onset, and increased LH pulse frequency, while partially prevented the negative impact of subnutrition on pubertal timing and LH pulsatility in mice.

CONCLUSIONS

Our data disclose a novel pathway whereby GRK2 negatively regulates kisspeptin actions in GnRH neurons, as major regulatory mechanism for tuning pubertal timing in nutritionally-compromised conditions.

Combinational exposure to Bisphenol A and a high-fat diet causes trans-generational Malfunction of the female reproductive system in mice

Bisphenol A (BPA) is a common endocrine disruptor and a high-fat diet (HFD) also affects fertility. However, little is known about the long-term consequences of simultaneous exposure to BPA and a HFD on reproductive health. Herein, we assessed the effects of maternal exposure to BPA in combination with a HFD on reproductive function in subsequent generations of female mice and evaluated its effects on the hypothalamic-pituitary-gonadal axis. We found that the combination of maternal exposure to BPA and a HFD led to increased urine BPA levels, precocious puberty, altered estrous cyclicity, decreased follicle numbers, and altered hypothalamic Kiss1 methylation status in F1 and F2 mice. Therefore, we demonstrated that maternal exposure to BPA in combination with a HFD exerts a trans-generational effect on female reproduction.

Precocious sexual maturation: Unravelling the mechanisms of pubertal onset through clinical observations

Puberty is a crucial biological process normally occurring at a specific time during the lifespan, during which sexual and somatic maturation are completed, and reproductive capacity is reached. Pubertal timing is not only determined by genetics, but also by endogenous and environmental cues, including nutritional and metabolic signals. During the last decade, we have learned much regarding the essential roles of kisspeptins and the neuropeptide pathways that converge on these neurones to modulate kisspeptin signalling, as well as neurokinin B and dynorphin, the co-transmitters of Kiss1 neurones in the arcuate nucleus, and the effects of melanocortins on puberty. Indeed, melanocortins are involved in transmitting the regulatory actions of metabolic cues on pubertal maturation. Intracellular metabolic sensors, such as the AMP-activated protein kinase and the fuel-sensing deacetylase SIRT1, have been shown to contribute to puberty. Further understanding of these signals and regulatory circuits will help uncover the intimacies of the central control of puberty, as well as how alterations in metabolic status, ranging from undernutrition to obesity, affect the pubertal process. Precocious puberty is rare and has a clear female predominance. Central precocious puberty (CPP) is diagnosed when premature activation of the hypothalamic-pituitary axis occurs. Its causes are heterogeneous, with alterations of the central nervous system being of special interest, and with environmental factors also playing a role in some cases. During the last decade, several mutations in different genes (including KISS1, KISS1R, MKRN3 and DLK1) that cause CPP have been discovered. Loss-of-function mutations in MKRN3 are the most common monogenic cause of CPP known to date. Here, we review and update what is known regarding the genotype-phenotype relationship in patients with CPP.

GABAB Receptor Antagonism from Birth to Weaning Permanently Modifies Kiss1 Expression in the Hypothalamus and Gonads in Mice

INTRODUCTION

The kisspeptin gene Kiss1 is expressed in two hypothalamic areas: anteroventral periventricular nucleus/periventricular nucleus (AVPV/PeN) and arcuate nucleus (ARC), and also in gonads. Several pieces of evidence suggests that gamma-amino butyric acid B receptors (GABAB) signaling can regulate Kiss1 expression. Here, we inhibited GABAB signaling from PND2 to PND21 and evaluated the hypothalamic-pituitary-gonadal (HPG) axis.

METHODS

BALB/c mice were treated on postnatal days 2-21 (PND2-PND21) with CGP55845 (GABAB antagonist) and evaluated in PND21 and adulthood: gene expression (qPCR) in the hypothalamus and gonads, hormones by radioimmunoassay, gonad histochemistry (H&amp;E), puberty onset, and estrous cycles.

RESULTS

At PND21, CGP inhibited Kiss1 and Tac2 and increased Pdyn and Gabbr1 in the ARC of both sexes and decreased Th only in female AVPV/PeN. Serum follicle-stimulating hormone (FSH) and testis weight were decreased in CGP-males, and puberty onset was delayed. In adults, Kiss1, Tac2, Pdyn, Pgr, Cyp19a1, and Gad1 were downregulated, while Gabbr1 was upregulated in the ARC of both sexes. In the AVPV/PeN, Kiss1, Th, Cyp19a1, and Pgr were decreased while Gad1 was increased in CGP-females, whereas Cyp19a1 was increased in CGP-males. Serum FSH was increased in CGP-males while prolactin was increased in CGP-females. Testosterone and progesterone were increased in ovaries from CGP-females, in which Kiss1, Cyp19a1, and Esr1 were downregulated while Hsd3b2 was upregulated, together with increased atretic and decreased ovulatory follicles. Testes from CGP-males showed decreased progesterone, increased Gabbr1, Kiss1, Kiss1r, and Esr2 and decreased Cyp19a1, and clear signs of seminiferous tubules atrophy.

CONCLUSION

These results demonstrate that appropriate GABAB signaling during this critical prepubertal period is necessary for the normal development of the HPG axis.

Distribution of androgen receptor mRNA in the prepubertal male and female mouse brain

Androgens are steroid hormones that play a critical role in brain development and sexual maturation by acting upon both androgen receptors (AR) and estrogen receptors (ERα/β) after aromatization. The contribution of estrogens from aromatized androgens in brain development and the central regulation of metabolism, reproduction, and behavior is well defined, but the role of androgens acting on AR has been unappreciated. Here, we map the sex specific expression of Ar in the adult and developing mouse brain. Postnatal days (PND) 12 and 21 were used to target a critical window of prepubertal development. Consistent with previous literature in adults, sex-specific differences in Ar expression were most profound in the bed nucleus of the stria terminalis (BST), medial amygdala (MEA) and medial preoptic area (MPO). Ar expression was also high in these areas at PND 12 and 21 in both sexes. In addition, we describe extra-hypothalamic and extra-limbic areas that show moderate, consistent and similar Ar expression in both sexes at both prepubertal time points. Briefly, Ar expression was observed in olfactory areas of the cerebral cortex, the hippocampus, several thalamic nuclei, and cranial nerve nuclei involved in autonomic sensory and motor function. To further characterize forebrain populations of Ar expressing neurons and determine whether they also coexpress estrogen receptors, we examined expression of Ar, Esr1 and Esr2 in prepubertal mice in selected nuclei. We found populations of neurons in the BST, MEA and MPO that coexpress Ar, but not Esr1 or Esr2, whereas others express a combination of the three receptors. Our findings indicate that various brain areas express Ar during prepubertal development and may play an important role in female neuronal development and physiology.

Gonadotrophin-releasing hormone and kisspeptin: It takes two to tango

Kisspeptin (Kp), a family of peptides comprising products of the Kiss1 gene, was discovered 20 years ago; it is recognised as the major factor controlling the activity of the gonadotrophin-releasing hormone (GnRH) neurones and thus the activation of the reproductive axis in mammals. It has been widely documented that the effects of Kp on reproduction through its action on GnRH neurones are mediated by the GPR54 receptor. Kp controls the activation of the reproductive axis at puberty, maintains reproductive axis activity in adults and is involved in triggering ovulation in some species. Although there is ample evidence coming from both conditional knockout models and conditional-induced Kp neurone death implicating the Kp/GPR54 pathway in the control of reproduction, the mechanism(s) underlying this process may be more complex than a sole direct control of GnRH neuronal activity by Kp. In this review, we provide an overview of the recent advances made in elucidating the interplay between Kp- and GnRH- neuronal networks with respect to regulating the reproductive axis. We highlight the existence of a possible mutual regulation between GnRH and Kp neurones, as well as the implication of Kp-dependent volume transmission in this process. We also discuss the capacity of heterodimerisation between GPR54 and GnRH receptor (GnRH-R) and its consequences on signalling. Finally, we illustrate the role of mathematical modelling that accounts for the synergy between GnRH-R and GPR54 in explaining the role of these two receptors when defining GnRH neuronal activity and GnRH pulsatile release.

MC3R links nutritional state to childhood growth and the timing of puberty

The state of somatic energy stores in metazoans is communicated to the brain, which regulates key aspects of behaviour, growth, nutrient partitioning and development1. The central melanocortin system acts through melanocortin 4 receptor (MC4R) to control appetite, food intake and energy expenditure2. Here we present evidence that MC3R regulates the timing of sexual maturation, the rate of linear growth and the accrual of lean mass, which are all energy-sensitive processes. We found that humans who carry loss-of-function mutations in MC3R, including a rare homozygote individual, have a later onset of puberty. Consistent with previous findings in mice, they also had reduced linear growth, lean mass and circulating levels of IGF1. Mice lacking Mc3r had delayed sexual maturation and an insensitivity of reproductive cycle length to nutritional perturbation. The expression of Mc3r is enriched in hypothalamic neurons that control reproduction and growth, and expression increases during postnatal development in a manner that is consistent with a role in the regulation of sexual maturation. These findings suggest a bifurcating model of nutrient sensing by the central melanocortin pathway with signalling through MC4R controlling the acquisition and retention of calories, whereas signalling through MC3R primarily regulates the disposition of calories into growth, lean mass and the timing of sexual maturation.

Sperm Cyst "Looping": A Developmental Novelty Enabling Extreme Male Ornament Evolution

Postcopulatory sexual selection is credited as a principal force behind the rapid evolution of reproductive characters, often generating a pattern of correlated evolution between interacting, sex-specific traits. Because the female reproductive tract is the selective environment for sperm, one taxonomically widespread example of this pattern is the co-diversification of sperm length and female sperm-storage organ dimension. In Drosophila, having testes that are longer than the sperm they manufacture was believed to be a universal physiological constraint. Further, the energetic and time costs of developing long testes have been credited with underlying the steep evolutionary allometry of sperm length and constraining sperm length evolution in Drosophila. Here, we report on the discovery of a novel spermatogenic mechanism—sperm cyst looping—that enables males to produce relatively long sperm in short testis. This phenomenon (restricted to members of the saltans and willistoni species groups) begins early during spermatogenesis and is potentially attributable to heterochronic evolution, resulting in growth asynchrony between spermatid tails and the surrounding spermatid and somatic cyst cell membranes. By removing the allometric constraint on sperm length, this evolutionary innovation appears to have enabled males to evolve extremely long sperm for their body mass while evading delays in reproductive maturation time. On the other hand, sperm cyst looping was found to exact a cost by requiring greater total energetic investment in testes and a pronounced reduction in male lifespan. We speculate on the ecological selection pressures underlying the evolutionary origin and maintenance of this unique adaptation.

FSH mediated cAMP signalling upregulates the expression of Gα subunits in pubertal rat Sertoli cells

Follicle Stimulating Hormone (FSH) acts via FSH-Receptor (FSH-R) by employing cAMP as the dominant secondary messenger in testicular Sertoli cells (Sc) to support spermatogenesis. Binding of FSH to FSH-R, results the recruitment of the intracellular GTP binding proteins, either stimulatory Gαs or inhibitory Gαi that in turn regulate cAMP production in Sc. The cytosolic concentration of cAMP being generated by FSH-R thereafter critically determines the downstream fate of the FSH signalling. The pleiotropic action of FSH due to differential cAMP output during functional maturation of Sc has been well studied. However, the developmental and cellular regulation of the Gα proteins associated with FSH-R is poorly understood in Sc. In the present study, we report the differential transcriptional modulation of the Gα subunit genes by FSH mediated cAMP signalling in neonatal and pubertal rat Sc. Our data suggested that unlike in neonatal Sc, both the basal and FSH/forskolin induced expression of Gαs, Gαi-1, Gαi-2 and Gαi-3 transcripts was significantly (p < 0.05) up-regulated in pubertal Sc. Further investigations involving treatment of Sc with selective Gαi inhibitor pertussis toxin, confirmed the elevated expression of Gi subunits in pubertal Sc. Collectively our results indicated that the high level of Gαi subunits serves as a negative regulator to optimize cAMP production in pubertal Sc.

Sex-specific pubertal and metabolic regulation of Kiss1 neurons via Nhlh2

Hypothalamic Kiss1 neurons control gonadotropin-releasing hormone release through the secretion of kisspeptin. Kiss1 neurons serve as a nodal center that conveys essential regulatory cues for the attainment and maintenance of reproductive function. Despite this critical role, the mechanisms that control kisspeptin synthesis and release remain largely unknown. Using Drop-Seq data from the arcuate nucleus of adult mice and in situ hybridization, we identified Nescient Helix-Loop-Helix 2 (Nhlh2), a transcription factor of the basic helix-loop-helix family, to be enriched in Kiss1 neurons. JASPAR analysis revealed several binding sites for NHLH2 in the Kiss1 and Tac2 (neurokinin B) 5' regulatory regions. In vitro luciferase assays evidenced a robust stimulatory action of NHLH2 on human KISS1 and TAC3 promoters. The recruitment of NHLH2 to the KISS1 and TAC3 promoters was further confirmed through chromatin immunoprecipitation. In vivo conditional ablation of Nhlh2 from Kiss1 neurons using Kiss1Cre:Nhlh2fl/fl mice induced a male-specific delay in puberty onset, in line with a decrease in arcuate Kiss1 expression. Females retained normal reproductive function albeit with irregular estrous cycles. Further analysis of male Kiss1Cre:Nhlh2fl/fl mice revealed higher susceptibility to metabolic challenges in the release of luteinizing hormone and impaired response to leptin. Overall, in Kiss1 neurons, Nhlh2 contributes to the metabolic regulation of kisspeptin and NKB synthesis and release, with implications for the timing of puberty onset and regulation of fertility in male mice.

Impact of pubertal onset on region-specific Esr2 expression

In female rats, pubertal onset is associated with maturation of the medial prefrontal cortex (mPFC) and mPFC-mediated behaviours. These behavioural and anatomical changes are likely a result of the effects of oestrogens at the nuclear oestrogen receptor (ER)β, which is expressed at higher levels than the ERα isoform in the adult mPFC. Researchers have previously quantified ERβ protein and Esr2 RNA in rodents during early postnatal development and adulthood, although an adolescent-specific trajectory of this receptor in the mPFC has not been documented. Given that Esr2 expression can fluctuate in the presence or absence of oestrogens, puberty and the subsequent rise in gonadal hormones could influence levels of ERβ in the adolescent brain. To further explore this, we used RNAscope® technology to quantify the amount of Esr2 mRNA in pre-pubertal adolescent, recently post-pubertal adolescent and adult female rats. We show that Esr2 expression decreases significantly in the mPFC, striatum and motor cortex between pre-pubertal adolescence and adulthood. In the mPFC, this decrease occurs rapidly at pubertal onset, with no significant decrease in Esr2 levels between the recently post-pubertal and adult cohort. By contrast, the striatum and motor cortex had no significant differences in the amount of Esr2 mRNA between pre- and post-pubertal females. Insofar as the amount of Esr2 expression is proportional to functional ERβ, these results suggest ERβ decreases in a region-specific pattern in response to pubertal onset and highlight a role for this receptor in the maturational events that occur in the female rat mPFC at puberty.

Observed and predicted ages at peak height velocity in soccer players

The purpose of the study was to evaluate predicted maturity offset (time before age at PHV) and age at PHV (chronological age [CA] minus maturity offset) in a longitudinal sample of 58 under-13 club level soccer players in central Portugal for whom ages at PHV were estimated with the SITAR model. Two maturity offset prediction equations were applied: the original equation which requires CA sitting height, estimated leg length, height and weight, and a modified equation which requires CA and height. Predicted maturity offset increased, on average, with CA at prediction throughout the age range considered, while variation in predicted maturity offset and ages at PHV within CA groups was considerably reduced compared to variation in observed ages at offset and at PHV. Predicted maturity offset and ages at PHV were consistently later than observed maturity offset and age at PHV among early maturing players, and earlier than observed in late maturing players. Both predicted offset and ages at PHV with the two equations were, on average, later than observed among players maturing on time. Intra-individual variation in predicted ages at PHV with each equation was considerable. The results for soccer players were consistent with similar studies in the general population and two recent longitudinal studies of soccer players. The results question the utility of predicted maturity offset and age at PHV as valid indicators of maturity timing and status.

Protein restriction during puberty alters nutritional parameters and affects ovarian and uterine histomorphometry in adulthood in rats

In a large part of the population inefficient ingestion of proteins, whether for cultural, aesthetic or economic reasons, is a global concern. Low-protein diets can cause severe functional complications, mainly during the development and maturation of organs and systems, including the female reproductive system. The present study investigated the effect of nutritional protein restriction during puberty on the oestrous cycle and expression of sex steroid receptors (AR, ERα e ERβ) in ovarian and uterine tissues of adult rats. Protein restriction promoted lower body weight gain, feed efficiency and higher caloric intake. There was an increase in the oestrus phase arrest without changing the total length of the oestrous cycle. The consumption of low-protein diet also reduced the thickness of the uterine endometrium (uterine epithelium and endometrial stroma) in addition to increasing the number of primary and atretic follicles in the ovaries. Furthermore, the low-protein diet reduced the levels of androgen receptor (AR) and increased the oestrogen receptor β (ERβ) in the ovary, while no significant changes were observed in the uterus. Our study reinforces the importance of adequate protein intake during puberty, since physiological changes in this developmental period interfere with the histomorphometry of the ovaries and uteri, possibly resulting in impaired folliculogenesis and fertility in the reproductive period.

Novel model to study the physiological effects of temporary or prolonged sex steroid deficiency in male mice

Sex steroids are critical for skeletal development and maturation during puberty as well as for skeletal maintenance during adult life. However, the exact time during puberty when sex steroids have the highest impact as well as the ability of bone to recover from transient sex steroid deficiency is unclear. Surgical castration is a common technique to study sex steroid effects in rodents, but it is irreversible, invasive, and associated with metabolic and behavioral alterations. Here, we used a low dose (LD) or a high dose (HD) of gonadotropin-releasing hormone antagonist to either temporarily or persistently suppress sex steroid action in male mice, respectively. The LD group, a model for delayed puberty, did not show changes in linear growth or body composition, but displayed reduced trabecular bone volume during puberty, which fully caught up at adult age. In contrast, the HD group, representing complete pubertal suppression, showed a phenotype reminiscent of that observed in surgically castrated rodents. Indeed, HD animals exhibited severely impaired cortical and trabecular bone acquisition, decreased body weight and lean mass, and increased fat mass. In conclusion, we developed a rodent model of chemical castration that can be used as an alternative to surgical castration. Moreover, the transient nature of the intervention enables to study the effects of delayed puberty and reversibility of sex steroid deficiency.NEW & NOTEWORTHY We developed a rodent model of chemical castration, which can be used as an alternative to surgical castration. Moreover, the transient nature of the intervention enables to study the effects of delayed puberty and reversibility of sex steroid deficiency.

Effects of peripheral oxytocin administration on body weight, food intake, adipocytes, and biochemical parameters in peri- and postmenopausal female rats

Recent studies have revealed that the administration of oxytocin has beneficial effects on the regulation of body weight, food intake, and metabolic functions, especially in obese individuals. Obesity is common in women after the menopause and drives many components of metabolic syndrome. Weight gain in menopausal women has been frequently reported. Although obesity and associated metabolic disorders are frequently observed in peri- and postmenopausal women, there are few medical interventions for these conditions. In this study, we evaluated the effects of chronic oxytocin administration on appetite, body weight, and fat mass in peri- and postmenopausal female rats. Sixteen naturally premenopausal or menopausal rats were intraperitoneally injected with oxytocin (1,000 μg/day) for 12 days. The daily changes in their body weight and food intake were measured at the same time as the oxytocin and vehicle injections. Intraperitoneally administering oxytocin for 12 days significantly reduced food intake, body weight, and visceral adipocyte size. In addition, oxytocin administration caused reductions in serum triglyceride and low-density lipoprotein-cholesterol levels, while it did not disturb hepatic or renal functions or locomotor activity. This is the first study to show the effects of oxytocin on the metabolic and feeding functions of peri- and postmenopausal female rats. Oxytocin might be a useful treatment for metabolic disorders caused by the menopause or aging.

The Role of Fetal, Infant, and Childhood Nutrition in the Timing of Sexual Maturation

Puberty is a crucial developmental stage in the life span, necessary to achieve reproductive and somatic maturity. Timing of puberty is modulated by and responds to central neurotransmitters, hormones, and environmental factors leading to hypothalamic-pituitary-gonadal axis maturation. The connection between hormones and nutrition during critical periods of growth, like fetal life or infancy, is fundamental for metabolic adaptation response and pubertal development control and prediction. Since birth weight is an important indicator of growth estimation during fetal life, restricted prenatal growth, such as intrauterine growth restriction (IUGR) and small for gestational age (SGA), may impact endocrine system, affecting pubertal development. Successively, lactation along with early life optimal nutrition during infancy and childhood may be important in order to set up timing of sexual maturation and provide successful reproduction at a later time. Sexual maturation and healthy growth are also influenced by nutrition requirements and diet composition. Early nutritional surveillance and monitoring of pubertal development is recommended in all children, particularly in those at risk, such as the ones born SGA and/or IUGR, as well as in the case of sudden weight gain during infancy. Adequate macro and micronutrient intake is essential for healthy growth and sexual maturity.

Pubertal timing in boys and girls born to mothers with gestational diabetes mellitus: a systematic review

CONTEXT

The incidence of gestational diabetes mellitus (GDM) has been on the rise, driven by maternal obesity. In parallel, pubertal tempo has increased in the general population, driven by childhood obesity.

OBJECTIVE

To evaluate the available evidence on pubertal timing of boys and girls born to mothers with GDM.

DATA SOURCES

We searched MEDLINE, EMBASE, CINAHL Plus, Cochrane library and grey literature for observational studies up to October 2019.

STUDY SELECTION AND EXTRACTION

Two reviewers independently selected studies, collected data and appraised the studies for risk of bias. Results were tabulated and narratively described as reported in the primary studies.

RESULTS

Seven articles (six for girls and four for boys) were included. Study quality score was mostly moderate (ranging from 4 to 10 out of 11). In girls born to mothers with GDM, estimates suggest earlier timing of pubarche, thelarche and menarche although for each of these outcomes only one study each showed a statistically significant association. In boys, there was some association between maternal GDM and earlier pubarche, but inconsistency in the direction of shift of age at onset of genital and testicular development and first ejaculation. Only a single study analysed growth patterns in children of mothers with GDM, describing a 3-month advancement in the age of attainment of peak height velocity and a slight increase in pubertal tempo.

CONCLUSIONS

Pubertal timing may be influenced by the presence of maternal GDM, though current evidence is sparse and of limited quality. Prospective cohort studies should be conducted, ideally coupled with objective biochemical tests.

Unilateral section of the superior ovarian nerve induces first ovulation in the Zucker fatty (fa/fa) rat

Hyperactivity in the sympathetic nervous system has been shown to be related to the development of ovarian pathologies. In addition, obesity has been found to be associated with multiple reproductive anomalies and is considered a chronic stress condition of low intensity with changes in the peripheral sympathetic activity. Therefore, in the present study, we aimed to evaluate if the information reaching the ovaries through the superior ovarian nerve (SON) modifies the ovarian function of Zucker fatty rats. We performed a unilateral section of the SON at 32 days of age and autopsies were carried out on the day of the first vaginal estrus. The results showed that fatty animals do not ovulate on the day of the first vaginal estrus and exhibit an increase in catecholaminergic fibers and the presence of precystic structures in the ovaries, without changes in the onset of puberty or in the secretion of ovarian and hypophyseal hormones. We also found that the section of the right SON resulted in ovulation on the day of the first vaginal estrus, which was accompanied by a decrease in ovarian noradrenaline content. The section of the left SON caused a delay in puberty without changes in the rest of the parameters. These results provide functional evidence that the peripheral sympathetic innervation participates in the regulation of ovarian functions in an animal model of genetic obesity.

The Gill-Oxygen Limitation Theory and size at maturity/maximum size relationships for salmonid populations occupying flowing waters

The slowing of growth as fish age has long been believed to be related to energy expenditure for maturation, and this rationalization has been used to explain why, across nearly all fish species, the relationship between size at first maturity (L_m ) and maximum (L_max ) or asymptotic length (L_∞ ) is relatively constant. In contrast, the Gill-Oxygen Limitation Theory (GOLT) postulates that (a) fish growth slows because as they grow, their two-dimensional ability to extract oxygen from the water diminishes relative to their three-dimensional weight gain, and (b) they can only invest energy for maturation if oxygen supply at their size at first maturity (Q_m ) exceeds that needed for maintenance metabolism (Q_∞ ). It has been reported previously across dozens of marine fish species that the relationship between Q_m and Q_∞ is linear and, further, it can be mathematically converted to L_m vs. L_∞ by raising both terms to the power of D (the gill surface factor), resulting in a slope of 1.36. If the GOLT is universal, a similar slope should exist for L_m ^D vs. L_∞ ^D relationships for freshwater species across multiple individual populations that reside in disparate habitats, although to our knowledge this has never been evaluated. For analysis, we used existing data from previous studies conducted on 51 stream-dwelling populations of redband trout Oncorhynchus mykiss gairdneri, Yellowstone cutthroat trout O. clarkii bouvieri and mountain whitefish Prosopium williamsoni. The resulting L_m ^D vs. L_∞ ^D slopes combining all data points (1.35) or for all species considered separately (range = 1.29-1.40) were indeed equivalent to the slope originally produced for the marine species from which the GOLT-derived relationship was first reported. We briefly discuss select papers both supporting and resisting various aspects of the GOLT, note that it could potentially explain shrinking sizes of marine fish, and call for more concerted research efforts combining laboratory and field expertise in fish growth research.

The localization and expression of gonadotropin inhibitory hormone in the hypothalamus of turkey hens during the prepubertal, pubertal and postpubertal phases

Gonadotropin inhibitory hormone (GnIH), initially discovered in birds as a hypothalamic neuropeptide, inhibits the synthesis and release of gonadotropins by affecting GnRH neurons and gonadotropes. Therefore, it may be a key neuropeptide in reproduction in birds. The aim of the present study was to investigate the prepubertal, pubertal, and postpubertal localization of GnIH and changes in hypothalamic GnIH expression in British United Turkey hens. In prepubertal, pubertal, and postpubertal periods, the brains of turkey hens (n = 15) were removed after fixation. Sections (30 μm) were prepared from the entire hypothalamus and stained immunohistochemically against GnIH antibody. Gonadotropin inhibitory hormone-immunoreactive neurons were observed in the paraventricular nucleus. These neurons were significantly more abundant in the prepubertal turkeys than pubertal and postpubertal turkeys (P < 0.05). The results suggested that GnIH neurons have an important role in regulating the pubertal events in British United Turkey hens.

Tachykinin Signaling Is Required for Induction of the Preovulatory Luteinizing Hormone Surge and Normal Luteinizing Hormone Pulses

Tachykinins (neurokinin A [NKA], neurokinin B [NKB], and substance P [SP]) are important components of the neuroendocrine control of reproduction by direct stimulation of Kiss1 neurons to control GnRH pulsatility, which is essential for reproduction. Despite this role of tachykinins in successful reproduction, knockout (KO) mice for Tac1 (NKA/SP) and Tac2 (NKB) genes are fertile, resembling the phenotype of human patients bearing NKB signaling mutations, who often reverse their hypogonadal phenotype. This suggests the existence of compensatory mechanisms among the different tachykinin ligand-receptor systems to maintain reproduction in the absence of one of them. In order to test this hypothesis, we generated complete tachykinin-deficient mice (Tac1/Tac2KO). Male mice displayed delayed puberty onset and decreased luteinizing hormone (LH) pulsatility (frequency and amplitude of LH pulses) but preserved fertility. However, females did not show signs of puberty onset (first estrus) within 45 days after vaginal opening, they displayed a low frequency (but normal amplitude) of LH pulses, and 80% of them remained infertile. Further evaluation identified a complete absence of the preovulatory LH surge in Tac1/Tac2KO females as well as in wild-type females treated with NKB or SP receptor antagonists. These data confirmed a fundamental role of tachykinins in the timing of puberty onset and LH pulsatility and uncovered a role of tachykinin signaling in facilitation of the preovulatory LH surge. Overall, these findings indicate that tachykinin signaling plays a dominant role in the control of ovulation, with potential implications as a pathogenic mechanism and a therapeutic target to improve reproductive outcomes in women with ovulation impairments.

ERα Signaling in GHRH/Kiss1 Dual-Phenotype Neurons Plays Sex-Specific Roles in Growth and Puberty

Gonadal steroids modulate growth hormone (GH) secretion and the pubertal growth spurt via undefined central pathways. GH-releasing hormone (GHRH) neurons express estrogen receptor α (ERα) and androgen receptor (AR), suggesting changing levels of gonadal steroids during puberty directly modulate the somatotropic axis. We generated mice with deletion of ERα in GHRH cells (GHRHΔERα), which displayed reduced body length in both sexes. Timing of puberty onset was similar in both groups, but puberty completion was delayed in GHRHΔERα females. Lack of AR in GHRH cells (GHRHΔAR mice) induced no changes in body length, but puberty completion was also delayed in females. Using a mouse model with two reporter genes, we observed that, while GHRHtdTom neurons minimally colocalize with Kiss1hrGFP in prepubertal mice, ∼30% of GHRH neurons coexpressed both reporter genes in adult females, but not in males. Developmental analysis of Ghrh and Kiss1 expression suggested that a subpopulation of ERα neurons in the arcuate nucleus of female mice undergoes a shift in phenotype, from GHRH to Kiss1, during pubertal transition. Our findings demonstrate that direct actions of gonadal steroids in GHRH neurons modulate growth and puberty and indicate that GHRH/Kiss1 dual-phenotype neurons play a sex-specific role in the crosstalk between the somatotropic and gonadotropic axes during pubertal transition.SIGNIFICANCE STATEMENT Late maturing adolescents usually show delayed growth and bone age. At puberty, gonadal steroids have stimulatory effects on the activation of growth and reproductive axes, but the existence of gonadal steroid-sensitive neuronal crosstalk remains undefined. Moreover, the neural basis for the sex differences observed in the clinical arena is unknown. Lack of ERα in GHRH neurons disrupts growth in both sexes and causes pubertal delay in females. Deletion of androgen receptor in GHRH neurons only delayed female puberty. In adult females, not males, a subset of GHRH neurons shift phenotype to start producing Kiss1. Thus, direct estrogen action in GHRH/Kiss1 dual-phenotype neurons modulates growth and puberty and may orchestrate the sex differences in endocrine function observed during pubertal transition.

Aspects of the reproductive biology of two pelagic sharks in the eastern Atlantic Ocean

This study used data provided by the Chinese Longline Fishery Scientific Observer Programme from the tropical eastern Atlantic Ocean to estimate the reproductive parameters of the blue shark (Prionace glauca) and crocodile shark (Pseudocarcharias kamoharai). Sizes ranged from 80 to 298 cm fork length (FL) for blue sharks and from 48 to 99 cm FL for crocodile sharks. Sexual segregation was observed during different months for both sharks. The sex ratio for blue sharks was 1.38 F:1 M, and 1 F:2.79 M for crocodile sharks. The size of adult blue sharks ranged from 144 to 280 cm for males and from 174 to 298 cm for females; and that of crocodile sharks from 63 to 97 cm for males and 78-99 cm for females. The size at 50% of maturity for blue sharks was estimated at 191.7 cm FL for females and 197.5 cm FL for males, and that of crocodile sharks was assessed at 84.9 cm FL for females and 78.5 cm FL for males. Most sexually matured females were pregnant; their means were 207.2 ± 16.4 cm FL for blue sharks and 89.4 ± 4.3 cm FL for crocodile sharks. Mature sizes for both species were significantly different among months. Embryonic sizes also varied widely among months for crocodile sharks, but a slight change was recorded for those of blue sharks. The observed mean size at birth and litter size were 34.5 cm FL and 37 ± 12 for the blue sharks, and that of the crocodile sharks, 39.5 cm FL and a dominant four embryos in the uterus. Due to the observed increasing catch trend of blue sharks and the slow reproductive cycle of crocodile sharks, this study presents the need of implementing conservation measures to ensure the sustainability of both species in their habitat.

Diet during early life defines testicular lipid content and sperm quality in adulthood

Childhood obesity is a serious concern associated with ill health later in life. Emerging data suggest that obesity has long-term adverse effects upon male sexual and reproductive health, but few studies have addressed this issue. We hypothesized that exposure to high-fat diet during early life alters testicular lipid content and metabolism, leading to permanent damage to sperm parameters. After weaning (day 21 after birth), 36 male mice were randomly divided into three groups and fed with a different diet regimen for 200 days: a standard chow diet (CTRL), a high-fat diet (HFD) (carbohydrate: 35.7%, protein: 20.5%, and fat: 36.0%), and a high-fat diet for 60 days, then replaced by standard chow (HFD_t). Biometric and metabolic data were monitored. Animals were then euthanized, and tissues were collected. Epididymal sperm parameters and endocrine parameters were evaluated. Testicular metabolites were extracted and characterized by 1H-NMR and GC-MS. Testicular mitochondrial and antioxidant activity were evaluated. Our results show that mice fed with a high-fat diet, even if only until early adulthood, had lower sperm viability and motility, and higher incidence of head and tail defects. Although diet reversion with weight loss during adulthood prevents the progression of metabolic syndrome, testicular content in fatty acids is irreversibly affected. Excessive fat intake promoted an overaccumulation of proinflammatory n-6 polyunsaturated fatty acids in the testis, which is strongly correlated with negative effects upon sperm quality. Therefore, the adoption of high-fat diets during early life correlates with irreversible changes in testicular lipid content and metabolism, which are related to permanent damage to sperm quality later in life.