Melanocortin-4 receptor in the medial amygdala regulates emotional stress-induced anxiety-like behaviour, anorexia and corticosterone secretion

Stress integration by an ascending adrenergic-melanocortin circuit

Stress is thought to be an important contributing factor for eating disorders; however, neural substrates underlying the complex relationship between stress and appetite are not fully understood. Using in vivo recordings from awake behaving mice, we show that various acute stressors activate catecholaminergic nucleus tractus solitarius (NTSTH) projections in the paraventricular hypothalamus (PVH). Remarkably, the resulting adrenergic tone inhibits MC4R-expressing neurons (PVHMC4R), which are known for their role in feeding suppression. We found that PVHMC4R silencing encodes negative valence in sated mice and is required for avoidance induced by visceral malaise. Collectively, these findings establish PVHMC4R neurons as an effector of stress-activated brainstem adrenergic input in addition to the well-established hypothalamic-pituitary-adrenal axis. Convergent modulation of stress and feeding by PVHMC4R neurons implicates NTSTH → PVHMC4R input in stress-associated appetite disorders.

A molecularly defined orbitofrontal cortical neuron population controls compulsive-like behavior, but not inflexible choice or habit

Habits are familiar behaviors triggered by cues, not outcome predictability, and are insensitive to changes in the environment. They are adaptive under many circumstances but can be considered antecedent to compulsions and intrusive thoughts that drive persistent, potentially maladaptive behavior. Whether compulsive-like and habit-like behaviors share neural substrates is still being determined. Here, we investigated mice bred to display inflexible reward-seeking behaviors that are insensitive to action consequences. We found that these mice demonstrate habitual response biases and compulsive-like grooming behavior that was reversible by fluoxetine and ketamine. They also suffer dendritic spine attrition on excitatory neurons in the orbitofrontal cortex (OFC). Nevertheless, synaptic melanocortin 4 receptor (MC4R), a factor implicated in compulsive behavior, is preserved, leading to the hypothesis that Mc4r+ OFC neurons may drive aberrant behaviors. Repeated chemogenetic stimulation of Mc4r+ OFC neurons triggered compulsive and not inflexible or habitual response biases in otherwise typical mice. Thus, Mc4r+ neurons within the OFC appear to drive compulsive-like behavior that is dissociable from habitual behavior. Understanding which neuron populations trigger distinct behaviors may advance efforts to mitigate harmful compulsions.

Stress-related cellular pathophysiology as a crosstalk risk factor for neurocognitive and psychiatric disorders

In this narrative review, we examine biological processes linking psychological stress and cognition, with a focus on how psychological stress can activate multiple neurobiological mechanisms that drive cognitive decline and behavioral change. First, we describe the general neurobiology of the stress response to define neurocognitive stress reactivity. Second, we review aspects of epigenetic regulation, synaptic transmission, sex hormones, photoperiodic plasticity, and psychoneuroimmunological processes that can contribute to cognitive decline and neuropsychiatric conditions. Third, we explain mechanistic processes linking the stress response and neuropathology. Fourth, we discuss molecular nuances such as an interplay between kinases and proteins, as well as differential role of sex hormones, that can increase vulnerability to cognitive and emotional dysregulation following stress. Finally, we explicate several testable hypotheses for stress, neurocognitive, and neuropsychiatric research. Together, this work highlights how stress processes alter neurophysiology on multiple levels to increase individuals' risk for neurocognitive and psychiatric disorders, and points toward novel therapeutic targets for mitigating these effects. The resulting models can thus advance dementia and mental health research, and translational neuroscience, with an eye toward clinical application in cognitive and behavioral neurology, and psychiatry.

Melanotan-II reverses memory impairment induced by a short-term HF diet

A high-fat (HF) diet has been shown to increase the risk of neurological impairments and neurodegenerative disorders. The melanotropins used in this study have been associated with diet-related disorders; however, there is an absence of studies on their effect on diet-induced neurobehavioral conditions. Here, we investigated the possible relationship among diet, Melanotan-II (MT-II) targeting melanotropin receptors, and the behavior of zebrafish (Danio rerio). Surprisingly, even a short-term HF diet lasting for ∼ 1 % of the zebrafish's life had a strong developmental effect. Zebrafish fed the HF diet showed an impairment in recognition memory, elevated anxiety levels, and reduced exploratory propensity after just three weeks compared to zebrafish fed the control diet. These HF diet-induced abnormalities were reversed by MT-II. Animals fed a HF diet and treated with MT-II demonstrated recognition memory, anxiety, and exploratory behavior similar to the control group. This study provides evidence that even a short-term HF diet has an impact on memory and emotions and is the first study to show that MT-II reverses these changes.

ECoG spiking activity and signal dimension are early predictive measures of epileptogenesis in a translational mouse model of traumatic brain injury

The latency between traumatic brain injury (TBI) and the onset of epilepsy (PTE) represents an opportunity for counteracting epileptogenesis. Antiepileptogenesis trials are hampered by the lack of sensitive biomarkers that allow to enrich patient's population at-risk for PTE. We aimed to assess whether specific ECoG signals predict PTE in a clinically relevant mouse model with ∼60% epilepsy incidence. TBI was provoked in adult CD1 male mice by controlled cortical impact on the left parieto-temporal cortex, then mice were implanted with two perilesional cortical screw electrodes and two similar electrodes in the hemisphere contralateral to the lesion site. Acute seizures and spikes/sharp waves were ECoG-recorded during 1 week post-TBI. These early ECoG events were analyzed according to PTE incidence as assessed by measuring spontaneous recurrent seizures (SRS) at 5 months post-TBI. We found that incidence, number and duration of acute seizures during 3 days post-TBI were similar in PTE mice and mice not developing epilepsy (No SRS mice). Control mice with cortical electrodes (naïve, n = 5) or with electrodes and craniotomy (sham, n = 5) exhibited acute seizures but did not develop epilepsy. The daily number of spikes/sharp waves at the perilesional electrodes was increased similarly in PTE (n = 15) and No SRS (n = 8) mice vs controls (p < 0.05, n = 10) from day 2 post-injury. Differently, the daily number of spikes/sharp waves at both contralateral electrodes showed a progressive increase in PTE mice vs No SRS and control mice. In particular, spikes number was higher in PTE vs No SRS mice (p < 0.05) at 6 and 7 days post-TBI, and this measure predicted epilepsy development with high accuracy (AUC = 0.77, p = 0.03; CI 0.5830-0.9670). The cut-off value was validated in an independent cohort of TBI mice (n = 12). The daily spike number at the contralateral electrodes showed a circadian distribution in PTE mice which was not observed in No SRS mice. Analysis of non-linear dynamics at each electrode site showed changes in dimensionality during 4 days post-TBI. This measure yielded the best discrimination between PTE and No SRS mice (p < 0.01) at the cortical electrodes contralateral to injury. Data show that epileptiform activity contralateral to the lesion site has the the highest predictive value for PTE in this model reinforcing the hypothesis that the hemisphere contralateral to the lesion core may drive epileptogenic networks after TBI.

Interaction of fatty acid quality indices and genes related to lipid homeostasis on mental health among overweight and obese women

The aim of this study is to investigate the interaction of fatty acid quality indices and genes related to lipid homeostasis on mental health among overweight and obese women. This cross-sectional study included 279 overweight and obese women for N6/N3 ratio and 378 overweight and obese women for CSI aged 18-58 years. Mental health were evaluated using Depression Anxiety Stress Scales (DASS-21). The anthropometric indices, biochemical parameters, body composition and dietary fat quality were measured. MC4R (rs17782313) and Caveolin-1 (CAV-1) (rs3807992) were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. The results of the study showed that after adjusting for age, energy intake, thyroid disease, physical activity, and BMI, a positive interaction between TC genotype of MC4R and CSI on depression (β = 0.39, CI = 0.12, 0.66, P = 0.004), and DASS-21 (β = 0.074, CI = 0.04, 1.44, P = 0.036). Also, there were a marginal significant interactions between AG genotype of CAV-1 and N6/N3 ratio on depression in adjustment model1 (β = 16.83, CI = - 0.19, 33.85, P = 0.053). Our findings showed that increasing adherence to fatty acid quality indices by considering genes related to lipid homeostasis was related to increasing depression in our population.

Role of brain NUCB2/nesfatin-1 in stress and stress-related gastrointestinal disorders

Since the discovery of NUCB2/nesfatin-1 as a novel anorexigenic factor, the expanding function of this peptide has been elucidated in recent years. Increasing evidence suggests that NUCB2/nesfatin-1 is also involved in the regulation of stress and stress-related gastrointestinal disorders. Therefore, we investigated the relationship between NUCB2/nesfatin-1, stress and stress-related gastrointestinal disorders and summarized the results of these studies. Different stressors and duration of stress activate different NUCB2/nesfatin-1-associated brain regions and have different effects on serum corticosterone levels. Central and peripheral NUCB2/nesfatin-1 mediates stress-related gastrointestinal disorders but appears to be protective against inflammatory bowel disease. NUCB2/nesfatin-1 plays an important role in mediating the brain-gut crosstalk, but precise clarification is still needed to gain more insight into these complex relationships.

Lateral septum as a melanocortin downstream site in obesity development

The melanocortin pathway is well established to be critical for body-weight regulation in both rodents and humans. Despite extensive studies focusing on this pathway, the downstream brain sites that mediate its action are not clear. Here, we found that, among the known paraventricular hypothalamic (PVH) neuron groups, those expressing melanocortin receptors 4 (PVH^Mc4R) preferably project to the ventral part of the lateral septum (LSv), a brain region known to be involved in emotional behaviors. Photostimulation of PVH^Mc4R neuron terminals in the LSv reduces feeding and causes aversion, whereas deletion of Mc4Rs or disruption of glutamate release from LSv-projecting PVH neurons causes obesity. In addition, disruption of AMPA receptor function in PVH-projected LSv neurons causes obesity. Importantly, chronic inhibition of PVH- or PVH^Mc4R-projected LSv neurons causes obesity associated with reduced energy expenditure. Thus, the LSv functions as an important node in mediating melanocortin action on body-weight regulation.

The Melanocortin System: A Promising Target for the Development of New Antidepressant Drugs

Major depression is one of the most prevalent mental disorders, causing significant human suffering and socioeconomic loss. Since conventional antidepressants are not sufficiently effective, there is an urgent need to develop new antidepressant medications. Despite marked advances in the neurobiology of depression, the etiology and pathophysiology of this disease remain poorly understood. Classical and newer hypotheses of depression suggest that an imbalance of brain monoamines, dysregulation of the hypothalamic-pituitary-adrenal axis (HPAA) and immune system, or impaired hippocampal neurogenesis and neurotrophic factors pathways are cause of depression. It is assumed that conventional antidepressants improve these closely related disturbances. The purpose of this review was to discuss the possibility of affecting these disturbances by targeting the melanocortin system, which includes adrenocorticotropic hormone-activated receptors and their peptide ligands (melanocortins). The melanocortin system is involved in the regulation of various processes in the brain and periphery. Melanocortins, including peripherally administered non-corticotropic agonists, regulate HPAA activity, exhibit anti-inflammatory effects, stimulate the levels of neurotrophic factors, and enhance hippocampal neurogenesis and neurotransmission. Therefore, endogenous melanocortins and their analogs are able to complexly affect the functioning of those body’s systems that are closely related to depression and the effects of antidepressants, thereby demonstrating a promising antidepressant potential.

Increased intrinsic and synaptic excitability of hypothalamic POMC neurons underlies chronic stress-induced behavioral deficits

Chronic stress exposure induces maladaptive behavioral responses and increases susceptibility to neuropsychiatric conditions. However, specific neuronal populations and circuits that are highly sensitive to stress and trigger maladaptive behavioral responses remain to be identified. Here we investigate the patterns of spontaneous activity of proopiomelanocortin (POMC) neurons in the arcuate nucleus (ARC) of the hypothalamus following exposure to chronic unpredictable stress (CUS) for 10 days, a stress paradigm used to induce behavioral deficits such as anhedonia and behavioral despair [1, 2]. CUS exposure increased spontaneous firing of POMC neurons in both male and female mice, attributable to reduced GABA-mediated synaptic inhibition and increased intrinsic neuronal excitability. While acute activation of POMC neurons failed to induce behavioral changes in non-stressed mice of both sexes, subacute (3 days) and chronic (10 days) repeated activation of POMC neurons was sufficient to induce anhedonia and behavioral despair in males but not females under non-stress conditions. Acute activation of POMC neurons promoted susceptibility to subthreshold unpredictable stress in both male and female mice. Conversely, acute inhibition of POMC neurons was sufficient to reverse CUS-induced anhedonia and behavioral despair in both sexes. Collectively, these results indicate that chronic stress induces both synaptic and intrinsic plasticity of POMC neurons, leading to neuronal hyperactivity. Our findings suggest that POMC neuron dysfunction drives chronic stress-related behavioral deficits.

Evaluation of the posterior insular cortex involvement in anxiogenic response to emotional stress in male rats: Functional topography along the rostrocaudal axis

The insular cortex (IC) is engaged in behavioral and physiological responses to emotional stress. Control of physiological functions and behavioral responses has been reported to occur in a site-specific manner along the rostrocaudal axis of the IC. However, a functional topography of the IC regulation of anxiogenic responses caused by stress has never been evaluated. Therefore, we investigated the role of rostrocaudal subregions in the posterior IC in anxiogenic-like effect caused by exposure to acute restraint stress in male rats. For this, rats received bilateral microinjection of the non-selective synaptic inhibitor CoCl₂ or vehicle into either the rostral, intermediate or caudal portions of the posterior IC before exposure to acute restraint stress. Then, behavior in the elevated plus maze (EPM) was evaluated immediately after restraint stress. The behavior of non-stressed animals in the EPM was also investigated. We observed that acute restraint stress decreased the exploration of the EPM open arms in animals treated with vehicle in all regions of the posterior IC, thus indicating an anxiogenic-like effect. The avoidance of the EPM open arms was completely inhibited in animals subjected to microinjection of CoCl₂ into the intermediate posterior IC. Nevertheless, the same pharmacological treatment into either the rostral or caudal subregions of the posterior IC did not affect the restraint-evoked behavioral changes in the EPM. Taken together, these results suggest that regulation of anxiogenic-like effect to emotional stress along the rostrocaudal axis of the posterior IC might occur in a site-specific manner, indicating a role of the intermediate subregion.

A thalamic circuit facilitates stress susceptibility via melanocortin 4 receptor-mediated activation of nucleus accumbens shell

AIMS

Central melanocortin 4 receptor (MC4R) has been reported to induce anhedonia via eliciting dysfunction of excitatory synapses. It is evident that metabolic signals are closely related to chronic stress-induced depression. Here, we investigated that a neural circuit is involved in melanocortin signaling contributing to susceptibility to stress.

METHODS

Chronic social defeat stress (CSDS) was used to develop depressive-like behavior. Electrophysiologic and chemogenetic approaches were performed to evaluate the role of paraventricular thalamus (PVT) glutamatergic to nucleus accumbens shell (NAcsh) circuit in stress susceptibility. Pharmacological and genetic manipulations were applied to investigate the molecular mechanisms of melanocortin signaling in the circuit.

RESULTS

CSDS increases the excitatory neurotransmission in NAcsh through MC4R signaling. The enhanced excitatory synaptic input in NAcsh is projected from PVT glutamatergic neurons. Moreover, chemogenetic manipulation of PVT^Glu -NAcsh projection mediates the susceptibility to stress, which is dependent on MC4R signaling. Overall, these results reveal that the strengthened excitatory neurotransmission in NAcsh originates from PVT glutamatergic neurons, facilitating the susceptibility to stress through melanocortin signaling.

CONCLUSIONS

Our results make a strong case for harnessing a thalamic circuit to reorganize excitatory synaptic transmission in relieving stress susceptibility and provide insights gained on metabolic underpinnings of protection against stress-induced depressive-like behavior.

Magel2 knockdown in hypothalamic POMC neurons innervating the medial amygdala reduces susceptibility to diet-induced obesity

Hyperphagia and obesity profoundly affect the health of children with Prader-Willi syndrome (PWS). The Magel2 gene among the genes in the Prader-Willi syndrome deletion region is expressed in proopiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (ARC). Knockout of the Magel2 gene disrupts POMC neuronal circuits and functions. Here, we report that loss of the Magel2 gene exclusively in ARC^POMC neurons innervating the medial amygdala (MeA) causes a reduction in body weight in both male and female mice fed with a high-fat diet. This anti-obesity effect is associated with an increased locomotor activity. There are no significant differences in glucose and insulin tolerance in mice without the Magel2 gene in ARC^POMC neurons innervating the MeA. Plasma estrogen levels are higher in female mutant mice than in controls. Blockade of the G protein-coupled estrogen receptor (GPER), but not estrogen receptor-α (ER-α), reduces locomotor activity in female mutant mice. Hence, our study provides evidence that knockdown of the Magel2 gene in ARC^POMC neurons innervating the MeA reduces susceptibility to diet-induced obesity with increased locomotor activity through activation of central GPER.

Association and interaction of the MC4R rs17782313 polymorphism with plasma ghrelin, GLP-1, cortisol, food intake and eating behaviors in overweight/obese Iranian adults

BACKGROUND

Recent studies have shown that obesity is largely influenced by heredity and created by the interactions between several genes and environmental and behavioral factors. This study aimed to examine association between variant rs17782313 near melanocortin-4 receptor (MC4R) gene and behavioral and hormonal factors then evaluated interactions between variant MC4R rs17782313 with behavioral and hormonal factors on obesity.

METHODS

This cross-sectional study included 403 subjects, overweight and/or obesity, aged 20-50 years from Iran. The MC4R rs17782313 data were measured by the PCR-RFLP method. Dietary intake, physical activity, stress, anxiety, depression, appetite and emotional eating were assessed by using validated questionnaires. Ghrelin, glucagon-like peptide-1 and cortisol were measured by radioimmunoassay in plasma samples. Participants were also divided into three groups based on rs17782313 genotype and BMI.

RESULTS

After adjustment for age, gender, energy intake and PA, significant associations were observed between food intake, appetite, emotional eating, stress and physical activity with MC4R rs17782313 (p ˂0.05). Also, significant interactions were observed between fat intake (p-interaction = 0.002), protein intake (p-interaction = 0.01), energy intake (p-interaction = 0.01), emotional eating (p-interaction = 0.02), appetite (p-interaction = 0.04), stress (p-interaction = 0.04), ghrelin (p-interaction = 0.03), cortisol (p-interaction = 0.04) and physical activity (p-interaction = 0.04) and MC4R rs17782313 in terms of BMI.

CONCLUSION

Interactions between the CC genotype and high intakes of fat and energy, emotional eating, high appetite, and too much stress with high levels of cortisol and ghrelin probably can have an effect on BMI in overweight/obese subjects.

Melanocortin Signaling Connecting Systemic Metabolism With Mood Disorders

Obesity and mood disorders are often overlapping pathologies that are prevalent public health concerns. Many studies have indicated a positive correlation between depression and obesity, although weight loss and decreased appetite are also recognized as features of depression. Accordingly, DSM-5 defines two subtypes of depression associated with changes in feeding: melancholic depression, characterized by anhedonia and associated with decreased feeding and appetite; and atypical depression, characterized by fatigue, sleepiness, hyperphagia, and weight gain. The central nervous system plays a key role in the regulation of feeding and mood, thus suggesting that overlapping neuronal circuits may be involved in their modulation. However, these circuits have yet to be completely characterized. The central melanocortin system, a circuitry characterized by the expression of specific peptides (pro-opiomelanocortins, agouti-related protein, and neuropeptide Y) and their melanocortin receptors, has been shown to be a key player in the regulation of feeding. In addition, the melanocortin system has also been shown to affect anxiety and depressive-like behavior, thus suggesting a possible role of the melanocortin system as a biological substrate linking feeding and depression. However, more studies are needed to fully understand this complex system and its role in regulating metabolic and mood disorders. In this review, we will discuss the current literature on the role of the melanocortin system in human and animal models in feeding and mood regulation, providing evidence of the biological interplay between anxiety, major depressive disorders, appetite, and body weight regulation.

Intracerebroventricular administration of α-melanocyte-stimulating hormone (α-MSH) enhances thigmotaxis and induces anxiety-like behavior in the goldfish Carassius auratus

α-Melanocyte-stimulating hormone (α-MSH) is a body pigmentation-regulating hormone secreted from the intermediate lobe of the pituitary in vertebrates. It is also produced in the brain, and acts as an anorexigenic neuropeptide involved in feeding regulation. In rodents, intracerebroventricular (ICV) administration of α-MSH has been shown to affect not only feeding behavior, but also psychomotor activity. However, there is still no information regarding the psychophysiological effects of α-MSH on behavior in fish. Therefore, we examined the effect of synthetic α-MSH on psychomotor activity in goldfish. Since this species prefers the edge to the central area of a tank, we used this as a preference test for assessing psychomotor activity. When α-MSH was administered ICV at 1 and 10 pmol g^-1 body weight (BW), the time spent in the edge area of a tank was prolonged at 10 pmol g^-1 BW. However, α-MSH at these doses did not affect locomotor activity. The action of α-MSH mimicked those of FG-7142 (a central-type benzodiazepine receptor (CBR) inverse agonist with an anxiogenic effect) at 10 pmol g^-1 BW and melanotan II (a melanocortin 4 receptor (MC4R) agonist) at 50 pmol g^-1 BW, whereas ICV administration of tofisopam (a CBR agonist with an anxiolytic effect) at 10 pmol g^-1 BW prolonged the time spent in the central area. The anxiogenic-like effect of α-MSH was abolished by treatment with the MC4R antagonist HS024 at 50 pmol g^-1 BW. These data indicate that α-MSH affects psychomotor activity in goldfish, and exerts an anxiogenic-like effect via the MC4R-signaling pathway.

Nerve injury alters restraint-induced activation of the basolateral amygdala in male rats

The amygdala is critical for the production of appropriate responses towards emotional or stressful stimuli. It has a characteristic neuronal activation pattern to acute stressors. Chronic pain and acute stress have each been shown to independently modulate the activity of the amygdala. Few studies have investigated the effect of pain or injury, on amygdala activation to acute stress. This study investigated the effects of a neuropathic injury on the activation response of the amygdala to an acute restraint stress. Chronic constriction injury of the right sciatic nerve (CCI) was used to create neuropathic injury and a single brief 15-min acute restraint was used as an emotional/psychological stressor. All rats received cholera toxin B (CTB) retrograde tracer injections into the medial prefrontal cortex (mPFC) to assess if the amygdala to mPFC pathway was specifically regulated by the combination of neuropathic injury and acute stress. To assess differential patterns of activity in amygdala subregions, cFos expression was used as a marker for "acute", restraint triggered neuronal activation, and FosB/ΔFosB expression was used to reveal prolonged neuronal activation/sensitisation triggered by CCI. Restraint resulted in a characteristic increase in cFos expression in the medial amygdala, which was not altered by CCI. Rats with a CCI showed increased cFos expression in the basolateral amygdala (BLA), in response to an acute restraint stress, but not in neurons projecting to the prefrontal cortex. Further, CCI rats showed an increase in FosB/ΔFosB expression which was exclusive to the BLA. This increase likely reflects sensitisation of the BLA as a consequence of nerve injury which may contribute to heightened sensitivity of BLA neurons to acute emotional/ psychological stressors.

κ-Opioid receptors in the medial amygdaloid nucleus modulate autonomic and neuroendocrine responses to acute stress

The medial amygdaloid nucleus (MeA) is a key neural structure in triggering physiologic and behavioral control during aversive situations. However, MeA role during stress exposure has not yet been fully elucidated. Thus, in the present study, we investigated the involvement of the MeA opioid neurotransmission in the modulation of autonomic, neuroendocrine and behavioral responses evoked by acute restraint stress (RS). The bilateral microinjection of naloxone (non-selective opioid antagonist) into the MeA potentiated RS-evoked autonomic responses and increased plasma corticosterone levels, in a dose-dependent manner. However, no effects were observed in RS-evoked increases on plasma oxytocin levels and anxiogenic-like behavior. Similar to naloxone, MeA pretreatment with the selective κ-opioid antagonist (nor-BNI) also enhanced heart rate and corticosterone increases induced by RS, whereas treatment with selective µ- or δ-opioid antagonists did not affect the physiologic and behavioral responses caused by RS. The present results showed MeA κ-opioid receptors modulate heart rate and corticosterone increases evoked by acute RS, reinforcing the idea of an inhibitory role exerted by MeA during aversive situations .

The Role of Melanocortin Plasticity in Pain-Related Outcomes After Alcohol Exposure

The global COVID-19 pandemic has shone a light on the rates and dangers of alcohol misuse in adults and adolescents in the US and globally. Alcohol exposure during adolescence causes persistent molecular, cellular, and behavioral changes that increase the risk of alcohol use disorder (AUD) into adulthood. It is established that alcohol abuse in adulthood increases the likelihood of pain hypersensitivity and the genesis of chronic pain, and humans report drinking alcohol to relieve pain symptoms. However, the longitudinal effects of alcohol exposure on pain and the underlying CNS signaling that mediates it are understudied. Specific brain regions mediate pain effects, alcohol effects, and pain-alcohol interactions, and neural signaling in those brain regions is modulated by neuropeptides. The CNS melanocortin system is sensitive to alcohol and modulates pain sensitivity, but this system is understudied in the context of pain-alcohol interactions. In this review, we focus on the role of melanocortin signaling in brain regions sensitive to alcohol and pain, in particular the amygdala. We also discuss interactions of melanocortins with other peptide systems, including the opioid system, as potential mediators of pain-alcohol interactions. Therapeutic strategies that target the melanocortin system may mitigate the negative consequences of alcohol misuse during adolescence and/or adulthood, including effects on pain-related outcomes.

The Melanocortin System behind the Dysfunctional Eating Behaviors

The dysfunction of melanocortin signaling has been associated with obesity, given the important role in the regulation of energy homeostasis, food intake, satiety and body weight. In the hypothalamus, the melanocortin-3 receptor (MC3R) and melanocortin-4 receptor (MC4R) contribute to the stability of these processes, but MC3R and MC4R are also localized in the mesolimbic dopamine system, the region that responds to the reinforcing properties of highly palatable food (HPF) and where these two receptors seem to affect food reward and motivation. Loss of function of the MC4R, resulting from genetic mutations, leads to overeating in humans, but to date, a clear understanding of the underlying mechanisms and behaviors that promote overconsumption of caloric foods remains unknown. Moreover, the MC4R demonstrated to be a crucial modulator of the stress response, factor that is known to be strictly related to binge eating behavior. In this review, we will explore the preclinical and clinical studies, and the controversies regarding the involvement of melanocortin system in altered eating patterns, especially binge eating behavior, food reward and motivation.

Methylglyoxal disturbs DNA repair and glyoxalase I system in Saccharomyces cerevisiae

Methylglyoxal (MG) is a highly reactive aldehyde able to form covalent adducts with proteins and nucleic acids, disrupting cellular functions. In this study, we performed a screening of Saccharomyces cerevisiae (S. cerevisiae) strains to find out which genes of cells are responsive to MG, emphasizing genes against oxidative stress and DNA repair. Yeast strains were grown in the YPD-Galactose medium containing MG (0.5 to 12 mM). The tolerance to MG was evaluated by determining cellular growth and cell viability. The toxicity of MG was more pronounced in the strains with deletion in genes engaged with DNA repair checkpoint proteins, namely Rad23 and Rad50. MG also impaired the growth and viability of S. cerevisiae mutant strains Glo1 and Gsh1, both components of the glyoxalase I system. Differently, the strains with deletion in genes encoding for antioxidant enzymes were apparently resistant to MG. In summary, our data indicate that DNA repair and MG detoxification pathways are keys in the control of MG toxicity in S. cerevisiae.

Activation of the ARCPOMC→MeA Projection Reduces Food Intake

Proopiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (ARC) plays an essential role in the control of food intake and energy expenditure. Melanocortin-4 receptors (MC4Rs) are expressed in key areas that are implicated in regulating energy homeostasis. Although the importance of MC4Rs in the paraventricular hypothalamus (PVH) has been well documented, the role of MC4Rs in the medial amygdala (MeA) on feeding remains controversial. In this study, we specifically examine the role of a novel ARCPOMC→MeA neural circuit in the regulation of short-term food intake. To map a local melanocortinergic neural circuit, we use monosynaptic anterograde as well as retrograde viral tracers and perform double immunohistochemistry to determine the identity of the neurons receiving synaptic input from POMC neurons in the ARC. To investigate the role of the ARCPOMC→MeA projection on feeding, we optogenetically stimulate channelrhodopsin-2 (ChR2)-expressing POMC fibers in the MeA. Anterograde viral tracing studies reveal that ARC POMC neurons send axonal projections to estrogen receptor-α (ER-α)- and MC4R-expressing neurons in the MeA. Retrograde viral tracing experiments show that the neurons projecting to the MeA is located mainly in the lateral part of the ARC. Optogenetic stimulation of the ARCPOMC→MeA pathway reduces short-term food intake. This anorectic effect is blocked by treatment with the MC4R antagonist SHU9119. In addition to the melanocortinergic local circuits within the hypothalamus, this extrahypothalamic ARCPOMC→MeA neural circuit would play a role in regulating short-term food intake.

Angiotensinergic receptors in the medial amygdaloid nucleus differently modulate behavioral responses in the elevated plus-maze and forced swimming test in rats

The brain renin-angiotensin system (RAS) has been implicated in anxiety and depression disorders, but the specific brain sites involved are poorly understood. The medial amygdaloid nucleus (MeA) is involved in expression of behavioral responses. However, despite evidence of the presence of all angiotensinergic receptors in this amygdaloid nucleus, regulation of anxiety- and depressive-like behaviors by angiotensinergic neurotransmissions within the MeA has never been reported. Thus, the present study aimed to investigate the role angiotensin II (AT₁ and AT₂ receptors) and angiotensin-(1-7) (Mas receptor) receptors present within the MeA in behavioral responses in the elevated plus-maze (EPM) and forced swimming test (FST). For this, male Wistar rats had cannula-guide bilaterally implanted into the MeA, and independent sets of animals received bilateral microinjections of either the selective AT₁ receptor antagonist losartan, the selective AT₂ receptor antagonist PD123319, the selective Mas receptor antagonist A-779 or vehicle into the MeA before the EPM and FST. Treatment of the MeA with either PD123319 or A-779 decreased the EPM open arms exploration, while losartan did not affect behavioral responses in this apparatus. However, intra-MeA microinjection of losartan decreased immobility in the FST. Administration of either PD123319 or A-779 into the MeA did not affect the immobility during the FST, but changed the pattern of the active behaviors swimming and climbing. Altogether, these results indicate the presence of different angiotensinergic mechanisms within the MeA controlling behavioral responses in the FST and EPM.

Tak1 in the astrocytes of mediobasal hypothalamus regulates anxiety-like behavior in mice

Anxiety disorder is characterized by excessive fear, anxiety, and avoidance of perceived threats in internal to oneself or the environment, however, the underlying mechanisms are less well understood. Here, we show that transforming growth factor-β-activated kinase 1 (Tak1) expressed in the astrocytes of mediobasal hypothalamus (MBH) plays a crucial role in anxiety-like behavior in mice. Our data demonstrate that deficiency of Tak1 in astrocytes increased anxiety level, but did not impact locomotor activity in mice. Astrocytic activation of Tak1 in the MBH mitigated the anxiety-like behavior, whereas suppression of Tak1 in MBH astrocytes promoted the anxiety-like behavior in mice. Collectively, these data suggest that Tak1 expressed in the MBH astrocytes could modulate the anxiety-like behavior in mice.

Genetic contributions to the etiology of anorexia nervosa: New perspectives in molecular diagnosis and treatment

Background

Anorexia nervosa is a multifactorial eating disorder that manifests with self‐starvation, extreme anxiety, hyperactivity, and amenorrhea. Long‐term effects include organ failure, disability, and in extreme cases, even death.

Methods

Through a literature search, here we summarize what is known about the molecular etiology of anorexia nervosa and propose genetic testing for this condition.

Results

Anorexia nervosa often has a familial background and shows strong heritability. Various genetic studies along with genome‐wide association studies have identified several genetic loci involved in molecular pathways that might lead to anorexia.

Conclusion

Anorexia nervosa is an eating disorder with a strong genetic component that contributes to its etiology. Various genetic approaches might help in the molecular diagnosis of this disease and in devising novel therapeutic options.

Anorexia nervosa is a multifactorial eating disorder with a strong genetic component that manifests with self‐starvation, extreme anxiety, hyperactivity, and amenorrhea. Through a literature search, here we summarize what is known about the molecular etiology of anorexia nervosa and propose genetic testing for this condition.

The Role of Genetic Variation of BMI, Body Composition, and Fat Distribution for Mental Traits and Disorders: A Look-Up and Mendelian Randomization Study

Anthropometric traits and mental disorders or traits are known to be associated clinically and to show genetic overlap. We aimed to identify genetic variants with relevance for mental disorders/traits and either (i) body mass index (or obesity), (ii) body composition, (and/or) (iii) body fat distribution. We performed a look-up analysis of 1,005 genome-wide significant SNPs for BMI, body composition, and body fat distribution in 15 mental disorders/traits. We identified 40 independent loci with one or more SNPs fulfilling our threshold significance criterion (P < 4.98 × 10^–5) for the mental phenotypes. The majority of loci was associated with schizophrenia, educational attainment, and/or intelligence. Fewer associations were found for bipolar disorder, neuroticism, attention deficit/hyperactivity disorder, major depressive disorder, depressive symptoms, and well-being. Unique associations with measures of body fat distribution adjusted for BMI were identified at five loci only. To investigate the potential causality between body fat distribution and schizophrenia, we performed two-sample Mendelian randomization analyses. We found no causal effect of body fat distribution on schizophrenia and vice versa. In conclusion, we identified 40 loci which may contribute to genetic overlaps between mental disorders/traits and BMI and/or shape related phenotypes. The majority of loci identified for body composition overlapped with BMI loci, thus suggesting pleiotropic effects.

Sex-dependent effects of MC4R genotype on HPA axis tone: implications for stress-associated cardiometabolic disease

The melanocortin-4 receptor (MC4R) facilitates hypothalamic-pituitary-adrenocortical (HPA) axis responses to acute stress in male rodents and is a well known to regulator of energy balance. Mutations in the MC4R is the most common monogenic cause of obesity in humans and has been associated with sex-specific effects, but whether stress regulation by the MC4R is sex-dependent, and whether the MC4R facilitates HPA responses to chronic stress, is unknown. We hypothesized that MC4R-signaling contributes to HPA axis dysregulation and metabolic pathophysiology following chronic stress exposure. We measured changes in energy balance, HPA axis tone, and vascular remodeling during chronic variable stress (CVS) in male and female rats with MC4R loss-of-function. Rats were placed into three groups (n = 9-18/genotype/sex) and half of each group was subjected to CVS for 30 days or were non-stressed littermate controls. All rats underwent an acute restraint stress challenge on Day 30. Rats were euthanized on Day 31, adrenals collected for weight, and descending aortas fixed for morphological indices of vascular pathophysiology. We observed a marked interaction between Mc4r genotype and sex for basal HPA axis tone and acute stress responsivity. MC4R loss-of-function blunted both endpoints in males but exaggerated them in females. Contrary to our hypothesis, Mc4r genotype had no effect on either HPA axis responses or metabolic responses to chronic stress. Heightened stress reactivity of females with MC4R mutations suggests a possible mechanism for the sex-dependent effects associated with this mutation in humans and highlights how stress may differentially regulate metabolism in males and females. Lay summary The hypothalamic melanocortin system is an important regulator of energy balance and stress responses. Here, we report a sex-difference in the stress reactivity of rats with a mutation in this system. Our findings highlight how stress may regulate metabolism differently in males and females and may provide insight into sex-differences associated with this mutation in humans.

Melanotan-II reverses autistic features in a maternal immune activation mouse model of autism

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder characterized by impaired social interactions, difficulty with communication, and repetitive behavior patterns. In humans affected by ASD, there is a male pre-disposition towards the condition with a male to female ratio of 4:1. In part due to the complex etiology of ASD including genetic and environmental interplay, there are currently no available medical therapies to improve the social deficits of ASD. Studies in rodent models and humans have shown promising therapeutic effects of oxytocin in modulating social adaptation. One pharmacological approach to stimulating oxytocinergic activity is the melanocortin receptor 4 agonist Melanotan-II (MT-II). Notably the effects of oxytocin on environmental rodent autism models has not been investigated to date. We used a maternal immune activation (MIA) mouse model of autism to assess the therapeutic potential of MT-II on autism-like features in adult male mice. The male MIA mice exhibited autism-like features including impaired social behavioral metrics, diminished vocal communication, and increased repetitive behaviors. Continuous administration of MT-II to male MIA mice over a seven-day course resulted in rescue of social behavioral metrics. Normal background C57 male mice treated with MT-II showed no significant alteration in social behavioral metrics. Additionally, there was no change in anxiety-like or repetitive behaviors following MT-II treatment of normal C57 mice, though there was significant weight loss following subacute treatment. These data demonstrate MT-II as an effective agent for improving autism-like behavioral deficits in the adult male MIA mouse model of autism.

The Role of Proopiomelanocortin and α-Melanocyte-Stimulating Hormone in the Metabolic Syndrome in Psychiatric Disorders: A Narrative Mini-Review

The metabolic syndrome (MetS) comprises abdominal obesity, preclinical or full diabetes type 2, arterial hypertension, and dyslipidemia and affects a significant proportion of the general population with a remarkably higher prevalence in patients suffering from psychiatric disorders. However, studies exploring the pathogenetic link between MetS and psychiatric diseases are rare. Here, we aim to narrow this gap in knowledge by providing a narrative review on this topic that focuses on two psychiatric diseases, namely on schizophrenia and posttraumatic stress disorder (PTSD) since we assume them to be associated with two different main causalities of MetS: in schizophrenia, MetS evidently develops or aggravates in response to antipsychotic drug treatment while it assumingly develops in response to stress-induced endocrine and/or epigenetic alterations in PTSD. First, we compared the prevalences of MetS and associated pathologies (which we took from the latest meta-analyses) among different psychiatric disorders and were surprised that the prevalences of arterial hypertension and hyperglycemia in PTSD almost doubles those of the other psychiatric disorders. Next, we performed a literature search on the neurobiology of MetS and found numerous articles describing a role for proopiomelanocortin (POMC) in MetS. Thus, we concentrated further analysis on POMC and one of its downstream effector hormones, α-melanocyte-stimulating hormone (α-MSH). We found some evidence for a role of POMC in both PTSD and schizophrenia, in particular in antipsychotic-induced MetS, as well as for α-MSH in schizophrenia, but, surprisingly, no study on α-MSH in PTSD. Taken together, our synopsis reveals, first, a potential interaction between the POMC system and stress in the assumingly at least partially shared pathogenesis of psychiatric disorders and MetS, second, that modulation of the POMC system, in particular of the melanocortin 3 and 4 receptors, might be a promising target for the treatment of MetS and, third, that the DNA methylation status of POMC might speculatively be a promising biomarker for MetS in general and, possibly, in particular in the context of stress-related psychiatric conditions such as PTSD. To best of our knowledge, this is the first review on the role of the POMC system in MetS in psychiatric disorders.

Adiponectin modulates ventral tegmental area dopamine neuron activity and anxiety-related behavior through AdipoR1

Adiponectin, a metabolic hormone secreted by adipocytes, can cross the blood-brain barrier to act on neurons in different brain regions, including those involved in stress-related disorders. Here we show that dopamine neurons in the ventral tegmental area (VTA) express adiponectin receptor 1 (AdipoR1). Intra-VTA infusion of adiponectin or the adiponectin mimetic AdipoRon in wild-type mice decreases basal dopamine neuron population activity and firing rate and reverses the restraint stress-induced increase in dopamine neuron activity and anxiety behavior. Adiponectin haploinsufficiency leads to increased dopamine neuron firing and anxiety behavior under basal conditions. Ablation of AdipoR1 specifically from dopamine neurons enhances neuronal and anxiogenic responses to restraint stress. The effects of intra-VTA infusion of adiponectin on neuronal activity and behavior were abolished in mice lacking AdipoR1 in dopamine neurons. These observations indicate that adiponectin can directly modulate VTA dopamine neuron activity and anxiety behavior, and that AdipoR1 is required for adiponectin-induced inhibition of dopamine neurons and anxiolytic effects. These results strengthen the idea of adiponectin as a key biological factor that links metabolic syndrome and emotional disorders.

The long-term effect of maternal dietary protein restriction on 5-HT1A receptor function and behavioral responses to stress in adulthood

Maternal nutrition impacts fetal development, and may play a role in determining resilience to stress and vulnerability to stress-precipitated psychiatric disorders, such as anxiety and depression. In this study, we examined the effect of a reduction in maternal dietary protein during pregnancy on the brain neurochemistry and behavior of offspring. We focused specifically on the serotonin system, the 5-HT1A receptor and the responsivity of offspring as adults to stress. Dams were fed either a low protein diet (10% protein by weight) or isocaloric control diet (20% protein by weight). The low protein diet did not alter maternal food intake and body weight, or litter size and the average birth weight of male or female littermates. 5-HT1A receptor function, as measured by quantitative autoradiography of 8-OH-DPAT (1 μM)-stimulated [35S]GTPγS binding, was markedly reduced in hippocampus of weanling female, but not male offspring (postnatal day, PND 21) of dams fed the low protein diet. The number of serotonergic cell bodies in the rostral raphe, and 5-HT metabolism in the limbic system of weanling offspring was not altered by maternal low protein diet. The deficit in hippocampal 5-HT1A receptor function observed in weanling female offspring persisted into adulthood (PND 112), and was accompanied by an increased sensitivity to stress, specifically increased immobility during a 15-minute forced swim challenge and increased anorexia following 30-minute restraint (PND 97-100). The present work begins to uncover important future directions for understanding the early developmental origins of resilience to stress, and factors that may put individuals at greater risk for stress-related psychiatric disorders.

A combinatorial modulation of synaptic plasticity in the rat medial amygdala by oxytocin, urocortin3 and estrogen

The medial nucleus of the amygdala (MeA) plays a pivotal role in a variety of mammalian social behaviors. Specifically, activity of the hypothalamic pro-social neuropeptide oxytocin in the MeA was shown to be crucial for social recognition memory. The MeA is also a hub of neuroendocrine activity and expresses a large number of receptors of neuropeptides and hormones. These include oxytocin receptor, estrogen receptor alpha and corticotropin-releasing factor (CRF) receptor type 2 (CRFR2). In a previous study we found that intracerebroventricular (ICV) oxytocin application to anesthetized rats promotes long-term depression (LTD) of the MeA response to electrical stimulation of its main sensory input, the accessory olfactory bulb (AOB). We also reported that this type of synaptic plasticity contributes to long-term social recognition memory. Here we used similar methodology to examine the possibility that various neuromodulators pose a combinatorial effect on synaptic plasticity in the MeA. We found that ICV administration of the CRF-related peptide urocortin3 fifteen minutes before oxytocin, caused long-term potentiation (LTP), via CRFR2 activation. Similarly, ICV administration of 17β-estradiol forty-five minutes before oxytocin induced LTP, which was blocked by an antagonist of the estrogen receptors alpha and beta. Notably, none of these two neuromodulators had any effect on its own, suggesting that they both turn the oxytocin-mediated synaptic plasticity from LTD to LTP. Finally, we found that application of 17β-estradiol, forty-five minutes before urocortin3 also caused LTP in the MeA response to AOB stimulation, even without oxytocin application. We suggest that the combinatorial modulation of the bidirectional synaptic plasticity in the AOB-MeA pathway by oxytocin, 17β-estradiol and urocotin-3 serves to modify social information processing according to the animal's internal state.

The impact of androgen actions in neurons on metabolic health and disease

The male hormone testosterone exerts different effects on glucose and energy homeostasis in males and females. Testosterone deficiency predisposes males to visceral obesity, insulin resistance and type 2 diabetes. However, testosterone excess predisposes females to similar metabolic dysfunction. Here, we review the effects of testosterone actions in the central nervous system on metabolic function in males and females. In particular, we highlight changes within the hypothalamus that control glucose and energy homeostasis. We distinguish the organizational effects of testosterone in the programming of neural circuitry during development from the activational effects of testosterone during adulthood. Finally, we explore potential sites where androgen might be acting to impact metabolism within the central nervous system.

Manual Acupuncture at PC6 Ameliorates Acute Restraint Stress-Induced Anxiety in Rats by Normalizing Amygdaloid Noradrenergic Response

Acupuncture improves ethanol withdrawal-induced anxiety in rats in an acupoint-dependent manner. Thus, the present study investigated the effects of acupuncture on acute restraint stress- (ARS-) induced anxiety. Male rats were exposed to ARS for 3 h followed by acupuncture at either PC6 (Neiguan), HT7 (Shenmen), or a nonacupoint (tail) once a day for three consecutive days. Five minutes after the third acupuncture treatment, anxiety-like behavior was evaluated in an elevated plus maze (EPM). Additionally, plasma corticosterone (CORT) levels were measured by radioimmunoassay and the concentrations of norepinephrine (NE) and 3-methoxy-4-hydroxy-phenylglycol (MHPG) in the central nucleus of the amygdala (CeA) were determined using high-performance liquid chromatography. Acupuncture at PC6, but not HT7 or a nonacupoint, attenuated anxiety-like behavior, but this attenuation was abolished by a postacupunctural intra-CeA infusion of NE. Acupuncture at PC6 also reduced the oversecretion of plasma CORT and inhibited increases in amygdaloid NE and MHPG induced by ARS. Further, Western blot analyses and real-time polymerase chain reaction assays revealed that acupuncture at PC6 prevented ARS-induced enhancements in the protein and mRNA expressions of tyrosine hydroxylase in the CeA. These results suggest that acupuncture performed specifically at acupoint PC6 reduces ARS-induced anxiety-like behavior by dampening amygdaloid noradrenergic responses.

Pituitary adenylate cyclase-activating polypeptide (PACAP) in the central nucleus of the amygdala induces anxiety via melanocortin receptors

RATIONALE

Anxiety disorders are the most common mental disorders in the USA. Characterized by feelings of uncontrollable apprehension, they are accompanied by physical, affective, and behavioral symptoms. The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) and its receptor PAC1 (PAC1R) are highly expressed in the central nucleus of the amygdala (CeA), and they have gained growing attention for their proposed role in mediating the body's response to stress.

OBJECTIVES

The aim of this study was to evaluate the anxiogenic effects of PACAP in the CeA and its effects on the hypothalamic-pituitary-adrenal (HPA) axis. Furthermore, the mechanism of action of PACAP in the CeA was investigated.

METHODS

PACAP was microinfused into the CeA of rats, and its effects in the elevated plus maze (EPM), the defensive withdrawal tests, and plasma corticosterone levels were evaluated. The ability of the melanocortin receptor antagonist SHU9119 to block PACAP effect in the EPM was assessed.

RESULTS

Intra-CeA PACAP exerted a dose-dependent anxiogenic effect and activated the HPA axis. In contrast, PACAP microinfused into the basolateral nucleus of the amygdala (BlA) had no effect. Finally, the anxiogenic effect of intra-CeA PACAP was prevented by SHU9119.

CONCLUSIONS

These data prove an anxiogenic role for the PACAP system of the CeA and reveal that the melanocortin receptor 4 (MC4R) system of CeA mediates these effects. Our data provide insights into this neuropeptide system as a mechanism for modulating the behavioral and endocrine response to stress and suggest that dysregulations of this system may contribute to the pathophysiology of anxiety-related disorders.

Concordance and incongruence in preclinical anxiety models: Systematic review and meta-analyses

Rodent defense behavior assays have been widely used as preclinical models of anxiety to study possibly therapeutic anxiety-reducing interventions. However, some proposed anxiety-modulating factors - genes, drugs and stressors - have had discordant effects across different studies. To reconcile the effect sizes of purported anxiety factors, we conducted systematic review and meta-analyses of the literature on ten anxiety-linked interventions, as examined in the elevated plus maze, open field and light-dark box assays. Diazepam, 5-HT1A receptor gene knockout and overexpression, SERT gene knockout and overexpression, pain, restraint, social isolation, corticotropin-releasing hormone and Crhr1 were selected for review. Eight interventions had statistically significant effects on rodent anxiety, while Htr1a overexpression and Crh knockout did not. Evidence for publication bias was found in the diazepam, Htt knockout, and social isolation literatures. The Htr1a and Crhr1 results indicate a disconnect between preclinical science and clinical research. Furthermore, the meta-analytic data confirmed that genetic SERT anxiety effects were paradoxical in the context of the clinical use of SERT inhibitors to reduce anxiety.

Interactions with the MC4R rs17782313 variant, mental stress and energy intake and the risk of obesity in Genome Epidemiology Study

Background

The melanocortin-4 receptor (MC4R) regulates metabolism by modulating eating behavior and MC4R variants (rs17782313 and rs571312) are associated with obesity in Asians and Caucasians. However, the impact of their interactions with nutritional and lifestyle factors on obesity are poorly described. Therefore, we investigated the interaction of MC4R variants and dietary patterns on the risk of obesity in Korean middle-aged adults.

Methods

Data collected included, genetic variations, anthropometric and biochemical measurements, dietary and lifestyle habits, and food intake. Data were obtained from the 8830 adults aged 40–69 years in the Ansung and Ansan cohort of the Korean Genome Epidemiology Study.

Results

The MC4R rs18882313 minor allele had a higher frequency in the obese group (P < 0.01). MC4R genotypes were not associated with differences in daily energy and macronutrient intakes. However, the intakes of processed foods and fat (as percentages of energy) were significantly higher and intake of fruits were significantly lower in subjects with MC4R minor alleles (P < 0.05). Interestingly, there was a positive interaction between MC4R variants and mental stress levels that were associated with the risk of obesity after adjusting for age, gender, residence area, daily energy intake, smoking status and physical activity (interaction P = 0.0384). Only in subjects with high stress were MC4R minor alleles associated with higher BMIs after adjusting for confounders. The association was present without modulating energy and nutrient intake. In the group with energy intakes higher than estimated energy requirement (EER), subjects with MC4R minor alleles had higher BMIs than those with the major alleles (P < 0.001).

Conclusions

The interactions of mental stress and energy intakes with the MC4R minor allele genotype might be associated with increased risk of obesity in Korean adults. This research might identify subjects with a specific MC4R minor alleles as a human subset of people with a low metabolic tolerance for excessive energy intake, especially when under stress.

Agouti-related peptide neural circuits mediate adaptive behaviors in the starved state

In the face of starvation, animals will engage in high-risk behaviors that would normally be considered maladaptive. Starving rodents, for example, will forage in areas that are more susceptible to predators and will also modulate aggressive behavior within a territory of limited or depleted nutrients. The neural basis of these adaptive behaviors likely involves circuits that link innate feeding, aggression and fear. Hypothalamic agouti-related peptide (AgRP)-expressing neurons are critically important for driving feeding and project axons to brain regions implicated in aggression and fear. Using circuit-mapping techniques in mice, we define a disynaptic network originating from a subset of AgRP neurons that project to the medial nucleus of the amygdala and then to the principal bed nucleus of the stria terminalis, which suppresses territorial aggression and reduces contextual fear. We propose that AgRP neurons serve as a master switch capable of coordinating behavioral decisions relative to internal state and environmental cues.

Fear Memory

Fear memory is the best-studied form of memory. It was thoroughly investigated in the past 60 years mostly using two classical conditioning procedures (contextual fear conditioning and fear conditioning to a tone) and one instrumental procedure (one-trial inhibitory avoidance). Fear memory is formed in the hippocampus (contextual conditioning and inhibitory avoidance), in the basolateral amygdala (inhibitory avoidance), and in the lateral amygdala (conditioning to a tone). The circuitry involves, in addition, the pre- and infralimbic ventromedial prefrontal cortex, the central amygdala subnuclei, and the dentate gyrus. Fear learning models, notably inhibitory avoidance, have also been very useful for the analysis of the biochemical mechanisms of memory consolidation as a whole. These studies have capitalized on in vitro observations on long-term potentiation and other kinds of plasticity. The effect of a very large number of drugs on fear learning has been intensively studied, often as a prelude to the investigation of effects on anxiety. The extinction of fear learning involves to an extent a reversal of the flow of information in the mentioned structures and is used in the therapy of posttraumatic stress disorder and fear memories in general.

Transgenerational Social Stress, Immune Factors, Hormones, and Social Behavior

A social signal transduction theory of depression has been proposed that states that exposure to social adversity alters the immune response and these changes mediate symptoms of depression such as anhedonia and impairments in social behavior The exposure of maternal rats to the chronic social stress (CSS) of a male intruder depresses maternal care and impairs social behavior in the F1 and F2 offspring of these dams. The objective of the present study was to characterize basal peripheral levels of several immune factors and related hormone levels in the adult F2 offspring of CSS exposed dams and assess whether changes in these factors are associated with previously reported deficits in allogrooming behavior. CSS decreased acid glycoprotein (α1AGP) and intercellular adhesion molecule-1 (ICAM-1) in F2 females, and increased granulocyte macrophage-colony stimulating factor (GM-CSF) in F2 males. There were also sex dependent changes in IL-18, tissue inhibitors of metalloproteinases 1 (TIMP-1), and vascular endothelial growth factor (VEGF). Progesterone was decreased and alpha melanocyte stimulating hormone (α-MSH) was increased in F2 males, and brain-derived neurotrophic factor (BDNF) was decreased in F2 females. Changes in α1AGP, GM-CSF, progesterone, and α-MSH were correlated with decreased allogrooming in the F2 offspring of stressed dams. These results support the hypothesis that transgenerational social stress affects both the immune system and social behavior, and also support previous studies on the adverse effects of early life stress on immune functioning and stress associated immunological disorders, including the increasing prevalence of asthma. The immune system may represent an important transgenerational etiological factor in disorders which involve social and/or early life stress associated changes in social behavior, such as depression, anxiety, and autism, as well as comorbid immune disorders. Future studies involving immune and/or endocrine assessments and manipulations will address specific questions of function and causation, and may identify novel preventative measures and treatments for the growing number of immune mediated disorders.

Anorexia nervosa, seasonality, and polyunsaturated fatty acids

Anorexia nervosa is a serious neurobehavioral disorder marked by semistarvation, extreme fear of weight gain, frequently hyperactivity, and low body temperature. The etiology remains unknown. We present a speculation that a primary causative factor is that polyunsaturated fatty acids are skewed to prevent oxidative damage in phospholipid membranes. This causes a change in the trade off of oxidation protection vs homeoviscous adaptation to lower temperatures, which sets off a metabolic cascade that leads to the rogue state of anorexia nervosa.

Expression of Melanocortin-4 Receptor mRNA in Male Rat Hypothalamus During Chronic Stress

The effects of chronic stress and glucocorticoids receptor antagonist (RU486) on expression of melanocortin 4 receptor (MC4R) mRNA in arcuate nucleus (ARC) of male rats were evaluated. In this study, adult male Sprague Dawley rats were placed into four groups (n=6/group); stress, RU486, stress/RU486, and control groups. In stress group, the rats were restrained, 1 h/day, for 12 days. In RU486 group, the rats were injected RU486 for 12 days. In stress/RU486 group, the rats were injected RU486 1 h before the stress process for 12 days. Relative expression of MC4R mRNA was determined using real-time PCR. Relative expression of MC4R mRNA in the stress group was higher than that of the control rats (P<0.05). Relative expressions of MC4R mRNA were not different between the stress, RU486 and stress/RU486 groups (P>0.05). Chronic restraint stress causes increase in mRNA expression of MC4R in ARC and blockade of glucocorticoid receptors has no effect on this up-regulation.

High cortisol response to adrenocorticotrophic hormone identifies ewes with reduced melanocortin signalling and increased propensity to obesity

We have identified female sheep that have either high (HR) or low (LR) cortisol responses to adrenocorticotrophin. On a high-energy diet, HR have greater propensity to weight gain and obesity, although the underlying mechanisms remain to be determined. Hypothalamic appetite-regulating peptides (ARP) exert reciprocal effects on food intake and energy expenditure. We aimed to quantify the expression and function of ARP in LR and HR ewes (n = 4 per group). Gene expression for neuropeptide Y (NPY), agouti-related peptide (AgRP) pro-opiomelanocortin (POMC), melanin-concentrating hormone (MCH), orexin and the melanocortin receptors (MC3R and MC4R) was measured by in situ hybridisation. Expression of NPY, AgRP and POMC was similar in HR and LR, although expression of orexin, MCH, MC3R and MC4R was higher (P < 0.05) in LR. Intracerebroventricular infusions of a low dose (50 μg/h) of NPY, α-melanocyte-stimulating hormone (αMSH), orexin and MCH were performed between 10.00 h and 16.00 h in meal-fed ewes (n = 6-7 per group). Skeletal muscle and retroperitoneal (RP) fat temperatures were recorded using dataloggers. Post-prandial thermogenesis in muscle was higher (P < 0.05) in LR. There was little effect of ARP infusion on muscle or fat temperature in either group. Infusion of these doses of NPY, MCH or orexin did not stimulate food intake in meal-fed ewes, although αMSH reduced (P < 0.01) food intake in LR only. Using 24-h ARP infusions with ad lib. feeding, NPY increased (P < 0.001) food intake in both groups but αMSH was only effective in LR (P < 0.05). In summary, we show that HR are resistant to the satiety effects of αMSH and this coincides with a reduced expression of both the MC3R and MC4R in the paraventricular nucleus of the hypothalamus. We conclude that an increased propensity to obesity in HR female sheep is associated with reduced melanocortin signalling.