Nutritional interventions for promoting stress resilience: Recent progress using psychosocial stress models of rodents

Gut-brain axis modulation by sudachi peel extract enhances resilience to chronic social defeat stress in mice

BACKGROUND

Sudachitin, an anti-inflammatory compound from Citrus sudachi peel, may influence stress resilience. We examined whether sudachi peel extract affects depression-like behaviors and gut microbiota dysbiosis in mice subjected to chronic social defeat stress (CSDS).

METHODS

First, we examined the effect of sudachitin on depression-like behavior and plasma interleukin-6 (IL-6) levels following lipopolysaccharide (LPS, 0.5 mg/kg) administration. Next, we investigated whether supplementation with sudachi peel extract could modulate the gut microbiota dysbiosis induced by CSDS.

RESULTS

Sudachitin prevented LPS-induced depression-like behavior and the rise in plasma IL-6. In control mice, CSDS increased IL-6, induced splenomegaly, and caused anhedonia-like behavior. These changes were absent in the sudachi peel extract group. Although alpha-diversity of the gut microbiota remained abnormal under CSDS, beta-diversity was significantly altered by sudachi peel extract. Moreover, plasma IL-6 levels and Iba1 expression in the prefrontal cortex correlated with the relative abundance of certain gut bacteria.

LIMITATIONS

The exact mechanisms behind the resilience-promoting effects of sudachi peel extract remain unclear.

CONCLUSION

Sudachi peel extract supplementation enhances resilience to CSDS by preventing anhedonia, reducing plasma IL-6 levels and splenomegaly, and modulating gut microbiota composition. Further research is needed to clarify these anti-inflammatory pathways and the roles of additional pro-inflammatory cytokines.

Oral Supplementation of L-Carnosine Attenuates Acute-Stress-Induced Corticosterone Release and Mitigates Anxiety in CD157 Knockout Mice

Corticosterone, an end product of the hypothalamic-pituitary-adrenal (HPA) axis, is a crucial stress hormone. A dysregulated HPA axis and corticosterone release play pivotal roles in the onset and persistence of symptoms of stress-related psychiatric disorders, such as anxiety. The intake of nutrients, probiotics, and prebiotic supplements decreases blood corticosterone levels. The dipeptide L-carnosine is composed of beta-alanine and L-histidine and is commercially available as a nutritional supplement for recovery from fatigue. L-carnosine is involved in stress-induced corticosterone responses and anxiety behaviors in rodents. Here, we assessed the effect of L-carnosine in CD157 knockout (KO) mice, a murine model of autism spectrum disorder (ASD). The uptake of L-carnosine suppressed the increase in plasma corticosterone levels in response to acute stress and attenuated anxiety-like behaviors in CD157 KO mice. These results suggest that L-carnosine supplementation may relieve anxiety by suppressing excessive stress responses in individuals with ASD.

Longitudinal Associations between Healthy Eating Habits, Resilience, Insomnia, and Internet Addiction in Chinese College Students: A Cross-Lagged Panel Analysis

This study aimed to explore the longitudinal associations between healthy eating habits, resilience, insomnia, and Internet addiction by using a cross-lagged panel analysis of Chinese college students. Overall, 807 Chinese college students completed questionnaires on healthy eating habits, resilience, insomnia, and Internet addiction from August 2020 (time 1, T1) to November 2020 (time 2, T2), and were selected for the data analyses. Healthy eating habits (T1) had significant effects on resilience (T2; β = 0.064, p < 0.05) and insomnia (T2; β = -0.064, p < 0.05), but not Internet addiction (T2; β = -0.028, p > 0.05). Insomnia (T1) negatively predicted resilience (T2; β = -0.098, p < 0.01). Insomnia was bidirectionally associated with Internet addiction (Internet addiction at T1 to insomnia at T2: β = 0.085, p < 0.01; insomnia at T1 to Internet addiction at T2: β = 0.070, p < 0.05). Additionally, Internet addiction (T1) significantly predicted resilience (T2; β = -0.075, p < 0.05). This study further expanded the understanding of the longitudinal associations between healthy eating habits, resilience, insomnia, and Internet addiction, which provided higher-level evidence and important implications for the interventions for reducing college students' Internet addiction, developing healthy eating habits, and improving resilience and sleep health.

The Psychoneuroimmunological Model of Moral Distress and Health in Healthcare Workers: Toward Individual and System-Level Solutions

Healthcare is presently experiencing a global workforce crisis, marked by the inability of hospitals to retain qualified healthcare workers. Indeed, poor working conditions and staff shortages have contributed to structural collapse and placed a heavy toll on healthcare workers' (HCWs) well-being, with many suffering from stress, exhaustion, demoralization, and burnout. An additional factor driving qualified HCWs away is the repeated experience of moral distress, or the inability to act according to internally held moral values and perceived ethical obligations due to internal and external constraints. Despite general awareness of this crisis, we currently lack an organized understanding of how stress leads to poor health, wellbeing, and performance in healthcare workers. To address this critical issue, we first review the literature on moral distress, stress, and health in HCWs. Second, we summarize the biobehavioral pathways linking occupational and interpersonal stressors to health in this population, focusing on neuroendocrine, immune, genetic, and epigenetic processes. Third, we propose a novel Psychoneuroimmunological Model of Moral Distress and Health in HCWs based on this literature. Finally, we discuss evidence-based individual- and system-level interventions for preventing stress and promoting resilience at work. Throughout this review, we underscore that stress levels in HCWs are a major public health concern, and that a combination of system-level and individual-level interventions are necessary to address preventable health care harm and foster resilience in this population, including new health policies, mental health initiatives, and additional translational research.

Impact of Medical School on the Relationship between Nutritional Knowledge and Sleep Quality-A Longitudinal Study of Students at Wroclaw Medical University in Poland

The aim of this study was to investigate the impact of the first year of medical school on the relationship between nutritional knowledge and sleep. To achieve this, first-year medical students at Wroclaw Medical University were invited to participate in the study during both the initial and final months of their first academic year. The study included 570 students in the initial period and 705 in the latter. The research questionnaire comprised the KomPAN, assessing nutritional knowledge, and the Pittsburgh Sleep Quality Index (PSQI), evaluating sleep quality. The majority of students demonstrated at least sufficient nutritional knowledge, while approximately two-thirds of students experienced poor sleep in both periods. Notably, sleep quality further deteriorated in the second period (PSQI total score: 6.86 vs. 7.38, p = 0.0157). This change was influenced mainly by a decrease in sleep duration and an increase in the use of sleep medications (both p < 0.0001). The significant difference in overall sleep quality between different nutritional knowledge levels emerged only in the second semester, where students with the highest nutritional knowledge slept the best, while those with the lowest slept the worst (p = 0.0001). Crucially, in both periods, the use of sleep medications was highest among individuals with insufficient nutritional knowledge. Throughout the academic year, the usage increased for all except those with the highest nutritional knowledge, who exhibited the best sleep (p < 0.0001). The escalating use of sleep medications among medical students warrants greater attention, and leveraging the relationship between nutritional knowledge and sleep could prove beneficial, as positive habits in one domain may positively influence the other.

Relationship between Vitamin Intake and Resilience Based on Sex in Middle-Aged and Older Japanese Adults: Results of the Shika Study

Epidemiological studies reported that resilience, generally regarded as the ability to manage stress in the face of adversity, correlates with mental health in middle-aged and older adults. Currently, there is limited information on eating habits that affect resilience. Therefore, this cross-sectional study investigated the relationship between vitamin intake and resilience based on sex in community-dwelling middle-aged and older individuals in Shika town, Ishikawa Prefecture, Japan. A total of 221 participants (106 men and 115 women) aged 40 years or older were included in the analysis. We assessed vitamin intake and resilience using a brief-type self-administered diet history questionnaire (BDHQ) and the resilience scale (RS), respectively. A two-way analysis of covariance (ANCOVA) revealed that higher intakes of β-carotene and vitamin K were associated with higher RS in women, but not in men. Furthermore, a multiple logistic regression analysis stratified by sex showed that β-carotene and vitamin K were significant independent variables for RS only in women. The present study suggests that higher intakes of β-carotene and vitamin K were associated with higher resilience among middle-aged and older women. The results obtained demonstrate that β-carotene and vitamin K intakes may enhance resilience by strengthening stress tolerance.

Effect of the dietary intake of fish oil on psycho-social behavioral disorder caused by social-defeat stress

Exposure to psychosocial stress is a risk factor for human diseases such as depression. Social defeat stress (SDS) is a well-known rodent model of human psychosocial stress, and animals exposed to SDS show social avoidance behavior. Fish oil, which is rich in docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), is expected to decrease the risk of depressive disorders. In this study, we determined whether fish oil affects the social behavior of SDS-exposed mice and measured serotonin levels and expression of genes related to tryptophan (TRP) metabolism in the hippocampus. The experimental animals were fed a diet containing fish oil during SDS exposure. For the fish oil treatment, experimental mice were fed a diet containing fish oil at low (L-FO), middle (M-FO), and high (H-FO) concentrations. The control group was supplemented with an equivalent amount of canola oil (no fish oil: N-FO). After the SDS protocol, we performed a social interaction test and assessed the sociality of experimental mice. In the N-FO group, SDS-exposed mice showed negative social interactions compared with non-stressed mice. The L-FO and H-FO groups showed negative social interactions after SDS exposure; however, the M-FO group did not exhibit negative social behavior. The serotonin levels of SDS-exposed mice were lower than those of non-stressed mice in the N-FO group. In contrast with these results in the N-FO group, there was no difference in serotonin levels between SDS-exposed and non-stressed mice in the FO groups. In addition, the expression of genes related to TRP metabolism in SDS-exposed mice increased in the N-FO group, but not in the FO group. These results suggest that fish oil improves the psychosocial behavioral disorders caused by SDS. This improvement could be explained by the increase in serotonin synthesis in the hippocampus.

Clinical Application Value of Lactobacillus Plantarum PS128 in Patients with Anxiety Disorders

Objective

PS128 is a novel psycho biotic strain, it has been reported to play an important role in neuropsychiatric disorders. This study investigated the clinical effect of PS128 supplementation on patients with anxiety.

Methods

A total of 200 patients with anxiety were recruited, and divided into two groups (n = 100/group). The control group received oral treatment with citalopram, and the PS128 group received PS128 capsules based on citalopram treatment. Hamilton Anxiety Scale (HAMA) and Self-Rating Anxiety Scale (SAS) were used to evaluate the anxiety levels. After 2 months of continuous administration, clinical efficacy was evaluated according to HAMA score.

Results

There was no significant difference in HAMA and SAS scores between the two groups before treatment. With the treatment prolonged, the HAMA and SAS score decreased gradually in both control and PS128 groups, and the decrease rate of PS128 group was significantly greater than that of the control group. The clinical effective rates of PS128 group were higher than those in the control group, high levels of clinical cure rate were also detected in the PS128 group. Compared with the control group (22%), the incidence of adverse reactions was significantly reduced for patients in the PS128 group (4%).

Conclusion

The treatment effect of citalopram combined with PS128 against anxiety is satisfactory clinically. It can greatly improve the anxiety symptoms of patients, increase the cure rate, reduce adverse reactions.

Preclinical models of deep craniofacial nociception and temporomandibular disorder pain

Chronic pain in temporomandibular disorder (TMD) is a common health problem. Cumulating evidence indicates that the etiology of TMD pain is complex with multifactorial experience that could hamper the developments of treatments. Preclinical research is a resource to understand the mechanism for TMD pain, whereas limitations are present as a disease-specific model. It is difficult to incorporate multiple risk factors associated with the etiology that could increase pain responses into a single animal. This article introduces several rodent models which are often employed in the preclinical studies and discusses their validities for TMD pain after the elucidations of the neural mechanisms based on the clinical reports. First, rodent models were classified into two groups with or without inflammation in the deep craniofacial tissues. Next, the characteristics of each model and the procedures to identify deep craniofacial pain were discussed. Emphasis was directed on the findings of the effects of chronic psychological stress, a major risk factor for chronic pain, on the deep craniofacial nociception. Preclinical models have provided clinically relevant information, which could contribute to better understand the basis for TMD pain, while efforts are still required to bridge the gap between animal and human studies.

Differential effects of different diets on depressive-like phenotypes in C57BL/JJmsSLc mice

Identical mouse models tested using the same protocols in different laboratories can produce inconsistent results. Indeed, little information is available regarding suitable diets for mouse models of disease in the field of neuroscience. Thus, neuroscientists often select experimental diets based on personal judgment. Recent studies have reported a strong interaction between depression and gut microbiota. Furthermore, diets can impact the composition of the microbiota. To confirm whether diet influences the phenotype and gut microbiota of depressive mice, we examined the effects of two widely used commercial diets, non-purified (CRF-1) and semi-purified (AIN-93 G) commercial diets on behavior, plasma levels of corticosterone, and cecum microbiota at 1 and 5 weeks after restraint in repeatedly restrained mice. Exposure to repeated stress induced similar depression-like phenotypes 1 week after stress in CRF-1 and AIN-93 G fed mice. However, mice fed the AIN-93 G diet showed greater vulnerability than the others 5 weeks after restraint. The Firmicutes to Bacteroidetes ratio and α-diversity were lower in the cecum at 5 weeks after stress in mice fed the AIN-93 G diet compared to 1 week after stress in mice fed the AIN-93 G diet. These data suggest that diet type affects stress sensitivity via different gut microbiota and that diet selection is important in neuroscience research and data reproducibility.

Harnessing the Neurobiology of Resilience to Protect the Mental Well-Being of Healthcare Workers During the COVID-19 Pandemic

Healthcare workers are at a high risk of psychological morbidity in the face of the COVID-19 pandemic. However, there is significant variability in the impact of this crisis on individual healthcare workers, which can be best explained through an appreciation of the construct of resilience. Broadly speaking, resilience refers to the ability to successfully adapt to stressful or traumatic events, and thus plays a key role in determining mental health outcomes following exposure to such events. A proper understanding of resilience is vital in enabling a shift from a reactive to a proactive approach for protecting and promoting the mental well-being of healthcare workers. Research in the past decade has identified six areas that provide promising leads in understanding the biological basis of individual variations in resilience. These are: (1) the key role played by the monoamines noradrenaline and serotonin, (2) the centrality of the hypothalamic-pituitary-adrenal axis in influencing stress vulnerability and resilience, (3) the intimate links between the immune system and stress sensitivity, (4) the role of epigenetic modulation of gene expression in influencing the stress response, (5) the role played by certain neuropeptides as a natural “brake” mechanism in the face of stress, and (6) the neurobiological mechanisms by which environmental factors, such as exercise, diet, and social support, influence resilience to subsequent life events. Though much of this research is still in its early stages, it has already provided valuable information on which strategies – including dietary changes, lifestyle modification, environmental modification, psychosocial interventions, and even pharmacological treatments – may prove to be useful in fostering resilience in individuals and groups. This paper examines the above evidence more closely, with a specific focus on the challenges faced by healthcare workers during the COVID-19 pandemic, and provides suggestions regarding how it may be translated into real-world interventions, as well as how the more tentative hypotheses advanced in this field may be tested during this critical period.

Nutritional interventions for promoting stress resilience: Recent progress using psychosocial stress models of rodents

Prevention of stress‐induced adverse effects is important for animals and humans to maintain their quality of life (QOL). Stress decreases the productivity of farm animals and induces abnormal behaviors, which is one of the major problems in animal welfare. In humans, stress increases the risk of mental illness which adversely impacts QOL. Stress is, thus, a common health problem for both animals and humans, and stress prevention and promotion of stress resilience could improve animal and human health and QOL. Among various stresses, psychosocial stress experienced by individuals is particularly difficult to prevent and it could, thus, prove beneficial to attempt to increase resilience to psychosocial stress. There exist a few critical interventions for promoting such resilience, environmental enrichment being one. However, this review describes recent progress in nutritional interventions that could confer resilience to psychosocial stress. The efficacy of this intervention is studied in the social defeat model mouse, which is a standard model for studying psychosocial stress. Several nutrients were found to rescue stress vulnerability using the models. Furthermore, probiotics and prebiotics became crucial dietary interventions for combating psychosocial stress. Collectively, dietary intake of appropriate nutrients will be more important for maintaining QOL in animals and humans.