Ghrelin signalling and obesity: at the interface of stress, mood and food reward

Hair cortisol levels are associated with overweight and obesity in the ELSA-Brasil cohort

Introduction

Hair cortisol level has recently been identified as a promising marker for detecting long-term cortisol levels and a marker of hypothalamic-pituitary-adrenal cortex (HPA) axis activity. However, research on the association between obesity and an altered cortisol metabolism remains controversial.

Objective

This study aimed to investigate the relationship between hair cortisol levels and overweight and obesity in participants from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil).

Methods

This was a cross-sectional study involving 2,499 participants from the second follow-up (visit 3, 2017-2019) attending research centers in Rio de Janeiro and Rio Grande do Sul states. Hair samples were collected, and cortisol levels were analyzed using enzyme-linked immunosorbent assay (ELISA) kits. Cortisol levels were classified as low (< 40 pg/mg), medium (40-128 pg/mg), or high (> 128 pg/mg). The participants were classified as eutrophic, overweight, or obese according to their weight (kg) and height (m2). Odds ratios (ORs) with 95% confidence intervals (95%CI) were estimated.

Results

Of the 2499 individuals, 30% had eutrophic weight, 40% were overweight, and 30% were obese. Notably, cortisol levels gradually increased with increasing body weight. Among participants with high hair cortisol levels, 41.2% were classified as overweight and 34.2% as obese. Multinomial logistic regression analysis indicated that participants with high cortisol levels were 43% (OR =1.43; 95%CI: 1.02-2.03) more likely to be overweight and 72% (OR =1.72; 95%CI:1.20-2.47) more likely to be obese than participants with low hair cortisol levels. After adjustment for all covariates, high cortisol levels remained associated with obesity (OR = 1.54; 95%CI:1.02-2.31) and overweight (OR =1.33; 95%CI:0.91-1.94).

Conclusion

In the ELSA-Brazil cohort, hair stress were positively associated with overweight and obesity. These results underscore the importance of considering stress and cortisol as potential factors in obesity prevention and intervention efforts, and highlight a novel aspect of the complex relationship between stress and obesity in the Brazilian population.

Essential oils improve nursery pigs' performance and appetite via modulation of intestinal health and microbiota

Optimal intestinal health and functionality are essential for animal health and performance, and simultaneously intestinal nutrient transporters and intestinal peptides are also involved in appetite and feed intake control mechanisms. Given the potential of essential oil (EO) in improving animal performance and improving feed palatability, we hypothesized that dietary supplementation of cinnamaldehyde and carvacrol could improve performance and appetite of nursery pigs by modulating intestinal health and microbiota. Cinnamaldehyde (100 mg/kg), carvacrol (100 mg/kg), and their mixtures (including 50 mg/kg cinnamaldehyde and 50 mg/kg carvacrol) were supplemented into the diets of 240 nursery pigs for 42 d, and data related to performance were measured. Thereafter, the influence of EO on intestinal health, appetite and gut microbiota and their correlations were explored. EO supplementation increased (P < 0.05) the body weight, average daily gain (ADG) and average daily feed intake (ADFI) of piglets, and reduced (P < 0.05) diarrhea rates in nursery pigs. Furthermore, EO increased (P < 0.05) the intestinal absorption area and the abundance of tight junction proteins, and decreased (P < 0.05) intestinal permeability and local inflammation. In terms of intestinal development and the mucus barrier, EO promoted intestinal development and increased (P < 0.05) the number of goblet cells. Additionally, we found that piglets in the EO-supplemented group had upregulated (P < 0.05) levels of transporters and digestive enzymes in the intestine, which were significantly associated with daily gain and feed utilization. In addition, EO supplementation somewhat improved appetite in nursery pigs, increased the diversity of the gut microbiome and the abundance of beneficial bacteria, and there was a correlation between altered bacterial structure and appetite-related hormones. These findings indicate that EO is effective in promoting growth performance and nutrient absorption as well as in regulating appetite by improving intestinal health and bacterial structure.

Satiety: a gut-brain-relationship

Many hormones act on the hypothalamus to control hunger and satiety through various pathways closely associated with several factors. When food is present in the gastro intestinal (GI) tract, enteroendocrine cells (EECs) emit satiety signals such as cholecystokinin (CCK), glucagon like peptide-1 (GLP-1) and peptide YY (PYY), which can then communicate with the vagus nerve to control food intake. More specifically, satiety has been shown to be particularly affected by the GLP-1 hormone and its receptor agonists that have lately been acknowledged as a promising way to reduce weight. In addition, there is increasing evidence that normal flora is also involved in the peripheral, central, and reward system that impact satiety. Moreover, neurologic pathways control satiety through neurotransmitters. In this review, we discuss the different roles of each of the GLP-1 hormone and its agonist, gut microbiomes, as well as neurotransmitters and their interconnected relation in the regulation of body's satiety homeostasis.

A study of roflumilast treatment on functional and structural changes in hippocampus in depressed Adult male Wistar rats

Depression is a common stress disability disorder that affects higher mental functions including emotion, cognition, and behavior. It may be mediated by inflammatory cytokines that interfere with neuroendocrine function, and synaptic plasticity. Therefore, reductions in inflammation might contribute to treatment response. The current study aims to evaluate the role of Protein Kinase (PKA)- cAMP response element-binding protein (CREB)- brain derived neurotropic factor (BDNF) signaling pathway in depression and the effects of roflumilast (PDE4 inhibitor) as potential antidepressant on the activity of the PKA-CREB-BDNF signaling pathway, histology, and pro-inflammatory cytokine production. Forty Adult male Wistar rats were divided into 4 groups: Control group, Positive Control group: similar to the controls but received Roflumilast (3 mg / kg / day) by oral gavage for the last 4 weeks of the experiment, Depressed group which were exposed to chronic stress for 6 weeks, and Roflumilast-treated group which were exposed to chronic stress for 6 weeks and treated by Roflumilast (3 mg / kg / day) by oral gavage for the last 4 weeks of the experiment. The depressed group showed significant increase in immobility time with significant decrease in swimming and struggling times, significant decrease in hippocampal PKA, CERB, BDNF, Dopamine, Cortisone, and Superoxide dismutase while hippocampal Phosphodiesterase-E4, Interleukin-6, and Malondialdhyde levels were significantly elevated. These findings were significantly reversed upon Roflumilast treatment. Therefore, it could be concluded that depression is a neurodegenerative inflammatory disease and oxidative stress plays a key role in depression. Roflumilast treatment attenuated the depression behavior in rats denoting its neuroprotective, and anti-inflammatory effects.

Gut microbiota associated with appetite suppression in high-temperature and high-humidity environments

BACKGROUND

Food is crucial for maintaining vital human and animal activities. Disorders in appetite control can lead to various metabolic disturbances. Alterations in the gut microbial composition can affect appetite and energy metabolism. While alterations in the gut microbiota have been observed in high-temperature and high-humidity (HTH) environments, the relationship between the gut microbiota during HTH and appetite remains unclear.

METHODS

We utilised an artificial climate box to mimic HTH environments, and established a faecal bacteria transplantation (FMT) mouse model. Mendelian randomisation (MR) analysis was used to further confirm the causal relationship between gut microbiota and appetite or appetite-related hormones.

FINDINGS

We found that, in the eighth week of exposure to HTH environments, mice showed a decrease in food intake and body weight, and there were significant changes in the intestinal microbiota compared to the control group. After FMT, we observed similar changes in food intake, body weight, and gut bacteria. Appetite-related hormones, including ghrelin, glucagon-like peptide-1, and insulin, were reduced in DH (mice exposed to HTH conditions) and DHF (FMT from mice exposed to HTH environments for 8 weeks), while the level of peptide YY initially increased and then decreased in DH and increased after FMT. Moreover, MR analysis further confirmed that these changes in the intestinal microbiota could affect appetite or appetite-related hormones.

INTERPRETATION

Together, our data suggest that the gut microbiota is closely associated with appetite suppression in HTH. These findings provide novel insights into the effects of HTH on appetite.

FUNDING

This work was supported by the National Natural Science Foundation of China and Guangzhou University of Chinese Medicine.

Parkinson's disease and gut microbiota: from clinical to mechanistic and therapeutic studies

Parkinson's disease (PD) is one of the most prevalent neurodegenerative diseases. The typical symptomatology of PD includes motor symptoms; however, a range of nonmotor symptoms, such as intestinal issues, usually occur before the motor symptoms. Various microorganisms inhabiting the gastrointestinal tract can profoundly influence the physiopathology of the central nervous system through neurological, endocrine, and immune system pathways involved in the microbiota-gut-brain axis. In addition, extensive evidence suggests that the gut microbiota is strongly associated with PD. This review summarizes the latest findings on microbial changes in PD and their clinical relevance, describes the underlying mechanisms through which intestinal bacteria may mediate PD, and discusses the correlations between gut microbes and anti-PD drugs. In addition, this review outlines the status of research on microbial therapies for PD and the future directions of PD-gut microbiota research.

Activation of neurons in the insular cortex and lateral hypothalamus during food anticipatory period caused by food restriction in mice

Mice fed a single meal daily at a fixed time display food anticipatory activity (FAA). It has been reported that the insular cortex (IC) plays an essential role in food anticipation, and lateral hypothalamus (LH) regulates the expression of FAA. However, how these areas contribute to FAA production is still unclear. Thus, we examined the temporal and spatial activation pattern of neurons in the IC and LH during the food anticipation period to determine their role in FAA establishment. We observed an increase of c-Fos-positive neurons in the IC and LH, including orexin neurons of male adult C57BL/6 mice. These neurons were gradually activated from the 1st day to 15th day of restricted feeding. The activation of these brain regions, however, peaked at a distinct point in the food restriction procedure. These results suggest that the IC and LH are differently involved in the neural network for FAA production.

Male mice engaging differently in emotional eating present distinct plasmatic and neurological profiles

Objective: Stressed individuals tend to turn to calorie-rich food, also known as 'comfort food' for the temporary relief it provides. The emotional eating drive is highly variable among subjects. Using a rodent model, we explored the plasmatic and neurobiological differences between 'high and low emotional eaters' (HEE and LEE).Methods: 40 male mice were exposed for 5 weeks to a protocol of unpredictable chronic mild stress. Every 3 or 4 days, they were submitted to a 1-h restraint stress, immediately followed by a 3-h period during which a choice between chow and chocolate sweet cereals was proposed. The dietary intake was measured by weighing. Plasmatic and neurobiological characteristics were compared in mice displaying high vs low intakes.Results: Out of 40 mice, 8 were considered as HEE because of their high post-stress eating score, and 8 as LEE because of their consistent low intake. LEE displayed higher plasma corticosterone and lower levels of NPY than HEE, but acylated and total ghrelin were similar in both groups. In the brain, the abundance of NPY neurons in the arcuate nucleus of the hypothalamus was similar in both groups, but was higher in the ventral hippocampus and the basal lateral amygdala of LEE. The lateral hypothalamus LEE had also more orexin (OX) positive neurons. Both NPY and OX are orexigenic peptides and mood regulators.Discussion: Emotional eating difference was reflected in plasma and brain structures implicated in emotion and eating regulation. These results concur with the psychological side of food consumption.

Relationships among Postpartum Weight Retention, Stress, and Disinhibited Eating: A Scoping Review

Postpartum weight retention (PPWR) is a significant contributor to maternal cardiometabolic disease risk. The transition to motherhood is a stressful time period in which women report consuming food to cope, an eating behavior that is associated with PPWR. In this scoping review, we identified original research and review articles published since 2010 that examined relationships among PPWR, maternal stress, and disinhibited eating. In total, 16 articles met the inclusion criteria. Findings were inconsistent related to PPWR and stress. PPWR and disinhibited eating were not significantly correlated; however, disinhibition scores were higher during the postpartum period compared to prenatally. Stress and disinhibited eating were directly correlated in 4 studies. Our findings suggest these concepts, particularly disinhibited eating, have not been robustly examined during the postpartum period. Additionally, instruments used to measure maternal stress vary widely and should be further studied and refined.

Obese-associated gut microbes and derived phenolic metabolite as mediators of excessive motivation for food reward

BACKGROUND

Excessive hedonic consumption is one of the main drivers for weight gain. Identifying contributors of this dysregulation would help to tackle obesity. The gut microbiome is altered during obesity and regulates host metabolism including food intake.

RESULTS

By using fecal material transplantation (FMT) from lean or obese mice into recipient mice, we demonstrated that gut microbes play a role in the regulation of food reward (i.e., wanting and learning processes associated with hedonic food intake) and could be responsible for excessive motivation to obtain sucrose pellets and alterations in dopaminergic and opioid markers in reward-related brain areas. Through untargeted metabolomic approach, we identified the 3-(3'-hydroxyphenyl)propanoic acid (33HPP) as highly positively correlated with the motivation. By administrating 33HPP in mice, we revealed its effects on food reward.

CONCLUSIONS

Our data suggest that targeting the gut microbiota and its metabolites would be an interesting therapeutic strategy for compulsive eating, preventing inappropriate hedonic food intake. Video Abstract.

Ghrelin receptor agonist MK0677 and overnight fasting do not rescue deficient fear extinction in 129S1/SvImJ mice

The hunger hormone ghrelin has been implicated in the modulation of anxiety- and fear-related behaviors in rodents and humans, while its dysregulation may be associated with psychiatric illness. Along these lines, the ghrelin system has been suggested as a potential target to facilitate fear extinction, which is the main mechanism underlying cognitive behavioral therapy. So far, this hypothesis has not been tested in individuals that have difficulties to extinguish fear. Thus, we investigated pharmacological (ghrelin receptor agonist MK0677) and non-pharmacological (overnight fasting) strategies to target the ghrelin system in the 129S1/SvImJ (S1) mouse strain, which models the endophenotype of impaired fear extinction that has been associated with treatment resistance in anxiety and PTSD patients. MK0677 induced food intake and overnight fasting increased plasma ghrelin levels in S1 mice, suggesting that the ghrelin system is responsive in the S1 strain. However, neither systemic administration of MK0677 nor overnight fasting had an effect on fear extinction in S1 mice. Similarly, our groups previously reported that both interventions did not attenuate fear in extinction-competent C57BL/6J mice. In summary, our findings are in contrast to several studies reporting beneficial effects of GHSR agonism and overnight fasting on fear- and anxiety-related behaviors in rodents. Rather, our data agree with accumulating evidence of divergent behavioral effects of ghrelin system activation and underscore the hypothesis that potential benefits of targeting the ghrelin system in fear extinction may be dependent on factors (e.g., previous stress exposure) that are not yet fully understood.

SOphrology Intervention to Improve WELL-Being in Hospital Staff (SO-WELL): Protocol for a Randomized Controlled Trial Study

INTRODUCTION

Stress at work and psychosocial risks are a major public health problem. Sophrology and neurolinguistic programming (NLP) have demonstrated benefits in terms of mental, physical and social health, both in the general population and in patients, and both in and out of hospital settings. However, these approaches have never been provided at the hospital for the benefit of health professionals at risk of suffering at work. In general, we aim to demonstrate the effectiveness of a hospital sophrology/NLP intervention for health care professionals at risk of stress-related disorders. The secondary objectives are to study (i) within-group, and (ii) between-group): (1) effects on mental, physical, and social health; (2) persistence of effect; (3) relationships between job perception and mental, physical, and social health; (4) intervention success factors (personality and job perception, attendance and practice, other); (5) effects on other stress biomarkers (other measures of autonomic nervous system activity, DHEAS, cortisol, etc.).

METHODS

Our study will be a randomized controlled prospective study (research involving the human person of type 2). The study will be proposed to any health-care workers (HCW) or any non-HCW (NHCW) from a healthcare institution (such as CHU of Clermont-Ferrand, other hospitals, clinics, retirement homes). Participants will benefit from NLP and sophrology interventions at the hospital. For both groups: (i) heart rate variability, skin conductance and saliva biomarkers will be assessed once a week during the intervention period (6 to 8 sophrology sessions) and once by month for the rest of the time; (ii) the short questionnaire will be collected once a week during the whole protocol (1-2 min); (iii) the long questionnaire will be assessed only 5 times: at baseline (M0), month 1 (M1), month 3 (M3), month 5 (M5) and end of the protocol (M7).

ETHICS AND DISSEMINATION

The protocol, information and consent form had received the favorable opinion from the Ethics Committee. Notification of the approval of the Ethics Committee was sent to the study sponsor and the competent authority (ANSM). The study is registered in ClinicalTrials.gov under the identification number NCT05425511 after the French Ethics Committee's approval. The results will be reported according to the CONSORT guidelines.

STRENGTHS AND LIMITATIONS OF THIS STUDY

The psychological questionnaires in this study are self-assessed. It is also possible that responses suffer from variation. For the study, participants need to attend 6 to 8 sophrology sessions and one visit per month for 7 months, which might seem demanding. Therefore, to make sure that participants will complete the protocol, two persons will be fully in charge of the participants' follow-up.

Relationship between psychological stress and ghrelin concentrations in pregnant women with overweight or obesity

Exposure to, perception of, and response to stress have all been shown to influence appetite and dietary behaviors in non-pregnancy human and animal studies, mediated in part by the appetite stimulating hormone ghrelin. Yet, the impact of prenatal stress on biological pathways associated with appetite in the context of pregnancy is not well understood. The objective of this study was to assess the relationship between these layered dimensions of stress with fasting and postprandial plasma ghrelin concentrations among Hispanic pregnant women with overweight or obesity, a population known to experience heightened levels of stress. Thirty-three non-diabetic Hispanic women with pre-pregnancy body mass index of 25.0-34.9 kg/m2 participated in a crossover study at 28-32 weeks' gestation. At each visit, participants provided fasting blood and saliva samples, consumed a standardized mixed-meal, and completed a 15-minute task: friendly conversation (control) or the Trier Social Stress Test (experimental stress exposure). Six timed blood and saliva samples were collected up to 2 h from baseline and assayed for ghrelin and cortisol, respectively, and area-under-the-curve (AUC) values were computed. Day-to-day stress levels were assessed by the Perceived Stress Scale. Physiological and psychological stress reactivity was determined by cortisol AUC and change in self-reported affect state, respectively, during the experimental stress visit. Maternal perceived stress was positively associated with ghrelin concentrations in the fasted (β = 0.06, p = 0.02) and postprandial state (β = 0.05, p = 0.02). Mean ghrelin AUC was not significantly different following acute stress versus control. Measures of acute stress reactivity were not associated with ghrelin AUC. Contrary to our hypothesis, among Hispanic pregnant women with overweight and obesity, exposure to an acute stress induction task did not alter postprandial ghrelin concentrations, and changes in individual psychological and physiological stress reactivity did not associate with postprandial ghrelin. However, our findings suggest that maternal report of general perceived stress over the last month is associated with higher fasting and postprandial ghrelin concentrations. Differences in the effects of short-term stress exposure versus day-to-day perception of stress on appetite and food intake in pregnancy deserves further investigation.

Effects of Ambient Particulate Matter (PM2.5) Exposure on Calorie Intake and Appetite of Outdoor Workers

Malaysia has been experiencing smoke-haze episodes almost annually for the past few decades. PM2.5 is the main component in haze and causes harmful impacts on health due to its small aerodynamic size. This study aimed to explore the implications of PM2.5 exposure on the dietary intake of working individuals. Two phased 13-weeks follow-up study was conducted involving 440 participants, consisting of two cohorts of outdoor and indoor workers. Ambient PM2.5 concentrations were monitored using DustTrakTM DRX Aerosol Monitor. Data on Simplified Nutritional Appetite Questionnaire (SNAQ) and 24 h diet recall were collected weekly. The highest PM2.5 concentration of 122.90 ± 2.07 µg/m3 was recorded in August, and it vastly exceeded the standard value stipulated by US EPA and WHO. SNAQ scores and calorie intake were found to be significantly (p < 0.05) associated with changes in PM2.5 exposure of outdoor workers. Several moderate and positive correlations (R-value ranged from 0.4 to 0.6) were established between SNAQ scores, calorie intake and PM2.5 exposure. Overall findings suggested that long hours of PM2.5 exposure affect personal dietary intake, potentially increasing the risk of metabolic syndromes and other undesired health conditions. The current policy should be strengthened to safeguard the well-being of outdoor workers.

Gut microbial response to host metabolic phenotypes

A large number of studies have proved that biological metabolic phenotypes exist objectively and are gradually recognized by humans. Gut microbes affect the host's metabolic phenotype. They directly or indirectly participate in host metabolism, physiology and immunity through changes in population structure, metabolite differences, signal transduction and gene expression. Obtaining comprehensive information and specific identification factors associated with gut microbiota and host metabolic phenotypes has become the focus of research in the field of gut microbes, and it has become possible to find new and effective ways to prevent or treat host metabolic diseases. In the future, precise treatment of gut microbes will become one of the new therapeutic strategies. This article reviews the content of gut microbes and carbohydrate, amino acid, lipid and nucleic acid metabolic phenotypes, including metabolic intermediates, mechanisms of action, latest research findings and treatment strategies, which will help to understand the relationship between gut microbes and host metabolic phenotypes and the current research status.

Obesity in Adolescents: Understanding the Combined Role of Food Security and Emotional and Behavioral Disorders

PURPOSE

To examine the associations and interactions between levels of food security and emotional and behavioral disorders with obesity in adolescents.

METHODS

Multiple logistic regression modeling was used to analyze the association of adolescent obesity with levels of food security and emotional and behavior disorders in children aged 12-17 years using data from National Health Interview Survey 2016-2018 combined years. Presence of emotional and behavioral disorders within food security categories was added to logistic regression modeling to examine interactions.

RESULTS

When added individually to multiple logistic regression models, marginal and low food security, Attention Deficit Hyperactivity Disorder (ADHD) and anxiety were associated with increased odds of obesity, but very low food security and depression were not. Within the group of adolescents with very low food security, those with anxiety, depression, or ADHD had a nearly two to three-fold increase in odds of obesity compared to adolescents with very low food security and no emotional and behavioral disorders. A similar increase in the odds of obesity with the presence of anxiety, depression, or ADHD was not seen in the adolescents with high food security.

DISCUSSION

This study finds a significant interaction between food security level and emotional and behavioral disorders. The distinction that very low food security in adolescents is only associated with obesity when either anxiety, depression or ADHD are present, but not independently, is an important contribution to understanding complex interactions contributing to obesity.

Fright but not fight‐or‐flight: Violent video games elevated stress markers, but did not impact muscle function, memory recall or food intake, in a randomized trial in healthy young men

Objectives

Regular video game playing has been linked with obesity, but the underlying mechanisms remain unclear. Drawing on evolutionary life history theory, we hypothesized that playing violent video games, through activating the stress response, might increase the immediate demand for fuel by muscle and brain tissue, resulting in elevated appetite and food consumption.

Methods

We randomized 71 young adult men to play video games, involving either violent content or nonviolent puzzle‐solving, for 1 h. Over this period, we measured stress markers (blood pressure [BP], heart rate, visual‐analogue scale [VAS] self‐ratings), muscle function (handgrip strength) and cognitive function (memory recall test). Appetite was assessed by VAS, and by food intake using a test‐meal after the intervention. Linear mixed‐effects models were fitted to assess group effects and group:time effects.

Results

During the intervention, the violent video game group showed elevated systolic BP (∆ = 4.7 mm Hg, 95% CI 1.0, 8.4) and reported feeling more alert but less calm or happy. They showed no difference in grip strength or memory recall. They reported lower feelings of “fullness” but consumed similar food‐energy during the test‐meal.

Conclusions

Although playing a video game with violent content elevated physiological and perceived stress markers compared with a nonviolent game, this was not associated with markers of altered fuel distribution toward two tissues (muscle and brain) that contribute to the “fight‐or‐flight” response. Rather than more energy being allocated to the brain overall, energy may have been reallocated within the brain. This may explain why there was no compensatory increase in energy intake in the violent video game group.

Central and cardiac stress resiliences consistently linked to integrated immuno-neuroendocrine responses across stress models in male mice

Stress resilience, and behavioural and cardiovascular impacts of chronic stress, are theorised to involve integrated neuro-endocrine/inflammatory/transmitter/trophin signalling. We tested for this integration, and whether behaviour/emotionality, together with myocardial ischaemic tolerance, are consistently linked to these pathways across diverse conditions in male C57Bl/6 mice. This included: Restraint Stress (RS), 1 hr restraint/day for 14 days; Chronic Unpredictable Mild Stress (CUMS), 7 stressors randomised over 21 days; Social Stress (SS), 35 days social isolation with brief social encounters in final 13 days; and Control conditions (CTRL; un-stressed mice). Behaviour was assessed via open field (OFT) and sucrose preference (SPT) tests, and neurobiology from frontal cortex (FC) and hippocampal transcripts. Endocrine factors, and function and ischaemic tolerance in isolated hearts, were also measured. Model characteristics ranged from no behavioural or myocardial changes with homotypic RS, to increased emotionality and cardiac ischaemic injury (with apparently distinct endocrine/neurobiological profiles) in CUMS and SS models. Highly integrated expression of HPA axis, neuro-inflammatory, BDNF, monoamine, GABA, cannabinoid and opioid signalling genes was confirmed across conditions, and consistent/potentially causal correlations identified for: i) Locomotor activity (noradrenaline, ghrelin; FC Crhr1, Tnfrsf1b, Il33, Nfkb1, Maoa, Gabra1; hippocampal Il33); ii) Thigmotaxis (adrenaline, leptin); iii) Anxiety-like behaviour (adrenaline, leptin; FC Tnfrsf1a; hippocampal Il33); iv) Depressive-like behaviour (ghrelin; FC/hippocampal s100a8); and v) Cardiac stress-resistance (noradrenaline, leptin; FC Il33, Tnfrsf1b, Htr1a, Gabra1, Gabrg2; hippocampal Il33, Tnfrsf1a, Maoa, Drd2). Data support highly integrated pathway responses to stress, and consistent adipokine, sympatho-adrenergic, inflammatory and monoamine involvement in mood and myocardial disturbances across diverse conditions.

Dysfunctional Heteroreceptor Complexes as Novel Targets for the Treatment of Major Depressive and Anxiety Disorders

Among mental diseases, major depressive disorder (MDD) and anxiety deserve a special place due to their high prevalence and their negative impact both on society and patients suffering from these disorders. Consequently, the development of novel strategies designed to treat them quickly and efficiently, without or at least having limited side effects, is considered a highly important goal. Growing evidence indicates that emerging properties are developed on recognition, trafficking, and signaling of G-protein coupled receptors (GPCRs) upon their heteromerization with other types of GPCRs, receptor tyrosine kinases, and ionotropic receptors such as N-methyl-D-aspartate (NMDA) receptors. Therefore, to develop new treatments for MDD and anxiety, it will be important to identify the most vulnerable heteroreceptor complexes involved in MDD and anxiety. This review focuses on how GPCRs, especially serotonin, dopamine, galanin, and opioid heteroreceptor complexes, modulate synaptic and volume transmission in the limbic networks of the brain. We attempt to provide information showing how these emerging concepts can contribute to finding new ways to treat both MDD and anxiety disorders.

Hunger Hormones in Disruptive Mood Dysregulation Disorder in Adolescents: An Exploratory Study

Background:

Hunger hormones, including ghrelin and leptin, are associated with appetitive behaviors in various psychiatric disorders. Biochemical and hormonal status in disruptive mood dysregulation disorder (DMDD) in adolescents is largely unexplored.

Objectives:

The study aimed to assess levels of leptin and ghrelin and find their association with lipid profiles in adolescents with DMDD.

Methods:

Twenty adolescents with a DSM 5 diagnosis of DMDD with age and gender-matched 19 healthy controls were recruited, followed by clinical assessment. They were assessed for leptin, ghrelin, and lipid profiles, respectively.

Results:

Adolescents with DMDD were comparable in age, education, family income, domicile status, psychiatric illness in the family, and body mass index (BMI) with matched controls. There was no difference in mean lipid profile and ghrelin in both groups. However, the DMDD group had statistically significant higher mean level of leptin as compared to the control group (t=1.84, p < 0.05). As measured by the Modified Overt Aggression Scale in DMDD, aggression showed a significant positive correlation with measures of lipid profile.

Conclusion:

Adolescents with DMDD have elevated serum leptin levels. Further research is needed to confirm this finding.

Effect of ghrelin on hypoxia-related cardiac angiogenesis: involvement of miR-210 signalling pathway

OBJECTIVE

Hypoxia is the main stimulus for angiogenesis. Hypoxia-inducible factor (HIF)-1α, vascular endothelial growth factor (VEGF), and miR-210 are involved in the hypoxia-induced angiogenesis. This study examined the effects of hypoxia and/or ghrelin on miR-210, HIF-1α, and VEGF levels in the heart of rats.

METHODS

Wistar rats were randomly divided into 4 groups (n = 6): control; ghrelin, received daily intraperitoneal injections of ghrelin; hypoxia, was exposed to hypoxic condition; hypoxia + ghrelin, was exposed to hypoxic condition and received intraperitoneal injections of ghrelin, for 2 weeks. Myocardial angiogenesis, the expression level of miR-210, and protein levels of HIF-1α and VEGF were assayed in the heart samples.

RESULTS

Hypoxia increased myocardial angiogenesis and cardiac levels of miR-210, HIF-1α, and VEGF. However, ghrelin inhibited these hypoxia-induced changes. Interestingly, ghrelin had no significant effect on miR-210, HIF-1α, and VEGF levels in normoxic condition.

CONCLUSION

Ghrelin may be useful as an anti-angiogenic factor.

Early detection of cannabinoids in biological samples based on their affinity interaction with the growth hormone secretagogue receptor

Herein we report on the early detection of cannabinoids in urine samples according to their affinity profiles in competitive assays with labelled ghrelin (GHR). We have demonstrated for the first time that cannabidiol (CBD) and 11-nor-Δ⁹-tetrahydrocannabinol-9-carboxylic acid (carboxy-THC) act as extracellular ligands for the growth hormone secretagogue receptor (GHS-R1a), strongly promoting the binding of ghrelin (GHR), the endogenous ligand of GHS-R1a. The affinity profiles of CBD and carboxy-THC are significantly different from the profiles of synthetic GHR mimetics such as CJC-1295 or [D-Arg¹-D-Phe⁵-D-Trp^7,9-Leu¹¹]-Substance P peptides, which are the most common interferents; the cannabinoids promoted the GHR/GHS-R1a interaction, while the ghrelin mimetics acted rather as competitive inhibitors. The analysis of 1:4 diluted urine samples proved that the proposed method displays good linearity and sensitivity in the range of 5-30 ng/mL for both CBD and carboxy-THC, whereas GHR mimetics display no interference at concentrations up to 100 ng/mL. The results were validated by comparison with the gas chromatography tandem mass spectrometry reference method. CBD may exert the same promoting effect on the interaction of GHS-R1a with other GHR mimetics listed as performance-enhancing substances.

The critical role of gut microbiota in obesity

Obesity is a global epidemic characterized by energy disequilibrium, metabolic disorder, fat mass development, and chronic low-grade inflammation, which significantly affects the health state of individuals of all ages and strains the socioeconomic system. The prevalence of obesity is rising at alarming rates and its etiology involves complicated interplay of diet, genetic, and environmental factors. The gut microbiota, as an important constituent of environmental factors, has been confirmed to correlate with the onset and progression of obesity. However, the specific relationship between obesity and the gut microbiota, and its associated mechanisms, have not been fully elucidated. In this review, we have summarized that the microbial diversity was significantly decreased and the Firmicutes/Bacteroidetes ratio was significantly increased in obesity. The altered gut microbiota and associated metabolites contributed to the progression of the disease by disrupting energy homeostasis, promoting lipid synthesis and storage, modulating central appetite and feeding behavior, as well as triggering chronic inflammation, and that the intentional manipulation of gut microbiota held promise as novel therapies for obesity, including probiotics, prebiotics, and fecal microbiota transplantation.

Ghrelin mediated regulation of neurosynaptic transmitters in depressive disorders

Ghrelin is a peptide released by the endocrine cells of the stomach and the neurons in the arcuate nucleus of the hypothalamus. It modulates both peripheral and central functions. Although ghrelin has emerged as a potent stimulator of growth hormone release and as an orexigenic neuropeptide, the wealth of literature suggests its involvement in the pathophysiology of affective disorders including depression. Ghrelin exhibits a dual role through the advancement and reduction of depressive behavior with nervousness in the experimental animals. It modulates depression-related signals by forming neuronal networks with various neuropeptides and classical neurotransmitter systems. The present review emphasizes the integration and signaling of ghrelin with other neuromodulatory systems concerning depressive disorders. The role of ghrelin in the regulation of neurosynaptic transmission and depressive illnesses implies that the ghrelin system modulation can yield promising antidepressive therapies.

•

Ghrelin is the orexigenic type of neuropeptide.

•

It binds with the growth hormone secretagogue receptor (GHSR).

•

GHSR is ubiquitously present in the various brain regions.

•

Ghrelin is involved in the regulation of depression-related behavior.

•

The review focuses on the neurotransmission and signaling of ghrelin in neuropsychiatric and depressive disorders.

Over-feeding the gut microbiome: A scoping review on health implications and therapeutic perspectives

The human gut microbiome has gained increasing attention over the past two decades. Several findings have shown that this complex and dynamic microbial ecosystem can contribute to the maintenance of host health or, when subject to imbalances, to the pathogenesis of various enteric and non-enteric diseases. This scoping review summarizes the current knowledge on how the gut microbiota and microbially-derived compounds affect host metabolism, especially in the context of obesity and related disorders. Examples of microbiome-based targeted intervention strategies that aim to restore and maintain an eubiotic layout are then discussed. Adjuvant therapeutic interventions to alleviate obesity and associated comorbidities are traditionally based on diet modulation and the supplementation of prebiotics, probiotics and synbiotics. However, these approaches have shown only moderate ability to induce sustained changes in the gut microbial ecosystem, making the development of innovative and tailored microbiome-based intervention strategies of utmost importance in clinical practice. In this regard, the administration of next-generation probiotics and engineered microbiomes has shown promising results, together with more radical intervention strategies based on the replacement of the dysbiotic ecosystem by means of fecal microbiota transplantation from healthy donors or with the introduction of synthetic communities specifically designed to achieve the desired therapeutic outcome. Finally, we provide a perspective for future translational investigations through the implementation of bioinformatics approaches, including machine and deep learning, to predict health risks and therapeutic outcomes.

A review of sex differences in the mechanisms and drivers of overeating

Disordered eating is often associated with marked psychological and emotional distress, and severe adverse impact on quality of life. Several factors can influence eating behavior and drive food consumption in excess of energy requirements for homeostasis. It is well established that stress and negative affect contribute to the aetiology of eating disorders and weight gain, and there is substantial evidence suggesting sex differences in sub-clinical and clinical types of overeating. This review will examine how negative affect and stress shape eating behaviors, and how the relationship between the physiological, endocrine, and neural responses to stress and eating behaviors differs between men and women. We will examine several drivers of overeating and explore possible mechanisms underlying sex differences in eating behavior.

Assessing the role of ghrelin and the enzyme ghrelin O-acyltransferase (GOAT) system in food reward, food motivation, and binge eating behavior

The peripheral peptide hormone ghrelin is a powerful stimulator of food intake, which leads to body weight gain and adiposity in both rodents and humans. The hormone, thus, increases the vulnerability to obesity and binge eating behavior. Several studies have revealed that ghrelin's functions are due to its interaction with the growth hormone secretagogue receptor type 1a (GHSR1a) in the hypothalamic area; besides, ghrelin also promotes the reinforcing properties of hedonic food, acting at extra-hypothalamic sites and interacting with dopaminergic, cannabinoid, opioid, and orexin signaling. The hormone is primarily present in two forms in the plasma and the enzyme ghrelin O-acyltransferase (GOAT) allows the acylation reaction which causes the transformation of des-acyl-ghrelin (DAG) to the active form acyl-ghrelin (AG). DAG has been demonstrated to show antagonist properties; it is metabolically active, and counteracts the effects of AG on glucose metabolism and lipolysis, and reduces food consumption, body weight, and hedonic feeding response. Both peptides seem to influence the hypothalamic-pituitary-adrenal (HPA) axis and the corticosterone/cortisol level that drive the urge to eat under stressful conditions. These findings suggest that DAG and inhibition of GOAT may be targets for obesity and bingeing-related eating disorders and that AG/DAG ratio may be an important potential biomarker to assess the risk of developing maladaptive eating behaviors.

Gut peptides and the microbiome: focus on ghrelin

PURPOSE OF REVIEW

In this review, we present recent insights into the role of the gut microbiota on gastrointestinal (GI) peptide secretion and signalling, with a focus on the orexigenic hormone, ghrelin.

RECENT FINDINGS

Evidence is accumulating suggesting that secretion of GI peptides is modulated by commensal bacteria present in our GI tract. Recent data shows that the gut microbiome impacts on ghrelinergic signalling through its metabolites, at the level of the ghrelin receptor (growth hormone secretagogue receptor) and highlights concomitant changes in circulating ghrelin levels with specific gut microbiota changes. However, the mechanisms by which the gut microbiota interacts with gut peptide secretion and signalling, including ghrelin, are still largely unknown.

SUMMARY

The gut microbiota may directly or indirectly influence secretion of the orexigenic hormone, ghrelin, similar to the modulation of satiety inducing GI hormones. Although data demonstrating a role of the microbiota on ghrelinergic signalling is starting to emerge, future mechanistic studies are needed to understand the full impact of the microbiota-ghrelin axis on metabolism and central-regulated homeostatic and non-homeostatic controls of food intake.

The Role of the Gut Microbiota in the Gut-Brain Axis in Obesity: Mechanisms and Future Implications

Interaction between the gut and the brain is essential for energy homeostasis. In obesity, this homeostasis is disrupted, leading to a positive energy balance and weight gain. Obesity is a global epidemic that affects individual health and strains the socioeconomic system. Microbial dysbiosis has long been reported in obesity and obesity-related disorders. More recent literature has focused on the interaction of the gut microbiota and its metabolites on human brain and behavior. Developing strategies that target the gut microbiota could be a future approach for the treatment of obesity. Here, we review the microbiota–gut–brain axis and possible therapeutic options.

Ghrelin as a Biomarker of Stress: A Systematic Review and Meta-Analysis

Introduction: Ghrelin is an orexigenic hormone which favors food-seeking behavior and has been postulated to be a biomarker of stress. We conducted a systematic review and meta-analysis on the evolution of ghrelin levels following acute stress. Methods: The PubMed, Cochrane Library, Embase, and ScienceDirect databases were searched for studies reporting ghrelin levels before and after acute stress in humans. Results: We included ten studies for a total of 348 patients. Acute stress (intervention) was always in a laboratory. Acute stress was psychological (Trier Social Stress Test), physical, or mixed (cold pressure test). The overall meta-analysis demonstrated an increase in ghrelin after the stress intervention (ES = 0.21, 95CI 0.09 to 0.34) compared with baseline levels. Stratification by time demonstrated an acute increase in ghrelin levels in the five minutes immediately following the initiation of stress (0.29, 0.10 to 0.48) but without any difference after. Obese individuals had a more significant (ES = 0.51, 95CI 0.18 to 0.84) and prolonged increase in ghrelin levels for up to 45 min compared with non-obese individuals who had a significant increase only five minutes after stress. Moreover, the ghrelin levels increased in response to stress with BMI (coefficient 0.028, 0.01 to 0.49; p = 0.013) and decreased with the time after the stress intervention (coefficient -0.007, −0.014 to −0.001; p = 0.025). Conclusion: Ghrelin is a biomarker of stress, with a short-term increase following acute stress. Obese individuals have both a higher and prolonged response, emphasizing the link between obesity and stress.

Gut Hormones in Health and Obesity: The Upcoming Role of Short Chain Fatty Acids

We are currently facing an obesity pandemic, with worldwide obesity rates having tripled since 1975. Obesity is one of the main risk factors for the development of non-communicable diseases, which are now the leading cause of death worldwide. This calls for urgent action towards understanding the underlying mechanisms behind the development of obesity as well as developing more effective treatments and interventions. Appetite is carefully regulated in humans via the interaction between the central nervous system and peripheral hormones. This involves a delicate balance in external stimuli, circulating satiating and appetite stimulating hormones, and correct functioning of neuronal signals. Any changes in this equilibrium can lead to an imbalance in energy intake versus expenditure, which often leads to overeating, and potentially weight gain resulting in overweight or obesity. Several lines of research have shown imbalances in gut hormones are found in those who are overweight or obese, which may be contributing to their condition. Therefore, this review examines the evidence for targeting gut hormones in the treatment of obesity by discussing how their dysregulation influences food intake, the potential possibility of altering the circulating levels of these hormones for treating obesity, as well as the role of short chain fatty acids and protein as novel treatments.

Impact of High Fat Diet and Ethanol Consumption on Neurocircuitry Regulating Emotional Processing and Metabolic Function

The prevalence of psychiatry disorders such as anxiety and depression has steadily increased in recent years in the United States. This increased risk for anxiety and depression is associated with excess weight gain, which is often due to over-consumption of western diets that are typically high in fat, as well as with binge eating disorders, which often overlap with overweight and obesity outcomes. This finding suggests that diet, particularly diets high in fat, may have important consequences on the neurocircuitry regulating emotional processing as well as metabolic functions. Depression and anxiety disorders are also often comorbid with alcohol and substance use disorders. It is well-characterized that many of the neurocircuits that become dysregulated by overconsumption of high fat foods are also involved in drug and alcohol use disorders, suggesting overlapping central dysfunction may be involved. Emerging preclinical data suggest that high fat diets may be an important contributor to increased susceptibility of binge drug and ethanol intake in animal models, suggesting diet could be an important aspect in the etiology of substance use disorders. Neuroinflammation in pivotal brain regions modulating metabolic function, food intake, and binge-like behaviors, such as the hypothalamus, mesolimbic dopamine circuits, and amygdala, may be a critical link between diet, ethanol, metabolic dysfunction, and neuropsychiatric conditions. This brief review will provide an overview of behavioral and physiological changes elicited by both diets high in fat and ethanol consumption, as well as some of their potential effects on neurocircuitry regulating emotional processing and metabolic function.

Microbiota-gut-brain axis as a regulator of reward processes

Our gut harbours trillions of microorganisms essential for the maintenance of homeostasis and host physiology in health and disease. In the last decade, there has been a growing interest in understanding the bidirectional pathway of communication between our microbiota and the central nervous system. With regard to reward processes there is accumulating evidence from both animal and human studies that this axis may be a key factor in gating reward valence. Focusing on the mesocorticolimbic pathway, we will discuss how the intestinal microbiota is involved in regulating brain reward functions, both in natural (i.e. eating, social or sexual behaviours) and non-natural reinforcers (drug addiction behaviours including those relevant to alcohol, psychostimulants, opioids and cannabinoids). We will integrate preclinical and clinical evidence suggesting that the microbiota-gut-brain axis could be implicated in the development of disorders associated with alterations in the reward system and how it may be targeted as a promising therapeutic strategy. Cover Image for this issue: https://doi.org/10.1111/jnc.15065.

Gut-brain axis: A matter of concern in neuropsychiatric disorders…!

The gut microbiota is composed of a large number of microbes, usually regarded as commensal bacteria. It has become gradually clear that gastrointestinal microbiota affects gut pathophysiology and the central nervous system (CNS) function by modulating the signaling pathways of the microbiota-gut-brain (MGB) axis. This bidirectional MGB axis communication primarily acts through neuroendocrine, neuroimmune, and autonomic nervous systems (ANS) mechanisms. Accumulating evidence reveals that gut microbiota interacts with the host brain, and its modulation may play a critical role in the pathology of neuropsychiatric disorders. Recently, neuroscience research has established the significance of gut microbiota in the development of brain systems that are essential to stress-related behaviors, including depression and anxiety. Application of modulators of the MGB, such as psychobiotics (e.g., probiotics), prebiotics, and specific diets, may be a promising therapeutic approach for neuropsychiatric disorders. The present review article primarily focuses on the relevant features of the disturbances of the MGB axis in the pathophysiology of neuropsychiatric disorders and its potential mechanisms.

Unravelling the role of gut microbiota in Parkinson's disease progression: Pathogenic and therapeutic implications

In recent years, researchers have shown interest in bi-directional interaction between the brain and gut, called "gut-brain axis". Emerging pieces of evidence indicate that disturbances in this axis is found to be associated with the Parkinson's disease (PD). Several clinical investigations revealed the crucial role of gut microbiota in the pathogenesis of PD. It has been suggested that aggregation of misfolded protein α-syn, the neuropathological hallmark of PD, might begin in gut and propagates to the CNS via vagus nerve and olfactory bulb. Emerging evidences also suggest that initiation and progression of PD may be due to inflammation originating from gut. It has been shown that microbial gut dysbiosis causes the production of various pathogenic microbial metabolites which elevates pro-inflammatory environment in the gut that promotes neuroinflammation in the CNS. These observations raise the intriguing question - how gut microbial dysbiosis could contribute to PD progression. In this context, various microbiota-targeted therapies are under consideration that can re-establish the intestinal homeostasis which may have greater promise in the prevention and treatment of PD. This review focuses on the role of the gut microbiota in the initiation, progression of PD and current therapeutic intervention to deplete the severity of the disease.

Bifidobacterium longum counters the effects of obesity: Partial successful translation from rodent to human

Background

The human gut microbiota has emerged as a key factor in the development of obesity. Certain probiotic strains have shown anti-obesity effects. The objective of this study was to investigate whether Bifidobacterium longum APC1472 has anti-obesity effects in high-fat diet (HFD)-induced obese mice and whether B. longum APC1472 supplementation reduces body-mass index (BMI) in healthy overweight/obese individuals as the primary outcome. B. longum APC1472 effects on waist-to-hip ratio (W/H ratio) and on obesity-associated plasma biomarkers were analysed as secondary outcomes.

Methods

B. longum APC1472 was administered to HFD-fed C57BL/6 mice in drinking water for 16 weeks. In the human intervention trial, participants received B. longum APC1472 or placebo supplementation for 12 weeks, during which primary and secondary outcomes were measured at the beginning and end of the intervention.

Findings

B. longum APC1472 supplementation was associated with decreased bodyweight, fat depots accumulation and increased glucose tolerance in HFD-fed mice. While, in healthy overweight/obese adults, the supplementation of B. longum APC1472 strain did not change primary outcomes of BMI (0.03, 95% CI [-0.4, 0.3]) or W/H ratio (0.003, 95% CI [-0.01, 0.01]), a positive effect on the secondary outcome of fasting blood glucose levels was found (-0.299, 95% CI [-0.44, -0.09]).

Interpretation

This study shows a positive translational effect of B. longum APC1472 on fasting blood glucose from a preclinical mouse model of obesity to a human intervention study in otherwise healthy overweight and obese individuals. This highlights the promising potential of B. longum APC1472 to be developed as a valuable supplement in reducing specific markers of obesity.

Funding

This research was funded in part by Science Foundation Ireland in the form of a Research Centre grant (SFI/12/RC/2273) to APC Microbiome Ireland and by a research grant from Cremo S.A.

Correlations Between Stress, Depression, Body Mass Index, and Food Addiction Among Korean Nursing Students

This study examined the relationships between stress, depression, body mass index, and food addiction in South Korean nursing students. Data from 323 nursing students in Seoul, Gangwon-do, Jeollanam-do, Gyeongsangnam-do, and Jeju-do were collected via self-report questionnaires and analyzed using chi-square tests, Mann-Whitney U tests, logistic regression analyses, and the receiver operating characteristic curve using SPSS 21.0. Overall, 7.1% of students were classified as having a food addiction. Stress and depression affected food addiction, and food addiction influenced obesity. Depression and stress combined were predictors of food addiction. These findings suggest that effective stress management and interventions for depression prevention may be beneficial to prevent food addiction in nursing students.

Microbiota and Obesity: Where Are We Now?

Simple Summary

Emerging new data reported in the international scientific literature show that specific alterations in the human gut microbiota are characteristic in obesity and obesity-related metabolic diseases. Obesity is conditioned by a multitude of factors, and the microbiota is certainly an important player. The analysis of the data obtained from experimental studies allow us to hypothesize that changes in the composition of the microbiota may be the cause, and not simply the consequence, of alterations in human metabolism. Clinical trials on wide samples that investigate the role of diet-induced modulation of the gut microbiota on the host metabolism are needed to understand the interactions at the molecular level for the observed correlations between metabolism and microbiota changes.

Abstract

Genetic and environmental factors are underlying causes of obesity and other metabolic diseases, so it is therefore difficult to find suitable and effective medical treatments. However, without a doubt, the gut microbiota—and also the bacteria present in the oral cavity—act as key factors in the development of these pathologies, yet the mechanisms have not been fully described. Certainly, a more detailed knowledge of the structure of the microbiota—composition, intra- and inter-species relationships, metabolic functions—could be of great help in counteracting the onset of obesity. Identifying key bacterial species will allow us to create a database of “healthy” bacteria, making it possible to manipulate the bacterial community according to metabolic and clinical needs. Targeting gut microbiota in clinical care as treatment for obesity and health-related complications—even just for weight loss has become a real possibility. In this topical review we provide an overview of the role of the microbiota on host energy homeostasis and obesity-related metabolic diseases, therefore addressing the therapeutic potential of novel and existing strategies (impact of nutrition/dietary modulation, and fecal microbiota transplantation) in the treatment of metabolic disease.

Effects of microbiome changes on endocrine ghrelin signaling - A systematic review

The 28-amino acid peptide hormone ghrelin plays a unique role in the gut-brain axis: It is mainly produced peripherally in gastric X/A-like cells but stimulates food intake centrally via hypothalamic nuclei; thus, providing orexigenic communication between the gut and central food intake-regulatory centers. Another component of the gut-brain axis that gained increasing interest in recent years due to its ability to influence central signaling via metabolites is the gut microbiome. Interestingly, there is increasing evidence that changes in the microbiome are related to alterations in ghrelin expression, secretion, activation and signaling. Since ghrelin is supposedly implicated in the pathogenesis of obesity, changes in the microbiome were hypothesized to improve obesity via modulation of ghrelin abundance and receptor interaction. To shed more light on the association between the microbiome and ghrelin a systematic search of Medline, EMBASE and Web of science using the search term combination "microbiome AND ghrelin" was performed. As a result of the search, 42 publications were included into this systematic review, of which 30 publications reported preclinical and 12 manuscripts presented clinical data. In addition to a critical analysis of the present data, gaps in knowledge were highlighted in order to foster further research.

The Good, the Bad and the Unknown Aspects of Ghrelin in Stress Coping and Stress-Related Psychiatric Disorders

Ghrelin is a peptide hormone released by specialized X/A cells in the stomach and activated by acylation. Following its secretion, it binds to ghrelin receptors in the periphery to regulate energy balance, but it also acts on the central nervous system where it induces a potent orexigenic effect. Several types of stressors have been shown to stimulate ghrelin release in rodents, including nutritional stressors like food deprivation, but also physical and psychological stressors such as foot shocks, social defeat, forced immobilization or chronic unpredictable mild stress. The mechanism through which these stressors drive ghrelin release from the stomach lining remains unknown and, to date, the resulting consequences of ghrelin release for stress coping remain poorly understood. Indeed, ghrelin has been proposed to act as a stress hormone that reduces fear, anxiety- and depression-like behaviors in rodents but some studies suggest that ghrelin may - in contrast - promote such behaviors. In this review, we aim to provide a comprehensive overview of the literature on the role of the ghrelin system in stress coping. We discuss whether ghrelin release is more than a byproduct of disrupted energy homeostasis following stress exposure. Furthermore, we explore the notion that ghrelin receptor signaling in the brain may have effects independent of circulating ghrelin and in what way this might influence stress coping in rodents. Finally, we examine how the ghrelin system could be utilized as a therapeutic avenue in stress-related psychiatric disorders (with a focus on anxiety- and trauma-related disorders), for example to develop novel biomarkers for a better diagnosis or new interventions to tackle relapse or treatment resistance in patients.

Developmental stage-dependent relationships between ghrelin levels and hippocampal white matter connections in low-weight anorexia nervosa and atypical anorexia nervosa

INTRODUCTION

Disruptions in homeostatic and hedonic food motivation are proposed to underlie anorexia nervosa (AN) and atypical AN, restrictive eating disorders which commonly onset in puberty. Ghrelin, a neuroprotective hormone that drives hedonic eating is increased in AN and is expressed in the hippocampus. White matter (WM) undergoes significant change during puberty in regions involved in food motivation, particularly WM tracts connected with the hippocampus. The association between ghrelin and WM region of interest (ROI) with hippocampal connections in restrictive eating disorders, particularly in adolescence during key neurodevelopmental growth, is unknown.

METHODS

We evaluated fasting plasma ghrelin and WM microstructure (measured by free-water corrected fractional anisotropy (FA-t)) in WM ROIs with hippocampal connections - the fornix and the hippocampal portion of the cingulum - in 56 adolescent females (age range: 11.9 - 22.1 y; mean: 19.0 y) with low-weight eating disorders including AN and atypical AN (N = 36) and healthy controls (N = 20).

RESULTS

FA-t in the fornix or hippocampal portion of the fornix did not differ between groups. Ghrelin was higher in AN/atypical AN vs. HC and was positively correlated with puberty stage in the AN/atypical AN group, but not the HC group. The correlation between ghrelin and FA-t in the fornix was significantly different in females with AN/atypical AN compared to controls. In AN/atypical AN, pubertal stage moderated the relation between fasting plasma ghrelin and FA-t in the fornix: higher fasting ghrelin was associated with lower FA-t in the fornix in late-post-puberty, but was not associated with FA-t in the early to mid stages of puberty.

CONCLUSIONS

In post-pubertal females with low-weight AN/atypical AN, higher levels of ghrelin are associated with lower FA-t in the fornix. This relationship is not evident in the early to mid stages of puberty in AN/atypical AN or in HC, and may reflect a lack of possible neuroprotective effects of ghrelin in late-post puberty only. Understanding the effects of ghrelin on WM microstructure longitudinally and following recovery from AN/Atypical AN and how this differs across pubertal stages will be an important next step. These findings could ultimately inform treatment staging and aid in diagnosis and detection of AN/atypical AN.

The associations of BMI with mean diffusivity of basal ganglia among young adults with mild obesity and without obesity

Obesity causes a wide range of systemic diseases and is associated with mood and anxiety disorders. It is also associated with dopaminergic reward system function. However, the relationships between microstructural properties of the dopaminergic system and body mass index (BMI) have not been investigated. In this study, we investigated the associations of BMI with mean diffusivity (MD), diffusion tensor imaging measure in areas of the dopaminergic system (MDDS) in 435 healthy young adults with mild obesity and without obesity (BMI < 40). We detected the association between greater BMI and lower MD of the right globus pallidus and the right putamen. These results suggest that the property of the dopaminergic system is associated with BMI among young adults with mild obesity and without obesity.

Rapid and Prolonged Antidepressant-like Effect of Crocin Is Associated with GHSR-Mediated Hippocampal Plasticity-related Proteins in Mice Exposed to Prenatal Stress

Prenatal stress (PNS) has a prolonged and adverse effect on offspring, leading to a significantly increased vulnerability to developing depression in their later life. Traditional therapies have delayed onset and limited efficacy; thus, it remains an urgent need to find novel medications with fast-onset and high-efficacy potentials. Crocin, with its structure clearly examined, has shown antidepressant-like effects. However, few studies extensively investigated its effect especially in mice exposed to PNS. Using an established PNS model, we tested whether crocin could have a rapid and persistent antidepressant-like effect in PNS mice. Growth hormone secretagogue receptor (GHSR) and phosphoinositide 3-kinase (PI3K) inhibitors were used to test their effects in antidepressant-like effect of crocin. Hippocampal GHSR-PI3K signaling was examined both in PNS mice treated with a single dose of crocin and in combination of GHSR inhibitor. PNS mice showed depression-like behaviors at juvenile and adulthood, and crocin induced an instant and persistent antidepressant-like response in PNS mice in a dose-dependent manner. Moreover, crocin increased the expression of hippocampal synaptic plasticity-associated proteins through the restoration of GHSR-PI3K signaling. Inhibitions of both GHSR and PI3K abolished the effect of crocin in alleviating depressive-like behaviors. More importantly, GHSR inhibitor JMV2959 blocked the enhanced expression of hippocampal plasticity-related proteins induced by crocin. The present study demonstrated that crocin induced a fast-onset and prolonged antidepressant effect in PNS mice and suggested that GHSR-PI3K signaling may play a key role in crocin's effect at least partially by a restoration of hippocampal synaptic plasticity-associated proteins.

Immune-Kynurenine Pathways and the Gut Microbiota-Brain Axis in Anxiety Disorders

Anxiety disorders are a complex set of illnesses in which genetic factors, particularly stress, play a role in the etiopathogenesis. In recent years, inflammation and intestinal microbiota have also been included in this complex network of relationships. The functions associated with tryptophan catabolism and serotonin biosynthesis have long been associated with anxiety disorders. Tryptophan catabolism progresses toward the path of the kynurenine in the presence of stress and inflammation. The catabolism of kynurenine is a pathway in which many enzymes play a role and a large number of catabolites with neuroactive properties occur. The body's serotonin biosynthesis is primarily performed by enterochromaffin cells located in the intestines. A change in the intestinal microbiota composition (dysbiosis) directly affects the serotonin biosynthesis. Stress, unhealthy nutrition, and the use of antibiotics cause dysbiosis. In the light of this new perspective, the role of dysbiosis-induced inflammation and kynurenine pathway catabolites activated sequentially come into prominence in the etiopathogenesis of anxiety disorders.

Physiological Effect of Ghrelin on Body Systems

Ghrelin is a relatively novel multifaceted hormone that has been found to exert a plethora of physiological effects. In this review, we found/confirmed that ghrelin has effect on all body systems. It induces appetite; promotes the use of carbohydrates as a source of fuel while sparing fat; inhibits lipid oxidation and promotes lipogenesis; stimulates the gastric acid secretion and motility; improves cardiac performance; decreases blood pressure; and protects the kidneys, heart, and brain. Ghrelin is important for learning, memory, cognition, reward, sleep, taste sensation, olfaction, and sniffing. It has sympatholytic, analgesic, antimicrobial, antifibrotic, and osteogenic effects. Moreover, ghrelin makes the skeletal muscle more excitable and stimulates its regeneration following injury; delays puberty; promotes fetal lung development; decreases thyroid hormone and testosterone; stimulates release of growth hormone, prolactin, glucagon, adrenocorticotropic hormone, cortisol, vasopressin, and oxytocin; inhibits insulin release; and promotes wound healing. Ghrelin protects the body by different mechanisms including inhibition of unwanted inflammation and induction of autophagy. Having a clear understanding of the ghrelin effect in each system has therapeutic implications. Future studies are necessary to elucidate the molecular mechanisms of ghrelin actions as well as its application as a GHSR agonist to treat most common diseases in each system without any paradoxical outcomes on the other systems.

The Mechanism of Traditional Chinese Medicine for the Treatment of Obesity

Obesity is the lipid deposition caused by the imbalance between energy intake and consumption caused by a variety of factors. Obesity can lead to multiple systemic complications. At present, the treatment of obesity is mainly lifestyle intervention, drug weight loss, and weight loss surgery, but the curative effect is limited or the side effects are serious. Traditional Chinese medicine plays a unique role in the treatment of obesity. Existing studies have found that traditional Chinese medicine can treat obesity in a variety of ways, such as regulating intestinal microflora, enhancing hormone level, regulating fat metabolism, and so on. In this review, we will introduce and summarize the mechanism of traditional Chinese medicine in the treatment of obesity.

Stress management in obesity during a thermal spa residential programme (ObesiStress): protocol for a randomised controlled trial study

INTRODUCTION

Stress and obesity are two public health issues. The relationship between obesity and stress is biological through the actions of stress on the major hormones that regulate appetite (leptin and ghrelin). Many spa resorts in France specialise in the treatment of obesity, but no thermal spa currently proposes a specific programme to manage stress in obesity. The ObesiStress protocol has been designed to offer a new residential stress management programme. This thermal spa treatment of obesity implements stress management strategies as suggested by international recommendations.

METHODS AND ANALYSIS

140 overweight or obese participants with a Body Mass Index of >25 kg/m² and aged over 18 years will be recruited. Participants will be randomised into two groups: a control group of usual practice (restrictive diet, physical activity and thermal spa treatment) and an intervention group with stress management in addition to the usual practice. In the present protocol, parameters will be measured on five occasions (at inclusion, at the beginning of the spa (day 0), at the end of the spa (day 21), and at 6 and 12 months). The study will assess the participants' heart rate variability, cardiac remodelling and function, electrodermal activity, blood markers, anthropometric profile, body composition, psychology and quality of life via the use of questionnaires and bone parameters.

ETHICS AND DISSEMINATION

The ObesiStress protocol complies with the ethics guidelines for Clinical Research and has been approved by the ethics committee (CPP Sud-Est VI, Clermont-Ferrand - ANSM: 2016-A01774-47). This study aimed to highlight the efficacy of a 21-day thermal spa residential programme of stress management in obesity through objective measurements of well-being and cardiovascular morbidity. Results will be disseminated during several research conferences and articles published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT03578757.