Ghrelin is a hormone associated with feeding and energy balance. Not surprisingly, this hormone is secreted in response to acute stressors and it is chronically elevated after exposure to chronic ...stress in tandem with a number of metabolic changes aimed at attaining homeostatic balance. In the present review, we propose that ghrelin plays a key role in these stress‐induced homeostatic processes. Ghrelin targets the hypothalamus and brain stem nuclei that are part of the sympathetic nervous system to increase appetite and energy expenditure and promote the use of carbohydrates as a source of fuel at the same time as sparing fat. Ghrelin also targets mesolimbic brain regions such as the ventral segmental area and the hippocampus to modulate reward processes, to protect against damage associated with chronic stress, as well as to potentially increase resilience to stress. In all, these data support the notion that ghrelin, similar to corticosterone, is a critical metabolic hormone that is essential for the stress response.
Bisphenol-A (BPA) is a well-known endocrine disrupting compound (EDC), capable of affecting the normal function and development of the reproductive system, brain, adipose tissue, and more. In spite ...of these diverse and well characterized effects, there is often comparatively little known about the molecular mechanisms which bring them about. BPA has traditionally been regarded as a primarily estrogenic EDC, and this perspective is often what guides research into the effects of BPA. However, emerging data from in-vitro and in-silico models show that BPA binds with a significant number of hormone receptors, including a number of nuclear and membrane-bound estrogen receptors, androgen receptors, as well as the thyroid hormone receptor, glucocorticoid receptor, and PPARγ. With this increased diversity of receptor targets, it may be possible to explain some of the more puzzling aspects of BPA pharmacology, including its non-monotonic dose-response curve, as well as experimental results which disagree with estrogenic positive controls. This paper reviews the receptors for which BPA has a known interaction, and discusses the implications of taking these receptors into account when studying the disruptive effects of BPA on growth and development.
•Bisphenol-A exerts a range of non-estrogenic effects.•Care should be taken in selecting positive controls, given BPA's range of activity.•Non-estrogenic effects can account for many phenotypes produced by BPA exposure.
A review is provided of current evidence supporting the actions of the stomach‐derived peptide ghrelin on ventral tegmental area (VTA) dopamine cells to increase food intake and other appetitive ...behaviours. Ghrelin is a 28 amino‐acid peptide that was first identified as an endogenous ligand to growth hormone secretagogue receptors (GHS‐R). In addition to the hypothalamus and brain stem, GHS‐R message and protein are distributed throughout the brain, with high expression being detected in regions associated with goal directed behaviour. Of these, the VTA shows relatively high levels of mRNA transcript and protein. Interestingly, ghrelin infusions into the VTA increase food intake dramatically, and stimulate dopamine release from the VTA. Moreover, VTA dopamine neurones increase their activity in response to ghrelin in slice preparations, suggesting that ghrelin increases food intake by modulating the activity of dopaminergic neurones in the VTA. On the basis of these data as well as the fact that VTA dopamine cells respond to other metabolic hormones such as insulin and leptin, it is proposed that VTA dopamine cells, similar to cells in the mediobasal hypothalamus, are first‐order sensory neurones that regulate appetitive behaviour in response to metabolic and nutritional signals.
Ghrelin is a hormone predominantly produced in and secreted from the stomach. Ghrelin is involved in many physiological processes including feeding, the stress response, and in modulating learning, ...memory and motivational processes. Ghrelin does this by binding to its receptor, the growth hormone secretagogue receptor (GHSR), a receptor found in relatively high concentrations in hypothalamic and mesolimbic brain regions. While the feeding and metabolic effects of ghrelin can be explained by the effects of this hormone on regions of the brain that have a more permeable blood brain barrier (BBB), ghrelin produced within the periphery demonstrates a limited ability to reach extrahypothalamic regions where GHSRs are expressed. Therefore, one of the most pressing unanswered questions plaguing ghrelin research is how GHSRs, distributed in brain regions protected by the BBB, are activated despite ghrelin's predominant peripheral production and poor ability to transverse the BBB. This manuscript will describe how peripheral ghrelin activates central GHSRs to encourage feeding, and how central ghrelin synthesis and ghrelin independent activation of GHSRs may also contribute to the modulation of feeding behaviours.
The COVID-19 pandemic has imposed a wide variety of unprecedented challenges, many of which appear to be disproportionately affecting the mental health and well-being of young adults. While there is ...evidence to suggest university students experience high rates of mental health disorders, less is known about the specific impacts of the COVID-19 pandemic on student mental health and how they are coping with this stress. To address this gap, we conducted an online study among undergraduate students (
= 366) to examine the impact of the COVID-19 pandemic on academics, social isolation, and mental health, as well as the extent to which they have been implementing a variety of coping strategies. The pandemic had a more pronounced negative effect on female students' academics, social isolation, stress and mental health compared to male counterparts. Moreover, for females, frequent use of social media as a coping mechanism was associated with greater perceived negative impacts on their academic performance and stress levels, compared to males. However, frequent social media use related to similar negative mental health effects for both males and females. While male and female students both reported using substances to cope, for males the use of cannabis was associated with greater negative impacts on academic outcomes, stress and mental health compared to females. These findings highlight the need for adequate student support services across the post-secondary sector, and point to the importance of gender informed interventions to address the impacts of the COVID-19 pandemic.
Abstract
Bisphenol-A (BPA) is a component of polycarbonate and other plastics to which humans are regularly exposed at low levels. BPA is characterized as an endocrine disruptor because of ...observations of its estrogenic activity in various experimental models. We have previously shown evidence of disrupted hypothalamic feeding circuitry and leptin sensitivity in adult BPA-exposed animals subjected to a high-fat diet, but because these animals were already exhibiting a diet-induced obese phenotype, we could not rule out the possibility that these observations were simply consequences of the obesity, not a preexisting phenotype produced by BPA exposure. Here, we studied leptin sensitivity and hypothalamic structure in young BPA-exposed animals before the onset of a body weight or metabolic phenotype. Pregnant and lactating CD-1 mice were exposed to either BPA or diethylstilbestrol (DES) at low, environmentally relevant doses via their diet. Studies of leptin function and neurobiology were conducted on offspring at several time points. Young adult offspring from this experiment were resistant to leptin-induced suppression of food intake, body weight loss, and hypothalamic pro-opiomelanocortin (POMC) upregulation. Both male and female BPA-exposed mice showed a reduced density of POMC projections into the paraventricular nucleus of the hypothalamus (PVN). BPA- and DES-exposed pups had respectively delayed and blunted postnatal leptin surges, and POMC projections into the PVN were rescued in female BPA-exposed animals given daily injections of supplemental leptin. Our findings suggest that BPA, a putative obesogen, may exert its effects through developmental programming of the hypothalamic melanocortin circuitry, permanently altering the neurobiology of metabolic homeostasis.
The endocrine disruptor bisphenol A (BPA) delays the onset of the postnatal leptin surge and results in abnormal development of the hypothalamic melanocortin system in mice to promote obesity.
Depression is accompanied by an array of neurobiological variations, including altered HPA axis activity, monoamine, growth factor and inflammatory immune functioning. In addition, a recent ...perspective has entertained the possible role for oxytocin in depressive disorders. Given the involvement of oxytocin in prosocial behaviors such as attachment, affiliation, trust, and social support seeking, it is not surprising this neuropeptide might be involved in the development or maintenance of depressive disorders. This view is supported by evidence that oxytocin interacts with various neuroendocrine, neurotransmitter, and inflammatory processes that have previously been implicated in depression. Thus, it might be profitable to consider the contribution of oxytocin in the context of several neurobiological changes provoked by stressors. The current review examines the relation between oxytocin and depression with a specific focus on the interactions between the oxytocinergic system and stressor-provoked biological and psychosocial responses. The possibility is also considered that oxytocin might increase the salience of social cues, such that positive or negative experiences result in exaggerated responses that may influence affective states.
•Ghrelin-O-acyltransferase (GOAT) mRNA expression is present in the hypothalamus of rats.•Hypothalamic GOAT mRNA expression changes in response to changes in energy state.•Knockdown of hypothalamic ...GOAT expression via chronic intracerebroventricular infusions of a GOAT antisense-morpholino decreases and weight gain in rats fed a high fat diet.
The enzyme ghrelin O-acyltransferase (GOAT) activates the orexigenic peptide ghrelin by transferring an acyl group from fatty acids to the serine-3 residue of the ghrelin molecule. This allows ghrelin to bind to its only known receptor, the growth hormone secretagogue receptor type 1a (GHSR1a). While studies have examined the hypothalamic transcriptional response of GOAT to metabolic challenge in mice, little has been examined in the rat hypothalamus. Furthermore, it has not been possible to identify the role of central GOAT separate from that of the periphery, since previous studies either knocked out GOAT system-wide or administered a GOAT inhibitor intraperitoneally. To determine if central GOAT expression is modulated by changes in energy state, we subjected rats to either forty-eight hours of food deprivation or three weeks of food restriction and found that GOAT mRNA increases significantly in both the hypothalamus and the stomach fundus in response to both metabolic challenges. We also found increases in hypothalamic ghrelin mRNA and stomach GHSR1a mRNA in response to food deprivation, as well as increases in hypothalamic GHSR1a mRNA in response to food restriction. We then conducted a second study where we continuously infused amorpholino antisense oligonucleotide into the lateral ventricles of rats to knock-down GOAT centrally while the animals were exposed to a high fat diet. Our results show that rats receiving the GOAT antisense gained less weight, and decreased their caloric efficiency when eating a high fat diet compared to control animals. These data suggest that central GOAT plays a role in modulating metabolism in rats.
Ghrelin is considered one of the most potent orexigenic peptide hormones and one that promotes homeostatic and hedonic food intake. Research on ghrelin, however, has been conducted predominantly in ...males and particularly in male rodents. In female mammals the control of energy metabolism is complex and it involves the interaction between ovarian hormones like estrogen and progesterone, and metabolic hormones. In females, the role that ghrelin plays in promoting feeding and how this is impacted by ovarian hormones is not well understood. Basal ghrelin levels are higher in females than in males, and ghrelin sensitivity changes across the estrus cycle. Yet, responses to ghrelin are lower in female and seem dependent on circulating levels of ovarian hormones. In this review we discuss the role that ghrelin plays in regulating homeostatic and hedonic food intake in females, and how the effects of ghrelin interact with those of ovarian hormones to regulate feeding and energy balance.
Smoking decreases appetite, and smokers often report that they smoke to control their weight. Understanding the neurobiological mechanisms underlying the anorexic effects of smoking would facilitate ...the development of novel treatments to help with smoking cessation and to prevent or treat obesity. By using a combination of pharmacological, molecular genetic, electrophysiological, and feeding studies, we found that activation of hypothalamic α3β4 nicotinic acetylcholine receptors leads to activation of pro-opiomelanocortin (POMC) neurons. POMC neurons and subsequent activation of melanocortin 4 receptors were critical for nicotinic-induced decreases in food intake in mice. This study demonstrates that nicotine decreases food intake and body weight by influencing the hypothalamic melanocortin system and identifies critical molecular and synaptic mechanisms involved in nicotine-induced decreases in appetite.
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