Body shape rather than facial emotion of others alters interpersonal distance in patients with anorexia nervosa

OBJECTIVE

The study investigated interpersonal distance in patients with anorexia nervosa (AN), focussing on the role of other's facial expression and morphology, also assessing physiological and subjective responses.

METHOD

Twenty-nine patients with AN and 30 controls (CTL) were exposed to virtual characters either with an angry, neutral, or happy facial expression or with an overweight, normal-weight, or underweight morphology presented either in the near or far space while we recorded electrodermal activity. Participants had to judge their preferred interpersonal distance with the characters and rated them in terms of valence and arousal.

RESULTS

Unlike CTL, patients with AN exhibited heightened electrodermal activity for morphological stimuli only, when presented in the near space. They also preferred larger and smaller interpersonal distances with overweight and underweight characters respectively, although rating both negatively. Finally, and similar to CTL, they preferred larger interpersonal distance with angry than neutral or happy characters.

DISCUSSION

Although patients with AN exhibited behavioural response to emotional stimuli similar to CTL, they lacked corresponding physiological response, indicating emotional blunting towards emotional social stimuli. Moreover, they showed distinct behavioural and physiological adjustments in response to body shape, confirming the specific emotional significance attached to body shape.

The role of dysregulated ghrelin/LEAP-2 balance in anorexia nervosa

LEAP-2 is a ghrelin antagonist with an anorexigenic drive. This study investigates the evolution of plasma ghrelin and LEAP-2 concentrations in 29 patients with anorexia nervosa (AN) before and after refeeding and compares it to physiological adaptations during fasting in healthy controls or to mouse model of chronic food restriction and refeeding. Acute and chronic food restriction decrease LEAP-2 and increase ghrelin concentrations in both humans and mice, while patients with AN displayed higher ghrelin and LEAP-2 concentrations before than after refeeding (p = 0.043). After 6 months follow-up, patients with unstable weight gain (n = 17) had significantly decreased LEAP-2 concentrations after refeeding (p = 0.044), in contrast to patients with stable weight gain (n = 12). We provide evidence that the ghrelin/LEAP-2 system is not regulated according to the nutritional status in AN, in contrast to what is physiologically expected when coping with food restriction.

Are anxiety and depression associated with cognition and cardiovascular function in young male and female adults?

The results of recent studies suggested that emotional disorders (such as anxiety and depression), cognitive impairments and cardiovascular disorders are related on the subclinical level. These major health issues are often concomitant and have complex, sex-dependent relationships; it is therefore important to study these issues concomitantly in the general population, in order to gain a better understanding of early-stage subclinical relationships between these conditions. The objective of this exploratory study was to assess correlations between anxiety, depression, cognition, and endothelial function in young adults from the general population. Endothelial function (via the reactive hyperaemia index (RHI) was assessed with a plethysmographic device. Depression and anxiety were self-reported via the Beck Disorder Inventory II and the State-Trait Anxiety Inventory, respectively. The Cambridge Neuropsychological Test Automated Battery was used to measure performances in visuospatial memory, visuospatial working memory, and sustained attention. Performances in inhibition and flexibility were evaluated with the Color Word Interference Test. Forty-four young adults (21 males; mean ± standard deviation age: 25.8 ± 1.1; 23 females; mean age: 25.6 ± 1.4) were included in the study. Anxiety was correlated with a low RHI (r = -0.40, p = 0.015, 95% CI [-0.64, -0.08]). In females, the depression score was positively correlated with the number of errors in the visuospatial memory task (r = 0.42, p = 0.049; 95% CI [-0.002, 0.70]) and visuospatial working memory (r = 0.57, p = 0.005; 95% CI [0.10, 0.79]). In males, high anxiety and depression scores were negatively correlated with the number of errors in visuospatial working memory task (anxiety: r = -0.77, p = 0.001; 95% CI [-0.91, -0.43]; depression r = -0.61, p = 0.004, 95% CI [-0.82, -0.22], respectively). However, the relationship between cognitive performance and RHI was not significant. Our data suggest that anxiety and depression could be differentially related to cognitive and endothelial functions in a non-clinical population of young adults. More research is needed to confirm these results, understand the pathophysiological mechanisms in more details, and assess the importance of a sex-specific approach.

Chronic food restriction in mice and increased systemic ghrelin induce preference for running wheel activity

OBJECTIVES

In eating disorders, particularly anorexia nervosa (AN), patients exhibit intense physical activity which is inappropriate regarding food restriction and chronic undernutrition, and exacerbates weight loss and energy deprivation. Rodent models of food restriction exhibit increased running wheel activity in the food anticipation period, also known as Food Anticipatory Activity (FAA). FAA probably has various physiological and/or neurobiological origins. Plasma concentrations of the orexigenic hormone ghrelin are, for example, increased during FAA. We hypothesize that the drive for physical activity in chronic food restriction is triggered by metabolic factors but also relies on motivational aspects that we aim to decipher in this study.

METHODS

Young female C57Bl6/J mice were exposed to a paradigm based on a progressive 50% quantitative food restriction alone (FR) or associated with running wheel activity (Food Restriction Wheel: FRW) in their home-cage during 15 days. We measured preference for running wheel in a three-chamber apparatus in which animals could choose to explore either a known running wheel or a novel object. Testing took place either during resting or during FAA. We calculated the time spent in each compartment and the activity in running wheels. After progressive refeeding over 10 days, mice were tested again when refed. Plasma levels of both ghrelin isoforms were measured with selective immunoassays.

RESULTS

When tested during FAA period, food restricted mice displayed increased preference for the running wheel compared to ad libitum fed controls. Both FR and FRW mice exhibited increased running time and distance in the wheel and running distance was correlated with ghrelin levels. Similar preference and behavior were found when testing took place during the resting period. Animals housed without an active wheel also exhibited active running. Progressive refeeding resulted in body weight restoration, a decrease in FAA and completely abolished preference for the running wheel. Refed animals displayed similar behavior as ad libitum fed controls.

CONCLUSIONS

These data provide evidence that food restriction-induced physical activity is closely correlated with metabolic adaptations to nutritional status implicating ghrelin in the quantity of physical activity.

Methodological considerations for ghrelin isoforms assay in clinical evaluation in anorexia nervosa

The growing interest concerning the role of metabolic sensors in various eating disorders requires the implementation of a strict methodology to collect, store and process blood samples in clinical studies. In particular, measurement of isoforms of the appetite-stimulating hormone, ghrelin, has been challenging in clinical settings. Indeed the acyl ghrelin (AG) isoform is rapidly degraded into desacyl ghrelin (DAG) by blood esterases, thus optimal conditions for the conservation of AG and accurate determination of AG/DAG ratio should be used. Here, we compared different protease inhibitors (Aprotinin, PHMB, AEBSF) during blood collection, increasing delays (0–180 min) before centrifugation, plasma supplementation with various HCl concentrations, storage durations of frozen plasma (8 and 447 days) and immunoenzyme-assay procedures (one-step versus sequential) in healthy subjects. Optimal conditions were obtained by collecting blood with aprotinin and supplementation of plasma with 0.1 N HCl with subsequent freezing for at least 8 days and using one-step assay. Under such conditions, different patterns of secretion of ghrelin isoforms were characterized in patients with restrictive-type anorexia nervosa (AN-R) before and after nutritional recovery. We illustrate the pulsatile variations of ghrelin isoforms according to the time around a meal and hunger rates in 3 patients with AN-R. This study offers a comprehensive comparison of various conditions using selective and specific immunoassays for both ghrelin isoforms in order to optimize assay sensitivity and consistency among procedures. These assay conditions could therefore be widely used to elucidate precisely the role of ghrelin isoforms on eating behavior in physiological and pathological situations.

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Treatment conditions and assay procedures are critical for ghrelin isoforms level determination in plasma.

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Specific treatment conditions allow long term stability of ghrelin isoforms.

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HCl supplementation of plasma before freezing improves AG/DAG ratio on the short and long term.

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Variations of ghrelin isoforms occur with meal timing and chronic nutritional status in patients with anorexia nervosa.

Clinical meaning of body temperatures in anorexia nervosa and bulimia nervosa

OBJECTIVE

Bradycardia is one of the common cardiac abnormalities in patients with eating disorders. It ensues from hypometabolism, which results from reduced caloric intake and consequential weight loss. Hypothermia is another consequence of hypometabolism. While at-rest metabolism and body mass index (BMI) are typically used to assess hypometabolism and estimate potential bradycardia, we hypothesised that body temperature, which is easy to measure, could also capture the presence of this threatening cardiovascular condition.

METHOD

We monitored heart rate continuously for 72 h, measured resting energy expenditure (REE) and assessed body temperature in 12 body parts for 58 patients with anorexia nervosa (AN) and 29 patients with bulimia nervosa (BN).

RESULTS

Palm temperature reflects bradycardia in both AN and BN, explaining 18% of its variance (p < 0.001), capturing this aspect even more efficiently than BMI. We also observe different correlations between palm temperature, abdominal temperature, BMI, REE and levels of physical activity.

CONCLUSION

Palm temperature could be used as a warning of bradycardia, a serious cardiovascular condition which can be difficult to detect in short visits with outpatients. Further studies are needed to determine how useful bradycardia and palm temperature could be to assess severity and prognosis of the disorder.

Ghrelin Gene Deletion Alters Pulsatile Growth Hormone Secretion in Adult Female Mice

Using preproghrelin-deficient mice (Ghrl-/-), we previously observed that preproghrelin modulates pulsatile growth hormone (GH) secretion in post-pubertal male mice. However, the role of ghrelin and its derived peptides in the regulation of growth parameters or feeding in females is unknown. We measured pulsatile GH secretion, growth, metabolic parameters and feeding behavior in adult Ghrl-/- and Ghrl+/+ male and female mice. We also assessed GH release from pituitary explants and hypothalamic growth hormone-releasing hormone (GHRH) expression and immunoreactivity. Body weight and body fat mass, linear growth, spontaneous food intake and food intake following a 48-h fast, GH pituitary contents and GH release from pituitary explants ex vivo, fasting glucose and glucose tolerance were not different among adult Ghrl-/- and Ghrl+/+ male or female mice. In vivo, pulsatile GH secretion was decreased, while approximate entropy, that quantified orderliness of secretion, was increased in adult Ghrl-/- females only, defining more irregular GH pattern. The number of neurons immunoreactive for GHRH visualized in the hypothalamic arcuate nucleus was increased in adult Ghrl-/- females, as compared to Ghrl+/+ females, whereas the expression of GHRH was not different amongst groups. Thus, these results point to sex-specific effects of preproghrelin gene deletion on pulsatile GH secretion, but not feeding, growth or metabolic parameters, in adult mice.

Exploring the Mechanisms of Recovery in Anorexia Nervosa through a Translational Approach: From Original Ecological Measurements in Human to Brain Tissue Analyses in Mice

Anorexia nervosa (AN) is a severe eating disorder where caloric restriction, excessive physical activity and metabolic alterations lead to life-threatening situations. Despite weight restoration after treatment, a significant part of patients experience relapses. In this translational study, we combined clinical and preclinical approaches. We describe preliminary data about the effect of weight gain on the symptomatology of patients suffering from acute AN (n = 225) and partially recovered (n = 41). We measured more precisely physical activity with continuous cardiac monitoring in a sub-group (n = 68). Using a mouse model, we investigated whether a long-term food restriction followed by nutritional recovery associated or not with physical activity may differentially impact peripheral and central homeostatic regulation. We assessed the plasma concentration of acyl ghrelin, desacyl ghrelin and leptin and the mRNA expression of hypothalamic neuropeptides and their receptors. Our data show an effect of undernutrition history on the level of physical activity in AN. The preclinical model supports an important role of physical activity in the recovery process and points out the leptin system as one factor that can drive a reliable restoration of metabolic variables through the hypothalamic regulation of neuropeptides involved in feeding behavior.

Increased cognitive flexibility mediates the improvement of eating disorders symptoms, depressive symptoms and level of daily life functioning in patients with anorexia nervosa treated in specialised centres

OBJECTIVE

Poor cognitive flexibility has been highlighted in patients with anorexia nervosa (AN), contributing to the development and maintenance of symptoms. The aim of the present study is to investigate how enhanced cognitive flexibility is involved in treatment outcomes in patients with AN.

METHOD

One hundred thirty female out-patients treated for AN have been assessed at baseline and after 4 months of treatment. Path analyses were used to investigate the mediating role of cognitive flexibility, measured through the Brixton test, on a wide range of outcomes: body mass index, eating disorder symptoms, daily life functioning, anxiety, depression, emotions, self-rated silhouette.

RESULTS

Cognitive flexibility was improved during treatment, and enhanced cognitive flexibility explains a significant part of level of the improvement in daily life functioning (26%), reduction of eating disorder symptoms (18%) and reduction of depressive symptoms (17%). Others outcomes were also improved, but these improvements were not mediated by cognitive flexibility.

CONCLUSIONS

Results suggest that enhancing cognitive flexibility could help reduce rigid cognitive and behavioural patterns involved in AN, thus improving everyday functioning and clinical severity. Further studies combining different types of cognitive flexibility evaluation as well as neuroimaging may be necessary to better establish which of its aspects are involved in patients' improvement.

Does physical activity associated with chronic food restriction alleviate anxiety like behaviour, in female mice?

Anorexia nervosa (AN) is an eating disorder characterized by excessive weight loss, persistent food restriction and inappropriate physical activity relative to declining energy balance. The comorbidity with depression and/or anxiety disorders might contribute to the "chronicization" of the disease. We aimed here to question first the link between physical activity and anxiety from a clinical investigation of AN patients (n = 206). Then, using a rodent model mimicking numerous physiological and metabolic alterations commonly seen in AN patients, we examined whether 1) chronic food restriction increased anxiety-like behaviour and 2) physical activity plays a role in regulating anxiety levels. To this end, we exposed young female mice to a chronic food restriction (FR, n = 8) paradigm combined or not with access to a running wheel (FRW, n = 8) for two weeks. The mice were compared to a group of mice fed ad libitum without (AL, n = 6) or with running wheel access (ALW, n = 8). We explored anxiety-like behaviour of all mice in the following tests: hyponeophagia, marble burying, elevated plus maze, open field, and the light and dark box. On the last day, we used a restraint test of 30 min duration and measured their stress reactivity by assaying plasma corticosterone. In the open field and the elevated plus-maze, we found that FRW mice behaved similarly to AL and ALW mice whereas FR mice did not express anxiety-like behaviour. The FRW mice displayed the lowest latency to reach the food in the hyponeophagia test. Regarding stress reactivity, FRW mice exhibited corticosterone reactivity after acute stress that was similar to the control mice, while FR mice did not fully return to basal corticosterone at one hour after the restraint stress. Taken together, these data demonstrate a differential reactivity to acute stress in FR conditions and a beneficial effect of running wheel activity in ALW and FRW conditions. Moreover, we report the absence of a typical anxiety-like behaviour associated with the food restriction (FR and FRW groups). We conclude that this model (FR and FRW mice) did not express typical anxiety-like behaviour, but that physical activity linked to food restriction improved coping strategies in an anxiogenic context.

A Metabolic Perspective on Reward Abnormalities in Anorexia Nervosa

Anorexia nervosa (AN) is the psychiatric disorder with the highest mortality rate; however, the mechanisms responsible for its pathogenesis remain largely unknown. Large-scale genome-wide association studies (GWAS) have identified genetic loci associated with metabolic features in AN. Metabolic alterations that occur in AN have been mostly considered as consequences of the chronic undernutrition state but until recently have not been linked to the etiology of the disorder. We review the molecular basis of AN based on human genetics, with an emphasis on the molecular components controlling energy homeostasis, highlight the main metabolic and endocrine alterations occurring in AN, and decipher the possible connection between metabolic factors and abnormalities of reward processes that are central in AN.

Overexpression of Wild-Type Human Alpha-Synuclein Causes Metabolism Abnormalities in Thy1-aSYN Transgenic Mice

Parkinson’s disease is a progressive neurodegenerative disorder characterized by loss of dopaminergic neurons, pathological accumulation of alpha-synuclein and motor symptoms, but also by non-motor symptoms. Metabolic abnormalities including body weight loss have been reported in patients and could precede by several years the emergence of classical motor manifestations. However, our understanding of the pathophysiological mechanisms underlying body weight loss in PD is limited. The present study investigated the links between alpha-synuclein accumulation and energy metabolism in transgenic mice overexpressing Human wild-type (WT) alpha-synuclein under the Thy1 promoter (Thy1-aSYN mice). Results showed that Thy1-aSYN mice gained less body weight throughout life than WT mice, with significant difference observed from 3 months of age. Body composition analysis of 6-month-old transgenic animals showed that body mass loss was due to lower adiposity. Thy1-aSYN mice displayed lower food consumption, increased spontaneous activity, as well as a reduced energy expenditure compared to control mice. While no significant change in glucose or insulin responses were observed, Thy1-aSYN mice had significantly lower plasmatic levels of insulin and leptin than control animals. Moreover, the pathological accumulation of alpha-synuclein in the hypothalamus of 6-month-old Thy1-aSYN mice was associated with a down-regulation of the phosphorylated active form of the signal transducer and activator of transcription 3 (STAT3) and of Rictor (the mTORC2 signaling pathway), known to couple hormonal signals with the maintenance of metabolic and energy homeostasis. Collectively, our results suggest that (i) metabolic alterations are an important phenotype of alpha-synuclein overexpression in mice and that (ii) impaired STAT3 activation and mTORC2 levels in the hypothalamus may underlie the disruption of feeding regulation and energy metabolism in Thy1-aSYN mice.

Adipokines and bone status in a cohort of anorexic patients

INTRODUCTION

Bone loss in anorexia nervosa (AN) is multifactorial; its mechanisms are not yet clearly understood and may vary depending on disease duration and severity. To determine to what extent adipokines may be involved in the bone alterations found in anorexic patients, we evaluated plasma levels for leptin, adiponectin and Pref-1 against other clinical and biological parameters in a population of anorexic patients split according to weight and bone status.

METHODS

Plasma concentrations of leptin, total adiponectin, high molecular weight (HMW) adiponectin, and Pref-1 were measured. The ratio of HMW adiponectin to total adiponectin - HMW (percentage) - was calculated. We divided our population into 5 groups with different phenotypes characterizing the severity of the disease and/or the severity of bone involvement: 1 - Normal BMD and body mass index (BMI): recovery from AN; 2 - Osteopenia (-2<Z-score<-1) and BMI>17kg/m²; 3 - Osteopenia and BMI≤17kg/m²; 4 - Osteoporosis (Z-score≤-2) and BMI>17kg/m²; 5 - Osteoporosis and BMI≤17kg/m².

RESULTS

The study involved 80 anorexia nervosa patients. Mean BMI was 16.8±2.4kg/m². No significant difference was found in total and HMW adiponectin plasma concentrations between the 5 groups. HMW (percentage) was significantly higher in group 5 compared to group 1. Leptin was significantly lower in groups 3 and 5 compared to the other groups. For the whole group femoral neck and hip BMD correlated negatively with total adiponectin and HMW adiponectin. No correlation was found between BMD (whatever the site) and plasma leptin. Multivariate analysis revealed that 2 factors - leptin and BMI - explained 10% of the variance in spine BMD. For femoral neck BMD, the 2 explanatory factors were BMI and total adiponectin which explained 14% of the variance in BMD. For total hip BMD, 27% of the variance in BMD was explained by 3 factors: leptin, BMI, and total adiponectin.

CONCLUSION

Bone status in anorexia nervosa is mainly determined by BMI, leptin and adiponectin.

Metabolic and neuroendocrine adaptations to undernutrition in anorexia nervosa: from a clinical to a basic research point of view

The exact mechanisms linking metabolic and neuroendocrine adaptations to undernutrition and the pathophysiology of anorexia nervosa (AN) are not fully understood. AN is a psychiatric disorder of complex etiology characterized by extreme starvation while the disease is progressing into a chronic state. Metabolic and endocrine alterations associated to this disorder are part of a powerful response to maintain whole body energy homeostasis. But these modifications may also contribute to associated neuropsychiatric symptoms (reward abnormalities, anxiety, depression) and thus participate to sustain the disease. The current review presents data with both a clinical and basic research point of view on the role of nutritional and energy sensors with neuroendocrine actions in the pathophysiology of the disease, as they modulate metabolic responses, reproductive functions, stress responses as well as physical activity. While clinical data present a full description of changes occurring in AN, animal models that integrate either spontaneous genetic mutations or experimentally-induced food restriction with hyperactivity and/or social stress recapitulate the main metabolic and endocrine alterations of AN and provide mechanistic information between undernutrition state and symptoms of the disease. Further progress on the central and peripheral mechanism involved in the pathophysiology of eating disorders partly relies on the development and/or refinement of existing animal models to include recently identified genetic traits and better mimic the complex and multifactorial dimensions of the disease.

Long-Term Energy Deficit in Mice Causes Long-Lasting Hypothalamic Alterations after Recovery

Although the short-term effects of fasting or energy deficit on hypothalamic neuropeptide circuitries are now better understood, the effects of long-term energy deficit and refeeding remain to be elucidated. We showed that after a long-term energy deficit, mice exhibited persistent hypoleptinemia following the refeeding period despite restoration of fat mass, ovarian activity, and feeding behavior. We aimed to examine the hypothalamic adaptations after 10 weeks of energy deficit and after 10 further weeks of nutritional recovery. To do so, we assessed the mRNA levels of the leptin receptor and the main orexigenic and anorexigenic peptides, and their receptors regulated by leptin. Markers of hypothalamic inflammation were assessed as leptin can also participate in this phenomenon. Long-term time-restricted feeding and separation induced significant increase in mRNA levels of hypothalamic orexigenic peptides, while both Y1 and Y5 receptor mRNAs were downregulated. No changes occurred in the mRNA levels of orexin (OX), melanin-concentrating hormone, pro-opiomelanocortin, 26RFa (26-amino acid RF-amide peptide), and their receptors despite an increase in the expression of melanocortin receptors (MC3-R and MC4-R) and OXR1 (OX receptor 1). The refeeding period induced an overexpression of leptin receptor mRNA in the hypothalamus. The other assessed mRNA levels were normalized except for Y2, Y5, MC3-R, and MC4-R, which remained upregulated. No convincing changes were observed in neuroinflammatory markers, even if interleukin-1β mRNA levels were increased in parallel with those of Iba1 (ionized calcium-binding adaptor molecule 1), a marker of microglial activation. Normalization of leptin-regulated functions and hypothalamic gene expressions in refed mice with low plasma leptin levels could be sustained by recalibration of hypothalamic sensitivity to leptin.

Interleukin-7 Plasma Levels in Human Differentiate Anorexia Nervosa, Constitutional Thinness and Healthy Obesity

Introduction

Interleukin-7 (IL-7) is a cytokine involved in energy homeostasis as demonstrated in rodents. Anorexia nervosa is characterized by restrained eating behavior despite adaptive orexigenic regulation profile including high ghrelin plasma levels. Constitutional thinness is a physiological condition of resistance to weight gain with physiological anorexigenic profile including high Peptide YY plasma level. Healthy obesity can be considered as a physiological state of resistance to weight loss with opposite appetite regulating profile to constitutional thinness including low Peptide YY plasma level. No studies in IL-7 are yet available in those populations. Therefore we evaluated circadian plasma levels of IL-7 in anorexia nervosa compared to constitutional thinness, healthy obese and control females.

Materials and Methods

10 restrictive-type anorexia nervosa women, 5 bingeing/purging anorexia nervosa woman, 5 recovered restrictive anorexia nervosa women, 4 bulimic females, 10 constitutional thinness women, 7 healthy obese females, and 10 normal weight women controls were enrolled in this cross-sectional study, performed in endocrinology unit and academic laboratory. Twelve-point circadian profiles of plasma IL-7 levels were measured in each subject.

Results

24h mean IL-7 plasma levels (pg/ml, mean±SEM) were decreased in restrictive-type anorexia nervosa (123.4±14.4, p<0.0037), bingeing/purging anorexia nervosa (24.2±5.6, p<0.001), recovered restrictive anorexia nervosa (64.2±16.1, p = 0.01) and healthy obese patients (51±3.2, p<0.001) compared to controls (187.7±28.6). Bulimic patients (197.4±42.7) and constitutional thinness patients (264.3±35.8) were similar to controls.

Conclusions

Low IL-7 is part of the adaptive profile in restrictive-type anorexia nervosa, confirming its difference with constitutional thinness. Healthy obesity, with low IL-7, is once again in mirror image of constitutional thinness with normal high IL-7.

New Insights in Anorexia Nervosa

Anorexia nervosa (AN) is classically defined as a condition in which an abnormally low body weight is associated with an intense fear of gaining weight and distorted cognitions regarding weight, shape, and drive for thinness. This article reviews recent evidences from physiology, genetics, epigenetics, and brain imaging which allow to consider AN as an abnormality of reward pathways or an attempt to preserve mental homeostasis. Special emphasis is put on ghrelino-resistance and the importance of orexigenic peptides of the lateral hypothalamus, the gut microbiota and a dysimmune disorder of neuropeptide signaling. Physiological processes, secondary to underlying, and premorbid vulnerability factors-the "pondero-nutritional-feeding basements"- are also discussed.

The use of animal models to decipher physiological and neurobiological alterations of anorexia nervosa patients

Extensive studies were performed to decipher the mechanisms regulating feeding due to the worldwide obesity pandemy and its complications. The data obtained might be adapted to another disorder related to alteration of food intake, the restrictive anorexia nervosa. This multifactorial disease with a complex and unknown etiology is considered as an awful eating disorder since the chronic refusal to eat leads to severe, and sometimes, irreversible complications for the whole organism, until death. There is an urgent need to better understand the different aspects of the disease to develop novel approaches complementary to the usual psychological therapies. For this purpose, the use of pertinent animal models becomes a necessity. We present here the various rodent models described in the literature that might be used to dissect central and peripheral mechanisms involved in the adaptation to deficient energy supplies and/or the maintenance of physiological alterations on the long term. Data obtained from the spontaneous or engineered genetic models permit to better apprehend the implication of one signaling system (hormone, neuropeptide, neurotransmitter) in the development of several symptoms observed in anorexia nervosa. As example, mutations in the ghrelin, serotonin, dopamine pathways lead to alterations that mimic the phenotype, but compensatory mechanisms often occur rendering necessary the use of more selective gene strategies. Until now, environmental animal models based on one or several inducing factors like diet restriction, stress, or physical activity mimicked more extensively central and peripheral alterations decribed in anorexia nervosa. They bring significant data on feeding behavior, energy expenditure, and central circuit alterations. Animal models are described and criticized on the basis of the criteria of validity for anorexia nervosa.

Physical activity: benefit or weakness in metabolic adaptations in a mouse model of chronic food restriction?

In restrictive-type anorexia nervosa (AN) patients, physical activity is usually associated with food restriction, but its physiological consequences remain poorly characterized. In female mice, we evaluated the impact of voluntary physical activity with/without chronic food restriction on metabolic and endocrine parameters that might contribute to AN. In this protocol, FRW mice (i.e., food restriction with running wheel) reached a crucial point of body weight loss (especially fat mass) faster than FR mice (i.e., food restriction only). However, in contrast to FR mice, their body weight stabilized, demonstrating a protective effect of a moderate, regular physical activity. Exercise delayed meal initiation and duration. FRW mice displayed food anticipatory activity compared with FR mice, which was strongly diminished with the prolongation of the protocol. The long-term nature of the protocol enabled assessment of bone parameters similar to those observed in AN patients. Both restricted groups adapted their energy metabolism differentially in the short and long term, with less fat oxidation in FRW mice and a preferential use of glucose to compensate for the chronic energy imbalance. Finally, like restrictive AN patients, FRW mice exhibited low leptin levels, high plasma concentrations of corticosterone and ghrelin, and a disruption of the estrous cycle. In conclusion, our model suggests that physical activity has beneficial effects on the adaptation to the severe condition of food restriction despite the absence of any protective effect on lean and bone mass.

Long-term physiological alterations and recovery in a mouse model of separation associated with time-restricted feeding: a tool to study anorexia nervosa related consequences

Background

Anorexia nervosa is a primary psychiatric disorder, with non-negligible rates of mortality and morbidity. Some of the related alterations could participate in a vicious cycle limiting the recovery. Animal models mimicking various physiological alterations related to anorexia nervosa are necessary to provide better strategies of treatment.

Aim

To explore physiological alterations and recovery in a long-term mouse model mimicking numerous consequences of severe anorexia nervosa.

Methods

C57Bl/6 female mice were submitted to a separation-based anorexia protocol combining separation and time-restricted feeding for 10 weeks. Thereafter, mice were housed in standard conditions for 10 weeks. Body weight, food intake, body composition, plasma levels of leptin, adiponectin, IGF-1, blood levels of GH, reproductive function and glucose tolerance were followed. Gene expression of several markers of lipid and energy metabolism was assayed in adipose tissues.

Results

Mimicking what is observed in anorexia nervosa patients, and despite a food intake close to that of control mice, separation-based anorexia mice displayed marked alterations in body weight, fat mass, lean mass, bone mass acquisition, reproductive function, GH/IGF-1 axis, and leptinemia. mRNA levels of markers of lipogenesis, lipolysis, and the brown-like adipocyte lineage in subcutaneous adipose tissue were also changed. All these alterations were corrected during the recovery phase, except for the hypoleptinemia that persisted despite the full recovery of fat mass.

Conclusion

This study strongly supports the separation-based anorexia protocol as a valuable model of long-term negative energy balance state that closely mimics various symptoms observed in anorexia nervosa, including metabolic adaptations. Interestingly, during a recovery phase, mice showed a high capacity to normalize these parameters with the exception of plasma leptin levels. It will be interesting therefore to explore further the central and peripheral effects of the uncorrected hypoleptinemia during recovery from separation-based anorexia.

Ghrelin: central and peripheral implications in anorexia nervosa

Increasing clinical and therapeutic interest in the neurobiology of eating disorders reflects their dramatic impact on health. Chronic food restriction resulting in severe weight loss is a major symptom described in restrictive anorexia nervosa (AN) patients, and they also suffer from metabolic disturbances, infertility, osteopenia, and osteoporosis. Restrictive AN, mostly observed in young women, is the third largest cause of chronic illness in teenagers of industrialized countries. From a neurobiological perspective, AN-linked behaviors can be considered an adaptation that permits the endurance of reduced energy supply, involving central and/or peripheral reprograming. The severe weight loss observed in AN patients is accompanied by significant changes in hormones involved in energy balance, feeding behavior, and bone formation, all of which can be replicated in animals models. Increasing evidence suggests that AN could be an addictive behavior disorder, potentially linking defects in the reward mechanism with suppressed food intake, heightened physical activity, and mood disorder. Surprisingly, the plasma levels of ghrelin, an orexigenic hormone that drives food-motivated behavior, are increased. This increase in plasma ghrelin levels seems paradoxical in light of the restrained eating adopted by AN patients, and may rather result from an adaptation to the disease. The aim of this review is to describe the role played by ghrelin in AN focusing on its central vs. peripheral actions. In AN patients and in rodent AN models, chronic food restriction induces profound alterations in the « ghrelin » signaling that leads to the development of inappropriate behaviors like hyperactivity or addiction to food starvation and therefore a greater depletion in energy reserves. The question of a transient insensitivity to ghrelin and/or a potential metabolic reprograming is discussed in regard of new clinical treatments currently investigated.

A natural variant of obestatin, Q90L, inhibits ghrelin's action on food intake and GH secretion and targets NPY and GHRH neurons in mice

Background

Ghrelin and obestatin are two gut-derived peptides originating from the same ghrelin/obestatin prepropeptide gene (GHRL). While ghrelin stimulates growth hormone (GH) secretion and food intake and inhibits γ-aminobutyric-acid synaptic transmission onto GHRH (Growth Hormone Releasing Hormone) neurons, obestatin blocks these effects. In Humans, GHRL gene polymorphisms have been associated with pathologies linked to an unbalanced energy homeostasis. We hypothesized that one polymorphism located in the obestatin sequence (Q to L substitution in position 90 of the ghrelin/obestatin prepropeptide, rs4684677) may impact on the function of obestatin. In the present study, we tested the activity of native and Q90L obestatin to modulate ghrelin-induced food intake, GH secretion, cFos activity in GHRH and Neuropeptide Y (NPY) neurons and γ-aminobutyric-acid activity onto GHRH neurons.

Methodology/Principal findings

Food intake, GH secretion and electrophysiological recordings were assessed in C57BL/6 mice. cFos activity was measured in NPY-Renilla-GFP and GHRH-eGFP mice. Mice received saline, ghrelin or ghrelin combined to native or Q90L obestatin (30 nmol each) in the early light phase. Ghrelin stimulation of food intake and GH secretion varied considerably among individual mice with 59–77% eliciting a robust response. In these high-responders, ghrelin-induced food intake and GH secretion were reduced equally by native and Q90L obestatin. In contrast to in vivo observations, Q90L was slightly more efficient than native obestatin in inhibiting ghrelin-induced cFos activation within the hypothalamic arcuate nucleus and the nucleus tractus solitarius of the brainstem. After ghrelin injection, 26% of NPY neurons in the arcuate nucleus expressed cFos protein and this number was significantly reduced by co-administration of Q90L obestatin. Q90L was also more potent that native obestatin in reducing ghrelin-induced inhibition of γ-aminobutyric-acid synaptic transmission onto GHRH neurons.

Conclusions/Significance

These data support the hypothesis that Q90L obestatin partially blocks ghrelin-induced food intake and GH secretion by acting through NPY and GHRH neurons.

Changes in CRH and ACTH synthesis during experimental and human septic shock

CONTEXT

The mechanisms of septic shock-associated adrenal insufficiency remain unclear. This study aimed at investigating the synthesis of corticotropin-releasing hormone (CRH) and vasopressin (AVP) by parvocellular neurons and the antehypophyseal expression of ACTH in human septic shock and in an experimental model of sepsis.

OBJECTIVE

To test the hypothesis that ACTH secretion is decreased secondarily to alteration of CRH or AVP synthesis, we undertook a neuropathological study of the antehypophyseal system in patients who had died from septic shock and rats with experimental faecal peritonitis.

METHODS

Brains obtained in 9 septic shock patients were compared to 10 nonseptic patients (controls). Parvocellular expression of AVP and CRH mRNA were evaluated by in situ hybridization. Antehypophyseal expression of ACTH, vasopressin V1b and CRH R1 receptors and parvocellular expression of iNOS in the PVN were evaluated by immunohistochemistry. The same experiments were carried out in a fecal peritonitis-induced model of sepsis. Data from septic rats with (n = 6) or without (n = 10) early death were compared to sham-operated (n = 8) animals.

RESULTS

In patients and rats, septic shock was associated with a decreased expression of ACTH, unchanged expression of V1B receptor, CRHR1 and AVP mRNA, and increased expression of parvocellular iNOS compared to controls. Septic shock was also characterized by an increased expression of CRH mRNA in rats but not in patients, who notably had a greater duration of septic shock.

CONCLUSION

The present study suggests that in humans and in rats, septic shock is associated with decreased ACTH synthesis that is not compensated by its two natural secretagogues, AVP and CRH. One underlying mechanism might be increased expression of iNOS in hypothalamic parvocellular neurons.

Interleukin-7, a new cytokine targeting the mouse hypothalamic arcuate nucleus: role in body weight and food intake regulation

Body weight is controlled through peripheral (white adipose tissue) and central (mainly hypothalamus) mechanisms. We have recently obtained evidence that overexpression of interleukin (IL)-7, a critical cytokine involved in lymphopoiesis, can protect against the development of diet-induced obesity in mice. Here we assessed whether IL-7 mediated its effects by modulating hypothalamic function. Acute subcutaneous injection of IL-7 prevented monosodium glutamate-induced obesity, this being correlated with partial protection against cell death in the hypothalamic arcuate nucleus (ARC). Moreover, we showed that IL-7 activated hypothalamic areas involved in regulation of feeding behavior, as indicated by induction of the activation marker c-Fos in neural cells located in the ventromedial part of the ARC and by inhibition of food intake after fasting. Both chains of the IL-7 receptor (IL-7Rα and γ_c) were expressed in the ARC and IL-7 injection induced STAT-3 phosphorylation in this area. Finally, we established that IL-7 modulated the expression of neuropeptides that tune food intake, with a stimulatory effect on the expression of pro-opiomelanocortin and an inhibitory effect on agouti-related peptide expression in accordance with IL-7 promoting anorectic effects. These results suggest that the immunomodulatory cytokine IL-7 plays an important and unappreciated role in hypothalamic body weight regulation.

Vasopressin synthesis by the magnocellular neurons is different in the supraoptic nucleus and in the paraventricular nucleus in human and experimental septic shock

Impaired arginine vasopressin (AVP) synthesis and release by the neurohypophyseal system, which includes the neurohypophysis and magnocellular neurons of the paraventricular and supraoptic nuclei, have been postulated in septic shock, but changes in this system have never been assessed in human septic shock, and only partially experimentally. We investigated AVP synthesis and release by the neurohypophyseal system in 9 patients who died from septic shock and 10 controls, and in 20 rats with fecal peritonitis-induced sepsis and 8 sham-operation controls. Ten rats died spontaneously from septic shock, and the others were sacrificed. In patients with septic shock, as in rats that died spontaneously following sepsis induction, AVP immunohistochemical expression was decreased in the neurohypophysis and supraoptic magnocellular neurons, whereas it was increased in the paraventricular magnocellular neurons. No significant change was observed in AVP messenger RiboNucleic Acid (mRNA) expression assessed by in situ hybridization in either paraventricular or supraoptic magnocellular cells. This study shows that both in human and experimental septic shock, AVP posttranscriptional synthesis and transport are differently modified in the magnocellular neurons of the supraoptic and paraventricular nuclei. This may account for the inappropriate AVP release in septic shock and suggests that distinct pathogenic mechanisms operate in these nuclei.

Confinement to the open arm of the elevated-plus maze as anxiety paradigm: behavioral validation

Exposure to the open arm of the elevated-plus maze was used to assess the neurobiological correlates of anxiety in the high-anxiety-related behavior (HAB) and low-anxiety-related behavior (LAB) rat lines. The authors sought to determine whether this mild stressor could be considered a valuable anxiety test revealing specific behavioral differences. Behavioral parameters scored were submitted to a discriminant and factor analysis to investigate emotional parameters discriminating HAB and LAB rats. Principal component analysis showed that the HAB rats' behavior was driven by anxiety, whereas the LAB rats' behavior was mainly explained by locomotor activity. Moreover, the rats displayed behaviors that reflected distinct coping strategies confirming anxiogenic open arm effects and differential appraisals of the stressor dependent on the genetic predisposition to either hyper- or hypo-anxiety.

Immune challenge induces differential corticosterone and interleukin-6 responsiveness in rats bred for extremes in anxiety-related behavior

Disturbances in mood such as anxiety and depression are often associated with altered hypothalamo-pituitary-adrenal (HPA) axis reactivity, but also with changes in cytokine production, such as interleukin-6 (IL-6), an essential immune factor produced by macrophages and lymphocytes during inflammatory processes. The reciprocal relationship between the HPA axis and the immune system is now well established. In order to understand better the endocrine reactivity of anxious individuals faced with an immune challenge, a model of innate anxiety-related behavior, HAB and LAB rats (HABs, high and LABs, low anxiety-related behavior) was used in this study. We sought to determine whether injection of lipopolysaccharide (LPS) induced a differential HPA axis reactivity and plasma IL-6 release in HABs and LABs. After LPS injection, the plasma adrenal corticotrophic hormone increase did not differ between HABs and LABs, whereas a larger increase in plasma corticosterone levels occurred in HABs than in LABs at 2 h after injection. Moreover, basal IL-6 levels were lower in HABs than in LABs, leading to a higher IL-6 2 h/basal ratio in HABs. In conclusion, we propose for the first time a link between the endocrine and immune systems of HABs and LABs and suggest that IL-6 could be a neuroendocrine correlate of trait anxiety in HABs.

Impact of prenatal stress on neuroendocrine programming

Since life emerged on the Earth, the development of efficient strategies to cope with sudden and/or permanent changes of the environment has been virtually the unique goal pursued by every organism in order to ensure its survival and thus perpetuate the species. In this view, evolution has selected tightly regulated processes aimed at maintaining stability among internal parameters despite external changes, a process termed homeostasis. Such an internal equilibrium relies quite heavily on three interrelated physiological systems: the nervous, immune, and endocrine systems, which function as a permanently activated watching network, communicating by the mean of specialized molecules: neurotransmitters, cytokines, and hormones or neurohormones. Potential threats to homeostasis might occur as early as during in utero life, potentially leaving a lasting mark on the developing organism. Indeed, environmental factors exert early-life influences on the structural and functional development of individuals, giving rise to changes that can persist throughout life. This organizational phenomenon, encompassing prenatal environmental events, altered fetal growth, and development of long-term pathophysiology, has been named early-life programming. Over the past decade, increased scientific activities have been devoted to deciphering the obvious link between states of maternal stress and the behavioral, cognitive, emotional, and physiological reactivity of the progeny. This growing interest has been driven by the discovery of a tight relationship between prenatal stress and development of short- and long-term health disorders. Among factors susceptible of contributing to such a deleterious programming, nutrients and hormones, especially steroid hormones, are considered as powerful mediators of the fetal organization since they readily cross the placental barrier. In particular, variations in circulating maternal glucocorticoids are known to impact this programming strongly, notably when hormonal surges occur during sensitive periods of development, so-called developmental windows of vulnerability. Stressful events occurring during the perinatal period may impinge on various aspects of the neuroendocrine programming, subsequently amending the offspring's growth, metabolism, sexual maturation, stress responses, and immune system. Such prenatal stress-induced modifications of the phenotypic plasticity of the progeny might ultimately result in the development of long-term diseases, from metabolic syndromes to psychiatric disorders. Yet, we would like to consider the outcome of this neuroendocrine programming from an evolutionary perspective. Early stressful events during gestation might indeed shape internal parameters of the developing organisms in order to adapt the progeny to its everyday environment and thus contribute to an increased reproductive success, or fitness, of the species. Moreover, parental care, adoption, or enriched environments after birth have been shown to reverse negative long-term consequences of a disturbed gestational environment. In this view, considering the higher potential for neonatal plasticity within the brain in human beings as compared to other species, long-term consequences of prenatal stress might not be as inexorable as suggested in animal-based studies published to date.

Prenatal stress alters the negative correlation between neuronal activation in limbic regions and behavioral responses in rats exposed to high and low anxiogenic environments

Behavioral adaptation to an anxiogenic environment involves the activity of various interconnected limbic regions, such as the amygdala, hippocampus and prefrontal cortex. Prenatal stress (PS) in rats affects the ability to cope with environmental challenges and alters brain plasticity, leading to long-lasting behavioral and neurobiological alterations. We examined in PS and control animals whether behavioral reactivity was correlated to neuronal activation by assessing Fos protein expression in limbic regions of rats exposed to a low or high anxiogenic environment (the closed and open arms of an elevated plus maze, respectively). A negative correlation was found between behavioral and neuronal activation, with a lower behavioral reactivity and a higher neuronal response observed in rats exposed to the more anxiogenic environment (the open arm) with respect to the less anxiogenic environment (the closed arm). Interestingly, the variation in the neurobehavioral response between the two arms of the maze was less pronounced in rats that had been subjected to PS. This study provides a remarkable example of how long-lasting changes in brain plasticity induced by PS affect the ability of limbic neurons to cope with anxiogenic stimuli of different strength.

Maternal stress alters endocrine function of the feto-placental unit in rats

Prenatal stress (PS) can cause early and long-term developmental effects resulting in part from altered maternal and/or fetal glucocorticoid exposure. The aim of the present study was to assess the impact of chronic restraint stress during late gestation on feto-placental unit physiology and function in embryonic (E) day 21 male rat fetuses. Chronic stress decreased body weight gain and food intake of the dams and increased their adrenal weight. In the placenta of PS rats, the expression of glucose transporter type 1 (GLUT1) was decreased, whereas GLUT3 and GLUT4 were slightly increased. Moreover, placental expression and activity of the glucocorticoid "barrier" enzyme 11beta-hydroxysteroid dehydrogenase type 2 was strongly reduced. At E21, PS fetuses exhibited decreased body, adrenal pancreas, and testis weights. These alterations were associated with reduced pancreatic beta-cell mass, plasma levels of glucose, growth hormone, and ACTH, whereas corticosterone, insulin, IGF-1, and CBG levels were unaffected. These data emphasize the impact of PS on both fetal growth and endocrine function as well as on placental physiology, suggesting that PS could program processes implied in adult biology and pathophysiology.

Effect of hindlimb unloading on motor activity in adult rats: impact of prenatal stress

Environmental changes that occur in daily life or, in particular, in situations like actual or simulated microgravity require neuronal adaptation of sensory and motor functions. Such conditions can exert long-lasting disturbances on an individual's adaptive ability. Additionally, prenatal stress also leads to behavioral and physiological abnormalities in adulthood. Therefore, the aims of the present study were (a) to evaluate in adult rats the behavioral motor adaptation that follows 14 days of exposure to simulated microgravity (hindlimb unloading) and (b) to determine whether restraint prenatal stress influences this motor adaptation. For this purpose, the authors assessed rats' motor reactivity to novelty, their skilled walking on a ladder, and their swimming performance. Results showed that unloading severely impaired motor activity and skilled walking. By contrast, it had no effect on swimming performance. Moreover, results demonstrated for the first time that restraint prenatal stress exacerbates the effects of unloading. These results are consistent with the role of a steady prenatal environment in allowing an adequate development and maturation of sensorimotor systems to generate adapted responses to environmental challenges during adulthood.

Prenatal stress has pro-inflammatory consequences on the immune system in adult rats

The in utero environment is critical for initiating the ontogeny of several physiological systems, including the immune surveillance. Yet, little is known about adverse early experiences on the offspring's immunity and vulnerability to disease. The present work aimed at investigating the impact of restraint prenatal stress (PS) on the development and responsiveness of in vitro and in vivo cellular and humoral immunity of male progeny aged 7 weeks and 6 months. In adult 6-month-old rats, we detected increased circulating CD8(+)-expressing and NK cells in PS rats as compared to controls, associated with higher mRNA expression of IFN-gamma. In addition, in vitro stimulation with phytohemagglutinin-A induced an increase in both the proliferation of T lymphocytes and the secretion of IFN-gamma in PS rats. Interestingly, these alterations were undetectable in younger PS rats (7-week old), except for a slight increase in the mRNA expression of several pro-inflammatory cytokines in peripheral blood mononuclear cells. Moreover, in vivo neutralization of IFN-gamma in young rats had no effects in PS group. In conclusion, we report for the first time long-lasting pro-inflammatory consequences of PS in rats.

Genes involved in obesity: Adipocytes, brain and microflora

The incidence of obesity and related metabolic disorders such as cardiovascular diseases and type 2 diabetes, are reaching worldwide epidemic proportions. It results from an imbalance between caloric intake and energy expenditure leading to excess energy storage, mostly due to genetic and environmental factors such as diet, food components and/or way of life. It is known since long that this balance is maintained to equilibrium by multiple mechanisms allowing the brain to sense the nutritional status of the body and adapt behavioral and metabolic responses to changes in fuel availability. In this review, we summarize selected aspects of the regulation of energy homeostasis, prevalently highlighting the complex relationships existing between the white adipose tissue, the central nervous system, the endogenous microbiota, and nutrition. We first describe how both the formation and functionality of adipose cells are strongly modulated by the diet before summarizing where and how the central nervous system integrates peripheral signals from the adipose tissue and/or the gastro-intestinal tract. Finally, after a short description of the intestinal commensal flora, rangingfrom its composition to its importance in immune surveillance, we enlarge the discussion on how nutrition modified this perfectly well-balanced ecosystem.

Chemical stimulation of visceral afferents activates medullary neurones projecting to the central amygdala and periaqueductal grey

Cholecystokinin (CCK) stimulates gastrointestinal vagal afferent neurones that signal visceral sensations. We wished to determine whether neurones of the nucleus of the solitary tract (NTS) or ventrolateral medulla (VLM) convey visceral afferent information to the central nucleus of the amygdala (CeA) or periaqueductal grey region (PAG), structures that play a key role in adaptive autonomic responses triggered by stress or fear. Male Sprague-Dawley rats received a unilateral microinjection of the tracer cholera toxin subunit B (CTB, 1%) into the CeA or PAG followed, 7 days later, by an injection of CCK (100 microg/kg, i.p.) or saline. Brains were processed for detection of Fos protein (Fos-IR) and CTB. CCK induced increased expression of Fos-IR in the NTS and the VLM, relative to control. When CTB was injected into the CeA, CTB-immunoreactive (CTB-IR) neurones were more numerous in the rostral NTS ipsilateral to the injection site, whereas they were homogeneously distributed throughout the VLM. Double-labelled neurones (Fos-IR+CTB-IR) were most numerous in the ipsilateral NTS and caudal VLM. The NTS contained the higher percentage of CTB-IR neurones activated by CCK. When CTB was injected into the PAG, CTB-IR neurones were more numerous in the ipsilateral NTS whereas they were distributed relatively evenly bilaterally in the rostral VLM. Double-labelled neurones were not differentially distributed along the rostrocaudal axis of the NTS but were more numerous in this structure when compared with the VLM. NTS and VLM neurones may convey visceral afferent information to the CeA and the PAG.

Prenatal stress alters Fos protein expression in hippocampus and locus coeruleus stress-related brain structures

Prenatal stress (PS) durably influences responses of rats from birth throughout life by inducing deficits of the hypothalamo-pituitary-adrenal (HPA) axis feedback. The neuronal mechanisms sustaining such alterations are still unknown. The purpose of the present study was to determine whether in PS and control rats, the exposure to a mild stressor differentially induces Fos protein in hippocampus and locus coeruleus, brain areas involved in the feedback control of the HPA axis. Moreover, Fos protein expression was also evaluated in the hypothalamic paraventricular nucleus (PVN) that reflect the magnitude of the hormonal response to stress. Basal plasma corticosterone levels were not different between the groups, while, PS rats exhibited higher number of Fos-immunoreactive neurons than controls, in the hippocampus and locus coeruleus in basal condition. A higher basal expression of a marker of GABAergic synapses, the vGAT, was also observed in the hypothalamus of PS rats. Fifteen minutes after the end of the exposure to the open arm of the elevated plus-maze (mild stress) a similar increased plasma corticosterone levels was observed in both groups in parallel with an increased number of Fos-immunoreactive neurons in the PVN. Return to basal plasma corticosterone values was delayed only in the PS rats. On the contrary, after stress, no changes in Fos-immunoreactivity were observed in the hippocampus and locus coeruleus of PS rats compared to basal condition. After stress, only PS rats presented an elevation of the number of activated catecholaminergic neurons in the locus coeruleus. In conclusion, these results suggest for the first time that PS alters the neuronal activation of hippocampus and locus coeruleus implicated in the feedback mechanism of the HPA axis. These data give anatomical substrates to sustain the HPA axis hyperactivity classically described in PS rats after stress exposure.

Altered hypothalamo-pituitary-adrenal and sympatho-adrenomedullary activities in rats bred for high anxiety: central and peripheral correlates

Wistar rats have been selectively bred for high (HABs) or low (LABs) anxiety-related behavior based on results obtained in the elevated-plus maze. They also display robust behavioral differences in a variety of additional anxiety tests. The present study was undertaken to further characterize physiological substrates that contribute to the expression of this anxious trait. We report changes in brain and peripheral structures involved in the regulation of both the hypothalamo-pituitary-adrenal (HPA) and sympatho-adrenal systems. Following exposure to a mild stressor, HABs displayed a hyper-reactivity of the HPA axis associated with a hypo-reactivity of the sympatho-adrenal system and a lower serotonin turnover in the lateral septum and amygdala. At rest, HABs showed a higher adrenal weight and lower tyrosine hydroxylase and phenylethanolamine-N-methyltransferase mRNAs expression in their adrenals than LABs. In the anterior pituitary, HABs also exhibited increased proopiomelanocortin and decreased vasopressin V1b receptor mRNAs expression, whereas glucocorticoid receptor mRNA levels remained unchanged. These results indicate that the behavioral phenotype of HABs is associated with peripheral and central alterations of endocrine mechanisms involved in stress response regulation. Data are discussed in relation to coping strategies adopted to manage stressful situations. In conclusion, HABs can be considered as an useful model to study the etiology and pathophysiology of stress-related disorders and their neuroendocrine substrates.

Stress during gestation induces lasting effects on emotional reactivity of the dam rat

Human and animal studies indicate that repeated stress during pregnancy can produce long-term biological and behavioural disorders in the offspring. In contrast, although maternal stress is supposed to induce an increase of maternal anxiety, few studies have been conducted to demonstrate it. Therefore, in the present study we examined the emotional reactivity in stressed (chronic restraint stress applied 3 x 45 min per day during the last week of pregnancy) and unstressed females rats after the weaning of their pups. Restraint stress procedure reduced the body weight gain both during pregnancy and up to four weeks after the stress period. Stressed dams presented a reduction of exploration and of corticosterone levels when exposed to a novel environment (25 and 49 days post-stress). They spent less time in the open arms of the elevated plus-maze (26 days post-stress). Finally, they showed no increase in the time spent in immobility after a second exposure to the forced-swim test (35-36 days post-stress). In the contrary, such differences were not observed when the chronic stress procedure was applied on virgin females. Overall, our results show that, chronic stress during gestation induces lasting effects on emotional reactivity of the dams, thus indicating that gestation constitutes a critical period in the vulnerability to stressful events also for the mother.

Neurobiological correlates of high (HAB) versus low anxiety-related behavior (LAB): differential Fos expression in HAB and LAB rats

BACKGROUND

Two Wistar rat lines selectively bred for either high (HAB) or low (LAB) anxiety-related behavior were used to identify neurobiological correlates of trait anxiety.

METHODS

We used Fos expression for mapping of neuronal activation patterns in response to mild anxiety-provoking challenges.

RESULTS

In both lines, exposure to an open field (OF) or the open arm (OA) of an elevated plus-maze induced Fos expression in several brain areas of the anxiety/fear circuitry. Rats of the HAB type, which showed signs of a hyperanxious phenotype and a hyperreactive hypothalamic-pituitary-adrenal axis compared with LAB rats, exhibited a higher number of Fos-positive cells in the paraventricular nucleus of the hypothalamus, the lateral and anterior hypothalamic area, and the medial preoptic area in response to both OA and OF. Less Fos expression was induced in the cingulate cortex in HAB than in LAB rats. Differential Fos expression in response to either OA or OF was observed in few brain regions, including the thalamus and hippocampus.

CONCLUSIONS

The present data indicate that the divergent anxiety-related behavioral response of HAB versus LAB rats to OF and OA exposures is associated with differential neuronal activation in restricted parts of the anxiety/fear circuitry. Distinct hypothalamic regions displayed hyperexcitability, and the cingulate cortex showed hypoexcitability, which suggests that they are main candidate mediators of dysfunctional brain activation in pathologic anxiety.

Motor cortical control of cardiovascular bulbar neurones projecting to spinal autonomic areas

There is evidence that the motor cortex is involved in cardiovascular adjustments associated with somatic motor activity, as it has functional connections with the ventrolateral medulla, a brainstem region critically involved in the control of blood pressure and the regulation of plasma catecholamine levels. The ventrolateral medulla sends projections to the spinal intermediolateral nucleus, where preganglionic neurones controlling heart and blood vessels (T2 segment) and adrenal medulla (T8 segment) are found. The aim of the present study was to determine whether electrical stimulation of the rat motor cortex induces cardiovascular responses and Fos expression in ventrolateral medulla neurones projecting to the T2 and T8 segments. After a set of experiments designed to record cardiovascular parameters (blood pressure and plasma catecholamine levels), injections of retrograde tracer (Fluorogold) were performed in the intermediolateral nucleus of two groups of rats, at the T2 or at the T8 segmental levels. Five days later, the motor cortex was stimulated in order to induce Fos expression in the ventrolateral medulla. Stimulation of the motor cortex induced: (1). hypotension and a significant decrease in plasma noradrenaline levels, and (2). a significant increase in the number of the double-labelled neurones in the rostral ventrolateral medulla projecting to T2. These data demonstrate that cardiovascular adjustments, preparatory to, or concomitant with, motor activity may be initiated in the motor cortex and transmitted to cardiac and vasomotor spinal preganglionic neurones, via the ventrolateral medulla.

Reliability of high and low anxiety-related behaviour: influence of laboratory environment and multifactorial analysis

The reliability of behavioural data constitutes a major concern in the neuroscience field. Indeed, discrepancies in the behavioural patterns of mice or rats in the same anxiety tests performed in different laboratories have been reported recently. The question raised by such data addressed, in particular, the selection and breeding of two lines of rats on the basis of their high (HAB) and low (LAB) anxiety-related behaviour in the elevated plus-maze test at the Max Planck Institute of Psychiatry in Munich (Germany). As the majority of the behavioural data in these animals has been derived from research carried out in this institute, the aims of the present study were: (1) to test the reliability of the differences in anxiety-related behaviour of these rats in two other laboratories (Villeneuve d'Ascq, France and Innsbruck, Austria); and (2) to determine how the different behavioural traits were associated in both HAB and LAB rats by a principal component analysis. Results were in agreement with the studies performed in Munich, as the divergence in anxiety-related behaviour of the two lines was highly consistent in all tests performed in Villeneuve d'Ascq and Innsbruck. Moreover, the most important parameters to discriminate the two lines were similar to those found in a previous study. Finally, the principal component analysis again confirmed that the selection of HAB and LAB rats is based on anxiety-related behaviour rather than locomotor activity.

Hypodynamia--hypokinesia induced variations in expression of fos protein in structures related to somatosensory system in the rat

There have been many reports describing modifications of the sensory and motor cortex following various types of disuse. Hypodynamia--hypokinesia is characterized by the absence of weight-bearing and by a decrease in motor activity. We have shown a reorganization of the cortical cartography after hypodynamia--hypokinesia. In order to give an anatomical account for this cortical plasticity, we set out to determine whether cerebral and spinal structures exhibited variations of their neuronal activation. For this purpose, immunocytochemical detection of Fos protein was performed in the rat brain and spinal cord. Following stimulation of the sciatic nerve, Fos protein was detected in the primary and secondary somatosensory cortex in control rats and in rats submitted to an episode of 14 days of hypodynamia--hypokinesia. Results showed that the stimulation of the sciatic nerve induced an increase in the number of Fos-immunoreactive neurons in all these structures. Moreover, after hypodynamia--hypokinesia, the number of Fos-immunoreactive neurons was increased in the primary and secondary somatosensory cortex and in the spinal cord. These results provide evidence for a higher activation of cortical cells after hypodynamia--hypokinesia in comparison to controls. These data support the hypothesis that hypodynamia--hypokinesia contributes to the development of functional plasticity.

Activation of ventrolateral medullary neurons projecting to spinal autonomic areas after chemical stimulation of the central nucleus of amygdala: a neuroanatomical study in the rat

Several studies have shown that the central nucleus of amygdala is involved in cardiovascular regulation. The control of this function may be mediated by activation of the ventrolateral medulla neurons that project to preganglionic neurons located in the intermediolateral nucleus of the spinal cord. The aim of the present study was to examine whether stimulation of the central nucleus of amygdala activated ventrolateral medulla neurons projecting to the intermediolateral nucleus. For this purpose, the injection of a retrograde tracer, the cholera toxin b subunit (CTb), into the intermediolateral nucleus of the T2 segment was combined with immunohistochemical detection of Fos protein following chemical stimulation of the central nucleus of amygdala. Results showed that retrogradely labeled neurons were found throughout the ventrolateral medulla. Moreover, chemical stimulation of the central nucleus of amygdala induced: (1) a decrease of arterial blood pressure; (2) an expression of Fos protein mainly in sub-populations of neurons located in the intermediate and caudal parts of the ventrolateral medulla; (3) a significantly higher number of double labeled neurons (CTb-immunoreactive/Fos-immunoreactive) in the rostral part of the ventrolateral medulla than in the other parts of this region. These results show that the central nucleus of amygdala influences the activity of brainstem neurons projecting to the intermediolateral nucleus. Data were discussed in terms of descending amygdalofugal pathways involved in the hypotension.

Cortical control of somato-cardiovascular integration: neuroanatomical studies

This paper will discuss experiments dedicated to the exploration of pathways linking the sensorimotor cortex (SMC) and the main bulbar nuclei involved in cardiovascular control: the nucleus tractus solitarius (NTS), the dorsal nucleus of the vagus (DMV) and the rostral ventrolateral medulla (RVLM). Results obtained through neurofunctional and neuroanatomical methods are presented in order to bring new answers to relevant points concerning somato-cardiovascular integration: firstly to show the ability of the SMC to influence neurons in bulbar cardiovascular nuclei, and secondly to identify pathways that transmit such influences. The neurofunctional approach, based on the identification of Fos-like immunoreactive neurons, indicated that the SMC has functional connections with cardiovascular bulbar nuclei. The neuroanatomical approach, which employed retrograde and anterograde axonal tracing methods, provided evidence of direct projections from the SMC to NTS/DMV and RVLM. Furthermore, experiments showed clearly that corticospinal neurons sent collaterals to bulbar cardiovascular nuclei, especially to the RVLM. Direct cortical projections to the NTS/DMV and the RVLM provide the anatomical basis for cortical influences on the baroreceptor reflex and sympathetic vasomotor mechanisms for blood pressure control, and support the hypothesis of cortical commands coupling somatic and cardiovascular outputs for action.

Mu opioid receptor mRNA expression in neuronal nitric oxide synthase-immunopositive preoptic area neurons

Nitric oxide (NO) as well as beta-endorphin are involved in the neuroendocrine control of gonadotropin-releasing hormone (GnRH) secretion. Recently, morphological and microdialysis experiments have suggested that beta-endorphin may exert an inhibitory influence on NO release in the preoptic area of rat hypothalamus. The present study determines if the mu opioid receptor mRNA is expressed in neuronal NO synthase (nNOS)-immunopositive neurons and if this expression varies among the regions of the basal forebrain being examined. We found, through the use of immunohistochemical and in situ hybridization techniques, that the mu opioid receptor mRNA is expressed in a representative subpopulation of nNOS-immunoreactive neurons in the rat preoptic area. Interestingly, the mu opioid receptor mRNA/nNOS-immunoreactive coexpression is predominant in the rostral and median preoptic area, containing most of GnRH cell bodies. These results strongly suggest that beta-endorphin, via an action through mu opioid receptors, may directly participate in the regulation of NO production in the preoptic area. Our results strengthen the hypothesis that beta-endorphin may participate in GnRH neuronal modulation at the cell body level by regulating NO release from the interneurons of the preoptic area that express nNOS.

Double immunocytochemistry for the detection of Fos protein in retrogradely identified neurons using cholera toxin B subunit

The focus of this paper was to describe a method combining the neuroanatomical technique of retrograde transport of cholera toxin B subunit (CTB) with the technique of Fos functional labeling. This method allowed us to evaluate whether neurons identified by retrograde tracing were activated following chemical stimulation of another brain area. We have used this method at the light microscopic level to determine whether the stimulation of the rostral ventrolateral medulla activated retrogradely labeled adrenal sympathetic preganglionic neurons in the spinal cord. CTB-containing neurons, Fos immunoreactive neurons and double labeled neurons were observed in spinal autonomic areas. These results suggest that the rostral ventrolateral medulla exerts a descending activation upon identified adrenal preganglionic neurons. The method described in this protocol can be applied for other brain areas in order to establish if a given structure can activate an identified population of neurons linked with a particular target of central or peripheral nervous system.