Body weight impact on puberty: effects of high-calorie diet on puberty onset in female rhesus monkeys

Cholecystokinin (CCK) Is a Mediator Between Nutritional Intake and Gonadal Development in Teleosts

Nutritional intake is closely linked to gonadal development, although the mechanisms by which food intake affects gonadal development are not fully understood. Cholecystokinin (CCK) is a satiety neuropeptide derived from the hypothalamus, and the present study observed that hypothalamic CCK expression is significantly influenced by food intake, which is mediated through blood glucose levels. Interestingly, CCK and its receptors were observed to exhibit a high expression in the hypothalamus-pituitary-gonad (HPG) axis of grass carp (Ctenopharyngodon idellus), suggesting that CCK is potentially involved in regulating fish reproduction through the HPG axis. Further investigations revealed that CCK could significantly stimulate the expression of gonadotropin-releasing hormone-3 (GnRH3) in the hypothalamus. In addition, single-cell RNA sequencing showed that cckrb was highly enriched in pituitary follicle-stimulating hormone (FSH) cells. Further study confirmed that CCK can significantly induce FSH synthesis and secretion in primary cultured pituitary cells. Additionally, with primary cultured ovary cells as a model, the in vitro experiment demonstrated that CCK directly induces the expression of lhr, fshr, and cyp19a1a mRNA. This indicates that hypothalamic CCK may act as a nutrient sensor involved in regulating gonadal development in teleosts.

Kisspeptin a potential therapeutic target in treatment of both metabolic and reproductive dysfunction

Kisspeptins (KPs) are proteins that were first recognized to have antimetastatic action. Later, the critical role of this peptide in the regulation of reproduction was proved. In recent years, evidence has been accumulated supporting a role for KPs in regulating metabolic processes in a sexual dimorphic manner. It has been proposed that KPs regulate metabolism both indirectly via gonadal hormones and/or directly via the kisspeptin receptor in the brain, brown adipose tissue, and pancreas. The aim of the review is to provide both experimental and clinical evidence indicating that KPs are peptides linking metabolism and reproduction. We propose that KPs could be used as a potential target to treat both metabolic and reproductive abnormalities. Thus, we focus on the consequences of disruptions in KPs and their receptors in metabolic conditions such as diabetes, undernutrition, obesity, and reproductive disorders (hypogonadotropic hypogonadism and polycystic ovary syndrome). Data from both animal models and human subjects indicate that alterations in KPs in the case of metabolic imbalance lead also to disruptions in reproductive functions. Changes both in the hypothalamic and peripheral KP systems in animal models of the aforementioned disorders are discussed. Finally, an overview of current clinical studies involving KP in fertility and metabolism show fewer studies on metabolism (15%) and only one to date on both. Presented data indicate a dynamic and emerging field of KP studies as possible therapeutic targets in treatments of both reproductive and metabolic dysfunctions.

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.

An Evolutionary Model for the Ancient Origins of Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a common endocrinopathy of reproductive-aged women, characterized by hyperandrogenism, oligo-anovulation and insulin resistance and closely linked with preferential abdominal fat accumulation. As an ancestral primate trait, PCOS was likely further selected in humans when scarcity of food in hunter-gatherers of the late Pleistocene additionally programmed for enhanced fat storage to meet the metabolic demands of reproduction in later life. As an evolutionary model for PCOS, healthy normal-weight women with hyperandrogenic PCOS have subcutaneous (SC) abdominal adipose stem cells that favor fat storage through exaggerated lipid accumulation during development to adipocytes in vitro. In turn, fat storage is counterbalanced by reduced insulin sensitivity and preferential accumulation of highly lipolytic intra-abdominal fat in vivo. This metabolic adaptation in PCOS balances energy storage with glucose availability and fatty acid oxidation for optimal energy use during reproduction; its accompanying oligo-anovulation allowed PCOS women from antiquity sufficient time and strength for childrearing of fewer offspring with a greater likelihood of childhood survival. Heritable PCOS characteristics are affected by today's contemporary environment through epigenetic events that predispose women to lipotoxicity, with excess weight gain and pregnancy complications, calling for an emphasis on preventive healthcare to optimize the long-term, endocrine-metabolic health of PCOS women in today's obesogenic environment.

Aromatase Inhibition Eliminates Sexual Receptivity Without Enhancing Weight Gain in Ovariectomized Marmoset Monkeys

Context

Ovarian estradiol supports female sexual behavior and metabolic function. While ovariectomy (OVX) in rodents abolishes sexual behavior and enables obesity, OVX in nonhuman primates decreases, but does not abolish, sexual behavior, and inconsistently alters weight gain.

Objective

We hypothesize that extra-ovarian estradiol provides key support for both functions, and to test this idea, we employed aromatase inhibition to eliminate extra-ovarian estradiol biosynthesis and diet-induced obesity to enhance weight gain.

Methods

Thirteen adult female marmosets were OVX and received (1) estradiol-containing capsules and daily oral treatments of vehicle (E2; n = 5); empty capsules and daily oral treatments of either (2) vehicle (VEH, 1 mL/kg, n = 4), or (3) letrozole (LET, 1 mg/kg, n = 4).

Results

After 7 months, we observed robust sexual receptivity in E2, intermediate frequencies in VEH, and virtually none in LET females (P = .04). By contrast, few rejections of male mounts were observed in E2, intermediate frequencies in VEH, and high frequencies in LET females (P = .04). Receptive head turns were consistently observed in E2, but not in VEH and LET females. LET females, alone, exhibited robust aggressive rejection of males. VEH and LET females demonstrated increased % body weight gain (P = .01). Relative estradiol levels in peripheral serum were E2 >>> VEH > LET, while those in hypothalamus ranked E2 = VEH > LET, confirming inhibition of local hypothalamic estradiol synthesis by letrozole.

Conclusion

Our findings provide the first evidence for extra-ovarian estradiol contributing to female sexual behavior in a nonhuman primate, and prompt speculation that extra-ovarian estradiol, and in particular neuroestrogens, may similarly regulate sexual motivation in other primates, including humans.

Anthropogenic effects on body size and growth in lab-reared and free-ranging Macaca mulatta

The impact of anthropogenic pressures upon primates is increasingly prevalent, and yet the phenotypic aspects of these impacts remain understudied. Captive environments can pose unique pressures based on factors like physical activity levels and caloric availability; thus, maturation patterns should vary under differing captive conditions. Here, we evaluate the development and growth of two Macaca mulatta populations (N = 510) with known chronological ages between 9 months and 16 years, under different levels of captive management, to assess the impact of varying anthropogenic environments on primates. To track growth, we scored 13 epiphyseal fusion locales across long bones in a skeletal sample of lab-reared M. mulatta (n = 111), including the right tibia, femur, humerus, ulna, and radius. We employed a three-tier scoring system, consisting of "0" (unfused to diaphysis), "1" (fusing), and "2" (fused). To record body size, we collected five linear measures of these long bones, from the proximal and distal ends, and total lengths. Means and standard deviations were generated to compare samples; t-tests were used to determine significant differences between means. These values were compared to available data on the free-ranging, provisioned M. mulatta population of Cayo Santiago. The free-ranging monkeys (n = 274) were found to exhibit larger linear skeletal lengths (p < 0.05) than lab-reared specimens. Generally, the free-ranging macaques reached fusion at earlier chronological ages and exhibited an extended duration of the fusing growth stage. These observations may reflect the protein-rich diet provided to free-ranging monkeys and conversely, restricted movement and relaxed natural selection experienced by lab-reared monkeys.

Review Nutritional interventions during adolescence and their possible effects

Nutrition is one of the most important factors affecting pubertal development. Increasing demands for energy proteins and micronutrients are necessary to cope with the rapid linear pubertal growth and development, change in body composition, and increased physical activity. Adequate nutrition is a key permissive factor for the normal timing and tempo of pubertal development. Severe primary or secondary malnutrition also can adversely delay the onset and progression of puberty. The higher incidence of anorexia nervosa and bulimia in adolescents imposes a nutritional risk on pubertal development. Here we provide an overview of nutritional requirements (macronutrients and micronutrients) necessary to cope with these changes. In addition, we discuss possible nutritional interventions trials and their effects on several aspects of growth and development in undernourished and stunted adolescents, in low- and middle-income countries (LMIC), who require nutritional rehabilitation. This mini-review sums up some important findings in this important complex that links between nutrition, nutritional interventions, and pubertal development.

The Role of Pediatric Nutrition as a Modifiable Risk Factor for Precocious Puberty

Puberty is a critical phase of growth and development characterized by a complex process regulated by the neuroendocrine system. Precocious puberty (PP) is defined as the appearance of physical and hormonal signs of pubertal development at an earlier age than is considered normal. The timing of puberty has important public health, clinical, and social implications. In fact, it is crucial in psychological and physical development and can impact future health. Nutritional status is considered as one of the most important factors modulating pubertal development. This narrative review presents an overview on the role of nutritional factors as determinants of the timing of sexual maturation, focusing on early-life and childhood nutrition. As reported, breast milk seems to have an important protective role against early puberty onset, mainly due to its positive influence on infant growth rate and childhood overweight prevention. The energy imbalance, macro/micronutrient food content, and dietary patterns may modulate the premature activation of the hypothalamic-pituitary-gonadal axis, inducing precocious activation of puberty. An increase in knowledge on the mechanism whereby nutrients may influence puberty will be useful in providing adequate nutritional recommendations to prevent PP and related complications.

Histological Analysis of Reproductive System in Low-Dose Nonylphenol-treated F1 Female Mice

Previously, we reported adverse effects of low-dose nonylphenol (NP) exposure on the reproductive parameters of F1 female mice. In the present study we further investigated the pathohistological effect of NP exposure on the reproductive organs in F1 female mice. NP exposures were continuously conducted from parental pre-mating period until the postnatal day (PND) 33 of F1 offspring for vaginal examination. Mice were sacrificed on PND 30 and the reproductive tissue weights were measured. The initial (at PND 21) body weights of the NP-50 group animals were significantly lower than those of control group animals, and the weight deficit were recovered when the terminal (PND 33) body weights were measured. Early vaginal opening was found in NP group animals (p<0.05). Pathohistological studies revealed that NP-treated F1 animals showed prominent increase in the ovarian follicle numbers (p<0.01), and decrease in the diameter of uterine myometrium (p<0.01), and increase in the diameter of luminal epithelium (p<0.05). The present study demonstrated that the subchronic low-dose NP exposure induced early beginning of puberty and pathohistological abnormalities in ovary and uterus of F1 mice. Further studies are needed to achieve a better understanding on the action mechanism of NP in pubertal onset and to find a way to avoid a hazardous situation provoked by NP exposure.

Mutations in growth hormone gene affect stability of protein structure leading to reduced growth, reproduction, and milk production in crossbred cattle-an insight

The GH has a multifaceted role in growth, reproduction, and milk production. Nonsynonymous mutations identified as L153V were observed from GH1 (L) to GH2 (V) with higher genotypic frequency for GH1 being 0.87. GH2 (V) allele was identified as a rare allele and the population followed Hardy-Weinberg equilibrium. LL homozygote variant had significantly better growth, reproduction, and expected milk production at different ages in crossbred (CB) males. Reports are scanty explaining the molecular mechanism of how individuals with LV genotype were phenotypically inferior to that of wild-type LL. In the present study, it was explored that GH peptide with LV heterozygotes of GH gene, were observed to have reduced structural stability thermodynamically and thus functionally leads to reduced economic traits in CB animals. The fact was first time reported and confirmed through genomic analysis, bioinformatics, and later confirmed through immunohistochemistry. Differential expression analysis of the GH gene with respect to other genes in the hypothalamus-pituitary growth axis of CB cattle was also studied to have a complete insight of the GH gene.

Irisin in the primate hypothalamus and its effect on GnRH in vitro

Irisin, encoded by the FNDC5 gene, is a recently discovered endocrine factor mainly secreted as a myokine and adipokine. However, irisin/FNDC5 expression has also been reported in different other organs including components of the reproductive axis. Yet, there is the scarcity of data on FNDC5/irisin expression, regulation and its reproductive effects, particularly in primates. Here, we report the expression of FNDC5/irisin, along with PGC1A (peroxisome proliferator-activated receptor gamma coactivator 1-alpha) and ERRA (estrogen-related receptor alpha), in components of the reproductive axis of marmoset monkeys. Hypothalamic FNDC5 and ERRA transcript levels are developmentally regulated in both male and female. We further uncovered sex-specific differences in FNDC5, ERRA and PGC1A expression in muscle and the reproductive axis. Moreover, irisin and ERRα co-localize in the marmoset hypothalamus. Additionally, in the arcuate nucleus of rhesus monkeys, the number of irisin+ cells was significantly increased in short-term fasted monkeys as compared to ad libitum-fed monkeys. More importantly, we observed putative interaction of irisin-immunoreactive fibers and few GnRH-immunoreactive cell bodies in the mediobasal hypothalamus of the rhesus monkeys. Functionally, we noted a stimulatory effect of irisin on GnRH synthesis and release in mouse hypothalamic neuronal GT1-7 cells. In summary, our findings show that FNDC5 and irisin are developmentally, metabolic-status dependently and sex-specifically expressed in the primate hypothalamic-pituitary-gonadal axis and exert a stimulatory effect on GnRH expression and release in mouse hypothalamic cells. Further studies are required to confirm the reproductive effects of irisin in vivo and to illuminate the mechanisms of its regulation.

Postcranial Skeletal Differences in Free-Range and Captive-Born Primates

Skeletal morphology is important in evolutionary, genetic, developmental, physiological, and functional studies. Although samples from free-ranging individuals may be preferable, constraints of sample size, demography, or conservation status may necessitate the inclusion of captive-born individuals. Captivity may be associated with physical, physiological, or behavioral differences that may affect skeletal form. This study assesses differences in postcranial skeletal form between free-range and captive-born Macaca mulatta and Saguinus oedipus. Samples included free-range M. mulatta from Cayo Santiago (Caribbean Primate Research Center) and captive-born macaques from the Wisconsin National Primate Research Center. S. oedipus samples included free-range born and captive-born individuals from the Oak Ridge Associated Universities Marmoset Research Center. Twenty-four dimensions of various bones, including the scapula, upper limb, innominate and lower limb, were recorded for adults. Age of epiphyseal closure was recorded for immature captive-born M. mulatta. Analysis of variance and principal component analyses tested significant differences between free-range born and captive-born individuals in each species. Significant differences were present in size and shape of postcrania between free-range and captive-born within taxa. Free-range macaques were larger than captive-born macaques, but this pattern did not consistently carry over to the Saguinus samples. Shape differences, while present throughout the skeleton, were especially prominent in the scapula. Differences in developmental timing, nutrition, and physical activity can be expected to contribute to the observed differences in postcranial skeletal form. These differences should be considered when captive-born primates are included in morphological or evolutionary studies. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc. Anat Rec, 302:761-774, 2019. © 2018 Wiley Periodicals, Inc.

PI3K signalling in leptin receptor cells: Role in growth and reproduction

Nutrition and growth are important signals for pubertal development, although how they are perceived and integrated in brain circuits has not been well defined. Growth hormones and metabolic cues both recruit phosphatidylinositol 3-kinase (PI3K) signalling in hypothalamic sites, although whether they converge into the same neuronal population(s) is also not known. In this review, we discuss recent findings from our laboratory showing the role of PI3K subunits in cells directly responsive to the adipocyte-derived hormone leptin in the coordination of growth, pubertal development and fertility. Mice with deletion of PI3K p110α and p110β catalytic subunits in leptin receptor cells (LR^Δα+β ) have a lean phenotype associated with increased energy expenditure, locomotor activity and thermogenesis. The LR^Δα+β mice also show deficient growth and delayed puberty. Deletion of a single subunit (ie, p110α) in LR cells (LR^Δα ) causes a similar phenotype of increased energy expenditure, deficient growth and delayed pubertal development, indicating that these functions are preferably controlled by p110α. The LR^Δα mice show enhanced leptin sensitivity in metabolic regulation but, remarkably, these mice are unresponsive to the effects of leptin on growth and puberty. PI3K is also recruited by insulin and a subpopulation of LR neurones is responsive to i.c.v. insulin administration. Deletion of insulin receptor in LR cells causes no changes in body weight or linear growth and induces only a mild delay in pubertal completion. Our findings demonstrate that PI3K in LR cells plays an essential role in growth and reproduction. We will also discuss the potential neural pathways underlying these effects.

Neuroanatomical Framework of the Metabolic Control of Reproduction

A minimum amount of energy is required for basic physiological processes, such as protein biosynthesis, thermoregulation, locomotion, cardiovascular function, and digestion. However, for reproductive function and survival of the species, extra energy stores are necessary. Production of sex hormones and gametes, pubertal development, pregnancy, lactation, and parental care all require energy reserves. Thus the physiological systems that control energy homeostasis and reproductive function coevolved in mammals to support both individual health and species subsistence. In this review, we aim to gather scientific knowledge produced by laboratories around the world on the role of the brain in integrating metabolism and reproduction. We describe essential neuronal networks, highlighting key nodes and potential downstream targets. Novel animal models and genetic tools have produced substantial advances, but critical gaps remain. In times of soaring worldwide obesity and metabolic dysfunction, understanding the mechanisms by which metabolic stress alters reproductive physiology has become crucial for human health.

Putative Effects of Obesity on Linear Growth and Puberty

Childhood obesity is a major public health problem that has grown to epidemic proportions throughout the world. Obesity is influenced by genetic and environmental factors. The nutritional status plays an important role in growth and body weight regulation. Excess adiposity during childhood can affect the process of growth and puberty. Obese children are frequently tall for their age, with accelerated epiphyseal growth plate maturation despite low growth hormone levels. Several regulatory hormones may affect the process of linear growth in the constellation of obesity, as high levels of insulin and leptin are observed in obese children. Leptin can act as a skeletal growth factor, with a direct effect on skeletal growth centers. The finding that overweight children, especially girls, tend to mature earlier than lean children has led to the hypothesis that the degree of body fatness may trigger the neuroendocrine events that lead to the onset of puberty. Leptin receptors have been identified in the hypothalamus, as well as in gonadotrope cells, ovarian follicular cells, and Leydig cells. The increased leptin and androgen levels seen in obese children may be implicated in their earlier onset of puberty and accelerated pubertal growth. This review is focused on the interaction between childhood obesity and growth and pubertal processes.
.

Changes in the Responsiveness of the Hypothalamic-Pituitary-Gonadal Axis to Kisspeptin-10 Administration during Pubertal Transition in Boys

In human, no studies are available regarding changes in kisspeptin1 receptor (KISS1R) sensitivity during pubertal transition. In this study, healthy boys were classified into 5 Tanner stages of puberty (n = 5/stage). Human kisspeptin-10 was administered to boys at each Tanner stage and to adult men (n = 5) as an IV bolus for comparison. Serial blood samples were collected for 30 min pre- and 120 min post-kisspeptin injection periods at 30 min interval for measuring plasma LH and testosterone levels. There was insignificant effect of kisspeptin on LH and testosterone levels in boys of Tanner stages I-III. At Tanner stage IV, the effect of kisspeptin on plasma LH was insignificant. However, a paired t-test on a log-transformed data showed a significant (P < 0.05) increase in mean peak post-kisspeptin testosterone level. In Tanner stage V, a significant (P < 0.05) increase was observed in mean post-kisspeptin peak LH level as compared to the mean basal LH value. Post-kisspeptin plasma testosterone levels were also significantly (P < 0.05) increased as compared to the pre-kisspeptin level in Tanner stage V. Our data suggest that sensitivity of KISS1R on GnRH neurons with reference to LH stimulation in boys develops during the later part of puberty reaching to adult level at Tanner stage V. This trial is registered with WHO International Clinical Trial Registration ID NCT03286517.

Estrogen Effects on the Mammary Gland in Early and Late Life and Breast Cancer Risk

A woman has an increased risk of breast cancer if her lifelong estrogen exposure is increased due to an early menarche, a late menopause, and/or an absence of childbearing. For decades, it was presumed that the number of years of exposure drove the increased risk, however, recent epidemiological data have shown that early life exposure (young menarche) has a more significant effect on cancer risk than late menopause. Thus, rather than the overall exposure it seems that the timing of hormone exposure plays a major role in defining breast cancer risk. In support of this, it is also known that aberrant hormonal exposure prior to puberty can also increase breast cancer risk, yet the elevated estrogen levels during pregnancy decrease breast cancer risk. This suggests that the effects of estrogen on the mammary gland/breast are age-dependent. In this review article, we will discuss the existing epidemiological data linking hormone exposure and estrogen receptor-positive breast cancer risk including menarche, menopause, parity, and aberrant environmental hormone exposure. We will discuss the predominantly rodent generated experimental data that confirm the association with hormone exposure and breast cancer risk, confirming its use as a model system. We will review the work that has been done attempting to define the direct effects of estrogen on the breast, which are beginning to reveal the mechanism of increased cancer risk. We will then conclude with our views on the most pertinent questions to be addressed experimentally in order to explore the relationship between age, estrogen exposure, and breast cancer risk.

Hypothesis: Irisin is a metabolic trigger for the activation of the neurohormonal axis governing puberty onset

A large body of data suggests that body weight influences puberty onset and adult reproduction. However, the underlying mechanism of how body weight influences puberty onset and fertility is not completely understood. The hypothalamic neuronal circuit regulating reproduction is restrained by inhibitory signals during childhood. At the time of puberty, these inhibitory signals are weakened and supplanted by stimulatory signals that, in turn, stimulate the release of gonadotropin-releasing hormone (GnRH) - a hypothalamic neuropeptide governing reproduction. A number of studies, however, suggest that puberty commencement occurs when body (fat) weight reaches a certain threshold, which is critical for the initiation of puberty and for support of the adult reproductive function. Previously, various signals have been studied which might link body (fat) weight-related information to the hypothalamic neuronal network regulating reproduction. However, the nature of the signal(s) that may link body fat and/or muscle mass with the hypothalamic neuronal network governing reproduction is still unclear. It has been intuitively speculated that augmentation of such signal(s) will cause a restriction of inhibitory input and activation of stimulatory input to GnRH secreting neurons at the time of puberty onset. Therefore, the unveiling of such signal(s) will greatly help in understanding the mechanism of puberty onset. Recently, it has been shown that expression of fibronectin type III domain containing-5 (FNDC5) mRNA in central and peripheral tissues upsurges during postnatal development, especially around the time of puberty onset. Moreover, the systemic level of irisin - one of the protein products of the FNDC5 gene that is secreted as myokine and adipokine - also rises during postnatal development and correlates with the timing of puberty onset. Therefore, we propose here that irisin might serve as a possible signal for linking body fat/muscle mass with the hypothalamic center governing reproductive function. We hypothesize that irisin acts as a trigger for the activation of the hypothalamic neuronal network monitoring the onset of puberty.

Endocrine assessment of ovarian cycle activity in wild female mountain gorillas (Gorilla beringei beringei)

Variability of fertility (i.e. number of births per female per year) has been reported in females of many primate species but only a few studies have explored the associated physiological and behavioral patterns. To investigate the proximate mechanisms of variability in fertility of wild female mountain gorillas (Gorilla beringei beringei), we quantified the occurrence of ovulation, matings, and successful pregnancies among females. We examined the profiles of immunoreactive pregnanediol-3-glucuronide (iPdG) for sixteen females (seven nulliparous and nine parous females, including one geriatric female; average sampling period for fecal sample collection and behavioral observations per female=175 days; SD=94 days, range=66-358 days) monitored by the staff of the Dian Fossey Gorilla Fund's Karisoke Research Center in Parc National des Volcans, Rwanda. We quantified ovarian cycles from iPdG profiles using an algorithm that we developed by adjusting the method of Kassam et al. (1996) to the characteristics of ovarian cycle profiles based on fecal hormone measurements. The mean length of ovarian cycles was 29±4 days (median: 28 days, N=13 cycles), similar to ovarian cycle lengths of other great apes and humans. As expected, we found that female mountain gorillas exhibit longer follicular phases (mean±SD: 21±3 days, N=13 cycles) than luteal phases (mean±SD: 8±3 days, N=13 cycles). We also found that the frequency of ovarian cycles was greater in parous females (i.e. 20 ovarian cycles across 44 periods of 28 days; 45.5%) than in nulliparous females (i.e. two ovarian cycles across 34 periods of 28 days; 6%). However, the frequency of days on which matings were observed did not differ significantly between parous and nulliparous females, nor between pregnant and non-pregnant females. Five pregnancies were detected with iPdG levels, but only three resulted in live births, indicating miscarriages of the other two. In sum, this study provides information on the underlying endocrine patterns of variation in fertility depending on parity, mating behavior, and pregnancy success in a critically endangered great ape.

The involvement of gonadotropin inhibitory hormone and kisspeptin in the metabolic regulation of reproduction

Recently, kisspeptin (KP) and gonadotropin inhibitory hormone (GnIH), two counteracting neuropeptides, have been acknowledged as significant regulators of reproductive function. KP stimulates reproduction while GnIH inhibits it. These two neuropeptides seem to be pivotal for the modulation of reproductive activity in response to internal and external cues. It is well-documented that the current metabolic status of the body is closely linked to its reproductive output. However, how reproductive function is regulated by the body's energy status is less clear. Recent studies have suggested an active participation of hypothalamic KP and GnIH in the modulation of reproductive function according to available metabolic cues. Expression of KISS1, the KP encoding gene, is decreased while expression of RFRP (NPVF), the gene encoding GnIH, is increased in metabolic deficiency conditions. The lower levels of KP, as suggested by a decrease in KISS1 gene mRNA expression, during metabolic deficiency can be corrected by administration of exogenous KP, which leads to an increase in reproductive hormone levels. Likewise, administration of RF9, a GnIH receptor antagonist, can reverse the inhibitory effect of fasting on testosterone in monkeys. Together, it is likely that the integrated function of both these hypothalamic neuropeptides works as a reproductive output regulator in response to a change in metabolic status. In this review, we have summarized literature from nonprimate and primate studies that demonstrate the involvement of KP and GnIH in the metabolic regulation of reproduction.

Neonatal amygdala lesions advance pubertal timing in female rhesus macaques

Social context influences the timing of puberty in both humans and nonhuman primates, such as delayed first ovulation in low-ranking rhesus macaques, but the brain region(s) mediating the effects of social context on pubertal timing are unknown. The amygdala is important for responding to social information and thus, is a potential brain region mediating the effects of social context on pubertal timing. In this study, female rhesus macaques living in large, species-typical, social groups received bilateral neurotoxic amygdala lesions at one month of age and pubertal timing was examined beginning at 14 months of age. Pubertal timing was affected in neonatal amygdala-lesioned females (Neo-A), such that they experienced significantly earlier menarche and first ovulation than did control females (Neo-C). Duration between menarche and first ovulation did not differ between Neo-A and Neo-C females, indicating earlier first ovulation in Neo-A females was likely a consequence of earlier menarche. Social rank of Neo-A females was related to age at menarche, but not first ovulation, and social rank was not related to either event in Neo-C females. It is more likely that amygdalectomy affects pubertal timing through its modulation of GABA-ergic mechanisms rather than as a result of the removal of a social-contextual inhibition on pubertal timing.

High-fat diet decreases the expression of Kiss1 mRNA and kisspeptin in the ovary, and increases ovulatory dysfunction in postpubertal female rats

BACKGROUND

Female reproductive health is noticeably compromised by obesity. The underlying mechanisms remain to be elucidated. Accumulating evidence indicates that the expression level of ovarian Kiss1 peaks in the afternoon during prooestrus, suggesting local regulatory roles for Kiss1 in the ovulatory process. We used a diet-induced model of obesity to evaluate whether the ovarian Kiss1 system is affected by obesity, and, to investigate the association of the Kiss1 system with ovulatory disorders in female rats.

METHODS

Post-weaning, female, Sprague-Dawley rats were randomly fed either a high-fat diet (HFD) or a normal chow diet (NCD) until they reached postnatal day 30 (PND 30), PND 42, or PND 70. The timing of vaginal opening was recorded, and oestrous cyclicity was monitored for 2 consecutive weeks immediately post puberty and again at 8-9 weeks of age. Tissues from the left ovary were collected for determination of the levels of Kiss1 and G protein-coupled receptor 54 (GPR54) mRNA, and tissues from the right ovary were collected for assessment of the immunoreactivity (IR) of the corresponding protein products, kisspeptin and GPR54.

RESULTS

The high-fat diet resulted in a significantly higher body weight and an earlier puberty onset. Oestrous cyclicity was disrupted by the HFD with significant reductions in the expression of ovulation-related genes. A marked suppression of ovarian Kiss1 mRNA levels was observed during prooestrus and oestrus at PND 42, and, during prooestrus, oestrus, and metoestrus at PND 70 in the HFD rats compared with the NCD controls. In the HFD group, the immunoreactivity of kisspeptin was significantly lower in theca cells from antral follicles during prooestrus and oestrus at PND 42, and, during prooestrus, oestrus at PND 70. At the prooestrus stage, in the HFD group the immunoreactivity of kisspeptin was also lower in the theca cells of preovulatory follicles at both PND 42 and PND 70.

CONCLUSIONS

Exposure of female rats to an post-weaning, high-fat diet has long-term deleterious effects on ovulation, that may involve down-regulation of ovarian Kiss1 mRNA and kisspeptin.

Uncovering steroidopathy in women with autism: a latent class analysis

Background

Prenatal exposure to increased androgens has been implicated in both polycystic ovary syndrome (PCOS) and autism spectrum conditions (ASC), suggesting that PCOS may be increased among women with ASC. One study suggested elevated steroidopathic symptoms (‘steroidopathy’) in women with ASC. As the symptoms are not independent, we conducted a latent class analysis (LCA). The objectives of the current study are: (1) to test if these findings replicate in a larger sample; and (2) to use LCA to uncover affected clusters of women with ASC.

Methods

We tested two groups of women, screened using the Autism Spectrum Quotient - Group 1: n = 415 women with ASC (mean age 36.39 ± 11.98 years); and Group 2: n = 415 controls (mean age 39.96 ± 11.92 years). All participants completed the Testosterone-related Medical Questionnaire online. A multiple-group LCA was used to identify differences in latent class structure between women with ASC and controls.

Results

There were significant differences in frequency of steroid-related conditions and symptoms between women with ASC and controls. A two-class semi-constrained model best fit the data. Based on response patterns, we identified the classes as ‘Typical’ and ‘Steroidopathic’. The prevalence of the ‘Steroidopathic’ class was significantly increased within the ASC group (ΔG² = 15, df =1, P = 0.0001). In particular, we confirmed higher frequencies of epilepsy, amenorrhea, dysmenorrhea, severe acne, gender dysphoria, and transsexualism, and differences in sexual preference in women with ASC.

Conclusions

Women with ASC are at increased risk for symptoms and conditions linked to steroids. LCA revealed this steroidopathy despite the apparent underdiagnosis of PCOS.

A critical view of the use of genetic tools to unveil neural circuits: the case of leptin action in reproduction

The remarkable development and refinement of the Cre-loxP system coupled with the nonstop production of new mouse models and virus vectors have impelled the growth of various fields of investigation. In this article, I will discuss the data collected using these genetic tools in our area of interest, giving specific emphasis to the identification of the neuronal populations that relay leptin action in reproductive physiology. A series of mouse models that allow manipulation of the leptin receptor gene have been generated. Of those, I will discuss the use of two models of leptin receptor gene reexpression (LepR(neo/neo) and LepR(loxTB/loxTB)) and one model of leptin signaling blockade (LepR(flox/flox)). I will also highlight the differences of using stereotaxic delivery of virus vectors expressing DNA-recombinases (Flp and Cre) and mouse models expressing Cre-recombinase. Our findings indicate that leptin action in the ventral premammillary nucleus is sufficient, but not required, for leptin action in reproduction and that leptin action in Kiss1 neurons arises after pubertal maturation; therefore, direct leptin signaling in Kiss1 neurons is neither required nor sufficient for the permissive action of leptin in pubertal development. It also became evident that the full action of leptin in the reproductive neuroendocrine axis requires the engagement of an integrated circuitry, yet to be fully unveiled.

Metabolic programming of puberty: sexually dimorphic responses to early nutritional challenges

Body energy stores and metabolic cues influence the onset of puberty. However, the pubertal impact of early nutritional challenges has been only fragmentarily addressed. We evaluated here the consequences, in terms of pubertal timing and hormonal markers, of various nutritional manipulations during pre- or postnatal maturation in rats of both sexes. Males and females were submitted to gestational undernutrition (UNG) or peripubertal (SUB) subnutrition or were raised in large (LL; underfeeding) or small (SL; overfeeding) litters. In addition, groups of UNG, LL, and SL rats were fed on a high-fat diet (HFD) after weaning. Postnatal overfeeding resulted in higher body weights (BWs) during pubertal transition in both sexes, but only SL males displayed overtly advanced external signs of puberty. Postnatal underfeeding persistently decreased BW gain during puberty, yet the magnitude of pubertal delay was greater in LL males. In contrast, regardless of postnatal nutrition, HFD tended to advance the onset of puberty in females but did not alter pubertal timing in males. Likewise, SUB females displayed a marked delay in BW gain and puberty onset, whereas despite similar reduction in BW, SUB males showed normal timing of puberty. These sex divergences were also detected in various hormonal and metabolic indices so that postnatal overnutrition consistently increased LH, FSH, leptin, and insulin levels only in pubertal females, whereas HFD decreased gonadotropin levels in SL females but increased them in SL males. Notably, UNG rats did not show signs of delayed puberty but displayed a striking sex dimorphism in serum insulin/glucose levels, regardless of the diet, so that only UNG males had signs of presumable insulin resistance. Our data disclose important sex differences in the impact of various early nutritional challenges on the timing of puberty, which may help to explain the different trends of altered puberty and related comorbidities between sexes.

Nonhuman primate models of polycystic ovary syndrome

With close genomic and phenotypic similarity to humans, nonhuman primate models provide comprehensive epigenetic mimics of polycystic ovary syndrome (PCOS), suggesting early life targeting for prevention. Fetal exposure to testosterone (T), of all nonhuman primate emulations, provides the closest PCOS-like phenotypes, with early-to-mid gestation T-exposed female rhesus monkeys exhibiting adult reproductive, endocrinological and metabolic dysfunctional traits that are co-pathologies of PCOS. Late gestational T exposure, while inducing adult ovarian hyperandrogenism and menstrual abnormalities, has less dysfunctional metabolic accompaniment. Fetal exposures to dihydrotestosterone (DHT) or diethylstilbestrol (DES) suggest androgenic and estrogenic aspects of fetal programming. Neonatal exposure to T produces no PCOS-like outcome, while continuous T treatment of juvenile females causes precocious weight gain and early menarche (high T), or high LH and weight gain (moderate T). Acute T exposure of adult females generates polyfollicular ovaries, while chronic T exposure induces subtle menstrual irregularities without metabolic dysfunction.

Environmental and social influences on neuroendocrine puberty and behavior in macaques and other nonhuman primates

This article is part of a Special Issue "Puberty and Adolescence". Puberty is the developmental period when the hypothalamic-pituitary-gonadal (HPG) axis is activated, following a juvenile quiescent period, and reproductive capacity matures. Although pubertal events occur in a consistent sequence, there is considerable variation between individuals in the onset and timing of pubertal events, with puberty onset occurring earlier in girls than in boys. Evidence in humans demonstrates that social and environmental context influences the timing of puberty onset and may account for some of the observed variation. This review analyzes the nonhuman primate literature, focusing primarily on rhesus macaques (Macaca mulatta), to examine the social and environmental influences on puberty onset, how these factors influence puberty in males and females, and to review the relationship between puberty onset of adult neuroendocrine function and sexual behavior. Social and environmental factors influence the timing of puberty onset and pubertal events in nonhuman primates, as in humans, and the influences of these factors differ for males and females. In nonhuman primates, gonadal hormones are not required for sexual behavior, but modulate the frequency of occurrence of behavior, with social context influencing the relationship between gonadal hormones and sexual behavior. Thus, the onset of sexual behavior is independent of neuroendocrine changes at puberty; however, there are distinct behavioral changes that occur at puberty, which are modulated by social context. Puberty is possibly the developmental period when hormonal modulation of sexual behavior is organized, and thus, when social context interacts with hormonal state to strongly influence the expression of sexual behavior.

Beware of primate life history data: a plea for data standards and a repository

Life history variables such as the age at first reproduction and the interval between consecutive births are measures of investment in growth and reproduction in a particular population or species. As such they allow for meaningful comparisons of the speed of growth and reproduction between species and between larger taxa. Especially in primates such life history research has far reaching implications and has led for instance to the "grandmother hypothesis". Other links have been proposed with respect to dietary adaptations: Because protein is essential for growth and one of the primary sources of protein, leaves, occurs much less seasonally than fruits, it has been predicted that folivorous primates should grow faster compared to frugivorous ones. However, when comparing folivorous Asian colobines with frugivorous Asian macaques we recently documented a longer, instead of a shorter gestation length in folivores while age at first reproduction and interbirth interval did not differ. This supports earlier findings for Malagasy lemurs in which all life history variables tested were significantly longer in folivores compared to frugivores. Wondering why these trends were not apparent sooner, we tried to reconstruct our results for Asian primates with data from four popular life history compilations. However, this attempt failed; even the basic, allometric relationship with adult female body mass that is typical for life history variables could not be recovered. This negative result hints at severe problems with data quality. Here we show that data quality can be improved significantly by standardizing the variables and by controlling for factors such as nutritional conditions or infant mortality. Ideally, in the future, revised primate life history data should be collated in a central database accessible to everybody. In the long run such an initiative should be expanded to include all mammalian species.

Dietary lipid and cholesterol induce ovarian dysfunction and abnormal LH response to stimulation in rabbits

BACKGROUND/AIM

Excess of fat intake is dramatically increasing in women of childbearing age and results in numerous health complications, including reproductive disorders. Using rabbit does as a biomedical model, the aim of this study was to evaluate onset of puberty, endocrine responses to stimulation and ovarian follicular maturation in females fed a high fat high cholesterol diet (HH diet) from 10 weeks of age (i.e., 2 weeks before normal onset of puberty) or a control diet (C diet).

METHODOLOGY/PRINCIPAL FINDINGS

Three experiments were performed, each including 8 treated (HH group) and 8 control (C group) does. In experiment 1, the endocrine response to Gonadotropin releasing hormone (GnRH) was evaluated at 13, 18 and 22 weeks of age. In experiment 2, the follicular population was counted in ovaries of adult females (18 weeks of age). In experiment 3, the LH response to mating and steroid profiles throughout gestation were evaluated at 18 weeks of age. Fetal growth was monitored by ultrasound and offspring birth weight was recorded. Data showed a significantly higher Luteinizing hormone (LH) response after induction of ovulation at 13 weeks of age in the HH group. There was no difference at 18 weeks, but at 22 weeks, the LH response to GnRH was significantly reduced in the HH group. The number of atretic follicles was significantly increased and the number of antral follicles significantly reduced in HH does vs. controls. During gestation, the HH diet induced intra-uterine growth retardation (IUGR).

CONCLUSION

The HH diet administered from before puberty onwards affected onset of puberty, follicular growth, hormonal responses to breeding and GnRH stimulation in relation to age and lead to fetal IUGR.

Leptin signaling in Kiss1 neurons arises after pubertal development

The adipocyte-derived hormone leptin is required for normal pubertal maturation in mice and humans and, therefore, leptin has been recognized as a crucial metabolic cue linking energy stores and the onset of puberty. Several lines of evidence have suggested that leptin acts via kisspeptin expressing neurons of the arcuate nucleus to exert its effects. Using conditional knockout mice, we have previously demonstrated that deletion of leptin receptors (LepR) from kisspeptin cells cause no puberty or fertility deficits. However, developmental adaptations and system redundancies may have obscured the physiologic relevance of direct leptin signaling in kisspeptin neurons. To overcome these putative effects, we re-expressed endogenous LepR selectively in kisspeptin cells of mice otherwise null for LepR, using the Cre-loxP system. Kiss1-Cre LepR null mice showed no pubertal development and no improvement of the metabolic phenotype, remaining obese, diabetic and infertile. These mice displayed decreased numbers of neurons expressing Kiss1 gene, similar to prepubertal control mice, and an unexpected lack of re-expression of functional LepR. To further assess the temporal coexpression of Kiss1 and Lepr genes, we generated mice with the human renilla green fluorescent protein (hrGFP) driven by Kiss1 regulatory elements and crossed them with mice that express Cre recombinase from the Lepr locus and the R26-tdTomato reporter gene. No coexpression of Kiss1 and LepR was observed in prepubertal mice. Our findings unequivocally demonstrate that kisspeptin neurons are not the direct target of leptin in the onset of puberty. Leptin signaling in kisspeptin neurons arises only after completion of sexual maturation.

Control of puberty: genetics, endocrinology, and environment

PURPOSE OF REVIEW

The aim of this review is to summarize recent advances regarding the genetic components of the complex and coordinated process of puberty, an update of the genes implicated in disorders of puberty, the endocrinologic changes of puberty, and influences of environment in the light of our current understanding of the mechanism of the onset of puberty.

RECENT FINDINGS

The timing of puberty varies greatly in the general population among ethnic groups throughout the world, suggesting the genetic control of puberty. Several studies on the pathological conditions of pubertal onset provide unique information about the interactions of either the genetic susceptibility of or environmental influences on hypothalamic control of pubertal onset. However, these findings suggested that no isolated pathway or external factor is solely responsible for the neuroendocrine control of puberty.

SUMMARY

Puberty is initiated by gonadotropin-releasing hormone from the hypothalamus followed by a complex sequence of endocrine changes and is regulated by both genetic and environmental factors. New attempts to use genetics and genomics might enhance our understanding of the spectrum of pubertal development.

The effects of kisspeptin on gonadotropin release in non-human mammals

The Kiss1 gene encodes a 145-amino acid pre-peptide, kisspeptin, which is cleaved into smaller peptides of 54, 14, 13, and 10 amino acids. This chapter reviews in detail the effects of kisspeptin on gonadotropin secretion in non-human mammals. Studies of kisspeptin's effects have included both acute and chronic administration regimens via a number of administration routes. Acute kisspeptin stimulates gonadotropin secretion in a wide range of species of non-human mammals, including rats, mice, hamsters, sheep, pigs, goats, cows, horses, and monkeys. In general, the stimulatory effect of kisspeptin treatment is more pronounced for LH than FSH secretion. Kisspeptin is thought to exert its stimulatory effects on LH and FSH release via stimulation of GnRH release from the hypothalamus, since pre--administration of a GnRH antagonist prevents kisspeptin's stimulation of gonadotropin secretion. Although the kisspeptin receptor is also expressed on anterior pituitary cells of some species, and incubation of anterior pituitary cells with high concentrations of kisspeptin can stimulate in vitro LH release, the contribution of direct effects of kisspeptin on the pituitary is thought to be negligible in vivo. Continuous kisspeptin administration results in reduced sensitivity to the effects of kisspeptin, in some species. This desensitization is thought to occur at the level of the kisspeptin receptor, since the response of the pituitary gland to exogenous GnRH is maintained. Overall, the findings discussed in this chapter are invaluable to the understanding of the reproductive role of kisspeptin and the potential therapeutic uses of kisspeptin for the treatment of fertility disorders.

Social and emotional predictors of the tempo of puberty in female rhesus monkeys

A cascade of neuroendocrine events regulates the initiation and progression of female puberty. However, the factors that determine the timing of these events across individuals are still uncertain. While the consequences of puberty on subsequent emotional development and adult behavior have received significant attention, what is less understood are the social and environmental factors that actually alter the initiation and progression of puberty. In order to more fully understand what factors influence pubertal timing in females, the present study quantified social and emotional behavior; stress physiology; and growth and activity measures in juvenile female rhesus monkeys to determine what best predicts eventual puberty. Based on previous reports, we hypothesized that increased agonistic behavior resulting from subordinate status in their natal group, in combination with slowed growth, reduced prosocial behavior, and increased emotional reactivity would predict delayed puberty. The analyses were restricted to behavioral and physiological measures obtained prior to the onset of puberty, defined as menarche. Together, our findings indicate that higher rates of aggression but lower rates of submission received from group mates; slower weight gain; and greater emotional reactivity, evidenced by higher anxiety, distress and appeasing behaviors, and lower cortisol responsivity in response to a potentially threatening situation, predicts delayed puberty. Together the combination of these variables accounted for 58% of the variance in the age of menarche, 71% in age at first ovulation, and 45% in the duration of adolescent sterility. While early puberty may be more advantageous for the individual from a fertility standpoint, it presents significant health risks, including increased risk for a number of estrogen dependent cancers and as well as the emergence of mood disorders during adulthood. On the other hand, it is possible that increased emotional reactivity associated with delayed puberty could persist, increasing the risk for emotional dysregulation to socially challenging situations. The data argue for prospective studies that will determine how emotional reactivity shown to be important for pubertal timing is affected by early social experience and temperament, and how these stress-related variables contribute to body weight accumulation, affecting the neuroendocrine regulation of puberty.

Kisspeptin and puberty in mammals

Since the discovery of the G-protein coupled receptor 54 (kisspeptin receptor) and its ligand, kisspeptin, our understanding of the neurobiological mechanisms that govern the pituitary-gonadal axis has evolved dramatically. In this chapter, we have reviewed progress regarding the relationship between kisspeptin and puberty, and have proposed a novel hypothesis for the role of kisspeptin signaling in the onset of this crucial developmental event. According to this hypothesis, although kisspeptin neurons in the arcuate nucleus (ARC) are critical for puberty, this is simply because these cells are an integral component of the hypothalamic GnRH pulse generating mechanism that drives intermittent release of the decapeptide, as an increase in GnRH is obligatory for the onset of puberty. In our model, ARC kisspeptin neurons play no "regulatory" role in controlling the timing of puberty. Rather, as a component of the neural network responsible for GnRH pulse generation, they subserve upstream regulatory mechanisms that are responsible for the timing of puberty.

Cordyceps sinensis biomass produced by submerged fermentation in high-fat diet feed rats normalizes the blood lipid and the low testosterone induced by diet

This study investigated the effect of Cordyceps sinensis biomass supplementation obtained from submerged fermentation on blood lipid and low testosterone induced by high-fat diet (HFD). The experiments were carried out using a long-term intake of HFD and HFD plus Simvastatin or C. sinensis (4 months). Our results show that plasma cholesterol, triglycerides and LDL were decreased by Cordyceps sinensis biomass supplementation (CSBS). A long-term intake of HFD caused a significant liver damage which has been reverted by CSBS. CSBS normalized decreasing testosterone levels observed in high-fat diet feed rats. All these findings lead us to suggest that C. sinensis was able to decrease blood lipid concentration, increase hepatoprotective activity and normalize testosterone levels.

Peripubertal-onset but not adult-onset obesity increases IGF-I and drives development of lean mass, which may lessen the metabolic impairment in adult obesity

It has been suggested that adult metabolic dysfunction may be more severe in individuals who become obese as children compared with those who become obese later in life. To determine whether adult metabolic function differs if diet-induced weight gain occurs during the peripubertal age vs. if excess weight gain occurs after puberty, male C57Bl/6J mice were fed a low-fat (LF; 10% kcal from fat) or high-fat (HF; 60% kcal from fat) diet starting during the peripubertal period (pHF; 4 wk of age) or as adults (aHF; 12 wk of age). Both pHF and aHF mice were hyperinsulinemic and hyperglycemic, and both showed impaired glucose tolerance and insulin resistance compared with their LF-fed controls. However, despite a longer time on diet, pHF mice were relatively more insulin sensitive than aHF mice, which was associated with higher lean mass and circulating IGF-I levels. In addition, HF feeding had an overall stimulatory effect on circulating corticosterone levels; however, this rise was associated only with elevated plasma ACTH in the aHF mice. Despite the belief that adult metabolic dysfunction may be more severe in individuals who become obese as children, data generated using a diet-induced obese mouse model suggest that adult metabolic dysfunction associated with peripubertal onset of obesity is not worse than that associated with adult-onset obesity.

Leptin signaling and circuits in puberty and fertility

Leptin is an adipocyte-derived hormone involved in a myriad of physiological process, including the control of energy balance and several neuroendocrine axes. Leptin-deficient mice and humans are obese, diabetic, and display a series of neuroendocrine and autonomic abnormalities. These individuals are infertile due to a lack of appropriate pubertal development and inadequate synthesis and secretion of gonadotropins and gonadal steroids. Leptin receptors are expressed in many organs and tissues, including those related to the control of reproductive physiology (e.g., the hypothalamus, pituitary gland, and gonads). In the last decade, it has become clear that leptin receptors located in the brain are major players in most leptin actions, including reproduction. Moreover, the recent development of molecular techniques for brain mapping and the use of genetically modified mouse models have generated crucial new findings for understanding leptin physiology and the metabolic influences on reproductive health. In the present review, we will highlight the new advances in the field, discuss the apparent contradictions, and underline the relevance of this complex physiological system to human health. We will focus our review on the hypothalamic circuitry and potential signaling pathways relevant to leptin’s effects in reproductive control, which have been identified with the use of cutting-edge technologies of molecular mapping and conditional knockouts.

Tonic control of kisspeptin release in prepubertal monkeys: implications to the mechanism of puberty onset

Previously we have shown that a reduction in γ-amino butyric acid (GABA) inhibition is critical for the mechanism initiating puberty onset because chronic infusion of the GABA(A) receptor antagonist, bicuculline, significantly increased GnRH release and accelerated the timing of menarche and first ovulation in female rhesus monkeys. Because previous studies in our laboratory indicate that in prepubertal female monkeys, kisspeptin release in the medial basal hypothalamus is low, whereas kisspeptin-10 can stimulate GnRH release, we hypothesized that a low level of kisspeptin release prior to puberty onset is due to tonic GABA inhibition. To test this hypothesis we examined the effects of bicuculline infusion on kisspeptin release using a microdialysis method. We found that bicuculline at 1 μM dramatically stimulates kisspeptin release in the medial basal hypothalamus of prepubertal monkeys but had little effect on kisspeptin release in midpubertal monkeys. We further examined whether bicuculline-induced GnRH release is blocked by the presence of the kisspeptin antagonist, peptide 234. We found that inhibition of kisspeptin signaling blocked the bicuculline-induced stimulation of GnRH release, suggesting that kisspeptin neurons may relay inhibitory GABA signals to GnRH neurons. This implies that a reduction in tonic GABA inhibition of GnRH release is, at least in part, mediated through kisspeptin neurons.