Psychoneuroendocrine characteristics of common obesity clinical subtypes

Repetitive transcranial direct current stimulation modulates the brain-gut-microbiome axis in obese rodents

Background

Complex interactions between the brain, gut and adipose tissue allow to recognize obesity as a neurometabolic disorder. The recent data have shown that gut microbiota can play a potential role in obesity development. Transcranial direct current stimulation (tDCS) is a safe and non-invasive technique to modulate the activity of cerebral cortex and other connected brain areas also in context of appetite control. The objective of this study was to evaluate the effects of repetitive anodal tDCS (AtDCS) of prefrontal cortex on feeding behavior, metabolic status and selected phyla of gut microbiota in rats with obesity induced by high-calorie diet (HCD).

Methods

32 female Wistar rats were equally divided into 4 subgroups depending on diet effect (lean versus obese) and type of stimulation (active versus sham tDCS versus no stimulation). Feed intake, body weight, blood lipoproteins and leptin levels as well as Firmicutes and Bacteroidetes in intestines and stool were examined.

Results

HCD changed feeding behavior and metabolic parameters typically for obesity-related ranges and resulted in an abundance of Firmicutes at the expanse of Bacteroidetes in the large intestine and stool. AtDCS decreased appetite, body weight, and cholesterol levels. In addition, AtDCS reduced ratio of the average number of Firmicutes to average number of Bacteroidetes in all examined tissues.

Conclusions

Repetitive AtDCS is not only effective for appetite restriction but can also modulate gut microbiome composition which demonstrates the existence of the brain–gut–microbiome axis and points at this technique as a promising complementary treatment for obesity. However, the effects should be further replicated in human studies.

Effect of obesity on inhibitory control in preadolescents during stop-signal task. An event-related potentials study

Preadolescence is a period in which structural and functional changes occur in brain network reorganization that relate to the development of executive control functions, particularly in the areas of attention and cognitive inhibition. Obesity has been associated with a deficit in executive functions and behavioral and electrophysiological differences using the go/no-go task (proactive inhibition), but no study has assessed brain-electrical activity using the stop-signal task (reactive inhibition) in this population. Therefore, we hypothesized that obese preadolescents would show less efficiency in reactive inhibition than their same-age non-obese peers. To test this hypothesis, event-related potentials (ERPs) were collected during a stop-signal task and compared between 27 obese preadolescents (mean BMI = 25.9; 9.65 years old) and 29 normal-weight preadolescents (mean BMI = 17.5; 9.60 years old). No significant differences between groups were observed in behavioral responses. As for ERPs, the obese group had an electrophysiological pattern associated with less efficient conflict monitoring during the "no-go" condition (i.e., less modulation of N200 latency based on the experimental condition), differences in attentional allocation in the "go" condition (less modulation of P300a latency based on experimental condition), and difficulties in rule retrieval from working memory associated with the trial-type in both experimental conditions (smaller P300b amplitude). We conclude that obese preadolescents displayed less ability to modulate conflict-monitoring in the "no-go" condition and attention allocation in the "go" condition, evidencing differences between groups in the development of attention and inhibitory control.

Dehydroepiandrosterone (DHEA) and dehydroepiandrosterone-sulfate (DHEAS) and emotional processing - A behavioral and electrophysiological approach

Dehydroepiandrosterone (DHEA) and dehydroepiandrosterone-sulfate (DHEAS) may have mood enhancement effects: higher DHEAS concentrations and DHEA/cortisol ratio have been related to lower depression scores and controlled trials of DHEA administration have reported significant antidepressant effects. The balance between DHEAS and DHEA has been suggested to influence brain functioning. We explored DHEAS, DHEA, cortisol, DHEA/cortisol and DHEAS/DHEA ratios relations to the processing of negative emotional stimuli at behavioral and brain levels by recording the electroencephalogram of 21 young women while performing a visual task with implicit neutral or negative emotional content in an audio-visual oddball paradigm. For each condition, salivary DHEA, DHEAS and cortisol were measured before performing the task and at 30 and 60min intervals. DHEA increased after task performance, independent of the implicit emotional content. With implicit negative emotion, higher DHEAS/DHEA and DHEA/cortisol ratios before task performance were related to shorter visual P300 latencies suggesting faster brain processing under a negative emotional context. In addition, higher DHEAS/DHEA ratios were related to reduced visual P300 amplitudes, indicating less processing of the negative emotional stimuli. With this study, we could show that at the electrophysiological level, higher DHEAS/DHEA and DHEA/cortisol ratios were related to shorter stimulus evaluation times suggesting less interference of the implicit negative content of the stimuli with the task. Furthermore, higher DHEAS/DHEA ratios were related to reduced processing of negative emotional stimuli which may eventually constitute a protective mechanism against negative information overload.

Elevated homocysteine level in first-episode schizophrenia patients--the relevance of family history of schizophrenia and lifetime diagnosis of cannabis abuse

Accumulating evidence indicates that elevated homocysteine (Hcy) level occurs in first-episode schizophrenia (FES) patients. We included 56 FES patients and 53 healthy controls (HC). Plasma level of Hcy was significantly higher in FES patients than HC (p = 0.044). In addition, plasma levels of high-density lipoproteins (HDL) and folate were significantly lower in FES than in HC (p < 0.001). Positive family history of schizophrenia was associated with lower plasma HDL (p = 0.041) and vitamin B12 (p = 0.017), as well as higher level of Hcy (p = 0.017). Patients with FES, who abused cannabis, had higher levels of Hcy (p = 0.017), as well as lower levels of vitamin B12 (p = 0.017) and HDL (p = 0.041). Plasma Hcy negatively correlated with duration of untreated psychosis (r = -0.272, p = 0.042). There was a positive correlation between Hcy level and the severity of negative symptoms (r = 0.363, p = 0.006) and general psychopathology (r = 0.349, p = 0.008) assessed using Positive and Negative Syndrome Scale (PANSS). Vitamin B12 level was negatively associated with the severity of negative symptoms (r = -0.406, p = 0.002), while folate level negatively correlated with general psychopathology score (r = -0.365, p = 0.006) in PANSS. These results indicate that the severity of one-carbon metabolism alterations and HDL deficiency might be associated with family history of schizophrenia and cannabis abuse. Lower vitamin B12 and folate along with elevated Hcy may influence the severity of FES psychopathology.

The relationship between dehydroepiandrosterone (DHEA), working memory and distraction--a behavioral and electrophysiological approach

Dehydroepiandrosterone (DHEA) and dehydroepiandrosterone-sulphate (DHEAS) have been reported to have memory enhancement effects in humans. A neuro-stimulatory action and an anti-cortisol mechanism of action may contribute to that relation. In order to study DHEA, DHEAS and cortisol relations to working memory and distraction, we recorded the electroencephalogram of 23 young women performing a discrimination (no working memory load) or 1-back (working memory load) task in an audio-visual oddball paradigm. We measured salivary DHEA, DHEAS and cortisol both before each task and at 30 and 60 min. Under working memory load, a higher baseline cortisol/DHEA ratio was related to higher distraction as indexed by an enhanced novelty P3. This suggests that cortisol may lead to increased distraction whereas DHEA may hinder distraction by leading to less processing of the distractor. An increased DHEA production with consecutive cognitive tasks was found and higher DHEA responses attributed to working memory load were related to enhanced working memory processing as indexed by an enhanced visual P300. Overall, the results suggest that in women DHEA may oppose cortisol effects reducing distraction and that a higher DHEA response may enhance working memory at the electrophysiological level.

The multidimensional nature of metabolic syndrome in schizophrenia: lessons from studies of one-carbon metabolism and DNA methylation

Large data sets indicate that the prevalence of metabolic syndrome (MetS) is significantly higher in patients with schizophrenia in comparison with the general population. Given that interactions between genes and the environment may underlie the etiology of MetS in subjects with schizophrenia, it is feasible that epigenetic phenomena can serve as the etiological consensus between genetic and environmental factors. However, there is still a striking scarcity of studies aimed at investigating the role of aberrant DNA methylation in the development of MetS in this group of patients. This article provides an update on the epigenetics of schizophrenia and reviews studies on the role of one-carbon metabolism and aberrant DNA methylation in the development of MetS.

Food intake and reward mechanisms in patients with schizophrenia: implications for metabolic disturbances and treatment with second-generation antipsychotic agents

Obesity is highly prevalent among patients with schizophrenia and is associated with detrimental health consequences. Although excessive consumption of fast food and pharmacotherapy with such second-generation antipsychotic agents (SGAs) as clozapine and olanzapine has been implicated in the schizophrenia/obesity comorbidity, the pathophysiology of this link remains unclear. Here, we propose a mechanism based on brain reward function, a relevant etiologic factor in both schizophrenia and overeating. A comprehensive literature search on neurobiology of schizophrenia and of eating behavior was performed. The collected articles were critically reviewed and relevant data were extracted and summarized within four key areas: (1) energy homeostasis, (2) food reward and hedonics, (3) reward function in schizophrenia, and (4) metabolic effects of the SGAs. A mesolimbic hyperdopaminergic state may render motivational/incentive reward system insensitive to low salience/palatability food. This, together with poor cognitive control from hypofunctional prefrontal cortex and enhanced hedonic impact of food, owing to exaggerated opioidergic drive (clinically manifested as pain insensitivity), may underlie unhealthy eating habits in patients with schizophrenia. Treatment with SGAs purportedly improves dopamine-mediated reward aspects, but at the cost of increased appetite and worsened or at least not improved opiodergic capacity. These effects can further deteriorate eating patterns. Pathophysiological and therapeutic implications of these insights need further validation via prospective clinical trials and neuroimaging studies.

Personality, manual preference and neuroendocrine reactivity in hirsute subjects

Behavioral and neuroendocrine differences may be postulated in hirsute subjects since central effects of gonadal steroids are well established. We conducted a controlled clinical study with 25 consecutive young hirsute participants compared with 20 consecutive controls. Neuropsychological evaluation included the Minnesota Multiphasic Personality Inventory (MMPI) and the Edinburgh Inventory of Manual Preference (EIMP). Neuroendocrine reactivity was assessed by the adrenocorticotropic hormone (ACTH) and cortisol responses to corticotropin releasing hormone (CRH). Hirsute participants presented a flattened personality profile with lower neurotic triad scores--146 +/- 20 versus 166 +/- 28. Left-hand preference was more common in hirsute participants--4/21 versus 0/20. Decreased ACTH [area under the curve (AUC)--36 +/-2 8 vs. 72 +/- 63 pg/ml h] and cortisol (AUC--18 +/- 4 vs. 25 +/- 10 microg/dl h) responses to CRH were found in the hirsute group. In the hirsute group, higher manual preference scores were associated with lower ACTH responses to CRH, while the opposite association was found in the control group. In the hirsute group, the hyporeactive hypothalamic-pituitary-adrenal (HPA) axis was associated with lower behavior-deviant scores, while in the control group, the hyporeactive HPA axis was associated with more psychopathology. We conclude that personality and HPA axis reactivity are different in hirsute female participants when compared with controls, with a trend for differences regarding handedness. Personality and handedness are differently associated with HPA reactivity. Distinctive features in hirsute participants are probably established very early during ontogenic development.

Schizophrenia, the metabolic syndrome and diabetes

The prevalence of diabetes is increased in patients with schizophrenia. Although many reasons, including hereditary and lifestyle factors, contribute to this association, recently there has been heightened interest in the subject because of the link between the use of the newer atypical anti-psychotic drugs and the development of diabetes. These drugs cause significant weight gain and this may be one of the mechanisms by which they increase incident diabetes. The increased prevalence of diabetes among people with schizophrenia has implications for the delivery of care by psychiatrists, diabetologists and primary care.

Cortisol, prolactin, growth hormone and neurovegetative responses to emotions elicited during an hypnoidal state

The present study describes the responses of cortisol, prolactin and growth hormone (GH) to emotions elicited during sessions in which an hypnoidal state was induced. The purpose of the study was to provide answers for the following questions: 1) Do sessions with an emotional content have more hormonal surges than baseline, relaxation-only, sessions? 2) Does the induction of a fantasy of pregnancy and nursing elicit a prolactin response? 3) Are there any associations between surges of different hormones? 4) Are hormonal responses related to the intensity, type, or mode of expression of the emotions? For this purpose, thirteen volunteers and twelve patients with minor emotional difficulties were studied during sessions under hypnosis. The period of observation lasted for about three hours. Heart rate (HR), skin conductance (SC) and vagal tone (VT) were monitored. Serum cortisol, prolactin and growth hormone were sampled every 15 minutes. The volunteers had three types of sessions- "blank", consisting of relaxation only (12 sessions), "breast feeding", in which a fantasy of pregnancy and breast feeding was induced (12 sessions) and "free associations" in which the subjects were encouraged to evoke experiences or feelings (17 sessions). The patients had only sessions of free associations (38 sessions). Sessions of free associations had more hormonal surges than "blank" and "breast feeding" sessions. This was true for cortisol (8/17 v.3/24; p < 0.03), prolactin (7/17 v. 3/24; p < 0.05) and GH (9/17 v. 4/24; p < 0.02). During the 55 sessions of free associations (volunteers plus patients) there were 32 surges of cortisol, 18 of prolactin and 28 of GH. Cortisol and prolactin surges were negatively correlated (p < 0.03). GH had no significant association with either cortisol or prolactin. Visible emotions were positively associated with GH surges (p < 0.05). but not with cortisol or prolactin. Cortisol surges were correlated positively with evocations of real events (p < 0.01) and negatively with evocations containing defensive elements (p < 0.01). Cortisol correlated positively with shock and intimidation (p < 0.02) and negatively with rage (p < 0.04). The AUC of the cortisol peaks during shock and intimidation was significantly higher than that of the pool of all other cortisol peaks (12.4 micromol x min x l(-1) v. 7.1 micromol x min x l(-1); p < 0.005). Rage had a marginally significant positive association with prolactin surges (p=0.07). The distribution of GH surges did not show any significant association with types of emotions. The present study provides evidence that cortisol, prolactin and GH respond to psychological stress in humans. However, they are regulated differently from one another. Cortisol and prolactin surges appear to be alternative forms of response to specific emotions. GH surges depend on the intensity of the emotion, probably as a consequence of the associated muscular activity. The current paradigm of stress, implying corticotrophin-releasing hormone (CRH) as the initial step of a cascade of events, is insufficient to account for the diversity of hormonal changes observed in psychological stress in humans.