Endocannabinoids as potential biomarkers: It's all about pre-analytics

Endocannabinoid analysis in GlucoEXACT plasma: Method validation and sample handling recommendations

Endocannabinoids (ECs), such as anandamide and 2-arachidonyl glycerol (2-AG), contribute to the pathology of inflammatory, malignant, cardiovascular, metabolic and mental diseases. The reliability of quantitative analyses in biological fluids of ECs and endocannabinoid-like (EC-like) substances depends on pre-analytical conditions such as temperature and "time-to-centrifugation". Standardization of these parameters is critical for valid quantification and implementation in clinical research. In this study, we compared concentrations obtained with GlucoEXACT blood collection tubes versus K3EDTA tubes and employed the optimized procedure to assess ECs profiles in patients with inflammatory skin disease and healthy controls. A UHPLC-MS/MS method was validated for human plasma from GlucoEXACT blood collection tubes according to EMA and FDA guidelines, and pre-analytical conditions were systematically modified to assess analyte stability and optimize the procedures. The results showed significantly lower concentrations of ECs and EC-like substance concentrations with GlucoEXACT tubes compared with K3EDTA tubes, and GlucoEXACT extended the time window of stable concentrations. The strongest method-disagreement occurred for 1/2-AG suggesting that GlucoEXACT delayed ex vivo isomer rearrangement. Hence, GlucoExact tubes were superior in terms of stability and reliability. However, although absolute concentrations obtained with GlucoExact and K3EDTA differed, linear regression studies showed high agreement (except for 1/2-AG), and both methods showed similar EC profiles and similar disease-dependent pro-inflammatory patterns in dermatology patients. Hence, despite the obstacles in EC analyses, implementation of optimized pre-analytical blood collection and sample processing procedures provide reliable insight into peripheral ECs.

The circulating and central endocannabinoid system in obesity and weight loss

Major advances have been made in obesity treatment, focusing on restoring disturbances along the gut-brain axis. The endocannabinoid system (ECS) is a neuromodulatory signaling system, present along the entire gut-brain axis, that plays a critical role in central and peripheral regulation of food intake and body weight. Evidence on the impact of weight loss on the ECS is, however, more limited. Therefore, we set out to review the existing literature for changes in central and circulating endocannabinoid levels after bariatric surgery and other weight loss strategies in humans. The PubMed, Embase and Web of Science databases were searched for relevant articles. Fifty-six human studies were identified. Most studies measuring circulating 2-arachidonoylglycerol (2-AG) found no difference between normal weight and obesity, or no correlation with BMI. In contrast, studies measuring circulating arachidonoylethanolamine (AEA) found an increase or positive correlation with BMI. Two studies found a negative correlation between BMI and cannabinoid receptor type 1 (CB1) receptor availability in the brain. Only one study investigated the effect of pharmacological weight management on circulating endocannabinoid concentrations and found no effect on AEA concentrations. So far, six studies investigated potential changes in circulating endocannabinoids after bariatric surgery and reported conflicting results. Available evidence does not univocally support that circulating endocannabinoids are upregulated in individuals with obesity, which may be explained by variability across studies in several potential confounding factors (e.g. age and sex) as well as heterogeneity within the obesity population (e.g. BMI only vs. intra-abdominal adiposity). While several studies investigated the effect of lifestyle interventions on the circulating ECS, more studies are warranted that focus on pharmacologically and surgically induced weight loss. In addition, we identified several research needs which should be fulfilled to better understand the role of the ECS in obesity and its treatments.

Association of Serum Endocannabinoid Levels with Pancreatitis and Pancreatitis-Related Pain

Background and Aims: This investigation examined the association of pancreatitis and pancreatitis-related pain with serum levels of two endocannabinoid molecules such as anandamide (AEA) and 2-arachidonoylglycerol (2-AG) and two paracannabinoid molecules such as oleoylethanolamide (OEA) and palmitoylethanolamide (PEA). Methods: A case-control study was conducted within the Prospective Evaluation of Chronic Pancreatitis for Epidemiological and Translational Studies, including participants with no pancreas disease (N = 56), chronic abdominal pain of suspected pancreatic origin or indeterminate chronic pancreatitis (CP) (N = 22), acute pancreatitis (N = 33), recurrent acute pancreatitis (N = 57), and definite CP (N = 63). Results: Circulating AEA concentrations were higher in women than in men (p = 0.0499), and PEA concentrations were higher in obese participants than those who were underweight/normal or overweight (p = 0.003). Asymptomatic controls with no pancreatic disease had significantly (p = 0.03) lower concentrations of AEA compared with all disease groups combined. The highest concentrations of AEA were observed in participants with acute pancreatitis, followed by those with recurrent acute pancreatitis, chronic abdominal pain/indeterminant CP, and definite CP. Participants with pancreatitis reporting abdominal pain in the past year had significantly (p = 0.04) higher concentrations of AEA compared with asymptomatic controls. Levels of 2-AG were significantly lower (p = 0.02) among participants reporting abdominal pain in the past week, and pain intensity was inversely associated with concentrations of 2-AG and OEA. Conclusions: Endocannabinoid levels may be associated with stage of pancreatitis, perhaps through activation of the CB1 receptor. Validation of our findings would support the investigation of novel therapeutics, including cannabinoid receptor-1 antagonists, in this patient population.

Advances in targeted liquid chromatography-tandem mass spectrometry methods for endocannabinoid and N-acylethanolamine quantification in biological matrices: A systematic review

Liquid chromatography paired with tandem mass spectrometry (LC-MS/MS) is the gold standard in measurement of endocannabinoid concentrations in biomatrices. We conducted a systematic review of literature to identify advances in targeted LC-MS/MS methods in the period 2017-2024. We found that LC-MS/MS methods for endocannabinoid quantification are relatively consistent both across time and across biomatrices. Recent advances have primarily been in three areas: (1) sample preparation techniques, specific to the chosen biomatrix; (2) the range of biomatrices tested, recently favoring blood matrices; and (3) the breadth of endocannabinoid and endocannabinoid-like analytes incorporated into assays. This review provides a summary of the recent literature and a guide for researchers looking to establish the best methods for quantifying endocannabinoids in a range of biomatrices.

A Sensitive Ultrahigh-Performance Liquid Chromatography/Tandem Mass Spectrometry Method for the Simultaneous Analysis of Phytocannabinoids and Endocannabinoids in Plasma and Brain

Introduction: Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) are major chemical constituents of cannabis, which may interact either directly or indirectly with the endocannabinoid and endocannabinoid-like ("paracannabinoid") systems, two lipid-based signaling complexes that play important roles in physiology. Legislative changes emphasize the need to understand how THC and CBD might impact endocannabinoid and paracannabinoid signaling, and to develop analytical approaches to study such impact. In this study, we describe a sensitive and accurate method for the simultaneous quantification of THC, its main oxidative metabolites [11-hydroxy-Δ9-THC (11-OH-THC) and 11-nor-9-carboxy-Δ9-THC (11-COOH-THC)], CBD, and a representative set of endocannabinoid [anandamide and 2-arachidonoyl-sn-glycerol (2-AG)] and paracannabinoid [palmitoylethanolamide (PEA) and oleoylethanolamide (OEA)] compounds. Analyte separation relies on the temperature-dependent shape selectivity properties of polymerically bonded C18 stationary phases. Materials and Methods: Analytes are extracted from tissues using acetonitrile precipitation followed by phospholipid removal. The ultrahigh-performance liquid chromatography/tandem mass spectrometry protocol utilizes a commercially available C18 polymeric-bonded phase column and a simple gradient elution system. Results: Ten-point calibration curves show excellent linearity (R2>0.99) over a wide range of analyte concentrations (0.02-500 ng/mL). Lowest limits of quantification are 0.05 ng/mL for anandamide, 0.1 ng/mL for 11-OH-THC and OEA, 0.2 ng/mL for THC and CBD, 0.5 ng/mL for 11-COOH-THC, 1.0 ng/mL for 2-AG, and 2.0 ng/mL for PEA. The lowest limits of detection are 0.02 ng/mL for anandamide, 0.05 ng/mL for 11-OH-THC and OEA, 0.1 ng/mL for THC and CBD, 0.2 ng/mL for 11-COOH-THC, 0.5 ng/mL for 2-AG, and 1.0 ng/mL for PEA. Conclusions: An application of the method is presented, which showed that phytocannabinoid administration elevates endocannabinoid levels in plasma and brain of adolescent male and female mice.

Genetic variation of the 5-HT1A rs6295, 5-HT2A rs6311, and CNR1 rs1049353 and an altered endocannabinoid system in depressed patients

BACKGROUND

The reasons for developing depression are not fully understood. However, it is known that the serotonergic system plays a role in the etiology, but the endocannabinoid system receives attention.

METHOD

In this study, 161 patients with a depressive disorder and 161 healthy participants were examined for the distribution of the CNR1 rs4940353, 5-HT2A rs6311, and 5-HT1A rs6295 by high-resolution melting genotyping. The concentration of arachidonoyl ethanolamide (AEA) and 2-arachidonoylglycerol (2-AG) in the blood was measured by liquid chromatography-tandem mass spectrometry. Additionally, depression and anxiety symptoms were evaluated based on self-questionnaires. Fifty-nine patients participated in a second appointment to measure the concentration of AEA, 2-AG, and symptoms of depression and anxiety.

RESULTS

We observed higher AEA and decreased 2-AG concentrations in patients with depression compared to healthy participants. During the treatment, the concentrations of AEA and 2-AG did not change significantly. In patients higher symptoms of anxiety correlated with lower concentrations of 2-AG. Gender differences were found concerning increased 2-AG concentration in male patients and increased anxiety symptoms in female patients. Genotypic variations of 5-HT1A rs6295 and 5-HT2A rs6311 are associated with altered serotonergic activity and serotonin content in patients.

CONCLUSION

In conclusion, it seems that the endocannabinoid system, especially the endocannabinoids 2-AG and AEA, and genetic variations of the 5-HT1A and 5-HT2A could play a role in patients with depression and may be involved in a depressive disorder.

SPME as a green sample-preparation technique for the monitoring of phytocannabinoids and endocannabinoids in complex matrices

The endocannabinoid system (ECS), particularly its signaling pathways and ligands, has garnered considerable interest in recent years. Along with clinical work investigating the ECS' functions, including its role in the development of neurological and inflammatory conditions, much research has focused on developing analytical protocols enabling the precise monitoring of the levels and metabolism of the most potent ECS ligands: exogenous phytocannabinoids (PCs) and endogenous cannabinoids (endocannabinoids, ECs). Solid-phase microextraction (SPME) is an advanced, non-exhaustive sample-preparation technique that facilitates the precise and efficient isolation of trace amounts of analytes, thus making it appealing for the analysis of PCs and ECs in complex matrices of plant and animal/human origin. In this paper, we review recent forensic medicine and toxicological studies wherein SPME has been applied to monitor levels of PCs and ECs in complex matrices, determine their effects on organism physiology, and assess their role in the development of several diseases.

Monitoring of age- and gender-related alterations of endocannabinoid levels in selected brain regions with the use of SPME probes

INTRODUCTION

The endocannabinoid system consists of different types of receptors, enzymes and endocannabinoids (ECs), which are involved in several physiological processes, but also play important role in the development and progression of central nervous system disorders.

OBJECTIVES

The purpose of this study was to apply precise and sensitive methodology for monitoring of four ECs, namely anandamide (AEA), 2-arachidonoyl glycerol (2-AG), N-arachidonoyl dopamine (NADA), 2-arachidonyl glyceryl ether (2-AGe) in selected brain regions of female and male rats at different stages of development (young, adult and old).

METHODS

Biocompatible solid-phase microextraction (SPME) probes were introduced into the intact (non-homogenized) brain structures for isolation of four ECs, and the extracts were subjected to LC-MS/MS analysis. Two chemometric approaches, namely hierarchical cluster analysis (HCA) and Principal Component Analysis (PCA) were applied to provide more information about the levels of 2-AG and AEA in different brain structures.

RESULTS

2-AG and AEA were extracted and could be quantified in each brain region; the level of 2-AG was significantly higher in comparison to the level of AEA. Two highly unstable ECs, NADA and 2-AGe, were captured by SPME probes from intact brain samples for the first time.

CONCLUSION

SPME probes were able to isolate highly unstable endogenous compounds from intact tissue, and provided new tools for precise analysis of the level and distribution of ECs in different brain regions. Monitoring of ECs in brain samples is important not only in physiological conditions, but also may contribute to better understanding of the functioning of the endocannabinoid system in various disorders.

Pre-analytical sample handling standardization for reliable measurement of metabolites and lipids in LC-MS-based clinical research

The emerging disciplines of lipidomics and metabolomics show great potential for the discovery of diagnostic biomarkers, but appropriate pre-analytical sample-handling procedures are critical because several analytes are prone to ex vivo distortions during sample collection. To test how the intermediate storage temperature and storage period of plasma samples from K3EDTA whole-blood collection tubes affect analyte concentrations, we assessed samples from non-fasting healthy volunteers (n = 9) for a broad spectrum of metabolites, including lipids and lipid mediators, using a well-established LC-MS-based platform. We used a fold change-based approach as a relative measure of analyte stability to evaluate 489 analytes, employing a combination of targeted LC-MS/MS and LC-HRMS screening. The concentrations of many analytes were found to be reliable, often justifying less strict sample handling; however, certain analytes were unstable, supporting the need for meticulous processing. We make four data-driven recommendations for sample-handling protocols with varying degrees of stringency, based on the maximum number of analytes and the feasibility of routine clinical implementation. These protocols also enable the simple evaluation of biomarker candidates based on their analyte-specific vulnerability to ex vivo distortions. In summary, pre-analytical sample handling has a major effect on the suitability of certain metabolites as biomarkers, including several lipids and lipid mediators. Our sample-handling recommendations will increase the reliability and quality of samples when such metabolites are necessary for routine clinical diagnosis.

Cannabinoid-1 receptor activation modulates lipid mobilization and adipogenesis in the adipose tissue of dairy cows

Amplified adipose tissue (AT) lipolysis and suppressed lipogenesis characterize the periparturient period of dairy cows. The intensity of lipolysis recedes with the progression of lactation; however, when lipolysis is excessive and prolonged, disease risk is exacerbated and productivity compromised. Interventions that minimize lipolysis while maintaining adequate supply of energy and enhancing lipogenesis may improve periparturient cows' health and lactation performance. Cannabinoid-1 receptor (CB1R) activation in rodent AT enhances the lipogenic and adipogenic capacity of adipocytes, yet the effects in dairy cow AT remain unknown. Using a synthetic CB1R agonist and an antagonist, we determined the effects of CB1R stimulation on lipolysis, lipogenesis, and adipogenesis in the AT of dairy cows. Adipose tissue explants were collected from healthy, nonlactating and nongestating (NLNG; n = 6) or periparturient (n = 12) cows at 1 wk before parturition and at 2 and 3 wk postpartum (PP1 and PP2, respectively). Explants were treated with the β-adrenergic agonist isoproterenol (1 μM) in the presence of the CB1R agonist arachidonyl-2'-chloroethylamide (ACEA) ± the CB1R antagonist rimonabant (RIM). Lipolysis was quantified based on glycerol release. We found that ACEA reduced lipolysis in NLNG cows; however, it did not exhibit a direct effect on AT lipolysis in periparturient cows. Inhibition of CB1R with RIM in postpartum cow AT did not alter lipolysis. To evaluate adipogenesis and lipogenesis, preadipocytes isolated from NLNG cows' AT were induced to differentiate in the presence or absence of ACEA ± RIM for 4 and 12 d. Live cell imaging, lipid accumulation, and expressions of key adipogenic and lipogenic markers were assessed. Preadipocytes treated with ACEA had higher adipogenesis, whereas ACEA+RIM reduced it. Adipocytes treated with ACEA and RIM for 12 d exhibited enhanced lipogenesis compared with untreated cells (control). Lipid content was reduced in ACEA+RIM but not with RIM alone. Collectively, our results support that lipolysis may be reduced by CB1R stimulation in NLNG cows but not in periparturient cows. In addition, our findings demonstrate that adipogenesis and lipogenesis are enhanced by activation of CB1R in the AT of NLNG dairy cows. In summary, we provide initial evidence which supports that the sensitivity of the AT endocannabinoid system to endocannabinoids, and its ability to modulate AT lipolysis, adipogenesis, and lipogenesis, vary based on dairy cows' lactation stage.

A GPCR-based yeast biosensor for biomedical, biotechnological, and point-of-use cannabinoid determination

Eukaryotic cells use G-protein coupled receptors to sense diverse signals, ranging from chemical compounds to light. Here, we exploit the remarkable sensing capacity of G-protein coupled receptors to construct yeast-based biosensors for real-life applications. To establish proof-of-concept, we focus on cannabinoids because of their neuromodulatory and immunomodulatory activities. We construct a CB₂ receptor-based biosensor, optimize it to achieve high sensitivity and dynamic range, and prove its effectiveness in three applications of increasing difficulty. First, we screen a compound library to discover agonists and antagonists. Second, we analyze 54 plants to discover a new phytocannabinoid, dugesialactone. Finally, we develop a robust portable device, analyze body-fluid samples, and confidently detect designer drugs like JWH-018. These examples demonstrate the potential of yeast-based biosensors to enable diverse applications that can be implemented by non-specialists. Taking advantage of the extensive sensing repertoire of G-protein coupled receptors, this technology can be extended to detect numerous compounds.

GPCRs are used for diverse sensing in eukaryotes. Here the authors use GPCRs to construct yeast-based biosensors, focussing on cannabinoids, and use these to screen agonists and antagonists, as well as generate a portable detection device.

Pre-analytical challenges for the quantification of endocannabinoids in human serum

Endocannabinoids (ECs) are potent lipid mediators with high physiological relevance. They are involved in a wide variety of diseases like depression or multiple sclerosis and are closely connected to metabolic parameters in humans. Therefore, their suitability as a biomarker in different (patho-)physiological conditions is discussed intensively and predominantly investigated by analyzing systemic concentrations in easily accessible matrices like blood. Carefully designed pre-analytical sample handling is of major importance for high-quality data, but harmonization is not achieved yet. Whole blood is either processed to serum or plasma before the onset of analytical workflows and while knowledge about pre-analytical challenges in plasma handling is thorough they were not systematically investigated for serum. Therefore, the ECs AEA and 2-AG, and closely related EC-like substances 1-AG, DHEA, and PEA were examined by LC-MS/MS in serum samples of nine healthy volunteers employing different pre-analytical sample handling protocols, including prolonged coagulation, and storage after centrifugation at room temperature (RT) or on ice. Furthermore, all analytes were also assessed in plasma samples obtained from the same individuals at the same time points to investigate the comparability between those two blood-based matrices regarding obtained concentrations and their 2-AG/1-AG ratio. This study shows that ECs and EC-like substances in serum samples were significantly higher than in plasma and are especially prone to ex vivo changes during initial and prolonged storage for coagulation at RT. Storage on ice after centrifugation is less critical. However, storage at RT further increases 1-AG and 2-AG concentrations, while also lowering the already reduced 2-AG/1-AG ratio due to isomerization. Thus, avoidance of prolonged processing at RT can increase data quality if serum as the matrix of choice is unavoidable. However, serum preparation in itself is expected to initiate changes of physiological concentrations as standard precautionary measures like fast and cooled processing can only be utilized by using plasma, which should be the preferred matrix for analyses of ECs and EC-like substances.