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.

The paraventricular nucleus of the hypothalamus - the concertmaster of autonomic control. Focus on blood pressure regulation

The autonomic nervous system regulates internal organs and peripheral circulation, which enables the maintenance of homeostasis in vertebrate species. One of the brain regions involved in autonomic and endocrine homeostasis regulation is the paraventricular nucleus of the hypothalamus (PVN). The PVN is a unique site at which multiple input signals can be assessed and integrated. The regulation of the autonomic system by the PVN and, especially, the sympathetic flow, depends upon the integration of inhibitory and excitatory neurotransmitter action. The excitatory neurotransmitters such as glutamate and angiotensin II, and inhibitory neurotransmitters such as γ‑aminobutyric acid and nitric oxide, play a key role in the physiological function of the PVN. Moreover, arginine-vasopressin (AVP) and oxytocin (OXT) are important in the regulation of sympathetic system activity. The PVN is also crucial for maintaining cardiovascular regulation, with its integrity being pivotal for blood pressure regulation. Studies have shown that pre‑autonomic sympathetic PVN neurons increase blood pressure and the dysfunction of these neurons is directly related to elevated sympathetic nervous system activity under hypertension. Etiology of hypertension in patients is not fully known. Thus, understanding the role of PVN in the generation of hypertension may help to treat this cardiovascular disease. This review focuses on the PVN's inhibitory and excitatory neurotransmitter interactions that regulate sympathetic system activity in physiological conditions and hypertension.

DNA hypermethylation of Kiss1r promoter and reduction of hepatic Kiss1r in female rats with type 2 diabetes

Kisspeptin, produced from the brain and peripheral tissues, may constitute an important link in metabolic regulation in response to external cues, such as diet. The kisspeptin system is well described in the brain. However, its function and regulation in the peripheral tissues, especially in relation to metabolic disease and sex differences, remain to be elucidated. As Kiss1 and Kiss1r, encoding for kisspeptin and kisspeptin receptors, respectively, are altered by overnutrition/fasting and regulated by DNA methylation during puberty and cancer, epigenetic mechanisms in metabolic disorders are highly probable. In the present study, we experimentally induced type 2 diabetes mellitus (DM2) in female Wistar rats using high-fat diet/streptozocin. We analysed expression and DNA methylation of Kiss1 and Kiss1r in the peripheral tissues, using quantitative-reverse-transcription PCR (qRT-PCR) and pyrosequencing. We discovered differential expression of Kiss1 and Kiss1r in peripheral organs in DM2 females, as compared with healthy controls, and the profile differed from patterns reported earlier in males. DM2 in females was linked to the increased Kiss1 mRNA in the liver and increased Kiss1r mRNA in the liver and adipose tissue. However, Kiss1r promoter was hypermethylated in the liver, suggesting gene silencing. Indeed, the increase in DNA methylation of Kiss1r promoter was accompanied by a reduction in Kiss1r protein, implying epigenetic or translational gene repression. Our results deliver novel evidence for tissue-specific differences in Kiss1 and Kiss1r expression in peripheral organs in DM2 females and suggest DNA methylation as a player in regulation of the hepatic kisspeptin system in DM2.

Similar Trajectories in Current Alcohol Consumption and Tick-Borne Diseases: Only Parallel Changes in Time or Links Between?

In a modern world, both tick-borne diseases and alcohol consumption are among major public health threats. In the present opinion article, we pose the question, whether these two health problems: alcohol consumption and tick-borne diseases prevalence can be related. We hypothesize that it is possible due to at least three factors: outdoor places chosen for alcohol consumption, behavioral changes induced by alcohol, and possible stronger attraction of human hosts after alcohol consumption to ticks. Many important clues are coming from social studies about people’s preference of places to consume alcohol and from studies regarding the attraction of people consuming alcohol to mosquitos. These data, however, cannot be directly transferred to the case of alcohol consumption and ticks. Therefore, we suggest that more detailed studies are needed to better understand the possible individual attractiveness of people to ticks and ways alcohol may influence it.

Animal Foetal Models of Obesity and Diabetes - From Laboratory to Clinical Settings

The prenatal period, during which a fully formed newborn capable of surviving outside its mother's body is built from a single cell, is critical for human development. It is also the time when the foetus is particularly vulnerable to environmental factors, which may modulate the course of its development. Both epidemiological and animal studies have shown that foetal programming of physiological systems may alter the growth and function of organs and lead to pathology in adulthood. Nutrition is a particularly important environmental factor for the pregnant mother as it affects the condition of offspring. Numerous studies have shown that an unbalanced maternal metabolic status (under- or overnutrition) may cause long-lasting physiological and behavioural alterations, resulting in metabolic disorders, such as obesity and type 2 diabetes (T2DM). Various diets are used in laboratory settings in order to induce maternal obesity and metabolic disorders, and to alter the offspring development. The most popular models are: high-fat, high-sugar, high-fat-high-sugar, and cafeteria diets. Maternal undernutrition models are also used, which results in metabolic problems in offspring. Similarly to animal data, human studies have shown the influence of mothers' diets on the development of children. There is a strong link between the maternal diet and the birth weight, metabolic state, changes in the cardiovascular and central nervous system of the offspring. The mechanisms linking impaired foetal development and adult diseases remain under discussion. Epigenetic mechanisms are believed to play a major role in prenatal programming. Additionally, sexually dimorphic effects on offspring are observed. Therefore, further research on both sexes is necessary.

Obesity is associated with increased level of kisspeptin in mothers' blood and umbilical cord blood - a pilot study

OBJECTIVE

Kisspeptin (KP) is a major regulator of reproductive functions. It has also been shown to be involved in the metabolic changes associated with obesity. According to the well-established concept of prenatal programming, environmental factors can influence physiological and behavioral systems at the early stages of development. Thus, we hypothesized that in pregnant women, obesity can be associated with alterations in the levels of KP. We also assumed that the observed changes in obese mothers' blood (MB) would be reflected in the umbilical cord blood (CB).

MATERIALS AND METHODS

We collected MB and CB from obese and nonobese women and analyzed the differences in metabolic and hormonal profiles, including KP concentration, using commercially available assays.

RESULTS

We found that the level of KP was increased in the MB and CB of obese patients compared to nonobese subjects (p<0.05). A strong correlation was observed between the concentration of KP in MB and CB (r=0.8343; p<0.01). Moreover, we detected that the differences in the adipokine profile observed in the MB were not reflected in CB.

CONCLUSIONS

Our results indicate that blood KP concentration can serve as a valuable marker in pregnant women. However, further studies are needed to understand the alterations of this peptide in obese pregnant woman and their potential effects on offspring.

Two weeks of moderate intensity locomotor training increased corticosterone concentrations but did not alter the number of adropin-immunoreactive cells in the hippocampus of diabetic type 2 and control rats

Adropin (ADR) plays a role in metabolism regulation and its alterations in obesity and diabetes have been found. Treatment with ADR was beneficial in metabolic diseases, and physical exercise increased ADR concentrations in obese patients. However, data on the distribution of ADR in the brain are sparse. The role of metabolic status and physical exercise on its expression in the brain is undiscovered. We hypothesized that diabetes type 2 (DM2) and/or exercise will alter number of ADR-immunoractive (-ir) cells in the rat brain. Animals were divided into groups: diabetes type 2 (receiving high-fat diet and injections of streptozotocin) and control (fed laboratory chow diet; C). Rats were further divided into: running group (2 weeks of forced exercise on a treadmill) and non-running group. Body mass, metabolic and hormonal profiles were assessed. Immunohistochemistry was run to study ADR-ir cells in the brain. We found that: 1) in DM2 animals, running decreased insulin and increased glucose concentrations; 2) in C rats, running decreased insulin concentrations and had no effect on glucose concentration in blood; 3) running increased corticosterone (CORT) concentrations in DM2 and C rats; 4) ADR-ir cells were detected in the hippocampus and ADR-ir fibers in the arcuate nucleus of the hypothalamus, which is a novel location; 5) metabolic status and running, however, did not change number of these cells. We concluded that 2 weeks of forced moderate intensity locomotor training induced stress response present as increased concentration of CORT and did not influence number of ADR-ir cells in the brain.

Effects of Ovariectomy and Sex Hormone Replacement on Numbers of Kisspeptin-, Neurokinin B- and Dynorphin A-immunoreactive Neurons in the Arcuate Nucleus of the Hypothalamus in Obese and Diabetic Rats

KNDy neurons co-expressing kisspeptin (KP), neurokinin B (NKB) and dynorphin A (DYN A) in the arcuate nucleus of the hypothalamus (ARC) are key regulators of reproduction. Their activity is influenced by metabolic and hormonal signals. Previously, we have shown that orchidectomy alters the KP-, NKB-, and DYN A-immunoreactivity in the high-fat diet-induced (HFD) obesity and diabetes type 2 (DM2) models. Considering the potential sex difference in the response of KNDy neurons, we have hypothesized that ovariectomy (OVX) and post-ovariectomy replacement with estradiol (OVX+E₂) or estradiol and progesterone (OVX+E₂+P₄) will also affect these neurons in HFD and DM2 females. Thus, each of these treatment protocols were employed for control, HFD, and DM2 groups of rats leading to nine experimental conditions within which we have determined the number of KP-, NKB-, or DYN-immunoreactive (-ir) neurons and assessed the metabolic and hormonal profiles of the animals. Accordingly: (1) no effects of group and surgery were observed on the number of KP-ir neurons; (2) the overall number of NKB-ir neurons was higher in the OVX+E₂+P₄ and OVX+E₂ animals compared to OVX; (3) overall, the number of DYN A-ir neurons was higher in DM2 vs. control group, and surgery had an effect on the number of DYN A-ir neurons; (4) the metabolic and hormonal profiles were altered in HFD and DM2 animals compared to controls. Current data together with our previously published results indicate sex-specific differences in the response of KNDy neurons to DM2.

Neuroanatomical connections between kisspeptin neurones and somatostatin neurones in female and male rat hypothalamus: a possible involvement of SSTR1 in kisspeptin release

Somatostatin (SST) a neuropeptide involved in the central modulation of several physiological functions, is co-distributed in the same hypothalamic areas as kisspeptin (KP), the most potent secretagogue of the gonadotropin-releasing hormone (GnRH) secretion known to date. As SST infused intracerebroventricularly (icv) evoked a potent inhibition of GnRH release, we explored neuroanatomical relationships between KP and SST populations in male and female rats. For that, intact males and ovariectomised oestradiol-replaced females were killed and their brains processed in order to simultaneously detect KP, SST and synapsin, a marker for synapses. We observed numerous appositions of KP on SST neurones both in female and male arcuate nucleus (ARC) and ventromedial hypothalamus. A large association between SST terminals and KP neurones at the level of the pre-optic area (POA) was also observed in female rats and in a more limited frame in males. Finally, most KP neurones from the ARC showed SST appositions in both sexes. To determine whether SST could affect KP cell activity, we assessed whether SST receptors (SSTR) were present on KP neurones in the ARC. We also looked for the presence of SSTR1 and SSTR2A in the brain of male rats. Brains were processed through a sequential double immunocytochemistry in order to detect KP and SSTR1 or KP and SSTR2A. We observed overlapping distributions of immunoreactive neurones for SSTR1 and KP and counted approximately one third of KP neurones with SSTR1. In contrast, neurones labelled for SSTR2A or KP were often juxtaposed in the ARC and the occurrence of double-labelled neurones was sporadic (<5%). These results suggest that SST action on KP neurones would pass mainly through SSTR1 at the level of the ARC. This article is protected by copyright. All rights reserved.

Kisspeptin and Metabolism: The Brain and Beyond

Apart from the well-established role of kisspeptin (Kp) in the regulation of reproductive functions, recent data described its action in the control of metabolism. Of particular interest for the review is the population of Kp neurons localized in the arcuate nucleus (ARC) of the hypothalamus, the site of the brain where reproductive and metabolic cross talk occurs. However, within the hypothalamus Kp does not work alone, but rather interacts with other neuropeptides, e.g., neurokinin B, dynorphin A, proopiomelanocortin, the cocaine- and amphetamine-regulated transcript, agouti-related peptide, and neuropeptide Y. Beyond the brain, Kp is expressed in peripheral tissues involved in metabolic functions. In this review, we will mainly focus on the local action of this peptide in peripheral organs such as the pancreas, liver, and the adipose tissue. We will concentrate on dysregulation of the Kp system in cases of metabolic imbalance, e.g., obesity and diabetes. Importantly, these patients besides metabolic health problems often suffer from disruptions of the reproductive system, manifested by abnormalities in menstrual cycles, premature child birth, miscarriages in women, decreased testosterone levels and spermatogenesis in men, hypogonadism, and infertility. We will review the evidence from animal models and clinical data indicating that Kp could serve as a promising agent with clinical applications in regulation of reproductive problems in individuals with obesity and diabetes. Finally, emerging data indicate a role of Kp in regulation of insulin secretion, potentially leading to development of further therapeutic uses of this peptide to treat metabolic problems in patients with these lifestyle diseases.

GnRH Neurons Provide Direct Input to Hypothalamic Tyrosine Hydroxylase Immunoreactive Neurons Which Is Maintained During Lactation

Gonadotropin releasing hormone (GnRH) neurons provide neuronal input to the preoptic area (POA) and the arcuate nucleus (Arc), two regions involved critically in the regulation of neuroendocrine functions and associated behaviors. These areas contain tyrosine hydroxylase immunoreactive (TH-IR) neurons, which play location-specific roles in the neuroendocrine control of both the luteinizing hormone and prolactin secretion, as well as, sexually motivated behaviors. Concerning changes in the activity of GnRH neurons and the secretion pattern of GnRH seen under the influence of rising serum estrogen levels and during lactation, we tested the hypothesis that the functional state of GnRH neurons is mediated via direct synaptic connections to TH-IR neurons in the POA and Arc. In addition, we examined putative changes of these inputs in lactating mice and in mothers separated from their pups. Confocal microscopic and pre-embedding immunohistochemical studies on ovariectomized mice treated with 17β-estradiol (OVX+E2) provided evidence for direct appositions and asymmetric synapses between GnRH-IR fiber varicosities and TH-IR neurons in the POA and the Arc. As TH co-localizes with kisspeptin (KP) in the POA, confocal microscopic analysis was continued on sections additionally labeled for KP. The TH-IR neurons showed a lower level of co-labeling for KP in lactating mice compared to OVX+E2 mice (16.1 ± 5% vs. 57.8 ± 4.3%). Removing the pups for 24 h did not alter significantly the KP production in TH-IR neurons (17.3 ± 4.6%). The mean number of GnRH-IR varicosities on preoptic and arcuate TH cells did not differ in the three animal models investigated. This study shows evidence that GnRH neurons provide direct synaptic inputs to POA and Arc dopaminergic neurons. The scale of anatomical connectivity with these target cells was unaltered during lactation indicating a maintained GnRH input, inspite of the altered hormonal condition.

Kisspeptin-10 inhibits proliferation and regulates lipolysis and lipogenesis processes in 3T3-L1 cells and isolated rat adipocytes

INTRODUCTION

Kisspeptin, which is encoded by the KISS1 gene and acts via GPR54, plays a role in the regulation of reproductive functions. Expression of KISS1 and GRPR54 has been found in peripheral tissues, including adipose tissue, and was shown to be influenced by metabolic status.

PURPOSE

We hypothesized that kisspeptin could be involved in regulation of lipid metabolism in the mouse 3T3-L1 cell line and in isolated rat adipocytes.

METHODS

First, we characterized expression profiles of KISS1 and GPR54 mRNA and proteins in adipose cells isolated from male rats. Secondly, we studied the effects of kisspeptin-10 on cell proliferation and survival in 3T3-L1 cells. Thirdly, we assessed the rapid action of kisspeptin-10 on lipid metabolism and glucose uptake using 3T3-L1 cells and rat primary adipocytes. Finally, we examined the effects of kisspeptin-10 on the secretion of leptin and adiponectin in rat adipocytes.

RESULTS

We have found that: (1) KISS1 and GPR54 were expressed in mouse 3T3-L1 cells and isolated rat adipocytes; (2) kisspeptin-10: (i) inhibited cell proliferation, viability and adipogenesis in 3T3-L1 and decreased expression of PPAR-γ and CEBPβ-genes, which are involved in the differentiation processes and adipogenesis; (ii) increased lipolysis in 3T3-L1 cells and rat adipocytes by enhancing expression of periliphin and hormone-sensitive lipase; (iii) modulated glucose uptake and lipogenesis; (iv) stimulated leptin and decreased adiponectin secretion from rat adipocytes.

CONCLUSION

Kisspeptin-10 could play a role in the regulation of lipid metabolism in mouse 3T3-L1 cells and rat adipocytes.

Effects of Orchidectomy and Testosterone Replacement on Numbers of Kisspeptin-, Neurokinin B-, and Dynorphin A-Immunoreactive Neurones in the Arcuate Nucleus of the Hypothalamus in Obese and Diabetic Rats

Neurones expressing kisspeptin, neurokinin B and dynorphin A, located in the arcuate nucleus of the hypothalamus (ARC), are important regulators of reproduction. Their functions depend on metabolic and hormonal status. We hypothesised that male rats with high-fat diet-induced obesity (DIO) and/or streptozotocin-induced diabetes mellitus type 1 (DM1) and type 2 (DM2) will have alterations in numbers of immunoreactive (-IR) cells: kisspeptin-IR and/or neurokinin B-IR and dynorphin A-IR neurones in the ARC in the sham condition. In addition, orchidectomy alone (ORX) and with testosterone treatment (ORX+T) will unmask possible deficits in the response of these neurones in DIO, and/or DM1 and DM2 rats. Rats were assigned to four groups: a control (C) and one diabetic group (DM1) were fed a regular chow diet, whereas the obese group (DIO) and the other diabetic group (DM2) were fed a high-fat diet. To induce diabetes, streptozotocin was injected. After 6 weeks, each group was divided into three subgroups: ORX, ORX+T and sham. After another 2 weeks, metabolic and hormonal profiles were assessed and immunocytochemistry was performed. We found that: (1) under sham conditions: (i) DM1 and DM2 animals had higher numbers of kisspeptin-IR cells than controls and (ii) DM2 rats had increased numbers of neurokinin B-IR and dynorphin A-IR cells compared to C animals; (2) ORX and ORX+T treatments unmasked deficits of the studied neurones in DM1 and DM2 but not in DIO animals; and (3) DIO, DM1 and DM2 rats had altered metabolic and hormonal profiles, in particular decreased levels of testosterone. We concluded that alterations in numbers of kisspeptin-IR and neurokinin B-IR neurones in the ARC and their response to ORX and ORX+T may account for disruptions of metabolic and reproductive functions in diabetic but not in obese rats.

Effects of high-fat diet-induced obesity and diabetes on Kiss1 and GPR54 expression in the hypothalamic-pituitary-gonadal (HPG) axis and peripheral organs (fat, pancreas and liver) in male rats

Recent data indicates that kisspeptin, encoded by the KISS1 gene, could play a role in transducing metabolic information into the hypothalamic-pituitary-gonadal (HPG) axis, the mechanism that controls reproductive functions. Numerous studies have shown that in a state of negative energy balance, the hypothalamic kisspeptin system is impaired. However, data concerning positive energy balance (e.g. diabetes and obesity) and the role of kisspeptin in the peripheral tissues is scant. We hypothesized that: 1) in diet-induced obese (DIO) male rats and/or rats with diabetes type 1 (DM1) and type 2 (DM2), altered reproductive functions are related to an imbalance in Kiss1 and GPR54 mRNA in the HPG axis; and 2) in DIO and/or DM1 and/or DM2 rats, Kiss1 and GPR 54 expression are altered in the peripheral tissues involved in metabolic functions (fat, pancreas and liver). Animals were fed a high-fat or control diets and STZ (streptozotocin - toxin, which destroys the pancreas) was injected in high or low doses to induce diabetes type 1 (DM1) or diabetes type 2 (DM2), respectively. RT-PCR and Western blot techniques were used to assess the expression of Kiss1 and GRP54 in tissues. At the level of mRNA, we found that diabetic but not obese rats have alterations in Kiss1 and/or GPR54 mRNA levels in the HPG axis as well as in peripheral tissues involved in metabolic functions (fat, pancreas and liver). The most severe changes were seen in DM1 rats. However, in the case of protein levels in the peripheral tissues (fat, pancreas and liver), changes in Kiss1/GPR54 expression were noticed in DIO, DM1 and DM2 animals and were tissue-specific. Our data support the hypothesis that alterations in Kiss1/GPR54 balance may account for both reproductive and metabolic abnormalities reported in obese and diabetic rats.

Neuronal basis of reproductive dysfunctions associated with diet and alcohol: From the womb to adulthood

The theory that individuals are born as tabula rasa and that their knowledge comes from experience and perception is no longer true. Studies suggest that experience is gained as early as in the mother's womb. Moreover, environmental stressors like alcohol or inadequate diet can affect physiological systems such as the hypothalmic-pituitary-gonadal (HPG) axis. The effects of these stressors can manifest as alterations in sexual development and adult reproductive functions. In this review, we consider and compare evidence from animal models and human studies demonstrating the role of environmental stressors (alcohol and under- or overnutrition) on the HPG axis. We review the role of alcohol and inadequate diet in prenatal reproductive system programming and consider specific candidate neurons in the adult hypothalamus through which reproductive function is being regulated. Finally, we review evidence from animal studies on the role that alcohol and diet play in fertility and reproductive disorders. We conclude that in order to better understand reproductive failure in animals and humans we need to consider in utero development and pay more attention to early life experience when searching for the origins of reproductive diseases.

Prenatal alcohol exposure alters response of kisspeptin-ir neurons to estradiol and progesterone in adult female rats

BACKGROUND

Prenatal alcohol exposure (PAE) has adverse effects on reproductive function and hypothalamic-pituitary-gonadal (HPG) activity. Kisspeptin neurons play a role in mediating feedback effects of estradiol (E2 ) and progesterone (P4 ) on the HPG axis. We hypothesized that PAE will have long-term effects on the response of kisspeptin neurons to E2 and P4 .

METHODS

Adult female rats (53 to 58 days) from prenatal ad libitum-fed control (C), pair-fed (PF), and alcohol-exposed (PAE) groups were subjected to Sham ovariectomy (OVX) or OVX without or with replacement with low or high physiological levels of E2 and P4 , and terminated under basal conditions. E2 and P4 levels, and the response of kisspeptin-ir neurons in the arcuate (ARC) and anteroventral periventricular (AVPV) nuclei to these hormones, were measured. As the E2 signal is conveyed to kisspeptin neurons via estrogen receptor-α (ER-α), we investigated PAE effects on the number of kisspeptin-ir/ER-α-ir neurons. To determine whether PAE alters interactions between kisspeptin and gonadotropin-releasing hormone (GnRH) neurons, close contacts between kisspeptin-ir fibers and GnRH-ir cell bodies were examined.

RESULTS

Our data present the novel finding that kisspeptin-ir neurons in the ARC of PAE females show differential responses to E2 and to the combined treatment with E2 and P4 compared with controls: (i) OVX increased the number of kisspeptin-ir neurons in C and PF, but not PAE females compared with their Sham counterparts; (ii) E2 replacement restored kisspeptin-ir cell numbers to Sham levels in C and PF females but caused a robust down-regulation of kisspeptin-ir neurons below Sham levels in PAE females; (iii) OVX and replacement with high physiological concentrations of E2 resulted in fewer kisspeptin-ir cells in PAE than C females; (iv) OVX and replacement with high levels of both E2 and P4 markedly decreased the number of kisspeptin-ir neurons, below levels observed following E2 alone, in PF and C females, but had no significant effect in PAE females.

CONCLUSIONS

These data suggest that a possible mechanism underlying adverse effects of PAE on HPG function involves actions of alcohol on the kisspeptin system.

Insulin: its role in the central control of reproduction

Insulin has long been recognized as a key regulator of energy homeostasis via its actions at the level of the brain, but in addition, plays a role in regulating neural control of reproduction. In this review, we consider and compare evidence from animal models demonstrating a role for insulin for physiological control of reproduction by effects on GnRH/LH secretion. We also review the role that insulin plays in prenatal programming of adult reproduction, and consider specific candidate neurons in the adult hypothalamus by which insulin may act to regulate reproductive function. Finally, we review clinical evidence of the role that insulin may play in adult human fertility and reproductive disorders. Overall, while insulin appears to have a significant impact on reproductive neuroendocrine function, there are many unanswered questions regarding its precise sites and mechanisms of action, and their impact on developing and adult reproductive neuroendocrine function.

Prenatal alcohol exposure results in long-term serotonin neuron deficits in female rats: modulatory role of ovarian steroids

BACKGROUND

Previous studies on male rodents found that prenatal alcohol exposure (PAE) decreases the number of serotonin immunoreactive (5-HT-ir) neurons in the brainstem. However, data on the effects of PAE in females are lacking. In light of known sex differences in responsiveness of the 5-HT system and known effects of estrogen (E2 ) and progesterone (P4 ) in the brain, we hypothesized that sex steroids will modulate the adverse effects of PAE on 5-HT neurons in adult females.

METHODS

Adult females from 3 prenatal groups (Prenatal alcohol-exposed [PAE], Pair-fed [PF], and ad libitum-fed Controls [C]) were ovariectomized (OVX), with or without hormone replacement, or underwent Sham OVX. 5-HT-ir cells were examined in key brainstem areas.

RESULTS

Our data support the hypothesis that PAE has long-term effects on the 5-HT system of females and that ovarian steroids have a modulatory role in these effects. Intact (Sham OVX) PAE females had marginally lower numbers of 5-HT-ir neurons in the dorsal raphe nucleus of the brainstem compared with PF and C females. This marginal difference became significant following removal of hormones by OVX. Replacement with E2 restored the number of 5-HT-ir neurons in PAE females to control levels, while P4 reversed the effects of E2 . Importantly, despite these differential responses of the 5-HT system to ovarian steroids, there were no differences in E2 and P4 levels among prenatal treatment groups.

CONCLUSIONS

These data demonstrate long-term, adverse effects of PAE on the 5-HT system of females, as well as differential sensitivity of PAE compared with control females to the modulatory effects of ovarian steroids on 5-HT neurons. Our findings have important implications for understanding sex differences in 5-HT dysfunction in depression/anxiety disorders and the higher rates of these mental health problems in individuals with fetal alcohol spectrum disorder.

Prenatal alcohol exposure reduces the proportion of newly produced neurons and glia in the dentate gyrus of the hippocampus in female rats

Prenatal alcohol exposure (PAE) alters adult neurogenesis and the neurogenic response to stress in male rats. As the effects of stress on neurogenesis are sexually dimorphic, the present study investigated the effects of PAE on adult hippocampal neurogenesis under both nonstressed and stressed conditions in female rats. Pregnant females were assigned to one of three prenatal treatments: (1) alcohol (PAE)-liquid alcohol (ethanol) diet ad libitum (36% ethanol-derived calories); (2) pair-fed-isocaloric liquid diet, with maltose-dextrin substituted for ethanol, in the amount consumed by a PAE partner (g/kg body wt/day of gestation); and (3) control-lab chow ad libitum. Female offspring were assigned to either nonstressed (undisturbed) or stressed (repeated restraint stress for 9 days) conditions. On day 10, all rats were injected with bromodeoxyuridine (BrdU) and perfused either 24 hours (cell proliferation) or 3 weeks (cell survival) later. We found that PAE did not significantly alter cell proliferation or survival, whereas females from the pair-fed condition exhibited elevated levels of cell survival compared to control females. Importantly, however, the proportion of both new neurons and new glial cells in the hippocampal dentate gyrus was reduced in PAE compared to control females. Exposure to stress did not alter neurogenesis in any of the prenatal treatment groups. In summary, compared to females from the control condition, prenatal dietary restriction enhanced the survival of new neurons, whereas PAE altered the differentiation of newly produced cells in the adult dentate gyrus. Alterations in hippocampal neurogenesis following PAE may contribute to learning and memory deficits seen in individuals with fetal alcohol spectrum disorders.

Stress-induced suppression of hippocampal neurogenesis in adult male rats is altered by prenatal ethanol exposure

In adulthood, both alcohol (ethanol) and stress are known to suppress hippocampal neurogenesis in male rats. Similarly, most studies report that prenatal alcohol exposure (PAE) reduces cell proliferation and/or cell survival in the hippocampus of adult males. Furthermore, PAE is known to have marked effects on behavioral and hypothalamic-pituitary-adrenal (HPA) responsiveness to stressors. However, no studies have examined the modulation of adult hippocampal neurogenesis by stress in PAE animals. We hypothesized that, in accordance with previous data, PAE would suppress basal levels of adult hippocampal neurogenesis, and further that stress acting on a sensitized HPA axis would have greater adverse effects on adult hippocampal neurogenesis in PAE than in control rats. Adult male offspring from PAE, pair-fed (PF) control, and ad libitum-fed control (C) groups were subjected to restraint stress (9 days, 1 h/day) or left undisturbed. Rats were then injected with bromodeoxyuridine (BrdU) on day 10, perfused 24 h (proliferation) or 3 weeks (survival) later, and brains processed for BrdU immunohistochemistry. We found that (1) under non-stressed conditions, PAE rats had a small but statistically significant suppressive effect on levels of hippocampal neurogenesis and (2) unexpectedly, repeated restraint stress significantly reduced neurogenesis in C and PF, but not PAE rats. We speculate that the failure of PAE males to mount an appropriate (i.e. suppressive) neurogenic response to stressors, implies reduced plasticity and adaptability or resilience, which could impact negatively on hippocampal structure and function.

Effects of prenatal ethanol exposure on hypothalamic-pituitary-adrenal function across the estrous cycle

BACKGROUND

Rats prenatally exposed to ethanol (E) typically show increased hypothalamic-pituitary-adrenal (HPA) responses to stressors in adulthood. Importantly, prenatal ethanol may differentially alter stress responsiveness in male and female offspring, suggesting a role for the gonadal hormones in mediating the effects of ethanol on HPA activity. We investigated the role of ethanol-induced changes in hypothalamic-pituitary-gonadal (HPG) activity in the differential HPA regulation observed in E compared to control females across the estrous cycle.

METHODS

Peripheral hormones and changes in central neuropeptide mRNA levels were measured across the estrous cycle in adult female offspring from E, pair-fed (PF) and ad libitum-fed control (C) dams.

RESULTS

Ethanol females showed normal estrous cyclicity (vaginal smears) but delayed sexual maturation (vaginal opening). Both HPG and HPA activity were differentially altered in E (and in some cases, PF) compared to control females as a function of estrous cycle stage. In relation to HPG activity, E and PF females had higher basal and stress estradiol (E(2)) levels in proestrus compared to other phases of the cycle, and decreased GnRH mRNA levels compared to C females in diestrus. Further, E females had greater variation in LH than PF and C females across the cycle, and in proestrus, only E females showed a significant LH increase following stress. In relation to HPA activity, both basal and stress CORT levels and overall ACTH levels were greater in E than in C females in proestrus. Furthermore, AVP mRNA levels were increased overall in E compared to PF and C females.

CONCLUSIONS

These data demonstrate ethanol-induced changes in both HPG and HPA activity that are estrous phase-specific, and support the possibility that changes in HPA activity in E females may reflect differential sensitivity to ovarian steroids. E females appear to have an increased HPA sensitivity to E(2), and a possible shift toward AVP regulation of HPA activity. That PF were similar to E females on some measures suggests that nutritional effects of diet or food restriction played a role in mediating at least some of the changes observed.

Effects of prenatal ethanol exposure on regulation of basal hypothalamic-pituitary-adrenal activity and hippocampal 5-HT1A receptor mRNA levels in female rats across the estrous cycle

Prenatal ethanol exposure, like other early adverse experiences, is known to alter hypothalamic-pituitary-adrenal (HPA) activity in adulthood. The present study examined the modulatory effects of the gonadal hormones on basal HPA regulation and serotonin Type 1A receptor (5-HT(1A)) mRNA levels in adult female rats prenatally exposed to ethanol (E) compared to that in females from pair-fed (PF) and ad libitum-fed control (C) conditions. We demonstrate, for the first time, long-lasting consequences of prenatal ethanol exposure for basal corticosterone (CORT) regulation and basal levels of hippocampal mineralocorticoid (MR), glucocorticoid (GR) and serotonin Type 1A (5-HT(1A)) receptor mRNA, as a function of estrous cycle stage: (1) basal CORT levels were higher in E compared to C females in proestrus but lower in E and PF compared to C females in estrus; (2) there were no differences among groups in basal levels of adrenocorticotropin (ACTH), estradiol or progesterone; (3) hippocampal MR mRNA levels were decreased in E compared to PF and C females across the estrus cycle, with the greatest effects in proestrus, whereas E (but not PF or C) females had higher hippocampal GR mRNA levels in proestrus than in estrous and diestrus; (4) 5-HT(1A) mRNA levels were increased in E compared to PF and C females in diestrus. That alterations were revealed as a function of estrous cycle stage suggests a role for the ovarian steroids in mediating the adverse effects of ethanol. Furthermore, it appears that ethanol-induced nutritional effects may play a role in mediating at least some of the effects observed. The resetting of HPA activity by early environmental events could be one mechanism linking early life experiences with long-term health consequences. Thus, changes in basal CORT levels, a shift in the MR/GR balance and alterations in 5-HT(1A) receptor mRNA could have important clinical implications for understanding the secondary disabilities, such as an increased incidence of depression, in children with FASD.

Evidence that gamma-aminobutyric acid is part of the neural circuit mediating estradiol negative feedback in anestrous ewes

Seasonal anestrus in ewes is driven by an increase in response to estradiol (E2) negative feedback. Compelling evidence indicates that inhibitory A15 dopaminergic (DA) neurons mediate the increased inhibitory actions of E2 in anestrus, but these neurons do not contain estrogen receptors. Therefore, we have proposed that estrogen-responsive afferents to A15 neurons are part of the neural circuit mediating E2 negative feedback in anestrus. This study examined the possible role of afferents containing gamma-aminobutyric acid (GABA) and nitric oxide (NO) in modulating the activity of A15 neurons. Local administration of NO synthase inhibitors to the A15 had no effect on LH, but GABA receptor ligands produced dramatic changes. Administration of either a GABA A or GABA B receptor agonist to the A15 increased LH secretion in ovary-intact ewes, suggesting that GABA inhibits A15 neural activity. In ovariectomized anestrous ewes, the same doses of GABA receptor agonist had no effect, but combined administration of a GABA A and GABA B receptor antagonist to the A15 inhibited LH secretion. These data are consistent with the hypothesis that endogenous GABA release within the A15 is low in ovary-intact anestrous ewes and elevated after ovariectomy. Using dual immunocytochemistry, we observed that GABAergic varicosities make close contacts on to A15 neurons and that A15 neurons contain both the GABA A-alpha1 and the GABA B-R1 receptor subunits. Based on these data, we propose that in anestrous ewes, E2 inhibits release of GABA from afferents to A15 DA neurons, increasing the activity of these DA neurons and thus suppressing episodic secretion of GnRH and LH.

Prenatal alcohol exposure: foetal programming, the hypothalamic-pituitary-adrenal axis and sex differences in outcome

Prenatal exposure to alcohol has adverse effects on offspring neuroendocrine and behavioural functions. Alcohol readily crosses the placenta, thus directly affecting developing foetal endocrine organs. In addition, alcohol-induced changes in maternal endocrine function can disrupt the normal hormonal interactions between the pregnant female and foetal systems, altering the normal hormone balance and, indirectly, affecting the development of foetal metabolic, physiological and endocrine functions. The present review focuses on the adverse effects of prenatal alcohol exposure on offspring neuroendocrine function, with particular emphasis on the hypothalamic-pituitary-adrenal (HPA) axis, a key player in the stress response. The HPA axis is highly susceptible to programming during foetal and neonatal development. Here, we review data demonstrating that alcohol exposure in utero programmes the foetal HPA axis such that HPA tone is increased throughout life. Importantly, we show that, although alterations in HPA responsiveness and regulation are robust phenomena, occurring in both male and female offspring, sexually dimorphic effects of alcohol are frequently observed. We present updated findings on possible mechanisms underlying differential effects of alcohol on male and female offspring, with special emphasis on effects at different levels of the HPA axis, and on modulatory influences of the hypothalamic-pituitary-gonadal hormones and serotonin. Finally, possible mechanisms underlying foetal programming of the HPA axis, and the long-term implications of increased exposure to endogenous glucocorticoids for offspring vulnerability to illnesses or disorders later in life are discussed.

Immunocytochemical colocalization of GABA-B receptor subunits in gonadotropin-releasing hormone neurons of the sheep

GABA has been shown to play an important role in the control of gonadotropin-releasing hormone (GnRH) and luteinizing hormone secretion in many mammals. In sheep, seasonal differences in the ability of GABA-B receptor antagonists to alter pulsatile luteinizing hormone secretion have led to the hypothesis that this receptor subtype mediates the increased inhibitory effects of estradiol on GnRH and luteinizing hormone pulse frequency seen during the non-breeding season (anestrus). The aim of the present study was to use multiple-label immunocytochemistry to determine if ovine GnRH neurons contain the GABA-B receptor subunits R1 and/or R2, and to determine whether there are seasonal differences in the colocalization of these subunits in GnRH neurons. A majority of GnRH cells in the preoptic area, anterior hypothalamic area, and medial basal hypothalamus of both breeding season and anestrous ewes contained either GABA-B R1 or R2 subunits; a subset of GnRH neurons in breeding season (42%) and anestrous ewes (60%) contained both subunits. In contrast to colocalization within cell bodies, GnRH fibers in the median eminence did not colocalize GABA-B receptor subunits. Although the percentage of GnRH neurons expressing GABA-B receptor subunits tended to be higher in anestrus than in the breeding season, there were no significant seasonal differences in R1 and R2 subunit colocalization in GnRH cell bodies. Thus, while GABA may act directly on GnRH cell bodies via GABA-B receptors in the sheep, any role that GABA-B receptors may play in seasonal reproductive changes is likely mediated by other neurons afferent to GnRH cells.

Prenatal alcohol exposure and fetal programming: effects on neuroendocrine and immune function

Alcohol abuse is known to result in clinical abnormalities of endocrine function and neuroendocrine regulation. However, most studies have been conducted on males. Only recently have studies begun to investigate the influence of alcohol on endocrine function in females and, more specifically, endocrine function during pregnancy. Alcohol-induced endocrine imbalances may contribute to the etiology of fetal alcohol syndrome. Alcohol crosses the placenta and can directly affect developing fetal cells and tissues. Alcohol-induced changes in maternal endocrine function can disrupt maternal-fetal hormonal interactions and affect the female's ability to maintain a successful pregnancy, thus indirectly affecting the fetus. In this review, we focus on the adverse effects of prenatal alcohol exposure on neuroendocrine and immune function, with particular emphasis on the hypothalamic-pituitary-adrenal (HPA) axis and the concept of fetal programming. The HPA axis is highly susceptible to programming during fetal development. Early environmental experiences, including exposure to alcohol, can reprogram the HPA axis such that HPA tone is increased throughout life. We present data that demonstrate that maternal alcohol consumption increases HPA activity in both the maternal female and the offspring. Increased exposure to endogenous glucocorticoids throughout the lifespan can alter behavioral and physiologic responsiveness and increase vulnerability to illnesses or disorders later in life. Alterations in immune function may be one of the long-term consequences of fetal HPA programming. We discuss studies that demonstrate the adverse effects of alcohol on immune competence and the increased vulnerability of ethanol-exposed offspring to the immunosuppressive effects of stress. Fetal programming of HPA activity may underlie some of the long-term behavioral, cognitive, and immune deficits that are observed following prenatal alcohol exposure.

The premammillary hypothalamic area of the ewe: anatomical characterization of a melatonin target area mediating seasonal reproduction

Recent evidence suggests that the ovine premammillary hypothalamic area (PMH) is an important target for the pineal hormone, melatonin, and its role in seasonal reproduction. In rodents, the PMH is a complex region consisting of several cell groups with differing neurochemical content and anatomical connections. Therefore, to obtain a better understanding of the potential neural targets for melatonin in this area of the sheep brain, we have undertaken a detailed anatomical characterization of the PMH, including its nuclear divisions and the location of neuropeptide/neurotransmitter cells within them. By combining immunocytochemistry for NeuN, a neuronal marker, with Nissl staining in anestrous, ovariectomized, estradiol-treated ewes, we identified three nuclei within the PMH: a caudal continuation of the hypothalamic arcuate nucleus (cARC), the ventral division of the premammillary nucleus (PMv), and the ventral tuberomammillary nucleus (TMv). The cARC contained neurons that were immunoreactive for tyrosine hydroxylase, dynorphin, estrogen receptor alpha, cocaine- and amphetamine-regulated transcript peptide (CART), and nitric oxide synthase (NOS). The PMv was also characterized by the presence of cells that contained NOS and CART, although the size of these cells was larger than that of their corresponding phenotype in the cARC. By contrast, in the TMv, of the markers examined in the present study, only fibers immunoreactive for orexin were seen. Thus, the ovine PMH is a heterogeneous region comprised of three subdivisions, each with distinct morphological and neurochemical characteristics. This anatomical map of the PMH provides a basis for future studies to determine the functional contribution of each component to the influence of melatonin on seasonal reproduction.