Long-term consumption of sugar-sweetened beverage during the growth period promotes social aggression in adult mice with proinflammatory responses in the brain

Dynamic human gut microbiome and immune shifts during an immersive psychosocial intervention program

BACKGROUND

Although depression is a leading cause of disability worldwide, the pathophysiological mechanisms underlying this disorder-particularly those involving the gut microbiome-are poorly understood.

METHOD

To investigate, we conducted a community-based observational study to explore complex associations between changes in the gut microbiome, cytokine levels, and depression symptoms in 51 participants (Mage = 49.56, SD = 13.31) receiving an immersive psychosocial intervention. A total of 142 multi-omics samples were collected from participants before, during, and three months after the nine-day inquiry-based stress reduction program.

RESULTS

Results revealed that depression was associated with both an increased presence of putatively pathogenic bacteria and reduced microbial beta-diversity. Following the intervention, we observed reductions in neuroinflammatory cytokines and improvements in several mental health indicators. Interestingly, participants with a Prevotella-dominant microbiome showed milder symptoms when depressed, along with a more resilient microbiome and more favorable inflammatory cytokine profile, including reduced levels of CXCL-1.

CONCLUSIONS

These findings reveal a potentially protective link between the Prevotella-dominant microbiome and depression, as evidenced by a reduced pro-inflammatory environment and fewer depressive symptoms. These insights, coupled with observed improvements in neuroinflammatory markers and mental health from the intervention, may highlight potential avenues for microbiome-targeted therapies for managing depression.

Effects of Excessive Sucrose Intake on Aggressive Behavior and Peripheral Stress-Related Hormone and Catecholamines in BALB/c Mice during Adolescent Development

As binge eating and unbalanced diets increase the prevalence of obesity and metabolic disorders, it has been noted that the increase in psychiatric disorders is also a consequence of diet. The present study examined aggressive behavior and peripheral stress-related hormone and catecholamine levels in BALB/c mice fed a high-sucrose diet during adolescent development. BALB/c mice are rarely used in research assessing the effect of diet, but were used for ethnic and personal differences and as a new experimental model. BALB/c mice were fed a diet in which all carbohydrate components were replaced with sucrose for 4 wk and were subjected to the resident-intruder and social dominance tube test. Plasma insulin, corticosterone, and catecholamine levels were also compared to mice fed a control diet. The high-sucrose diet did not alter body weight, glucose tolerance, and plasma insulin levels in BALB/c mice, indicating that the diet was resilient to obesity. Mice fed a high-sucrose diet exhibited increased aggressive behaviors in the resident-intruder test and had a significantly higher win rate in the tube test. Increases in adrenal weight and plasma corticosterone as well as noradrenaline and adrenaline levels were exhibited in mice fed a high-sucrose diet. In particular, this is the first evidence of increased social dominance and hyperplasia of the adrenal glands by a sucrose diet. Sucrose diet intake increased aggression in mice and caused elevated peripheral hormones involving the HPA axis and the sympathetic nervous system, indicating that this may be a central nervous system-mediated effect of excess sucrose.

Dynamic Human Gut Microbiome and Immune Shifts During an Immersive Psychosocial Therapeutic Program

Background

Depression is a leading cause of disability worldwide yet its underlying factors, particularly microbial associations, are poorly understood.

Methods

We examined the longitudinal interplay between the microbiome and immune system in the context of depression during an immersive psychosocial intervention. 142 multi-omics samples were collected from 52 well-characterized participants before, during, and three months after a nine-day inquiry-based stress reduction program.

Results

We found that depression was associated with both an increased presence of putatively pathogenic bacteria and reduced microbial beta-diversity. Following the intervention, we observed reductions in neuroinflammatory cytokines and improvements in several mental health indicators. Interestingly, participants with a Prevotella-dominant microbiome showed milder symptoms when depressed, along with a more resilient microbiome and more favorable inflammatory cytokine profile, including reduced levels of CXCL-1.

Conclusions

Our findings reveal a protective link between the Prevotella-dominant microbiome and depression, associated with a less inflammatory environment and moderated symptoms. These insights, coupled with observed improvements in neuroinflammatory markers and mental health from the intervention, highlight potential avenues for microbiome-targeted therapies in depression management.

Differential Alterations of Expression of the Serotoninergic System Genes and Mood-Related Behavior by Consumption of Aspartame or Potassium Acesulfame in Rats

The use of aspartame (ASP) and potassium acesulfame (ACK) to reduce weight gain is growing; however, contradictory effects in body mass index control and neurobiological alterations resulting from artificial sweeteners consumption have been reported. This study aimed to evaluate the impact of the chronic consumption of ASP and ACK on mood-related behavior and the brain expression of serotonin genes in male Wistar rats. Mood-related behaviors were evaluated using the swim-forced test and defensive burying at two time points: 45 days (juvenile) and 95 days (adult) postweaning. Additionally, the mRNA expression of three serotoninergic genes (Slc6a4, Htr1a, and Htr2c) was measured in the brain areas (prefrontal cortex, hippocampus, and hypothalamus) involved in controlling mood-related behaviors. In terms of mood-related behaviors, rats consuming ACK exhibited anxiety-like behavior only during the juvenile stage. In contrast, rats consuming ASP showed a reduction in depressive-like behavior during the juvenile stage but an increase in the adult stage. The expression of Slc6a4 mRNA increased in the hippocampus of rats consuming artificial sweeteners during the juvenile stage. In the adult stage, there was an upregulation in the relative expression of Slc6a4 and Htr1a in the hypothalamus, while Htr2c expression decreased in the hippocampus of rats consuming ASP. Chronic consumption of ASP and ACK appears to have differential effects during neurodevelopmental stages in mood-related behavior, potentially mediated by alterations in serotoninergic gene expression.

Nutritional Criminology: Why the Emerging Research on Ultra-Processed Food Matters to Health and Justice

There is mounting concern over the potential harms associated with ultra-processed foods, including poor mental health and antisocial behavior. Cutting-edge research provides an enhanced understanding of biophysiological mechanisms, including microbiome pathways, and invites a historical reexamination of earlier work that investigated the relationship between nutrition and criminal behavior. Here, in this perspective article, we explore how this emergent research casts new light and greater significance on previous key observations. Despite expanding interest in the field dubbed 'nutritional psychiatry', there has been relatively little attention paid to its relevancy within criminology and the criminal justice system. Since public health practitioners, allied mental health professionals, and policymakers play key roles throughout criminal justice systems, a holistic perspective on both historical and emergent research is critical. While there are many questions to be resolved, the available evidence suggests that nutrition might be an underappreciated factor in prevention and treatment along the criminal justice spectrum. The intersection of nutrition and biopsychosocial health requires transdisciplinary discussions of power structures, industry influence, and marketing issues associated with widespread food and social inequalities. Some of these discussions are already occurring under the banner of 'food crime'. Given the vast societal implications, it is our contention that the subject of nutrition in the multidisciplinary field of criminology-referred to here as nutritional criminology-deserves increased scrutiny. Through combining historical findings and cutting-edge research, we aim to increase awareness of this topic among the broad readership of the journal, with the hopes of generating new hypotheses and collaborations.

Sugar-sweetened beverage consumption retarded weight gain but not induced depression and anxiety-like behaviors in mice

AIMS

To assess the effects of sugar-sweetened beverage (SSB) consumption and exercise on behaviors.

METHODS

Twenty-four male mice were divided into four groups: the water + sedentary (WS), the SSB + sedentary (CS), the water + exercise (WE), and the SSB + exercise (CE). After three-month of interventions, forced swim test (FST), open field test (OFT), and morris water maze (MWM) were conducted. Then, mRNA levels of MAO-A, COMT, and 5-HT1A and protein levels of synapsin, STAT3, A2AR, CRTC1, CREB, and BDNF were measured.

RESULTS

Under a similar baseline body weight condition, SSB consumption reduced the weight gain from the 3rd week (p < 0.05, or p < 0.01). Exercise decreased the escape latency in the CE group when compared to the CS group on day5 (p < 0.01) and increased the time in the target quadrant in the WE group than the WS group on day4 (p < 0.05) and 5 (p < 0.01) during MWM. No significant differences were found during the FST and OFT. COMT mRNA level was increased after SSB consumption (p < 0.05), but no differences were found in the MAO-A and 5-HT1A mRNA levels and the concerned biomarkers, all of which were previously reported to be associated with depression and anxiety-like behaviors.

CONCLUSION

SSB consumption reduced weight gain but not result in depression and anxiety-like behaviors in mice. Therefore, the behavioral effects of exercise were not significant. This is not consistent with the results of previous epidemiological surveys of humans.

Soft drink consumption and depressive symptoms among the adolescents of United States: The mediating role of aggressive behaviors

BACKGROUND

There is limited evidence for the association among soft drink consumption, aggressive behaviors, and depressive symptoms among the adolescents.

METHODS

Data were derived from a national representative sample of Youth Risk Behavior Surveys of United States during 2011 to 2019. Binary logistic regression models with complex sampling design were used to estimate the effect of soft drink consumption on aggressive behaviors and depressive symptoms. Mediating analysis was used to explore the association between soft drink consumption and depressive symptoms by aggressive behaviors.

FINDINGS

The total prevalence of depressive symptoms was 3l.2 % (30.3 %-32.0 %). Compared with none of soft drink consumption, <1 time/day (OR: 1.29, 95%CI: 1.19-1.41), 1-2 times/day (OR: 1.49, 95%CI: 1.33-1.67), and ≥3 times/day (OR: 1.95, 95%CI: 1.70-2.24) were significantly associated with increased risk of aggressive behaviors. High levels of soft drink consumption (1-2 times/day, OR: 1.19, 95%CI: 1.07-1.32; ≥3 times/day, OR: 1.61, 95%CI: 1.42-1.81) and aggressive behaviors (OR: 1.98, 95%CI: 1.84-2.13) were found to be significantly associated with increased risk of depressive symptoms. A linear dose-response relationship of soft drink consumption with aggressive behaviors and depressive symptoms was found in this study (all p < 0.001). Aggressive behaviors partially mediated the association between soft drink consumption and depressive symptoms and each pathway was statistically significant.

LIMITATIONS

The causal relationship was not able to certain because of the cross-sectional design.

CONCLUSIONS

The mediating role of aggressive behaviors on the association of high levels of soft drink consumptions with depressive symptoms should be paid more attention among the adolescents.

Ten-week high fat and high sugar diets in mice alter gut-brain axis cytokines in a sex-dependent manner

Diets high in fat and sugar induce inflammation throughout the body, particularly along the gut-brain axis; however, the way these changes in immune signaling mediate one another remains unknown. We investigated cytokine changes in the brain and colon following prolonged high fat or sugar diet in female and male adult C57BL/6 mice. Ten weeks of high fat diet increased levels of TNFα, IL-1β, IL-6, IFNγ, and IL-10 in the female hippocampus and altered cytokines in the frontal cortex of both sexes. High sugar diet increased hippocampal cytokines and decreased cytokines in the diencephalon and frontal cortex. In the colon, high fat diet changed cytokine expression in both sexes, while high sugar diet only increased TNFα in males. Causal mediation analysis confirmed that colon IL-10 and IL-6 mediate high fat diet-induced neuroimmune changes in the female hippocampus and male frontal cortex. Additionally, high fat diet increased food consumption and weight gain in both sexes, while high sugar diet decreased male weight gain. These findings reveal a novel causal link between gut and brain inflammation specific to prolonged consumption of high fat, not high sugar, diet. Importantly, this work includes females which have been under-represented in diet research, and demonstrates that diet-induced neuroinflammation varies by brain region between sexes. Furthermore, our data suggest female brains are more vulnerable than males to inflammatory changes following excessive fat and sugar consumption, which may help explain the increased risk of inflammation-associated psychiatric conditions in women who eat a Western Diet rich in both dietary components.

The Effects of Exercise and Restriction of Sugar-Sweetened Beverages on Muscle Function and Autophagy Regulation in High-Fat High-Sucrose-Fed Obesity Mice

BACKGROUND

Autophagy maintains muscle mass and healthy skeletal muscles. Several recent studies have associated sugar-sweetened beverage (SSB) consumption with diseases. We investigated whether muscle dysfunction due to obesity could be restored by SSB restriction (SR) alone or in combination with exercise (EX) training.

METHODS

Obese mice were subjected to SR combined with treadmill EX. Intraperitoneal glucose tolerance test, grip strength test, hanging time test, and body composition analysis were performed. Triglyceride (TG) and total cholesterol (TC) serum concentrations and TG concentrations in quadriceps muscles were analyzed. Western blot and reverse transcription-quantitative polymerase chain reaction helped analyze autophagy-related protein and mRNA expression, respectively.

RESULTS

SR alone had no significant effect on fasting blood glucose levels, glucose tolerance, and muscle function. However, it had effect on serum TC, serum TG, and BCL2 interacting protein 3 expression. SR+EX improved glucose tolerance and muscle function and increased serum TC utilization than SR alone. SR+EX reduced P62 levels, increased glucose transporter type 4 and peroxisome proliferator-activated receptor γ coactivator-1α protein expression, and improved grip strength relative to the high-fat and high-sucrose liquid (HFHS) group, and this was not observed in the HFHS+EX group.

CONCLUSION

SR induced mitophagy-related protein expression in quadriceps, without affecting muscle function. And, the combination of SR and EX activated mitophagy-related proteins and improved muscle function.

TSPO: an emerging role in appetite for a therapeutically promising biomarker

There is accumulating evidence that an obesogenic Western diet causes neuroinflammatory damage to the brain, which then promotes further appetitive behaviour. Neuroinflammation has been extensively studied by analysing the translocator protein of 18 kDa (TSPO), a protein that is upregulated in the inflamed brain following a damaging stimulus. As a result, there is a rich supply of TSPO-specific agonists, antagonists and positron emission tomography ligands. One TSPO ligand, etifoxine, is also currently used clinically for the treatment of anxiety with a minimal side-effect profile. Despite the neuroinflammatory pathogenesis of diet-induced obesity, and the translational potential of targeting TSPO, there is sparse literature characterizing the effect of TSPO on appetite. Therefore, in this review, the influence of TSPO on appetite is discussed. Three putative mechanisms for TSPO's appetite-modulatory effect are then characterized: the TSPO–allopregnanolone–GABA_AR signalling axis, glucosensing in tanycytes and association with the synaptic protein RIM-BP1. We highlight that, in addition to its plethora of functions, TSPO is a regulator of appetite. This review ultimately suggests that the appetite-modulating function of TSPO should be further explored due to its potential therapeutic promise.

Acute effect of cola and caffeine on locomotor activity in drosophila and rat

Caffeine is well known for reducing fatigue and its effect on behavior is widely studied. Usually, caffeine is not ingested in its pure form but rather in sugar-sweetened beverages such as cola. Our aim was to compare the acute effect of cola and caffeine on locomotor activity. Rats and flies ingested cola or caffeine solution for 24 hours. The open field test revealed higher locomotor activity in cola groups for both flies and rats. Surprisingly, no differences have been observed between caffeineand control group. We conclude that caffeine itself does not explain the effect of cola on locomotor activity. Effect of cola cannot be generalized and interpreted for any caffeinated drink with other contents. Rather, the observed effect on locomotor activity may be caused by interaction of caffeine with other substances present in cola.

Soft Drink Consumption and Mental Health in Adolescents: A Longitudinal Examination

PURPOSE

Previous studies showed associations between soft drink consumption and mental health problems in adolescents, but the direction of these effects is unknown. This study examines the hypotheses that soft drink consumption predicts aggression and depressive symptoms over time and that these mental health problems predict soft drink consumption.

METHODS

Interviews were conducted with 5,147 children and their caregivers from three sites at child ages 11, 13, and 16. At each time point, youth reported on their frequency of consuming soft drinks, aggressive behavior, and depressive symptoms. An autoregressive cross-lagged path model tested reciprocal relationships between soft drink consumption, aggressive behavior, and depressive symptoms over time.

RESULTS

More frequent consumption of soft drinks was associated with more aggressive behavior at each time point and depressive symptoms at ages 11 and 13 (r = .04 to .18, p ≤ .002). After adjusting for covariates and stability of each behavior over time, soft drink consumption at ages 11 and 13 predicted more aggressive behavior at the next time point (β = .08 and .06, p < .001). Aggressive behavior at age 13 also predicted more soft drink consumption at age 16 (β = .06, p = .002). Soft drink consumption at age 13 predicted fewer depressive symptoms (β = -.04, p = .007), but depressive symptoms did not predict soft drink consumption.

CONCLUSIONS

More frequent consumption of soft drinks may contribute to aggressive behavior in adolescents over time; there is some support for reciprocal relationships. There is no evidence for soft drink consumption contributing to adolescents' depression. Future research should examine longitudinal effects over shorter intervals.

Dehydration Impairs Physical Growth and Cognitive Development in Young Mice

Infancy and childhood are periods of physical and cognitive development that are vulnerable to disruption by dehydration; however, the effects of dehydration on cognitive development during the periods have not yet been fully elucidated. Thus, the present study used a murine model to examine the effects of sustained dehydration on physical growth and cognitive development. Three-week-old C57BL/6J mice were provided either ad libitum (control group) or time-limited (15 min/day; dehydration group) access to water for 4 weeks. Physical growth was examined via a dual-energy X-ray absorptiometry whole-body scan, and cognitive development was assessed using the Barnes maze test. RNA-sequencing and qPCR analyses were carried out to assess the hippocampal transcriptome and the expression of key neurotrophic factors, respectively. These analyses showed that dehydrated mice exhibited a reduced body mass and tail length, and they spent four times longer completing the Barnes maze test than control mice. Moreover, dehydration significantly dysregulated long-term potentiation signaling and specifically decreased hippocampal brain-derived neurotrophic factor (Bdnf) expression. Collectively, these data confirm dehydration inhibits physical growth and suggest that it impairs cognitive development by altering the hippocampal transcriptional network in young mice; thus, they highlight the importance of water as a vital nutrient for optimal growth and development during infancy and childhood.

Poor Diet, Stress, and Inactivity Converge to Form a "Perfect Storm" That Drives Alzheimer's Disease Pathogenesis

North American incidence of Alzheimer's disease (AD) is expected to more than double over the coming generation. Although genetic factors surrounding the production and clearance of amyloid-β and phosphorylated tau proteins are known to be responsible for a subset of early-onset AD cases, they do not explain the pathogenesis of the far more prevalent sporadic late-onset variant of the disease. It is thus likely that lifestyle and environmental factors contribute to neurodegenerative processes implicated in the pathogenesis of AD. Herein, we review evidence that (1) excess sucrose consumption induces AD-associated liver pathologies and brain insulin resistance, (2) chronic stress overdrives activity of locus coeruleus neurons, leading to loss of function (a common event in neurodegeneration), (3) high-sugar diets and stress promote the loss of neuroprotective sex hormones in men and women, and (4) Western dietary trends set the stage for a lithium-deficient state. We propose that these factors may intersect as part of a "perfect storm" to contribute to the widespread prevalence of neurodegeneration and AD. In addition, we put forth the argument that exercise and supplementation with trace lithium can counteract many of the deleterious consequences associated with excessive caloric intake and perpetual stress. We conclude that lifestyle and environmental factors likely contribute to AD pathogenesis and that simple lifestyle and dietary changes can help counteract their effects.

Probiotic food consumption is associated with lower severity and prevalence of depression: A nationwide cross-sectional study

OBJECTIVE

It has been suggested that probiotics have beneficial effects on a variety of health problems including immunologic diseases and metabolic disorders, however, the effects on brain function are yet to be fully studied. The aim of this study was to evaluate the association between probiotic food consumption and depression status through a cross-sectional analysis of a nationwide, large population-based data.

METHODS

The study population included 26 118 individuals 19 to 64 y of age who participated in the Korean National Health and Nutrition Examination Survey (KNHANES, 2012-2016). A food frequency questionnaire was used to assess probiotic food consumption. Depression status was determined by two different methods including a Patient Health Questionnaire (PHQ-9) and self-reported clinical diagnosis.

RESULTS

Compared with the lowest tertile of probiotic food consumption, the highest tertile had significantly lower odds in PHQ-9 depression severity (odds ratio [OR], 0.48; 95% confidence interval [CI], 0.28-0.81; P = 0.0065) and self-reported clinical depression (OR, 0.59; 95% CI, 0.35-0.96; P = 0.0129). Although there was no significant association between probiotic food consumption and clinical depression in women (OR, 0.85; 95% CI, 0.47-1.54; P = 0.3081), men showed a significantly lower prevalence of clinical depression (OR, 0.24; 95% CI, 0.06-0.92; P = 0.0256) in the highest tertile.

CONCLUSIONS

These results suggest that probiotic food consumption might have beneficial effects on depression, particularly in men. Further studies are required to identify the mechanistic relations between probiotics and depression.

Social status predicts response to dietary cycling in female rhesus monkeys

With the prevalence of obesity among women the United States surpassing 40%, it is critical to understand how environmental factors influence appetite, body fat accumulation, and the ability to lose weight and maintain weight loss. Psychosocial stress exposure is a risk factor for increased consumption of calorically dense diets (CDD), which are high in fat and sugars and promote both increased food intake and weight gain. However, it remains unclear how appetite is affected by psychosocial factors when people striving to lose weight restrict intake of unhealthy, calorically dense foods. Using a translational non-human primate model of chronic psychosocial stressor exposure in females (n = 16), mediated by social subordination, we examined ad libitum food intake, weight change, and social behavior during three consecutive, 15-week dietary conditions: 1) obesogenic, dietary choice; 2) chow-only; and 3) a switch back to dietary choice. Data showed that a choice dietary environment that includes both chow and CDD promotes increased calorie consumption of CDD in subordinate female rhesus monkeys during the baseline choice and back-to-choice phases (p = 0.016). Removal of the CDD during the chow-only phase resulted in mild inappetence (p = 0.005) and a loss in body weight (p < 0.001) in subordinate females. Reintroduction of the CDD to subordinate, but not dominant, females was associated with increased calorie intake that surpassed baseline intake (p < 0.001), and greater body weight gain (p = 0.026). There were no effects of diet cycling on total food intake and body weight change in dominant females (p's > 0.05). Overall, our results suggest that adverse psychosocial experience is associated with increased preference for highly palatable, calorically dense food in a choice dietary environment.

Unlimited sucrose consumption during adolescence generates a depressive-like phenotype in adulthood

Depression is highly prevalent worldwide, but its etiology is not fully understood. An overlooked possible contributor to the epidemic of depression is feeding styles, particularly at early age when the brain is intensely changing. We have previously reported that unlimited sucrose consumption during adolescence leads to enduring changes in brain reward function. Here, we tested the hypothesis that sucrose consumption during adolescence would lead to a 'depressive-like' phenotype. Adolescent male rats were given unlimited access to 5% sucrose in their home cages from postnatal day 30 to postnatal day 46 and their emotional behavior was subsequently examined at adulthood. Sucrose consumption during adolescence caused anhedonia, decreased motivation for saccharin, increased immobility in the forced swim test and exacerbated anxiety-like behavior. Additionally, sucrose consumption during adolescence decreased cell proliferation in the hippocampus in adulthood. Chronic treatment with imipramine (10 mg/kg) normalized behavior and restored cell proliferation in the hippocampus of adult rats with a history of sucrose consumption during adolescence. A similar sucrose consumption starting at adulthood only increases immobility in the forced swim test, suggesting that sucrose intake affects also adults' behavior but to a lesser degree. Overall, our findings reveal an unsuspected protracted effect of sucrose consumption on behavior and suggest that unlimited sucrose consumption during critical periods of brain development may play an important role in the etiology of reward-related disorders such as depression.

Skewed Dendritic Cell Differentiation of MyD88-Deficient Donor Bone Marrow Cells, Instead of Massive Expansion as Myeloid-Derived Suppressor Cells, Aggravates GVHD

Graft-versus-host disease (GVHD), a life-threatening complication after bone marrow transplantation (BMT), is induced by activation of alloreactive donor T cells. Our previous study demonstrated that transplantation of myeloid differentiation factor 88 (MyD88)-deficient knockout (KO) bone marrow (BM) resulted in aggravation of GVHD. Here, to understand the cellular mechanism, we performed longitudinal in vivo imaging and flow cytometric analyses followed by transcriptome and functional examination of donor MyD88-KO BM progenies in GVHD hosts, using a major histocompatibility complex-matched but minor histocompatibility antigen-mismatched C57BL/6→BALB.B model. In GVHD hosts with MyD88-KO BMT, donor BM-derived CD11b⁺Gr-1⁺ cells were found to undergo cell death, a fate significantly different from the explosive expansion shown by the wild type (WT) counterparts, and also from the moderate expansion of the WT or MyD88-KO BM-derived cells in non-GVHD hosts. It was also revealed that MyD88-KO CD11b⁺Gr-1⁺ cells preferred differentiation into CD11c⁺ dendritic cells (DCs) to expansion as myeloid-derived suppressor cells in GVHD hosts or in high inflammatory in vitro conditions. These CD11c⁺ DCs comprised the majority of MyD88-KO CD11b⁺Gr-1⁺ apoptotic cells in GVHD hosts. Their ability to cross-present alloantigens of host origin contributed to the enhancement of T cell alloreactivity, causing GVHD aggravation and eventually death through the killing function of activated T cells. These results provide insights into the roles of MyD88 in myelopoiesis of donor BM and the protective effects in GVHD hosts, helpful information for development of a strategy to control GVHD.

Animal models of social stress: the dark side of social interactions

Social stress occurs in all social species, including humans, and shape both mental health and future interactions with conspecifics. Animal models of social stress are used to unravel the precise role of the main stress system - the HPA axis - on the one hand, and the social behavior network on the other, as these are intricately interwoven. The present review aims to summarize the insights gained from three highly useful and clinically relevant animal models of psychosocial stress: the resident-intruder (RI) test, the chronic subordinate colony housing (CSC), and the social fear conditioning (SFC). Each model brings its own focus: the role of the HPA axis in shaping acute social confrontations (RI test), the physiological and behavioral impairments resulting from chronic exposure to negative social experiences (CSC), and the neurobiology underlying social fear and its effects on future social interactions (SFC). Moreover, these models are discussed with special attention to the HPA axis and the neuropeptides vasopressin and oxytocin, which are important messengers in the stress system, in emotion regulation, as well as in the social behavior network. It appears that both nonapeptides balance the relative strength of the stress response, and simultaneously predispose the animal to positive or negative social interactions.

Interplay Between the Gut-Brain Axis, Obesity and Cognitive Function

Obesity continues to be one of the major public health problems due to its high prevalence and co-morbidities. Common co-morbidities not only include cardiometabolic disorders but also mood and cognitive disorders. Obese subjects often show deficits in memory, learning and executive functions compared to normal weight subjects. Epidemiological studies also indicate that obesity is associated with a higher risk of developing depression and anxiety, and vice versa. These associations between pathologies that presumably have different etiologies suggest shared pathological mechanisms. Gut microbiota is a mediating factor between the environmental pressures (e.g., diet, lifestyle) and host physiology, and its alteration could partly explain the cross-link between those pathologies. Westernized dietary patterns are known to be a major cause of the obesity epidemic, which also promotes a dysbiotic drift in the gut microbiota; this, in turn, seems to contribute to obesity-related complications. Experimental studies in animal models and, to a lesser extent, in humans suggest that the obesity-associated microbiota may contribute to the endocrine, neurochemical and inflammatory alterations underlying obesity and its comorbidities. These include dysregulation of the HPA-axis with overproduction of glucocorticoids, alterations in levels of neuroactive metabolites (e.g., neurotransmitters, short-chain fatty acids) and activation of a pro-inflammatory milieu that can cause neuro-inflammation. This review updates current knowledge about the role and mode of action of the gut microbiota in the cross-link between energy metabolism, mood and cognitive function.