The Relationship of Endocannabinoidome Lipid Mediators With Pain and Psychological Stress in Women With Fibromyalgia: A Case-Control Study

Endocannabinoid concentrations in major depression: effects of childhood maltreatment and relation to hippocampal volume

Evidence from preclinical animal models suggests that the stress-buffering function of the endocannabinoid (eCB) system may help protect against stress-related reductions in hippocampal volume, as is documented in major depressive disorder (MDD). However, stress exposure may also lead to dysregulation of this system. Thus, pathways from marked stress histories, such as childhood maltreatment (CM), to smaller hippocampal volumes and MDD in humans may depend on dysregulated versus intact eCB functioning. We examined whether the relation between MDD and peripheral eCB concentrations would vary as a function of CM history. Further, we examined whether eCBs moderate the relation of CM/MDD and hippocampal volume. Ninety-one adults with MDD and 62 healthy comparison participants (HCs) were recruited for a study from the Canadian Biomarker Integration Network in Depression program (CAN-BIND-04). The eCBs, anandamide (AEA) and 2-arachidonylglycerol (2-AG), were assessed from blood plasma. Severe CM history was assessed retrospectively via contextual interview. MDD was associated with eCBs, though not all associations were moderated by CM or in the direction expected. Specifically, MDD was associated with higher AEA compared to HCs regardless of CM history, a difference that could be attributed to psychotropic medications. MDD was also associated with higher 2-AG, but only for participants with CM. Consistent with hypotheses, we found lower left hippocampal volume in participants with versus without CM, but only for those with lower AEA, and not moderate or high AEA. Our study presents the first evidence in humans implicating eCBs in stress-related mechanisms involving reduced hippocampal volume in MDD.

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.

Endocannabinoid levels in female-sexed individuals with diagnosed depression: a systematic review

BACKGROUND

Major depressive disorder (MDD) is a highly prevalent mental health disorder with females experiencing higher rates of depression (11.6%), anxiety (15.7%) and physiological distress (14.5%) than males. Recently, the Endocannabinoid system (ECS) has been proposed to be a key contributing factor in the pathogenesis and symptom severity of MDD due to its role in neurotransmitter production, inflammatory response and even regulation of the female reproductive cycle. This review critically evaluates evidence regarding ECS levels in female-sexed individuals with depressive disorders to further understand ECS role.

MATERIALS AND METHODS

A systematic literature review of available research published prior to April 2022 was identified using PubMed (U.S. National Library of Medicine), CINAHL (EBSCO), Web of Science, AMED and Scopus (Elsevier). Studies were included if they reported ECS analysis of female-sexed individuals with depression and were excluded if they did not differentiate results between sexes, assessed mental health conditions other than depression, tested efficacy of endocannabinoid/n-acylethanolamine/cannabis or marijuana administration and that were unable to be translated. Critical appraisal of each included study was undertaken using the Joanna Briggs Institute Critical Appraisal Tool for Systematic Reviews.

RESULTS

The 894 located citations were screened for duplicates (n = 357) and eligibility by title and abstract (n = 501). The full text of 33 studies were reviewed, and 7 studies were determined eligible for inclusion. These studies indicated that depressed female-sexed individuals have altered levels of ECS however no significant pattern was identified due to variability of study outcomes and measures, limiting overall interpretation.

DISCUSSION

This review suggests potential involvement of ECS in underlying mechanisms of MDD in female sexed-individuals, however no pattern was able to be determined. A major contributor to the inability to attain reliable and valid understanding of the ECS levels in female-sexed individuals with depression was the inconsistency of depression screening tools, inclusion criteria's and analysis methods used to measure eCBs. Future studies need to implement more standardised methodology to gain a deeper understanding of ECS in female-sexed individuals with depressive disorders. TRIAL REGISTRATION : This review was submitted to PROSPERO for approval in April 2022 (Registration #CRD42022324212).

Ultramicronized N-palmitoylethanolamine associated with analgesics: Effects against persistent pain

Current epidemiological data estimate that one in five people suffers from chronic pain with considerable impairment of health-related quality of life. The pharmacological treatment is based on first- and second-line analgesic drugs, including COX-2 selective and nonselective nonsteroidal anti-inflammatory drugs, paracetamol, antidepressants, anti-seizure drugs and opioids, that are characterized by important side effects. N-palmitoylethanolamine (PEA) is a body's own fatty-acid ethanolamide belonging to the family of autacoid local injury antagonist amides. The anti-inflammatory and pain-relieving properties of PEA have been recognized for decades and prompted to depict its role in the endogenous mechanisms of pain control. Together with its relative abundance in food sources, this opened the way to the use of PEA as a pain-relieving nutritional intervention. Naïve PEA is a large particle size lipid molecule with low solubility and bioavailability. Reducing particle size is a useful method to increase surface area, thereby improving dissolution rate and bioavailability accordingly. Micron-size formulations of PEA (e.g., ultramicronized and co-(ultra)micronized) have shown higher oral efficacy compared to naïve PEA. In particular, ultramicronized PEA has been shown to efficiently cross the intestinal wall and, more importantly, the blood-brain and blood-spinal cord barrier. Several preclinical and clinical studies have shown the efficacy, safety and tolerability of ultramicronized PEA. This narrative review summarizes the available pharmacokinetic/pharmacodynamic data on ultramicronized PEA and focuses to its contribution to pain control, in particular as 'add-on' nutritional intervention. Data showing the ability of ultramicronized PEA to limit opioid side effects, including the development of tolerance, have also been reviewed.

Pain and the biochemistry of fibromyalgia: patterns of peripheral cytokines and chemokines contribute to the differentiation between fibromyalgia and controls and are associated with pain, fat infiltration and content

Objectives

This explorative study analyses interrelationships between peripheral compounds in saliva, plasma, and muscles together with body composition variables in healthy subjects and in fibromyalgia patients (FM). There is a need to better understand the extent cytokines and chemokines are associated with body composition and which cytokines and chemokines differentiate FM from healthy controls.

Methods

Here, 32 female FM patients and 30 age-matched female healthy controls underwent a clinical examination that included blood sample, saliva samples, and pain threshold tests. In addition, the subjects completed a health questionnaire. From these blood and saliva samples, a panel of 68 mainly cytokines and chemokines were determined. Microdialysis of trapezius and erector spinae muscles, phosphorus-31 magnetic resonance spectroscopy of erector spinae muscle, and whole-body magnetic resonance imaging for determination of body composition (BC)-i.e., muscle volume, fat content and infiltration-were also performed.

Results

After standardizing BC measurements to remove the confounding effect of Body Mass Index, fat infiltration and content are generally increased, and fat-free muscle volume is decreased in FM. Mainly saliva proteins differentiated FM from controls. When including all investigated compounds and BC variables, fat infiltration and content variables were most important, followed by muscle compounds and cytokines and chemokines from saliva and plasma. Various plasma proteins correlated positively with pain intensity in FM and negatively with pain thresholds in all subjects taken together. A mix of increased plasma cytokines and chemokines correlated with an index covering fat infiltration and content in different tissues. When muscle compounds were included in the analysis, several of these were identified as the most important regressors, although many plasma and saliva proteins remained significant.

Discussion

Peripheral factors were important for group differentiation between FM and controls. In saliva (but not plasma), cytokines and chemokines were significantly associated with group membership as saliva compounds were increased in FM. The importance of peripheral factors for group differentiation increased when muscle compounds and body composition variables were also included. Plasma proteins were important for pain intensity and sensitivity. Cytokines and chemokines mainly from plasma were also significantly and positively associated with a fat infiltration and content index.

Conclusion

Our findings of associations between cytokines and chemokines and fat infiltration and content in different tissues confirm that inflammation and immune factors are secreted from adipose tissue. FM is clearly characterized by complex interactions between peripheral tissues and the peripheral and central nervous systems, including nociceptive, immune, and neuroendocrine processes.

Serum levels of endocannabinoids and related lipids in painful vs painless diabetic neuropathy: results from the Pain in Neuropathy Study

ABSTRACT

N-arachidonoylethanolamine (also known as anandamide) and 2-arachidonoylglycerol are activators of the cannabinoid receptors. The endocannabinoid system also includes structurally and functionally related lipid mediators that do not target cannabinoid receptors, such as oleoylethanolamide, palmitoylethanolamide, and stearoylethanolamide. These bioactive lipids are involved in various physiological processes, including regulation of pain. The primary aim of the study was to analyze associations between serum levels of these lipids and pain in participants in the Pain in Neuropathy Study, an observational, cross-sectional, multicentre, research project in which diabetic patients with painless or painful neuropathy underwent deep phenotyping. Our hypothesis was that painful neuropathy would be associated with higher levels of the 5 lipids compared with painless neuropathy. Secondary aims were to analyze other patient-reported outcome measures and clinical data in relationship to lipid levels. The lipid mediators were analyzed in serum samples using liquid chromatography tandem mass spectrometry (LC-MS/MS). Serum levels of anandamide were significantly higher in the painful group, but the effect size was small (Cohen d = 0.31). Using cluster analysis of lipid data, patients were dichotomized into a "high-level" endocannabinoid group and a "low-level" group. In the high-level group, 61% of patients had painful neuropathy, compared with 45% in the low-level group ( P = 0.039). This work is of a correlative nature only, and the relevance of these findings to the search for analgesics targeting the endocannabinoid system needs to be determined in future studies.

The Basic Science of Cannabinoids

The cannabis plant has been used for centuries to manage the symptoms of various ailments including pain. Hundreds of chemical compounds have been identified and isolated from the plant and elicit a variety of physiological responses by binding to specific receptors and interacting with numerous other proteins. In addition, the body makes its own cannabinoid-like compounds that are integrally involved in modulating normal and pathophysiological processes. As the legal cannabis landscape continues to evolve within the United States and throughout the world, it is important to understand the rich science behind the effects of the plant and the implications for providers and patients. This narrative review aims to provide an overview of the basic science of the cannabinoids by describing the discovery and function of the endocannabinoid system, pharmacology of cannabinoids, and areas for future research and therapeutic development as they relate to perioperative and chronic pain medicine.

Endocannabinoid and psychological responses to acute resistance exercise in trained and untrained adults

INTRODUCTION

This study examined the effects of acute resistance exercise on circulating endocannabinoid (eCB) and mood responses in trained and untrained healthy adults.

METHODS

Thirty-two healthy adults (22.1 ± 2.9 years) were recruited from trained (reporting resistance exercise at least twice per week for ≥ previous three months) and untrained (performing no resistance exercise for ≥ previous three months) groups. Participants (13 male, 19 female) completed three sets of resistance exercise (16 repetitions at 50% 1-repetition max, 12 repetitions at 70% 1-repetition max, 8 repetitions at 80% 1-repetition max). Resistance machines targeted the legs, chest, back, and abdominal muscles. Mood states, affect, and circulating eCB concentrations were evaluated before and after resistance exercise.

RESULTS

There were significant decreases in AEA, PEA, and OEA levels following acute resistance exercise (p <0.05; ds = -0.39, -0.48, -0.65, respectively), with no significant group differences or group by time interactions. 2-AG did not change significantly. Positive affect increased significantly following resistance exercise (p = 0.009), while negative affect decreased (p <0.001). Depressive symptoms, anger, confusion, and total mood disturbance decreased significantly (p <0.05), while vigor increased significantly following resistance exercise (p = 0.005). There were no significant group differences or group by time interactions for any psychological outcomes.

CONCLUSION

These results indicate that acute resistance exercise may reduce eCB and related lipid concentrations, which is opposite to the increase in lipids typically observed with acute aerobic exercise. Furthermore, psychological improvements occur after resistance exercise regardless of decreases in eCBs, supporting the notion that psychological changes with exercise likely occur through a wide variety of biological and environmental mechanisms.

Endocannabinoids, cortisol, and development of post-traumatic psychopathological trajectories

OBJECTIVE

Our prior published work using the 2-factor model of PTSD identified four subgroups of trauma survivors on average 6 months following trauma: Resilient, Dysphoria, High Comorbid, and Severe Comorbid. Some findings indicate that low and high cortisol responses may increase risk for the development of PTSD and depression respectively, yet ways in which cortisol interacts with other physiological systems to enhance risk is unclear. This study examined the role of circulating eCBs in the development of previously identified psychopathological trajectories that is differentiated by cortisol in traumatically injured adults (N = 169).

METHODS

Circulating concentrations of eCBs, 2-arachidonoylglycerol (2-AG) and N-arachidonoylethanolamine (AEA) were measured during post-injury hospitalization and on average 6 months following trauma. Differences in 2-AG and AEA among the subgroups were tested using multivariate ANCOVA.

RESULTS

Dysphoria (with highest cortisol levels) and High Comorbid subgroups exhibited higher post-injury AEA compared to the Resilient group. Dysphoria subgroup showed a significant decline in AEA by 6 months compared to Resilient and High Comorbid subgroups.

CONCLUSION

Change in AEA over time in individuals with high post-injury cortisol may serve as a buffer against risk for severe psychopathology. Assessing AEA and cortisol levels concurrently across time may serve as indicators of risk.

Cannabinoids and the endocannabinoid system in fibromyalgia: A review of preclinical and clinical research

Characterised by chronic widespread musculoskeletal pain, generalised hyperalgesia, and psychological distress, fibromyalgia (FM) is a significant unmet clinical need. The endogenous cannabinoid system plays an important role in modulating both pain and the stress response. Here, we appraise the evidence, from preclinical and clinical studies, for a role of the endocannabinoid system in FM and the therapeutic potential of targeting the endocannabinoid system. While many animal models have been used to study FM, the reserpine-induced myalgia model has emerged as perhaps the most translatable to the clinical phenotype. Inhibition of fatty acid amide hydrolase (FAAH) has shown promise in preclinical studies, ameliorating pain- and anxiety-related behaviour . Clinically, there is evidence for alterations in the endocannabinoid system in patients with FM, including single nucleotide polymorphisms and increased levels of circulating endocannabinoids and related N-acylethanolamines. Single entity cannabinoids, cannabis, and cannabis-based medicines in patients with FM show promise therapeutically but limitations in methodology and lack of longitudinal studies to assess efficacy and tolerability preclude the current recommendation for their use in patients with FM. Gaps in the literature that warrant further investigation are discussed, particularly the need for further development of animal models with high validity for the multifaceted nature of FM, balanced studies to eliminate sex-bias in preclinical research, and ultimately, better translation between preclinical and clinical research.

Plasma proteins from several components of the immune system differentiate chronic widespread pain patients from healthy controls - an exploratory case-control study combining targeted and non-targeted protein identification

Chronic widespread pain (CWP), including fibromyalgia (FM), is characterized by generalized musculoskeletal pain and hyperalgesia. Plasma proteins from proteomics (non-targeted) and from targeted inflammatory panels (cytokines/chemokines) differentiate CWP/FM from controls. The importance of proteins obtained from these two sources, the protein-protein association network, and the biological processes involved were investigated. Plasma proteins from women with CWP (n = 15) and CON (n = 23) were analyzed using two-dimensional gel electrophoresis analysis and a multiplex proximity extension assay for analysis of cytokines/chemokines. Associations between the proteins and group were multivarietly analyzed. The protein-protein association network and the biological processes according to the Gene Ontology were investigated. Proteins from both sources were important for group differentiation; the majority from the two-dimensional gel electrophoresis analysis. 58 proteins significantly differentiated the two groups (R2 = 0.83). A significantly enriched network was found; biological processes were acute phase response, complement activation, and innate immune response. As with other studies, this study shows that plasma proteins can differentiate CWP from healthy subjects. Focusing on cytokines/chemokines is not sufficient to grasp the peripheral biological processes that maintain CWP/FM since our results show that other components of the immune and inflammation systems are also highly significant.

Fibromyalgia in women: association of inflammatory plasma proteins, muscle blood flow, and metabolism with body mass index and pain characteristics

Supplemental Digital Content is Available in the Text.

Metabolism and inflammation interact in fibromyalgia with obesity that can lead to chronic low-grade inflammation.

Introduction:

Obesity is a common comorbidity in fibromyalgia (FM). Both FM and obesity have been connected to low-grade inflammation, although it is possible that previously reported inflammatory alterations in FM primarily may be linked to increased body mass index (BMI).

Objective:

This study aimed to investigate whether the inflammatory plasma protein profile, muscle blood flow, and metabolism and pain characteristics (clinical parameters and patient-reported outcome measurements) differed between female patients with FM with and without obesity.

Methods:

Patients with FM underwent clinical examinations, physical tests, and answered questionnaires. They were dichotomized according to BMI (<30 kg/m² [n = 14]; ≥30 kg/m² [n = 13]). Blood samples were collected and analyzed using a panel of 71 inflammatory plasma proteins.

Results:

There were significant (P < 0.05) differences in blood pressure, pulse, max VO2, pain intensity, physical capacity, and Fibromyalgia Impact Questionnaire between the groups; the obese group had higher blood pressure, pulse, pain intensity, and Fibromyalgia Impact Questionnaire. There were 14 proteins that contributed to the group belonging. The 4 most important proteins for the group discrimination were MIP1β, MCP4, IL1RA, and IL6, which showed higher concentrations in obese patients with FM. Significantly decreased blood flow and increased concentration of pyruvate were detected in obese patients compared with nonobese patients. There was significant correlation between inflammatory proteins and sedentary behavior and health status in obese patients with FM.

Conclusions:

These findings suggest that metabolism and inflammation interact in female patients with FM with obesity and might cause chronic low-grade inflammation. Screening for obesity and monitoring of BMI changes should be considered in the treatment of patients with FM.

Identification of the Involvement of Potassium Channels in Fibromyalgia

Fibromyalgia is a central sensitivity syndrome that presents with chronic pain, fatigue, cognitive dysfunction, and disordered sleep. The pathophysiology which due to multisensory hypersensitivity of the central nervous system involves neuronal excitability leading to central sensitization. Treatments of the challenges associated with the complexities of fibromyalgia involve combinations of pharmacological and non-pharmacological therapeutic approaches which often offer limited benefit. Potassium (K+) channels play a fundamental role in establishing and maintaining stability of neuronal activity. The large molecular diversity and distribution of K+ channels support involvement in a broad range of physiological functions. In nociceptive pathways, neuronal hyperexcitability leading to pain sensation has been associated with reduced function of K+ channels and loss of cellular control. This article reviews the evidence of involvement of K+ channels in fibromyalgia. A potential role both in the pathophysiological processes responsible for the symptoms of fibromyalgia and as therapeutic targets for the management of the condition is considered.

Fibromyalgia: Associations Between Fat Infiltration, Physical Capacity, and Clinical Variables

Background

Obesity is a risk factor for the development of fibromyalgia (FM) and generally most studies report increased Body Mass Index (BMI) in FM. Obesity in FM is associated with a worse clinical presentation. FM patients have low physical conditioning and obesity further exacerbates these aspects. Hitherto studies of FM have focused upon a surrogate for overall measure of fat content, ie, BMI. This study is motivated by that ectopic fat and adipose tissues are rarely investigated in FM including their relationships to physical capacity variables. Moreover, their relationships to clinical variables including are not known. Aims were to 1) compare body composition between FM and healthy controls and 2) investigate if significant associations exist between body composition and physical capacity aspects and important clinical variables.

Methods

FM patients (n = 32) and healthy controls (CON; n = 30) underwent a clinical examination that included pressure pain thresholds and physical tests. They completed a health questionnaire and participated in whole-body magnetic resonance imaging (MRI) to determine body composition aspects.

Results

Abdominal adipose tissues, muscle fat, and BMI were significantly higher in FM, whereas muscle volumes of quadriceps were smaller. Physical capacity variables correlated negatively with body composition variables in FM. Both body composition and physical capacity variables were significant regressors of group belonging; the physical capacity variables alone showed stronger relationships with group membership. A mix of body composition variables and physical capacity variables were significant regressors of pain intensity and impact in FM. Body composition variables were the strongest regressors of blood pressures, which were increased in FM.

Conclusion

Obesity has a negative influence on FM symptomatology and increases the risk for other serious conditions. Hence, obesity, dietary habits, and physical activity should be considered when developing clinical management plans for patients with FM.

Serum Concentrations of the Endocannabinoid, 2-Arachidonoylglycerol, in the Peri-Trauma Period Are Positively Associated with Chronic Pain Months Later

Endocannabinoid signaling and the hypothalamic-pituitary-adrenal axis are activated by trauma and both stress systems regulate the transition from acute to chronic pain. This study aimed to develop a model of relationships among circulating concentrations of cortisol and endocannabinoids (eCBs) immediately after traumatic injury and the presence of chronic pain months later. Pain scores and serum concentrations of eCBs and cortisol were measured during hospitalization and 5–10 months later in 147 traumatically injured individuals. Exploratory correlational analyses and path analysis were completed. The study sample was 50% Black and Latino and primarily male (69%); 34% percent endorsed a pain score of 4 or greater at follow-up and were considered to have chronic pain. Path analysis was used to model relationships among eCB, 2-arachidonolyglycerol (2-AG), cortisol, and pain, adjusting for sex and injury severity (ISS). Serum 2-AG concentrations at the time of injury were associated with chronic pain in 3 ways: a highly significant, independent positive predictor; a mediator of the effect of ISS, and through a positive relationship with cortisol concentrations. These data indicate that 2-AG concentrations at the time of an injury are positively associated with chronic pain and suggest excessive activation of endocannabinoid signaling contributes to risk for chronic pain.

Toward Composite Pain Biomarkers of Neuropathic Pain-Focus on Peripheral Neuropathic Pain

Chronic pain affects ~10-20% of the U.S. population with an estimated annual cost of $600 billion, the most significant economic cost of any disease to-date. Neuropathic pain is a type of chronic pain that is particularly difficult to manage and leads to significant disability and poor quality of life. Pain biomarkers offer the possibility to develop objective pain-related indicators that may help diagnose, treat, and improve the understanding of neuropathic pain pathophysiology. We review neuropathic pain mechanisms related to opiates, inflammation, and endocannabinoids with the objective of identifying composite biomarkers of neuropathic pain. In the literature, pain biomarkers typically are divided into physiological non-imaging pain biomarkers and brain imaging pain biomarkers. We review both types of biomarker types with the goal of identifying composite pain biomarkers that may improve recognition and treatment of neuropathic pain.

Advances in the management of fibromyalgia: what is the state of the art?

INTRODUCTION

Fibromyalgia (FM) is a chronic pain syndrome associated with fatigue, insomnia, dyscognition, and emotional distress. Critical illness mechanisms include central sensitization to nociceptive and non-nociceptive stimuli often resulting in hypersensitivity to all sensory input.

AREAS COVERED

The clinical presentation of FM can vary widely and therefore requires therapies tailored to each patient's set of symptoms. This manuscript examines currently prescribed therapeutic approaches supported by empirical evidence as well as promising novel treatments. Although pharmacological therapy until now has been only moderately effective for FM symptoms, it represents a critical component of every treatment plan.

EXPERT OPINION

Currently approved pharmacological therapies for FM symptoms have limited but proven effectiveness. Novel therapies with cannabinoids and naltrexone appear promising. Recent functional imaging studies of FM have discovered multiple brain network abnormalities that may provide novel targets for mechanism-based therapies. Future treatment approaches, however, need to improve more than clinical pain but also other FM domains like fatigue, insomnia, and distress.

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.

Palmitoylethanolamide: A Natural Compound for Health Management

All nations which have undergone a nutrition transition have experienced increased frequency and falling latency of chronic degenerative diseases, which are largely driven by chronic inflammatory stress. Dietary supplementation is a valid strategy to reduce the risk and severity of such disorders. Palmitoylethanolamide (PEA) is an endocannabinoid-like lipid mediator with extensively documented anti-inflammatory, analgesic, antimicrobial, immunomodulatory and neuroprotective effects. It is well tolerated and devoid of side effects in animals and humans. PEA's actions on multiple molecular targets while modulating multiple inflammatory mediators provide therapeutic benefits in many applications, including immunity, brain health, allergy, pain modulation, joint health, sleep and recovery. PEA's poor oral bioavailability, a major obstacle in early research, has been overcome by advanced delivery systems now licensed as food supplements. This review summarizes the functionality of PEA, supporting its use as an important dietary supplement for lifestyle management.

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.

Alterations in Anandamide Synthesis and Degradation during Osteoarthritis Progression in an Animal Model

Osteoarthritis (OA) is a degenerative joint disease manifested by movement limitations and chronic pain. Endocannabinoid system (ECS) may modulate nociception via cannabinoid and TRPV1 receptors. The purpose of our study was to examine alterations in the spinal and joint endocannabinoid system during pain development in an animal model of OA. Wistar rats received intra-articular injection of 3mg of sodium monoiodoacetate (MIA) into the knee joint. Animals were sacrificed on day 2, 7, 14, 21, 28 after injection and lumbar spinal cord, cartilage and synovium were collected. Changes in the transcription levels of the ECS elements were measured. At the spinal level, gene expression levels of the cannabinoid and TRPV1 receptors as well as enzymes involved in anandamide synthesis and degradation were elevated in the advanced OA phase. In the joint, an important role of the synovium was demonstrated, since cartilage degeneration resulted in attenuation of the changes in the gene expression. Enzymes responsible for anandamide synthesis and degradation were upregulated particularly in the early stages of OA, presumably in response to early local joint inflammation. The presented study provides missing information about the MIA-induced OA model and encourages the development of a therapy focused on the molecular role of ECS.

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.

Significant correlation between plasma proteome profile and pain intensity, sensitivity, and psychological distress in women with fibromyalgia

Fibromyalgia (FM) is a complex pain condition where the pathophysiological and molecular mechanisms are not fully elucidated. The primary aim of this study was to investigate the plasma proteome profile in women with FM compared to controls. The secondary aim was to investigate if plasma protein patterns correlate with the clinical variables pain intensity, sensitivity, and psychological distress. Clinical variables/background data were retrieved through questionnaires. Pressure pain thresholds (PPT) were assessed using an algometer. The plasma proteome profile of FM (n = 30) and controls (n = 32) was analyzed using two-dimensional gel electrophoresis and mass spectrometry. Quantified proteins were analyzed regarding group differences, and correlations to clinical parameters in FM, using multivariate statistics. Clear significant differences between FM and controls were found in proteins involved in inflammatory, metabolic, and immunity processes. Pain intensity, PPT, and psychological distress in FM had associations with specific plasma proteins involved in blood coagulation, metabolic, inflammation and immunity processes. This study further confirms that systemic differences in protein expression exist in women with FM compared to controls and that altered levels of specific plasma proteins are associated with different clinical parameters.

Altered relationship between anandamide and glutamate in circulation after 30 min of arm cycling: A comparison of chronic pain subject with healthy controls

The insufficient knowledge of biochemical mechanisms behind the emergence and maintenance of chronic musculoskeletal pain conditions constrains the development of diagnostic and therapeutic tools for clinical use. However, physical activity and exercise may improve pain severity and physical function during chronic pain conditions. Nevertheless, the biochemical consequences of physical activity and exercise in chronic pain need to be elucidated to increase the precision of this therapeutic tool in chronic pain treatment. The endocannabinoid system has been suggested to play an important role in exercise-induced reward and pain inhibition. Moreover, glutamatergic signalling has been suggested as an important factor for sensation and transmission of pain. In addition, a link has been established between the endocannabinoid system and glutamatergic pathways. This study examines the effect of dynamic load arm cycling (30 min) on levels of lipid mediators related to the endocannabinoid system and glutamate in plasma of chronic pain subjects and pain-free controls. Pain assessments and plasma levels of arachidonoylethanolamide (anandamide), 2-aracidonoylglycerol, oleoylethanolamide, palmitoylethanolamide, stearoylethanolamide and glutamate from 21 subjects with chronic neck pain (chronic pain group) and 11 healthy controls were analysed pre and post intervention of dynamic load arm cycling. Pain intensity was significantly different between groups pre and post exercise. Post exercise, anandamide levels were significantly decreased in health controls but not in the chronic pain group. A strong positive correlation existed between anandamide and glutamate in the control group post exercise but not in the chronic pain group. Moreover, the glutamate/anandamide ratio increased significantly in the control group and differed significantly with the chronic pain group post exercise. The altered relationship between anandamide and glutamate after the intervention in the chronic pain group might reflect alterations in the endocannabinoid-glutamate mechanistic links in the chronic pain group compared to the pain-free control group.

Plasma protein patterns are strongly correlated with pressure pain thresholds in women with chronic widespread pain and in healthy controls-an exploratory case-control study

Chronic widespread pain (CWP) is a complex pain condition characterized by generalized musculoskeletal pain and often associated with other symptoms. An important clinical feature is widespread increased pain sensitivity such as lowered pain thresholds for mechanical stimuli (pressure pain thresholds [PPT]). There is a growing interest in investigating the activated neurobiological mechanisms in CWP, which includes fibromyalgia. In CWP, strong significant correlations have been found between muscle protein patterns and PPT. This explorative proteomic study investigates the multivariate correlation pattern between plasma proteins and PPT in CWP and in healthy controls (CON). In addition, this study analyses whether the important proteins for PPT differ between the 2 groups.Using 2-dimensional gel electrophoresis, we analyzed the plasma proteome of the CWP (n = 15) and the CON (n = 23) and proteins were identified using mass spectrometry. For both the CWP and the CON, the associations between the identified proteins and PPT were analyzed using orthogonal partial least square in 2 steps.Significant associations between certain plasma proteins and PPT existed both in CWP (R = 0.95; P = .006) and in CON (R = 0.89; P < .001). For both groups of subjects, we found several proteins involved in PPT that reflect different biological processes. The plasma proteins as well as the biological processes involved in PPT differed markedly between the 2 groups of subjects.This study suggests that plasma protein patterns are associated with pain thresholds in CWP. Using the plasma proteome profile of CWP to study potential biomarker candidates could provide a snapshot of ongoing systemic mechanisms in CWP.

Practical Considerations of Hypotheses and Evidence in Cannabis Pharmacotherapy: Refining Expectations of Clinical Endocannabinoid Deficiency

An Industry founded on the promotion of presumed health and wellness benefits of cannabis use continues to grow in the United States, despite the lack of substantial evidence in support of the many claims being made. Several hypotheses exist regarding the role of endocannabinoids in human health and the pertinence of phytocannabinoids as pharmacotherapies for addressing their dysregulation. An opinion is offered regarding the tenuous nature of these assumptions and questions are raised regarding how best to interpret the complex metabolic interplay of the still vaguely defined endocannabinoid system.

Anhedonia to Gentle Touch in Fibromyalgia: Normal Sensory Processing but Abnormal Evaluation

Social touch is important for interpersonal interaction. Gentle touch and slow brushing are typically perceived as pleasant, the degree of pleasantness is linked to the activity of the C-tactile (CT) fibers, a class of unmyelinated nerves in the skin. The inability to experience pleasure in general is called anhedonia, a common phenomenon in the chronic pain condition fibromyalgia. Here, we studied the perception and cortical processing of gentle touch in a well-characterized cohort of fibromyalgia. Patients and controls participated in functional brain imaging while receiving tactile stimuli (brushing) on the forearm. They were asked to provide ratings of pleasantness of the tactile stimulus and ongoing pain. We found high distress, pain catastrophizing, and insomnia, and a low perceived state of health in fibromyalgia. Further, patients rated both slow (CT-optimal) and fast (CT-suboptimal) brushing as less pleasant than healthy participants. While there was no difference in brain activity during touch, patients showed deactivation in the right posterior insula (contralateral to the stimulated arm) during pleasantness rating and activation during pain rating. The opposite pattern was observed in healthy participants. Voxel-based morphometry analysis revealed reduced grey matter density in patients, in the bilateral hippocampus and anterior insula. Our results suggest anhedonia to gentle touch in fibromyalgia with intact early-stage sensory processing but dysfunctional evaluative processing. These findings contribute to our understanding of the mechanisms underlying anhedonia in fibromyalgia.

The Potential Benefits of Palmitoylethanolamide in Palliation: A Qualitative Systematic Review

Palmitoylethanolamide (PEA) is a nutraceutical endocannabinoid that was retrospectively discovered in egg yolks. Feeding poor children with known streptococcal infections prevented rheumatic fever. Subsequently, it was found to alter the course of influenza. Unfortunately, there is little known about its pharmacokinetics. Palmitoylethanolamide targets nonclassical cannabinoid receptors rather than CB1 and CB2 receptors. Palmitoylethanolamide will only indirectly activate classical cannabinoid receptors by an entourage effect. There are a significant number of prospective and randomized trials demonstrating the pain-relieving effects of PEA. There is lesser evidence of benefit in patients with nonpain symptoms related to depression, Parkinson disease, strokes, and autism. There are no reported drug-drug interactions and very few reported adverse effects from PEA. Further research is needed to define the palliative benefits to PEA.

A double-blind randomized placebo controlled study assessing safety, tolerability and efficacy of palmitoylethanolamide for symptoms of knee osteoarthritis

BACKGROUND

The aim of the study was to assess the safety, tolerability and efficacy of palmitoylethanolamide (PEA) when dosed at 300 mg and 600 mg per day on symptoms of knee osteoarthritis.

METHODS

This was a single site, comparative, double-blind placebo controlled study in adults with mild to moderate knee osteoarthritis with 111 participants randomized to receive 300 mg PEA, 600 mg PEA or placebo each day, in divided doses b.i.d, for 8 weeks. The primary outcome was the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). The secondary outcomes were the Numerical Rating Scales (NRS) for pain, the Depression Anxiety Stress Scale (DASS), the Perceived Stress Scale (PSS), the Pittsburg Sleep Quality Index (PSQI), the Short Form Health Survey (SF-36), the use of rescue pain medication and clinical safety assessment.

RESULTS

There was a significant reduction in the total WOMAC score in the 300 mg PEA (p = 0.0372) and the 600 mg PEA (p = 0.0012) groups, the WOMAC pain score (300 mg PEA, p = 0.0074; 600 mg PEA, p =  < 0.001), the WOMAC stiffness score (PEA 300 mg, p < 0.0490; 600 mg PEA, p = 0.001) and in the WOMAC function score in the 600 mg PEA group (p = 0.033) compared to placebo. The NRS pain evaluations for "worst pain" and "least pain" were significantly reduced in the 300 mg PEA group (p < 0.001, p = 0.005) and the 600 mg PEA group (p < 0.001, p < 0.001) compared to placebo. There was a significant reduction in anxiety (DASS) in both active treatment groups (300 mg PEA, p = 0.042; 600 mg PEA group (p = 0.043) compared to placebo. There were no changes in the clinical markers and the product was well tolerated.

CONCLUSIONS

The study demonstrated that palmitoylethanolamide may be a novel treatment for attenuating pain and reducing other associated symptoms of knee osteoarthritis. Further studies on the pharmacological basis of this anti-inflammatory effect are now required.