Sleep disorders in a naturalistic cohort of Dutch psychiatric outpatients: prevalence rates and associations with psychopathology symptom severity and well-being

Sleep problems are very common in individuals with a mental disorder. Given the abundant evidence indicating the negative impact of disturbed sleep on mental health outcome, insight into the prevalence of all types of sleep disorders in specific mental disorders and neurodevelopmental conditions is of practical importance. Therefore, we estimated the prevalence of six types of sleep disorders with the Holland Sleep Disorders Questionnaire in an overall mental health sample (n = 1082) and separately for different mental and neurodevelopmental conditions. Furthermore, associations between specific sleep disorders, psychopathology and well-being were studied. The impact of the total number of sleep disorders on these associations was examined. Overall, 46.2% of all participants scored above the cut-off for having a sleep disorder. Specifically, 26.8% scored on insomnia, 12.1% on sleep breathing disorders, 9.7% on hypersomnia, 13.7% on circadian rhythm sleep-wake disorders, 11.2% on parasomnia, and 17.9% on sleep-related movement disorders. Most sleep disorders were associated with greater severity of psychopathology and lower well-being. These associations got stronger with an increasing number of sleep disorders. Our study revealed higher suspected prevalence of most sleep disorders in a mental disorder sample compared to the general population. Moreover, the presence of sleep disorder(s) was strongly associated with symptom severity and reduced well-being. These findings extend the notion that early detection and treatment of sleep disorders in mental health populations is essential for psychiatric outcome.

Effectivity of (Personalized) Cognitive Behavioral Therapy for Insomnia in Mental Health Populations and the Elderly: An Overview

Insomnia is very prevalent in psychiatry and is considered a transdiagnostic symptom of mental disorders. Yet, it is not only a consequence of a mental condition but may also exert detrimental effects on psychiatric symptom severity and therapeutic response; thus, adequate insomnia treatment is particularly important in psychiatric populations. The first choice of intervention is cognitive behavioral therapy for insomnia (CBT-I) as it is rather effective, also in the long run without side effects. It is offered in various forms, ranging from in-person therapy to internet-delivered applications. CBT-I protocols are typically developed for individuals with insomnia disorder without co-occurring conditions. For an optimal therapeutic outcome of CBT-I in individuals with comorbid mental disorders, adaptations of the protocol to tailor the treatment might be beneficial. Based on a literature search using major search engines (Embase; Medline; APA Psych Info; and Cochrane Reviews), this paper provides an overview of the effectiveness of the different CBT-I applications in individuals with diverse comorbid mental conditions and older adults and describes the functionality of CBT-I protocols that have been personalized to specific psychiatric populations, such as depression, substance abuse, and schizophrenia spectrum disorder. Finally, we discuss urgent needs for insomnia therapy targeted to improve both sleep and psychopathologies.

Role of miR-181c in Diet-induced obesity through regulation of lipid synthesis in liver

We recently identified a nuclear-encoded miRNA (miR-181c) in cardiomyocytes that can translocate into mitochondria to regulate mitochondrial gene mt-COX1 and influence obesity-induced cardiac dysfunction through the mitochondrial pathway. Because liver plays a pivotal role during obesity, we hypothesized that miR-181c might contribute to the pathophysiological complications associated with obesity. Therefore, we used miR-181c/d^-/- mice to study the role of miR-181c in hepatocyte lipogenesis during diet-induced obesity. The mice were fed a high-fat (HF) diet for 26 weeks, during which indirect calorimetric measurements were made. Quantitative PCR (qPCR) was used to examine the expression of genes involved in lipid synthesis. We found that miR-181c/d^-/- mice were not protected against all metabolic consequences of HF exposure. After 26 weeks, the miR-181c/d^-/- mice had a significantly higher body fat percentage than did wild-type (WT) mice. Glucose tolerance tests showed hyperinsulinemia and hyperglycemia, indicative of insulin insensitivity in the miR-181c/d^-/- mice. miR-181c/d^-/- mice fed the HF diet had higher serum and liver triglyceride levels than did WT mice fed the same diet. qPCR data showed that several genes regulated by isocitrate dehydrogenase 1 (IDH1) were more upregulated in miR-181c/d^-/- liver than in WT liver. Furthermore, miR-181c delivered in vivo via adeno-associated virus attenuated the lipogenesis by downregulating these same lipid synthesis genes in the liver. In hepatocytes, miR-181c regulates lipid biosynthesis by targeting IDH1. Taken together, the data indicate that overexpression of miR-181c can be beneficial for various lipid metabolism disorders.

Fluoxetine and environmental enrichment similarly reverse chronic social stress-related depression- and anxiety-like behavior, but have differential effects on amygdala gene expression

The adverse effects of stress on brain and behavior have long been known and well-studied, with abundant evidence linking stress to, among other things, mood and anxiety disorders. Likewise, many have investigated potential treatments for stress-related mood and anxiety phenotypes and demonstrated good response to standard antidepressant medications like selective serotonin reuptake inhibitors (SSRIs), as well as environmental manipulations like exercise or enrichment. However, the extent to which stress and various treatments act on overlapping pathways in the brain is less well understood. Here, we used a widely studied social defeat stress paradigm to induce a robust depression- and anxiety-like phenotype and chronic corticosterone elevation that persisted for at least 4 weeks in wild type male mice. When mice were treated with either the SSRI fluoxetine or an enriched environment, both led to similar behavioral recovery from social defeat. We then focused on the amygdala and assessed the effects of social defeat, fluoxetine, and enrichment on 168 genes broadly related to synaptic plasticity or oxidative stress. We found 24 differentially expressed genes in response to social defeat stress. Interestingly, fluoxetine led to broad normalization of the stress-induced expression pattern while enrichment led to expression changes in a separate set of genes. Together, this study provides additional insight into the chronic effects of social defeat stress on behavior and gene expression in the amygdala. The findings also suggest that, for a subset of genes assessed, fluoxetine and environmental enrichment have strikingly divergent effects on expression in the amygdala, despite leading to similar behavioral outcomes.

The clinical relevance of early identification and treatment of sleep disorders in mental health care: protocol of a randomized control trial

BACKGROUND

Sleep disorders are a risk factor for developing a variety of mental disorders, have a negative impact on their remission rates and increase the risk of relapse. Early identification and treatment of sleep disorders is therefore of paramount importance. Unfortunately, in mental health care sleep disorders are often poorly recognized and specific treatment frequently occurs late or not at all. This protocol-paper presents a randomized controlled trial investigating the clinical relevance of early detection and treatment of sleep disorders in mental health care. The two aims of this project are 1) to determine the prevalence of sleep disorders in different mental disorders, and 2) to investigate the contribution of early identification and adequate treatment of sleep disorders in individuals with mental disorders to their sleep, mental disorder symptoms, general functioning, and quality of life.

METHODS

Patients newly referred to a Dutch mental health institute for psychiatric treatment will be screened for sleep disorders with the self-assessment Holland Sleep Disorders Questionnaire (HSDQ). Patients scoring above the cut-off criteria will be invited for additional diagnostic evaluation and, treatment of the respective sleep disorder. Participants will be randomly assigned to two groups: Immediate sleep diagnostics and intervention (TAU+SI-T0), or delayed start of sleep intervention (TAU+SI-T1; 6 months after inclusion). The effect of sleep treatment as add-on to treatment as usual (TAU) will be tested with regard to sleep disorder symptoms, general functioning, and quality of life (in collaboration with a psychiatric sleep centre).

DISCUSSION

This trial will examine the prevalence of different sleep disorders in a broad range of mental disorders, providing information on the co-occurrence of specific sleep and mental disorders. Further, this study is the first to investigate the impact of early treatment of sleep disorders on the outcome of many mental disorders. Moreover, standard sleep interventions will be tailored to specific mental disorders, to increase their efficacy. The results of this trial may contribute considerably to the improvement of mental health care.

TRIAL REGISTRATION

This clinical trial has been retrospectively registered in the Netherlands Trial Register (NL8389; https://www.trialregister.nl/trial/8389) on February 2th, 2020.

Nitrated meat products are associated with mania in humans and altered behavior and brain gene expression in rats

Mania is a serious neuropsychiatric condition associated with significant morbidity and mortality. Previous studies have suggested that environmental exposures can contribute to mania pathogenesis. We measured dietary exposures in a cohort of individuals with mania and other psychiatric disorders as well as in control individuals without a psychiatric disorder. We found that a history of eating nitrated dry cured meat but not other meat or fish products was strongly and independently associated with current mania (adjusted odds ratio 3.49, 95% confidence interval (CI) 2.24-5.45, p < 8.97 × 10^-8). Lower odds of association were found between eating nitrated dry cured meat and other psychiatric disorders. We further found that the feeding of meat preparations with added nitrate to rats resulted in hyperactivity reminiscent of human mania, alterations in brain pathways that have been implicated in human bipolar disorder, and changes in intestinal microbiota. These findings may lead to new methods for preventing mania and for developing novel therapeutic interventions.

Early Changes in Adipose Tissue Morphology, Gene Expression, and Metabolism After RYGB in Patients With Obesity and T2D

CONTEXT

Roux-en-Y gastric bypass (RYGB) surgery effectively prevents or treats type 2 diabetes (T2D). Adipose tissue (AT) mechanisms may be of importance.

OBJECTIVE

To assess the relationship between early changes in whole-body and AT metabolism in surgically treated patients with T2D.

DESIGN AND SETTING

A randomized single-center study.

PATIENTS

Nineteen patients with T2D with body mass index 30 to 45 kg/m2.

INTERVENTIONS

Thirteen patients were assessed at baseline and 4 and 24 weeks after RYGB (preceded by a 4-week low-calorie diet) and compared with 6 control patients continuing standard medical treatment: oral glucose tolerance test, subcutaneous AT biopsies for gene expression, adipocyte size, glucose uptake, lipolysis, and insulin action.

RESULTS

At 4 and 24 weeks post-RYGB, all patients but one had stopped diabetes medication. Fasting glucose, HbA1c, and insulin levels decreased and the Matsuda index increased compared with baseline (P < 0.01 for all), indicating improved whole-body insulin sensitivity. Mean adipocyte size significantly reduced, more at 4 than at 24 weeks; at 4 weeks, glucose uptake per adipocyte was lowered, and isoproterenol-stimulated lipolysis tended to increase, whereas the fold insulin effects on glucose uptake and lipolysis were unchanged. Expression of genes involved in fatty acid oxidation, CPT1b and adiponectin, was increased at 4 weeks, whereas leptin and E2F1 (involved in cell proliferation) were reduced (P < 0.05 for all).

CONCLUSION

Glycemic control and in vivo insulin sensitivity improved 4 weeks after RYGB, but adipocyte insulin sensitivity did not change despite a marked reduction in adipocyte size. Thus, mechanisms for a rapid improvement of T2D after RYGB may occur mainly in other tissues than adipose.

Maternal high-fat diet results in cognitive impairment and hippocampal gene expression changes in rat offspring

Consumption of a high-fat diet has long been known to increase risk for obesity, diabetes, and the metabolic syndrome. Further evidence strongly suggests that these same metabolic disorders are associated with an increased risk of cognitive impairment later in life. Now faced with an expanding global burden of obesity and increasing prevalence of dementia due to an aging population, understanding the effects of high-fat diet consumption on cognition is of increasingly critical importance. Further, the developmental origins of many adult onset neuropsychiatric disorders have become increasingly clear, indicating a need to investigate effects of various risk factors, including diet, across the lifespan. Here, we use a rat model to assess the effects of maternal diet during pregnancy and lactation on cognition and hippocampal gene expression of offspring. Behaviorally, adult male offspring of high-fat fed dams had impaired object recognition memory and impaired spatial memory compared to offspring of chow-fed dams. In hippocampus, we found decreased expression of Insr, Lepr, and Slc2a1 (GLUT1) among offspring of high-fat fed dams at postnatal day 21. The decreased expression of Insr and Lepr persisted at postnatal day 150. Together, these data provide additional evidence to suggest that maternal exposure to high-fat diet during pregnancy and lactation can have lasting effects on the brain, behavior, and cognition on adult offspring.

FKBP5 expression in human adipose tissue: potential role in glucose and lipid metabolism, adipogenesis and type 2 diabetes

PURPOSE

Here, we explore the involvement of FKBP51 in glucocorticoid-induced insulin resistance (IR) in human subcutaneous adipose tissue (SAT), including its potential role in type 2 diabetes (T2D). Moreover, we assess the metabolic effects of reducing the activity of FKBP51 using the specific inhibitor SAFit1.

METHODS

Human SAT was obtained by needle biopsies of the lower abdominal region. FKBP5 gene expression was assessed in fresh SAT explants from a cohort of 20 T2D subjects group-wise matched by gender, age and BMI to 20 non-diabetic subjects. In addition, human SAT was obtained from non-diabetic volunteers (20F/9M). SAT was incubated for 24 h with or without the synthetic glucocorticoid dexamethasone and SAFit1. Incubated SAT was used to measure the glucose uptake rate in isolated adipocytes.

RESULTS

FKBP5 gene expression levels in SAT positively correlated with several indices of IR as well as glucose area under the curve during oral glucose tolerance test (r = 0.33, p < 0.05). FKBP5 gene expression levels tended to be higher in T2D subjects compared to non-diabetic subjects (p = 0.088). Moreover, FKBP5 gene expression levels were found to inversely correlate with lipolytic, lipogenic and adipogenic genes. SAFit1 partly prevented the inhibitory effects of dexamethasone on glucose uptake.

CONCLUSIONS

FKBP5 gene expression in human SAT tends to be increased in T2D subjects and is related to elevated glucose levels. Moreover, FKBP5 gene expression is inversely associated with the expression of lipolytic, lipogenic and adipogenic genes. SAFit1 can partly prevent glucose uptake impairment by glucocorticoids, suggesting that FKBP51 might be a key factor in glucocorticoid-induced IR.

Altered Glucose Uptake in Muscle, Visceral Adipose Tissue, and Brain Predict Whole-Body Insulin Resistance and may Contribute to the Development of Type 2 Diabetes: A Combined PET/MR Study

We assessed glucose uptake in different tissues in type 2 diabetes (T2D), prediabetes, and control subjects to elucidate its impact in the development of whole-body insulin resistance and T2D. Thirteen T2D, 12 prediabetes, and 10 control subjects, matched for age and BMI, underwent OGTT and abdominal subcutaneous adipose tissue (SAT) biopsies. Integrated whole-body ¹⁸F-FDG PET and MRI were performed during a hyperinsulinemic euglycemic clamp to asses glucose uptake rate (MRglu) in several tissues. MRglu in skeletal muscle, SAT, visceral adipose tissue (VAT), and liver was significantly reduced in T2D subjects and correlated positively with M-values (r=0.884, r=0.574, r=0.707 and r=0.403, respectively). Brain MRglu was significantly higher in T2D and prediabetes subjects and had a significant inverse correlation with M-values (r=-0.616). Myocardial MRglu did not differ between groups and did not correlate with the M-values. A multivariate model including skeletal muscle, brain and VAT MRglu best predicted the M-values (adjusted r²=0.85). In addition, SAT MRglu correlated with SAT glucose uptake ex vivo (r=0.491). In different stages of the development of T2D, glucose uptake during hyperinsulinemia is elevated in the brain in parallel with an impairment in peripheral organs. Impaired glucose uptake in skeletal muscle and VAT together with elevated glucose uptake in brain were independently associated with whole-body insulin resistance, and these tissue-specific alterations may contribute to T2D development.

The effects of scheduled running wheel access on binge-like eating behavior and its consequences

Binge eating disorder (BED) is an eating disorder involving repeated, intermittent over consumption of food in brief periods of time, usually with no compensatory behaviors. There are few successful treatments and the underlying neural mechanisms remain unclear. In the current study, we hypothesized that voluntary running wheel (RW) activity could reduce binge-like eating behavior in a rat model. Rats were given intermittent (3 times/wk) limited (1hr) access to a high-fat food (Crisco), in addition to continuously available chow. Crisco was available every Mon, Wed, and Fri for 1hr before dark onset. Rats were divided into 2 groups: those with RW access during the first half of the experiment and sedentary during the second half (RW-SED) and those that were sedentary during the first half of the experiment and had RW access during the second half (SED-RW). Crisco intake was significantly less in both groups during the period of time with a RW present. Within the bingeing RW-SED rats, the gene expression of the orexigenic neuropeptides AgRP and NPY were similar to a non-bingeing sedentary control (CON) group, while the expression of the anorexigenic neuropeptide POMC was significantly increased relative to the SED-RW and CON groups. Despite elevated POMC, the rats continued to binge. Additionally, within both groups, the gene expression of the D2R and Oprm1 in the NAc and the VTA were altered suggesting that the reward system was stimulated by both the bingeing behavior and the running wheel activity. Overall, access to a RW and the resulting activity significantly reduced binge-like behavior as well as modulated the effects of binging on brain appetite and reward systems.

Roman high and low avoidance rats differ in their response to chronic olanzapine treatment at the level of body weight regulation, glucose homeostasis, and cortico-mesolimbic gene expression

Olanzapine, an antipsychotic agent mainly used for treating schizophrenia, is frequently associated with body weight gain and diabetes mellitus. Nonetheless, studies have shown that not every individual is equally susceptible to olanzapine's weight-gaining effect. Therefore, Roman high and low avoidance rat strains were examined on their responsiveness to olanzapine treatment. The Roman high avoidance rat shares many behavioral and physiological characteristics with human schizophrenia, such as increased central dopaminergic sensitivity, whereas the Roman low avoidance rat has been shown to be prone to diet-induced obesity and insulin resistance. The data revealed that only the Roman high avoidance rats are susceptible to olanzapine-induced weight gain and attenuated glucose tolerance. Here it is suggested that the specific olanzapine-induced weight gain in Roman high avoidance rats could be related to augmented dopaminergic sensitivity at baseline through increased expression of prefrontal cortex dopamine receptor D1 mRNA and nucleus accumbens dopamine receptor D2 mRNA expression. Regression analyses revealed that olanzapine-induced weight gain in the Roman high avoidance rat is above all related to increased prolactin levels, whereas changes in glucose homeostasis is best explained by differences in central dopaminergic receptor expressions between strains and treatment. Our data indicates that individual differences in dopaminergic receptor expression in the cortico-mesolimbic system are related to susceptibility to olanzapine-induced weight gain.

Stress coping style does not determine social status, but influences the consequences of social subordination stress

Chronic stress exposure may have negative consequences for health. One of the most common sources of chronic stress is stress associated with social interaction. In rodents, the effects of social stress can be studied in a naturalistic way using the visual burrow system (VBS). The way an individual copes with stress, their "stress coping style", may influence the consequences of social stress. In the current study we tested the hypothesis that stress coping style may modulate social status and influence the consequences of having a lower social status. We formed 7 VBS colonies, with 1 proactive coping male, 1 passive coping male, and 4 female rats per colony to assess whether a rat's coping style prior to colony formation could predict whether that individual is more likely to become socially dominant. The rats remained in their respective colonies for 14days and the physiological and behavioral consequences of social stress were assessed. Our study shows that stress coping style does not predict social status. However, stress coping style may influence the consequences of having a lower social status. Subordinate passive and proactive rats had distinctly different wound patterns; proactive rats had more wounds on the front of their bodies. Behavioral analysis confirmed that proactive subordinate rats engaged in more offensive interactions. Furthermore, subordinate rats with a proactive stress coping style had larger adrenals, and increased stress responsivity to a novel acute stressor (restraint stress) compared to passive subordinate rats or dominant rats, suggesting that the allostatic load may have been larger in this group.

Prenatal high-fat diet alters placental morphology, nutrient transporter expression, and mtorc1 signaling in rat

OBJECTIVE

This study aimed to determine how the rat placenta and fetus respond to maternal high-fat (HF) diet during gestation and to identify the possible mechanisms.

METHODS

Pregnant Sprague-Dawley rats were fed with standard chow (13.5% fat) or HF (60% fat) diet during gestation. Placentas were collected on gestation day 21.

RESULTS

HF dams had greater fat mass, higher plasma leptin, lower plasma adiponectin, and impaired glucose tolerance during pregnancy. The placental labyrinth thickness was reduced in both male and female fetuses of HF dams. In HF male placentas, glucose transporter 3 gene expression, system A amino acid transporter (SNAT) 2 gene expression, and SNAT2 protein expression were increased through the activation of the mTORC1 4EBP1 branch. In HF female placentas, gene expression of insulin-like growth factor 2 (IGF2) and IGF2 receptor was elevated compared to placentas of females fed standard chow. Although male and female placentas responded differently to prenatal HF diet exposure, both male and female fetal weight was not altered by maternal HF diet.

CONCLUSIONS

Placenta responds and adapts to maternal metabolic changes by altering placental layer thickness, mTORC1 signaling, expression of nutrient transporters, and growth factors in a sex-specific manner.

Failure to upregulate Agrp and Orexin in response to activity based anorexia in weight loss vulnerable rats characterized by passive stress coping and prenatal stress experience

We hypothesize that anorexia nervosa (AN) poses a physiological stress. Therefore, the way an individual copes with stress may affect AN vulnerability. Since prenatal stress (PNS) exposure alters stress responsivity in offspring this may increase their risk of developing AN. We tested this hypothesis using the activity based anorexia (ABA) rat model in control and PNS rats that were characterized by either proactive or passive stress-coping behavior. We found that PNS passively coping rats ate less and lost more weight during the ABA paradigm. Exposure to ABA resulted in higher baseline corticosterone and lower insulin levels in all groups. However, leptin levels were only decreased in rats with a proactive stress-coping style. Similarly, ghrelin levels were increased only in proactively coping ABA rats. Neuropeptide Y (Npy) expression was increased and proopiomelanocortin (Pomc) expression was decreased in all rats exposed to ABA. In contrast, agouti-related peptide (Agrp) and orexin (Hctr) expression were increased in all but the PNS passively coping ABA rats. Furthermore, DNA methylation of the orexin gene was increased after ABA in proactive coping rats and not in passive coping rats. Overall our study suggests that passive PNS rats have innate impairments in leptin and ghrelin in responses to starvation combined with prenatal stress associated impairments in Agrp and orexin expression in response to starvation. These impairments may underlie decreased food intake and associated heightened body weight loss during ABA in the passively coping PNS rats.

Exposure to activity-based anorexia impairs contextual learning in weight-restored rats without affecting spatial learning, taste, anxiety, or dietary-fat preference

Relapse rates are high amongst cases of anorexia nervosa (AN) suggesting that some alterations induced by AN may remain after weight restoration.

OBJECTIVE

To study the consequences of AN without confounds of environmental variability, a rodent model of activity-based anorexia (ABA) can be employed. We hypothesized that exposure to ABA during adolescence may have long-term consequences in taste function, cognition, and anxiety-like behavior after weight restoration.

METHODS

To test this hypothesis, we exposed adolescent female rats to ABA (1.5 h food access, combined with voluntary running wheel access) and compared their behavior to that of control rats after weight restoration was achieved. The rats were tested for learning/memory, anxiety, food preference, and taste in a set of behavioral tests performed during the light period.

RESULTS

Our data show that ABA exposure leads to reduced performance during the novel object recognition task, a test for contextual learning, without altering performance in the novel place recognition task or the Barnes maze, both tasks that test spatial learning. Furthermore, we do not observe alterations in unconditioned lick responses to sucrose nor quinine (described by humans as "sweet" and "bitter," respectively). Nor Do we find alterations in anxiety-like behavior during an elevated plus maze or an open field test. Finally, preference for a diet high in fat is not altered.

DISCUSSION

Overall, our data suggest that ABA exposure during adolescence impairs contextual learning in adulthood without altering spatial leaning, taste, anxiety, or fat preference.

Corticosterone administration in drinking water decreases high-fat diet intake but not preference in male rats

One of the mechanisms through which regular exercise contributes to weight maintenance could be by reducing intake and preference for high-fat (HF) diets. Indeed, we previously demonstrated that wheel-running rats robustly reduced HF diet intake and preference. The reduced HF diet preference by wheel running can be so profound that the rats consumed only the chow diet and completely avoided the HF diet. Because previous research indicates that exercise activates the hypothalamic-pituitary-adrenal axis and increases circulating levels of corticosterone, this study tested the hypothesis that elevation of circulating corticosterone is involved in wheel running-induced reduction in HF diet preference in rats.Experiment 1 measured plasma corticosterone levels under sedentary and wheel-running conditions in the two-diet-choice (high-carbohydrate chow vs. HF) feeding regimen. The results revealed that plasma corticosterone is significantly increased and positively correlated with the levels of running in wheel-running rats with two-diet choice.Experiments 2 and 3 determined whether elevated corticosterone without wheel running is sufficient to reduce HF diet intake and preference. Corticosterone was elevated by adding it to the drinking water. Compared with controls, corticosterone-drinking rats had reduced HF diet intake and body weight, but the HF diet preference between groups did not differ. The results of this study support a role for elevated corticosterone on the reduced HF diet intake during wheel running. The elevation of corticosterone alone, however, is not sufficient to produce a robust reduction in HF diet preference.

Anorexia nervosa as a motivated behavior: Relevance of anxiety, stress, fear and learning

The high comorbidity between anorexia nervosa (AN) and anxiety disorders is well recognized. AN is a motivated behavioral disorder in which habit formation is likely to contribute to the persistence of abnormal eating and exercise behaviors. Secondary alterations in brain circuitry underlying the reward value of food and exercise, along with disturbances in neuroendocrine hunger and satiety signaling arising from starvation and excessive exercise, are likely contributors to the maintenance of anorectic behaviors in genetically vulnerable individuals. The potential role of fear conditioning in facilitating onset of AN, or of impaired fear extinction in contributing to the high relapse rates observed following weight restoration, is of interest. Evidence from animal models of anxiety and human laboratory studies indicate that low estrogen impairs fear extinction. Low estradiol levels in AN may therefore play a role in perpetuating fear of food and fat in recently weight restored patients. Translational models including the activity based anorexia (ABA) rodent model of AN, and neuroimaging studies of fear extinction and conditioning, could help clarify the underlying molecular mechanisms and neurocircuitry involved in food avoidance behaviors in AN. Moreover, the adaptation of novel treatment interventions with efficacy in anxiety disorders may contribute to the development of new treatments for this impairing disorder.

Individual differences in the effects of prenatal stress exposure in rodents

Exposure to prenatal stress alters the phenotype of the offspring in adulthood. When the prenatal and adult environments do not match, these alterations may induce pathology risk. There are, however, large individual differences in the effects of prenatal stress. While some individuals seem vulnerable, others appear to be relatively resistant to its effects. In this review we discuss potential mechanisms underlying these individual differences with a focus on animal models. Differences between rodent models selected for stress coping traits are discussed. In addition, the role of circulating factors, like glucocorticoids and cytokines, factors involved in brain development and influences of epigenetic and genetic factors in prenatal stress induced phenotype are covered.

Long-term impact of early life events on physiology and behaviour

This review discusses the effects of stress and nutrition throughout development and summarises studies investigating how exposure to stress or alterations in nutrition during the pre-conception, prenatal and early postnatal periods can affect the long-term health of an individual. In general, the data presented here suggest that that anything signalling potential adverse conditions later in life, such as high levels of stress or low levels of food availability, will lead to alterations in the offspring, possibly of an epigenetic nature, preparing the offspring for these conditions later in life. However, when similar environmental conditions are not met in adulthood, these alterations may have maladaptive consequences, resulting in obesity and heightened stress sensitivity. The data also suggest that the mechanism underlying these adult phenotypes might be dependent on the type and the timing of exposure.

Prenatal stress and stress coping style interact to predict metabolic risk in male rats

Both prenatal stress (PNS) exposure and a passive stress-coping style have been identified as risk factors for insulin resistance in rats. In the current study, we test the hypothesis that PNS and stress-coping style may interact in predicting susceptibility for metabolic disease. To test this hypothesis, adult male control and PNS offspring were behaviorally characterized using a defensive burying test to have either a passive or proactive stress-coping style. In adulthood, all rats were fed either a standard chow or a high-fat diet for 3 weeks. After 3 weeks of diet exposure, glucose and insulin levels were assessed during an oral glucose tolerance test. Under high-fat diet conditions, PNS rats display elevated glucose and insulin responses to the oral glucose tolerance test, indicative of glucose intolerance. Interestingly, these effects of PNS were far more pronounced in rats characterized by a passive stress-coping style. Additionally, the passively coping PNS rats also gained more weight on the high-fat diet than all other rats tested. This observation suggests that a stressful prenatal environment in combination with a passive stress-coping strategy may prime an individual to be sensitive to diet-induced obesity and type 2 diabetes.

Similarities and differences between "proactive" and "passive" stress-coping rats in responses to sucrose, NaCl, citric acid, and quinine

A stress-coping style describes a set of behavioral and physiological measures that characterize an individual's response to stressful stimuli. It would follow that different stress-coping styles are associated with differential sensitivity for taste stimuli. Animals with stress-coping characteristics better suited to an environment in which new foods are more frequently encountered may show enhanced orosensitivity to cues that signal toxins and/or nutritional value. Here, rats were categorized as "proactive" or "passive" based on results from a defensive burying test. Next, the brief-access taste procedure was used to compare unconditioned licking responses to a concentration array of compounds that humans describe as "sweet" (sucrose), "salty" (NaCl), "sour" (citric acid), and "bitter" (quinine) across the 2 groups. Both groups displayed concentration-dependent lick responses to sucrose, NaCl, citric acid, and quinine. The passive group initiated significantly fewer trials to sucrose than the proactive rats, but the groups did not significantly differ in trial initiation for the other 3 test compounds. Thus, differences in food intake, body weight, and glucose homeostasis between the stress-coping styles are not likely driven by alterations in orosensory responsivity. However, the current findings lend support to the hypothesis that the 2 groups differ in reward-related signaling mechanisms.

Prenatal stress decreases Bdnf expression and increases methylation of Bdnf exon IV in rats

There is ample evidence that exposure to stress during gestation increases the risk of the offspring to develop mood disorders. Brain-derived neurotrophic factor (Bdnf) plays a critical role during neuronal development and is therefore a prime candidate to modulate neuronal signaling in adult offspring of rat dams that were stressed during gestation. In the current study, we tested the hypothesis that alterations in Bdnf expression in prenatally stressed (PNS) offspring are mediated by changes in DNA methylation in exons IV and VI of the Bdnf gene. We observed decreased Bdnf expression in the amygdala and hippocampus of prenatally stressed rats both at weaning and in adulthood. This decrease in Bdnf expression was accompanied by increased DNA methylation in Bdnf exon IV in the amygdala and hippocampus, suggesting that PNS-induced reduction in Bdnf expression may, at least in part, be mediated by increased DNA methylation of Bdnf exon IV. Expression of DNA methyltransferases (Dnmt) 1 and 3a was increased in PNS rats in the amygdala and hippocampus. Our data suggest that PNS induces decreases in Bdnf expression that may at least in part be mediated by increased DNA methylation of Bdnf exon IV.

Early postweaning exercise improves central leptin sensitivity in offspring of rat dams fed high-fat diet during pregnancy and lactation

Maternal high-fat (HF) diet has long-term consequences on the metabolic phenotype of the offspring. Here, we determined the effects of postweaning exercise in offspring of rat dams fed HF diet during gestation and lactation. Pregnant Sprague-Dawley rats were maintained on chow or HF diet throughout gestation and lactation. All pups were weaned onto chow diet on postnatal day (PND) 21. At 4 wk of age, male pups were given free access to running wheels (RW) or remained sedentary (SED) for 3 wk, after which all rats remained sedentary, resulting in four groups: CHOW-SED, CHOW-RW, HF-SED, and HF-RW. Male HF offspring gained more body weight by PND7 compared with CHOW pups and maintained this weight difference through the entire experiment. Three weeks of postweaning exercise did not affect body weight gain in either CHOW or HF offspring, but reduced adiposity in HF offspring. Plasma leptin was decreased at the end of the 3-wk running period in HF-RW rats but was not different from HF-SED 9 wk after the exercise period ended. At 14 wk of age, intracerebroventricular injection of leptin suppressed food intake in CHOW-SED, CHOW-RW, and HF-RW, while it did not affect food intake in HF-SED group. At death, HF-RW rats also had higher leptin-induced phospho-STAT3 level in the arcuate nucleus than HF-SED rats. Both maternal HF diet and postweaning exercise had effects on hypothalamic neuropeptide and receptor mRNA expression in adult offspring. Our data suggest that postweaning exercise improves central leptin sensitivity and signaling in this model.

Models and mechanisms of metabolic regulation: genes, stress, and the HPA and HPG axes

A variety of models have been developed to better understand the mechanisms underlying individual variation in susceptibility to obesity. This review discusses several of these models and explores their role in understanding individual vulnerability to metabolic disease and the environmental factors around which metabolic perturbations occur. Recently, the focus of models has shifted towards heterogeneous populations, in which individuals characterized by a high vulnerability and individuals that are seemingly resistant can be identified. The use of these heterogeneous studies has lead to the identification of several novel biomarkers predicting obesity. This review therefore focuses on nontraditional factors, which are not directly implicated in metabolic regulation. First, the evidence from rodent knockout models for genetic factors involved in obesity is discussed. Second, the role of a stressful environment, particularly the early life environment is investigated along with a discussion of circadian disruption and metabolic disorders. Finally, the impact of sex-steroids, as exemplified by polycystic ovarian syndrome, is discussed. Overall, the data presented in our review demonstrate that in most cases interplay between genetic and environmental factors best predicts disease development. Our review shows that susceptibility to obesity may be explained by complex interactions between traditional homeostatic mechanisms, such as the hypothalamic peptide, and less studied mechanisms, like steroids and neurotrophic factors.

Forced and voluntary exercise counteract insulin resistance in rats: the role of coping style

There are large individual differences in the success rates of exercise intervention programs aimed at the prevention and treatment of obesity-related disorders. In the present study, we tested the hypothesis that differences in coping style may impact the success rates of these intervention programs. We tested insulin responses before and after voluntary wheel running in both passive (insulin resistant) Roman Low Avoidance (RLA) and proactive (insulin sensitive) Roman High Avoidance (RHA) rats using intravenous glucose tolerance tests (IVGTTs). To control for a potential difference between voluntary and forced exercise, we also included RLA and RHA rats that were subjected to forced running. We found the following: 1) when given the opportunity to run voluntarily in a running wheel, passive RLA rats run more than proactively than RHA rats; 2) voluntary exercise leads to a normalization of insulin responses during an IVGTTs in RLA rats; and 3) there were no behavioral and physiological differences in efficacy between voluntary and forced running. We conclude that exercise, both forced and voluntary, is a successful lifestyle intervention for the treatment of hyperinsulinemia, especially in individuals with a passive coping style.

Personality, a key factor in personalized medicine?

The incidence of health problems resulting from obesity is growing and obesity and its related diseases has become one of the main causes in death in industrialized societies. Environmental influences are crucial for the interactions between genetic, neurohormonal and metabolic factors that may be important in understanding individual differences in the development of obesity and metabolic diseases like type 2 diabetes. In particular the interactions between the personality of an individual and the environment play a key role in predicting the chance for successful treatment. Our experimental data clearly point out that the success of interventions designed to prevent or treat metabolic diseases could be considerably improved by adjusting the intervention to the personality of the individual. Furthermore, certain physiological and neuroendocrine characteristics of a personality are strong indicators for pathology development, both in experimental animals and humans. Future research should focus on the identification of easily measurable physiological and neuroendocrine markers indicative of the coping style or personality in humans.

Individual variation in the (patho)physiology of energy balance

There are large individual differences in the susceptibility for metabolic disorders such as obesity, the metabolic syndrome and type 2 diabetes. Unfortunately, most animal studies in this field ignore the importance of individual variation which limits the face validity of these studies for translation to the human situation. We have performed a series of studies that were particularly focused on the individual differences in the (patho)physiology of energy balance. The studies were performed with passive and proactive individuals of two different rat strains: the Roman High and Low Avoidance rats and the Wild type Groningen rat. The data reveal that passive and proactive individuals differ significantly on several parameters, i.e. body composition, Hypothalamic-Pituitary-Adrenal (HPA) axis activity, plasma levels of insulin and leptin, intestinal transit time, systolic blood pressure and meal patterns. We also found that the selection line of the Roman Low Avoidance rat may be considered as a non-obese animal model for the metabolic syndrome, since these rats display, under sedentary conditions, many of the related symptoms such as hypertension, visceral adiposity and insulin resistance during an intravenous glucose tolerance test. These symptoms disappeared when the animals were allowed to exercise voluntarily in a running wheel. We conclude that experiments with passive and proactive individuals are highly relevant for studying the (patho)physiology and behavior of energy balance and the related metabolic disorders.

Neurobiology of hyperactivity and reward: agreeable restlessness in anorexia nervosa

Restricted food intake is associated with increased physical activity, very likely an evolutionary advantage, initially both functional and rewarding. The hyperactivity of patients with anorexia nervosa, however, is a main problem for recovery. This seemingly paradoxical reward of hyperactivity in anorexia nervosa is one of the main aspects in our framework for the neurobiological changes that may underlie the development of the disorder. Here, we focus on the neurobiological basis of hyperactivity and reward in both animals and humans suggesting that the mesolimbic dopamine and hypothalamic orexin neurons play central roles. The paper represents an invited review by a symposium, award winner or keynote speaker at the Society for the Study of Ingestive Behavior [SSIB] Annual Meeting in Portland, July 2009.