Weight loss and improved mood after aerobic exercise training are linked to lower plasma anandamide in healthy people

Peripheral endocannabinoids in major depressive disorder and alcohol use disorder: a systematic review

BACKGROUND

Major Depressive Disorder (MDD) and Alcohol Use Disorder (AUD) are two high-prevalent conditions where the Endocannabinoid system (ECS) is believed to play an important role. The ECS regulates how different neurotransmitters interact in both disorders, which is crucial for controlling emotions and responses to stress and reward stimuli. Measuring peripheral endocannabinoids (eCBs) in human serum and plasma can help overcome the limitations of detecting endocannabinoid levels in the brain. This systematic review aims to identify levels of peripheral eCBs in patients with MDD and/or AUD and find eCBs to use as diagnostic, prognostic biomarkers, and potential therapeutic targets.

METHODS

We conducted a systematic literature search according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines from the earliest manuscript until October 22, 2023, in three electronic databases. We included studies of human adults who had a current diagnosis of AUD and/or MDD and evaluated plasma or serum endocannabinoids. We carefully considered known variables that may affect endocannabinoid levels.

RESULTS

We included 17 articles in this systematic review, which measured peripheral eCBs in 170 AUD and 359 MDD patients. Stressors increase peripheral 2-arachidonyl-glycerol (2-AG) concentrations, and 2-AG may be a particular feature of depression severity and chronicity. Anxiety symptoms are negatively correlated with anandamide (AEA) concentrations, and AEA significantly increases during early abstinence in AUD. Studies suggest a negative correlation between Oleoylethanolamide (OEA) and length of abstinence in AUD patients. They also show a significant negative correlation between peripheral levels of AEA and OEA and fatty acid amide hydrolase (FAAH) activity. Eicosapentaenoylethanolamide (EPEA) is correlated to clinical remission rates in depression. Included studies show known variables such as gender, chronicity, symptom severity, comorbid psychiatric symptoms, length of abstinence in the case of AUD, and stress-inducibility that can affect peripheral eCBs.

CONCLUSIONS

This systematic review highlights the important role that the ECS plays in MDD and AUD. Peripheral eCBs appear to be useful biomarkers for these disorders, and further research may identify potential therapeutic targets. Using accessible biological samples such as blood in well-designed clinical studies is crucial to develop novel therapies for these disorders.

A Systematic Review and Meta-Analysis on the Effects of Exercise on the Endocannabinoid System

Introduction: The endocannabinoid (eCB) system plays a key role in maintaining homeostasis, including the regulation of metabolism and stress responses. Chronic stress may blunt eCB signaling, and disruptions in eCB signaling have been linked to stress-related psychiatric disorders and physical health conditions, including anxiety, depression, post-traumatic stress disorder (PTSD), diabetes, and obesity. Pharmacological and nonpharmacological behavioral interventions (e.g., exercise) that target the eCB system may be promising therapeutic approaches for the prevention and treatment of stress-related diseases. In this study, we perform a systematic review and the first meta-analysis to examine the impact of exercise on circulating eCB concentrations. Materials and Methods: We performed a review of the MEDLINE (PubMed) database for original articles examining the impact of exercise on eCBs in humans and animal models. A total of 262 articles were screened for initial inclusion. Results: Thirty-three articles (reporting on 57 samples) were included in the systematic review and 10 were included in the meta-analysis. The majority of samples that measured anandamide (AEA) showed a significant increase in AEA concentrations following acute exercise (74.4%), whereas effects on 2-arachidonoylglycerol (2-AG) were inconsistent. The meta-analysis, however, revealed a consistent increase in both AEA and 2-AG following acute exercise across modalities (e.g., running, cycling), species (e.g., humans, mice), and in those with and without pre-existing health conditions (e.g., PTSD, depression). There was substantial heterogeneity in the magnitude of the effect across studies, which may relate to exercise intensity, physical fitness, timing of measurement, and/or fasted state. Effects of chronic exercise were inconsistent. Conclusions: Potential interpretations and implications of exercise-induced mobilization of eCBs are discussed, including refilling of energy stores and mediating analgesic and mood elevating effects of exercise. We also offer recommendations for future work and discuss therapeutic implications for exercise in the prevention and treatment of stress-related psychopathology.

Aerobic Fitness Is Associated with Cerebral μ-Opioid Receptor Activation in Healthy Humans

INTRODUCTION

Central μ-opioid receptors (MORs) modulate affective responses to physical exercise. Individuals with higher aerobic fitness report greater exercise-induced mood improvements than those with lower fitness, but the link between cardiorespiratory fitness and the MOR system remains unresolved. Here we tested whether maximal oxygen uptake (V̇O2peak) and physical activity level are associated with cerebral MOR availability and whether these phenotypes predict endogenous opioid release after a session of exercise.

METHODS

We studied 64 healthy lean men who performed a maximal incremental cycling test for V̇O2peak determination, completed a questionnaire assessing moderate-to-vigorous physical activity (MVPA; in minutes per week), and underwent positron emission tomography with [11C]carfentanil, a specific radioligand for MOR. A subset of 24 subjects underwent additional positron emission tomography scan also after a 1-h session of moderate-intensity exercise and 12 of them also after a bout of high-intensity interval training.

RESULTS

Higher self-reported MVPA level predicted greater opioid release after high-intensity interval training, and both V̇O2peak and MVPA level were associated with a larger decrease in cerebral MOR binding after aerobic exercise in the ventral striatum, orbitofrontal cortex, and insula. That is, more trained individuals showed greater opioid release acutely after exercise in brain regions especially relevant for reward and cognitive processing. Fitness was not associated with MOR availability.

CONCLUSIONS

We conclude that regular exercise training and higher aerobic fitness may induce neuroadaptation within the MOR system, which might contribute to improved emotional and behavioral responses associated with long-term exercise.

Influence of diet on acute endocannabinoidome mediator levels post exercise in active women, a crossover randomized study

The extended endocannabinoid system, also termed endocannabinoidome, participates in multiple metabolic functions in health and disease. Physical activity can both have an acute and chronic impact on endocannabinoid mediators, as does diet. In this crossover randomized controlled study, we investigated the influence of diet on the peripheral response to acute maximal aerobic exercise in a sample of active adult women (n = 7) with no underlying metabolic conditions. We compared the impact of 7-day standardized Mediterranean diet (MedDiet) and control diet inspired by Canadian macronutrient intake (CanDiet) on endocannabinoidome and short-chain fatty acid metabolites post maximal aerobic exercise. Overall, plasmatic endocannabinoids, their congeners and some polyunsaturated fatty acids increased significantly post maximal aerobic exercise upon cessation of exercise and recovered their initial values within 1 h after exercise. Most N-acylethanolamines and polyunsaturated fatty acids increased directly after exercise when the participants had consumed the MedDiet, but not when they had consumed the CanDiet. This impact was different for monoacylglycerol endocannabinoid congeners, which in most cases reacted similarly to acute exercise while on the MedDiet or the CanDiet. Fecal microbiota was only minimally affected by the diet in this cohort. This study demonstrates that endocannabinoidome mediators respond to acute maximal aerobic exercise in a way that is dependent on the diet consumed in the week prior to exercise.

Investigating the Long-Term Effect of an Interdisciplinary Multimodal Rehabilitation Program on Levels of Bioactive Lipids and Telomerase Activity in Blood from Patients with Chronic Pain

Mechanism-based diagnosis and therapies for chronic pain are lacking. However, bio-psycho-social interventions such as interdisciplinary multimodal rehabilitation programs (IPRPs) have shown to be relatively effective treatments. In this context we aim to investigate the effects of IPRP on the changes in levels of bioactive lipids and telomerase activity in plasma, and if these changes are associated with changes in pain intensity and psychological distress. This exploratory study involves 18 patients with complex chronic pain participating in an IPRP. Self-reports of pain, psychological distress, physical activity, and blood samples were collected before the IPRP and at a six-month follow-up. Levels of arachidonoylethanolamide (AEA) and 2-arachidonoylglycerol (2-AG), palmitoylethanolamide (PEA), oleoylethanolamide (OEA), stearoylethanolamide (SEA), and telomerase activity were measured. Pain intensity was decreased, and SEA levels were increased at the six-month follow up. A significant correlation existed between changes in SEA levels and pain intensity. AEA levels, were inversely correlated with physical activity. Furthermore, 2-AG and telomerase activity was significantly correlated at the six-month follow-up. This study confirms that IPRP is relatively effective for reduction in chronic pain. Changes in SEA were correlated with changes in pain intensity, which might indicate that SEA changes reflect the pain reduction effects of IPRP.

Investigating the Immediate Influence of Moderate Pedal Exercises during an Assembly Work on Performance and Workload in Healthy Men

Physical inactivity has increased in prevalence among adults in industrialized and developing countries owing to the fact that the majority of job situations require individuals to remain seated for extended periods of time. This research aims to evaluate the influence of cycling on a stationary bike while executing a keyboard assembly task on the task completion time, error percentage, and physiological and subjective measurements. The physiological measures were electroencephalography (EEG) and electrocardiographic (ECG) signal responses, whereas the subjective measures were subjective workload ratings and subjective body discomforts. Two variables were evaluated, namely assembly methods (with versus without pedal exercises at a moderate intensity) and session testing (pre- versus post-test). Thus, the repeated measures design (i.e., assembly method by session testing of participants) was used. According to the completion time, error %, participant self-reports, and ECG and EEG statistical analysis data, the participants' performances in the keyboard assembly task did not decrease while they performed pedaling exercises (p > 0.05). Additionally, when participants completed the assembly task while executing the pedaling exercises, the mean inter-beat (RR) intervals significantly reduced (p < 0.05) while the mean heart rate increased (p < 0.05), which mean that pedaling exercises caused physical workloads on the participants. Participant performance was unaffected by performing a workout while performing the assembly activity. Thus, administrations should encourage their employees to engage in short sessions of moderate-intensity exercise similar to the suggested exercise in the study to improve a person's physical health during work without interfering with the effectiveness of work.

Quality of Life and a Surveillant Endocannabinoid System

The endocannabinoid system (ECS) is an important brain modulatory network. ECS regulates brain homeostasis throughout development, from progenitor fate decision to neuro- and gliogenesis, synaptogenesis, brain plasticity and circuit repair, up to learning, memory, fear, protection, and death. It is a major player in the hypothalamic-peripheral system-adipose tissue in the regulation of food intake, energy storage, nutritional status, and adipose tissue mass, consequently affecting obesity. Loss of ECS control might affect mood disorders (anxiety, hyperactivity, psychosis, and depression), lead to drug abuse, and impact neurodegenerative (Alzheimer's, Parkinson, Huntington, Multiple, and Amyotrophic Lateral Sclerosis) and neurodevelopmental (autism spectrum) disorders. Practice of regular physical and/or mind-body mindfulness and meditative activities have been shown to modulate endocannabinoid (eCB) levels, in addition to other players as brain-derived neurotrophic factor (BDNF). ECS is involved in pain, inflammation, metabolic and cardiovascular dysfunctions, general immune responses (asthma, allergy, and arthritis) and tumor expansion, both/either in the brain and/or in the periphery. The reason for such a vast impact is the fact that arachidonic acid, a precursor of eCBs, is present in every membrane cell of the body and on demand eCBs synthesis is regulated by electrical activity and calcium shifts. Novel lipid (lipoxins and resolvins) or peptide (hemopressin) players of the ECS also operate as regulators of physiological allostasis. Indeed, the presence of cannabinoid receptors in intracellular organelles as mitochondria or lysosomes, or in nuclear targets as PPARγ might impact energy consumption, metabolism and cell death. To live a better life implies in a vigilant ECS, through healthy diet selection (based on a balanced omega-3 and -6 polyunsaturated fatty acids), weekly exercises and meditation therapy, all of which regulating eCBs levels, surrounded by a constructive social network. Cannabidiol, a diet supplement has been a major player with anti-inflammatory, anxiolytic, antidepressant, and antioxidant activities. Cognitive challenges and emotional intelligence might strengthen the ECS, which is built on a variety of synapses that modify human behavior. As therapeutically concerned, the ECS is essential for maintaining homeostasis and cannabinoids are promising tools to control innumerous targets.

Circulating endocannabinoids and prospective risk for depression in trauma-injury survivors

Biological mechanisms associated with response to trauma may impact risk for depression. One such mechanism is endocannabinoid signaling (eCB), a neuromodulatory system comprised of the CB1 subtype of cannabinoid receptors (CB1R), encoded by the CNR1 gene, and two primary endogenous ligands: 2-arachidonoylglycerol (2-AG) and N-arachidonylethanolamine (AEA), hydrolyzed by monoacylglycerol lipase (gene name MGLL) and fatty acid amide hydrolase (gene name FAAH). Preclinical data suggest that eCB/CB1R signaling acts as a stress buffer and its loss or suppression increases depression-like behaviors. We examined circulating concentrations of the eCBs (2-AG and AEA) days and six months after a traumatic injury as a marker of eCB/CB1R signaling and as predictors of Center for Epidemiologic Studies of Depression Scale-Revised [CESD-R] scores as a measure of depression severity six months after injury. We also explored associations of CNR1, FAAH, and MGLL genetic variance with depression severity at six months. Results from hierarchical multiple linear regressions showed that higher 2-AG serum concentrations after trauma predicted greater depression at six months (β = 0.23, p = 0.007); neither AEA after trauma, nor 2-AG and AEA at six months were significant predictors (p's > 0.305). Carriers of minor allele for the putative single nucleotide polymorphism in the CNR1 gene rs806371 (β = 0.19, p = 0.024) experienced greater depression at six months. These data suggest that the eCB signaling system is highly activated following trauma and that eCB/CB1R activity contributes to long-term depression risk.

Circulating endocannabinoid concentrations in grieving adults

Bereavement is one of the most intense, distressing, and traumatic events an elderly person will experience. The symptom responses to bereavement vary, particularly during the first year. However, the neurobiology underlying the symptom variance in grief is poorly understood. The endocannabinoid signaling (ECS) system is stress-responsive; mounting evidence implicates the central ECS in psychopathology. The current study aimed to investigate the hypothesis that the ECS is abnormal in grief, using circulating eCB concentrations as a biomarker of central ECS. A predominantly older sample of grief participants, within 13 months following the death of a loved one, and healthy comparison (HC) participants were studied. Associations of circulating eCBs with symptom variance in grievers were also examined. A total of 61 (grief: n = 44; HC: n = 17) adults completed cross-sectional clinical assessments and a fasting blood draw. Assessments included the Inventory of Complicated Grief scale; the 17-item Hamilton Depression Rating Scale; and the Hamilton Anxiety scale. Serum eCB concentrations (i.e., N-arachidonoylethanolamine [AEA] and 2-arachidonoylglycerol [2-AG]) were quantified using isotope dilution, liquid chromatography-mass spectrometry. Relative to HC participants, grievers had significantly elevated serum AEA but similar 2-AG concentrations. In grievers, serum AEA concentrations were positively associated with depressive and anxiety symptoms, but only in those with low grief symptoms. These novel findings indicate that elevated circulating eCB concentrations are found following bereavement. The eCB signaling response varies based on the degree of grief severity. Circulating eCB measures may have the potential to serve as biomarkers of prolonged grief disorder.

Meet Your Stress Management Professionals: The Endocannabinoids

The endocannabinoid signaling system (ECSS) is altered by exposure to stress and mediates and modulates the effects of stress on the brain. Considerable preclinical data support critical roles for the endocannabinoids and their target, the CB1 cannabinoid receptor, in the adaptation of the brain to repeated stress exposure. Chronic stress exposure increases vulnerability to mental illness, so the ECSS has attracted attention as a potential therapeutic target for the prevention and treatment of stress-related psychopathology. We discuss human genetic studies indicating that the ECSS contributes to risk for mental illness in those exposed to severe stress and trauma early in life, and we explore the potential difficulties in pharmacological manipulation of the ECSS.

Can Physical Activity Support the Endocannabinoid System in the Preventive and Therapeutic Approach to Neurological Disorders?

The worldwide prevalence of neurological and neurodegenerative disorders, such as depression or Alzheimer's disease, has spread extensively throughout the last decades, becoming an enormous health issue. Numerous data indicate a distinct correlation between the altered endocannabinoid signaling and different aspects of brain physiology, such as memory or neurogenesis. Moreover, the endocannabinoid system is widely regarded as a crucial factor in the development of neuropathologies. Thus, targeting those disorders via synthetic cannabinoids, as well as phytocannabinoids, becomes a widespread research issue. Over the last decade, the endocannabinoid system has been extensively studied for its correlation with physical activity. Recent data showed that physical activity correlates with elevated endocannabinoid serum concentrations and increased cannabinoid receptor type 1 (CB1R) expression in the brain, which results in positive neurological effects including antidepressant effect, ameliorated memory, neuroplasticity development, and reduced neuroinflammation. However, none of the prior reviews presented a comprehensive correlation between physical activity, the endocannabinoid system, and neuropathologies. Thus, our review provides a current state of knowledge of the endocannabinoid system, its action in physical activity, as well as neuropathologies and a possible correlation between all those fields. We believe that this might contribute to finding a new preventive and therapeutic approach to both neurological and neurodegenerative disorders.