Opioid system influences gut-brain axis: Dysbiosis and related alterations

The potential of food-derived peptides in alleviating depressed mood: Function, evaluation and mechanism

Food-derived peptides offer a promising approach to alleviating depressive symptoms due to their safety and natural origin, avoiding the adverse side effects of conventional pharmacological treatments. This review aims to explore their potential in mitigating depressive symptoms. Antidepressant peptides from both animal and plant sources have been reviewed, while the animal models and evaluation methods used to assess their efficacy have been summarized. The review highlights four major mechanisms underlying their effects, namely modulation of gut microbiota and production of neuroactive metabolites, alteration of molecules associated with nervous system, normalization of hypothalamic-pituitary-adrenal axis dysregulation to reduce cortisol production, and suppression of pro-inflammatory cytokines linked to neuroinflammation. It also highlights the role of gut-brain axis in mediating the mechanisms, which has been insufficiently elucidated. However, the efficacy of antidepressant peptides for clinical use has not been established. The present review provides a reference for developing dietary interventions with food-derived peptides to supplement current therapeutic approaches.

Assessing the impact of common pain medications on gut microbiota composition and metabolites: insights from a Mendelian randomization study

Introduction. The relationship between analgesic use and gut microbiota alterations has garnered increasing attention. However, the causal link between these two factors remains to be elucidated. Given the prevalence of analgesic use and the significant role of gut microbiota in human health, clarifying this relationship is of great importance.Hypothesis/Gap Statement. Existing observational studies are limited in their ability to establish causality between analgesic use and gut microbiota alterations. Therefore, there is a need for robust causal inference methods to explore this relationship and uncover the underlying mechanisms.Aim. This study aims to investigate the causal associations between genetic susceptibility to four common analgesics (NSAIDs, salicylic acid, opioids, and anilides) and gut microbiota composition, as well as circulating metabolites, using a two-sample Mendelian randomization approach.Methodology. A two-sample Mendelian randomization was used to investigate the potential association between genetic susceptibility to four analgesic uses and gut microbiota composition, as well as circulating metabolites. Summary-level statistics of genome-wide association studies were obtained from primarily European ancestry cohorts, including 466,457 participants from the UK Biobank and 18,340 individuals from the MiBioGen consortium.Results. Only one suggestive causal association was found between NSAID use and elevated abundance of gut microbiota, namely group Eubacterium xylanophilum. In addition, salicylic use was correlated with an increased abundance of the family Prevotellaceae (P=0.006), while it was negatively associated with the abundance of 8 microbiota traits, including genus Clostridiumsensustricto1, Adlercreutzia, Akkermansia, family Clostridiaceae1, Verrucomicrobiaceae, phylum Verrucomicrobia, class Verrucomicrobiae and order Verrucomicrobiales with P value ranging from 0.009 to 0.043. No clear evidence was found between opioid and anilide use and gut microbiota alteration. Meanwhile, salicylic use was potentially causally associated with four metabolites, including acetoacetate, creatinine, omega-3 fatty acids and triglycerides in very large high-density lipoprotein, with P values ranging from 0.005 to 0.046.Conclusion. The results of this study offer powerful evidence that the long-term use of salicylic acid may substantially impact gut microbiota composition and circulating metabolites. Further investigations are needed to uncover the underlying mechanisms.

The "brain-gut" mechanism of postherpetic neuralgia: a mini-review

Postherpetic neuralgia (PHN), a representative type of neuropathic pain, has attracted much research on its diagnosis and therapy at the molecular level. Interestingly, this study based on the brain-gut axis provided a novel point of view to interpret the mechanism of PHN. Past neuroanatomical and neuroimaging studies of pain suggest that the prefrontal cortex, anterior cingulate cortex, amygdala, and other regions of the brain may play crucial roles in the descending inhibition of PHN. Dominant bacterial species in patients with PHN, such as Lactobacillus, generate short-chain fatty acids, including butyrate. Evidence indicates that disturbance of some metabolites (such as butyrate) is closely related to the development of hyperalgesia. In addition, tryptophan and 5-HT in the intestinal tract act as neurotransmitters that regulate the descending transmission of neuropathic pain signals. Concurrently, the enteric nervous system establishes close connections with the central nervous system through the vagus nerve and other pathways. This review aims to investigate and elucidate the molecular mechanisms associated with PHN, focusing on the interplay among PHN, the gut microbiota, and relevant metabolites while scrutinizing its pathogenesis.

Recent advances in nanotherapeutics for HIV-associated neurocognitive disorders and substance use disorders

Substance use disorders (SUD) and HIV-associated neurocognitive disorders (HAND) work synergistically as a significant cause of cognitive decline in adults and adolescents globally. Current therapies continue to be limited due to difficulties crossing the blood-brain barrier (BBB) leading to limited precision and effectiveness, neurotoxicity, and lack of co-treatment options for both HAND and SUD. Nanoparticle-based therapeutics have several advantages over conventional therapies including more precise targeting, the ability to cross the BBB, and high biocompatibility which decreases toxicity and optimizes sustainability. These advantages extend to other neurological disorders such as Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS). This review summarizes recent advances in nanotechnology for application to HAND, SUD, and co-treatment, as well as other neurological disorders. This review also highlights the potential challenges these therapies face in clinical translation and long-term safety.

Positive allosteric modulation of µ-opioid receptor - A new possible approach in the pain management?

The antinociceptive effect of the opioid drugs is achieved through activation of the µ-opioid receptor (MOP). The orthosteric and allosteric sites of opioid receptors may be modulated, orthosteric site by endogenous i.e.β-endorphin and exogenous opioids (morphine, oxycodone, fentanyl); whereas BMS-986121, BMS-986122, Comp5, MS1, Ignavine or even oxytocin act on the allosteric site of the MOP. Opioid therapy is associated with numerous side effects, such as: respiratory depression, sedation, constipation, and importantly, prolonged therapy can influence the development of tolerance, overdose, and addiction. Opioid tolerance is a result of MOP internalization and desensitization, preceded by MOP phosphorylation, performed by protein kinases such as: PKA, PKC, GRKs or CaMKII. In vitro and in vivo data suggest that positive allosteric modulators may enhance antinociception triggered by orthosteric ligands and reduce side effects, which would allow the dose of opioids to be reduced and thus provide a more effective therapy. In this review, we present that positive modulation of the allosteric sites of MOP may constitute a new strategy for pain therapy.

Effect of perioperative dexmedetomidine on recovery of postoperative gastrointestinal function in patients with general anesthesia: a systematic review and meta-analysis

BACKGROUND

There is controversy surrounding the influence of dexmedetomidine on the recovery of postoperative gastrointestinal dysfunction in patients under general anesthesia. The main purpose of this meta-analysis is to evaluate the effect of dexmedetomidine administration during the perioperative period on the recovery of gastrointestinal function in patients under general anesthesia.

METHODS

A systematic review and meta-analysis with trial sequential analysis was performed to identify randomized controlled trials comparing dexmedetomidine administration with placebo for the recovery of gastrointestinal function. The primary outcomes were gastrointestinal function; first oral feeding time; incidences of postoperative nausea and vomiting, postoperative nausea, and postoperative vomiting; time to first bowel sound; time to first flatus; and time to first defecation. The secondary outcome was the length of hospital stay.

RESULTS

A total of 20 studies comparing 2,470 participants were included in this meta-analysis. Perioperative dexmedetomidine administration did not result in a significant reduction in the time to first oral feeding (MD= -7.91, 95% CI = - 16.45 to 0.62, P = 0.07). However, dexmedetomidine administration was associated with a decreased incidence of postoperative nausea and vomiting (RR = 0.72, 95% CI = 0.58 to 0.88, P = 0.001), time to first flatus (MD= -6.73, 95% CI= -10.31 to -3.15, P = 0.0002), and time to first defecation (MD= -12.01, 95% CI = -22.40 to -1.61, P = 0.02).

CONCLUSIONS

Perioperative dexmedetomidine administration can promote the recovery of gastrointestinal function and reduce the length of hospital stay after abdominal surgery. The optimal dose and timing of dexmedetomidine and the influence on non-abdominal surgery need further investigation.

TRIAL REGISTRATION

The study protocol was registered in the PROSPERO database (registration number: CRD42023443708) on July 9, 2023.

Gut-brain axis and neurodegeneration: mechanisms and therapeutic potentials

This paper reviews the effects of gut microbiota in regulating neurodegenerative diseases through controlling gut-brain axis. Specific microbial populations and their metabolites (short-chain fatty acids and tryptophan derivatives) regulate neuroinflammation, neurogenesis and neural barrier integrity. We then discuss ways by which these insights lead to possible interventions - probiotics, prebiotics, dietary modification, and fecal microbiota transplantation (FMT). We also describe what epidemiological and clinical studies have related certain microbiota profiles with the courses of neurodegenerative diseases and how these impact the establishment of microbiome-based diagnostics and individualized treatment options. We aim to guide microbial ecology research on this key link to neurodegenerative disorders and also to highlight collaborative approaches to manage neurological health by targeting microbiome-related factors.

Nutritional Modulation of the Gut-Brain Axis: A Comprehensive Review of Dietary Interventions in Depression and Anxiety Management

Mental health is an increasing topic of focus since more than 500 million people in the world suffer from depression and anxiety. In this multifactorial disorder, parameters such as inflammation, the state of the microbiota and, therefore, the patient's nutrition are receiving more attention. In addition, food products are the source of many essential ingredients involved in the regulation of mental processes, including amino acids, neurotransmitters, vitamins, and others. For this reason, this narrative review was carried out with the aim of analyzing the role of nutrition in depression and anxiety disorders. To reach the review aim, a critical review was conducted utilizing both primary sources, such as scientific publications and secondary sources, such as bibliographic indexes, web pages, and databases. The search was conducted in PsychINFO, MedLine (Pubmed), Cochrane (Wiley), Embase, and CinAhl. The results show a direct relationship between what we eat and the state of our nervous system. The gut-brain axis is a complex system in which the intestinal microbiota communicates directly with our nervous system and provides it with neurotransmitters for its proper functioning. An imbalance in our microbiota due to poor nutrition will cause an inflammatory response that, if sustained over time and together with other factors, can lead to disorders such as anxiety and depression. Changes in the functions of the microbiota-gut-brain axis have been linked to several mental disorders. It is believed that the modulation of the microbiome composition may be an effective strategy for a new treatment of these disorders. Modifications in nutritional behaviors and the use of ergogenic components are presented as important non-pharmacological interventions in anxiety and depression prevention and treatment. It is desirable that the choice of nutritional and probiotic treatment in individual patients be based on the results of appropriate biochemical and microbiological tests.

Understanding the impact of the gut microbiome on opioid use disorder: Pathways, mechanisms, and treatment insights

The widespread use of opioids for chronic pain management not only poses a significant public health issue but also contributes to the risk of tolerance, dependence, and addiction, leading to opioid use disorder (OUD), which affects millions globally each year. Recent research has highlighted a potential bidirectional relationship between the gut microbiome and OUD. This emerging perspective is critical, especially as the opioid epidemic intensifies, emphasizing the need to investigate how OUD may alter gut microbiome dynamics and vice versa. Understanding these interactions could reveal new insights into the mechanisms of addiction and tolerance, as well as provide novel approaches for managing and potentially mitigating OUD impacts. This comprehensive review explores the intricate bidirectional link through the gut-brain axis, focusing on how opiates influence microbial composition, functional changes, and gut mucosal integrity. By synthesizing current findings, the review aims to inspire new strategies to combat the opioid crisis and leverage microbiome-centred interventions for preventing and treating OUD.

The Modulatory Effects and Therapeutic Potential of Cannabidiol in the Gut

Cannabidiol (CBD) is a major non-psychotropic phytocannabinoid that exists in the Cannabis sativa plant. CBD has been found to act on various receptors, including both cannabinoid and non-cannabinoid receptors. In addition, CBD has antioxidant effects that are independent of receptors. CBD has demonstrated modulatory effects at different organ systems, such as the central nervous system, immune system, and the gastrointestinal system. Due to its broad effects within the body and its safety profile, CBD has become a topic of therapeutic interest. This literature review summarizes previous research findings with regard to the effect of CBD on the gastrointestinal (GI) system, including its effects at the molecular, cellular, organ, and whole-body levels. Both pre-clinical animal studies and human clinical trials are reviewed. The results of the studies included in this literature review suggest that CBD has significant impact on intestinal permeability, the microbiome, immune cells and cytokines. As a result, CBD has been shown to have therapeutic potential for GI disorders such as inflammatory bowel disease (IBD). Furthermore, through interactions with the gut, CBD may also be helpful in the treatment of disorders outside the GI system, such as non-alcoholic liver disease, postmenopausal disorders, epilepsy, and multiple sclerosis. In the future, more mechanistic studies are warranted to elucidate the detailed mechanisms of action of CBD in the gut. In addition, more well-designed clinical trials are needed to explore the full therapeutic potential of CBD on and through the gut.

Sex differences in opioid response: a role for the gut microbiome?

Opioid drugs have been long known to induce different responses in males compared to females, however, the molecular mechanisms underlying these effects are yet to be fully characterized. Recent studies have established a link between the gut microbiome and behavioral responses to opioids. Chronic opioid use is associated with gut dysbiosis, or microbiome disruptions, which is thought to contribute to altered opioid analgesia and reward processing. Gut microbiome composition and functioning have also been demonstrated to be influenced by sex hormones. Despite this, there is currently very little work investigating whether sex differences in the gut microbiome mediate sex-dependent responses to opioids, highlighting a critical gap in the literature. Here, we briefly review the supporting evidence implicating a potential role for the gut microbiome in regulating sexually dimorphic opioid response and identify areas for future research.

Opioid Use and Gut Dysbiosis in Cancer Pain Patients

Opioids are commonly used for the management of severe chronic cancer pain. Their well-known pharmacological effects on the gastrointestinal system, particularly opioid-induced constipation (OIC), are the most common limiting factors in the optimization of analgesia, and have led to the wide use of laxatives and/or peripherally acting mu-opioid receptor antagonists (PAMORAs). A growing interest has been recently recorded in the possible effects of opioid treatment on the gut microbiota. Preclinical and clinical data, as presented in this review, showed that alterations of the gut microbiota play a role in modulating opioid-mediated analgesia and tolerability, including constipation. Moreover, due to the bidirectional crosstalk between gut bacteria and the central nervous system, gut dysbiosis may be crucial in modulating opioid reward and addictive behavior. The microbiota may also modulate pain regulation and tolerance, by activating microglial cells and inducing the release of inflammatory cytokines and chemokines, which sustain neuroinflammation. In the subset of cancer patients, the clinical meaning of opioid-induced gut dysbiosis, particularly its possible interference with the efficacy of chemotherapy and immunotherapy, is still unclear. Gut dysbiosis could be a new target for treatment in cancer patients. Restoring the physiological amount of specific gut bacteria may represent a promising therapeutic option for managing gastrointestinal symptoms and optimizing analgesia for cancer patients using opioids.

Past, present, and future of microbiome-based therapies

Technological advances in studying the human microbiome in depth have enabled the identification of microbial signatures associated with health and disease. This confirms the crucial role of microbiota in maintaining homeostasis and the host health status. Nowadays, there are several ways to modulate the microbiota composition to effectively improve host health; therefore, the development of therapeutic treatments based on the gut microbiota is experiencing rapid growth. In this review, we summarize the influence of the gut microbiota on the development of infectious disease and cancer, which are two of the main targets of microbiome-based therapies currently being developed. We analyze the two-way interaction between the gut microbiota and traditional drugs in order to emphasize the influence of gut microbial composition on drug effectivity and treatment response. We explore the different strategies currently available for modulating this ecosystem to our benefit, ranging from 1st generation intervention strategies to more complex 2nd generation microbiome-based therapies and their regulatory framework. Lastly, we finish with a quick overview of what we believe is the future of these strategies, that is 3rd generation microbiome-based therapies developed with the use of artificial intelligence (AI) algorithms.

Long access heroin self-administration significantly alters gut microbiome composition and structure

Introduction

It is well known that chronic opioid use disorder is associated with alterations in gastrointestinal (GI) function that include constipation, reduced motility, and increased bacterial translocation due to compromised gut barrier function. These signs of disrupted GI function can be associated with alterations in the gut microbiome. However, it is not known if long-access opioid self-administration has effects on the gut microbiome.

Methods

We used 16S rRNA gene sequencing to investigate the gut microbiome in three independent cohorts (N=40 for each) of NIH heterogeneous stock rats before onset of long-access heroin self-administration (i.e., naïve status), at the end of a 15-day period of self-administration, and after post-extinction reinstatement. Measures of microbial α- and β-diversity were evaluated for all phases. High-dimensional class comparisons were carried out with MaAsLin2. PICRUSt2 was used for predicting functional pathways impacted by heroin based on marker gene sequences.

Results

Community α-diversity was not altered by heroin at any of the three phases by comparison to saline-yoked controls. Analyses of β-diversity showed that the heroin and saline-yoked groups clustered significantly apart from each other using the Bray-Curtis (community structure) index. Heroin caused significant alterations at the ASV level at the self-administration and extinction phases. At the phylum level, the relative abundance of Firmicutes was increased at the self-administration phase. Deferribacteres was decreased in heroin whereas Patescibacteria was increased in heroin at the extinction phase. Potential biomarkers for heroin emerged from the MaAsLin2 analysis. Bacterial metabolomic pathways relating to degradation of carboxylic acids, nucleotides, nucleosides, carbohydrates, and glycogen were increased by heroin while pathways relating to biosynthesis of vitamins, propionic acid, fatty acids, and lipids were decreased.

Discussion

These findings support the view that long access heroin self-administration significantly alters the structure of the gut microbiome by comparison to saline-yoked controls. Inferred metabolic pathway alterations suggest the development of a microbial imbalance favoring gut inflammation and energy expenditure. Potential microbial biomarkers and related functional pathways likely invoked by heroin self-administration could be targets for therapeutic intervention.

A2 milk consumption and its health benefits: an update

Milk is a widely consumed nutrient-rich food containing protein variants such as casein A2 and A1. A1 differs from A2 in an amino acid at position 67 (Pro67 to His67). The breakdown of β-casein yields β-casomorphins (BCM), among which BCM-7 is extensively studied for its effects on the human body. Animal studies have shown that A1 β-casein milk increases digestive transit time and enhances myeloperoxidase activity. Individuals with lactose intolerance prefer A2 milk to conventional A1 milk, as BCM-7 in A1 milk can lead to inflammation and discomfort in sensitive individuals. A2 milk, which contains A2 β-casein, is believed to be more easily digestible than A1 β-casein. Its popularity has grown owing to reports linking A1 casein to diseases such as type 1 diabetes, heart disease, and autism. A2 milk has gained popularity as an alternative to A1 milk, primarily because of its potential benefits for individuals with certain diseases. This review aims to provide an updated understanding of A2 milk consumption and its health benefits. This review aims to provide an updated understanding of A2 milk consumption and its health benefits.

Does gut brain axis has an impact on Parkinson's disease (PD)?

Parkinson's Disease (PD) is becoming a growing global concern by being the second most prevalent disease next to Alzheimer's Disease (AD). Henceforth new exploration is needed in search of new aspects towards the disease mechanism and origin. Evidence from recent studies has clearly stated the role of Gut Microbiota (GM) in the maintenance of the brain and as a root cause of various diseases and disorders including other neurological conditions. In the case of PD, with an unknown etiology, the GM is said to have a larger impact on the disease pathophysiology. Although GM and its metabolites are crucial for maintaining the normal physiology of the host, it is an undeniable fact that there is an influence of GM in the pathophysiology of PD. As such the Enteroendocrine Cells (EECs) in the epithelium of the intestine are one of the significant regulators of the gut-brain axis and act as a communication mediator between the gut and the brain. The communication is established via the molecules of neuroendocrine which are said to have a crucial part in neurological diseases such as AD, PD, and other psychiatry-related disorders. This review is focused on understanding the proper role of GM and EECs in PD. Here, we also focus on some of the metabolites and compounds that can interact with the PD genes causing various dysfunctions in the cell and facilitating the disease conditions using bioinformatical tools. Various mechanisms concerning EECs and PD, their identification, the latest studies, and available current therapies have also been discussed.

Nutrition and Chronobiology as Key Components of Multidisciplinary Therapeutic Interventions for Fibromyalgia and Associated Chronic Fatigue Syndrome: A Narrative and Critical Review

Fibromyalgia (FM) is often accompanied by chronic fatigue syndrome (CFS). It is a poorly understood disorder that mainly affects women and leads to chronic pain, fatigue, and insomnia, among other symptoms, which decrease quality of life. Due to the inefficiency of current pharmacological treatments, increasing interest is being directed towards non-pharmacological multicomponent therapies. However, nutrition and chronobiology are often overlooked when developing multicomponent therapies. This narrative and critical review explore the relevance of nutritional and chronobiological strategies in the therapeutic management of FM and the often-associated CFS. Reviewed literature offers scientific evidence for the association of dietary habits, nutrient levels, body composition, gut microbiota imbalance, chronobiological alterations, and their interrelation with the development and severity of symptoms. This review highlights the key role of nutrition and chronobiology as relevant and indispensable components in a multidisciplinary approach to FM and CFS.

Deciphering the Causality between Gut Microbiota Dysbiosis and Poisoning by Narcotics and Psychodysleptics: A Mendelian Randomization Analysis

BACKGROUND

This study investigates the connection between gut microbiota and poisoning caused by narcotics and psychodysleptics, using Mendelian randomization (MR) to explore possible causal relationships.

METHODS

The study employed the MR analysis, leveraging genetic variants as instrumental variables to facilitate robust causal inference. Data for gut microbiota was extracted from the MiBioGen study, integrating genome-wide genotyping data with 16S fecal microbiota profiles. Outcome metrics were based on the Finngen study. Genetic instruments were meticulously extracted based on stringent criteria, and harmonized with SNP outcomes associated with "Poisoning by narcotics and psychodysleptics (hallucinogens)". The inverse-variance weighted (IVW) method was utilized for MR analysis, supplemented by sensitivity analyses including MR-Egger Regression, Weighted Median Approach, and Leave-One-Out Cross-Validation.

RESULTS

Among various microbial groups, nine showed significant statistical links. Specifically, Class Negativicutes (OR 5.68, 95% CI 2.13-15.16, p = 0.0005) and Order Selenomonadales (OR 5.68, 95% CI 2.13-15.16, p = 0.0005) were notably associated. These findings were consistent across different sensitivity analyses.

CONCLUSION

The relationship between gut microbiota and the adverse effects of narcotics and psychodysleptics is an emerging area of research. Our MR study identifies certain microbes that might influence the body's response to these substances. These insights could help in predicting and treating the effects of narcotics and psychodysleptics in the future.

An update on the effects of food-derived active peptides on the intestinal microecology

The intestinal microecology is a research hotspot, and neologisms related to the gut such as gut-brain axis, gut-lung axis, gut-bone axis, gut-skin axis, gut-renal axis, and gut-liver axis have emerged from recent research. Meticulous investigation has discovered that food-derived active peptides (FDAPs) are bioactive substances that optimize the structure of the gut microbiota to improve human health. However, few reviews have summarized and emphasized the nutritional value of FDAPs and their mechanisms of action in regulating the composition of the gut microbiota. We aim to provide an update on the latest research on FDAPs by comparing, summarizing, and discussing the potential food sources of FDAPs, their physiological functions, and regulatory effects on the intestinal microecology. The key findings are that few studies have analyzed the potential mechanisms and molecular pathways through which FDAPs maintain intestinal microecological homeostasis. We found that an imbalance in the ratio of Bacteroidetes and Firmicutes in the gut microbiota and abnormal production of short-chain fatty acids are key to the occurrence and development of various diseases. This review provides theoretical support for future comprehensive research on the digestion, distribution, metabolism, and excretion of FDAPs and the mechanisms underlying the interactions between FDAPs and the intestinal microecology.

Endogenous Opioids in Crohn's Disease

Caring for patients with Crohn's disease (CD) is a serious challenge in modern medicine. The increasing incidence of CD among adolescents and the severe course of the disease create the need for new methods of diagnosis and therapy. Endogenous opioids are a group of low molecular weight chemical compounds with analgesic and anti-inflammatory properties. Endorphins, enkephalins, and dynorphins may have potentially beneficial effects on the course of CD. Previous research data on this topic are inconsistent. Some authors have reported an increase in the concentration of leukocytes during the course of inflammatory bowel disease (IBD) while others have described a downward trend, explained by DPP-IV enzyme activity. Even fewer data are available on plasma endo-opioid level. There is also a lack of comprehensive studies that have assessed the endo-opioid system in patients with IBD. Therefore, the objective of this study was to measure the serum concentrations of human β-endorphin, human proenkephalin (A), and human big dynorphin in CD patients in the acute phase of the disease, during hospital treatment, and in the remission state. All determinations were performed using ELISA kits. The results of our study showed that the concentrations of all the tested endo-opioids, especially β-endorphin and proenkephalin (A), were reduced in adolescents with CD compared to those in the healthy control group, during the acute phase of the disease, and in the remission state. Modulation of the endogenous opioid system and the use of selective nonnarcotic agonists of opioid receptors seems to be promising goals in the future treatment of CD.

Small fish, big discoveries: zebrafish shed light on microbial biomarkers for neuro-immune-cardiovascular health

Zebrafish (Danio rerio) have emerged as a powerful model to study the gut microbiome in the context of human conditions, including hypertension, cardiovascular disease, neurological disorders, and immune dysfunction. Here, we highlight zebrafish as a tool to bridge the gap in knowledge in linking the gut microbiome and physiological homeostasis of cardiovascular, neural, and immune systems, both independently and as an integrated axis. Drawing on zebrafish studies to date, we discuss challenges in microbiota transplant techniques and gnotobiotic husbandry practices. We present advantages and current limitations in zebrafish microbiome research and discuss the use of zebrafish in identification of microbial enterotypes in health and disease. We also highlight the versatility of zebrafish studies to further explore the function of human conditions relevant to gut dysbiosis and reveal novel therapeutic targets.

Annual Research Review: Prenatal opioid exposure - a two-generation approach to conceptualizing neurodevelopmental outcomes

Opioid use during pregnancy impacts the health and well-being of two generations: the pregnant person and the child. The factors that increase risk for opioid use in the adult, as well as those that perpetuate risk for the caregiver and child, oftentimes replicate across generations and may be more likely to affect child neurodevelopment than the opioid exposure itself. In this article, we review the prenatal opioid exposure literature with the perspective that this is not a singular event but an intergenerational cascade of events. We highlight several mechanisms of transmission across generations: biological factors, including genetics and epigenetics and the gut-brain axis; parent-child mechanisms, such as prepregnancy experience of child maltreatment, quality of parenting, infant behaviors, neonatal opioid withdrawal diagnosis, and broader environmental contributors including poverty, violence exposure, stigma, and Child Protective Services involvement. We conclude by describing ways in which intergenerational transmission can be disrupted by early intervention.

Does a Little Difference Make a Big Difference? Bovine β-Casein A1 and A2 Variants and Human Health-An Update

For over 20 years, bovine beta-casein has been a subject of increasing scientific interest because its genetic A1 variant during gastrointestinal digestion releases opioid-like peptide β-casomorphin-7 (β-CM-7). Since β-CM-7 is involved in the dysregulation of many physiological processes, there is a growing discussion of whether the consumption of the β-casein A1 variant has an influence on human health. In the last decade, the number of papers dealing with this problem has substantially increased. The newest clinical studies on humans showed a negative effect of variant A1 on serum glutathione level, digestive well-being, cognitive performance score in children, and mood score in women. Scientific reports in this field can affect the policies of dairy cattle breeders and the milk industry, leading to the elimination of allele A1 in dairy cattle populations and promoting milk products based on milk from cows with the A2A2 genotype. More scientific proof, especially in well-designed clinical studies, is necessary to determine whether a little difference in the β-casein amino acid sequence negatively affects the health of milk consumers.

Release of an anti-anxiety peptide in casein hydrolysate with Aspergillus oryzae protease

Food protein-derived peptides with agonistic effects on receptors have great potential for treating anxiety, hypertension, and stress. In the present study, opioid peptides with agonistic activities for δ-receptor-expressing HEK293 cells were screened from casein hydrolysates prepared with five types of food grade proteolytic enzymes, among which casein hydrolysate with Aspergillus oryzae protease ASD showed the highest opioid activity. Eluted fractions showing potent opioid activity were further purified for active peptides by reverse phase-HPLC. The peptide in the active fraction was identified as YPFPGPIPNS, a member of β-casomorphin (CM-10) (β-casein 60-69). Various CM-10 derivative peptides were synthesized and their characteristic features for specificities towards δ- and μ-receptors were determined. Peptides 5 to 12 amino acids long showed relatively higher opioid activities for δ- and μ-receptors. CM-10 was docked into the optimized δ-receptor model. The CDOCKER energies of the CM-10 derivatives were consistent with their opioid activities. In the elevated plus-maze study, CM-10 showed a significant anti-anxiety effect in BALB/c mice at a dose of 10 mg per kg body weight when administered orally, but not via intravenous injection. Furthermore, intravital imaging revealed that Ca²⁺ signaling was induced in the small intestinal villi of a Yellow Cameleon 3.60 (YC3.60)-expressing mouse upon injection with CM-10. However, this decreased in the presence of δ- or μ-receptor antagonists. These results suggest that the opioid peptide CM-10 prepared from casein with ASD has an anti-anxiety effect through interaction with gut δ- and/or μ-opioid receptors in the mouse gut.

Food-Specific IgG4 Antibody-Guided Exclusion Diet Improves Conditions of Patients with Chronic Pain

INTRODUCTION

Chronic pain is related to gastrointestinal (GI) functions because food components affect inflammation and pain through their action on the GI immune and/or neural system and because many analgesics interact with the gut to alter its structure and function. Immunoglobulin G4 (IgG4) are food-specific antibodies resulting from exposure of the gut immune system to nutrients. High IgG4 levels have been found to be associated with inflammation.

METHODS

IgG4 were determined (both with the rapid test and enzyme-linked immunosorbent assay, ELISA) in men and women outpatients with chronic pain. All subjects were asked to exclude for 4 weeks all foods to which they had high blood levels of IgG4 antibodies. Pain and quality of life questionnaires were administered before (visit 1) and after (visit 2) the personalized exclusion diet period. Visual analogue scale (VAS), Italian Pain Questionnaire (QUID) and Margolis (MA) questionnaires were administered to determine pain intensity, pain features and pain extent, while Short Form Health Survey (SF-36) and Profile of Mood States (POMS) were used to test the quality of life and mood state. The nutritional status was evaluated in all subjects. Subject groups were women of reproductive age (pre-MW), women in menopause for at least 1 year (MW) and men.

RESULTS

Fifty-four subjects with chronic pain (n = 12 neuropathic, n = 14 diffuse pain, n = 11 headache, n = 17 low back pain) completed the two visits and the 1-month exclusion diet. At visit 1, 47 (87%) subjects showed medium/high levels of IgG4 to at least one food. The foods showing the highest IgG4 values were eggs, dairy products, cereals and dried fruit. At visit 2, IgG4 levels were decreased, increased or unchanged. In all groups, the 4-week exclusion diet resulted in a significant reduction in all pain measures and an improvement of quality of life parameters. In particular, at visit 2, the VAS score determined in the morning decreased by more than 50%.

CONCLUSIONS

A food elimination diet based on IgG4 antibody levels may be effective in reducing pain and improving quality of life in patients with chronic pain.

Pain and Opioid-Induced Gut Microbial Dysbiosis

Opioid-induced dysbiosis (OID) is a specific condition describing the consequences of opioid use on the bacterial composition of the gut. Opioids have been shown to affect the epithelial barrier in the gut and modulate inflammatory pathways, possibly mediating opioid tolerance or opioid-induced hyperalgesia; in combination, these allow the invasion and proliferation of non-native bacterial colonies. There is also evidence that the gut-brain axis is linked to the emotional and cognitive aspects of the brain with intestinal function, which can be a factor that affects mental health. For example, Mycobacterium, Escherichia coli and Clostridium difficile are linked to Irritable Bowel Disease; Lactobacillaceae and Enterococcacae have associations with Parkinson’s disease, and Alistipes has increased prevalence in depression. However, changes to the gut microbiome can be therapeutically influenced with treatments such as faecal microbiota transplantation, targeted antibiotic therapy and probiotics. There is also evidence of emerging therapies to combat OID. This review has collated evidence that shows that there are correlations between OID and depression, Parkinson’s Disease, infection, and more. Specifically, in pain management, targeting OID deserves specific investigations.

The Current View on the Paradox of Pain in Autism Spectrum Disorders

Autism spectrum disorder (ASD) is a neurodevelopmental disorder, which affects 1 in 44 children and may cause severe disabilities. Besides socio-communicational difficulties and repetitive behaviors, ASD also presents as atypical sensorimotor function and pain reactivity. While chronic pain is a frequent co-morbidity in autism, pain management in this population is often insufficient because of difficulties in pain evaluation, worsening their prognosis and perhaps driving higher mortality rates. Previous observations have tended to oversimplify the experience of pain in autism as being insensitive to painful stimuli. Various findings in the past 15 years have challenged and complicated this dogma. However, a relatively small number of studies investigates the physiological correlates of pain reactivity in ASD. We explore the possibility that atypical pain perception in people with ASD is mediated by alterations in pain perception, transmission, expression and modulation, and through interactions between these processes. These complex interactions may account for the great variability and sometimes contradictory findings from the studies. A growing body of evidence is challenging the idea of alterations in pain processing in ASD due to a single factor, and calls for an integrative view. We propose a model of the pain cycle that includes the interplay between the molecular and neurophysiological pathways of pain processing and it conscious appraisal that may interfere with pain reactivity and coping in autism. The role of social factors in pain-induced response is also discussed. Pain assessment in clinical care is mostly based on subjective rather than objective measures. This review clarifies the strong need for a consistent methodology, and describes innovative tools to cope with the heterogeneity of pain expression in ASD, enabling individualized assessment. Multiple measures, including self-reporting, informant reporting, clinician-assessed, and purely physiological metrics may provide more consistent results. An integrative view on the regulation of the pain cycle offers a more robust framework to characterize the experience of pain in autism.

The gut microbiome and melanoma: A review

Disturbances in the microbial ecosystem have been implemented in chronic inflammation, immune evasion and carcinogenesis, with certain microbes associated with the development of specific cancers. In recent times, the gut microbiome has been recognised as a potential novel player in the pathogenesis and treatment of malignant melanoma. It has been shown that the composition of gut microbiota in early-stage melanoma changes from in situ to invasive and then to metastatic disease. The gut bacterial and fungal profile has also been found to be significantly different in melanoma patients compared to controls. Multiple studies of immune checkpoint inhibitor (ICI) therapies have shown that the commensal microbiota may have an impact on anti-tumor immunity and therefore ICI response in cancer patients. When it comes to chemotherapy and radiotherapy treatments, studies demonstrate that gut microbiota are invaluable in the repair of radiation and chemotherapy-induced damage and therapeutic manipulation of gut microbiota can be an effective strategy to deal with side effects. Studies demonstrate the oncogenic and tumor-suppressive properties of the gut microbiome, which may play a role in the pathogenesis of melanoma. Despite this, investigations into specific interactions are still in its infancy, but starting to gain momentum as more significant and clinically relevant effects are emerging.

The placenta as a target of opioid drugs†

Opioid drugs are analgesics increasingly being prescribed to control pain associated with a wide range of causes. Usage of pregnant women has dramatically increased in the past decades. Neonates born to these women are at risk for neonatal abstinence syndrome (also referred to as neonatal opioid withdrawal syndrome). Negative birth outcomes linked with maternal opioid use disorder include compromised fetal growth, premature birth, reduced birthweight, and congenital defects. Such infants require lengthier hospital stays necessitating rising health care costs, and they are at greater risk for neurobehavioral and other diseases. Thus, it is essential to understand the genesis of such disorders. As the primary communication organ between mother and conceptus, the placenta itself is susceptible to opioid effects but may be key to understanding how these drugs affect long-term offspring health and potential avenue to prevent later diseases. In this review, we will consider the evidence that placental responses are regulated through an endogenous opioid system. However, maternal consumption of opioid drugs can also bind and act through opioid receptors express by trophoblast cells of the placenta. Thus, we will also discuss the current human and rodent studies that have examined the effects of opioids on the placenta. These drugs might affect placental hormones associated with maternal recognition of pregnancy, including placental lactogens and human chorionic gonadotropin in rodents and humans, respectively. A further understanding of how such drugs affect the placenta may open up new avenues for early diagnostic and remediation approaches.

SEX-DEPENDENT IMPACT OF MICROBIOTA STATUS ON CEREBRAL μ -OPIOID RECEPTOR DENSITY IN FISCHER RATS

μ‐opioid receptors (MOPr) play a critical role in social play, reward and pain, in a sex‐ and age‐dependent manner. There is evidence to suggest that sex and age differences in brain MOPr density may be responsible for this variability; however, little is known about the factors driving these differences in cerebral MOPr density. Emerging evidence highlights gut microbiota's critical influence and its bidirectional interaction with the brain on neurodevelopment. Therefore, we aimed to determine the impact of gut microbiota on MOPr density in male and female brains at different developmental stages. Quantitative [³H]DAMGO autoradiographic binding was carried out in the forebrain of male and female conventional (CON) and germ‐free (GF) rats at postnatal days (PND) 8, 22 and 116–150. Significant ‘microbiota status X sex’, ‘age X brain region’ interactions and microbiota status‐ and age‐dependent effects on MOPr binding were uncovered. Microbiota status influenced MOPr levels in males but not females, with higher MOPr levels observed in GF versus CON rats overall regions and age groups. In contrast, no overall sex differences were observed in GF or CON rats. Interestingly, within‐age planned comparison analysis conducted in frontal cortical and brain regions associated with reward revealed that this microbiota effect was restricted only to PND22 rats. Thus, this pilot study uncovers the critical sex‐dependent role of gut microbiota in regulating cerebral MOPr density, which is restricted to the sensitive developmental period of weaning. This may have implications in understanding the importance of microbiota during early development on opioid signalling and associated behaviours.

Casomorphins and Gliadorphins Have Diverse Systemic Effects Spanning Gut, Brain and Internal Organs

Food-derived opioid peptides include digestive products derived from cereal and dairy diets. If these opioid peptides breach the intestinal barrier, typically linked to permeability and constrained biosynthesis of dipeptidyl peptidase-4 (DPP4), they can attach to opioid receptors. The widespread presence of opioid receptors spanning gut, brain, and internal organs is fundamental to the diverse and systemic effects of food-derived opioids, with effects being evidential across many health conditions. However, manifestation delays following low-intensity long-term exposure create major challenges for clinical trials. Accordingly, it has been easiest to demonstrate causal relationships in digestion-based research where some impacts occur rapidly. Within this environment, the role of the microbiome is evidential but challenging to further elucidate, with microbiome effects ranging across gut-condition indicators and modulators, and potentially as systemic causal factors. Elucidation requires a systemic framework that acknowledges that public-health effects of food-derived opioids are complex with varying genetic susceptibility and confounding factors, together with system-wide interactions and feedbacks. The specific role of the microbiome within this puzzle remains a medical frontier. The easiest albeit challenging nutritional strategy to modify risk is reduced intake of foods containing embedded opioids. In future, constituent modification within specific foods to reduce embedded opioids may become feasible.

The Role of Dysbiosis in Critically Ill Patients With COVID-19 and Acute Respiratory Distress Syndrome

In late December 2019, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) quickly spread worldwide, and the syndrome it causes, coronavirus disease 2019 (COVID-19), has reached pandemic proportions. Around 30% of patients with COVID-19 experience severe respiratory distress and are admitted to the intensive care unit for comprehensive critical care. Patients with COVID-19 often present an enhanced immune response with a hyperinflammatory state characterized by a "cytokine storm," which may reflect changes in the microbiota composition. Moreover, the evolution to acute respiratory distress syndrome (ARDS) may increase the severity of COVID-19 and related dysbiosis. During critical illness, the multitude of therapies administered, including antibiotics, sedatives, analgesics, body position, invasive mechanical ventilation, and nutritional support, may enhance the inflammatory response and alter the balance of patients' microbiota. This status of dysbiosis may lead to hyper vulnerability in patients and an inappropriate response to critical circumstances. In this context, the aim of our narrative review is to provide an overview of possible interaction between patients' microbiota dysbiosis and clinical status of severe COVID-19 with ARDS, taking into consideration the characteristic hyperinflammatory state of this condition, respiratory distress, and provide an overview on possible nutritional strategies for critically ill patients with COVID-19-ARDS.

Microbiome and substances of abuse

There is a growing amount of evidence showing a reciprocal relation between the gut microbiota and the brain. Substance use disorders (SUD), which are a major cause of preventable morbidity and mortality worldwide, have an influence on the gut microbiota and on the gut-brain axis. The communication between the microbiota and the brain exists through different pathways: (1) the immune response elicited by bacterial products, coupled with alterations of the intestinal barrier allowing these products to enter the bloodstream, (2) the direct and indirect effects of bacterial metabolites such as short chain fatty acids (SCFAs) or tryptophan on the brain, (3) and the hypothalamic-pituitary-adrenal (HPA) axis, whose peripheral afferents can be influenced by the microbiota, and can in turn activate microglia. Among substances of abuse, alcohol has been the subject of the greatest number of studies in this field. In some but not all patients suffering from alcohol-use-disorder (AUD), alcohol alters the composition of the gut microbiota and the permeability of the intestinal barrier, directly and through dysbiosis. It has also been well demonstrated that alcohol induces a peripheral inflammation; it is still unclear whether it induces a central inflammation, as there are contradictory results in human studies. In animal studies, it has been shown that neuroinflammation increases during alcohol withdrawal. Literature on opioids and stimulants is less numerous. Chronic morphine intake induces dysbiosis, increased intestinal permeability and a probable neuroinflammation, which could explain symptoms such as tolerance, hyperalgesia and deficit in reward behavior. Cocaine induces a dysbiosis and conversely the microbiome can modulate the behavioral response to stimulant drugs. Tobacco cessation is associated with an increase in microbiota diversity. Taken together, the findings of our narrative literature review suggest a bidirectional influence in the pathogenesis of substance use disorders.

Narrative review on potential role of gut microbiota in certain substance addiction

As a neuropsychiatric disorder, substance addiction represents a major public health issue with high prevalence and mortality in many countries. Recently, gut microbiota has been certified to play a part in substance addiction through various mechanisms. Hence, we mainly focused on three substance including alcohol, cocaine and methamphetamine in this review, and summarized their relationships with gut microbiota, respectively. Besides, we also concluded the possible treatments for substance addiction from the perspective of applying gut microbiota. This review aims to build a bridge between substance addiction and gut microbiota according to existing evidences, so as to excavate the possible bi-directional function of microbiota-gut-brain axis in substance addiction for developing therapeutic strategies in the future.

The trimebutine effect on Helicobacter pylori-related gastrointestinal tract and brain disorders: A hypothesis

The localization of bacterial components and/or metabolites in the central nervous system may elicit neuroinflammation and/or neurodegeneration. Helicobacter pylori (a non-commensal symbiotic gastrointestinal pathogen) infection and its related metabolic syndrome have been implicated in the pathogenesis of gastrointestinal tract and central nervous system disorders, thus medications affecting the nervous system - gastrointestinal tract may shape the potential of Helicobacter pylori infection to trigger these pathologies. Helicobacter pylori associated metabolic syndrome, by impairing gut motility and promoting bacterial overgrowth and translocation, might lead to brain pathologies. Trimebutine maleate is a prokinetic drug that hastens gastric emptying, by inducing the release of gastrointestinal agents such as motilin and gastrin. Likewise, it appears to protect against inflammatory signal pathways, involved in inflammatory disorders including brain pathologies. Trimebutine maleate also acts as an antimicrobial agent and exerts opioid agonist effect. This study aimed to investigate a hypothesis regarding the recent advances in exploring the potential role of gastrointestinal tract microbiota dysbiosis-related metabolic syndrome and Helicobacter pylori in the pathogenesis of gastrointestinal tract and brain diseases. We hereby proposed a possible neuroprotective role for trimebutine maleate by altering the dynamics of the gut-brain axis interaction, thus suggesting an additional effect of trimebutine maleate on Helicobacter pylori eradication regimens against these pathologies.

Gut microbiota, immunity and pain

The interplay between microbiota and nervous system has been associated with a variety of diseases, including stress, anxiety, depression and cognition. The growing body of evidences on the essential role of gut microbiota in modulating acute and chronic pain has opened a new frontier for pain management. Gut microbiota is involved in the development of visceral, inflammatory and neuropathic pain. Bacterial alterations due to chronic opioid administration have been directly related to the development of drug tolerance, which can be potentially restored by the use of probiotics and antibiotics. In this review we describe the mechanisms underlying the brain/gut axis and the relationship between gut microbiota, immunity and pain.